QassTiv\ 5" \ _
Book i—i
■flo\
ELECTRICAL ENGINEER fS
POCKET - BOOK
A Hand - "book
of useful data for Electricians
and Electrical Engineers
Horatio A. Poster
with the Collaboration of Eminent
Specialists.
Third Edition, Corrected,
llinth Thousand.
New York:
D. Van No strand Company
London:
E. & P. N. Spon, Ltd. 1903
-'"'i
t »+■■.*■.<.„
j2 ""
(^PREFACE.
It is with some little trepidation that this book is put
before the public, in view of the frequent important, and
even radical, changes that up to the present have char-
acterized the development of electrical engineering. It
has, however, been thought that the science has now
reached a stage which renders necessary some manual
that will be of assistance to the active worker in the
various branches.
This book is not an encyclopedia, nor is it intended
for a text-book, but it is hoped that as a compendium of
useful data it may assist the practicing electrician and
engineer.
The matter included is representative of American
practice, and no effort has been made to include any
other, except in special cases. No excuse is offered for
the very considerable amount of matter taken from
trade publications of the larger electrical manufacturers,
as in this country the engineers retained by such works
are specialists — often the best in their various
branches ; and it is an accident of condition only that in
some cases has compelled the use of more of the publi-
cations of one company than of another, based upon
available published material.
Manufacturers have been most kind in supplying any
special data and descriptions asked for ; and the author's
thanks are in particular due to a large circle of asso-
iii
IV PREFACE.
ciates for suggestions, revisions, critical proof-reading,
and the various other details involved in a compilation
of this kind, of whom the following deserve especial
mention for valuable aid rendered : Messrs. E. E. Idell,
W. D. Weaver, T. C. Martin, Prof. Samuel Sheldon,
E. B. Raymond, John S. Griggs, Jr., William Wallace
Christie, J. J. Crain, G-rahame H. Powell, Prof. Erancis
B. Crocker, A. 1ST. Mansfield, E. M. Hewlett, C. E. Scott,
H. S. Putnam, Charles Henry Davis, Townsend Wolcott,
Walter S. Moody, Herbert Laws Webb, Charles Thorn,
William Maver, Jr., Joseph Appleton, Prof. Alex. G-.
McAdie, Thorburn Reid, Max Osterberg, Max Loewen-
thal, J. G-. White & Co. The especial thanks of the
author are due to the indefatigable co-operation of Mr.
Charles E. Speirs, of the D. Van ISTostrand Co., who
has rendered most valuable assistance in properly get-
ting the matter into shape for publication.
In closing, the author begs that readers will not hesi-
tate to point out errors found in the text or tables, as
many will doubtless crop out in the close examination
by numerous readers.
LIST OF CONTRIBUTORS.
SECTION.
Symbols, Units and Instruments.
Resistance, Electrical Measurements.
Cable Testing (re-Written).
Conductors (Properties of).
Conductors (Relation and Dimension of).
Electric Lighting.
Lightning Arresters.
Electric Street Railways.
Storage Batteries.
Telephony.
Magnetic Properties of Iron.
Electromagnets.
Determination of Wave Form.
Electricity Meters.
Dynamos and Motors.
Dynamos and Motors Standard and Test.
Static Transformers.
Telegraphy.
Switchboards and Switching Devices.
Transmission of Power.
Electricity in U. S. Navy.
Certain Uses of Electricity in U. S. Army.
Electro-chemistry, Electro-metallurgy.
Electric Heating, Cooking, and Electric
Welding.
Mechanical Section.
Lightning Conductors.
Miscellaneous Section.
Underwriter's Code.
Index Electrical Section.
Index Mechanical Section.
REVISED BY
Prof. Samuel Sheldon.
Prof. Samuel Sheldon.
Mr. William Maver, Jr.
Prof. Samuel Sheldon.
Prof. Samuel Sheldon.
Mr. Townsend Wolcott.
Mr. Townsend Wolcott.
Mr. John S. Griggs, Jr.
Mr. Townsend Wolcott.
Mr. Herbert Laws Webb.
Prof .Samuel Sheldon.
Mr. Townsend Wolcott.
Mr. Townsend Wolcott.
Prof. Samuel Sheldon.
Mr. E. B. Raymond.
Mr. E. B. Raymond.
J Mr. Walter S. Moody.
I Mr. Townsend Wolcott.
( Mr. Chas. Thorn.
I Mr. Herbert Laws Webb.
Mr. E. M. Hewlett.
Mr. T. C. Martin.
Mr. J. J. Crain.
Mr. Grahame H. Powell.
Prof. Francis B. Crocker.
| Mr. Max Osterberg.
* Mr. Max Loewenthal.
( Mr. Wm. Wallace Christie.
t Mr. F. E. Idel.
Prof. Alex. G. McAdie.
Mr. Townsend Wolcott.
Mr. Max Loewenthal.
Mr. Win. Wallace Christie.
J
CONTENTS.
PAGE
Symbols, Units, Instruments 1
Resistance Measurements 38
Magnetic Properties of Iron 64
Electro-magnets 81
Relation and Dimensions of Conductors 92
Properties of Conductors 140
Cable Testing 220
Dynamos and Motors 230
Dynamo and Motor Standards 293
The Static Transformer 331
Electric Lighting 38G
Electric Street Railways 423
Transmission of Power 548
Storage Batteries 552
Switchboards 585
Lightning Arresters 601
Electricity Meters 615
Telegraphy 636
Telephony 645
Electro-Chemistry and Electro-Metallurgy 675
Electric Heating, Cooking, and Welding 683
Operation of Electric Mining Plants 696
Lightning Conductors 701
Determination of Wave Form , 705
Electricity in the IT. S. Army 711
Electricity in the U. S. Navy 727
Miscellaneous 757
National Code Rules and Requirements 762
Mechanical Section 791
Index 977
vii
SYMBOLS, UNITS, INSTRUMENTS.
CHAPTER I.
ELECTRICAL ENGINEERING SYMBOLS
The following list of symbols has been compiled from various sources as
being those most commonly in use in the United States. Little variation
will be found from similar lists already published except the elimination of
some that may be considered exclusively foreign. The list has been revised
by competent authorities and may be considered as representing the best
usage.
fundamental.
I, Length, cm. = centimeter ;
in., or //=inch, ft. or ' =
foot.
M, Mass. gr. = mass of 1
gramme ; kg. = 1 kilo-
gramme.
T, t, Time. s = second.
Derived: geometric.
5, s, Surface.
V, Volume.
a, /3, Angle.
Mechanical.
v, Velocity.
m, Momentum.
<u, Angular velocity.
a, Acceleration.
g, Acceleration due to gravity
= 32.2 feet per second.
F, /, Force.
W, Work.
P, Power.
6, Dyne, 10 5 = 10 dynes.
e, Ergs.
ft. lb., Foot-pound.
H.p. , h.p. ; H\ Horse-power.
I.H.P., Indicated horse-power.
B.H.P., Brake horse-power.
E.H.P., Electrical horse-power.
J, Joules' equivalent.
p, Pressure.
K, Moment of inertia.
Derived Electrostatic.
q, Quantity.
i, Current.
e, Potential Difference.
r, Resistance.
k, Capacity.
sk, Specific Inductive capacity.
Derived Magnetic.
9TL
Strength of pole.
Magnetic moment.
Jp, Intensity of magnetization.
;}£, Horizontal intensity of
earth's magnetism.
JC, Field intensity.
*, Magnetic Flux.
(B, Magnetic flux density or
magnetic induction.
J£, Magnetizing force.
gr, Magnetic force.
(ft, Reluctance, Magnetic re-
sistance.
ft., Magnetic permeability.
K, Magnetic susceptibility.
v, Reluctivity (specific mag-
netic resistance).
Derived electromagnetic.
R, Resistance, Ohm.
12, do, megohm.
E, Electromotive force, volt.
U, Difference of potential, volt.
/, Intensity of current, Ampere.
Q, Quantity of electricity, Am-
pere-hour ; Coulomb.
C, Capacity. Farad.
W, Electric Energy, Watt-hour ;
Joule.
P, Electric Power, Watt ; Kilo-
Avatt.
p, Resistivity (specific resis-
tance), Ohm-centimeter.
6, Conductance, Mho.
•y, Conductivity (specific con-
ductivity.
L, Inductance (coefficient of
Induction), Henry.
v, Ratio of electro-magnetic to
electrostatic unit of quan-
tity =3 X 10™ centimeters
per second approximately.
Symbols in general use.
D, Diameter,
r, Radius.
tf Temperature.
0, Deflection of galvanometer
, needle.
A SYMBOLS, UNITS, INSTRUMENTS.
A\n, Number of anything. R.p.m., Revo) utions per minute.
7r, Circumference ~ diameter : C.P. Candlepower.
3.141592. — o— Incandescent lamp.
a), 2 n is = 6.2831 X frequency, in |
alternating current. X Arc lamp.
r*J Frequency, periodicity, cy- j
cles per second. _ji_ -r=^ n„ 1
G, Galvanometer. HI" or ^H Condenser.
S, Shunt. —J|||— Battery of cells.
N, n, Isorth pole of a magnet. -*-i J
S, s, South pole of a magnet. jq/ Dynamo or motor, d.c.
A.M. Ammeter. y(F\
V.M. Voltmeter. <^S^ Dynamo or motor, a.c.
A.C. Alternating current. /?v
D.C. Direct current. /%0) Converter.
P.D. Potential difference. . .
C.G.S. Centimeter, Gramme, Second \^^ Static transformer
system. r™n
B. & S. Brown & Sharpe wire gauge. -orrrrTOTr Inductive resistance.
B.W.G., Birmingham Wire gauge. -vwwwv Non-inductive resistance.
CHAPTER II.
JEUECTJRICAU E,\<;n'EERM-(; unrixs.
Judex, dotation.
Electrical units and values oftentimes require the use of lar^e numbers
of many figures both as whole numbers and in decimals. In order to avoid
this to a great extent the index method of notation is in universal use in
connection with all electrical computations.
In indicating a large number, for example, say, a million, instead of writ-
ing 1,000,000, it would by the index method be written 10|; • and 35 000 000
would be written 35 x 10".
A decimal is written with a minus sign before the exponent, or -JU— 01
= 10-2 ; and .00048 is written 48 X 10~5.
The velocity of light is 30,000,000,000 cms. per sec. and is written 3 x 1010.
In multiplying numbers expressed in this notation the significant figures
are multiplied, ami to their product is annexed 10, with an index equal to
the sum of the indices of the two numbers.
In dividing, the significant figures are divided, and 10, with an index equal
to the difference of the two indices of the numbers is annexed to the divi-
dend.
Fundamental Units.
The physical qualities, such as force, velocity, momentum, etc., are ex-
pressed in terms of length, mass, time, and for electricity the system of
terms in universal use is that known as the C. G. S. system,
viz. : — The unit of length is the Centimeter.
The unit of mass is the Gramme.
The unit of time is the Second.
Expressed in more familiar units, the Centimeter is equal to .3937 inch in
length ; the Gramme is equal to 15.432 grains, and represents the mass or
quantity of a cubic centimeter of water at 4° C, or 39.2° Fah. ; the Second is
*ne HgiB^.ij? part of a sidereal day, or the ?5^gn part of a mean solar day.
These units, are also often called absolute units.
^Derived Geometric Units.
The unit of area or surface is the square centimeter.
The unit of volume is the cubic centimeter.
I»erived Iflechanical Units.
Velocity is the rate of change of position, and is uniform velocity when
equal distances are passed over in equal spaces of time ; unit velocity is a
rate of change of one centimeter per second.
1
ELECTRICAL ENGINEERING UNITS. 3
Angular Velocity is the angular distance about a center passed through n
one second of time. Unit angular velocity is the velocity of a body moving
in a circular path, whose radius is unity, and which would traverse a unit
angle in unit time. Unit angle is 57°, 17', 44.8" approximately ; i.e., an angle
whose arc equals its radius.
Momentum is the quantity of motion in a body, and equals the mass times
the velocity.
Acceleration is the rate at which velocity changes ; the unit is an accel-
eration of one centimeter per second per second. The acceleration due to
gravity is the increment in velocity imparted to falling bodies by cravitv
and is usually taken as 32.2 feet per second, or 981 centimeters per second'
This value differs somewhat at different localities. At the North Pole g =
983.1 ; at the equator g = 9/8.1 ; and at Greenwich it is 981.1.
Force acts to change a body's condition of rest or motion.' It is that which
tends to produce, alter, or destroy motion, and is measured by the change
of momentum produced. s
The unit of force is that force wllich, acting for one second on a mass of
one gramme, gives tiie mass a velocity of one centimeter per second ; this
unit is called a dyne. The force of gravity or weight of a mass in dynes may
be found by multiplying the mass in grammes by the value of g at the par-
ticular place where the force is exerted. The pull of gravity on one pound
in the United States may he taken as 445,000 dynes.
Work is the product of a force into the distance through which it acts.
The unit is the erg, and equals the work done in pushing a mass through a
distance of one centimeter against a force of one dyne. As the " weight"
of one gramme is 1 x 981, or 981 dynes, the work done in raising a weight of
one gramme through a height of one centimeter against the force of gravity,
or 981 dynes, equals 1 x 981 =981 ergs.
One kilogramme-meter = 100 000 x 981 ergs.
Kinetic energy is the work a body is ahle to do by reason of its motion.
Potential energy is the work a body is able to do by reason of its position.
The unit of energy is the erg.
Power is the rate of working, and the unit is the watt = 10' ergs per sec.
Horse-power is the unit of power in common use and, although a somewhat
arbitrary unit, it is difficult to compel people to change from it to any other.
It equals 33,000 lbs- raised one foot high in one minute, or 550 foot-pounds
per sec.
1 ft.-lb. = 1.356 x 107ergs.
1 watt = 107 ergs per second.
1 horse-power = 550 x 1.356 x 107 ergs = 746 watts. If a cunent of 7 ara-
E I 727?
peres flow through It ohms under a pressure of E volts, then — = — - =
represents the horse-power involved.
. The French "force de chevaV = 736 watts = 542.48 ft. lbs. per sec.=
.9863 H. P.. and 1*H. P = 1.01385 "force de cheval."
Heat. The Joul WJ= 107 ergs, and is the work done, or heat generated, by
a watt second, or ampere flowing for a second through a resistance of an ohm.
If 77= heat generated in gramme calories,
7 = current in amperes,
i? = e.m.f. in volts,
7? = resistance in ohms, and
/= time in seconds,
then 77=0.24 72 Jit — 0.24 Elt. gramme calories or therms.
Then IEI = nm= ^ =EQ= Joules.
or, as 1 horse-power = 550 foot-pounds of work per second,
Joules = ffg EQ = .7373 EQ ft. lbs.
Heat TTsaits.
The British Thermal Unit is the amount of heat required to raise the
temperature of one pound of water from 60° F. to 61°, = 1 pound-degree-
Fah. = 251.9 French units.
The therm, or French calorie, is the amount of heat required to raise the
4 SYMBOLS, UNITS, INSTRUMENTS.
temperature of a mass of 1 gramme of water from 4° C. to 5° C. = 1 gramme-
degree-centigrade = .00396 B.T.U.
Water at 4° C. is at its maximum density.
Joules equivalent, J, is the amount of energy equal to a heat unit.
For a B.T.U., or pound-degree-Fah., J — 1.06 x 1010 ergs., or = 772.55 foot-
pounds.
For one pound-degree — Centigrade, J = 1.91 X 1010 ergs.
For a calorie J = 4.16 X 107 ergs.
The heat generated in t seconds of time is
I*Rt Elt . _ . ie .._
— =- = —j- , where J = 4.16 x 107,
and /, R, and E are expressed in practical units.
Electrical Units.
There are two sets of electrical units derived from the fundamental
C. G. S. units; viz., the electrostatic and the electromagnetic. The first is
based on the force exerted between two quantities of electricity, and the sec-
ond upon the force exerted between a current and a magnetic pole. The
ratio of the electrostatic to the electromagnetic units has been carefully de-
termined by a number of authorities, and is found to be some multiple or
sub-multiple of a quantity represented by v, whose value is approximately
3 x 1010 centimeters per second. Convenient rules for changing from one to
the other set of units will be stated later on in this chapter.
Electrostatic Units.
As yet there have been no names assigned to these. Their values are as
follows : —
The unit of quantity is that quantity of electricity which repels with a
force of one dyne a similar and equal quantity of electricity placed at unit
distance (one centimeter) in air.
Unit of current is that which conveys a unit of quantity along a conduc-
tor in unit time (one second).
Unit difference of potential or unit electro-motive force exists between two
points when one erg of work is required to pass a unit quantity of electricity
from one point to the other.
Unit of resistance is possessed by that conductor through which unit cur-
rent will pass under unit electro-motive force at its ends.
Unit of capacity is that which, when charged by unit potential, will hold
one unit of electricity ; or that capacity which, when charged with one unit
of electricity, has a unit difference of potential.
Specific inductive capacity of a substance is the ratio between the capacity
of a condenser having that substance as a dielectric to the capacity of the
same condenser using dry air at 0C C. and a pressure of 76 centimeters as
the dielectric.
Magnetic Units.
Unit Strength of Pole (symbol m) is that which repels another similar and
equal pole with unit force (one dyne) when placed at unit distance (one
centimeter) from it.
Magnetic Moment (symbol 91t) is the product of the strength of either
pole into the distance between the two poles.
Intensity of Magnetization is the magnetic moment of a magnet divided
by its volume, (symbol (£,).
Intensity of Magnetic Field (symbol J£ ) is measured by the force it exerts
upon a unit magnetic pole, and therefore the unit is that intensity of field
which acts on a unit pole with a unit force (one dyne).
Magnetic Induction (symbol $) is the magnetic flux or the number of
magnetic lines per unit area of cross-section of magnetized material, the
area being at every point perpendicular to the direction of flux. It is equal
to the magnetizing force or field intensity J£ multiplied by the permeability
ij.: the unit is the gauss.
Magnetic Flux (symbol $) is equal to the average field intensity multiplied
by the area. Its unit is the maxwell.
Magnetizing Force (symbol J£ ) per unit of length of a solenoid equals
ELECTRICAL ENGINEERING UNITS.
4 n iVJ-f- L where N=. the number of turns of wire on the solenoid ; L =
the length of the solenoid in cms., and /= the current in absolute units.
Magnetomotive Force (symbol $ ) is the total magnetizing force developed
in a magnetic circuit by a coil, equals 4 n- NI, and the unit proposed is the
gilbert.
Reluctance, or Magnetic Resistance (symbol (${), is the resistance offered to
the magnetic flux by the material magnetized, and is the ratio of magneto-
motive force to magnetic flux; that is, unit magnetomotive force will generate
a unit of magnetic flux through unit reluctance : the unit is the oersted; i.e.,
the reluctance offered by a cubic centimeter of vacuum.
Magnetic Permeability (symbol /u.) is the ratio of the magnetic induction
(ft to the magnetizing force J£, that is ^ = /u.
Magnetic Susceptibility (symbol k) is the ratio of the intensity of mag-
netization to the magnetizing force, or k = ^ •
Reluctivity, or Specific Magnetic Resistance (symbol v), is the reluctance
per unit of length and of unit cross-section that a material offers to being
magnetized.
Electromagnetic Units.
Resistance (symbol R) is that property of a material that opposes the flow
of a current of electricity through it; and the unit is that resistance which,
with an electro-motive force or pressure between its ends of one unit, will
permit the flow of a unit of current.
The practical unit is the ohm, and its value in C.S.G. units is 109. The
standard unit is a column of pure mercury at 0° C, of uniform cross-section,
106.3 centimeters long, and 14.4521 grammes weight. For convenience in use
for very high resistances the prefix meg is used; and the megohm, or million
ohms, becomes the unit for use in expressing the insulation resistances of
submarine cables and all otber high resistances.
Electro-motive Force (symbol E) is the electric pressure which forces the
current through a resistance, and unit E.M.F. is that pressure which will
force a unit current one ampere through a unit resistance. The unit is the
volt, and the practical standard adopted by the international congress of elec-
tricians at Chicago in 1893 is the Clark cell, directions for making which
will be given farther on. The E.M.F. of a Clark cell is 1.434 volt at 15° C.
The value of the volt in C.G.S. units is 108. For small E.M.F's. the unit
millivolt, or one-thousandth volt, is used.
Difference of Potential, as the name indicates, is simply a difference of
electric pressure between two points. The unit is the volt.
Current (symbol /) is the intensity of the electric current that flows
through a circuit. A unit current will flow through a resistance of one
ohm, with an electro-motive force of one volt between its ends. The unit
is the ampere, and is practically represented by the current that will electro-
lytically deposit silver at the rate of .001118 gramme per second. Its value
in C.G.S. units is 10 _1. For small values the milliampere is used, and it
equals one-thousandth of an ampere.
The Quantity of Electricity (symbol Q) which passes through a given cross-
section of an individual circuit in t seconds when a current of I amperes is
flowing is equal to It units. The unit is therefore the ampere-second. Its
name is the Coulomb, and its value in C.G.S. units is 10 J.
Capacity (symbol C) is the property of a material condenser for holding
a charge of electricity. A condenser of unit capacitv is one which will be
charged to a potential of one volt by a quantitv of 1 coulomb. The unit is
the/a?w/, its C.G.S. value is lO 9; and this being so much larger than ever
obtains m practical work, its millionth part, or the micro-farad, is used as
the practical unit, and its value in absolute units is 10 1S. A condenser of
one-third micro-farad capacity is the size in most common use in the United
States.
Electric Energy (symbol W) is represented by the work done in a circuit
or conductor by a current flowing through it. The unit is the Joule, its
absolute value is 107 ergs, and it reprepresents the work done by the flow
for one second of unit current (1 ampere) through 1 ohm.
Electric Power (symbol P) is measured in watts, and is represented by a
current of 1 ampere under a pressure of 1 volt, or 1 Joule per second. The
SYMBOLS, UNITS, INSTRUMENTS.
bbrevia-
ons of
the
ractical
Units.
£
,=
■
2
2 wr* !
<G ft
1
bfic
£©"2|
d
o
&
2 -c -
O . ^ a-
©d
0
i|| &
0)
fl-t
g§
$
.2.3 •
2 2 © ^
Fh
Pa «« -5
+^.3 ft to © £
gs
ft
li
©
oM © © 2 o C ©
> -£ ft g ft ~ S<
^ ^ o
© «2i§
|.Sd-s
£ 60
©
^ ©
h
-d
~'3
©02
*;5
© §
Sg 1
3 3
©t
Q
S 28 §
1/2 , ^ © • ©
ft © © Q^ ©
« ■ -5 -C bfl
1 So H
^
tt0
tf
O
< 5 "3 "
©
*>
=0
l-fl
**&■
SS |
t
(>
£
&i
£ eft 3
^
Kj
•5 C?
<1
bc~
.3.2
^ihi»w*i&i ig^
mi ii
i
II 1
ii in
11
flH
05 ^ «
§ 3
8 (^
«h
•, ^
-SJ, *.
Vj ^
v
02,0
■4^S>
02 «
a 3
8 fe^te
A, ^
©
>>
'
s
• ."£
^
a
G?
I
u
g
o
o
'3
be
©
>
©
£ ■
i
c
fi fl
©
o o
Pm
s
<
ii
iE-
© 1
- <
3
>
s
J
5
<
c; 3
© s
1
a
3
o
1
ELECTRICAL ENGINEERING UNITS.
o>H
P
e « e ert c
^ w E*< ^
8 r 53 s £ "S
e g e e ~ S
Q> | ^ o 6 o
ii* -i-- i
& ,Q £*
£ £ *
< < <
ii ii ii
l^l^^jSl^i^l^^hlT^^'^,:
£ll II II II I II ,ii II II || || II II II II II II
a, ^
•■ *■* $&^'H»®U^£ *
6
'. ■ s
DQ
«.
K
>>
o a
© be
s 3 ^
§ a
S C
c Moment
tftnsitv
(Magnetic) Force ....
c Induction
zing Forcet
nnotive Force
ice (Magnetic Resistance) .
->ilitv .........
2
05
33 °
CSC
Ck 3 O" Q Pk P3 Occ 35 S h Pm^SSSm Oh «} P4
SYMBOLS, UNITS, INSTRUMENTS.
Abbrevia-
tions of
the
Practical
Units.
>
a
ft
.a
iS
S
©
0
W
c
©
•is *
*o
G
^
? ±5
'3
t3
©
©S .
e3
c3 fl
©
6
£
i
08
"o
a
£ -*
a
A
_©
©
63
C
>
"J
J3
3
ft
■^ =3
©
a
a
li
C
O
Pn
c
!*
,a
0
© «2 o5
h
0
0
0
0
0 0
1
t> dD
© .
<H -
op
2M
H
&o
© ^
i^1;l
H
Eh
2.tL
fl
Eh e;
H
E*
Eh
H
Dim
sions 0
Phys:
Quant
i-
^
Eh
S
Eh E-
>>
C5|N
n
^
hC
2? a
^
«
^
^ ^
^
tq
w>a
Eh
.3.2
K)j
S Aj
b;:::
Eh
0>|Kjbq fcj^l^
^|ft^,a^-
■*,
6qi^
Si
1
II
II
II
1
1! 1
II
1
II
1
1
°w
ft
K]
*h
O"
O ^ ft
«■
C
?- ^
N)
a o5
&
w
01
3^
05
5.
£>0
CO ^2
ft
" ftq*
^
c?
Q-
c
* *■ 4
N
A
"©
c
g
©
^
a a
j
1
0
SB
3
© a
73 a
0
a
fl
O
t»»
O
0
6C
oa
©~
^
Ph
© .
«a ••
3
G?
"3
s
a
0
o|
©
3
Q
O
0
©
>
s
c
» i
c
p.
©
a
t
i
•a »
co ^
a
I
^ V
'■5 £
a
~
5
© c
©
83
I
- © a
T
"2 ^
(
< eS
C
0
I
%
H
M
3"
c
£
ps
C
0 0
P^
1
INTERNATIONAL ELECTRICAL UNITS.
watt equals 107 absolute units, and 746 watts equals 1 horse-power. In elec-
tric lighting and power the unit kilowatt, or 1000 watts, is considerably used
to avoid the use of large numbers.
Resistivity (symbol p) is the specific resistance of a substance, and is the
resistance in ohms of a centimeter cube of the material to a flow of cur-
rent between opposite faces.
Conductance (symbol G) is that property of a metal or substance by which
it conducts an electric current, and equals the reciprocal of its resistance.
The unit proposed for conductance is the Mho, but it has not come into
prominent use as yet.
Conductivity (symbol v) is the specific conductance of a material, and is
therefore the reciprocal of its resistivity. It is often expressed in compari-
son with the conductivity of some standard metal such as silver or copper,
and is then stated as a percentage.
Inductance (symbol L), or coefficient of self-induction, of a circuit is that
coefficient by which the time rate of charge of the current in the circuit
must be multiplied in order to give the E.M.F. of self-induction in the
circuit. The practical unit is the henry, which equals 109 absolute units,
and exists in a circuit when a current varying 1 ampere per second produces
a, volt of electro-motive force in that circuit. As the henry is so large as to
be seldom met with in practice, 1 thousandth of it, or the milli-henry , is the
unit most in use.
Below will be found a few rules for reducing values stated in electrostatic
units to units in the electro-magnetic system. To reduce
electrostatic potential to volts, multiply by 300 ;
" capacity to micro-farads, divide by 900,000 ;
" quantity to coulombs, divide by 3 x 109 ;
" current to amperes, divide by 3 x 109;
" resistance to ohms, multiply by 9 X 1011.
IHTTERHfATIOMAL ELECTRICAL "UHFITS.
At the International Congress of Electricians, held at Chicago, August 21,
1893, the following resolutions met with unanimous approval, and being
approved for publication by the Treasury Department of the United States
Government, Dec. 27, 1893, and legalized by act of Congress and approved
by the President, July 12, 1894, are now recognized as the International
units of value for their respective purposes.
RE SOL VED, That the several governments represented by the delegates
of the International Congress of Electricians be, and they are hereby,
recommended to formally adopt as legal units of electrical measure the
following : —
1. As a unit of resistance, the International ohm, which is based upon the
ohm equal to 10 9 units of resistance of the C.G.S. system of electro-magnetic
units, and is represented by the resistance offered to an unvarying electric
current by a column of mercury at a temperature of melting ice, 14.4521
grammes in mass, of a constant cross-sectional area, and of the lengtb 106.3
centimeters.
2. As a unit of current, the International ampere, which is one-tenth of the
unit of current of the C.G.S. system of electro-magnetic units, and which is
represented sufficiently well for practical use by the unvarying current
which, when passed through a solution of nitrate of silver in water, in
accordance with the accompanying specification (A) deposits silver at the
rate of 0.001118 gramme per second.
3. As a unit of electro-motive force the international volt which is the
E.M.F. that, steadily applied to a conductor whose resistance is one Inter-
national ohm, will produce a current of one international ampere, and
which is represented sufficiently well for practical use by — — of the E.M.F.
between the poles or electrodes of the voltaic cell known as Clark's cell at
a temperature of 15° C, and prepared in the manner described in the ac-
companying specification (B).
4. "As the unit of quantity, the International coulomb, which is the quan-
tity of electricity transferred by a current of one international ampere in
one second.
5. As the unit of capacity the international farad, which is the capacity
10 SYMBOLS, UNITS, INSTRUMENTS.
of a conductor charged to a potential of one international volt by one inter-
national coulomb of electricity.
6. As the unit of work, the joule, which is 10 7 units of work in the C.G.S.
system, and which is represented sufficiently well for practical use by the
energy expended in one second by an international ampere in an inter-
national ohm.
7. As the unit of power, the watt, which is equal to 10 7 units of power in the
C.G.S. system, and which is represented sufficiently well for practical use
by the work done at the rate of one joule per second.
8. As the unit of induction, the henry, which is the induction in the cir-
cuit when the E.M.F. induced in this circuit is one international volt, while
the inducing current varies at the rate of one international ampere per
second
Specification A.
In employing the silver voltameter to measure currents of about one
ampere, the following arrangements shall be adopted :
The kathode on which the silver is to be deposited shall take the form of
a platinum bowl not less than 10 cms. in diameter, and from 4 to 5 cms. in
depth.
The anode shall be a disk or plate of pure silver some 30 sq. cms. in area,
and 2 or 3 cms. in thickness.
This shall be supported horizontally in the liquid near the top of the
solution by a silver rod riveted through its center.
To prevent the disintegrated silver which is formed on the anode from
falling upon the kathode, the anode shall be wrapped around with pure
filter paper, secured at the back by suitable folding.
The liquid shall consist of a neutral solution of pure silver nitrate, con-
taining about 15 parts by weight of the nitrate to 85 parts of water.
The resistance of the voltameter changes somewhat as the current passes.
To prevent these changes having too great an effect on the current, some
resistance, besides that of the voltameter, should be inserted in the circuit.
The total metallic resistance of the circuit should not be less than 10 ohms.
Method of making- a Measurement. — The platinum bowl is to
be washed consecutively with nitric acid, distilled water, and absolute
alcohol ; it is then to be dried at 160° C, and left to cool in a desiccator.
When cold it is to be weighed carefully.
It is to be nearly filled with the solution, and connected to the rest of the
circuit by being placed on a clean copper support to which a binding-screw
is attached
The anode is then to be immersed in the solution so as to be well covered
by it, and supported in that position ; the connections to the rest of the
circuit are then to be made.
Contact is to be made at the key, noting the time. The current is to be
allowed to pass for not less than half an hour, and the time of breaking
contact observed. *
The solution is now to be removed from the bowl, and the deposit washed
with distilled water, and left to soak for at least six hours. It is then to be
rinsed successively with distilled water and absolute alcohol, and dried in a
hot-air bath at a temperature of about 160° C. After cooling in a desiccator
it is to be weighed again. The gain in mass gives the silver deposited
To find the time average of the current in amperes, this mass, expressed
m grammes, must be divided by the number of seconds during which the
current has passed and by 0.001118.
In determining the constant of an instrument bv this method the current
should be kept as nearly uniform as possible, and the readings of the instru-
ment observed at frequent intervals of time. These observations give a
curve from which the reading corresponding to the mean current (time
average of the current) can be found.
^"he cu.rrent is calculated from the voltameter results, corresponding to
this reading. ^ &
The current used in this experiment must be obtained from a battery and
not from a dynamo, especially when the instrument to be calibrated is an
electrodynamometer.
Specification B. — The Volt.
The cell has for its positive electrode, mercury, and for its negative elec-
trode, amalgamated zinc ; the electrolyte consists of a saturated solution of
SPECIFICATION B.
11
zinc sulphate and mercurous sulphate. The electromotive force is 1.434 volts
at 15° C., and, between 10° C. and 25° C, by the increase of 1° C. in tempera-
ture, the electromotive force decreases by .00115 of a volt.
1. .Preparation of the Mercury. — To secure purity it should be
first treated with acid in the usual manner, and subsequently distilled in
vacuo.
•£. Preparation of the Zinc Amalgam. — The zinc designated in
commerce as "commercially pure" can be used without further prepara-
tion. For the preparation of the amalgam one part by weight of zinc is to
be added to nine (9) parts by weight of mercury, and both are to be heated
in a porcelain dish at 100° C. with moderate stirring until the zinc has been
fully dissolved in the mercury.
3. Preparation of the Mercurous Sulphate. — Take mercurous
sulphate, purchased as pure, mix with it a small quantity of pure mercury,
and wash the whole thoroughly with cold distilled water by agitation in a
bottle ; drain oil' the water and repeat the process at least twice. After the
last washing, drain off as much of the water as possible. (For further de-
tails of purification, see Note A.)
4t. Preparation of the Zinc Sulphate Solution. — Prepare a
neutral saturated solution of pure re-crystallized zinc sulphate, free from
iron, by mixing distilled water with nearly twice its weight of crystals of
pure zinc sulphate and adding zinc oxide in the proportion of about 2 per
cent by weight of the zinc sulphate crystals to neutralize any free acid. The
crystals should be dissolved by the aid of gentle heat, but the temperature
to which the solution is raised must not exceed 30° C. Mercurous sulphate,
treated as described in 3, shall be added in the proportion of about 12 per
cent by weight of the zinc sulphate crystals to neutralize the free zinc oxide
remaining, and then the solution filtered, while still warm, into a stock
bottle. Crystals should form as it cools.
3. Preparation of the Mercurous Sulphate and Zinc Sul-
phate Paste. — For making the paste, two or three parts by weight of
mercurous sulphate are to be added to one by weight of mercury. If the
sulphate be dry, it is to be mixed with a paste consisting of zinc sulphate
crystals and a concentrated zinc sulphate solution, so that the whole con-
stitutes a stiff mass, which is permeated throughout by zinc sulphate crys-
tals and globules of mercury.
If the sulphate, however, be moist, only zinc sulphate crystals are to be
added ; care must, however, be taken that these occur in excess, and are
not dissolved after continued standing. The mercury must, in this case
also, permeate the paste in little globules. It is advantageous to crush the
zinc sulphate crystals before using, since the paste can then be better
manipulated.
To set un the Cell. — The containing glass vessel, represented in the
accompanying figure, shall consist of two limbs closed at bottom, and joined
above to a common neck fitted with a ground-glass
stopper. The diameter of the limbs should be at
least 2 cms. and their length at least 3 cms. The
neck should be not less than 1.5 cms. in diameter.
At the bottom of each limb a platinum wire of
about 0.4 mm. in diameter is sealed through the
glass
To set up the cell, place in one limb mercury,
and in the other hot liquid amalgam, containing 90
parts mercury and 10 parts zinc. The platinum
wires at the bottom must be completely covered
by the mercury and the amalgam respectively. On
the mercury, place a layer one cm. thick of the
zinc and mercurous sulphate paste described in 5.
Both this paste and the zinc amalgam must then
be covered with a layer of the neutral zinc sul-
phate crystals one cm. thick. The whole vessel must
then be filled with the saturated zinc sulphate solu-
tion, and the stopper inserted so that it shall just
touch it, leaving, however, a small bubble to guard
against breakage when the temperature rises.
Before finally inserting the glass stopper, it is to be brushed round its
upper edge with a strong alcoholic solution of shellac, and pressed firmly
in place. (For details of filling the cell see Note B.)
12
SYMBOLS, UNITS, INSTRUMENTS.
r.
rh
>^
©
-c
fco'i*
o> !•*
« s
3
CO Is
CO
s
wȤ
O t-i
SI
£
in
oi
2
o
q
sr
q
g
®
H.P.
sec,
Eng-
lish.
lis
CO i-l
11©
1
io
id
1
s
o
CO
©
q
ill.
IO
q
^
q
, -d
£
m
si
r~
£
CO
O)
«
si
oo
rH
©
CO
o g
©
-i°
£a
£
si"
q
5
53
t2
C]
m
o£3
i-< beg
—*|o
SL
8
IO
-H
o
1
I
^
in
c"t
m
Hr
s|-
■<#
r3
OS
o
o
©
S3
O
,H
rH
o
©
l""
o8g
os
c
t>
IO
C
8
o
s
t~
p
co
©
OS
i
8
o
d
©
§
'v.1
of
cT
CO
o"
CS
©
8
d
c
1
CO
8
1-1
rH
'""'
1-1
1
L~
N
-IS
©
CO
CO
q
^
1
s
d
CO
CO
8
*#
1
IO
1
■*
1-1
1-1
rH
^
t-
§8*
111
si-
8
OS
co
os
2
^
in
s
o
§iS
©
m
o
1
©
Oh^
CO
~
©
^S
IO
,_,
CO
_
©
^_
m
m IS
l|s
I1
q
o
oi
ib
in
8
o
q
III
in
8
I
CO
©
Kilo-
gram-
degree
2
3
3
<n|
S
os
in
os
15
coL
o ,©
ah
SI!
Ol ItH
©
q
CO
©
s
1
©
If
© ©
-
o
o
o
3
in
OS
os
IO
00
©
d
CO
§
'3
CO
1
CO
CO
d
}2
©
©
bJOitf)
^j 53
~ls
-
in
1
CO
3
©
©
o
1
§
OS
CO
@
in
CO*
<*
d
g
in
in
©
—
o
*
cS
©
©
X
X
X
OS
x
X
X
X
to
CO
m
H
s
I*
CO
X
IO
T*
rt<
"
«
ci
o
O
K
2
n
O
ft
03
o
§
03
<D
fcJO
03
m
$
d
g
V
^
s
s
OS
tJO
CJO
-d
o
g
?
o
o
ft
ft
t
X)
1
bo
03
3
5
u
3
-d
s
O
o
Ph
5
B
ft
o
o
w
03
o
DESCRIPTION OF INSTRUMENTS. 13
JSTotes to the Specifications.
(A). The Mercurous Sulphate. — The treatment of the mercurous
sulphate has for its object the removal of any mercuric sulphate which de-
composes in the presence of water into an acid and a basic sulphate. The
latter is a yellow substance — turpeth mineral — practically insoluble in
water ; its presence, at any rate in moderate quantities, has no effect on the
cell. If, however, it be formed, the acid sulphate is also formed. This is
soluble in water, and the acid produced affects the electromotive force. The
object of the washings is to dissolve and remove this acid sulphate, and for
this purpose the three washings described in the specification will suffice in
nearly all cases. If, however, much of the turpeth mineral be formed, it
shows that there is a great deal of the acid sulphate present ; and it will then
be wiser to obtain a fresh sample of mercurous sulphate, rather than to try
by repeated washings to get rid of all the acid.
The free mercury helps in the process of removing the acid ; for the acid
mercuric sulphate attacks it, forming mercurous sulphate.
Pure mercurous sulphate, when quite free from acid, shows on repeated
washing a faint yellow tinge, which is due to the formation of a basic mer-
curous salt distinct from the turpeth mineral, or basic mercuric sulphate.
The appearance of this primrose yellow tinge, which is due to the formation
of a basic mercurous salt distinct from the turpeth mineral, or basic mer-
curic sulphate, may be taken as an indication that all the acid has been
removed ; the washing may with advantage be continued until this tint
appears.
(B). Filling1 the Cell. — After thoroughly cleaning and drying the
glass vessel, place it in a hot-water bath. Then pass through the neck of
the vessel a thin glass tube reaching to the bottom to serve for the intro-
duction of the amalgam. This tube should be as large as the glass vessel
will admit. It serves to protect the upper part of the cell from being
soiled with the amalgam. To fill in the amalgam, a clean dropping-tube
about 10 cms. long, drawn out to a fine point, should be used. Its lower end
is brought under the surface of the amalgam heated in a porcelain dish, and
some of the amalgam is drawn into the tube by means of the rubber bulb.
The point is then quickly cleaned of dross with filter paper, and is passed
through the wider tube to the bottom, and emptied by pressing the bulb.
The point of the tube must be so fine that the amlagam will come out only
on squeezing the bulb. This process is repeated until the limb contains the
desired quantity of the amalgam. The vessel is then removed from the
water-bath. After cooling, the amalgam must adhere to the glass, and
must show a clean surface with a metallic luster.
For insertion of the mercury, a dropping-tube with a long stem will be
found convenient. The paste may be poured in through a wide tube reach-
ing nearly down to the mercury and having a funnel-shaped top. If the
paste does not run down freely it may be pushed down with a small glass
rod. The paste and the amalgam are then both covered with the zinc sul-
phate crystals before the concentrated zinc sulphate solution is poured in.
This should be added through a small funnel, so as to leave the neck of the
vessel clean and dry.
For convenience and security in handling, the cell may be mounted in a
suitable case so as to be at all times open to inspection.
In using the cell, sudden variations of temperature should, as far as
possible, be avoided, since the changes in electromotive force lag behind
those of temperature.
CHAPTER III.
description of KsrsxauMBsarTS.
Although no attempt will be made here to fully describe all the different
instruments used in electrical testing, some of the more important will be
named and the more common uses to which they may be put mentioned.
The four essential instruments for all electrical testing of which all other
instruments are but variations, are: the battery, the galvanometer, the
resistance-box, and the condenser, and following Avill be found a concise
description of the more important types of each.
14 SYMBOLS, UNITS, INSTRUMENTS.
BATTERIES.
These in their different forms are used as a source of current, not only for
testing, but for many other purposes where smaller currents than those
supplied by dynamos are required.
Batteries are of two kinds, — primary, in which the E.M.F. is generated by
chemicals in the cell itself ; and secondary, or storage, in which the elec-
trical energy from some outside source is chemically stored in the battery,
which becomes an independent source of current when the charging source
is removed. Secondary batteries will be treated in a separate chapter.
The types of primary battery most commonly in use in America are the
gravity cell, used mostly for telegraph and closed-circuit work ; the Lelanche
cell, used for ordinary open-circuit work, as for door bells, telephone bells
and other signals ; the Fuller cell, used for telephone and for telegraph pur-
poses ; the chloride of silver cell, used largely for testing-purposes, as it is
small enough to enable a large number of individual cells to be grouped in
a box convenient for carrying about ; and the Edison- Lalande cell, useful
in places requiring strong battery currents.
Another form of battery that has come extensively into use since about
1890 is the dry battery. This does not have the usual liquid solutions, but is
partly filled with a substance that will hold the moisture for a considerable
time. There are, therefore, no liquids to spill ; and they make very handy
sources of current for house bells, telephones, etc., where the users do not
care to be bothered with creeping salts or any of the other troubles inherent
in the common forms of liquid cells.
Tfie Oravity Cell.
The elements are copper and zinc ; the solution is sulphate of copper, or
" bluestone," dissolved in water. The usual form (see Fig. 2) is a glass jar,
about 8 inches high and 6 inches diameter. The
copper is made of two or more layers fastened in
the middle, spread out, and set on edge in the
bottom of the cell, the terminal being a piece of
gutta-percha insulated copper wire extending up
through the solution.
The zinc is usually cast with fingers spread outf,
and a hook for suspending from the top of the jar
as shown, the terminal being on top of the hook.
This form of zinc is commonly called" crowfoot,"
and the battery often goes by that name. Some-
times star-shaped zincs are suspended from a tri-
pod across the top of the jar. The " bluestone "
crystals are placed in the bottom of the jar about
the copper, the jar then being filled with water to
just above the " crowfoot " or zinc. A table-
spoonful of sulphuric acid is added. A saturated
solution of copper sulphate forms around the cop-
Fig. 2. per ; and, after use, a zinc srdphate solution is
formed around the zinc, and floats upon the cop-
per sulphate solution. The line of separation between the two solutions
is called the blue line. As the two solutions are kept separate because of
their different specific gravities, the name " gravity cell " is employed.
This cell does not polarize, and the E.M.F. is practically constant or uni-
form at about 1 volt on a closed circuit. If the circuit is not closed, and the
cell does not have work enough to prevent mixing of the two solutions, the
copper sulphate coming in contact with the zinc will become decomposed ;
the oxygen forming oxide of zinc, and the copper depositing on the zinc hav-
ing an appearance like black mud.
Care of the CJravity Cell. — For ordinary " local work" about three
pounds of " bluestone" per cell is usually found best. When this is gone
it is better to clean out the cell, and supply new solution, than to try to re-
plenish. " Bluestone" crystals should not be smaller than a pea nor as
large as an egg. In good condition the solution at the bottom should be a
bright blue, changing to water-color above. A brownish color in any part
denotes deterioration.
To prevent evaporation of the solution it is well to pour a layer of good
mineral oil over the top when the cell is first set up. This oil should be
BATTERIES.
15
odorless, free from naphtha or acid, and non-inflammable under 400° F. If
oil is not used, dipping the top of the jar in melted paraffin for about an
inch, will prevent the salts of the solution from climbing over the edge. In
starting a new battery it is best to short circuit the cells for twenty-four or
forty-eight hours to form zinc sulphate and lower the internal resistance.
The internal resistance of the ordinary gravity cell is 2 to 3 ohms, depending
on a number of conditions, such as the size of plates, the nearness together,
and the nature of the solution.
Never let the temperature of gravity cells get below 65° or 70° F., as the
internal resistance increases very rapidly with a decrease in temperature.
The JLeclanche Cell.
This cell is one of the most commonly used outside of telegraphy, and up
to the advent of the so-called dry cell was practically the only one in use for
house and telephone work. The elements are zinc and carbon, with per-
oxide of manganese about the carbon plate for a depolarizing agent. As
usually constructed — for there are many modifications of the type — the jar
is of glass, about 7 inches high and 5 inches in diameter, or sometimes square.
The zinc is in the form of a stick, about a half inch diameter, by 7 inches
long, and is placed in one corner of the jar in a solution of sal-ammoniac.
The carbon plate is placed in a porous cup within the .iar, and the space
around the carbon in the cup is filled with small pieces of carbon and gran-
ulated peroxide of manganese. The sal-ammoniac solution passes through
the porous cup and moistens the contents. This cell will polarize if worked
hard or short circuited, but recuperates quickly if left on open circuit for
a while. The resistance of the Leclanche cell varies with its size and con-
dition, but is generally less than one ohm. The initial E.M.F. is about 1.5
volt. It is desirable not to use too strong a solution of sal-ammoniac, as
crystals will be deposited on the zinc ; and not to let the solution get too
weak, as chloride of zinc will form on the zinc ; both conditions will mate-
rially increase the internal resistance of the cell, and impair its efficiency.
Without knowing the dimensions of cells it is not possible to state the amount
of sal-ammcniac to use ; but perhaps as good a way as any is to add it to
the water until no more will dissolve, then add a little water so that the
solution will be weaker than saturation. Keep all parts clean, and add
sal-ammoniac and water when necessary. |
^^
Chloride of Silver Cell.
The elements of this cell are a rod of chemi-
cally pure zinc, and a rod of chloride of silver
in a water solution of sal-ammoniac.
As ordinarily constructed the jar is of glass, about 2J
inches long by "finch diameter, with the zinc and silver
rods set in as per Fig. 3. The solution is poured in,
and a plug of paraffin wax hermetically seals the jar.
Suitable terminals are cast in or secured to the rods.
As the greatest use made of these cells is for testing
purposes in connection with a galvanometer, they are
usually arranged in groups in a case, with terminals
so arranged as to allow the use of as many as may be
necessary for any particular test. Fig. 4 shows a port-
able testing-battery of 50 chloride of silver cells, with
attaching plugs and reversing-key. Fig. 4. shows the
interior construction of such a battery, which after
being made up is surrounded with paraffin wax, which
keeps it well insulated. The E.M.F. of the chloride of
silver cell is 1.03 volts, and the internal resistance
varies with age, being about 4 ohms at first. Care
should be taken not to short circuit these cells, as
they are weakened thereby ; and where they are much FlG. 3.
used, frequent tests of individual cells for E.M.F.
should be made ; they will vary considerably.
Fuller Cell.
The elements of this cell are zinc in a dilute solution of sulphuric acid,
and carbon in a solution of electropoin. Electropoin consists of three parts
bichromate of potash, one part sulphuric acid, and nine parts water. The
16
SYMBOLS, UNITS, INSTRUMENTS.
zinc plate is in the form of a cone, and is placed in the hottom of a porous
cup inside a glass jar. The carbon plate is outside the porous cup.
About two ounces of mercury are placed in the porous cup with the zinc,
for amalgamation, and the cup is filled with a dilute solution of sulphuric
acid. The outside jar is filled with the electropoin. In this the carbon
plate is immersed.
The E.M.F is 2 volts, and the internal resistance is about half an ohm.
The solution is originally of an orange color. When this becomes bluish in
tint, add more crystals. Should the color be normal and the cell be weak,
add fresh sulphuric acid.
Edison-Lalande Cell.
The elements of this cell (see Fig. 5) are zinc, and copper oxide in a water
solution of caustic potash. The plates are suspended side by side from the
cover of the jar. The copper oxide, which is plated with a thin film of me-
tallic copper to reduce the resistance when the cell is first started, is held in
BATTERIES.
17
a frame attached to the cover. A layer of oil is
poured on top of the solution to prevent creep-
ing salts. The E.M.F. is low, starting at .78
volt, and after working for a time it decreases.
The internal resistance is also low, being about
e025 ohm for the largest cell. Very strong cur-
rents can be taken from this cell : for instance
the cell having an E.M.F. of .75 volt and resist-
ance of .025 ohm will produce 30 amperes on
short circuit. The makers advise, in setting up
the cell, that only one half of the sticks of
caustic potash be placed in the jar first, and
that water be then poured in up to within about
an inch of the top of the jar. Then stir until
the potash is dissolved, when one may add the
remainder of the potash sticks, stirring as
before.
Dry Batteries).
The general appearance of a cell of dry bat-
tery is shown in Fig. 6, and the construction
varies slightly in the different makes. The
Burnley dry cell is made of a zinc tube (see Fig- 6)
also as 'the containing jar, a carbon cylinder is the negative element, and an
exciting solution composed of 1 part sal-ammoniac, 1 part chloride of zinc, 3
parts plaster, .87 parts flour, and 2 parts water. In constructing the cell a
plunger somewhat larger than the carbon element is placed in the middle of
Fig
s one element, which acts
M
^-fj— r
CM
. .
'
'
■,l,l,ftn„0.,.l.
the zinc jar, and the above solution mixture poured in around it, quickly be-
coming stiff, after -which the plunger is withdrawn, the carbon inserted in
place, and the surrounding space filled wTith another mixture consisting of 1
part sal-ammoniac, 1 part chloride of zinc, 1 part peroxide of manganese, 1
part granulated carbon, 3 parts plaster, 1 part flour, and 2 parts water. After
the ingredients are all in place the top is sealed with bitumen or other suit-
able compound. A terminal is fastened to the zinc cup, and another to the
carbon plate. The E.M.F. of the Burnley cell is 1.4 volt ; the internal re-
sistance about .3 ohm, and it gives practically constant E.M.F. during its life.
The Gasner dry cell, shown in Fig. 7, consists of a zinc cup as the positive
SYMBOLS, UNITS, INSTRUMENTS.
element, a cylinder composed of carbon and manganese for the negative
element, and an exciting solution which becomes comparatively hard, made
up of the following ingredients, viz. : 1 part by weight of oxide of zinc. 1
part sal-ammoniac, 3 parts plaster, 1 part chloride of zinc, and 2 parts water.
The E.M.F. and resistance are about the
same as for the cell last described.
Standard Cells.
Clark Cell. — The form of cell called
Clark, specifications for making which
will be found in the chapter on units,
is the one most used for a standard of
E.M.F. The positive element is mercury,
and the negative is amalgamated zinc, the
electrolytes being saturated solutions of
sulphate of zinc and mercurous sulphate.
At 15° C. the E.M.F. is 1.434 volt, and
between the points 10° and 25° C. the in-
crease of 1° C. decreases the E.M.F. .00115
volt.
Carhart-Clark Cell.— This cell has
the same elements as Clark, but the so-
lution of zinc sulphate is saturated at 0°
C. The E.M.F. is 1.440 volt, and the tem-
perature coefficient about half that of the
Clark cell.
Weston Standard Cell.— The ele-
ments are mercury and cadmium amalgam
in a saturated solution of cadmium sul-
phate. The E.M.F. is 1.019 to 1.022 volt,
and the temperature coefficient 0.01 per
cent per degree centigrade. These cells
remain constant over long periods. Ob-
servations extending over several months showed a variation of less than
0.0001 volt.
Arrangement of Battery Cells.
Series. — When it is desired to obtain an E.M.F. greater than that of one
cell, two or more are connected together in series ; that is, the positive termi-
nal of one cell is connected to the negative terminal of the next, and so on
Fig. 8. Carhart Clark Standard
Cell.
V
1 — avvww] rr?
Fig. 9. Battery Cells in Series.
until the number of cells required to produce the E.M.F. wanted are con-
nected. For example, the E.M.F. of one cell of Leclanche is 1.47 volt, then
10 cells connected in series as iw Fig. 9 would give an E.M.F. at the ex-
treme terminals of 14.7 volts.
Multiple. — If it be desired to obtain more current strength, i.e., more
amperes without change of E.M.F., then more cells must be placed along
side the others, that is, in parallel Avith the first row ; each row or series of
cells producing the same E.M.F. and joined together at the ends, positive
BATTERIES.
19
terminals to positive terminals, and negative to negative, adding their cur-
; rents together at the same E.M.F. as in Fig.^10 below.
If still more current strength be needed, another series of cells may be
added, and their current added to the circuit, making three times the current
of one series.
Fig. 10. Battery Cells in Multiple.
The reason for this is, that when two or more resistances are placed in
parallel or multiple, the equivalent resistance is decreased, as is shown in
another chapter. If the resistance of one series be 10 ohms, the resistance
I of two series in multiple would be one-half of ten, or 5 ohms ; that of three
I series in parallel, one-third, or 3.33 ohms ; and of four series, 2.5 ohms.
Let
E = E.M.F. of a single cell,
r = internal resistance of one cell,
R =: external resistance in a circuit.
Then for n cells arranged in series, the current which will flow will be
represented by the formula,
r + -
If R is very small as compared with nr, then / — » or the current is the
same as that from one cell on short circuit. r
[f, as in telegraph work, nr is very small as compared with R, then
/= — , or the current increases in proportion to the number of cells.
The value of r is nearly inversely proportional to the area of the plates
when fronting each other in the liquid, and directly as their distance apart.
Therefore, if the area of the plate is increased a times,
/ =
E
aE
~~ r + aR'
Let xV= the total number of cells in the battery,
ns = number of cells in each series,
nP = number of sets or series in parallel.
Then the internal resistance of the whole battery
nsr
To find the best arrangement of a given number of cells (N) to obtain a
maximum current (/) working through an external resistance (R), make
nP
: R, or the internal resistance of the whole battery equal to R,
In any circuit /:
total E.M.F.
and for any arrangement
20 SYMBOLS, UNITS, INSTRUMENTS.
nP ""
When arranged for maximum current through a given external resistance It,
. fmt , . /Xr
lis = y — and np = 1/ — •
To find the greatest current that can be obtained from a given number of
cells (JV ) through a given external resistance (R),
- 2 Vi
'-v/£-
To find the number of cells in series (n8) and in parallel («p) required to
give a current (7) through an external resistance (R) and to have an effi-
ciency {F).
_,„. . „ External work
Efficiency h — —= - —
J Total work
r-R r
Jt,fur x n«r
\1lp J np
The internal resistance of the whole battery is
risr _ R (1 — F)
nP F
, nsEF
and J=^T
1R
ne = FF
Ir
GAIiVAWOMKTKJRS.
These are instruments for measuring the magnitude or direction of electric
currents. The term galvanometer can also be properly applied to the many
types of indicating instruments, such as voltmeters and ammeters, where a
needle or pointer is under the influence of some directive force, such as the
earth's field, a spring, a weight, a permanent magnet, or other means, and
is deflected from zero by the passing of an electric current through its
coils.
Nearly all galvanometers can be separated into two classes. The first is
the moving-needle class. A magnetized needle of steel is suspended with
its axis horizontal so as to move freely in a horizontal plane. The suspen-
sion is by means of a pivot or fiber of silk, of quartz, or of other material.
The needle normally points in a north and south direction under the influence
of the earth's magnetic field, or in the direction of some other field due to
auxiliary magnets. Near to the needle, and frequently surrounding it, is
placed a coil of wire whose axis is at right angles to the'nornial direction of
the needle. When a current is passed through the coil the needle tends to
turn into a new position, which lies between the direction of the original
field and the axis of the coil.
The second class is the moving coil or d'Arsonval class. A small coil is
suspended by means of a fine wire between the poles of a. magnet. Its axis
is normally at right angles with the lines of the field. Current is led into
the coil by means of the suspension wire, and leaves the coil by a flexible
wire attached underneath it.
The figure of merit of a galvanometer is (a) the current strength required
to cause a deflection of one scale division ; or (ft) it is the resistance that
must be introduced into the circuit that one volt may cause a deflection of
one scale division. This expression for the delicacy of a galvanometer is
GALVANOMETERS.
21
insufficient unless the following quantities are also given : the resistance
of the galvanometer, the distance of the scale from tne mirror, the size of
the scale divisions, and the time of vibration of the needle.
The sensitiveness of a galvanometer is the difference of potential neces-
sary to be impressed between the galvanometer terminals in order to pro-
duce a deflection of one scale division.
Movingr-Needle CJalvanonieters.
(a.) The Tangent Galvanometer. If the inside diameter of the coil which
surrounds a needle, held at zero by the earth's field, be at least 12 times the
length of the needle, then the deflections of the needle which correspond to
different current strengths sent through the coils, will be such that the
current strengths will vary directly as the tangents of the angles of deflec-
tion. Such an instrument is called a tangent galvanometer. It was for-
merly much used for the absolute measurement of current. It has, however,
many correction factors, some of which are of uncertain magnitude ; and,
furthermore, for accuracy in the results yielded by it one must have an
exact knowledge of the value of the horizontal component of the earth's
magnetism. This quantity is continually changing, and is affected much
by the presence of large masses of iron and the existence of heavy currents
in the vicinity.
Let r = the radius of a tangent galvanometer coil, in centimeters
n = the number of turns in the coil,
H— the horizontal intensity of the earth's magnetism,
/ = the current of the coil in absolute units, and
e = the deflection of the needle, then
Fig. 11. Tangent Galvanometers.
22
SYMBOLS, UNITS, INSTRUMENTS.
For convenience the term
2wn
2nn
5C tan 6.
.e., the strength of the field produced
at the center of the coil by the unit of current, is called the constant of the
galvanometer, and is represented by G, whence
JC
I = — tan 0
G
The current in amperes equals 10 I.
(b.) Thomson Galvanometers. The most sensitive galvanometers made are
of a type due to Lord Kelvin. Fig. 12 shows one form of this instrument. The
moving system consists of a slender quartz rod, to the center of which is
fastened a small glass mirror. Parallel to the plane of the mirror, and at
one end of the quartz tube, is fas-
tened a complex of carefully se-
lected minute magnetic needles.
The north ends of those needles
all point in the same direction.
At the other end of the quartz
tube is fastened a similar complex
with the polarity reversed. Were
the two complexes of exactly
equal magnetic moment, then,
when suspended in the earth's
field, no directive action would be
felt. In fact, this action is very
small. The combination forms
what is called an astatic system.
Each magnetic complex is in-
closed between two wire coils.
The four coils are supplied with
binding-posts, so as to permit of
connection in series or in parallel.
Current is sent through them in
the proper direction, to produce
in each case deflections the same
way. Quartz fiber, which ex-
hibits no elastic fatigue and
which is very strong, is used as
a suspension. An adjustable
magnet is mounted on the top of
the galvanometer. By means of
it the directive action of the
earth's field can be modified to
any extent. Under weak direc-
tive force the sensitiveness in-
creases greatly, and the period of
oscillation of the needle becomes
long. The limit of sensitiveness
is largely influenced by the pa-
k tience of the observer.
' For very precise work the de-
flections of the needle are ob-
served by means of a telescope
and scale. Fig. 13 shows such an
instrument. The moving mirror
l'eflects an image of the scale into
the objective of the telescope.
Continuous work with the tele-
scope is apt to injure the eyes, and is certainly tiresome. Where much gal-
vanometer work is being done by the same person, a ray of light from a
small electric, gas, or oil lamp is so directed as to be reflected from the
mirror on the needle upon a divided scale. Such a lamp and scale is shown
in Fig. 14. In order to bring the needle quickly to rest when under the in-
Fig. 12. — Thomson Reflecting Astatic
Galvanometer with Four Coils
GALVANOMETERS.
23
24
SYMBOLS, UNITS, INSTRUMENTS.
fluence of a current, some method of damping must be employed. One
method is to attach a mica vane to the moving system, and allow it to swing
in an inclosed chamber which contains air or oil. Sometimes the moving
needle is inclosed in a hollow made in a block of copper. The eddy currents
induced by the moving needle react upon it and stop its swinging.
Movingf-Coil Galvanometers.
These galvanometers are to be preferred in all cases except where the
utmost of delicacy is required. In the most sensitive form, with permanent
magnetic field, they can be made to deflect one millimeter with a scale dis-
tance of one meter, when one microvolt is impressed between the terminals
of the coil. This is sufficient for nearly all purposes. The sensitiveness can
be further increased by using an electromagnetic field. The moving-coil
Fig. 15,
form of galvanometer has the following good points : its readings are but
slightly affected by the presence of magnetic substances in the vicinity, and
are practically independent of the earth's field ; the instrument can be easily
made dead-beat ; and many forms are not much affected by vibrations.
Fig. 15 shows a form of D'Arsonval galvanometer of high sensibility. The
coil (shown to the right) is inclosed in an aluminium tube. Eddy currents
are induced in this tube when the coil swings. They cause damping, and,
with a proper thickness of tube, the system may be made aperiodic.
Ballistic Galvanometers.
Galvanometers are also used for measuring or comparing quantities of
electricity such as flow in circuits when a condenser is discharged or mag-
netic flux linkages are disturbed. The time of oscillation of the needle
GALVANOMETERS. 25
must in such cases be long as compared with the duration of the discharge.
If there be no damping of the needle the quantities of electricity are pro-
portional to the sines of half the angle of the first throws of the needle. All
galvanometers have some damping. The comparison of quantities of elec-
tricity can easily be made with galvanometers of moderate, or even strong
damping. Absolute determination of quantity by means of the ballistic
galvanometer requires great experimental precautions. (See the Galvano-
meter, by E. L. Nichols.)
Voltmeters.
These are indicating instruments which show the pressure impressed upon
their terminals. They are in nearly all cases galvanometers of practically
constant high resistance. Through them flow currents which are directly
proportional to the impressed voltages. A pointer, connected to the mov-
ing element, moves over a scale which is empirically graduated to cor-
respond with the impressed voltages. The resistances of commercial
voltmeters in ohms run from 10 to 150 times the full scale readings in .
volts. Thus a 150-volt voltmeter may have a resistance of from 1500 to
22,500 ohms. The directive forces to bring the needle back to zero are
generally obtained from springs, gravity, or magnets. Moving-coil instru-
ments can be made so as to have high resistances and perfect damping.
Moving-needle instruments are in common use for alternating current cir-
cuits. The needle is of soft iron, and is given an alternating polarity by the
currents flowing because of the impressed voltages, which are being meas-
ured. Hot-wire voltmeters form a distinct class of instruments. The ex-
pansions of a wire as a result of the passage of different currents of electricity
are taken up by a spring. A pointer connected with the spring moves over
an empirically divided scale. These instruments have a lower resistance
per volt than the other types. They are quite dead beat. They record
either alternating or direct currents.
Ammeters.
The scale of a voltmeter might be graduated and marked so as to indicate
the currents passing through it instead of the volts impressed upon its
terminals. It would then be an ammeter. To be of value its resistance
must be small. Many ammeters consist of millivoltmeters connected to the
terminals of shunts through which the currents to be measured are passed.
The scales are graduated so as to indicate the currents passing through the
shunts. The shunt type of instrument is particularly applicable to switch-
boards.
]|Torttarnp's Oscillating- Current Galvanometer.
From catalogue of James G. Biddle.
The working of this instrument depends upon the principle that when a
metallic disk is suspended in a coil, the plane of the disk making with the
plane of the coil an angle of about 45° the disk will tend to rotate, when
alternating currents are sent through the coil, so as to increase this angle.
The instrument is constructed to be exceedingly sensitive, to have a mini-
mum of self-inductance, and practically no capacity. The disk is made of
pure silver, about Jj77 thick and 9 mm. in diameter. Three coils are furnished
with each instrument. One coil has about 20 turns of No. 20, one about 40
turns of No. 42, and one about 100 turns of No. 36 B & S copper wire. Each
coil is wound in two halves, so that the silver disk may be dropped down
through the suspension tube and between the two halves of the coil. The
inside diameter of the coils is about 1 mm. greater than the diameter of the
disk. On either side of the hard-rubber upright piece which supports the
coils are the poles of a permanent magnet. The coils are set at an angle of
45° to the line joining the two poles, and the silver disk hangs so that its
plane is in this line.
The silver disk is fastened upon a light glass stem which carries a very small
and thin mirror. This system is suspended upon an exceedingly fine'quartz
fiber. The complete period of swing of the system is about 12 seconds, and
the magnet quickly dampens the oscillations to zero. For small angles the
26
SYMBOLS, UNITS, INSTRUMENTS.
deflections are proportional to the square of the current and to its frequency.
Hence as long as the frequency remains constant two currents are to each
other as the square roots of the respective deflections indicating them.
This instrument replaces and is far superior to the telephone in all cases
where feeble, rapidly varying currents are to be detected or compared.
The telephone fails to be of service when the frequency of the currents
becomes very great ; the present instrument responds to currents of any
frequency, including such as are set up in a Hertzian resonator. Since the
self-induction of the instrument is very minute, it can be connected in series
with any circuit in which rapidly oscillating currents are passing, without
appreciably changing their frequency. The instrument, therefore, serves
in the performance of many Hertzian experiments.
Giitlrauonieter $Iiunt Boxes.
It is often desirable to use a galvanometer oi high sensibility for work
demanding a much lower sensibility. Again, it may be convenient to cali-
brate a galvanometer of low
sensibility, while it would be
inconvenient to calibrate a more
sensitive one It is therefore
useful to he able to change the
sensibility in a known ratio.
Convenience dictates that sim-
ple ratios be used, and those
almost universally taken are 10,
100, and 1000 ; that is §, g\, or d|9,
part of the current flowing is allowed to go through the galvanometer while
the remainder is diverted through a shunt. In Fig. 16 let
G = the resistance of the galvanometer, and
S = the resistance of the shunt,
the joint resistance of the two is — — — s •
br -j- S
1 = the total current flowing in the circuit, and
Ij = the part flowing through the galvanometer,
- - + 1 = the Multiplying power of the shunt.
Fig. 16.
then
If
if
then
1, ~~ S — S
The resistance of a shunt which will give
certain multiplying power, n, is
equal to
- 1
Fig. 17 shows a form
of shunt used with a galvanometer, al-
though it is perfectly feasible to use an
ordinary resistance box for the purpose.
Messrs. Ayrton & Mather have developed
a new shunt, which can be used with any
galvanometer irrespective of its resist-
ance : following is a diagram of it.
A and B are terminals for the galvano-
meter connections. B and C are the in-
going and outgoing terminals for battery
circuit. To short circuit G, place plugs
in j and f. To throw all the current
through G, put a plug in f only. To use
the shunts, place a plug in h, and leave it
there until through using. In this method
it is not necessary to know the resistance
of either G or r. The shunt box can
therefore be used with any galvanometer.
Temperature variations make no differ-
ence, provided they do not take place
during one set of tests. The resistance
r may be any number of ohms, but in order not to decrease the sensibility
too much r should be at least as large as G. The resistance r is divided for
use as follows : permanent attachments to the various blocks are made at
Fig. 17.
points in the coil corresponding with
1000, 100,
RESISTANCES.
27
Fig. 18. Ayrton & Mather's Universal Shnnt.
RESISTANCES.
The unit of resistance, the international ohm, is represented hy the resist-
ance of a uniform column of mercury 106.3 cm. long and 14.4521 grammes in
mass, at 0° C ; but in practice it is not convenient to compare resistances
with such a standard, and therefore sec-
ondary standards (Fig. 19) of resistance
are made up, and standardized with a
great degree of precision. These second-
ary standards are made of wire. The ma-
terial must possess permanency of con-
stitution and of resistivity, must have a
small temperature coefficient of resistiv-
ity, must have a small thermo-electric
power when compared with copper, and
should have a fairly high resistivity.
Manganin when properly treated pos-
sesses all of these qualities. Platinoid is
also frequently used. An assemblage of
standards of various convenient magni-
tudes in a single case is called a resistance
box, or rheostat.
The form of resistance box most fre-
quently met with is some type of " Wheat-
stone's bridge," the theory of which is
described elsewhere.
The coils are usually of silk insulated
wire wound non-inductively on spools,
with the ends attached to brass blocks, so
arranged that brass plugs can be inserted
in a hole between two blocks, thus short circuiting the resistance of the
particular bobbin over which the plug is placed. By non-inductive winding
is meant that the wire is first doubled, then the closed end is placed on the
bobbin and the wire wound double about the bobbin. By this method any
electromagnetic action in one wire is neutralized by an equivalent action
in the other, and there is no inductive effect when the circuit is opened
or closed.
The Post-office bridge, Figs. 20 and 21, is one of the most convenient
forms. One arm of the bridge has separate resistances of the following
values : 1, 2, 3, 4, 10, 20, 30, 40, 100, 200, 300, 400, 1000, 2000, 3000, and 4000 ohms.
Fig. 19.
28
SYMBOLS, UNITS, INSTRUMENTS.
Another arm is left open for the unknown resistance, x, which is to be
measured. The remaining two arms each have three resistance coils of
10, 100, and 1000 ohms respec-
tively. Two keys are sup-
plied with the P.O. bridge,
one for closing the bat-
tery circuit, and the other
for closing the galvanometer
circuit. The battery key
should be closed first ; and in
some instruments the two
keys are arranged with the
battery key on top of the gal-
vanometer key, so that but
one finger and one pressure
are necessary.
Prof. Anthony has devised
a resistance box in which
, there are ten one ohm coils,
Fig. 20. Standard Resistance Coils with 1Q fc 10 hundreds, and 10
Wheatstone Bridge (Post Office Pattern). thousands. Any number of
any group can be connected either in series or in multiple. The means of
accomplishing this are seen clearly in the cut.
§tandard low Resistances.
Resistances of the ordinary form,
which are smaller than ^j ohm, are
very difficult to measure with great ac-
curacy, owing to the uncertainty of the
magnitude of the resistance of the leads
and contact devices. Fortunately it is
seldom that such a form oi resistance is
used. Instead, the resistance between
two potential points on a properly
shaped conductor is used. Such stand-
ard resistances of agists, j??^ ibxa etc»>
ohms are now on the market, and are
known as the Reichsanstalt form. They
are made to carry very heavy currents.
Fig. 23 shows such a resistance supplied
with heavy contact terminals and a
cooling coil. When this resistance is
carrying a current, the drop between
the two small terminals is such as
would result from passing the same
current through I0J<j
Fig. 21.
ohm
< o\i>*:\»i:it*.
If one terminal of a source of E.M.F. be connected to a conductor,
and the other terminal be
connected to another con-
ductor adjacent to the
first but insulated from)
it, it will be found that
the two conductors ex-
hibit a capacity for ab-
sorbing a charge of elec-
tricity that is somewhat;
analogous to the filling ol
a pipe with water before
a pressure can be exerted
The charge will remain ir
the conductors after the,
removal of the source oi
^ „, , supply. This capacity oil irj
ilG. 22. Standard Resistance ('nils with "Wheat- rhe conductors to hole fet
stone Bridge (Anthony Form;. under a given E.M.F. 2 |d|
CONDENSERS.
29
charge of electricity is governed by the amount of surface exposed, by
the nearness of the surfaces to each other, by the quality of the in-
sulating material, and by the degree of insulation from each other. If
the terminals of a battery be con-
nected, through a battery and sensi-
tive galvanometer, to a long sub-
marine cable conductor and to the
earth, it will be found that a very i
considerable time will elapse before 1
the needle will settle down to a
steady point. This shows that the
cable insulation has been filled with
electricity ; and it is common in so
imeasuring the insulation resistance
of a cable to assume a standard length
iof time, generally three minutes,
during which time such electrifica-
tion shall take place.
A condenser is an arrangement of
metallic plates and insulation so
made up that it will take a standard
charge of electricity at a certain
pressure. The energy represented by
the charge seems to be stored up in
the insulation between the conduct-
ing plates in the form of a stress. This property of insulating materials
to take on a charge of static electricity is known as inductive capacity,
and a table in the section on the testing of capacity shows the specific in-
ductive capacities of different substances.
The unit of capacity is the international farad, which is defined as the
capacity of a condenser which requires one coulomb (1 ampere for 1 second)
to raise its potential from zero to one volt.
Fig. 23.
Figs. 24 and 25. Queen Standard Condensers.
As the farad is far larger than ever is met in practice, the practical unit
is taken as one-millionth farad or the micro-farad.
The commercial standard most in use is the \ micro-farad, although
adjustable condensers are often used, arranged so as to combine into many
micro-farads or fractions of the same. Fig. 24 shows the ordinary a micro-
farad condenser, and Fig. 25 one that is adjustable for different values.
Diagram 26 shows an outline of the connections inside an adjustable con-
denser. The ordinary commercial condenser is most usually made up of
30
SYMBOLS, UNITS, INSTRUMENTS.
Fig. 27. Modified Mascart Electrometer.
CONDENSERS.
31
sheets of tin foil separated from each other hy some insulator such as
paraffined paper or mica. Every alternate sheet of foil is connected to a
common terminal. As the capacity of a condenser depends upon the near-
ness of the conductors to each other, and upon the area of the same, the
insulating material is made as thin as possible, and still be safe from leakage
or puncture. Many sheets of foil are joined together as described to make
up the area. In adjustable condensers, the sheets are separated into bundles,
and arranged so that any of them can be plugged in or out to add to or
lessen the total capacity. If connected in multiple as shown, or if the
positive side of one condenser be connected to the negative side of another,
or a number of them are thus added together, then the condensers are said
to be arranged in " cascade" or in series. This is seldom done unless it be
to obtain greater variation in capacity.
Electrometer. — Another instrument used somewhat in cable work, or
where the measurement of electrostatic capacities or potentials is common,
is the electrometer. A type of electrometer commonly used is the quadrant
electrometer, for which we
are indebted to Lord Kel-
vin. The needle is a thin,
flat piece of aluminium sus-
pended in a horizontal po-
sition by a thin metallic
wire, in close proximity to
four quadrants of thin sheet
brass, that are supported on
insulators without touching
each other. Opposite quad-
rants are connected by fine
wires. A charge of elec-
tricity is given the needle by
connecting the suspension
filament with a Leyden jar
or other condenser.
If the needle be charged
positively it will be attracted
by a negative charge and re-
pelled by a positive charge.
If, therefore, there be a dif-
ference of potential between
<?he pairs of quadrants, the
needle will be deflected from
zero. The usual mirror,
scale, and lamp are used
with this instrument, as in
the case of the rerlectin:
galvanometer. A form is
shown in Fig. 27.
Electrostatic Volt-
meter.
A modification of the elec-
trometer, used for indicat-
ing high, and in some cases low, alternating current potentials is the elec-
trostatic voltmeter of Lord Kelvin. It is constructed on the principle
of an air condenser.
In the high potential instrument, Fig. 28, the needle is made of a thin
aluminium plate suspended vertically on delicate knife-edges, with a pointer
extending from the upper part to a scale.
On either side of the needle, and parallel to its face, are placed two
quadrant plates metallically connected and serving as one terminal of the
circuit to be measured, while the needle serves as the other and opposite
terminal. Any electrical potential difference between the needle and the
plates will deflect the needle out of its neutral position. Calibrated weights
can be hung on the bottom of the needle to change the value of the scale
indications.
In the multicellular voltmeter, see Fig. 29, the needle consists of a number
of thin plates, suspended horizontally and between corresponding quad-
Fig. 28. Kelvin's Electrostatic Voltmeter.
32
SYMBOLS, UNITS, INSTRUMENTS.
Fig. 29. Another Form of Lord
Kelvin's Electrostatic Volt-
meter.
this fixed coil, and at right angles
thereto, is suspended a movable coil
of few turns. A carefully wound
helical spring joins the movable coil
to a torsion screw above the dial. A
pointer on this torsion screw shows
on the dial the degrees of angle
through which it may be twisted.
The lower ends of the movable coil
dip into mercury cups to make con-
nection with tbe fixed coil. If cur-
rent flows through the two coils in
series, the movable coil is turned
from its position at right angles with
the fixed coil, and tries to arrange
itself in the same plane as the latter,
according to law above.
rant plates, thus multiplying
the force tending to deflect the
needles, and serving to indicate
lower potential differences than
the form described above is
capable of.
THE ELECTRO-D¥-
IIAMOMETER.
If currents be sent through
two coils of Avire, which are ca-
pable of movement as regards
each other, they Avill tend to
place themselves in such a posi-
tion as to bring the lines of force
of their magnetic fields parallel
to each other and in the same
direction. The Siemen's electro-
dynamometer acts according to
this principle.
Fig. 30 below shows the form
most used in the United States.
It consists of a fixed coil usually
having two divisions, — one of a
few turns of heavy wire for
heavy currents, and another of
many turns of finer wire for
smaller currents. Outside of
ELECTRO-DYNAMOMETERS. 33
The torsion screw is then turned in the opposite direction until the force
of the spring overcomes the electrodynamic action of the coils, and the
movable coil is brought to zero.
If A be a constant depending upon the character of the torsion spring, 1
be the current, and d be the angle of deflection of the torsion screw to
return the movable coil to zero, then
I— A y]d.
The electro-dynamometer is suited to measure alternating currents of ordi-
nary frequencies.
Wattmeter. — If the movable coil be of very fine wire, and have a coil
of very high and non-inductive resistance in series with it, and if the fixed
coil be of heavy wire, then the instrument may be used for measuring the
work of a circuit in watts, by connecting the fixed coil in series with the
circuit under test, and the movable coil across the terminals of the cir-
cuit. In this case, if the voltage current be i„ and the series current
in the movable coil be i2, then the power equals K iti2, where K is a constant
of the instrument. The two currents are supposed to be in phase with each
other. If the movable coil be not brought back to zero, but a pointer con-
nected with it be permitted to move over a graduated scale, the scale can be
calibrated directly in watts.
Weston's well-known wattmeter is constructed substantially on this
principle.
In order that a wattmeter (electro-dynamometer) may be reliable for
measuring alternate-current power, it is needful tha t the fine-wire circuit,
which is to be connected as a shunt to the apparatus under measurement,
should have as little self-induction as possible in proportion to its resis-
tance. The latter may be increased by adding auxiliary non-inductive
resistances. The instrument must itself be so constructed that there shall
not be any eddy currents set up by either circuit in the frames, supports, or
case ; otherwise the indications will be false.
Kelvin's Composite Electric Balance.
This instrument is employed much as a standard for comparison of instru-
ments used in all practical work for both continuous and alternating currents.
It can be used as a voltmeter, ampere-meter, or wattmeter. The principle
Fig. 31. Kelvin's Standard Composite Balance.
of its action is similar to that of the electro-dynamometer. The attraction
and repulsion between movable and stationary coils is balanced by the at-
traction of gravity on a sliding weight connected with the movable coils.
Above is a cut of the instrument in its latest form, and the diagram fol-
lowing shows the theory on which the instrument works.
In both cut and diagram the same letters indicate the same parts, a and
b are two coils of silk-covered copper wire placed one above the other as
shown, with their planes horizontal, and the whole being mounted on a
slab of slate which is supported on leveling screws.
34
SYMBOLS, UNITS, INSTRUMENTS.
Two coils cand d, of similar wire are made in rings that are secured to the
ends of a balance beam B, which is suspended at its center by two flat liga-
ments of fine copper wire.
When for use with continuous currents two other coils, g and h, made of
strip copper, and of cross-section heavy enough to carry large currents, say
500 amperes, are secured to the base plate at the left in the same relative
position as are the coils a and b at the right. When the instrument is to be
used in the measurement of alternating currents, the coils g and h are made
of two or three turns of a stranded copper conductor, each wire of which is
insulated ; and, to as far as possible annul the effects of induction, the strand
is given one turn or twist for each turn around the coil.
The coils c and d of the balance are suspended equidistant between the
right and left pairs of coils, with planes parallel to their planes, and centers
coinciding with their centers.
To Set the Balance. — Level the instrument with the adjustable legs, turn
the stop screws back out of contact with the cross trunnions and front plate
of the beam, leaving it free.
To Use as Voltmeter or Centi-ampere Meter. — Connect the instrument to
the circuit or source of E.M.F. through a non-inductive resistance R, as shown
— wwwwy^ h
Fig. 32. Diagram of the Kelvin Composite Balance.
in the preceding diagram, the resistance terminal to T and the other ter-
minal to T, ; throw the switch Hto the right to the " volt" contact.
One of the weights v ?«,, v w.,, v wM is then used on the scale beam, and a
is balance obtained. The current flowing in the instrument is then calcu-
lated by a comparison of the scale-reading with the certificate accompanying
the instrument. The volts E.M F. at the terminals are calculated from the
current flowing and the resistance in circuit, including the non-inductive
resistance used, by Ohm's law, v r= IR.
To Use as Hekto-amprre Meter.— Turn the switch H to "watts," insert
the thick wire coils in circuit with the current in such a way that the right-
hand end of the beam rises. Use the " sledge" alone or the weight marked
w.w.
Terminals E and Ex are then introduced into the circuit, and a measured
current passed through the suspended coils g and h ; and the constants given
in the certificate for the balance used in this way are calculated on the as-
sumption that this current is .25 ampere. Any other current may be used,
Bay I ampere, then the constant becomes J-f- .25 or 4 I.
ELECTRO-DYNAMOMETERS. 35
The current flowing in the suspended coils g and h may be measured by
the instrument itself, arranged lor the measurement of volts. To do this,
first measure the current produced by the applied E.M.F. through the coils
of the instrument and the external resistance, then turn the switch H to
" watt," and introduce into the circuit a resistance equal to that of the fixed
coils.
To Use as a Wattmeter. — Insert the thick wire coils in the main circuit ;
then join one end of the non-inductive resistance R to one terminal of the
fine wire coils, and the other end of R to one of the leads ; the other termi-
nal of the fine wire coils is connected to the other lead. The current flowing
and the E.M.F. may now be determined by the methods described above.
The watts can then be calculated from the E.M.F. of the leads, and the
current flowing in the thick wire coils by the formula,
Pw=VI=iIR,
"Where i = current in the suspended coil circuit.
/= current in the thick wire coils.
R = resistance in the circuit.
When working with alternating currents the non-inductive resistance R
must be large enough to prevent any difference of phase of the current
flowing in the fine wire coils and the E.M.F. of the circuit.
36
SYMBOLS, UNITS, INSTRUMENTS.
Table of Doubled Square Roots for lord Kelvin's Stand-
ard Electric Balances.
0
10b
200
300
400
500
600
700
800
900
0
0.000
20.00
28.28
34.64
40.00
44.72
4S.99
52.92
56.57
60.00
0
1
2.000
20.10
28.35
34.70
40.05
44.77
49.03
52.95
56.60
60.03
1
?,
2.828
20.20
28.43
34.76
40.10
44.S1
49.07
52.99
56.64
60.07
?,
3
3.464
20.30
2S.50
34.81
40.15
44.86
49.11
53.03
56.67
60.10
3
4
4.000
20.40
28.57
34.87
40.30
44.90
49.15
53.07
56.71
60.13
4
5
4.472
20.49
28.64
34.93
40.25
44.94
49.19
53.10
56.75
60.17
5
fi
4.899
20.59
28.71
34.99
40.30
44.99
49.23
53.14
56.78
60.20
6
7
5.292
20.69
28.77
35.04
40.35
45.03
49.27
53.18
56.82
60.23
7
8
5.657
20.78
28.84
35.10
40.40
45.08
49.32
53.22
56.85
60.27
8
9
6.000
20.88
28.91
35.16
40.45
45.12
49.36
53 25
56.89
60.30
9
10
6.325
20.98
28.98
35.21
40.50
45.17
49.40
53.29
56.92
60.33
10
11
6.633
21.07
29.05
35.27
40.55
45.21
49.44
53.33
56.96
60.37
11
1?,
6.928
21.17
29.12
35.33
40.60
45.25
49.48
53.37
56.99
60.40
12
13
7.211
21.26
29.19
35.38
40.64
45.30
49.52
53.40
57.03
60.43
13
14
7.483
21.35
29.26
35.44
40.69
45.34
49.56
53.44
57.06
60.46
14
15
7.746
21.45
29.33
35.50
40.74
45.39
49.60
53.48
57.10
60.50
15
1fi
8.000
21.54
29.39
35.55
40.79
45.43
49.64
53.52
57.13
60.53
16
17
8.246
21.63
29.46
35.61
40.84
45.48
49. 6S
53.55
57.17
60.56
17
18
8.485
21.73
23.53
35.67
40.89
45.52
49.72
53.59
57.20
60.60
18
19
8.718
21.82
29.60
35.72
40.94
45.56
49.76
53.63
57.24
60.63
19
20
8.944
21.91
29.66
35.78
40.99
45.61
49.80
53.67
57.27
60.66
20
21
9.165
22.00
29.73
35.83
41.04
45.65
49.84
53.70
57.31
60.70
21
22
9.381
22.09
29.80
35.89
41.09
45.69
49.88
53.74
57.34
60.73
22
23
9.592
22.18
29.87
35.94
41.13
45.74
49.92
53.78
57.38
60.76
23
24
9.798
22.27
29.93
36.00
41.18
45.78
49.96
53.81
57.41
60.79
24
25
10.000
22.36
30.00
36.06
41.23
45.83
50.00
53.85
57.45
60.83 25
26
10.198
22.45
30.07
36.11
41.28
45.87
50.04
53.89
57.48
60.86 i 26
27
10.392
22.54
30.13
36.17
41.33
45.91
50.08
53.93
57.52
60.89
27
28
10.583
22.63
30.20
36.22
41.38
45.96
50.12
53.96
57.55
60.93
28
29
10.770
22.72
30.27
36.28
41.42
46.00
50.16
54.00
57.58
60.96
29
30
10.954
22.80
30.33
36.33
41.47
46.04
50.20
54.04
57.62
60.99
30
31
11.136
22.89
30.40
36.39
41.52
46.09
50.24
54.07
57.65
61.02
31
32
11.314
22.98
30.46
36.44
41.57
46.13
50.28
54.11
57.69
61.06
32
33
11.489
23.07
30.53
36.50
41.62
46.17
50.32
54.15
57.72
61.09
33
34
11.662
23.15
30.59
36.55
41.67
46.22
50.3C
54.18
57.76
61.12
34
35
11.832
23.24
30.66
36.61
41.71
46.26
50.40
54.22
57.79
61.16
35
36
12.000
23.32
30.72
36.66
41.76
46.30
50.44
54.26
57.83
61.19
36
37
12.166
23.41
30.79
36.72
41.81
46.35
50.48
54.30
57.86
61.22
37
38
12.329
23.49
30.85
36.77
41.86
46.39
50.52
54.33
57.90
61.25
38
39
12.490
23.58
30.92
36.82
41.90
46.43
50.56
54.37
57.93
61.29
39
40
12.649
23.66
30.98
36.88
41.95
46.48
50.60
54.41
57.97
61.32
40
41
12.806
23.75
31.05
36.93
42.00
46.52
50.64
54.44
58.00
61.35
41
42
12.961
23.83
31.11
36.99
42.05
40.56
50.68
54.48
58.03
61.38
42
43
13.115
23.92
31.18
37.04
42.10
46.60
50.71
54.52
58.07
61.42
43
44
13.266
24.00
31.24
37.09
42.14
46.65
50.75
54.55
58.10
61.45
44
45
13.416
21.08
31.30
37.15
42.19
46.69
50.79
54.59
58.14
61.48
45
46
13.565
24.17
31.37
37.20
42.24
46.73
50.83
54.63
58.17
61.51
46
4V
13.711
24.25
31.43
37.26
42.28
46.78
50.87
54.66
58.21
61.55
47
48
13.856
24.33
31.50
37.31
42.33
46.82
50.91
54.70
58.24
61.58
48
49
14.000
24.41
31.56
37.36
42.38
46.86
50.95
54.74
58.28
61.61
49
50
14.i42
24.49
31.62
37.42
42.43 | 46.90
50.99 54.77
58.31
61.64
50
CONDENSERS.
37
0
100
200
300
400
500
600
700
800
900
51
14.283
24.58
31.69
37.47
42.47
46.95
51.03
54.81
58.34
61.68
51
52
14.422
24.66
31.75
37.52
42.52
46.99
51.07
54.85
58.38
61.71
52
53
14.560
24.74
31.81
37.58
42.57
47.03
51.11
54.88
58.41
61.74
53
54
14.697
24.82
31.87
37.63
42.61
47.07
51.15
54.92
58.45
61.77
54
55
14.832
24.90
31.94
37.68
42.66
47.12
51.19
54.95
58.48
61.81
55
Rfi
14.967
24.98
32.00
37.74
42.71
47.16
51.22
54.99
58.51
61.84
56
57
15.100
25.06
32.06
37.79
42.76
47.20
51.26
55.03
58.55
61.87
57
58
15.232
25.14
32.12
37.84
42.80
47.24
51.30
55.06
58.58
61.90
58
59
15.362
25.22
32.19
37.89
42.85
47.29
51.34
55.10
58.62
61.94
59
GO
15.492
25.30
32.25
34.95
42.90
47.33
51.38 | 55.14
58.65
61.97
60
61
15.620
25.38
32.31
38.00
42.94
47.37
51.42
55.17
58.69
62.00
61
62
15.748
25.46
32.37
38.05
42.99
47.41
51.46
55.21
58.72
62.03
62
63
15.875
25.63
32.43
38.11
43.03
47.46
51.50
55.24
58.75
62.06
63
64
16.000
25.61
32.50
38.16
43.08
47.50
51.54
55.28
58.79
62.10
64
65
16.125
25.69
32.56
38.21
43.13
47.54
51.58
55.32
58.82
62.13
65
fifi
16.248
25.77
32.62
38.26
43.17
47.58
51.61
55.35
58.86
62.16
66
67
16.371
25.85
32.68
38.31
43.22
47.62
51.65
55.39
58.89
62.19
67
68
16.492
25.92
32.74
38.37
43.27
47.67
51.69
55.43
58.92
62.23
68
69
16.613
26.00
32.80
38.42
43.31
47.71
51.73
55.46
58.96
62.26
69
70
16.733
26.08
32.86
38.47
43.36
47.75
51.77
55.50
58.99
62.29
70
71
16.852
26.15
32.92
38.52
43.41
47.79
51.81
55.53
59.03
62.32
71
71?
16.971
26.23
32.98
38.57
43.45
47.83
51.85
55.57
59.06
62.35
72
73
17.088
26.31
33.05
38.63
43.50
47.87
51.88
55.61
59.09
62.39
73
74
17.205
26.38
33.11
38.68
43.54
47.92
51.92
55.64
59.13
62.42
74
75
17.321
26.46
33.17
38.73
43.59
47.96
51.96
55.68
59.16
62.4
75
76
17.436
26.53
33.23
38.78
43.63
48.00
52.00
55.71
59.19
62.48
76
77
17.550
26.61
33.29
38.83
43.68
48.04
52.04
55.75
59.23
62.51
77
78
17.664
26.68
33.35
38.88
43.73
48.08
52.08
55.79
59.26
62.55
78
7D
17.776
26.76
33.41
38.94
43.77
48.12
52.12
55.82
59.30
62.58
79
80
17.889
26.83
33.47
38.99
43.82
48.17
52.15
55.86
59.33
62.61
80
81
18.000
26.91
33.53
39.04
43.86
48.21
52.19
55.89
59.36
62.64
81
8','
18.111
26.98
33.59
39.09
43.91
48.25
52.23
55.93
59.40
62.67
82
83
18.221
26.06
33.65
39.14
43.95
48.29
52.27
55.96
59.43
62.71
83
84
18.330
27.13
33.70
39.19
44.00
48.33
52.31
56.00
59.46
62.74
84
85
18.439
27.20
33.7G
39.24
44.05
48.37
52.35
56.04
59.50
62.77
85
86
18.547
27.28
33.82
39.29
44.09
48.41
52.38
56 07
59.53
62.80
86
87
18.655
27.35
33.88
39.34
44.14
48.46
52.42
56.11
59.57
62.83
87
88
18.762
27.42
33.94
39.40
44.18
48.50
52.46
56.14
59.60
62.86
88
89
18.868
27.50
34.00
39.45
44.23
48.54
52.50
56.18
59.63
62.90
89
90
18.974
27.57
34.06
39.50
44.27
48.58
52.54
56.21
59.67
62.93
90
91
19.079
27.64
34.12
39.55
44.32
48.62
52.57
56.25
59.70
62.96
91
92
19.183
27.71
34.18
39.60
44.36
48.66
52.61
55.28
59.73
62.99
92
98
19.287
27.78
34.23
39.65
44.41
48.70
52.65
56.32
59.77
63.02
93
94
19.391
27.86
34.29
39.70
44.45
48.74
52.69
56.36
59.80
63.06
94
95
19.494
27.93
34.35
39.75
44.50
48.79
52.73
56.39
59.83
63.09
95
96
19.596
28.00
34.41
39.80
44.54
48.83
52.76
56.43
59.87
63.12
96
97
19.698
28.07
34.47
39.85
44.59
48.87
52.80
56.46
59.90
63.15
97
98
19.799
28.14
34.53
39.90
44.63
48.91
52.84
56.50
59.93
63.18
98
99
19.900
28.21
34.58
39.95
44.68
48.95
52.88
56.53
59.97
63.21
99
100
20.000
28.58
34.64
40.00
44.72
48.99
52.92
56.57
60.01)
63.25
100
MEASUREMENTS.
RESISTANCE MEA§VREMEMTS.
Ohm's la w is the foundation of all electrical testing, and is written in
the following forms : —
E — IR;
and
/= the current strength in amperes,
R = the resistance in ohms,
E = the electromotive force in volts.
The Resistance of multiple Circuits equals the reciprocal of
the sum of the reciprocals of the resistances of each circuit individually.
In the figure the joint resistance Rx of the two cir-
cuits r and rx, between a and b.
Rx = l- and the resistance required to he joined
in parallel with r to give Rx is
_rXRl
1 — r — Rt
and the total resistance of the figure, neglecting that
of the battery and connections,
= R + T-^-
r + ri
The joint resistance of any number of resistances in parallel, as, a, b, c, d,
e, etc., will be
I+l + i + J-etc.
Joint Insulation Resistance. — If n
of the figure, and y
: total insulation resistance
insulation resistance of the
section From a to c, then the insulation resistance
x of the section from b to c will be
_ y X n _
~ y — n'
The Current Strengths in Parallel or
Multiple Circuits are in proportion to the con-
ductivities of the separate branches, or inversely
proportional to their respective resistances.
In the figure, total current flowing in R,
r + rt
Fig.
Rr -f Rrx -f- rrx
Rr -\- Rrx -\- rrx '
it = E r- ,
Rr -\- Rrx -f- rrx
"Wheatstone's Rridsre. — For accurate meas-
urement of resistance the Wheatstone's bridge
method is more generally used than any other.
PRECISE COMPARISON OF SMALL RESISTANCES.
39
The diagram Fig. 4 shows the theoretical connections of the bridge.
In the diagrams Fig. 4 and Fig. 6 a, b, and JR are known resistances, and
x the unknown resistance to he measured. G is
the galvanometer ; B is a battery of several cells,
the number being varied according to the resist-
ance of x. a and b are adjustable, but may be
left equal to each other ; when R may be ad-
justed until there is no deflection of the galva-
nometer needle.
Then a : b : : R:x
and ax = bR
bR
and x =
a
Fig. 4. Note. — Always close the battery key before
closing the galvanometer key, to avoid an in-
stantaneous deflection of the galvanometer, which may be due to inductance
in one of the arms of the bridge. This deflection might occur even though
the resistances be properly balanced.
If a = b the value of x is the same as R. Should x be higher than the
capacity of R, or lower than its smallest unit, then a and b can be arranged
to multiply or divide the resistance value of R, and the equation still remains
a : 6 : : R : x.
For example,
let
and in practice the ratio a :
by 100.
Again, let
a =10
b = 1000
72 = 200;
10: 1000:: 200: a;
10 a; = 200,000
x = 20,000 ;
= 100, and any reading as R would be multiplied
a = 1000
6 = 10
72 = 200
1000 : 10 : : 200 : x
1000 x = 2000
and the ratio a : b = TJDi and any reading as 72 would be divided by 100.
I*ost-©ffice Sridg'e. — A very convenient form of Wheatstone's bridge
is shown in Fig. 5, of which the connections are shown in diagram 6. The
letters and figures are the s
further explanation.
Fig. 6.
$ as in the former diagrams, and will need no
40
MEASUREMENTS.
Fig. 7 is a form of bridge designed by Prof. Anthony which employs a
smaller number of plugs than are used in ordinary forms of bridges, and
thereby dispenses with much of the accompanying contact resistance.
Fig. 8.
Slide-wire Bridgre. — A very convenient form of bridge for ordinary
use where extreme accuracy is not de-
manded is the slide-wire bridge, shown in
Fig. 8. It consists of a wire one meter
long and about 1.5 mm. diameter stretched
parallel with a meter scale divided into
millimeters. A contact key is so arranged
as to be moved along the wire so that con-
tact with it can be made at any point.
A known resistance R is connected as
shown ; x is the unknown resistance ; the
galvanometer and the battery are joined
up as shown in the figure ; after closing
the key kY the contact 3 is then moved
along the wire until the galvanometer needle returns to zero ;
then again ; a : b : : R : x,
bR
and x =: — •
a
The Cary-J^oster IVEetliod. — For the very precise comparison of
nearly equal resistances of from 1 to 100 ohms this method yields exquisite
results. In Fig. 9, St and S2 represent the two
nearly equal resistances to be compared, and Rit
R2 represent nearly equal resistances, which, for
best results, should not differ much in magnitude
from Si and S2. S-y and S2 are connected by a
slide-wire whose resistance per unit length p is
known. The battery and galvanometer are con-
nected as in the diagram. A balance is obtained
by moving the contact c along the stretched wire.
Suppose the length of the wire on the left-hand
side to the point of contact to be a units. Then
exchange St and S2 for each other without alter-
ing any other connections in the circuit. Upon
producing a new balance, let ax be the length of
wire to the left of the contact.
Fig.
9. Cary-Foster
Bridge.
Then
: S, + (a — aj p.
Special commutators are upon the market which have for their purpose
the easy exchange of S\ and S2.
To avoid thermal effects, which are quite considerable with resistances
made of some materials, the battery should be commutated for each position
of the resistances to be compared. The readings for the two balances ac-
companying the battery commutation should be averaged.
PRECISE COMPARISON OF SMALL RESISTANCES. 41
Fig. 10. Thomson's Double Bridge.
Thomson's J»out»le JBridg-e. — If the resistances in a Wheatstone's
bridge be much less than one ohm in magnitude, the accuracy of the results
obtained is inferior. Samples of
copper or other wires of moderate
lengths and diameters have such
small resistances that the resistiv-
ities of the materials of which
they are constructed cannot be
determined satisfactorily by this
method. Thomson designed a
modified form of bridge which
gives very satisfactory results.
Its construction is represented
diagrammatically in Fig. 10, where
the unknown low resistance x is
compared with a standard low re-
sistance R. R and x represent
the resistances of measured lengths of standard wire and test wire respec-
tively. These two wires are firmly joined at ?/. The uncertainty of the
exact point of separation between them would make it difficult to connect
the galvanometer so as to yield a reliable balance. By the insertion of two
auxiliary resistances n and o of such magnitudes that n : o = R : x = a : b,
and by connecting the galvanometer through the key l\ to a point between
n and o, results of very good accuracy may be obtained.
Precise Comparison of* Very Small Resistances. — For com-
paring the low resistances of ammeter shunts, etc., with standard side ter-
minal resistances of the Reichsanstalt
form, the method of Sheldon yields
very accurate results. The unknown
resistance x, Fig. 11, which may be as-
sumed to be supplied with branch po-
tential points a b, is connected by heavy
conductors in series with a standard re-
sistance R, having potential points c d.
From the two free terminals T T1 of
these resistances are shunted two 10,000
ohm resistance boxes S P, adjusted to
the same normal temperature, and
wound with wire of the same or negli-
gable temperature coefficient, and con-
nected in series. From the point of
connection e, between the two boxes, connection is made to one terminal of
the galvanometer g, the other terminal being connected successively with
the potential points a, b, c, and d. At the outset all the plugs are removed
from the box S, and all are in place in the box P. After connecting T and
T1 with a source of heavy current, plugs are transferred from one box to the
corresponding boles in the other box (this keeps the total resistance in the
two boxes constant) until no deflection is observed in the galvanometer.
This operation is repeated for each of the potential points a, b, c, and d. Rep-
resenting the resistances in the box S on the occasion of each of these bal-
ances by Sa, Sb, Sc, and Sd respectively, we have the following expression
for the value of the unknown resistance : —
Fig. 11. Precise Measurement.
. Sa — Sb
' Sc — Sd
R.
"Differential Galvanometer method. — In galvanometers hav-
ing two coils wound side by side, when two separate and equal currents are
sent through the coils, but in opposite directions, the needle will not move.
If the currents are unequal the needle will be deflected in proportion to the
difference of current strength ; and, as the current can be varied by varying
the resistance, this instrument will serve for comparing an unknown resist-
ance with a known resistance.
To determine if the coils have equal effect on the needle, connect them in
series opposition, and pass a current through them ; if there be any deflec-
tion of the needle one of the coils will have to be moved until the needle
stands at zero ; or with the coils in multiple a resistance can be placed in
series with the coil taking the most current.
42
MEAS UREMENTS.
RESISTANCE OE WIRES.
By Simple Substitution. — Place the resistance to be measured in
series with a galvanometer and battery or other source of steady current,
and note the deflection of the needle. Replace the unknown resistance with
a known adjustable resistance, and change the latter resistance until the
same deflection of the galvanometer needle is obtained as with the unknown
resistance ; then the unknown resistance equals the value of the known
resistance that is necessary to produce the same deflection.
Other methods and applications are shown in the section on voltmeter
tests.
RESISTANCE OE «AIVAXOMEIER8.
When a second galvanometer is available, by far the most simple and sat-
isfactory method is to measure the resistance of the galvanometer by any
of the ordinary Wheatstone's bridge methods. Take the temperature at
the same time, and, if the instrument has a delicate system, remove the
needle and suspension.
Half Reflection UKethod. — Connect the galvanometer in series Avith
a resistance r and battery as in the following figure.
r Note the deflection d ; then increase r so that the new
deflection dx will be one-half the first, or - =- dx ; call
the new resistance r, ; then
Resistance of Galvanometer =r r, — 2r.
jiIG 22. If tne instrument be a tangent galvanometer, then
d and dx should represent the tangents of the deflec-
tions.
Thomson's Method.— Connect the galvano-
meter, as a; in a Wheatstone's bridge, as in Fig. 13.
Adjust r until the deflection of G is the same,
whether the key is closed or open.
G = rb.
I — vV&V-^A
The result is independent of the resistance of the
battery. The battery should be connected from the
junction of the two highest resistances to that of
the two lowest. -r iu. ±o.
RESISTANCE OE RATTERIES.
Condenser Method. — For this test is needed a condenser C, a ballistic
galvanometer G, a double contact key ku a resistance E,
of about the same magnitude as the supposed resistance
of the battery B, and a single contact key k2. Connect as
in the following figure. With the key k2 open, press the
key kx, and observe the throw 0t in the galvanometer.
Then, after the needle has come to rest, with key k2
closed, repeat the operation observing the throw 92.
Then the resistance of the battery
X-R 01 ~ fl3 .
Reduced Reflection method. — Connect the
battery B in circuit with a galvanometer G and a resist- Fig. 14.
ance r as in Fig. 15. Note the deflection d, and then in-
crease r to 7*! and note the smaller deflection dx ; then, if the deflections of
the galvanometer be proportional to the currents,
_ r1dl — rd
If rx is such that
then
-<2r+G).
RESISTANCE OF AERIAL LINES.
43
Fig. 16.
The E.M.F. of the battery is supposed to remain unaltered during the
measurement.
HH ance's Method. — Connect the battery as x
in Wheatstone's bridge as in Fig. 16. Adjust r until
the deflection of G is the same whether the key be
closed or open.
Then B = r~.
a
The galvanometer should be placed between the
junction of the two highest resistances and that of ^— "It*
the two lowest.
Resistance of Battery while Working-.
— Connect the battery B with a resistance r, and
also in parallel with a condenser C, galvanometer G, and key k ; shunt the
battery through s with key k\, as in Fig. 17.
Close the key k, and note the deflection d of
the galvanometer, keeping k closed, close kx and
note dlf the deflection in the opposite direction.
Then the battery resistance
B = s i^_.
A 1 dlS
d — dt —
(I s
If r be large, the term — — is negligible, and
B-
dx
s being the multiplying power of the shunt.
Workshop Method, Applicable as well to Dynamos. — "With
dynamo or battery on open circuit, take the voltage across the terminals
with a voltmeter, and call it d ; take another reading dl at the same points
with the battery or dynamo working on a known resistance r : then the in-
ternal resistance R = — - — - r.
dx
In the case of storage batteries, if the current I be read from an inserted
ammeter when charging, the resistance of the battery is
and when discharging B = ~ 1 .
RESISTANCE OF AERIAL LO£S OR HOUSE
CIRCUITS.
Conductor Resistance. — "When the circuit has metallic return, it is
easily measured by any of the Wheatstone's bridge methods, or, if the circuit
conductor can be supplied with current through an ammeter, then the fall
of potential across the ends of the con-
ductor will give a measure of the resistance
by ohms law, viz.,
_, . , drop in volts
Resistance = — .
current
If the circuit has earth return as in tele-
graph and some telephone circuits, then
place far end of the line to earth, and con-
Earth^^ nect with bridge as in Fig. 18.
Then the total resistance x of the line and
FlG« 18* earth, is x = r - .
If a second line be available, the resistance of the first line can be deter-
mined separated from that of earth, as well as the resistance of earth.
44 MEASUREMENTS.
Let r = resistance of first line
r/ =z resistance of second line
rt/ = resistance of earth.
First connect the far end of r and r, together, and get the total resistance
R ; connect r and r/n and measure the resistance R, ; connect r, and rm and
get total resistance R„. Then if
T_R + R,+R„
2
r = T—R„
r,= T—R.
r„= T—R.
This test is particularly applicable to finding the resistance of trolley wires,
feeders, and track.
IHTiULATIOar RESISTAirCE OF ELECTRIC CIR-
CUITS IJ¥ BUII.M1V&S.
In the United States it is quite common to specify that the entire installa-
tion when connected up shall have an insulation resistance from earth of at.
least one megohm.
The National Code gives the following : —
The wiring of any building must test free from grounds ; i.e., each main
supply line and every branch circuit should have an insulation resistance of
at least 100,000 ohms, and the whole installation should have an insulation
resistance between conductors and between all conductors and the ground
(not including attachments, sockets, receptacles, etc.) of not less than the
following : —
Up to 5 amperes . . 4,000,000. Up to 200 amperes . . 100,000.
Up to 10 amperes . . 2,000,000. Up to 400 amperes . . 50,000.
Up to 25 amperes . . 800,000. Up to 800 amperes . . 25,000.
Up to 50 amperes . . 400,000. Up to 1,600 amperes . . 12,500.
Up to 100 amperes . . 200,000.
All cut-outs and safety devices in place in the above.
Where lamp-sockets, receptacles, and electroliers, etc., are connected,
one-half of the above will be required.
Professor Jamison's rule is : —
E.M F
Resistance from earth = 100 nnn
Kempe's rule is : —
Resistance in megohms
A rule for use in the U. S. Navy is : —
Resistance = 300,000 x
number of outlets
Institution of Electrical Engineers' rule is : —
7900 X E.M.F.
number of lamps
75
number of
lamps '
E.M.F.
R-
' number of lamps
Phoenix Fire Office rule for circuits of 200 volts is that
12.5 megohms
The least R =
number of lamps
Twenty-five English insurance companies have a rule that the leakage
from a circuit shall not exceed ^suis part of the total working current.
MEASUREMENT OF ELECTROMOTIVE FORCE.
45
Below is a table giving the approximate insulation allowable for circuits
having different loads of lamps.
For a circuit having —
25 lamps, insulation should exceed . . 500,000 ohms.
50 lamps, insulation should exceed . . 250,000 ohms.
100 lamps, insulation should exceed . . 125,000 ohms.
500 lamps, insulation should exceed . . 25,000 ohms.
1000 lamps, insulation should exceed . . 12,000 ohms.
All insulation tests of lighting circuits should be made with the working
current. (See page 58, voltmeter test.)
In the following table Uppenborn shows the importance of testing with
the working voltage.
Table I. shows the resistance between the terminals of a slate cut out.
Table II. shows the resistance between two cotton-covered wires twisted.
I.
II.
Volts.
Megohms.
Volts.
Megohms.
5
10
13.6
27.2
68
53
45
24
5
10
16.9
27.2
281
188
184
121
MEASUKEMEajT OE ELECTROMOTIVE EORCE.
Of Batteries. — This can usually be measured near enough for all
practical purposes by Weston or other high-class low-reading voltmeters
(see voltmeter tests) ; but if greater accuracy be wanted, it can be obtained
by comparing with a standard cell by the following method : —
Eord Hayleigvn's Compensation Method. — In the following
diagram let R and Rx be two 10,000-ohm
rheostats, B be the battery of larger E.M.F.
than either of the cells to be compared, JSX be
one of the cells under test, G be a sensitive
galvanometer, HR be a high resistance to
protect the standard cell, and k be a key.
Obtain a balance, so that the galvanometer
shows no deflection on closing the key k, by
transferring resistance from one box to the
other, being careful to keep the sum of the
resistances in the boxes equal to 10,000 ohms.
Observe the resistance in R and call it R±.
Repeat with the other cell -82, and call the
resistance R2. Then the E.M.F. 's of the two cells
E1:E2 = R-i: R2.
Electrometer Method. — Connect the cell whose E.M.F. it is desired
to measure to the terminals of a quadrant electrometer, and note the deflec-
tion d. Then substitute the standard cell for the first cell, and note the
deflection dx.
Then, if e = the E.M.F. of the cell to be measured,
and e1 = the E.M.F. of the standard,
d1:d::el:e,
_de1
and
d,
TITieatstone's Method. — Connect the cell or battery to be compared
in circuit with a galvanometer and high resistance r, and note the deflection'
d ; then add another high resistance rx (about equal to r), and note the de-
46
MEASUREMENTS.
flection dv Next, connect the cell with which the first is to be compared in
circuit with the galvanometer, and connect in resistance until the gal-
vanometer deflection is the same as d ; then add further resistance iintn
the galvanometer deflection is the same as d, ; then, if e = the E.M.-b . ot the
first cell, and E = the E.M.F. of the cell with which it is compared,
r1:R::e:E,
v Rxe
and E — — — •
MEASUROG CAPACITY.
Arrangement of Condensers. In Parallel. — Joi
of the several condenser-
35
like poles
i.gether as
in the figure ; then, the joint capacity
of the set is equal to the sum of the
several capacities.
Total capacity = 0 + 0 + c„ -\- <•„,.
Condensers in Series. — Join
the unlike poles as if connecting up
battery cells in series as in Fig. 21,
then the joint capacity of all is the
Fig. 20.
reciprocal of the sum of the reciprocals of the several capacities
Capacity C =
"1
1
Capacity l*y Direct Discharge.—
Charge a standard condenser, Fig. 22, C'« by
a battery E for a certain time, say 30 sec-
onds ; tlien discharge it through a ballistic
galvanometer G ; note the throw d.
Next charge the condenser to be measured,
C., by the same Lattery and for the same length of time, and dischaige tins
1 - same galvanometer noting the throw d1 ;
Fig
h
through the same galvanometer noting t
Then Cs : C± :: d : dv
and
<h-
Fig
Thomson's Method. - This method is that most gen-
erally used for comparing capacities of condensers, cables,
etc.
Fig. 23.
B = battery, say 10 chloride of silver cells.
R = variable resistance.
Rx = fixed resistance.
G — galvanometer.
C— standard condenser.
C, = cable or condenser to be measured,
1, 2, 3, 4, 5 == keys.
MEASURING CAPACITY.
47
Test. — Close key 1, thus joining the two resistances R and Rx to earth.
Then if Fand Vx = the potentials at the junctions of the battery with the
resistances R and Rx,
V: V-.r.RiR^.
Close keys 2 and 3 simultaneously for a certain length of time, and charge
the condenser Cand cable C\ to potentials F"and V-, respectively.
If C and Cx be the respective capacities (in microfarads) of the condenser
and cable, and Q and Qx the charges given to them,
Q:Q1::VC: l\Cx.
Release keys 2 and 3, then close key 4 for a fixed time, to allow the charges
of condenser and cable to mix, then if Q is not = Qx when the key 5 is closed
cutting in the galvanometer, there is a deflection. Change the ratio of R to
Rx until on trial there is no deflection.
Then VC= VXCX
or VX:V::C:CX
but we found Vx: V::RX:R
or RX:R :: C : Cx
R
Bridge method. — For comparing the capacities of two condensers,
Cs and 6, which are approximately the same, connect as in Fig. 24 through
two rather high inductionless resistances
Rx and R2 to the key k which makes and
breaks contacts at each end. E is a bat-
tery. A galvanometer is inserted between
the ends of the condensers where they
join the resistances. Adjust the resist-
ances so that no deflection results when
the key is manipulated.
R^
-Cs
R2
■VvA/VV 1
Then
: Cs
Fig. 24.
^V
Intermittent Current TIetltod. — If a tuning fork, making n com-
plete vibrations per second, and provided with a stylus, be connected as in
Fig. 25, it will charge the condenser to the voltage of the battery E, and then
discharge it through the galvanometer G, n times
per second. The effect on the galvanometer will
be the same as though a constant current of
strength, nEC, were flowing through it, where C is
the capacity of the condenser. To determine the
value of this current, connect the battery directly
to the galvanometer through a total resistance R,
r— j'L so adjusted as to give the same deflection as
;C) ^:£ before
Fig. 25.
Then
nEC=l.
. C =
n R '
Coefficient of Self-Induction T, of a Coil or Circuit. — The
coefficient of self-induction of a coil or circuit is the equivalent in volts that
would be produced in that coil or circuit by a rate of change of current
equivalent to a uniform change of one ampere of current per second. It is
numerically equal to the number of lines of force linked with the circuit
per unit current in it.
For example, if we have a coil of 150 turns of wire carrying 2 amperes and
producing 200,000 lines of force, or 200 kilogausses, then one ampere would
produce 100,000 lines ; and if it took the current one second to die out when
the circuit was opened, then each turn would cut 100,000 lines in that time,
and 150 turns would be equivalent to 1 turn cutting 15,000,000 lines. 1 volt
= 108 lines cut by one coil ; therefore
15,000,000
= .15 volts, or .15 henry rr L.
ASS
48
MEASUREMENTS.
MFASUHEiWFNTS OF COXFFIGIEHTS OF IUDFC
TAUCE.
Determination of the coefficients of inductance may be made with a
Wheatstone's bridge, condenser, and variable non-
inductive resistance ; connect up as follows : —
In the cut let A and B be equal constant arms of
the bridge ; R, the variable arm ; r, a variable non-
inductive resistance in series with the inductive
resistance, Ind. R, to be measured, and the ohmic
resistance of which is P^, C being a condenser
placed as a shunt around the two resistances.
The resistance r is employed to enable one to use
a condenser C of practicable size. Adjust C, r,
and R, until there is no deflection of the galva-
nometer when the battery circuit is opened ;
then L—C{r-\- Rtf.
Another Method : —
Let r — resistance of article to be measured,
L — coefficient of self-induction of article,
R = resistance = to r,
C = capacity of a condenser in microfarads.
Then proceed as follows : —
1st. Balance for constant currents by adjusting rlt
both h and kL being closed.
2d. After closing the galvanometer key klf close
key k, and note the throw 01 in the ballistic galva-
nometer.
3d. Substitute in the bridge, for the article whose
inductance is being measured, the condenser C
shunted by the resistance R = r.
4th. Repeat the operation 2, and note the galva-
nometer throw 0o.
Then
L = Cr* -
- 1,000,000 henrys.
Kt-J
To Compare Two Coefficients of Self-
Induction. — Let the connections be made as in
the cut, the two coefficients of self-induction being
x and y in the arms A and B.
Balance the bridge so there is no movement of tbe
galvanometer needle, the key k being closed, when
kx is opened or closed suddenly.
Then, if the total resistance of the arm A, includ-
ing the coil x be A, and the resistance of the arm B
is B, including the coil y, the coefficient of the coil
x and that of the coil y are such that
, x a A
we have - = T = — .
y b B
MiEASTTKFIWENT OF SELF-IWDIJCTA^CE WITH AN
ALTERNATING CURRENT OF KNOWN
FREftFEUfCT.
For this test is needed a high resistance or electrostatic alternating cur-
rent voltmeter, a direct current ammeter, and a non-inductive resistance.
Connect as in Fig. 29, where /?, is an inductive resistance to be measured,
and S a switch for short-circuiting tbe ammeter ; the A. C. dynamo of fre-
quency n is so arranged that its terminals may be disconnected, and a
battery be substituted therefore.
Witb the connections as in Fig. 29, close the switch S, and take the drop
with the voltmeter from a to b and the drop from a to C ; then disconnect
MEASUREMENT OF MUTUAL INDUCTANCE.
49
the A. C. dynamo, and connect the battery B ; open the switch s, and vary
the continuous current until the drop from a to Cis the same as with the
alternating current, both measurements being made with the same volt-
meter ; then note the current shown by the ammeter, and measure the drop
from a to b with the voltmeter. Call the drop across JRt from a to b, with
alternating current, E, ami the same with continuous current, Ex, and the
reading of the ammeter with the latter, i".
Then L = - =-±- ,
2lT?lI
If the resistance Bx be known, and the ammeter be suitable for use with
alternating currents, the switch and non-inductive resistance may be dis-
VI
B1
pensed with. We then have L = -
where L is the value of the al-
ternating current.
Note. — The resistance of the voltmeter must be high enough to render
its current negligible as compared with that through the resistance Bx.
MEASUIlEIflEMT OF MUTCAI IHT>UCTA]¥CI3.
Let Af=the mutual inductance between
rJ^* two coils,
Let L =z the self-inductance of one coil,
Let Lt = the self-inductance of the other
coil,
Let Ln = the self-inductance of both coib
connected in series,
Let LJ/t = the self-inductance of both coil-:.
connected in opposition to each
other.
Then, since Llt — L + Lx -f 2 M
and L/// = L-\-L/ — 2M
Another Method with battery is as
follows : connect as in Fig. 30 where A and
D are the two coils whose mutual induc-
tance, Mv is required. R and Rx are two
non-inductive resistances, and C is a con-
MM
50
ME AS U REM EXTS .
denser placed in shunt to R -\- Rv Closing and opening the key k produces
deflections of the galvanometer G by the mutual induction of the coils and
proportional to M — CRRV Varying Ogives different deflections in which,
a being the first deflection and d[ a second deflection,
M— CRRl _M— C\RRt
d ~ dx
d being the second value of the capacity of the condenser.
Then M = CRRX when d is reduced to zero.
measuring} the iufdhctawce ©e aerial
mutes.
In the following figure a line is shown Avith a load of lamps or other trans-
lating devices, although for the purpose of getting the line inductance
alone, it Avould most likely be
i | | closed on itself.
Connect up for a Wheat-
stone's bridge method as
shown in the cut ; close the
key, and manipulate the sliiler
p until a balance is obtained ;
then vary the capacity of the
condenser C until there is no
movement of the needle when
the battery circuit is broken
with the key.
Then, disregarding line ca-
pacity, the inductance is
L = cr2,
and, if C =r capacity of the
line, and R be the resistance of the same,
then L = cr2 + § CR2.
MEASUREMENT OF HCTCAI ITOUCTABfCE OE
AERIAL LOES.
To measure the mutual inductance of a pair of parallel lines, connect up
as in the cut below. Earth both ends of each line separately, and, to avoid
trouble from earth currents, put a small battery in secondary line with ad-
justable shunt as shown. Adjust R and C until there is no movement of
BATTERY
the galvanometer needle, when the circuit of the battery is opened with the
key ; then, if
R = the resistance of the rheostat R as finally arranged,
Rt = the resistance of secondary line,
C — the capacity of the condenser as finally arranged,
and M= mutual inductance,
M = CRRX.
MEASUREMENT OF CURRENT CIRCUITS.
51
CURREiTfT CIBCUITS.
In circuits carrying alternating currents, and having an inductance in
some part of their length, either in the shape of motors or other inductive
load, as unloaded transformers, and the self-induction of the wires them-
selves, the ordinary methods of measurement of the power or watts con-
veyed are not available, as the current is seldom exactly in phase with the
E.M.F., and therefore the value of the current multiplied by the E.M.F. will
not be the true watts of the circuit.
In all alternating circuits the power, at any instant of time, is equal to
the product of the instantaneous values of the current and voltage at that
time. If the current be in phase with the voltage, each will have zero values
at the same instant of time, and will have maximum positive and maximum
negative values simultaneously. Inasmuch as the product of two negative
quantities is a positive quantity, the power of the circuit, Avith no phase dif-
ference, is made up of positive pulsations varying in magnitude from 0 to
a maximum. The latter is equal to the product of the maximum values of
the current and E.M.F. If, however, the current differ by 90° in phase from
Si*
u." \
A
»
Uj
=8
£
~=
($
1
M
ly
/f
s^
V
&/
k
♦;
■/i/
"«
f /{
9'L
5*
\%
Y
1
K\
K?
■*
^
■©.
\
^
/\
6
\
^
the voltage, i.e., each having 0 value when the other has a maximum value,
the power will consist of a series of pulsations, first positive and then nega-
tive, and the algebraic value of the work done, i.e., power times its dura-
tion, would be equal to zero. The result is that no permanent work is done,
and the circuit is said to have a " Power Factor " of 0. The current which
flows is called a wattless current. If the phase difference be less than 90°
and more than 0°, at some instants of time the product of the volts and am-
peres will be negative, but oftener will be positive. The fractional part of
the whole which is positive is called the power factor. It can be shown that
the power factor is equal to the cosine of the angle of phase difference.
Inasmuch as an ampere of alternating current is one whose maximum
value is 1.41 amperes (V^), and a volt of alternating current is one whose
maximum value is 1.41 volts, the following relations hold true : —
If
True Watts ='
/= maximum value of E.M.F.,
d =: maximum value of current,
6 = angle of lag of current behind the E.M.F.,
2
- x Cos e.
52
M E A S V R E M E X T S .
: E.M.F. by voltmeter : Vinean2,
: current by ammeter : Vmean2,
: angle of lag,
z watts measured by watt meter,,
then
; Cos 6 = Power factor,
W -
w
Exl~
or tbe power factor is tbe value by which the observed volt-amperes must
be multiplied to give the true watts.
If a wattmeter be without self-induction in its fine wire coils, and tbe
supporting part be not subject to eddy currents, then it may be used for
measuring the value of power in A. C." circuits ; in, fact, in all full tests of
alternating-current work it is necessary to have wattmeter, ammeter, and
voltmeter readings.
Three Voltmeter Method. Ayrton & Sumpner.
This method is good where the voltage can be regulated to suit the load.
In the above figure let the non-induc-
tive resistance li be placed in series with
the load a b ; take the voltage V across
the terminals of li ; Vx across the load
a b, and F2 across both, or from a to c.
Then the
J7 2 _ yi _ T'2
True watts — —
Fig. 34.
W- V
21i
The best conditions are when V = >
and, if li — \ ohm,
Three Ampere Meter Method {not recommended).
This method, due to Fleming, can be used when it is not convenient to
regulate the potential of load a b.
In Fig. 35 R is a non-inductive resistance _ x
connected in shunt to the inductive load
a b, with the three ammeters connected as
shown,
Then True watts = f (J22 — A2 — At2).
Comhined Voltmeter and
ter Method.
Fig. 35.
This method, devised also by Fleming, is quite accurate, and enables the
accuracy of instruments in use to be
a x checked. In Fig. 36 R is a non-inductive
resistance connected in shunt to the induc-
tive load a b, and the voltmeter V measures
the p. d. across x y. A and Ax are ammeters
connected as shown ; then
True watts = f (a? — An- — (^f) ■
If the voltmeter V takes an appreciable
amount of current, it may be tested as fol-
lows : disconnect E and Fat y, and see that A and .-/, are alike ; then con-
nect /,' and V at y again, and "disconnect the load a b. Then At = current
taken by li and V in multiple.
As regards all the above mentioned tests with 3 voltmeters, ammeters, etoi,
it may be said that they were developed at a time when no good alternating
current instruments were available. Since then a number of good A. C.
voltmeters have been developed, and more recently the inclined coil instru-
ments of the General Electric Co., and Sehallenberger instruments of the
Westinghauss Co., have placed instruments in our hands that make alternat-
ing-current testing nearly as easy as d. c. testing.
TESTS WITH VOLTMETER.
53
TESTS WITH VOLTMETER.
The following are a few of the more important tests for which a voltmeter
is especially adapted, and have mostly been condensed from a very fine
article by H. Maschke, Ph.D. published in the Electrical World in April,
1892.
The scales of the better known portable instruments of to-day read in gen-
eral from 0 to 150 volts, or from 0 to 750 volts, and in special instruments the
two scales are combined, so that by connecting one wire to one or the other
of two binding posts either scale is available. Instruments for battery use
read from 0 to 15 volts with a second scale reading as low as J-0, or 1.5 volts.
Millivoltmeters reading from 0 to J^, or 0 to TJn, etc., with divisions capable
of being read as low as TooVoo volt, are also obtainable.
None of the refined laboratory methods will be given here, as the reader is
referred to the text-books for such tests.
ELECTROMOTIVE FORCE OE BATTERIES.
The positive post of voltmeters is
usually at the right, and marked -4-
In a battery the zinc is commonly neg-
ative, and should therefore be" con-
nected to the left or negative binding
post.
For single cells or a small number,
a low-reading voltmeter, say one read-
ing to 15 volts, will be used, the con-
nections being as per diagrams.
FJi|i|i|i|i|i|(
+
Fig. 37.
Fig. 38.
ELECTROMOTIVE EORCE
OE D1SAMOS.
For voltage within range of the instrument available for the purpose, it is
only necessary to connect one terminal of the voltmeter to a brush of one
polarity, and the other terminal to a brush of the opposite polarity, and
read direct from the scale of the instrument. As continuous current volt-
meters usually deflect forward or back according to which pole is connected,
it is necessary sometimes to reverse the lead wires, in which case the polar-
ity of the dynamo is also determined. Of course the voltage across any cir-
cuit may be taken in the same way, or the dynamo voltage may be taken at
the switchboard, in which case the drop in the leads sometimes enters into
the calculations. Following are diagrams of the connections to bipolar and
multipolar dynamos : —
/\4-
m
Fig. 39.
Fig. 40.
In the case of arc dynamos or other machines giving high voltage, it is
necessary to provide a multiplier in order to make use'of the ordinary in-
strument; and the following is the rule for determining the resistance
which, when placed in series with the voltmeter, will provide the necessary
multiplying power.
u
MEAS HKEMENTS.
e = upper limit of instrument scale, for example 150 volts,
E = upper limit of scale required, for example 750 volts,
R =z resistance of the voltmeter, for example 18,000 ohms,
r = additional resistance required, in ohms.
r = R ^ll or r — 18,000 75°~„15° = 72,000 ohms.
150
The multiplying power :
E 750
B
Should the exact resistance not be available, then with any available
resistance i\ the regular scale readings must be multiplied by ( -^ + 1 ) •
IMPOBTOCE ©_F HriCJH BHIISTAH'CE I OH
VOXTMETEKSi.
It is highly important, as reducing the error in measurement, that the in-
ternal resistance of a voltmeter be as high as practicable, as is shown in the
following example : —
Let E in the figure be a dynamo, battery, or other
source of electric energy, sending current through the
resistance r ; and vm. be a voltmeter indicating the
pressure in volts between the terminals A and B. Be-
fore the vm. is connected to the terminals A and B there
will be a certain difference of potential, which will be
less Avhen the voltmeter is connected, owing to the les-
sening of the total resistance between the two points ;
if the resistance of the vm. be high, this difference will
be very small, and the higher it is the less the error.
Following are the formulas and computations for de-
termining the error.
In the above figure let E be the E.M.F. of the dynamo,
r the resistance of the circrut as shown between A and
B, and r-. be the resistance of the leads A and B plus
that of the dynamo, and let R be the resistance of the voltmeter ; then before
the vm. is connected the difference between A and B will be
— 'Wvwvw — ,
Fig. 41.
r -f-rj
X E,
and after connecting the voltmeter it will be
R X r
1 R X r + r X rx + rx X R
The difference between the two results e and ex is then
X -
" X rx
- X elt
and this difference will be smaller the greater the resistance R of the vn
Example : —
Let E =10 volts
r = 10 ohms
rx = 2 ohms
R = 500 ohms
then
and
500 X 10
X 500
X 10 = .0333.
1 — 500 X 10 + 10 X 2 +
_ _ 2_ 10 X 2
6 ~ Cl - 500 X 10 + 2
If R be made 1000 ohms, then
1000 x 10
€l ~" 1000 X 10 + 10 X 2 -)- 2 X 1000
X 10 = 8.3056,
X 10 = 8.32,
S ~~ el — -mnn X :
,10X2
X 10 = .0166,
POMPARISOX OF E.M.F. OF BATTERIES.
or just one half of fche error ; it may be said that the error is therefore in
inverse proportion to the resistance of thevm.
If the error of measurement is not to exceed a stated per cent p, then r
and r, must be such that — , — 1 is smaller than „.,„'' ohms.
1 r + rt 100
It the circuit is not closed by a resistance i
between A and B
then with vm. connected
and the error between the true value and that shoAvn on the vm. is
and this error decreases in inverse proportion to the increase of the ratio
between It and the internal resistance of the current generator rx.
If the error is not to exceed p per cent, then the internal resistance rx must
be less than ohms.
TheE.M.F. of high-resistance cells cannot be correctly measured by the
above method, even with voltmeters of relatively high resistance, but it is
better done by one of the methods mentioned below.
COMPARISON OIT E.M.I\ &W BATTERIES.
Wlieatstf one's JfletStod. — To compare E.M.F. of two batteries A and
A", with low-reading voltmeters, let E be the E.M.F. of A ; and E, the E.M.F.
of X.
— n/VVVVVVVVV
Fig. 42.
First connect battery A in series with the voltmeter and a resistance r,
switch B being closed, and note the deflection V; then open the switch B,
and throw in the resistance rx, and note the deflection Vx. Now connect bat-
tery X in place of A, and close the switch B, and vary the resistance r until
the same deflection F"of voltmeter is obtained and call the new resistance r2 ;
next open the switch B, or otherwise add to the resistance r2 until the deflec-
tion Vx of the voltmeter is produced ; call this added, resistance r3, then
E:E1::r1 : ra.
If E be smaller than Et, the voltmeter resistance R may be taken as r, and
it is better to have rx about twice as large as the combined resistance of r
and the resistance of A.
It is not necessary that the internal resistance of the cells be small as
compared with B.
Poggcmlorff's Ifletliod Modified Iby Clark.
To Compare the E.M.F. of a battery cell or element with a standard cell.
Let S be a standard cell,
Tbe a cell for comparison with the standard,
B~be a, battery of higher E.M.F. than either of the above elements.
A resistance r is joined in series with the battery B and a slid© wire A D.
A millivoltmeter is connected as shown, both its terminals being connected
to the like poles of the battery B and the Standard *9.
ia
56
MEASUREMENTS.
FlG. 43.
Move the contact C along the wire until the pointer of the instrument
stands at zero, and let r1 be the resistance of A C.
Throw the switch b so as to cut out the standard S, and cut in the cell T ;
now slide the contact 6\ along the wire until the pointer again stands at
zero, and call the resistance of A C\ r2,
Then the E.M.Fs. of the two cells
T: S ::r2 : rv
If a meter bridge or other scaled wire be used in place of A D, the results
may be read directly in volts by arranging the resistance r so that with the
pointer at zero the contact C is at the point 144 on the wire scale, or at 100
times the E.M.F. of the standard S, which may be supposed to be a Clark
cell. All other readings will in this case be in hundredths of volts ; and
should the location of Cx be at 175 on the scale when the pointer is at zero
on the voltmeter, then the E.M.F. of the cell, being compared, will be 1.75
volts.
MEASIIRIIC} CUMIIE]¥T STRENGTH WITH A.
TOLTMETER.
If the resistance of a part of an electric circuit be known, taking the drop
in potential around such resistance will determine the current flowing by
ohms law viz., I— — .
In the figure let r be a known resistance be-
tween the points A and B of the circuit, and /
the strength of current to be determined ; then
if the voltmeter, connected as shown, gives a
deflection of V volts, the current flowing in r
V
will be 1= — .
For the corrections to be applied in certain
cases, see the section on Importance of High
Resistance for Voltmeters.
Always see that the resistance r has enough
carrying capacity to avoid a rise of temperature
which would change its resistance.
If the reading is exact to — volt the meas-
p j Fig. 44.
urement of current will be exact to am-
p X r
peres. If r = .5 ohm, and the readings are taken on a low-reading volt-
meter, say ranging from 0 to 5 volts, and that can be read to ^ volt, then
the possible error will be
300 x .5 — 150
MEASURING RESISTANCE WITH A VOLTMETER. 57
If r be made equal to 1 ohm, then the volts read also mean amperes.
Measurement of "Very Heavy Currents with a. Milli-
voltmeter.
For this purpose the method outlined above is most generally used with
the substitution of a millivoltmeter for the voltmeter.
Where portable instruments are used, there must be a calibrated shunt
fur the millivoltmeter, the shunt being made up of a metal that does not
vary in resistance with change of temperature, and which is placed in series
in the circuit, the millivoltmeter simply giving the drop around this shunt,
its scale being graduated in amperes.
For switchboard instruments the method is the same, being varied some-
times by using as a shunt a measured part of a conductor or bus bar in place
of a special resistance.
MEASURING RESISTAIIfCE WITH A VOLTMETEB.
General Methods. — In the figure, let Ir: the unknown resistance
that is to be measured, r = a known resistance, E, the dynamo or other
steady source of E.M.F.
When connected as shown in the figure, let
the voltmeter reading be V; then connect the
voltmeter terminals to r in the same manner
and let the reading be Vx ; then
X:r\: V : Vx
and x=r^-^.
If, for instance, r = 2 ohms and V = 3 volts
and V1 = 4 volts then
v 2x3 .' .
X =. — - — = 1.5 ohms.
If readings can be made to rJ-n volt, the error of resistance measurement
will then be
100 XTb (-y + jr) Per
cent.
and for the above example would be
1 (J + A) = 0.58%.
Should there be a considerable difference between the magnitudes of the
two resistances X and r, it might be better to read the drop across one of
them from one scale, and to read the drop across the other on a lower scale.
Resistance Measurement with Voltmeter and Ammeter.
The most common modification of the above method is to insert an am-
meter in place of the resistance r in the last figure, in which case X=-j.
where /is the current flowing in amperes as read from the ammeter.
If the readings of the voltmeter be correct to T-J-ff and the ammeter read-
ings be correct to the same degree, the possible error becomes :
100 x (iniU+ tsrt) = Per cent-
measurement of Very Small Resistances with a HEillivolt-
meter and Ammeter.
By using a millivoltmeter in connection with an ammeter, very small re-
sistances, such as that of bars of copper, armature resistance, etc., can be
accurately measured.
58
M E A S U R K1\I E N TS .
Fig. 46.
In order to have a reasonable degree of accuracy in measuring resistance
by the "drop" method, as this is called, it is necessary that as heavy cur-
rents as may be available be used. Then, if E be the dynamo or other source
of steady E.M.F., X be the required resistance of a portion of the bar, /' be
the drop in potential between the points a and b, and 1 be the current flow-
ing in the circuit as indicated by the ammeter, then
' x=f
The applications of this method are endless, and but a few, to which it is
especially adapted, need be mentioned here. They are the resistance of
. armatures, the drop being taken from opposite commutator bars and not
from the brush-holders, as then the brush-contact resistance is taken in ; the
resistance of station instruments and all switchboard appliances, such as
the resistance of switch contacts ; the resistance of bonded joints on electric
railway work, as described in the chapter on railway testing.
.vS«'i«.*(as-«»iii€*nt of Mig-le Resistances.
With the ordinary voltmeter of high internal resistance, let R be the re-
sistance of the voltmeter, X be the resistance to be measured. Connect them
up in series with some source of electro-
motive force as in the following figure.
Close the switch b, and read the voltage
V with the resistance of the voltmeter
alone in circuit ; then open the switch,
thus cutting in the resistance A", and take
another reading of the voltmeter, Vr
Then X — r[Z.— \\.
If the readings of the voltmeter be cor-
rect to ^ of a volt the error of the above
10 / V + V,
result will be
g(£^)>
CTEASirnilfG ^ME JATSA2,AT*«;V OF HftEffT»'»
A I¥I» POWER CIBCIITS WITH A iOITMETEH.
For rough measurements, where the exact insulation resistance is not re-
quired, but it is wished to determine if such resistance exceeds some stated
figure or rate, then the method above given will do, when applied as fol-
lows : —
Let X = insulation resistance to ground as in figure,
X, = insulation resistance to ground of opposite lead,
/(• = resistance of voltmeter,
V— potential of dynamo E,
V, = reading of voltmeter, as connected in figure,
Vtl =r reading of voltmeter, when connected to opposite lead.
MEASURING THE INSULATION.
59
"^r Ground
FIG. 48.
and
X, = R\
V„
The above formula can be modified to give results more nearly correct by
taking into account the fact that the path through the resistance R of the
voltmeter is in parallel with the leak to ground on the side to which it is
connected as shown in the following figure : —
In this case the voltage V of the circuit will not only send current through
the lamps, but through the leaks e f to ground, and through the ground to
d and c, thence through d to b, and'c to a, these two last paths being in par-
allel, therefore having less resistance than if one alone was used ; thus if r
be the resistance of the ground leak b d, and rx be the resistance of the leak
l' ,/", and R be the resistance of the voltmeter, then the total resistance by
way of the ground, between the conductors, would be
R X r
R + r^r»
and if V= voltage of the circuit,
v = reading of voltmeter from a to c,
v, = reading of voltmeter from q to c.
Then r = R(V-<P + *Z\
and
-«(-
-(«+»/) \
The sum of the resistance r + rx will be = R
V v + v, )
Insulation Resistance of Arc Circuits.
As arc lamps are by much the larger extent run in series, the insulation
resistance of their circuits is found in a manner similar to that for multiple
60
MEASUREMENTS.
circuits, but the formula differs a little. Let the following figure be a
typical arc circuit, with a partial ground at c.
First find the total voltage V between a and b of the circuit. This can
most handily be done with a voltmeter having a high resistance in a sepa
rate box and so calibrated with the voltmeter as to multiply its readings bj
-* * * * * *—
some convenient number. For convenience in locating the ground, get the
average volts per lamp by dividing the total volts V by the number of lamps
on the circuit ; the writer has found 48 volts to be a good average for tbe
ordinary 10 ampere lamp. With the 16 lamps shown in the above figure, V
would probably be about 768 volts.
Next take a voltmeter reading from each end of the circuit to ground.
Call the reading from a to ground v, and from b to ground r/? R being the
resistance of voltmeter as before, and r the insulation resistance required.
' V
-(»-
■tvA
Then i
\ v T '<-'/ /
and the location of the ground, provided there be but one and the general
insulation of the circuit be good, will be found closely proportional to the
readings v and v, ; in the above figure say we find the voltmeter reading
from a to ground to be '28, and from b to ground to be 36 ; then the distance
of the ground c from the two ends of the circuit will be in proportion to the
readings 28 and 36 respectively.
There being 16 lamps on the circuit, the number of lamps between a and c
would be 28 -|- (28 + 36) = §§ of 16 = 7, and from b to c would be 36 -f-
(28 + 36) = §| of 16 = 9 ; that is, the ground would most likely be found be-
tween the seventh and eighth lamps, counting from a.
Insulation across a Double I»ole Fuse Block or €>tJ»:«
Similar Device where Both Terminal!* are on
the Same Base.
Let ff be fuses in place on a base,
V — potential of circuit,
R = resistance of voltmeter,
v = reading of voltmeter,
required the resistance r across the base
a a, to b &..
V— v
Then r — R .
MEASUH1XG THE IWS1T- Fig. 51.
LATIOli OF BYlfAMOS.
The same formula as that used for measuring high resistances (see Fig.
47) applies equally well to determining the insulation of dynamo conductors
from the iron body of the machine
MEASURING THE INSULATION RESISTANCE.
61
Connect, as in Fig. No. 52, all symbols having the same meaning as
before.
Let r = insulation resistance of dynamo, then
r^-(f-l).
MEA§rKIIIfG THE IlillATIOlf RESISTANCE ©e
MOTORS.
Where motors are connected to isolated plant circuits with known high
insulation, tbe formula vised for insulation of dynamos applies ; but where
tbe motors are connected to public circuits of questionable insulation it is
necessary to first determine the circuit insulation, which can be done by
using the connections shown in Fig. 48. Fig. 53 shows tbe connections to
motor for determining its insulation by current from an operating circuit.
Here, as before, the insulation
total connected devices
If r = total resistance of circuit and motor in multiple to ground, and r,
is the insulation of the circuit from ground, then X, the insulation of the
motor will be X= — .
MEASUREMENT OF THE RESISTANCE OF THE
HITMAN BODY.
The jars jj of the following figure (No. 51) are filled with a weak solution
of caustic potash ; the person whose resistance is to be measured places his
"lands in the jars, if the measurement is to be made from hand to hand, or
62
MEASUREMENTS.
makes an equally good connection with, any other desirable portion of the
body.
First take a reading of the voltmeter with the switch K closed ; then
voltmet.
subject
■■■it plunge his hands
jars, open the switch A,
-' another reading of the
r. The resistance r of the
ill be
■ft-*
in which It is the resistance of
voltmeter,
Fis the reading of volt-
meter alone,
V, is the reading of volt-
meter with switch K
open and the subject
in series with volt-
meter.
1HEASVRE1HEIIT OF THE OTEBIA1 RE§I§TAHfCE
OF A BATTFRT.
3 following figure (No. 55), let E be the cell or battery whose resistance
is to be measured, A' be a switch, and
r a suitable resistance.
Liet V = the reading of voltmeter
with the kev, A', open
(this is the E.M.F. of the
battery), and
V, — the reading of voltmeter
with key, A', closed (this
is the drop across the re-
sistance r),
Then the battery resistance
— yp — - ohms.
Fig. 55.
-r x -
nieyiexn-froelicii keihod.
In the following figure (No. 56), let E be the cell or battery to be measured,
K a switch for closing resistance r to
B or c ; r, rx and r2 be suitable resis- *■.
tances connected as' shown. The volt-
meter should of course be a low-reading
one. Close by the key A", A and c, and
read the voltmeter ; next close by the
key A', A and B, and rend the volt-
meter; then adjust r2 until the volt-
meter reading is the same for either
position of the key K, and r., is then
equal to the resistance of the battery E.
In most cases it is best to connect
some known resistance in series with the cell, so that the current may not
be excessive and harm the celV ; if this be done, of course it is necessary to
deduct this known resistance from the final reading r2.
Fig. 56.
COSDECTIVITY WITH A MILIIVOITIHETEB.
This is a quick and convenient method of roughly comparing the conduc-
tivity of a sample of metal with that of a standard niece.
In" Fig. 57, R is a standard bar of copper of 100% conductivity at 70° F. ;
this bar may be of convenient length for use in the clamps, but of known
CONDUCTIVITY WITH A MILLIVOLTMETER.
63
cross section. X is the piece of metal of unknown conductivity, but of the
same cross section as the standard. E is a source of steady current, and if
a storage battery is available it is much the better for the purpose. M is a
millivoltmeter with the contact device d. The distance apart of the two
points may be anything, so long as it remains unaltered and will go between
the clamps on eitner 01 the bars.
Now with the current tioAving through the two bars in series the fall of
potential between two points the same distance apart and on the same flow-
FlG, 57.
line will, on either bar, be in proportion to the resistance, or in inverse pro
portion to the conductivity ; therefore by placing the points of d on the bars
in succession, the readings of the millivoltmeter will give the ratio of the
conductivities of the two pieces.
For example : —
if the reading from B = 200 millivolts,
and tbe reading from X = 205 millivolts,
then the percentage conductivity of X as compared with R is
205 : 200 : : 100 : conductivity of X,
200 X 100 Q„
205 =97-5%°
MAGNETIC PROPERTIES OP IRON.
With a given excitation the flux <t> or flux-density (B of an electromagnet
will depend upon the quality of the iron or steel of the core, and is usually
rated as compared with air.
If a solenoid of wire be traversed with a current, a certain number of
magnetic lines of force, 3£,will be developed per square centimetre of the
core of air. Now, if a core of iron be thrust into the coil, taking the place of
the air, many more lines of force will flow ; and at the centre of the solenoid
these will be equal to (^ lines per square centimetre.
As iron or steel varies considerably as to the number of lines per square
centimetre (ft which it will allow to traverse its body with a given excitation,
its conductivity towards lines of force, which is called its permeability, is
numerically represented by the ratio of the flux-density when the core is
present, to the flux-density when air alone is present. This permeability
is represented by /u..
The permeability /x of soft wrought iron is greater than that of cast iron ;
and that for mild or open-hearth annealed steel castings as now made for
dynamos and motors is nearly, and in some cases quite, equal to the best
soft wrought iron.
The number of magnetic lines that can be forced through a given cross-
section of iron depends, not only on its permeability, but upon its satura-
tion. For instance, if but a small number of lines are flowing through the
iron at a certain excitation, doubling the excitation will practically double
the lines of force ; when the lines reach a certain number, increasing the
excitation does not proportionally increase the lines of force, and an excita-
tion may be reached after which there will be little if any increase of lines
of force, no matter what may be the increase of excitation.
Iron or steel for use in magnetic circuits must be tested by sample before
any accurate calculations can be made.
Data for (B-3C Curves.
Average First Quality American Metal.
(Sheldon.)
d
A
Cast Iron.
Cast Steel.
Wrought Iron
Sheet Metal.
-j H z!J
2£s
CO
M 53 .
w
X CD .
j
oi
X a>
^
&a'1
2<s -
IS!
S as
a a-:
1 ®
5 &a
« cc""!
e!|
<s|f
Op; ^
°
X *
\a £
W^
W £
10
7.95
20.2
4.3
27.7
11.5
74.2
13.0
83.8
14.3
92.2
20
15.90
40.4
5.7
36.8
13.8
89.0
14.7
94.8
15.6
100.7
30
23.85
60.6
6.5
41.9
14.9
96.1
15.3
98.6
16.2
104.5
40
31.80
80.8
7.1
45.8
15.5
100.0
15.7
101.2
16.6
107.1
50
39.75
101.0
7.6
49.0
16.0
103.2
16.0
103.2
16.9
109.0
GO
47.70
121.2
8.0
51.6
16.5
106.5
16.3
105.2
17.3
111.6
70
55.65
141.4
8.4
59.2
16.9
109.0
16.5
106.5
17.5
112.9
80
63.65
161.6
8.7
56.1
17.2
111.0
16.7
107.8
17.7
114.1
90
71.60
181.8
9.0
58.0
17.4
112.2
16.9
109.0
18.0
116.1
100
79.50
202.0
9.4
60.6
17.7
114.1
17.2
110.9
18.2
117.3
150
119.25
303.0
10.6
68.3
18.5
119.2
18.0
116.1
19.0
122.7
200
159.0
404.0
11.7
75.5
19.2
123.9
18.7
120.8
19.6
126.5
r,o
198.8
505.0
12.4
80.0
19.7
127.1
19.2
123.9
20.2
130.2
you
238.5
606.0
13.2
85.1
20.1
129.6
19.7
127.1
20.7
133.5
JC = 1.258 ampere turns per cm. = .495 ampere turns per inch.
64
MAGNETIC PROPERTIES OF IRON.
65
Co) s
g I
i 11
§
a
UL"
1
g
LU
1
1
g
T
g
1
\
g
ill
\
s
H
g
\_M_
;\
F
<
i\ B\ 1
o
Ul
\ \
8
<
o
f\\
.1 \
S
Ij
\\\
1
_ g
:>
\\\
i
g
>
\\
?
_J
D
^rr
1-
?\
tt
*\
u
C5
<
i\
I
DC
UJ
<■
i\ \\
\ \\
\i ^
\
\
\\
V
ssS
.
T-r
^1
honi auvn&s aad s-naMxvwoira
Fig. 1. Magnetic Properties of Iron.
6Q
MAGNETIC PROPERTIES OF IRON.
In large generators, having toothed armatures and large flux densities in
the air-gap, the flux is carried chiefly by the teeth. This results in a very
high tooth flux density, and a corresponding reduced permeability. The
related values of (g,3Cand m. are given in the following table. These values
are for average American sheet metal.
Permeability at Hig-h Flux Densities.
Ampere
Ampere
(B
Kilomax-
3C
Turns per
Turns per
Kilo-
wells per
V-
cm. Length.
Inch Length.
grammes.
Square in.
200
159
404
19.8
127
99.0
400
318
808-
21.0
135
52.5
600
477
1212
21.5
138
35.8
800
637
1616
21.8
140
27.3
1000
795
2020
22.0
142
22.0
1200
954
2424
22.3
144
1.8
1400
1113
2828
22.5
145
1.6
METHODS OF HG1EK.W B XI .X« THE HACKETIC
4tr.4LITIKM OF IRON AID §TF£I.
The methods of determining the magnetic value of iron or steel for elec-
tro-magnetic purposes are divided by Prof. S. P. Thompson into the follow-
ing classes : Magnetometric, Balance, Ballistic, and Traction.
The first of these methods, now no longer used to any extent, consists in
calculating the magnetization of a core from the deflection of a magneto-
meter needle placed at a fixed distance.
In the Balance class, the deflection of the magnetometer needle is bal-
anced by known forces, or the deflection due to the difference in magnetiza-
tion of a known bar and of a test bar is taken.
The Ballistic method is most frequently used for laboratory tests, and for
such cases as require considerable accuracy in the results. There are really
two ballistic methods, the Ring method and the Dirided-bar method.
In either of these methods the ballistic galvanometer is used for measur-
ing the currents induced in a test coil, by reversing the exciting current, or
cutting the lines of force.
Ring- Method. — The following cut shows the arrangement of instru-
ments for this test, as used by Prof. Rowland. The ring is made of the
sample of iron which is to undergo test, and is uniformly wound with the
CELLS ^=- l_ <
Fig. 2. Connections for the Ring Method.
exciting coil or circuit, and a small exploring coil is wound over the excit-
ing coil at one point, as shown. The terminals of the latter are connected
to the ballistic galvanometer.
MAGNETIC TEST METHODS. 67
The method of making a test is as follows : —
The resistance, R, is adjusted to give the highest amount of exciting cur-
rent. The reversing switch is then commutated several times with the gal-
vanometer disconnected. After connecting the galvanometer the switch is
suddenly reversed, and the throw of the galvanometer, due to the reversal
of the direction of magnetic lines, is recorded. The resistance, R, is then
adjusted for a somewhat smaller current, which is again reversed, and the
galvanometer throw again recorded. The test is carried on with various
exciting currents of any desired magnitude. In every case the exciting cur-
rent and the corresponding throw of the galvanometer are noted and
recorded.
If i — amperes flowing in the exciting coil,
nx = number of turns of wire in exciting coil,
I = length in centimetres of the mean circumference of the ring,
then the magnetizing force
ae= § xf or 1.257 x«.
If I" = length of the ring in inches, then
0C"=.495X^.
If 0 = the throw of the galvanometer,
K= constant of the galvanometer,
R = resistance of the test coil and circuit,
n2 = number of turns in the test coil,
a = area of cross-section of the ring in centimetres, then
^p 10s RK9
To determine K, the constant of the galvanometer, discharge a condenser
of known capacity, which has been charged to a known voltage, through it,
and take the reading 01, then
If c — capacity of the condenser in microfarads,
e = volts pressure to which the condenser is charged,
then the quantity passing through the galvanometer upon discharge in
coulombs is Q^i^oo-
and the galvanometer constant
~ 1,000,000 01'
Dividecl-lSar Uletliod. — As it is often inconvenient or impossible to
obtain samples in the form of division in» -ammeter
a ring, and still more incon-
venient to wind the coils on it,
Hopkinson devised the di-
vided-bar method, in which
the sample is a long rod \"
diameter, inserted in closely
fitting holes in a heavy
wrought iron yoke, as shown ■ C0ILS
in the following cut. _ /~^\ v to v--meah.cength
In the cut the exciting coils \£_J l of test piece!
are in two parts, and receive ballistic
current from the battery and galvanometer . , ,.
through the ammeter, resist- FlG. 3. Arrangement for Hopkinson s ai-
ance, and reversing switch, vided-bar method of measuring permea-
as shown. bility. _
The test bar is divided near the centre at the point indicated m tlie cut,
and a small light test coil is placed over it, and so arranged with springs as
68
MAGNETIC PROPERTIES OF IRON.
to be thrown clear out of the yoke when released by pulling out the loose
end of the test bar by the handle shown.
In operation, the exciting current is adjusted by the resistance J?, the test
bar suddenly pulled out by the handle, thus releasing the test coil and pro-
ducing a throw of the galvanometer. As the current is not reversed, the
induced pressure is due to jVonly, and the equation for (^ is
10» R K t
and
X— TTv X
"Where L = the mean length of the test rod as shown in the cut.
In using the divided-bar method, a correction must be made, for the rea-
son that the test coil is much larger than the test rod, and a number of
lines of force pass through the coil that do not through the rod. This cor-
rection can easily be determined by taking a reading with a wooden test
rod in place of the metal one.
An examination of the cut will show that the bar and yoke can also be
used for the method of reversals.
The fourth or Traction class is exceedingly simple, and was devised by
Prof. Silvanus P. Thompson.
The following cut shows the method with sufficient clearness. A heavy
yoke of wrought iron has a small hole in one end through which the test
rod is pushed, through the exciting coil
shown, and against the bottom of the
yoke, which is surfaced true and smooth,
as is the end of the test rod.
In operation, the exciting current is ad-
justed by the resistance 11, and the spring
balance is then pulled until the sample or
test rod separates from the yoke, at which
time the pull in pounds necessary to pull
them apart is read. Then
(B = 1,317 X
sll
+ JC-
Fig.
Where P = pull in pounds as shown on
the balance,
A = area of contact of the rod
and yoke in square inches.
J(Ms found as in the Hopkinson method
preceding this.
Following is a description of a practical adaptation of the permeameter to •
shop-work as used in the factory of the Westinghouse Electric and Manu-
facturing Co. at Pittsburgh, Pa.
S. P. Thompson's per-
meameter.
The Permeameter, as used Ity the IVestiiigrhouse Electric
and Mfg-. Co,
Design and Description prepared by Mr. C. E. Skinner.
A method of measuring the permeability of iron and steel known as the
" Permeameter Method " was devised by Prof. Silvanus P. Thompson, and is
based on the law of traction as enunciated by Clerk Maxwell. According to
this law the pull required to break any number of lines of force varies as the
square of the number of lilies broken.' (A complete discussion of the theory
of the permeameter, with the derivation of the proper formula for calculating
the results from the measurements will be found in the " Electro Magnet,"
by Prof. S. P. Thompson.,
A permeameter which has been in use for several years in the laboratory
of the Westinyhouse Electric and Manufacturing Company, and which has
given excellent satisfaction, is shown in the accompanying drawings. The
THE PERMEAMETER, 69
yoke, A, consists of a piece of soft iron 1" x %\" x 2J", with a rectangular
opening in the centre 2J" x 4". The sample, X, to he tested is %" in diam-
eter and 1\" long, and is introduced into the opening through a %" hole in the
yoke, as shown in the drawing. The test sample is finished very accurately to
\" in diameter, so that it makes a very close tit in the hole in the yoke. The
lower end of the opening in the yoke and the lower end of the sample are
accurately faced so as to make a perfect joint. The upper end of the sam-
ple is tapped to receive a \" screw %" long, twenty threads per inch, by
means of which a spring balance is attached to it. The magnetizing coil, C,
is wound on a brass spool, S, 4" long, with the end flanges turned up so that
it may be fastened to the yoke by means of the screws. The axis of the coil
coincides with the axis of the yoke and opening. The coil has flexible leads,
which allow it to be easily removed trom the opening for the inspection of
the surface where contact is made between the yoke and the test sample.
The spring balance, F, is suspended from an angle iron fastened to the up-
right rack, 7, which engages with the pinion. J. The balance is suspended
exactly over the centre of the yoke through which the sample passes, to
avoid any side pull. A spring buffer, K. is provided, which allows perfectly
free movement of the link holding the sample for a distance of about \'f,
and then takes up the jar consequent upon the sudden release of the sample.
The frame, B, which supports the pulling mechanism, is made of brass, and
has feet cast at the bottom, by means of which the complete apparatus is
fastened to the table. Two spring balances are provided, one reading to 30
lbs. and the other to 100 lbs. These spring balances are of special construc-
tion, having comparatively long scales. (They were originally made self-
registering ; but this was found unnecessary, as a reading could be taken
with greater rapidity and with sufficient accuracy without the self-register-
ing mechanism.) Any good spring balance may be used. The spring should
be carefully calibrated from time to time over its Avhole range ; and if there
is a correction it will be found convenient to use a calibration curve in cor-
recting the readings. With a sample \" in diameter, or § of a square inch
area cross-section, the maximum pull required for cast iron is about 25 lbs.,
and for mild cast steel about 70 lbs.
With the number of turns on the coil given above, the current required
for obtaining a magnetizing force of JC^ 300, is about 12.5 amperes. This
is as high a value as is ever necessary in ordinary work. For furnishing the
current a storage battery is ordinarily used, and the variations made by
means of a lamp board which has in addition a sliding resistance, so that
variations of about .01 ampere may be obtained over the full range of cur-
rent from 0.1 ampere to 12.5 amperes.
The operation of the permeameter is as follows : —
The sample to be tested is first demagnetized by introducing it into the
field of an electro-magnet with a wire core, through which an alternating
current is passing, and gradually removing it from the field of this electro-
magnet. The sample is then introduced into the opening in the yoke, care
being taken to see that it can move without friction. Measurements are
taken Avith the smallest current to be used first, gradually increasing
to the highest value desired. In no case should a reading be taken with a
current of less value than has been reached with the sample in position,
unless the sample is thoroughly demagnetized agaiti before reading is taken.
It is usually most convenient to make each successive adjustment of cur-
rent with the sample out of position, then introduce the sample and give it
a half turn, to insure perfect contact between the sample and tiie yoke. The
lower end of the sample and the surface on which it rests should be care-
fully inspected to see that no foreign matter of any kind is present which
might introduce serious errors in the measurements. The pull is made by
turning the pinion slowly by means of a handle, E, carefully noting each
position of the index of the spring balance as it advances over the scale,
and noting the point of release. The mean of three or four readings is
usually taken as the corrected value for pull, the current in the coil remain-
ing constant. With practice the spring balance can be read to within less
than 1% ; and as the square root of the pull is taken, the final error becomes
quite small, especially with high readings.
The evaluation of the results for the above permeameter are obtained by
the use of the following formula : —
.70
MAGNETIC PROPERTIES OF IRON.
Where % = number of turns in the magnetizing coil = 223,
i = current in amperes,
I = length of magnetic circuit in centimetres, estimated in this
case as 11.74.
Substituting the known values in the above formula we have
3C = 23.8 i.
The number of lines of force per square centimetre,
(B = 1,317 y/^ + OC-
Where P = pull in lbs.
A = area of the sample in square inches = 0.3068.
^fC^ value of the magnetizing force for the given pull.
THE PEEMEAMETER.
fl
Substituting the value of A in the above formula we have
(£=:2,3S0Vp + 3e.
There are several sources of error in measurements made by the permea-
meter which should be carefully considered, and eliminated as far as possible.
a. The unavoidable air gap between the sample and the yoke where it
passes through the hole in the upper part of the yoke, together with the
more or less imperfect contact at the lower end of the sample, increases the
magnetic reluctance and introduces errors for which it is impossible to make
due allowance. By careful manipulation, however, these can be reduced
to a minimum, and be made practically constant.
b. As the magnetization becomes greater the leakage at the lower end of
the sample increases more rapidly ; and there is considerable error at very
high values from this source, as the leakage lines are not broken with the
rest.
c. Errors in the calibration and reading of the spring balance. None
but the best quality of spring balance should be used, and the average of
several readings taken with the current remaining perfectly constant for
each point on the (&-3C curve. As the square root of the pull is taken, the
errors due to reading the spring balance make a larger and larger percent-
age error in (R as P approaches zero, thus preventing accurate determina-
tions being made at the beginning of the curve.
72
MAGNETIC PROPERTIES OF IRON.
From the above it will be seen that the permeameter is not well adapted
for giving the absolute values of the quality of iron and steel, but is especially
suitable for comparative values, such as are noted in ordinary work, where
a large number of samples are to be quickly measured. A complete curve
can be taken and plotted in ten minutes. By suitable comparison of known
samples measured by more accurate methods, the permeameter readings may
be evaluated to a sufficient degree for use in the calculations of dynamo
electric machinery.
CORE BOSSES.
These result from Hysteresis and Eddy currents.
Professor Ewing has given the name Hysteresis to that quality in iron
which causes the lagging of the induction behind the magnetic force. It
causes a loss when the direction of the induction is reversed, and results in
a heating of the iron. It increases in direct proportion to the number of
reversals, and as the 1.6th power of the maximum value of the induction in
the iron core. The heat produced has to be dissipated either by radiation
or conduction, or by both. Steinmetz gives the following formula for hys-
teresis loss in ergs per cubic centimeter, of iron per cycle ; h = -q (ft1-6,
where 17 = a constant depending upon the kind of iron.
M j-*teretif Constants tor Different Mat a* rial*.
Material.
Very soft iron wire . .
Very thin soft sheet iron
Thin good sheet iron . .
Thick sheet iron . . .
Most ordinary sheet iron
Transformer cores . .
Soft annealed cast steel
Soft machine steel . .
Cast steel
Cast iron
Hardened cast steel . .
Hysteretic Constant.
.002
.0015
.003
.0033
.004
.003
.008
.0094
.012
.016
.025
Eddy Currents are the local currents in the iron core caused by the E.M.F's
generated by moving the cores in the field, and increase as the "square of the
number of revolutions per second. The cure is to divide or laminate the
core so that currents cannot flow. These currents cause heating, and unless
the core be laminated to a great degree, are apt to heat the armature core so
much as to char the insulation of its windings.
Wiener gives tables showing the losses by Hysteresis and Eddy currents
at one cycle per second, under different conditions. These are changed
into any number of cycles by direct proportion. Following are the
tables : —
CORE LOSS.
73
Hysteresis factors for ^Different Core Densities.
(Wiener.)
Watts dissipated at
A r
Watts dissipated at
A FREQUENCY OF ONE
A
a frequency of one
COMPLETE MAGNETIC
b1-! yA
2 ~ S
e> ~ o
W H «
fc m °
COMPLETE MAGNETIC
an K m
o u e
0«H
CYCLE PER SECOND.
CYCLE PER SECOND.
Sheet iron.
Iron
wire.
Sheet iron.
Iron
wire.
W <tj p
5 « N
p. eft.
p. lb.
p.c.ft.
per lb.
p.c.ft.
per lb.
p.c.ft.
perlb.
V
rj-i-480
V
Tj-HSO
< K fa
V
tH-4S0
V
ri^-480
10,000
1.25
.0026
14.3
.030
66,000
25.72
.0537
294.0
.613
15,000
2.40
.0050
27.4
.057
67,000
26.34
.0550
301.0
.628
20,000
3.79
.0079
43.3
.090
68,000
26.97
.0563
308.2
.643
25,000
5.42
.0113
62.0
.129
69,000
27.61
.0576
315.5
.658
30,000
7.30
.0152
83.5
.174
70,000
28.26
.0589
322.8
.673
31,000
7.70
.0160
88.0
.183
71,000
28.91
.0603
330.1
.688
32,000
8.10
j0168
92.6
.192
72,000
29.56
.0617
337.6
.704
33,000
8.50
.0177
97.2
.202
73,000
30.22
.0631
345.1
.720
34,000
8.91
.0186
101.8
.212
74,000
30.89
.0645
352.9
.736
35,000
9.33
.0195
106.5
.222
75,000
31.56
.0659
360.7
.752
36,000
9.76
.0204
111.5
.332
76,000
32.23
.0673
368.5
.768
37,000
10.20
.0213
116.5
.242
77,000
32.91
.0687
376.3
.784
38,000
10.65
.0222
121.6
.253
78,000
33.60
.0701
384.2
.800
39,000
11.10
!0231
126.8
.264
79,000
34.29
.0715
392.1
.817
40,000
11.55
.0240
132.0
.275
80,000
34.99
.0730
400.0
.834
41,000
12.01
.0250
137.2
.286
81,000
35.69
.0745
408.0
.851
42,000
12.48
.0260
142.5
.297
82,000
36.40
.0760
416.0
.868 .
43,000
12.96
.0270
148.0
.308
83,000
37.11
.0775
424.0
.885
44,000
13.45
.0280
153.7
.320
84.000
37.82
.0790
432.4
.902
45,000
13.95
.0290
159.4
.332
85,000
38.54
.0805
440.8
.919
46,000
14.45
.0300
165.1
.344
86,000
'39.27
.0820
449.2
.936
47,000
14.95
.0311
170.8
.356
87,000
40.01
.0835
457.0
.954
48,000
15.45
.0322
176.6
.368
88,000
40.75
.0850
466.0
.972
49,000
15.96
.0333
182.4
.380
89,000
41.50
.0865
474.5
.990
50,000
16.48
.0344
188.3
.392
90,000
42.25
.0881
483.0
1.008
51,000
17.01
.0355
194.3
.405
91000
43.00
.0897
491.5
1.023
52,000
17.55
.0366
200.6
.418
92,000
43.76
.0913
500.0
1.042
53,000
18.10
.0377
206.9
.431
93,000
44.53
.0929
509.0
1.064
54,000
18.65
.0388
213.2
.444
94,090
45.30
.0945
518.0
1.080
55,0u0
19.21
.0400
219.5
.457
95,000
46.07
.0961
527.0
1.098
56,000
19.78
.0412
226.0
.470
96,000
46.85
.0977
536.0
1.116
57,000
20.35
.0424
232.6
.484
97,000
47.63
.0993
545.0
1.135
58,000
20.92
.0436
239.2
.498
98,000
48.41
.1009
554.0
1.154
59,000
21.50
.0448
245.8
.512
99,000
49.20
.1025
563.0
1.173
60,000
22.09
.0460
252.5
.526
100,000
50.00
.1041
572.0
1.192
61,000
22.69
.0472
259.4
.530
105,000
54.06
.1127
618.0
1.290
62,000
23.29
.0485
266.3
.554
110,000
58.23
.1215
666.0
1.388
63,000
23.89
.0498
273.0
.568
115,000
62.53
.1305
715.0
1.490
64,000
24.50
.0511
280.0
.583
120,000
66.95
.1400
765.0
1.595
65,000
25.11
.0524
287.0
.598
125,000
71.50
.1500
817.5
1.705
74 MAGNETIC PROPERTIES OF IRON.
Tl»e Stei»-l»y°i§tep Method of Hysteresis Test.
The samples for hysteresis tests, being generally of sheet iron, are made
in the form of annular disks whose inner diameters are not less than {j of
their external diameter. A number of these disks are stacked on top of
each other, and the composite ring is wound with one layer of wire form-
ing the magnetizing coil of nt turns. This coil is connected through a re-
versing switch to an ammeter in series with an adjustable resistance, and a
storage battery. A secondary test coil of »2 turns is connected with a bal-
listic galvanometer, as shown in Fig. 7.
Fig. 7.
To make the test, adjust the resistance for the maximum exciting current.
Reverse the switch several times, the galvanometer being disconnected.
Then connect the galvanometer, and reduce the current by moving the con-
tact arm of the rheostat up one step. This rheostat must be so constructed
that an alteration in resistance can be made wit/tout ojienhuj the i-ircuit even
for an instant. Note the throw in the galvanometer corresponding to the
change in exciting current. Follow this method by changing resistance
step-by-step until the current reaches zero. Reverse the direction, and in-
crease step-by-step up to a maximum and then back again to zero. Reverse
once more, and increase step-by-step to the original maximum. In every
case note and record the value of the exciting current i, and the corre-
sponding throw of the galvanometer, 6. Form a table having the following
headings to its columns : —
i, X. 6> change of (B, ($>.
Values of Hare obtained from the formula,
47r n %
JC = ' , when I = average circumference of the test ring.
Change of (Bis obtained by the formula,
10s R K 9
a n2 '
where all letters have the same significance as in the formula on page 67.
Remember that we started in our test with a maximum unknown value of (B,
and that we gradually decreased this by steps measurable by the throw of
the galvanometer, and that we afterwards raised the (Bin an opposite direc-
tion to the same maximum unknown value, and still further reduced this to
zero, and after commutation produced the original maximum value. Ac-
cording to this, if due consideration be paid to the sign of the (B which is
determined by the direction of the galvanometer throw, the algebraic
sum of the changes in (B should be equal to zero ; the algebraic sum of the
first or second half of the changes in (B should be equal to twice the value
of the original maximum, (B- Taking this maximum value as the first under
the column of the table headed (B, and applying algebraically to this the
changes in (B for successive values, we obtain the completed table. Plot
a curve of 3Cam"l(B* Tne area enclosed represents the energy lost in carry-
ing the sample through one cycle of magnetization between* the maximum
limits -(-(Band — (B- Measure this area, and express it in the same units as
is employed for the co-ordinate axes of the curve. This area divided by 4ir
CORE LOSS.
75
gives the number of ergs of work performed per cycle upon one cubic centi-
meter of the iron, the induction being carried to the limits -f- (Band — (B-
The "Wattmeter Method of Hysteresis Tests.
Inasmuch as the iron, a sample of which is submitted for test, is generally
to be employed in the manufacture of alternating-current apparatus, it is
desirable to make tbe test as nearly as possible under working conditions.
If the samples be disks, as in the previous method, and these be shellacked
on both sides before being united into the composite test-ring in order to
avoid as much as possible foucault current losses, the test can be quickly
made according to the method outlined in the following diagram : —
Fig. 8. Wattmeter Test for Hysteretic Constant.
Alternating current of / alternations per second is sent through the test-
ring. Its voltage, E, and current strength, i, are measured by the alternating-
current voltmeter, V, and ammeter, A. If r be the resistance of the test-
ring coil of 7i1 turns, then the watts lost in hysteresis W, is equal to the
wattmeter reading W — i2r. If the volume of the iron be V cubic centi-
meters, and the cross section of the iron ring be a square centimeters, then
Steinmetz's hysteretic constant
V = -
107 W
Vf
'V2tt nxfa\
EW )
Foucault current losses are neglected in this
formula, and the assumption is made that the
current is sinusoidal.
Kwiisg-',-* Hysteresis Tester. — In this in-
strument, Fig. 9, the test sample is made up of
about seven pieces of sheet iron §" wide and 3"
long. These are rotated between the poles of a
permanent magnet mounted on knife edges.
The magnet carries a pointer which moves
over a scale. Two standards of known hyster-
esis properties are used for reference. The de-
flections corresponding to these samples are
plotted as a function of their hysteresis losses,
and a line joining the two points thus found is
referred to in subsequent tests, this line show-
ing the relation existing between deflection and
hysteresis loss. The deflections are practically
tbe same, with a great variation in the thick-
ness of the pile of test-pieces, so that no cor-
rection has to be made for such variation. This
instrument has the advantage of using easily
prepared test samples.
Fig. 9.
Hysteresis Meter, Used by General Electric Co.
Designed and Described by Frank Holden.
During the last few weeks of the year 1892 there was built at the works of
the General Electric Company, in Lynn, Mass., under the writer's direction,
an instrument, shown in Fig. 10, by which the losses in sheet iron were
determined by measuring the torque produced on the iron, which was
punched in rings, when placed between the poles of a rotating electro-mag-
net. The rings were held by a fibre frame so as to be concentric with a
7(5
MAGNETIC PROPERTIES OF IRON.
vertical shaft which worked freely on a pivot bearing at its lower end
They had a width of 1 centimeter, an outside diameter of 8.9 centimeters,
and enough were used to make a cylinder about
1.8 centimeters high. The top part of this in-
strument, which rested on a thin brass cylin-
der surrounding the rings, was movable. On
the upper surface was marked a degree scale,
over which passed a pointer, with which the
upper end of a helical spring rotated. It was
so constructed that when the vertical shaft
with the rings and the upper part of the instru-
ment with the spring was put in place, the
lower end of the spring engaged with the shaft,
and consequently rotated with the rings. A
pointer moving with the lower end of the spring
reached to the zero of the degree scale when
the apparatus was ready for use. By this ar-
rangement it was found what distortion it was
necessary to give the spring in order to bal-
ance the effect of the rotating magnet, and the
spring having been calibrated, the ergs spent
Fig. 10. Hysteresis Meter, on the rings per cycle were determined by mul-
tiplying the degrees distortion by a constant.
A coil, so arranged that it surrounded but did not touch the rings, made
contact at its ends with two fixed brushes that rested in diametrically oppo-
site positions on a two-part commutator, which revolved with a magnet.
The segments were connected each to a collector ring against which rubbed
a brush, the latter two brushes being joined through a sensitive Weston
voltmeter. If this were so arranged that the coil was at right angles to the
1000
.\-(,o
3000
4!A\!
5000
t
'
X)
7000
.
CYCL
SUO0
- c
"
ex
)
-
r
E
:WJ
7000
0000
/
2000
-
3000
1000
Fig. 11.
induction, when the brushes changed contact from one segment to the other,
it is evident, the self-induction of the circuit being negligible, that the
mean value of the current in the circuit was proportional to the total flux
through the coil. Knowing the constant of the voltmeter, the deflection Avas
easily calculated from the speed of the magnet, the number of turns in the
coil, cross-section of the rings, and the resistance of the circuit. From an
induction of 2,000 gausses to at least 10,000 gausses, the leakage across the
interior space of the rings was negligible.
Carried on the shaft below the magnet was a pulley around wThich passed
a flat belt driven with a pulley of the same size on an electric motor, so that
the speed of the magnet could be found by observing that of the motor. In
operating, the deflections to be produced on the voltmeter at a certain speed,
with the desired induction in the rings, were first calculated. Five hundred
HYSTERESIS METER.
revolutions per minute was generally adopted as the speed in this case.
The motor being run at the desired speed, the magnetizing current was ad-
justed until the calculated deflection was produced on the voltmeter. Keep-
ing the magnetizing current constant, the speed was changed successively in
value to certain values, and the corresponding distortions of the spring
necessary to balance the effect of the magnet noted. When this process
was carried out at different induction values, and the ergs expended per
cycle on the rings plotted as a function of the speed, a series of lines was
produced, as shown in Figs. 11 and 12. It was found that the slope of the
lines decreased very rapidly with the decrease in thickness of the iron sheet
used so as to indicate that had it been thin enough the slope would have
been zero between 100 and 800 revolutions per minute, which was about the
highest speed permissible. From this it would seem that, in these tests, the
total loss per cycle had two components ; one remaining constant, due to
hysteresis, and the other varying as the speed of the magnets, due to cur-
rents induced in the iron.
Fig. 15 gives observations of eddy current loss and thickness of iron sheet
on this assumption. The line drawn is a parabola, so that it would appear
that with the range of observations made the loss varied about as the square
of the thickness of the sheets.
1000 2000 3000' 4000 5000 6000 7000
7000 =
6000-
6000-
4000;
3000^
r
-;
i
1
:
-
C
3
,
/
400 500 GOO 700
REVOLUTIONS PER MINUTE
Fm. 12.
Fig. 11 gives lines from iron .04 centimeters thick. Speed readings were
not taken lower than 250 revolutions per minute, as it had been found that
the lines were always straight, and speeds below this value could not be
read with the tachometer available for this particular test. Plotting the
hysteresis as a function of the induction, in this case the points are all quite
close to a curve whose equation is, Ergs = A constant x (Density per square
centimeter)1-47, three points in the latter calculated curve being shown by
the crosses. The iron, a test on which is shown in Fig. 12, was .1 centimeter
thick, and shows a greater eddy current loss. The equation for the hystere-
sis curve for this sample is, Ergs = A constant x (Density per square centi-
meters)1-4, some points in the latter curve being shown by crosses, as before.
The eddy current losses for these two samples are plotted as functions of
the induction in Fig. 14. The curves drawn are parabolas; showing that in
these cases the eddy current loss varied approximately as the square of the
induction, although there were often greater variations from that law than
these two samples show. The average exponent for the hysteresis curves
was a little over 1.5, although it varied from 1.4 to 1.7. Rings tested in this
manner were wound and tested with a ballistic galvanometer, using the
step-by-step method. There were discrepancies of as much as 4 per cent be-
tween the two results, but an average of ten tests showed the ballistic gal-
vanometer method gave results 2.5 per cent lower than the other. This
difference is easily attributable to experimental errors.
It being noticed that for a given induction in the rings, the magnetizing
currents for different samples did not vary much, it was planned shortly
78
MAGNETIC PROPERTIES OF IRON.
after completing the above apparatus to construct a modified instrument
which would use electro-magnets of such high reluctance that the variations
of the rings would be negligible, and induction
be dependent only on the current. By making
the electro-magnets of suitable iron and of
about one-third the cross-section of the rings
used, the iron may he so highly saturated
that the induction will remain quite constant
Fig. 13. Modified Hyster- under considerable variation in the magnet-
esis Meter. izing current, thus rendering unnecessary
any accurate comparisons of magnetizing
currents, and the rings can be at about their maximum permeability when
thus magnetized. Such an instrument is shown in Fig. 13 in its original ex-
perimental form, with the rings in position ready for test. The rings are
here allowed to rotate in opposition to the action of a spring and carry a
pointer over a scale, so that is is quite direct reading. Twenty-five compar-
90C0 -r-r
„„„
7000 -gAus
? "
^ *Z
S *'_
* '
S
30C0-^?
/
0 21
io 4<jo a
0 800 1000 1200 1400 1600
Fig. 14.
isons of this instrument with the original one gave results that agreed
within 6 per cent in all cases, and more than half were within 2 per cent of
agreement. Permanent magnets had been previously tried, but the attempt
seemed to show that the instrument would not, in that case, compare sam-
ples of iron widely different in character ; and the writer not being able to
■■
700
iat direction
ince its com- i
lectady.
l.i
1
>
.9
-
H
r,Kr>
F
-,fi
/■
/■
-
*
/
/
/
/
•■2
give any att
were attem
The instr
pletion at tl
) 100 200 300 400 000 COO 700 800 900 100011001200130014
ergs per cm3 per cycle
Fig. 15.
ention to the matter, no further investigat
pted.
iment first described has been in use contii
ae works of the General Electric Company,
D01S00J
onsin
mousl
inScl
HI)
tl
ys
iei
EDDY CURRENT FACTORS.
79
E»I>Y CURRENT FACTORS FOR DIFFERED!
CORE DENSITIES AUD EOR VARIOUS
1AHIj¥ATI01S.
(Wiener.)
tH O W
Watts dissipated
Watts dissipated
PER CUBIC FOOT OF
PER CUBIC FOOT OF
g©H
IRON AT
A FRE-
H ° H
IRON AT A FRE-
1 §
H °
QUENCY OF 1 CYCLE
H ?
S S O
QUENCY OF 1 CYCLE
PEE
SECOND.
PER SECOND.
0gfe
-, w fe
w 3 H &
Thickness of lamination,8
Thickness of lamination, 8
'%%%£
.010"
.020"
.040"
.080"
< «M 02
.010"
.020"
.040"
.080"
10,000
.0007
.003
.012
.046
66,000
.0315
.126
.503
2.013
15,000
.0016
.007
.026
.104
67,000
.0325
.130
.519
2.075
20,000
.0029
.012
.046
.185
68,000
.0335
.134
.534
2.137
25,000
.0045
.018
.072
.288
69,000
.0345
.138
.550
2.200
30,000
.0065
.026
.104
.416
70,000
.0355
.142
.566
2.265
31,000
.0070
.028
.111
.444
71,000
.0365
.146
.582
2.330
32,000
.0074
.030
.118
.472
72,000
.0375
.150
.599
2.396
33,000
.0079
.032
.126
.503
73,000
.9385
.154
.616
2.463
34,000
.0084
.034
.134
.534
74,000
.0396
.158
.633
2.530
35,000
.0089
.036
.142
.567
75,000
.0407
.163
.650
2.600
36,000
.0094
.038
.150
.600
76,000
.0418
.167
.668
2.670
37,000
.0099
.040
.158
.633
77,000
.0429
.171
.685
2.740
38,000
.0104
.042
.167
.667
78,000
.0440
.176
.703
2.810
39,000
.0110
.044
.176
.703
79,000
.0451
.180
.721
2.883
40,000
.0116
.046
.185
.740
80,000
.0462
.185
.740
2.958
41,000
.0122
.049
.194
.777
81,000
.0474
.190
.758
3.033
42,000
.0128
.051
.204
.815
82,000
.0486
.194
.777
3.108
43,000
.0134
.954
.214
.855
83,000
.0498
.199
.796
3.184
44,000
.0140
.056
.224
.896
84,000
.0510
.204
.815
3.260
45,000
.0146
.059
.234
.937
85,000
.0523
.209
.835
3.340
46,000
.0153
.061
.245
.979
86,000
.0535
.214
.855
3.420
47,000
.0160
.064
.256
1.022
87,000
.0548
.219
.875
3.500
48,000
.0167
.067
.267
1.066
88,000
.0560
.224
.895
3.580
49,000
.0174
.070
.278
1.110
89,000
.0573
.229
.916
3.662
50,000
.0181
.072
.289
1.055
90,000
.0586
.234
.937
3.745
51,000
.0188
.075
.300
1.200
91,000
.0599
.240
.958
3.830
52,000
.0195
.078
.312
1.248
92,000
.0612
.245
.979
3.915
53,000
.0202
.081
.324
1.297
93,000
.0625
.250
1.000
4.000
54,000
.0210
.084
.337
1.346
94,000
.0638
.255
1.021
4.085
55,000
.0218
.087
.349
1.397
95,000
.0651
.261
1.043
4.170
56,000
.0226
.091
.362
1.448
96,000
.0665
.266
1.064
4.257
57,000
.0234
.094
.375
1.500
97,000
.0679
272
1.086
4.345
58,000
.0242
.097
.389
1.555
98,000
.0693
.277
1.109
4.436
59,000
.0251
.101
.403
1.610
99,000
.0707
.283
1.132
4.528
60,000
.0260
.104
.416
1.665
100,000
.0722
.289
1.156
4.622
61,000
.0269
.108
.430
1.720
105,000
.0797
.319
1.274
5.095
62,000
.0278
.111
.444
1.776
110,000
.0875
.350
1.398
5.593
63,000
.0287
.115
.458
1.833
115,000
.0955
.382
1.528 6.113
64,000
.0296
.118
.473
1.891
120,000
.1040
.416
1.664 6.655
65,000
.0305
.122
.486
1.951
125,000
.1128
.451 1.806 7.222
80
MAGNETIC PROPERTIES OF IRON.
SPECIFIC EXEHGY DliilPAXIOS IHT AMUIATUIIE
CORE.
(Wein er.)
Hysteresis
LOSS
FOR
Eddy-current loss for
SHEET IRON AT
PRE-
030" (.075 CM.) LAMINATION,
Magnetic
QUENCY OF ONE MAG-
AT ONE CYCLE FER SECOND
density.
NETIC CYCLE
FER
FROFORTIONAL TO
FRF-
SECOND (IN
WATTS).
QUENCY (IN WATTS).
Lilies
Gaus-
of force
Per
Per
Per
Per
Per
Per
Per
Per
ses.
per
sq. in.
cm.3
c. ft.
kg.
lb.
cm.3
c. ft.
kg-
lb.
2,000
12,900
.00007
1.98
.0091
.0041
.0000004
.011
.000051
.000023
3,000
19,350
.00013
3.68
.0140
.0077
.0000009
.026
.000119
.000054
4,000
25,800
.00020
5.75
.0265
.0120
.0000016
.046
.000212
.000096
5,000
32,250
.00029
8.20
.0378
.0171
.0000025
.071
.000327
.000148
6,000
3S,700
.00039
11.03
.0508
.0230
.0000036
.102
.000471
.000213
7,000
45,150
.00050
14.15
.0652
.0295
.0000049
.139
.000640
.000290
8,000
51,600
.00062
17.5
.0806
.0365
.0000064
.181
.000833
.000377
9,000
58,050
.00074
20.9
.0963
.0436
.0000081
.229
.001054
.000478
10,000
64,500
.00087
24.6
.1133
.0513
.0000100
.283
.001303
.000590
11,000
70,950
.00102
28.3
.1303
.0590
.0000121
.343
.001580
.000715
12,000
77,400
.00118
33.1
.1524
.0690
.0000144
.408
.001878
.000850
13.000
83.850
.00134
37.9
.1745
.0790
.0000169
.479
.002204
.000998
14,000
90,300
.00150
42.7
.1966
.0890
.0000196
.555
.002553
.001157
15,000
96,750
.00168
47.5
.2193
.0990
.0000225
.637
.002923
.001328
16,000
103,200
.00187
52.9
.2440
.1103
.0000256
.725
.no;:;; Mi
.001512
17,000
109,650
.00206
58.3
.2680
.1212
.0000289
.818
.003770
.001708
18,000
116,100
.00225
63.7
.2932
.1328
.0000324
.917
.004220
.001911
19,000
122,550
.00246
69.6
.3200
.1450
.0000361
1.022
.004710
.002130
20,000
129,000
.00267
75.6
.3480
.1575
.0000400
1.133
.005225
.002362
ELECTRO-MAGNETS,
PROP£RTIE§ OF.
Residual Magnetism is the magnetization remaining in a piece of magnetic
material after the magnetizing force is discontinued.
Retentiveness is the measure of the magnitude of residual magnetism.
Coercive Force is the force which holds the residual magnetism, and is
measured by the strength of the reverse field required to remove all mag-
netism.
Permanent magnetism is residual magnetism of great coercive force, as in
hard steel, which has little retentiveness ; Avhile soft iron has great reten-
tiveness but little coercive force.
The following paragraphs are condensed from S. P. Thompson's " The
Electromagnet."
Magneto-Motive Force. — The magneto-motive force, or magnetiz-
ing power of an electro-magnet is proportional to the number of turns of
wire and the amperes of current flowing through them ; that is, one ampere
flowing through ten coils or turns will produce the same magneto-motive force
as ten amperes flowing through one coil or turn.
If n = number of turns in the coil,
I=z amperes of current flowing,
1.257 = -^ (to reduce to C. G. S. units).
Magneto-motive force = 1.257 x nl=z $ .
Intensity of Magnetic Force. — Intensity of magnetic force in an
electro-magnet varies in different parts of the magnet, being strongest in
the middle of the coil, and weaker toward the ends. In a long electro-mag-
net, say a length 100 times the diameter, the intensity of magnetic force will
be found nearly uniform along the axis, falling off rapidly close to the ends.
In a long magnet, such as described above, and in an annular ring wound
evenly over its full length, the value of the magnetic force, J£, is deter-
mined by the following expression : —
3C — 1.257 —=- , in which 1 = centimeters.
If the length is given in inches, then
3C= -495-^— , in which lu= inches.
If intensity of the magnetic force is to be expressed in lines per sq. inch,
3C//= 3-193 X^.
Value of £fC at the centre of a Single-turn of Conductor. —
In a single ring or turn of wire of radius r, carrying / amperes of current
3C= *,: X |= -6284 X '- ■
Force on Conductor (carrying* current)
in a Magnetic Field. — A conductor carrying
current in a magnetic field is repelled from the
field Dy a certain mechanical force acting at right
angles both to the conductor itself and to the lines
of force in the field ; see cut.
The magnitude of this repelling force is deter-
mined as follows, assuming the held to be uniform.
3C = magneto-motive force, or intensity of the
held.
I = length of conductor across the field in cm.
l/y = ditto in inches.
/ = amperes of current flowing in the conductor.
F = repelling force.
no I j
■ vyi'J-L .Fin grains
F in dynes = ~f^-
10
F in dynes -
25.4
FlG. 1. Action of Mag-
netic Field, on Con-
ductor carrying cur-
rent.
161 '
81
32 ELECTRO-MAGNETS.
Work done by Conductor (carrying- Current) in moving:
across a Magnetic Field.
If the conductor described in the preceding paragraph he moved across
the field of force, the work done will be determined as follows : in addition
to the symbols there used, let b = breadth of field in and acrosB which the
conductor is moved ; w = work done in ergs.
bl = area of field,
N=bl x <f> = number of lines of force cut,
ni
Rotation ©f Conductor (carrying- current) around a Magnet
role.
If a conductor (carrying current) be so arranged that it can rotate about
the pole of a magnet, the force producing the rotation, called torque, will be
determined as follows : The whole number of lines of force radiating from
the pole will be 4tt times the pole strength m.
4n- ml „ „„_ T
10 = — -yr— = 1.257 ml.
Dividing by the angle 2 tt, the torque, T, is
Every magnetic circuit tends to place itself so as to embrace the maximum
flux.
Tioo electric conductors carrying currents tend to place themselves in position
such that their mutual flux may be maximum ; otherwise stated : if two cur-
rents run parallel and in the same direction, each produces a field of its
own, and each conductor tends to move across the other's field.
In two coils or conductors lying parallel to each other, as in a tangent gal-
vanometer, the mutual force varies directly in proportion to the product of
their respective ni, and inversely as the axial distance they are apart.
Principle of tlie Mag-netic Circuit. — The resistance that a mag-
netic circuit offers to the passage or flow of magnetic lines of force or flux,
has been given the name of reluctance, symbol (ft., and is analogous to resist-
ance, to the flow of electric current in a conductor.
The magnetic flux or lines of force are treated as current flowing in the
magnetic circuit, and denoted by the symbol 0.
The above two factors, together with the magneto-motive force described in
the early part of this chapter, bear much the same relation to each other
as do resistance, current, and E.M.F. of electric circuits, and are expressed
as follows : —
.. „ -Magneto-motive force
Magnetic flux = 5 — _ — ,
reluctance
9 (ft
10
Av.'
1.257 ni
_^
An
■■*£.
1.257
EXCITING POWER AND TRACTION.
83
If dimensions are in inches, and A is in square inches, then
nl=<f>-^- X 3132.
and <f> = ($/' A".
The law of Traction. — The formula for the pull or lifting-power
of an electro-magnet is as follows : —
Pull (in dynes) = ^- .
Pull (in grammes) =
Pull (in pounds) =
In inch measure, Pull (in pounds) =
&2A
11,183,000
" 72,134,000 '
Magnetization and Traction of Electro Mag-net*.
(B
(B"
Dynes
Grammes
Kilogs
Pounds
Lines per
Lines per
per
per
per
per
sq. cm.
sq- inch.
sq. cm.
sq. cm.
sq. cm.
sq. inch.
1,000
6,450
39,790
40.56
.0456
.577
2,000
12,900
159,200
162.3
.1623
2.308
3,000
19,350
358,100
365.1
.3651
5.190
4,000
25,800
636,600
648.9
.6489
9.228
5,000
32,250
994,700
1,014
1.014
14.39
6,000
38,700
1,432,000
1,460
1.460
20.75
7,000
45,150
1,950,000
1,987
1.987
28.26
8,000
51,600
2,547,000
2,596
2.596
36.95
9,000
58,050
3,223,000
3,286
3.286
46.72
10,000
64,500
3,979,000
4,056
4.056
57.68
11,000
70,950
4,815,000
4.907
4.907
69.77
12,000
77,400
5,730,000
5,841
5.841
83.07
13,000
83,850
6,725,000
6,855
6.855
97.47
14.000
90,300
7,800,000
7,550
7.550
113.1
15,000
96,750
8,953,000
9,124
9.124
129.7
16,000
103,200
10,170,000
10,390
10.390
147.7
17,000
109,650
11,500,000
11,720
11.720
166.6
18,000
116,100
12,890,000
13,140
13.140
186.8
19,000
122,550
14,360,000
14,630
14.630
208.1
20,000
129,000
16,920,000
16,230
16.230
230.8
Exciting- Power and Traction. — If we can assume that there is
no magnetic leakage, the exciting power may he calculated from the follow-
ing expression ; all dimensions being in inches, and the pull in pounds.
w/=:2661 X — X
If dimensions are in metric measure,
w/=3951 - V_Pullinkilos
, \/ Pull in lbs.
> 1 : :
Area in sq. ms.
Area in sq. cms.
£ = 4965
"\yPull in kilos
Area sq. cm.
84 ELECTRO-MAGNETS.
Winding- of Mag-in't Coils.
The following nomenclature is employed : —
D = diameter of insulated wire in mils.
d = diameter of bare wire in mils.
t = thickness of insulation on wire in inches ( i.e., - — - — j •
L ■=. total length of wire in coil in feet, a, b, h, and Z = coil dimensions in
inches.
K= ratio of diameter of insulated wire to bare wire.
V= volume of winding space in cubic inches.
N= total number of convolutions on spool.
Tzr number of layers of wire on spool.
n = number of convolutions per linear inch.
p = resistance in international ohms of mil-foot of pure copper wire.
(10.35 ohms at 20° C.)
li — total resistance of coil in ohms.
r = resistance per foot of wire in ohms.
f =.-■=. feet in one ohm.
r
lm = mean length of convolution in inches.
The winding will vary between two extremes, one the " square" winding
in which it is assumed that
the convolutions lie to-
gether as if the wire was
of square cross-section, and
the other the " conical "
winding in which it is as-
sumed that the wires lie
together as if the wire was
of hexagonal cross-section.
On the assumption that
the same volume is occu-
pied by insulating mate-
rial about 15 percent more
copper volume is obtained
Tby the " conical " method
of winding.
The squar
-
1-
*
f
t
b
1
a
I
1
t
h
1
assumed in the following, unless otherwise specified.
The diameter of wire necessary to fill a given coil space with
ber of convolutions is
/lOOOUOO / li /500UU0 / (a — h)
D=V-n*— = v n '
winding is
i given num-
y*
50U(n i, , / (a— b)
K*N
K*N
The total length of wire of given diameter which can be wound in a given
coil space is
L
65450 I (a- — 1 2)
From the above formula the dimensions of a spool to hold a specified length
of wire of given diameter may be determined.
If a and b are known
l-
If b and I are known
If a and / are known
0545 Mrt3 — b-)
— JD'iL + G545° lhZ
a— V 65450 I
_ k /65450 lb* — DH
b— V 05450/
WINDING OF MAGNET COILS.
85
The l-esistance of a coil expressed as a function of the volume is
p _ 862500 V
Ix - DM* '
If the volume of wire is increased ten per cent to allow for the layers fit-
ting into one another,
_ W8700 V
K- Did* '
Hence the diameter of i
resistance is
: necessary to fill a given volume with a given
948700 V
The last three formulae are general, whatever the shape of the spool, i.e.,
whether the core is of circular, square, rectangular, elliptical, etc., cross-
section.
The next smaller gauge number than the diameter corresponding to the
formula should be used in order to allow for irregularities in winding and
for insulation between the layers.
If R is taken at other than 68° F (20° C), a new value of R, i.e., R', must be
taken, where
R' = R (1 -f 0.0022 0/),
where 6/ is the rise in temperature above 68° F.
A formula known as Brough's formula is often applicable to the calcula-
tions of the diameter of wire necessary to give a stater resistance.
For circular cores,
d = F y/677400(^- -fr, / + fiJ _tm
Hi
For square cores, Fig. 3,
d _ |~ ^862500 (a2 - ft2) / + ^1* _
For rectangular cores, Fig. 4,
d = |~ /431250 (A - a) (A + B + cTTt>) + ^"1*
For core made up of square and two semi-circles, Fig. 5,
radius of core-circle, b.
radius of outer-circle, b.
86
ELECTRO -MAGNETS.
d _ I 4/862500 (B — b) [n (B -f 6) + 2 a]
+ t*
Thickness of Wire B nsulat ion. — The thickness of insulation upon
wire varies with the manufacturer, and no fixed value can be given to cover
all cases. The following table represents the practice of several large man-
ufacturers. To determine the diameter of insulated wire, add to the dia-
meter of the bare wire.
FOR COTTON.
FOE SILK.
B & S Gauge
Single
Double
Single
Double
OtolO
10 to 18
18 up
7 mils
5 mils
4 mils
14 mils
10 mils
8 mils
2 mils
4 mils
The above values correspond to It in the formulas.
Relation of Ampere-turns to Dimensions of Coil.
For a coil of static dimensions it can be shown that
NI— 1AG lm (1. + 0.0022 0/) '
where E = difference of potential across terminals of coil.
The ampere-turns are independent of the length of the coil, of the thick-
ness of insulation, and of the method of winding, depending upon the
diameter of the wire, the mean length of a turn, and the temperature of
the coil.
To keep the number of ampere-turns constant in a coil of given volume,
d* of the wire must vary inversely as E.
Relations Holding- between Constants of Coils.
In the following it is assumed that the thickness of insulation is propor-
tional to the diameter of wire, and that all coils are uniformly wound. The
results obtained under this consideration are practically but not strictly
correct.
The weight of copper required to fill a given coil volume is constant,
whatever the size of the wire used.
The resistance in a given volume varies inversely as the fourth power of
the diameter of the wire used.
The resistance in a given volume varies inversely as the square of the
cross-sectional area of the wire used.
The number of convolutions in a fixed volume varies inversely as the
square of the diameter, or inversely as the cross-sectional area of the wire
used.
The resistance of a coil of given volume varies directly as the square of
the number of turns.
The magnetic effect produced by an electro-magnet of given shape, size,
and construction is proportional 'to the product of the current into the
square root of the resistance of the coil.
If two coils of same dimensions are wound with different size wire, the
current must vary with the cross-sectional area of the wire, in order tc
obtain the same heating effect, or same temperature rise.
For same energy loss E2 must vary inversely as (area)2 of Avire, or foi
same heating effect the voltage across terminals of coil must vary inversely
as the cross-sectional area of the wire used.
.
AMPERAGE AND DEPTH OF WINDING FOR MAGNETS. 87
AETER]¥ATJL]¥G-C1JRREj¥T ELECTHO-MAGSETi.
The cores of electro-magnets to be used with alternating currents must be
laminated, and the laminations must run at right angles to the direction in
which eddy currents would be set up. Eddy currents tend to circulate par-
allel to the coils of the wire, and the laminations must therefore be longitu-
dinal to or parallel with the axis of the cores.
The coils of an alternating-current electro-magnet offer more resistance to
the passage of the alternating current than the mere resistance of the con-
ductor in ohms. This extra resistance is called inductance, and this com-
bined with the resistance of the conductor in ohms produces the quality
called impedance. (See Index for Impedance, etc.)
If L = coefficient of self-induction,
Ar= periods per second,
E = resistance,
and,
Impedance = V^+^Wi
Maximum E.M.F.
Maximum current =
Mean current =
Impedance
Mean E.M.E.
Impedance.
If the current lags behind the E.M.F. by the angle <j>, then
_ . Mean E.M.F.
Mean current r= -=- — —, X cos <p.
Resistance
HEATIIG OE 1IAGIE1 COILS.
Professor Forbes.
7= current permissible.
rt = resistance of coil at permissible temperature.
Permissible temperature = cold r x 1.2.
t = rise in temperature C°.
s = sq. cms. surface of coil exposed to air.
^7^)003 x t X~s
~~ .24 X r± ■'
PERMISSIBLE AMPERAGE AUB PERMISSIBLE
BEP1R OE WUVBIHTG EOR MAGIVETS WITH
COTIOI-COYEREB WIRE.
(Walter S. Dix, Electrical Engineer, Dec. 21, 1892.)
" M
2X W
Where I = current ;
W = emissivity in watts per sq. inch ;
u> = ohms per mil-foot ;
M= circular mils ;
T= turns per linear.inch ;
n = number of layers in depth.
The emissivity is taken at .4 watt per sq. in. for stationary magnets for a
rise of temperature of 35° C. (63° F.). For armatures, according to Esson's
experiments, it is approximately correct to say that .9 watt per sq. in. will
be dissipated for a rise of 35° 0.
The insulation allowed is .007 inch on No. 0 to No. 11 B. and S. ; .005 inch
on No. 12 to 24 ; and .0045 inch on No. 25 to No. 31 single ; twice these values
for insulation of double-covered wires. Fifteen per cent is allowed for
imbedding of the wires.
The standard of resistance employed is 9.612 ohms per mil-foot at 0°. The
running temperature of tables is taken at 25° + 35° = 60° C. The column
giving the depth for one layer is the diameter over insulation.
ELFX'TRO-MAGNETS.
I OOOONCOOOMINffliiONt-iOOJM'^OlNCOnHrf*
"t[^d8(I OC^r^<»t>iqCCCOC5Crjt-;<»-<*COC<]r-<OOiCOt^<riin
•duiy j
•q^daa
> t- I- cd 10 ■* CO
•duiy
? t- CS GO CO 00 OS
- d d d d ■* •*
•q^daa
ocdcn ^ ooascoc
co cd 06 cs'ci i-H ic c: co ob"
00 «5 ^J OS CO b; CO t-; CO iH iq C« CO •«# «# OS « t; OS t> i-J t>
d<cjcNdcci^ddcoco^^ddo6i>i>dddd'<*
I go >-i o c- o c r- :■■> ~ » - ■ -■ -t< o ci co ■"*< go co lo go co
q^dad I ocoooioio^(NNqo>ooi-;tB(OTi|i|nNDjiHqo
S3 C3 (M IM (N <M
•dray
IHrtHHHffig
•q^doa
t- in Tf cd gs c
iccqco'-jqc
gj >n cj o4 c-j c
'loit-co-torii-ci-j
q ■>* cq cq oi oj nqqa
•duiy
^i>-iqqcqqocqoqiqt-;cqq5jq^
StOcdcONHOOOOlOlOMrirtHOO
C CI CI d 01 CI — HrtHHHHHrl
TL'-HOOJ'^COtMOOt-CSwi
•q^daQ qcqaqi>.qqiq'#cqcqo}CN;'-Hqqasqoo
•duty
CNoqqT-fOST^qoqt^cqcqqqiqcAc:
Tj< as as d ■* co i-<" d t^ t-' io <*" CO CN t-h c
,_ CCClClClClClClClrt HHHrtHHr
I mcir-HCHcc ci HOooMHino
*md9(X iq-*-* cqtNCNrHi-^qq qqoocq t-c-
w^rn«oqqiNq^q«D(Nq'*05!NqNiooTi*H
CO CO CO CO C ' I fiUin^-n-li-l^^rHOSCOt^t^
•Tlldaa I q
LO CO CO OS CD c
MrttOlOrHOl
qqqoqoooqt^t^qqqqiqiqiq-*
TfTf -i
•duiy
•fNccrtcirtqqqioqrt'fNoqo
GOOJi-Ht^inCOoiaJ^-^r-irHCOt^lCT)
Tf TJH -^ CO CO CO Ol Qj f)CK^(NHHHr
•q^dea |
©cocot>yoc<iccooc<ii^t^cocoeNi©5c~incoeNi©oot-
•duiy
I
^oqqc<jC^qcqcqqcNeNTi<i
C C i © GO -* CO* 00 GO •* ■# rH ©
*<-t<Tt< COCO CO 05 CI CI CI CI CI
5i>iO'*cocN'-Hd
•mdaa
.,
■dmy
toooo-f woati
SSSSSSS*
q t> iq i>; q q •<#
ho* io(et>HOai>NaiOHri
(M«(N«(S«N<SHHrtHHHrH
co <m cn th o © a
~q©i-HT^cqoq©
-lOlNIOMHOlt-
OC1 CI CI CI C) — —
•qoui .I'BSuii
j8d suanj,
|t-t-;q(M*l>^
co co eo ■* ■* ■* t)< ■*' iri
loujujocc
^ool--* ci : --
2 co co ci q -h co oi
»L-t>c6odosos©
aad -sq^i
s §
'0 S99.I§8p 09
ye c^ooj aad siuqo
nwanoiN
OOcNCOOSOSCSCMincOCOOSiH
oooooooc
ooooooo
caoHcor)
iiiiii
'SITM -nqno.no
5 co CD 01 !
388335
©■S83S
•seqoui 'ajBq -wbict
ȣco3 *co~
S^c*?
to CO t~O0 OS O »-i <M CO
's p«^ a I
AMPERAGE AND DEPTH OF WINDING FOR MAGNETS. 89
a
a *5
e i
6, «
6d
a.
a
I aiowoaoooooiNinoomco^noiciMOt-
•dray
«OH«01rH|>CflCDTt<WC»0^aOffi3rHO
•rtfdea; I ^
H00Mt-t-O5H-*Q0(Mt»nOJ0l
OWfflO^NO
•dray
•tndaa; I
5H!OHt>T)<f0W«lCC0rtlf
2 10 rj< -* co co co c o c i -■ : * i :: \ ::
•dray
OClNO^OMH^n-ft-tDMIMt-^i
i-H OS CO OS 00 "# © I>- -* CN C: i
^i* co^ cn cn cn cn i-5 i-i r-5 r-5 °9 ^ ^ ^ ^ **. °"
•q^a
CNOSOSC^Tf-HasoOCOlC
CO J] C) M W OJ H H H T-
« H Tj( W |> O Ci L*. ' +COHOOO
■^ n* co co co cn (m' th* i-h* i-h i-i* °? °9 v. •"■
3*8888
-q^dsa
O00CN*HlOCS-t<©COC0©t~''#TtiCN©0!
- o co o io ^ ^ ■# o: co co ci w ci c^ h r
•dray
OOTfNOOOOHCOCDrlicOLOC
•q;d9a
ciHioooj^oocicci
cq co jc iq -* n; *# co co cn cn o
a ■* CO CM iH ©
•dray
-i as © co to i-i t>
•q;daci
_*d id n" co" co'_co_cn cn r-5 i-5 i-5 i-5
NCOHCOt>CO o"t~ — |i"c<l COOOOlOOTtiT^OOSOcMlCa
■<*■*■* CO ■"
1> O IO CO -h CO ii 71 -l-X-*rl<OOLOOOt>»t>-*rH
■ '.; -
CO CO 1_Q* Tt* jj CO* CO CN O* i-H* H r-H* -i ^ g CO CO .O Tf< T^ CO CO
•q^dso;
OCOCICNCNCNOCOO*
CS OS 00 r-
•dray
oocoociHosaHHot-ii -'-hnSS
CO ■# CO -* CO <* !>; CI t- CN OS CO CO r-H r-t © 00 t> CC i
l>'l>'cOlOlQTi"co"co'c-*C>*i-'i-'T-"i-*iMi-?
•q^daa
•ipdaa
•dray
•q^d9Q[
•dray
.tod sxi.inx
aad -sq-i P<AOQ
•q sasjgap 69
^1? ij.ooj aed sraqo
saqoni 'e.reg[ •uretQ
:
. cs^Mt-a
5S»«oi>-icooc-cnloo
OH'jHoicoaij(iaNO)nt'«nMNooioc"oi>
J5 c9 £? Sg - .' - -foit-i>ccoco*if
coiqoicqiccocoioooc-ic-coGicoi-ioiaii-Hcj:
d o co t>" t- co" io rf co" CO <N CN rH* i-H* ^ "^ *~i ^ a
CM CM i-l i-i *-H i-H
qooooooooooooooo
uO-tMOO"
^5cccincon3§*?),:
6 to*^* co co* cn" cn" cn CN rH i-5 ** •
•4 i-H OS 00 00 OS t>
wqqN^Hqoqq^qoqqcjqoqqoT-
t-H i-l CN -# -* CO l>" OS CN *#" t-* 05 CO CO i>" OS " " OS CO CO CO CO
S3 5J8§§1§§§8 §§§1111
35 g a a £r
N O lfi 00 -tl Cl 00 Cl >-< -f O M Q M lA o • • -
IO00t0§*§CCCTNg*0O
■* •# CO CN CN i— IHH lOCNO
og£gg£S^coJco£c*:c^c3^K£3S3S
•sSive*)
^ CO TMOCOt>OOfflOnC
3
90
ELECTRO-MAGNETS.
.lad sujiij,
CI L~ l-;'l|Clr>KK>f'*HO X L- L.0 O CO 01
in" •#-#-#-* •*'fococofococ^o5c5c<ic^c4ci
OSHOSOOOOO-t-tflfeS^^tlccriS
—- 35 X -O SO l--' CO CO H rH d ci OD 06 t> d to 1Q
MHOHiot-«««H»ionoHOM!o
tc-t^oinqqa t~ t- lo ic -r -f co ci h i-h
CI CI CN CI CI CI r-i r-5 rH r-i H r-i r-i r-i r-i r-i r-i r-i
•f?HOMOgO^OHTtHN(MiOOiNt-
" :i- - i r. -i- X l-XNCCOH ci -t O t~
M C-j « H q o o c; X X X L - t~ t - '-O CO CO lO
i^-Ht^qqqqi^t^cot^THoqr-iiqcqcoo
eocor>corHO?o'oeic4c5CJ«dcO"*eoC'i'-H
00COr-<ciC0-+<X[~CO-*OTCOOlC0COCl-+iX
CI I- t- lO -t* CO ih ~ CI C t~ L- CO LO -+l -r CO 01
CI Ol <N CI CI Ol CI Ol rH rH rH tH rH rH i-H rH i-H r-i
oo-#q^Lqc^coGOoo©rHC5cqoiincot~t~
t^io^inTHt^oo500-*cit-ci-i c t~ i.o
C5COCOl^t~=OOLOLOlO-Ti-*COCOCOCOiMO<)
tt»ODt»Ht-COHO»0!OON«0(MtOa>
cocococo^'^''*'j<iniciriir5CD?o«ot^t>t>
o ci § cs ^ o
»o ci cs t~ co lo
r- i-j © © © ©
_©io-t<cox-±irHCoco
-+ co »- oi cj co co l.0 o t- oi a co oi -f c co ci
-p o o t- uo -+ oi r i : . : l.o lo -f co
oioioiT-jrHrHrHT-jT-joqqqqqqqq
C5 O 01 CO C5 © CO Ol LO CI CO CS rH Ci 01 -H 00 CI
-p X X r ■ 2 | ;+ "/- 7- "- '.- "•" '- O l.^ t- CO CO Ol
Soooooi: ~ ~ — ~
ooscr. : - o O O
qoqqoqqqoooqoqoqoq
OHCO-*T|iOCOO!010LOHTt(S«300T(l
ojoi'-fcoofOjcciooHaHOOi
f ~ :Z 2 :i O) w m CO Ol l-'inOt-B^M
COtOWlOlO-f-tl'tCOCOClOlCltlr-IHHi-l
-+< © t- co ci rg eo th lo ci x -? -p x •*
X i.O l-O CO 01 0 1 O © X X CO CO -P ~P CO Ol CI i-H
C I : K I C 1 C j ? 1 C 1 C) rt H H H H H H H H H
<M co ># \a co i> oo © o i-i
IMJO^IO <D C- 00 «
•Oo09
^ooj jad sraqo
•sjuu .
JTJXtlO.110
•saqout
'axejj 'ureiQ
SPACES OCCUPIED BY WIRES.
91
Table of Spaces occupied by Wire* of Different Sizes, with
Single Cotton Insulation, tog-ether with Data of
the Copper.
Compiled by Schuylek S. Wheeler.
Data of the Insulated Wire.
m c3.3
.202 .
C « ®
o
a ^5
S 2
No.
lit
2 2
©M
3 02
H
o.2
o
03 ©
ft
>
1
2
3
4
4.5
4.87
22.1
1.84
.0004576
.24
7.
4
.75
5
5.09
5.82
29.6
2.46
.0007738
.24
9.
5
.74
6
5.66
6.41
36.3
3.02
.0011963
.24
11.5
6
.74
7
6.2
7.3
45.3
3.77
.001780
.24
14.
7
.73
8
7.05
8.
56.5
4.7
.0029654
.24
17.5
8
.73
9
7.66
8.42
64.5
5.37
.0042574
.24
22.
9
.73
10
8.54
9.6
82.
6.83
.00683
.238
27.
10
.72
11 *
9.7
11.
116.7
9.72
.012254
.236
34.
11
.72
12
11.2
12.8
143.4
11.95
.0150654
.233
42.
12
.71
13 *
12.
14.
168.
14.
.03627
.23
55.
13
.71
14
13.
15.4
200.
16.66
.0431627
.227
68.
14
.70
15
15.37
17.9
275.5
22.96
.071520
.224
87.
15
.68
16
16.74
19.4
324.7
27.06
.108757
.22
110.
16
.64
17
17.74
21.33
378.4
31.53
.15980
.217
140.
17
.62
18 *
19.5
23.
448.5
37.38
.2389
.19
175.
18
.61
19
22.77
24.9
567.
47.25
.39165
.185
220.
19
.60
20
25.7
29.7
763.3
63.60
.6464
.184
280.
20
.58
21
28.3
32.5
920.
76.6
.98163
.182
360.
21
.57
22
31.
36.
1116.
93.
1.502
.18
450.
22
.55
23
34.4
40.36
1390.3
115.86
2.36
.178
560.
23
.52
24
36.9
44.6
1649.
137.4
3.53
.168
715.
24
.45
25
38.
47.
1790.
149.2
4.734
.145
910.
25
.43
26 *
42.
50.5
2100.
170.
7.
.14
1165.
26
.41
27 *
48.
55.5
2600.
210.
10.5
.135
1445.
27
.40
28
53.28
61.1
3256.
271.3
17.63
.13
1810.
28
.39
29 *
59.
68.
4000.
335.
27.
.125
2280.
29
30
63.26
76.8
4860.
405.
41.84
.121
2805.
30
.38
31
32
33
34
35
36
RELATION AND DIMENSIONS OP CON-
DUCTORS FOR DISTRIBUTION.
REJLATIOIY OF E.]?I.F. ; CFBREVT; DISTANCE,
CROS§-§ECTIOX, AX1> WEICHT OP
coaroucxoiis.
a. Current or E.M.F. varies directly with the amount of energy trans-
mitted.
b. Given the work done, loss on the line, and the E.M.F. at the motor
terminals and point of distribution ; then the cross-section of conductor
varies directly with the distance and weight as the square of the distance.
c. With the same conditions as above, the weight of conductor will vary
inversely as the square of the E.M.F. at the motor terminals.
d. With a given cross-section of conductor, the distance over which a
given amount of power can be transmitted will vary as the square of the
E.M.F.
e. Given, the weight of conductor, the amount of power transmitted, and
the loss in distribution ; then the distance over which the power can be
transmitted will vary directly as the E.M.F.
PRECI§IO]¥ OF CALCEIATIOiri OF WISTRIB1T
IWCi: SYiTEMS.
While it is possible and in every way the best to make complete compu-
tations for the conductors for isolated plants and for plants of a permanent
nature, it is practically impossible to make anything like precise computa-
tions for large public systems of distributions, such as a large Edison
system.
In the early days of the Edison stations, exact sizes of conductors were
computed for' entire systems ; but when the network system vras introduced,
and it became possible to keep the E.M.F. constant all over a system by
varying the number of feeders, all such exact computations were dropped ;
and to-day such systems are equipped with a few standard sizes of conduc-
tors, feeders being of one or two sizes only, and mains being of but two or
three sizes, judgment of the management being used as to which size will
best fit given conditions.
ECOHOmiCAL COHTDITIO^i.
In the laying out of a system of electrical distribution, there are eight
points to bear in mind in order to obtain the best economy ; and they have
been so well stated by Abbott, that I quote from his book the following : —
" 1. The conductors must be so proportioned that the energy transmitted
through them will not cause an undue rise of temperature.
2. The conductors must have such mechanical properties as to enable
them to be successfully erected, and so durable as to require a minimum
of annual maintenance.
3. The conductors may be so designed as to entail a minimum first cost in
line construction.
ECONOMICAL CONDITIONS. 93
4. The conductors may be designed to attain a minimum first cost for
station construction.
5. The conductors may be so designed as to reduce first cost of plant, and
cost of operation and maintenance to a minimum.
6. The conductors may be designed to secure minimum total first cost of
installation.
7. The conductors may be so designed as to secure maximum conditions
of good service.
8. The conductors may be so designed as to attain a maximum of income
with a minimum of station first cost."
1. If cost of production of electric energy is low, and cost of conductors
high, make conductors small in cross-section, and of such size that the in-
terest on its cost plus the expense of maintaining it will be a minimum, and
balance the cost of energy lost in heating.
In no case, however, should the conductor be made of a size so small as to
heat dangerously, for which see tables in " ^National Code."
When the cost of electric energy is high, and that of the conductors low,
then the cross-section of conductor must be larger, in order that the cost of
energy lost may not be too high ; but the balance, with that of interest and
maintenance, should still be maintained.
2. In all cases, conductors of sufficient size to have mechanical strength
to suit the particular position they are to occupy, should be used. Due
attention should be given to liability of siioav and sleet, breaking of poles,
etc., if conductors are overhead.
3. When a plant is installed for a temporary purposerand the line sal-
vage will be small, while no harm will be done to the generating plant, the
cost of the line should be a minimum, and the conductors may well be of a
size just sufficient to carry the current with safety, both as regards heating
and mechanical strength.
4. The minimum first cost of station can be obtained, as far as influenced
by the distribution system, by reducing the losses in the conductors to a
minimum, thus calling for the smallest amount of current to do the work.
5. As a decrease in the expenditure for line and construction demands an
increase in the cost of central station, and apparatus for producing the
extra energy lost in the line, and increases the operating expense of the
station likewise, it is evident there must be a point where the total of
the interest and depreciation on the line can be made practically equal to
the cost of the energy lost in the line ; and at this point the expenses will
be the least. Care must be used in applying this law, which was first stated
by Lord Kelvin in 1881, as follows : " The most economical area of conductor
will be that for which the annual interest on capital outlay equals the
annual eost of energy wasted." One side of this equation would be the
interest, depreciation, repairs, and maintenance of the conductor, the other
would be the cost of producing the energy at the generator terminals, in-
cluding interest, depreciation, and operating expense.
Kapp says that the above law only applies where the capital outlay is
proportional to the weight of metal contained in the conductor, a condition
seldom obtaining in practice, and states the correct rule as folloAvs : —
" The most economical area of conductor is that for which the annual cost
of energy wasted is equal to the annual interest on that portion of the cap-
ital outlay which can be considered to be proportional to the weight of
metal used."
Prof. George Forbes, in his Cantor lectures in 1S85, called that portion of the
cost of the distributing system which is proportional to the weight of metal
used, " the cost of laying one additional ton of copper ; " and he shows that,
for a given rate of interest charge (inclusive of depreciation), and a given
cost of copper, " the most economical section of the conductor is indepen-
dent of the E.M.F., and of the distance, and is proportional to the current."
Professor Forbes at the same time published some tables to facilitate the
calculations ; and Prof. H. S. Carhart has enlarged them, and reduced the
values to United States money.
94
CONDUCTORS.
000S$
©
©
SI
S
CN
©
CO
8
CO
©
©
©
©
I
g
§
g
0081$
8
CO
cm
8
CO
CO
©
CO
©
13
CO
3
©
g
OS
0091 $
§
OS
CM
8
00
CM
i
I
rf
13
CO
13
§
1
00tl$
|
eo
OS
CM
CM
3
1
CO
CO
CO
9
©
13
8
13
o
00SI$
o
3
|
OS
CO
cm
o
?5
CO
3S
CO
"#
O
1
OOITt
o
1
5
CO
00
05
o
CM
©
CO
eo
OS
CO
O
8
0001 $
I
o
o
o
o
o
o
1
1
o
s
CO
8
5:
006$
o
s
1
<M
1
1
1
CO
8
CO
CM
CO
©
1
008$
1
CO
8
CI
CO
CM
"*
1
OS
CM
CO
13
88
CM
o
CO
1
091$
©
o
8
13
O
1
|
§
o
o
CM
©
S3
O
8
CO
13
CO
00Z$
o
o
8
a
o
CM
1
1
O
3
8
1
1
099$
1
CO
©
I
I
t;
o
CO
IO
<M
1
1
1
1G
CO
009$
o
5
CM
©
o
CO
8
|
o
-*
<#
1
CM
OS
CO
CM
©
CM
5
099$
8
CO
CO
o
©
§8
©
8
©
©
CM
I
r?
OS
CM
w
009$
o
o
s
o
o
©
s
o
©
8
1
1
§
8
I
8
o
9i*$
o
8
o
CO
©
o
IQ
©
-*
s
13
t~
o
OS
CO
09*$
i
8
8
1
g
I
o
CM
|
CM
CO
00
CM
9St$
s
8
s
o
00
o
o
13
o
1
OS
CO
CO
13
©
CO
00*$
o
©•
3j
o
o
o
©
1
CO
8
CI
CO
1
8
§
92£$
o
1
s
s
o
GO
©
©
o
8
©
1
1
o
X
09S$
13
8
CM
2
1
CO
8
1
o
©
1
o
CM
CO
o
1-2
9SS$
1
8
CO
3
<M
8
OS
8
o
00
©
8
g
a
i
Q
00£$
o
1
1
§
8
1
©
1
8
©
©
©
13
CO t- CO OS © CM ■<* COOOO
uoi^'eioajcfop ptre ;saja^nx joj gdhb.m.oh'b iBtixray
a
95
H to
0S9'S^
96^'9S8
SOOOHHIMNCOM
x -+ i-H l~ "t r; l~ 1-1 t - :- — l: n i> n a n h f
B3S8£
3 lH «D Tt< rt l> «
r -t- r> c -x •
5 cr i-i oi ci
t< !N O 00 CD •*
gSoSggg
- ",= i- :: ~) — ~ X — >~ -tiin — -x r~ i- -H
t- cs u~ -t< -+i c: rt ?i - « c c r. i> t- - c; -t -i< n r: ci
- - ' - v — -. i " -r -+ i- c i- k c. c i- *i k -t
ooooooi-(T-iT-trHi-n-iT-ii-ii-n-iT-ic)ci-:i*i-:i
i ,: - c-:ir.-rir: -i- x ~ c — m r-t -* in «
- - - x — . — :n c: -t< i- c i- x r. c ti ^ -t ;-. •.
9AT'6SS
¥ffc'9IS
*8Z'SSI
«s
-~u x c :
3 r: 2' 2 fe"
^SS
CO -fi L". L- CC ~ ^i £1 ;
o»atnooD«
H (N -N <M Cl <M CO K
i
,-h rn ,_ cm c"i ci cj r-
OOOOiOOiSOiOOi.'
sssssss
(•jo^jauoS put? 'jaAvod aApoxn
'sSuipntiq no uoi4i3ioo.idop pm? jsaJG^ut
jo OAisnxoni) •sp3uiuua:} Jo^'jetraS ye
jaAVod-asaoq x'60?-1^08!8 8U0 J° *so° IBiuray ,
96
CONDUCTORS.
The engineer first decides on what will be the cost of laying one additional
ton of copper, and the rate of interest (4- depreciation) ; then, referring to
the first table, he finds in the top line the amount corresponding to his cost
of copper, and follows it down to the line corresponding to the rate of inter-
est he is to charge ; and the number found at this intersection must then
be taken to the second table, where, commencing on the line giving, at the
left, the estimated cost of one electrical horse-power per annum, he follows
to the right, stopping at the number nearest in value to that determined
from the first table. At the top of this column will be found the area in
circular mils and in square inches of the most economical conductor for 100
amperes of current, and size for other currents is in proportion.
The preceding rule determines the most economical cross-section of con-
ductor for a maximum current, and not for the varying current of practice ;
therefore it is necessary to multiply the result obtained from the previous
tables by a ratio found in the following table, which was also calculated by
Professor Forbes from the following formula : —
Mean current = current
v''
'(i)*l+(|)2*2 + (i)2*3 + *4
where tx, t2, £3, t± represent the number of hours per annum during which
one-quarter, one-half, three-quarters of the full current and the full current
is respectively passing through the conductor.
TO FIND MEAN ANNUAL CURRENT.
Fraction of time per year
during which
is passing through the
conductor.
Fraction of time per year
during which
is passing through the
conductor.
0
0
0
0
A
1
0
0
0
0
i
0
1
0
\
0
\
2
1.000
.944
.901
.884
.875
.838
.820
.810
.790
.771
I
1
0
0
i
0
0
5
1
1
\
a
0
0
i
0
0
0
6
.7G0
.744
.729
.718
.685
.661
.650
.611
.586
.545
The figures in the columns headed, " £ current," " | current," " f current,"
and " Full current," represent fractions of the total annual time during
which i, |, | of the full current and the full current is passing through the
conductor.
The figures in the column headed " Ratio" are those with which the most
economical area for the maximum current must be multiplied to obtain the
most economical area for a varying current.
The following table constructed under the direction of Professor Forbes,
by the writer, will assist in approximate quick determinations, and can be
used for any cost of power or copper.
For example : What would be the most economical density of current for
a line, with copper at 14 cents per pound, and power costing 19 dollars per
horse-power per annum.
Multiply the constant difference, .0406 in column h, by the cost of power,
19 x .0406= .7714, and divide this result by the cost of copper in cents, 14,
or ^-^ = .0551.
Now look in column/ of differences for the nearest number to this result.
HORSE-POWER AT MOTOR-TERMINALS.
9T
which is .0546 ; and to the left in the first column will be found 375 amperes
per square inch.
All other data can be calculated from the data given in the other columns.
I. Horse-power at Motor-Terminals. 7.46 amperes at
lOO volts, distance lOO feet.
Am. Inst. E.E. standard, pure, soft-drawn copper at 20° C; 1000 ft., 1 sq. in.
weighs 3851.16 lbs.; R= .008129.
.at)
§28
r $
S fe o
2 cLa
02 ffl
o
O
ft-2-d
ftfl ti
g 03 ft
O
03 a ft
a> w o
ftrto
^°
lO
9
5
Ift
u 6
Sis
o so
Pressure
required at
Generator
terminals.
•rH qj
cvg
l§
a.
6.
c.
d.
e.
/•
9-
h.
m.
X.
lOO
125
150
175
.07460
.05968
.04973
.04262
574.58
459.68
383.06
328.28
$57,458
45.968
38.306
32.828
$2.8729
2.2984
1.9153
1.6414
.5745
.3831
.2739
.01626
.02032
.02439
.02845
$.1626
.2032
.2439
.2845
101.626
102.032
102.439
102.845
1.626
2.032
2.439
2.845
200
225
250
275
.03730
.03316
.02984
.02713
287.28
255.40
208.94
28.728
25.540
22.984
20.894
1.4364
1.2770
1.1492
1.0447
.2050
.1594
.1278
.1045
.03252
.03658
.04065
.04471
.3252
.3658
.4065
.4471
103.252
103.658
104.065
104.471
3.252
3.658
4.065
4.471
300
325
350
375
.02486
.02295
.02131
.01989
191.52
176.79
164.14
153.22
19.152
17.679
16.414
15.322
.9576
.8839
.8207
.7661
.0871
.0737
.0632
.0546
.04878
.05284
.05691
.06097
.4878
.5284
.5691
.6097
104.878
105.284
105.691
106.097
4.878
5.284
5.691
6.097
400
425
450
475
.01865
.01755
.01658
.01570
143.64
135.19
127.70
120.97
14.364
13.519
12.770
12.097
.6182
.6759
.6385
.6048
.0479
.0423
.0374
.0337
.06504
.06910
.07317
.07723
.6504
.6910
.7317
.7723
106.504
106.910
107.317
107.723
6.504
6.910
7.317
7.723
500
525
550
575
.01492
.01420
.01356
.01297
114.92
109.44
104.47
99.93
11.492
10.944
10.447
9.993
.5746
.5472
.5223
.4996
.0302
.0274
.0249
.0227
.08130
.08536
.08942
.09348
.8130
.8536
.8942
.9348
108.130
108.536
108.942
109.348
8.130
8.536
8.942
9.348
600
625
650
675
.01244
.01193
.01147
.01105
95.76
91.93
88.39
85.12
9.576
9.193
8.839
8.512
.4788
.4596
.4419
.4256
.0208
.0192
.0177
.0163
.09756
.10162
.10568
.10974
. 1.9756
| 1.0162
3 1.0568
I 1.0974
109.756
110.162
110.568
110.974
9.756
10.162
10.568
10.974
900
725
750
775
.01066
.01029
.00995
.00962
82.08
79.25
76.61
74.14
8.208
7.925
7.661
7.414
.4104
.3962
.3830
.3707
.0152
.0142
.0132
.0123
.11382
.11788
.12194
.12600
g 1.1382
53 1.1788
!H 1.2194
€ 1.2600
111.382
111.788
112.194
112.600
11.382
11.788
12.194
12.600
soo
825
850
875
.00933
.00905
.00878
.00854
71.82
69.64
67.59
65.66
7.182
6.964
6.750
6.566
.3591
.3482
.3379
.3283
.0116
.0109
.0103
.0096
.13008
.13414
.13820
.14226
g 1.3008
•£ 1.3414
g 1.3820
O 1.4226
113.008
113.414
113.820
114.226
13.008
13.414
13.820
14.226
ooo
925
950
975
.00829
.00807
.00785
.00766
63.84
62.12
60.48
58.93
6.384
6.212
6.048
5.893
.3192
.3106
.3024
.2946
.0091
.0086
.0082
.0078
.14634
.15040
.15446
.15852
1.4634
1.5040
1.5446
1.5822
114.634
115.040
115.446
115.852
14.634
15.040
15.446
15.852
lOOO
.00746
57.46
5.746
.2873
.0073
.16258
1.6258
116.258
16.258
Res. of 100 ft., 1 sq. in. at
80° C. = .010.0678.
98 CONDUCTORS.
6. When a plant is installed for more or less temporary work, it is, of
course, policy to make the first cost a minimum ; and again, in many places,
and perhaps in most places, it is impossible to predetermine the cost of
power per unit, or number of hours it will be necessary to run, or the num-
ber of hours of heavy and of light load, and many other items necessary to
be known in order to determine and calculate the most economical form of
plant to install.
In such cases it is often necessary to feel one's way by installing a plant of
low cost until the market is developed or its direction determined, after
which it is much easier to lay out a plant that will produce the most econom-
ical results.
Sprague says that the least cost of plant is determined when the variation
in the cost of the generator is equal to that in the cost of the line ; which is
practically true, provided the cost of motors and generators per horse-power
or unit capacity is the same. Sprague then develops the following law : —
" With fixed conditions of cost and of efficiency of apparatus, the number
of volts fall to get the minimum cost of plant, is a function of distance
alone, and is independent of the E.M.F. used at the motor."
" With any fixed couple and commercial efficiency, the cost of the wire
bears a definite and fixed ratio to the cost of the generating plant."
" The cost of the wire varies directly with the cost of the generating
plant."
" If we do not limit ourselves in the E.M.F. used, the cost per horse-power
delivered exclusive of line erection is, for least cost and for a given commer-
cial efficiency, absolutely independent of the distance."
Without going into the detail, if we work out problems based on the above
laws, the result shows that the law first stated by Professor Forbes, i.e., that
" the most economical section of conductor is independent of the distance
or E.M.F., and is proportional to the current," is correct.
Badt develops the following law : —
" For minimum initial cost of plant, and assuming certain prices per
horse-power of motors and generators and power plant (all erected and
ready for operation), and assuming a certain price per pound for copper (de-
livered at the poles), the total cost of the plant, excluding line construction,
is a constant for a certain efficiency of the electric system, no matter what
the E.M.F. of the motor and the distance may be."
" At a given efficiency of the electric system, the E.M.F. of the motor and
distance will increase and decrease in the same ratio."
7. In designing for the accomplishment of the best service, series circuits
can be economically laid out under some of the previous rules ; but in de-
signing circuits for parallel distribution, they must be arranged for furnish-
ing a constant and unvarying pressure at the lamps or motors of the
customer, regardless of the cost of conductors ; and therefore service require-
ments and not minimum first cost govern, as no service will be a paying
investment that has not a uniform pressure and is not continuous in its
character.
Parallel distribution is fully treated in another chapter.
8. It is the attempt of all engineers to attain a maximum income from a
minimum first cost of plant.
If power is cheap and transportation costly, it is better to construct plant
under Section 3. In some cases, though, so much of the station capacity
might be wasted in the conductors as to leave little from which an income
could be received ; but increasing the carrying capacity of the conductors
somewhat, provided it did not cost too much to accommodate the extra
machinery, would enable a paying income to be made.
In order to determine the proper relation of line to station and plant, it is
necessary to study the prospective loads. If street-lighting by series arcs is
to be one of the sources of income, then a study of the hours of lighting
must be made, and all the data as to number of hours burning, etc., will be
found in the chapter on lighting schedules.
For parallel and other methods of distribution, it will be necessary for
some one acquainted with the system to make the necessary examination of
the territory, and determine from its nature the probable load-curves.
CALCULATION OF SIZE OF CONDUCTORS.
99
Efficiency in Electric Pow*ir transmission.
From Badt's " Electric Transmission Hand-Book."
1.
2.
3.
4.
5.
6.
£o
2s|
II
^.SS
Hz
Iff
w-Sl
? °
Mech. H
be deliv
at gene:
pulle;
N.
I.
1.00
1.1111
0.0
1.1111
1.2346
81.00
1.00
1.1111
1.0
1.1223
1.2470
80.19
1.00
1.1111
2.0
1.1337
1.2597
79.38
1.00
1.1111
3.0
1.1454
1.2727
78.57
1.00
1.1111
4.0
1.1574
1.2860
77.76
1.00
1.1111
5.0
1.1696
1.2995
76.95
1.00
1.1111
6.0
1.1721
1.3134
76.14
1.00
1.1111
7.0
1.1947
1.3275
75.33
1.00
1.1111
8.0
1.2077
1.3419
74.52
1.00
1.1111
9.0
1.2210
1.3567
73.71
1.00
1.1111
10.0
1.2345
1.3717
72.90
1.00
1.1111
12.5
1.2698
1.4109
70.88
1.00
1.1111
15.0
1.3072
1.4524
68.85
1.00
1.1111
17.5
1.3468
1.4964
66.83
1.00
1.1111
20.0
1.3888
1.5447
64.80
1.00
1.1111
32.5
1.4336
1.5929
62.78
1.00
1.1111
25.0
1.4815
1.6461
60.75
1.00
1.1111
27.5
1.5325
1.7028
58.73
1.00
1.1111
30.0
1.5873
1.7636
56.70
1.00
1.1111
32.5
1.6464
1.8293
54.68
1.00
1.1111
35.0
1.7094
1.8993
52.65
1.00
1.1111
37.5
1.7778
1.9753
50.63
1.00
1.1111
38.3
1.8000
2.0000
50.00
1.00
1.1111
40.0
1.8518
2.0576
48.60
1.00
1.1111
42.5
1.9323
2.1470
46.58
1.00
1.1111
45.0
2.0210
2.2446
44.55
1.00
1.1111
47.5
2.1164
2.3515
42.53
1.00
1.1111
50.0
2.2222
2.4622
40.50
CAICUIATIOI OF THE SIZE OE COaTDUCTOKS
FOR COITIHUOIJ8 CUit5*EI¥TS.
Parallel distribution : —
Resistance of one mil-foot pure copper at"0° C = 9.59 ohms ;
Temp, coefficient for 70° F. = 1.084
Resistance of 1 mil-foot of pure copper at 70° F.= 10.395 ohms ;
Resistance of 1 mil-foot of 96% conductivity
copper wire at 70° F. = 10.81 ohms ;
dia 2 — Length in feet x 10-81
RAsiat:5irn->A ^ '
100 CONDUCTORS.
Resistance of a copper wire conductor is then equal to
Length in feet X 10.81 „ ,
diaT = ^.ohms.
and the cross-section in circular mils or
lgth in
Resistance
For lamps : —
Let w — watts per candle-power ;
then candle-power x w = watts per lamp, = W;
and if E=i voltage, or P.D. of circuit ;
W
then — = 1= current in amperes per lamp.
A voltage at which lamps are to he run is usually assumed, and a drop or
loss of pressure of a certain percentage of this, determined on, and all wiring
is calculated with those points as data. For instance, the most common
voltage is 110 or thereabouts, and 5% drop, or 5.5 volts, is commonly assumed
as the loss in pressure ; then the size of wire to produce this drop, with a
given number of lamps, A7, taking, say, I amperes will be
10.81 x 2 distance X I ,. „ . n ... -.
n~^5 ?-? = dia.2, or circular mils of copper. (3)
volts drop 5.5 v '
For example : 120 lamps taking .5 amp. each are to be wired at a distance
of 60 feet from the dynamo to the centre of distribution, at a drop of 3 volts.
_ 10.81 x 2 x fiCK X 60 amps. „... . ., x. „ ^ ,0
Then, — — — 25944 cir. mils, or No. 6 B. and S.
3 volts.
If the hot resistance of one lamp be given, and the number of lamps and
distance, with the percentage of loss, then
.. 10.81 x 2 distance x no. of lamps 100 — % loss
cir. mils = =r — r-r tt^ ^ — X — tt^t1 (4)
Resistance of one lamp % loss.
Example : — Take the same case as above: 120 lamps ; distance 60 feet;
drop in circuit, 3 % ; hot resistance of lamp, 200 ohms.
10.81 X 2 X 60' X 120 100 — 3 „„.. . ..
Then, ^ X — „ — = 25944 cir. mils.
For motors : —
1 Electric horse-power = 746 watts.
Therefore, horse-power x 746 = watts.
And watts -~ volts = amperes.
Let E= volts at terminals of motor,
v = volts lost in conductor.
I4-» = E.M.F. at generator terminals.
I=i current required at motor to deliver A7"mechanical h.p. at shaft
of motor.
D= single distance between motor and generator.
AT:= number of mechanical h.p. delivered at motor shaft.
A =area of cross-section of conductor in cir. mils.
R — conductor resistance both ways.
wt =i weight in pounds of conductor copper.
m % = commercial efficiency of motor.
g % = commercial efficiency of generator.
I % — commercial efficiency of whole system.
c % = per cent of energy lost in conductor.
all % expressed as a decimal, as, 90 % = .90,
A7"
Then, —^ = electrical horse-power delivered at motor terminals :
m%
746 & /»
and 7=-^^ = amperes. (5)
By formula No. 1, R = -, — '- — = resistance of conductor both ways.
SIZES OF CONDUCTORS. 101
The drop or loss in the line v=zl R, or
V = IXDX 21.02. (6)
(7)
Substituting the value for I,
. 746 xi^X Dx 21.62
we have, A = ^ — „ ; (8)
E X m% X v w
, , . . 16128.5 XJ^XD
and reducing we have, — = = .
& ' EXm%xv
Example : —
Motor 20 h.p. m% =90%.
Yolts at terminals = 500.
Distance = 200 ft.
Loss in conductors = 5 % .
Then, E.M.F. of generator = ^ = 526.3 volts,
and drop in line, v = 526.3 — 500 = 26.3 ;
•o ^ t, ^ t /« t 746 V 746 X 20
But by formula (5), /= v,^m0/ » or I = = 33 amperes ;
' Exm% 500 X .90
and the National code only allows 8 amperes for No. 16, and 33 amperes
would need at least No. 10 wire.
The volts drop and per cent loss in No. 10 B. and S. wire, required to carry
the 33 amperes as above shown, will be found as follows : —
R of No. 10 B. and S. = .0009972 per foot ;
R of 400 ft. = .39888 ohms ;
Volts drop = IR — 33 x 39888 = 13.16 volts ;
Volts at generator = 500 + 13. = 513.
Per cent drop = — - = 2.5 %.
513
SIZJES OF COXDIICTORi FOR ¥1¥CA]¥I»ESCI3]¥T
CIRCOTi.
(By W. D. Weaver.)
The most accurate method of determining the proper sizes of incandescent
lamp conductors is to refer all measurements back to the dynamo, converter,
or street tap.
To illustrate, suppose we have an installa-
tion of 150 lights, consisting of a feeder or
dynamo main 20 feet long (to distributing
point), and several mains, A, B, and C, their
lamps and lamp centres being respectively
60, 50, and 40 in number, and 38, 60, and 90
feet from the end of the feeder. Let us
calculate the sizes of the feeder and one
main, and of one branch having 12 lamps,
with centre 20 feet from the main, the
branch starting 18 feet from the distribut- »
ing point. (See cut.) ~Fig. 1.
To find the size of the branch wire, refer
to the appropriate table with 20 + 18 + 20
feet, or 58 feet for 12 lamps.
To find the size of the main, imagine the branches on one side to be
revolved (or lay them out thus on a diagram), so that all are on the same side
sl
B
- ,
1
%
c c
,1
| ' .
CENTRE, 90 F.EET
U:
sl;
10*2 CONDUCTORS.
of the main ; then estimate or calculate the lamp centre of the resultant group,
which in this case we will suppose to be 23 feet from the main, and 38 feet
from the distributing- point measured along the main, and refer to the table
with 2i> + .-;s + 2:> feet for 12 + 30 + is lamps, or 81 feet for GO lamps.
To find the size of the feeder, suppose the mains to be revolved about the
distributing point so that they all overlap, and with all the branches on one
.side of the^overlapping mains ; then estimate or calculate the lamp centre
of the resultant group (comprising all the lamps), which in this case we will
suppose to be 'JO feet from the overlapping mains measured at right angles,
and 48 feet from the distributing point measured along the main, and refer
to the table with '20 + 48 -f- 20 feet, or 88 feet for 150 lights, or for the largest
number of lights that will ever be used at one time.
In simple 'cases the quantities maybe estimated either directly (especially
for branches) or from rough diagrams ; and for more complex cases, or where
a perfectly accurate result is desired, the following rules are given : —
For 1$ randies, follow the method given above.
For jfiiiiia*. multiply the number of lamps on each branch of a main by
the distance of their lamp centre from the distributing point, always meas-
ured along the lead of the main and branch ; add the products thus obtained
for all the branches'on the main, and divide by the whole number of lamps
on the branches. Add the length of feeder, and refer to the table with the
resultant distance and lamps.
Example : — (See cut, main A.)
(18 + 20) X 12= 456
(33+30) X 30—1890
(60 + 15) X 18 = 1350
456 + 1890 + 1350 , OA Q1 , , „ „.
io_l 'M _l i' +20 = 81 feet for 60 lamps.
For .'Fenders, add the sum of the products obtained as above for all
the mains, divide by the entire number of lamps on the feeder, add the
length of the feeder, and refer to the table with this distance and all the
lamps on the feeder, or the largest number that will ever be used at one time.
Example : — (See cut.)
Main A. 456 + 1890 + 1350= 3696
Main B. 60 X 50 =3000
Main C. 90 X 40 =3600
3696 + 3000 + 3609 OQ
! ! U20 = SX feet for 150 lamps.
150
Care must be taken not to confound a lamp centre (so-called) Avith a geo-
metrical centre. For example, suppose a series of branches of equal length
radiating from the end of a main like the spokes of a wheel, and having
lamps at equal intervals. Here the geometrical centre is the radiating
point, while the lamp centre is on a circle passing through the centres of
the various groups, or the length of the radius from the radiating point. In
the case of the main A given above, the geometrical centre is 15 feet from
the main, while the true lamp centre is 23 feet. It is to preclude the error
of geometrical centres that the branches and mains are laid down, or ima-
gined, revolved.
$ul»-l>raiiches and 'Taps may in general be considered as groups of
lamps directly on the branch itself, and thus included in the calculation for
the branch.
The above method is applicable to all systems of wiring, and is particularly
valuable and economical in securing proper distribution of light on low volt-
age circuits having a small percentage of loss. By stringing the branches
first, when possible, this method may he easily followed without the aid of
a diagram, even in complex cases. With the "closet" system of wiring,
diagrams and calculations as a rule will not be required.
The " tree" system of wiring is to be avoided where possible, on account
of the unequal distribution of light it entails. In many cases, secondary
centres of distribution may be substituted ; and if carefully calculated, the
weight of wire in the latter case need not exceed that in the former.
The voltmeter should always be connected with the centre of distribution,
and not with the feeder near the dynamo, unless it is desirable to have a
steady light in a particular locality, when it should be connected with the
line there.
t
y
1
CALCULATION OF SIZE.
108
Owing to the exceedingly small current passing through a voltmeter, the
resistance oil even a very small wire in ordinary cases will not practically
affect its readings. Where the line is very long, a No. 12 or 14 insulated
iron wire may be used, and the voltmeter at the dynamo set once for all by
comparison with a standard voltmeter temporarily attached at the point
which is to be maintained at a constant potential.
CAlCULATIOlf OF THE SIZE OF CO\Dt CTOHM
FOR AETEJR]¥ATI]1T« CHRBEIT CIRCUITi.
When alternating currents first came into use, it was customary to calcu-
late the sizes of conductors by the ordinary rules used in connection with
direct currents. This did very well as long as small currents were in use,
and distances were comparatively short ; but before long new effects began
on the lines that were unaccountable to any one not familiar with the action
of such currents in a conductor, and this led to a more thorough study of the
problems.
Briefly stated there are, besides the ohmic resistance of the copper, the
following effects, due to tli3 use of alternating currents : —
Skin effect, a retardation of the current due to the property of alternating
currents of apparently flowing along the outer surface or shell of the con-
ductor, thus not making use of the full area.
Inductive effects, a, self-induction of the current due to its alternations, in-
ducing a counter E.M.F. in the conductor ; and b, mutual inductance, or the
effect of other alternating current circuits.
Capacity Effects, due to the fact that all lines of conductors act as electri-
cal condensers, which are alternately charged and discharged with the
fluctuations of the E.M.F.
Skin Effect.
The increase in resistance due to skin effect can be found by the use of the
following table : —
Skin Effect Factors, for Conductors carrying* Alternating-
Currents.
Note. — For true resistance, multiply ohmic resistance by factor from
this table.
Diam.
and
Frequencies.
B.&S.
gauge.
15
20
25
33
40
50
60
80
100
130
2"
1.111
1.160
1.265
1.405
1.531
1.682
1.826
2.074
2.290
2.560
If
1.072
1.114
1.170
1.270
1.366
1.495
1.622
1.841
2.030
2 272
13
1.042
1.064
1.098
1.161
1.223
1.321
1.420
1.610
1.765
1.983
i\
1.019
1.030
1.053
1.084
1.118
1.176
1.239
1.374
1.506
1.694
{*
1.010
1.019
1.035
1.059
1.080
1.124
1.168
1.270
1.382
1.545
1.005
1.010
1.020
1.038
1.052
1.080
1.111
1.181
1.263
1.397
I"
1.002
1.002
1.007
1.014
1.016
1.028
1.040
1.066
1.100
1.156
\"
1.001
1.001
1.002
1.005
1.006
1.007
1.008
1.011
1.022
1.039
0000
1.001
1.003
1.005
1.005
1.006
1.010
1.015
1.027
000
1.001
1.002
1.002
1.005
1.007
1.010
1.017
00
1. 01
1.001
1.002
1.004
1.006
1.010
0
1.001
1.002
1.005
1.008
1
1.001
1.002
1.005
2
1.001
1.002
3
1.001
4
1.000
104
CONDUCTORS.
For other frequencies, Emmet gives the following tahle : —
Product of Cir. Mils
by Cycles per sec.
10,000,000
1.00
20,000,000
1.01
30,000,000
1.03
40,000,000
1.05
50,000,000
1.08
60,000,000
1.10
70,000,000
1.13
80,000,000
1.17
90,000,000
1.20
100,000,000
1.25
125,000,000
1.34
150,000,000
1.43
Factors in the above table multiplied by the resistance in ohms will give
the resistance of circular copper conductors to alternating currents.
Effects of Self-induction. — Owing to the periodic variations of
current in alternating-current circuits, a counter E.M.F. is set up, which
does not coincide with the current, and which is not continuous, but periodic ;
and, owing to the fact that such E.M.F. is the strongest when the current is
increasing or decreasing most rapidly, the counter E.M.F. differs in phase
with the current by 90°.
If there be no inductive effect in a circuit (without considering anything
else at present), the current produced by an impressed E.M.F. would be in
phase, and the watts would be, as in direct currents, the product of the
E.M.F. and current. Taking into account the inductive effect, the current
is never in phase with the impressed E.M.F., and the watts are therefore
never equal to the product of the two, but are less, according to the angle
of phase difference ; and if they could be in quadrature, the product would
be zero.
The E.M.F. impressed on the circuit may be
said to be made up of two components, one in
phase with the current, as in direct currents,
and the other in quadrature with it, as shown
below in a right-angle triangle.
ef.eect.ive or energy e.m.f. Counter or inductive E.M.F. varies with the
Fig. 2. frequency of alternations ; but if the out-going
and returning wires are close together, there is
little induction ; if wound in a coil, the self-induction is much increased,
and if an iron core be introduced into the coil, the flux is very much in-
creased, and therefore the self-induction.
Impedance. — In a plain, alternating-current circuit without iron, the
current due to a given E.M.F. will depend upon a resistance which is the
resultant of two components : its resistance as in
direct currents, and its inductive resistance, or
the current divided into the inductive E.M.F.
These two components are compounded at right
angles, and the resultant is called impedance, and
can be represented by the same triangle as was
used to illustrate the two E.M.F.'s and their
resultant.
Impedance also varies with the rate of alternations the same as does the
counter or inductive E.M.F.
If we have a circuit including a number of parts
____— --^'lu. *n series, each having a different angle of lag, and
ir~ ^^ \. g represented as below by different triangles joined
/I *■&%*>*' !■* together, it will be seen that the sum of all the
/-" X^^ " E.M.F.'s impressed upon the parts or impedances
jy^f ^N | is greater than the E.M.F. impressed upon the
^_ — 1 \° whole circuit ; and in order to arrive at the latter
total ENtBGY e.m f. value, it is necessary to lay out each case sepa-
Fig. 4. rately, all the horizontal lines representing energy
ENERGY resistance
Fig. 3.
CALCULATION OF SIZE.
105
E.M.F.'s (or resistances), and all the vertical lines representing inductive
E.M.F.'s (or resistances, now called reactances).
To find the impedance equal to two impedances in parallel, construct a
parallelogram, the adjacent sides of which will
he the reciprocals of their values ; the diagonal
of this parallelogram will be the reciprocal of
the value of the resulting impedance ; and, as
the lines representing the given impedances are
joined at the proper phase angle with each other,
the direction of the diagonal will represent the
resulting phase.
In the above figure -^ = §.
Fig. 5.
-r— = AD = 1.3 ohms.
Ax
If two impedances, connected in parallel, have such values as to give a
phase difference of 90°, i.e., are at right angles with each other, their result-
ant value can be found by constructing a right-
angle triangle, whose adjacent sides represent
in direction and length the values of the two
impedances in parallel. Join the two ends,
and a line drawn from this hypothenuse at
right angles and meeting the others at their
junction, will be equal to and in tbe direction
of the resultant value.
Yig. 6. -^ ac and ce are tw0 impedances in parallel,
with a difference in phase of 90°, then cd equals
in direction and in length the resultant of the two.
Capacity Effects. — A condenser connected in multiple across the
leads of an a. c. circuit is charged as the E.M.F.
rises, and discharged as the E.M.F. falls, thus
returning E.M.F. to the line just at the time
that the inductive E.M.F. is opposing the line
E.M.F., and both can be so arranged as to neu-
tralize each other, or enough capacity can be
introduced to cause a negative lag-angle, as shown
in the following figure.
When a condenser or a line having capacity is
subjected to an alternating E.M.F., current will
flow in to fill the capacity equal to E X CX w,
where E is the E.M.F., C, tbe capacity in farads, and io = 2Tr N.
Thus, if a line has a capacity of 3 micro-farads, 2? = 2000 volts, and .ZV=30,
then —
Fig. 7.
Amperes 7=
1,000,000
X 2000X30X6.28 = .7536.
Ceo
And a condenser may be said to have a reactance of
This reactance is also in quadrature with the energy E.M.F., as is the in-
ductive reactance, but acting in the opposite direction to that of the induc-
tance ; and may therefore be so arranged as to neutralize it. Line capacity
acts like a condenser placed in multiple at the middle point of the length
of the line.
Lag angles and power factors of alternating-current motors of the induc-
tion type vary with the load they carry and with the design and size, some
of large size having power factors as high as 97% at full load, while poorly
designed motors may have but 75% or less.
Synchronous motors run with a separately excited field, which may be so
varied as to produce a leading or lagging current, or be made to take from or
return energy to the line. When running with but little load, with field cur-
rent high, energy will be absorbed from the line as the impressed E.M.F.
106
CONDUCTORS.
rises, and returned to the line as it falls, thus acting like a condenser, and
tending to steady the E.M.F. of the circuit, which maybe disturbed and
lowered by the inductance of induction motors.
Closed circuit transformers with secondary open have a power factor of
about 70%, and when loaded with non-inductive load, large sizes have a
power factor of over'.YJ1;;,, with an induction component of say 6%, even at
halt-load the power factor is over 99%.
In the ordinary alternating-current lighting circuits, the elements are, the
lamps, the secondary circuits, the transformers, the primary mains, and
feeders.
li distances are considerable and the wires large, there will be some in-
duction due to the primary and secondary mains ; but most of the effect will
come from the transformer, provided, of course, that nothing but incandes-
cent lamps are used as load on the seci mdary. With good-sized transformers,
the total power factor will be above 99%.
In the following table will be found the angles of lag, together with the
power-factors ami factors of induction due to each, from which may be com-
puted the effects on lines of different inductances.
Power IT actor* and Induction Factors for Different
Angles of Lag*.
Ch3
«3
£ i.?
ft°£
o .
£ o
-£1
£ Ji.%
ft -d
£ bJO
u -
be
o o
^ft
U 1 S
c £ "
ft°^
,2 to
if. %
a hi
> s
4
o so
ft°^
bo
O
O
'xfi
o
O
o
O
o
O
.3
m
1
.9998
.0174
24
.9135
.4067
46
.6946
.7193
69
.3584
.9336
2
.9994
.0349
25
.9063
.4226
47
.6820
.7313
70
.3420
.9397
3
.9986
.0523
26
.8988
.4384
48
.6691
.7431
71
.3256
.9455
4
.9976
.0698
27
.8910
.4540
49
.6561
.7547
72
.3090
.9511
5
.9%2
.0872
28
.8829
.4695
50
.6428
.7660
73
.2924
.9563
6
.9945
.1045
29
.8746
.4848
51
.6293
.7771
74
.2756
.9613
7
.9925
.1219
30
.8660
.5000
52
.6156
.7880
75
.2588
.9659
8
.9903
.1392
31
.8572
.5150
53
.6018
.7986
76
.2419
.9703
9
.9877
.1564
32
.8480
.5299
54
.5878
.8090
77
.2249
.9744
10
.9848
.1736
33
.8387
.5446
55
.5736
.8191
78
.2079
.9781
11
.9816
.1908
34
.8290
.5592
56
.5592
.8290
79
.1908
.9816
12
.9781
.2079
35
.8191
.5736
57
.5446
.8387
80
.1736
.9848
13
.9744
.2249
36
.8090
.5878
58
.5299
.8480
81
.1564
.9877
14
.9703
.2419
37
.7986
.6018
59
.5150
.8572
82
.1392
.9903
15
.9659
.2588
38
.7880
.6156
60
.5000
.8660
83
.1219
.9925
10
.9613
.2756
39
.7771
.6293
61
.4848
.8746
84
.1045
.9945
17
.9563
.2924
40
.7660
.6428
62
.4695
.8829
85
.0872
.9962
18
.9511
.3090
41
.7547
.6561
63
.4540
.8910
86
.0698
.9976
19
.9455
.3256
42
.7431
.6691
64
.4384
.8988
87
.0523
.9986
20
.9397
.3420
43
.7313
.6820
65
.4226
.9063
88
.0349
.9994
21
.9336
.3584
44
.7193
.6946
6d
.4067
.9135
89
.0174
.9998
22
.9272
.3746
45
.7071
.7071
67
.3907
.9205
23
.9205
.3907
68
.3746
.9272
Inductive Resistance of 'ILines. — As previously stated, two par-
allel wires carrying alternating currents induce in each other counter or in-
ductive E.M.F.'s that tend to retard the flow of current. The closer together
these wires are, the less is this effect, and the more nearly the current waves
are to the simple harmonic curve, the less is the retardation.
The counter E.M.F. is somewhat larger for small wires than for large,
^^■^■■^■^^■^
INDUCTANCE FACTORS.
107
provided the current and distance between centres be the same, and the
effect is about 150 times greater in iron wire circuits than with copper, as
will be seen by reference to the following formulae, by which both are cal-
culated.
ODrClAIGE FACTORS.
In Tables I. and II. below are given the formula? for inductance of two
parallel wires of copper and of iron ; and in Table III. the inductance per
mile for two copper wires has been computed for different inter-axial dis-
tances.
Table I. — Inductance for Parallel Copper Wires,
Insulated.
Formula,
d — distance apart, centre to centre, of wires
r = radius of wires.
L = inductance of each wire in millihenrys.
- .5 + ( 2 log e - j 10 b > per centimeter.
L per centimeter — .000,000,5 + .000,004,6 log-
L per inch
= .000,001.27 + .000,011,68 log-.
L per foot
= .000,015,24 + .000,14
i d
L per 1,000 feet
= .01524 +.14
i d
log — .
L per mile
= .08.5 + .741
i d
Talile II. — Inductance for Parallel Iron Wires,
Insulated.
d = distance apart, centre to centre, of wires.
r = radius of wires.
Z = inductance of each wire in millihenrys.
L =z 75. +( 2 log e - j 10-6, per centimeter.
L per centimeter — : .000,075 + .000,004,6 log -.
d
L per inch
L per foot
L per 1,000 feet = .2286 + .14 log
L per mile = .12,075 + .741 log-.
: .000,191 + .000,011,68 log - .
:. 002,286 +.000,14 log-.
d
108
CONDUCTORS.
each of Two Copper Wires Parallel to each other.
Interaxial Distance in Inches.
B. and S.
gauge.
3.
6.
12.
24.
36.
48.
0000
0.907
1.130
1.353
1.576
1.707
1.799
000
0.944
1.168
1.391
1.614
1.745
1.836
00
0.982
1.205
1.425
1.651
1.784
1.874
0
1.019
1.242
1.465
1.688
1.818
1.911
1
1.056
1.280
1.502
1.725
1.856
1.949
2
1.094
1.317
1.540
1.764
1.893
1.986
3
1.131
1.354
1.577
1.800
1.931
2.023
4
1.168
1.392
1.614
1.838
1.968
2.061
5
1.206
1.429
1.652
1.875
2.005
2.099
6
1.243
1.466
1.689
1.912
2.043
2.135
7
1.280
1.503
1.727
1.949
2.079
2.172
8
1.317
1.540
1.764
1.986
2.117
2.209
9
1.355
1.578
1.801
2.025
2.155
2.248
10
1.392
1.615
1.838
2.061
2.192
2.285
11
1.429
1.652
1.875
2.099
2.229
2.322
12
1.467
1.690
1.913
2.135
2.266
2.359
Inductance in Millihenrys per lOOO feet of Copper
Circuit.
2 AERIAL WIRES.
Interaxial
Distance.
\" dia.
£" dia.
\" dia.
B. and S.
0000
000
00
0
3"
.248
.283
.333
.344
.358
.373
.386
6
.333
.369
.417
.428
.442
.456
.471
12
AM
.451
.500
.513
.527
.540
.555
24
.500
.538
.587
.597
.611
.625
.640
48
.587
.621
.671
.681
.695
.710
.724
Interaxial
Distance.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
3"
.400
.415
.429
.442
.457
.472
.484
.499
.513
.527
6
.485
.498
.513
.527
.541
.555
.570
.583
.597
.612
12
.570
.583
.597
.612
.626
.640
.654
.668
.683
.696
24
.654
.668
.682
.696
.711
.724
.738
.753
.767
.781
48
.738
.752
.767
.781
.795
.808
.823
.837
.851
.865
Rift
= millihenrys per centimeter ;
= millihenrys per 1000 ft. of copper wire.
Inductive resistance =
2 77 n x millihenrys from above table _
henrys per 1000 feet of circuit.
Inductive drop = current X inductive resistance.
INDUCTANCE OF THREE-PHASE SYSTEM.
109
IHTRTJCTAUCE PER MTEE OF CIRCUIT THREE-
PHASE SYSTEM, ©O p. p. s.
(Dr. P. A. C
. Perrine in Trans. A
.I.E.
E.)
02
<D
02
gx .
43
N
02
3-5 3
hi
S .9
^ 00
M B ^
<b td
02 W
fx§3
43
M
02
"5 ^^
s
S .3
§xo
14s
3000
.46
12
.00234
0.884
2
.258
12
.00267
1.008
18
.00256
.967
18
.00288
1.088
24
.00270
1.015
24
.00304
1.148
48
.00312
1.178
48
.003<*4
1.299
000
.41
12
.00241
.910
3
.229
12
.00274
1.035
18
.00262
.989
18
.00294
1.110
24
.00277
1.046
24
.00310
1.171
48
.00318
1.201
48
.00351
1.335
00
.365
12
.00248
.937
4
.204
12
.00280
1.057
18
.00269
1.016
18
.00300
1.133
24
.00285
1.076
24
.00315
1.189
48
.00330
1.246
48
.00358
1.351
0
.325
12
.00254
.959
5
.182
12
.00286
1.080
18
.00276
1.042
18
.00307
1.159
24
.00293
1.106
24
.00323
1.220
48
.00331
1.250
48
.00356
1.344
1
.289
12
.00260
.983
6
.162
12
.00291
1.098
18
.00281
1.061
18
.00313
1.182
24
.00298
1.125
24
.00329
1.243
48
.00338
1.276
48
.00360
1.393
7
.144
12
.00298
1.125
9
.114
12
.00310
1.171
18
.00310
1.204
18
.00332
1.253
24
.00336
1.269
24
.00348
1.314
48
.00377
1.423
48
.00389
1.469
8
.128
12
.00303
1.144
10
.102
12
.00318
1.201
18
.00325
1.227
18
.00340
1.284
24
.00341
1.288
24
.00355
1.340
48
.00384
1.450
48
.00396
1.495
Rasis of Table.
Lab = 2 V3 Ylog \r)-\-j I — self-ind. in C. G. S. units for loop a. b. (per cm.)
L 0.434 J
Lab — 0.000558 T2.303 logw (—\ + .25] L, in henrys.
Inductive drop in loop ab =z Lab X 2 n X f X I-
d = distance between wires (inch).
r = radius of wire (inch).
L — length of circuit in miles.
f=. cycles per second.
1=. current in one wire.
Por self-induction of one wire divide Lab by V3.
110
CONDUCTORS.
Inductive Resistance of Two Parallel Insulated Wires.
FREQUENCY 100.
lnteraxial Distance.
Diam.
r
5
11"
3"
6"
12"
24"
48"
B. & S.
gauge.
Olims
Ohms
Ohms
Ohms
Ohms
Ohms
Ohms
Ohms
per
per
per
per
per
per
per
per
1000 ft.
1000 ft.
1000 ft.
1000 ft.
1000 ft.
1000 ft.
1000 ft.
1000 ft.
dist.
dist.
dist.
dist.
dist.
dist
dist.
dist.
o//
.106
.159
.213
.267
.322
11
.128
.182
.236
.290
.344
1
.106
.160
.213
.267
.321
.375
|
.128
.182
.236
.290
.344
.398
i
.159
.213
.267
.321
.375
.429
0000
.060
.114
.168
.222
.275
.329
.383
.437
000
.0G9
.123
.177
.230
.284
.338
.392
.446
00
.078
.132
.186
.239
.293
.347
.401
.455.
0
.087
.141
.195
.248
.302
.356
.410
.464
1
.096
.150
.203
.257
.311
.366
.419
.473
2
.105
.158
.212
.266
.320
.375
.428
.482
3
.114
.167
.221
.275
.329
.384
.437
.491
4
.122
.176
.230
.284
.338
.393
.446
.500
5
.131
.185
.239
.293
.346
.402
.455
.509
6
.140
.194
.248
.301
.355
.411
.464
.518
7
.149
.203
.256
.310
.364
.419
.473
.527
8
.158
.212
.265
.319
.373
.428
.482
.536
9
.167
.220
.274
.328
.382
.437
.491
.545
10
.176
.229
.283
.337
.391
.746
.500
.554
Inductive resistances at other frequencies are proportional to this table.
CAPACITY OJP COIS.IKUCTOMS.
The following formulae have been developed by examination of the best
authorities.
Table I. — Capacity of Insulated lead-Protected Cables.
/.• = specific inductive capacity of insulating material. See index for
table.
D = diameter of cable outside of insulation.
d = diameter of conductor.
Microfarads per centimeter length,
Microfarads per inch length,
Microfarads per foot length,
Microfarads per 1,000 feet length,
Microfarads per mile length,
.000,000,241,5.*.
.000,000,613,4. k.
. D
log -3-
.000,007,361. k.
. D
l0g7z'
.007,361. k.
i D
log?r
.038,83 k.
i D
lOg-g.
CAPACITY OF CONDUCTORS.
Ill
Table II. — Capacity of Sing-le Overhead Wires with
Kartla Return.
h= height above ground in mils or centimeters.
d— diameter of conductor in mils or centimeters.
Microfarads per centimeter length,
Microfarads per inch length,
Microfarads per foot length,
Microfarads per 1,000 feet length,
Microfarads per mile length,
.000,000,613,4
l0gd-
.000,007.361
. 4ft
l0grf '
.007,361
log-
log-
Taule III. — Capacity of each of Two Parallel Bare
JEraal Wii-e.*, Insulated.
D — distance apart from centre to centre.
r= radius of wirerr A of diameter.
Microfarads per centimeter length,
Microfarads per inch length,
Microfarads per foot length,
Microfarads per 1,000 feet iength,
Microfarads per mile length,
.000,000,120,8
log - •
■000,000,306,7
log- -
.000.003,681
i D
.003,681
i D
.019,42
Capacities per 1,000 ft. of Copper Circuit, 3 Wires.
AERIAL. MICROFARADS.
Interaxial
distance.
1" dia.
f" dia.
\" dia.
B. and S.
0000
000
00
0
3
.00946
.00815
.00682
.0066
.00631
.00605
.00581
6
.00682
.00611
.005326
.0052
.00502
.00485
.00469
12
.005326
.00489
.00436
.00428
.00416
.00404
.00393
24
.00436
.004075
.00371
.00364
.00356
.00347
.00339
48
.00371
.003492
.00322
.00317
.00311
.00304
.00298
112
CONDUCTORS.
Capacities per 1,000 ft. of Copper Circuit.
(Continued.)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
|l
3
.005585
.005375
.00518
.00501
.00484
.00468
.00454
.00441
.004275
.00416
fi
.004545
.00441
.00428
.00415
.00404
.00393
.00383
.00374
.00364
.003555
12
.00383
.00374
.00364
.00355
.00347
.00339
.00331
.00324
.00317
.00310
24
.00331
.00324
.00317
.00310
.003035
.00298
.00292
.00286
.00281
.00275
48
.00292
.002865
.00281
.00275
.00271
.00265
.00261
.00256
.00251
.00247
Capacity and Self-induction to Balance each other on
Circuits. Microfarads, or Henrys.
A. C. Cbehore.
o1
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
15
112.58
56.29
37.53
28.15
22.52
18.76
16.08
14.07
12.51
11.258
20
63.328
31.664
21.109
15.832
12.666
10.555
9.047
7.916
7.036
6.3328
25
40.528
20.264
13.509
10.132
8.106
6.755
5.789
5.066
4.503
4.0528
33
23.259
11.629
7.419
5.815
4.652
3.877
3.323
2.907
2.584
2.3259
40
15.831
7.915
5.277
3.958
3.166
2.638
2.262
1.979
1.759
1.5831
60
7.036
3.518
2.345
1.759
1.407
1.173
1.005
.889
.782
.7036
80
3.958
1.979
1.319
.989
.792
.659
.566
.495
.439
.3958
100
2.533
1.266
.844
.633
.507
.422
.362
.316
.281
.2533
130
1.498
0.749
.499
.375
.299
.249
.214
.187
.166
.1498
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
15
10.235
9.38
8.66
8.04
7.505
7.035
6.622
6.255
5.925
5.629
20
5.757
5.2775
4.8714
4.5235
4.222
3.958
3.7252
3.518
3.3330
3.1664
25
3.684
3.3775
3.1175
2.8945
2.702
2.533
2.3840
2.2515
2.1330
2.0264
33
2.114
1.9385
1.7891
1.6615
1.551
1.4535
1.3682
1.292
1.2242
1.1629
40
1.439
1.3190
1.2179
1.1310
1.055
.9895
.9312
.8795
.8332
.7915
60
.639
.5865
.5412
.5025
.469
.4445
.4139
.3910
.3703
.3518
80
.359
.3295
.3044
.2830
.264
.2475
.2328
.2195
.2083
.1979
100
.2303
.2110
.1948
.1810
.169
.1580
.1490
.1405
.1333
.1266
130
.1362
.1245
.1152
.1070
.0996
.0935
.8812
.0830
.0788
.0749
106
= (2tT«)2
Where L = coefficient of self induction.
C= capacity.
106r= microfarads.
n = frequency.
CAPACITY IN MICRO-FARADS.
113
CAPACITY Il¥ ]?i:iCII©-EA»AI»S A1JTD CHARGI1TG
CURREIVT, REM MILE OF CIRCUIT, THREE-
PHASE SYSTEM.
(Dr. F. A. C. Perrine in Trans. A.I.E.E.)
Line E.M.F. — 10,000 volts. 60 P.P.S.
02
u P
w
si
•2 rt
CD ft
13 J
o ^
o P
5 2
5
5-S
A ~
3.5
35
5-S
■2 a
^ «
0000
.46
12
.0226
.0492
4
.204
12
.01874
.0408
18
.0204
.0447
18
.01726
.0377
24
.01922
.0418
24
.01636
.0356
48
.01474
.0364
48
.01452
.0317
000
.41
12
.0218
.0474
5
.182
12
.01830
.0399
18
.01092
.0414
18
.01690
.0368
24
.01876
.0408
24
.01602
.0349
48
.01638
.0356
48
.01426
.0311
00
.375
12
.0214
.0465
6
.162
12
.01788
.0389
18
.01946
.0423
18
.01654
.0360
24
.01832
.0399
24
.01560
.0342
48
.01604
.0349
48
.0140
.0305
0
.325
12
.02078
.0453
7
.144
12
.01746
.0389
18
.01898
.0413
18
.01618
.0352
24
.01642
.0379
24
.01538
.0335
48
.01570
.0342
48
.01374
.0290
1
.289
12
.02022
.0440
8
.128
12
.01708
.0372
18
.01952
.0403
18
.01586
.0341
24
.01748
.0380
24
.01508
.0328
48
.0154
.0337
48
.01350
.0294
2
.258
12
.01972
.0372
9
.114
12
.01660
.0364
18
.01818
.0305
18
.01552
.0337
24
.01710
.0372
24
.01478
.0317
48
.01510
.0328
48
.01326
.0289
3
.229
12
.01938
.0421
10
.102
12
.01636
.0356
18
.01766
.0385
18
.01522
.0329 *
24
.01672
.0364
24
.01452
.0310
48
.01480
.0322
48
.01304
.0284
JSasis of Table.
1
C— -
3l09. <±)
in electro-static units per cm. of circuit.
c_ 0.0776 x L
in micro-farads between one wire and neutral point for L miles of circuit.
Charging current per wire = jz — ■ -
V3 x 106
d = distance between wires (inch). E = E.M.F. between wires.
r = radius of wire (inch). /= cycles per second.
L — length of circuit in miles. C — capacity in M.F. between one wire
and neutral point.
Charging current three-phase =:—-(= 15.5%) X charging current single-
"V3
phase for same d, r, L, and E.
114
CONDUCTORS.
inPEDAUCE A]¥I> REACI.4KCE OF AITEHSAT-
THHG CUBREiYT CIRCUIT'S.
By Steinmetz.
Let Ez: resistance in ohms.
L = impedance.
E = power E.M.F.
err impressed E.M.F.
(a = 2w7l.
L =r coefficient of self-induction.
I = current.
c = capacity.
Then :
In circuits containing Resistance* and Inductance,
Impedance, Z, — VR2 -f L2 a>2,
and e = VE2 + 12 L2 w2 ;
or diagrammatically,
Fig. 8. Fig. 9.
Circuits containing Resistance and Capacity.
Impedance, Z,= VR2 -4-
and e = Ve2 -
or diagramatically,
Fig. 10. Fig. 11.
Circuits containing Resistance, Inductance, and Capacity.
Impedance, Z,=
Vw
+ (lw
-£)'■
and e
matically,
_ 3
E2 + I
(— M-
Fig. 12.
Fig. 13.
IMPEDANCE AND REACTANCE.
115
Impedance factors and Multipliers.
Frequency = 100.
. <D
Dist. between
Dist. between
Dist. between
Dist. between
go
M e3
centres, 6".
centres, 12//.
centres, 24".
centres, 48".
Factor.
Multi-
plier.
Factor.
Multi-
plier.
Factor.
Multi-
plier.
Factor.
Multi-
plier.
2„
30.813
.094844
41.263
.170170
51.717
.26737
62.171
.386420
14
19.809
.039142
25.692
.065905
31.574
.099596
37.459
.140223
1
10.362
.010636
12.919
.016683
15.573
.024151
18.182
.032957
a
6.4873
.004108
7.9445
.006212
9.4039
.008745
10.869
.011712
2
3.3829
.001044 .
4.0118
.001509
4.6474
.002059
5.2874
.002696
0000
2.9793
.000787
3.5060
.001129
4.0400
.001532
4.5787
.001996
000
2.5004
.000525
2.9078
.000746
3.3225
.001000
3.7426
.00130-1
00
2.1227
.000351
2.4341
.000492
2.7528
.000658
3.0794
.000848
0
1.8316
.000235
2.0679
.000328
2.3130
.000435
2.5642
.000558
1
1.6021
.000157
1.7778
.000216
1.9622
.000285
2.1531
.000363
2
1.4306
.000105
1.5592
.000143
1.6958
.000187
1.8386
.000238
3
1.3024
.000069
1.3944
.000094
1.4935
.000123
1.5982
.000155
4
1.2092
.000046
1.2737
.000062
1.3439
.000081
1.4190
.000101
5
1.1428
.000031
1.1868
.000041
1.2357
.000053
1.2884
.000066
6
1.0968
.000020
1.1266
.000027
1.1598
.000035
1.1960
.0000438
7
1.0649
.0000134
1.0847
.0000176
1.1070
.0000225
1.1313
.0000277
8
1.0440
.0000089
1.0573
.0000118
1.0722
.0000140
1.0S86
.000018
9
1.0288
.0000058
1.0373
.0000076
1.0470
.0000096
1.0576
.0000119
10
1.0196
.0000039
1.0234
.0000049
1.0309
.0000063
1.0377
.000007
To find factor for any frequency, V(Multiplier X/2) -+■ 1 = factor required.
For convenience of the engineer impedance factors for the frequencies
most generally used have been computed by Prof. Forbes, and follow. To
find the true drop in line, multiply ohmic drop by factors in tables below.
Diameters are given in inches and B. & S. gauge.
Impedance factors
<o
8
<v
«
° . .•
v . .-
g
C-3 cjO
Pi
= ~ -
is °
%BS
|-S J
-*--; CJO
= a r
3.5 3
R a 3
gflo
+Z"* V
r*
.2 £3 cs
&al
2 CO %
a«*
•2 ^ a
.222 cs
Fr
zquency
/=15
Ft
i (p(c>/r)/
f— 25
1
1.842
2.182
2.535
2.904
2
7.7638
10.37
12.912
15.55
if
1.387
1.546
1.720
1.903
n
5.014
6.454
7.831
9.017
A
1.111
1.157
1.210
1.267
i
2.7i r>4
3.3826
4.012
4.642
0000
1.085
1.120
1.167
1.203
*
1.889
2.209
2.543
2.885
000
1.057
1.081
1.108
1.137
1.285
1.393
1.513
1.637
00
1.038
1.054
1.068
1.090
0
1.0264
1.036
1.048
1.061
0000
1.3068
1.3996
1.498
000
1.152
1.2104
1.2763
1.345
/— 2
0
00
1.1034
1.1422
1.1876
1.235
1
2.291
2.771
3.261
3.768
0
1.0710
1.0973
1.1277
1.160
*
1.624
1.863
2.116
2.378
1
1.0478
1.0676
1.0853
1.108
*
1.190
1.263
1.351
1.441
2
1 .0324
1.0443
1.0583
1.071
0000
1.146
1.206
1.271
1.341
3
1.0216
1.0293
1.03S4
1.048
000
1.100
1.139
1.184
1.233
4
1.0142
1.0191
1.0247
1.031
00
1.067
1.093
1.123
1.155
5
1.0094
1.0126
1.0162
1.0203
0
1.046
1.063
1.084
1.106
6
1.0063
1.0084
1.0107
1.0134
116
CONDUCTORS.
Impedance factors. — Continued.
*
8
8
8
8
* •!§ .-
8 • § •
<D
is!
m
3 - c
5^£
.52 £2 s
.2 = =
A O
A ^
■~Zg
rt.S £
hi
Frequency f = 25
/=60
1
r,.2<;xi
7.8194
9.3778
10.938
7
1.0042
1.0055 1 1.0070
1.0087
1
3.9738
4.8334
5.6995
6.5698
8
1.0027
1.0035 1.0045
1.0056
2.1817
2.5365
2.9009
3.2718
9
1.0018
1.0023 1.0029
1.0036
0000
1.9583
2.2505
2.5527
2.8614
10
1.0011
1.0015 | 1.0019
1.0024
000
1.7002
1.9194
2.1480
2.3838
00
1.5040
1.6651
1.8352
2.0134
0
1.3593
1.4763
1.6019
1.7627
/=33
/= 80
1
3.51
4.381
5.221
6.081
1
8.3108
10.387
12.474
14.557
1
2.332
2.781
3.237
3.700
|
5.2244
6.3840
7.5478
8.7151
h
1.436
1.625
1.803
1.982
2.7720
3.2649
3.7339
4.2722
0000
1.362
1.495
1.634
1.780
0000
2.4577
2.8683
3.2873
3.7119
000
1.252
1.344
1.445
1.551
000
2.0SS4
2.4024
2.7249
3.0536
00
1.173
1.238
1.311
1.384
00
1.8011
2.0376
2.2825
2.5"55
0
1.121
1.165
1.215
1.268
0
1.5833| 1.7597
1.9451
2.1373
f = 40
/=130
1
4.2447
5.2661
6.2961
7.3302
1 | 13.444 16.832
20.227
23.623
f
2.7520
3.3072
3.8719
4.4428
1
S.3925 10.295
12.191
14.104
1.6342
1.8480
2.0726
2.3050
*
4.3185 5.1487
5.9842
6.8233
0000
1 .5033
1.6753
1.8579
2.0480
0000
3.7828 4.4814
5.1860
5.8942
000
1.35«6
1.4808
1.6136
1.7553
000
3.1426 3.6878
4.2387
4.7939
00
1.2493
1.3371
1.4326
1.5354
00
2.6316 3.0529
3.4808
3.9161
0
1.1747
1.2345
1.3023
1.3756
0
2.2328
1 2.5567
2.8898
3.2283
To find true drop in line, multiply ohmic drop by factors in these tables.
* Diameter in inches, Gauge Brown & Sharp.
Impedance Determinations tor Three-phase Circuit*. —
In theory the phases of a three-phase circuit differ 120°, although seldom
exactly so in practice. This phase difference affects each wire as if it had
one return wire in place of two ; and in calculating the inductive effects,
each wire must be treated as if it had a return wire in the position of one of
the other two, that is, the three wires may be treated as if each was a sepa-
rate circuit having no return wire.
Two- or Quarter-phase Circuits. — As used at Niagara, the two
phases are separate, and all inductive determinations can be made as if for
two separate and adjacent circuits.
Mutual Induction of Circuits. — When two alternating-current
circuits are carried close together, and especially if the adjacent wires of
the two circuits lie near together as compared to the two wires of the cir-
cuit, there is apt to be an interference or mutual induction of one current
or the other, unless measures are taken to prevent it. It is caused by the
linking together of lines of force from the two circuits, and must be com-
pensated for by so arranging the relative positions of the circuits that at
some other point on the line an equal number of lines will be interlinked in
the opposite direction, and thus neutralize each other.
When alternating circuits were first erected, it was customary to place all
the right-hand wires of the circuit on one side of a pole, and all the left-hand
wires on the other ; and most commonly the two outside wires were of one
circuit, the next two inside the next circuit, and so on.
In many places where this method was used, and the distances great and
the current high, it was soon found that incandescent lamps fluctuated in a
regular periodic manner, which was first laid to engine fly-wheels and too
heavily loaded engines. Of course, this was soon found to be an error, the
fault discovered, and the conductors rearranged.
IMPEDANCE AND REACTANCE.
117
The effect is caused by one circuit acting as a secondary to the other ; and
if the cycles are similar, the mutual induction will tend to increase the
drop in one circuit and diminish it in the other. If, however, the cycles are
not alike, the potential will rise and fall periodically when the maximum
values coincide, or the tops of the waves come into step at the same
moment. Both conditions are annoying, and under certain particular
arrangements are capable of producing damaging results.
Mutual induction, or rather its evil effects, can be overcome by arranging
the conductors in such relative positions as to make the flux from one part
of a circuit counteract that in another part, as shown in the following
diagrams.
If lines are not very long, and potentials not too high, so as to induce bad
effects from static capacity, it will be sufficient to place both wires of a cir-
cuit near together as compared with the distance between adjacent circuits.
Arrangement of JLines for no Mutual Induction.
The above change should be made so as to cover the entire distance, each
location of circuit being for one-quarter of the entire length.
Niagara, JLine. — The conductors on this line are bare cables of 19
strands, equivalent to 350,000 circuit mils, and are arranged as shown in
the following diagram. The first arrangement was with two three-wire cir-
A
Fig. 15. Niagara-Buffalo Line. 11000 to 22000 Volts.
cuits on the upper cross-arm, the wires being 18 inches apart. So much
trouble was experienced from short circuits by wires and other material
being thrown across the conductors, that the middle wire was lowered to
the bottom cross-arm as shown, since which time no trouble has been
experienced. With porcelain insulators tested to 40,000 volts there is no
appreciable leakage. These circuits are interchanged at a number of
points to avoid inductive effects.
118
CONDUCTORS.
Three-phase Circuit*.— The diagram (Fig. 16) shows the favorite
arrangement of one of the larger companies as it makes lines conveniently
accessible for repairs. Under the ordinary loads usual in the smaller
plants the unbalancing effect is so small as to be inappreciable.
-18 >k 1
I
Fig. 16. Convenient Arrangement of Three-phase Lines for 6000-10000 Volts.
Balanced JLine, Three-Phase. — The following diagram shows
an arrangement of the conductors of a three-phase circuit, which will be
balanced in all its effects if there be but one circuit. The distances, 18
inches apart, are about standard for pressures as high as 12,000 volts.
8- 4 18
Fig. 17. Balanced Arrangement for Three-phase Lines.
This arrangement is perhaps not so convenient for repairs, but is symmet-
rical in all respects.
If there be more than one circuit of this balanced arrangement, and the
difference of phase is enough so that interference is found, then one or
more of the circuits will have to be changed as shown in the following
IMPEDANCE AND REACTANCE.
119
diagram (Fig. 18), the principle being to bring each of the three wires
a circuit into the same relation with other circuits for an equal length
or distance.
Fig. 18. Arrangement of Three Three-phase Circuits, each Equilaterally
Placed. In this Arrangement there is no Effect from One Circuit on
Another.
Three-phase Circuit in Same I*la«e. — It is sometimes advan-
tageous to place all the conductors on one cross-arm on the same level as
in the preceding diagram. In this case, if the load is heavy enough to
cause interference between conductors, then two interchanges of wires
should be made, dividing the circuit into three equal parts as shown. This
will bring every wire into similar relations with all others, and tbe interfer-
ence will therefore be the same on all. In order that this balancing effect
should be correct along a line having branches, the reversals should be
made between all branches; for instance, between the dynamo and the
first branch there should be two reversals as shown, and between the first
and second branches the reversals should be repeated, and so on.
120
CONDUCTORS.
. If Wires of Three-phase Circuit are on same Plane, then they should be
interchanged twice between Points when Branches are attached, as 2
Fzo.2, Another Arrangement ^Two-phase Circuit. No Keversal of
mmmr^^^m^^m^m^
IMPEDANCE AND REACTANCE. 121
reversals of wires are needed, the inductive effects of the wires of one
circuit on those of the other are neutralized.
Two-Phase Circuits in Same Plane. — If the phases are treated
as separate circuits, and carried well apart, the interference is trifling ; and
should the loads carried be heavy enough to cause noticeable effect, the re-
versal of one of the phases in the middle of its length will obviate it. The
following diagram illustrates the meaning.
J>C
Fig. 23. Arrangement of Two-phase Four-wire Circuit with "Wires on
same Plane. Wires of One Phase should be interchanged at the Middle
Point of the Distance between Branches, and between its Origin and
First Branch.
Messrs. Scott and Mershon of the Westinghouse Electric and Manufactur-
ing Co. have made special studies of the question of mutual induction of
circuits, both in theory and practice ; and their papers can be found in the
files of the technical journals, and supply full detail information.
AI/EEltarATIXtt WIRING AIVI9 CODiOCVIO]V§.
By General Electric Company.
General Wiring- formulae.
The following general formulae may be used to determine the size of con-
ductors, volts lost in the line, and current per conductor for any system of
electrical distribution.
Area of conductor, Circular Mils =
PXE2'
P X E
Volts loss in line = ■ x M.
W
Current in main conductors = — x T.
Z)rr Distance of transmission (one way), in feet.
W = Total watts delivered to consumer.
P = Per cent loss in line of W.
E = Voltage between main conductors at receiving or consumers' end
of circuit.
In using the above formulae and constants, it should be particularly
observed that P stands for the per cent loss in the line of the delivered power,
and not for the per cent loss in the line of the power at the generator.
In continuous-current, three-wire systems, the neutral wire for feeders
should be made of one-third the section obtained by the formula! for either
of the outside wires. In both continuous and alternating current systems,
the neutral conductor for secondary mains and house-wiring should be taken
as large as the other conductors.
When both motors and lights are used, on the Monocyclic System, the
primary circuit should be figured as if all the power was transmitted over
the outside wires, and the size of the power wire should be in the proportion
to either outside wire, as the motor load in amperes is to the total load in am-
peres. Secondary wires leading directly to induction motors on the Mono-
cyclic System should all be of the same size as for a single-phase circuit of
the same kilowatt capacity and power-factor. The three lines of three-
phase circuits should be made of the same cross-section.
122
CONDUCTORS.
<
o
"e3
Values of K.
Values of T.
System.
Per cent power factor.
Per cent power factor.
100
95
90
85
80
100
95
90
85
80
Single-phase ....
Two-phase (four-wire)
Three-phase (three-wire)
6.04
12.08
9.06
2160
11 ISO
11 ISO
2400
1200
1200
2601)
i;;:;o
i;j:;o
:;ooo
ir.00
lr.oo
;;:>xo
1090
1690
1.00
.50
.58
1.05
.53
.61
1.11
.55
.64
1.17
.59
.68
1.25
.62
.72
The value of K for any particular power factor is obtained by dividing
2160, the value for continuous current, by the square of that power factor
for single-phase, and by twice the square of that power factor for three-
wire three-phase, or four-wire two-phase.
The value of M depends on the size of wire, frequency and power factor.
It is equal to 1 for continuous current, and for alternating current with 100
per cent power factor and sizes of wire given in the following table of
wiring constants.
The figures given are for wires 18 inches apart, and are sufficiently accu-
rate for all practical purposes, provided the displacement in phase between
current and E.M.F. at the receiving end is not very much greater than that
at the generator ; in other words, provided that the reactance of the line is
not excessive, or the line loss unusually high. For example, the constants
should not be applied at 125 cycles if the largest conductors are used, and
the loss 20 % or more of the power delivered. At lower frequencies, how-
ever, the constants are reasonably correct, even under such extreme con-
ditions. They represent about the true values at 10 % line loss, are close
enough at all losses less than 10 %, and often, at least for frequencies up to
40 cycles, close enough for even much larger losses. Where the conductors
of a circuit are nearer each other than 18", the volts loss will be less than
given by the formulae, and if close together, as with multiple conductor
cable, the loss will be only that due to resistance.
The value of T depends on the system and power factor. It is equal to 1
for continuous current, and for single-phase current of 100 per cent power
factor.
The value of A and the weights of the wires in the table are based on
.O00J03O2 lb. as the weight of a foot of copper wire of one circular mil area.
In using the above formulae and constants, it should be particularly
observed that P stands for the per cent loss in the line of the delivered
power, not for the percent loss in the line of the power at the generator ;
and that E is the potential at the end of the line and not at the generator.
When the power factor cannot be more accurately determined, it may be
assumed to be as follows for any alternating system operating under aver-
age conditions : Lighting with no motors, 95% ; lighting and motors to-
gether, 85 % ; motors alone, 80 %.
In continuous current three-wire systems, the neutral wire for feeders
should be made of one-third the section obtained by the formulae for either
of the outside wires. In both continuous and alternating current systems,
the neutral conductor for secondary mains and house-wiring should be
taken as large as the other conductors.
When both motors and lights are used on the Monocyclic System, the pri-
mary circuit should be figured as if all the power was transmitted over the
outside wires, and the ^ize of the power wire should be in the proportion to
either outside wire as the motor load in amperes is to the total load in am-
peres. Secondary wires leading directly to induction motors on the Mono-
cyclic system should all be of the same size as for a single-phase circuit of
the same kilowatt capacity and power factor. The three wires of a three-
phase circuit, and the four wires of a two-phase circuit should all be made
the same size, and each conductor should be of the cross section given by
the first formulae.
WIRING CONSTANTS.
123
o o
§ 8
§
o
r-l CI
co
"*
m co
t- 00
© ©
6
o
p
c3
c3
CO
O
CD
O
o
CD
O
t?5
_^ o
^§
Ph
6 1
© ■*
•# ©
CO CM
in
CM
CM
OS t~
in
3
2 2
^ ^
q q
s
3 &
o
CO
cn
CO O
s
s
q £-<
-r CS
t-h q
q 8
O
os
CO CO
CO ■*
oo
ci
CO
t? §
®
cS
t- o
-i< ©
§ ^
©
cn ei
§g
£
CO lO
1C ■*
m
co
s
tH CO
y-i ©
© -5H
© ©
<d
to
O
o
8
8 S
ci i-i
CO
os
CO CM
l^
o
S 8
q q
© ©
© ©
8
© t-
s
>#
># m
s
2
q q
q 8
8 8
o
55 CO
8
o
s s
§
3
q q
§ ^
§ 1
S
CO •#
3
CO
<N rH
■*
rj
q q
CO CM
© ©
8 8
O
o
4*1
O
CO
CO LO
g
CO
b- O
q
s
q q
8 8
§ §
• IO
§ 2
8
§5
00 (M
q
q
o o
q q
q 8
8 8
8
in "#
1
3
£ S
C ;
q
q q
8 8
8 8
o
S S
IO
©
■* i-l
q
q
q q
S R
0>
'3
o
8
o
0) ©
Ph £
o
Ph
S
s§ ^
CO
s
CO o
q ©
s
o
q
q 8
© ©
© ©
8 8
IO
3 5i
CO
o
S ^
o
q
q
o o
© ©
8 8
8 8
o
©
.a s
s
5
q q
q
CO
q
q q
8 8
© ©
© ©
OS
S3 s
-r
p
l- LO
q q
q
q
8 8
8 8
1 1
9.1
•su
IAV J«
no *o oos ^«
39.1 0001 -I9<I
90ire^sisay;
© ■*
1 g
©-
LO
i
11
§
2
CO
CO 00
CO ©
§ ol
■*. q
•spi
noj '
88 J 0001 -^d
I jo iq§i9A\
CO CM
k §
CO IO
1
8
OS
CO
CO CO
^ °5
CO CO
ol §
CO
CO
05
Q
§5 §
CO ©
8 §
'SIII\[ J'Bino.TTO
•OJTAi 'B9JY
11
1-1 t^~
©
©
CO
o
'q
1 §
CO CO
00 CO
CO
o
© >n
CO CO
00 CM
S 8
co in
© co"
1 1
CO ©
■a
9JTA1 ;o
•OR
i i
s °
©
o
o
r-l CM
co-*
124
CONDUCTORS.
The venerators are rated by tlieir volt-ampere capacity and their apparent
watts, and not their actual watts, so that the size has to be increased if the
power-factor of the system is low.
xnA^rsFomfTEiis.
For lighting circuits using small transformers, the voltage at the prima-
ries of the step-down transformers should be made about 3% higher than the
secondary voltage multiplied by the ratio of transformation, to allow for the
drop in transformers. In large lighting transformers this drop may be as low
as 2%. Standard lighting transformers have a ratio of 10 to 1 or some mul-
tiple thereof.
For motor circuits, the voltage at the primaries of step-down transformers
should be made about 5% higher than the secondary voltage multiplied by
the ratio of transformation. Transformers used with 110 volt motors on any
60-cycle system should have a ratio of 4J to 1, 9 to 1, or 18 to 1 respectively
for 1040, 2080, and 3120 volt generators. Transformers with a ratio of 10 or
20 to 1 should on no account be installed with motors operated from Mono-
cyclic generators of standard voltage. The transformer capacity inkilotcatts
should be the same as the motor rating in horse-power for medium-sized
motors, and slightly larger for small motors, and where only two trans-
formers are used.
Capacities of Transformers to l»e used with ©©-Cycle
Induction JfEotors.
Kilowatts per Transformer.
Size of Motor.
Horse-Power.
Two Transformers.
Three Transformers.
1
.6
.6
2
1.5
1
3
2
1.5
5
3
2
n
4
3
10
5
4
15
7.5
5
20
10
7.5
30
15
10
50
25
15
75
25
onrcTiow motor§.
The standard (General Electric) induction motors for three-phase and for
monocyclic circuits are wound for 110 volts, 220 volts, and 550 volts ; motors
of 50 H. P. and above are, in addition, wound for 1040 volts and 2080 volts.
Motors for the two latter voltages are not built in sizes of less than 50 H. P.
Where the four-wire three-phase distribution system is used, motors can
also be wound for 200 volts.
The output of an indtiction motor varies with the square of the voltage at
the motor terminals. Thus, if the volts at the terminals happen to be 15%
low, that is, only 85% of the rated voltage, a motor, which at the rated volt-
age gives a maximum of 150% of its rated output, will be able to give at the
15% lower voltage, only (T8,fo)2 X 150= 108 % of its rated output, and at full
load will have no margin left to carry over sudden fluctuations of load while
running.
INDUCTION" MOTORS.
125
Thus it is of the utmost importance to take care that the volts at the motor
terminals are not below the rated volts, hut rather slightly above at no load,
so as not to drop below rated voltage at full-load or over-load.
The output of the motor may be increased by raising the potential ; in
this case, nowever, the current taken is increased, especially at light loads.
The direction of rotation of an induction motor on a three-phase or mono-
cyclic circuit, can be reversed by changing any two of the leads to the field.
Like all electrical apparatus, the induction motor works most efficiently
at or near full load, and its efficiency decreases at light load. Besides this,
when running at light load, or no load, the induction motor draws from the
lines a current of about 30% to 35% of the full-load current. This current
does not represent energy, and is not therefore measured by the recording
watt-meter ; it constitutes no waste of power, being merely what is called an
idle or "wattless" current. If, however, many induction motors are ope-
rated at light loads from a generator, the combined wattless currents of the
motors may represent a considerable part of the rated current of the gene-
rator, and thus the generator will send a considerable current over the line.
This current is wattless, and does not do any work, so that in an extreme
case an alternator may run at apparently half -load or nearly full-load cur-
rent, and still the engine driving it run light. While these idle currents are
in general not objectionable, since they do not represent any waste of
power, they are undesirable when excessive, by increasing the current-heat-
ing of the generator. Therefore ft is desirable to keep the idle currents in
the system as low as possible, by carefully choosing proper capacities of
motors. These idle currents are a comparatively small per cent of the total
current at or near full-load of the motor, but a larger per cent at light loads.
Therefore care sbould be taken not to install larger motors than necessary
to do the required work, since in this case the motors would have to work
continuously at light loads, thereby producing a larger per cent of idle cur-
rent in the system than would be produced by motors of proper capacity ;
that is, motors running mostly between half-load and full load.
Current taken l>y General Electric Co. Three-phase In-
duction Motors at HO Volts.
Starting
Starting
H. P. of Motor.
Full-Load
Current at
Current
Current.
150% of Full-
at Full-Load
Load Torque.
Torque.
1
6.3
19
2
12
36
3
18
54
5
28
*42-84
28
10
54
70
54
15
81
120
81
20
112
167
112
30
168
252
168
50
268
400
268
75
390
585
390
100
550
825
550
150
780
1180
780
* The 5 H. P. motor is made with or without starting-switch.
The current taken by motors of higher voltage than 110 will be proportion-
ally less. The above are average current values, and in particular cases the
values may vary slightly.
126
CONDUCTORS.
Isolated motors running on the Monocyclic System are operated from two
transformers, connected as shown in Fig. 24. Where there is no high-tension
transmission line, the step-up and step-down transformers are not required,
and only the two motor transformers shown at the right in the diagram are
used.
The connections of a Monocyclic circuit for the operation of a three-wire
Fig. 24.
Fig. 25.
secondary lighting system and motors is shown in Fig. 25. The main trans-
former has three terminals brought out from each winding, and a supple-
mentary motor transformer is used and connected as shown.
Where this connection is used for the operation of a single motor, the kilo-
watt rating of the supplementary transformer should be about one-half of
the motor rating in horse-power. This arrangement is primarily intended
for secondary mains carrying lights and a number of motors. Judgment
should be exercised in the use of this arrangement, since, if the motors con-
nected are large as compared with the total capacity of the transformers,
the fluctuations of load may effect the lights to an objectionable degree
through variations of drop in the transformers. The motor load being in-
ductive, it will cause wider variations of voltage in the transformers than
would be experienced with the same current delivered to lights.
The connections of three transformers, with their primaries, to the genera-
tor and their secondaries to the induction motor, in a three-phase system,
are shown in Fig. 26. The three transformers are connected with their pri-
maries between the three lines leading from the generator, and the three
secondaries are connected to the three lines leading to the motor, in what is
called delta connection.
The connection of two transformers for the supply of an induction motor
from a three-phase generator is shown in Fig. 27. It is identical with the
Fig. 26.
Fig. 27.
arrangement in Fig. 26, except that one of the transformers is left out, and
the two other transformers are made correspondingly larger. The copper
(•Muired in any three-wire, three-phase circuit for a given power and loss is
"5%, as compared with the two-wire single-phase, or four-wire two-phase
system having the same voltage between lines.
'The connections of three transformers for a low-tension distribution sys-
tem by the four-wire three-phase system are shown in Fig. 28. The three
3H
transformers have their primaries joined in delta connection, and their sec-
ondaries in "Y" connection. The three upper lines are the three main
three-phase lines, and the lowest line is the common neutral. The difference
APPLICATIONS OF GENERAL WIRING FORMULA. 127
of potential between the main conductor is 200 volts, while that between
either of them and the neutral is 115 volts. 200 volt-motors are joined to the
mains, while 115 volt-lamps are connected between the mains and the neutral.
The neutral is similar to the neutral wire in the Edison three-wire system,
and only carries current when the lamp load is unbalanced.
The potential between the main conductors should be used in theformuhe,
and the section of neutral wire should be made in the proportion to each of
the main conductors that the lighting load is to the total load. When lights
only are used, the neutral should be of the same size as either of the three
main conductors. The copper then required in a four- wire three-phase sys-
tem of secondary distribution to transmit a given power at a given loss is
about 3.3.3%, as compared with a two-wire single-phase system, or a four-wire
' vo-phase system having the same voltage across the lamps.
The connections of two transformers for supplying motors on the four-wire
vo-phase system are shown in Fig. 29. This system practically consists of
two separate single-phase circuits, half the power being transmitted over
each circuit when the load is balanced. The copper required, as compared
with the three-phase system to transmit given power with given loss at the
same voltage between lines, is 133£ % — that is, the same as with a single-
phase system.
APPIICATIOIS OF GEITERAL WIRING
EORMEL^.
Contirfuous Current.
TWO-WIRE SYSTEM.
Example : 500 half ampere, 110 volt-lamps. Distance to lights, 1000 ft.;
loss in line — 10% of delivered power.
10 X HO2
: 490,900 CM.
v 1+ i ' * i 10 x no X 1 „ ..
Volts drop to lamp = —— = 11 volts.
THREE-WIRE SYSTEM.
Example : GOO half-ampere, 110 volt-lamps. Distance to distribution point,
1500 ft. Vrolts between outside lines at distributing point, 220. Loss in line
= 8% of delivered power.
Area of outside conductors =
2160 X 1500 X (600 X -5 X 110) _ „. 1ftn n ^
8 X 220* - "'6'100 °-M-
The area of the neutral feeder is 276,100 x \ = 92,030 CM.
8 X 220 X 1
Volts drop in circuit = — — — 17.6.
220-f-17.6=i237.6 volts at station between outside lines; and 118.8 volts
between outside wires and neutral.
Alternating- Currents.
TWO-WIRE SIXGLE-PHASE SYSTEM. 125 CYCLES.
Example: 1000, 16 c.p., 3.6 watt, 104 volt-lamps. 10 to 1 transformers
Distance. 2000 ft. to generator. 2 volts less in secondary wiring. Drop in
transformers for lighting is 3%. Loss in primary line to be equal to about
"% of power delivered at transformers. Efficiency of transformers. 97%.
Volts at transformer primaries = 106 X 10 X 1.03= 1091.8. 1000 X 16 X 3.6 =
57,600 watts. -^ — —== about 60,600 watts at transformer primaries.
C.M. = TXfffS X 2400 =48,800 CM.
128 CONDUCTORS.
No. 3 B. and S. = 52,633 CM.
2000 X 60,600 X 2400
= 4.64% loss of delivered power, in primary wiring.
o2j ooo x loyi.o
Volts loss in primary lines =
4.64 x 1091.8 X 1.35 co .
m = 68A-
1091.8 + 68.4 = 1160.2 volts at generator.
TWO-WIRE SYSTEM. 60 CYCLES.
Example : The same load and losses as for the previous problem.
Volts at transformor primaries = 106 x 10 X 1.03 = 1091.8.
Load at transformer primaries = 60,600 watts.
No. 3 B. and S. wire gives 4.64% loss in primary wiring.
Volts loss in primary lines =
4.64 X 1091.8 X 1.11 _fi „
ioo =56-2-
1091.8 + 56.2 = 1148 volts at generator.
TWO-WIKE SYSTEM, WITH THREE-WIRE SECONDARIES. 60 OR 125 CYCLES.
The primary wiring is identical with that for the two-wire system. The
secondary wiring is calculated, using the voltage between outside lines, and
the three wires are made of the same cross-section. The drop in voltage on
the secondary wiring as obtained by the formula is the drop between outside
lines, and is twice the drop to each individual lamp.
Monocyclic System. ©O Cycles.
MOTOR AND LIGHTS ON SEPARATE TRANSFORMERS. (See Fig. 15.)
Example : 1500 half-ampere, 104 volt-lamps. One 25 H.P. 110 volt-induc-
tion motor ; efficiency, 85%. Distance from generator to transformers,
3000 ft. Distance from transformers to motor, 100 ft. Loss in motor circuit,
2|%. Loss of energy in transformers, 3%. Loss in primary circuit, 4%.
Generator voltage, 1040 at no load.
25 X 746
Input at motor = - — — — = 21,940 watts.
- 245,000. No. 0000 B. and S. wire = 211,600
2.5 x no2
CM.; but as two No. 0 B. and S. will give the same loss, and -— = 69.2% as
great a drop in voltage, they are preferable. Making each motor lead of two
No. 0 B. and S. wires in parallel, then P = ^|g^|^g = 2.9%.
WU1 , . 2.9X110X1.28 .
Volts lOSS tO motors = — = 4.
Volts at primaries of transformers for motors = 1.05 X 9 X (110 + 4) = 1076.
Volts on secondaries of lighting transformers = = 104.5
l.Uo X 1"
Watts at primaries of motor transformers =
21,940 X 1-029 =23200
Watts at primaries of lighting transformers =
1500 X-5X104J =80)8Q(K
Total watts delivered at transformers = 23,200 + 80,800=104,000.
Power factor of load is
23,200 X -80 + 80,800 X .95 _
104,000 ~~
K=2» = M10.
APPLICATION OF GENERAL WIRING FORMULAE. 129
CM.:
4 X 10762
Taking No. 000 B. and S. wire = 167,805 CM., then P =_
2610 = 4.19%.
Drop in primary circuit =
4.19 X 1076 1.49 X 80.8 + 1.62 X 23.2 oa c 1t
100 X 104 = GS'5 V0lfcs-
Voltage between outside lines at generator = 1076 -f 68.5 = 1144.5 volts.
Current in main conductors = 777™ — t- = 106.1 amperes.
Wto X -91
Primary teazer wire = "" '" - x 167,805 = 37,400 CM. required.
104,000
Use No. 4 B. and S., with a section of 41,742 CM.
THEEE-WIEE SECONDARY FOR MOTORS AND LIGHTS. 60 CYCLES.
(See Fig. 16.)
Example : Distance from generator to transformers, 1000 ft. Ratio of
main transformers, 9 to I. The load consists of 1000 half-ampere, 110 volt-
lamps, and four 10-11. P. induction-motors. The distance from transformers
to motors is 200 ft., and the length of three-wire lighting feeders is 150 ft.
The drop in lighting feeders and motor circuits to be about 10 volts. Loss
in primary circuit to be 3%.
Lamp load = .5 X 110 X 1000 = 55,000 watts.
P X E X M
Assuming a per cent loss such that — — will be about 10 volts, then
CM. = 159°5*5^° X 2400 = 163,600 CM.
Taking No. 000 B. and S. wire with an area of 167,805 CM., we have P =
150X55,000 2100_gll
167,805 X 220^ X ^0 _ LA*.
T7 .. , . v ... „ , 2.44X220X1.49 0
\ olts loss in lighting feeders = = 8.
Voltage at transformers = 220 + 8 = 228.
Size of neutral feeder = ~\ — = 55,935 CM., or about No. 2 B. and S.
area, 66,373 CM.
Input on each 10 H. P. motor at full-load with an efficiency of 84% is equal to
10X746__
.84
P X E X M
Assuming a per cent loss such that — is about 8 volts, we have,
= 3380 = 35,500 CM.
' ' — 3.5 X 2202 '
No. 5 B. and S. = 33,102 CM. taken for section of motor leads.
„ 200 X 8881 X 3380 _
33,102 X 2202
= 3.75.
17U1 ^ . 3.75 X 220 X 1
Volt loss to motors = — = 8.25.
The motor load is 4 x 8881 X 1.0375 = 36,800 watts.
The lighting load is 55,000 X 1.0244 = 56,340 watts.
56,340 + 36,800 = 93,140 watts.
Assuming transformer efficiencies of 97%, — ^— = 96,000 watts load on
transformers.
The voltage at the transformer primaries, allowing 4% drop in trans-
formers, is 228 X 9 X 1.04 = 2134.
130 CONDUCTORS.
_ „ _ 1000 X 96,000 56,340 X 2400 + 36,800 X 3380 . . nnn„ __
°'M— 3X21342" X 967M) -19,000 CM.
no. 7 B. and S. = 20,816 CM.
19,000 ._
^- 20,816 X^--'-
o 74 y 21 34 v 1
Volts loss in line = "^ — ' = 58.5. 2134 -f 58.5 == 2192.5 volts a
; 36.8
J 93.4
CM., but this is too small for outside work, hence we would use two No. 7
wires, and one No. 8 wire for the primary circuit.
Three-Phase System. ©O Cycles.
three-wire transmission. (See Figs. 17 and 18.)
Example. — Required : the size of conductors and drop in line to transmit
5000 H.P. 3J miles, with a loss equal to about 10% of the delivered power.
Voltage between lines at receiving end, 5000. Power factor of load, 85%.
10 X 50002
Two No. 0000 B. and S. wires per branch would answer ; but the drop in
1.32
voltage will be only — — , or 71.4% as great for the same loss of power, if we
take four No. 0 B. and S. wires in parallel, or a line of twelve No. 0 B. and
S. wires in all. The loss will be P = 528£ X ^ ^./ °° ^J46 X 1500 = 9.79%
of delivered power, i.e., .0979 X 5000 = 489.5 H.P. lost in line.
Tr 1+ , .. .. 9.79X5000X1.32 „„„ _
Volts lost in line = = 646 volts.
Voltage at generator = 5000 + 646 = 5646 volts.
^1000 v 74fi
Current in line =: — — — — x .659 = 506.5 amperes.
FOUR-WIRE SECONDARY SYSTEM. (See FlG. 19.)
Example. — Required: the size of conductors from transformers to the
distributing centre of a four-wire secondary system for lights and motors.
The load consists of four 15 H.P., 200 volt-induction motors, and 750 half-
ampere, 16 c.p., 115 volt-limps. Length of secondary wiring from trans-
formers to distribution centre, 600 ft. About 15 volts drop on lighting
circuits from transformers to distributing centre. Efficiency of motors, 85%.
5 volts droi. on circuits from distributing centre to motors. Voltage at dis-
tributing point between main lines is 205. Current in main lines for motors
. 4 X 15 X 746 X .725 1(V1
1S— ^85x-200 = W1 amperes.
Current from transformers for lamps is
(750 X .5 X 115) X .607
i 2oo = amPeres.
Total current from transformers is 131 -f- 191 = 322 amperes.
W
For motors, 191 = £- X -725. W— 54,000.
205
W
For lamps, 131 = ^ X .607. JF= 44,240. Total watts = 98,240. jj
Taking for trial two No. 0B. and S. wires in parallel for each of the main1 "li
APPLICATION OF GENERAL WIRING FORMULAE. l3i
conductors, as preferable to one No. 0000, then P r
9.75.
X 105,592 X 2052 '
1200 X 44,240 + 1690 X 54,000 _
98,249
Volts loss in lines = 9.75X205X1.32 = 26.4.
Volts at transformers between main lines = 231.4.
Actual drop between main conductors and neutral to distributing point =
26.4x^=15.2 volts.
131 X 2 X 105 592
The section of the neutral conductor should be about — - — - — =
86,000 CM. We may use one No. 1 B. and S. wire, with a section of 83,694
CM. for the neutral.
Two-I*hase System. O© Cycles.
FOUR-WIRE TRANSMISSION. (See FlG. 20.)
Example. — Required : the size of conductors and drop in line to transmit
5000 H.P. 3-J miles, with a loss equal to about 10% of the delivered power.
Voltage between lines at receiving end, 5000. Power factor of load is 85%.
Taking four No. 0 B. and S. wires in parallel, the line will consist of six-
5280 X 3 5 X 5000 X 746
teen No. 0 B. and S. wires in all. The loss will be P = —. ' ..AO ^ _nnn2
4 X 105.592 X 5000^
X 1500 = 9.79% of delivered power, or .0979 x 5000=489.5 H.P. lost in the line.
Volts lost in line =
PXJgX_jf=9.79x 5000X1.32
100 100
Volts at generating end of line = 5646.
,.. ,. 5000x746 „„„
Current in lme = — — — x -588 = 438.6 amperes.
Alternating'-Current Arcs.
Power factor is about .75. Calculate wire for apparent watts, not real
watts.
Chart and Table for calculating: Alternating--Current
IJines.
Ralph D. Mershon, in American Electrician.
The accompanying table, and chart on page 137 include everything neces-
sary for calculating the copper of alternating-current lines.
The terms, resistance volts, resistance E.M.F., reactance volts, and react-
ance E.M.F., refer to the voltages for overcoming the back E.M.F.'s due to
resistance and reactance respectively. The following examples illustrate
the use of the chart and table.
Problem. — Power to be delivered, 250 k.w.; E.M.F. to be delivered, 2000
volts ; distance of transmission, 10,000 ft.; size of wire, No. 0; distance be-
tween wires, 18 inches ; power factor of load, .8 ; alternations, 7200 per min-
ute. Find the line loss and drop.
The power factor is that fraction by which the apparent power or volt-am-
peres must be multiplied to give the true power or watts. Therefore the
250 k w
apparent power to be delivered is - — -^^ = 312.5 apparent k.w., or 312,500
volt-amperes, or apparent watts. The current, therefore, at 2000 volts will be
312 500
— -'— = 156.25 amperes. From the table of reactances, under the heading
" 18 inches," and corresponding to No. 0 wire, is obtained the constant, .228.
Bearing the instructions of the table in mind, the reactance volts of this
132 CONDUCTORS.
line are 156.25 (amperes) x 10 (thousands of feet) x .228 = 356.3 volts, which
are 17.8 per cent of the 2000 volts to be delivered.
From the column headed " Resistance Volts," and corresponding to No. 0
wire, is obtained the constant .197. The resistance volts of the line are,
therefore, 156.25 (amperes) X 10 (thousands of feet) X .197 = 307.8 volts, which
are 15.4 per cent of the 2000 volts to be delivered.
Starting, in accordance Avith the instructions of the sheet, from the point
where the vertical line, which at the bottom of the sheet is marked " Load
Power Factor .8," intersects the inner or smallest circle, lay off horizontally
and to the right the resistance E.M.F. in per cent (15.4), and "from the
point thus obtained," lay off vertically the reactance E.M.F. in per cent
(17.8). The last point falls at about 23 per cent, as given by the circular arcs.
This, then, is the drop in per cent of the E.M.F. delivered. The drop in per
cent of the generator E.M.F. is, of course, " t 0 = 18.7 per cent.
The resistance volts in this case being 307.8, and the current 156.25 am-
peres, the energy loss is 307.8 x 156.25 = 48.1 k.w. The percentage lots is
tr-x- ' = 16.1. Therefore, for the problem taken, the drop is 18.7 per cent,
and the energy loss is 16.1 per cent.
If the problem be to find the size of wire for a given drop, it must be solved
by trial. Assume a size of wire, and calculate the drop in the manner above
indicated; the result in connection with the table will show the direction
and extent of the change necessary in the size of wire to give the required
drop.
The table is made out for 7200 alternations per minute, but will answer
for any other number. For instance, for 16,000 alternations, multiply the
reactances by 16000 -f 7200 = 2.22.
As an illustration of the method of calculating the drop in a line and trans-
former, and also of the use of the table and chart in calculating low-voltage
mains, the following example is given : —
Problem. — A single-phase, induction motor is to be supplied with 20 am-
peres at 200 volts ; alternations, 7200 per minute ; power factor, .78. The
distance from transformer to motor is 150 ft., and the line is No. 5 wire, 6
inches betAveen centres of conductors. The transformer reduces in the ratio
2000 : 200, and has a capacity of 25 amperes at 200 volts ; when delivering this
current and voltage, its resistance E.M.F. is as 2.5 per cent, and its reactance
E.M.F. 5 per cent, both of these constants being furnished by the makers.
Find the drop.
The reactance of 1000 ft. of circuit, consisting of two No. 5 wires, 6 inches
apart, is .204. The reactance-volts, therefore, are .204 x j^ X 20= .61 volts.
The resistance-volts are .627 x -^ X 20 = 1.88 volts. At 25 amperes, the re-
sistance-volts of the transformers are 2.5 per cent of 200, or 5 volts. At 20
amperes they are ^ of this, or 4 volts. Similarly, the transformer reactance
volts at 25 amperes are 10, and at 20 amperes are 8 volts. The combined re-
actance-volts of transformer and line are 8 + .61 = 8.61, Avhich is 4.3 per cent
of the 200 volts to be delivered. The combined resistance-volts are 1.88 + 4,
or 5.88, Avhich is 2.94 per cent of the E.M.F. to be delivered. Combining the^e
quantities on the chart Avith a power factor of .78, the drop is 5 per cent of
the delivered E.M.F., or ~ = 4.8 per cent of the impressed E.M.F. The
105
transformer must therefore be supplied with 2000+ .952 = 2100 volts, in order
that 200 volts shall be delivered to the motor.
To calculate a four-Avire, two-phased transmission circuit, compute, as
above, the single-phased circuit required to transmit one-half the poAver at
the same voltage. The two-phase transmission will require tAVO such
circuits.
To calculate a three-phase transmission, compute, as above, a single-phase
circuit to carry one-half the load at the same voltage. The three-phase
transmission Avill require three Avires of the size obtained for the single-phase
circuit, and with the same distance (triangular) betAveen centres.
By means of the table calculate the Resistance- Volts and the Reactance-
±
APPLICATION OF GENERAL WIRING FORMULAE. 133
Volts in the line, and find what per cent each is of the E.M.F. delivered at
the end of the line. Starting from the point on the chart where the vertical
line corresponding with power factor of the load intersects the smallest
circle, lay off in per cent the resistance E.M.F. horizontally and to the right ;
from the point thus obtained lay off upward in per cent the reactance E.M.F.
The circle on which the last point falls gives the drop in per cent of the
E.M.F. delivered at the end of the line. Every tenth circle-arc is marked
Avith the per cent drop to which it corresponds.
3
3
eg
§1
o ^
b
Reactance-Volts in 1000 ft. of Line (= 2000 ft. of Wire)
of
^
•S|
a
lor One Ampere (V Mean Square) at 7200 Alternations
per Minute for the Distance given between Centres of
Wire
B.&S.
- tf.
5-7
60
IE
>
Conductors.
"7 £ 5
£
£.3 <
2
1"
2"
3"
6"
9"
12"
IS"
24"
30"
36"
0000
639
.098
.046
.079
.111
.130
.161
.180
.193
.212
.225
.235
.244
000
507
.124
.052
.085
.116
.135
.167
.185
.199
.217
.230
.241
.249
00
402
.156
.057
.090
.121
.140
.172
.190
.204
.222
.236
.246
.254
0
319
.197
.033
.095
.127
.145
.177
.196
.209
.228
.241
.251
.259
1
253
.248
.063
.101
.132
.151
.183
.201
.214
.233
.246
.262
.265
2
201
.313
.074
.106
.138
.156
.188
.203
.220
.238
.252
.270
3
159
.394
.079
.112
.143
.162
.193
.212
.225
.244
.257
.267
.275
4
126
.497
.085
.117
.149
.167
.199
.217
.230
.249
.262
.272
.281
5
loo
.627
.090
.121
.154
.172
.204
.223
.236
.254
.268
.278
.286
6
79
.791
.095
.127
.158
.178
.209
.228
.241
.260
.272
.283
.291
7
63
.997
.101
.132
.164
.183
.214
.233
.246
.265
.278
.288
.296
8
50
1.260
.103
.138
.169
.188
.220
.238
.252
.270
.284
.293
.302
134
CONDUCTORS.
CHARGIiYG CURHEIT I»EM TIIIE OW CIRCUIT.
Two Parallel Wires.
Line E.M.F.= 10,000 Volts; Frequency =60 P.P.S; Sine Wave Assumed.
Stanley Electric Manufacturing Co., Pittsfield, Mass.
Charging
Current
in
Amperes.
12
.0426
18
.0385
24
.0362
48
.0315
12
.0411
18
.0375
24
.0353
48
.0308
12
.0403
18
.0366
24
.0345
48
.0302
12
.0392
18
.0358
24
.0328
48
.0296
12
.0381
18
.0349
24
.0329
48
.02905
12
.0372
' 18
.0342
24
.0322
48
.0284
12
.0365
18
.0333
24
.0315
48
.0279
03
a a ©
Charging
Current
in
Amperes.
12
.0353
4
18
.0326
24
.0308
48
.0274
12
.0345
5
18
.0319
1 24
.0302
1 48
.0269
1 12
.0337
6
i 18
.0312
! 24
.0296
48
.0264
12
.0329
7
18
.0305
24
.0290
48
.0259
12
.0322
8
18
.0295
24
.0284
4S
.02545
12
.0315
9
18
.02925
24
.0278
48
.0250
12
.0308
10
IS
.0285
24
.0273
48
.0246
Charging currents = -
7?-- Line E.M.F.
N=. Frequency.
k Capacity per mile of line in E.M.F.
£5
CHARGING CURRENT PER MILE OF CIRCUIT. 135
It-h-* coloco©co t~i-iom© „
, W t-h CO t- CC o co co © © COClrl , w
-f 01 © ~. — >- : : -r - X —. cc © © <q J^
0 cc ci © t-r.connoji
, _. lornsxcoti-'-: : 1 1~ co
„ actanocc cc :o x - o 1
-i r.'J:i:i-t x cc © x :o — . co
^niw^w'-si' x o ci co © co ©
• ,_; ^ ^ _; ?i eg
o "•
C! CO C f I- M O O rt O W 1>
^_j , ij; J5 ^ CO cc co tO-*tC2t-i
<r; Ol |SoOOO^»iOOOrtiOOt^
1-1 I * th h th ri i-i ri <ci co co
0 ■* I- CO ■# © o
lOMMt-^nt'OM-i X c
- • 1 r_~ -f CI MQMHt-fflfflO^
<1 CO CO^lOOl-OrtCOOOO
Ml T-i T-i T-i CN CN
li-i l> OO O 3 lO CO rt N O iO O
, . r»O00artl»L-ML".-t 1-0 ©
<i1gw^^Bi>ooqeo<»qiqrH
pg S3
^cl
i tOHOoiooioMoi-rco^
p CN It— i CM CI W* LO t~ C3 ^ lO O t-
1-1 1 _; ,_; ^ ,-i t-: -i t-h" t-h cn in co co
■BWPA
ooo'oi -s"<r<i
butt jo \mo
8iii3.req0
•sojiaV Z
spjoioij\[
oonB^onpui
■aout^sisay;
■SUM
XEpiOJIQ
■K9JY
•^SPAl
I „ ->; x -" x 3 t- ci Lo ~ f
'co cc- ~i oV C co © ~ ci -t- x
© ©- fi c ; c"i © :c :e co •# -# -*.
5 CO CO CO CO CO CO cc
© co © © © cc
., .-. ~. r. r
38838
y%\\
-4 o i-o © © -j t^ l2 '- x co x
888888888888
cc ic ri :o -h i.o i - cc — x x cc
- -: c i --. i - -r cc -f ~ :o r. co
~ co -* co co co_ q co t- -H co ■#
" tH T-i -i CI CI CO
© 2 o o o ©
CO -# © ip CI t-
-h co © © ©
■* CO CN CI t-i
sssas
5 © ri (N CO rj< IC © t> 0
<li^
•i in co T-t © t-h
r. i- i-i co cc co c ! cc —
; i -r r. i - - cc co ci x
- X Cj rn -P C O CO ©
' T-H T^ T-i CN CN CO
CO t-h OX © CI CI CO 10 — X CC CC
x © co i- © l~ x -r x x © co
O; CO © © CN CO OOOrHlQrHL-
•t-tt-Ht-Ht-tt-tCm'cNCOCO
-V Ci © t-i © © CO © CO -r : : i 0
-f -- r. ~ c i x cc co i-i-xci
-T CO C0_ L- CO © t-t -* L- t-i © oo
T-i t-h T-i p-j c-i co
I Tf rr CH- l- LO - C CO
o cc" x ?! i.o-i c ',-:
-. CO 0 I cO X CJ X -*
' rt t4t-^ T-i ci ci co
»-f t'fflTj«C
o — CO CO To X i1- CO CO
r1- v.- ^ rt ~ r. U
^"cv?
-' 05 © C3 © Ci -f h Tfi © i>. © c;
r ,-■ -, co io cc cc — t-h <n •* o t- a
7' r~ © CC © CO © © C- t- t- t- t- L-
r ■ ~ ' CC l'- — © tt CI CO -* CO C£
J1 CO -« -ht -h co LO CO CO i-O i0 '.-
X
CD ?
i'to
r^ -
Tr. o r;
c
a
bn
S
/^■^
P
C2 cS
■* — ce
"m «
r;
oxll
CJ
0
?S<NtiH
b
ssoi
■Sec II
^
S'oS^i
§SSH
o
8 SS
'-■
yj ^H
■1
I II 'I r0jll
II b ^ ^5^
ICG
CONDUCTORS.
TABLE ©F I9TD1JCTAJICE ASD IMPEDANCE.
Per Mile of Wire.
Stanley Electric Manufacturing Co., Pittsfield, Mass.
3
<D
11
C
z - t
Inductance.
Impedance.
N
N
N
N
N
N
H
N
N
N
N
N
Dp
O
6££
133
125
66.6
60
40
25
133
125
66.6
60
40
25
~6
.00113
.944
.887
.473
4„3
".284
7177
"981
.926
.542
.502
.389
.319
12
.00135
1.13
1.06
.565
.509
.339
.212
1.161
1.093
.624
.574
.431
.340
Oil
.'2656
IS
.00148
1.24
1.16
.619
.558
.372
.232
1.268
1.190
.674 .618
.457
.353
24
.00156
1.30
1.22
.652
.538
.392
.245
1.327
1.249
.704! .645
.474
.361
6
.00116
.969
.911
.4sr,
.437
.291
7lS2
1.025
.971
.589 .551
.444
.381
12
.00139
1.16
1.09
.581
.524
.349
.218
1.207
1.140
.671
.622
.484
.400
too
.3348
is
.00152
1.27
1.19
.o:;6
.573
.382
.259
1.313
1.236
.719
.664
.508
.411
24
.00161
1.34
1.26
.673
.607
.404
.253
1.381
1.304
.752
.693
.525
.420
" (
.00121
1.01
~950
.506
.456
77304
.190
T7095
1.040
.659
.622
.52~6
.463
12
.0014.3
1.19
1.12
.538
,539
.3,59
.225
1.263
1.197
.732
.685
.554
.479
00 ,Y££A
is
.0015(1
1.30
1.22
.652
.588
.392
.245
1.367
1.291
.777
.724
.576
.488
24
.00165
1.38
1.30
.690
.622
.414
.259
1.443
1.367
.809
.752
.591
.495
(
.00124
I76~4~
~973
7r> l < >
7467
73lT
7l95
1.169
1.109
.744 .709
.617
.567
0
.5328
12
.00147
1.23
1.15
.615
.554
.369
.231
1.340
1.267
.814
.769
.648
.581
IS
.001 CO
1.34
1.26
m\
.603
.402
.251
1.442
1.368
.855
.805
.667
.589
24
.ook;;)
1.41
1.33
.707
.637
.425
.265
1.507
1.433
.887
.830
.682
.595
6
.00128
1.07
1.00
.535
7482
.322
.20T
17263
1.204
.858
.826
.744
.700
.6706
12
.00150
1.25
1.18
.627
.565
.377
.236
1.419
1.357
.918
.877
.770
.711
1
is
.00163
1.36
1.28
.682
.614
.409
.256
1.5K
1.445
.956
.909
.785
.718
24
.00172
1.44
1.35
.719
.648
.432
.270
1.580
1.507
.983
.933
.798
.723
6
760130
l76<T
1.02
.544
.490
77327
7204
1.379
1.324
1.005, .977
.906
.869
.8448
l'_
.00154
1.29
1.21
.644
.580
.3*7
.242
1.542
1.476
1.062 1.025
.929
.879
*
18
.00166
1.39
1.30
.(594
.625
.417
.261
1.627
1.550
1.093,1.051
.942
.884
24
6
.00176
1.47
1.12
1.38
T705~
.736
.560
.663
.505
.442
7337
.270
.210
1.(95
1.547
1.618
1.1201.074
.953
.889
.00134
17497,1.205 1.180
1.119 1.187
3
1.067
11
.00158
1.32
1.24
.661
.595
.597
.248
1.697
1.636 1.255 1.222
1.138
1.695
is
.00170
1.42
1.33
.711
.641
.427
.267
1.776
1.705 1.282 1.245
1.149
1.100
24
.00179
1.50
1.41
.749
.674
.450
.281
1.841
1.768 1.304 1.262
1.158
1.103
6
700138
1.15
1.08
'.577
.520
.547
7217
i7rfo
1.726 174644.443
1.390
1.363
4
1.346
12
.00162
1.35
1.27
.678
.610
.407
.254
1.906
1.851
1.507,1.478
1.406
1.370
IS
.00173
1.44
1.36
.724
.652
.435
.272
1.971
1.913
1.5284.496
1.415
1.373
24
.00182
1.52
1.43
.761
.686
.457
.286
2.030
1.964 1.546 1.511
1.421
1.376
<
.00141
1.18
1.11
.590
.531
354
.221
2.009
2.030
1.79911.781
1.736
1.714
5
1.700
12
.00165
1.38
1.30
.690
.622
.414
.259
2.1 '30
2.140
1.835 1.810
1.750
1.720
IS
.00177
1.48
1.39
.740
.667
.445
.278
2.254
2.196
1.854 1.826
1.757
1.723
24
.00187
1.56
1.47
.782
.705
.470
.294
2.307
2.247
1.871 1.840
1.764
1.725
6
.00145
1.21
1.14
7606
.546
.364
.228
2.457
2.423 277222 2.207
2.1(9
2.150
6
2.138
12
.00168
1.40
1.32
.703
.635
.422
.264
2.556
2.513 2.251 2.230
2.179
2.154
IS
.00181
1.51
1.42
.757
.682
.455
.284
2.618
2.567 2.268 2.244
2.186
2.157
24
.00190
1.59
1.49
.795
.716
.477
.298
2.664
2.606 ,2.281 ,2.255
2.191
2.159
6
.00149
1.24
1.17
7623
.561
.574
.234
2.969
2.941
2.769
2.756
2.724
2.708
7
2.698
12
.00172
1.44
1.35
.719
.648
.43,2
.270
3.058
3.017
2.792
2.775
2.732
2.711
IS
.00184
1.54
1.44
.770
.693
.462
.289
3.107
3 058
2.806
2.786
2.737
2.713
24
6
.00194
1.62
1.28
1.52
1.20
.811
.640
.731
.577
.487
.384
.305
.240
3.147
3.639
5.697
37611
2.817
3.406
2.795
3.455
2.742
3.428
2.715
.00153
3.414
8
3.406
12
.00175
1.46
1.37
.732
.659
.440
.275
3.706
3.671
3.4S4
3.469
3.454
3.417
IS
.00188
1.57
1.48
.786
.708
.472
.295
3,. 730
3.714
5.495
5.479
5.459
3.419
24
6
.00197
1.65
1.31
1.55
1.23
.824
.657
.742
.592
,495
.394
.309
.246
3.785
4.4SS
3.742
47466
3.504
4.543
3.486
4.354
5.442
477311
3.420
.00157
4.^00
9
4.293
12
.00179
1.50
1.41
749
.674
.430
.281
4.548
4.519
4.558
4.5,46
4.317
4.3C2
IS
.00192
1.60
1.51
.803
.72.3
.482
.301
4. r.si
4.551
4.567
4.554
4.520
4.304
24
.00201
1.68
1.58
841
.757
.nor,
.316
4.610
4.575
4.375
4.559
4 323
4.305
~6
.00161
1.34
1.26
.673
.607
.404
.253"
5.580
5.502
5.459
5.451
5.432
57423
10
5.417
12
.00184
1.54
1.44
770
.693
.462
.289
5.632
5.(05
5.471
5.461
5.437
5.425
IS
.00196
1.64
1.54
820
.739
.492
.508
5.660
5.632
5.479
5.467
5.439
5.426
24
.00205
1.71
1.61
.857
.772
.515
.322
5.680
5.651
5.484
5.472
5.441
5.427
D" = distance in inches between the wires. N = cycles per second.
BELL WIRING.
137
':!>
<^
-
:.._;
it_.
.-.-.'
:?t'--::;:
-■-
;-
^
<:
: ■::
^^
\
'-.
'S:
::'- 1
X
:^s
Each Small Divis
""
r!
■
\
N
\
~^
\-
~
X\
— ^
K
S
\
V
.:■
\
V
^
vS
N
V
•\
^v-
\
K^
^
^
x
X
Nr
V
V
V
\
k
■o
\ ■
V
\
^V
\
\
\
\
\
\
V
V
\
V
N
v|
■ •
— :
:\
N\
\ " ■
■ \
v :.
\
X
\
k
V.
p
V
-X
:A
~~.~:
k;
V
^
\ ■■■
^
S '•■'
\
V
^
-V—
\
1
\
^\
• ■ ■
\
:A
\
v.:-\
~:
\
\"'
\
V
\
V ■
Y
. ■ ■
>v-,
V
\
A
A
A
_\
\
V'
V -
Ah
V
A
: .
■ : :
\--.
■v.
\
^T
\
■ ■■■ \
-
V-
\
V
V
t
■"
'
:\
. \
v \
r
V
v
A"
...
■
4
-V-
1
b
1
-4
P
-4
p
V
Vrj
\
\
\
£
k
u
h
k
V
,:
;
■ -
X
#
A:
^
\
-v
n
'\
-
■\-:.
A
\
.A
5
\
A
■v;
A
A
-"
i
— -
\
— — t
I
\
\
\
-:-
J
. : .(
:;
,-
, ;
- :
:::.
!!!!
n:i
fit]
!!!l
ItlJ
i
:!;!
;i!
Load Power Factors
10 20 30
Drop in Percent of
E.3I.E. Delivered
BEII WIMIWCJ.
The following diagrams show various methods of connecting up-call bells
for different purposes, and will indicate ways in which incandescent lamps
may also be'connected to accomplish different results.
=£■ 6=6=
Fig. 31. One Bell, operated by one Fig 32. One Bell, operated by Two
Push, Pushes.
138
CONDUCTORS.
Fig. 33. Two Bells, operated by One
Push.
FrG. 34. Two Bells, operated by
Two Pushes.
When two or more hells are required to ring from one push, the common
practice is to connect them in series, i.e., wire from one directly to the next,
and to make all but one single-stroke ends. Bells connected in multiple
arc, as in diagram No. 24, give better satisfaction, although requiring more
J-
Fig. 35. Three-line Factory Call.
A number of Bells operated by
any number of pushes. All bells
rung by each push.
Fig. 36. Simple button, Three-
line Return Call. One set of
battery.
\t
-ft-
FlG. 37. Simple Button, Two-Line
and Ground Return Call. One set
of Battery.
Fig. 38. Two-Line Return Call.
Illustrating use of Return Call
Button. Bells ring separately.
A
Fig. 39. One-Line and Ground Return
Call. Illustrating use of Return Call-
Button. Bells ring separately.
Fig. 40. Simple Button, Two-
Line Return Call. Bells rinj
together.
Fig. 41. Simple-Button, One-Line
and Ground Return Call. Bells
ring together. The use of com-
plete metallic circuit in place of
ground connection is advised in
all cases where expense of wire
is not considerable.
FlG. 42. Four Indication Annuncia-
tor. Connections drawn for two
buttons only. A burglar alarm cir-
cuit is similar to the above, but
with one extra Avire running from
door or window-spring side of bat-
tery to burglar alarm in order to
operate continuous ringing attach-
ment.
BELL WIRING.
139
G
i*L
I
Fig. 43. Four Indication Annuncia-
tor, with extra Bell to ring from one
Push only. Illustrating use of
three-point hutton.
Fig. 44. Acoustic Telephone with
Magneto Bell Return Call. Ex-
tension Bell at one end of line.
In running lines between any two points, use care to place the battery, if
possible, near the push-button end of the line, as a slight leakage in fheVir-
cuit will not then weaken the battery.
IP
T MAT
Fig. 45. Diagram of Burglar-Alarm Mat, two Bells,
one Push and Automatic Drop ; all operated by one
battery. Both bells ring from one push or mat, as
desired, by changing the switch.
When mat is to be used, throw it into the circuit
by the switch, so that when the circuit is closed by a
person stepping on the mat, the automatic drop will
keep it closed, and both bells will continue to ring
until the drop is hooked up again.
(;as-li<-hi wraiNG.
Fig. 46. Pendent and A utomatic Gas-
Lighting Circuit, with Switch-board.
Fig. 47. Pendent Gas-Lighting Cir-
cuit, with Switch-board, Relay,
and Tell-Tale Bell.
Fig. 48. Diagram showing
arrangement of circuits
for Fire-Alarm or District-
Messenger Service.
Fig. 1 represents the engine-house or cen-
tral station containing the local or open cir-
cuit (8).
2 Represents the main or closed circuit on
which is located the fire-alarm or messenger
boxes (9).
3 Is the automatic register and winder.
4 Is the electro-mechanical gong.
5 Is the battery of open-circuit cells.
6 Is the battery of closed-circuit cells.
7 Is the relay and relay bell.
Instead of, or in addition to, the gong (4),
may be used a mechanical tower strike.
PROPERTIES OP CONDUCTORS.
Pure and Soft Copper.
Specific gravity, pure annealed, at 60° F 8.89 lbs.
Cubic foot Aveighs 555 lbs.
Cubic inch weighs 32 lbs.
1,000 foot 1 inch square rod weighs 3,851 lbs.
Tensile strength at 100° per square inch 23,366 lbs.
Specific resistance 1 cubic centimeter 0° C 000001594 ohm.
Resistance 1 cubic inch 15.5° C. or 60° F 0000006774 ohm.
Resistance 1 foot of 1 square inch section 20° C 000008128 ohm.
Resistance 1 mil-foot 0° C 9.59 ohms.
Weight per mile of copper wire is
(dia. in mils)2
Resistance per mile in ohms, of pure copper at 60° F., is
54,892
(dia. in mils)2
Specific conductivity of pure copper is 100, commercial copper runs from 96
to 102 per cent of the standard.
Percentage of conductivity is found by measuring the resistance of a sample
of the same length and weight as the standard, and at the same tem-
perature, then if R = resistance of standard, and r = the resistance
of sample, . = per cent conductivity.
• * Percentage Conductivity of any Sample.
The percafitK Je conductivity of any sample of a conductor, as referred to
a standam, carPbe determined as follows : —
Let R = resistance of a unit weight and length of the standard, at tempera-
ture t, from tables.
I = length of wire to be tested,
w =z weight of wire to be tested,
r = computed resistance of a pure standard copper wire of the same
dimensions and temperature as the test sample.
r1 = observed resistance at temperature t of the wire under test in ohms.
Then as the resistance of a conductor is directly proportional to its length,
and inversely proportional to its weight per unit of length (its cross-section),
Rl* .
r = ohms.
By actual test, the resistance of the wire having been found to be r' at tem-
perature t, then
r1 : r : : 100 : x
and the percentage of conductivity of the wire is
_100r
r'
Rise of Resistance witn Temperature.
The resistance of conductors is not a linear function of the temperature,
and hence its variation with the temperature must, for very precise work,
be represented in the ordinary formula : —
140
risp: of resistance.
141
R = r (1 + a t ± b t2)
Where R = resistance at the temperature t,
r = resistance at 0° C,
t = temperature in degrees C,
a and b = numerical constants from table below.
The following values of the constants have been found, but they are really
applicable to the original samples under test only : —
Metals (very pure)
Mercury
German silver (Cu 60- - Zn 26— Ni 14) . .
Platinum silver (Pt 67 — Ag 33) . . . .
Platinoid (Cu 59 — Zn 25.5 — Ni 14 — W 55)
Silver gold
.00382
+.00000126
000882
—.000000362
.000443
+.000000152
.00031
"
.00021
"
0006999
—.000000062
For ordinary calculations the formula may be written and used as fol-
lows : —
R = r (1 + at)
the values of a being given in the following table : —
Metal.
a
Silver
.00377
.00388
Gold
.00365
.00390
.00247
.00453
Tin
.00365
.00387
.00389
.00354
.00088
.00028 to 00044
The following table gives the value of the principal practical units of resis-
tance which existed previous to the establishment of the International Units.
UXIT
LXTERXATIOKAL
OHM.
B.A.
OHM.
Legal ohm
1884.
SlEMEKS'S
OHM.
International ohm
B. A. ohm . . .
Legal ohm . . .
Siemms'sohm . .
1
0.9866
0.9972
0.9407
1.0136
1.
1.0107
0.9535
1.0028
0.9894
1.
0.9434
1.0630
1.0488
1.0600
1.
Thus to reduce British Association ohms to international ohms we divide
by 1.0136, or multiply by 0.9866 ; and to reduce legal ohms to international
ohms we divide by 1.0028, or multiply by 0.9972, etc.
142
PROPERTIES OF CONDUCTORS.
HARD-DRAWIV COPPER TELEGRAPH WIRE.
(J. A. Roebling's Sons Co.)
Furnished in half-mile coils, either bare or insulated.
Approximate
SizeB. &S.
Gauge.
Resistance in
Ohms
per Mile.
Breaking
Strength.
Weight per
Mile.
Size of E. B. B.
Iron Wire
equal to
Copper.
9
4.30
625
209
2 t?
10
5.40
525
166
3 g
11
6.90
420
131
4 I
12
8.70
330
104
6 $.
13
10.90
270
83
6§3
14
13.70
213
66
Is
15
17.40
170
52
16
22.10
130
41
10 |
In handling this wire the greatest care should be observed to avoid kinks,
binds, scratches, or cuts. Joints should be made only with Mclntire Con-
nectors.
On account of its conductivity being about five times that of Ex. B. B.
Iron Wire, and its breaking strength over three times its weight per mile,
copper may be used of which the section is smaller and the weigbt less than
an equivalent iron wire, allowing a greater number of wires to be strung on
the poles.
Besides this advantage, the reduction of section materially decreases the
electrostatic capacity, while its non-magnetic character lessens the self-in-
duction of the line, both of which features tend to increase the possible
speed of signalling in telegraphing, and to give greater clearness of enuncia-
tion over telephone lines, especially those of great length.
IE.4I»-E]|TCASED AKTI.IIBITCTI©1¥ TELEPHOUE
A\ll> TELEGRAPH CABLE!.
(Roebling's.)
Plaix Cables, Lead
For Metallic
For Telegraph
Encased.
Circuit.
Circuits.
No. of
Size Wire
No. of
Size Wire
No. of
Size Wire
Wires.
B.&S. Gauge.
Pairs.
B.&S. Gauge.
Wires.
B. &S. Gauge.
4
IS
5
18
3
14
7
18
15
18
4
14
10
18
25
18
7
14
50
18
50
18
10
14
100
18
75
18
20
50
100
14
14
14
■■^^■^^■^H
COPPER WIRE TABLE.
143
d
oseoTjjoeooiooq
o
OOONOOt-OOMCO-tOOrHO (N OS "* © 1* r-i OS
i— © X CO tll-COXf-MKMOf O © 01 L.0 O LO
iq ;:::m':---:i -o_ © © :jq»oa^co(NiNrt
S
©
©' ::' ©' x ©* i~ -? yi oi - f r-Tr-Ti-T
.a
o
Q
Ph
®30ioNOiOMrt
w
OOOWLOOOOMNOOt>(M^Mt't-drt»l>
© i-h © 01 " to i" -T — '- © 01 co © — © -v lo X oi I-
7i i - i -y r~ 7 j t - i.q © x o i x -i_ — _ x t - i--. -f :o oi oi i-i
oc -)T t-T cT t-^ loT •*" cd" of of r-T i—" t-T
r-1
®
d
CO l>- rH CO LO ** CO
ooooMo-*riNLOHioaP3Lodd6^fflt-.'
■jihiOsx- x CO © co — © © © © : t © © r- -t ©
-f 01 -C ",— , -TO ©, — __'-0_ © l- .71 © L-© LOCO MNrt
(N
©
Cl3fi"ocO «D lO TP"« <N <N r-Tr-Ti-T
h
rH©01©t-t~OT*<© «- «, „ . _,,
•; '7 x :: •* i- i- " v: » i- ri :i :i 71 o o -f
a .
L0 —j -f i-i © © 7 1 — ©_ i.0_ X © . 7 1 X i-i lO L- "T •* © -"0
+3fQ
qjr-i
,_"-' " nn(NClM-*LOoSc> 3
£
d
Ol Ol -* 1Q O
o
(oootOHt-mooct-o
tmt:N«ni;-i;oqncicioc3
O b- <n o ■# o ■* i- cc" 71 oi -*' © id © © © cd cn «-i d
i - -i- x :: lo -+ i- i-i lo — © © t" Ol i-i r-i
lo © «qqqa ^jihh
®
©©Tifofr-fr-T
s
o
d
t-eccotoao
Mffl-lTfO^rit-Tr.
©
003t-CO-*cqc0^t-T-i0^t>:l-.0
a
®
© os •# ■* co co id LidddrHTco^HN ■* oi i-i r-i
: i -.; "7 — : " i " 7 > .7 /. / - L- -f 71 M M
t^qqqx^rit- i<Ni-iri
o
i-rt-"*oq~TH"r-r
3
^
£
d
0^i^,0l3
© Ol Ol 01 Nf«0 i- 71
o
© T)< rr 10 t- — i- LO X -r X OS i-i © 01
© Ol t- O CO 00 © OS © t-h d © © r-i CS 01 t- tT CO r-i r-i
© CO L— O "+1 CO rt © 71 © Ol C- LO CO 1-1 r-
© CI- 71 © 7J CO lO CO 71 i-i
©
co co ococsr-T
ft +3
©CN 00 CO CO CO t- CO CO LO 2§
LO © OO LO CO © CO -f 01 T 77 © CO -f © t---t X x : 1
- 0 7i r. co to r. © © © C7 © © —, -t< © ,o 01 © i- - :
1- © © 'i-i LO © LO 0 1 © t- 77 — •. T '■: -.'. 0 77 .77
— lO f CO ClClnrt-OOCOOCCOCOO :.
©©©©©"©©©©© © © ©' ©■ ©" © © © ©■ © ©
pi
©©C0L^O1CO©~H©COr-it-C0L0t~©t^lOCO©©!
. s
r © — x to oi co x © r-i i o to x lo — o i to 71 1.0 ■ - 1 -.
T-^L- LO X_ 1 - r- 77 1 - © © C0_©r 01 r-^-+ r- ©_ 71 1 0 © TO
F1
CO r?
o'T-T-tTof ■-' oi i-i oTid © to o r ~ x* --' lo -r1' to' oi o T — '
TO 00 © CO O O -* CO Ol C" i-l i-H H
So
©
IG
^ A
«*J
£ ._
5 S*
||
OOOOOOOOOOOOOO^OOONt-COOO
© © © — o. i ■ ■ ■ : -r .0 j -. 7 i i— © x : : :o i - © O co -f
© OOrHLO ©_C0 © L- H Ol CO LO © CO 01 O rH rt 01 LO ©
b
" ; r • f £ :f © of -5 £2 © © ©" cd ©" rx" ©" o" -T cd 7171
— © CO © X © LO -* CO 01 Ol "H i-h r-i
O <g
NHrtrt
©
©
c« ©
5|
©
^ CO 00 © CO © -* CO © © CO LO ■* © it X © © ^ - ' °
to :- -t — ;;:-©-+ h oi -t co -H — © © 1 1< — £t -J
© © © 01 X 10 Ol © X © -f 01 — _ _ . xi-©l-- ^
- "t - -. :" • ! ?! -!•!-: -t rt. rt. -1 rn © © © © >_. •_ r
©©©©©©©©©©©©©©©©©© 0- q <5
o
M
0 ~ ©©i-!Oico-PLO©t^ao©©i-ioico-*fL.o©c--
1©© ^^^^^^^^
H
D\AiV
s^'a
144
PROPERTIES OF CONDUCTORS.
(SOt-OOH(SOt-«
co o> 1-1 ** ?j .:; q oi ; -: -r r r. — © o lo -* o
tfflOIMfflt-W'JMMNHHHOO
OiOWM<NHrlrt
i; T^OlO © C5 I- © T CO © © CO -P CO 7t< I- 11 L- 00 © CO
i i-" x © lo -r -? t- ~ i- to ©' x © lo ■* co oi oi -i ri i-i ©
g3?i
t» CO lO H C! U'
a-*ioH oi lo -t< © to -+ © © © 7
3 CM © L— © -* CO «
C0©5©ScN©
CO CO <N ri ri i-H ©
-HOfflSt-t-lOt-HrtOOOOOO
o qnSqoSrtNiow't oi.© © q5
T-Trn i-Tcfcf of-* IO © co © 'to © n"© co"
n -i n ci ci to
2StFX
23??:
: in -t< )
©©©©©©©C
SOOOOOOOOOOOOO©
lO 1Q i-l © © 10 - i-O
tO tO C0 Ol LO i- to © to 0 I -
co oi c- © to ■/. ~ -t "-: -i- i.o — © - © © -i- ci
ifNHNOr.... .. . I . S © C£ - ' r-i j o © ©
© -r< to i x i - o i •-; © © © -t- o i — — © © © © © — © ©
© to I- i- © © ~t< oi — — © © - •©©©©©
© -f oi h -ri ©©©©©©©©©©©©© c; © © © ©
©*©©©'©©©©©©©©©©©©© ©'©©'©'©©
© © co t- co -t oi © o
. - © © i-0 lo © to © © c<
-ocooc-t- © X n t- -£ oi ■
■ « ©: 2 ° S
" '-"- £ r ? '~ ' "
t- -£ © 2< ©1 © © © ©5 © 5 © ©©■©■©_©©© q 5 5
©©"©©©©©©©©©©©©©'o©©©©©'©©
C0 00HO51
O CM to CO c- to -r © © iO L-
D © © © © © ©
©©©©©©'©©©"©"©'©" © © ©_© ©©'©"_©©'©©
co -p © -t1 1~- oi © -r t~ "lo © "t-
to © oi to t>; cq CO LO in © © © co oi t- © iq to C-; O;
© OI Ol © -r © t~ H © CO 10 © CO 01 © © i -p © m' o"
' - - n r: - Q r- & cq © qi ~ -
-ffl^WMINHHH
n ■# Lq q ■* t-
OiMiOCl too
-- iq L~ Ol 1 t- LO © X L-
i)< 00 01 © 01 © -t © -t< -i © © © © to ©
0 i X 0 I -i -i< © © 0 1 10 © lO 01 © t- © LO
■_ 0 I © X © LO -f CO 01 Ol n ri ri
oo © © in m co io n i.o
© © © © m t- © © in -+i © t -. : i i o f. - — i.o © to -p
CO CO © -P CO 10 ^< © © 01 © 01 © © © © to © © -f ~ 10 —
© in h x jq oi © i - ro -r o_i — ~ r i- r- © io io — to to to
© © © © © ©©©©©©©© © c ©©©©©© ©5
©"_©_©_©' ©©©"©©'©_©"©©©'©'©'©©*©'©'©'©©
CO © © n 01 -o -1-10 © l- X © © i 0 1 to -f LO © I- X © ©
HHMCNOKIC) 010 1 Old 0 1 CO to to CO tO CO tO CO CO CO -#
w q ^ QrZ co ^ 3 m
S rt co m-S"^03 B 9 iS
§ Od ©■ ©??Si © -^02
1 ^! § *$%* 2 6-2
S "21 0 'g©^'J Is P ;
^ „• r3 © *43 o © ^ 2 ~v •" — ^ ■
"? ia -^-5 © i 3) i bD ^ > - ';
•Io-?© ft S^g.5 -g 3 i
•S-3"-SS 2 -°-=§^ ©- S '
an ra to cs *-• Cv>s4H'a N© i
^•|2ii S J^S.S' &= ^
-selts ■"- §J*s 2§o ^
^•^^
+3 s, c^ o 73 CO
git, the com
^presenting •<
W. G. wires
st fourth sig
as follows :
Resistance 1
per = 0.1469 B
14365 B. A. U.
141729 interna
and 80° C, 1.
significant di
half a unit, r
B. &S. or A.
ch, the neare
^©&qH
'43 cpoS
-SSINIP
SS^in
© II j5^ „ S
«P
5^111
CO
fto.73 d
c« fl
3n com
of cop
3f hard
or 20°
ried to
correc
diamet
No. 3(
05 T3
"1 ©
2 J3
© 0
^'tSgOOcSt^cj
^bV2 Jg^s^-© ^'S
©«^ -silSS-S &*
S^^ . |j] 1^ I 11-3 *» a
i^l""Hiiflilll
S«„ Cv_„cDt-lrt^H-g<p
? 2 q 2 © 2 ^ a "3 g rQ .■§
tjejeo ^ SMS ° 'S'3* °
© ^ 2 "S °°
COPPER WIRES.
145
6
©
0.00006058
0.00007G40
0.00009633
0.000 r_J15
0.0001532
0.0001932
0.0002435
0.0003071
0.0003873
0.0004883
0.000G158
0.00077G5
0-0009791
0.001235
0.001557
©
0.00005407
O.O0OOG893
0.00008692
0.000109G
0.0001382
0.0001743
0.0002198
0.2002771
0.0003495
0.0004406
0.0U0C55G
0.0007007
0.0008835
0.001114
0.001405
" h ^ S m S !
© r j
OOOOOOOC__
© O O 3 © © O =5 © © O ~ ■
©©©©©©©©©©©©.©©©
dddddddddddddd©
Hffl H Iffl lfl(
§* H « o
© © © © 5 ~ -- -i co \z ~. !o ^? © <n
3 3 8 8 § § 3 3 3 8 § 3 § 8 i
■■- lo 1- s i: i> o to hot- ©
CO CO —i -+ -t- © i- ~. x -h —i ci m io ©
© h c-l ro i- x c- — . -t- i- x © c-1 •& co
© © © C © - — : i :-. i - x -* <oi 10 ©
© © © © © © ~ - ~_ ; h o n o
©©oooo©© © © © © © © ©
dddd©ddddddd©dd
:o UO rH tH CO o
© i-i co i- x © i.o co -m co <M
£• <N © © X L- CO © Ol © © LO LO CO 10
© tj rH oo -t< t- -i ~ — r. r io © t- -f
©©©©©©rH-HC^-TL-OlOrHO
oooooocc:o*-hc)o
©©©©©© ©©©©©©©©©
146
PROPERTIES OF CONDUCTORS.
!2SI
, i-H l- O -*
. LO n O O
— i 01 CO CO -f CO L- Cl 01 LO Cl LO n O O CO O r-i L- O 01 LO 01 O Cl CO LO 00 CO
o — o o o o o o i-i i-H — i ci co -v i- oo 00 O 01 CO O LO 0 1 O rl -+ —I CM Cl
SOOOOCOOOO O O O O O O O h i-i i-H Cl 01 CO -cH LO W 00 O Cl
OOOOOOOOOOOOOc
> O O O O O n iH
Cl o
. j a § c-o
5 H g g ^ O N » H
h a i- -t :i ■;
i-i i-o -t co ci i-i ^ o oo o ci t- lo
i- S l-~ L; -' ^ ° >~ 9 p — — ?-' v
oooooopooqoo q "q q o o d *h i-t
= = O — i-i — ••
O O O O O O (
) O O O O O c
lO l> OJ rj
doooo'oooo'odddi-H
cocinciciLOrfiao
x. o ci i- o l: i- n -f co ci ci n h lo co s o
lo c-. lo i-i :o o co o '-1 i- — co oo co i- c: i- t- o r, a o lo -f ti ci lo •#
.1 ii ci co -c lo co x o oi o co i-o oi ~ ii -r — co - c: co o oo -r ci oo o t-
o o o o o o o o ti ii ii ci ci co -r lo oo x c oi co c oo ci h ci lo co -h
oooooooooqoqopoopOiiniicioico-c*Loqcop
■ n Cl =t< O
I 00 CO
i lo lo to oi -t w a
d dddoo n«'*»6<oioH io ■
O LO c
= 5 :
S g 2 8 §
LO p Cl CO © O O j
CO CO Cl L~ t- rl CM <
n' of -* «T g" if t£ I
O n 0
d o d d d d i-' <
!H Cl CO LO <
Cl CO CO LCD
t^'cO rj tg
CN CO
q o l-j i5
I 05 N N
» L- n GO CO LO Cl L- CO
; Cl Cl Cl ii p CO p ci p p CO <cH C-l
i co lo co co d co" ci -ti oo oo oc oo' d '
n Cl CO LO CO CO n CO CO o ,
Cl O rl Cl (
i cl §
I co CO CO co co co co :
COPPER WIRES.
147
5 <2 ^
o*
o
©
5
—
£
©
(M
8
05
ia
S
£|
^
2
§
(ti)
co
<*
CO
lO
co
<N
o
g;,
o
c
M
—
m
i.
-*
fV,
,_,
-t<
s
rs
LO
•-
-
rJ-
L-
y
rH
'.*
!--
IS)
lr
i-
ii
OS
L~
lO
*#
-f
CO
IN
LM
1-1
1-1
ooooNOffirtiooaaO"*
i-t m >o co cr. oit«t-t-oooi(NHco
Ci-*C5i-lOt--#Tt<COCjT-(COT-lt-
COO30000i-ICOu0<MCOt- „ _
© CI 00 LO l^ CI !N CO <M i-H © CO 00 ©
eO00(M00CO©C50000©!MiH©Th
© t-"
CO iH ©
w § o
d
©
©
—
"#
t.
©
CO CO
©
11,120
8,537
5,456
3,497
|
of
|
!-
s
CO
3
*
■<#
1 s
d
©
s
a
lO
©
r.
CO
00 CN
®
12,420
9,538
6,096
3,907
00
co
—
03
cc
X
2
CO
CO
r.
T
CO
CO
~j
© ■*
CO =# So ..
*©c--*c-icioccoiq
<N ON rH r-i 1-1 O © © ©
© © © c =_
© © . o ©'
i-l CO © ©
© CO ^ CO
•o "tf co co
©ooooooo©©©©©©
©©©e5o3oo»*©^©coeco
t a. "t ° ^ ° °~ ^, "*.- ^i- "r- °i °i. °l.
~ ©" c-f o oo t-T of ^ jh t£
p co ^ 13
© © © o © © ©
m © © ~ -f
©©©©©©©©o©'©©o©
s.qn^S | § 1 ° °
148
PROPERTIES OF CONDUCTORS.
eo
X
eo
in
>*
3
^
^
-
X
CO
|
2
r.
?!
©
"
©
o
-*
co
eo
U5
ci
©
eo
g
d
©'
in
X
01
:o
©
so
•&
X
s
©
U0
CO
<N
©
■■#
1-.
co"
cl
<N
in
q
in
q
in
q
q
so
q
©
s
x
■*
cS
-*
i>
UO
■*
-
o
©
eo
lO
■*
©
-c
CO
**
rH"
X
X
_
X
-f
lO
05
X
X
co
-r
05
©
-+
q
CO
so
q
os
X
IO
is
8
d
-#
o
01
X
X
so
m
-'
^"
i
S3
s
g
co
3
co
eo
CO
^
so
<*
eo
so
q
in
©
©
LO
m
-J
coo
co
X
01
01
©
©
<M
cq
co
<*
so
p-
35
co
v;
"?
CO
>*
se
X
©
CN
SO
£
CN
o
s
r^
IN
8
rt
1-1
r"1
"
<N
X
"*
lO
so"
2
S
<N
CO
©
S
©
©
^
©
-+
CO
2
©
CO
r.
©
©
1-
£
-t1
©
1
©
©
©
CO
?i
01
ss
eo
X
f2
?!
3
q
5
©
©
©
8
2
2
©
©
©
8
8
50
d
d
d
©
©
d
d
©
©
©
-
©
©'
©
©
d
CO
X
eo
1
so
CO
5
lO
©
1
CO
>*
c
1
i0
©
to
-J
CI
~
©
©
©
2
©
©
2
eo
2
so
bO
CO
3
©
3
q
©
CO
©
©
q
©
1
--2
CO
r'
9
■*
oi
d
d
d
d
d
d
d
d
d
d
d
d
©
©
©
©
©
©
^
X
©
<#
t-
X
m
©
©
■y.
^
_
X
m
r*
|
ts
r\
Zj!
""£
Lr
5
5J
£_!
CO
2
x-
2
2
©
©
1
©
S?
00
X
■_*
?!
S
3
?:
~
^
5
s
2
©
©
1
5
2
§
©
©
©
3
5
3
CO
"
in
d
d
d
©
d
d
©
©
d
©
d
©
©
©'
©
X
©
X
•-CO
©
^
<N
^
x
X
2?
to
IM
m
gj
gj
X
1
|
X
©
8
co
©
g
^
X
^
CO
cr.
^
l-O
d
To
©
-f
l~
9
q
^
CO
3
•2
L~
3
o'i
J5
-r
(N
-
~
iffl
'2
s
X
3
— '
I
©
1 §
©
q
q
d
©
©
1
=
©
©
1 p
©
©
O
3
2
8
2
©
©
cr.
©
2
©
©
©
§
©
©
d
©
©
©
d
d
d
©
d
d
d
©
-
d
d
©
©
©
d
©
d
©
©
©
©'
©
^ x x -;
^h -H X
"* ® m- ^ ^i^
g oi -f lo d o -f -t h co
■* O-l t- X -H
i-h in © <n ■* ©
eo oo eg © oq cs i
© ©
s s s s t &
, Tf t^ tl O I- X
-T © eo in >* x~ o-f h h th
ssss^
qqqqqqqqq
o©o ©o©©©
o©©©p©o©©©©o©©©©©©©©x©©©©
oi © eh x i- X >- *(5 ^h co co oi ft ci ci h h h « -; h o ~ -i a
<Hr^©©©©© © CO©©©©©©©©©©©© Q. ©©q
©©©©©©©'© ©. ©<©©©©©©©©©©©©©© ©': i
1<NC<ISMXXXXXC0
=1 © r^ Cl x
^B^m^H^H
COPPER WIRES.
149
o ©
§ s
q q
l^©-*<--ir-icO©i-it--©CO©
CO©CNCOT-H©-fr-llO©OTt<
GO t-1 -* 10 C5 CI to <-H Oi t- 00 rH
ooooSooooooo
oooooooooooo
ooqqoooooooo
ddddd o'dodooo
8 c3
oooooooo
8 8
o © © o ©
H^ ®
CO l- o © -p
^ © §
© © © ©
8 8
©©©©©©©©©©©©©©
© —-■ CO © ?l *-h i-i ©
Ol N O h fi io <* H w
© i-H <M CO id © © CO CO -+i ©
©©©0©©0©©©0
©©OO©©©©©©©
3 g
S q S
^ CO © CO -H
3 3 8
3 i
C3 ^ ^ O © ©
s "S s s r -
8 S
©©©©©©©©©©©©
co © co o cn ci © © © rH m — i oi -h
© _< _| C-I Tt< L-5 L- © ■+ © (N © —I ©
8 8
8 8 8
©©©©©©©©
© © © © —I
© © © © ©
© © © © ©
150
PROPERTIES OF CONDUCTORS.
O CJ © ~-
g I g
8 8 1 I "
w - a is
©ooooooooooooo
© s
© o © © © q
© © © i-*
o © © o
o o o © o o
£2 f° £2 Z.
i.-. ^ © IC ~*
ic * n n ifl
s g ■ S S 3
? 2 23 £ £
© © © q © © ©
S ~ S 3
!* § S « H if »
© © © © 1-; ^ _i i
s s
©©©©©©©©©©©©©©©©©©©©
© © © © ©
i © CI o t- ^
) — i — I- CI
i$ ^ Zi if,
oo o n o
©©©■©©©'©■©©'©©
©q©q ©©*©©©©
©©'©©©'©©©'
© © © © © © ©
© .-i
© ■* cb q
•S58SS25Sa!?I|||
fH CI "# ©
I o
© © © ©
3SS
©©<©©©© "-1 M M O O ffl |
>§ S3 2 ? n 2 s s 0
Sci^^cicieocJ
OOOOHHKisq
©©'©©©©©©''--
SS3
© © CO —
3 S H
?; w i
<MCI<NC1C1<NOC«CO
COPPER WIRES.
151
TABLE ©E »IIflEJ\SIOMS, WEIGHT, AID RE.
SliTABfCE ©E PWItE COPPER WIRE.
(Edison or Circular Mil Gaug'e.)
Weight. Sp. gr. 8.889.
6 £,^
3 •
3 p
^!S
hi
o
o
£
a 'I3
°'a
eS 5
^h
pii
g
o
A *&
b
§^>
s 1
ft
ft
3
3,000
12.5
54.78
.009084
2.597
5
5,000
18.3
70.72
.015139
7.214
8
8,000
26.0
89.55
.024220
18.464
12
12,000
35.2
109.55
.036328
41.538
15
15,000
41.6
122.48
.045410
64.9.92
20
20,000
51.6
141.43
.060548
115.372
25
25,000
61.0
158.12
.075682
180.278
30
30,000
70.0
173.21
.090817
259.722
35
35,000
73.6
187.09
.105955
353.340
40
40,000
86.8
200.00
.121082
461.440
45
45,000
94.9
212.14
.136227
584.098
50
50,000
102.7
223.61
.151357
721.026
55
55,000
110.3
234.53
.166501
872.547
60
60,000
117.7
244.95
.181625
1,038.258
65
65,000
125.0
254.98
.196772
1,218.5S6
70
70,000
132.1
264.58
.211901
1,413.264
75
75,000
139.1
273.87
.227043
1,622.457
80
80,000
146.0
282.85
.242176
1,845.952
85
85,000
152.8
292.55
.257303
2,083.759
90
90,000
159.5
300.00
.272434
2,336.405
95
95,000
165.1
308.23
.287587
2,603.046
100
100,000
172.6
316.23
.302709
2,884.082
110
110,000
185.4
331.67
.332991
3,489.958
120
120,000
198.0
346.42
.363267
4,153.433
130
130,000
210.2
360.56
.393527
4,874.226
140
140,000
222.2
374.17
.423797
5,652.899
150
150,000
234.0
387.30
.454061
6,484.573
160
160,000
245.6
400.00
.484328
7,383.042
170
170,000
257.0
412.32
.514622
8,835.525
180
180,000
268.3
424.27
.544884
9,344.686
190
190,000
279.4
435.89
.575140
10,411.241
200
200,000
290.4
447.22
.605427
11,536.681
220
220,000
312.0
469.05
.665975
13,959.567
240
240,000
333.0
489.90
.726498
16,612.114
260
260,000
353.5
509.91
.787058
19,496.997
280
280,000
373.7
529.16
.847605
22,612.233
300
300,000
393.6
547.73
.908140
25,957.464
320
320,000
413.1
565.69
.968672
29,533.696
340
340,000
432.3
583.10
1.029214
33,340.181
360
360,000
4
51.3
600.00
1.089738
37,376.652
1 Mil Foot = 9.718 B. A. Units @ 0° C. (Dr. Matthiessen.)
152
PROPERTIES OF CONDUCTORS.
TABLE OF MHUEWSTOarS, WEIGHT, AKD RESIS-
TANCE OF PURE COPPER WIRE — Continued.
(Edison or Circular Mil Craug-e.)
Length.
Resistance. Legal ohms at 75° Fahr.
110.087
66.054
41.288
27.527
22.022
16.516
13.213
11.011
9.4381
8.2589
7.3407
6.6069
6.0060
5.5059
5.0820
4.7192
4.4044
4.1292
3.8865
3.6706
3.4773
3.3035
3.0031
2.7528
2.5411
2.3596
2.2023
2.0647
1.9432
1.8353
1.7387
1.6517
1.5016
1.3765
1.2706
1.1798
1.1012
1.0323
.9716
.9177
285.9
476.5
762.3
1,143.4
1,429.2
1,905.7
2,382.0
2,859.9
3,334.9
3,811.0
4,287.7
4,763.8
5,240.5
5,716.5
6,192.9
6,669.4
7,146.0
7,622.3
8,098.4
8,574.7
9,C51.6
9,527.6
10,480.6
11,433.6
12,386.0
13,338.7
14,291.3
15,243.9
16,197.4
17,149.9
18,102.1
19,055.4
20,961.1
22,866.0
24,772.1
26,677.8
28,583.1
30,488.3
32,393.8
34,298.7
.0651602
.0240743
.0154178
.0055470
.0038522
.0028301
.0021671
.0017120
.0013868
.0011467
.00096315
.00082057
.00070758
.00061635
.00054172
.00047990
.00042807
.00038415
.00034673
.00028656
.00024070
.00020514
.00017690
.00015409
•00013544
.00011995
.00010701
.00009604
.00008667
.00007163
.00006019
.00005129
.00004422
.00003852
.00003386
.00002099
.00002675
.003497600
3
.002098640
5
.001311780
8
.000874578
12
.000699663
15
.000524745
20
.000419807
25
.000349840
30
.000299863
35
.000262400
40
.000233227
45
.000209914
50
.000190821
55
.000174931
60
.000161465
65
.000149937
70
.009139938
75
.000131193
80
.000123480
85
.000116622
90
.000110477
95
.000104960
100
.000095410
110
.000084460
120
.000080730
130
.000074970
140
.000069997
150
.000065600
160
.000061735
170
.000058309
180
.000055242
190
.000052478
200
.000047707
220
.000043733
240
.000040368
260
.000037484
280
.000034986
300
.000032799
320
.000030870
1 340
.000029155
360
1 Mil Foot = 9.718 B. A. Units @ 0° C. (Dr. Matthiessen.)
CAPACITY OF COPPER WIRES. 153
SAFE CARRYING CAPACITY OF COPPER
WIRE§.
Below will be found the formulae of Forbes and Kennelly for safe carrying
capacity of copper conductors. The results, which would be obtained by
using these formulae, have been somewhat modified in practice, and the
reader is referred to the tables in the "National Code" for capacities
recommended by the underwriters.
Size of Conductors.
(Prof. G. Forbes.)
Bare Overhead Wires. — The relation between the diameter of a
conductor and the current it can safely carry without over-heating is
2 H
1— DH-
Ui X .24
"Where 1= Current in amperes.
D — Diameter of wire in centimeters.
t z= Excess of temperature C. of wire over the air.
H=z Coefficient of radiation and convection = .0003.
R = Specific electrical resistance of material per b. cm. at the lim-
iting temp.
.24 = Calories in a Joule.
Insulated Overhead Wires. — For gutta-percha and india-rubber
insulation,
L V t V tL.
\
1= k I \ .48 It X * X 10 + 3Z>3 log.
e D1 )
Where Dx = Diameter of conductor.
IX = Diameter of insulated cable.
t = Excess of temperature of conductor over air.
k = Heat conductivity of insulator ; for G.-P. = .00048 ; for I.-R. =
.00041.
Kennelly's Mule of the Sate Diameter of an Insulated
Panelled Wire.
If the limiting safe diameter of an insulated panelled wire be such that
twice the proposed full load upon it shall only raise its temperature 40° C,
then the best formula is
d = .0147 1\
d being in inches and I in amperes ; or approximately
f/ = 70
Heating of Bare Conductors S»y a Current.
The temperature to which a bare copper wire freely suspended in still air
will be raised when traversed by a current is approximately
"tfs
X 90,000 + t°,
T° = temperature of wire in F°.
t° = temperature of air in F°.
1 = current in amperes.
d = diameter of wire in mils.
For a given presumable maximum elevation of temperature the requisite
diameter is approximately
154 PROPERTIES OF CONDUCTORS.
1 11 OX WIRE.
Iron.
Specific gravity . 7.7
Cubic foot weighs 480 lbs.
Cubic inch weighs 2779 lb.
Tensile strength per square inch ...... 50,000 to 60.000 lbs.
Specific resistance 1 cubic centimeter at 0° C. . .0000005 ohms.
Resistance per mil foot 58 ohms.
Steel.
Specific gravity . 7.932
Cubic foot weighs 490 lbs.
Cubic inch weiglis 2834 lb.
Tensile strength per square inch 55,000 to 80,000 lbs.
Specific resistance 1 cubic centimeter at 0° C. . .000013 ohms.
Resistance per mil foot 82 ohms
The above items are for the metals as metals, and not when in wire. Re-
sistance of iron wire varies so much, by reason of drawing and hardening,
that it is not practicable to state specific resistances, weights, and strengths.
The following tables give approximate averages.
OALYAAIZED 1 HOX WIKffi FOB TEJLBCiltAPH:
AXJL* TEiEPHOSE LOES.
(Trenton Iron Co.)
Weight per HKile-Ohm. — This term is to be understood as distin-
guishing the rrs'nt.mce of material only, and means the weight of such
material required per mile to give the resistance of one ohm. To ascertain
the mileage resistance of any wire, divide the "weight per mile-ohm" by
the weight of the wire per mile. Thus in a grade of Extra Best Best, of
which the weight per mile-ohm is 5,000, the mileage resistance of No. 6
(weight per mile 525 lbs.) would be about 9§ ohms ; and No. 14 steel wire,
8500 lbs weight per mile-ohm (95 lbs. weight per mile), would show about 69
ohms.
Sizes of Wire used in Telegraph and Telephone lines.
No. 4. Has not been much used until recently ; is now used on important
lines where the multiplex systems are applied.
No. 5. Little used in the United States.
No. 6. Used for important circuits between cities.
No. 8. Medium size for circuits of 400 miles or less.
No. 9. For similar locations to No. 8, but on somewhat shorter circuits ;
until lately was the size most largely used in this countrv.
Nos. 10, 11. For shorter circuits, railway telegraphs, private lines, police
and fire alarm lines, etc.
No. 12. For telephone lines, police and fire alarm lines, etc.
Nos. 13, 14. For telephone lines, and short private lines ; steel wire is
used most generally in these sizes.
The coating of telegraph wire with zinc as a protection against oxidation
is now generally admitted to be the most efficacious method.
The grades of line wire are generally known to the trade as " Extra Best
Best" (E. B. B.), " Best Best" (B. B.)', and " Steel."
" Extra Best Best " is made of the very best iron, as nearly pure as any
commercial iron, soft, tough, uniform, and of very high conductivity, its
weight per mile-ohm being about 5,000 lbs.
The " Best Best" is of iron, showing in mechanical tests almost as good
results as the E. B. B., but not quite as soft, and being somewhat lower in
conductivity ; weight per mile-ohm about 5.700 lbs.
The Trenton " Steel" wire is well suited for telephone or short telegraph
lines, and the weight per mile-ohm is about 6,500 lbs.
TESTS OF TELEGRAPH WIRES.
155
The following are (approximately) tlie Aveights per mile of various sizes of
galvanized telegraph wire, drawn by Trenton Iron Co.'s gauge :
Lbs. 720. 610. 525. 450. 375. 310 . 250. 200. 160. 125.
TESTS ©E TEIEGRAPH WIRE.
The following data are taken from a tab^e given by Mr. Prescott relating
to tests of E. B. B. galvanized wire furnished the Western Union Telegraph
Co. :
Wei
ght.
Resistance.
Temp. 75.8° Fahr.
"i ^
^
6
%
*s -
O
Ph^ a
o
z
"So^
3
s
3d
I 8
a
ID
1
+2 "5
1 £
3
o
fo
o
4
.238
1,043.2
886.6
6.00
958
5.51
5
.220
891.3
673.5
7.85
727
7.26
6
.203
758.9
572.2
9.20
618
8.54
3.05
7
.180
596.0
449.9
11.70
578
10.86
3.40
8
.165
501.4
378.1
14.00
409
12.92
3.07
9
.148
403.4
304.2
17.4
328
16.10
3.38
10
.134
330.7
249.4
21.2
269
19.60
3.37
11
.120
265.2
200.0
26.4
216
24.42
2.97
12
.109
218.8
165.0
32.0
179
29.60
3.43
14
.083
126.9
95.7
55.2
104
51.00
3.05
.Joints in Telesrrapn Wires. — The fewer the joints in a line the
better. All joints should be carefully made and well soldered over, for a
bad joint may cause as much resistance to the electric current as several
miles of wire.
WEIGHT ANR RESISTANCE OE GALVANIZED
IRON WIRE PER TSXMJE.
(Roebling.)
Gauge.
B. &S.
Weight
per
Mile.
Resistance.
Ohms.
Gauge.
B.&S.
Weight
per
Mile.
Resistance.
Ohms.
6
7
8
9
10
550
470
385
330 *
268
10
12.1
14.1
16.4
20
11
12
14
16
216
170
100
62
20
32.7
52.8
91.6
156
PROPERTIES OF CONDUCTORS.
SIMS, WEIOHT, I.B<L\«-TIB A1VI» STItEKGTH OF
IRON Willi],
(Trenton Iron Co.)
a
° V
.i-3
.2 ^
2
<2 m
Tensile Strength (Ap-
s S°
®-m
'% ° -^
O S
proximately) of Char-
HO
■-i 3
™ flS>H
o s
|!
coal Iron Wire in
Pounds.
So
S|
o'rt.5 2
<
-^ o
ft
_bc-3
Bright.
Annealed.
00000
.450
.15904
1.863
2.833.248
12,598
9,449
0000
.400
.12566
2.358
2,238.878
9,955
7,466
000
.360
.10179
2.911
1,813.574
8,124
6,091
00
.330
.08553
3.465
1,523.861
6,880
5,160
0
.305
.07306
4.057
1,301.678
5,926
4,445
1
.285
.06379
4.645
1,136.678
5,226
3,920
2
.265 ■
.05515
5.374
982.555
4,570
3,425
3
.245
.04714
6.286
839.942
3,948
2,960
4
.225
.03976
7.454
708.365
3,374
2,530
5
.205
.03301
8.976
588.139
2,839
2,130
6
.190
.02835
10.453
505.084
2,476
1,860
7
.175
.02405
12.322
428.472
2,136
1,600
8
.160
.02011
14.736
358.3008
1,813
1,360
9
.145
.01651
17.950
294.1488
1,507
1,130
10
.130
.01327
22.333
236.4384
1,233
925
11
.1175
.01084
27.340
193.1424
1,010
758
12
.105
.00866
34.219
154.2816
810
607
13
.0925
.00672
44.092
119.7504
631
473
14
.080
.00503
58.916
89.6016
474
356
15
.070
.00385
76.984
68.5872
372
280
16
.061
.00292
101.488
52.0080
292
220
17
.0525
.00216
137.174
38.4912
222
165
18
.045
.00159
186.335
28.3378
169
127
19
.040
.0012566
235.084
22.3872
137
103
20
.035
.0009621
308.079
17.1389
107
80
.031
.028
.0007547
.0006157
392.772
481.234
13.4429
10.9718
22
0 "* 3D CO 6
23
.025
.0004909
603.863
8.7437
$?§§ | $' Oj -
24
.0225
.0003976
745.710
7.0805
fslllof*
25
.020
.0003142
943.396
5.5968
26
.018
.0002545
1,164.689
4.5334
27
.017
.0002270
1,305.670
4.0439
III! f-J =11
28
.016
.0002011
1,476.869
3.5819
29
.015
.0001767
1,676.989
3.1485
*JI^lo'S'dIB'"' fl
30
.014
.0001539
1,925.321
2.7424
§il^3fc|i I
31
.013
.0001327
2,232.653
2.3649
32
.012
.0001131
2,620.607
2.0148
ga><*H^-~~ga>_<u g
33
.011
.0000950
3,119.092
1.6928
34
.010
.00007854
3,773.584
1.3992
35
.0095
.00007088
4,182.508
1.2624
cs»gs^.2aq*^ J
36
.009
.00006362
4.657.728
1.1336
37
.0085
.00005675
5.222.035
1.0111
38
.008
.00005027
5.896.147
.89549
39
.0075
.00004418
6,724.291
.78672
40
.007
.00003848
7,698.253
.68587
Hf|g°c
eSoas |
IRON WIRES. 1T)7
WEIGHTS OF IROW Aj¥» iTEEL WIRE.
Weight per 1000'.
No.
Diameter in
Mils.
B. &S.
Wrought Iron.
Steel.
0000
4G0
561
566
000
409. 64
445
449
00
36-1.8
353
356
0
324.86
280
282
1
289.3
222
224
2
257.63
176
178
3
229.42
139
141
4
201.31
111
112
5
181.94
87.7
88.5
6
162.02
69.6
70.2
7
144.28
55.2
55.7
8
128.49
43.8
44.1
9
114.43
34.7
35
10
101.S9
27.5
27.8
11
90.74
21.8
22
12
80.81
17.3
17.5
GAllAHflZED SICJ]¥AIi $rF32 A* fl». 8EVEK WI1IJES.
Diameter,
Weight per 1000'.
Estimated
Breaking
Inches.
Bare Strand.
Double Braid
W. P.
Triple Braid
W. P.
Weight.
1-2
520
616
677
8,320
15-32
420
510
561
6,720
7-16
360
444
488
5,720
3-8
290
362
398
4,640
5-16
210
270
297
3,360
9-32
160
214
235
2,560
17-64
120
171
188
1,920
1-4
100
148
163
1,600
7-32
80
122
134
1,280
3-16
60
96
105
960
11-64
43
76
84
688
9-64
33
60
66
528
1-8
24
48
53
384
3-32
20
38
42
320
iTRAIDEB W1RK CARIES.
(Everett.)
Ratio of area of copper to area of circular or available space
copper area
available area.
158
PROPERTIES OF CONDUCTORS.
If n= number of concentric layers around one central strand,
The number of wires that will strand will be 3n (n -+- 1) + 1.
Number of Strands.
available area
1.000
.778
.760
.755
.753
.752
toll «' it tiling: Core. — The number, iV, of sheathing wires having a di-
ameter, d, which will cover a core having a diameter, I), is
DATA OUT CABLES.
Below is given a table showing the actual circular mils, the diameter bare
inches, and the number and size of strands (wires) generally used in the
manufacture of cables.
(General Electric Company.)
Make up.
Approx.
Actual
Circular
Diam.
Bare
Weight of
Size of Cable.
Copper
Mils.
Inches.
No.
Wires.
Size wire.
per
1000 feet.
8B.&S.
18,000
.147
7
16 B. &S.
57
6B.&S.
28,600
.180
1
6
15 B. &S.
16 B. W. G.
85
5B. &S.
35,300
.209
1
6
16 B. W. G.
15 B. W. G.
112
4B.&S.
44,300
.234
1
6
15 B. W. G.
12 B. W. G.
140
3B.&S.
55,900
.263
1
6
12 B. & S.
11 B. &S.
178
2B. &S.
70,600
.295
1
6
11 B. &S.
10 B. &S.
224
1 B. &S.
80,275
.335
19
16 B. W. G.
255
OB.&S.
106,500
.378
1
6
12
15 B. W. G.
12 B. & S.
15 B. W. G.
338
00B.&S.
134,200
.425
1
12
12 B. & S.
11 B. &S.
12 B. &S.
426
000 B. & S.
167,500
.475
14
11 B. &S.
13 B. W.G.
532
0000 B. & S.
216,900
.524
1
6
13
10 B. & S.
12 B. W. G.
10 B. &S.
650
CABLES. 159
BATA OH" CABLES — Continued.
Make up.
Approx.
Actual
Circular
Diam.
Bare.
Weight of
Size of Cable.
Copper
Mils.
Inches.
No.
Wires.
Size "Wire.
per
1000 feet.
250,000 C. M.
250,200
.568
7
13
.117 inch.
12 B. W. G.
790
300,000 C. M.
304,600
.637
37
11 B. & S.
949
350,000 C. M.
350,400
.680
12
25
10B.&S.
13 B. W. G.
1,092
400,000 C. M.
402,600
.735
7
12
18
10 B. &S.
12 B. W. G.
10 B. &S.
1,224
500,000 C. M.
506,400
.820
37
.117 inch.
1,550
600,000 CM.
601,500
.900
37
24
10 B. &S.
13 B. W. G.
1,874
750,000 CM.
75*1 ,800
1.020
15
46
.117 inch.
12 B. W. G.
2,331
800,000 C M.
800,600
1.037
42
19
.117 inch.
12 B. W. G.
2,462
900,000 C M.
903,700
1.096
12
49
8B.&S.
11 B. W. G.
2,815
1,000,000 CM.
1,007,000
1.157
61
8B.&S.
3,13S
1,250,000 CM.
1,250,600
1.296
7
84
11 B. W. G.
.117 inch.
3,831
1,500,000 C M.
1,512,300
1.412
91
8 B. & S.
4,681
2,000,000 0. M.
2,001,700
1.652
82
45
SB. & S.
11 B. W. G.
6,237
MIT STAl'BAMB WIMES.
In the following table are given sizes and prices of Navy Standard Wire
is per specifications issued by the Navy Department in March, 1897.
M
$•§
2
Diameter
Diameter in
32ds
u
45
0) 03
d
M
o^
Incl
ies.
of an incli
x a"S
2
<
0«2
£.3
Over
copper.
Over
Para
rubber.
Over
vulc.
rubber.
Over
tape.
Over
braid.
3*3
>
3^
4,107
l
14
.06408
.0953
7
9
11
56.9
$60.00
9,016
7
19
.10767
.1389
10
12
14
103
110.00
11,368
7
18
.12090
.1522
10
12
14
10S.5
110.00
14,336
7
17
.13578
.1670
10
12
14
115.5
110.00
18,081
7
16
.15225
.1837
11
13
15
140
130.00
22.799
7
15
.17121
.2025
12
14
16
165|
150.00
30,856
19
18
.20150
.2328
12
14
16
184
165.00
33,912
19
17
.22630
.2576
13
15
17
218
190.00
49,077
19
16
.25410
.2854
14
16
18
260|
210.00
60,0S8
37
18
.28210
.3134
15
17
19
314
260.00
75,776
37
17
.31682
.3481
16
18
20
371
290.00
99,064
61
18
.36270
.3940
18
20
22
463
385.00
124,928
61
17
.40734
.4386
19
21
23
557
415.00
157,563
61
16
.45738
.4S85
20
22
24
647
460.00
198,677
61
15
.51363
.5449
22
24
26
794
535.00
250,527
61
14
.57672
.6080
24
26
28
970
615.00
296,387
91
15
.62777
.6590
26
28
30
1,138
750.00
373,737
91
14
.70488
.7361
29
31
33
1,420
900.00
413,639
127
15
.74191
.7732
30
32
34
1,553
1,000.00
160
PROPERTIES OF CONDUCTORS.
IPECIAI CAHLEft FOR §TR£ET-€AR WIRIHT6.
Car wiring cables have a wrapping between the wire and rubber to facili-
tate stripping for soldering. The 7-14 single braid is adapted for ordinary
car wiring for two 25 h.p. motors. The triple braid is recommended for taps
to motors, as it will stand abrasion and is more durable than rubber tubing.
The 75-25 braided to .500" diameter is standard for field leads of the GE-800
motor, and fits the -rubber bushings in the motor frame. The 49-22 braided
to .025" diameter is standard for armature leads of the GE-800, and for all
leads of the GE-1000 motors. These cables are also well adapted for leads
for suspending arc lamps.
(General Electric Company.)
I
a P
u
p'3
%u
List price.
=3^
1"?
a> <d
'■B^
£&
'P u
6 on
.Sffl
gM
g &
■H J-c
Single
Triple
braid.
ft .3
££
Q
§H
He
braid.
*7
14
6
.192
.385
.500
.062
$73.50
.$89.00
49
23
6
.200
.393
.500
.062
116.50
131.50
*75
25
6
.216
.410
.500
.062
120.00
135.00
*7
12
4
.243
.433
.553
.062
108.50
127.50
*49
22
4
.228
.418
.625
.062
139.50
160.00
* Carried in stock.
ITAADIRD lll'BBER COVE1IED WHITE CORE
WIRES AJ*» CABLE!.
(Made by General Electric Company.)
Rubber covered wires and cables are insulated with two or more coats of
rubber, the inner coat in all cases being free from sulphur or other sub-
stance liable to corrode the copper, the best grade of line Para being em-
ployed. All conductors are heavily and evenly tinned.
Five distinct finishes can be furnished as follows: — White or black braid,
plain lead jacket, le?^d jacket protected by a double wrap of asphalted jute,
lead jacket armored with a special steel tape, white armored, for submarine
use.
For use in conduits the plain lead covering is recommended, or if corro-
sion is especially to be feared, the lead and asphalt. For use where no con-
duit, is available, the band steel armored cable is best, as it combines
moderate flexibility with great mechanical strength, enabling it to resist
treatment which would destroy an unarmored cable.
In addition to the ordinary galvanometer tests, wires and cables are
tested with an alternating current (as specified in table) before shipping.
Are also prepared to quote promptly on wire armored cables for subaqueous
circuits, but as the conditions and requirements of the weight of armor
vary greatly, do not list them. Inquiries for quotations on these cables
should state the length and size of cable, depth of water, character of bot-
tom and current, in order that a proper weight of armor may be selected.
The tables following give list prices, dimensions, insulation resistance per
mile, test pressure, and break-down pressure on all sizes of wires and cables
in ordinary use. For underground and submarine work it is recommended
that cables be not worked at more than one-half the pressure with which
they are tested. If wires or cables are run on insulators in dry places they
may be safely worked at test pressure.
Cables will be leaded according to the table given below, unless otherwise
specified. Cables with any thickness of lead required can be supplied.
Cables up to \" diameter over insulation, lead gy thick.
" over \" to %" diameter over insulation, lead A" thick.
« r to \\» " » " " 53/' "
« 1\\ to If' " " " xV' «
" " larger than 1|" '-s " " s
161
« i
n *
M 3
« g
B
©
: s
: H
H-
•papre-ig;
•SUIHO§9J\[
■©HH
jad aoire;sis
-a^I uot^upisiii
•S9t[oni
•psprBjg;
j8^utbt.<i
•surqosax\[
■»UIA[
jed ooire^sis
-8>j uopBinsuj
•eaqouj
•pgpreig;
la^ureid
•suiq;o§8j\[
■QIIH
•paprejg;
ja^ureiQ
•surqo§8j\[
■»nw
jod aoura^sis
•saqoui
•pspreag
•surqo§8j\[
■onre
J9d ooire^sis
-a^j noi^'Binsiri
•seqonj
•poprejg
•sumoSaj\[
jod eorre^sis
-9^ nop'Bxug'ni
oooot-cot~oc5'#co'#o
ooooooooooooo
ooooooooooooo
<NC^© o oo^c^ir^o o co co co co_
i-rictLti-irj x o co o o <m
"*. "^ "^ ^ "*. ioioiq«(Ooet-
8888888888888
OD CO OC CO -*-*■■# Ol^iN <N <N <N rj_
1 - O L- — — CO o oi -t< O Ci oi o
ooooooooooooo
ooooooooooooo
(OOC)QOO(SCOHlOiO(B«
C5 O] CO CO CO CO Th -# •# "# 1C iq iq
ooooooooooooo
S S S °1 n 3§§§q^ 8 {?
<Jiiflffl(Ot«Mt-(OC5Mn^O
O'-ifl"tOrt-tO00H'*NH
o; oi oi oi o] co co co co -* -* tj; io
ooooooooooooo
0:00:0 lO, i-0 o o o o o
© o_o_oo^t-- n i> w 10 uo 10 10
oioooinoei
O X OS l-j co eg
000000 -11014
JOJ lA-B9q 00 j;
OO^NOOOOlO^MNrtO
162
PROPERTIES OF CONDUCTORS.
222S2S2Soooooooooooooooooo<=>=>
- = - ~ ^ - ~ - - ~ ~ _ —
« = = ^« ' v <~o_ lo co :o c-. co co co co ~i ol oi ?i el 5 o o o o i- S o
NNNrlrtHHHH t-T t-Tm r-Tr-TT-TTH iH l-Tr-Tr-Tr* t-T r-Tr-Tr-T
^^icirfjo»d«o t~ l- gc o o io c m !- ol CO '4 ^ 2? g £2 CO o
SSiSSissnn
liiiia§3883888888gSg88S8888§
CO -
fie
3 —
0 CO
in
-+
o
-f 10 ICO
572
625
672
722
771
875
945
988
048
133
§:::::::
HH
1-1
000000000000000000000 nolens
o o c o c o o o o io ico ci-i-.ooooooo nl sa rAT
ci ci ci ci c : c c c t- t- n i- l- L-o lo uo ooioo L1 .l // e •1<J±
Aavqvl oox
i0
c5
01
3 c?
||S
M
CN
TjH -f LO W O CD b- *
000000000000000 • • • uop'BXiis
OOOOi-.i:l-COCOOOOO . . . _TTT Sfl tat
• jLveaq oox
ooooo •noi^ins
S2gg§8 -Wfz/^JOJ
jfA-Beq oox
oinoooouTfcociHoooooooaooooooooo
rHr-iT-iTH OC c 2 © O ©
OOOOOOOOOOOOOOO
°o"o'oo"d ©' o ©' ©~ o~ ©" o" q"
IO O iO
CNCOC0^ScOl>00Ci O^Nia ©
HHrt"N
163
s
■M 000' I
jad eoud ^sn
•WOOO'l J8<i
^qgto^ -xoaddy
•'U 000' t
aod ooud ^siq"
'W 000' I -rad
-mSie^. -xoaddy
•W OOO'I
aod 9oi.id ^sxq;
"W OOO'I i9d
^qSpjW. - xoaddy
"W 000'T
jed eoiad ^srj
"W 000' X J9<I
^qSpAV 'xoaddy
II
'o
>
•u OOO'I
jad aoiad ^srq;
'« 000' I -T9<J
iqSpAY •xoaddy
*W 000'T
aod aotad ^stq;
•»j OOO'I J8d
iqSPiW. -xoaddy
ooooooooooooo
qioioiqqoqooowoq
<M 00
©OSi-HOOSi-HOOGOCDOIOOiriGO
•^-^aL-OSCOl.'-O-fwSTtii-' OS
©oooinooooooiqio
x id oi co is id co o id id id c>5 qj
rOHOMocoqjj^t-riO
CS COOl
t^t^t^tOirOi-icOicOcoaO'*'*
Sr-l?Hr-ll-n-l<N<NeOeCCO-*lQ
ooooooooooooo
oooiooooooiqoio©
ooLodoiwdinoodojjo
ol^cooooS3Sooocooo
aq«Moq
cico't^o'ooooootOT-iojcot-io
r-lr-li-lr-ICNtNCOCQ^-#
oqqioqiqqqqqqujio
co oo id oi co i> © id ci o^ t^ t^ s^i
Tt<-#0©t-COi-liN-*OCO.-llO
OS ffllON
HHHNINMK
oaociiot^T-
o-* eo«ot-«o
t^co"oc4co-*mi-ic-5i-icot-o
NW-*K3OON<0fflMI>C0H
HrlriCJCNCO'*
oooooo-
qioiqqqq
h h c) « co io
CO CM i-H OS 00 ^#
os so ci t-J t-" <m"
rH CI CO Tf< 1Q CO
o5
ri
co«OTt<cNOco«oiO'*eocNi-i©
164
PROPERTIES OF CONDUCTORS.
qoiqiqqoioiqiqqiqqqoiqqqquuqqcicqqooo
d 6 co ^ 6 6 c h m d i> o m id t^ lq irj o t^ l- >q 'i e 6 in d d 6
-©IHIOC*
©rtC0ON^00H«0?)iHOt0l00DI>C0OT)iO(N
»<*010»0f - - - O <M rJH 00 t- CO © <N ©
co^inio^Qoaocm'ot-THioortiooiowco
mcocococo-^ioo
©iq©©iniqiq©o©©©io©o©5in©©©o©©©©©©
ioc4©TH«ocoo6o©udc>idc5oco©©©©idid©©©c5©©c5
HNMiot'C ■! ::.::".-....:..::"-::■.:
■QCO'#-TlW©©l.'~00CS
CO OS 05 Ifl ©s
9g?2l5P!202S$2S,^SS^ciS?,-|ocoi-i«5coiM-*©©r>oom
i-li-lr-lT-l<MC3<MCOCOTrlTi<©l-CO©T-HC0lO©©-*©©Tt<00lC#'-t
g388338§g888g33888g§38388883
HrlHHHNClCIClMK-i " rt -f "f C N rH lO (N
lO <N rlj 00 OS JO
SS^2S2PS2^S3^nlc~1<:ac="-ococicicoooijn©cocoaot--^t:
HHrtiHOtNMcoco^iocot-bc-'- : r. :: -c -+ co r
si Cl CO CO tH in «
©©©©©©©©©©©©©©©©©©©©©
iq©©©in©©©©LOLO©©©©©©iq©©©
icc^oicocoidcocdidcO'H©"""'
lO©t-00©CN--H© -'
o © m ■* co © t-
si co co rt< io © t>
JS CO © © <N CO
^©©l_O©©©©C-5t-©-*-*OllCeirH0OUt)©CO
- - - - ' _ .- : ' - _
ggSg8S388888888
c4t>«Ot^THiH00idl>00©ci»d©©
coco-*int-©©OT*ic-©-i--
HHtHiHNIMIMCO'*
SNiOHHte
r)5 oi oo id © as c-i in
-;'.■.- i ".: • i ■■ ~ • ' .:■■.■■:■■• \
HHrtNC-lCOM'tlOa
© © © in ©
CN COCOf ©
cicS^
©^^©oo©io^co^TH©©©©©©©©ogg©o©©o©
© © © © © c: © ©. — .. ©©_©_©© <=
"'ooooooooooqoo
10©10©0©10©©©10©©
c^coco^io©t-co©©i>) in ©_
SPECIAL FINISHES.
165
Below is a table of prices at wliicli special finishes for any of the fore-
going wires and cables can be furnished.
C. L. Plain lead cover over the rubber.
C. L. A. Lead cover with jute and asphalt over the lead.
C. L. A. I. Lead cover, jute and asphalt and band iron armored.
To obtain the price of the cable desired, add to the list price of the rubber
covered cable braided, the list price of the finish desired for the diameter
nearest to that of the braided cable.
A cable having a lead cover, jute and asphalt over the lead, and wire
armored (C. L. A. W.), in addition to the above special finishes can also be
furnished. Prices on application.
To obtain approximate weight of cable having special finish, add to the
weight of the cable the weight of the special finish as given below.
SPECIAL FO'ISHES,
(General Electric Company.)
Diameter
C
Approx.
Weight
per
1000 feet.
. L.
List price
per
1000 feet.
C.
L. A.
C. L
. A. I.
of
Braided
Cable.
Inches.
Approx.
Weight
per
1000 feet.
List price
per
1000 feet.
Approx.
Weight
per
1000 feet.
List price
per
1000 feet.
.200
157
$30.00
252
$60.00
, . .
.225
170
31.50
268
62.50
. .250
191
34.00
297
66.50
.275
214
37.00
327
70.50
.300
227
38.50
345
73.00
.325
345
53.00
475
89.50
.350
376
57.00
514
94.50
1,131
$193.50
.375
391
59.00
534
97.00
1,162
197.50
.400
424
63.00
574
102.00
1,229
206.50
.425
438
65.00
590
105.50
1,254
212.00
.450
473
69.00
634
111.50
1,325
222.00
.475
498
72.50
665
115.00
1,370
227.50
.500
519
75.00
691
117,00
1,417
230.00
.550
567
79.00
751
125.00
1,506
241.50
.600
620
85.50
816
133.00
1,616
255.50
.650
656
90.00
864
139.00
1,901
294.00
.700
1,118
144.50
1,352
199.00
2,498
369.00
.750
1,194
153.00
1,442
209.50
2,632
384.50
.800
1,194
153.00
1,442
209.50
2,632
384.50
166 PROPERTIES OF CONDUCTORS.
SJPECIAE FlUfliHES- Cow^wwerf.
Diameter
C
. L.
c.
L. A.
C. L
. A. I.
of
Braided
Cable.
Inches.
Approx.
Weight
per
1000 feet.
List price
per
1000 feet.
Approx.
Weight
per
1000 feet.
List price
per
1000 feet.
Approx.
Weight
per
1000 feet.
List price
per
1000 feet.
.850
1,258
160.50
1,516
218.00
2,742
398.50
.900
1,317
167.00
1,583
226.50
2,847
411.50
.950
1,423
179.50
1,707
241.50
3,022
433.50
1.000
1,482
186.50
1,773
249.00
3,132
447.00
1.05
1,556
190.00
1,859
257.50
3,263
461.00
1.1
1,631
201.00
1,946
267.50
3,397
477.00
1.15
1,705
210.00
2,030
277.50
3,820
533.50
1.2
1,795
220.00
2,131
291.50
3,987
559.00
1.25
1,854
225.50
2,201
298.50
4,098
572.50
1.3
1,959
237.50
2,322
313.00
4,294
595.50
1.35
2,018
240.00
2,393
317.50
4,409
607.00
1.4
2,851
330.00
3,257
415.00
5,419
724.00
1.45
2,989
348.00
3,410
432.50
5,639
750.50
1.5
3,008
350.00
3,432
434.50
5,681
755.00
1.6
3,362
378.00
3,717
470.00
6,097
810.00
1.7
3,400
392.50
3,872
488.00
6,335
827.50
1.8
3,615
416.50
4,113
515.50
6,694
882.00
1.9
3,792
436.00
4,309
538.00
6,987
905.50
2
3,988
457.50
4,529
563.00
7,315
945.00
In leading cables a tape is used over the rubber in place of the regular
braid.
For thickness of lead used on above finishes, see page h21. If other thick-
nesses than these are desired, special prices will be quoted upon application.
PAPER OilLATED AAI» LEADED WJTtES AND
CABLEI.
There will be found on the following pages data and prices of a full line
of paper insulated and lead covered wires and cables. All cables insulated
with the fibrous covering depend for their successful operation and mainte-
nance upon tbe exclusion of moisture by the lead sheath; and this fact
should constantly be borne in mind in handling this class of cables, conse-
quently the lead on these cables is ext^a heavy. The use of jute and asphalt
covering over the lead is strongly recommended on all this class of cables,
inasmuch as the life of the cable is absolutely dependent upon that of the
lead. Paper insulated cables cannot be furnished without the lead covering.
WIRES AND CABLES.
ijfBqds y pire
e^ap .19 ao
•saqoui
•pi39T[ J9A0
.I919UTeiQ
"S8t[0UJ
*P138T[
ss9U5[0iqx
■smqoSai\[
90U'B^SIS9JI
uoi^upisui
tH tJH eo t- cm li ' - ~ :-.'..• - <~. - — - ~ i - — '-•" '2- Z- :~ t '-■
ao)00o>oOr-i-HHrt:iM-ti-tL;c3 vr i-c;q?i co iq
' t-I r-5 " ' ri ri H H rH rH rt rt H rt ri H TH tH ri iM' IN N N
C -i< - -1 I-
OOOrtHrtf
^«H5^«H£»h«He
oooooooooooooooooooooooog
o o g o o — . ■ . '','-? — '■ ~
Ht-niOH(Ortin*3'-sooa«iNHrjiffi't'*HO'Offl
iOi>t-HS- : r. ~. M t- go cn
ooooaooocoooOHHH?iM::t li o^ccoooi-iNiq
" ^ ' ' 'rtHrHriHHHrHHr-iH^rHHoiNji«
CHOHMO-fClM«^TPNt-NOOafU-?l?IC5CC-tff
K S 'O O T< M I- :1 'J ~ 1 1 I- X CI X M -iT.XTjrillt-H
Li Li O t- LI Li -O L~ I- 1- GO X Ci O O ^h T-i "M II CI Li t" CO OS N
•S9tpni
^"tfqdsy puu
9;np J9A0
■i9;9ttreig
"S9r[0UI
PB9T J9AQ
.I9^9ttret(J
•sgqoui
■p^l
ss9tnpii|x
•saiqo§9i\[
^^«K^H2"£o£«S^~^:3
oooooooooooooooooogoooooo
oooiooc' jiooooooioog
LI Li 11 11 LI LI ". l i OiJ^IJIClClMHHO^lOU
•sgqoui
9^nf J9AQ
.T9}9UrBI(I
l"CJM.H'3"tl>Nt-fflOClNSflflO«0^>*
i mxht t- ii ci x ct go -h — . -h :c ci -oo^to
O Cf.CCOH 11 11 CI CI -H -H Li cscihnt?
•S9qOUJ
•p^l J9A0
J9^9Xni?T(I
OflHt-Onir
•S9qouj
•pi39rj
SS9U2[0pqX
£««^5««B«-*
•smqo§9j\[
•9HM -^J
90U'BJSIS9'JJ
CM
be®
Is
=3.
ooo<x
V ooo«
s
' O T '
<lrH0000000 0 030000
s888888888888
° o © o ooo'o o go
iooi:: '.
o co n •* Li n c
168
PROPERTIES OF CONDUCTORS.
%^K OOOI --9 J
80u<i s>sri
•188^ 0001
9syeunxo.iddy
oooooc ~ >- c lo = 5ciSoqqcqq8oq82
22S°3:s>St5;
~Sol
« S -3 P Lo - f^ -¥ - ? 3 £ r :" -■ '--■ •* ^ omwioncb
oo t> co -* x os co .q so l~_ x 3 £-__ os ol -* x 5 co. x £ co co lo co
rtrt t-i n rl i-l llcTof ci CO Co'cO •* ■* rti~«Tt-^(X cTr-T
i s^O^ 0001 -9<I
"S88SS8 g§SSSS S§§8lSSSS88SS
*inio»t-xx © q? e- ~ ■=? —
ililT-TofcfcO
■»->9.i oooi
jod ^qSiaAV
8syeunxo.iddy
-h so co CO X L- i-i ~ Ct-l-OONO-f coos r'
O t- rtWO L- i-^CO -# iO (O I - -T CC O^ — I •+ L- — LO L-
<5M«MT)<lO(OI>aiH
^9£ 0001 J9<I
---------
ooooooomo
cj --h os cs co co
88.8S
5 5 O C fe 13 O lO c c
o. q , j -^ x o :: — -
MNcocomeoioiQOCON
HHHNlNn
•5»9 J ooox
jod ^xxSte^
8~,eiuixo.iddy
» io a ■# w h uo « -t o co i- e Lt <m c ^ w -f -t ;i h a o o
CO CS CS CO LO CO -h O O i-l — X >o — CO l- C -f 01 10 CO n CO X -*
t- t- hcon x c-j -t; ioc'cz '-I1-. — ~l—,r-/irt ^ci.T^'~l0i,'l
r-Ti-T r-^-H rH i-Tilil of efcO CO CO CO •# -#~LO (> CO Gfi-T
199jI 000T -9J
9DU«I "SII
~ t£~~ -------- - ~ ~ ~ ~ ~ ~ - — — © c © o
qqqqqqqqqqqqqiaqqqiqqqqqqS >q
© .1 CO i-i ri -,-' x — - co' so — ' ::' o ! x' i - co' oi x OS oi -h CO i-i o-i co"
- ". CO CS -f t- l>
CN CO CO i-i CO -+ os co 10 I - co -+ -V o. It 01 ~
HHHNHHi-HNflCKCCOt-tiO-l-
rl rt N N CO
•?90£ ooox
jsd ?q;§i8AV
e~«raixo.iddy
qncjOOONonaHrtMcnoo-foON-coffl
0 OS LO 1-0 O OS OS t- tt»H-t I- CO O! X OS 0 I SO so X X
1 LO CD © Ol & CO ># KC] 1.0 L- (OS CM L0 1> CT. lOtDOl-CC
-T r-Tii i-Tr-TiTii oi olci ei' co co co ■* lo co i^coo
W*£ oooi -^a
8^88
o o o o c o i" ~ -o "c — ~ c c ~ ;ooooo
lo o o lo q o o —_ o c lo_ © ic uq uq qoioqaq
" O (s^ oi i-O iO o i i - t- i.o v: lo \~ io '-:' t! -'■ --
— i c i - 2 ' — )<Cco-*
i-H-KMCVIi-l^iCOO^OJCOCOCO^ir
'198 J 0001
aed m§PA\.
oi)i3 imxcuddy
irtHriNNNMeOMK
?S^
?99jI 0001 .X9J
80l.I<I s)St^
b^ttSu co f2 £- c'
88888S8888888S8g8S888~
- - HciN-tox-t-fx-iLo'rtOLod
X 01 1-- t- CO OS X -ti CO CO CO CO -i CO -f
<m co •# ** io no co t- x cs co i-o. c :-, =
iHT-Tofofco
•?99J 0001
,iod s^nSiOAV
ejumixo.iddy
•5 CO Ol OS CD LO -f t^ O -H O CO CO X CS t^ CO LO OS OS il -i
i co i~ oi i- — so -t oi o i ~r i-O C ' h - - " -t - -t :
5WLOQOHC1 CO LO il CO 1-0 X H CO CD tH CO -* -+ UO C£
S)CNKMCOCOCO-*lOCDt>
O
58888888888
ooooooooooo
"" 9 S 9 2 2" o" o" o" o" o"
cci-.coi- — io — r;
CM CO CO ■* LO t- O OI LO o
telephone cables.
169
TELEPHONE CABLEi.
(By John A. Roebling's Son's Co.)
Lead-encased for "Undei'g'rouiid or Aerial Use.
The insulation of these cables is dry paper. The company manufac-
tures several styles of 19 B. & S. G., 20 B. & S., G., and 22 B. & S. G., ac-
cording to the use for which they are intended. The most common size
is 19 B. & S. G. They also supply terminals and hangers.
Specifications for Telennone Cafoles.
l. Conductors.
Each conductor shall be .03589 inches in diameter (19 B. & S. G.), and
have a conductivity of 98 per cent, of that of pure soft copper.
2. Coke.
The conductor shall be insulated, twisted in pairs the length of the twist
not to exceed three inches, and formed into a core arranged in reverse
layers.
3. Sheath.
The core shall be enclosed in a pipe composed of lead and tin, the amount
of the tin shall be not less than 2^ per cent. The pipe shall be formed
around the core, and shall be free from holes or other defects, and of uni-
form thickness and composition.
4. Electrostatic Capacity.
The average electrostatic capacity shall not exceed .080 of a microfarad
per mile, each wire being measured against all the rest, and a sheath
grounded ; the electrostatic capacity of any wires so measured shall not
exceed .085 of a microfarad per mile.
5. Insulation Resistance.
Each Avire shall show an insulation of not less than 500 megohms per
mile, at 60° F., when laid, spliced, and connected to terminal ready for use ;
each wire being measured against all the rest and sheath grounded.
6. Conductor Resistance.
Each conductor shall have a resistance of not more than 47 B. A. ohms,
at 60° F., for each mile of cable, after the cable is laid, and connected to the
terminals.
IEIEPHOXE CABLES,
By John A. Roebling's Son's Co.
Number pairs.
Outside diameters.
Inches.
Weights 1000 feet.
Pounds.
1
&
214
2
I
302
3
515
4
629
5
S
747
6
U
877
7
B
912
10
U
1,214
12
if
1,375
15
l
l,5o6
170 PROPERTIES OF CONDUCTORS.
TELEPHONE CABIES-OMrfiiiiKd.
Number Pairs.
Outside Diameters.
Inches.
Weights 1000 feet.
Pounds.
18
It1*
1,758
20
H
1,940
25
h%
2,332
30
h7E
2,748
35
H
2,985
40
h\
3,176
45
if
3,365
50
if
3,678
55
ill
3,867
60
if
4,055
65
lit
4,241
70
2
4,430
80
2»
4,804
90
2i
5,180
100
2§
5,505
TELEGRAPH CABLEi.
By John A. Roebling's Son's Co.
Eead-enca«ed for Underground "Use.
These cables are made of either rubber, cotton, or paper insulation. The
sizes and weights are approximately correct for rubber and cotton insula-
tion. Both sizes and weights are slightly reduced for paper insulation. In
all cases the cables are lead-encased.
Specifications for Teleg-rapn Cables.
1. Conductors.
Each conductor shall be .064 inches in diameter (14 B. & S. G.), and have
a conductivity of 98 per cent of that of pure copper.
2. Coke.
The conductors shall be insulated to 3% with cotton, and formed into a
core arranged in reverse layers. This core shall be dried, and saturated
with approved insulating compound.
3. Sheath.
' The core shall be enclosed in a pipe composed of lead and tin. The
amount of tin shall not be less than 2.9 per cent. The pipe shall be formed
around the core, and shall be free from holes or other defects, and of uni-
form thickness and composition.
4. Insulation Besistance.
The wire shall show an insulation of not less than 300 megohms per mile,
at 60° P., when laid, spliced, and connected to terminals ready for use, each
wire being measured against all the rest and the sbeath grounded.
5. Conductor Resistance.
Each conductor shall have a resistance of not more than 28 International
ohms, at 60° F., for each mile of cable, after the cable is laid, and connected
up to the terminals.
TKLKGRAPH CABLES.
171
TELEGRAPH CABLES.
By John A. Roebling's Son's Co.
14 B. & S. G.
Insulated to 362.
16 B. &S.C.
Insulated to g52.
18 B. & S. G.
Insulated to &.
S
is
SB
<D ® •
43 CD
btfn
^2
!2 ® ©
4?££
f
ft
I
ft
1
299
421
546
670
793
Outside
diameters,
Inches.
S ©
'©§
1
2
3
4
5
i
ft
4
1
1
308
438
573
810
972
1
Iff
ift
i
291
3o6
421
4»6
551
6
7
10
12
15
if
if
It's
1ft
1,132
1,295
1,512
1,873
2,263
il
Is
if
X
il
946
965
1,155
1,327
1,518
%
IB
8
1
il
616
681
820
978
1,148
18
20
25
30
35
li
1ft
1ft
1ft
Hi
2,523
2,756
3,250
3,515
3,910
1ft
1*
1ft
If
1ft
1,880
2,076
2,496
2,768
3,040
I
il
l
ift
ift
1,318
1,477
1,690
1,903
2,116
40
45
50
55
60
if
lit
2
2ft
4,175
4,441
4,835
5,100
5,365
1*
1ft
If
144
If
3,312
3,533
3,755
3,978
4,200
ift
ift
i|
ll76
2,330
2,471
2,628
2,8b6
3,104
65
70
80
90
100
2ft
ZI5
5,631
5,897
6,408
6,916
7,375
lit
li
2
2ft
2|
4,422
4,644
5,087
5,402
5,720
m
u
if
iii
if
3,245
3,402
3,798
4,027
4,275
AERIAL CABLES.
By John A. Roebling's Son's Co.
These cables a*e nvadeW Jonbh^^ated rubber wix
taped. After
These cables are made from double-coatea ™™™rekivtevver which
of mecSliS injury. The ordinary size for telegraphic work is 14 B. & S,
tasnSeato°4]i trace wire can he placed in each layer, if desired.
172
PROPERTIES OF CONDUCTORS.
Specifications for 14 B. & S. Aerial Cable.
1. CONDUCTORS.
Each conductor shall be .064 inches in diameter (14 B. &S. G.), and have
a conductivity of 98 per cent of that of pure copper.
The conductors shall be insulated to s62 with rubber and tape, and formed
into a core arranged in reverse layers.
3. Protective Covering.
The core shall be covered with two wraps of friction tape and one wrap of
tarred jute. Over this there shall be a braid saturated with weatherproof
compound.
4. Insulation Resistance.
Each wire shall show an insulation resistance of not less than 300 meg-
ohms per mile, at 60° F., after being immersed in water 24 hours. This test
shall be made on the core after all the conductors are laid up, but before
the outside coverings are put on.
5. Conductor Resistance.
Each conductor shall have a resistance of not more than 28 international
ohms, at 60° F., for each mile of cable.
AERIAL CABLES.
By John A. Roebling's Son's & Co.
Rubber Insulation.
14 B. & S. G.
16 B. &S. G.
18 B. & S. G.
Insulated to g62.
Insulated to gV
Insulated to 342.
OflH
© ® a5
s ^ S
bo5"
II
iS » ©
-2 S^
oil
2
1
102
i
92
i
82
3
h
149
T7S
126
"35
104
4
&
183
h
155
TB
127
5
li
226
1
193
2
151
6
1
260
ii
222
&
175
7
xl
297
1
251
200
10
\%
401
S
335
256
12
l
'65
H
393
1
296
15
Is
563
1
468
il
355
18
ll35
651
llV
541
I
413
AERIAL CABLES.
173
AERIAI CA.'B'Kj'ES— Confirmed.
14 B. & S. G.
16 B.
& S. G.
18 B. &S. G.
o
Insulated to g62.
Insulated to 352.
Insulated to s42 .
s|
01 S .
■2©
®JL
a) S .
S O
P o
!2 » «
I-SS
O-CiM
p S 2
'So
"2 ^ a>
d«« 2
&2
20
li
714
Ji
593
§1
' 452
25
If
863
1t3s
708
11
541
30
1&
1,008
H
824
l
633
35
H
1,147
ll55
938
iiV
723
40
1»
1,268
If
1,053
H
813
45
If
1,431
U
1,182
h%
903
50
If
1,577
IS
1,311
H
994
§UBMA»OE CABLES.
By John A. Roebling's Son's Co.
£
Armor
wires.
Total weights. Pounds.
uB
Outside
diameters.
& %
si
*8
Number
of wires.
Numbers,
B. W. G.
1,000 feet.
Mile.
i
12
8
1,250
6,600
2
15
8
1,722
9,092
3
U
14
6
2,363
12,477
4
1ft
16
6
2,794
14,752
5
1ft
16
6
4
2,968
15,671
6
1|
16
4
3 822
20,180
7
11
16
3
3,972
20,972
10
n
18
5,404
28,533
The core consists of 7 X 22 B. & S. tinned copper wires, insulated with
rubber to 385 of an inch, laid up with proper jute bedding.
Telegraph cables can be supplied with gutta-percha insulation. This is
the best insulation for submarine work, and its reliability and durability
more than make up the difference in co6t between it and any other insula-
tion.
174 PROPERTIES OF CONDUCTORS.
AirMIIfUM.
(From paper by Alfred E. Hunt, S. B., and book published by tbe Pitts-
burg Reduction Company.)
Specific gravity 2.68
Cubic foot weighs, cast 159.6 lbs.
Cubic foot weighs, rolled 167.1 "
Cubic inch weighs, cast .0924 "
Cubic inch weighs, rolled .0967 "
Tensile strength in pure soft wire, per square inch . . 26,000
Tensile strength in pure hard-drawn rods, per square inch, 40,000
Conductivity as related to 100% cond. copper:
99|%pure 63.09%
99% pure 62.17%
98% pure 56.17%
"Weight per mile of aluminum wire is .004817 (diameter in mils).
Aluminum for Electrical Conductors.
(From paper by Alfred E. Hunt, S. B.)
1. Any given volume of copper is^= or 3.332 times heavier than an
equal volume of aluminum. 2.68
2. The equivalent price of fourteen cents per pound for copper for any
length of any equivalent section of aluminum wire or bar would be 14 cents
times the factor 3.332, or 46.65 cents per pound. That is, one thousand feet
of wire of, say, one-tenth inch diameter, would cost equally as much if
bought of copper at 14 cents per pound or aluminum at 46.65 cents per
pound. Aluminum, therefore, at 29 cents per pound is only 62% of the cost
of copper at 14 cents per pound, section for section.
3. Reckoning the copper conductor to have its maximum of 100 per cent
conductivity, and the aluminum to have a conductivity of 63 per cent (which
the Pittsburg Reduction Company are ready to guarantee for their special
pure aluminum metal for electrical conductors), then for an equivalent
electrical conductivity a given section of copper that can be placed at 100
should be increased in area in round numbers to 160 to give an equal con-
ductivity.
4. Due to their relative specific gravities, the weight of the given equal
length of the aluminum conductor with 160 sectional area will be only forty-
eight per cent of the weight of the copper conductor with sectional area of
100, having the same electrical conductivity.
100 y 8.93 = 893, weight of the copper.
160 x 2.68 =428.8, weight of the aluminum.
|||-8 =48 per cent.
5. As to their relative cost for electrical conductors of equal conductiv-
ity, aluminum at twenty-nine cents per pound is the most economical con-
ductor, as compared with copper at fourteen cents per pound.
Taking as an illustration, an aluminum conductor to replace a copper
wire of No. 10 B. & S. gauge (about one-tenth of an inch diameter), the
aluminum wire of equal, in fact somewhat superior, electrical conductivity
would be of No. 8 B. & S. gauge ( slightly over one-eighth of an inch
diameter).
The weight of a mile of No. 10 copper wire is 162.32 pounds ; and its cost
at 14 cents per pound would be equal to $22.72.
The weight of a mile of No. 8 aluminum wire would be 79.46 pounds, and
at twenty-nine cents per pound would cost $23.04.
Forty-eight per cent of the weight of No. 10 copper wire, which will
give equal electrical conductivity in aluminum wire, would only weigh
77.91 pounds; so that, more accurately, $22.59 would be the cost of a mile
of aluminum wire at 29 cents per pound to replace a mile of No. 10 copper
wire at 14 cents per pound, costing $22.72.
6. The Continental requirements in tensile strength for soft copper
wire, rods, and bars used as electrical conductors is twenty-two kilograms
per square millimeter; the English requirement being similarly fourteen
tons per square inch; and our American requirement is about its equivalent
of 32,000 pounds per square inch.
ALUMINUM.
175
08
"53 ?$
« i
II
o,-<
1
176
PROPERTIES OF CONDUCTORS.
40,000
42,000
44,000
46,000
48,000
50 000
51,000
53,000
55,000
o
8fc
P.
.4605
.5818
.7325
.9235
1.187
1.468
1.852
2.335
3.084
Comparative
weight of given
lengths of
equal Conduc-
tivity, Copper
at 100.
t^
o
0
<
P3
3
S3 £
33,000
34,000
35,000
36,000
37,000
39,000
40,000
41,000
42,000
Comparative
section of equal
Conductivity,
Copper at 100.
ID
§
o
.4288
.5408
.6820
.8600
1.105
1.367
1.724
2.173
2.741
(A
a
o
o
CO
lO
d
ft
®5
27,000
27,000
28,000
29.000
30,000
32,000
33,000
35,000
39,000
6
d
in
3
Oft
.4012
.5058
.6380
.8044
1.034
1.278
1.613
2.033
2.565
is
s
204.31
181.94
162.02
144.28
128.49
114.43
101.89
90.74
80.81
.9
I?
3
. a
■*lflSDt>OOOiO'~l<N
ALUMINUM WIRE.
177
TABLE ©E RESISTANCES OF PURE AIUMIHTUM
WIRE.*
(Pittsburg Reduction Company.)
Pure aluminum weighs 167.111 pounds to the cubic foot. The conductivity
of pure aluminum is 60% of the conductivity of pure copper.
Resistance at 75% P.
Am. Gauge,
B. &S. No.
R
Ohms 1,000 ft.
Ohms per mile.
Feet per ohm.
Ohms per lb.
0000
.08177
.43172
12,229.8
.00042714
000
.10310
.54440
9,699.0
.00067022
00
.13001
.68645
7,692.0
.00108116
0
.16385
.86515
6,245.4
.0016739
1
.20672
1.09150
4,637.35
.0027272
2
.26077
1.37637
3,836.22
.0043441
3
.32872
1.7357
3,036.12
.0069057
4
.41448
2.1885
2.412.60
.0109773
5
.52268
2.7597
1,913.22
.017456
6
.65910
3.4S02
1,517.22
.027758
7
.83118
4.3885
1,203.12
.044138
8
1.06802
5.5355
964.18
.070179
9
1.32135
6.9767
756.78
.111561
10
1.66667
8.8000
600.00
.17467
11
2.1012
11.0947
475.908
.28211
12
2.6497
13.9900
377.412
.44856
13
3.3412
17.642
299.29S
.71478
14
4.3180
22.800
231.582
1.16225
15
5.1917
27.462
192.612
1.7600
16
6.6985
35.368
149.286
2.8667
17
8.4472
44.602
118.380
4.5588
18
10.6518
56.242
93.882
7.2490
19
13.8148
72.942
72.384
12.1916
20
16.938
89.430
59.0406
18.328
21
21.358
112.767
46.8222
29.142
22
26 920
142.138
37.1466
46.316
23
33.962
179.32
29.4522
73.686
24
42.825
226.12
23.3508
117.170
25
54.000
2S5.12
18.5184
186.28
26
68.113
359.65
14.6814
296.32
27
85.865
453.37
11.6460
485.56
28
108.277
571.70
9.2358
749.02
29
136.535
720.90
7.3242
1,190.97
30
172.17
908.98
5.8087
1,893.9
31
212.12
1,119.98
4.7144
2,941.5
32
273.97
1,445.45
3.6528
4,788.9
33
345.13
1,822.3
2.8974
7,610.7
34
435.38
2,298.8
2.2969
12,109.4
35
548.92
2,898.2
1 .8218
19,251.
36
692.07
3,654.2
1.4449
30,600.
37
872.93
4,609.2
1.1456
48,661.
38
1,100.62
5,811.2
.9086
76.658.
39
1,387.47
7,325.8
.7207
121,881.
40
1,749.50
9,236.8
.5716
193,835.
* Calculated on the basis of Dr. Matthiessen's standard, viz. : 1 mile of
pure copper wire of TV inch diameter equals 13.59 ohms at 15.5° C. or
59.9° F.
178
PROPERTIES OF CONDUCTORS.
Care iaa Erecting- Aluminum liines.
The fact that the wire will permanently 'elongate if seriously strained,
makes it necessary to use the utmost care in the erection of lines, and also
the known high coefficient of expansion with temperature changes taken in
conjunction with this property renders care in line stringing especially im-
portant and difficult.
The following tahle has been gotten out by the Pittsburg Reduction
Company, after exhaustive experiments.
Table of Deflections and Tensions for Aluminum Wire.
1= Deflection in inches at center of span.
S = Factor, which multiply by weight of foot of wire to obtain tension.
Maximum Load = 15,000 per square inch.
(Trans. A. I. E. E.)
t = —
20°
— 10°
0°
10°
20°
30°
Span.
S
X
s
X
s
X
S
X
10
S
X
11A
S
js:
80
12940
1
1660
51
1176
84
961
833
781
12|
100
12940
1*
2083
71
1470
l'0i
1202
V2h
1042
141
933
1G
120
12940
If
2500
8f
1768
121
1400
15|
1251
171
1120
191
150
12940
2f
3038
Hi
2540
Mi
1788
m
1552
21-3-
1390
24
175
12940
34
3643
12|
2576
17|
2104
21|
1822
■-i
1630
281
200
12940
4f
4206
Mi
2947
20|
2403
241
2084
28}
1930
31 1
* = 40°
50°
69°
70°
80°
90°
Span.
S
X
S
X
S
X
8
X
S
X
S
X
80
680
14£
630
151
589
16f
555
171
527
181
502
m
100
869
17|
768
19
735
20|
695
214
658
22|
628
231
120
1022
214
946
22f
885
24|
835
251
792
271
755
28f
150
1265
26f
1177
28f
1060
30|
1039
324
987
341
941
351
175
1488
304
1377
33|
1279
351
1215
37|
1152
391
1099
411
200
1672
35J
1574
381
1473
40|
1393
43
1316
454
1256
47|
ALUMINUM WIRE.
179
J H
• i I
ft m g
©S3
ft U g
S ^ i-
* ,_ be
2^ B
B S3 -S
«*|
P3 o a
01675
01763
01861
01969
02092
02232
02392
02575
02789
03044
03347
03720
04184
04782
0558
06698
07912
09958
12563
1584
2004
2515
3182
4012
0
p
o
w
2
||
0)
o
8
33
Pm
1,408
1,340
1,270
1,202
1,135
1,067
1,001
938
878
806
740
665
567
502
436
375
280
252
192
155
132
108
88
72
<
B
6
33
Pw
4,860
4,617
4,374
4,131
3,888
3,645
3,402
3,159
2,916
2,673
2,430
2,187
1,924
1,701
1,458
1,215
1,028
816
647
513
407
323
256*
203
0)
o
8
ioin
920
874
828
782
736
690
644
598
552
506
460
414
368
322
276
230
195
155
123
97
77
61
48
38
H
H
ft
iZSO
<D o
ft
152
125
092
062
035
999
963
927
891
855
819
770
728
679
630
590
530
470
420
375
330
291
261
231
1
o
O
1,000,000
950,000
900,000
850,000
800,000
750.000
700,000
650,000
600,000
550,000
500,000
450,000
400,000
350,000
300,000
250,000
211,600
167,805
133,079
105,534
83,694
66,373
52,634
41,742
i
13 i
3 . cs
3BO
~ .............. .
180
PROPERTIES OF CONDUCTORS.
Aluminum wire, rods, and bars will be furnished of 63 per cent electrical
conductivity, which will have an equal tensile strength per unit of area
with the copper, and therefore with the electrical conductivity equivalent
of 4S per cent of the weight of the copper and sectional area of 160 against
the area of the copper section 100, the tensile strength of the aluminum con-
ductors will be as 100 for the copper is to 160 for the aluminum. This
would mean, if a square inch of copper conductor was used of, say, 32,000
pounds per square inch tensile strength, the equal conductivity area of 1.6
inches of aluminum would have a tensile strength of 51,200 pounds.
It has already been determined that with aerial lines, the snow and ice
load is practically as heavy on lengths of small wire as upon larger sections,
so that no objection upon this score can probably be found to the use of the
larger sections of aluminum wire.
Both on account of having only 48 per cent of the weight, and on account
of having about 60 per cent more strength, the aluminum conductor could
be used in much longer spans betAveen supports, and the number of expen-
sive poles and insulators can be materially diminished.
GERMAN SUITOR.
German silver is most extensively used for resistances.
A cubic foot weighs about 530 lbs. ; specific gravity, 8.5.
Composition : copper, 4 parts ; zinc, 1 part ; nickel, different per
centages.
Specific resistance, 20.9, or 13 times copper.
1 mil-foot, resistance 125.91 ohms.
Temperature variation, for 1° C. .044% from 0 to 100° C.
RE§ISTAIVCE§ OF CTORMAUT §I1VER WIRE.
(American Gauge.)
18%
30%
Size.
Ohms per
Ohms per
Ohms per
Ohms per
1,000 feet.
pound.
1,000 feet.
pound.
No. 8
11.772
.23598
17.658
.35397
9
11.832
.37494
17.7*8
.56241
10
18.72
.59652
28.08
.89478
11
23.598
.94842
35.397
1.42263
12
29.754
1.50786
44.631
2.26179
13
37.512
2.39778
56.268
3.59667
14
47.304
3.8124
70.956
5.7186
15
59.652
6.0624
89.478
9.0936
16
75.222
9.639
112.833
14.458
17
94.842
15.327
142.263
22.990
18
119.61
24.3702
179.41
36.5553
19
155.106
40.9896
232.659
61.4844
20
190.188
61.614
285.282
92.421
21
239.814
97.974
359.721
146.961
22
302.382
155.772
453.573
233.658
23
381.33
247.734
571.99
371.601
24
480.834
393.93
721.251
590.89
25
606.312
626.31
909.468
939.46
26
764.586
995.958
1,146.879
1,493.937
27
964.134
1,583.622
1,446.201
2,375.433
28
1,215.756
2,518.075
1,823.634
3,777.112
SILVER WIRES.
181
RESISTANCES OJP GERKA1V SIIVER WIRE-
Continued.
18%
30%
Size.
Ohms per
Ohms per
Ohms per
Ohms per
1,000 feet.
pound.
1,000 feet.
pound.
No. 29
1,533.06
4,004.082
2,229.59
6,006.123
30
1,933.038
6,36S.356
2,899.557
9,552.534
31
2,437.236
10,119.978
3,655.854
15,179.967
32
3,073.77
16,096.356
4,610.65
24,144.534
33
3,875.616
25.589.628
5,813.424
38,384.442
34
4,888.494
40,712.76
7.332.741
61,069.14
35
6,163.974
64,729.87
9,245.961
97,094.80
36
7,770.816
102,876.482
11,656.224
154,314.723
37
9,797.166
163,524.78
14,695.749
245,287.17
38
12,357.198
257,764.68
18,535,797
386,647.02
39
15,570.828
409,546.8
23,356.242
614,320.2
40
19,653.57
652,024.62
29,480.35
978,036.93
RELATIVE RESISTANCES OE METAI AIIOY§.
Copper 1.
Platinum silver —
SESriSS} 20.5 approximately.
German silver —
Copper, 4 parts )
Nickel, 2 parts > 12.8 approximately.
Zinc, 1 part )
Gold-Silver —
Infer, IpS?} ll:6 approximately.
Platinoid —
German Silver, with \ p. c. of Tungsten . . . 19.2 approximately.
RELATIVE COKRUCTIVITIEi ©E METAL§ AND
ALLOTS.
(Weiller.)
1. Pure silver 100
2. Pure copper 100
3. Refined and crystallized copper 99.9
4. Telegraphic silicious bronze 98
5. Alloy of copper and silver (50 per cent) 86.65
6. Pure" gold ° • 78
7. Silicide of copper, with 4 per cent of Silicium 75
8. Silicide of copper, with 12 per cent of silicium 54.7
9. Aluminum, 99- « 63.09
10. Tin with 12 per cent of sodium 46.9
11. Telephonic silicious bronze 35
12. Copper with 10 per cent of lead 30
13. Pure zinc 29.9
14. Telephonic phosphor-bronze 29
15. Silicious brass with 25 per cent of zinc 26.49
16. Brass with 35 per cent of zinc 21.5
17. Phosphor tin 17.7
182
PROPERTIES OP CONDUCTORS.
18.
19.
20.
Alloy of gold and silver (50 per cent) 16.12
Swedish iron „ 16
Pure Banca tin ,'.'.. 15.45
Antinionial copper 12.7
Aluminum bronze (10 per cent) 12.6
Siemens's steel , 12
Pure platinum 10.6
Copper with 10 per cent of nickel 10.6
Cadmium amalgam (15 per cent) ............ 10.2
Dronier mercurial bronze 10.14
Arsenical copper (10 per cent) 9.1
Pure lead 8.88
Bronze with 20 per cent of tin ............. 8.4
Pure nickel 7.89
Phosphor-bronze with 10 per cent of tin ......... 6.5
Phosphor-copper with 9 per cent of phosphorus 4.9
Antimony 3.88
TEOTPEHATUJUB OF C©ari>XJCXO«S WIIH
COBFJFICIFH-TiS.
(From Kempe.)
Por metals the resistance increases as the temperature increases. The
formula which represents the effect of temperature may be written
lit = Bo (1 + o>t + (B^2)
where lit is the resistance at the final temperature, Ho is the resistance at
the standard temperature, t is the increase in temperature, and oo and (£>
are coefficients.
Por most purposes the following approximate formula may be used :
Rt = Jio (1 + oo t).
The value of oo for use in the approximate formula is given in the follow-
ing table, ooe being the value per centigrade degree, and oo/per Fahrenheit
degree.
Metal.
00c
oo/
Silver
0.00377
0.00210
Copper
0.00388
0.00215
Gold
0.00365
0.00203
Aluminum
0.00390
0.00217
Platinum
0.00247
0.00137
Iron
0.00453
0.00252
Tin
0.00365
0.00203
Lead
0.00385
0.00214
Mercury
0.00088
0.00049
Alloy, 2Pt + l Ag . .
0.00022 to 0.00031
0.00012 to 0.00017
2 Au + 1 Ag .
0.00065
0.00036
8 Pt + 1 Ir . .
0.0013
0.00072
German Silver . . .
0.00028 to 0.00044
0.00016 to 0.00024
TEMPERATURE.
183
Dividing- Coefficients for Correcting- the observed Resist-
ance of Crutta-Percha at any Temperature to 1 .VJ JP.
Temp.
F.°
Coeff.
Temp.
F.
Coeff.
Temp.
F.°
Coeff.
Temp.
F.°
Coeff.
90
.3197
77.5
.8269
65
2.139
52.5
5.533
89.5
.3320
77
.8589
64.5
2.222
52
5.748
89
.3449
76.5
.8922
64
2.308
51.5
5.970
88.5
.3583
76
.9267
63.5
2.397
51
6.202
88
.3722
75.5
.9627
63
2.490
50.5
6.442
87.5
.3866
75
1.000
62.5
2.587
50
6.692
87
.4016
74.5
1.039
62
2.687
49.5
6.951
86.5
.4171
74
1.079
61.5
2.792
49
7.220
86
.4343
73.5
1.121
61
2.899
48.5
7.500
85.5
.4501
73
1.164
60.5
3.012
43
7.791
85
.4675
72.5
1.209
60
3.128
47.5
8.093
84.5
.4856
72
1.256
59.5
3.250
47
8.406
84
.5044
71.5
1.305
59
3.376
46.5
8.732
83.5
.5240
71
1.355
58.5
3.506
46
9.070
83
.5443
70.5
1.408
58
3.642
45.5
9.422
82.5
.5654
70
1.463
57.5
3.783
45
9.787
82
.5873
69.5
1.519
57
3.930
44.5
10.17
81.5
.6100
69
1.578
56.5
4.082
44
10.56
81
.6337
68.5
1.639
56
4.240
43.5
10.97
80.5
.6582
68
1.703
55.5
4.405
43
11.39
80
.6837
67.5
1.769
55
4.575
42.5
11.84
79.5
.7102
67
1.837
54.5
4.753
42
12.29
79
.7378
66.5
1.908
54
4.937
41.5
12.77
78.5
.7663
66
1.982
53.5
5.128
41
13.27
78
.7960
65.5
2.059
53
5.327
40.5
13.78
Example : The insulation resistance at 62° F. of a wire insulated with
Gutta-percha is 500 meghoms ; what is the resistance at 75° F. ?
Resistance =: 500 -f- 2.687 = 186.1 megohms.
Dividing Coefficients for Correcting the observed Resist-
ance of Hooper's India-It ubber at any Temperature
to ¥5° E*.
Temp.
F.°
Coeff.
Temp.
F.=
Coeff.
Temp.
F.°
Coeff.
Temp.
F.°
Coeff.
90
.680
80.5
.868
71
1.108
61.5
1.414
89.5
.691
80
.880
70.5
1.122
61
1.433
89
.698
79.5
.891
70
1.137
60.5
1.451
88.5
.708
79
.902
69.5
1.152
60
1.470
88
.716
78.5
.914
69
1.167
59.5
1.489
87.5
.726
78
.926
68.5
1.182
59
1.508
87
.735
77.5
.938
68
1.197
58.5
1.527
86.5
.745
77
.950
67.5
1.212
58
1.547
86
.754
76.5
.963
67
1.228
57.5
1.567
85.5
.764
76
.975
66.5
1.244
57
1.587
85
.774
75.5
.987
66
1.260
56.5
1.608
84.5
.784
75
1.000
65.5
1.276
56
1.629
84
.794
74.5
1.013
65
1.293
55.5
1.650
83.5
.804
74
1.026
64.5
1.309
55
1.671
83
.814
73.5
1.039
64
1.326
54.5
1.693
82.5
.825
73
1.053
63.5
1.343
54
1.715
82
.836
72.5
1.068
63
1.361
53.5
1.737
81.5
.846
72
1.080
62.5
1.378
53
1.759
81
.857
71.5
1.094
62
1.396
52.5
1.782
184
PROPERTIES OF CONDUCTORS.
Dividing- Coefficients — Continued.
Temp.
F.°
Coeff.
Temp.
F.°
Coeff.
Temp.
F.°
Coeff.
Temp.
F.°
Coeff.
52
1.805
49
1.949
46
2.106
43
2.274
51.5
1.828
48.5
1.975
45.5
2.133
42.5
2.303
51
1.852
48
2.000
45
2.160
42
2.333
50.5
1.876
47.5
2.026
44.5
2.188
41.5
2.363
50
1.900
47
2.052
44
2.216
41
2.394
49.5
1.925
4G.5
2.079
43.5
2.245
40.5
2.424
Mean Temperature.
A piece of wire or cable whose length is I, and temperature t°, when con-
nected to another wire or cable whose length is lv and temperature tx°, has
a mean temperature
It + LU
linear H\pan§ioii of Metals due to Change of
Temperature.
A rod or wire I feet long will, by an increase of temperature of t°, increase
its length to
I (1 + at°) feet,
where a has the following values : — Value of a for
Metal.
Zinc
Lead
Brass
Copper
Iron
Steel
Platinum
Glass <
Specific Heat,
F.°
.000016540
.000015830
.000010500
.000009560
.000006830
.000006381
.000004910
.000004870
c.°
.00002976
.00002848
.00001890
.00001720
.00001229
=00001145
.00000884
.00000876
Specific heat
Specific heat
Element.
of equal
Element.
of equal
Weights.
Weights.
Water
1.0000
Rhodium
.0580
Lithium . .
.9408
Silver
.0570
Sodium • . .
.2934
Cadmium
.0567
Magnesium .
Aluminum .
.2499
.2143
Tin
Iodine
.0562
.0541
Sulphur . .
.1776
Antimony ....
.0508
Potassium
.1696
Tellurium ....
.0474
Manganese .
.1140
Thallium
.0336
Iron ....
.1138
Tungsten
.0334
Nickel . . .
.1091
Iridium .....
.0325
Cobalt . . .
.1070
Platinum
.0324
Zinc ....
.0955
Gold
.0324
Copper . . .
.0951
Mercury (liquid) . .
.0333
Bromine (solid)
.0843
Lead
.0314
Arsenic . .
.0814
Bismuth
.0308
Palladium .
.0593
Osmium
.0306
^m^^m^^^^^m
COEFFICIENTS.
185
If W = "weight of one substance whose temperature is T and specific heat S,
w = weight of another substance whose temperature is t
and specific
heat
s.
Temperature of mixture = -Trri , z=L,
WS -f- ivs 1
w
(h — t)
s-sw
(T - t)'
Temperature Coefficients of the .Resistivity of Pure
Copper.
, Temp.
a
o
5 2
Temp.
a
o
.2Mi c3
.£ bJO^ «6
O
O
o o
Matth
Meter-
Stand*
Intern
Ohms.
o
O
o o
i-hQ
0°.
F°.
0°.
F°.
Matt
Mete
Stan
Intel
Ohm
0
32.0
1.
0.
0.14173
20
08.0
1.07968
.033294
0.15302
1
:w.s
1.003S8
.00168C
0.14228
21
o:t.s
1.08378
.034939
0.15360
2
35.0
1.00776
.003358
0.142S3
22
71.6
1.08788
.036581
0.15418
3
87.4
1.01166
.005036
0.14338
23
73.4
1.09200
.038222
0.15477
4
80.2
42.0
1.01558
.006712
0.14394
24
75.2
1.09612
.039859
0.15535
5
1.01950
.008386
0.14449
25
77.0
1.10026
.041494
0.15594
0
42. S
1.02343
.010059
0.14505
26
7S..S
1.10440
.043127
0.15653
7
44.0
1.02738
.01173C
0.14561
27
so.o
1.10856
.044758
0.15711
8
46.4
1.03134
.013400
0.14617
28
82.4
1.11272
.046385
0.15770
9
48. 2
1.03531
.015068
0.14673
29
84.2
1.11689
.048(
»11
333
0.15830
10
50.0
1.03929
.016734
0.14730
30
80.0
1.12107
.049
0.15889
11
51.8
1.04328
.018399
0.14786
40
104
1.16332
.065699
0.164S8
12
->>;.()
1.04728
.020062
0.14843
50
122
1.20625
.081436
0.17095
13
5,-.. 4
1.05129
.021723
0.14900
60
140
1 .24965
.096787
0.17711
11
15
57.2
1.05532
.023382
0.14957
70
158
1.29327
.111
0.18329
50.0
1.05935
.02503S
0.15014
80
176
1.33681
.126
0.18946
16
Cil.S
1.08339
.02669-
0.15071
90
104
1.37995
.139863
0.1'. 558
17
02.0
1.06745
.02834b
0.15129
100
212
1.42231
.152995
0.20158
18
04.4
1.07152
.02999£
0.15186
19
00.2
1.07559
.031646
0.15244
I 1
]
Heat Conducting
»• Power of JfEetals.
Relative hea
t
Relative heat
Metal.
conducting
power.
Metal.
conducting
power.
Silver
100
43.6
Go
Cot
d. . . .
98.1
8*.5
Tin ... .
Steel . . .
42.2
>per (rolled)
39.7
Copper (cast)
81.1
Platinum
38.0
Aluminum . .
66.5
Sodium . .
36.5
Zinc ....
64.1
Iron (cast) .
35.9
Bismuth . .
61.0
Lead . . .
28.7
Cadmium . .
57.7
Antimony .
21.5
186
PROPERTIES OF CONDUCTORS.
RE8ISTAICE METALS.
Following are data on modern resistance metals, supplied by Hermann
Boker & Co., of 101-103 Duane Street, New York.
The resistance data are from tests by Helmlioltz and tbe German Impe-
rial Physical and Technical Institute of Charlottenburg, Germany.
Dimensions, Resistances, and Weijrlits of Resistance
Wires.
i
Ohms per 1000 feet.
Feet per Lb.
Approxi-
6
SZ3
A
1
mately.
S
s
<
Xfl
eg
%
Cm
® I
© S u
■5 Jo
3 a?
3 £
z >
14
.0641
4107.
125.9
73.5
63.7
49.7
56.6
85.
79.2
10
.0508
2583.
200.3
116.9
101.4
78.9
90.1
135.3
125.9
17
.0453
2048.
252.6
147.4
127.8
99.6
113.9
170.6
158.7
18
.0403
1624.
318.6
185.9
161.2
125.6
143.4
215.5
200.5
19
.0359
1289.
401.4
234.3
203.1
158.2
181.1
271.0
252.
20
.0320
1024.
506.5
295.6
256.3
199.7
227.9
342.3
318.4
21
.0285
812.3
641.5
374.4
324.6
252.9
288.7
433.
402.6
22
.0253
640.1
805.7
470.1
407.7
317.5
362.6
543.5
505.5
23
.0225
506.25
1022.1
596.6
517.2
402.8
459.9
689.6
641.4
24
.0201
404.
1280.7
747.6
648.
504 9
576.3
870.
809.1
25
.0179
320.4
1620.
945.6
819.7
638.9
729.
1098.
1021.2
26
.0159
252.8
2036.5
1192.9
1030.5
802.8
916.4
1370.
1274.1
27
.0142
201.6
2566.2
1497.8
1298.5
1011.5
1154.8
1724.
1604.
28
.0126
158.8
3238.1
1890.1
1638.5
1276.4
1457.1
2174.
2022.
29
.0113
127.7
4125.
2407.8
2087.2
1626.
1856.2
2777.
2583.
30
.0100
100.
5148.7
3005.3
2605.2
2029.5
2316.9
3448.
3207.
31
.0089
79.2
6491.6
3789.2
32S4.7
2558.8
2921.2
4347.
4043.
32
.0080
64.
8187.5
4779.1
4142.8
3227.3
3684.3
5555.
5167.
33
.0071
50.4
10322.
6025.1
5222.9
4068.9
4644.9
7142.
6600.
34
.0063
39.69
13020.
7600.4
6588.1
5132.6
5659.
9090.
8354.
35
.0056
31.56
16416.
9582.7
8308.5
6471.1
7387.2
11100.
10323.
36
.005
25.
20698.
12081.
10473.
8158-8
9314.1
14286.
13280.
37
.0044
19.83
26094.
15229.
13203.
10285.
11743.
17543.
16315.
38
.004
16.
32916.
19213.
16655.
12975.
14712.
22220.
20665.
39
.0035
12.25
41495.
24218.
20996.
16357.
18672.
27700.
25761.
40
.0031
9.61
52373.
30570.
26500.
20644.
23567.
35714.
33215.
RESISTANCE METALS.
187
maximum Amperes for Safe Constant XiOad with
Free Radiation.
Nickeline I.
B. &S.
Gauge No.
Superior.
la la.
and
German
Silver.
Nickeline II.
18
11.8
15.75
17.2
18.2
19
10.25
13.6
14.4
15.6
20
8.5
11.5
12.1
13.0
21
7.2
9.7
10.0
11.0
22
6.0
8.0
8.4
9.1
23
5.2
6.8
7.1
7.8
24
4.5
5.8
6.0
6.5
25
4.0
4.9
4.8
5.5
26
3.5
4.1
4.1
4.6
27
3.0
3.6
3.6
4.0
28
2.7
3.1
3.1
3.5
29
2.5
2.9
2.9
3.2
30
2.3
2.7
2.7
2.9
32
2.0
2.5
2.5
2.63
34
1.7
2.2
2.2
2.3
36
1.5
2.0
2.0
2.0
Resistance Ribbon. " Superior " Crrade.
■3©
.2 s
Ohms per
100 feet
<% it,
&$
H
Jin.
Jin.
fin.
I in.
fin.
fin.
fin.
lin.
8
.128
25.36
12.68
8.45
6.34
5.07
4.22
3.62
3.17
9
.114
28.59
14.29
9.53
7.14
5.71
4.76
4.08
3.57
10
.101
32.22
16.11
10.74
8.05
6.44
5.37
4.60
4.02
11
.0907
35.93
17.96
11.98
8.98
7.18
5.99
5.13
5.49
12
.0808
40.19
20.09
13.39
10.04
8.04
6.69
5.74
5.02
13
.0719
45.61
22 80
15.20
11.40
9.12
7.60
6.51
5.70
14
.0641
50.72
25 36
16.90
12.68
10.14
8.45
7.24
6.34
15
.0571
57.18
28.59
19.06
14.29
11.43
9.53
8.16
7.14
16
.0508
64.44
32.22
21.48
16.11
12.89
10.74
9.20
8.05
17
.0452
71.86
35.93
23.95
17.96
14.37
11.97
10.28
8.98
18
.0403
80.38
39.19
26.79
20.09
16.07
13.39
11.48
10.04
19
.0359
91.22
45.61
30.40
22.80
18.24
15.20
13.03
11.40
20
.0320
101.44
50.72
33.81
25.36
20.29
16.90
14.50
12.68
21
.0284
114.36
57.18
38.12
28.59
22.87
19.06
16.33
14.29
22
.0253
128.88
64.44
42.96
32.22
25.77
21.46
18.41
16.11
23
.0225
143.72
71.86
47.90
35.93
28.74
23.95
20.53
17.96
24
.0201
160.76
80.38
53.59
40.19
32.15
26.79
22.96
20.09
25
.0179
182.44
91.22
60.81
45.16
36.49
30.40
26.06
22.80
26
.0159
202.88
101.44
67.62
50.72
40.57
33.81
28.98
25.36
27
.0142
228.72
114.36
76.24
57.18
45.74
38.12
32.67
28.59
28
.0126
257.76
128.8S
S5.92
64.44
51.55
42.96
36.82
32.22
29
.0112
287.44
143.72
95.81
71.86
57.49
57.90
41.06
35.93
30
.0100
321.52
160.76
107.17
80.38
64.30
53.59
45.93
40.19
31
.0089
364.88
182.44
121.62
91.22
72.97
60.81
52.12
45.16
32
.0079
405.76
202.88
135.25
101.44
81.15
67.62
57.96
50.72
33
.0071
457.44
228.72
152.48
114.36
91.49
76.24
65.33
57.18
34
.0063
515.52
257.76
171.84
128.88
103.10
85.92
73.64
64.44
35
.0056
574.88
287.44
191.62
143.72
114.97
95.81
82.12
71.86
36
.005
643.04
321.52
214.34
160.76
128.60
107.17
91.86
80.38
37
.0044
729.76
364.88
243.25
182.44
145.95
121.62
104.25
91.22
38
.0039
811.52
405.76
270.50
202.88
162.30
135.25
115.93
101.44
The number of feet to the pound of any size of the above ribbon can be
found by dividing the constant 0.26 by the cross sectional area in square inches.
188
PROPERTIES OF CONDUCTORS.
Resistance Ribbon. la la Quality.
6
<^> .
Ohms per
1000 feet
<3&
5o
PQJS
H
g m.
tin.
§ in-
5 in.
f in.
f in.
fin.
lin.
8
.128
14.81
7.40
4.93
3.70
2.96
2.'46
2.11
1.85
9
.114
16.69
8.34
5.56
4.17
3.34
2.78
2.38
2.08
10
.101
18.80
9.40
6.26
4.70
3.76
3.13
2.70
2.35
11
.0907
20.97
10.48
6.99
5.24
4.19
3.49
2.99
2.62
12
.0b08
23.46
11.73
7.82
5.86
4.69
3.91
3.35
2.93
13
.07i9
26.63
13.31
8.87
6.65
5.32
4.43
3.80
3.32
14
.06*1
29.62
14.81
9.87
7.40
5.92
4.93
4.22
3.70
15
.0o71
33.38
16.69
11.12
8.34
6.68
5.56
4.77
4.17
16
.0508
37.60
18.80
12.53
9.40
7.52
6.26
5.37
4.70
17
.0*52
41.94
20.97
13.98
10.48
8.38
6.99
5.99
5.24
18
.0403
46.92
23.46
15.64
11.73
9.38
7.82
6.70
5.86
19
.0359
53.26
26.63
17.78
13.31
10.64
8.87
7.60
6.65
20
.0320
59.24
29.62
19.75
14.81
11.84
9.87
8.46
7.40
21
.0284
66.76
33.38
22.25
16.69
13.55
11.12
9.53
8.34
22
.0253
75.20
37.60
25.07
18.80
15.04
12.53
10.74
9.40
23
.0225
83.88
41.94
27.96
20.97
16.77
13.98
11.98
10.48
24
.0W1
93.84
46.92
31.28
23.46
18.77
15.64
13.40
11.73
25
.0179
106.52
53.26
35.50
26.63
21.30
17.78
15.21
13.31
26
.0159
118.48
59.24
39.49
29.62
23.69
19.75
16.91
14.81
27
.01*2
133.52
66.76
44.50
33.38
26.70
22.25
19.07
16.69
28
.0126
150.40
75.20
50.13
37.60
30.08
25.07
21.50
18.80
29
.0112
167.76
83.88
55.92
41.94
33.55
27.96
23.96
20.97
30
.0100
187.68
93.84
62.56
46.92
37.53
31.28
26.81
23.46
31
.00&9
213.04
106.52
71.01
53.26
42.60
35.50
30.43
26.63
32
.0079
236.96
li8.*8
78.98
59.24
47.40
39.49
33.82
29.62
33
.0071
267.04
133.o2
89.01
66.76
53.40
44.50
38.15
33.38
34
.0063
300.80
150.40
100.26
75.20
60.16
50.13
42.97
37.60
35
.0056
335.52
167.76
111.84
83.88
67.10
55.92
47.93
41.94
36
.005
375.36
187.68
125.12
93.84
75.07
62.56
53.62
46.92
37
.0044
426.08
213.04
142.02
106.52
85.21
71.01
60.87
53.26
88
.004
473.92
236.96
157.97
118.48
94.78
78.98
67.64
59.24
Specific Resistance and Temperature Coefficient.
Specific
Resistance
at 20° C,
Coefficient for
1°C.
Superior
la la, hard
la la, soft
Nickeline No. II., hard
Nickeline No. II., soft .
Nickeline No. I., hard .
Nickeline No I., soft .
German Silver, average
Manganin
Constantin
85.4 to
86.5
50.2
47.1
33.9
32.3
43.6
40.7
31.5
47.5
50. — 55
.00067 to
.00073
— .000011
+ .00u005
■ .000168
-- .000181
- .000076
- .000077
- .00025
: .00001
: .00001
"SUPERIOR" WIRE.
Specific gravity, 8.4.
Specific resistance at 20° C, 86 microhms.
Coefficient of temperature, mean value, for l°C.,-f 0.00065.
BOKER S WIRES.
189
Resistance of one circular mil foot of " Superior " wire f
ohms.
20° C, 517.5
This resistance material does not rust, nor show any sign of oxidation at
ordinary temperature, and it shows no sign of deterioration after being sub-
mitted to a temperature just below a visible red heat as a permanent load.
Prices of JBare Wire per Pound.
B. &S.
Gauge.
Inch.
Superior.
la la.
Nickeline
I.
Nickeline
11.
15 and
heavier
.057
$1.07
$.078
$0.66
$.61
16
.05082
1.09
.80
.69
.63
17
.04525
1.09
.80
.69
.63
18
.0403
1.09
.80
.69
.63
19
.0358
1.09
.80
.69
.63
20
.0319
1.09
.80
.69
.63
21
.0284
1.121
.85
.72
.66
22
.0253
1.16
.88
.75
,70
23
.0225
1.16
.88
.75
.70
24
.0201
1.24
.94
.78
.74
25
.0179
1.26
.96
.83
.77
26
.0159
1.28
.96
.85
.79
27
.01419
1.33
1.04
.90
.84
28
.01264
1.37
1.09
.94
.88
29
.01125
1.40
1.12
.97
.91
30
.010
1.45
1.17
1.02
.96
31
.00892
1.52
1.24
1.09
1.03
32
.00795
1.60
1.33
1.16
1.10
33
.00708
1.69
1.45
1.26
1.20
34
.0063
1.81
1.55
1.38
1.33
35
.0056
1.98
1.75
1.55
1.49
36
.005
2.56
2.20
2.13
2.07
37
.00445
4.21
3.85
3.72
3.72
38
.00396
6.36
6.00
5.93
5.87
39
.00353
8.11
7.75
7.68
7.62
40
.00314
10.36
10.00
9.93
9.87
.00196
15.60
15.25
15.18
15.12
190
PROPERTIES OF CONDUCTORS.
Prices of Silk Covered IFire per Pound.
9
tjj
S3
a
o
Superior.
la la.
Nickeline I.
Nickeline II.
O
6
6
<D
6
CO
a
r2
£2
£
<6
,0
0
£
P
p
O
s
P
P
P
o
P
P
W
m
A
ai
O
02
Q
cc
A
20
.031 and
eavier
$1.90
$2.60
$1.50
$2.20
$1.52
$2.22
$1.47
$2.17
21
.0284
2.00
2.70
1.60
2.30
1.62
2.32
1.57
2.27
22
.0253
2.05
2.75
1.65
2.35
1.67
2.37
1.62
2.32
23
.0225
2.10
2.80
1.70
2.40
1.72
2.42
1.67
2.37
24
.0201
2.15
2.90
1.75
2.50
1.77
2.52
1.72
2.47
25
.0179
2.30
3.10
1.90
2.70
1.92
2.72
2.87
2.67
2G
.0159
2.50
3.30
2.10
2.90
2.12
2.92
2.07
2.87
27
.0141
2.70
3.60
2.30
3.20
2.32
3.22
2.27
3.17
28
.0126
2.85
3.90
2.45
3.50
2.47
3.52
2.42
3.47
2i»
.01125
3.15
4.20
2.75
3.80
2.77
3.82
2.72
3.77
30
.010
3.40
4.50
3.00
4.10
3.02
4.12
3.00
4.07
Ml
.0089
3.70
4.90
3.30
4 50
3.32
4.52
3.27
4.47
32
.0079
4.10
5.30
3.70
4.90
3.72
4.92
3.67
4.87
83
.0070
4.40
5.90
4.00
5.50
4.02
5.52
4.00
5.47
34
.0063
4.90
6.40
4.50
6.00
4.52
6.02
4.47
5.97
35
.0056
5.70
7.00
5.30
6.60
5.32
6.62
5.27
6.57
36
.005
6.90
8.65
6.50
8.25
6.52
8.27
6.47
8.22
37
.00445
9.90
12.40
9.50
12.00
9.52
12.02
9.47
11.97
38
.0039
12.40
16.90
12.00
16.50
12.02
16.52
12.00
16.47
311
.00353
15.40
20.40
15.00
19.50
15.02
19.52
15.00
19.47
40
.00314
18.40
22.90
18.00
22.50
18.02
22.52
18.00
22.47
The above prices are for wire, single or double, covered with green or
white silk.
Prices of Resistance {Sheets per Pound
B. &S.
Gauge.
Inch.
Superior.
la la.
Nickeline
I.
Nickeline
II.
28 and
heavier
.0126
$1.02
$0.69
$0.63
$0.57
29
.01125
1.05
71
.65
.60
30
.010
1.05
71
.65
.60
31
.0089
1.07
74
.67
.62
32
.0079
1.07
74
.67
.62
33
.007
1.09
76
.69
.65
34
.0063
1.09
76
.69
.65
35
.0056
1.11
78
.72
.66
36
.005
1.11
78
.72
.66
37
.0044
1.11
78
.72
.66
38
.0039
1.11
78
.72
.66
The above prices are for sheets of maximum width of 12 inches,
imum length of 7 to 8 feet.
KRTTPP's RESISTANCE WIRES. 191
Prices for Resistance Tapes in long* lengths per Pound.
B.&S.
i Gauge.
Inch.
Superior.
la la.
Nickeline
I.
Nickeline
II.
18 and
heavier
.0403
$1.08
$0.73
$0.66
$0.61
19
.0358
1.10
.74
.67
.62
20
.0319
1.10
.74
.67
.62
21
.0284
1.10
.74
.67
.62
22
.0253
1.10
.74
.67
.62
23
.0225
1.10
.74
.67
" .62
24
.0201
1.10
.74
.67
.62
25
.0179
1.10
.74
.67
.62
26
.0159
1.10
.74
.67
.62
27
.0141
1.10
.74
.67
.62
28
.0126
1.10
.74
.67
.62
29
.01125
1.14
.77
.70
.65
30
.010
1.14
.77
.70
.65
31
.0089
1.17
.79
.73
.67
32
.0079
1.17
.79
.73
.67
33
.007
1,21
.83
.76
.70
34
.0063
1.21
.83
.76
.70
35
.0056
1.30
.87
.80
.75
36
.005
1.30
.87
.80
.75
37
.0044
1.30
.87
.80
.75
38
.0039
1.30
.87
.80
.75
The above prices are tapes about f-inch wide and narrower. Maximum
length of tapes is about 300 feet.
KRUPP'S RESISTANCE WIRES.
Following will be found data of the Krupp resistance wires supplied by
the American agents, Thomas Prosser & Son, 15 Gold Street, New York.
Hrnpp's Resistance Metals.
Specific gravity 8.102
Specific resistance at 20° C. mean 85.13 microhms.
Temperature coefficient, mean 0007007.
Resistance per circular mil-foot 314.067 obms.
Resistance per 1000', 1 square inch area 8513 ohms.
This metal can be permanently loaded with current sufficient to raise its
temperature to 600° C. (1112° F.) without undergoing any structural change.
192 PROPERTIES OF CONDUCTORS.
Table of K rupp's Resistance ^Fires.
Diam.
• Diam.
in inches.
Near-
est
B. &S.
Gauge
Feet
per
lb.
Resistance
n ohms per foot.
in m.m.
at
at
at
at
No.
68° F.
176° F.
284° F.
428° F.
5
.1968
4
9
.0132
.0138
.0143
.0150
*h
.1772
5
12
.0163
.0170
.0176
.0184
4
.1575
6
15
.0206
.0215
.0224
.0235
3|
.1378
7
19
.0269
.0280
.0291
.0307
3
.1181
9+
26
.0368
.0382
.0396
.0417
n
.1083
9—
31
.0437
.0455
.0472
.0497
H
.0984
10
37
.0528
.0550
.0570
.0601
2J
.0885
11
46
.0653
.0679
.0705
.0742
2
.0787
12
58
.0825
.0860
.0892
.0940
If
.0689
13
76
.1078
.112
.116
.123
1*
.0590
15
104
.1468
.153
.159
.167
1-1
.0492
16
150
.2115
.220
.229
.241
1
.0393
18
234
.3305
.344
.356
.376
|
.0295
21
415
.5870
.610
.633
.667
5
.0196
24
937
1.324
1.38
1.43
1.51
IPrice List per Pound.
B. &S. Nos.
4 to 10 inclusive .
$1.10
B. & S. Nos
11 to 12 inclusive .
1.15
B. & S. Nos
13 to 15 inclusive .
1.20
B. & S. No.
16
1.25
B. & S. No.
18
1.30
B. & S. No.
21 .
1.35
B. & S. No.
24
1.40
Table of Specific Resistance.
Substance.
Specific
resistance
in microhms
per cubic cm.
Relative
conductance.
Metals at 0° C.
1.570
1.603
1.492
1.620
2.077
2.889
8.982
9.638
15.
19.63
94.34
6 X 1010
2400 to 42000
about 4000
100.
98.1
105
98
Gold .
76
Aluminum (annealed)
54
17
16
Iron (telegraph wire)
Lead
10
8.3
1.6
Carbon (graphite)
Carbon arc light)
RESISTANCE OF DIELECTRICS. 193
Table of Specific Resistance — Continued.
Specific
resistance
Relative
Substance.
in microhms
per cubic cm.
conductance.
Alloys.
German silver (Cu 60, Zn 26, Ni 14) . .
20.76
7-6
Platinum-Silver (Pt 67, Ag 33) ... .
2.4
6.5
Platinoid (Cu59, Zn 25.5, Ni 14, W 55) .
32.5
4.8
Manganin (Cu 84, Ni 1
2, Mn 3.5) . . .
47.5
3.3
Superior ....
86.
la la, hard ....
50.2
la la, soft ....
47.1
Niekeline I., hard .
43.6
Ni.-keline 1., soft .
40.7
Niekeline II., hard
33.9
Nk-keline II., soft .
32.3
Krupp's metal . .
85.13
Constantin ....
50 to 52
John A. Roebling's Son's Co., Climax .
78.5
Liquids at 18° C.
Pure water
26.5 X 108
Dilute H, S04 5%
386 X 10*
H, S04 30 %
137 X 10*
H, S04 80%
918 X 10*
ZnS0424% . . . . . . . . .
214 X 105
HNO330%
129 X 10*
Insulators.
Glass at 20° C
91 X 1018
Glass at 200° C
22.7 X 1012
Gutta-percha
4.5 X 1020
RESISTANCE OF DIEL£CTRIC§.
Insulating materials or non-conductors, such as glass, wood, india-rubber,
gutta-percha, etc., are termed dielectrics, and vary in resistance, not only
with the material, but with its kind and quality.
The following table gives the
Specific Resistance of Insulators.
Material.
Resistance in
megohms per
cubic centimeter.
450 x 10°
28000 X 10°
194 PROPERTIES OF CONDUCTORS.
Specific Resistance of Insulators. — Continued.
Material.
Resistance in
megohms per
cubic centimeter.
Hooper's Compound
Paraffine
15000 x 10°
34000 X 10G
8 X 10G
1 X io6
.35 X 106
350 X 10»
14 X 10u
1670 x 10"
450 X 10G
Disruptive Value of Dielectrics.
In a paper on the " Dielectric Strength of Air," June 27, 1898, before the
Am. Inst. E. E., Chas. P. Steinmetz gave the results of numerous tests with
different shapes of electrodes and under various conditions. Following
are his conclusions and some of his tables and curves.
1st. At constant voltage and constant Avave shape, that is constant ratio
between maximum and effective E.M.F., the striking distance is a constant,
especially between sharp points, where the tests have been repeated over
/
'
/
•/
/
/
*
Y
/
>
/
r
K
7
19 20 30 40 50 60 70 SO 90 100 110 120 130 HO 150
KILOVOLTS EFFECTIVE
Fig. 0. Points, Smooth Core Alternator, 125 Cycles.
and over again, and independent of the atmospheric condition, the frequency,
etc., to such an extent that the striking distance between needle points
offers the most reliable means to determine very high voltages. For this
reason, it is used in this manner as final check in all high potential insula-
tion tests of the General Electric Company.
DISRUPTIVE VALUE OF DIELECTRICS.
195
2d. No physical law has been found to represent satisfactorily all the
observations. Some point to the existence of a constant dielectric strength
of air, analogous to the tensile strength of mechanics. Others point to the
existence of a spurious counter E.M.E. of the spark or transition resistance
from electrode to air.
3d. Constant dielectric strength. Cylinders of 1.11 in. diameter give an
average disruptive strength of air of 60 kilovolts per inch. Cylinders of
.315 in. diameter, an average dielectric strength of 77. Spheres at very
small distance point toward the latter value. As a disturbing factor in this
case, enters the electrostatic brush discharge, which by a partial breakdown
of the air surrounding the electrodes changes and increases the size and
decreases the distance of the effective terminals.
z.t>
I'
I
"0
//
1
/
/
/
|l.5
<*
(*■€■
*y
//
1 ^
'S
,*>
/$/
.5
<jC
ST'"
<^y
/
->
/I
*
11
10
9
1
0
20
30
i
ECT
0
VE-
5
0
''/
//
/
■v
.<
■
2 7
I
/
5
4
3
2
1
///
/$/
^
^/
W
,«
£y
''/
,\<v
%
>'
<*2
&&£
10 20 30 40 50 60 70 80 90 100 110 120130140
KILOVOLTS EFFECTIVE
Fig. 0. Comparison of Points and Spheres. Smooth Core
Alternator, 125 Cycles.
4th. Counter E.M.F. of the sparks. The tests with sharp points give 22
kilovolts, or 11 kilovolts for a single transition from terminal to air. Spheres
give curves pointing to a similar phenomenon. Electric conductors in-
serted at right angles into or parallel with the discharge, point to the exis-
tence of a counter E.M.F. of the same magnitude. The beginning of the
electrostatic brush discharge is at a potential of this magnitude also.
196
PROPERTIES OF CONDUCTORS.
TABLE. — POIXTS.
2\" needles. 125 cycles.
Smooth Core
Alternator :
Ironclad Alternator :
A-10-30-1500.
A
-10-60-1500.
of .
Kilovolts: effective.
of .
Kilovolts : effective.
d a>
C3r3
3-3
** 2
p'rt
d.
?T3
^'3
c3
3
5'"
d.
3' •
it
fee
. p
3 d
3 °°
tL "
<
ti'"
^.3
<
1-3 .3
•n S
.25
4.25
.25
4.13
.5
10.0
.5
9.0
10.0
9.5
11.0
14.5
1.0
20.4
1.0
16.0
1S.5
17.7
22.0
25.3
1.5
29.3
1.5
24.3
26.0
25.1
31.0
35.5
2.0
35.2
2.0
30.5
30.5
30.5
38.0
43.0
2.5
40.4
2.5
33.9
35.0
34.4
43.5
50.3
3.0
45.6
3.0
36.3
38.0
37.1
48.0
54.5
3.5
49.4
3.5
42.2
41.7
42.0
51.0
63.0
4.0
52.5
4.0
41.3
45.0
43.2
55.5
4.5
59.6
4.5
45.5
48.0
46.7
61.0
5.0
61.0
5.0
48.4
50.5.
55.0
49.5
5.5
65.7
5.5
53.0
54.0
6.0
69.8
69.5
69.65
6.0
56.1
58.8
57.4
6.5
73.4
74.7
74.05
6.5
59.8
62.0
60.9
7.0
77.5
79.2
78.35
7.0
63.3
64.7
64.0
7.5
83.8
83.0
83.4
7.5
67.5
69.0
68.3
8.0
86.8
87.3
87.05
8.0
70.9
73.4
72.1
8.5
90.5
90.2
90.35
8.5
75.8
76.0
75.9
9.0
95.0
93.7
94.35
9.0
79.S
79.2
79.5
9.5
97.7
96.3
97.0
9.5
84.8
82.5
83.6
10.0
101.5
99.0
100.25
10.0
88.8
86.4
87.6
10.5
107.0
103.0
105.0
10.5
93.5
89.5
91.5
11.0
111.5
107.5
109.5
11.0
97.7
93.0
95.4
11.5
114.0
110.5
112.5
11.5
102.0
12.0
121.0
116.0
118.5
12.0
107.7
12.5
125.5
120.0
122.75
12.5
111.0
13.0
133.0
123.0
128.0
13.0
117.5
13.5
135.0
127.0
131.0
13.5
122.5
14.0
140.0
129.0
134.5
14.0
128.0
14.5
144.0
136.0
140.0
14.5
134.4
15.0
150.0
15.0
138.3
15.5
155.0
16.0
159.5§
* 85° F. Weather sultry.
t 75°-80° P. Weather clear and hright.
j 70° F. Weather cool and cloudy.
§ Internal discharges in intermediary transformers F' F".
VALUES OF VARIOUS DIELECTRICS.
197
/
//
/
/'
^
/
/
/,->
♦
/<?
/
//
/
>
/
«
«
-^
s£
-
10 20 30 40 50 60 70 80 90 100 110 120 130
KILOVOLTS EFFECTIVE
Points in Air. Fog and Steam at Atmospheric Pressure.
Ironclad Armature, 125 Cycles.
Values of Various Dielectrics.
Steinmetz, February, 1893. A. I. E. E.
Electrostatic
gradient at
Formula for
Calculating tbe
Material.
0 5 I 25
Sparking Distance.
Kilovolts,
in Kilovolts per
Centimeter.
D
E = P. D.in
Kilovolts.
Air
139
4170
130
16.7
3200
52
130
339
81
80
64
30
16
36
43
10.1
11.9
1660.0
15.3
.86
D = . 24 ^ + .0145^z
D = 7.66 E -\- 2.3 E*
D = 7.66 E
D = 3E
D = 12.4 E
D = 12.5 E
D = 15.7 E
D = 30E
D = 60E
& = 28E
D = 23E
D = 55(E — 2)2
Vulcanized fiber, red . . .
Dry wood fiber
Paraffined paper ....
Melted paraffine ....
Boiled linseed oil ... .
Turpentine oil
Copal varnisb
Crude lubricating oil (min-
eral oil)
Vulcabeston
Asbestos paper
Creeping discbarge . . .
198 PROPERTIES OF CONDUCTORS.
Tests of Vulcanized India-Rubber.
Lieutenant L. Vladomiroff , a Russian naval officer, has recently carried
out a series of tests at the St. Petersburg Technical Institute with a view to
establishing rules for estimating the quality of vulcanized India-rubber.
The following, in brief, are the conclusions arrived at, recourse being had
to physical properties, since chemical analysis did not give any reliable
result : 1. India-rubber should not give the least sign of superficial crack-
ing when bent to an angle of 180 degrees after five hours of exposure in
a closed air-bath to a temperature of 125° C. The test-pieces should be 2.4
inches thick. 2. Rubber that does not contain more than half its weight of
metallic oxides should stretch to five times its length without breaking.
3. Rubber free from all foreign matter, except the sulphur used in vulcan-
izing it, should stretch to at least seven times its length without rupture.
4. The extension measured immediately after rupture should not exceed 12%
of the original length, with given dimensions. 5. Suppleness may be deter-
mined by measuring the percentage of ash formed in incineration. This
may form the basis for deciding between different grades of rubber for
certain purposes. 6. Vulcanized rubber should not harden under cold.
These rules have been adopted for the Russian navy. — Iron Age, June 15,
1893.
CJUTTA-PERCHA.
Specific gravity, 0.9693 to 0.981.
Weight per cubic foot, 60.56 to 61.32 pounds.
Weight per cubic inch, 0.560 to 0.567 oz.
Softens at 115 degrees F.
Becomes plastic at 120 degrees F.
Melts at 212 degrees F.
Oxidizes and becomes brittle, shrinks and cracks when exposed to the air,
especially at temperatures between 70 and 90 degrees F.
Oxidation is hastened by exposure to light.
Oxidation may be delayed by covering the gutta-percha insulation with a
tape which has been soaked in prepared Stockholm tar.
Where gutta-percha is kept continually under water there is no notice-
able deterioration, and the same applies where gutta-percha leads are cov-
ered with lead tubing.
Stretched gutta-percha, such as is used for insulating cables, will stand
a strain of 1,000 pounds per square inch before any elongation.
The breaking strain is about 3,500 pounds per square inch.
The tenacity of gutta-percha is increased by stretching it.
Where Z)= diameter of gutta-percha insulation, and d = diameter of con-
ductor of copper (both dimensions in mils) the weight of gutta-percha per
knot is -_.
When w — Aveight of stranded copper conductor per knot in pounds, and
W = weight of gutta-percha per knot in pounds, then outer diameter
= V70.4 w + 491 W mils.
If the conductor is solid, then, outer diameter
— V55 w + 491 W mils.
After one minute's electrification, the insulation resistance per knot
of best quality gutta-percha insulated cable will be,
= 750 (log D — log d.) megohms at 75° F.
Resistance of Gutta-JPercha under Pressure. — The resistance
of gutta-percha under pressure increases according to the following formula, j
when R — the resistance at the pressure of the atmosphere, and r the resis-
tance at p pounds per square inch.
r = R(1 + 0.00023 p).
GUTTA-PERCHA. 199
Resistance of Griitta-Pcrclia decreases with Rise of Tem-
perature.- The resistance of gutta-percha decreases, as per the follow-
ing form'-" as the temperature rises, where
R = resistance at the low temperature,
r ■=. resistance at the high temperature,
t = difference in temperature, degrees F. ;
then log R = log r — t log 0.9399,
and log r-logR + t log 0.9399.
Capacity and Resistance of Ccutta-Percha.
The resistance of a plate of gutta-percha one foot square and .001 inch
thick = 1.066 megohms at 75° F. The electrostatic capacity of the same
piece at the same temperature is .1356 microfarads.
The product of the resistance in megohms by the electrostatic capacity
in microfarads, both taken at 75° F., after one minute's electrification =
144.4.
Ratio of D -)- d for strand and solid conductors.
For stranded conductor insulated with gutta-percha,
5=^1 + 6.97^.
d " it)
For solid conductor insulated with gutta-percha,
S
1 + 8.93—-
' w
In which D = outer diameter of cable,
and d =z diameter of conductor,
and W and to = weight of gutta-percha and of conductor respectively in
pounds.
The approximate electrostatic capacity of a gutta-percha insulated cable
per knot is
°-1877 microfarads.
log D — log d
The electrostatic capacity of a gutta-percha insulated cable compared Avith
one of the same size insulated with india rubber is about as 120 is to 100.
Jointingr Cfutta Percha Covered Hrire.
First remove the gutta-percha for about two inches from the ends of the
wires which are to be jointed. Fig. 4.
Next cross the wires midway from the gutta-percha, and grasp with the
pliers. Fig. 5.
200
PROPERTIES OF CONDUCTORS.
Then twist the wires, the overlapping right-hand wire first, and then,
reversing the grip of the pliers, twist the left-hand wire over the right. Cut
off the superfluous ends of the wires and solder the twist, leaving it as shown
in Fig. G.
Next warm up the gutta percha for about two inches on each side of the
wist. Then, first drawdown the insulation from one side, half way over
Fig. 7.
the twisted wires, Fig. 7, and then from the other side in the same way, Fig. 8.
Then tool the raised end down evenly over the under half with a heated
iron. Then warm up the whole and work the " drawdown " with the thumb
and forefinger until it resembles Fig. 9. Now allow the joint to cool and set.
Fig. 9.
Next roughen the drawdown with a knife, and place over it a thin coating
of Chatterton's compound for one inch, in the center of the drawdown,
which is also allowed to set.
Next cut a thick strip of gutta-percha, about an inch wide and six inches
long, and wrap this, after it has been well warmed by the lamp, evenly over
the center of the drawdown. Fig. 10.
Fig. 10.
The strip is then worked in each direction by the thumb and forefinger
over the drawdown until it extends about 2 inches from center of draw-
down. Then tool over carefully where the new insulation joins the old,
after which the joint should be again warmed up and worked with the fore-
finger and thumb as before. Then wet and soap the hand, and smooth and
round out the joint as shoAvn in Fig. 11.
Between, and at every operation, the utmost care must be exercised to
remove every particle of foreign matter, resin, etc.
JOINTS IN CABLES.
201
Joints in Jtubner Insulated Cables.
Preparation of Ends. — Remove the outside protecting braid or
tape, and bare the conductor of its rubber insulation for two or three inches
back from the end. Clean the metal carefully by scraping with a knife or
with sandpaper.
Tfletal Joint. — If solid conductor, scarf tbe ends with a file so as to
give a good long contact surface for soldering. If conductor is stranded,
carefully spread apart the strands, cutting out the centres so conductors
can be butted together, the loose ends interlacing as in Fig. 9, and bind
wires down tight "as in Fig. 10. with gas or other pliers. Solder carefully,
using no acid ; resin is the best, although jointers often use a spermaceti
candle as being handy to use and easy to procure. Large cables are easiest
soldered by dipping the joint into a pot of molten solder, or by pouring the
molten metal over the joint.
The insulation of all kinds of joints is done in the same manner, the only
difference in the joint being the manner in which the conductors are joined
together. Following are some of the styles of joining conductors, which
are afterward insulated with rubber, and covered with lead when necessary.
Seeley's Cable Connectors. —Tbe cuts below show a style of cop-
per connectors very handy in joining cables. They are copper tinned over,
and after putting in place can be " sweated" on with solder ; when dry can
be insulated as previously described.
202 PROPERTIES OF CONDUCTORS.
Insulating- the Joint. — Jointers must have absolutely dry and
clean hands, and all tools must be kept in the best possible condition of
cleanliness. Clean the joint carefully of all dux and solder ; scarf back the
rubber insulation like a lead-pencil for an inch or more with a sharp knife.
Carefully wind the joint with three layers of pure unvulcanized rubber,
taking care not to touch the strip with the hands any more than neces-
sary ; over this wind red rubber strip ready for vulcanizing. Lap the tape
upon the taper ends of the insulation, and make the covering of the same
diameter as the rubber insulation on the conductor, winding even and
round. Cover the rubber strip with two or three layers of rubber-saturated
lead covering-. — 11 the insulation is covered and protected by lead, a
loose sleeve is slipped over one end before jointing, and slipped back over
the joint when the insulation is finished, a plumber's wiped joint being
made at the ends.
Fig. 17.
Joints in Waring Cahles. — This cable is covered with cotton,
thoroughly impregnated with a composition of hydro-carbon oils applied at
high temperature, the whole being covered with lead to protect the insula-
tion. The insulating properties of this covering are very high if the lead is
kept intact.
Metal joints are made as usual, and a textile tape may be used for cover-
ing the bare copper. A large lead-sleeve is then drawn over the joint,
and wiped onto the lead covering at either end ; then the interior space is
filled with a compound similar to that with which the insulation is im-
pregnated.
Joints in Paper Insulated Cahles. — This cable is covered or
insulated with narrow strips of thin manila paper wound on spirally, after
which the Avhole is put into an oven and thoroughly dried, then plunged
into a hot bath of resin oil, which thoroughly impregnates the paper. This
insulation is not the highest in measurement, but the electrostatic capacity
is low and the breakdown properties high. When used for telephone pur-
poses the paper is left dry, and is wound on the conductor very loosely, thus
leaving large air spaces and giving very low electrostatic capacity.
Joints are made as in the Waring cable by covering the conductor with
paper tape of the same kind as the insulation, then pulling over the lead
sleeve, which is finally filled with paraftine wax.
Hundreds of miles of such cables being thus employed at pressures ran-
ging from 500 to 10,000 volts — notably in the Metropolitan district of New
York.
Cost of Straight or Sleeve Joints Insulated with Ruhhei
On rubber-insulated, lead covered cable.
Plumber 1 hour .25
Insulator i hour .15
Helper 1 hour .15
Red rubber 1 oz. @ $1.00 per lb. .07
Pure rubber . . . , 1 oz. @ $2.00 per lb. .15
Grimshaw tape . 1 oz. @ .50 per lb. .03
UNDERGROUND CONSTRUCTION. 203
Copper sleeve .035
Lead sleeve .06
Solder 1$ lbs. @ .20 .30
Pasters . . . . 2 .005
Coal • .10
Candle (for flux) .01
Total . $1.31
Cost of T Joint on Rubber Insulated Cable.
T on rubber-insulated lead-covered cable.
Plumber H hour $.375
Insulator § hour .225
Helper 1£ hour .225
Red rubber li oz. @ $1.00 per lb. .11
Pure rubber 1£ oz. @ 2.00 per lb. .23
Grimshaw tape 1J oz. @ .50 per lb. .05
Solder 2 lbs. @ .20 per lb. .40
Lead T .26
Copper T .075
Pasters .0075
Candle .01J
Coal .10
Total $2.07
UHTDEItOieOUHTJ* EJLECTKICAI, COISTRrCflOI.
Mr. Louis A. Fei'guson, in paper before the National Electric Light Asso-
ciation in May, 1899, gives the results of his observations as to the cost of
laying and maintaining underground conductors. Labor, fittings, paving,
and laying one length "of Edison main tube costs from $5.45 in unimproved
streets', with no paving, to $29.81 in asphalt. The annual cost of supervision
and maintenance amounts to 1.9% per annum of the original investment.
The total cost per duct foot of laid conduit of various types is given in the
following table, where the higher price is for asphalt pavement, and the
lower one for no pavement.
National conduit $16.74 to $57.24
Francis conduit 14.66 to 55.16
Lithocite conduit 15.18 to 55.6S
Camp tile 14.14 to 54.64
Three-inch iron pipe 22.50 to 66.00
Manholes as used in Chicago cost for size 2/ + 2' x 3' from $32.18 to $38.63 ;
for size 8'x8'x 8' $194.65 to $224.72.
I,AW OF B. & S. CflTCIE.
The absence of a wire table may often be compensated for by remember-
ing the following approximate facts concerning the B. & S. gauge.
Diameter of No. 10 wire = .1 inch.
Resistance of No. 10 per 1000 feet =r 1 ohm.
Weight of No. 10 per 1000 feet = 31.37 lbs.
Diameters are halved for every six units increase in gauge No.; i.e., No. 16
has half the diameter of No. 10, and No. 4 has twice the diameter of No. 10.
Accordingly cross-sectional areas double at every decrease of three in the
gauge number.
The gauge numbers correspond to cross-sections and conductivities which
vary as an inverse geometrical progression having a ratio of 1 .26.
204
PROPERTIES OF CONDUCTORS.
FISIlfG EITECT8 O*' E^ECTMC CIRREITI.
By W. H. Preece, F. R. S. See " Proc. Roy. Soc," vol. xliv., March 15, 1888. M
The Law — I = a d §, where /, current ; a, constant ; and d, diameter —
is strictly followed; and the following are the final values of the constant
"a," for the different metals as determined by Mr. Preece : —
Inches. Centimeters. Millimeters.
Copper 10,244 2,530 80.0
Aluminum .... 7,585 1,873 59.2
Platinum 5,172 1,277 40.4
German Silver. . . . 5,230 1,292 0.8
Platinoid 4,750 1,173 37.1
Iron 3,148 777.4 24.6
Tin 1,642 405.5 12.8
Alloy (lead and tin 2 to 1) 1,318 325.5 10.3
Lead 1,379 340.6 10.8
Table Chiving- the J&iameters of Wires of Various IVlateri
als Which Will lie ITuse«l by a Current of Given
Strength. — W. H. Preece, F. R. S. d= (
(I\*P
Diameter in Inches.
.5
Tj5
~
C
g s
0ni
.5 »2
£K
jgg
Jo
i
to
111
ai
Suo
CO
<d e
o«l
III
III
C II
ill
J"
eh£
111
3~
1
0.0021
0.0026
0.0033
0.0033
0.0035
0.0047
0.0072
0.0083
0.0081
2
0.0034
0.0041
0.0053
0.0053
0.0056
0.00^4
0.0113
0.0132
0.0128
3
0.0044
0.0054
0.0070
0.0U69
0.0074
0.0097
0.0149
0.0173
0.0168
4
0.0053
0.0065
0.0084
0.0084
0.0089
0.0117
0.0181
0.0210
0.0203
5
0.0062
0.0076
0-0098
0.0097
0.0104
0.0136
0.0210
0.0243
0.0236
10
0.0098
0.0120
0.0155
0.0154
0.0164
0.0216
0.0334
0.03S6
0.0375
15
0.0129
0.0158
0.0203
0.0202
0.0215
0.0283
0.0437
0.0506
0.0491
20
0.0156
0.0191
0.02-±6
0.0245
0.0261
0.0343
0.0529
0.0613
0 0595
25
0.0181
0.0222
0.0286
0.0284
0.0303
0.0398
0.0614
0.0711
C.0690
30
0.0205
0.0250
0.0323
0.0320
0.0342
0.0450
0.0694
0.0803
(.0779
35
0.0227
0.0277
0.0358
0.0356
0.0379
0.0498
0.0769
0.0890
0.0864
40
0.0248
0.0303
0.0391
0.0388
0.0414
0.0545
0.0840
0.0973
0.0944
45
0.0268
0.0328
0.0423
0.0420
0.0448
0.0589
0.0909
0.1052
0.1021
50
0.0288
0.03o2
0.0454
0.0450
0.0480
0.0632
0.0975
0.1129
0.1095
60
0.0325
0.0397
0.0513
0.0d09
0.0542
0.0714
0.1101
0.1275
0.1237
70
0.0360
0.0-140
0.0568
0.0564
0.0601
0.0791
0.1220
0.1413
C.1371
80
0.0394
0.0481
0.0621
0.06' 6
0.0657
0.0864
0.1334
0.1544
0.1499
90
0.0426
0.0520
0.0672
0.0667
0.0711
0.0935
0.1443
0.1671
0.1621
100
0.0457
0.0558
0.0720
0.0715
0.0762
0.1003
0.1548
0.1792
0.1739
120
0.0516
0.0630
0.0814
0.0808
0.0861
0.1133
0.1748
0.2024
0.1964
140
0.0572
0.0698
0.0902
0.0895
0.0954
0.1255
0.1937
0.2243
0.2176
160
0.0625
0.0763
0.09S6
0.0978
0.1043
0.1372
0.2118
0.2452
0.2379
180
0.0676
0.0826
0.1066
0.1058
0.1128
0.1484
0.2291
0.2652
0.2573
200
0.0725
0.0886
0.1144
0.1135
0.1210
0.1592
0.2457
0.2845
0.2760
225
0.0784
0.0958
0.1237
0.1228
0.1309
0.1722
0.2658
0.3077
0.29S6
250
0.0841
0.1028
0.1327
0.1317
0.1404
0-1848
0.2851
0.3301
0.3203
275
0.0897
0.1095
0.1414
0.1404
0.1497
0.1969
0.3038
0.3518
0.3413
300
0.0950
0.1161
0.1498
0.1487
0.1586
0.2086
0.3220
0.3728
0.3617
TABLES OF LENGTHS AND STRAINS.
205
TABLES OJF JLENCTUKS AND STRAINS IIV gPAIS
or wjlris and suspension cau££§.
By Jolin A. Roebling's Son's Co.
The formulae used in calculating these tables of lengths and strains in
spans of wire are those of a catenary of small deflection. They are given
in Weisbach's " Mechanics of Engineering," page 297 (seventh American
edition, translated by Eckley B. Coxe, A. M.).
In these tables the horizontal strain at the centre of the span is given
The strain at any other point equals the strain at the centre plus the weight
of a length of the wire equal to the perpendicular distance of that point
from the lowest point of the wire in the span. For ordinary snans this is
negligible. For any given wire the longest possible span is one where the
deflection is about one-third of the span.
The effects of temperature on the strains of wires in spans is at first sight
so great as to render the other considerations of little importance. The
table, page 65, is calculated on the assumption that the supports of the
spans arc perfectly nyiu under all conditions of strain, and that the wire is
inelastic. This is never true in practice. The changes in direction in a
pole line afford a chance for the strains, due to a shortening of the wire by
a fall in temperature, to be taken up by a bending of the supports.
If the elastic limit of hard-drawn copper wire of 60,000 pounds breaking
strain be taken at 20,000 pounds, then S will equal 20,000 divided by 3.85, the
weight of a piece of copper one foot long and one square inch in section.
This makes S equal 5.195. Looking at the table of values of S, page 74h, this
value for a span of 130 feet comes between a deflection of .003 and .004. In
the same way the allowable deflection for any other span of hard-drawn
copper could be found, or for any other material, by substituting the proper
terms for the elastic limit and the weight per foot given above. Some of
the tables give data for telegraph wire, poles for which are spaced by the
number per mile, while other tables are for conductors on poles spaced by
the foot, such as electric light and power lines.
Actual deflection of wires of all construction depends much on the judg-
ment of the linemen and the tools at hand.
The following gives the practice of some of the telegraph and telephone
companies in their line construction :
SPECIFICATIOM§ JFOIt STANDARD CONSTRUC-
TION OF HARD-DRAWN COPPEB.
Spans in feet.
5 £^
75
100
115
130
150
200
S _ =3
Sag in inches.
—30
1
2
2%
3%
4%
8
—10
VA
2K
3
VA
5
9
00
VA
VA
3%
*K
5%
10X
30
lw
3
4
5%
6X
12
60
2K
4#
5%
7
9
15X
80
3*
5%
7
83*
11 X
18X
100
*H
7
9
11
14
22X
206 PROPERTIES OF CONDUCTORS.
For spans between 400 and 600 feet, the dip shall he l-40th of the span.
For spans between 600 and 1000 feet, the dip shall be l-30th of the span.
Another company uses 40 poles to the mile, and in the East allows three-
inch dip at centre of spans. In the West, where the variation' of tempera-
ture is greater, 10 inches dip is allowed in summer, and 8 inches in the
winter. This construction applies to both copper and iron wire, and has
been found by actual experience to give satisfactory results :
The following formulae were used in calculating the tables :
(1) S X «j = horizontal strain on wire at centre of span.
<2> »=t + l
>=>b+*m
(4) X = 3S~*W-
(5) x— /3yl — 3j
y-
w
In these formulae
- one-half span.
: one-half length of wire in span.
= deflection at centre in same units as y.
w = weight per foot of wire.
Suppose Ave have a span of 200 feet of hard-drawn copper wire weighing
one pound to 10 feet, and a deflection of two feet or .01 of the span.
« •=(£)" + ••
== 2500.33 +.
(3) 1 = 100 [1 + 1(^)1.
= 100.026 6 +.
21 = 200.053 +.
(4) x = 7501 — V56,205,001 — 30,000.
(4)
T — /30,0(
"->J-
In calculating the table, page h65, the deflection of the line was determined
at — 10° F. by formula 4, the value of S being 30,000 divided by 3.85 or 7,792.
For the other temperatures the length of the wire was calculated from the
following formula :
Length = I (1 -}- .000009 3 t )
Here t is the difference in temperature in degrees Fahrenheit.
By formula 5 the deflection corresponding to the new length was found.
The coefficients of linear expansion for each degree Fahrenheit are
follows :
Copper, .000 009 3.
Iron, .000 006 8.
Lead, .000 016.
TEMPERATURE EFFECTS. 207
TEMPEBATURE EFFECTS IEf §PAWS.
i
Temperature in
degrees
Fahrenheit.
Ph
_g
—10°
30°
40°
50°
60°
70°
80°
90°
100°
Deflections in inches.
50
.5
6
8
9
9
10
11
11
12
60
.7
8
10
11
11
12
13
13
14
70
1.
10
11
12
13
14
15
15
17
80
1.2
11
13
14
15
16
17
IS
19
90
1.6
13
14
16
17
18
19
20
21
100
1.9
14
16
17
19
20
21
23
£4
110
2.3
16
18
19
21
22
24
25
26
120
2.8
17
19
21
22
24
26
' 27
28
130
3.2
19
21
23
25
26
28
29
31
140
3.7
20
23
25
27
28
30
32
33
150
4.3
oo
24
26
28
30
32
34
36
160
4.9
23
26
28
30
32
34
36
38
170
5.5
25
28
30
32
35
37
38
40
180
6.2
26
29
32
34
37
39
41
43
190
7.
28
31
34
36
39
41
43
45
200
7.7
31
33
36
38
41
43
45
48
Hard-drawn copper wire, 60,000 pounds strength per square inch.
Strain at — 10° F., 30,000 pounds per square inch.
The following tables give the dip in feet and inches of No. 0 B. & S. cop-
per trolley wire between spans 125' apart, and the strain in pounds for vari-
ous temperatures :
Initial Maximum Strain SOOO I<l»s.
Temperature F.
Dip.
Strain.
—10°
3.7"
2000 lbs.
0°
9.7"
774 "
32°
V 6"
415 "
50°
V 10"
340 "
70°
2' 1"
300 "
90°
2/ 4//
267 "
10°
3.7"
2000 "
32°
V 2"
534 "
50°
V 6"
415 "
70°
1/ 10"
340 "
90°
2' 1"
300 "
32°
3.7"
2000 "
50°
V
623 "
70°
V 5''"
440 "
90°
V 10"
340 "
From the preceding tables the proper height of eyebolts can be deter-
mined for various spans and temperatures with a given minimum height of
trolley wire above the track.
208
PROPERTIES OF CONDUCTORS.
Sag's and Tensions for Suspended Wires.
The tension when the temperature is lowest, i.e., when the strain is great-
est, should not exceed one-fourtb of the breaking strain.
The sag varies with the material, but not with the gauge; the tension
varies directly with the weight per foot of the wire.
d = VM(L-Q.L=f4M'. t
' 8d
also,
I = span ;
w = weight of unit length ;
d = sag (or dip; ;
L = length of wire in span ;
t = tension;
w for 400-lbs. Iron = .075758 lb. per foot.
" 150 " Copper = .028409 " "
" 100 " " = .018939 " "
Coefficient of expansion for iron :
Coefficient of expansion for copper :
.00000683 per deg. F.
: .00000956 "
TABIE OF TBJarSIMB STRESftTH FOR COPPER
WIRE.
«h
<H
«H
w.
O
o
cc
<%
J8
j»g
,d
ffl .
.£Pfe
•S°t3
PQ
2°^
^■3
tpbJO
^fl
CD
? §0
■S P
^o
bc-i
bog
3*
2%
o
is
'%■<
o
sa
%<
N
0>
£
N
<D
w
PQ
PQ
<£
m
m
Lbs.
Lbs.
Lbs.
Z&s.
0000
9971
5650
9
617
349
000
7907
4480
10
489
277
00
6271
3553
11
388
219
0
4973
2818
12
307
174
1
3943
2234
13
244
138
2
3127
1772
14
193
109
3
2480
1405
15
153
87
4
1967
1114
16
133
69
5
1559
883
17
97
55
6
1237
700
18
77
43
7
980
555
19
61
34
8
778
440
20
48
27
Length of wire and deflection.
209
o » o o » ho M M O M 'm LC O OO O t« H O N b CO » OO O (
ro t- = ■ ) - o i- ~ l: — l- co i-ryn-i;:!; x o oo ■ — o <
t- © cq q -* q co Xj l- ci , — -r — ■ co :-. x 1.0 co x . : x '_ i.o co ■/:
d ?i h -j -^ , ;i -t -i ri :o . i- ^ ^ - -i t~ i- oo" ~. co oi co co co d I '
co i~ -h co ci •— o _. /. x i- i - co -- ■ ■
*r
5 t4 <n ■* co cs c
ooH^co'^HOOHiiNaoocoojMoo^HO
i- — r. co :- — ~ i- i- :- — - i- co -f :: — ~ oc X l-
co : i s- x t-i q oo -f co — i i-t::t co co oo co i.o : i —
!OHldd oo' 1 i-< I- oo Co ci C i co -- ' :0 d i -'• i 0 0 i ~ 7. co"
l- i- co co l- il* -f -* co co :: :i:i:r.i _„,_,-, co co
o|h^,.
o © co oo o t-
s Hoocomi>
f oi ci i:o lo x oi i- oo ~ - -: : i c co co — — o
; /: oo t:i;.-.[. -.-t::;!- ~ x i - - i.o i o
-os ht o i . : -)-_ co. q :~. ci to q x t-i l- -# i-j ©
Jdolrtt-eooLi d ci — ' cd d 1 1- io o i © xj d
3 CO ITS I LO -+ T CO CO CO 0 1 0 1 0 I 0 I >-i ■- — — _ O
CM <-H -* CO 00
CO 0 j 0 I --i ■
~ (0 ?' ? f1
- - :
100a
CO CO 'X uo -f
x ;-o co — co
HM50CS CM
- o: co ? i Lc
i oo o o oo
> P i-i s ;2
oj c o, 4 I;
g 4 8 s
oo ^ fi* co co
in co CO CO L.0
ed|i^sd
oj d oo co
CO OS — I «*
oj cs d co d
© OS O CN JO c
L0 CO X X CO
" io od ci
~ ^ -I- ~o ':
?^8 "*°
CM S CS o CM
' teas
~ oo /: x f- i~
COtrtOOl-
-* oi d l- id
gnSoa
01 01 01 01 01
t — i co o io>
^^'88S
Z. ~ OJ x -
r. i - .-:' : .
~ ~ '- ' ~ '.
ON-f oco
-h co co co oi
HfflOOOH
23 5 id Si 5
01 CO CO T*< oi
t- -#" oi d t^ io
ssi^a
10 01 CO CO CO
SgS8!5
CO t- IO CO CM
fe te t- ■> t-
-
t>TjH(NOI>lO
o-tqi?
CO CO 01 O X
^8SSc|
CO UO CO 01 H
O CO O O CO
p p & s a
UO -* CO CM i-l
CO CO CO CO CO
OCONOOO
'o^lcolSJ
^322Sdo
M O 01 I-
• = '-.' z
•fHodo
Ol Ol 01 01
? oi oi oi oi
5COOO CO
•5 P 12 S :2
10 i.O -H CO CO
CO CO CM 00 id
iS ■* -+i co co
:-;v,. 7jh
^?^a
« i> n o i> co
t-^oidt^id
CO 1.0 -+ 01 01
-1 01 01 Ol 01
ClOOOO
--j co io x oi
c^cm322
^OCOiOiC-*
OC0OOC0
J* rt< co eo cm
oocqtHco^
o eg c-i oo" id
J2 -*1 -* CO CO
o oo t- co q
CMCMC^
MONO
OOC5C0
q^ 388
oi oi oi oi oi
= =3^
OTtHOUOO
-*' T-i d os d
ol^olo^
i§8^8
:8Sc!
COCO 10- 00 CO OH
M CM CN CM CM CO CO <
l?0%
U0> CO t- 00 OS
illll'
US""
©cot- oo©
nidrid00
co^c?8^8
t^ -* CM © t^ g
210
PROPERTIES OF CONDUCTORS.
ft
fi-N
Sg
sa
0 ft
3 g
ft a,
ui sxredg
O rl Ol Ol CO
60066
O -H <N Ol CO
00000
S38S
co co o -
HNW^ liO
5 OCO
DOOOO
Ot>MfflO
t> OS O r-H CO
g^S p-®
00 CO op
60066
So'SSo
1-1 CI CO tH m
SSggS
CIOICOCO^
S2922
NLOMOM
OOO rH T-i
tH (M CO "# IO
■■#0001 coo
OOOOH
66666
fflMOOM
OOOOO
Sg8§g
O ^ Ol 01 CO
qqooo
tH 01 CO ■<* 10
co oi co -h o
O-IHCl CO
qqoqo
66 666
N LO 00 o n
qqq q q
66666
1-1 (N co -# m
00c
o^oooo
o co co o to
00006
g|tLOgg
qqoqn
co t- co o o
KQOrtW
n ci n 5 S
t- co co q q
dp'odri
C0-+001-1
LO CO t- t- 00
6 6666
-# o o UO C£
2S22S
CO 01 -H !>• O
UO CO 01 L-j CO
CO CO -# -# -*
32222
Th CO 0-1 CO o
01 01 CO CO CO
- :i ri ?'] :
§§Sii
00000
CO l^ CO CO O
S383S
oqqoo
LENGTH OF WIRE AND DEFLECTION.
211
tocootoco
3§3838
OHNNM
t-*H80
t- lo m o oo
d^d coco
i-IOI C0<# 13
31 I3 00OM
d th oi oi co
1-131 C0rt< 13
1-H31 O0-# 13
lOOLlOO
i-l 3) CO -# 13
13 3 l- O 13
Tf Oi CO 00 <M
o S d 13 S3
(M 13 CO O CO
nooejo
co co o co co
2 S 9 d rf
HNC0°iO
co c-i co T* o
(M 13 00 O CO
6J6 jo"
1-131 CO *# 13
•%99£ I OOOOO
in su^ds I rH ^ M ** ^
SOOH-fO
- .-? 3 _; : i
- L- 1-; CO O
idi>» d
h q S i> ffl
CO C- CO COO
CO CO r-J OS L-
CO t~ CO C5 O
CO 13 X O 01
i-i co t-j t- oq
CO CO tH -# >3
§1111
M3gO«
i-i oi 3! oi eg
TH CO C5 i-H ■*
cot-oacid
OI 13 t>; CO H
CO t- 00 00 O
OOOOO
Ills
0 ^ 13 CO
^ 01 -+ 10 CD
bhi- jo x»
i-i 31 CO -* 13
i-i OI CO -* 13
13 O 13 O CO
COrHCO CO t-
*j5 13 13. d co
i-i oi ot -r 13
;! 3 ~.
$§
^co^
CO O CO 00 O
OS 3J ■* !>; O
oi co co oo •*
CO CO i-J CO CO
01 31 00 CO CO
t- CO OC1-C
CO 13 00 © 35
Ah 31 CO *# 13
GO 31 ^ t- O
£hco°> CD 00
888.SS.
• ~:. '- i.
t2cOC5oS
i-t rH i-l c-1 31
cocdSt???
oo ■* 13 d t>
2||3S
3113C0O00
C3CDC^C0CD
IS§1S
§1111
31 13 00 O 00
CD CO 3 CO 13
00 00 Tf CO -*
oo oo d d d
S522S
13 13 13 d d
0 O CD 00
CO 31 00 -# O
^cqoqSoo
ooooo
212
PROPERTIES OF CONDUCTORS.
H
to
M
:
to
-
s
s
SB
is
A
H
g
«4
ft
o
H
H
n
coeioi-H i-h Iddososci
38S32
doooocot^
x oo oo oo t-
rlOCOO
COCO CO CS
Tt< rHOOlOOl
tJ i>: d «o CO
cococ- o-#
rHCS t> COtF
CO id id lO id
222gg^
COCOOCSO
id id -* ■<# ■*
n q a i> w
£833
CO CO CO CO CO
cioioioioi
t- -jj CO CO CO
HOO-.OSN
COCOoioioi
^ si <*> :* «> «£ oi co © io -h co c« oo ■#
HOOOOt- CD CO LO LO -f -t1 CO CO CM Ol
m'NHi-"h HHrtrtrt rt'r-irHTHr-?
33S3S 83S38|8S3g88
Klt^Nltnto Ico co co co co id id id id id in
t^t>t-cococococococoUoiomioioio
cS-jfci
°< cn S3 8 o
^-*tJ<c
CO CO CO CO CO
•#10t-OM
I -H © CO CO © i
i o n a a i-fooco
■ CO"*(NOC500CDlO
icocotocoidididoid id id id ■■*< •*
mooioh oo lo n h q
O oo i>- iq •* c-j t-j o os oo
) CO OS CO-*
iid>*n5^
i N a n h
> CS 30 c- t-
> oi oi (N oi
Ht-n»io
I N (M N N O-. I
> © © © © ©
°-«>8gg
odood
q rjj o iq o
^ridoiq
OICNOI O
HOOSMOO t-t-OOLO
2%
0^<M COrf< 1
l COt- 00 OS OHNK
I O) OI CI O) CO CO CO W
i-i ri tj< in c- ©
t-MO
L- q CO
CO CO CO CO CO
CO CO CO CO CO
CO CO CO CO coo
OS 00 00 t- CO CO
oi ci oi oi oi oi
■* t— t-i m o -f o lo o io h
q --. i-_ -f_ -* co oi w?j«^
ci oi oi oi oi oi oi oi oi oi oi
O 00 CO CO -H
© OS t> W -H
lO CO — < CO CO
q o o cs os
HHHOO
OS t^ LO •# OI
odood
• mcoooocc
■* oi o oo co I
P.cqqqqcc
© © © © © C
COOIOOSOO t- CD lO -cK CO
i-OiO 1-0 -H ■# -f -cM -t< -V -f
i ^^Jh^oc
■■^■MHMI^I^^
DEFLECTIONS OF WIRE.
213
o ©©©©
CO CO § CN ©
Tfi id © t> 00
QOOOU1
'rHCN COCO
ooooo
© o © © o
z> ©©©©
= © © © ©
D CN 00 •+ ©
' rH i-i CM' CO
©©©C©
' rH t-i CN <n
§§§§§
iq © o © iq
* -A A cn oi
©© © © ©
L~ © 1 * © ' ~
Th OS CO 00 CN
©O© O©
n ©-©?=!
j< ># id © c-
© © © © ©
co •* id id ©
11111
CO -# •*' id ©
©© ©© ©
cd co ■* -#' id
33838
© W © LO ©
i I ,- ?
HNNNM
©©©©©
©© © ©©
© © © © ©
© © S l> CN
©©t>t^c6
©©©©©
S © S © lo
© ©©©©
i- © i- © ■-.
oi-^oqcot^
■* id id © ©
©©©©©
1~ © 1.0 © 1-
00 CN iq © CN
CO "#■*'"* id
OO©©©
© 1.0 © i- ©
Ifl t>; © CN iO
A HNfifi
S3g§S
CN «# © 00 ©
HrtrtHN
©o©o ©
i-H rH i-l CN CN
i-l CN CO -# lO
©©© ©©
c © © © ©
00 © -V CN ©
©©©©©
© t- »q <N o
CN CN CO tjh id
iiiii
-i rH c-i co n?
sssss
■* ©. t-co©
© A r-5 CN CO
©© © © ©
os © © >h c4
6 os os © r-j
© ©© ©©
~ ~ ~ ~ §
CO 00 OS OS ©
©©©© ©
Iffl UO © © t-
©©o©c
-*ididid«
©© ©©©
© i.O © 1 0 ©
ocMist^q
■* A ■* <# id
© © © ©©
<M tJJ © CO ©
CO COCO CO"*
-* lS E~ O0 ©
CN CN CN CN CO
©©©©©
©©©©o
©t>co©©
©©©©©
214
PROPERTIES OF CONDUCTORS.
<M ■# CO 00 O
ooooo
oooo o
ooooo
ooooo
ooooo
ooooo
ci -* <d go o
ooooo
00 § °< CN 8
88888
00 'O -p CI o
ci^coidt^
r-i CM (M (M C3
§88s
ssssi
ooooo
8S8S8
oi 6 oi co id
ooooo
— O O - ~
-t< CO 01 CO q
rH C-i Th 1C t-
o o ooo
ooooo
1C CO GO OS rl
CO CO C5 CM LO
rHC3C0"ldcd
22292
ooooo
88888
■># id co oo oi
ooooo
S3888
h e4 co •* co
ISSS
t-OOOOd
ooooo
SP92S
tMCN CC#m
t-i <M CO •* LO
OOOOO
S 8 § 8 lo
tJ< tt CO M C5
OHcqCO-*
OOOOO
SCO t-fflio
" rH OS CO TJH
OOOOO
Hcicc-#
38838
OOHNM
OOOOO
2S8S
TABLE OF STRAINS AT CENTRE OF SPANS. 215
II
a*
|s
«3
■r--iZZ
© o © h © © oi -3 n? £ i '
T~£ ?"- T- -v1 y-
© E~ O -f ©
— ^ — ■ i- —
; x -^ -/. ©
.5* ocooc
-w X X p -S
_ ^ 5 co >o
CO r-t O 00 L-
co co co on <n
ui steeds
•9ITW
-3 © 5 lo i - icLoo i- -
'^-Z^l
© co o © oo
-: — - i- -r
© CO LO 00 01
i-i co* lo' © rj
CO CO 00 l~ t-
Co oi oi co lo
o © © cn" in"
.-J P P Lo '-2
SqcMoq oji
i-i m in x g <* i
•# rf ^ t* ■* it? tF K co :o j co co co co :-; :
-f -T <* » CO I rl I- r-
' -f o © -+' oi co' r
C1HQ00 l-B3
*h 00 ©©GO©©
; " 00 ;J ^ Cj
co © l- co x ci
J © L~ © L-
X © CO CC -f
OI i-H Ci L- ©
CO CO O O LO
0 rti IO t>
CO 0.1 0J LO c
© ci oi x' x
cj p :i I- ::
x -t © :;
l^oco
quoco
© t> ■* co >o
3 -s q: :•:- u-
CN OI OI OI 01
co r ". :o
© 01 -+1 Ci
. Ci £ 10 "+
■* CO 00 00 00
§ joi "? ^ if'
-*■ — co :
ir '•"■ -" [
ONOtHCO
~ 'C- 2 ,x ,'i
co t- o CO CO
o-pqoq
SSSScS
01 © L-; cn in
§ h o o ci
MHOl CO
© ci CO t~ *3
2 a te I1 .-
^OOOiOCl
>-; co lo i> to
onoioK
lilll
oi o lo m o
~. ™ L" '-'-. -
(0 0 1 X 1.0 0
io" 01 CO CC 01
X CO X CO ©
■# ■* LO 00 Ci
O^COOCO
P S te S £3
- i' ," '-
sS^coi
O — 1 CD © 00
© OI 00 © LO
LO LO LO LO TH
©00©©00
O0 00 00 CO CO
goiolSS
L0 LO © L0 LO
© •+ £.-r c
CO CO © CO CO
: j b" x co ~
©lOtH ©©
© 00 © 00
© 00 C^ CO ©
'"= = ="i r- ~1
: ■■ •: i ~ oi
00©COCi
zi ^ co go ©
©CiCOCp
© t- © I> ©
© -+t t^ r- ItH
© 00 ■* t- CO
co© t-o<#
CO CO CO CO CO
©©©©C0 0(
i3gc*S
i o; -r oi oi
©-H©C0©
oi •* co lo
co c. c. x
Ol g LO CO ©
© 00 CO CO ©
10 X — i0 CO
■^olol
COLO CO t-^©
ggocgco
^-cH 00 00 00
-1 01 01 c
: ^ L- op Ci © .
1 cs © S £J ^
©' CO 00 LO © ©' '
CO © © © LO ©
OJ C_l -+ X 0(
• oo io © o in
5 ©" oi r-5 w
I ©CO©©
^ ^ •* LO CO ©
© CO © CO © i
: io ^- co '-.
) 00 CO CO ©
1-B
co^
£322©-!=
216
PROPERTIES OF CONDUCTORS.
.2
0)
O
US
©
rH
s
q
§
CO
8
1
CO
o
q
«
s
q
q
1
8
•^98,
i ui Sl
reclg
C co 13 :■'
" oi :■:
OOOOC
©O-H rHrH
go t- co <3 -t
--. i- — i- -
thOItJhuoc:
©31 CO lOH
00 CD -* CO rH
13 i- t>; CO ©
CO L- 13 ■* oi
o co o 13 co
83mSS
CO t- rH 13 CO
-# CO 31 r- ©
CO 01 i-i © ©
£2 £■ ^ « 55
© © 01 -t- 13
3^8
^3
CO CO 13 CO rH
OH^CO*
qqq q©
dddod
88£88
13 O 13 q 13
C-i <3 t^ © 35
CO CD © 01 13
CO CO O CO CO
OOHrtH
13 d i3 d gi
o o o o o
rH 31 CO 13 CD
qqqoo
de'eidd
SK88S
33S
q t- CO 13 CO
OCO CO O CO
oi oi oi co c-
OO ooo
difloia'd
10 l_- © 01 o
CO-* 13 13 CO
O rH CO 13 CO
O OOOO
dodoo
gjg§§§
ooooo
tOt-MOO
rHOcOCDiO
C5COCOOCO
© © go j> ©
5=C« 0*1
CO O rH 00 13
13 O 13 d 13
t- q oi 13 l-
- l~ ~ l~ ■'■
•v oi rid CO
co -r oi o l-
3. H CO 10 CO
rH 31 31 31 31
co oi co q 13
rH O CO CO 13
os q o h oi
6l 31 31 31 CO
rH © 00 CD 13
OO O rH31
.:
0 CO CO o-
OOOrtMlt
wbhi;q
loo3»..
r* 13 13 13 CO
©©CO© _
qqqqq
t- O 31 13 ^
rSgSSel
qooq^
odd d
CO 13 CO t^ CO
TABLE OF STRAINS AT CENTRE OF SPANS.
217
rtCOQtSOO
CO 00 l~ © UO
L~ IQ CO rH Ci
HWLOOOO
CO CD © CO ©
d 06 oo t~ ©
•h co ia t> o
CO © 8 CO §
00 © © CO ©
id d d d d
(M IC t- O CM
N O 00 rt N
LOO«HO
oq i>- lo >* oi
CM O 00 rH CO
i- CO 10 — X
cooo:;o
rH ci co d cd
co co o ci lo
?5^5?
o q S S oq
d © d d d
10 c l0 c lO
co© © co©
ct co co r: to
oi lo t~^ d oi
CO 01 X lO —
1-CTHtNOO
ills?
© d •# ■* co
i- CO L0 l- c/
CI t^lOCOr-
d d oi io y
^ •- ^ ~. o
CO CO OI ■* f
~ = '/ '.- ",
co .-. - ' i o t^
i-l th CM CI O
-i oi ci oi co
©■* ,-tc5 t-
tj5 d d i-i t>
CM 01 OI CO CO
©©co©©
0 g CO IO CO
d oi co d t-^
10 ~ CO L- i-i
01 CM CO CO TJH
~ co co co H
01 t- OI CO CO
f-MOOCl
CO "# LO IO CD
CO " CO 10 CO
©COCO t-CD
£©:§£©■
oi oi rn o d
CO oi OI CM CM
CD O CO CD O
© 0 1 -t- CO 00
COCO CD^CM
t-h co d d ci
C1 <M CM CO CO
CD O CO CD ©
JOrHCOriCO
cocococo^
CO CO Tin ■* •*
f^^
d CO ^t % 01
© IO IO ^ CO
©<# Cl©O0
eg d ci d d
CI CI CO CO c^
decoo t^d
CO L0 t^ CO 2
CO CO CO CO TM
CO 01 ^t LO £
CO CO rO c~ io
CO CC*Tt< r}<
-^ChcOh
i^ii^
© CO © © CO
© 00©rH CO
h ci d d ©
© CO CO CO. 01
© CO © t^ LO
COt-;©©^
ci co d d d
© CO © rt CO
c©o© ©
CO © © CO ©
lo qtoHto
CO CO 01 CO 10
•1)00,3; TIT su-Bds
opooo
218
PROPERTIES OF CONDUCTORS.
^ x :o!-:i
Ol rH L- OS CN
t^ rh i-5 06 ©
t-^ lo oi ©' co'
OS 00 I— © LO
I- LO -0 i-l ~j
OHNnn
noowo
co — ■ lo co i-H
LO rH l- CO OS
co t> lo ■* c4
HMLO I- ©
rH CO W CO CO
os oo t^ jo jo
?..' j';?',?
"oi^
55 -2 2 r-5 ■;
©oo©©co
oi in co ©' co
© Ol CO -)■ rH
TH:ot --2 co
CO © OS Ol LO
CO © OS CO ©
O0t-©LOrH
WgHOO
ti5 od s4 © ©
I- 10 0.1 CO t-
3335
oo©ioco-*
lOHt^mo;
i£thi>coq6
CO CO © CO SO
lo - © 'ol x
OS © oi ©' id
00 © -f © ©
L- © © © O
CO CM r-H © OS
^ CO i.O oi CO
© rH LO © •*
© rH LO © -H
00 © I- id Ol
rH O O © O
rn o =s : i ©
92 ?? 3! ^ S
h © 00 L- LO
LO © © I- CO
rH CO LO I- ©
LO © L- CO ©
'-'- t ;
© t- CO © ©
©© CO ~ ©
SSoo'S©'
(OOOTHTjHtd
LO CM © t- LO
11111
-ji © © rH t^
OS rH Ol rH lO
— © X © 10
0OSLO©©
3HCOLOH
rH t- 01 00 rH
10 •+ -J CO CO
lo oi os ©* oo
x co i-oi ..:
x co i - o i -
© © T-H •<* «
© © ■* rH Ot
■H 00 ■* © ?
-J os t^ lo oi
© © 00 © ©
rH © CO © LO
■* © m th t-
-#COrH©00
CO © L0. © ©
t- LO rf 00 rH
00 tH LO © t-
© LO rH g 00
"I S3 gig
© rH OI © rH
OI •# © 00 rH
- ir © © ©
©CO©©©
CS ©' rH r-
© LO rH © Ol
1^ CO © rH O0'
-H© t-OS©
CO © © rH ©
§8S8g
0 © © CO ©
- io © !- co
© co © © eo
oi lo co © oo
Ol 01 Ol 01
O -H © t- 0-
o©oo© o
V&$'<
Ol — I © CO t-
- i •- - co i ■
: © i - i - i ■
.5 x> oi © c
01 CO 10 © -/
"' Ol Ol Ol c<
© CO LO © <
© 00 i0 C l
L0 -H Ol rH C
rH © 00 © L0
-H © LO -H --
00 rH GO © ©
COCSTtH©©"
HHCICICM
LO © 00 CJ1 rH
■IBQjl m streds
© t~C0©©
©©©oo
BREAKING WEIGHTS. 219
jtfotes.
Comparative Resistance of Woods (Addenbrooke). The
measurements were made along the grain by inserting terminals two inches
apart in sound, dry, well-seasoned pieces of the woods, each piece being
3" x §" X I". Other tests across the grain gave results from 50 to 100 per
cent higher.
Wood. Megohms. Wood. Megohms.
Mahogany ... 48 Lignum Vitae . . . 397
Pine . ... 214 Walnut . . . .478
Kosewood . . . 291 Teak . . . ' 734
BREAKI9TG WElGfHTI COPPER AND SIJLICOI¥
BROAXE WIRES.
Breaking weight hard-drawn copper wire per 1000 C. M. = 47.12 lbs.
Breaking weight soft-drawn or annealed copper wire per 1000 C. M. =
26.69 lbs.
Breaking weight No. 0 B. & S. hard-drawn copper wire = 4973 lbs.
Breaking weight No. 0B. & S. soft-drawn or annealed copper wire =
2817 lbs.
Breaking weight silicon bronze wire per square inch, 80920 lbs.
Breaking weight No. 4 B. W. G. silicon bronze wire, 3600 lbs.
Horse-power lost in copper conductor at a density of 1000 amperes per
square inch cross section, is equal to the number of thousands of cubic
inches of copper -+- 10%.
— By Prof. G. Forbes
rzheensioxs of cross arm§.
Regular size, 3J inches X 4J inches, IJ-incTi holes.
Special size, 4 inches X 5 inches, U-inch holes.
2-pin, 3 feet long ; 4-pin, 4 or 5 feet long ; 6-pin, 6 feet long.
CABLE TESTING.
Cables — I nderg-iound ami Submarine.
The majority of the methods of tests and measurements given herein are
applicable to both aerial, underground, and submarine cables.
I nsulation Resistance,
Direct Deflection iVKethod, with Minor Galvanometer.—
This method, Fig. 1, is generally used in this country in underground and
submarine work.
^XXXXXXXXXXXXXXXsS
CABLE
Fig. l.
a and b = leads.
G = galvanometer, Thomson or D'Arsonval, mirror type.
£zr shunts for G, usually i, TJ-5, TCfJn0.
B = battery, 20, 50, or 100 chloride silver cells.
R = resistance box of 100,000 ohms.
BK=. battery reversing key.
SK=z short-circuit key for G.
First connect a to lower contact point of SK. and take constant of G,
using iooo shunt, and small number of cells, say 5 (depending upon the sen-
sitiveness of G), with standard resistance R only in circuit, b being discon-
nected as shown. If 5 cells are used in taking constant, and 100 cells are
to be used for test,
Constant :
G deflec. X shunt X R X 20
= megohms.
1,000,000
After obtaining the constant, measure insulation resistance of lead b, by
joining it to SK instead of a, disconnecting the far end of b from the cells.
The result should be infinity ; but if not, deduct this deflection from the
deflection to be obtained in testing the cable proper. Now connect the far
end of b to the conductor of the cable, the far terminal of latter being free.
Then open S K carefully, and observe if there are any earth currents from
the cable. If any, note deflection due to the same, and deduct from bat-
tery reading if in the same direction, or add to it if in opposite direction.
Short-circuit G with SK, and close one knob of B K, using, say, the j%n shunt.
After a few seconds open SK; if spot goes off the scale, use'a higher shunt.
If deflection is low, use a lower shunt. After one minute's electrification,
note the deflection. The result may be worked out from this reading, but
the current should be kept on for three or five minutes longer, and readings
taken at end of each minute. The deflection should decrease gradually.
At the end of the last minute of test, open BK, and allow the cable to
220
CABLE TESTING.
221
discharge fully. Then close £A~ and press the other knob of BK, revers-
ing the battery. After a few moments, open SK, and take readings of deflec-
tions as before.
The insulation resistance
where d is the deflection at a gi
constant
ren time, and S is the shunt used. If no
shunt is used,
Note that in the above constant, the ordinary constant is multiplied by 20
for the reason that the battery is increased '20-fold, or 5 :: 100, In case the
same battery is vised for testing as for obtaining the constant, then
constant :
G detlec. X S X R
1,000,000
If there be no earth currents, the readings with opposite poles of battery
to the cable should not vary appreciably at any given minute. Pronounced
variation between the readings at given times and unsteady deflection indi-
cate defective cable.
Insulation Itesistance l»y Uletliod. of 1a»mm of Cliarg-**.
The insulation resistance of a cable or other conductor having considera-
ble capacity may be measured by its loss of charge. Let one end of the
conductor be insulated, and the other end attached to an electrometer, in
the manner shown in Fig. 2.
ELECTROMETER
Fig. 2.
Let It =. Insulation resistance in megohms per mile.
(,'= Capacity in microfarads per mile.
E = potential of cable as charged.
e =z potential of cable after a certain time.
Depress one knob of key K, and throw key K' to the right, and charge the
cable for one minute; then throw key K/ to the left, thus connecting the
cable to the electrometer. Note the deflection E. Noting the movement of
the spot for one minute, take reading e at end of minute, then
26.06
4 ~~ C log E
If an electrometer is not conveniently at hand, use a reflecting galvanom-
eter, and after charging cable as before, take an instantaneous discharge,
noting deflection E due thereto. Recharge cable as before, then open K'
and at end of one minute, the galvanometer having been disconnected from
cable in the meantime, take another discharge-reading of cables, and apply
the same formula as before. If a condenser of low capacity be inserted be-
tween K' and the galvanometer, the latter need not be disconnected. The
advantage of the use of the electrometer is that "the actual loss of potential
of the cable may be observed as it progresses.
222
Testing- Joints of Cables by Clark's Method.
In the figure (Fig. 3) the letters refer to the parts as follows :
Fig. 3.
G is a high-resistance mirror galvanometer.
S is the shunt.
/.", is the short-circuit key. It may he on the shunt hox or separate.
K,/ is a reversing key.
KN/ is a discharge key.
B the hattery, usually 100 cells chloride of silver.
C is a I microfarad standard condenser.
The joint to he tested is placed in a well-insulated trough, nearly filled
with salt water. A copper plate attached to the lead wire is placed in the
water to ensure a good connection with the liquid. The connections are
made as shown in the figure, one end of the cable being free. To make test
close K /n for a half minute; then release it (first depressing one knob of
key K„), thereby discharging the condenser C, through the galvanometer,
and note the deflection, if any. A perfect piece of cable of the same length
as the joint is then placed in the vessel, and if the results with the joint are
practically equal to those obtained with the perfect cable, the joint is passed.
When the deflection is very low, it is evident that the joint is sound, and it
may then be considered unnecessary to compare it with the piece of cable.
It is very important that the trough and apparatus be thoroughly insulated.
Electrometer Method. — This method possesses the advantage that
it dispenses with a condenser, and thereby avoids possible misleading re-
sults due to elective absorption by that instrument. The connections for
the electrometer test are shown in the accompanying figure (Fig. 4).
ELECTROMETER
Fig. 4.
B is a battery of about 10 cells.
B, is a battery of 100 or more cells.
As in the preceding test, it is here highly essential that the insulation of
the trough should be practically perfect, or at least known, so that if not
perfect, proper deductions may be made for deflections due to it alone.
To test the insulation of the trough, depress Kt, and close switch S. This
CABLE TESTING.
223
charges the quadrants of the electrometer, and produces a steady deflection
of its needle, and shows the potential due to the small battery B. Now
open switch S, still keeping K, closed, and watch the deflection of needle
for about two minutes. If the insulation of the trough is not perfect, there
will be a circuit, so to speak, from the earth at the trough to the earth
shown in the figure, and a fall in the deflection will be the result. If, how-
ever, the drop of potential is not more than is indicated by a fall of two or
three divisions, the insulation of the trough will suffice. The electrometer
is discharged by closing switch S, which short-circuits the quadrants, K,
being open at this time. The joint is now connected as in the figure.
Switch .5 is opened, and key Ku depressed, thus charging the joint with the
large battery Br This produces a quick throw of the needle, due to the
charging of the joint. Next, keeping Ktl closed, discharge the electrometer
by closing switch S for a moment. The switch is then opened, and if the
joint is imperfect as to its insulation, the deflection will rise as the elec-
tricity accumulates in the trough. The deflections are recorded after one
and two minutes, and are compared, as in the previous test, with a piece of
perfect cable. The results obtained with the joint should not greatly ex-
ceed those of the cable proper.
IMrect Reflection Iffethod. — The insulation resistance of joints -
may also be tested by the direct deflection method already described, and
when great accuracy is not required, is preferable, owing to its simplicity.
Capacity.
Capacity tests are usually made by the aid of standard condensers. Con-
densers, or sections of the plates of condensers, may be arranged in parallel
or in series (cascade).
Arrang-ement of Condensers — Parallel. — Join like terminals
of the condensers together, as in the figure ; then the joint capacity of the
condensers is equal to the sum of the respective capacities.
Capacity, C= C + C, + C„ + Ctll.
mi mi iiu liu
Fig. 5.
Condensers in Series or Cascade. — Join the terminals, as in
Fig. 6. The total capacity of the condensers as thus arranged is equal to
the reciprocal of the sum of the reciprocals of the several capacities, or
Capacity in series = 1
Fig. 6.
Condensers are now constructed so that these two methods of arranging
the plates of a condenser may conveniently be combined in pne condenser,
thereby obtaining a much wider range of capacities.
224
Testing Capacity l>y Direct Discharge. — It is frequently de-
sirable to know the capacity of a condenser, a wire, or a cable. This may
be ascertained by the aid of a standard condenser, a trigger key, and an
astatic or ballistic galvanometer. First, obtain a constant. This is done by
noting the deflection </, due to the discbarge of the standard condenser after
a charge of, say, 10 seconds from a given E.M.F. Then discharge the other
condenser, wire, or cable through the galvanometer after 10 seconds charge,
and note the deflection d'. The capacity c' of the latter is then
_ d,
C/ ~ °d'
c being the capacity of the standard condenser.
Capacity hy Thomson's method. — This method is used with
accurate results in testing the capacity of long cables. In the figure (Fig. 7)
Fig. ',
B = battery, say 10 chloride silver cells.
B =. adjustable resistance.
Bt— fixed resistance.
G = galvanometer.
C = standard condenser.
1, 2, 3, 4,5, keys.
To test, close key 1, thus connecting the battery B, through the resist-
ances R, By, to earth. Then
V: V,:\ B : R,
where Fand V, — the potentials at the junctions of the battery with/? B,.
Next close keys 2 and 3 simultaneously for, say 5 minutes, thereby char-
ging the condenser to potential V, and the cable to potential V,
Let Cbe the capacity in microfarads of the condenser, and C, capacity of
cable, and let Q and Q, be their respective charges when the keys were
closed. Then Q : Q, :: VC : V,C,.
Open keys 2 and 3, keeping key 1 closed for say 10 seconds, to allow the
charges of cable and condenser to mix or neutralize, in which case, if the
charges are equal, there will be no deflection of the galvanometer when key
5 is closed. If there is a deflection, it is due to a preponderance of charge
in Cor C,. Change the ratio of B to Bn until no deflection occurs.
Then, VC — V, C,
or V, : V:\ C : Cr
But we found V, : V :: R. : R
or B,: B :: C : Cr
and
C,—
C microfarads.
Testing- Capacities hy Tord Kelvin's Head-Beat, IVIiilti-
•ellular Voltmeter. — Suitable for short lengths of cable.
M F= multicellular voltmeter.
AC= air condenser.
CABLE TESTING.
225
B = battery.
S =z switch.
Q — total charge in condenser and M V, due to battery.
Ca = capacity of A C.
Cb = capacity of cable.
Fig. 8.
First close switch S on upper point 1, and charge JJ/Fand AC to a desired
potential, V. Next move switch S from point 1 to lower point 2, and note
the potential V, at M V.
Then Q = V(C + Ca) = V,(C+ Ca+ Cb), where Cis the capacity of volt-
meter. Ordinarily C'can be neglected, as compared with the capacities of
AC and the cable, in which case, by transposition,
Cb=(V—V/)Ca+V/.
Conductors of telephone cables are measured for capacity with the lead
sheathing or armor and all conductors but the one under test grounded.
locating- Crosses in Cables or Aerial Wires.— I*rof. Ayr-
ton Method. — To locate the cross at d (Fig. 9) arrange the connections
Fig. 9.
as shown. This is virtually a "Wheatstone bridge, in which one of the wires,
71, is one of the arms of same. Adjust r until a (x -f- y) = br, when r will be
equal to x + y, if a = 6.
d
226 CABLES.
Next connect the battery to line m instead of to earth, as in Fig. 10, and
adjust a until ax = by.
Then -4-=^-
and as x + y =: r in the first arrangement,
, b X r
hence, x = ^— ;
& -f a
This test may be varied by transposing G and the battery, in Fig. 9, which
is the old method of making this test.
'.Locating- Vault.-* in Aerial Wires or Cables by the Loop
Test. — Two conductors are necessary for this test, or both ends of a cable
must be available at the testing-point. Also it is assumed there is but one
defect in the conductor. The resistance of the fault itself is negligible in
this test.
Measure the resistance L of the loop by the ordinary Wheatstone bridge,
— Murray's Method. Connect as in Fig. 11, in which a and b are the
arms of a Wheatstone bridge, and y x are resistances to fault, the conduc-
tors being joined at J" (in the case of aerial wire, for instance). Close key
and note the deflection of needle due to earth current, if any. This is called
the false zero.
Fig. 11.
Now apply the positive or negative pole of the battery, by depressing one
of the knobs of reversing key K, and balance to the false zero previously
obtained by varying the resistance in arms a ox b. Then, by Wheatstone
bridge formula,
ax = by,
and I = x -
To ascertain distance in knots or miles from 2 to F, divide x by resistance
per knot or mile ; to ascertain distance from 1 to F, divide y by resistance
per knot or mile.
The foregoing test is varied in the case of comparatively short lengths of
cable, in the maimer shown in Fig. 12, in which the positions of the battery
and galvanometer are transposed. Otherwise the test and formula are the
same. It is advisable to reverse the connections of cable or conductors at 2
asd 1, and take the average of results obtained in the different positions.
jfo "this' latter method, battery B should be of low resistance, and well insu-
lated.
Best conditions for making test, according to Kerape. — Resistance of b
should be as high as necessary to give required range of adjustment in d.
CABLE TESTING.
227
Resistance of galvanometer should not be more than about five times the
resistance of the loop.
Fig. 12.
Varley Loop Test. — Measure resistance of looped cable or conduc-
tors as before. Then connect, as shown in Fig. 13, in which ris an adjustable
resistance. Obtain false zero as before. Then close key K, and adjust r for
balance. In testing, when earth current is present, the best results are
obtained when the fault is cleared by the negative pole, and just before it
begins to polarize.
where x is the distance of fault, in ohms, from point 2 of cable proper.
Then x -f- by the resistance of the cable or conductor per knot or mile
gives the distance of fault in knots or miles.
Locating- faults in Insulated "Wires. — The following, so to
speak, "rule of thumb," or point to point electro-mechanical methods of
locating faults in unarmored cables, in which the defect is not a pronounced
one, have been found successful.
Warren's Iflethod. — The cable should be coiled on two insulated
drums, one-half on each drum. The surface of the cable between the drums
is carefully dried. One end of the conductor is connected to a battery which
is grounded. The other terminal is connected to the insulated quadrants
of an electrometer, the other pairs of quadrants of which are connected to
the earth. Both drums being well insulated, no loss of potential is observed
after three or four minutes. An earth wire is now connected first to one
and then another of the drums, and the fault will be found on the drum
which shows the greater fall on the electrometer. The coil is now uncoiled
from the defective drum to the other drum, and tests are made at intervals
until the defect is found.
228 CABLES.
JF. Jacob coils the core from a tank to a drum. The battery is con-
nected between the tank and the conductor, one end of. which is free. A
galvanometer is joined betAveen the tank and drum, which need only be
partially insulated. The needle shows when the fault has passed to the
drum, and it can be localized by running the galvanometer lead along the
insulated wire.
Insulating- Cable Ends for Tests. — Much care must be exer-
cised in order to insure accurate results in testing for insulation resistance.
The ends should be well cleaned and thoroughly dry. The ends are for this
purpose sometimes immersed in boiling paraffin wax for a few seconds ; at
other times they may be dried by the careful application of heat from a
spirit lamp.
Copper Resistance, or Conductivity of Cables.
The copper resistance of the submarine and underground cables used in
telephony and telegraphy are always tested at the factory, usually by the
Wheatstone bridge method. In such a case both ends of the cable are ac-
cessible. "When the cable is laid, if the far end is well grounded, the cop-
per resistance may be measured, either by the Wheatstone bridge method,
or by a substitution method, as follows. First, note the deflection due to
copper resistance of conductor. Then substitute an adjustable resistance
box and vary the resistance in the box until the deflection equals that due
to cable. This latter resistance is the resistance of the cable. If there are
earth currents on the cable, take readings of cable resistance with each
pole of battery. Should there be any difference between the results ob-
tained with the respective poles of the battery, the actual resistance will,
according to F. Jacob, be equal to the harmonic mean of the two results, i.e.,
a = ——.
r -f- r
where R is the actual resistance, r is the resistance with -f- pole, r' is the
resistance with — pole.
Testing- Submarine Cable During- Manufacture and
laying.
Tlie Core of the cable, that is, the insulated copper conductor, is
made, as a rule, in lengths of 2 knots, which are coiled upon wooden drums,
and are then immersed in water at a temperature of 75° F. for about 24
hours. The coils are then tested for copper resistance, insulation resis-
tance, and capacity ; the results of which tests, together with data as to
length of coils, Aveigbt, etc., are entered on suitably prepared blanks.
After the tests of some of the coils have been made, the jointing up of
the cable begins, which is followed by the sheathing or armoring. The
joints are tested after 24 hours immersion in water. During the sheathing
process, continuous galvanometer or electrometer tests are made of the
core, to see that no injury befalls the cable during this process. In fact,
practically continuous tests of the cable for insulation resistance, copper
resistance, and capacity should be made until the laying of the cable begins.
During laying, the cable should be tested continuously, and communica-
tion should be practically constant between the ship and the shore. An
arrangement to permit such tests and communication is shown in Fig. 14.
I
■ |HKD-«aHE=
CABLE TESTING. 2*29
In this figure, G, is a marine galvanometer, B is a battery of about 100
cells on ship-board. In the shore station, L is a lever of key A", C is a con-
denser, 6r2 is a galvanometer. Normally key A' is open and the cable is
charged by battery B. If, while the cable is being paid out a defect occurs
in the insulation, or if the conductor breaks, a noticeable throw of the galva-
nometer follows, and the ship should be stopped and the cause ascertained.
By pre-arrangement the lever of shore key A' is closed, say every 5 minutes,
thereby charging the condenser C, which causes a throw of the galvanom-
eters' needles. If the ship or shore fails to get these periodic signals, or
if they vary as to their strength, it indicates the occurrence of a defect.
At the end of every hour the ship reverses the battery, which reverses the
direction of the deflection of the galvanometers. If the ship desires to
communicate with the shore, the battery is not reversed at the hour, or it
is reversed before the hour. If the shore wishes to speak with the ship, the
key A is opened and closed several times in succession. In either event,
both connect in their regular telegraphing apparatus for conversation.
Compound Caliles, that is, cables of more than one conductor, have
their conductors connected in series for these tests. If there is an even
number of conductors, two of them must be connected in parallel.
DYNAMOS.
COHTTMltflJOTJS CVRREIVT MACHOES.
Electro Iflotive Torce.
The E.M.F. of a dynamo depends upon,
a, The speed of revolution of the armature,
b, The number of conductors on the armature,
c, The method of connecting same,
d, The total flux or lines of force forced through the armature core by the
field magnets.
If the above four items be expressed in C.G.S. measure, the absolute
E.M.F. will be expressed in the same units, which can be changed to volts
by dividing by 100,000,000 or 108. Then for a two-pole dynamo,
Let rev = revolutions of armature per second,
n ■= number of external conductors all around the armature,
$ = the total flux passing through the armature core from pole to
pole,
E = total E.M.F. generated by the machine,
V=z E.M.F. at machine terminals r= E — rl where rl= volts drop or
loss in the machine itself.
™„, 1? - rev- X n X *
and
108
E X 108
rev. X n
For multipolar dynamos, in addition to the above symbols,
let p = number of pairs of poles,
<!>/ = flux from one pole,
then in a Series wound multipolar dynamo ;
„ rev. X p X n x $/
E- w
* _ E x io8
rev. x p X n
In a Multiple wound multipolar dynamo,
rev. X n X $>,
E~ W
AETEIllSfATiarO CURRENT MACHINES.
For alternating or periodically varying currents there are three values of
the E.M.F. used, or of which the value is required :
a, The maximum value, or the top of the wave,
6, The instantaneous value of a point in the wave,
c, the virtual E.M.F., or Vmean2 value of the full wave.
230
alternating' current machines. 231
In addition to the symbols used for continuous currents, let
k= a constant varying from 1.1 to 2.5 depending on the relative widths of
the armature coils and pole-pieces, usually taken as 2.22.
0 = angle through which the armature coil is turned at the instant
taken.
Then, for single-phase alternators,
maximum E =
2tt x n x 3y X rev. X p
108
In this case n = number turns in series, and $ = maximum flux enclosed
per turn,
, E max. x 108
and $, =
2tt x»X rev. X p
-r, „ 2?r x » X $/ X rev. x p X sin 9
Instantaneous E ■— — ' <ia — -^
108
In this case n = number turns in series, and 4> = maximum flux enclosed
per turn,
&/ = 7\
E inst. X 108
Virtual E =
2tt x n x rev. x p X sin 9
rev. x p X k X */ X n
In this case n = number of conductors joined in series with one another
around the armature,
_ E vir. X 10s
' rev. x p X k x n
For multiphase alternators
n = the number of conductors in series in a phase, and in two-phase ma-
chines the E.M.F.'s of each phase would be the same as in a single-phase
dynamo.
In three-phase alternators the E.M.F. between terminals will depend upon
the method of connecting the armature conductors. The two most common
methods are called the delta connection and the Y or star connection, both
shown in the following diagrams.
DELTA CONNECTION Y OR STAR CONNECTION
Figs. 1 and 2. , Values of E.M.F. in three-phase connections when x=y = z.
In the delta- connected armature the E.M.F.'s between terminals are those
generated in each coil, as shown in the diagram.
In the Y-connected armature the E.M.F. between any two terminals is
the E.M.F. generated by one of the coils in that phase multiplied by the V3
or 1.732.
Two-phase circuits are sometimes connected as a three-phase circuit ; that
is, both phases have a common return wire. In this case the pressure, be-
tween the two outgoing wires is V2 x E, and the current in the common
return will be / V2, both conditions are on the assumption that E and / in
each phase is the same.
232 DYNAMOS.
V=z the E.M.F. at machine terminals where
E = total E.M.F. generated. Then, in alternators the E.M.F.'s are
shown in the following diagram, the load of the alternator
heing non-inductive, and the armature reaction being neglected,
2n n LI X Ir = V at machine terminals.
V=^(2n?iLI)2-{-(l7')2 when L =z coefficient of self-induction, r = re-
sistance of armature + external circuit.
Continuous Current Machines.
The current in a dynamo depends upon
a. Its E.M.F.
b. The resistance of its internal circuit + the resistance of the external
circuit on which it is working.
c. Any counter or opposing E.M.F. in circuit, such as storage batteries
being charged or motors being run.
Then let
sE — total E.M.F. of the dynamo,
e = counter E.M.F. of the circuit,
R = internal resistance of the dynamo,
r — resistance of external circuit,
1=. current in amperes flowing.
Then if the external circuit have no counter E.M.F., as when supplying cur-
rent for incandescent lamps,
E
/=^nr7 = amPeres
or, if a storage battery is being charged and its opposing E.M.F. — e
r E~€
then I = -g—. —
If E, — external E.M.F. of dynamo as measured by voltmeter at brushes
at the load in question
fhor. r— ~L
Alternating- Current Dynamos.
In alternating-current machines another factor in addition to the resist-
ance of the circuits, internal and external, tends to retard or reduce the
current, viz., the reactance of the circuits (see index for reactance and
impedance).
Let L = coefficient of self-induction of armature,
L' = coefficient of self-induction of external circuit,
n = number of cycles, ~~
to rr 27T h,
EQ = open-circuit voltage of alternator,
other symbols same as for d.c. machine,
then, reactance = w L ohms,
impedance = Vi?2 +(&> L )2 ohms,
In A.C. dynamos E = Vmean2 = E
233
OTE, = l{r*-{- aI/>) —y
B + rz-{- o>I/ + <oL*
(r>+<^f
*& X 7t tuvn^ x" 10— ^
The inductance L of a circuit in henrys is the ratio — ? rr L
I (c.y.s.) max.
$V}(X l(V-8
or if 1 is expressed in virtual amperes then L = — ■
n $ = L I V2 108 and the E.M.F. of self-inductance is
E = V2 it n * v 10-8 where v =. cycles per second,
or E = 2?r v L I volts.
If to =1 2ttv, to!/ = reactance of the circuit in ohms, and the E.M.F. of self-
inductance of the circuit is =
M=. ImL = reactance voltage.
Energ-y in Balanced Three-phase Circuit.
In the following diagram of a Y connected multiphase generator and cir-
cuits, let
ey = E.M.F. of any phase in the armature,
iy = current of any phase in the armature,
E = E.M.F. between mains,
/= current in any main,
w, = energy of one phase of the armature,
JV= total energy,
Wy = C, 1/
but E = e, V3
I=i.
W—2>w,-
V3
In the following diagram of a delta connected multiphase generator and
circuits, let
e2 = E
7=i2V3
w% = e2 i2
W=3w* = ^|/= 1.732 E I
V3
~ 1.732 E
Therefore for any balanced three-phase system,
the energy is equal to the product of the E.M.F. pIG 5
between any pair of mains and the current in one
main, divided by V3 ; the result being multiplied by the cosine of the angle
of lag ; i.e., the power factor.
234
DYNAMOS.
then,
It •— resistance per leg of Y-connected armature,
r =z resistance per phase of A connected armature,
I-R loss in Y-connected armature = 3 I2R
I2Rl
3 in A connected armature =
Energy in Three-phase Circuits.
Jj ■=. current in any one of the three -wires of external circuit,
i =z current in one phase of the armature for delta connection,
W — watts output of a balanced three-phase generator,
1.732 = V3
.577 = 1 ~ V3
E = volts between terminals (or lines) on either delta or Y system,
v = volts of one phase of the armature if connected in " Y,"
R — resistance per leg, of Y connected armature,
r = resistance per phase of A connected armature,
W— 3 I, v = — '.—— I' E 1.732 (either with Y or A armature.
V3
For A
= »^-
v3
for A
v, = E
— - — - = 1.732 E /, which shows statement in brackets to be true.
V3
ir- W
W-
v W-
' E X 1.732
V, = 1.732 i in delta system.
I2R loss in Y connected armature = 3 I/Ji.
I2R loss in A connected armature = 3 ( — /- ) r
W3/
: I,*r.
■ : 5
e,j
E,
E,
E
b
E
Fig. 6.
ik i,
E
E=E,
E=^E/= 1.732 E,.
I AMPERES =1. 732 XZW
/ AMPERES = 1.732X2 or y
/AMPERES = 1. 732 X V or X
I AMPERES = Z
3i Z AMPS.
<^ V AMPS.
/ AMPERES =V
i2T
I AMPERES = 05
Delta Connection.
Star or Y Connection.
FIGS. 8 and 9. Values of current in three-phase connections, where x = y=.z.
CURRENTS.
235
Direction of Current in a Conductor.
To determine in which direction the current in a conductor is flowing,
place a compass underneath it. If the north pole of the needle points to the
left, the current is flowing forward or away from the observer. With the
compass above the conductor, if the north pole of the needle points to
the right the current is still flowing away from the observer.
These results are often shown as in the accompanying cuts.
Direction of Current about an Electromag-net, and
location of its Poles.
If the direction of the current flowing in the wire of the coil is not known,
then with a magnet find the north pole of the magnet, by approaching the
compass to one of the poles ; the north-pointing pole will be repelled by the
north pole of the magnet, but attracted by the sonth pole.
Then by placing the right hand on the coil, with the thumb extended at
right angles and pointing in the same direction as the north pole of the core,
current will be flowing in the direction pointed by the fingers.
Of course, if we know the direction of the current, and wish to find the
north pole of the magnet, placing the hand on top of the coil, as above, with
the fingers extended in the direction in which the current is flowing, the
north pole of the core is in the direction in which the thumb is extended.
Another way is to look at pole of magnet. If current is going round right-
handed you have a south pole ; if left-handed, a north. See " Corkscrew "
Rule.
""fcCTfON
DYNAMO •. RIGHT HAND.
Fig. 12.
Direction of Current in a Dynamo
Armature.
A simple rule is : facing the commutator
of the dynamo, speaking now especially of
the bipolar type, and assuming the left pole
to be north or -f-. and the armature to
be revolving counter clock-wise, then the
current is flowing to the right across the face
of the armature, or the left brush is positive,
or the terminal from which current will
flow, returning by the negative or right-hand
brush.
Reversing the direction of rotation will
reverse the polarity of the terminals.
The accompanying figure illustrates a
graphic method, called Fleming's Right-
hand Rule.
236
DYNAMOS.
Direction of Rotation in a motor.
Knowing the direction of current in the circuit, or which is the posi-
tive and which the negative terminals of the circuit, the direction of rota-
tion of the armature can easiest be determined
by use of the accompanying diagram (Fig. 12),
which is called Fleming's " left-hand rule."
field magnets.
In the paragraph on the E.M.F. of dynamos,
preceding, the symbol $ is used to indicate the
total flux or quantity of magnetic lines forced
through the core of the armature by the field
magnets.
This value of course depends upon the degree
of excitation, i.e., the amount of current and
number of turns of wire on the field magnets.
To determine this value in an existing ma-
chine, run it at a proper speed, and measure
the E.M.F. with a voltmeter.
Then
E x 10s MOTOR LEFT HANO.v
<I> — for continuous current machines. C
rev. X n Fig. 13.
and
$rr — r for alternating current dynamos.
rev. xn xp Xk
and if (& = magnetic induction, or Gauss = lines of force per square centi-
meter,
and A =z area of cross-section of armature core in square centimeters.
Then density of lines in armature = (B = — .
Magnetic Circuit of a Dynamo.
The path over which lines of force flow, be it iron or air, is called the
magnetic circuit, and is subject to laws analogous to those for electric con-
ductors. It has its magnetio resistance, which is directly proportional to
the length of the circuit, and inversely proportional to its cross-section and
permeability, the latter being somewhat analogous to conductivity in an
electric conductor.
In a dynamo the path through field-magnet cores, pole-pieces, field-yoke,
air-gaps, and armature core, forms the magnetic circuit of tbat machine.
The calculation of its value follows well-known laws, and is as easily car-
ried out as the calculation of the resistance or conductance value of an
electric conductor or path.
In any piece of iron
Let I = length of the piece.
s = cross-section of the same,
ju. — permeability rr (B -f- 30,,
In the magnetic circuit of a dynamo
let
Aa = area of cross-section of armature core,
Ag = area of cross-section of air-gap under the full pole-piece + a per-
centage for fringe.
Am = area of cross-section of magnet core,
AP — area of cross section of pole-piece,
Ay — area of cross-section of yoke,
I = length of any part,
$ — total flux,
237
Total reluctance = (-^-) + (-2L) + (J*-\ + (J*-) + (JlU)
call this total reluctance 7»',n,
Then
._1.257X»X /
i?m
total flux through magnetic circuit,
and ?i = number of turns of wire, and /—current in
amperes.
Application of Magnetic Circuit to Dynamo Design.
Let (B = flux per square centimeter, then in any part of tne magnetic cir-
cuit of a dynamo,
/T> $
KiD=z~, and after it is decided at what induction it is best to work the
A
iron of the circuit the cross-section
(B
The armature core is invariably of laminated soft annealed wrought iron
or steel, while the magnet cores and yokes are often of cast iron, although
most generally to-day some part, if not all, of the core is of mild cast steel.
If cast iron is used, it is only necessary to increase the cross-section to
satisfy the equation
Experience has shown that there is a very considerable leakage of lines of
force in an electro magnet ; some cutting across without going through the
armature path, others leaking across corners, etc. This leakage, amounting
to 30 to 50 per cent of the the total flux, has to be made up by increasing the
ampere turns of the magnets beyond that necessary to furnish the requisite
flux for the armature part of the circuit, by a percentage or amount repre-
sented by the leakage.
This leakage has been determined for different types of field magnets by
Edison and others, and a table of such values follows. In dynamo calcula-
tion the leakage value may be represented by v.
Stray Field in Dynamos.
Name of Dynamo.
Field.
Arma-
ture.
Remarks.
Value
of v.
Edison-Hopkinson
Bipolar
Drum
Poles next to bed-plate
1.32
Edison (American)
Bipolar
Drum
Poles next to bed-plate
1.40
General Electric Co.
Multipolar
Drum
Direct driven
1.25
Kapp
Bipolar
Drum
Yoke next to bed-plate
1.30
Siemens ....
Bipolar
Drum
Yoke next to bed-plate
1.30
Manchester . . .
Double magnet
Long
Bed and one pole cast
1.49
2 pole
ring
together
Ferranti ....
Double magnet
core-
Ordinary pattern alter-
2.00
Multipolar
lessdisk
nating.
The following formulae are useful in calculating approximately the mag-
netic leakage in a dynamo :
238
DYNAMOS.
1. The permeance, or reciprocal of magnetic reluctance, between two
parallel opposed surfaces is
A±A2
where d is the distance between the surfaces in centimeters, and where At
and A2 are the areas of the surfaces in square centimeters (see Fig. 14).
Ai -dHA2
Fig. 14,
Fig. 15.
2. The permeance between two equal rectangular areas situated in the
same plane, having corresponding sides parallel and a common axis of sym-
metry, is
if — is large (see Fig. 15),
T(D-
d))
f% — d — f^,
Fig. 16.
where L = length of each rectangle, measured perpendicularly to common
axis of symmetry (i.e., to the plane of the paper in the figure)
in centimeters.
d = distance between adjacent parallel sides in centimeters.
D = distance between remote parallel sides in centimeters.
3. The permeance between two equal rectangular areas at right angles to
one another, having one pair of sides in the one parallel to the correspond-
ing pair in the other, is
2D + d (n
- 2) j
where d, Z), £,, and L2 are the lengths in centimeters
of the dimensions shown in Fig. 17.
If d r= _D, the permeance in this case becomes
As the resistance of the two air-gaps in any dynamo Fig. 17.
is usually more than 80% of the total resistance of the
magnetic circuit, the length of the iron part of the circuit is of little conse-
quence excepting in cost of material, and is determined largely by the
amount and style of winding necessary for the field magnet coils.
Other considerations govern the length of air-gap, such as sparking at
the brushes, heating of pole-tips, heating of teeth in Paccinotti ring, regula-
tion of voltage, current, etc., thus compelling the use of more magnetizing
force to overcome that part of the circuit than all other parts combined.
If
then
Jim = total reluctance of the magnetic circuit of a dynamo,
ampere turns :
<*> Rm
'' L257
CURRENTS. 239
and, as it is necessary to know the ampere-turns required for each part of
the circuit, the items may be tabulated as follows : —
Formula' for Different parts of the Mag-netic Circuit of a
Dynamo.
Square centimetre units.
Armature core ; ampere-turns = $ x —. — * — -~ 1.257
Magnet cores ; ampere-turns =
Pole-pieces ; ampere-turns =
Yoke ; ampere-turns z
Am X
' Ap X hp
h
For square inch units the divisor will be 1.257 X 2.54 = 3.193, or better,
Armature core ; ampere-turns z
■ Aa
The two air-gaps ; ampere-turns = <t> x -/ X -3132
Magnet cores ; ampere-turns = $ x —. ■ X .3132
An
X H™
h
Ap
X HP
ly
Pole-pieces ; ampere-turns = $ X —. X .3132
Ap X HP
Yoke ; ampere-turns = $ X -; — X .3132
Ay X f-y
Types of Dynamos as Determined \>y tlieir Connections.
There are five types of dynamo connections in common use in the United
States, viz.: —
1. Magneto machines.
2. Separately excited machines.
3. Series machines. .
4. Shunt machines.
5. Compound wound machines ; this last having two classes, i.e., long
shunt and short shunt.
The above types apply especially to continuous current dynamos, but alter-
nating current machines are usually made separately excited as per No. 2,
and are sometimes made self -excited , from separate coils on the armature,
connected to a commutator on the shaft adjacent to the collecting-rings.
Other alternating current dynamos, in fact nearly all those used in the
United States to-day for lighting, or for lighting and power purposes, that
have been constructed since 1891, are of the type known as composite wound,
in which the fields are separately excited from an outside source, and in
addition to this a heavy wire series winding is also wound on the field coils,
and a portion of the current from tbe main circuit is shunted through them,
being passed through a commutator on the armature shaft first to be
rectified.
This current is of course in proportion to that flowing in the main circuit,
and adds excitation in proportion to the load, thus keeping the terminal
pressure practically constant under all conditions. Alternators for trans-
mission of power are not " composite " wound.
240
Compensated Revolving- Field Alternators.
The General Electric Company in October, 1899, placed on the market a
new type of multiphase alternator, which is claimed to overcome many of
the faults common to the old style of machine, especially when used on
combined lighting and motor loads. While it has been found a compara-
tively easy matter to compound and over-compound for non-inductive loads,
it has been heretofore quite difficult to add excitation enough to compound
for inductive loads which require considerably more field current than do
loads of a non-inductive nature.
The following description is taken from the bulletin issued by the makers
describing the machine, which is of the revolving field type : —
"The means by which this result is accomplished areas follows: The
shaft of the alternator which carries the revolving field carries also the
armature of the exciter, which has the same number of poles as the alter-
nator, so that the two operate in synchronous relation. In addition to the
commutator, which delivers current to the fields of ooth the exciter and the
alternator, the exciter has three collector rings through which it receives
current from one or several series transformers inserted in the lines leading
from the alternator. This alternating current, passing through the exciter
armature, reacts magnetically upon the exciter field in proportion to the
strength and phase relation of the alternating current. Consequently the
magnetic field and hence the voltage of the exciter, are due to the combined
effect of the shunt field current and the magnetic reaction of the alternating
current. This alternating current passes through the exciter armature in
such a manner as fro give the necessary rise of exciter voltage as the non-
inductive load increases, and without other adjustment, to give a greater
rise of exciter voltage with additions of inductive load."
Following are cuts of the types mentioned above.
magneto dynamo
Fig. 18.
separately excited dynamo
Fig. 19.
/
\
/
\
d
b
J
Fig. 21.
241
CONNECTIONS OF TYPE AS SINGLE-PHASE
ALTERNATINB CURRENT GENERATORS
WITH COMPOSITE FIELD 2300 VOLTS
&s e-Go-
/is 0-90-900 r(
*s a-iao-soo r<
Be
\Col lector s'de Leach succeeding spool,
pra 24. — General Electric Composite wound alternator.
242
DYNAMOS
CONNECTIONS OF TYPE AS SINGLE-PHASg
ALTERNATINB CURRENT GENERATORS
WITH COMPOSITE FIELD 1150 VOLTS
y?se-60
**S 6-90-9-00 Foi
jqs s-120-900 rQi
Stationary Shur
-nutator-Col lector
L toward the observer.The arrows correspond to
U— !j (H__JfJ those on spool f I anges. the spools being so placed
: — that the arrows point in opposite directions on
Collector side^ each»succeedlng spool.
Fig. 25. — General Electric Composite wound alternator.
CURRENTS.
248
CONNECTIONS OF TYPE AS SINGLE-PHASE
ALTERNATING CURRENT GENERATORS
WITH COMPOSITE FIELD E300 VOLTS
AS 14-120-1070 Form A.
, r— The observer- Is supposed -to be lookinjg
♦I Sir face of Pole Piece marked A. The series -fi
A ■ w'mdfng should be nearest armat.ure,that
tLJt UL toward observer. The arrows cor-responc
^rri-J^ ■ -Chose on spool flanges the spools being s<
Fig. 26. — General Electric Composite wound alternator.,
244
CONNECTIONS OF TYPE AS SINGLE-PHASE
ALTERNATING CURRENT GENERATORS
WITH COMPOSITE FIELD 1150 VOLTS
AS 14-120-1070 Form A
Commutator-C.
inerof plaong spools.
~U II It if face of pole piece marked A.-The series fiel
A winding should be nearest armature.that i
Ji tUt iL *ra"d °tose™%- The *z°V cor?spond *
Fig. 27. — General Electric Composite wound alternator
CURRENTS.
245
•ept for alternating current
uilly rinds a struct r:iihv;ty
unos are separately excited
constant current circuits,
Magneto dynamos are now used in the United States only for ringing tele-
phone bells,* and for other .signalling purp<
Separately excited dynamos are seldom m
production ; with the exception that one o
power-house where the shunt fields of all t
from one generator.
Series dynamos are used for arc light) _
where many lamps are distributed over wide area The constant potential
arc lamp, both for continuous and alternating currents, has reached such a
degree of perfection and low cost as to encourage its use to a very great
extent to displace the old style constant current lamp. Series dynamos are
also often used as boosters to vary the voltage on a line automatically in
proportion with load.
Shunt dynamos are used for charging storage batteries, and for large cen-
tral stations supplying constant potential current, and this applies especially
to the " Edison " stations throughout the country. It is easier to adjust the
load between large machines when shunt wound, and in these large stations
attendance is always at hand.
Compound wound dynamos are used in street railway power-houses, in
order to keep the pressure somewhere near constant under the great varia-
tion in output ; and are used to a very considerable extent, it may be said
almost wholly, in isolated plant work, in order to save attendance and
adjustment of the field rheostat
DIIAMO GHABACIBRISTIGi.
Dr. John Hopkisson is said to have devised the " characteristic " or curve
of properties of the dynamo, to show the results to be expected in a certain
design of machine, and to indicate actual results after completion, although
it is also said that Deprez first used the name.
The characteristics most commonly developed are as follows : —
1. Magnetization or saturation curve.
2. External characteristic.
3. Curve of magnetic distribution.
1. Mag'iietization Curve. — This curve is always determined for
each newlype of dynamo by reputable builders, and can easily be determined
by any one having available a separate exciting current, a voltmeter, and
an ammeter.
The turns of wire on the field remaining the same, it is sufficient to read
the amperes in the field, voltage at the brushes, and revolutions of the arm-
ature. Curve, Fig. 28, following shows the result of such a test. In a case
where, like the above, the dynamo is already in existence, the field is ex-
cited from some outside source, and the
■u curve determined by gradual increase
of the current in the field, and the volts
at the brushes are read after each such
change.
The accompanying curve is the re-
sultant of trie magnetizing force neces-
sary to force the flux through the
following parts, in the case of a bipolar
dynamo, all of which may be of differ
ent character : —
a. Armature core.
b. Two air-gaps.
c. Two polec-pieces.
d. Yoke.
e. And to overcome leakage of mag-
netic lines.
Individual curves for each of these parts can be predetermined by use of
formulas for calculating the magnetic circuit of dynamos, and from a com-
bination of those curves the curve shown above can be constructed, showing
the aggregate excitation necessary to produce certain voltages.
For sample of such a composite curve the reader is referred to page 149
of the fifth edition of S. P. Thompson's book, Dynamo Electric Machinery.
This curve is valuable not only to show the character of one machine, but
is useful to compare different machines by, and for that reason some stan-
FiG. 28. Magnetization Curve.
246
dard ratio of the scales on which the curves are based should be settled
upon.
2. External Characteristic. — This curve is a curve of results, in
which the dynamo is excited from its own current, and with the speed con-
stant, the terminal voltage is read for different values of load.
The curves for series, shunt, and compound wound machines all differ.
The observations are best plotted in a curve in which the ordinates repre-
sent volt values, and abscissa? amperes of load.
Series dynamo. In a series machine all the current flowing magnetizes
the field, the volts increase with the current, and if fully developed the
curve is somewhat like the magnetization curve, being always below it,
however, due to the loss of pressure in overcoming internal resistance and
armature reactions.
The following diagram (armature reaction being neglected) is a sample of
the external characteristic of a series dynamo.
To construct this curve from an existing
machine, the curve of terminal voltage can
be taken from the machine itself by driving
its armature at a constant speed, and varying
the load in amperes.
The curve " drop due to internal resistance,"
sometimes called the " loss line," can be con-
structed by learning the internal resistance
of the machine, and computing one or more
values by ohms law, and drawing the straight
line through these points, as shown.
The curve of total voltage is then con-
structed by adding together the ordinates of
the "terminal voltage" and "drop due to
internal resistance."
A very good sample of curve from a modern
series machine is to be found in the following
description of the Brush arc dynamo.
Following is a characteristic curve of the new Brush 125-lt. Arc Dynamo
V0V-TM3E_
AMPERES LOAD
Fig. 29. External Charac-
teristic of Series Dynamo.
6832
^-
^N
0500
_z
^
\
1
\
t
\
5600
1
4500
1
3500
0U0O
1
2500
1
1
1500
CHARACTERISTIC CURVE
SPEED-500 REV. PER MIN.
1000
I
soo
0
1
0 7 8 9 10 11 12 13 14
Fig. 30. Characteristic curve of Brush 125-Light Arc
Dynamo ivithout Regulator,
D Y X A M O C H A R A C T E K T S T I C S .
247
machine without any regulator. The readings were all taken at the spark-
less position of commutation. This curve is remarkable from the fact that
after we get over the bend, the curve is almost perpendicular, and is prob-
ably the nearest approach to a constant current meichine ever attained.
By winding more wire on the armature the machine could have been made
to deliver a constant current of 9.6 amperes at all loads, without shutting
-'
nn
/
-r\
/
/
COMMERCIAL EFFICIENCY
AMPERES 9.6
SPEED £00 R.P.M.
""
/
1
"
Fig. 31. Electrical Efficiency Curve of
Brush 125-Light Arc Dynamo.
'
y
y
y
/
/
COMMERCIAL EFFICIENCY
AMPERES 9. S
SPEED 500 R.P.M.
/
/
f
Fig. 32. Commercial Efficiency Curve of
Brush 125-Light Arc Dynamo.
any of the current from the field ; but this would have increased trie internal
resistance, and also have made the machine much less efficient at light
loads. By the present method of regulation the 1-li loss at one-quarter load
is reduced from 4,018 to 3,367 watts, the gain being almost one electrical
horse-power.
Fig. 31 is a curve of the electrical efficiency. It will be noticed that this
at full load reaches 94 per cent, which is accounted, for by the liberal allow-
ance of iron in the armature, thus reducing the reluctance of the magnetic
circuit, and by the large size of the wire used on both field and armature.
Fig. 32 is a curve of the commercial efficiency. At full load this is Dver
90 per cent, and approaches very closely the efficiency of incandescent
dynamos of equal capacity, but the most noteworthy point is the high effi-
ciency shown at one-quarter load.
Fig. 33 is a curve of the machine separately excited, with no current in the
armature. The ordinates are the volts at the armature terminals, and the
abscissa) the amperes in the field. This is in reality a permeability curve of
the magnetic circuit. By a comparison of the voltage shown here when
248
DYNAMOS.
there are nine amperes in the field, with that of the machine when deliver-
ing current, can be seen the enormous armature reaction. The curve also
/
/
/
MW
/
E. M. F.
500
Fig. 33. Permeability Curve of Magnetic Circuit
of Brush 125-Light Arc Dynamo.
indicates a new departure in arc dynamo design, namely, that the magnetic
circuit is not worked at nearly as high a point of saturation as in the old
types.
Shunt dynamo. The shunt dynamo has, besides an external characteristic,
shown below, an internal characteristic. The first is developed from the
volts read while the load in amperes is being added, the armature revolu-
tions being kept constant.
Adding load to a shunt dynamo means simply reducing the resistance of
tne external circuit. With all shunt machines there is a point of external
resistance, as at n, beyond which, if the resistance is further reduced, the
volts will drop away abruptly, and finally reach zero at a short circuit.
X
<x___
^ >
$/
y -/f
**° 1
d//
i v^t
\$&.
z^^-^^"
!
/^"^ AMPE
E TURNS IN
FIELD
Fig. 34. External Characteristic
of Shunt-wound Dynamo.
Fig. 35. Internal Character-
istic of Shunt Dynamo.
The internal characteristic, or, more correctly, curve of magnetization, of
a shunt dynamo, is plotted on the same scale as those previously described,
from the volts at the field terminals and the amperes flowing in the field.
DYNAMO CHARACTERISTICS.
249
The resistance line o a only applies to the point a on the curve, and the
resistance value a b for that point is determined hy ohms law, or as fol-
lows : As the curve of magnetization is determined from the reading of
volts plotted vertically and amperes horizontally, and as r = ^- or r = ^-~
1 o b
and — r = tang a ob, therefore the resistance at any point on thecui've will
be the tangent of the angle made by joining that point to the origin o.
Compound di/namo. As the compound dynamo is a combination of the
series and shunt machines, the characteristics of both may be obtained
from it.
The external characteristic is of con-
siderable importance where more than
one dynamo is to be connected to the
same circuit, or when close regulation
is necessary.
Fig. 36 is a sample curve from a com-
pound-wound dynamo, where the in-
crease of magnetization of the fields
due to the series coils and load causes
the terminal voltage to rise as the load
is increased. This is commonly done
to make up for drop in feeders to the
centre of distribution. It is impossi-
ble in ordinary commercial dynamos
AMPERES
Characteristic of Over-
FlG.
compounded Compound - wound
Dynamo,
to make this curve closely approach a straight line, and the author has
found it difficult for good makes to approach a straight line of regulation
nearer than 1| per cent either side of it for the extreme variation.
Curve of magnetic Distribution. — This curve .is constructed
from existing dynamos to show the distribution of the field about the pole-
pieces ; it can be plotted on the regular rectangular co-ordinate plan, or on
the polar co-ordinate.
The following cuts illustrate the commonest methods of getting the data
for the curve. With the dynamo running at the speed and load desired, the
Fig. 37.
Fig. 38.
pilot brush, a, in the first cut, or the two brushes, a and b, in the second cut,
is started at the brush x, and moving a distance of one segment at a time,
the difference in volts between the brush x and the location of the pilot
brush, a, is read on the voltmeter.
Where the one pilot brush is used, the total difference between that and
the origin is read ; Avhile Avith two brushes, as a and b, which are commonly
fastened to a handle in such a manner as to be the width of a segment apart,
just the difference between the two adjacent segments is read, and the total
difference is determined by adding the individual differences together.
250 DYNAMOS.
In taking the distribution curve on a commutator, with the two-brush,
method of S. P. Thompson, the curve of potential maybe plotted in two
ways, viz. : the heights of the ordinates may be made equal to the sum of
all the readings to the given point, or they may be made equal to the reading
at each bar, in which case the curve will indicate the value of the induction
at each point of the field where a reading is made.
Potential curves of this kind are often plotted on a circle, the circle itself
representing the commutator, with the segments plotted as radial ordi-
nates, which are made equal in value to the readings of the voltmeter
brushes.
ARiWATlKES.
Armatures for continuous current dynamos differ much in practice from
those used for alternating-current machines, although the former produce
alternating currents that are rectified or turned in the same direction by a
commutator.
Direct-current armatures are divided into two general forms,— drum arma-
tures, in which the conductors are placed wholly on the surface or ends of
a cylindrical core of iron ; and ring armatures, in which the conductors are
wound on an iron core of ring form, the conductors being wound on the out-
side of the ring and threaded through its interior.
Another form used somewhat abroad is the disk armature, in which the
conductors are arranged in disk form, the plane of which is perpendicular to
the shaft, and without iron core, as the disk revolves in a narrow slot be-
tween the pole-pieces.
Armature Cored.
In some early dynamos cores were made of solid iron ; but the heat from
Foucault or eddy currents was found so excessive as to endanger the insula-
tion of the conductors, and the loss in the core reduced the efficiency greatly.
Iron wire wound on a frame constructed for the purpose was then intro-
duced in place of solid cores. This answers the purpose for ring armatures
fairly well, but there is considerable waste space, as round wire is always
used.
To-day armature cores are invariably made of thin sheet iron or annealed
soft steel from .015 to .025 inch thick.
In order to prevent Foucault currents in such laminated cores, it is necessary
to insulate the disks from each other in some manner. Very thin tissue
paper between disks, rust on the surfaces, varnish, oil, or paint, are all
used for the purpose. Most of the better builders of to-day use a light
japan on the disks, with a layer of good insulating paper about every half
inch. Open spaces are left in the core about every two inches for ventila-
tion.
Armature cores are divided again as to outer surface into smooth bod;/
and toothed; the latter calied formerly the Pacinnotti armature, after it's
inventor.
The smooth body armature core is enough smaller in diameter than the
inner circle of the pole faces, to allow laying on the winding ; the full
diameter of the toothed armature core is only enough smaller than the field
pole space to allow proper air-gap, and slots are provided ir» its periphery in
which are laid the conductors. The toothed ring armature is used to-day in
the United States to perhaps a greater extent than any other form, although
the winding is of the drum form used with multipolar dynamos.
The toothed armature is said by Professor Crocker to possess the follow-
ing advantages and disadvantages over the smooth body.
Advantages :
1. The reluctance of air-gap is minimum.
2. The conductors are protected from injury.
3. The conductors cannot slip along the core by action of the electrody-
namic force.
4. Eddy currents in the conductors are avoided.
5. If the teeth are practically saturated by the field magnetism, they
oppose the shifting of the lines by armature reaction.
■M^B^^^MI
A R M A T U RES . 251
Disadvantages,
1. More expensive.
2. The teeth tend to generate eddy currents in the pole-pieces.
3. Self-induction of the armature is increased.
If the slots are made less in width than 2| or 3 times the air-gap, so that
the lines spread and become nearly uniform" over the pole faces, hut little
effect will be felt from eddy currents induced in the pole faces. When it is
not possible to make such narrow slots, pole-pieces must be laminated in
the same plane as the disks of the armature core, or the gap must be consid-
erably increased.
Hysteresis in the armature core can be avoided to a great extent by using
the best soft sheet iron or mild steel, Avhich must be annealed to the softest
point by heating to a red heat and cooling very slowly. Disks are always
punched, and are somewhat hardened in the process ; annealing will not
only remove the hardness, but will remove any burrs that may have been
raised.
Disks should be punched of such careful dimensions as to need no filing or
truing up after being assembled. Turning down the surface of a smooth-
body armature core burrs the disks together, and is apt to cause dangerous
heating in the core when finished. Light filing is all that is permissible for
truing up such a surface. Slotted cores should be filed as little as possible,
and can sometimes be driven true with a suitable mandril.
End plates of iron are seldom satisfactory, and the use of gun metal or
other bronze is to be commended. Bolts through the core must be insulated,
or currents will be induced in them as in any conductor.
Cores were formerly designed of small diameter, especially so in those of
the drum type ; but now the dimensions of the core take no particular shape,
excepting in some cases it is said to be better to make the cross-section of
each side of ring-armature cores approximately square, although cores of
a rectangular cross-section ansAver better the purpose for avoiding excessive
heating, and for least cost.
The size of core is determined first by the number and size of conductors
it has to carry to produce the required E.M.F. ; and secondly, by the surface
necessary to avoid excessive rise of temperature.
Armature conductors are usually made GOO to 800 circular mils per ariipere,
and the number of paths through the armature between which the current
is divided is determined by the design of the winding and the number of
poles. In a bipolar closed-coil winding there are two paths, each carrying
one-half the total current, while a four-pole closed-coil winding may have
either two or four circuits. The method of determining the number of con-
ductors necessary to produce the required E.M.F. is explained in the early
part of this chapter. For losses in cores of armatures, see chapter on Mag-
netic Qualities of Iron.
Armature shafts must be very strong and stiff, to avoid trouble from the
magnetic pull should the core be out of centre. They are made of machin-
ery steel, and have shoulders to prevent too much side play.
Core Insulation. — A great variety of material is used for insulating
the core, including asbestos, which is usually put next to the core to prevent
damage from heating of that part ; oiled or varnished paper, linen, and silk ;
press board ; mica and micanite. For the slots of slotted cores the insula-
tion is frequently made into tubes that will slide into the slots, and the con-
ductors are then threaded through. Special care must be taken at corners
and at turns, for the insulation is often cut at such points. The armature
conductors of the Niagara dynamos are insulated by a layer of mica wound
on to the bar a inch thick, and then pressed, into place under high and hot
steam pressure.
Armature Windings.
For all small dynamos, and in many of considerable size, the winding is of
double cotton-covered wire. Where the carrying capacity is more than the
safe carrying capacity of a No. 8 B. & S. gauge, the conductor should be
stranded. In large dynamos, rectangular copper bars, cables of twisted cop-
per, and in some cases large cable compressed into rectangular shape, are
more commonly used. If the copper bars are too wide, or wide enough so
that one edge of the bar enters the field perceptibly before the remaining
252
DYNAMOS.
parts of the bar, eddy currents are induced in it ; such bars are therefore
made quite narrow, and it is common to slope the pole face a trifle, so that
the bars may enter the field gradually.
Methods or arrangement of windings are of a most complex nature, and
only the most general in use will be described here, and these only in theory.
Parshall & Hobart have described about all the possible combinations ;
S. P. Thompson, Hawkins & Wallis, and others have also written quite fully
on the subject.
Ifiipolar windings are not windings at all, as the armature is simply a
cylinder or disk of metal ; and as none have as yet been put to practical use,
no further comment will be made on them.
ISing- or Cri-amnie Windings.
The form of core does not to-day deter line the form of winding, for,
while the drum core is always of necessity wound with the drum winding,
the ring core can be wound with either the ring or drum winding, as will be
explained.
The simplest form of ring winding is the two-circuit single winding, where
a continuous conductor is wound about the ring, and taps taken off to the
commutator at regular intervals.
The first variation on this will be the multi-circuit single winding, used
Avhere there are more than one pair of poles. Fig. 40 ' shows the four-
circuit single winding.
Where it is advisable to reduce the number of brushes in use, the multi-
circuit winding can be cross-connected ; that is, tbo.se parts of the winding
occupying similar positions in the various fields are connected in parallel to
the same commutator bar. Fig. 41 shows one of the simplest forms of
cross-connected armatures.
Where, from the shape of the frame, the magnetic circuits are somewhat
unequal, the winding shown in Fig. 42 will average up the unequal
induction values, and prevent sparking to some extent. It also halves the
number of commutator segments ; that is, there are two coils connected
to each segment instead of One, as in the previously mentioned windings.
If n = number of coils, and p = number of poles, any coil is connected
across to one ( - ± 1 I in advance of it.
\ p
Multiple Winding'* for Ring' Arniatiirvs. - An important clai
of windings much in use at present, and for many purposes invaluable, is
the double, triple, quadruple, etc., wound ring In these classes two or
more entirely separate and distinct Avindings are employed, each connected
to its own set of segments, the segments of the different windings following
each other in consecutive order.
Fig. 43 shows the simplest form of two-circuit double winding, used in
ARMATURES.
253
a bipolar machine. As no two segments of the same circuit are adjacent,
the liability of short-circuit of the commutator is diminished.
Two-circuit Winding"!* for Multipolar Field*. — This is an
important class of windings, and, as it has but two circuits irrespective of
the number of poles, has the advantage over the multiple-circuit windings
that it needs but — as many conductors as are necessary in that class, and
therefore needs but - as much space for insulation.
n
But two sets of brushes are necessary for the two-circuit windings, unless
the current is heavy enough to require a long commutator, in which case
other sets of brushes can be added, up to the number of poles.
In the short-connection type of this class, conductors under adjacent field
poles are connected together so that the circuits from brush to brush are
influenced by all the poles, and are therefore equal.
In the long-connection type the conductors under every other pole are con-
nected, so that the conductors from brush to brush are influenced by but
one-half the number of poles.
The number of coils in a two-circuit long-connection multipolar winding is
determined by the formula
Avhere S = the number of coils, n = the number of poles, and y = the
pitch. The number of commutator segments is equal to the number of
coils, and must be odd for machines with an even number of pairs of poles,
but may be either odd or even for machines having an odd number of pairs
of poles.
The pitch, y, is the number of coils advanced over for end connections, as,
for instance, in an armature with a pitch of 7 the end of coil number 1 is
connected to the beginning of coil 1 -j- 7 = 8, and from 8 to 8 -f- 7 = 15, and
so on. In multipolar ring long-connection windings y may be any integer,
but not so in drum windings.
Mr. Kapp gives, in the following table, the best practice as to angular
distance between brushes for this class of windings.
254
Number
of poles.
Angular distance between brushes.
Degrees.
Degrees.
Degrees.
Degrees.
Degrees.
2
180
4
90
6
60
180
8
45
135
10
36
108
180
12
30
90
150
14
25.7
77
128
180
16
22.5
67.5
112
158
18
60
100
140
180
20
54
90
126
162
Fig. 44 shows a simple form of two-circuit multipolar single winding, and
Fig. 45 another sample as used with a greater number of poles.
Fig. 45.
Both of the above samples are of the long-connection type. In the short-
connection type the formula for determining the number of coils is
S = ny ± 2,
and Fig. 46 is a sample diagram of one of the type.
Two-circuit Multiple-wound Multipolar Ring's. — The for-
mula for determining the number of coils and other factors for this class
of windings is
ARMATURES.
255
£=— X y ±m
where S= number of coils,
n = number of poles,
y = pitch,
m z= number of windings, as double, triple, etc.
" m " will equal a number of independently re-entrant windings equal to the
greatest common factor of y and m.
The following figure is a diagram of a two-circuit doubly re-entrant, double
wound ring armature :
in
Fig. 47.
Fig. 48 is a diagram of a two-circuit, singly re-entrant, double-wound ring.
Drum WiiB4li]i£'.«>,
In order that the E.M.F.'s generated in the coils of a drum armature may
be in the same direction, it is necessary that the two sides of each coil be in
fields of opposite polarity, and therefore the sides of the coils are connected
256
DYNAMOS.
across the ends of the core ; directly across, for bipolar machines, and part
way so for those of the multipolar type.
Figure 49 shows the Von Hefner- Alteneck drum winding, used principally
in small and smooth core armatures.
Fig. 49.
A sample of two-layer, two-circuit single winding is shown in Fig. 50.
Multiple-circuit Single- wound, Multipolar Drums. — In this
class of winding there must be an even number of bars ; and for single wind-
ings the pitch at one end must exceed that of the other by 2, and must both
be odd. If n is the number of poles, and c the number of face conductors,
the average pitch y should be about — . For chord windings y should be as
much smaller than — as convenient.
■1
ARMATURES.
257
In iron-clad windings the number of conductors must be a multiple of the
number of conductors per slot.
Following is a diagram of a six-circuit, single windinq.
Fig. 51
«
Two-circuit. Sing-le-wouud, Brum Armatures. —In this type
of winding, the pitch y is always, forward, and must be an odd number, the
connections leading the winding* from a certain bar under one pole to a bar
similarly situated under the next pole in advance. Two-circuit drum wind-
ings have for a given voltage — as many conductors as multiple-circuit
windings.
258
DYNAMOS.
When as many sets of brushes are used as there are poles, careful adjust-
ment of the brushes is necessary in order to avoid excessive flow of current
and bad sparking at any one set of brushes, with symbols the same as in the
previous paragraph, c = n y ± 2.
The following diagram shows the connections of a two-circuit single
winding.
Two-circuit, Multiple-wound, Drum Armatures.— With the
same symbols as before, and m =r number of windings, the general formula
is c =: n y ± 2 m.
ARMATURES.
259
This is a large class, and many combinations have been worked, Figs. 53
and 54 showing two of the simpler ones ; the first a two-circuit triple wind-
ing, and the second a two-circuit double winding.
Alternating* current Armatures.
Almost any continuous current armature winding may in a general way
be used for alternating currents, but they are not well suited for such work,
and special windings better adapted for the purpose are designed.
Alternating current armature windings are open-circuit windings, except-
ing in the rotary converter, where the rings are tapped directly on to the
direct current armature windings.
Early forms of armature windings of this type, as first used in the United
States, had pan-cake or flat coils bound on the periphery of the core. In
the next type the coils were made in a bunched form, and secured in lai'ge
slots across the face of the core. Both these types were used for single-
phase machines. After the introduction of the multiphase dynamo, arma-
ture windings began to be distributed in subdivided coils laid in slots of the
core ; and this is the preferred method of to-day, especially so in the case of
revolving field machines.
The single coil per pole type of winding gives the larger E.M.F., as the
coils are thus best distributed for influence by the magnetic field. This type
also produces the highest self-induction with its attendant disadvantages.
The pan-cake and diatril»if< d-cn'd windings are much freer from self-induc-
tion, but do not generate as high E.M.F. as does the single-coil windings.
In well-considered multiphase windings the E.M.F. is but little less for
distributed coils than for single coils, and has other advantages, especially
where the use of step-up transformers permits the use of low voltages, and
consequently light insulation for the coils. The distributed-coil winding
offers better chance for getting rid of heat from the armature core, and the
conductor can in such case be made of less cross-section than would be
required for the single-coil windings.
The greater number of coils into which a winding is divided, the less will
be the terminal voltage at no load. Parshall & Hobart give the following
ratio for terminal voltage under no-load conditions :
260
DYNAMOS,
Single-coil windings 1. for the same total number of conductors, the
spacing of conductors being uniform over the whole circumference.
Two-coil winding = .707.
Three-coil winding = .667.
Four-coil winding = .654.
When the armature is loaded, the current in it reacts to change the termi-
nal E.M.F., and this may be maintained constant by manipulation of the
exciting current. With a given number of armature conductors this reac-
tion is greatest with the single coil per pole winding, and the ratios just
given are not correct for full-load conditions.
Single-phase "Winding's. — The following diagram shows one of the
simplest forms of single-phase winding, and is a single coil per pole winding.
Another similar winding, but with bars in place of coils, is shown in the
following figure. It can be used for machines of large output.
ARMATURES,
26i
The following figure shows a good type of three bars per pole winding,
which is simple in construction.
Two-phase "Wineliiisrs. — The following diagram shows a good type
of winding for quarter-phase machines. It utilizes the winding space" to
good advantage, and is applicable to any number of coils per pole per phase.
Fig. 59 is a diagram of a bar winding for a quarter-phase machine, with
four conductors per pole per phase.
Three-phase Winding's. — Fig. 60 is a diagram of a three-phase
262
DYNAMOS.
winding connected in Y, in which one end of each of the three windings
is connected to a common terminal, the other ends being connected to
three collector rings.
Fig. 61 is a sample of a three-phase delta winding, in which all the con-
ductors on the armature are connected in series, a lead being taken off to a
collector ring at every third of the total length.
Fig. 61.
In the Y windings the proper ends to connect to the common terminal and
to the rings may be selected as follows : Assume that the conductor in the
middle of the pole-piece is carrying the maximum current, and mark its direc-
tion by an arrow ; then the current in the conductors on either side of and ad-
jacent to it will be in the same direction. As the maximum current must be
coming from the common terminal, the end toward which the arrow points
must be connected to one of the rings, while the other end is connected to
the common terminal. It is quite as evident that the currents in the two
adjacent conductors must he flowing into the common terminal, and there-
fore the ends toward which the arrows point must be connected to the com-
mon terminal, while their other ends are connected to the remaining two
rings.
In a delta winding, starting with the conductors of one phase in the mid-
dle of pole-piece, assume the maximum current to be induced at the
moment in this conductor ; then but one-half the same value of current
will be included at the same moment in the other two phases, and its path
ARMATURES. 263
and value will best be shown in the following diagram, in which x may be
taken as the middle collector-ring, and the maximum current to be flowing
from x toward z. It will be seen that no current
is coming in over the line y, bat part of the current
at z will have been induced in branches b and c.
Most three-phase windings can be connected
either in Y or delta ; but it must be borne in mind
that with the same windings the delta-connection
will stand 1.732 times as much current as the Y-
~-i much voltage.
Heating- of Armatures.
Fig. 62. Path ami Value
of Current in Delta- The temperature an armature will attain during
connected Armature, a long run depends on its peripheral speed, the
means adopted for ventilation, the heating of the
conductors by eddy currents, the heating of the iron core by hysteresis and
eddy currents, the ratio of the diameter of tbe insulated conductor to that
of its copper core, the current density in the conductor, the radial depth of
winding, whether the armature is of cylinder or drum type, and the amount
and character of the cooling surface of the wound armature.
The higher the peripheral speed of the armature the less is the rise of
temperature in it. Mr. Esson gives, as the result of some experiments on
armatures with smooth cooling surfaces, the following approximate rule :
55 W 350 W
~ S (1 + 0.00018 V) S' (1 + 0.00059 P)'
where C° = difference of temperature between the hottest part of the arm-
ature and the surrounding air in degrees, Centigrade,
W= watts wasted in armature,
S = active cooling surface in square inches,
S' = active cooling surface in square centimeters,
V= peripheral speed of armature in feet per minute,
V' ■=. peripheral speed in meters per minute
The more efficient the means adopted for ventilating the armature by cur-
rents of air, the smaller is the temperature rise. Some makers leave spaces
between the winding at intervals, thus allowing the air free access to the
core and between the conductors. A draught of air through the interior of
the armature assists cooling, and should be arranged for whenever possible.
For heavy currents it is sometimes necessary to subdivide the conductors
to prevent eddy currents ; stranded conductors, rolled or pressed hydraulic-
ally, of rectangular or wedge-shaped section, have been used. Such subdi-
vision should be parallel to the axis of the conductor, and preferably effected
br the use of stranded wires rather than laminse. Few armature conductors
of American dynamos of to-day are divided or laminated in any degree
whatsoever. Solid copper bars of approximately rectangular cross-section
are often used, and little trouble is found from Foucault currents.
The power wasted by eddy currents in an armature core is proportional to
the square of the maximum magnetic induction and to the frequency of
change of magnetic induction in the iron.
Mr. Kapp considers 1.5 square inches (9.7 square centimeters) of cooling
surface per watt Avasted in the armature, a fair allowance.
Esson gives the following for armatures revolving at 3000 feet per minute.
W '=. watts wasted in heat in winding and core,
S = cooling surface, exterior, interior, and ends, in square inches,
S, = cooling surface, exterior, interior, and ends, in square centimeters,
T =. temperature difference between hottest part of armature and
surrounding air in C°.
m 35 W 225 W
Then T = or — - —
Specifications for standard electrical apparatus for U.S. Navy say, " No
264 DYNAMOS.
part of the dynamo, field, or armature windings shall heat more than 50° F.
above the temperature of the surrounding air after a run of four hours at
maximum rated output."
According to the British Admiralty specification for dynamos, the tem-
perature of the armature one minute after stopping, after a six hours' run,
must not exceed 30° F. above that of the atmosphere. In this test the ther-
mometer is raised to a temperature of 30° F. above that of the atmosphere
before it is placed in contact with the armature, and the dynamo complies
(or does not comply) with the specification according as the thermometer
does not (or does) indicate a further rise of temperature.
The best dynamo makers to-day specify 40° and 45° C. as the maximum
rise in temperature of the hottest part of a dynamo, or 55° if the tempera-
ture of the commutator surface is to be measured.
Armature Reactions.
In continuous current dynamos, with no special devices for reversing
the currents in the armature sections as they successively pass under the
brushes, it is necessary, in order to avoid sparking, to give the brushes a
forward lead ; the lead usually varies with the output of the dynamo.
With the forward lead given to the brushes the effect of the armature cur-
rent is to weaken and distort the magnetic field set up by the field-magnets ;
a certain number — depending on the lead of the brushes — of the armature
ampere-turns directly oppose those on the field-magnets, and render a some-
what lai'ger number of these ineffective, except as regards wasting power ;
the remaining armature ampere-turns tend to set up a magnetic field at
right angles to the main field, with the result that the resultant field is
rotated forward in the direction of motion of the armature, and that tbe
field-strength is reduced in the neighborhood of every trailing pole-piece
horn, and is increased in that of every leading pole-piece horn. When,
therefore, the brushes have a forward lead each armature section as it
comes under a brush enters a part of the field, of which tbe strength is
reduced by the armature cross-induction ; and, if this reduction is great,
the field-strength necessary for reversing the current in the section (in the
short time that the section is short-circuited under the brush) may not be
obtained, and sparkless collection may thus be rendered impossible.
Various devices for reversing the currents in the armature sections, as
they pass successively under the brushes, without giving a forward lead to
the brushes, have been proposed ; a number of these are described in the
paper by Mr. Swinburne; an improvement of Mr. W. B. Sayers consists in
interposing auxiliary coils between the joints of adjacent armature sections
and the corresponding commutator bars. Each auxiliary coil is wound on
the armature with a lead relatively to the two main armature sections and
the commutator bar which it connects together. Tbe result of this arrange-
ment is that the difference between the E.M.F.s in the two auxiliary coils
connecting any given armature section to the two corresponding commuta-
tor bars may be made sufficient to reverse the current in the armature sec-
tion when short-circuited under a brush, even if the brush has a backward
instead of a forward lead. Mr. Sayers's invention not only makes it possible
to reduce the air-gap very considerably, but also, by enabling a backward
lead to be given to the brushes, to make the armature winding assist that
on the field-magnets in producing the required magnetic field for the arma-
ture. Both these results assist in reducing the weight and excitation of the
field-magnets.
For a two-pole dynamo the back ampere-turns are given by the formula,
180
where 6 = angular lead of brushes in degrees,
JlT— number of conductors, counted round periphery of armature,
in series,
/=: armature current in amperes ;
and, according to Prof. S. P. Thompson, the number of ampere-turns on the
field-magnets required to compensate for the back ampere-turns on the
armature is v X (A.T.)a, where v is the coefficient of magnetic leakage.
ARMATURES. 265
In the Thompson-Ryan dynamo the effects of armature reaction are neu-
tralized by a special winding through slots across the faces of the pole-pieces,
parallel Avith the axis of the armature; this winding is in series with the
armature, and the same current flowing in both, but in such direction tbat
all effects on the field magnets are neutralized, the ampere-turns of the shunt
are therefore much less than in other dynamos, there is no sparking under
any ordinary conditions of load, the brushes are placed permanently when
the machine is set up, and the efficiency is high under a wide range.
This dynamo is not compound- wound in the usual meaning of the term,
but the effects of compounding can be obtained by varying the position of
the brushes, a backward lead, tending to raise the voltage by assisting the
field magnets, as the current or load increases.
I* rag" on Armature Conductors. — In dynamos, each armature
conductor has to be driven in opposition to an effort or drag proportional at
every instant to the product of the current carried by the conductor into
the strength of the magnetic field. This drag on a conductor varies, there-
fore, with the position of the conductor relatively to the field-magnet poles,
and is a maximum when the conductor passes through that part of the air-
gap at which the magnetic induction is greatest. The arrangements for
driving the armature conductors must, of course, be adapted to the greatest
value of the drag to which a conductor is exposed, and this is given for
smooth core armatures by the formulae below.
Let /= current in amperes carried by each conductor,
(B = maximum induction in air-gap per square centimeter,
F ■=. maximum drag on a conductor in lbs. per foot of length.
Then F — -^§^ or .00000685 / ($>
140,000
In slotted armatures the drag comes upon the core teeth instead of the
conductors.
Current Density in Armature Conductors. —This should be
determined so that the I2r loss, plus the hysteresis loss in the armature,
does not exceed the less of the two limiting values assigned by the condi-
tions of efficiency and freedom from overheating respectively ; in practice
current densities of 2,000 to 3,000 amperes per square inch are common, and
in drum armatures the current density is sometimes higher. American
practice gives 600 to 800 circular mils per ampere.
Surface necessary for Safe Temperature.
Esson gives the following method of determining the surface necessary for
a magnet coil to keep its heat within assigned limits.
Let w ■=. watts wasted in heating,
s =r cooling surface in square inches of coil, not including end flanges
and interior,
s, = same as above in square centimeters,
t =. temperature of hottest part above surrounding air,
then
£F°=99 - or *C° = 335 -
s s/
Maximum current = Vrfe^- F X s1^
99 X hot r
Hot r = cold r -f- 1% for each additional 4.5° F.
266
DYNAMOS.
TmI>1«> of Cooling* Surfaces.
Excess temperature above sur-
rounding air.
Cooling surface per watt in
F.°
C.°
square inches.
sq. centimeters.
15
3.G7
23.7
30
— .
3.30
21.3
—
20
2.75
17.8
40
—
2.48
ICO
—
25
2.20
14.2
50
—
1.98
12.8
—
30
1.83
11.8
60
—
1.65
10.7
—
35
1.57
10.1
70
—
1.41
9.1
—
40
1.3S
8.9
Notes. — The number of ampere-turns necessary to overcome an air-gap
of one-half inch equals the number of lines of force per square centimeter.
Approximate rule by G. Forbes.
Current l>ensity.
(Esson.)
The current density per square centimeter section in the magnet winding
of ordinary machines is about half the current density in the armature.
§af« Continuous Output of X&ynamos and Motors.
(Albion Snell.)
_ | Drums Watts = IcVn .015.
uynamos { Cylinders Watts = Mhi .01.
I Drums
Brake H.P. = IcPn .000015.
nh \ Cylinders Brake H.P. = .00001.
I rr length of armature in inches,
d = diameter of armature in inches,
n — number of revolutions per minute.
<Syrostatic Action on Dynamos in Ships.
(Lord Kelvin.)
L— -
and P -
L = moment of couple on axis,
P = pressure on each bearing,
Wz= weight of armature,
k = radius of gyration about axis,
O = ^ A = maximum angular velocity of dynamo in radians
per second due to rolling of ship,
A = -^k = amplitude in radians per second,
' JS0 "
(Radian is unit angle in circular measure.)
SYNCHRONIZERS.
267
d =z degrees of roll from mean position.
T = periodic time in seconds.
u) i=. 2nn =z angular velocity of armature in radians per second.
«;— number of revolutions of armature per second.
I = distance between bearings.
g =z acceleration due to gravity.
Note. — On applying the above formula to dynamos, where IV, k, and o>
are great, it will be found advisable to place their plane of rotation athwart-
ships, in order to avoid as far as possible wear and tear of bearings due to
the gyrostatic action.
§YACHROIIZKK$».
There are numerous methods of determining when alternators are in step,
some acoustic, but mostly using incandescent lamps as an indicator.
In the United States it is most common to so connect up the synchronizer
that the lamp stays dark at synchronism ; in England it is more usual to
have the lamp at full brilliancy at synchromism, and on some accounts the
latter is, in the writer's opinion, the better of the two, as, if darkness indi-
cates synchronism, the lamp breaking its filament might cause the machines
to be thrown together when clear out of step ; on the other hand, it is some-
times difficult to determine the full brilliancy.
The two following cuts show theory and practice in connecting synchro-
jy^) ^y®
4© /&
^^vM&AMM/-
h
I
Fig. G4. Synchronizer Connections.
Lamp lights to full c.p. when dyna-
mos are in synchronism.
Fig. 63. Synchronizer Connections.
W hen connected as shown, the lamp
will show full c.p. at synchronism.
If a and b are reversed, darkness of
lamp will shoiv synchronism.
Two transformers having their primaries connected, one to the loaded
and the other to the idle dynamo, have their secondaries connected in series
through a lamp ; if in straight series the lamp is dark at synchronism ; if
the secondaries are cross-connected the lamp lights in full brilliance at
synchronism.
Note on tlie Parallel It«iniiing- of Alternators. — There is
little if any trouble in running alternators that are driven by water-wheels,
owing to the uniform motion of rotation. With steam-engine driven ma-
chines it is somewhat different, owing to more or less pulsation during a
stroke of the engines, caused by periodic variations in the cut-off, which
causes oscillations in the relative motion of the two or more machines,
accompanied by periodic cross currents. Experiments have proved that a
sluggish governor for engines driving alternators in parallel is more desi-
268 DYNAMOS.
rable than one that acts too quickly ; and it is sometimes an advantage to
apply a dashpot to a quick-acting governor, one that will allow of adjust-
ment while running. It is quite desirable also that the governors of engines
designed to drive alternators in parallel shall be so planned as to allow of
adjustment of speed while the engine is running, so that engines as well as
dynamos may be synchronized, and load may be transferred from one
machine to the others in shutting down. Foreign builders apply a bell con-
tact to the same part of all engines that are to be used in this way, and throw
machines together when the bells ring at the same time. These bells would
also serve to determine any variation, if not too small, in the speed of the
machines, and assist in close adjustment.
Manufacturers do not entirely agree as to the exact allowance permissible
for variation in angular speed of engines, some preferring to design their
dynamos for large synchronizing power, and relatively wide variation in
angular speed, while others call for very close regulation in angular varia-
tion of engine speed, and construct their dynamos" with relatively little syn-
chronizing power.
Dynamos of low armature reaction have large synchronizing power, but if
accidentally thrown out of step are liable to heavy cross-currents. On the
contrary, machines with high armature reaction have relatively little syn-
chronizing power, and are less liable to trouble if accidentally thrown out
of step.
The smaller the number of poles the greater may be the angular variation
between two machines without causing trouble, thus low frequencies are
more favorable to parallel operation than high ; and this is especially so
where the dynamos are used to deliver current to synchronous motors or
rotary converters-.
Specifications for engines should read in such a manner as to require not
more than a certain stated angular variation of speed during any stroke of
the machine, and this variation is usually stated in degrees departure from
a mean speed.
The General Electric Company states it as follows : —
"We have . . . fixed upon two and one-half degrees of phase departure
from a mean as the limit allowable in ordinary cases. It will, in certain
cases, be possible to operate satisfactorily in parallel, or to run synchronous
apparatus from machines whose angular variation exceeds this amount,
and in other cases it will be easy and desirable to obtain a better speed con-
trol. The two and one-half degree limit is intended to imply that the max-
imum departure from the mean position during any revolution shall not
exceed ^- of an angle corresponding to two poles of a machine. The angle
of circumference which corresponds to the two and one-half degrees of
phase variation can be ascertained by dividing two and one-half by one-half
the number of poles ; thus, in a twenty-pole machine, the alloAvable angular
variation from the mean would be -^ = .25 of one degree."
Some foreign builders of engines state the conditions as follows : Calling !N
the number of revolutions per minute, the weight of all the rotary parts of
the engine should be such that under normal load the variation in speed dur-
. ,. Nmax. — Nmin. .ni , 1 _, , , 1
me one revolution — will not exceed — — • Some state -—r-
N average 250 200
Oudin says : " The regulation of an engine can be expressed as a percent-
age of variation from that of an absolutely uniform rotative speed. A close
solution of the general problem shows that 1J° of phase displacement cor-
responds to a speed variation, or " pulsation," Avith an alternator of two n
poles, as follows : —
In the case of a single cylinder or tandem compound engine —
5.5%
A cross compound
A working out of the problem also shows . . . that no better results are
obtained from a three-crank engine than a two-crank.
The Westinghouse Company designs its machines with larger synchro-
nizing effect by special construction between poles, and allows somewhat
SYNCHRONIZERS.
269
larger angular variation, stating it as follows : The variation of the fly-
wheel through the revolution at any load not exceeding 25% overload, shall
not exceed one-sixtieth of the pitch angle between two consecutive poles
from the position it would have if the motion were absolutely uniform at
the same mean velocity. The maximum allowable variation, which is the
amount which the armature forges ahead plus the amount which it lags
behind the position of absolute uniform motion is therefore one-thirtieth of
the pitch angle between two poles.
The number of degrees of the circumference equal to one-thirtieth of the
pitch angle is the quotient of 12 divided by the number of poles.
Alternators in Parallel.
To connect an idle alternator in parallel with one or more already in use :
Excite the fields of the idle machine until at full speed the indicator shows
bus bar pressure, or the pressure that may have been determined on as the
best for connecting the particular design of alternator in circuit.
Connect in the synchronizer to show when the machines are in step, at
which point the idle machine may be connected to the bus bars. The load
will now be unequally divided, and must be equalized by increasing the driv-
ing-power of the idle dynamo until it takes on its proper part of the load.
Very little control over the load can be had from the field rheostats.
To disconnect an alternator fron the bus bars : Decrease its driving power
slowly until the other machines have taken all the load from it, when its
main switch may be opened and the dynamo stopped and laid off.
Current leads
from brushes to binding-posts, must be ample to produce no appreciable
drop in voltage. The following table gives current densities, etc., for brush-
holders, cables, conductor-rods, cable-lugs, binding-posts, and switches.
Average Current Densities for Cross-section and Contact
Surface of Various materials.
Material.
Current density.
Square Mils
per Ampere.
Amperes per
Square Inch.
1
Cross section . y
J
Copper wire . . .
Copper rod ....
! Copper-wire cable .
Copper casting . .
Brass casting . . .
500 to 800
800 " 1,200
600 " 1,000
1,400 '• 2,000
2,500 " 3,300
1,200 to 2,000
800 " 1,200
1,000 " 1,600
500 " 700
300 " 400
Brush contact .
Copper brush . . .
Carbon brush . . .
5,700 " 6,700
28,500 " 33,500
150 " 175
30 " 35
Sliding contact [
Copper — copper . .
±5i ass <^braBB . .
( 10,000 " 15,000
) 20,000 " 25,090
62 " 100
40 " 50
Screwed contact j
Copper — copper
-Brass ^coPPe1" •
lirass <brass m .
( 5,000 " 8,000
) 10,000 " 15,000
120 " 200
67 " 100
Gano S. Dunn says, in brushes of soft carbon § square inch will stand 60
amperes maximum.
270
MOTORS.
COHfTIUfrOUi CURRENT.
Theory.
The revolution of a motor armature in its field develops an E.M.F. which
is counter to or opposes the impressed E.M.F., and therefore acts like re-
sistance to reduce the amount of current flowing ; it is called the counter
E.M.F.
Lat E = applied E.M.F. at motor terminals,
encounter E.M.F.,
E =. resistance of motor armature,
I —
E —
e
R
Total watts
W —
EI-.
-E
E —
R
Useful watts w z
-el
= .e
E-
R
W =. w -\- watts wasted in heat,
W=w + I*R
' E(E — e)
Now w— EI—I2R
and 7=|-.= maximum value of w obtained by equating to 0 the differ-
ential coefficient of w with respect to I.
but /= — when the armature is standing, and no counter E.M.F. is being
developed ; therefore the maximum rate of work will be obtained when the
efficiency is 50%, and the speed of the armature is such as to produce
— E.
€ ~ 2
jr w=E I— I2R
but I R = E — e
E = 2E — 2e,
E , E
e=2;andc = 2S
and the ifl[;eiency
W
Theory i bally, and neglecting all losses but the one above mentioned, the
motot wUl be at its maximum efficiency when it is run at the required speed,
and produces the required power, and e is maximum, or as nearly equal to
E as can be obtained.
CONTINUOUS CURRENT.
271
then
and
If
and, as
Speed and Torque.
a) -= 2n rev. =.2w x rev. per sec. = angular velocity.
T=: torque,
<oT= power (mechanical) in foot-pounds per sec,
e 1= electric power in watts.
la r= current in armature,
w = e /a =00 T x ^ := 2tt x rev. x T ^
550 550
10»
where
and
and
2tt X rev. X T X [
number of wires on the periphery of the armature,
flux in the armature core,
_ la X rev. X $ X n
550 — TO5
Torque in pounds at 1 foot radius will then be
Tr=Ia~ -f- 13.56 X 107
If <f> is constant Twill be proportional to la, and Twill be greatest, there-
fore, when the armature is standing, and la = -^.
If
r — resistance of the armature
then
/« = ?—'
and
T .•*« ™X*
r X 13.56 X 107
or T = 0, when rev. n * = E x 108.
, . E X 108 2n x T x 13.56 X r X 1015
Speed in rev. per sec. = r— -
n x $ n2 4>2
If r is small and $ is relatively large, the second term may be neglected.
The stronger the field, i.e., the <t>, the slower will be the speed ; and if $ is
constant the speed is proportional to E.
§ei'ie§-Wound Motor.
Yalues in C. G. S. units.
In a series motor R= ra -f- rm where ra = resistance of the armature, at "
rm = resistance of the fields :
Let $ sat. = complete saturation of field magnets,
and I' — diacritical cnrrent, or current at half saturation,
/+/'
"Writing Ffor -
/ +
— -f- 13.56 X 107 — torque in pounds at 1 ft. radius.
/= -^p in C. G. S. units.
in C. G. S. units.
272
In a series motor the current is the same tinder the same load at any
speed. In other words, the torque is almost directly proportional to the
current. The following curves show the speed and torque curves ior a
series motor on a constant potential circuit.
TORQUE
Fig. 65.
NIiunt-%T$'omi>rf Motor.
Values in C, G. S. units.
: / — Is, where Is z
E
T-
and if Y
"~ E + E'
tion in field magnets,
- ra I.
$ sat. x
current in the shunt field.
where E' is the E M F, to givt half satura-
E
E-{- E>
_ T E + E'
b 1= _x-^— + -
=A [*(»+?).-".']
Brushes on a motor must he set back of the neutral point, or with a
" backward lead." This tends to demagnetize the fields, and as weakening
the fields of a motor tends to increase the speed, tne increase oi load on a
shunt-wound motor tends to prevent the speed failing, and the shunt motor
is very nearly self-regulating.
JLeonar-cTs System oi* Motor Control.
Wherever it becomes necessary to vary the speed and torque of a contin-
uous current electric motor to any considerable degree, any of the rheostat
methods introduce very considerable losses, and are apt to induce bad
sparking at the commutator.
H. Ward Leonard, E.E., invented the method shown in Fig. 66, which
gives most excellent results, although to some extent complicated, and is
highly efficient.
The driving motor, or rather motor which it is wished to control, is pro-
vided with a separately excited field, which can be varied by its rheostat to
produce any rate of speed, from just turning to the full speed of which it
may be capable. Current is supplied to its armature from a separate gen-
erator, and by varying the separately excited field of this generator, the
amount of current supplied to the motor armature can be varfed at will, and
the torque therefore changed to suit the circumstances.
The generator is driven at constant speed by direct connection to a motor
which gets its current from an outside source, or to another generator
driven by some other motive power, say a steam engine. This driven gen-
ALTERNATING CURRENT MOTORS.
273
erator supplies current for exciting the fields of the secondary generator
and main motor.
By reversing the field of the generator, the current in its armature is
reversed, and therefore so is the direction of rotation of the motor armature.
Fig. 67 shows the Leonard system adapted to electric street railway motor
control.
MOTttR. 6ENERAT0R
Leonard's System of Motor
Control.
Fig. 67. Leonard's System of
Electric Propulsion.
ALTERMATIWG CURRENT MOTORS.
While the single-phase alternating current motor has been quite well de-
veloped during the last few years, it has as yet come but little into use,
owing largely to its inductive effect on the line, and poor efficiency and un-
satisfactory operation. On the contrary, the multiphase motor has been so
far developed as to bring it into very strong competition with the direct
current motor, owing probably to its extreme simplicity, lacking all brushes,
commutators, and other troublesome attachments.
Fig. 68. Connections for Standard
S. F. A. C. Motor of the Fort
Wayne Electric Corporation.
Only the most elementary formula? will be given here, and the reader is
referred to the numerous books treating on the subject ; among others,
S. P. Thompson, Steinmetz, Jackson, Kapp, and others.
Following is a statement of the theory of the multiphase motor, condensed
from a pamphlet of the Westinghouse Electric and Manufacturing Company.
274
Elementary Theory of the Multiphase Induction Motor.
If a horse-shoe magnet he held over a compass the needle will take a posi-
tion parallel to the lines of force which flow from one pole to the other.
It is perfectly obvious that if the magnet he rotated the needle will follow.
If a four-pole electromagnet he substituted for the horse-shoe, and current
be made to flow about either one of the sets of poles separately, the needle
will take its position parallel with the lines of force that may be flowing, as
will be seen by the following figures.
Fig. 69.
Fig. 70.
If the two sets of poles are excited at the same time by currents of equal
strength, then the needle will take its position diagonally, half way be-
tween the two sets of poles, as will be seen by the following diagram.
It is now easily conceivable that if one of these currents is growing
stronger while the other is at the same time
becoming weaker, the needle will be at-
tracted toward the former until it reaches
its maximum value, when if the currents
are alternating, the strong current having
reached its maximum begins to weaken,
and the other current having not only re-
versed its direction hut begun to grow
strong, attracts the needle aAvay from the
first current and in the same direction of
rotation. If this process be continually
repeated, the needle will continue to re-
volve, and its direction of rotation will he
determined by the phase relation of the
two currents, and the direction of rotation
can be reversed by reversing the leads of
one phase.
If the compass needle be replaced by an
iron core wound with copper conductors,
secondary currents will be induced in
these windings, which will react on the field windings, and rotation will
be produced in the core just as it Avas in the compass needle. Two cranks
at right angles on an engine shaft are analogous with the quarter-phase
motor, and three to the three-phase motor, which depends on the same
principle for its working.
Fig. 71.
Theory of Multiphase Induction M otor.
Condensed from S. P. Thompson.
The following names and symbols are used for designating the parts and
properties of the induction motor : —
ALTERNATING CURRENT MOTORS. 275
Stator — stationary part, nearly always corresponding to the field.
Rotor = rotating part, corresponding to the armature of the d.c. motor.
Q =1 angular speed of the rotating magnetic field := 2n rev. -^- m, where
m = number of pairs of poles,
to = angular speed of rotor = 2n rev.., -|-m, where rer.o = number of rev-
olutions per second.
T = torque between the stator and rotor.
Analytical Theory of F*olyi»lia«e Induction Motors.
©
Let r — resistance per circuit of stator.
r, = resistance per circuit of rotor,
being reduced to primary system by square of the ratio of turns.
Let d = number of poles,
x = inductance of primary , per circuit,
x, = inductance of secondary, per circuit,
reduced to primary system by square of the ratio of turns.
Let S = per cent of slip,
I— current per circuit of stator,
E =z applied E.M.F. per circuit,
Z = impedance of whole motor per circuit,
JV= frequency of applied E.M.F.
Let the primary and secondary consist of p. circuits on a p. phase system.
n — primary turns per circuit,
tij = secondary turns per circuit,
Let a — — ratio of transformation,
n,
Then
/(neglecting ex. current) - ^ + ^ '_ ^ ^ + ^
Torque T-
Max. torque :
-teJXKrsSrp + SUXj + xM
p r, E'2S (\ — S)
Z (P/ + gr)* _|_ £2 (X/ + xf
dp £2
' S7riV;[r-f ^r2 + {X/ + x)2\
Max. power = — — f- — — at the slip S = '. r.
2 [r + r, + Z] r rt + Z
Starting current = i — -=,
cj. j.- dpE- r.
Starting torque = "T^v x \72
Note that the maximum torque is independent of rotor resistance r„ and
thus the speed at maximum torque depends on the rotor resistance. Current
at maximum torque is also independent of rotor resistance.
The maximum torque occurs at a lower speed than the maximum output.
A resistance can be chosen that when inserted in the rotor, the maximum
276
torque will be obtained at starting ; tbat is, the speed at which maximum
torque occurs can be regulated by the resistance in the rotor.
o SYNCHRONISM
Fig. 72. Torque curves for Polyphase Induction Motor.
Curves 1, 2, and 3 show the effect of successive increases of rotor resist-
ance, rotor run on part of curve a — b ; for here a decrease of speed due to
load increases the torque.
Speed of Induction Motor, — The speed or rotating velocity of
the magnetic field of an induction motor depends upon the frequency
(cycles per second) of the alternating current in the field, and the number
of poles in the field frame, and may be expressed as follows : —
rev. = revolutions per minute of the magnetic field,
p = number of poles,
/ =: frequency ; then
f
rev. = 120 -
P
The actual revolutions of the rotor will be less than shown by the formula,
owing to the slip which is expressed in a percentage of the actual revolu-
tions ; therefore the actual revolutions at any portion of the load on a
motor will be
rev. X slip due to the part of the load actually in use.
actual speed = rev. (1 — % of slip.)
Tbe following table by Wiener, in the American Electrician, shows the
speeds due to different numbers of poles at various frequencies.
Speed of Rotary Field for Different H>iml»ers of I*oles
and for Various Frequencies.
o
Speed of Revolving Magnetism, in Revolutions per Minute, when
%l
Frequency is :
25
30
33§
40
50
60
66|
80
100
120
125
133J
2
1500
1870
2000
2400
3000
3600
4000
4800
6000
7200
7500
8000
4
750
900
1000
1200
1500
1800
2000
2400
3000
3600
3750
4000
6
500
600
667
800
1000
1200
1333
1600
2000
2400
2500
2667
8
375
450
500
600
750
900
1000
1200
1500
1800
1875
2000
10
300
360
400
480
600
720
800
960
1200
1440
1500
1600
12
250
300
333
400
500
600
667
800
1000
1200
1250
1333
14
214
257
286
343
428
514
571
686
857
1029
1071
1143
16
188
225
250
300
375
450
500
600
750
900
938
1000
18
167
200
222
267
333
400
444
533
667
800
833
889
'20
150
180
200
240
300
360
400
480
600
720
750
800
22
136
164
182
217
273
327
364
436
545
655
682
720
24
125
150
167
200
250
300
333
400
500
600
625
667
ALTERNATING CURRENT MOTORS.
277
Slip. — The slip, or difference in rate of rotation between rotating field
and rotor, is due to the resistance opposed to rotor current.
Slip varies from 1 per cent in a motor designed for very close regulation
to 40 per cent in one badly designed, or designed for some special purpose.
Weiner gives the following table as embodying the usual variations :
Slip of Induction Motors.
Capacity of Motor, H.P.
Slip, at full load, per cent.
Usual limits.
Average.
§
20
to 40
30
I
10
" 30
20
i
10
" 20
15
1
8
" 20
14
2
8
" 18
13
3
8
" 16
12
5
7
" 15
11
n
6
" 14
10
10
G
" 12
9
15
5
" 11
8
20
4
" 10
7
30
3
" 9
6
50
2
" 8
5
75
1
" 7
4
100
1
" 6
35
150
1
" 5
3
200
1
" 4
25
300
1
" 3
2
Core of Stator and Rotor. — Both the field-frame core, or Stator,
and the armature core, or Rotor, are built up of laminated iron punchings in
much the same manner as are the armature cores of ordinary dynamos.
The windings in both cases are laid in slots across the face of either part,
and for this reason both parts are punched in a series of slots or holes for
the reception of the windings. The following cuts, taken from the " Ameri-
can Electrician," show the usual form of slots used.
s. 73 and 74. Forms of Punchings of Induction Motors.
The number of slots in thesfafor mustbe a multiple of the number of poles
and number of phases, and Weiner gives the following table, in the " Ameri-
can Electrician," as showing the proper number to be used in various cases,
both for two- and three-phase machines. In practice the number of poles
is determined by the speed required and the available frequency ; then the
number of slots is so designed as to be equally spaced about the whole inner
periphery of the stator.
278 MOTORS.
H'uml»er of Slots in W idd-Frame of Induction Motors.
Capacity of Motor.
Number of
Poles.
Slots per
Pole.
Slots per Pole per Phase.
Two-Phase.
Three-Phase.
i H.P. to 1 H.P.
4 to 8
3
4
-h
1
\ H.P. to 1 H.P.
4 to 6
6
"2
3
-
4 to 10
5
6
2*
3
2
2 H.P. to 5 H.P.
4 to 6
7
8
9
3*
4"
3
6 H.P. to 50 H.P.
6 to 12
7
8
9
f
3
4 to 8
10
11
VI
5
H
6
1
10 to 20
8
4
3
50 HP. to 200 H.P.
8 to 12
10
11
12
13
5
9
64
4
6 to 10
14
15
16
h
-
The number of slots per pole per phase in the rotor must be prime to that
of the stator in order to avoid dead points in starting, and to insure smooth
running, and commonly range from 7 to 9 times the number of poles, or
any integer not divisible by the number of poles, in the squirrel cage or
single conductor per slot windings. The proper number of slots may be
taken from the following table by Weiner :
ALTERNATING CURRENT MOTORS.
279
IVumuer of Rotor Slots for Squirrel-Cag-e Induction Motors
up to 9 H.JP. Capacity.
Number
of
Poles, p.
Limits of Slots,
Number
7 p. to 9 p.
Number of Rotor Slots.
28 to 36
42 " 54
56 " 72
29, 30, 31, 33, 34, 35, 37.
43, 44, 45, 46, 47, 49, 50, 51, 52, 53.
57,58,59,60,61,62,63,65,66,67, 68, 69, 70,71.
In large machines, where there is more than one conductor in each slot
and in which the winding is connected in parallel, the number of slots in
the rotor' must be a multiple of both the number of phases and the number
of pairs of poles.
The following table gives numbers of slots for various field-slots :
H~uinl»er of Rotor-Slots for Induction Motors of Capacities
over S» H.I*.
Number of
Field-Slots per
Pole.
Number of Rotor-Slots. (n3
Field-Slots.)
f n«.
or § n«
Alls.
* n«.
" S n3
| ns.
" §"«
f lis.
" # lis
ftn..
" fns
|ns.
" |ns
Flux Rensity. — This must be settled for each particular case, as it
will be governed much by the quality of iron and the particular design of
the motor.
Hysteresis loss increases as the 1.6 power of the flux density; and eddy
current losses are proportional to the square of the density and also to the
square of the frequency.
The following table shows practical values :
f lux-Rensities for Induction Motors.
("Wiener.)
Flux
Density
, in Lines of Force pei
Square Inch.
Capacity
of
Motor,
H.P.
For Frequencies
from 25 to 40.
For Frequencies
from 60 to 100.
For Frequencies
from 120 to 180.
Practical
Values.
Aver-
age.
Practical
Values.
Aver-
age.
Practical
Values.
Aver-
Age.
i
\
12000 to 18000
15000" 25000
18000 " 32000
15000
20000
25000
10000 to 15000
12000 " 18000
15000 " 25000
12500
15000
20000
7000 to 11000
7500 " 12500
8000 " 17000
9000
10000
12500
280 MOTORS.
JTlux-Densities for Induction Motors — (Continued).
Flux-Density, in Lines of Force per Square Inch.
Capacity
of
Motor,
H.P.
For Frequencies
from 25 to 40.
For Frequencies
from 60 to 100.
For Frequencies
from 120 to 180.
Practical
Values.
Aver-
age.
Practical
Values.
Aver-
age.
Practical
Values.
Aver-
age.
1
5
10
20
50
100
150
200t
20000 to 40000
25(100 " 45000
30000 " 50000
4oooo " 60000
50000 " 70000
60000 " 80000
70000 " 90000
80000 " 100000
90000 " 110000
30000
35000
40000
50000
60000
70000
80000
90000
100000
18000 to 32000
20000 " 40000
25000 " 45000
30000 " 50000
35000 " 55000
40000 " 60000
45000 " 65000
50000 " 70000
60000 " 80000
25000
30000
35000
40000
45000
50000
55000
60000
70000
9000 to 11000
10000 " 25000
11000 " 29000
12500 " 32500
15000 " 35000
17500 " 37500
20000 " 40000
25000 " 45000
30000 " 50000
15000
17500
20000
22500
25000
27500
30000
35000
40000
In the earlier induction motors it was considered the most efficient method
to connect the driving current to the revolving part or rotor; and as it is
highly important that
the number of windings
on the rotor he prime to
that of the stator, Fig. 75
shows a winding with an
odd combination of con-
ductors, being 51, or three
times 17.
The stator windings
would then be bars, con-
nected at either end to a
heavy copper ring, this
forming a sort of " squir-
rel-cage."
In the modern ma-
chines the winding
shown would be in coils
on the stator, the three
ends being carried to
terminal blocks on the
outside of the machine
instead of to rings as
shown, and the " squirrel-
cage" would then be
placed on the rotor and
be made of bars as men-
tioned.
Starting- and Meg'-
Fig. 75.
ulating- Devices. — Small induction motors, up to about 5 h. p. capa-
city, are started by closing the circuit directly to the motor. In large ma-
chines this would not be safe, as the rotor is 'standing, and would act in a
lesser degree as the short-circuited secondary of a static transformer, and
cause a heavy rush of current.
Resistance in Rotor. — This is a favorite method with the General
Electric Company. A set of strongly constructed resistances is secured
inside the rotor ring, and so arranged Avith a lever that they may be closed
or short-circuited after the motor has reached its full speed. These resist-
SYNCHRONOUS MOTORS. 281
ances are in the armature circuits. In order to give maximum starting torque
total armature resistance should be
r, = Vr2 + (X/ -\- x)*
Where rx = rotor resistance per circuit reduced to held system.
xy = rotor reactance per circuit reduced to field system.
r = resistance per field circuit.
y = reactance per field circuit.
This' method serves the double purpose of keeping down the starting cur-
rent and increasing the starting torque.
Resistances in Stator. — Resistance boxes may be connected in the
circuits supplying induction motors ; three separate resistances in three-
phase circuits, and two separate resistances in two-phase circuits. They
must be all connected in such a manner as to be operated in unison. Under
these conditions the pressure at the field terminals is reduced, as is of course
the starting current and the starting torque. In order to start a heavy load,
under this arrangement, a heavy starting-current is necessary.
Compensators or Auto-Transformers. — This method is greatly
favored by the Westinghouse Electric and M anuf acturing Company, is used to
some extent by the General Electric Company, and consists of introducing an
impedance coil across the line terminals, the motor being fed, in starting,
from some point on the winding where the pressure is considerably less
than line pressure. This avoids heavy drafts of current from the line, thus
not disturbing other appliances attached thereto, but as regards starting-
current and torque has the same effect as resistances directly in the line ;
that is, greatly reduces both.
Rotor Windings Commntated. — In this arrangement all or a
part of the rotor windings are designed to be connected in series when
starting, and are thrown in parallel after standard speed is attained.
Another design has part of the conductors arranged in opposition to the
remainder in starting, but all are thrown in parallel in regular order when
running at standard speed. These commutated arrangements have not
been much used in the United States.
iYACHROXOUS MOTORS.
Alternators are convertible into motors ; and one alternator will run in
synchronism with another similar machine after it is brought to the same
speed, or, if of unlike number of poles, to some multiple of the speed of the
driven dynamo, provided the number of pairs of poles on the motor is
divisible into the multiple. Such motors will run as if geared to the driven
dynamo even up to two or three times its normal full torque or capacity.
Single-phase synchronous motors have no starting-torque, but synchronous
motors for multiphase circuits will come up to synchronism without much
load, giving about 25 % starting-torque, starting as induction motors, with
the d. c. field open.
When connected to lines on which are connected induction motors that
tend to cause lagging currents and low-power factor of the line, over excita-
tion of the synchronous motor fields acts in the same manner as a condenser
introduced in the line, and tends to restore the current to phase with the
impressed E.M.F., and therefore to do away with inductive disturbances. .
It is necessary to provide some source from which may be obtained con-
tinuous current for exciting the fields of the synchronous motor ; and this is
oftenest done by the use of a small d. c. dynamo belted from the motor-
shaft, the exciting ciirrent not being put into use until the motor armature
reaches synchronism.
In starting a synchronous motor the field is open-circuited, and current is
turned on the armature. In practice, field coils are connected in various ways
to obviate the dangers of induced voltage, and a low resistance coil similar
to the series winding of the d. c. machine is sometimes so arranged on the field
poles as to give the necessary reaction for starting. Another way is to use
a low-pressure excitation, and therefore few turns on the field coils ; also
the field coils are " split up " by a switch at starting. The field excitation is
thrown on after the rotating part approaches synchronism, wbich may be
indicated by a lamp or other suitable device at the operating switchboard.
Considerable care must be exercised in the use of synchronous motors, and
their best condition is where the load is quite steady, otherwise they intro-
282
duce inductive effects on the line that are quite troublesome. The field of
such a motor can be adjusted for a particular load, so there will be neither
leading nor lagging current, but unity power factor. If the load changes,
then tlie power factor also changes, until the field is readjusted ; if the load
has been lessened the current will lead, and if it increases the current Avill
lag. If induction motors are connected to the same line, with a synchro-
nous motor that has a steady load, then the field of the synchronous motor
can be over-excited to produce a Leading current, which will counteract the
effect of the lagging currents induced by the induction motors. If two or more
synchronous motors are connected to the same circuit, and the load on one
of them is quite variable, and its field is not changed to meet such changing
conditions, a pumping effect is liable to take place in the other motors, unless
especial provision has been made in the design of the motors to prevent it. It
is only necessary to arrange one of the motors of the number for preventing
this trouble, but better to make all alike. A copper shield between pole-
pieces, and covering a portion of the pole-tip, will prevent the trouble ; and
the Westinghouse Electric and Manufacturing Company use a heavy copper j
strap around each pole-piece, with a shoe covering part of the pole-tip in
the air-gap.
Theory of the synchronous motor.
GENERATOR
Let R =z resistance of Avhole circuit.
L =z self-inductance of whole circuit.
^o resultant.
Fig. 77.
Take the origin at 0.
Let E represent maximum value.
e = instantaneous value,
ex = Ex sin (pt. + <£),
e2= E2 sin (pt. — $),
where p — 2w n, and n number of complete periods per second.
e = E0 sin (pt. — <jj)
where i// = angle of lag of Z?n with respect to the origin.
E02 = E* + E<? + 2Ei E2 cos 2 <f>,
E,>EX
e;<ex
En leads,
En lags,
cos 4> -
tarn// -
E,
- /:.,
cos <f>
E9 + E,
(Et + E2)
Eo
Eq and <$> are known.
SYNCHRONOUS MOTORS.
283
Energy. Shifts the origin hy the angle \f/.
ex = Ex sin (pt. -f 4, + if,).
e2 — E2 sin (pt. — </> -f- »//).
E0
Now
I~-
and / lags behind E0 by the angle 6 where
. LP
tan 8 = -g- ■
By introducing the angle ty we are referring the E.M.F.'s of both machines
to the zero point of the resultant wave as origin.
In general
ei dt-
if.
EI ,
where
w = the energy in watts, and
© = lag or lead of /with respect to E.
E and /are maximum values.
T=r — , or the periodic time.
H
ojj = energy given to the circuit by the generator,
cj2 = energy absorbed from the circuit by the motor.
J_ / e, idtz
Ei _
[i = I sin (pt — 5)]
_E\ En
X~ 2 V7?2+^2X'
^w + r-p*
E,E0
0 cos (0 + \f> + 8
[cos (<f> -(- »W cos 5 -
sin ($ -f- i//) sin 6]
cos 5 -
VlP+p*!,*
" 1 — 2(/?2+^2i2
and substituting — <f> for + <j> we get
Re
3 (^-j-^)_ipsin(0 + ^)
-2(/P+j3«i>) (
J i? cos (<A — >A) + -£j9 sin (</> -
Now sin \f/ = V" — — sin ©>
cos \f/ :
Ex — E2
Substituting and reducing
1
An angle </
2— 2 B? + p,tf
introduced such that
[ ^i (iJ cos 2<j>-\- Lp sin 20) — E2 R
sin 2 01 =
cos 201 =
y/&+p*Lz
Lp
VR2-j-p*lS
284
Substitute in w2 , and
E2
2 li2 +2)*L2 \
<o2 is a maximum when
2 <f> + 2 <£i =: 90° or
j J£a Vy>>2 _j_ p2 i2 sin (2 0 + 2 «£i) — 7^27? \
that is, the " sine term " = unity.
w2 is positive provided
Ei ^ It
E.z Vlp+p*&
which shows that it is possible to have E2 greater than Ex if there is the
proper ratio of resistance and reactance in the circuit.
Now, if we plot from an actual motor the
armature current and the field excitation we
get a curve shown in Fig. 79.
This shows that the armature current
varies with the excitation for a given load.
The flatter curves are for increase of load.
Point a shows under excitation,
b shows over excitation,
c shows the excitation which
makes the power factor unity ; it is well
from the point of stability of operation to
slightly over excite, and this makes E2>EX ,
and also counteracts the inductive dfop in
the line, thus showing that the action of an
Fig. 79.
over excited synchronous motor is similar to a condenser.
Graphical treatment.
Eg = generator E.M.F.
Em = motor E.M.F.
Eo = resultant E.M.F.
Jo = resultant current.
O Igz=z projection of I0 on O Eg.
O lm = projection of Jo on O Em.
O Ig . O Eg — u)g = energy given up by
the generator.
O lm . OEm=. to™ — energy absorbed by
the motor from the cir-
cuit.
coto is negative, which shows that wm is the
motor, because it is taking energy from
the circuit ; and similarly wg is the gener-
ator, because O Eg . O Ig is positive, and
gives up energy to the circuit.
[For further discussion see Jackson's
Alternating Current and Jlternotivfj (.'ar-
rent Machines ; also Electrical World for
March 30 and April 6, 1895, by Bedell and
Ryan. The latter is the classic paper on the subject.]
ANGLE OF LAG POSITIVE
Fig. ?
MOTOR CHEHTEMATOIBS OH BTJTAMOTOHI.
These are of two styles, one for transforming continuous current of one
voltage into continuous current of a different voltage, and usually called in
America motor-generators; the second class transforms alternating current
into continuous current, or vice versa, the voltage not being changed except-
ing from A.C. Vmean2 values to d.c. values equal to the top of the A.C. wave ;
these latter machines are now called rotary converters, and are largely used
in connection Avith the circuits of the Niagara Falls Power Company and
other power transmission stations.
DYNAMOTOKS.
285
Motor-generators are now largely used in telegraph offices for reducing the
pressure of the supply current to voltages suitable for use in telegraphy
and for ringing and charging generators in telephone offices.
Theory. Let
E = voltage at motor terminals.
e — voltage at generator end terminals.
/ = current in motor armature.
/• = resistance of motor armature.
n = number of conductors in motor armature.
Ix z= current in generator armature part.
?-, = resistance of generator armature part.
Wj = number of conductors in generator armature part.
— — k := coefficient of transformation.
E = induced E.M.F. in motor part.
Ex = induced E.M.F. in generator part.
E — rev. x n X <$>■
Ey = rev. — nx x 4>-
E — E — r I
E1 = e + rJl.
ke— E = rl—Jerx Ix.
If it be assumed that losses by hysteresis and eddy currents be negligible,
or that E I = Ex Ix whence Ix = k I, then
-i -(**?)*
Such machines run without sparking at the commutator, as all armature
reactions are neutralized.
Continuous Current Boosters.
This is a type of motor generator much in use for raising or lowering the
pressure on long feeders on the low-pressure system of distribution, and is
to be found in most of the larger stations of the Edison companies. It is
also much used in connection with storage-battery systems in charging cells.
The " booster " consists of a series generator driven by a motor direct con-
nected to its armature shaft. The terminals of the generator are connected
in series with one leg of the feeder ; and it is obvious that the current in the
feeder will excite the series field just in proportion to the current flowing,
provided the design of the iron magnetic circuit is liberal enough so that
the field is way below saturation (on the straight part of the iron curve way
beloAV the knee). As the armature is being independently rotated in this field,
it will produce an E.M.F. approximately in proportion to such excitation,
which E.M.F. will be added to that of the feeder or will oppose that E.M.F., ac-
cording as the terminal connections are made. On three-wire systems two
generators are direct connected to one motor, and for convenience on one
bed-plate.
Such a booster can be so adjusted as to make up for line loss as it in-
creases with the load.
One danger of a booster that is not always taken into account is. that if
the shunt of the driving-motor should happen to open, or, in fact, anything
should happen to the driving-motor that would result in its losing its power,
the generator would immediately become a series motor, taking current
from the line to which it is connected, and by its nature would reverse in
direction of rotation, and increase in speed enormously, and if not discon-
nected from its circuits in time would result in a complete Avreck of the
machine. It is always safest to have the generator terminals connected to
their line through some automatic cut-out, so arranged that should
the shunt break, as suggested, it would actuate the device, and automati-
cally detach the booster from the circuit before harm could be done.
286 MOTORS.
KOTiRY COlfVERlERg.
A rotary converter is the name given to a machine designed for changing
alternating currents into continuous currents. If the same machine be
used inverted, i.e., for changing continuous currents into alternating, it is
sometimes known as an inverted converter. Again, if the same machine be
driven by outside mechanical power, both alternating and continuous cur-
rents may be taken from it, and it then becomes known as a double current
generator.
Theoretically the rotary converter is a continuous current dynamo with
collector rings added, which are connected by leads to certain parts of the
armature windings, sometimes at the commutator segments.
In the following figure, which represents in diagram the sing!e-])fiase
rotary converter, the collector rings r and rx are connected by leads to dia-
metrically opposite segments or coils of the armature at c and cx. It is
obvious that as the armature revolves the greatest difference of potential
between the rings, or maximum E.M.F., will be at the instant the segments
c and <?j pass under and coincide with the brushes B and Bx ; and this
E.M.F. will decrease as the rotation continues, until the lowest E.M.F.
will occur when the segments c and cx are directly opposite the centre of
the pole-pieces P and Px.
E ROTARY CONVERTER
Fig. 81.
The maximum alternating E.M.F. will be equal to the continuous cur-
rent voltage at the brushes B and Bx, and if the machine be designed to
produce a sinusoidal curve of E.M.F., then the alternating E.M.F., that is,
the Vmean2 or effective E.M.F., will be,
e = E sin 2w Nt. ore = -- = .707 E
V2
iVhere e — Vmean1 or effective voltage,
E = continuous current voltage, or maximum,
Nt = frequency of rotation.
In a bipolar machine the frequency is t, and in a machine with p poles the
Neglecting losses and phase displacement the supply of alternating cur.
rent to the rings must be / V~2 = 1.414 Ix where /is the continuous current
output.
If, as shown in Fig. 82, another pair of rings be added, and connected to
points on the winding at right angles to the first, then another and similar
ROTARY CONVERTERS.
287
E.M.F. will be produced, but in quadrature to tbe first. The E.M.F. will be
the same for each phase as in the single-phase connection previously shown,
and still neglecting phase displacement and losses the current will be for
each of the two phases
TWO PHASE, OR QUARTER PHASE
ROTARY CONVERTER
If three equidistant points on the armature windings be connected to
three rings, as shown in the following diagram, a three-phase converter is
produced.
THREE PHASE ROTARY CONVERTER
Fig. 83.
As the connections of a three-phase rotary are always delta, the E.M.F.'s
as compared with the continuous current E.M.F. E have the following
value :
E^ 3
Voltage between collector rings e1 = — -- = .612 E.
2"V2
IE 2/V"2
Alternating current input = i = - — = — - — rz .943 i.
Steinmetz, in the Electrical World of Dec. 17, 1898, gives the following
table of values of the alternating E.M.F. and current in units of continuous
current.
288
8 rt
3
co
li
» >
1 IN
rH
b 1
|<N
>
Sl«
|tM(!
>I1
in
li
Hl*
CO
CO
3
II
II
41
ii
II
>h
Two-
phase.
II
in
ii
o
li
II
Three-
phase.
li
-IS
CO
li
|eoi|<N
> >
1 IN
li
|<N|
Si
1
II
|«||«
> |> ■
fcJO o3
PI ^
CO
II
||0q
©
II
n
l«M
>
<*
ii
>
3
o O
o
-
-
-
-
o a
SP.E?o
lis
C3 <D
cp J
o
)
•
a?
1
icS
curt
ftc8
a
<4
ROTARY CONVERTERS.
289
The values of E.M.F. and of current stated above are theoretical, and are
varied in practice by reason of drop in armature conductors and phase
displacement. In converting from a.c. to d.c, if the current in the rotary
is in phase with the impressed E.M.F., armature self-induction has little
effect ; but with a lagging current, which may be due to under-excitation,
the induced d.c. E.M.F. is somewhat reduced ; and if the machine be over-
excited, thus producing a leading current, the induced d.c. E.M.F. will be
raised. The same is the case in converting from d.c. to a.c, the a.c. volts
being down on a lagging circuit.
The corrections for the theoretical ratios of voltages" as shown are, first
for drop in the armature ; and second, they have to be multiplied by the
factors shown above.
Steinmetz says that the current flowing in the armature conductors of a
rotary is the diif erence between the alternating current input and the con-
tinuous current output. The armature heating is therefore relatively small,
and the practical limit of overload is limited by the commutator, and is
usually far higher than in the continuous current generator.
In six-pbase rotaries the I'lR losses of the armature are but 29 % of the
regular I2lt loss in the armature as used for d.c. dynamo.
Kapp shows that width of pole-face has a bearing on the increase in out-
put of a rotary converter over the same machine used as a continuous cur-
rent dynamo. He compares the output of two converters, one in which
the pole-face is two-thirds the pole distance, and another in which it is one-
half the pole distance. In single-phase converters the output is not equal
to that of the d.c. dynamo, and two- and three-phase machines are much
different.
He gives, in the following table, the percentage of d.c. output of what
would be the output of the same machine used as a d.c. dynamo.
Pole-width.
*
5
llll II II
o o o o
1
88%
81
73
63
95%
Single-phase
.9
.8 .
88
80
.7 .... .
70
(Cos =
|Cos =
(Cos =
L
138
128
117
144
Three-phase
.9
.8
137
126
(Cos =
}Cos =
(Cos =
1
167
160
144
170
Two- or
.9
167
four-phase
.8
153
To find the voltage required between collector
verters, when
ings on rotary con-
T= number of turns in series between collector rings,
n = flux from one pole-piece into the armature,
n =z cycles per second,
E = required E.M.F.
For single-phase and two-phase machines
^ = 2.83 Tn<S> 10'*,
For three-phase machines
E = 3.69 Tn <K 10"8.
290 MOTORS.
The single-phase rotary has to he turned up to synchronous speed hy some
external power, as it will not start itself.
The polyphase rotary will start itself from the a.c. end, but takes a tre-
mendous lagging current, and therefore, where possible, it should be started
from its d.c. side.
The starting of rotaries that are connected to lines having lights also con-
nected, should always be done from the d.c. side, as the large starting cur-
rent taken at the moment of closing the switch will surely show in the
lamps. Polyphase rotaries are sometimes started, as are induction motors,
by use of a " compensator."
In starting a rotary, the field circuit must be opened until synchronism is
reached, after which it is closed. The d.c. side must also be' disconnected
from its circuit, as it is obvious that the current produced is alternating
until synchronism is reached. Care must be taken to keep the field circuit
closed when the d.c. side is connected in parallel with other machines, and
the a.c. side open, or the armature will run away and destroy itself.
As the change in excitation of the field of a rotary changes the d.c. voltage
but little, and on the other hand produces wattless currents, the regulation
of E.M.F. must be accomplished by some other method. This can be done by
changing the ratio of the static transformer by cutting in and out turns as
its primary, or by the introduction of self-induction coils in the a.c. leads to
the rotary.
The first introduces a complicated set of connections and contacts, but is
unlimited in range.
The second method seems especially suited for the purpose, but is some-
what limited in range. Theoretically the action is as follows : Suppose the
excitation to be low enough so that the current lags 90° behind the impressed
E.M.F., the E.M.F. of self-induction lags 90° behind the current, and is
therefore 180° behind the impressed E.M.F., and therefore in opposition to it.
On the other hand, if the excitation is large, and produces a leading current
of 90°, the E.M.F. of self-induction is in phase with the impressed E.M.F.
and adds itself to it. Therefore, with self-indiiction introduced in the a.c.
lines, it is only necessary to vary the excitation in order to change the con-
tinuous current E.M.F. A rotary can thus be compounded by using shunt
and series field, to maintain a constant E.M.F. under changes of load, the
compounding taking place, of course, in the a.c. lines and not in the field of
the machine, as usual in d.c. dynamos.
In handling the inverted converter care must be exercised in starting it
under load, as it is apt to run away if not connected in parallel with other
alternators. If they are started from the d.c. side, and have lagging cur-
rents flowing from a.c. side, this current will tend to demagnetize or weaken
the fields, and the speed of the armature is liable to accelerate to the dan-
ger limit.
A lagging current taken from an inverted rotary, even after having reached
synchronism, will cause an immediate increase in speed, and if enough lag-
ging will cause an approach to the danger point.
Running as a rotary, and converting from a.c. to d.c, the phase of the en-
tering current has no effect on the speed, this being determined by the
cycles of the driving generator, nor upon the commutation, simply influen-
cing the heat in the armature and ratio of voltages slightly.
Double-current generators are useful in situations where continuous cur-
rent can be used for a portion of the day and the current transferred through
the a.c. side to some other district for use in another portion of the day,
thus keeping the machine under practically constant load.
The size of double-current generators is limited by the size of the d.c. gen-
erator that can be built with the same number of poles as a good alternator.
The heating of the armature depends upon the sum and not the difference
of the currents, as in the rotary, and the capacity is therefore no greater
than a d.c. machine of the same total output.
Automatic compounding of double current generators is scarcely feasible
in practice, and the field must be very stable, as the demagnetizing effect of
the lagging a.c. currents tends to drop the excitation entirely. Such machines
run better separately excited.
CONVERTER ARMATURE WINDINGS.
291
COHTV£RTER ARMAXUR£ WIXR-lXGft.
Two-Circuit Winding- for Two-Phase Rotary Transformers.
The following diagram shows the connections of the four rings to the dif-
ferent sections of the armature. The connections are made at the commu-
tator segments at four points, although there are six poL
Two-Circuit Winding- for Three-Phase Rotary
Transformers.
The following diagram shows the connections of the three collector rings
to the continuous current winding of a six-pole dynamo. As in the last fig-
ure, the rings are connected to points on the commutator at nearly equi-
distant points.
292
]Iote.— Connection of Static Transformers and Rotary
Converters.
In the use of rotary transformers two or more of these machines are some-
times connected in multiple to the secondary of the static transformers, and
their direct current leads then connected in multiple to a common bus bar
circuit, as shown in Fig. 86.
GENERATOR
GENERATOR
vwmmmum
mu
WW
ROTARY ROTARY
Fig. :
Fig. 87.
"With tbe above connections currents are often formed in the rotaries that
disturb the point of commutation, and it becomes practically impossible to
adjust the brushes so they will not spark. Rather than connect across in
the above manner, it is better that each rotary have its own transformer, or
at least its own secondary on tbe static transformer, as shown in Fig. 87.
REPORT OF THE COMMITTEE ON
STANDARDIZATION.
AILERICAII OSTITUTE OJF ELKCTRICiL
i:\4xi\i:B:it*.
Practical Standards for Dynamo Electric Machinery.
In the year 1898 the American Institute of Electrical Engineers appointed
a committee on standardization, who turned in a report recommending a
number of definite ratings for electrical apparatus, which it is hoped will
meet with entire success. The absence of such standards in the past has
led to all sorts of indefinite ratings, especially as to temperature ; so that
the purchaser never could be sure of the quality of the apparatus he was
buying. The general plan covers about all the qualities necessary in elec-
trical apparatus ; and by courtesy of the American, Institute of Electrical En-
gineers, I am permitted to include the report entire ; and it will be found
following this. This report, after completion by the committee, was sub-
mitted to reputable manufacturers of such apparatus, who have agreed to
adopt the standards named. The names of the members of the committee
are: F. B. Crocker, Chairman,
Cary T. Hutchinson, Charles P. Steinmetz,
A. E. Kekkelly, Lewis B. Stillweel,
John Lieb, Jr., Eeihtj Thomson.
OEUTERAI, PIAI.
Efficiency. Sections 1 to 24.
(I) Commutating Machines, Sections 6 to 11
(II) Synchronous Machines, " 10 to 11
(III) Synchronous Commutating Machines, " 12 to 15
(IV) Rectifying Machines, " 16 to 17
(V) Stationary Induction Apparatus, " 18 to 19
(VI) Rotary Induction Apparatus, " 20 to 23
(VII) Transmission Lines, " 24
Rise of Temperature. Sections 25 to 31.
Insulation. Sections 32 to 41.
Regulation. Sections 42 to 61.
Variation and Pulsation. Sections 62 to 65.
Rating-. Sections 66 to 73.
Classification of Voltages and frequencies. Sections 74 to 78.
Overload Capacities. Sections 79 to 82.
Appendices. (I) Efficiency.
(II) Apparent Efficiency.
(III) Power Factor and Inductance Factor.
(IV) Notation.
Electrical Apparatus will be treated under the following heads :
I. Commutating- Machines, which comprise a constant magnetic
field, a closed coil armature, and a multi-segmental commutator connected
thereto.
Under this head may be classed the following : Direct-current generators ;
direct-current motors ; direct-current boosters ; motor-generators ; dyna-
motors ; converters and closed-coil arc machines.
A booster is a machine inserted in series in a circuit to change its voltage,
and may be driven either by an electric motor or otherwise. In the former
case it is a motor-booster.
A motor-generator is a transforming device consisting of two machines, a
motor and a generator, mechanically connected together.
A dynamotor is a transforming device combining both motor and genera-
tor action in one magnetic field, with two armatures, or with an armature
having two separate windings.
For Converters, see III.
293
294 DYNAMO AND MOTOR STANDARDS AND TESTING.
II. Synchronous Machines, which comprise a constant magnetic
field, and an armature receiving or delivering alternating currents in syn-
chronism with the motion of the machine ; i. e., having a frequency equal
to the product of the number of pairs of poles and the speed of the machine
in revolutions per second.
III. Synchronous Commutating- Machines. — These include:
1. Synchronous converters ; i. e., converters from alternating to direct, or
from direct to alternating current, and 2. Double current generators ; i. e.,
generators producing both direct and alternating currents.
A converter is a rotary device transforming electric energy from one form
into another without passing it through the intermediary form of mechanical
energy.
A converter may be either :
a. A direct-current converter, converting from a direct current to a direct
current or,
b. A synchronous converter, formerly called a rotary converter, convert-
ing from an alternating to a direct current, or vice versa. Phase converters
are converters from an alternating-current system to an alternating-current
system of the same frequency but different phase.
Frequency converters are converters from an alternating-current system of
one frequency to an alternating-current system of another frequency, with
or without changes of phase.
IV. Rectifying: Machines, or Pulsating'-Current Genera-
tors, which produce a unidirectional current of periodically varying
strength.
V. Stationary Induction Apparatus, i. e., stationary apparatus
changing electric energy from one form into another, without passing it
through an intermediary form of energy. These comprise —
a. Transformers, or stationary induction apparatus, in which the primary
and secondary windings are electrically insulated from each other.
b. Auto-transformers, formerly called compensators ; i. e., stationary in-
duction apparatus, in which part of the primary winding is used as a second-
ary winding, or conversely.
c. Potential regulators, or stationary induction apparatus having a coil
in shunt, and a coil in series with the circuit, so arranged that the ratio of
transformation between them is variable at will.
These may be divided into :
1. Compensator potential regulators, in which the number of turns of one
of the coils is changed.
2. Induction potential regulators, in which the relative positions of pri-
mary and secondary coils is changed.
3. Magneto-potential regulators, in which the direction of the magnetic
flux Avith respect to the coils is changed.
d. Reactive coils, or Reactance coils, formerly called cboking-coils, i. e.,
stationary induction apparatus, used to produce impedance or phase dis-
placement.
VI. Rotary Induction Apparatus, which consists of primary
and secondary windings, rotating with respect to each other. They com-
prise—
a. Induction motors.
b. Induction generators.
c. Frequency changers.
d. Rotary phase converters.
ErriciBifCY.
1. The " efficiency" of an apparatus is the ratio of its net power output
to its gross power input.*
3. Electric power should be measured at the terminals of the apparatus.
3. In determining the efficiency of alternating-current apparatus, the
electric power should be measured, when the current is in phase with the
E. M. F., unless otherwise specified, except Avhen a definite phase difference
is inherent in the apparatus, as in induction motors, etc.
* An exception should be noted in the case of storage batteries or apparatus for
storing energy, in which the efficiency, unless otherwise qualified, should be under-
stood as the ratio of the energy output to the energy intake in a normal cycle.
REPORT OF COMMITTEE ON STANDARDIZATION. 295
4 . Mechanical poAver in machines should he measured at the pulley, gear-
ing, coupling, etc., thus excluding the loss of power in said pulley, gearing,
or coupling, but including the bearing friction and windage. The magnitude
of bearing friction and windage may be considered as independent of the
load. The loss of power in the belt, and the increase of bearing friction due
to belt tension, should be excluded. Where, however, a machine is mounted
upon the shaft of a prime mover, in such a manner that it cannot be sepa-
rated therefrom, the frictional losses in bearings and in win'dage, which
ought, by definition, to be included in determining the efficiency, should be
excluded, owing to the practical impossibiity of determining them satisfac-
torily. The brush friction, however, should be included.
a. Where a machine has auxiliary apparatus, such as an exciter, the
power lost in the auxiliary apparatus should not be charged to the machine,
but to the plant consisting of machine and auxiliary apparatus taken to-
gether. The plant efficiency in such cases should be distinguished from the
machine efficiency.
:». The efficiency may be determined by measuring all the losses individ-
ually, and adding their sum to the output to derive the input, or subtract-
ing their sum from the input to derive the output. All losses should be
measured at, or reduced to, the temperature assumed in continuous opera-
tion, or in operation under conditions specified. (See Sections 25 to 31.)
In order to consider the application of the foregoing rules to various ma-
chines in general use, the latter may be conveniently divided into classes as
follows :
I. Commutating- JVfachines.
O. In commutating machines the losses are :
a. Bearing friction and windage. (See Section 4.)
b. Molecular magnetic friction and eddy currents in iron and copper.
These losses should be determined with the machine on open circuit, and at
a voltage equal to the rated voltage -\- Ir in a generator, and — Irin a mo-
tor, where /denotes the current strength, and r denotes the internal resist-
ance of the machine. They should be measured at the correct speed and
voltage, since they do not usually vary in proportion to the speed or to
any definite power of the voltage.
c. Armature resistance losses, l~r', where / is the current strength in
the armature, and r' is the resistance between armature brushes, excluding
the resistance of brushes and brush contacts.
d. Commutator brush friction.
• e. Commutator brush-contact resistance. It is desirable to point out that
with carbon brushes the losses (d ) and (e) are usually considerable in low-
roltage machines.
/. Field excitation. With separately excited fields, the loss of power in
the resistance of the field coils alone should be considered. With shunt
fields or series fields, hoAvever, the loss of poAver in the accompanying rheo-
stat should also be included, the said rheostat being considered as'an essen-
tial part of the machine, and not as separate auxiliary apparatus.
(b) and (c) are losses in the armature or " armature losses" ; (d) and (e)
" commutator losses ; " (/) " field losses."
7. The difference between the total losses under load and the sum of the
losses above specified, should be considered as "load losses," and are usu-
ally trivial in commutating machines of small field distortion. When the
field distortion is large, as is sIioavii by the necessity for shifting the brushes
betAveen no load and full load, or with variations of load, these load losses
may be considerable, and should be taken into account. In this case the
efficiency may be determined either by input and output measurements, or
the load losses may be estimated by the method of Section II.
8. Boosters should be considered and treated like other direct-current
machines in regard to losses.
O. In motor-generators, dynamotors or converters, the efficiency is the
electric output
electric input.
II. Synchronous machines.
lO. In synchronous machines the output or input should be measured
with the current in phase Avith the terminal £. M. F., except when otherwise
expressly specified.
296 DYNAMO AND MOTOR STANDARDS AND TESTING.
Owing to the uncertainty necessarily involved in the approximation of
load losses, it is preferable, whenever possible, to determine the efficiency of
synchronous machines by input and output tests.
11. The losses in synchronous machines are :
a. Bearing friction and windage. (See Sec. 4.)
b. Molecular magnetic friction and eddy currents in iron, copper, and
other metallic parts. These losses should be determined at open circuit of
the machine at the rated speed and at the rated voltage, -f- / r in a synchron-
ous generator, — I r in a synchronous motor, where i = current in armature,
r— armature resistance. It is undesirable to compute these losses from
observations made at other speeds or voltages.
These losses may be determined either by driving the machine by a motor,
or by running it as a synchronous motor, and adjusting its fields so as to get
minimum current input and measuring the input by wattmeter. The former
is the preferable method, and in polyphase machines the latter method is
liable to give erroneous results in consequence of unequal distribution of
currents in the different circuits caused by inequalities of the impedance of
connecting leads, etc.
c. Armature-resistance loss, which may be expressed by p I2 r ; Avhere r
rr resistance of one armature circuit or branch, I = the current in such
armature circuit or branch, and p= the number of armature circuits or
branches.
d. Load losses as defined in Section 7. While these losses cannot well be
determined individually, they may be considerable ; and, therefore, their
joint influence should be determined by observation. This can be done by
operating the machine on short circuit and at full-load current ; that is, by
determining what may oe called the " short-circuit core loss." With the
low field intensity and great lag of current existing in this case, the load
losses are usually greatly exaggerated.
One-third of the short-circuit core loss may, as an approximation, and in
the absence of more accurate information, be assumed as the load loss.
e. Collector-ring friction and contact resistance. These are generally
negligible, except in machines of extremely low voltage.
f. Field excitation. In separately-excited machines, the I2r of the field
coils proper should be used. In self-exciting-machines, however, the loss in
the field rheostat should be included. (See Section 6/.)
XXI. Synchronous Commutating- Machines.
13. In synchronous converters, the power on the alternating-current side
is to be measured with the current in phase with the terminal E. M. F.,
unless otherwise specified.
13. In double-current generators, the efficiency of the machine should be
determined as a direct-current generator, in accordance with Section 6, and
as an alternating-current generator in accordance with Section 11. The
two values of efficiency may be different, and should be clearly distin-
guished.
1-4. In synchronous converters the losses should be determined when
driving the machine by a motor. These losses are : —
a. Bearing friction and windage. (See Section 4.)
6. Molecular magnetic friction and eddy currents in iron, copper, and me-
tallic parts. These losses should be determined at open circuit and at the
rated terminal voltage, no allowance being made for the armature resist-
ance, since the alternating and the direct currents flow in opposite
directions.
c. Armature resistance. The loss in the armature is ql2r, where / =
direct current in armature, rr armature resistance, and q, a factor which
is equal to 1.37 in single-phasers, 0.56 in three-phasers, 0.37 in quarter-
phasers, and 0.26 in six-phasers.
d. Load losses. The load losses should be determined in the same
manner as described in Section 11 d, with reference to the direct-current
side.
e and/. Losses in commutator and collector friction and brush-contact
resistance. (See Sections 6 and 11.)
g. Field excitation. In separately-excited fields, the I2 r loss in the field
coils proper should be taken, while in shunt and series fields the rheostat
loss should be included, except where fields and rheostats are intentionally
modified to produce effects outside of the conversion of electric power, as
REPORT OF COMMITTEE ON STANDARDIZATION. 297
for producing phase displacement for voltage control. In this case 25 per
cent of the I2 r loss in the field proper at non-inductive alternating circuit
should be added as proper estimated allowance for normal rheostat losses.
(See Section 6/.)
ly». Where two similar synchronous machines are available, their effi-
ciency can be determined by operating one machine as a converter from
direct to alternating, and the other as a converter from alternating to direct,
connecting the alternating sides together, and measuring the difference be-
tween the direct-current input and the direct-current output. This process
may be modified by returning the output of the second machine through two
boosters into the first machine and measuring the losses. Another modifica-
tion might be to supply the losses by an alternator between the two machines,
using potential regulators.
IV. Rectifying- machines, or Pulsating'-Current Gener-
ators.
1©. These include : Open-coil arc machines, constant-current rectifiers,
constant potential rectifiers.
The losses in open-coil arc machines are essentially the same as in Sections
6 to 9 (closed-coil commutating machines). In alternating-current rectifiers,
however, the output must be measured by wattmeter and not by voltmeter
and ammeter, since owing to the pulsation of current and E. M. F., a consid-
erable discrepancy may exist between watts and volt-amperes, amounting to
as much as 10 or 15 per cent.
It. In constant-current rectifiers, transforming from constant-potential
alternating to constant direct current by means of constant-current trans-
formers and rectifying commutators, the losses in the transformers are to be
included in the efficiency, and have to be measured when operating the rec-
tifier, since in this case the losses are generally greater than when feeding
an alternating secondary circuit. In constant-current transformers the load
losses are usually larger than in constant-potential transformers, and thus
should not be neglected.
The most satisfactory method of determining the efficiency in rectifiers is
to measuie electric input and electric output by wattmeter. The input is
usually not non-inductive, owing to a considerable phase displacement and
to wave distortion. For this reason the apparent efficiency should also be
considered, since it is usually much lower than the true efficiency. The
power consumed by the synchronous motor or other source driving the recti-
fier should be included in the electric input.
"V. Stationary Induction .Apparatus.
18. Since the efficiency of induction apparatus depends upon the wave
shape of E. M. F., it should be referred to a sine wave of E. M. F., except
where expressly specified otherwise. The efficiency should be measured with
non-inductive load, and at rated frequency, except where expressly specified
otherwise. The losses are :
a. Molecular magnetic friction and eddy currents measured at open cir-
cuit and at rated voltage — Ir, where i = rated current, r= resistance of
primary circuit.
b. Resistance losses, the sum of the I2r of primary and of secondary in a
transformer, or of the two sections of the coil in the compensator Or auto-
transformer, where /= current in the coil or section of coil, r= resistance.
c. Load losses : i. e., eddy currents in the iron and especially in the cop-
per conductors, caused by the current. Tbey sbould be measured by short-
circuiting the secondary of the transformer and impressing upon the primary
an E. M. F. sufficient to send full-load current through the transformer. The
loss in the transformer under these conditions measured by Avattmeter gives
the load losses -\-I2r losses in both primary and secondary coils.
d. Losses due to the methods of cooling, as power consumed by the
blower in air-blast transformers, and power consumed by the motor driving
pumps m oil- or water-cooled transformers. Where the same cooling appara-
tus supplies a number of transformers, or is installed to supply future addi-
tions, allowance should be made therefor.
19. In potential regulators the efficiency should be taken at the maximum
voltage for which the apparatus is designed, and with non-inductive Joad,
unless otherwise specified.
298 DYNAMO AND MOTOR STANDARDS AND TESTING.
VET, Rotary Induction Apparatus.
20. Owing to the existence of load losses, and since the magnetic density
in the induction motor under load changes, in a complex manner, the effi-
ciency should be determined by measuring the electric input by wattmeter
and the mechanical output at the pulley, gear, coupling, etc.
21. The efficiency should be determined at the rated frequency, and the
input measured with sine waves of impressed E. M. E.
22. The efficiency may be calculated from the apparent input, the power
factor, and the power output. The same applies to induction generators.
Since phase displacement is inherent in induction machines, their apparent
efficiency is also important.
23. In frequency changers ; i. e., apparatus transforming from a poly
phase system to an alternating system of different frequency, with or with
out a change in the number of phases and phase converters ; i. e., apparatus
converting from an alternating system, usually single-phase, to another
alternating system, usually polyphase, of the same frequency, the efficiency
should also be determined by measuring both output and input.
III. Transmission Eines.
2-1. The efficiency of transmission lines should be measured with non-
inductive load at the receiving end, with the rated receiving pressure and
frequency, also with sinusoidal impressed E.M. F.'s, except where expressly
specified otherwise, and with the exclusion of transformers or other appa-
ratus at the ends of the line.
RISE OF TEMPERATURE.
€ren«ral Principles.
25. Under regular service conditions, the temperature of electrical ma
chinery should never be allowed to remain at a point at which permanent
deterioration of its insulating material takes place.
20. The rise of temperature should be referred to the standard conditions
of a room-temperature of 25° C, a barometric pressure of 760 mm., and nor-
mal conditions of ventilation ; that is, the apparatus under test should
neither be exposed to draught, nor enclosed, except where expressly spe-
cified.
21. If the room-temperature during the test differs from 25° C, the ob-
served rise of temperature should be corrected by \ per cent for each degree
C* Thus, with a room-temperature of 35° C, the observed rise of tempera-
ture has to be decreased by 5 per cent, and with a room-temperature of 15°
C, the observed rise of temperature has to be increased by 5 per cent. The
thermometer indicating the room-temperature should be screened from
thermal radiation emitted by heated bodies or from draughts of air.
When it is impracticable to secure normal conditions of ventilation on
account of an adjacent engine, or other sources of heat, the thermometer
for measuring the air-temperature should be placed so as fairly to indicate
the temperature which the machine would have if it were idle, in order
that the rise of temperature determined shall be that caused by the opera-
tion of the machine.
2$. The temperature should be measured after a run of sufficient dura-
tion to reach practical constancy. This is usually from 6 to IS hours, accor-
ding to the size and construction of the apparatus. It is permissible, how-
ever, to shorten the time of the test by running a lesser time on an overload
in current and voltage, then reducing the load to normal, and maintaining
it thus until the temperature has become constant.
In apparatus intended for intermittent service, as railway motors, starting
rheostats, etc , the rise of temperature should be measured after a shorter
time, depending upon the nature of the service, and should be specified.
In apparatus which, by the nature of their service, may be exposed to over-
load, as railway converters, and in very high voltage circuits, a smaller
* This correction is also intended to compensate, as nearly as is at present practi-
cable, for the error involved in the assumption of a constant temperature coefficient
of resistivity ; i.e., 0.4 per cent per deg. C, taken with varying initial temperatures.
REPORT OF COMMITTEE ON" STANDARDIZATION. 299
rise of temperature should be specified than in apparatus not liable to
overloads or in low-voltage apparatus. In apparatus built for conditions of
limited space, as railway motors, a higher rise of temperature must be
allowed.
30. In electrical conductors, the rise of temperature should be deter-
mined by their increase of resistance. For this purpose the resistance may
be measured either by galvanometer test, or by drop-of-potential method.
A temperature coefficient of 0.4 per cent per degree C, may be assumed for
copper.* Temperature elevations measured in this way are usually in excess
of temperature elevations measured by thermometers.
3«. It is recommended that the following maximum values of tempera-
ture elevation should not be exceeded : —
Comniutating machines, rectifying machines, and synchronous machines.
Field and armature, by resistance, 50° C.
Commutator and collector rings and brushes, by thermometer, 55° C.
Bearings and other parts of machine by thermometer, 40° C.
Rotary induction apparatus :
Electric circuits, 50° C, by resistance.
Bearings and other parts of the machine 40° C, by thermometer.
In squirrel-cage or short-circuited armatures, 55° C., by thermometer, may
be allowed.
Transformers for continuous service — electric circuits by resistance, 50°
C, other parts by thermometer,40°C, under conditions of normal ventilation.
Reactive coils', induction and magneto regulators and transformers of 15
K. W. or less — electric circuits by resistance 55° C, other parts by thermo-
meter 45° C.
Where a thermometer, applied to a coil or winding, indicates a higher
temperature elevation than that shown by resistance measurement, the
thermometer indication should be accepted. In using the thermometer, care
should be taken so to protect its bulb as to prevent radiation from it, and, at
the same time, not to interfere seriously with the normal radiation from the
part to which it is applied.
31. In the case of apparatus intended for intermittent service, the tem-
perature elevation Avhich is attained at the end of the period corresponding
to the term of full load, should not exceed 50° C, by resistance in electric
circuits. In the case of transformers intended for intermittent service, or
not operating continuously at full load, but continuously in circuit, as in the
ordinary case of lighting transformers, the temperature elevation above
the surrounding air-temperature should not exceed 50° C. by resistance in
electric circuits, and 40° C. by thermometer in other parts, after the period
corresponding to the term of full load. In this instance, the best load should
not be applied until the transformer has been in circuit for a sufficient time
to attain the temperature elevation due to core loss. With transformers
for commercial lighting, the duration of the full-load test may be taken as
three hours, unless otherwise specified. In the case of railway, crane, and
elevator motors, the conditions of service are necessarily so varied that no
specific period corresponding to the full load term can be stated.
Note by the Author. — The committee has not clearly stated the re-
quirements regarding the measurement of rise of temperature. They have
not said whether the readings should be made while the apparatus is run-
ning under load, or after it is stopped ; and in the case of such appliances or
apparatus as revolve, and thus produce more or less ventilation or cooling
effects, the temperature will be found to rise materially after stopping ; and
it is essential that readings be taken after the machine has ceased revolving ;
and to learn the highest temperatures, which are of course the dangerous
ones, readings should be taken at very short intervals, say every 15 seconds,
until the mercury begins to fall, or in case of resistance measurement, until
the galvanometer needle changes its direction of movement.
In large apparatus, that is to be operated practically continuously, and
this applies especially to large static transformers, the writer believes that
either a much lower limit of temperature rise, say 30° C, should be specified,
or that some accurate method of determining the actual temperature at the
hottest point should be adopted.
Professor Robb of Hartford recently specified that a temperature coil of
* By the. formula 7?T = A\ (1 -j- 0.004 6). Where Bt is the resistance at
room temperature, i?T the resistance when heated, and 0 the temperature
elevation ( T-t) in degrees centigrade.
300 DYNAMO AND MOTOR STANDARDS AND TESTING.
copper, one ohm resistance, should be placed at the point of highest temper-
ature in some large transformers, and insisted on locating the spot at which
the coil should be placed himself. Using the standards laid down by the
committee, there can be no doubt that the results will be entirely safe.
urJivxAxioisr.
33. The ohmic resistance of the insulation is of secondary importance
only, as compared with the dielectric strength or resistance to rupture by
high voltage.
Since the ohmic resistance of the insulation can be very greatly increased
by baking, but the dielectric strength is liable to be weakened thereby, it is
preferable to specify a high dielectric strength rather than a high insulation
resistance. The high voltage test for dielectric strength should always be
applied. ._. • ™ . ^
Insulation Resistance.
33. Insulation resistance tests should, if possible, be made at the pres-
sure for which the apparatus is designed.
The insulation resistance of the complete apparatus must be such that the
rated voltage of the apparatus will not send more than of the J
1,000,000
load current, at the rated terminal voltage, through the insulation. Where
the value found in this way exceeds 1 megohm, 1 megohm is sufficient.
Dielectric Strength.
3-4. The dielectric strength or resistance to rupture should be deter-
mined by a continued application of an alternating E.M.F. for one minute.
The source of alternating E.M.F. should be a transformer of such size that
the charging current of the apparatus as a condenser does not exceed 25 per
cent of the rated capacity of the transformer.
35». The high-voltage tests should not be applied when the insulation is
low, owing to dirt or moisture, and should be applied before the machine
is put into commercial service.
3<>. It should be pointed out that tests at high voltages considerably in
excess of the normal voltages are admissible on new machines, to determine
whether they fulfil their specifications, but should not be made subse-
quently at a voltage much exceeding the normal, as the actual insulation of
the machine may be weakened by such tests.
Stf. The test for dielectric strength should be made with the completely
assembled apparatus, and not with its individual parts ; and the voltage
should be applied as follows : —
1st. Between electric circuits and surrounding conducting material, and.
2d. Between adjacent electric circuits, where such exist, as in trans-
formers.
The tests should be made with a sine wave of E.M. F., or, where this is
not available, at a voltage giving the same striking distance between needle
points in air as a sine wave of the specified E. M. F., except where expressly
specified otherwise. As needles, new seAving-needles should be used. It
is recommended to shunt the apparatus during the test by a spark gap of
needle-points set for a voltage exceeding the required voltage by 10 per cent.
38. The following voltages are recommended for apparatus, not including
transmission lines or switchboards :
Rated Terminal Voltage. Capacity. Testing Voltage.
Not exceeding 400 volts Under 10 k. W. . 1000 volts
" " " 10 k. w. and over 1500 "
400 and over, but less than 800 volts. Under 10 k. w. . 1500 "
" " " " 10 k. w. and over 2000 "
800 " 1200 " Any ..... 3500 "
1200 " 2500 " Any ..... 5000 "
< Double the nor-
2500 " .... Any ..... j mal rated
( voltages.
Synchronous motor fields and fields of converters started
from the alternating current side 5000 volts.
Synchronous motors and synchronous converter field-coils should be tested
at 5000 volts, since in the starting of such machines a high voltage is
induced in their field-coils.
wm^^^^^mi^m^mmmma^
REPORT OF COMMITTEE ON STANDARDIZATION. 301
Alternator field circuits should be tested under a breakdown test voltage
corresponding to the rated voltage of the exciter referred to an output equal
bo the output of the alternator ; i.e., the exciter should be rated for this test
as having an output equal to that of the machine it excites.
Condensers should be tested at twice their rated voltage, and at their
rated frequency.
The above values are effective values, or square roots of mean square,
reduced to a sine wave of E. M. F.
30. In testing insulation between different electric circuits, as between
primary and secondary of transformers, the testing voltage must be chosen
corresponding to the high-voltage circuit.
•A©. In transformers of from 10,000 volts to 20,000 volts, it should be con-
lidered as sufficient to operate the transformer at twice its rated voltage,
by connecting first the one, and then the other terminal of the high-voltage
winding to the core and to the low-voltage winding. The test of dielectric
resistance between the low-voltage winding and the core should be in
accordance with the recommendation in Section 39 for similar voltages and
capacities.
41. When machines or apparatus are to be operated in series, so as to
employ the sum of their separate E.M. F.'s, the voltage should be referred
to this sum, except where the frames of the machines are separately insu-
lated, both from ground and from each other.
43. The term regulation should have the same meaning as the term " in-
herent regulation," at present frequently used.
43. The regulation of an apparatus intended for the generation of con-
tant potential, constant current, constant speed, etc., is to be measured by
the maximum variation of potential current, speed, etc., occurring within
the range from full load to no load, under such constant conditions of opera-
tion as give the required full-load values, the conditions of full load being
considered in all cases as the normal condition of operation.
: 4-4. The regulation of an apparatus intended for the generation of a
potential, current, speed, etc., varying in a definite manner between full
load and no load, is to be measured by the maximum variation of potential,
current, speed, etc., from the satisfied condition, under such constant con-
ditions of operation as give the required full-load values.
If the manner in which the variation in potential, current, speed, etc.,
between full load and no load, is not specified, it should be assumed to be a
simple linear relation.
The regulation of an apparatus may, therefore, differ according to its
qualification for use. Thus, the regulation of a compound wound generator
specified as a constant-potential generator, will be different from that it
possesses when specified as an over-compounded generator.
45». The regulation is given in percentage of the full-load value of poten-
tial, current, speed, etc., and the apparatus should be steadily operated dur-
ing the test under the same conditions as at full load.
40. The regulation of generators is to be determined at constant speed ;
of alternating apparatus at constant impressed frequency.
4?. The regulation of a generator unit, consisting of a generator united
with a prime mover, should be determined at constant conditions of. the
jrime mover ; i.e., constant steam pressure, head, etc. It would include the
nherent speed variations of the prime mover. For this reason the regula-
tion of a generator unit is to be distinguished from the regulation of either
the prime mover, or of the generator contained in it, and taken separately.
48. In apparatus generating, transforming, or transmitting alternating
currents, regulation should be understood to refer to non-inductive load ;
that is, to a load in which the current is in phase with the E. M. F., at the
output side of the apparatus, except Avhere expressly specified otherwise.
40. In alternating apparatus receiving electric power, regulation should
refer to a sine wave of E.M. F., except where expressly specified otherwise.
50. In commutating machines, rectifying machines, and synchronous
machines, as direct-current generators and motors, alternating-current and
aolyphase generators, the regulation is to be determined under the follow-
ng conditions :
a. At constant excitation in separately excited fields,
6. With constant resistance in shunt-field circuits, and
302 DYNAMO AND MOTOR STANDARDS AND TESTING.
c. With constant resistance shunting series fields ; i. e., the field adjust-
ment should remain constant, and should be so chosen as to give the required
full-load voltage at full-load current.
51. In constant-potential machines the regulation is the ratio of the
maximum diit'erence of terminal voltage from the rated full-load value
(occurring within the range from full-load to open circuit), to the full-load
terminal voltage.
53. In constant-current machines, the regulation is the ratio of the maxi-
mum difference of current from the rated full-load value (occurring within
the range from full-load to short circuit), to the full-load current.
53. In constant-power machines, the regulation is the ratio of maximum
difference of power from the rated full-load value (occurring within the
range of operation specified) to the rated power.
5-1. In over-compounded machines, the regulation is the ratio of the
maximum difference in voltage from a straight line connecting the no-load
and full-load values of terminal voltage as function of the current, to the
full-load terminal voltage.
55. In constant-speed continuous-current motors, the regulation is the
ratio of the maximum variation of speed from its full-load value (occurring
within the range from full load to no load) to the full-load speed.
5©. In transformers, the regulation is the ratio of the rise of secondary-
terminal voltage from full load to no load (at constant primary impressed
terminal voltage), to the secondary terminal voltage.
St. In induction motors, the regulation is the ratio of the rise of speed
from full load to no load (at constant impressed voltage), to the full-load
speed.
The regulation of an induction motor is, therefore, not identical with the
slip of the motor, which is the ratio of the drop in speed from synchronism
to synchronous speed.
5S. In converters, dynamotors, motor-generators, and frequency chan-
gers, the regulation is the ratio of the maximum difference of terminal volt-
age at the output side from the rated full-load voltage (at constant impressed
voltage and at constant frequency), to the full-load voltage on the output
side.
50. In transmission lines, feeders, etc., the regulation is the ratio of max-
imum voltage difference at the receiving-end, between no-load and full non-
inductive load, to the full-load voltage at the receiving-end, with constant
voltage impressed upon the sending-end.
©O. In steam engines, the regulation is the ratio of the maximum varia-
tion of speed in passing from full load to no load (at constant steam pressure
at the throttle), to the full-load speed.
©1. In a turbine or other water-motor, the regulation is the ratio of the
maximum variation of speed from full load to no load (at constant head of
water ; i.e., at constant difference of level between tail-race and head-race),
to the full-load speed.
Variation and Pulsation.
©2. In prime movers which do not give an absolutely uniform rate of
rotation or speed, as in steam engines, the "variation" is the maximum
angular displacement in position of the revolving member from the position
it would occupy at uniform rotation, expressed in degrees, that is, with one
revolution at 300° ; and the pulsation is the ratio of the maximum change of
speed in an engine cycle to the average speed.
©3. In alternators or alternating-current circuits in general, the varia-
tion is the maximum difference in phase of the generated wave of E. M. F.
from a wave of absolutely constant frequency, expressed in degrees, and is
due to the variation of the prime mover. The pulsation is the ratio of the
maximum change of frequency during an engine cycle to the average fre-
quency. n
©4. If n = number of poles, the variation of an alternator is — times the
variation of its prime mover if direct connected, and ~p times the variation
of the prime mover, if rigidly connected thereto in the velocity ratio p.
©5. The pulsation of an alternating-current circuit is the same as the
pulsation of the prime mover of its alternator.
m^^m^^^MHHIMMHB
REPORT OF COMMITTEE ON STANDARDIZATION. 303
RATI\fi,
66. Both electrical and mechanical power should he expressed in kilo-
watts, except when otherwise specified. Alternating-current apparatus
should be rated in kilowatts on the basis of non-inductive condition ; i. e.,
with the current in phase with the terminal voltage.
69. Thus the electric power generated by an alternating-current appara-
tus equals its rating only at non-inductive load, that is, when the current is
in phase with the terminal voltage.
©S. Apparent power should be expressed in kilovolt-amperes, as distin-
guished from real power in kilowatts.
©i>. If a power factor other than 100% is specified, the rating should be
expressed in kilovolt amperes and power-factor at full-load.
9©. The full-load current of an electric generator is that current which,
with the rated full-load terminal voltage, gives the rated kilowatts, but in
alternating-current apparatus only at non-inductive load.
91. Thus, in machines in which the full-load voltage differs from the no-
load voltage, the full-load current should refer to the former.
If P = rating of an electric generator, and Ez=. full-load terminal voltage,
the full-load current is :
p
1= — in a continuous-current machine or single-phase alternator.
1= — — - in a three-phase alternator.
p .
-2E1
9*3. Constant-current machines, such as series arc-light«generators, should
be rated in kilowatts based on terminal volts and amperes at full load.
93. The rating of a fuse or circuit breaker should be the current strength
at which it will open the circuit, and not the working-current strength.
Classification of "Voltag-es and frequencies.
94-. In direct-current, low-tension generators, the following average ter-
minal voltages are in general use, and are recommended :
125 volts. 250 volts. 550 volts.
95. In direct-current and alternating-current, low-pressure circuits, the
following average terminal voltages are in general use, and are recom-
mended :
110 volts. 220 volts.
In direct-current power-circuits for railway and other service, 500 volts may
be considered as standard.
9©. In alternating-current, high-pressure circuits at the receiving-end,
the following pressures are in general use, and are recommended ;
1,000 volts. 2,000 volts. 3,000 volts. 6,000 volts.
10,000 volts. 15,000 volts. 20,000 volts.
99. In alternating-current, high-pressure generators, or generating sys-
tems, the following terminal voltages are in general use, and are recom-
mended :
1150 volts. 2,300 volts. 3,450 volts.
These pressures allow of a maximum drop in transmission of 15% of the
pressure at the receiving-end. If the drop required is greater than 15%, the
generator should be considered as special.
98. In alternating-current circuits, the following approximate frequencies
are recommended as desirable :
25^. or 30~ 40~ 60^ 120^.*
These frequencies are already in extensive use, and it is deemed advisable
to adhere to them as closely as possible.
Overload Capacities.
90. All guaranties on heating, regulation, sparkling, etc., should apply
to the rated load, except where expressly specified otherwise, and in alter-
* The frequency of 120 ~ may be considered as covering the already existing com-
mercial frequencies between 120 <-%- and 140 -— ', and the frequency of 60'"w as covering
the already existing commercial frequencies between 60^ and 70--*'.
304 DYNAMO AXD MOTOR STANDARDS AND TESTING.
nating-current apparatus to the current in phase with the terminal E.M.F.,
except where a phase displacement is inherent in the apparatus.
50. All apparatus should be able to carry a reasonable overload with-
out self-destruction by heating, sparking, mechanical weakness, etc., and
with an increase of temperature elevation not exceeding 15° C. above those
specified for full loads. (See Sees. 25 to 31.)
51. Overload guaranties should refer to normal conditions of operation
regarding speed, frequency, voltage, etc., and to non-inductive conditions
in alternating apparatus, except where a phase displacement is inherent in
the apparatus.
S°2. The following overload capacities are recommended : —
1st. In direct-current generators and alternating-current generators, 25%
for one-half hour.
2d. In direct-current motors and synchronous motors, 25% for one-half
hour, 50% for one minute except in railway motors and other apparatus
intended for intermittent service.
3d. Induction motors, 25% for one-half hour, 50% for one minute.
4th. Synchronous converters, 50% for one-half hour.
5th. Transformers, 25% for one-half hour ; except in transformers con-
nected to apparatus for which a different overload is guaranteed, in which
case the same guaranties shall apply for the transformers as for the appa-
ratus connected thereto.
6th. Exciters of alternators and other synchronous machines, 10% more
overload than is required for the excitation of the synchronous machine at
its guaranteed overload, and for the same period of time.
APPENDIX I.
Efficiency of Phase-Displacing* Apparatus.
In apparatus producing phase displacement, as, for example, synchronous
compensators, exciters of induction generators, reactive coils, condensers,
polarization cells, etc., the efficiency should be understood to be the ratio of
the volt-ampere activity to the volt-ampere activity plus power loss.
The efficiency may be calculated by determining the losses individually,
adding to them the volt-ampere activity, and then dividing the volt-ampere
activity by the sum.
1st. In synchronous compensators and exciters of induction generators
the determination of losses is the same as in other synchronous machines
under Sections 10 and 11.
2d. In reactive coils the losses are molecular friction, eddy losses, and
I2r loss. They should be measured by wattmeter. The efficiency of reac-
tive coils should be determined with a sine wave of impressed E.M.F.,
except where expressly specified otherwise.
3d. In condensers, the losses are due to dielectric hysteresis and leakage,
and should be determined by wattmeter with a sine wave of E.M.E.
4th. In polarization cells, the losses are those due to electric resistivity
and a loss in the electrolyte of the nature of chemical hysteresis, and are
usually very considerable. They depend upon the frequency, voltage, and
temperature, and should be determined with a sine wave of impressed
E.M.F., except where expressly specified otherwise.
APPENDIX II.
Apparent Efficiency.
In apparatus in which a phase displacement is inherent to their operation,
apparent efficiency should be understood as the ratio of net-power output to
volt-ampere input.
Such apparatus comprise induction motors, reactive synchronous convert-
REPORT OF COMMITTEE ON STANDARDIZATION. 305
ers, synchronous converters controlling the voltage of an alternating-cur-
rent system, self-exciting synchronous motors, potential regulators, and
open magnetic circuit transformers, etc.
Since the apparent efficiency of apparatus generating electric power de-
pends upon the power factor of the load, the apparent efficiency, unless
otherwise specified, should be referred to a load power-factor of unity.
APPENDIX III.
Power Factor and Inductance Factor.
The power factor in alternating circuits or apparatus may be defined as
the ratio of the electric power in watts to volt-amperes.
The inductance factor is to be considered as the ratio of wattless volt-
amperes to total volt-amperes.
Thus, if p — power factor, q = inductance factor,
then p2 -(- q2 =. 1.
The power factor is the
(energy component of current or E.M.F.)
total current or E.M.F.
and the inductance factor is the
(wattless component of current or E.M.F.) true power
(total current or E.M.F.;
" volt-amperes '
Since the power-factor of apparatus supplying electric power depends
upon the power-factor of the load, the power-factor of the load should be
considered as Unity, unless otherwise specified.
APPENDIX IV.
The following notation is recommended : —
JE, e, voltage, E.M.F., potential difference, E, r, resistance,
1, i, current, X, x, reactance,
P, power, Z, z, impedance,
<j>, magnetic flux, L, I, inductance,
(£, magnetic density, C, c, capacity.
Vector quantities, when used, should be denoted by capital italics.
APPENDIX V.
Table of sparking distances in air between opposed sharp needle-points,
for various effective sinusoidal voltages, in inches and in centimeters.
Kilovolts
Distance.
Sq. Root of
Mean Square.
Inches.
Cms
5
0.225
0.57
10
0.47
1.19
15
0.725
1.84
20
1.0
2.54
25
1.3
3.3
30
1.625
4.1
35
2.0
5.1
40
2.45
6.2
45
2.95
7.5
50
3.55
9.0
Kilovolts
Sq. Root of
Mean Square.
60
70
80
90
100
110
120
130
140
150
Distance.
Inches. Cms.
11.8
14.9
18.0
21.2
24.4
27.3
30.1
32.9
35.4
4.65
5.85
7.1
8.35
9.6
10.75
11.85
12.95
13.95
15.0
306 TESTS OF DYNAMOS AND MOTORS.
TESTS OF DYNAMOS AIV» MOTORS.
All reliable manufacturers of electrical machinery and apparatus are now
provided with the necessary facilities for testing the efficiency and other
properties of their output, and where the purchaser desires to confirm the
tests and guaranties of the maker, he should endeavor to have nearly, and
in some cases all such tests carried out in his presence at the factory, unless
he may be equipped with sufficient facilities to enable him to carry out like
tests in his own shops after the apparatus is in place.
Some tests, such as full load and overload, temperature, and insulation
(except dielectric) tests are best made after the machinery has been installed
and is in full running order.
Owing to the ease and accuracy with which electrical measurements can
be made, it is always more convenient to make use of electrical driving
power for dynamos, and electrical load for the dynamo output, and in the
case of motors, a direct-current dynamo with electrical load makes the best
load for belting the motor to.
No really accurate tests of dynamo efficiencies can be made with water-
wheels, and only slightly better are those made by steam-engines, owing
to unreliability of friction cards for the engine itself and the change of fric-
tion with load.
"Where it is necessary to use a steam-engine for dynamo testing, all fric-
tion and low load cards should be taken with the steam throttled so low as
to cut off at more than half stroke, and to run the engine at the same speed
as when under load.
The tests of the engine as separated from the dynamo are as follows : —
a. Friction of engine alone.
b. Friction of engine and any belts and countershaft between it and the
dynamo under test.
Consult works on indicators and steam-engines for instructions for deter-
mining power of engines under various conditions.
The important practical tests for acceptance by the purchaser, or to deter-
mine the full value of all the properties of dynamos and motors, are to learn
the value of the following items : —
Rise of temperature under full load.
Insulation resistance.
Dielectric strength of insulation.
Regulation.
Overload capacity.
Efficiency, core loss.
Bearing friction, windage and brush friction.
I2R loss in field and field rheostat,
I2R loss in armature and brushes.
Note. — If a separate exciter goes with the dynamo, its losses will be
determined separately as for a dynamo.
Methods of determining each of the above-named items will be described,
and then the combinations of them necessary for any test will be outlined.
Temperature. — The rise of temperature in a dynamo, motor, or
transformer, is one of the most important factors in determining the life of
such piece of apparatus; and tests for its determination should be carried
out according to the highest standards that can be specified, and yet be
within reasonable range of economy. The A. I. E. E. standards state the
allowable rise of temperature above surrounding air for most conditions,
but special conditions must be met by special standards. For instance, no
ordinary insulation ought to be subjected to a degree of heat exceeding
212° F., or 100° C. And yet in the dynamo-room of our naval vessels the
temperature is said to at times reach '130° F., or even higher, which leaves a
small margin for safety. It is obvious that specifications for dynamos in
such locations should call for a much lower temperature rise in order to be
safe under full load.
For all practical temperature tests it is sufficient to run a machine under
its normal full-load conditions until it has developed its highest temperature,
although at times a curve of rise of temperature may be desired at various
loads.
TEMPERATURE. 307
All small dynamos, motors, and transformers, up to, say, 50 KW., will
reach maximum temperature in rive hours run under full load, if the tem-
perature rise is normal ; but larger machines sometimes require from 6 to 18
hours, although this depends quite as much on the design and construction
of the apparatus as on size, as, for instance, the 5,000 h.p. Niagara Falls Gen-
erators reach full temperature in live hours. Temperature tests can be
shortened by overloading the apparatus for a time, thus reaching full heat
in a shorter period.
On dynamos and motors the temperatures of all iron or frame parts, com-
mutators, and pole-pieces, have to be taken by thermometer laid on the
surface and covered by waste. Note that when temperatures are taken
with the machine running, care must be taken not to use enough waste to
influence the machine's radiation. Where there are spaces, as air spaces,
in armature cores or in the held laminations, that will permit the insertion
of a thermometer, it should be placed there. Temperature of field coils
should be taken by thermometer laid on the surface and covered with waste,
and by taking the" resistance of the coils first at the room temperature and
again while hot immediately after the heat run. Temperature rise of arma-
ture windings can be taken by surface measurement and by the resistance
method also ; although being nearly always of low resistance, very careful
tests by fine galvanometer and very steady current are required in order to
get anything like accurate results.
The formula for determining the rise of temperature from the rise of
resistance is as follows : —
Temperature l»y rise in resistance; for copper. — The in-
crease in resistance due to increase in temperature is 0. 4% for each degree
Cent, above zero, the resistance at zero being taken as the base. If then
tx = temperature of copper when cold resistance is measured,
Rx = resistance at temperature tx,
t2 = temperature of copper when hot resistance is taken,
B2 = resistance at temperature U,
Then first reducing to zero degrees, we have
The increase in resistance from 0 to t2 degrees is R2 — R0l and hence we
have for final temperature,
U - R2~Bo ^ 004 (2)<
Substituting (1)
_ J?2(1 + .00^1)-JZ1
It is usually most convenient to correct all cold resistances to a tempera-
ture of 20° C, in which case we first reduce to zero and then raise to 20°.
The general formula for obtaining the resistance at t degrees is
JRt = (1 + .004 t) B0.
Hence i?20 = 1.08 JR0 and in terms of the cold resistance at temperature t.
_ (1-08 Z?n)
2 (1 + .004 1) w#
Formula (3) then becomes, when the cold resistance is at 20°,
1.08 i?„ 1 TU
t* = mxX0-<m=27° Xr2m (5)-
As the first formula requires but one setting of the slide rule, and the sub-
traction of the constant 250 can usually be done mentally, the advantage of
the temperature equation in this form is very great as regards both speed
and accuracy.
The temperature co-efficients most generally are
For copper 004
Resistivity of copper =r .000001595 per cubic Cm.
Resistivity of G. S. = .00003468 per cubic Cm.
308 TESTS OF DYNAMOS AND MOTORS.
The following parts should be tested by the resistance method and the
surface method also :
Field coils series, and shunt.
Armature coils. In 3-phase machines, take resistance between all three
rings.
On transformers which are enclosed in a tank filled with oil,'temperatures
by thermometer should be taken on —
Outside case, in several places.
Oil, on top, and deeper by letting down thermometer.
Windings, by placing thermometer against same, even if under oil.
Laminations, by placing thermometer against same, even if under oil.
Terminals.
Boom, as with dynamos and motors.
Also resistance measurements of primary and secondary windings, from
which the temperature by resistance can be calculated* as shown.
On transformers cooled by air forced through spaces between windings
and spaces in laminations, temperatures by thermometer should be taken
on —
Outside frame.
Air, outgoing from coils.
Air, outgoing from iron laminations.
Windings.
Terminals.
Room, in two or more places.
Also resistance measurements, hot and cold, should be taken, from which
rise of temperature, by resistance can be calculated.
Finally, the cubic feet of air, and pressure to force same through spaces
(easily measured by " U " tube of water), should be measured.
When other fluids are used for cooling, such as water passing through
piping submerged in oil, in which also the windings and core are submerged,
or through windings of transformers themselves (made hollow for tbe pur-
pose), the temperature of incoming and outgoing fluid should be measured,
the quantity used and the pressure necessary to force it through the path
arranged, besides the other points mentioned above.
The following parts should be tested by thermometer on the surface : —
Room, on side opposite from steam-engine, if direct connected, and always
in two or more parts of the room, within six feet of machine.
Bearings, each bearing, thermometer held against inner shell, unless oil
from the well is found to be of same temperature as the bearing.
Commutators and collector rings.
Brush-holders and brushes, if thought hotter than the commutator.
Pole-tips, leading and following.
Armature teeth, windings, and spider.
Field frame.
Terminal blocks, for leads to switch-board, and those for leads from the
brushes.
Series shunt, if in a compound-wound machine.
Shunt field rheostat.
Careful watch of thermometers is necessary in all cases, as they will rise
for a time and then begin to fall ; and the maximum point is what is wanted.
British authorities state a definite time to read the thermometers after
stopping the machine.
Care must also be taken to stop the machine rotating as soon as possible,
so that it will not fan itself cool.
A handy method of constructing a curve showing the rise of temperature
in the stationary parts of a machine at full load is to insert a small coil of
fine iron wire in some crevice in the machine in the part of which the tem-
perature is desired. Connect the coil with a mirror galvanometer and
battery.
The temperature coefficient of iron is high, and the gradual increase in
resistance of the coil will cause the readings on the galvanometer to grow
gradually less ; and readings taken at regular intervals of time can be
plotted on cross-section paper to form a curve showing the changes in
temperature.
m^^^^m^^^m
TEMPERATURE. 309
Records of temperature test. — During all heat runs, which
should be on non-inductive load, such as a water-box, readings should be
taken every fifteen (15) minutes of the following items.
On direct and alternating current motors and generators —
Armature, Volts (between the various rings where machine is more than
single-phase, in the case of alternators, and between brushes,
in the case of a D. C. machine).
Amperes (in each line).
Speed.
Field, Volts.
Amperes.
On synchronous converters : —
Armature, Volts (between all rings on A. C. end, and between brushes on
D. C. end).
Amperes, per line A. C. end, also D. C. end.
Speed.
Field, Volts.
Amperes.
On transformers, compensators, potential regulators : —
Volts, primary.
Volts, secondary.
Amperes, primary.
Amperes, secondary.
Cycles.
Amount and pressure of cooling-fluid (if any is used).
On induction motors : —
Volts, between lines.
Amperes, in line.
Speed.
Cycles.
Overload. — The A. I. E. E. standards contain suggestions for overload
capacity (see page bl).
The writer has uniformly specified a standard overload of 25% for 3 hours,
and there seems to be no especial difficulty in getting machines for this
standard that do not heat dangerously under such conditions.
Insulation test. — Insulation resistance in ohms is of much less im-
portance than resistance against breakdown of the insulation under a
strain test, with alternating current of high pressure.
Make all insulation tests with a voltage as high, at least, as that at which
the machine is to be worked.
The following diagram shows the connections to be made with E some
external source of E.M.F. The formula used is
R = resistance of voltmeter.
E = E.M.F. across dynamo terminals. rmrm^,
e = reading of voltmeter connected as in [ ™l
diagram. K^M—S-
x = insulation resistance m ohms. anM4Tii^F ^^
Then x :
~§
=*(*-0- <^
According to the A. I. E. E. standards, FKAME'
the insulation resistance must be such that Fig. 1. Connections for volt-
the rated voltage of the machine will not meter test of insulation re-
send more than Tqoioorr of the full-load cur- sistance of a dynamo,
rent through the insulation. One megohm
is usually considered sufficient, if found by such a test. Where one megohm
is specified as sufficient, the maximum deflection that will produce that
value, and that must not be exceeded in the test, may be found by the fol-
lowing variation of the above formula :
_ BXE
e ~ 1,000,000 -f B
Strain test. — The dielectric strength of insulation should be deter-
mined by a continued application of an alternating E.M.F. for at least one
(1) minute. Trie transformer from which the alternating E.M.F. is taken
should have a current capacity at least four (4) times the amount of current
310 TESTS OF DYNAMOS AND MOTORS.
necessary to charge the apparatus under test as a condenser. Strain tests
should only be made with the apparatus fully assembled.
Connect on a D.C. machine as in the following diagram.
Strain tests should be made with a sine
wave of E.M.F., or with an E.M.F. having
the same striking distance between needle
points in air.
See article 40 A. I. E. E. standards for
proper voltages.
Stearnlation. — The test for regula-
tion in a dynamo consists in deterniini ng
its change in voltage under different
loads, or output of current, the speed be-
Fig. 2. Connections for strain ing maintained constant,
test of dynamo or motor or The test for regulation in a motor
transformer insulation. consists in determining its change of
speed, under different applied loads,
when the voltage is kept constant.
Standards. — For full details of standards of regulation of different
machines, see report of the Committee on Standardization of the A. I. E. E.
at the beginning of this chapter.
Herniation Tests, J>ynamios, Shunt or Compound, and
Alternators.
The dynamo must be run for a sufficient length of time at a heavy load to
raise its temperature to its highest limit ; the field rheostat is then adjusted,
starting with voltage a little low, and bringing up to proper value to obtain
the standard voltage at the machine terminals, and since a constant temper-
ature condition has been reached, must not again be adjusted during the
test. Adjust the brushes, in the case of a D. C. machine, for full-load con-
ditions, and they should not receive other adjustment during the test. This
is a severe condition, and not all machines will stand it ; but all good dy-
namos, Avith carbon brushes, Avill stand the test very well, provided the
brushes are adjusted at just the non-sparking point at no load.
Load is now decreased by regular steps, and when the current has settled
the following readings are taken : —
Speed of dynamo (adjusted at proper amount).
Current in output (a non-inductive load should be vised).
If alternator, current in each line if more than single-phase.
Volts at machine terminals.
Amperes, field.
Volts, field.
Note sparking at the brushes (they should not spark any with carbon
brushes).
Readings should be taken at at least ten intervals, from full load to open
circuit (no load) ; and load should then be put on gradually and by the same
steps as it was brought down ; and the same records should be made back
to full-load point, and beyond to 25% overload.
If the readings are to be plotted in curves, as they always should be, it
will make little difference if the intervals or steps are not all alike ; and
should the steps be overreached in adjusting the load, the load must not, in
any circumstances, be backed up or readjusted back to get regular inter-
vals or a stated value, as the conditions of magnetization change, and throw
the test all out. In case the current is broken, or the test has to be slowed
down in speed or stopped, it must be commenced all over again. Finally,
when the curves are plotted, draw, in the case of a compound-wound ma-
chine, a straight line joining the no-load voltage and the full-load voltage ;
and the ratio of the point of maximum departure of the voltage from this
line to the voltage indicated by the line at the point will be the regulation
of the machine. •
The readings as obtained give what is called a field compounding curve.
In the case of a shunt or separately excited machine, the procedure for the
test is the same ; but when the curve is plotted, the regulation is figured as
equal to the difference between the no-load voltage and full-load voltage,
divided by the full-load voltage. The curve is called a characteristic in
this case.
DYNAMO EFFICIENCY.
311
Regulation Tests, Motors, Shunt, Compound, and
Induction.
After driving the motor under heavy load for a length of time sufficient
to develop its full heat, full-rated load should be applied, the field rheostat,
if any is used, and brushes adjusted for the standard conditions ; then the
load should be gradually removed by regular steps, and the following read-
ings be made at each such step : —
Amperes, input.
Volts at machine terminals (kept constant).
Watts, if induction motor.
Speed of armature.
Note sparking at brushes.
Amperes, field (in D. C. machines).
At least ten steps of load should be taken from full-rated load to no load.
The ratio of the maximum drop in speed between no-load and full-load,
which will be at full-load, to the speed at full-load, is the regulation of the
motor.
Efficiency Tests. Urnamos.
The term efficiency has tAvo meanings as applied to dynamos ; viz., electrical
and commercial. The electrical efficiency of a dynamo is the ratio of elec-
trical energy delivered to the line at the dynamo terminals to the total electri-
cal energy produced in the machine. The commercial efficiency of a dynamo
is the ratio of the energy delivered at the terminals of the machine to the total
energy supplied at the pulley. Otherwise the electrical efficiency takes into
account only electrical losses, while the commercial efficiency includes all
losses, electrical, magnetic, and frictional.
Core-loss Test, and Test for friction and Windage.
These losses are treated together for the reason that all are obtained at
the same time, and the first can only be determined after separating out the
others.
A core-loss test is ordinarily run only on new types of dynamos and
motors, but is handy to know of any machine, and if time and the facilities
are available, should be run on acceptance tests by the consulting engineer.
It consists in running the armature at open circuit in an excited field, driv-
ing it by belt from a motor the input to which, after making proper deduc-
tions, is the measure of the power necessary to turn the iron core in a field
of the same strength as that in which it will work when in actual use.
Connect as in the following diagram, in which A is the dynamo or motor
under test, and B is the
motor driving the arma-
ture of A by means of
the belt. The field of A
must, of necessity, be
separately excited, as
its own armature circuit
must be open so that
there may be no current
generated in its conduc-
tors. Fig. 3. Connections for a test of core loss.
The motor field is sep-
aratelv excited and kept constant, so that its losses and the core loss ot tne
motor' itself being constant for all conditions of the test, may be cancelled
in the calculations. The motor B should be thoroughly heated ; and bear-
ings should be run Ion? enough to have reached a constant friction condi-
tion before start imi tins test, so that as little change as possible will taite
place in the different "constant" values. It is necessary to know accu-
rately the resistance of the armature, B, in order to determine its I-R loss
at different loads, and to use copper brushes to practically eliminate the
It is well t(f make a test run with the belt on in order to learn at what
speed it is necessary to run the motor in order to drive the armature A at its
proper and standard speed.
UNDER. TEST
312
TESTS OF D/NAMOS AND MOTORS.
Friction, core loss, and windage of motor. — The speed having
been determined, the belt is removed, and the motor field kept at its final
adjustment, and enough voltage is supplied to the motor armature to drive
it free at the standard speed. The watts input to the armature is then the
measure of the loss (I2li) in the motor armature plus the friction of its bear-
ings, plus its windage, plus core loss, or the total loss in the motor at no
load. This is called the " running light " reading.
friction and windage of dynamo. —After learning the losses
in the driving motor, the belt is put on and the dynamo is driven at its
standard speed without excitation, and in order to be sure of this a volt-
meter may be connected across the armature terminals ; if the slightest
indication of pressure is found, the dynamo field can be reversely excited,
to be demagnetized, by touching its terminals momentarily to a source of
E.M.F. Take a number of readings of the input to the motor in order to
obtain a good mean, and the friction and windage of dynamo is then the
input to the motor, less the " running light" reading previously obtained,
the I2R of motor armature having been taken out in each case.
Let Wx = watts input to motor,
nx — I2R in motor armature when driving dynamo,
/=: " running light" reading of motor,
}\ = friction and windage of dynamo armature,
n9 = I2R of motor armature when " running light,"
then /i = Wx - (% +/ +/i + n2) .
ISrnsh friction. — The friction of brushes is ordinarily a small portion
of the losses ; but when it is desirable that it should be separated from other
losses, it can be done at the same time and in the same manner as the test
for bearing friction. The brushes can be lifted free from the commutator
or collector rings when the readings of input to the driving motor for bearing
friction are taken ; dropping the brushes again onto the commutator and
taking other readings, the difference between these last readings and those
taken with brushes off will be the value of brush friction. Note, that allow-
ance must be made as before for increase of I2R loss in the motor armature.
Test for core loss. — Having determined the friction and other losses
that are to be deducted from the total loss, a current as heavy as will ever
be used is put on the dynamo field, the motor is supplied with current
enough to drive the dynamo at its standard speed, and the reading of watts
and current input to the motor armature is taken.
The dynamo field current is now gradually decreased in approximately
regular steps, readings of the input to the motor being taken at each such
step until zero exciting current is reached, when the exciting current is
reversed and the current increased in like steps until the highest current
reading is again reached. This may now be again decreased by intervals
back to zero, reversed and increased back to the starting-point, which will
thus complete a cycle of magnetization ; ordinarily this refinement is not,
however, necessary.
This test must always be carried through without stop ; and although it is
desirable to make the step changes in field excitation alike, if the excitation
be changed in excess of the regular step it must not be changed back for the
purpose of making the interval regular, as it will change the conditions of
the residual field. When the readings are plotted on a curve, regularity in
intervals of magnetization is not entirely necessary.
The following ruling makes a convenient method of tabulation : —
Dynamo.
Motor.
Speed
amperes
in
field
Speed
amperes
in
field
amperes
in
armature
i
volts
in
armature
e
Constant
Constant.
Constant.
^■MHH^^M
DYNAMO EFFICIENCY.
Computations,
313
watts in
armature
belt on
W„ = ie
Kunning
light
reading
/
I*R
in arm.
belt on
im
in arm.
belt off
Core loss
Plot on curve with exciting-current values on the horizontal scale, and
the core loss on the vertical, and the usual core-loss curve is obtained.
Separation of core loss into Hysteresis and JEddy
current loss.
3 due to hysteresis and friction vary directly with the speed ; losses
due to eddy currents vary "as the square of the speed.
Current and voltage must now be applied to the dynamo armature to
drive it as a motor at proper speed, with the current in the separately
excited field kept constant at proper value. Drive the motor (dynamo) at
say two different speeds, one of which may be A' times the other ; let
L — total loss in watts,
f\~=- loss in friction,
JI=z loss by hysteresis,
D = loss by eddy currents, or
L =f1 + H+ D at the first speed,
Lx = Kf, + KH-\- K"-D at second g
K X (1) = AA = Kf\ + lcH+ KB,
(2) — (3) = L, — KL — A2D — KD,
L1 — KL = KD{K—\),
If K = 2, then
D =
A(A-l)
_ LX — 2L
CD
(2)
(3)
(4)
(6)
(G)
2(2-1) 2
Kapp and Housman separately devised the above method of separating
the losses, but stated them somewhat differently.
With the field separately excited at a constant value, different values of
current are supplied to the armature at different voltages, to drive it as a,
motor. The results are plotted in a curve which is a straight line, rising as
the volts are increased.
The following diagram shows how the losses are plotted in curves. The
test as a separately excited motor is run at a number of different values of
voltage and current in the armature, and the results are plotted in a curve
as shown in the following diagram. The line a, b, is plotted from the results
of the current and volt readings.
The line a, c, is then drawn parallel to the base, and represents the sum
of all the other losses, as shown by previous tests, and they may be further
separated and laid off on the chart.
Foucault currents are represented in value by the triangle a, c, b.
If another run be made with a different value of excitation, a curve, %, 61}
or one below the original a, b, will be gotten, according to whether the total
losses have been increased or decreased.
If the higher values of current tend to demagnetize, by reason of the eddy
currents in the armature, the curve a, b, will curve upward somewhat at the
upper end.
It is thus seen how to measure core-loss, and friction and windage of a
dynamo; knowing this and the resistance of the various parts, the efficiency
is quickly calculated, thus
Let W= core-loss -f- friction (obtained as shown),
V = voltage of armature,
I=i current of dynamo armature,
Ix =r current of dynamo field,
R = resistance of armature and brushes,
jBx — resistance of field.
314
TESTS OF DYNAMOS AND MOTORS.
FOUCAUlT currents
HYSTERESIS
BOSH FRICTION
Then considering the above as the only losses (i.e., neglecting rheo-
stats, etc.),
Vc
EfficienCy = Vc+ItR + VRi+W
This is the simplest method of getting the efficiency, but does not take in
"load losses" «if any
should exist.
Anotnea' test for
efficiency. — It' the dy-
namo under test is not of
too large capacity, and a
load for its full output is
available, either in the
form of a lamp bank,
water rheostat, or other
adjustable resistance,
then one form of test is
to belt it to a motor.
By separately exciting
the motor fields, and run-
ning the motor free with
belt off, its friction can
be determined, and with
the resistance of the ar-
mature known, the input
to the motor in watts,
less the friction and the
I2R loss in its armature
at the given load, is a di-
rect measure of the
power applied at the pul-
ley of the dynamo. The
output in watts, meas-
ured at the dynamo terminals, then measures the efficiency of the machine.
Let,
W= watts input to motor,
I = losses in motor, friction, I-R, and core-loss,
W1 = watts output at dynamo terminals.
% of efficiency = 100 X ,,r _|_ . = commercial efficiency.
Knowing the current flowing in the armature and in the fields, and also
knowing the resistance of the same, the I2R losses in each may be calcu-
lated, which, added to the output at the dynamo terminals, shows the total
electrical energy generated in the ma-
chine.
If in ■= the 7 2R loss in the armature,
/= the I2R loss in the fields,
The electrical efficiency will be
% electrical efficiency
BEKBINQ. FRICTION AND WINDAGE
VOLTS IN ARMATURE".
d
Fig. 4. Diagram showing separation of losses
in dynamos.
:100 )
"',
W^ + m+f
GENERATOR
WATER
RHEOSTAT.
J FOB LOAD
The following diagram shows the
connections for this form of test.
It must be obvious that a steam-en-
gine, or other motive power that can
be accurately measured, may be used
in place of the electric motor ; but
measurements of mechanical power Fig. 5. Connections for efficiency
are so much more liable to error that test of a generator. Driven by an
they should be avoided where possible. electric motor.
The only objection to this method
is that the friction of the driving-motor varies with the load, and the loss
in the belt is not considered.
DYNAMO EFFICIENCY.
315
Kapp's Test with two Similar I)j-nani<w.
W&ere two similar dynamos are to be tested, and especially where their
capacity is so great as to make it difficult to supply load for them, it is com-
mon to test them by a sort of opposition method ; that is, their shafts are
either coupled or belted together, the armature leads are connected in series,
the field of one is weakened enough to make a motor of it ; this motor drives
the other machine as a generator, and its current is delivered to the motor.
The difference in currents between the two machines, and for exciting the
fields of each, is supplied by a separate generator.
The following diagram shows the switch
method of connecting two similar dyna-
mos for Kapp's test. D, is the dynamo ;
M, the machine with field weakened by
the resistance R, that acts as a moter, and
G, is the generator that supplies the en-
ergy necessary to make up the losses, ex-
citation, and differences.
Start the combination and get them to
standard voltage, as shown by the volt-
meter ; then take a reading of the cur-
rent with the switch on b, and another
with the switch on a. Let the first read- Fig-. 6. Connections for Kapp's
ing be m, and the, second d, and let x be method of efficiency test of two
the efficiency of either machine, then similar dynamos.
% efficiency of the combination = 100 X ~j, and
:V(lTOx»)
In using this formula the efficiency of the dynamo at its load is assumed
the same as the motor at its simultaneous load, which is usually true above
the | load point. The loss in motor-field rheostat should also be'allowed for.
Another similar method, called "pumping back," is to connect the shafts
of the two machines as before, by clutch or belt ; arrange the electrical
connections and instruments as in the following diagram.
D is the dynamo under test ; M is the similar machine used as a motor ;
and G is the generator for supplying cur-
rent for the losses and differences be-
tween M and D. The speed of the
combination, as well as the load on D,
can be adjusted by varying the field of M.
The motor, M, drives D by means of
the shaft or belt connection. M gets its
current for power from two sources, viz.,
G and D. In order to determine the
amount of mechanical power developed
by M, and also to be able to separate the
Fig. 7. Efficiency test of two magnetic and frictional losses in the two
similar dynamos. machines, a core-loss test should have
been made on the machine M at the same
speed, current, and E.M.F. as it is to have in the efficiency test. The loss
in the cable connections between M and D must also be taken into account,
and is equal to the difference in volts between voltmeters c, and b, X the
current flowing in ammeter n.
Let V— E.M.F. of D, shown on c,
V, = E.M.F. of M by vm. b,
V„ = E.M.F. of G by vm. a,
1 = amperes current from D by am. n,
I, — amperes current from G by am. I,
Ia = amperes current in M = I-\- In
e = drop in connections between I) and M = V — Vf/,
L = loss in connections between D and ~NL = e X I,
r = D's internal resistance,
rx = M's internal resistance,
w = core loss + armature loss + field loss -f- friction of M in
watts -f- L (loss in connections).
316
TESTS OF DYNAMOS AND MOTORS.
Then
W— the useful output of D = V X I,
W, = energy supplied by G = V„ X /,
W -\- W; — total energy supplied to M,
W -\- Wj — w — energy required to drive D,
% commercial efficiency of D =
I~r =z electrical loss in D,
% electrical efficiency =r
W+ W,
W
W + I-r
X 100.
The other way of calculating the efficiency with this arrangement is to
measure the output = Wx from G, Avith full load on D. Wx then is the
losses of both machines under load ; and knowing the I2R loss in the arma-
ture and field of each, the efficiency is quickly and accurately calculated.
This method is best, as no core loss is required, and includes the " load
losses."
ELECTRICAL METIffOJJ ©JF f)VPPL¥06 THE
LOSSES A.V C©I¥STAJ¥I- POTESTIAL.
Modification of " Kapp Method," by Prof. Wm. L. Puffer, from notes
privately printed for the students of the Massachusetts Institute
of Technology .
Specification.
Two similar shunt dynamos under full load, one as a motor driving the
other as a loaded dynamo through a mechanical coupling. Mains at same
voltage as dynamos, and only largo enough to supply the full-load losses of
both dynamos.
Line up the two dynamos carefully, and mechanically connect them by
a good form of mechanical coupling, strong enough to transmit the full load,
to the dynamo.
Connect the field magnet windings of each machine to the supply mains,
putting a suitable field rheostat in each. If desirable for any reason, the
field of the dynamo may be left connected as designed ; but the field of the
motor, whicli does not in any way enter as a quantity to be measured during
the test, should be connected to the supply mains.
Fig. 8. Diagram of Connections for Professor Puffer's Modifi-
cation of Kapp's Dynamo Test.
Method of Starting-.
Close the field circuit of the motor, and by the motor starting rheostat
gradually bring the motor up to full speed. The dynamo armature will be
also at proper speed and on open circuit. Now close the dynamo field and
adjust the field rheostat until the dynamo is at about normal voltage.
Adjust the speed roughly at first by the use of the field rheostat of the
motor, remembering that an added resistance will cause the speed to rise.
Next see that the voltage of the dynamo is equal to that of the motor, or,
in other words, that there is no difference of potential between opposite
sides of the main switch on the dynamo. Close this switch and there may,
or may not, be a small current in the dynamo armature. Now carefully
ELECTRICAL METHOD OF SUPPLYING LOSSES. 317
increase the armature voltage of the dynamo, watching the ammeter, and
weaken that of the motor ; a current will flow from the dynamo to the
motor, and the motor will transmit power mechanically to the dynamo.
The current which was first taken from the supply wires to run the motor
and dynamo armatures will increase somewhat. Ly a careful adjustment
of the two rheostats and the lead on each machine, the conditions of full
load of the dynamo may be produced. The motor is overloaded and its arm-
ature will carry the sum of the dynamo and supply currents. Great care
must be taken in adjusting the brushes of the machines, because of great
changes in the armature reactions which take place as the brushes are
moved. It is well to remember that a backward lead to the motor brushes
will increase the speed, as the armature reactions will considerably weaken
the effective field strength.
Cautions.
The increase of speed will raise the dynamo voltage, and cause the cur-
rent flowing in the armatures to greatly increase. A forward movement of
the motor brushes will reduce both speed and current. A forward move-
ment of the dynamo brushes will increase the armature reaction, and cut
down the current through the armatures, while a backward movement will
cause it greatly to increase. Yery great care must be taken in adjusting
the brush lead, as a movement of the brushes of either machine, Avhich
would be of little importance usually, will produce sometimes a change in
current value equal to the full-load current. It is quite possible but poor
practice to produce the load adjustment by use of the brushes alone.
It is best to have ammeters of proper size in all circuits, but those actually
required are in the dynamo leads and in the supply mains. A single volt-
meter is all that is required.
The field magnet circuits ought to be connected as shown, and the am-
meters placed so that the energy in the fields does not come into the test of
the losses in the armatures. The magnet of the machine under test, a
dynamo in this case, should be under the proper electrical conditions for
the load, yet not in the armature test, because the object of the test can best
be made the determination of the stray power loss under the conditions of
full load ; then having found, this, assume the exact values of E, /, and
speed, and so build up the data for the required efficiency under a desired
set of conditions which might not have been exactly produced during the
test.
Immediately after the run, all hot resistances should be measured as
rapidly and carefully as possible, to avoid any error due to a change in
temperature.
The energy given to the two armatures less the I2R in each armature,
will be the sum of all the armature losses of the two dynamos under the
conditions of the test, so that we measure directly the armature losses of
the dynamos while fully loaded.
It is evident that the two armatures are not under exactly the same con-
ditions, except as to speed, for the dynamo armature will have an intensity
of magnetic field that will give an armature voltage of Vt -f 7^i2^, while
the motor will be weaker as Vf is the same for both armatures, and the
motor armature voltage will be Vt — ^A^A. All the iron core losses will be
made much greater in the dynamo than in the motor. The motor armature
must carry a current equal to the sum of the dynamo and supply currents,
and will get much hotter ; its reaction will also be greater, and there will be
a tendency for greater sparking at the brushes.
The total stray power thus obtained may be divided between the two
armatures equally, but preferably in proportion to the armature voltages,
unless the true law for the armatures is known. All resistances of wires, etc.,
must be noted and corrections applied, unless entirely negligible.
The two 15-H.P. dynamos quoted in an early part of these notes were
tested by the class of '93, using this method. One of the full-load tests is
here given as a sample of calculation. The exact rating of the dynamos is
not known, but is nearlv 45 amperes at 220 volts, with the dynamo at a speed
of 1600 r.p.m.
318
TESTS OF DYNAMOS AND MOTORS.
The averages of the observed readings taken during the test, and after a
run of about five hours to become heated, was as below.
E\ainpl« of* Calculation.
(Connections as shown in Fig. 8.)
Volts at supply point ......... 220.3
Amperes of 15.71
Output of dynamo, amperes 45.80
Dynamo field current ......... 1.945
Speed 1594.
To Measure Armature Resistance.
Motor V— 1.952 /— 10.18
Dynamo V = 2.406 J = 10.08
The motor field is out of the test while the dynamo field is in the test.
Calculation.
Watts supplied 220.3 x 15.71 = 3461.
.3430= V
.1962=/
.5392 = 3461
Dynamo armatures It. = Motor armature R. =
2.406 .3813 R 1.952 .2905 R
10 os -OOSS ad 10.18 -0077 am
.3778 = 0.2387 ^2S2~8 = 0.1918
2 2
1 ' S R 7 J
ad ad am am
Ja = 45.80 + 1.94 = 47.74 Ja = 45.80 + 15.71 = 6151
47.74* = j.6789 I 61-512 = j.7889
( .6789 2 ( .7889
R .2387= .3778 I R D i?.1918 .2828 I R M
a a a a a
.7356 = 554.0 .8606 = 725.4
Dynamo Field
7=1.945 .2889
V— 220.3 .3430 Field D
.6319 = 428.4
Watts supplied = 3461
Dynamo field = 428.4
IR M = 725.4
IR D = J55JU)
Total heat lost = 1697.8 1698
Total stray power = 1763 JfandZ).
,_^ wm m ^_i
ELECTRICAL METHOD OF SUPPLYING LOSSES. 319
Vad lam
Vt + IaRa Vt — IaRa
47.74 X -2387 .6789 61.51 X .1918 .7889
.3778 .2828
/ R = 11.4 — .0567 IB= 11.8 = .07T7
Vt = 220.3 Vt = 2203
231.7= Vad 20S.5= Vam
Divide the total stray power between the two armatures as their
armature voltages.
Stray power dynamo.
231.7
.2462
X 1763- .6436
231.7 + 208.5 '
13649
Stray power dynamo = 928.0 = .9675
Stray power motor = 1763 — 928.0 = 835.0
The quantity 928.0 is the object of our test, i.e., the stray power when
as nearly as may be under actual running conditions.
Calculation of [Efficiencies.
As
run.
Output of dynamo = 220.3 X 45.80
.3430
.6609
^0039 = 10090
"Watts output
554
hRad
10090
428
Field
544
928
Stray power
428
11990
Watts input to the dynamo.
11062
= Work done by current.
Eff.
of Conv.
11062
.0437
.0789
11990
.9648 = 92.2 per cent.
Coin in.
Eff.
10090
.0039
.0789
11990
.9250 = 84.1 per cent.
Power
required to run Dynamo.
11990
.0789
.8727
"746
.2062 = 16.1 H. P.
In this test, carbon brushes were used, and the lead adjusted as carefully
as possible. If the exact rating of this dynamo had been 45 amperes and 220
volts at a speed of 1600, and we wished to find the efficiencies corresponding,
we should proceed in this way.
The test was made under conditions as nearly as possible to the rating,
and the stray power as found will not be perceptibly different from what it
would be under the exact conditions.
When the load has been as carefully adjusted as in this test, it is seldom
worth while to make these corrections, as they are smaller than changes pro-
320
TESTS OF DYNAMOS AND MOTORS.
duced by accidental charges of oiling, temperature, brush pressure, etc.,
of two separate tests.
Advantages of the Method.
Small amount of energy used in making the test, namely, only the losses.
No wire or water rheostat required. Test made under full load, and yet
the losses are directly measured. All quantities are expressed in terms de-
pending on the same standards, and therefore the efficiency will be but little
affected by any error in the standards. No mechanical power measure-
ments are made, and all measurements are electrical.
Disadvantages.
Requires two similar machines. Armature reactions are not alike in both
machines. Leads are not alike. The iron losses are not the same. No belt
pull on bearings. Must line up machines and use a good form of mechanical
coupling. Sometimes difficult to set the brushes on the motor. The motor
armature is much overloaded.
EXCITER
ELDS
OF MOTORS
Fig. 9. Diagram of Connections for Test of Street Car
Motors, Prof. Puffer.
Fig. 10. Diagram of Connections of Modification of the
Previous Diagram, by Prof. Puffer.
This method is of advantage in the test of railway series motors, if slightly
modified by the separate excitation of the motor fields. If the series field
ELECTRICAL METHOD OF SUPPLYING LOSSES.
321
windings were not separately excited there will be a great deal of unneces-
sary difficulty from great changes of speed as the load is varied. However,
one field may be kept in circuit on the machine used as a motor, as the test
can then be made with the motor under its exact conditions. There will be
a very great change of speed during adjustment of load, but there will be no
danger of injuring anything, as the separate excitation of the dynamo field
is an aid to steadiness. Railway motors, as generally made, will not stand
their full rated load continuously, and the motor is likely to get too hot if
not watched ; the machine used as a dynamo will run cold, as it will not
have a large current in it. The friction of brushes is very large in these
motors, and in general there is a want of accuracy in the division of the
total stray power between the two armatures. It can only be very approxi-
mately done bv the aid of curves showing the relation between speed and
stray power, and armature voltage and stray power.
Hopkinson's Test of two Similar Dynamos.
In the original Hopkinson method, the two dynamos to be tested were
placed on a common foundation with their shafts in line, and coupled to-
gether. The combination was then driven by a belt from an engine, or other
source of power, to a pulley on the dynamo shafts. The leads of both ma-
chines were then joined in series, and the fields adjusted so that one acted
as a motor driven by current from the other. The outside power in that
case supplied, and was a measure of the total losses in the combination, the
efficiency of either machine being taken as the square root of the efficiency
of the combination.
Many modifications of this test have been used, especially in the substitu-
tion of some method of electrically driving the combination, as the driving-
power is so much easier measured if electrical.
This test is someAvhat like that last given, but the two machines are con-
nected in series through the source of supply for the difference in power,
such as a storage battery or generator.
The following diagram shows the con-
nections for the Hopkinson test, with
a generator for supplying the differ-
ence in power.
In this test the output of G plus en-
ergy taken by Mt (motor driving the
system), gives losses of motor and dy-
namo (the losses of Mx being taken out.
These losses being known, the efficiency
can be calculated.
If the two machines D and M are
alike, G- supplies the I2R losses of ar-
matures, and M the friction, core
losses, and I2R of fields.
Another method useful where load and
current are both available, is to drive one of two similar dynamos as a
motor, and belt the second dynamo to it. Put the proper load on the dy-
namo, and the efficiency of the combination is the ratio of the watts taken
out of the dynamo to the watts supplied to the motor. The efficiency of
either machine, neglecting small differences, is then the square root of the
efficiency of both.
If W= watts put into the motor,
W, = watts taken from the dynamo,
x — efficiency per cent of the combination,
y =: efficiency of either machine.
_ W, X 100
X~ W
Fig. 11. Diagram of connections
for Hopkinson's test of two sim-
ilar dynamos.
The above test is especially applicable to rotary converters, the belt being
discarded, and the a c sides being connected by wires ; thus the first ma-
chine supplies alternating current to the second, which acts as a motor gen-
erator with an output of direct current. The only error (usually small) is
322
TESTS OF DYNAMOS AND MOTORS.
m.7>j
due to the fact that both machines are not running same load, since that
one supplies the losses of both.
Eleming-'s Modification of Hopkin-
son Test. — In this case the two dynamos under
test are connected together by belt or shafts, and
are driven electrically by an external source of
current, say a storage battery or another dynamo,
which is connected in series with the circuit of
the two machines. Figure 12 shows the con-
nections for this test, which will be found car-
ried out in full in Fleming's " Electrical Labo-
ratory Notes and Forms."
MOTOR TESTS.
Fig. 12.
PRONY BRAKE
Fig. 13.
Probably the most common method of testing the efficiency and capa-
city of motors is with the prony brake, although in factories where spare
dynamos are to be had, with load available for them, there can be no
question that belting the motor to the dynamo with an electrical load is
by far the most accurate, and
the easiest to carry out.
Prony brake test. — In
this test a pulley of suitable
dimensions is applied to the
motor-shaft, and some form of
friction brake is applied to the
pulley to absorb the power.
The following diagram shows
one of the simplest forms of
prony brake ; but ropes, straps,
and other appliances are also often used in place of the wooden brake shoes
as shown.
Note. — See Flather, " Dyndmmeters and the Measurement of Power.'''
As the friction of the brake creates a great amount of heat, some method
of keeping the pulley cool is necessary if the test is to continue any length
of time. A pulley with deep inside flanges is often used ; water is poured
into the pulley after it has reached its full speed, and will stay there by
reason of the centrifugal force until it is evaporated by the heat, or the
speed is lowered enough to let it drop out. Rope brakes with spring bal-
ances are quite handy forms.
The work done on the brake per m inute is the product of the following items:
I = the distance from the centre of the brake pulley to the point
of bearing on the scales, in feet,
n — number of revolutions of the pulley per second,
Power :
H.P.:
: weight in lbs. of brake bearing on scales.
-2tt I ni»
r I mo
~550
: foot-pounds per second, and
The input to the motor is measured in watts, and can be reduced to horse-
power by dividing the watts by 74G ; or the power absorbed by the brake
can be reduced to watts as follows : —
If the length, Z, be given in centimeters, and the weight, w, be taken in
grams, the power absorbed by the brake is measured directly in
ergs, and as one watt = 107 ergs, the
Watts output at the brake = — ^ — = W.
The watts input =
If the output is measured in I
W=2.72
W,
Input in h.p. = —^
Output H.P. = °m
107
W .
' W,
- feet and w = lbs., then
• I w.
= h.p.
550
h.p.
MOTOR EFFICIENCY.
323
If it is desired to know the friction and other losses in the motor, after the
brake test has been made, the brake can be removed, and the watts neces-
sary to drive the motor at the same speed as when loaded, can be ascertained.
Electrical load test (including loss in belting, and extra loss in bear-
ing s due to pull of belt) . — This test 'consists in belting a generator to the
motor and measuring the electrical output of the generator, which added to
the friction and other losses in the generator, makes up the load on the
motor. The efficiency is then measured as before, by tbe ratio of output to
input. The great advantage of this form of test is, that it can be carried on
for any length of time Avithout trouble from heat, and the extra loss in
bearings due to pull of belt is included, which is therefore an actual com-
mercial condition.
In this form of test the losses in the generator are termed counter torque,
and the method of determining them is given following this.
Counter torque. — In tests of some motors, especially induction mo-
tors, the load is supplied by belting the motor under test to a direct current
generator having a capacity of output sufficient to supply all load, including
overload. ,
In determining the load applied to the motor and the counter torque, it is
necessary to know, besides the /. E. or watts output of the generator, the
following : —
I2R of generator armature,
Core loss of generator armature,
Bearing and brush friction and windage of generator,
Extra bearing friction due to belt tension.
It is necessary to know the above items for all speeds at which the com-
bination may have been run during the testing. This is especially useful
in determining the breakdown point on induction and synchronous motors,
both of which can be loaded to such a point that they " fall out of step."
While the motor is under test especial note should be made of the speeds
at which the motor armature and generator armature rotate, and of the
watts necessary to drive the motor at the various speeds without load.
The counter torque will then be the sum of the following three items : —
W = 1 2R of generator armature,
Wc = core loss of generator armature,
F = bearing and brush friction and windage of the generator armature.
The field of the D. C. machine must be separately excited and kept at the
same value during the load tests and the tests for" stray power " and does
not enter into any of these calculations.
Belt-on test. — After disconnecting current from the motor under test,
and with the belt or other connection still in place, supply sufficient volt-
age to the D. C. machine armature to drive it as a motor at the speeds run
during the motor test, holding the field excitation to the same value as before,
but adjusting the voltage supplied to the armature for changing the speed.
Take readings of
Speed, i.e., number of revolutions of D. C. armature,
Volts at D. C. armature,
Amperes at D. C. armature.
Construct a curve of the power required to drive the combination at the
various speeds shown during the motor test.
Belt-off test. — Throw the belt or other connection off, and take read-
ings similar to those mentioned above, which will show the power necessary
to drive the D. C. machine without belt.
Then for any speed of the combination the " stray power'" will be found
as follows : —
W, =■ watts from belt-off curve, required fo drive the D. C. machine as
a motor.
W// = watts from belt-on curve, required to drive the combination.
Wc = core loss in D. C. armature.
F=z friction of D. C. machine, belt off.
F, = friction of motor under test, running light and without belt.
/ = increase in bearing friction of D. C. machine, due to belt tension.
fj = increase in bearing friction of motor, due to belt tension.
324 TESTS OF DYNAMOS AND MOTORS.
From the belt-off curve,
W, = wo + F. (1)
From the belt-on curve,
Wit = Wc + F + Fi +/ +/,. (2)
Subtract (1) from (2)
W„- W,-F,+f+f.
Wit-Wt — Ft =/+/,. (3)
The values of / and /, cannot be determined accurately ; but if the ma-
chines are of about the same size as to bearings and weights of moving
parts, it is very close to call them of equal value, when,
C Wit — W, — F,)
/or/, = ^ lJ *l) (4)
The friction F, of the motor under test has been previously found by
noting the watts necessary to drive it at the various speeds. If it is an in-
duction motor, the impressed voltage is reduced very low in determining
the friction in order that the core loss may be approximately zero.
As all the values of the quantities on the right-hand side of the equation (4)
are now known, /is determined, and may be added to W, to give the total
" stray power." A curve is then plotted from the values of " stray poioer "
at different speeds.
Counter torque = W,-\- f +,
Total load = I E + IUi + ( W, -f /),
Where I E =z watts load on the D. C. machine when it is being driven by
the motor,
If S = W, -f /= ^ stray poioer" then
Total load = I.E.+ I*R + S.
The value of / is so small when compared with the total load, that any
ordinary error in its determination will cut no figure.
Test of Street-Railway Motors.
The " pumping -bach " test, as described before, with some little modifica-
tion serves for testing street-railway motors. The following diagram shows
the arrangement and electrical connections.
The motors are driven mechanically by another motor, the input to which
is a measure of the
losses, frictional, core
losses, gears, bearings,
etc., in the two motors ;
the two motors are
connected in series,
through a booster, B,
care being taken to
make the connections
in such a manner as to
have the direction of
rotation the same ; Fig. 14. Diagram of connections and arrange-
and their voltages op- ment of street-railway motors,
posing.
Headings are taken and the efficiencies are calculated as in the " pumping-
back " test.
In eliminating the friction of bearings, etc., and of the driving-motor, it is
run first without belts, the input being recorded as taken, at the speed
necessary. The belt is then put on and a reading taken at proper speed,
with both the motors under load.
The load being adjusted by varying the field of booster B, the total losses
of the system are then IE from booster plus the difference between belt-on
reading with full load through the motors, and belt-off reading as noted
(allowance being made for change of I2R of driving-motor). If the two
motors are similar, half this value is the loss in one motor, from which the
efficiency can be calculated as previously shown.
Induction motors. — In addition to the tests to which the D. C. motor
MOTOR EFFICIENCY. 325
is ordinarily submitted, there are several others usually applied to the in-
duction motor, as follows : —
Excitation ; Stationary impedance; Maximum output ; and some variations
on the usual heat and efficiency tests.
Excitation : This is also the test for core loss-f- friction, allowance being
made for 1*11 of field ; with no belt on the pulley the motor is run at full
impressed voltage. Read the amperes of current in each leg, and total
watts input. The amperes give the excitatiou or " running-light" current,
and the watts give core loss + friction -f- I'2R of excitation current.
Stationary impedance: Block the rotor so it cannot move, and read volts
and amperes in each leg, and total watts input. This is usually done at
half voltage or less, and the current at full voltage is then computed by
proportion. This then gives the current at instant of starting, and a meas-
ure of impedance from which, knowing the resistance and core loss, other
data can be calculated, such as maximum output, efficiency, etc.
Maximum output : This might be called a brealc-doion test; as it merely
consists in loading the motor to a point where the maximum torque point is
passed and thus the motor comes to rest.
Keep the impressed voltage constant and apply load, reading volts, am-
peres in each leg, the total Avatts input, and revolutions ; also record the
,load applied at the time of taking the input. Then take counter torque as
explained before, from which the efficiency, the apparent efficiency, the
power factor, and maximum output are immediately calculated.
Iff eat test. — Run motor at full load for a sufficient length of time to
develop full temperature, then take temperatures by thermometer at the
following points : —
1. Room, not nearer to the motor than three feet and on each side of motor.
2. Surface of field laminations.
3. Ducts (field).
4. Field or stator conductors, through hole in shield.
5. Surface of rotor.
6. Rotor spider and laminations.
7. Bearings, in oil.
During heat run, read amperes and volts in each line.
Efficiency test. — Apply load to the motor, starting with nothing but
friction ; make readings at twelve or more intervals, from no load to break-
down point. Keep the speed of A. C. generator constant, also the iinpressed
voltage at the motor.
Read, Speed of motor.
Speed of A. C. dynamo.
Amperes input to motor, in each leg.
Volts impressed at motor terminals.
"Watts input to motor, by wattmeter.
Current and volts output from D. C. machine belted to motor,
Counter torque as explained above, and excitation reading watts.
From the above the efficiency, apparent efficiency, power factor
( zr -^- — . — ^—. ) , and maximum output can be calculated.
\ real efficiency /
In reading watts in three-phase motors, it is best to use two wattmeters,
connected as shown in following sketch : —
1, 2, 3, are the three-phase lines leading to the
motor.
A and B are two wattmeters.
b is the current coil of A, and b1 of B.
a is voltage coil of A, and a1 of B.
The sum of the deflections of A and B give total
watts input. At light loads one wattmeter usually
reads negative, and the difference is the total watts.
Results. — At the end of the preceding tests the
following results should be computed, and curves
plotted from them.
_ Speed of motor x 100.
') synchronism =
Synchronous speed.
326
TESTS OF DYNAMOS AND MOTORS.
% real efficiency =
% apparent efficiency =
Power factor -
_ Output of motor X 100
Input by wattmeter
Output of motor x 100
volt x amperes
Watts _ apparent efficiency
" Volt X amperes
Torque-pounds pull at 1 ft. radius =
real efficiency
5,250 H.P.
revolutions per minute"
The above results should be plotted on a sheet in curves similar to the fol-
lowing, taken from Steinmetz's article on " Induction Motors."
Fig. 16. Curves of results of tests of induction motor.
Synchronous motor. — Synchronous motors are separately excited,
and the D. C. exciter should have its qualities tested as a dynamo. Syn-
chronous motors are tested for Break-down point ; Starting current at differ-
ent points of location of the rotor ; Least exciting current for various loads.
All these in addition to the regular efficiency and other tests. Core losses,
friction, T^R losses, etc., can be found by any of the usual methods pre-
viously described.
Break-down point. Synchronous motors have but little starting-torque ;
and it is necessary to start them without load, throwing it on gradually
after the motor has settled steadily and without " hunting" on its synchro-
nous speed. The break-down point is found by applying load to the point
where the motor falls out of step, which will be indicated by a violent rush
of current in the ammeter simultaneous with the slowing down.
This test is usually carried out at about half voltage, the ratio of the load
on the motor at the moment of dropping out of step will be to the full load
of break-down as the square of the voltages, the load being adjusted at
minimum input in each case. For example, say a certain motor, built to
run at 2,000 volts, breaks down at 150 K.W., with an impressed voltage of
1,000. Then the true full break -down load will be
2,0002
X 150 =
) K.W.
^■■■■i^^^BlHH
SYNCHRONOUS MOTOR. 327
Starting current. Owing to consequent disturbance to the line, it is desi-
rable that the starting current of a synchronous motor be cut down to the
lowest point ; but it is difficult to reduce this starting current lower than
200% of full-load current. A synchronous motor also starts easier at certain
positions of its rotor as related to poles. With the rotor at rest, and the
location of the centre of its pole-pieces chalked on the opposite member,
the circuit is closed, the impressed voltage is kept constant, and the current
flowing in each leg of the circuit is read, and the time to reach synchro-
nism. Care should be taken to note the amount of the first rush of current,
and then the settling current at speed.
Least exciting current. The power factor of a synchronous motor will be
100 only when," with a given load on the motor, the exciting current is ad-
justed so that there is neither a leading nor lagging current in the armature.
Sometimes it is desirable to produce a leading current in order to balance
the effect of induction motors on the line, or inductance of the line itself.
This is done by over-exciting the fields.
With a given load on the motor, the 100 power-f actor is found by com-
paring the amperes in the motor armature with the exciting current in the
field. Starting with the excitation rather low, the armature current will be
high and lagging ; as the excitation is increased, the armature current will
drop, until it reaches a point where, as the excitation is still increased, the
armature current begins to rise, and keeps on rising as the exciting current
is increased, and on this side of the low point the armature current is
leading.
With no reason for making a leading current, the best point to run the
motor at is, of course, that at which the armature current is the lowest ; and
at that point the power-factor is 100.
Synchronous Impedance.- The E.M.F. of an alternating dynamo
is the resultant of two factors, i.e., the energy E.M.F. and inductive E.M.F.
The energy E.M.F. may be determined from the saturation curve by run-
ning the machine without load, and learning the field strength necessary to
produce full voltage.
The inductive E.M.F. is at right angles to the energy E.M.F., and is de-
termined by driving the machine at speed, short-circuiting the armature
through an ammeter, and exciting the field just enough to produce full-load
current in the armature. The amount of field current necessary to produce
full load is a measure of the inductive E.M.F., which can be determined from
the saturation curve as before, and the resultant E.M.F. will be
Resultant E.M.F. = Venergy E.M.F.2 + inductive E.M.F.2.
Saturation test. — This test shows the quality of the magnetic cir-
cuit of a dynamo, and especially the amount of current necessary to saturate
the field cores and yokes to a proper intensity. In this test it is important
that the brushes and commutator be in good condition, and that all contacts
and joints be mechanically and electrically tight.
The dynamo armature must be driven at a constant speed, and the leads
from the voltmeter placed to get readings from the brushes of the dynamo
must have the best of contacts.
The fields of the dynamo must be separately excited, and must have in
the circuit with them an ammeter and rheostat capable of adjusting the
field current for rather small changes of charge.
The armature must be without load, and a Aroltmeter must be connected
across its terminals.
Should there be residual magnetism enough in the iron to produce any
pressure without supplying any exciting current, such pressure should be
recorded ; or perhaps a better way is to start at zero voltage by entirely
demagnetizing the fields by momentary reversal of the exciting current.
To start the test, read the pressure, due to residual magnetism if not de-
magnetized, or if demagnetized, start at zero. Give the fields a small ex-
citing current, and read the voltage at the armature terminals ; at the same
time read the current in the fields, and the revolutions of the armature.
Increase the excitation in small steps until tbe figures show that the knee of
the iron curve has been passed by several points ; then reverse the operation,
decreasing the excitation by like amounts of current, until zero potential is
reached.
This is usually as far as it is necessary to go in practice ; but occasionally
328 TESTS OF DYNAMOS AND MOTORS.
it is well to complete the entire magnetic cycle by reversing the exciting cur-
rent, and repeating the steps and readings as above described.
The readings should be plotted in a curve with the amperes of exciting
current as abscissae, and volts pressure as ordinates.
The E.M.F. will be found to increase rapidly at first ; and this increase
will be nearly proportional to the exciting current until the " knee " in the
curve is reached, when the E.M.F. increase will not be proportional to the
excitation until after the "knee" is passed, when the increase in E.M.F.
will again become nearly proportional to the excitation, but the increase
will be at such a low rate as to show that the magnetic circuit is practically
saturated ; and it is not economical to work the iron of a magnetic circuit too
far above the knee, nor is it expedient to work it at a point much below the
" knee," except for boosters.
The exciting current must not be broken during this test, except possibly
at zero ; nor must its value be reduced or receded from in case a step should
be made longer than intended. Inequalities of interval in steps of excit-
ing current will make little difference when all are plotted on a curve. For
the same value of exciting current the down readings of E.M.F. will always
be higher than those on the up curve.
Resistance of field, coils. — The resistance of the shunt fields of a
dynamo or motor can be taken in any of the usual ways : by Wheatstone
bridge ; by the current flowing and drop of potential across the field termi-
nals ; and it is usual, in addition, to take the drop across the rheostat at the
same time. The resistance of each field coil should be taken to insure that
all are alike.
Resistance of series fields, and shunts to the same, must be taken by a dif-
ferent method, as the resistance is so low that the condition of contacts may
vary the results more than the entire resistance required. The test for re-
sistance of armatures following this is quite applicable. Of course any test
for low resistances is applicable ; but the one described is as simple as any,
and quite accurate enough for the purpose.
Resistance of armature. — In order to determine the I2R loss in a
generator or motor armature, its resistance must be measured with consider-
able care ; and the ordinary Wheatstone bridge method is of no use, for the
reason that the variable resistance of the contacts is often more tban that
of the armature itself. The drop
method, so useful with higher re-
sistance devices, is not accurate ^-r K ;,
enongh for the work ; and the storage ^L- f-^ — ■ ^a resistance
most accurate method is probably battery. :=t {armature. . smfr-
the direct comparison with a stan-
dard resistance by means of a
good galvanometer and a storage
battery.
Clean the brushes, commutator
surface, or surface of the col-
lector-rings, and in the case of a
D. C. machine, see that opposite Fig. 17. Diagram of arrangement for
brushes bear on opposite seg- measuring resistance of armatures,
ments.
Connect the galvanometer and its leads, the storage battery and resis-
tances, as in the following diagram. The standard resistance, R, will ordina-
rily be about .01 ohm, but may be made of any size to suit the circumstances.
The storage battery must be large enough to furnish practically constant
current during the time of testing. The galvanometer must be able to
stand the potentials from the battery ; and it is usually better to connect in
series with it a high resistance, so that its deflections may not be too high.
The deflection of the galvanometer should be as large as possible, and pro-
portional to the current flowing. The leads a, ax , and b and 615 are so ar-
ranged with the transfer switch that one pair after the other can be thrown
in circuit with the galvanometer ; and it is always well to take a deflection
first with R, then again after taking a deflection from the armature.
The leads a and ^ must be pressed on the commutator directly at the
brush contacts, and may often be kept in place by one of a set of brushes
Test. — Close the switch, k, and adjust the resistance, r, until the am-
meter shows the amount of current desired, and watch it long enough to be
ARMATURE FAULTS.
329
STORAGE .BATTERY
Fig. 18. Test for break in ar-
mature lead.
pure it is constant. Close the transfer switch on b and bL, and read the gal-
vanometer deflection, calling it d. Throw the transfer switch to the con-
tacts a, and a,, read the galvanometer deflection, and call it dv Transfer
the contacts back to b, and 6t and take another reading ; and if it differs
from dlt take the mean of the two.
Let x= resistance of the armature, then
* = n%
d
Note. — See Flemming's " Electrical Laboratory Notes and Forms."
Tests for faults in Armatures.
The arrangement of galvanometer for testing the resistance of an arma-
ture is the very best for searching for faults in the same, although it is not
often necessary to measure resistance. (See Figs. 15 to 18 inc., page 7.)
Test for open circuit. — Clean the brushes and commutator, then
apply current from some outside source, say a few cells of storage battery
or low pressure dynamo, through an am-
meter as in the following diagrams. Note
the current indicated in the ammeter ; ro-
tate the armature slowly by hand, and if the
break is in a lead, the flow of current will
stop when one brush bears on the segment
in fault. Note that the brushes must not
cover more than a single segment.
If on rotating the armature completely
around the deflection of the ammeter does
not indicate a broken lead, then touch the ter-
minals of the galvanometer to two adjacent
bars, working from bar to bar. The deflec-
tion between any two commutator bars
should be substantially the same in a perfect armature ; if the deflection
suddenly rises between two bars it is indicative of a high resistance in the
coil or a break (open circuit).
The following diagram shows the connec-
tions.
A telephone receiver may be used in place
of the galvanometer, and the presence of
current will be indicated by a " tick " in the
instrument as circuit is made or broken.
Test for short circuit. — Where two
adjacent commutator bars are in contact, or
a coil between two segments becomes short-
circuited, the bar to bar test with galvanom-
eter will detect the fault by showing no
deflection. If a telephone is used, it will be
silent when its terminal leads are connected
with the two segments in contact. See dia-
gram below for connections. If there be a short circuit between two coils
the galvanometer terminals
should include or straddle three
commutator bars. The normal
deflection will then be twice that
indicated between two segments
until the coils in fault are
reached, when the deflection will
drop. When this happens, test
each coil for trouble ; and if indi-
vidually they are all right, the
trouble' is between the two. The
following diagram shows the con-
nections.
Test for grounded arma-
ture. — Place one terminal of the
galvanometer on the shaft or
frame of the machine, and the other terminal on the commutator. (The
Fig. 19. Bar to bar test for
open circuit in coil.
Fig. 20. Bar to bar test for short cir-
cuit in one coil or between commuta-
tator segments.
330
TESTS OF DYNAMOS AND MOTORS.
SHORT CIRCUIT'
BETWEEN SEETKMB
storage battery, ammeter, and leads must be thoroughly insulated from
ground.) If, under these circumstances, there is any deflection of the gal-
vanometer, it indicates the presence
of a ground, or contact between the
armature conductors and the frame
of the machine. Move the terminal
about the commutator until the least
deflection is shown, and at or near
that point will be found the contact ;
in the particular coil connected be-
tween two segments showing equal
deflection, unless the contact happens
to be close to one segment, in which
case there will be zero deflection.
Contacts in field coils can be located
by the same method. The following
diagram shows the connections.
To determine if armature of mullipola,
Fig. 21 . Alternate bar test for short
circuit between sections.
Fig. 22. Test for ground in armature
coils.
In the above the brushes should 1
- dynamo is electrically centred, put
down brushes 1 and 2, and take volt-
age of machine ; put down brush 3,
and lift 1, take voltage again ; put
down brush 4 and lift 2, again tak-
ing voltage ; repeat the operation
with all the brushes, and the volt-
age with any pair should be the
same as that of any other pair if the
armature is electrically central.
The same thing can also be deter-
mined by taking the pressure curves
all around the commutator as shown
in the notes on characteristics on
dynamos.
exactly at the neutral point.
Test for E.M.r. of Xfeynamo without Running- it.
Prof. F. B. Crocker gives the following method (page 247 Trans. A. I. E. E.,
1897), for determining the E.M.F. of a dynamo without driving it by outside
power, provided a current of the proper voltage is at hand sufficient to give
it full torque as a motor.
Clamp a lever to the pulley, and weigh the torque, as a motor, at radius r,
with a spring balance or a platform scale.
r = radius of torque lever.
s = speed of revolutions per minute, as a dynamo.
p = pounds pull at radius r.
I— current.
E — E.M.F.
EI
2tt r sp
746 ~~
33,000
E-
r s p
Field strength is the same as if running as a dynamo ; and by tapping
the shaft when test is made, friction losses are partially eliminated, and the
method is sufficiently correct for all efficiencies.
^^^^M^^H
THE STATIC TRANSFORMER.
The static transformer is a device used for changing the voltage and cur-
rent of an alternating circuit in pressure and amount. It consists, essen-
tially, of a pair of mutually inductive circuits, called the primary and
secondary coils, and a magnetic circuit interlinked with both the primary
and secondary coils. This magnetic circuit is called the core of the trans-
former.
The primary and secondary coils are so placed that the mutual induction
between them is very great. Upon applying an alternating voltage to the
primary coil an alternating flux is set up in the iron core, and this alternat-
ing flux induces an E.M.F. in the secondary coil in direct proportion to the
ratio of the number of turns of the primary and secondary.
Technically, the primary is the coil upon which the E.M.F. from the line
or source of supply is impressed, and the secondary is the coil within which
an induced E.M.F. is generated.
The magnetic circuit or core in transformers is composed of laminated
sheet iron or steel. The following cuts represent sections of several dif-
ferent types.
pv.
fi
1 1
pJs
f
SjP
?
(
If
Si
VM
FlG. 1. Cores of some American Transformers.
p = primary winding ; s = secondary winding.
In those showing a double magnetic circuit the iron is built up through
and around the coils, and they are usually called the " Shell " type of trans-
former.
331
332 THE STATIC TRANSFORMER.
Those having a single magnetic circuit, and having the coils built around
the long portions or legs of the core, the short portions or yoke connecting
these legs at each end, are called " core " type of transformer.
The duties of a perfect transformer are :
(1) To absorb a certain amount of electrical energy at a given voltage and
frequency, and to give out the "same amount of energy at the same frequency
and any desired voltage.
(2) To keep the primary and secondary coils completely isolated from one
another electrically.
(3) To maintain the same ratio between impressed and delivered voltage
at all loads.
The commercial transformer, however, is not a perfect converter of energy,
although it probably approaches nearer perfection than any form of appa-
ratus used to transform energy. The difference between the energy taken
into the transformer and that given out is the sum of its losses. These
losses are made up of the copper loss and the core loss.
The core loss is that energy which is absorbed by the transformer when
the secondary circuit is open, and is the sum of the hysteresis and eddy cur-
rent loss in the core, and a slight copper loss in the primary coil, which is
generally neglected in the measurements.
The hysteresis luss is caused by the reversals of the magnetism in the
iron core, and differs with different qualities of iron With a given quality
of iron, this loss varies as the 1.6 power of the voltage with constant fre-
quency.
Steinmetz gives a law or equation for hysteresis as follows :
Wh = V (ft 1-6-
We. = Hysteresis loss per cubic centimeter per cycle, in ergs (= 10-7
joules).
■q = constant dependent on the quality of iron.
If Ar= the frequency,
Vz=. the volume of the iron in the core in cubic centimeters,
P = the power in watts consumed in the whole core,
then P = f]N V (ft1"6 107,
'l-N y (£1-6 10-7-
In Table A, on page 13, this hysteresis constant t\ is given for several
different transformers.
In the construction, the core loss depends on the following factors :
(1) Magnetic density,
(2) Weight of iron core,
(3) Frequency,
(4) Quality of iron,
(5) Thickness of iron,
(6) Insulation between the sheets or laminations.
The density and frequency being predetermined the weight or amount of
iron is a matter of design. The quality of the iron is very variable, and up to
the present time no method has been found to manufacture iron for trans-
formers which gives as great a uniformity of results as to the magnetic
losses as could be desired.
On the thickness of the laminations and the insulation between them de-
pend the eddy current losses in the iron. Theoretically1 the best thickness
of iron for minimum combined eddy and hysteresis loss at commercial fre-
quencies is from .010" to .015", and common practice is to use iron about
.014" thick.
The copper losses in a transformer are the sum of the I2E losses of both
the primary and secondary coils, and the eddy current loss in the conductors.
In any well-designed transformer, however, the eddy current loss in the
conductors is negligible, so that the sum of the I2R losses of primary and
secondary can be taken as the actual copper loss in the transformer.
i Bedell, Klein, Thomson, Elec. W., Dec. 31. 1898.
■m^hhmb^h^hm^^HHI
333
o
O
8
II
X
ci
2.90 "
3.04 "
2.10 "
6.57 "
2.12 "
2.22 "
2.24 "
2.06 "
2.28 "
ill
o
X
§
3.20 "
3.52 "
2.39 "
6.26 "
2.24 "
2.38 "
2.54 "
2.42 "
2.75 "
$ sb g
e
s
ii
o
4280
5400
7500
7720
75G0
4080
49G0
8460
6650
Ill
O t- CO
8
N
©
2050
2600
3G40
3750
3630
1960
2380
4670
3210
III
in co co
"el
o
O
o
S
II
q
015
011
017
020
067
021
007
031
011
021
018
H * rt t-
o o o o
ii
b-
q
iHooeooi-iTijia-noooO'*
OOOOOOOOOOO
2 £ 5 C^
o o o o
a
o
o
n
■*00t>«Oi0^(NCSOO-*Ort*t-
<NrH<MCOi-lcOT-iiOi-i*#COrOTfriCOt-
1Q
t~
OOCOi-l-#COTf<OOCOOOO
i-lrHdCICOdO-^r-ICOCl
^^
o
Ph
3
d
$
CO ■# O LO CO LO CO CI t- CS CO
OOCOOCICSCl^OOCOCOO
i-l O T-H |#
"""™:
l-H rl l-H CI
id
II
OS
.62
.46
.75
.85
2.14
.85
.32
1.42
.48
1.07
.82
^n
6
"
deoTjiiacot-oocsoi-fci
co i+i m co
334
THE STATIC TRANSFORMER.
TRAX§FORinER satATionrs.
Practically all successful designs of transformers are determined to
greater or less extent by the method of cut and try. Empirical methods
are of little value if the designer can obtain data on other successful trans-
formers for the same kind of work, and base the calculations for the new-
apparatus on the behavior of the old while under test.
For any transformer or reactive coil :
Let E = Vmean2 of the induced E.M.F.
<t> — total flux.
(§/' ■=. lines of force per square inch.
A = section of magnetic circuit in square inches.
N = frequency in cycles per second.
T= total turns of wire in series.
2tt
4-44 = ^ = VTXjr
Then E -
108
(1)
This equation is based on the assumption of a sine wave of electromotive
force, and is the most important of the formulae used in the design of an
alternating current transformer.
By substituting and transposing we can derive an equation for any un-
known quantity.
Thus if the volts, frequency, and turns are known, then —
Ex 108
(2)
But $ = ($/' A
Therefore A z
4.44 X A" X T x (
(3)
(4)
which equation gives at once the cross section of iron necessary for the
magnetic circuit after we have decided on the total primary turns, and the
density at which it is desired to work the iron.
Again, if the volts, frequency, cross section of core, and density are
known, we have, transposing equation (4),
Tzzz
E X 108
4.44XA^X(
'XA
1
L r
i
JR
1
or r
E
:
1
THE STATIC TRANSFORMER. 335
Fig. 2 is a curve giving the total fluxes as ordinates and capacities in k.w.
as abscissae. This curve represents approximately common practice for a
line of lighting transformers, to be operated at 60 cycles.
For any other frequency or for power work, a curve of total fluxes can be
drawn after three or more transformers have been calculated with quite
widely differing capacities.
HEag-netic densities in the cores of transformers vary considerably
with the different frequencies and different designs of various makers. The
practical limits of these densities are as follows :
For 25 cycle transformer from G0,000 to 90,000 C.G.S. lines per square inch.
For 60 cycle transformers from 40,000 to 60,000 lines per square inch.
For 125 cycles from 30,000 to 50,000 lines per square inch.
Densities for other frequencies are taken in proportion.
Current densities in transformer windings vary between 1000 and
2000 circular mills per ampere. Some makers design for greater current
density in the secondary than in the primary. The circular mils per am-
pere in transformers of the best design are often 1000 or 1500 in the primary
coil, and 1200 or 2000 for the secondary coil.
The proper adjustment of the current density should be such as to give
equal heat distribution throughout the coils, and the relative densities in
the two coils should be based on their relative radiating surfaces.
FEATURES OF DEilGIT.
In the design of a successful transformer, the features to be given partic-
ular attention are :
(1) Insulation between primary and secondary,
(2) Heating,
(3) Efficiencies,
(4) Regulation,
(5) Cost,
(6) Power factor and excitingcurrent.
Insulation.
The insulation of a transformer is really a measure of its durability, and
it must be obvious that if it is not well designed and properly constructed
to prevent the breakdown of its insulation, it is not a good investment ; and
the same reasoning holds good if the insulation deteriorates rapidly. Sim-
plicity of form and constructive details is a good point, and as transformers
are liable to be exposed to all sorts of weather and other conditions, they
should always be designed to withstand all of them.
Insulation between coils must be of the best possible kind, as electrical
connection here is a menace to life and property, and destruction of the
transformer also means costly repairs, loss of income while current is off,
and what is of more importance, great annoyance to customers.
A liberal margin of overload is necessary, and if specifications call for a
rise of temperature not exceeding 40° C, at full load, any ordinary overload
will do no harm, provided the insulation is safe. The rules of the Committee
on Standardization of the A. I. E. E. state the proper voltages to be used in
testing transformers for insulation, and the values so stated will be found in
the part of this chapter devoted to tests of transformers. The writer has
never been thoroughly satisfied with the methods in common use for deter-
mining the rise of temperature in transformers or dynamos or similar appli-
ances. The thermometer test is too superficial, and the resistance test is
the average only, while what is wanted is the hottest temperature at any
point, for "that is the danger point. It is probable that the ordinary small
commercial sizes of transformers do not need such refinements, but the
larger sizes would be much better tested with a special copper test coil
placed at the danger point during construction, with leads brought outside
for testing. This might not be necessary in more than one or two of the
same type and size, but would never be out of place in every one of the
larger sizes now coming so commonly into use in the modern power trans-
mission plant. Insulation materials for transformers are of numerous
kinds, and no two makers use identical combinations, although most use
the same or similar materials ; following is a list of those in common use ;
FEATURES OF DESIGN.
and the reader is referred to the list of specific resistances (see index) for the
breakdown point of most of them.
Oiled linen,
Oiled silk,
Mica,
Micanite, flakes of mica pasted together in different forms,
Fiber, and all the other forms of artificial board.
"Wires are nearly always double cotton covered.
As for oils for the oil-insulated transformers, the "Westinghouse Company
uses a clear thin oil much like signal-oil, and called lied Seal, while the Gen-
eral Electric Company uses a special transformer oil, which is heavy, but is
simply a good machine-oil freed from Avater.
An order to the Standard Oil Company for transformer oil will bring an
oil that will serve every ordinary purpose, and many times it will be found
that unless some particular oil is specified they will seldom send the same
twice. The laboratory of the National Board of Fire Underwriters has used
a number of different kinds in its high-testing transformers (40,000 volts),
and has never found any difference in results although ordered as stated
above.
Heating- and "Ventilation.
One of the necessary requirements of any piece of machinery is that
it must be able to operate for certain periods of time at its full load, and in
some cases over-load, without undue heating.
Fig. 3. G. E. Co. Type H Transformer — 20000 watts, oil-cooled.
In a transformer, the capacity for work increases directly as the volume
of material, densities and proportions remaining constant. The volume,
however, increases as the cube of the dimensions, and the radiating surface
as the square of the dimensions ; therefore, it is evident that the capacity
for work increases faster than the radiating surface. Since the losses are
also in proportion to the volume, the designer soon reaches a point where it
is necessary to provide additional means for ventilation or radiation of heat,
in order that the transformer may run under load without undue tempera-
ture rise.
Self-cooled transformers are those which require no artificial means for
THE STATIC TRANSFORMER.
337
dissipating the heat energy lost in the apparatus during operation. These
can be divided into two classes, the Ventilated or Natural Draft, and the
oil-cooled.
Fig. 4.— 500-k.w. Self-Cooling Transformer. W. E. & M. Co. Type, Oil-cooled.
The Ventilated or Natural Draft transformer is one in which
air is the direct means of absorbing the heat, it being designed so that cur-
rents of air readily pass through the transformer. Such transformers are not
well adapted for out-door installations, as they require a separate housing;
otherwise there is a liability of water or moisture getting inside of tbe case.
Oil-cooled transformers are those in which the coils and core are
immersed in oil, the oil acting as a medium to conduct the heat from the coils
to the surrounding tank. In addition to acting as a heat-conducting medium,
the oil also serves to preserve the insulation from oxidation, increases the
breakdown resistance of the insulation, and re-insulates the insulation in
case of a puncture.
The use of oil in a transformer results in a more rapid conduction between
the transformer proper and its case or tank, and the lowering of the tem-
perature increases the life of the transformer. Again, instances are known
of the discharge of " atmospheric electricity," or a discharge of lightning at
a distance that has punctured the insulation of a transformer, and when tilled
with oil, the oil flows in and repairs the rupture, which may be too small to
cause immediate damage. If a sufficient space is left inside the case, the oil
will get up a circulation by its own convection currents, the cooler oil rising
inside as it becomes more and more heated, the hot oil on the top falling
as it is cooled by contact with the inside surface of the tank.
This cooling may be further increased by making the containing case with
deep vertical corrugations, thus largely increasing its radiating surface.
The curves on page 1 8 serve to show the effect on the temperature of the
use of oil. Curve 1 represents the temperature rise (by resistance method)
of a transformer without oil ; curve 2, the temperature rise of the same
transformer with oil ; curve 3, the temperature rise of the oil ; curve 4, the
temperature rise of another transformer run without oil ; and curve 5, the
highest temperature rise accessible to thermometer, whose actual tempera-
ture (by resistance) is shown in curve 4.
When the transformers are of such a size that sufficient radiating surface
cannot be had in the tank to dissipate the heat, it becomes necessary to
provide artificial means for cooling the same. Some of the means adopted
are, water circulation, forced oil or air circulation. For both the water and
oil circulation the coils and core are immersed in oil.
The water-cooled transformer has its heatad oil cooled by means
of water cirevdating pipes placed in the oil. The transformer thus has the ad-
vantage of oil insulation, and the circulation of the cold water through the
pipes requires much less power than the pumping of the oil, and in addition
does not require external cooling apparatus. This method is subject to a
slight danger, due to possible leak of water pipes.
338
FEATURES OF DESIGN.
Transformers have been constructed in sizes up to about 2000 k.w., using
water circulation for
s
r.
-
i-
_L
S^
-
s
■"
E
n
>*
•
-
3
SI
/
CURVES SHOWING
DUE TO USE 0
Fig. 5.
S TRANSFORMERS
Am Air-Blast Transformer — or one in which ventilation and radi-
ation of heat is, by means of a blast or current of air, forced through the
transformer coils and core is shown in Fig. 8. In this transformer, the
Figs. 6 and 7. Natural Draft Transformer — Showing Case Removed.
coils are built up high and thin, and assembled with spaces between them,
the air being forced through these spaces. The iron core is also built up
of numerous openings through which the air is forced for cooling pur-
poses. This style of transformer has been constructed in sizes tip to about
1000 k.w.
THE STATIC TRANSFORMER.
339
The following tables show results of tests on a number of commercial
transformers by Mr. A. H. Ford.
Fig. 8. Air-Blast Transformer.
Si Heating* Tests.
Transformers in their cases. (Ford.)
Rise
Watts ra-
diated per
sq. in. of
Case.
w2.
Watts ra-
diated
Rise
Watts ra-
diated per
Watts ra-
diated
No.
in
Tempera-
per sq. in.
of Core
No.
in
Tempera-
sq. in. of
Case.
per sq. in.
of Core
ture °G.
and Coils.
ture °C.
and Coils.
w2.
1
31.4
.143
.175
9
310
.172
.300
24.3
.091
.107
39.4
.134
.234
57.4
.168
.198
2
20.1
.052
.110
12
31.6
.086
.145
15.2
.047
.098
20.5
.067
.113
47.8
.102
.214
51.8
.125
.211
30.8
.0S5
.190
21.5
.122
.206
3
20.8
.105
.121
13
60.0
.113
.131
17.5
.080
.093
49.4
.079
.104
50.2
.168
.195
38.4
.134
.155
5
21.8
.118
.166
14
43.4
.168
.266
19.1
.090
.127
32.1
.079
.130
40.8
.172
.242
101.8
.250
.396
40.6
.144
!203
76.9
.150
.234
6
62.4
.388
.542
15
25.4
.099
.150
52.3
.246
.346
21.2
.074
.112
86.8
.412
.580
67.5
.168
.255
72.2
.455
.640
51.6
.149
.225
7
20.0
.082
16
73.4
.225
.396
17.8
.058
66.1
.175
.242
56.3
.144
100.0
.340
.466
36.0
.100
70.0
.242
.334
840
THE STATIC TRANSFORMER.
C Heating- Tests.
Transformers out of their ct
(Ford.)
Watts
Watts
Rise in
radiated per
Rise in
radiated per
No.
Temperature
CC.
sq. in.
of Exposed
No.
Temperature
sq. in.
of Exposed
Surface.
Surface.
W.
W.
1
27.9
.175
11
27.0
.274
21.2
.107
18.9
.208
51.0
.222
52.2
50.4
.372
.320
2
14.6
13.6
.110
.098
41.4
.240
12
19.7
.145
42.4
.220
12.3
55.9
.113
.229
3
20.3
12.4
33.2
.122
.093
.167
53.8
.195
30.8
.136
14
29.1
24.0
.266
.125
4
16.2
.160
96.7
.382
13.4
.110
77.0
.286
59.4
.240
51.4
.200
15
25.1
.150
6
50.0
.547
14.3
.112
24.4
.346
61.3
.270
72.0
.595
59.4
.250
58.9
.655
7
14.0
.082
16
44.3
.396
6.4
.058
31.4
.243
75.0
.185
64.3
.438
19.0
.121
42.9
.304
Efficiencies.
The efficiency of a transformer is the ratio of the output watts to the input
watts. Thus
Efficiency :
Output watts _
Input watts
Output
output -\- core loss -4- copper loss
The core loss, which is made up of the hysteresis loss and eddy current
loss, remains constant in a constant potential transformer at all loads, while
the copper loss, or I2R loss, varies as the square of the current in the pri-
mary and secondary. Methods for determining all the losses are fully
described in the chapter on transformer testing.
In a service where a transformer is generally worked at full load, while
connected to the circuit, as in power work, the average or " all-day" effi-
ciency will be about the same as its full-load efficiency. By " all-day" effi-
ciency is meant the percentage which the energy used by the customer is of
the total energy sent into the transformer during twenty-four hours.
In lighting work the transformers are usually connected to the mains or
are excited the full twenty-four hours per day, while the customer draws
current from them during from three to five hours in the twenty-four. As-
suming on an average five hours full load, the losses will be 5 hours 12R and
FEATURES OF DESIGX.
341
24 hours core loss. The calculation of the " all-day " efficiency can, there-
fore, be made by the following formula :
. ■ _ . Full load X 5
All-day efficiency = = -. — — , — j^-jz _ , _, „ , =
J J Core loss x 24 -4- 1 2E X 5 + Full load X 5
From this it is evident that while for power work or continuous full load,
the relative amount of the core and copper losses will not affect the " all-
day" efficiency seriously, yet in the design of transformers which are
worked at full load only a short time, but are always kept excited, a large
core loss means a very low " all-day " efficiency.
The two tables on pages 112 and 113 show various efficiencies of a number
of transformers, giving maximum efficiencies and "all-day" efficiencies.
They also show the core loss of various commercial transformers as found
by Mr. Ford.
i him inn i
-C
TRANSFORMER IRON.AGEING TESTS.
BY H. F. PARSHALL
HYSTERESIS IN THE IRON AS RECEIVE
HYSTERESIS TRANSFORMER AFTER
SHORT PERIOD OF LIGHT WORK
HYSTERESIS TRANSFORMER AFTER
THREE YEARS OF HEAVY WORK
/
/
/
/
/
/
/
/
/
/
/
/
/
y
/
/
s
i
1
LINES PFR SQUARE CENTIMETER.
Fig. 9.
J
tk./
V
/
/
/
/
/
,'
TY
/
MANUFACTURE EY A.H. FORD,AT UNIVERSI
OF WISCONSIN. JAN. FEB. MAR. 1897.
B- TEST ON WAGNER TRANSFORMER,
FEB. MAR. APR. 1897.
/.
/
/
T^
L-
E
342
THE STATIC TRANSFORMER.
ll
c3 O
u o
o
Pm
©
II
634
520
730
565
615
400
465
656
657
590
672
384
656
182
630
430
595
585
620
700
640
1
n
o«oot-ooanoisffl®oooiooo(oooo
— . ■ : -i -'■.■'■, i .■ - ■ . < ". :-i~.- . ..: ,.. ' \ .--
t-t.OOO«C'JOl-fflt-0»t't-lO«lOfflW<0
q
p *
o
8
II
Hrn-o-fOLOOccoan^iaoHOoooNoo
oot'm :. ■ •;• i - : i r, : , : -:- -
OOOr-c-JHr-'O'-iOi-Hi-iT-tOOO^HiMOi-iCN
§
II
:oo9«o-f«cJ-ti-tiocONLOOi-OOtoocooo
:-. : i -f I- >o l- i- i- 01 I" 1- 1 i ■• --OWC03
OOOOOi-tOOTHOOOOOOtMi-irHOOTH
SI
©
CO
II
fflooo'-o-#oq«qoq«NcoiqLoqiMq(»Hq
oilOeo6MOiOiodi005tOI>iCfflodHr<)Or!N
CDGOCOGOOOCOOOOOt-OOt-COC-t^OOCOCiClOOCiCi
II
^«H»L'5oq-tooqqioqi>«oO'Hi»iaoi»
oo t^ d -* d d d d d d d d d -* d i- d oi d to d
t-O0000000t-O000t~O0CC0000O000l>OiOS00CSCi
1!
q^qqq-sijioNHN^fflqNioq^tDioiqN
© -*-#-* -+' l~ -* -*' O -*' CO -V Ol' ri -+ ci 'i 6 * ffl l>
oi o © c; © co © © © © © © © © © co © © © © ©
s
II
loqqqooiONNNffliotONqwoNqqHiq
oi •* id -t< >* i-H d -+ —I d -t- d co ■* l.o oi d t^ d t> c^
Si
6^
c3
cNoqt>;C^e^oo^icu5cqG5uqcocqoo-#ocqqoq
oi oi © d d -*' cc" i~ d -# d d d <£-v-+dciccdd>
rHCON-*COriC01SCO'<tCO(N«ltOLO'*'*«C100
o
1-1
p
©
CO
II
cDcoioqHqiotoqiaqiqq^nqqqqqq
co t^ co d d d d -+' d -+ d d oi d d © d oi © © •#
CO CN <* L- CO © «# -J< 01 ■* L~ IO 00 O UO CO O CN Ol C~ T*
Th^qwt>qcqt>ioioio<Neqjq>*qqqqioq
d ^ t-^ d id d oi d t-^ i-l t^ d t^ d oi d Tji © © © d
CMO<lCOlO-*05COCOC5COlO'*010-#COt^05T-ITjiO
OP
3
§88888888888888888888
-* o oi lo io lo lo i.o ■ '■' ~ io io io quo ©
r-H ' r-T r-T rT r-T r-T i-T -H r-T T-T r-T r-T r-T C<f of t>T E^ r-T -# ©~
•.
aqoinj^
rHcqeor^iocot-oooso^HCNco^iccot-oocJsorH
GENERAL ELECTRIC TYPE H TRANSFORMERS.
343
B bg
3-1
PS o
fe ®
» |5
^
S •
d
"53 a
O O lO O lO
lO O O tfi lA
N to S3 t O
CM CM CO Th IQ
1 1 1 1 1
c/.
«PU
H H H H
fc
o
5
^•d ,5
iyc3 ©
bo
£ Q,u
ri 5, ffl ,rl (fl
CO CO C5 C5 rH
lO t~ « iH
T3
.2I~' >>
^ g « -i o
O Ol Ci C5 CI
O Ol C3 C3 Q
3
I? JO
HfcS
-d
ID
os»
s
c o,2
.2^ S.
CO CD CO t- ^H
to iq iq o n
h iq to n oo
CO ■+ id io CO
'5
11°
° " ° " "
Ci © OS © ©
O
0)
*"-
o © c
o
©
is i> 6 is *
T^ CO ^ Ci
ci ci fi ci ri
i-l O lO
CD -# CO CO CO
2
©CNQj
eS
a
1
OOg
s
|oi d
oo « i; m h
rt CO t-
tH lO <M
©
cm <n ei cn cm
<N N CN ri r^
^ rl rl ^ ^
©
+*
-d
05 <B
oa
o
(=1.3©
o^ fc-,
CO CM CO i-l CO
t- lO CM CO CM
r-j
M ?^U
i-l CM CM CO CO
*# lO 1Q t- CO
3
°!3
o2
ce
s
0
o ©
r^
1^
8 8 8 3 §
O CO CO CO CO
§ O O H to
2
rH 7-1 CN CO CO
cjj
"©
a§
o
13
>5
cS
11111
O O O © O
o o © © ©
CO ■* io to h
O O O O O
8 8 8 8 §
^
o
344
THE STATIC TRANSFORMER.
Magnetic fatigue or aging* of iron subjected to magnetic reversals
is now well recognized, and precautions are taken to prevent it by all the
better class of transformer manufacturers. Unless great care is taken in
this respect the core loss is liable to increase very considerably after time has
elapsed, this loss increasing from 25 % to often more than 100 % of the ori-
ginal core loss. The following curves show the difference between carefully
selected and prepared iron, and ordinary commercial iron. The upper curve
shows a very great increase in iron loss after 80 days' run, while the two
lower curves show but little increase after the same length of time.
Curves lu and 11 also show results of aging tests by Mr. W. F. Parshall and
Mr. A. H. Ford.
AS
E
/■
•
~l
-10
'
E
/
0
" r
or'e|lqss!d
AGEING
/
1
p
4 u>v|s
r
BTA1
/
ON A
tlV
/
fa'ctured by
/
TRAN
sf,ormer|buil
/
|
i:
i [j
|
^
,kVe
30
**
TYPF
^
WNSFORM
^R
t
| | |
erJc
:v't
ON
E
. C
C
S
fP
ht
|
Nl
R
I
E
2%
C
SI
N
ov
1
96
|
CURVES SHOWING
Regulation.
The most important factor in the life of incandescent lamps is a steady
voltage, and a system of distribution in which the regulation of pressure is
not maintained to within 2 % is liable to considerable reduction in the life
and candle power of its lamps. For this reason it is highly important that
the regulation, i.e., the change of voltage due wholly to change of load on
the secondary of a transformer, be maintained within as close limits as
possible.
In the design of a transformer, good regulation and low-core loss are in
direct opposition to one another when both are desired in the highest de-
gree. For instance, assuming the densities will not be changed in the iron
or in the copper, if we cut the section of the core down one-half, we decrease
the core loss one-half. The turns of wire, however, are doubled, and the
reactance of the coils quadrupled, because the resistance changes with the
square of the turns in series.
A well-designed transformer, however, should give good results, both as
regards core loss and regulation, the relative values depending upon the
class of work it is to do, and the size of the transformer. The following
table shows the results of tests for regulation of a number of commercial
transformers obtained in the open market by Mr. Ford.
REGULATION OF TRANSFORMERS.
845
Q
2
Q
D
£
0
S
rt
»
■p<
*
fc
t
**
-d
es
O)
N
*""
a;
&
=J
e
13
IP"!
CO
§
cq
M
H
i
^
h
«
ft
*
>»
S
33
5
=5
ft
o
fl
fcfi
c3
1
Hi
s
II
^5
I> M CO rH r-J t* OS .in •-# ■Min|t-HO«HC)M
in " r-5 rH " .H . ' .HHrtn"
s
II
OHOCSOHO .^t>ON-HH»Q0NN00t-H
00 ' 'iHrJrici . CN "rHrHC^C^ci^
-d
o
o
CO
d
II
OOWOMtCNOOKOHtOOOUO
-* rr o oo os -r — 1 1 1 - i - o - .-: -r O 0O
II
rroooo-fj-Hinooocs-fjoeoorHO " ' °°. * "
T3
SO
II
Oioi C3
oi>*t>i>05qioaoo5ioioooH/o5 * * «q co to
o6^eit^o6o2eo^t^o4i>c4oot>ooio ' " c4 o4 r-i
II
(N «o os os co ■* co in os cs <n t~ in © <n os
^tddt^oseoiNrHt^rHooc'ioct^ooin
o
s
II
qNlOOOONMNHOONq^t-NiOWMffllOW
rHroMc4oirHcocicoMds^^^^c4c<is^(>ic-irH
§
ii
qHMio®Mqqqt>oqoq»ff]WHqq^qi>
ci co c<i co c4 r-i <* c4 ■*' c-^ c<i c6 ■* in in <m' co c4 c<> co t-h
H 3
ttOOOOO ooooooooooooooo
i- ~ .-. - •; : r :---■:.■ o © OO
H/ONi* i-OCO
d
6
HNn^mffl^ooaOrtNco^iatot-coaOH
346
THE STATIC TRANSFORMER.
Comparative Expense of Operating- JLarg-e and Small
Iransforme rs.
It is obvious that the design of the distributing system has quite as much
to do with the maintenance of a steady voltage as does the regulation of the
transformers, and the proper selection of the size of transformers to be
used requires skilled judgment.
When transformers were first used it was the custom to supply one for
each house, and sometimes two or three where the load was heavy. Expe-
rience and tests soon made it evident that the installation of one large
transformer in place of several small ones was very much more economical
in first cost, running expenses (cost of power to supply loss), and regulation.
Where transformers are supplied one for each house, it is necessary to
provide a capacity for 80 % of the lamps wired, and allowing an overload of
25 % at times, where one large transformer is installed for a group of houses,
capacity for only 50 % of the total wired lamps need be provided. For resi-
dence lighting, where the load factor is always very low, it is often best to
run a line of secondaries over the region to be served, and connect a few
large transformers to them in multiple.
A study of the following curves will show in a measure the results to be
expected by careful selection and placing of the transformers. The first
curve, Fig. 13, shows the relative cost per lamp or unit of transformers of
different capacity, showing how much cheaper large ones are than small
s.
fe2
o
I
> 1
H
3
V
-~.
c
1
0
2
0
3
.1
0
IGH
4
TS
0
5
0
6
0
Fig. 12. Relative Cost of Transformers of Different Capacities.
The second set of curves, Fig. 14, shows the power saved at different loads,
and using different sizes of transformers.
0 100 200 300 400
Fig. 13. Relative Efficiency of Large and Small Transformers.
COMMERCIAL TRANSFORMERS.
347
Power JFactor is the ratio of the actual watts in a line to the volt
amperes or apparent Avatts in that line. It is also defined as the cosine of
the angle of phase displacement of the current from the voltage in the
circuit.
The power factor of most commercial transformers is low at no load,
varying from 50 % to 70 %, while at high loads the power factor is very
nearly 100 per cent. For this reason it is better to distribute the trans-
formers on the line so that they will carry load enough most of the time to
keep the power factor reasonably high.
COIHMERCIA£ TRANSFORMERS.
The following tables show the trade numbers, capacities, and the ordinary
characteristics of some of the transformers in more common use at this
time, including Stanley Electric Co. : Westinghouse Electric and Manufac-
turing Co. ; " Wood," the Fort Wayne Electric Corporation ; Wagner
Electric and Manufacturing Co. ; General Electric Co., table for which will
be found on page 1 13
In order to show a comparison of the qualities of transformers as made
some time ago and at present, a table of tests by Dr. Fleming, F.R.S., is
also included.
IVAVLEY ELECTRIC MAlfrFACTURIIIfG CO.
LIGUXiaTG TRANSFORMERS.
Frequency == 66 P.P.S.
Efficiencies.
Regulation uniformly 2\ % at full load.
Type.
Full
Load
Output
in
K.W.
Full Load.
| Load.
\ Load.
\ Load.
| Load.
2G
\
93.0%
93.1%
92.2%
88.8%
80.7%
3G
I
93.0
93.2
93.0
89.5
82.5
4G
1
95.5
95.7
95.0
92.0
85.0
6G
1|
95.8
96.0
95.5
92.8
87.6
8G
2
95.9
95.9
95.5
93.5
88.5
10 G
n
96.0
96.2
95.8
93.5
90.4
15 G
3|
96.6
96.7
96.3
94.3
91.3
20 G
5
96.7
96.9
96.6
95.0
91.5
30 G
*2
96.8
97.0
96.7
95.5
92.2
40 G
10
96.8
96.9
96.8
95.7
92.6
60 G
15
97.2
97.2
97.2
96.9
94.8
80 G
20
97.8
97.7
97.5
96.9
95.1
100 G
25
97.6
97.8
97.8
97.2
95.5
348
THE STATIC TRANSFORMER.
..fifi P
,p.e.
H —
FUL
7b
L LOAD
37.91
1
3/4
1A
(
' 97.86
I 97. 49
95
s
1A
1/a
'
,
95.89
92.4-7
$
V,
REGULATION
1'/2
i
/
TYPE 400-W.
POWE^R TRANSFORMER
/
ST
ANLEY ELECTRIC M'F'G CO.
|
i
OUT
PUT
N KIL
3WAT
rs
i
FFFIC
IENCN
AT
33 P.
P.S.
FUL
•7/B
L LC
)AD
93.1
93.15
*
3/4
V?
93.14
97.91
>
v4
1/8
;
96.69
93.96
RE
GULA
TION
1 Vz k
"6^.
P
TV
OWE
PE 400-Vy.
R TRANSFORM
FR
ST
ANLE
»■ ELE
CTRIC
M'F'
SCO.
OUT
PUT
N KIL
DWAT
TS
25
50.
75.
10
STANDARD C. S. TRANSFORMERS.
349
ST4SDABI> C. S. IRAASf OltTIEIt^ OE WE§TIXC}<
HOUSE ELECTRIC .U'U MAJVVEACTURIVG CO.
Iron Eosses.
True.
Apparent.
Watts.
ir= i33£
^=60
JST= 133±
J^=60
1
250
6.80%
9.40%
8.90%
13.00%
2
500
5.20
6.80
6.60
9.70
4
1000
3.00
4.10
3.70
5.60
6
1500
2.50
3.30
3.20
4.70
8
2000
2.20
2.90
2.80
4.10
12
3000
1.70
2.20
2.20
3.10
16
4000
1.70
2.20
2.20
3.10
20
5000
1.60
2.10
2.10
2.85
25
6250
1.57
2.05
2.02
2.84
30
7500
1.54
2.00
1.90
2.70
40
10000
1.30
1.70
1.71
2.31
50
12500
1.06
1.40
1.40
1.85
60
15000
1.02
1.32
1.35
1.80
75
18750
0.92
1.20
1.17
1.61
100
25000
0.86
1.12
1.12
1.53
STAWAIID C. S. THAHTSEORIflEItS OP WEiTISG-
HOUSE EIEC1RIG -AJ¥B» MAMFACTrRIJITG CO.
Efficiencies.
Full Load.
| Load.
\ Load.
\ Load.
JV=133|
JY=60
^Tz=133i
^"=60
iV=133|
N=m
A=133J
jV=60
25
15
23
32
38
46
53
60
1
90.3%
87.7%
88.8%
85.3%
84.7%
79.8%
71.6%
62.0%
2
91.7
90.1
90.7
88.7
88.0
84.9
78.4
72.0
4
94.0
93.0
93.8
92.3
92.5
90.3
97.3
83.0
6
94.5
93.6
94.3
93.3
93.4
91.8
89.2
86.0
8
95.1
94.4
95.0
94.1
94.3
92.8
90.5
88.8
12
95.8
95.2
95.8
95.1
95.4
94.3
92.6
90.5
16
96.34
95.8
96.3
95.5
95.7
94.6
92.8
90.7
20
96.5
96.0
96.34
95.8
95.85
96.8
93.1
91.1
25
97.0
96.54
96.83
96.23
96.15
95.23
93.36
91.52
30
96.96
96.50
96.72
96.21
96.17
95.25
93.47
91.63
40
97.04
96.64
97.02
96.49
96.56
95.76
94.35
92.75
50
97.24
96.90
97.31
96.86
97.03
96.35
95.34
93.98
60
97.38
97.08
97.44
97.04
97.16
96.56
95.52
94.32
75
97.48
97.20
97.58
97.20
97.36
96.80
95.92
94.80
100
97.74
97.48
97.81
97.45
97.58
97.06
96.21
95.17
850
THE STATIC TRANSFORMER.
eq
'
8
o
CO
OS
CO
o
OS
01
ON
<M
s
CO
OJ
1
s
X
OS
<N
eo
3
jH
os
OS
LO
CO
L-
cc
-H
OS
<M
*-*
*3
1-1
"'
Jj
OJ
u;
OS
OO
US
OS
^
OS
13
rt
OS
OS
OS
35
OS
00
,_,
©
>o
»o
Si
eo
lJ-
t-
rH
<N
s
&
s
<M
OS
cT
£
ic
§
s
s
3
o
c.
■#
01
05
l-O
CO
os
os
CO
OS
2
55
p
o
o
o
c
50
00
s
eo
os
8
cs
o
00
CO
IO
OS
OS
os
os
*
L"~
o
id
£
IO
a
8
-
rH
*H
oi
3
CO
1
CO
OS
so
os
os
s
S
o
g
s
oo
to
CO
s
eo
en
C-l
00
ft
CO
8
<N
OS
os
OS
oo
s
IO
oo
o
t>
?1
us
LO
os
(N
1
8
M
^
OS
os
CO
os
8
-
to
,_,
<M
CO
LO
t-
OS
CO
os
s
t-
^
t-
&
'-;
r"1
CO
OS
OJ
oo
1
•d
1
T5
-d
h
w >>
s
rt
a5
^gP4
o
o
C
o
o *
ft
3S
£
-55
g
o
■j
CD
11
d
©
bo
o
ood
r/J OJ
ft
o
an
.3
c3
>>
PI
ft£
bo
3
£
cS
An 80
-d
ft
■
pi
o
be]
£
WAGNER TRANSFORMERS.
351
55 »
a *
& s
1
OS
ft
OS
s
ol
m
s
eS
q
m
s
s
©
c4
CO
OS
OS
<
•
t-
o
t-
q
©
q
A
8
lO
s
S3
oS
io
o3
co
-H
O
co
8
<M
CO
q
OS
g
o
s
.2
CO
CO
8
53
OS
g
s
OS
o
£
H
o
OS
o
o
S
§
o
■*
t-
00
*#
Tj5
LO
CO
OS
OS
OS
OS
Q
'*'■
£
CI
o
Tt<
o
o
q
id
cd
eo
OS
OS
OS
OS
OS
OS
«W
.
1
1Q
s
3
So
CO
o
q
00
*#
UO
id
OS
cs
OS
OS
OS
OS
1-1
_•
5
co
t£
liO
8
q
^
OS
s
lO
ol
OS
OS
OS
t^
1-1
i
Per
Cent
Of
trill
tion.
IS
8
o
IN
o
s
o
o
8
«
»Soao
IQ
3
8
o
8
CO
q
q
P-iQ 0.-3
CN
<N
ci
ci
O
-<"£ © =S
1Q
C<)
j2
8
Ki
oo
00
q
"*
eo
r£
CO
CN
CM
rH
rH
rH
rH
o
.g
8
g
8
8
g
O
8
s
cS
lO
lO
o
©
S
>J
£
r"'
oo
Tf
a
OS
o
bo
3
o
s
o
oo
o
8
8
8
I
352
THE STATIC TRANSFORMER.
e3
ft
co
eo
oo
3
_
00
t-
CO
CO
CO
to
8
oo
?
©
$
I-
od
os
CO
00
oo
oo
C0
OS
CO
CO
<j
-6
o
lO
SB
co
©
s
CO
=5
8
&
t-
CO
h^
§
>-
os
CO
CO
1
£
§8
8
©
CO
OS
d
o
i-q
in
N
to
3
8
s
CO
©
p
©
CO
CO
.2
rj5
od
d
c4
CO
<#
in
id
oo
OS
co
CO
CO
CO
CO
CO
CO
a
rtW
<x>
'o
50
H
d
e3
S
00
«
LO
8
00
CO
3
CO
£
in
"3
3
6
-+i
to
o
d
d
OS
CO
CO
CO
CO
CO
os
CO
os
6
H|S
„
03
CO
in
o
lO
^
§
»o
CO
00
§
«
CO
®
3
-IH
1
LO
d
d
d
d
t^
os
CO
CO
os
CO
CO
CO
CO
os
os
d
c3
s
<M
oo
co
M
to
eo
CO
CO
CO
>*
©
in
3
CO
"#
in
3
00
g
to
in
d
l^
OS
CO
CO
CO
CO
OS
1-1
d
c3
O
eo
CO
00
CO
$£
3
-*
s
CO
s
00
CO
,_}
CO
-l<
in
d
d
t^
HW
CO
OS
OS
OS
CO
OS
OS
CO
OS
OS
Per
Cent
of
eg illa-
tion.
to
CO
©
co
ig
o
in
o
o
in
o
o
tf
u
& "3 a"
OS
c4
O
m
3
OS
00
oq
s
CO
CO
p-So«
lO
in
1
8
Pho£^
Tji
co
to
«
00
cq
2
*j
*2
o
^
o
0
§
o
o
o
o
o
s
o
to
o
o
&,
c3
to
2
m
1
5
1
CO
fr-
s
o
e§
a
o3
ac
o
a
8
§
3
o
1
|
o
m
o
8
3
eo
WAGNER TRANSFORMERS.
353
8 *
S 5
e »
& .5
h H
* !
g 0
>>
o3
ft
3
rh
Ol
CO
£
o
q
q
*#
C5
05
^
d
o
CO
in
to
o
3
CO
s
o
5
s
s
CO
00
$
CO
c§
cd
©
-d
-*
"*
to
CO
CI
3
q
q
©
Tt<
id
05
©5
.®
1
w
•d
03
s
i?
3
iq
gj
g2
CO
C5
id
id
OS
OS
05
C5
C5
o
H^
<u
Ph
d
cS
q
«
So
o
CO
3
01
3
3
-*
id
CO
05
C5
C5
cs
OS
CJ
C5
»W
*d
e8
o
CO
co
C5
q
8
3
g
CO
3
js
id
CO
C5
©5
o
^
d
o
<#
lO
CO
CO
C5
**.
C?
ol
id
id
CD
t^
C5
05
05
™
«"* •
fills
8
lO
t2
oi
CN
o
iq
e>5
s
O
«
^
Per
Cent
Coppe
Loss
S
lO
lO
8
8
q
8
o
oq
ci
oi
c4
Ol
T~'
7-1
1-1
i? S 2 ©
CO
o
oi
8
%
3
3
CO
OS
«s
1
§
o
1
§
o
8
8
8
s
o
8
£>
*
1-1
oq
CO
"*
CO
'5
ft
6
3
o
a
o
o
8
8
8
I
354
THE STATIC TRANSFORMER.
>->
<#
50
os
CO
t-
o
S
CI
A
iq
o
iq
co
CO
t>
OS
©
3
■*
id
00
OS
©
as
as
©
©
©
<1
T3
ce
<N
00
S§
-f
o
OS
o
iq
Hi
3
©
oo
l
a
*
00
CO
©
as
©
©
o
Hi
i
t-
8
©
©
gj
©
CO
fH
58
cm
.2
t-^
o
as
8
eg
©
1
OS
id
as
©
CO
©
o
5fi
<M
OS
LO
co
t-
eb
©
s
H
>0
os
-#
co
"t
ci
3
g£
-V
3
»d
ed
ed
t>
[>
OS
©
©
©
©
©
©
©
©
a
®
o
c3
O
h!
<M
q
CI
©
CO
<N
t-
oo
P-i
00
CO
o
LO
os
<#
l>
id
oi
eo
ed
l>
©
OS
©
©
©
as
as
©
©
©
c3
O
Ttl
o
CO
©
^
OS
CO
©
s
©
iq
S
CO
T*
id
©
©
OS
OS
as
©
©
©
©
©
©
1-1
c3
8
05
OS
CO
00
CO
CO
S8
s
s
9
©
<*
3
si?
$
>r;
id
ed
©
t^
OS
as
as
©
©
©
©
as
as
©
^
o
i-
o
ia
10
s
©
3
3
s
©
°# J
eo
eo
co
CN
ci
ci
<N
(N
<N
c4
oi
Per
Cent
Copper
Loss.
o
o5
8
oi
8
ifl
OS
s
8
£
©
8
Sg.go
eo
§
OS
OS
8
3
N
OJ
©
©
os
00
(M
Phqh^
co
<M
1*.
■§
*
o
©
lO
O
8
o
©
2
CN
55
©
o
8
©
CO
1
o
8
©
ca
a
cS
a
1
o
§
o
CO
©
s
3
8
JO
©
1
§
3
TRANSFORMERS TESTED IN" 1392.
355
Leak-
age
drop
in
volts.
' " '
.25
.65
.45
.42
.97
1.02
.83
1.9
2.15
2.75
1.65
1.78
2.23
1.38
1.75
2.47
1.83
Total
drop
at full
load in
volts.
j q | ] "** | ^ h N N " tF oq | n q
Magne-
tizing
current
in per
cent of
full
current
23.0
21.6
8.1
7.4
9.0
7.0
2.4
1.61
1.79
59.0
47.5
1.85
3.05
10.2
4.42
8.7.
Iron
loss in
per
cent of
full
load.
15.4
14.6
5.9
5.15
6.8
6.2
1.84
1.31
1.52
2.02
3.73
2.75
1.46
2.33
8.2
2.4
3.8
u
eooo'THoiocot-T-imcMeomcst-'-HTtHr-i
COOt-t-t-COt-COOOCiOOt-t-COlOO
Appar-
ent
watts
at no
load.
432
808
600
816
1368
264
180
182
269
247
1775
2920
120
182
76
199
348
Power
absorb-
ed in
watts
at no
load.
288
540
444
578
1019
233
138
148
228
228
112
165
95
140
61.5
108
152
>>
2416
2400
2435
2447
2389
2400
2400
2400
2400
2400
2400
2400
2400
2400
2392
2400
2400
Magnetiz-
ing current
in am-
peres.
t- 1CCOC-1CO CO (O rt (i) O
rHCOOICOlOrtOoSi-lt-clboOOT-l
Maximum
output in
watts from
secondary.
1875
3750
7500
11250
15000
3750
7500
11250
15000
11250
3000
6000
6500
6000
750
4500
4000
B
p
a
03
ainti (1885) type .
(1885 rewound)
(1892 type) .
(1892 rewound)
burne Hedgehog .
inghouse . . .
.ey-Brush . . .
ison-Houston . .
D
356
THE STATIC TRANSFORMER.
SPECIAL TYPJES OJP TRASSFOMMER.
The ordinary static transformer is generally understood to be a constant
potential transformer, which is adapted to operate when connected in
parallel across a constant potential circuit.
When transformers are designed for special uses, it is customary to
designate them by name, indicative of the special work they are intended
to perform. A few of these transformers are here described.
Special High JPotential Transformer.
In making high potential tests of apparatus, it is very desirable to have a
transformer which is adapted to tbis work.
The General Electric Company is now supplying a transformer designed
for the purpose of making high potential tests up to 10000 volts. This trans-
former is tested up to a pressure of 35000 volts, and is so constructed as to
avoid any danger of breaking down as far as possible. Below is a cut, to-
gether with a diagram of its connections.
SECONDARY
5T~
.. VOLT MAINS'
g (OR 52 VOLTS WITH
~ connection
parallel)
WATER RHEOSTAT
The core is rectangular in form, the primary or low-tension side being
wound on one leg of the core, while the secondary or high-tension side is
divided into four separate coils, and mounted on a sleeve of heavy insulating
material, and placed over the opposite leg, the Avhole being immersed in oil.
In making high potential tests of apparatus, it is very desirable to have a
transformer which is adapted to the work.
A micrometer spark gap is mounted on top of the box or case, and con-
nected in shunt across the high potential terminals. The spark gap is set
for the desired voltage by the use of a calibration curve, or by a preliminary
calibration by means of a voltmeter connected to the low-tension side, the
ratio of transformation being known. The apparatus to be tested is then
connected to the high potential terminals, and the potential raised to the
desired amount.
SPECIAL TYPES OF TRANSFORMERS.
357
This transformer is most invaluable in testing all kinds of apparatus for
high-tension work.
Fig. 17. High Potential Testing Transformer.
Transformers for Constant; Secondary Current.
Several methods have been tried with more or less success to obtain con-
stant current at the secondaries of transformers.
The simplest and earliest system for obtaining a constant current in the
secondary is by means of transformers whose primaries are connected in
series, and a constant current maintained in the primary. This is shown in
diagram in Fig. IS. Series transformers for this purpose have never been
very successful, due to the trouble caused by the rise of potential in the
secondary when opened for any cause. Various devices (Fig. 18), such as
short-circuiting points separated by a paraffined paper, or a reactive or
choking coil connected across the secondary terminals, have been intro-
duced to prevent any complete opening of the secondary by reason of any
defect in the lamp or other device connected in the circuit.
CONSTANT CURRENT LINE
SERIES TRANSFORMERS
SHORT-
CIRCUIT
.POINTS
■ARC LAMPS-*
Fm. 18.
Reactive coils used as shunt devices have been used under different
names ; as compensators, choking coils, and economy coils.
358
THE STATIC TRANSFORMER.
A device of this kind has been introduced by the Westinghouse Electric
and Mfg. Company, and others, for use in street-lighting by series incan-
descent lamps. It is shown diagrammatically in Fig. 19. The lamp is
placed in shunt to the coil ; when the filament breaks, the total current
passes through the coil, maintaining a slightly higher pressure between its
terminals than when the lamp is burning. It is thus evident that the regu-
XT] CX_d_
-\Zr
lation of the circuit is limited, due to the excessive reactance of the coils
when several lamps are taken out of circuit.
Economy Coils or Compensators.
A modification of the above is built by several companies for use on ordi-
nary low potential circuits, where it is desired to run two or three arc
lamps. It is a single coil transformer, and is shown in Fig. 20, and diagram-
matically in Fig. 21, same page. If any lamp is cut out or open-circuited
the current in the main line decreases slightly. As more lamps are cut out
SECONDARY J CIRCUIT 1U v.
J D. P. SWITCH
] D. P. FUSE BOX
_J»i
K 1
1 A
n
i
14 AMPS s
*±$X-
<-
Fig. 20. Westinghouse Econ-
omy Coil. For A.C. arc lamps-
Fig. 21. Arrangement of Apparatus for
use of Economy Coil or Compensator.
the remaining lamps receive less current, and it is necessary to replace the
bad lamps in order to obtain normal current through the circuit.
Transformers for Constant Current from Constant Po-
tential.
The transformers represented in Fig. 22 show a design that will give out
an approximately constant current when connected to constant potential
circuits. The transformer has its core so designed that there is a leakage
path for the flux between the primary and secondary. This is shown in the
SPECIAL TYPES OF TRANSFORMERS.
359
diagram at a and b. At open secondary circuit there is little or no ten-
dency for the flux to leak across the gap. When current flows through the
secondary, thus creating a counter magneto-motive force, there is then a
-■SECONDARY
Fig. 22. Constant Current or Series Transformer.
leakage across this path, and if properly proportioned, this leakage will, act
to regulate the current in the secondary, so that it will be approximately
constant.
General Electric Constant Current Transformers.
The transformer just described has the disadvantage that its regulation
is fixed for any transformer, and may vary in transformers of the same
design, without any ready means of adjustment. The transformer also
regulates for constant current over but a limited range in the secondary
loads.
The General Electric Company constant current transformer shown in
Figs. 23 and 24, is constructed with movable secondary coils, and fixed pri-
mary coils.
FiG. 23. General Elec. Co.
Constant Current Trans-
formers for 50 lights.
FiG. 24. Connections for Alter-
nating Series Enclosed Arc
Lighting System, with 50, 75, or
100 Light Transformer.
The weight of the movable coil is partially counterbalanced, so that at
normal full-load current the movable coil or coils lie in contact (See Fig.
23) with the stationary coil, notwithstanding the magnetic repulsion between
them. When, however, one or more lamps are out of the circuit, the in-
creasing current increases the repulsion between the coils, and separates
them, reducing the current to normal. (See Fig. 24-) At minimum load, the
distance between the coils is maximum. The regulation is thus entirely
automatic, and is found to maintain practically constant current, or a de-
parture from constant current if desired. The transformer can be adjusted
for practically constant current for positive regulation ; i.e., increasing
current from full load to light loads, or for a negative regulation, i.e., de-
creasing current, from full load to light loads. This adjustment is obtained
360
THE STATIC TRANSFORMER.
by changing the position of a cam from which the counter-weights are sus-
pended. The curves shown in Fig. 27 show the range obtained in a 100-light
transformer.
Fig. 25. Full-Load Position
of Secondary Coils.
Fig.. 26. Half-Load Position
of Secondary Coils.
The transformers are enclosed in cast iron or sheet iron tanks filled with
transil oil. The oil, in addition to being an insulating and cooling medium,
serves to dampen any sudden movement of the secondary coils.
These transformers are connected to the regular constant potential mains,
and the larger sizes are arranged for multiple circuits in the secon-
dary. After having been started on a run, the transformers need no atten-
tion, as they are entirely automatic in their action.
Fig. 27. Diagram of Connections.
The full-load efficiency of this type is practically the same as that of a
constant potential transformer of the same capacity. The power factor of
the system at full load is about 85 per cent, due to the reactance of alternat-
ing arc lamps. At fractional loads, the power factors necessarily are much
lower, and it is therefore not desirable to operate such a system at light load.
RE
3ULATION
1 1 1
TEST 100 L. 1. G.
?.00
DISTANT
TIVE
BEG
iUr
ION,
CI
RRE
T T
ANS
"ORIV
ER.
to' 6. 6
noN
vea
&GVJL
*-n°
*-
S
N'
gM"
LOAD
FULL
LOAD
Fig. 28.
REGULATING RESISTANCE COIL.
361
REGVLATiarG REACTANCE COIL FOBS A. C. ARC
CMCU1TS.
Another and very simple device for regulating the current in a series cir-
cuit for A.C. arc lamps has been put on the market by the Manhattan Gen-
eral Construction Company. It consists of a single coil of insulated wire
arranged to enclose more or less of one leg of a "W "-shaped magnet, as
shown in the following cut. The coil is suspended from one end of a lever
Fig. 29. Regulating Reactance Coil by Manhattan General Construction Co.
and counterbalanced by a weight on the other, and so arranged that at all
points of its travel it just balances the varying magnetic pull of the coil.
The arc circuit is connected in series with "this coil with a switch to open
the circuit. Without current flowing, the normal position of the coil is at
the top or off the leg of the magnet. When the switch is closed, current
flows in the circuit (and coil), and draws the coil down on the leg to a point
where the reactance of the coil holds the current strength at a predeter-
Fig. 30. Diagram of Connections of the Regulating Reactance Coil
of the Manhattan General Construction Co.
362
THE STATIC TRANSFORMER.
mined point ; as, say, 6.6 amperes. It is said that this device will maintain
a current constant within one-tenth of an ampere.
The losses are the iron losses and I2R losses in the coil, which, with con-
stant current, are the same under all conditions of load.
As it is not always, or even often, that it is necessary to provide for regu-
lation of an arc circuit to the extent of its full load, the makers have
adopted the policy of supplying instruments to care for but that part of the
load that is expected to vary, in some cases 10 % of the circuit and in others
75 %, thus avoiding the need for larger apparatus, or for insulation for the
total voltage of the circuits. They claim another advantage in being able
to connect the device in one leg of the series circuit, and allowing the other
end of the circuit to be connected to the mains at any such point as may be
the nearest at hand. Fig. 30 shows the apparatus diagrammatically.
feeder Regulators.
An alternating current feeder regulator is essentially a transformer hav- .
ing its primary connected across the mains, and its secondary in series with
the mains. The secondary is arranged so that the voltage at its terminals
can be varied over any particular range.
Fig. 32. Internal Connections of a Stillwell Regulator.
MMH^^HMi
REGULATING RESISTANCE COIL.
363
The several different styles of feeder regulators have been devised, differ-
ing in principle of operation, but all of them have the primary coil con-
nected across the mains, and the secondary coils in series with the mains.
The " Stillwell " regulator, which was designed by Mr. L. 13. Stillwell, has
the usual primary and secondary coils, and effects the regulation of the cir-
cuit by inserting more or less of the secondary coil in series with the line.
This secondary coil has several taps brought out to a commutating switch,
as shown in Fig. 31. The apparatus is arranged so that the primary can
be reversed, and therefore be used to reduce as well as to raise the voltage
of the line. It is evident from an observation of the diagram that if two
of the segments connected to parts of the coils were to be short-circuited, it
would be almost certain to cause a burn-out. To prevent this, the movable
arm or switch-blade is split, and the two parts connected by a reactance,
Fig. 33.
this reactance preventing any abnormal local flow of current during the
time that the two parts of the switch-blade are connected to adjacent seg-
ments. The width of each half of the switch-arm must of necessity be less
than that of the space or division between the contacts or segment's.
As the whole current of the feeder flows through the secondary of the
booster, the style of regulator which effects regulation by commutating
the secondary cannot well be designed for very heavy currents because of the
destructive arcs which will be formed at the switch-blades. To overcome
this difficulty, Mr. Kapp has designed the modification which is shown in
Fig. 32 p. 362. In this regulator the primary is so designed that sections
of it can be commutated, thus avoiding an excessive current at the switch.
This regulator, however, has a limited range, as the secondary always has
an E.M.F. induced in it while the primary is excited ; and care must be
taken to see that there are sufficient turns between the line and the first
contact in order to avoid excessive magnetizing current on short circuit.
'CONTFtflU.iNG HAND
Fig. 34. Connections for M. R.
Feeder Regulator of G. E. Co.
Fig. 35. Diagram of Con-
nections of Feeder Po-
tential Regulator.
The General Electric Company have brought out a feeder regulator, in
which there are no moving contacts in either the primary or secondary, and
Avhich can be adapted for very heavy currents. This appliance is plainly
shown in Figs. 33 and 34. The two coils, primary and secondary, are set at
right angles in an annular body of laminated iron, and the central lami-
364
THE STATIC TRANSFORMER.
nated core is arranged so as to be rotated by means of a worm wheel and
shaft as shown.
The change in the secondary voltage, while boosting or lowering the line
voltage, is continuous, as is also the change from boosting or lowering, or
rice versa. In this regulator, the change of the secondary voltage is effect-
ed by the change in llux through the secondary coil, as the position of the
movable core is changed by the turning of the hand wheel and shaft. There
are, therefore, no interruptions to the flow of current through either the
primary or secondary coils, and the regulator is admirably adapted for in-
candescent lighting service, where interruptions in the flow of current, how-
ever instantaneous, are objectionable.
S. St. C. UEVICES fOR RE&riAII^C} A. C.
CIRCUIT!.
Where polyphase A. C. generators are used for lighting and power it is
necessary to provide some method by which the individual phases can be
separately and independently regulated.
The method used by this company for accomplishing this result is by
changing the effective turns on the armature. At one end of the winding
of each phase are several regulating coils from which are brought out to
suitable regulator heads taps which are mounted upon a terminal board
fastened to the machine ; or the regulator heads, if so desired, may be
mounted upon the switch-board. The following diagrams illustrate
he method of bringing out the regulating taps from the armature coils of a
two-phase generator.
Fig. 36. Two-phase Generator.
The regulator heads are similar to those used in connection with the
" Stillwell" regulator, and make use of a modification of the split finger
contact arm and choke-coil to prevent short circuit of the regulator coils.
DEVICES FOR REGULATING A. C. CIRCUITS. 865
PHASE A-B
vVWVWvWAVAVAW-WWV
PHASE E-F
^T
f— ? L t
I [ K { J I \ [\
oo © <b © o o © 6©
) c
1!
l '
5 1
Hi!
■!'.;ioJ!
CiR
SUIT
CIRCUIT
Fig. 37. Diagram of one Two-phase Generator and four Circuits.
GENERATOR No. 1
PHASE A-B PHASE E-F
GENERATOB NO. 2
PHASE A-B PHASE E-F
Fig. 38. Diagram of two Two-phase Generators in Parallel and three
Circuits.
366 THE STATIC TRANSFORMER.
Separate Circuit 13 emulations.
Where a number of circuits are run out from the same set of bus bars,
regulation of each circuit is provided for in this system by the use of a
single coil transformer from various points on the winding of which leads
are brought out to a regulator head, from which any part or all of the trans-
former may be thrown into service to increase the pressure on the line.
Figures 37 and 38 show in diagram the method of applying this device,
which is also provided with the split finger contact and choke-coil to prevent
short circuit.
TRANSFORMER COOECXIOM§.
Some of the advantages claimed for alternating current systems of dis-
tribution over the direct current systems is the facility with which the
potential, current, and phases can be changed by different connections of
transformers.
On single-phase circuits, transformers can be connected up to change
from any potential and current to any other potential and current ; but in
a multi-phase system, in addition to the changes of potential and current,
the phases can be changed to almost any form that may be desired The
following diagrams, taken from General Electric Company publications,
represent some of the results obtained by different transformer con-
nections.
Directions tor Connecting- Type M, Cr. JE. Transformers.
Figs. 39 and 40.
Transformers Wound for 1040 or 2080 Volts Primary and 52 or 104
Volts Secondary.
For 1040 volts primary and 52 volts secondary, See Fig. 42.
" 1040 " " " 104 " " " « 43
" 2080 « » " 52 •< " « « 46"
" 2080 " " " 104 " " « « 47]
Transformers Wound for 1040 or 2080 Volts Primary and 104 or 208
Volts Secondary.
For 1040 volts primary and 104 volts secondary, See Fig. 42.
" 1040 " « •« 208 " » « " 43
" 2080 " " » 104 » " « <» 46.
" 2080 •« " " 208 *« •« « " 47.
Transformers Wound for 1040 or 2080 Volts Primary and 115 or 230
Volts Secondary.
For 1040 volts primary and 115 volts secondary, see Fig. 42.
" 1040 " " " 230 •« " »« " 43.
«' 2080 " " " 115 " «' " »' 46.
" 2080 " « » 230 " » «« " 47.
TRANSFORMER CONNECTIONS.
367
Figs. 41, 42, and 43.
Transformers Wound for 1040 or 280 Volts Primary and 115 Volts
Secondary.
For 1040 volts primary and 115 volts secondary, see Fig. 44.
" 2080 '• " u 115 " " " " 4G.
Transformers Wound for 520 or 1040 Volts Primary and 115 or 230
Volts Secondary.
For 520 volts primary and 115 volts secondary, see Fig. 42.
» 520 " " ' " 230 " " " " 43.
" 1040 " " " 115 " " " " 46.
'• 1040 " «' " 230 " " " " 47.
Transformers Wound for 520 or 1040 Volts Primary and 115 Volts
Secondary .
For 520 volts primary and 115 volts secondary, see Fig. 42.
" 1040 " " " 115 " " " " 46.
Figs. 44, 45, and 46.
Transformers Wound for 1040 or 2080 Volts Primary and 52 or 104
Volts Secondary, Used on Three-Wire System.
For 1040 volts primary and 52-52 volts secondary, see Fig. 45.
" 20S0 " " " 52-52 " " " » 49.
Transformers Wound for 1040 or 2080 Volts Primary and 104 or 208
Volts Secondary, Used on Three-Wire System.
For 1040 volts primary and 104-104 volts secondary, see Fig. 45.
104-104
49.
Transformers Wound for 1040 or 208V Volts Primary and 115 or 230
Volts Secondary, Used on Three-Wire System.
For 1040 volts primary and 115-115 volts secondary, see Fig. 45.
" 2080 " " " 115-115 " " " " 49.
Transformers Wound for 520 or 1040 Volts Primary and 115 or 230
Volts Secondary, Used on Three- Wire System.
For 520 volts primary and 115-115 volts secondary, see Fig. 45.
" 1040 " " " 115-115 " " " '" 49.
All voltages for which a transformer is wound are stamped on the name
plate on the cover of the transformer box. These are the normal voltages
368
THE STATIC TRANSFORMER.
for which the transformer is designed, but all transformers can be used
satisfactorily for voltages that do not vary more than 10% above or below
the designed voltage.
Single-Phase.
The connections of the single-phase step-down and step-up transformers,
having parallel connections, need not be explained outside of the preceding
diagrams. For residence lighting, the most economical method of supply
is through single-phase transformers with three-wire secondaries. A tap
is brought out from the middle of the secondary winding, this tap connect-
ing to the middle or neutral of the three-wire system. In this way a few
large transformers can be connected by three-wire secondaries in a resi-
dence or other district, and will take care of a large number of connected
Fig. 47. Arrangement of Balancing Transformer for
Three-wire Secondaries.
Kapp shows a modification of the three-wire circuits, in Avhich the out-
side wires are fed by a single transformer, and the neutral wire is taken
care of by a balancing transformer, connected up at or near the center of
distribution. The capacity of the balancing transformer need be but half
the greatest variation in load between the two sides.
Some makers of transformers have the connection board in their trans-
formers so arranged that the two primary coils may be connected either in
Fig. 49. Single-Phase,
FiG. 48. Single- with 3-wire Secondary, Fig. 50. Two- Fig. 51. Three-
Phase. Useful for Residence Phase, 4 Wire, Two
Circuits. Wires. Phase,
series or parallel by mere changes of small copper connecting links, so
that the same transformer can be connected up for either 1000- or 2000-volt
circuits, and the secondary for either 50 or 100 volts.
Cfcuarter- Phase.
The plain two-phase or quarter-phase connection, Fig. 50, is simply two
single transformers connected to their respective phases, the phases being
kept entirely separate. In the three-wire, quarter-phase circuit, one of the
leads can be used as a common return, as shown in Fig. 51.
^^■^MB^^H
TRANSFORMER CONNECTIONS.
369
Three-Phase.
The three-pliase connections shown in diagram 52 are known as the
delta connections, and are of great advantage where continuity of ser-
vice is very important. The removal of any one transformer does not inter-
LwmwJ
fTBTJTJTi [WW
Fig. 52. Three-Phase
Delta Connection.
Fig-. 53. Three-Phase
Star Connection.
Fig. 54. Monocyclic
Connections.
rupt the three-phase distribution, and the removal of two transformers still
admits of power transmission on a single phase of the circuit.
The " Y " or star connection, as shown in diagram 53, has one of the
terminals of each primary and secondary brought to a common connec-
GENERATOR
TRANSFORMER
Fig. 55. Connections of Mono-
cyclic System for Light and
Power.
Fig. 56. Changing Quarter-phase to
Three-phase, Non-interchangeable
Step-up Transformers.
tion, the remaining three terminals being brought to the main line and the
distributing lines. The advantage of the star connection over the delta con-
nection is, that for the same transmission voltage each transformer is wound
370
THE STATIC TRANSFORMER.
for only 58% of the line voltage. In high-voltage transmission 'this admits
of much smaller transformers heing built for high potentials than is possi-
ble with the delta connection.
Diagram 55, p. 369, shows a device by Mr. C. P. Steinmetz for enabling
the lights and motors to run on the same single-phase circuit. The genera-
tor has a supplemental coil called the teazer ; one end of this coil is con-
nected into the middle of the main winding, the other being connected to
the power wire or teazer wire of the system. For lighting circuits, connec-
tions are made only to the two outside wires, or the main wires of the sys-
tem, or if it is desired to run three-wire system, the middle connection is
made in the middle of the main winding. Where motors are connected up,
the third connection is made to the teazer or power wire. This wire sup-
plies current to the motor only during the time of starting, because as soon
as the motor is up to synchronism it will then run as a single-phase machine,
and no current is taken from the teazer wire.
Arrangement of Transformers for Stepping- Up and Down
for Xiong' Distance Transmission-
Figures 56,57, and 58 show diagrammatically the connections for adapting
three-phase transmission to quarter-phase generators, with interchangeable
and non-interchangeable transformers. The diagrams are probably suffi-
ciently clear for the purposes of this article.
Fig. 57. Changing Quar-
ter-phase to Three-
phase. All Step-up
Transformers Inter-
changeable.
Fig. 58. Changing Quarter-
phase to Three-phase, and
back to Quarter-phase. All
Transformers Interchangea-
ble.
Three-T»lsase to Six-Phase Connections.
A rotary converter wound for six-phase has a greater capacity for work
than the same machine wound for three phases. Three-phase transmission,
however, is very economical, and in Fig. 54 is shown a diagram by which six
phases can be obtained from three phases by the use of only three trans-
formers.
Each transformer has two secondary coils. One secondary of each trans-
former is first connected into a delta, then the remaining secondary coils are
TRANSFORMER CONNECTIONS.
371
connected up into a delta, but in the reverse order of the first delta. This
is an equivalent of two deltas, one of which is turned 180° from the other.
In the diagram ABC represents one delta, and DEF the other.
twvwv^l pvwvwfj Vwvw
Fig. 59. Diagrams of Connections for Changing from Three-Phase to
Six-Phase.
In the same way the two secondaries can be connected up " Y," and one
" Y " turned 1S0° to obtain six phases. The disadvantage of " Y " connec-
tion, however, is that in case one transformer is burned out, it is not possi-
ble to continue running, as can be done with delta connections.
Ftg. 60. Method of Handling and Install-
ing Transformers.
From pamphlet of General Electric Company.
872
THE STATIC TRANSFORMER.
TRANSFORMER TEiTI^O.
Although the standard types of transformers of to-day are made on lines
found by long experience to be the best for all purposes, and are subject to
careful inspection and test at the factory in most cases, yet the various
makers have such different ideas as to the value of the different points,
that in order to obtain fair bids on such appliances when purchased, it is
always best to prepare specifications, and the buyer should be prepared to
conduct or check tests to determine whether the specifications have been
fulfilled. Large stations shotild have a full outfit of apparatus for conduct-
ing such tests ; but smaller purchasers can do quite well by having a compe-
tent superintendent, or by hiring an outside engineer to witness the tests at
the factory. It is not always necessary to put each individual transformer
through all the tests, but the break-down test for insulation should be ap-
plied to all.
Prof. Jackson gives the folloAving requirements for guaranties of trans-
formers.
Iron loss for 1000-volt transformers and for frequencies over 100 as
follows :
Capacity.
Iron Loss.
Exciting Current.
1000 watts
1500 watts
2000 watts
2500 watts
4000 watts
6500 watts
17500 watts
30 watts
40 watts
50 watts
60 watts
80 watts
100 watts
150 watts
.055 amperes.
.080 amperes.
.150 amperes.
.200 amperes.
For frequencies less than 100 it may be advisable to allow 10 % higher loss
to avoid excessive cost.
Note. — Guaranties for iron loss should cover ageing for at least one
year.
Drop in secondary pressure not to exceed 3 % between no load and full
load.
Rise of temperature after 10 hours' run under full load, 70° F.
(about 40° C).
Note. — This measurement was probably meant by Professor Jackson to
be made by thermometer. It is better to take the rise by resistance meas-
urement, in which case the allowable temperature is 50° C.
Risruptive streng-th of insulation after full-load run, between
coils and between primary coil and iron, at least 10 times the primary volt-
age. Insulation resistance to be not less than 10 megohms, and guaranteed
not to deteriorate with reasonable service.
Note. — See previous matter as to test voltage.
Exciting' current for 1000-volt transformers not to exceed values
given in the above table, when the frequency is above 100. The exciting
current increases as the frequency decreases, and varies inversely as the
voltage. For intermediate capacities proportional values may be expected.
He further says : " Transformers which do not meet the insulation and heat-
ing guaranties are unsafe to use upon commercial electric lighting and motor
circuits, while those which do not meet the iron loss, regulation, and exciting
current guaranties icaste the company's money. "
The characteristics of a transformer, to be determined by tests, are as
follows :
(1) Insulation strength between different parts.
(2) Core loss and exciting current.
(3) Resistances of primary and secondary and PR.
(4) Impedance and copper loss, direct measurement.
TRANSFORMER TESTING. 373
(5) Heating and temperature rise.
(6) Ratio of voltages.
(7) Regulation and efficiency, which may he calculated from the results
of tests (2), (3), and (1), or may be determined directly by test.
(8) Polarity.
The instruments required to make these tests should be selected for each
particular case, and consist of ammeters, voltmeters, and indicating watt-
For central station work, the following instruments will suffice for nearly
any case which may come up in ordinary practice.
A. C. voltmeter, reading to 150 volts, and with multiplier to say 2500 volts.
a! C. ammeter, reading to 150 amperes, with shunt multiplier if necessary
to carry the greatest output.
Indicating wattmeter, reading to 150 or 200 watts.
Note. _ jror full data and examples of transformer testing, see pamphlet
No. 8126, " Transformer Testing for Central Station Managers" by Gen-
eral Electric Company.
Insulation Test.
This is the simplest and most important test to he made, for the reason
that one of the principal functions of a transformer is its ability to thor-
oughly and effectually insulate the secondary circuit from the primary
circuit.
Tests of the insulation of practically all high potential apparatus are now
carried out by high pressure, rather than by test of the insulation resistance
by galvanometer. Some insulations will show a very high test by galva-
nometer, but will fail entirely under test with a voltage much exceeding that
at which it is to be used. On the other hand, it is not uncommon to find
insulation such that, while the galvanometer tests show low resistance, it
will not break down at all under the ordinary voltages. For this reason, it
is common practice among manufacturers of transformers to apply a mod-
erately high voltage, from two to three times the working voltage, for a
short period, usually about one minute.
According to the Committee on Standardization of the A. I. E. E., the
tests should be made with a sine wave of electromotive force, or where this
is not available, at a voltage giving the same striking distance between
needle points in air as a sine wave of the specified E.M.F., except where
expressly specified otherwise. For needles, new sewing-machine needles
should be used. It is recommended that the apparatus be shunted during
test by the spark gap set for a voltage exceeding the required voltage by
10 per cent.
The committee also recommends the following voltages for use in
testing :
In electric circuits of rated voltage up to 500 volts.
Apparatus of 10 k. w. capacity or less 1000 volts.
Apparatus over 10 k. w. capacity 1500 "
Of rated voltage over 500 but less than 1000 volts.
Apparatus of 10 k. w. capacity and less 2000 volts.
Apparatus over 10 k. w. capacity 3000 "
Of 1000 and more but less than 2500 volts 5000 volts.
" 2500 " " " " " 3500 " 7000 "
" 2500 " " " " " 6600 " 10000 "
" 6600 " " " " " li times rated voltage.
In standard transformers these insulation tests should be (1) between pri-
mary and secondary, and between primary and core and frame ; (2) between
secondary and core and case.
To obviate any induced potential strain, the secondary should be grounded
while making the test between the primary and secondary, and between
primary and core and case.
In testing between the primary and secondary, or between the primary
'and core and frame, the secondary must be connected to the core and
frame.
374
THE STATIC TRANSFORMER.
It is also important that all primary leads should be connected together
as well as all secondary leads, in order to secure throughout the winding a
uniform potential strain during the test.
Note. — See index for sparking-gap curve, and use new needles after every
discharge.
From one point of view, the factor of safety of the secondary need not be
greater than that of the primary, and if 10,000 volts is considered a sufficient
test for a 2000-volt primary, 1000 volts might be sufficient for a 200-volt sec-
ondary. But a thin film of insulation may easily withstand a. test of 1000
volts, although it is so weak mechanically as to be dangerous. A 200-volt
secondary should therefore be tested for at least 2500 volts in order to guar-
antee it against breakdown due to mechanical weakness.
The duration of the insulation test may vary somewhat with the magni-
tude of the voltage applied to the transformer. If the test is a severe one,
it should not be long continued ; for while the insulation may readily with-
stand the momentary application of a voltage five or ten times the normal
strain, yet continued applic ition of the voltage may injure the insulation
and permanently reduce its strength.
Attention has been called to the fact that in testing between the primary
and the core or the secondary, the secondary should be grounded. In test-
ing between one winding and the core, for example, an induced potential
strain is obtained between the core and the other winding which may be
Fig. 61.
much greater than the strain to which the insulation is subjected under
normal working conditions, and greater therefore than it is designed to
withstand. In testing between the primary and the core, the induced po-
tential between the secondary and the core may be several thousand volts,
and the secondary may thus be broken down by an insulation test applied
to the primary under conditions which do not exist in the natural use of
the transformer.
Attention is further called to the fact that during the test all primary
leads as well as all secondary leads should be connected together. If only
one terminal of the transformer winding is connected to the high potential
transformer, the potential strain to which it is subjected may vary through-
out the winding, and may even be very much greater at some point than at
the terminals to which the voltage is applied. Under such conditions the
reading of the static voltmeter affords no indication of the strain to which
the winding is subjected.
Indications which are best learned by experience reveal to the operator
the character of the insulation under test. The transformer in test requires
a charging current varying in magnitude with its size and design. From
the reading of the ammeter, placed in the low potential circuit of the test-
ing transformer, the charging current may be ascertained. It will increase
as the voltage applied to the insulation is increased.
If the insulation under test be good there will be no difficulty in bringing
the potential up to the desired point by varying the rheostat. If the insula-
TRANSFORMER TESTING.
375
tion be weak or defective, it will be impossible to obtain a high voltage
across it, and an excessive charging current will be indicated L»y the am-
meter.
Inability to obtain the desired potential across the insulation may be the
result merely of large electrostatic rapacity of tiie insulation and the conse-
quent high charging current required, so that the high potential trans-
former may not be large enougn to supply this current at the voltage
desired.
A breakdown in the insulation will result in a drop in voltage indicated
by the electrostatic voltmeter, an excessive charging current, and the burn-
ing of the insulation if the discharge be continued for any length of time.
Core loss and Exciting- Current.
In taking measurements of core loss and exciting current, the instruments
required are a wattmeter, voltmeter, and ammeter.
One of the two following described methods for connecting up the instru-
ments is usually employed, although several others might be shown. These
methods differ only in the way of connecting up the instruments, and are as
follows :
Method 1. — The voltmeter and pressure coil of the wattmeter are con-
nected directly to the terminals of the test transformer. When the pressure
of the voltmeter is at the standard voltage the reading of the wattmeter will
be the core loss in watts. It is evident from an inspection of diagram 62
that the wattmeter will indicate, in addition to the watts consumed by the
test transformer, the I2R or copper loss in both the pressure coil of the
wattmeter and voltmeter. This error, however, being constant for any
pressure, is easily corrected. This method is very good for accurate results,
and where the quantities to be measured are small it is most desirable.
TEST TRANS
Fig. 62. Core Loss (Method 1).
Method 3. —The current coils of the wattmeter are inserted between
a terminal of the test transformer and the terminal of the voltmeter and
pressure coil of the wattmeter (see diagram 63). In this method the error
introduced is the I2R loss in the current coil of the voltmeter. This is a
very much smaller error than in Method 1, but does not allow of an easy or
accurate correction, and the results obtained by it must, -therefore, be taken
without correction. For this reason Method 2 is more convenient, and for
the measurement of large core losses, and for commercial purposes, it is
sufficiently accurate.
Fig. 63. Core Loss (Method 2).
Core losses and exciting current should be measured from the low-poten-
tial side of the transformer to avoid the introduction of high voltage in the
test.
UTotes on Core loss and Excitation Current.
In an ordinary commercial transformer, a given core loss of 60 cycles may
consist of 70 per cent hysteresis and 30 per cent eddy current loss, while at
125 cycles the same transformer may have 55 per cent hysteresis loss and 45
per cent eddy current loss.
876 THE STATIC TRANSFORMER.
The core loss is also dependent upon the wave form of the impressed
E.M.F., a peaked wave giving somewhat lower core losses than a flat wave.
It is not uncommon to find alternators having such a peaked wave form
that the core loss obtained, if the transformer is tested with current from
them, will be 5 per cent to 10 per cent less than that obtained if the trans-
former is tested from a generator giving a sine wave. On the other hand,
generators are sometimes obtained which have a very flat wave form, so
that the core loss obtained will be greater than that obtained from the use
of a sine wave.
The magnitude of the core loss depends also upon the temperature of the
iron. Both the hysteresis and eddy current losses decrease slightly as the
temperature of the iron increases. It is well known that if the tempera-
ture be increased sufficiently, the hysteresis loss disappears almost entirely,
and since the resistance of iron increases with the temperature the eddy
current losses necessarily decrease. In commercial transformers, an in-
crease in temperature of 40° C. will cause a decrease in core loss of from 5
per cent to 10 per cent. An accurate statement of core loss thus necessi-
tates that the temperature and wave form be specified.
If, in the measurement of core loss, the product of impressed volts and
excitation current exceeds twice the measured watts, there is reason to
suspect poorly constructed magnetic joints or higher iron densities than are
allowable in a well-designed transformer.
Measurement of Resistance.
Resistance of the coils can be measured by either the Wheatstone Bridge
or Fall of Potential Method.
For resistances below one or two ohms it is generally more accurate to use
the Fall of Potential Method.
Resistances should always be corrected for temperature, common prac-
tice being to correct to 20° centigrade. For pure soft-drawn copper this cor-
rection is .4 % per degree centigrade. Readings should be taken at several
different current values, and the average value of all tbe readings will be
the one to use. (See Index for correction for rise of temperature.)
Having obtained the resistance of the primary and secondary coils, the
PR of both primary and secondary can be calculated ; the sum of the two
being (very nearly) equal to the copper loss of the transformer. If it is
preferred to measure the copper loss directly by wattmeter, then we must
make test No. 4.
The fall of potential method is subject to the following sources of error :
(1) With the connections as ordinarily made the ammeter reading includes
the current in the voltmeter, and in order to prevent appreciable error the
resistance of the voltmeter must be much greater than that of the resistance
to be measured. If the resistance of the voltmeter be 1000 times greater, an
error of £s of 1 percent will be introduced, while a voltmeter resistance 100
times the coil's resistance will mean the introduction of an error of 1 per
cent. Correction of the ammeter reading obtained in (3) may thus become
necessary, but whether or not it be essential will depend upon the accuracy
desired. (See example below.)
(2) The resistance of the voltmeter leads must not be sufficient to affect
the reading of the voltmeter.
(3) Since the resistance of copper changes rapidly with the temperature,
the current used in the measurement should be small compared with the
carrying capacity of the resistance, in order that the temperature may not
change appreciably during the test. If a large current is necessary, read-
ings must be taken quickly in order to obtain satisfactory results. If a
gradual increase in drop across the resistance can be detected within the
length of time taken for the test, it is evident that the current flowing
through the resistance is heating it rapidly, and is too large to enable accu-
rate measurement of resistance to be secured.
It is quite possible to use a current of sufficient strength to heat the wind-
ing so rapidly as to cause it to reach a constant hot resistance before the
measurement is taken, thus introducing a large error in the results. Great
care should be taken, therefore, in measuring resistance to avoid the use of
more current than the resistance Avill carry Avithout appreciable heating.
(4) Considerable care is necessary to determine the temperature of the
winding of the transformer. A thermometer placed on the outside of the
winding indicates only the temperature of the exterior. The transformer
TRANSFORMER TESTING.
377'
should be kept in a room of constant temperature for many hours in order
that the windings may reach a uniform temperature throughout. The
surface temperature may then be taken as indicative of that of the interior.
Impedance and Copper-Loss Xest.
Method 1. — In this method, -which was first described by Dr. Sumpner,
the secondary coil is short-circuited through an ammeter. A wattmeter
and a voltmeter are connected up in the primary circuit in a manner similar
to either of the two methods described for the core-loss test. An adjustable
resistance or other means for varying the impressed voltage is placed in
series with the primary circuit.
To make the test, the voltage is raised gradually until the ammeter shows
that normal full-load current is flowing through the secondary circuit.
Readings are then taken on the wattmeter and voltmeter.
This method of measuring the impedance and copper loss of a transformer
is now seldom used, on account of the liability to error due to the insertion
of the ammeter in the secondary. In addition to being inaccurate, it usu-
ally requires an ammeter capable of measuring a very heavy current.
Method 2. — This method differs from Method 1 only in that the sec-
ondary is short-circuited directly on itself, an ammeter being inserted in the
primary circuit. The diagram of connections is shown in Fig. 64. In con-
necting up the voltmeter and the potential coil of the wattmeter, the same
corrections hold as in the measurement of core loss and exciting current,
and connections made according to whether accuracy of results or simplicity
of test is the more imporant.
Fig. 64. Impedance Test with Wattmeter.
Having the readings of amperes, volts, and watts, we obtain from the
first two the impedance of the transformer. This impedance is the geo-
metrical sum of the resistance and reactance, and is expressed algebraically
as follows :
Z=ViJ2-+-(2B7lZ)8»
where z = Impedance,
7?= Resistance,
L =z Coefficient of self-induction,
/= Current in amperes,
n = Frequency in cycles per second,
2?r n L = reactance'of the circuit.
In a test on a transformer with secondary short-circuited as in Fig. 67
above, and primary connected to 2000 volts, the impedance volts were 97 at
full-load primary current of 2.5 amperes, then
97
Impedance = — = 38.8 ohms,
and
97 X 100
Impedance drop -
2000
; 4.85 per cent.
The reading on the wattmeter indicates the combined I2R of the primary
and secondary coils, and in addition includes a very small core loss, which
can be neglected, and an eddy current loss in the conductors.
In standard lighting transformers, the impedance voltage varies from
2 per cent to 8 per cent. In making this test, careful record of the fre-
quency should be made, as the impedance voltage will vary very nearly
with the frequency.
378
THE STATIC TRANSFORMER.
Heat Tests.
To test the transformer for its temperature rise, it is necessary to run it
at full excitation and full-load current for a certain length of time. An
eight-hour run at full load will usually raise the temperature to its highest
point, and in the case of lighting transformers a full-load run very seldom
continues longer than eight hours in practice. If it is desired to find just
what is the final temperature rise under full load (as is often the case with
transformers for power work) the transformer can be operated for two or
three hours at an overload of about 25 %, after which the load should be
reduced to normal, and the run continued as long as may be necessary.
There are several methods for making heat runs of transformers, and all
of them approximate the condition of the transformer in actual service.
Heat Test, Jflet Jiocl 1. — The primary is connected to a circuit of
the proper voltage and frequency, and the secondary loaded with lamps or
resistance until full-load current is obtained. The temperature of all acces-
sible parts should be obtained by thermometer, and the temperature rise
of the coils determined by increase of resistance. Frequent readings should
be taken during the run to see to what extent the transformer is heating.
Heat Test, Jfietliod 2. —Where the transformer is of large size, or
sufficient load is not obtainable, the motor generator method of heat test is
preferable. Two transformers of the same voltage, capacity and frequency
are required, and are connected up as shown in Fig„ 65.
<5h
THIS VOLTAGE TO BE APPROX. TWICE THE NOTE:
IMPEDANCE VOLTAGE OF EACH TRANSFORMER, ™
JT.MUST BE ADJUSTED UNTIL FULL LOAD
CURRENT ..FLOWS IN, TRANSFORMERS.
BE THAT 0
OF EACH
TRANSFORMER
Fig. 65.
The two secondaries are connected in parallel, and excited from circuit
A at the proper voltage and frequency. The two primaries are connected
in series in such a way as to oppose each other.
The resultant voltage at B will be zero, however, because the voltage of
the two primaries is equal and opposite. Any voltage impressed at B will
thus cause a current to flow independent of the exciting voltages at the
transformer terminals, and approximately twice the impedance voltage of
one transformer will cause full-load current to flow through the primaries
and secondaries of both transformers.
The total energy thus required to run two transformers at full load is
merely the losses in the iron and copper. Circuit A supplies the exciting
current and core losses, and circuit B the full-load current and copper
losses.
Heat Test, IfKetltotl 3. —When only one transformer is to be tested,
and this transformer is of large capacity, a modification of the motor gen-
erator method can be used as described below :
This method was first used in testing an 830 k.w. 25-cycle transformer made
for the Carborundum Company of Niagara Falls. The connections are
shown in Fig. 66.
Both primary and secondary windings are divided into two parts, the pri-
mary coils x and y being connected in multiple to the dynamo circuit, but
an auxiliary transformer capable of adding a few per cent E.M.F. to that
half of the primary is connected as shown in the y half.
TRANSFORMER TESTING.
379
By this means the primary coils are properly magnetized, and full-load
currents can be passed through them by varying the auxiliary E.M P.
The two halves of the secondary coils are connected in series in opposi-
tion to each other, and are subject to an auxiliary E.M.F. from the same
generator, but reduced to the proper voltage by the auxiliary trans-
former B.
The currents were measured in all three transformer circuits, and the
E.M.F. of one-half the secondary was measured.
The method is accurate enough for large units, and is quite handy where
no large dynamo can be gotten for supplying full-load currents, as in this
case current is required only for the transformer losses and for supplying
the auxiliary transformers.
Fig. 66. General Electric Method of Testing One
Large Transformer.
Temperature Rise.
To ascertain the temperature rise of the different parts of a transformer,
thermometers are placed on the various parts, and readings taken at fre-
quent intervals. These readings, however, indicate only the surface tern
perature of a body and not the actual internal temperature.
The average rise of temperature of the windings can be more accurately
determined by means of the increase of resistance of the conductor, and
is determined by knowing the resistances hot and cold.
Let Be = resistance of one coil, cold.
Eh = resistance of one coil, hot.
Te= temperature of one coil in cent, degrees, cold.
Th = temperature of one coil in cent, degrees, hot.
K=: temperature of coefficient of copper .004.
_ lih (1 + .004 TV) — Rr
This equation is based on the assumption that the resistance of pure cop-
per increases .4 % of its value at zero for every degree centigrade rise in
temperature.
If it be desired to know the temperature rise of both primary and second-
ary coils, their hot and cold resistances must be determined separately ; but
it is customary to determine the temperature rise by resistance of only one
coil, usually the primary, and comparing the secondary temperatures by the
thermometer measurements. The method for taking these measurements
is described in the paragraph in this section on measurement of resistance.
Ratio.
As a check against possible mistakes in winding the coils and connecting
up, a test should be made for ratio of voltages.
The ratio test is made at a fractional part of the full voltage at no-load
current, and should not be substituted for a regulation test. An error of one
or two per cent is quite admissible in making this test, because of its being
taken at partial voltages.
380
THE STATIC TRANSFORMER.
Regulation.
The regulation of a transformer can be determined either by direct meas-
urement or by calculation from the measurements of resistance and reac-
tance in the transformer. Since the regulation of any commercial trans-
former is at the most but a few per cent of the impressed voltage, and as
errors of observation are very liable to be fully one per cent, the direct
method of measuring regulation is not at all reliable.
Regulation l»j Direct Measurements.
Connect up the transformer with a fully loaded secondary, as in Fig. 67.
If the primary voltage is very steady, voltmeter No. 2 only will be neces-
sary, but it is better to use one on the primary circuit also as shown. A
Fig. 67. Test for Regulation of Transformer.
reading of voltmeter No. 2 is taken with no load, and again with load, the
difference in the two readings being the drop in voltage on the secondary.
We, therefore, have,
~ „ , , . ,-_ /100 X reading at no loadx
% Regulation = 100 — ( — - — — ° — - — )
V Reading at full load. /
Regulation by Calculation.
Several methods of calculating the regulation of transformers from the
measurements of resistance and reactive drop have been devised.
Below is a method by Mr. A. R. Everest, and recently published in the
electrical journals, which has been found to answer the requirements of
daily use.
Let IR =. Total resistance drop in transformer expressed as per cent of
rated voltage.
IX = Reactive drop, similarly expressed.
P = Proportion of energy current in load or power factor of load. For
non-inductive load P=l.
W = Wattless factor of primary current.
(With non-inductive load, JV = Magnetizing current expressed as
a fraction of full-load current. With inductive load, W =. Watt-
less component of load, plus magnetizing current.)
Then if volts at secondary tenminals r= 100 %,
Primary voltage —
Cor J¥on-I"n«luctive Loud.
E — V(100+ PCR -f- WIX)* ± (IX)2,
For Inductive Load:
In each of these equations the last
sents the drop " in quadrature."
V(ioo + PIR + WIX)* 4- (FIX + WIB)*.
ssion within parentheses repre-
The magnetizing current zr 1/ Exciting current
/ Core loss2
\ Voltage
wm^^mmam^am
TRANSFORMER TESTING.
381
For frequencies of 60 cycles or higher, magnetizing current may be taken
as 75 per cent of the exciting current.
Extracting the square root in the expression for regulation may be
avoided in the use of the following table :
Quadrature Drop.
Increase in
Pr
unary Voltage.
2.5 per
3
3.5 "
cent.
.025
.04
.06
per cent.
4 "
4.5 "
"
.08
.10
«
5
5.5 "
"
.13
.15
"
6 "
6.5 "
<< »
.18
.21
"
7.5 "
"
.24
.27
"
8 "
8.5 "
"
.31
.35
"
9
9.5 "
"
.39
.45
«
10 "
"
.50
"
"
As an example, take a 2 k.w. transformer having the following losses :
IR drop = 2%.
I X drop =3.5%.
Exciting current = 4 % or .04 ; then magnetizing current = 75% of this, or
.03.
X. JVon-Influctive lioad. — Secondary voltage = 100%.
Primary voltage in phases 100 + 2% + (.03 X 3.5%) = 102.1%.
Quadrature drop = 3.5% ; this from table adds .06% of total primary volt-
age =102.16%.
2.16
The drop is 2.16% of secondary voltage, or ' = 2.11% of primary voltage,
which is the true regulation drop.
2. Inductive load. — With a power factor of .86, wattless factor of
load = .5, and adding magnetizing current (which in most cases might be
neglected on inductive load), W becomes .52.
The primary voltage in phase is now 100% f 2% X .86 4-3.5 X .52 -f- 103.18%.
The quadrature drop is .86 X 3.5% X .52 X 2% -f 2.76%.
From this table this adds .03.
Primary voltage = 103.21%.
Regulation drop = ' = 3.11% of primary voltage. Regulation drop
should always be expressed finally in terms of primary voltage.
The above'described methods of transformer testing are in use by one of
the large manufacturers, and present average American shop practice.
The following matter is largely from the important paper by Mr. Ford
and presents the commonest theoretical test methods.
382 THE STATIC TRANSFORMER.
The efficiency of a transformer is the ratio of its net power output to its
gross power input, the output being measured with non-inductive load.
The power input includes the output together with the losses Avhich are as
follows :
(1) The core loss, which is determined by test at the rated frequency and
voltage.
(2) The P R loss of the primary and the secondary calculated from their
resistances.
Example.
Transformer, Type H, 60 Cycles, 5 k.w., 1000-2000 Volts Prim., 100-200
Volts Sec.
Amperes.
Primary, at 2000 volts 2.5
Secondary, at 200 volts 25
Resistance. Ohms at 20° C.
Primary 10.1
Secondary 0.067
At Full Load.
Losses. Watts.
Primary PR * 63
Secondary I2 R 42
Total PR 105
Core Loss 70
Total Loss 175
Output at Full Load 5000
Input " " " 5175
Efficiency 5000/5175 or 96.6%
At Half Load.
Losses. Watts.
Total PR 26
Core Loss 70
Total Loss 96
Output 2500
Input 2596
Efficiency 2500/2596 or 96.2%
The all-day efficiency of a transformer is the ratio of the output to the
input during 24 hours. The usual conditions of practice will be met if the
calculation is based on 5 hours at full load, and 19 hours at no load.
Output. Watt Hrs.
5 Hours at Full Load 25000
19 Hours at No Load 0
Total, 24 Hours 25000
Input.
5 Hours at Full Load 25875
19 Hours at No Load (Neglecting PR Loss due
to Excitation Current) 1330
Total, 24 Hours 27205
All-day Efficiency 25000/27205 or 91.9%
In calculating the efficiencies in both of the above examples, the copper
loss due to excitation current of the transformer has been neglected. This
current, in the example given above, is less than 3%, and its effect on the
loss of the transformer is thus negligible. Even at no load the total P R
loss introduced by it is less than one watt. It is quite necessary, however,
that the loss introduced by the excitation current should be checked in all
cases. In some transformers, for example, the excitation current may
reach 30% of the full-load current, and thus its effect is noticeable at large
loads, while at \ load the loss in the primary winding due to excitation
current is greater than the loss due to the load current.
POLAKITY. 383
Inasmuch as the losses in the transformer are affected by the tempera-
ture and the wave form of the E.M.F., the efficiency can be accurately
specified only by reference to some definite temperature, such as 25° C, and
by stating whether the E.M.F. is sine or otherwise.
The foregoing method of calculating the efficiency neglects what are
known as " load losses," i.e., the eddy current losses in the iron and the
conductors caused by the current in the transformer windings. The watts
measured in the impedance test include " load losses" and ll /Mosses to-
gether with a small core loss. Considering the core loss as negligible, the
" load losses" are obtained by subtracting from the measured watts the PR
loss calculated from the resistance of the transformer. It is sometimes
assumed that the " load losses " in a transformer when it is working under
full-load conditions are the same as those obtained with short-circuited
secondary, and it is stated that these losses should enter into the calcula-
tion of efficiency. Many tests have been made to determine whether or not
the above assumption is correct, and while the results cannot be considered
as conclusive, they indicate in every case that, under full-load conditions,
the "load losses" are considerably less than those measured with short-
circuited secondary. Inasmuch as these losses, in general, form a small
percentage of the total loss in a transformer, and in view of the difficulty
in determining them with accuracy, they may be neglected in the calcula^
tion of efficiency for commercial purposes. The measurement of watts in
the impedance test is, however, useful as a check on excessive eddy current
losses in a poorly designed transformer.
POIABI1Y.
Transformers are generally designed so that the instantaneous direction
of flow of the current in certain selected leads is the same in all transform-
ers of the same type. For example, referring to Fig. 71, the transformer
there shown is designed so that the current at any in-
R stant flows into the primary at A, and out of the sec-
■ * ondary at C. Some such system is necessary, in order
primary I J that transformers may run in parallel wben similar pri-
k mary and secondary leads on different transformers are
) connected together. The test which is made to determine
I l whether a given transformer is identical in this respect
«& with other transformers of the same type is known as
I J \ the polarity test.
J The polarity test should be unnecessary when banking
J transformers of the same type and design. When, how-
ever, transformers manufactured by different companies
\J A. are to be run in parallel, it is necessary to test them in
v second- ' order to avoid the possibility of connecting them in
I ARy I such a way as to short circuit the one on the other.
C D Their polarity may be determined by one of the follow-
Fig. 68. ing methods.
In Fig. 68 primary lead A should be of the same po-
larity as the secondary lead C. Connect the primary lead B to the second-
ary lead C. Apply 100 volts, saVi to the primary AB of the transformer.
The voltage measured from A toj) sncmld be greater than the applied volt-
age if the transformer is of the correct polarity. In other words, a trans-
former connected as shown should act as a booster to the voltage. If the
leads A and C are not of the same polarity, the voltage measured from A to
D should be less than that applied at AB.
If a standard transformer, known to have correct polarity and the same
ratio as the test transformer, is available, the simplest method for testing
the polarity is to connect the primaries and secondaries of the transformer
in parallel, placing a fuse in series with the secondaries. On applying volt-
age to the primaries of the transformers, if they are of the same polarity
and ratio, no current should flow in the secondary circuit, and the fuse will
remain intact. If the transformers are of opposite polarity, the connection
will short circuit the one transformer on the other, and the fuse selected
should therefore be small enough to blow before the transformers are
injured.
In nearly all transformers there will be a slight current in the secondaries
when connected as above. This current is known as the exchange current,
and should be less than 1 % of the normal full-load current of the trans-
former.
384
THE STATIC TRANSFORMER.
Efficiency =
DATA TO JBE METERM1AE1I BY TESTS.
Partly from a paper by Arthur Hillyer Ford, B. S.
I. Copper loss, to determine the efficiency.
II. Iron-core loss, hot and cold, to determine the efficiency : to separate
the hysteresis from the foucault current loss.
If W= watts output,
1 = watts iron-core loss,
C = watts copper loss,
then the
(wTT+cxm)
Foucault currents loss should decrease with an increase in tempera-
ture.
Hysteresis loss is supposed to be constant regardless of heat.
III. Open circuit or exciting current.
IV. Regulation, to determine the magnetic leakage.
V. Rise in temperature in case and out of case, for no load and full
load ; with and without oil.
VI. Insulation.
methods.
Opposition Method of Ayrton and lumpner.- This method
is especially valuable where the transformers to be tested are of large ca-
pacity, and a source of power great enough to put them under full load in
the ordinary way is unavailable. A supply of current of an amount some-
what greater than the total losses of both transformers is all that is neces-
sary. Following is a diagram of the connections, by which it will be seen
that the transformers are so connected that one feeds the other, or they
work in opposition.
TRANSFORMER
wnnrmr<ryrinnr<jX3"
.-H-J§£.
TRANSFORMER
MMVVW
OM SOURCE
F CURRENT
00-VOLTS
Fig. 69. Diagrams of Connections for Ayrton
and Sumpner Opposition Method of Testing
Transformers.
Tn making the test, current is turned on and the resistance R adjusted
until full-load current flows in the secondary, as shown by the ammeter A,
and the primary current and voltage in A and V is up to standard. Then
the watts read on W are equal to the iron losses in both transformers, and
W, the losses in the copper of the transformers plus the copper loss in the
leads and in the current coils of W/ and A.
DATA BY TESTS.
385
The total loss in both transformers is watts loss = W + W, — a, where a
is the loss in the leads and instruments which may be calculated by I2E.
Method of Dr. Humpner. Iron iioss. — The following diagram
shows the connections for Dr. Sumpner's test for iron losses. The low-
pressure side is connected to a source of current of the same pressure at
which the transformer is expected to work, thus producing the same pri-
mary voltage in the high-pressure side at which it is expected to work.
With the primary circuit open, the iron losses in the transformer are read
directly in watts on the wattmeter.
Fig. 70. Dr. Sumpner's Test for Iron Losses.
Copper Iioss. — The next diagram shows the connections for determin-
ing the copper losses. The low-pressure side is short-circuited through an
ammeter, the high-pressure side being connected to the 100-volt supply-
mains. The resistance R is then adjusted to obtain full-load or any other
desired current in the secondary, as shown by the ammeter. The reading
of the wattmeter will then show the total copper losses in the transformer
and in the ammeter plus a very small and entirely negligible iron loss. The
ammeter losses and that in the leads may be calculated by I2B. The small
iron loss can be separated or determined by disconnecting the ammeter and
adjusting R until the pressure on the primary is the same as in the copper-
loss test ; the wattmeter will then show the small iron 1 —
FiG. 71. Dr. Sumpner's Test for Copper Losses.
The iron loss is proportional to (jy1'6 and (g, the magnetic density is pro-
portional to the pressure at the terminals of the transformer, therefore the
iron loss is equal to A'.(glh where K is a constant and (ft the voltage. In the
iron-loss test the (ft = 1000 and in the copperdoss test
(B = 100.
K X 10001'6 = 63,000 K
K X 1001-* — 1,600 K— 2.5 % of total iron loss.
Heating, — Tests should be made at no load, at full load, and at inter-
mediate loads for rise of temperature of the transformers out of their cases,
in their cases, without oil and with oil, if full data is wanted. If a strictly
commercial test is all that is necessary, a test with the transformer at full
load and set up in the condition it is to be run, Avill be sufficient.
Surface temperatures can be taken by thermometers laid on and covered
with cotton waste. In oil-insulated transformers the temperature of the
oil should betaken in two places, — inside the coil, and between the coil
and case.
lieakasre Drop, — The drop in the secondary due to magnetic leakage
can be found by deducting from the measured total drop the I2R drop due
to the resistance of the coil.
ELECTRIC LIGHTING.
Velocity of light approximately 192,000 miles per second.
Composition of Sunlight.
Violet, the maximum chemical ray.
Indigo. Blue. Green.
Yellow, the maximum light ray.
Orange.
Red, the maximum heat ray.
Primary.
Secondary.
Tertiary.
Red,
Orange,
Brown,
Colors.
Yellow,
Purple,
Gray,
Blue.
Green.
Broken green.
Intensity of Illumination on a surface is inversely as the square
of the distance between the surface and the source of light.
Intensity :
Quantity of light
4/t x distance2
If light strikes the surface obliquely,
then
Quantity x Cos.i
Intensity = -
in x distance2
Where i is the angle of incidence, or the angle which the rays make with
the normal to the surface.
Intensity of lig-Iit in a given direction is proportional to the cosine of
the angle, the direction and the normal to the element of the luminous sur-
face from which the light is emitted.
Trotter gives in the following table the intensities of different sources of
light.
Intensities of Different Sources of liig-nt.
(Trotter.)
C. P. per Sq. In. C.P. per Sq.Cm.
Red. Green.
Platinum (Violle standard) ......
Sun's disk
Sky, near sun
Albo carbon on edge
White paper, horizontal, exposed to sum-
mer sky, noon
White paper, sun 60° high, paper facing
sun
Albo carbon, flat
Argand
Black velvet, summer sky, noon ....
White paper, reading without straining .
8.25
10.5
o. o;;:;;:
0.0018
1000000
120
60.7
35.2
17.2
8.7
5.24
0-07
0.0024
18.5
75.500
18.5
11.4
1.28
1.63
1.05
0.0052
0.00028
18.5
155,000
18.5
9.4
5.45
0.0109
0.0003
LIGHT. 387
Intensities of Different Sources of I.ijjlit — Continued.
Sperm candle = .
Moon, 35° above horizon
Moon, high , . .
Batswing (whole flame) ,
Methven standard
Incandescent carbon filament (glow lamp .
Crater of electric arc
White.
2
0.31
2
0.31
3
0.46
2.25
0.35
4.3
0.6GG
120
18.5
45,000
7,000
White.
Ulean Spherical Intensity is the intensity which the light from the
given source would have at unit distance, if it radiated uniformly in all
directions, the total quantity remaining unchanged.
Units of JLig-ht.
(From Guipel & Kilgour.)
The quantity of lig-lit emitted by a source of light is generally ex-
pressed in terms of that of some particular source, chosen as a standard of
reference, under specified conditions.
The following are the principal standard sources of light at present in use
or proposed :
1. The British standard candle is a spermaceti candle, seven-eighths of an
inch in diameter, weighing six to the pound, and burning 120 grains per
hour ; this is by no means a satisfactory standard, as it has been shown by
the experiments of M. Girout and others that the light emitted by different
specimens may vary by as much as 50 per cent.
2. The French stearine candle (l'etoile) weighs five to the pound, and burns
117.3 grains per hour ; this candle gives from 1 to 1.4 British candles, is
equally unsatisfactory, and is now seldom used.
3. The Methven screen consists of a 16 candle-power Argand burner with a
screen in which is pierced a small rectangular aperture of such a size and in
such a position with respect to the burner, that the light passing through
the aperture is equal to two British candles, Mr. Methven finds that, if the
height of the flame is kept constant, the light passing through the aperture
in the screen is not affected by variations in the quality of the gas. Mr.
W. S. Rawson traverses Mr. Methven's statement, and says that the light is
sensitive to small variations in the quality of the gas ; on the other hand
M. Violle agrees with Mr. Methven, if the aperture is properly placed with
respect to the burner. Mr. Rawson states further, as the result of his exper-
iments, that the distance of the screen from the burner, and of the grease-
spot from the screen, largely influence the photometrical results obtained ;
if corroborated by other observers, the latter would be a serious drawback
to the use of this standard.
4. The Harcourt pentane air-gas lamp burns with a mixture of air and
pentane, 576 volumes of air to one of liquid pentane — or 20 volumes of au-
to seven of pentane gas— at 60° F. ; the diameter of the burner is i inch,
and the height of the flame 2k inches, and the light emitted is equal to one
British candle. When protected from draughts this lamp gives excellent
results. Mr. W. J. Dibdin* considers that it complies with every demand
made upon it, and answers to the full all the claims made for it by the
inventor.
5. The Carcel lamp, which is the principal French standard, burns 42
grammes (648 grains) of purified colza oil per hour, Avith a flame 40 mm. (1.57
inches) high, and the light emitted equals 9^- British candles. From the
experiments of MM. Dumas and Regnault, it appears that between the
limits of 40 and 44 grammes of colza consumed per hour, the light emitted
may be taken as proportional to the colza burnt.
* Report to the Metropolitan Board of Works (see abstract in" The Elec-
trician," Vol. XIX. p. 287).
388
ELECTRIC LIGHTING.
The following conditions should he complied with when this lamp is
used :
mm.
in.
23.5
17.0
45.5
290
Gl
47
34
2
0.93
0.07
1.79
11 4
Interior diameter of outer air current
Distance from elbow to base of glass
2.40
1 85
Interior diameter of glass at top of chimney
Mean thickness of glass
1.34
0.U8
The wick should be of the type known as the lighthouse wick, woven with
75 strands, and weighing 3.G grammes per decimeter (170 grains per foot).
When carefully used this lamp appears to give satisfactory results.
6. The Amyl-acetate lamp of von Hefner Alteneck gives one British can-
dle with a height of 40 mm. (1.57 inches) for the flame. This lamp, which is
practically a carefully constructed spirit lamp, has great simplicity in its
favor, and, except for the color of its flame, appears to be satisfactory.
7. MM. Violle and Cornu have proposed that the light emitted by one
square centimeter of platinum at its melting point be taken as the standard.
This standard has a good deal in its favor, especially as the experiments of
Mr. C. R. Cross* have showed that the light emitted by a platinum wire of
definite length and diameter, is constant within a very narrow range (about
1 per cent) for different specimens of platinum at the melting-point.
According to the experiments of M. Violle, the light emitted by one square
centimeter of platinum at its melting-point is equal to 2.08 carcels, or be-
tween 19i and 19f British candles.
The following table is extracted from the complete table of results of
tests on severafstaiidard sources of light made by Mr. W. J. Dibdin, to ascer-
tain the deviation of different specimens from the mean.
Standard.
Total Number
of Tests.
No. within 1% of
the Mean.
Percentage No.
within 1% of the
Mean.
Candle ....
Methven . . .
Amyl-acetate
Pentane air-gas .
454
283
225
154
154
211
206 .
150
34
74
90
97
^lae (seaa-face illiamiiraatiom of a body is measured by the quantity of
light it receives per unit of surface from a standard source of light at a
fixed distance from it. Mr. Preece has proposed to take the quantity of
light received by one square foot of surface from a carcel, at a distance of
one meter, or from a British candle at a distance of 12.7' inches, and to call
it a lux. The quantity of light received by any surface would then be
expressed as so many luxes.
Sixteen c.p. and 1000 c.p. lamps produce a surface illumination of one lux
at about 4 ft. 2| in. and 33 ft. 5h in. respectively.
M. de Nerville, director of tbe Central Laboratory of Electricity, has made
a number of observations in Paris, employing as a unit a bougie-meter,
the bougie being a " bougie-decimal 'e," the tenth of a carcel. This unit
is equivalent to a standard candle at 3.34 feet distance. The bougie-meter
* Paper contributed to the American Academy, on "Experiments on the
Melting Platinum Standard of Light."
389
is a unit of very convenient magnitude, and is the same as the deci-lux of
Mr. Preece. It is practically the illumination at the foot of an ordinary gas
street lamp, say 13 candles at 12 feet. The relation between the bougie-
meter and the candle-foot is shown in the annexed table :
Boug-ie-
IWEeter.
Candle-power.
Feet.
Candle power.
Feet.
0.1
1.058
8
9.45
0.5
2.37
10
10.58
0.8
3.0
20
14.95
1.0
3.34
50
23.7
1.5
4.1
100
33.4
2
4.73
200
47.3
3
5.8
500
74.8
4
6.69
1000
105.8
5
7.48
2000
149.5
Measurement of Intensity of Xig-lit.
The instrument used for determining the- relative intensities of lights is
called a photometer ; following is a list of some of the |better types, "with a
short explanation of their principles.
Fig. 1. Portable Bunsen Photometer.
In all types let the following symbols mean the same.
i — intensity of one light at the distance d.
i% = intensity of the other light at the distance dv
390
ELECTRIC LIGHTING:.
Rumford's photometer compares the shadows of an opaque rod thrown
on a white screen by two lights.
When the shadows are of equal density,
i _ rf2
In BnnseinV photometer a piece of white paper, blotting-paper is good,
with a grease spot in its center, is placed between the two lights, Avith its
surface at right angles to the line of the rays ; moving the paper back and
forth between the lights until the grease spot disappears ; then the two
lights are to each other as the squares of the distances between each and the
screen : or
A — 11
H ~ (h2'
If the lamp under test be at a height li above the horizontal plane of the
photometer and standard lamp or candle, other symbols remaining the
same, then
c.p.ofthelamp= d, x J^-
In Ritchie's photometer two equal white surfaces are placed at an
angle with each other, and with the line of light and their brightness com-
pared, moving back and forth on the line of light until both surfaces are
alike in illumination ; the relative intensities of the lights are then the
same as with the Bunsen instrument.
Fig. 2. Prof. L. Weber's Portable Photometer.
j&yrton an«l 'Perry use what they call a dispersion photometer, in
which a concave lens is used in the path of the stronger light to reduce its
intensity by dispersion of its rays to a known degree.
This instrument is useful in measuring arc lamps.
Sal»ine's wedge photometer reduces the stronger light a known degree
by passing it through a medium of neutral tinted glass, which also allows
of the colored rays being compared.
In Toly's photometer, two slabs of paraffin wax, or translucent glass about
3" x 2" x h''\ ai*e fastened together back to back by Canada balsam, a sheet
I^H^^MH
391
of paper or silyer foil being first interposed, after which the edges and stir-
faces are ground smooth.
This slab is placed between the two lights, with the plane of the joint at
right angles to the line between the lights, and moved back and forth on
that line until the observer looking at the edge of the slab finds both sides
equally illuminated, when the relative intensities are as before. By revers-
ing the slab, a check can be had on the observation.
Prof. JL. Weber has invented one of the handiest and most accurate
photometers, description of which follows.
The apparatus consists of a tube, A, about 30 cm. long, which can be moved
up and down and swung in a horizontal plane on the upright, c. The stand-
ard light, S, a benzine lamp, is contained in a lantern fastened to the rigbt
end of the tube, A. Within tbe tube, A, a circular plate of opal glass can be
moved from or towards the light, S ; its distance from E is read in centi-
meters on the scale, s, by means of an index fastened to the pinion, P. At
right angles to tube, A, a second tube, B, is fastened. This tube can be
rotated in a vertical plane, and its position in reference to the horizontal
R =10,000 M M
Fig. 3.
is read on the graduated circle, C. A rectangular prism contained in tube
B in its axis of rotation receives light from the opal glass plate in tube A,
and reflects this light towards the eye-piece, O, so that the right half of the
field of vision is illuminated by this light, the left half is illuminated by the
light entering the tube, B, through g.
In making measurements, the tube B is pointed toward the source of
light to be measured. The light has to pass through a square box, g, in
which may be inserted one or more opal glass plates, in order to diminish
the intensity of the light, and thus to make it comparable with the standard
light. The apparatus permits the measurement of light in the shape of a
flame, as well as the measurement of diffused light.
Since the measurement of diffused light interests us most at present, a
short description of the method will not be out of place.
A white screen, the surface of which is absolutely without luster, fur-
nished as part of the apparatus, is placed in a convenient position, either hor-
izontal or vertical, or at any desired inclination, toward the source of light.
The photometer having been located at a convenient distance from the
screen, the tube B is pointed to the center of the screen. The distance of
the phonometer from the screen can be varied within very wide limits, the
only restrictions being that the field of vision receives no other light than
that emanating from the screen. The necessary precautions for adjustment
having been observed, the opal glass plate in the tube A is moved until both
halves of the field of vision appear equally illuminated. The distance, r, of
this glass plate from the standard light at the moment of equal illumina-
392
ELECTRIC LIGHTING.
tion is read on the scale on tube A in millimeters, and the intensity of
illumination on the white screen is calculated from the formula,
The constant Kis previously determined as follows :
A standard candle is placed exactly one meter distant from the white
screen, and the tube, B, of the photometer is pointed towards the screen, so
that the center of the screen, which is marked by a cross, is seen in the
center of tbe field of vision. As indicated in Fig. 3, the photometer must be
so placed that the eye looking through the eye-piece, sees nothing but the
white screen. The angle of inclination under which tbe screen is obseiwed
may be varied within wide limits without influencing the result ; it should,
however, not exceed 60 degrees from the normal to the screen.
Equal illumination of both halves of the field of vision baving been ob-
tained by means of adjusting the opal glass plate in tube A, the constant, K,
is found by calculation ;
Since r is read in millimeters, and R is made 1 meter or 10000 millimeters,
10000 instead of 1 must be taken in the formula for calculating the intensity
of illuminating in meter candles.
A second method permits of measurements of diffused light without the
intervention of a screen ; but for further details the reader is referred to the
description of tbe apparatus by Professor Weber, Elekrotechnische Zeit-
schrift, vol. v., p. 166.
Since the whole apparatus can easily be taken apart, and packed in a box
about 24x8x12 incbes, it recommends itself extremely well for out-of-door
work. In this case the benzine lamp might well be replaced by a small in-
candescent lamp, provided this lamp is standardized before and after each
set of experiments. Such miniature lamps been have found very con-
venient, and quite sufficiently constant in candle-power for several hundred
observations.
In the iLummer-Broclliun photometer, cut of the carriage of which is
shown below, the rays of light from the two sources under comparison enter
at the sides so as to strike the surfaces of the opaque gypsum screen. Dif-
fused light from these white surfaces reaches two parallel mirrors (inside)
at an angle of 45°, and is reflected to rigbt angled prisms which have the
outer portions of their hypothenuse surfaces cut away and coated with as-
phalt varnish to secui-e complete absorption. Light entering the prisms
from the mirrors is either transmitted or totally reflected at their surface of
contact, so that an observer at the telescope tube sees a circular disk of light
Fig. 4. Lummer-Brodhun Photometer Carriage.
393
from one side of the gypsum screen surrounded by an annular ring of light
from the other side, the boundary line between the two being sharply defined.
The sensibility of this instrument as proved both theoretically and prac-
tically, is between three and four times that of the Bunsen grease spot.
Illuminating- Power for internal lighting varies according to the
nature and color of the walls and objects inside of the room. Dark walls
require more lighting than light walls. Dr. Sumpner finds that dull walls
only reflect about 'JO per cent of the light incident upon them, whilst ordi-
nary tints reflect 40 to 50 per cent, clean Avhite surfaces 80 per cent, ordinary
mirrors 80 per cent, and very good mirrors 90 per cent. Hence well-whitened
rooms require only one-fiflh of the light required with dull Avails. The
amount of light also depends upon the height of the room. In rooms about
10 ft. high, a" 16-c.p. lamp placed 8 ft. from the floor gives 1 candle-foot on
the table and \ candle-foot on the floor. The following table may be used
as a rough guide, subject to the above conditions :
No. of 16-c.p. Lamps
per 100 Square Feet.
No. of Watts per sq.
ft. if 16-c.p. Lamp
Takes 50 Watts.
Approximate Effect.
1
1.5
2
3
4
0.5
0.75
1.0
1.5
2.0
Dull.
Medium.
Good.
Bright.
Brilliant.
Foree Bain gives the following table for number of incandescent lamps
required for good illumination :
Dimensions of Booms in Feet.
Number of
Lamps, Each
Height of Lamps
above Floor.
8 to 10 Can-
Length.
Width.
Height.
dle-powers.
Feet.
Inches.
15
15
12
2 to 3
G
9
18
18
15.1
5 " 6
7
0
24.6
24.6
17
9 " 12
8
1
33
33
22.5
16 " 20
2
3
40
40
30
25 " 30
11
4
65
65
45
40 " 50
13
2
72
72
50
100 " 120
18
6
With 16 candle-power lamps 75 per cent, and with 20 candle-power lamps
65 per cent of the above numbers will give equal illumination.
ARC IAMP§.
In the United States, arc lamps may be classed somewhat as follows :
Continuous Current Arc laiiip§.
low Potential, high current, using about 20 volts across the termi-
nals, and 30 amperes of current ; formerly largely in use ; now no longer
manufactured.
394
ELECTRIC LIGHTING.
Hijrli Potential : using 45 to 60 volts and 9.6 to 10 amperes for a nomi-
nal 2000-c.p. standard lamp. This lamp is more used than any other for
street lighting, and with the 1200-c.p. lamp, so called, taking 6.8 amperes
and 45 to 50 volts, includes the larger part of all arc lighting in the United
States.
Inclosed Arc, taking 5 amperes and about 80 volts ; this lamp is now
much used, as it needs recarboning but about once a week (100 to 150 hours).
The first of the three classes of arc lamps mentioned above is no longer in
use except on old circuits, but is always connected in series on constant
current dynamos.
The hig'h potential and inclosed arc lamps are connected in
series on constant current dynamos ; and with some slight difference in
mechanism are also connected to constant potential circuits.
Alternating' Current Arc lamps.
Alternating current arc lamps are made in great variety, and average
about 15 amperes for the 2000-c.p. arc, at 28 or 30 volts, but require about
35 volts to start promptly ; and are made for series or parallel circuits.
They are used largely on constant potential circuits in connection
with the regular transformer, or in connection with specially-designed
series transformers or regulators, for the description of which see chap-
ter on " Transformers." Owing to the reactive effect of these lamps,
they can be run one lamp across the terminals of a 100-volt circuit.
Some types use a resistance, others use a compensating coil, and still
others are so designed as to the actuating magnets as to require no extra
reactance in series with the lamp across a 100 or 104 or 110 volt constant
potential circuit.
The Westinghouse Electric and Mfg. Co. and others use, where required,
what is called an " economy coil," which is something like a small trans-
former placed across the terminals of a 100-volt a.c. circuit.
Three a.c. arc lamps can be connected to the terminals of this coil and if
one lamp goes out, the current drops in the main, bnt keeps automatically
the same in each remaining lamp circuit, as the coil i:ot in use on a lamp
' s the adjacent coils. Following is a diagram of the arrangement.
Fig. 5.
The Inclosed Arc lamp is the only radical change in arc lamp
practice during a number of years past, and is now being used for a great
part of all new work installed.
It has been found that by inclosing the tips of the carbons in a small
receptacle more or less approaching air-tight conditions, that combustion
of the carbons is practically complete, leaving no dust, and takes place at a
much slower rate, burning with the ordinary 12" x \" carbons from 50 to 150
hours continuously, according to the design of the lamp. The potential at
the arc is 75 or 80 volts, and according to the best modern practice the cur-
rent used is from 4.5 to 6 amperes. With this high voltage it is usual to
place an adjustable resistance in the top of the lamp, or near by, and one
lamp can then be connected directly across constant potential circuits of
100 to 125 volts.
Although there may be some question as to the lighting efficiency of the
inclosed arc, the very great advantages from carbon economy and infer-
quent trimming, as well as lack of dirt from carbon dust, render it very
desirable in practical use.
ARC LAMPS. 395
As the upper carbon stump can often be used as tbe lower when retrim-
ming, ordinary commercial lamps will require trimming not oftener than
once a month.
The safety of inclosed arcs appeals strongly to the underwriters, Avho
have no fear of sparks floating away from them to set goods afire in shops
and factories.
As the consumption of carbon is so slow, the feeding mechanism can be
very simple and the feed very regular, and if in addition to this a good
quality of carbon be used, the light is extremely steady and of the very best
quality.
If care is taken in selecting the globes, shadows of frame and arc can be
reduced to the last degree.
Ifletliods of It emulation in Arc JLuiiaps may be classified as
follows : —
Carbons lifted or separated by direct or main magnet ; shunt magnet
acting on a variable resistance to cut out the main magnet in feeding.
Carbons lifted by main magnet as before, and shunt acting to put the main
magnet (made movable) into position for feeding.
Carbons separated by main magnet armature; shunt circuiting magnet
acting to divert or shunt the magnetism of the main magnet from its arma-
ture.
Carbons separated by main magnet and shunt acting to free the carbon-
holder, independently of the support given by the main magnet.
Carbons separated by a spring allowed to act by the main magnet lifting a
weight which otherwise holds the spring from acting ; shunt magnet acts
against the spring, to feed and regulate the length of arc.
One carbon, generally the lower, separated by main magnet, while the
other holder is releasedror feeding only, such feeding being under the con-
trol either of a differential system or a shunt magnet only.
Carbons separated by main magnet, which lifts the shunt and its armature
together, while the shunt magnet armature, acting on the feeding mechan-
ism, controls the arc and feed of the carbons.
Carbon feeding mechanism independently attached to main magnet arma-
ture and to shunt armature so as to receive opposite movements of separa-
tion, and feed from each respectively.
Carbons separated by a feeding mechanism moved by the main magnet,
and fed by a further movement of said mechanism, causing release or re-
turn of same under the accumulated force of both shunt and main magnets,
acting in the same direction.
Differential clock gear for separation and feed of carbons under control
of the regulating magnet system, either simple or differential. Some of the
older clockwork lamps embodied this principle.
Carbons controlled by armature of a small electric motor under control of
a differential field which turns the armature in one direction for separating
and in the other or reversed direction for feeding the carbons.
Carbons controlled by a motor running at a certain speed when the arc is
of normal length, and varying in speed when the arc is too short or too long,
combined with a centrifugal governor on the shaft of the motor, acting on
variations of speed to gear motor shaft to screw carbons together or apart,
as needed to maintain the normal arc. This mechanism has been applied
to large arc lamps, such as naval search-lights, and has the advantage of
great positiveness, and an ability to handle heavy mechanism.
There are also a considerable number of modifications of these principles.
Searchlig'ht Projectors and focusing lamps for theatrical use and
for photo-engraving, etc., take large and varied quantities of current, as
tliey are always connected across the terminals of constant potential cir-
cuits, with a regulating resistance in series with the lamp. The General
Electric Company state in one of their bulletins the following as being the
approximate currents taken by the different sizes of searchlights :
Diam. of Projector. Amperes.
12 inch 18 to 20
18 " 30 " 35
24 " 50 " 60
30 " 75 " 90
36 " 90 " 100
60 " 125 " 150
396 ELECTRIC LIGHTING.
Tests for Arc ILig-ht Carbons.
For Open Arcs.
The satisfactory -working of arc lamps is largely dependent upon the
quality of the carbons used. If carbons are made of impure materials, they
will jump and flame badly. If not baked properly, they may cause annoy-
ance by excessive hissing or flaming, or become too hot because of high
resistance. If the material of which they are made has not been properly
prepared in its preliminary stages, the carbons will have either too short a
life, through giving a good quantity and quality of light, or will have good
life, but Avill burn with an excessive amount of violet rays, hence with poor
illumination.
For indoor use a free-burning, uncoated carbon of medium life should
be used, so as to give a good quality and quantity of light. If longer life is
desired they may be lightly coated with copper without materially interfer-
ing with the light. (About 1J lbs. to 2 lbs. of copper per thousand, &" x 12"
carbons, and a half pound more for £" x 12" carbons will give good results,
increasing the life from an hour to an hour and a half.)
For out-door use a more refractory burning carbon may be used to advan-
tage, giving a longer life, as the quality of the light is not so important.
Copper-coated carbons are also usually employed, and may have about four
pounds of copper per thousand for /g" x 12" carbons, and five pounds for
\" x 12". Other sizes in proportion.
All plain molded carbons, and most of the forced carbons, deposit dust
when burned in the open arc. Those depositing the most dust give out the
most light, but have the least life. Those depositing the least dust usually
have the longest life, but the light is of inferior quality on account of the
increase in the proportion of violet rays.
The quality of any carbon may be very quickly tested in any station by
using the following method, which has been largely employed by carbon
manufacturers.
The important points to be determined are therang-e, including the hiss-
ing, jumping, and flaming points, the resistance, and the life.
The JKang-e is found by trimming a lamp with the carbons to be tested,
allowing them to burn co good points and the lamps to become thoroughly
heated; then connect a voltmeter across the lamp terminals, and very
slowly and steadily depress the upper carbon until the lamp hisses, when
the voltage will make a sudden drop. This is called the Missing-- S*oiict,
and varies according to the temper of the carbon. It should be between 40
and 45 volts — preferably 42 volts. Then lengthen the arc somewhat, and
allow it to become longer by the burning away of the carbons. Presently
the arc will make small jumps or sputters out of the crater in the upper
carbon. This is the Jumping1- .Point, and should be not less than 58 or
60 volts. Let the arc still increase in length, carefully watching the volt-
age, and in most carbons there will soon be a decided 'flaming. This is the
JP lamingr-Point. This should not be less than 62 to 65 volts. Very im-
pure carbons will commence to jump and flame almost as soon as the volt-
age is raised above the hissing-point, and even the hissing-point in such
cases is very irregular and difficult to find. The Range is important as
being a practical test of the purity of the material used in the manufacture
of the carbon, an increase of a quarter of one per cent of impurity making
a very decided reduction in the extent of the Range. The hissing-point
should be 4 or 5 volts below the normal adjustment of the lamp to insure
steady burning.
Resistance. — The resistance is measured on an ordinary Wheatstone
bridge. ' Care must be taken that the contact points go slightly into the
carbon. A T7g" x 12" plain carbon should have a resistance of between .16
and .22 ohms, and \" x 12" between .14 and .18 ohms. T7H" x 12" carbons coated
with three pounds of copper per thousand, have a resistance between .05 and
.06 ohms, and ¥' x 12" with four pounds of copper between .04 and .05 ohms.
life. — The life of a carbon is most easily tested by consuming it
entirely in the lamp, observing, of course, the current and average voltage
during the entire time. A very quick and accurate comparative test of dif-
ferent carbons can be made, hoAvever, by burning the carbons to good points,
then weighing them, and let them burn one hour, then weigh them again.
The amount burned by both tipper and lower carbons shows the rate of
consumption which will accurately indicate the comparative merits of the
carbons tested as to life.
ARC LAMPS.
397
To calculate the life from a burning test of one hour, both carbons should
be first weighed, the upper carbon broken off to a 7-inch length, in order to
make the test at the average point of burning, and Avith the lower carbon,
burned to good points, weighed again, and after burning one hour in a
lamp that has already been warmed up, taken out and weighed. The
amount of two carbons 12 inches long consumed in a complete life-test is 63
per cent of the combined weight of both upper and lower carbons. There-
fore 63 per cent of the weight of the two carbons, divided by the rate per
hour obtained as above, will give the life approximately.
Idust. — The dust from burning carbons can be collected in the globe, or
better, in a paper bag suspended below the lamp. In an ordinary plain-
molded carbon this dust amounts to 4 per cent of the weight of the upper
carbon. A variation below this amount Avill indicate good life, but inferior
light. An excessive amount of dust would show a short life, but usually a
good quantity and quality of light. Coating a carbon with copper eliminates
this deposit of dust entirely.
Inclosed Arc Carbons.
Carbons' for inclosed arcs can be very conveniently tested as to their rel-
ative values in an open arc lamp as described above. As their diameters
regulate the admission of air to the inclosing globe, thus greatly affecting
their life, they should be carefully measured with micrometer calipers. A
greater variation than .00b" from the required diameter should not be per-
mitted. The deposit on the inside of the inclosing globe is caused by impu- (
rities, principally in the core. The relative injurious amount of this deposit
can be measured by carefully taking the globes off the lamps after burning,
and measuring the amount of light absorbed by them with an ordinary pho-
tometer, using an incandescent lamp as a source of light, and cutting the
light down by means of a hole in a screen so that it will pass through the
part of the globe to be measured. Twice the light so measured through
the globe, divided by the amount coming through the unobstructed hole,
will give the per cent of the light transmitted through the globe from the
arc. That carbon Avhose globe absorbs the least amount of light is, of
course, the most desirable.
The resistance of forced carbons, whether cored or solid, used in inclosed
arc lamps, is very important. Carbons of high resistance are difficult to
volatilize, and hence there is trouble in establishing the arc where small
currents are used, and in case of any interruption in reestablishing it after-
wards. This is especially true of carbons used in alternating arcs, and of
cored carbons. The resistance of forced carbons is usually much higher
than that of molded, ranging from two to four times as much. This will
undoubtedly be corrected Avhen the manufacturers become more familiar
with the requirements. The loAver the resistance the better the quality of
the light and the operation of the lamp.
Sizes of Carooi&s for JLrc Lamp§.
Open Arcs.
Continuous Current.
Upper.
Lower.
6.S amperes.
9.6
9.6
12 in. x r7g in.
12" X | "
11" X I "
7 in. x i7g in.
7 " X U "
8 " X * "
Alternating Ci
irrent.
15 amperes.
9?r in. x g in.
9h in. x § in.
Inclosed Arcs.
Continuous Current.
5 amperes.
3
12 in. X i in.
12 " X | "
5h in. x h in.
6^ " X | "
398
ELECTRIC LIGHTING.
Some variations are made on the above sizes to change the candle-power,
or to burn longer. An elliptical carbon % inch X j7g inch X 12 inches is
sometimes used in a single carbon lamp for all-night service; and the 12
and 14 inch x I inch is also used for the same purpose.
Carl»ons Mecoiiitnend&^d for Searcliliglit Projectors.
(Hardtmuth or Schmeltzer.)
Size of Lan
P-
Positive. Cored.
Negative. Solid.
12 inch
18 "
24 "
30 "
36 "
GO "
6 in. x | in.
12 " X £§ "
12 " x 1 "
12 " X 1| "
12 " X li "
12 " x n "
3^ in. x i9gin.
7 "X|"
7 " X | "
7 " X § "
7 " X 1 "
7 " X li "
Carbons Hecosnanenjled for Automatic and Hand-Feed
Focusing- JLainnM.
Continuous
Current.
Amperes.
Positive. Cored.
Negative. Solid.
5 to 10
10 " 18
18 " 20
25 " 30
G in. X T76 in.
6 " X t "
6 " X f "
6 " X | "
6 in. X t7b in.
6 " X \ "
6 " X f "
6 " X | "
Alternating
Current.
5 to 10
10 " 18
18 " 20
25 " 30
G in. x i76 in.
6 " X h "
6 " X f "
6 " X | "
Same as for Positive.
Candle-power of Arc Lamps.
The candle-power of an arc lamp is one of the most troublesome things to
determine in all electrical engineering ; the variations being great the arc
unsteady, and the implements for use in such determination being so liable
to error. Again, what is the candle-power of an arc lamp, or rather, what
is the meaning of the term?
When the lamp was first put forward, for some reason, now in great ob-
scurity, the regular 9.6 ampere lamp was called 2000 candle-power, and it
has always since been so called, although the word "nominal" has been
tacked on to the candle-power to indicate that it is a rating, and not an
actual measurement.
The candle-power of the arc varies with the angle to the horizon on which
the measurement is made ; in continuous current arcs the maximum can-
dle-power is at a point about 45 degrees below the horizontal if the upper
carbon is the positive, and of course above the horizontal if the negative
carbon is above.
In alternating current lamps the total light from the arc is somewhat
more regular in intensity, as both carbon tips are practically the same
shape. In the arc there are two points of maximum light, one about 60
degrees above the horizontal, and the other about the same angle below the
ARC LAMPS.
399
line, and the mean horizontal intensity also bears a greater ratio to the
mean spherical intensity than in the d.c. arc. In the a.c. arc much of the
light is above the horizontal plane, and it is necessary to arrange a reflector
above the arc to throw that portion of the light downward ; and this, to-
gether with a disagreeable hum inherent in the a.c. arc, has much reduced
the use of that class of lamps except for street-lighting.
Mean Spherical Candle-power is the mean of the candle-power
measured all over the surface of a sphere of which the arc is the center,
usually about one-third of the maximum candle-power. In practice the
spherical candle-power is seldom fully determined, but a fair approximation
may be had by the following formula :
Let S = mean spherical candle-power,
_£f = horizontal candle-power,
M= candle-power at the maximum.
Then * = £ + *
In a test of arc lamps in November, 1889, for the New York City Bureau
of Gas, Captain John Millis found the following results in his trial of the
Thomson-Houston lamps.
The same lamp was used, but connected to the different street circuits, all
measurements were made at 40 degrees below the horizontal, and j9g-iiicli
copper-plated carbons were used.
Ten readings were taken on each of four sides of the lamp when con-
nected to each circuit, with the following results :
Circuit No. 1.
" 2.
" 3.
" " 4.
" " 5.
Means
Candle-power.
2072.7
1981.0
2048.5
2000.2
2067.0
2033.9
Watts
482.88
485.10
493.22
494.40
495.36
490.19
Mean current, amperes
Mean volts ....
. . . 10.36
. . . 47.32
The results of tests of candle-power of arc lamps at the Antwerp Exposi-
tion, shown in the table below, would tend to verify the above trials.
Maxi-
mum
C.P.
Upper
Lower
Am-
peres.
Yolts.
Horizon-
tal C.P.
Hemi-
sphere
Hemi-
sphere.
Mean C. P.
Mean C.P
4
37.2
390
74
17
119
6
46.2
1090
168
63
298
6.8
46
1240
240
65
320
8
46
1550
334
70
385
10
45.5
2070
421
102
640
Mean
C.P.
Watts.
136
157
361
259
385
313
454
350
750
491
Arc lamp Efficiency. — The efficiency of an arc lamp is the ratio of
its mean spherical candle-power to the watts consumed between the lamp
terminals. Some energy is used up in the lamp-controlling mechanism, in
the carbons themselves, and the remainder is used on the arc. Arc-lamp
efficiency is sometimes described as the ratio of the watts used in the arc to
the watts used between the lamp terminals. This is true of the lamp as a
machine ; but the first statement is the correct one, as it is light that is
turned out, and not watts consumed in the arc that is the object of the
lamp, and the two depend so much on quality and adjustment of carbons,
even with the same consumption of current, as to make the latter method
erroneous.
400 ELECTRIC LIGHTING.
The steadiness of the arc depends somewhat upon the mechanism of the
lamp, but more largely on the quality of the carbon used.
The mechanism must be sensitive enough to keep the tips of the carbons
at practically the same distance apart ; and the quality of carbon must be
such as to keep the arc steadily in the center, or in the axis of the carbons,
for if the carbon mixture is not homogeneous, the arc will travel about at
the outer edge of the carbons, producing bad shadows, Cored carbons,
having the central axis of the carbon tilled with a softer and more volatile
material, are used for the steadiest light, and in combination with a solid
negative carbon of a diameter somewhat less than that of the cored positive
produces most excellent results.
If W= total watts supplied at terminals,
w = watts used in the arc,
I=z current supplied at lamp terminals,
E — potential between the lamp terminals,
i =z current through carbons or series coil, then the efficiency of the
lamp as a mechanism is
w ei
W~ ~£~I
Heat and Temperature Developed hy tlie Electric
Arc.
The temperature of the crater, or light-emitting surface of the arc, is the
same as the point of volatilization of carbon, and therefore constant under
constant atmospheric pressure. This temperature is variously stated by
different investigators : Dewar gives it as 6000° C; Rosetti, the positive as
3200° C, and the negative 2500° C.
The carbon in the crater is in a plastic condition during burning ; and with
the same adjustment of carbons, as to length of arc, the light per unit of
power increases with the current.
Hissing, naming, and rotating of the arc are some of the defects. Hissing
is due to a short arc, and was a constant accompaniment of the low poten-
tial, high current arc so prevalent during the earlier days of arc lighting.
Flaming and rotating are due to long arcs, and to impure carbons, or
carbons not properly baked.
With good carbons the length of arc, or distance between carbon tips
recommended by the Thomson-Houston Company, was for 6.8 ampere lamp,
B3S inch, and for 9.6 or 10 ampere lamps, ^ to 332 inch.
Heat developed by the electric arc in a given time is as follows :
Let H= heat in gramme-centigrade degrees.
E ■=. difference of potential of arc.
1 = current in amperes.
T= time in seconds.
Then
H— .24 EIT.
Balancing* Resistance for Arc JLamps on Constant
I*otential Circuit.
As the ordinary arc lamp takes but 45 to 50 volts, when used on constant
potential circuits of more than 50 volts, it is necessary to introduce a cer-
tain resistance in series, in order, first, to take up part of the voltage, and
second, to act in a steadying capacity to the arc ; in fact, until the dead
resistance was introduced in series with the arc lamp on constant potential
circuits, such lamps were entirely unsuccessful.
Prof. Elihu Thomson says, " a certain line voltage as a minimum is abso-
lutely necessary in working arc lamps on constant potential lines, whether
they be open arcs or inclosed arcs. Thus two 45 volt arcs in series, with
uncored carbons like the brand known as 'National,' cannot be safely
worked below 110 volts on the line with resistance in series with them.
More than 100 volts should, of course, be maintained for safety of the
service.
^m^^^mma^^^am
ARC LAMPS.
401
" The tests shew, also, that with a cored upper carbon, thelimit is lowered
several volts on the average, and it is known that the voltage of the arcs
may be safely reduced somewhat when cored positives are used.
"It is also shown that a 75 to 80 volt arc, run upon a constant potential
line, is stable at a considerably less line voltage than the open arc. It
would appear, also, that with either open or inclosed arcs at ordinary cur-
rent strengths of from 5 to 10 amperes, the steadying resistance in the
branch is required to cause a drop of about 15 to 20 volts, or waste energy
at the rate in watts of 15 to 20, multiplied by the amperes of current used in
the lamp."
Let E = E.M.F. or difference of potential between the circuit leads
e =. E.M.F. required at arc lamp terminals.
i = current required by tbe arc lamp.
R = dead resistance to be put in series.
r = resistance of the arc lamp burning.
r, = total resistance of dead resistance + lamp.
Then
e
r=i (1)
E
(2)
(3)
R = r, — r
As the E.M.F. of most of the circuits on which lamps of this type are used
is more than 100 volts, it is customary, and in fact economically n<
to place two arc lamps in series, and the formula (3) then becomes
B = r, — 2r.
Street liig-litfiiig- by Arc JLantps,
In New York City 10 ampere arcs are placed at street corners 250 feet
apart, giving excellent results. On Fifth avenue, New York, two 5 ampere
lamps on posts placed 125 feet apart, give good results.
St. Louis, Mo., one arc lamp on every other corner, illumination poor on
unlighted corner. Favorite distance in United States 200 to 300 feet.
For good illumination distance apart of arc lamps should not exceed six
times height of arc from ground.
For railroad yards 10 ampere arc lamps 30 feet from the ground and about
200 feet apart are found to give good results.
The following table shows some arrangements of arc lamps in foreign
cities :
Arc Lamps in Foreign Cities.
Amperes
per Arc.
Distance
apart in Ft.
Height of
Arc in Ft.
City of London Streets . „ .
Glasgow Streets ......
Hastings Streets .....
Berlin Streets ......
Milan Streets .......
Charing Cross Railroad Station ,
Cannon Street Railroad Station ,
St. Pancras Railroad Station . ,
Central Station, Glasgow . . ,
St. Enoch's Station, Glasgow .
Edinburgh Exhibition, 1886 . ,
Edinburgh Exhibition, 1886 . ,
115
160
300
ISO
60 to 80
18.0
18.0
26.7
25.0
18.0
35.0
14.0
19.5
12.0
18.0
402 ELECTRIC LIGHTING.
About J watt per square foot is a fair allowance for lighting large halls,
exhibitions, etc. ; 1 watt for large reading-rooms, libraries, etc. ; 2 watts for
intense illumination, such as is required at the South Kensington Museum.
light Cut off bv C-looes.
Clear glass 10 per cent.
Light ground glass 30 per cent.
Heavy ground glass 45 to 50 per cent.
Strong opal 50 to 60 per cent.
Trimming* Arc Stamps.
Good trimmer can clean and recarbon about 100 commercial arcs per day
if the lamps are not too far scattered.
For street lamps at ordinary distances trimmer should not be required to
recarbon and clean more than 80 double lamps per day.
I]¥CA]¥»EliCE]¥T LAMPS.
Temperature of filament should be as high as practicable commensurate
with an economical life ; it is generally about 2500° F.
At a temperature of 1800° F. it is said that an increase of 20° in tempera-
ture will increase the candle-power about 40 times.
Energy required for incandescent lamps is I2B or E I ; R being the
hot resistance of the lamp.
Heat units H required is
„ _z time in minutes.
Candle-power of a given current varies nearly as the fourth
power of the difference between the given current and the current required
to produce visible rays.
At and near normal candle-power the light varies as the sixth power of
the current, or
l=i f/^pT
y c. p.,
where 1= current for c.'p.
and i = current for c. pv
"Efficiency of Incandescent Lamps.
By efficiency is understood the ratio of the candle-power to the watts con-
sumed. It varies from 1 watt to 10 watts per candle, and even more in old
lamps, but generally in new lamps from 1\ to 4 watts are required. The
most economical efficiency, i.e., at which the cost of operating the lamp is
a minimum, depends upon the cost of the energy supplied, and of the lamp
renewal. When the former is cheap and the lamps poor and expensive, the
efficiency should be low ; when the reverse holds, the lamps should be run
at a high efficiency. It has been shown that the total cost of energy and
lamp renewals is a minimum, where the cost of lamp renewals is about 15
per cent of the whole. If the renewals cost more than 15 per cent, the
lamps are being used at too high an efficiency, and vice versa.
The efficiency of incandescence lamps with direct or alternating currents
is the same. (Ayrton and Perry.)
INCANDESCENT LAMPS. 403
"Watts consumed in incandescent) V^/V^2^2
lamps worked by alternating c
y V- 7t2 + r2
V/2 — square root of mean square of current measured on electrodyna-
moineter.
V ' E'i •=. square root of mean square of voltage measured on non-inductive
voltmeter.
t = the duration of one complete alternation.
r — resistance of filament in ohms.
I — coefficient of self-induction of filament.
Smashing- Point. — It is wasteful to run lamps invariably until they
break, owing to the decrease in efficiency as the lamp is used. In some
cases old lamps having very long lives have been found to take as much as
17 Avatts per candle. The point at which it is most economical to renew
the lamp has been termed the" smashing-point," and the following formula
may be used, on the assumption that the increase in watts per candle-power
is uniform, or approximately so.
If
B = cost of lamps per candle-power,
C= total cost of a candle-power of light for a given time b,
D = average cost per hour per candle during the given time b,
E = cost of energy per 1000 watt-hours,
a =i initial power in watts per candle,
b := hours lamp should be burned, i.e., " smashing-point,"
c = increase of watts per candle for each hour of use ;
„ C B . / . b\ E
D is minimum when b = i/200'
b = 1410 y — when c = .001
b = 1000 y - when c = .002
b= 815 y^
The Proper "Use of Incandescent Kianips.
(From a Circular of the General Electric Company.)
A lamp to give satisfaction must not only be properly made, but it must
also be properly used. A lamp of the highest quality may be so misused as
to give only a small fraction of its rated light capacity. Proper use, produ-
cing a maximum of light at a minimum expense, requires :
That the lamps be burned at marked voltage.
That the voltage be kept constant.
That lamps be replaced whenever they get dim.
404 ELECTKIC LIGHTING.
The last requirement is not considered economical by many users who
prize lamps that have long lite, and insist on using them as long as they
will burn. Let us see by an example if extremely long life is desirable.
As the cost of current varies greatly, we will assume an average cost of
one-half per cent per lamp hour. If a rated 16-candle-power lamp, burned
for 1000 hours, be burned an'additional 1000 hours, it takes practically the same
current during the last period, but gives an average light of only about 8
candles. The cost of current for the 2000 hours is .§10.00. A new lamp costs
20 to 25 cents; and had three lamps, with a life of about 700 hours each, been
used during the entire period, the average light would have been fully
doubled, at an added expense of not more than 50 cents, or 5 % of cost of
current. In other words, by adding 5 % to operating expense (representing
the cost of the two renewal lamps) the customer would add 100 % to the
light given. One new lamp gives a light equal to two old ones at half the;
cost of current. If the old lamps gave light enough, the new lamps would
halve the number of lamps in use, and produce the same light with half the:
current.
It is important to note that the above example is based on results obtained
with the highest grade of lamps. With an inferior quality of lamp the ar-
gument against extremely long life would be still stronger and the neces-
sity of frequent renewals of lamps much greater.
Thus, from any point of view, it is false economy to select lamps with a
sole regard for long life. Lamps should be renewed when dim, for in no
other way can light be produced economically.
The points to be remembered are as follows :
Do not run pressure above the voltage of the lamps. Increased pressure
means extra power; and although the old lamps may thus give more light
for awhile, every new lamp that does not break from the excessive pressure
will deteriorate very rapidly and give greatly diminished light.
Do not treat incandescent lamps like lamp chimneys, and use them until
they break. They should be renewed whenever they get dim.
Iiife and Candle-power of JLunip*.
(From Circular of General Electric Company.)
Since the prime function of an incandescent lamp is to give light, the best
lamp is that which gives maximum light at minimum cost. This is an ex-
ceedingly simple axiom, and yet few users of lamps follow it out in prac-
tice. Lamps are repeatedly selected for long life, irrespective of good, uni-
form candle-power. Lamps are often continued in use long atter their
candle-power has seriously diminished.
An examination of tbe characteristics of an incandescent lamp will give
a clear understanding of the principles applying to their selection and use.
A theoretically perfect lamp would maintain its normal candle-power in-
definitely, or until the lamp was broken. In practice the deterioration of
the lamp filament causes a steady loss of candle-power.
Regarding- lioss in Candle-power. — The drop in candle-power is
a characteristic of an incandescent lamp always to be borne in mind. Tbe
relative drop or loss of candle-power, other things being equal, determines
the comparative value of different lamps. We may have a lamp that loses
50 % in candle-power inside of 200 hours on a 3.1 watt efficiency basis. This
type is almost invariably furnished by the inexperienced manufacturer, and
there are many such lamps in the market. Considered from the standpoint
of life only, such lamps are excellent, because their filaments deteriorate to
such a degree that it is practically impossible to supply enough current to
brighten them up to the breaking point, but no discerning station manager
would want such dim lamps, even with unlimited life. As in the selection
of incandescent lamps so in their use — the exclusive consideration of life
leads to poor results. Loss of candle-power in a lamp sooner or later makes
it uneconomical to continue in use.
There is no lamp yet made which it is economical to burn over 1000 hours,
and in the great majority of cases the limit is under 600 hours.
INCANDESCENT LAMPS. 405
An incandescent lamp is nothing more than a transformer, receiving
current and transforming it into light. After a certain time this trans-
former may lose 50 % in efficiency, taking practically the same current, hut
giving only about one-half the light. A boiler or an engine suffering such
loss in efficiency would be promptly repaired or replaced. The renewal of
incandescent lamps is even more important. The old lamps jeopardize the
customer's trade with their poor and expensive ligbt. A customer cares
little how efficiently a station is operated, but is much concerned about the
quality of light furnished. At the present price of lamps, doubling the
number of lamp renewals adds little to cost of operation, while it increases
the lighting efficiency 40 % to 50 %. Some stations attempt to correct the
dimness of old lamps by raising the voltage, but this is bad practice, for the
increased pressure damages every neAV lamp placed in circuit. These prin-
ciples are carefully observed by many of the large lighting companies, and
a force of men is employed to weed out and replace all dim lamps. Some
such means of keeping the average life below 600 hours should be adopted
by every lighting company that has any regard for the economical produc-
tion of light, or the satisfaction of their customers.
A simple method is to fix the average life at 600 hours or less, and then
determine from the station record how many lamps should be renewed each
month to keep the average life Avithin this limit. The required number of
lamps should be renewed each month.
If, for example, a station decides on an average life not to exceed 600
hours and the station records show that on the average 60,000 lamp hours of
current are supplied monthly, then it would be necessary to renew- ' or
100 lamps a month.
Tlie Importance of Good Meg-ulation.
Proper Selection .assail Use of Transformers. — Poor regulation
of voltage probably results in more trouble with customers than any other
fault in electric lighting service.
Some central station managers act on the theory that so long as the life
of the lamp is satisfactory, an increase of voltage, either temporary or per-
manent, will increase the average light. The fact is that when lamps are
burned above their normal rating the average candle-power of all the, lamps
on the circuit is decreased ; and if the station is on a meter basis, it increases
the amount of the customers' bills.
Evils of Excessive "Voltage. — Excessive voltage is thus .a double
error — it decreases the total light of the lamps, and increases the power
consumed. The loss of light displeases the customers and discredits the
service. If light is sold by meter, the increased power consumption dissat-
isfies the customers ; if light is sold by contract, the additional power is a
dead loss to the station. If increased light is needed, 20 candle-power lamps
should be installed, instead of raising the pressure. Their first cost is the
same as 16 candle-power lamps ; they take but little more current than
16 candle-power lamps operated at high voltage, and give greater average
light.
Increased pressure also decreases the commercial life of the lamp ; and
this decrease is at a far more rapid rate than the increase of pressure, as
shown in the following table. This table shows the decrease in life of
standard 3.1 watt lamps, due to increase of normal voltage.
Per Cent of Normal Voltage. Life Factor.
100 1.000
101 .818
102 .681
103 .662
104 .452
105 .374
106 .310
Erorn this table it is seen that 3 % increase of voltage halves the life of a
lamp, while 6 % increase reduces the life by two-thirds.
406 ELECTRIC LIGHTING.
Irregular pressure, therefore, necessarily results in the use of lamps in
which the power consumption per candle is greater than a well regulated
pressure would allow. The result is reduced capacity of station, and
reduced station efficiency.
These remarks apply with special force to alternating current stations,
since we have here two sources of possible irregularity in voltage — the
generator and the transformer. Poor regulation is most apt to occur in the
transformers, and the utmost care should, therefore, be taken in their se-
lection and use. Tbe efficiency of the average lamp on alternating systems
is nearly 4 watts per candle. With good regulation obtained by the intell'
gent use of modern transformers, the use of lamps of an efficiency of 3.
watts per candle becomes practicable. It is thus possible to save 25 % i-
power consumption at the lamps, and increase the capacity of the station
and transformers by the same amount.
In the past two years, there has been a marked advance in the method of
making transformer installations. Tbe general adoption of higher voltage
secondaries gives smaller loss in wires, and permits the Use of larger trans- .i
former units, thus greatly improving the regulation. On this account 50-
volt lamps are gradually going out of use. The replacement of a number'
of small transformers by one large unit, and of old, inefficient transformers
by modern types, has also been of immense advantage to stations. A large
number of stations, however, still retain these old transformers, and load
their circuits with large numbers of small units. Such stations necessarily
suffer from loss of power, bad regulation, and a generally deteriorated
lighting service. Simply as a return on the investment, it would pay all
such stations to scrape their old transformers and replace them with large
and modern units.
Proper care in the selection of transformers considers the quality and the
size. Quality is the essential consideration, and should have preference to
first cost. No make of transformer should be permitted on a station's cir-
cuit that does not maintain its voltage well within 3 % from full load to no
load. The simple rule regarding 'size is to use as large units as possible,
and thus reduce the number of units as far as the distribution of service
permits. Every alternating station should aim to so improve regulation as
to permit the satisfactory use of 3- watt lamps.
Good regulation is eminently important to preserve the average life and
light of the lamps, to prevent the increase of power consumed by the lamps,
and to permit the use of lamps of lower power consumption, so that both
the efficiency and capacity of the station may be increased.
Constant voltage at the lamps can be maintained only by constant use of
reliable portable instruments. No sAvitchboard instrument should be
relied on, without frequent checking by some reliable standard. Owing to
the varying drop at different loads, constant voltage at the station is not
what is wanted. Pressure readings should be taken at customers' lamps at
numerous points, the readings being made at times of maximum, average
and minimum load. Not less than five to ten readings should be made at
each point visited, the volt-meter being left in circuit for four or five min-
utes, and readings being taken every fifteen seconds. The average of all the
readings gives the average voltage of the circuits. Lamps should be or- [
dered for this voltage, or if desired, the voltage of the circuits can be re-
duced or increased to suit the lamps in use. The practical points are to
determine the average voltage at frequent periods with a portable volt-
meter at various points of the circuits, and then to arrange the voltage of
the lamps and circuits so that they agree.
Candle-Hours — The Regulation of JLamp Value.
The amount of light given by lamps of the same efficiency is the only
proper measure of their value. The amount of light given, expressed in
candle-hours, is the product of the average candle-power for a given period
by the length of the period in hours.
Many of the best central station managers consider that a lamp has passed
its useful life when it has lost 20 % of its initial candle-power. In the case
of a 16 candle-power lamp, the limit would be 12.8 candle-power. The
period of time a lamp barns until it loses 20 % of its candle-power may
therefore be accepted as its useful life. The product of this period in hours
INCANDESCENT LAMPS.
407
by the average candle-power gives the " candle-hours " of light for any
given lamp.
The better a lamp maintains its candle-power under equal conditions of
comparison the greater will be the period of " useful lite," and therefore
the greater will be the " candle-hours." This measure is, therefore, the
only proper one with which to compare lamps and determine their quality.
The practical method of comparison is as follows : Lamps of similar
candle-power and voltage are burned at the same initial efficiency of 3.1
watts per candle on circuits whose voltage is maintained exactly normal.
At periods of 50, 75, or 100 hours the lamps are removed from the circuits
and candle-power readings taken, the lamps being replaced in circuit at the
end of each reading. Readings are thus continued until the candle-power
drops to 80 % of normal. The results obtained are then plotted in curves,
and the areas under these curves give the " candle-hours" and the relative
value of the different lamps.
"Variation in Candle-power and Efficiency.
In the following table is shown the variation in candle-power and effi-
ciency of standard 3.1 watt lamps due to variation of normal voltage.
Per Cent of Normal
Per Cent of Normal
Efficiency in Watts
per Candle.
Voltage.
Candle-power.
90
53
4.68
91
57
4.46
92
61
4.26
93
65
4.1
94
69*.
3.92
95
74
3.76
96
79
3.6
97
84
3.45
98
89
3.34
99
94*
3.22
100
100
3.1
101
106
2.99
102
112
2.9
103
118
2.8
104
124*
2.7
105
131*
2.62
106
138*
2.54
Example: Lamps of 16 candle-power, 105 volts, and 3.1. watts, if burned
at 98 %of normal voltage, or 103 volts, will give 89 % of 16 candle-power, or
14J candle-power, and the efficiency will be 3.34 watts per candle.
liamp Renewals.
The importance and necessity of proper lamp renewals applies forcibly to
all stations, regardless of the cost of power, and whether lamp renewals are
charged for or furnished free. The policy of free-lamp renewals at the
present low price of lamps is, however, preferable for both station and cus-
tomer. Free-lamp renewals gi ve a station that full and complete control of
their lighting service so requisite to perfect results.
Since, however, a large number of companies charge for renewals, we
offer some suggestions as to the best method of inducing customers to re-
new their old lamps, for it is evident that some inducement is necessary.
Offering new lamps in exchange for dim lamps at a reduction in price is
one good method. A customer, for example, would save by paying, say
half price, for the renewal of a dim lamp, instead of waiting and paying
full price when the lamp burns out.
408 ELECTRIC LIGHTING.
Another method is to offer lamps for renewals at less than cost, say 15
cents each, and reserve the right to say when lamps shall be renewed. Such
a plan works well, as no customer can justly complain when the company
renews lamps at less than cost.
As profit on the sale of lamps is certainly secondary in importance to the
sale of current and the improvement in quality of light, either of the above
plans should commend themselves to all Central Stations not furnishing
free renewals.
Whatever method be adopted, the one chief principle of good economical
lighting service should never be forgotten, viz. : that the average life of
lamps should never exceed GOO hours.
Points to l»e Rrniembered.
That a constant pressure at the lamps must be maintained.
That the lamps are not to be used to the point of breakage — they should
be renewed when they become dim.
That satisfaction to customers, and the success of electric lighting, are
dependent upon good, full, and clear light, which old, black, and dim
lamps cannot give.
That to furnish a good, full, and clear light is as much a part of the
Lighting Company's business as to supply current to light the lamps.
That a company should always endeavor to keep the average life of lamps
within 600 hours.
That to renew dim lamps properly on the free renewal system, inspectors
should examine the circuits regularly when the lamps are burning. If
lamp reneAvals are charged to customers, induce them to exchange their
dim lamps.
[Faults in Incandescent lamps.
Rapid loss of Candle-Power. — Rapid loss of candle-power is
one defect in incandescent lamps, and we have shown that all lamps suffer
a gradual loss of candle-power as they are used. A very rapid loss in can-
dle-power is, however, a real fault, due to inexperienced manufacture, or
use at excessive voltage. The remedy is to purchase only lamps of standard
reputation, produced by the experienced manufacturer, and to maintain
pressure at normal on the lamps. The pressure should be carefully tested
with accurate portable instruments at the lamp sockets ; and if found high,
the pressure should be regulated to accord with the voltage of lamps', or
lamps supplied to accord with the pressure.
Slackening' of l$ull»s. — Another defect in incandescent lamps is the
blackening of bulbs, although this is more often a supposed defect than a
real one. A lamp may lose in candle-power and show but little blackening ;
and on the other hand, a lamp may get quite black and lose little in candle-
power. Thus a 50-volt lamp which has a more stable filament than the 110-
volt lamp, often shows considerable blackening with little loss of candle-
power.
Blackening in good lamps results from either high pressure or excessive
life. This is a supposed fault. The best of lamps, if burned too long, will
always show a certain amount of blackening. The remedies are, of course,
regulation of pressure and frequent renewals.
The above are the most important defects to be found in incandescent
lamps.
General Illumination.
The subject of illumination has been divided by Mr. E. L. Elliott, to whom
we are indebted for many suggestions, into the following sub-divisions : In-
tensity or Brilliancy, Distribution, Diffusion, and Quality.
Intensity or Brilliancy. — The average brilliancy of illumination re-
quired will depend on the use to which the light is put. " " A dim light that
would be very satisfactory for a church Avould be wholly inadequate for a
library, and equally unsuitable for a ballroom."
The illumination given by one candle at a distance of one foot is called
the " candle-foot," and is taken as a unit of intensity. In general, intensity
of illumination should nowhere be less than one candle-foot, and the demand
INCANDESCENT LAMPS. 409
for light at the present time quite frequently raises the brilliancy to double
this amount. As the intensity of light varies inversely with the square of
the distance, a 16 candle-power lamp gives a candle-foot of light at a dis-
tance of four feet. A candle-foot of light is a good intensity for reading
purposes.
Assuming the 16 candle-power lamp as the standard, it is generally found
that two 16 candle-power lamps per 100 square feet of floor space give good
illumination, three very bright, and four brilliant. These general figures
will be modified by the height of ceiling, color of walls and ceiling, and
other local conditions. The lighting effect is reduced, of course, by an
increased height of ceiling. A room with dark walls requires nearly three
times as many lights for the same illumination as a room with walls painted
white. With the amount of intense light available in arc and incandescent
lighting, there is danger of exceeding " the limits of effective illumination
and producing a glaring intensity," which should be avoided as carefully as
too little intensity of illumination.
Distribution of Lig-Iit. — Distribution considers the arrangement of
the various sources of light, and the determination of their candle-power.
The object should be to " secure a uniform brilliancy on a certain plane, or
within a given space. A room uniformly lighted, even though compara-
tively dim, gives an effect of much better illumination than where there is
great brilliancy at some points and comparative darkness at others. The
darker parts, even though actually light enough, appear dark by contrast,
while the lighter parts are dazzling. For this reason naked lights of any
kind are to be avoided, since they must appear as dazzling points, in
contrast with the general illumination."
The arrangement of the lamps is dependent very largely upon existing
conditions. In factories and shops, lamps should be placed over each ma-
chine or bench so as to give the necessary light for each workman. In the
lighting of halls, public biuldings, and large rooms, excellent effects are
obtained by dividing the ceiling into squares and placing a lamp in the
center of each square. The size of square depends on the height of ceiling
and the intensity of illumination desired. Another excellent method con-
sists in placing the lamps in a border along the Avail near the ceiling.
For the illumination of show windows and display effects, care must be
taken to illuminate by reflected light. The lamps should be so placed as to
throw their rays upon the display without casting any direct rays on the
observer.
The relative value of high candle-power lamps in case of an equivalent
number of 16 candle-power lamps is worthy of notice. Large lamps can be
efficiently used for lighting large areas, but in general, a given area will be
much less effectively lighted by high candle-power lamps than by an equiva-
lent number of 16 candle-power lamps. For instance, sixteen 64 candle-
power lamps distributed over a large area will not give as good general
illumination as sixty-four 16 candle-power lamps distributed over the same
area. High candle-power lamps are chiefly useful when a brilliant light is
needed at one point, or where space is limited and an increase in illuminat-
ing effect is desired.
Diffusion of ILig-lit. — "Diffusion refers to the number of rays that
cross each point. The amount of diffusion is shown by the character of the
shadow. Daylight on a cloudy day may be considered perfectly diffused ;
it produces no shadows whatever. The light from the electric arc is least
diffused, since it emanates from a very small surface ; the shadows cast
by it have almost perfectly sharp outlines. It is largely due to its high
state of diffusion that daylight, though vastly more intense than any artifi-
cial illumination, is the easiest of all lights on the eyes. It is a common
and serious mistake, in case of weak or overstrained eyes, to reduce the
intensity of the light, instead of increasing the diffusion."
Quality of liig-ht. — "Aside from difference in intensity, light pro-
duces many different effects upon the optic nerves and their centers in the
brain. These different impressions we ascribe to difference in the quality
of the light. Thus, ' hard light,' ' cold light,' ' mellow light,' ' ambient
light,' etc., designate various qualities. Quality in light is exactly analogous
to timber or quality in sound, which is likewise independent of intensity.
The most obvious differences in quality are plainly those called color. But
color is by no means the element of quality. The proportion of invisible
rays and the state of diffusion, are highly important factors, but on account
410
ELECTRIC LIGHTING.
of not being directly visible, tbey have been generally overlooked, and are
but imperfectly understood."
luminosity of Incandescent lamps.
As showing the quality of incandescent light, we present here a curve
showing the relative luminosity of an incandescent lamp at different regions
of the visible spectrum.
On this subject Mr. E. L. Nichols states the following :
" The most important wave lengths, so far as light-giving power is con-
cerned, are those which form the yellow of the spectrum, and the relative
luminosity falls off rapidly both toward the red and the violet. The longer
waves have, however, much more influence upon the candle-power than the
more refrangible rays.
LUMINOSITY OF
NCANDESCENT LAMP
CFERRY.)
ORANGE YELLOW
Fig. 6. Regions of Spectrum.
" Luminosity is the factor which we must take into account in seeking a
complete expression for the efficiency of any source of illumination, and the
method to be pursued in the determination of luminosity must depend upon
the use to Avhich the light is applied. If Ave estimate light by its power of
bringing out the colors of natural objects, the value which Ave place upon
the blue and violet rays must be very different from that Avhich AA'ould be
ascribed to them if Ave consider merely their power of illumination as ap-
plied to black and white. In a picture gallery, for instance, or upon the
stage, the value of an illuminant increases Avith the temperature of the
incandescent material out of all proportion to the candle-power, whereas,
candle-poAver affords an excellent measure of the light to be used in a
reading room."
Relative Value of Arc and Incandescent lig-hting-.
The relative value of the arc and incandescent systems of lighting is fre-
quently difficult to determine. Incandescent lamps have the advantage that
they can be distributed so as to avoid the shadoAvs necessarily cast by one
single source of light. Arc lamps used indoors Avith ground or opal globes
cutting off half the light, have an efficiency not greater than two or three
INCANDESCENT LAMPS. 411
times that of an incandescent lamp. Nine 50 watt, 16 candle-power lamps
consume the same power as one full 450 watt arc, lump. It has been found
that unless an area is so large as to require 200 or 300 incandescent lights
distributed over it, arc lamps requiring equal total power will not light the
area with as uniform brilliancy.
The Correct Use of Eig-ht.
How to Avoid Harmful Effects on the Eyes. — An objection
frequently urged against the incandescent lamp is that it is harmful to the
eyes and ruins the sight. This is true only in so far as the lamp may be im-
properly used. Any form of light as frequently misused would produce the
same harmful results. Few people think of attempting to read by an un-
shaded oil lamp, and yet many will sit in the glare of a clear glass incan-
descent lamp. Incandescent lamps are more generally complained of,
because, unlike oil or gas, they can be used in any position. Bookkeepers
and clerks are often seen with an incandescent lamp at the end of a drop
hanging directly in front of their eyes — an impossible position of the light
from gas or oil.
The first hygienic consideration in artificial lighting is to avoid the use of
a single bright light in a poorly illuminated room. In working under such
a light the eye is adapted to the surrounding darkness, and yet there is one
spot in the middle of the eye that is kept constantly fixed on the very bright
light. The brilliancy of the single light acting on the eye adjusted to dark-
ness, works harm. There should be a general illumination of the room in
addition to any necessary local light. , If sufficient general illumination is
provided, the eye is adjusted to the light, and the local light can be safely
used. The ideal arrangement provides general illumination so strong that
a pencil placed on the page of a book casts two shadows of nearly equal
intensity — one coming from the general light and the other from the local
light.
Care should also be taken to prevent direct rays from striking the eye.
The light that reaches the eye by day is always reflected. In reading or
writing, to avoid shadows, the light should come over the left shoulder.
Only the reflected rays can then reach the eye.
Another point to be avoided is the careless, general use of clear glass,
unshaded lamps. Frosted bulbs should be used in place of clear glass
where soft light for reading is required. The intensity of light reflected
from a small source is increased, and intense light injures the eye. With a
clear glass globe the whole volume of light proceeds directly from the small
surface of the lamp filament. With a frosted bulb the light is radiated
from the whole surface of the bulb, and while the total illuminating effect
is practically undiminished, the light is softened by diffusion, to the great
comfort and relief of the eyes.
Finally, the use of old, dim, and blackened lamps, giving but a small
fraction of their proper light, is very often a source of trouble in not supply-
ing a sufficient quantity of light. Users of lamps are not otfen aware of
the loss in candle-j)ower a lamp undergoes, and so it happens that lamps
are retained in use long after their efficient light-giving power has vanished.
Proper attention to lamp renewals on the part of Central Stations is neces-
sary to correct this evil.
The correct use of light requires :
That there should be general illumination in addition to the light near at
hand.
That only reflected light should reach the eye. The light should be so
placed as to throw the direct rays on the book or work, and not in the eye.
That the light should be placed so that shadows will not fall on the work
in hand.
That shades and frosted bulbs should be used to soften the light.
That lamps be frequently renewed to keep the light up to full candle-
power.
Eife of Incandescent Eamps.
In the early days that lamp which had the longest life was said to be the
best ; the desideratum, however, as has been seen, is not long life, but
412
ELECTRIC LIGHTING.
constancy of candle-power (combined with high efficiency and low cost) dur-
ing the period of use up to the smashing point. If an initial efficiency too
high be adopted, the constancy is inferior ; to prove this, Messrs. Siemens
and Halske have made a number of tests, obtaining the following net
results :
1| initial watts rose to 4.46 watts after burning 55 hours.
2 initial watts rose to 3.99 watts after 90 hours.
1\ initial watts rose to 3.58 watts after 150 hours.
The table below contains the mean values of tests of more than 500 lamps
of 49 different types, and taken from 28 different factories ; The watts per
candle-power and fall of candle-power are given.
Table of Average Caiidlv-Powcr anil Efficiency of Lamps
at Different Periods of their Lives.
Initial Consumption in Watts.
1
2.0 to 2.5
2.5 to 3.0
3.0 to 3.5
3.5 to 4.0
4.0 upwards.
m
ft
ft
ft
ft
ft
o
o
"3
P3
P^
ft
SR
Ph'
3
c3
SR
ft
5R
Ph"
ft
SR
Ph
ft
"c8
W
O
£
o
t
U
^
O
^
o
fe
0
100
2.4
100
2.9
100
3.3
100
3.8
100
4.5
100
84
2.8
93
3.0
95
3.4
96
4.1
96
4.7
200
70
3.3
85
3.3
91
3.5
91
4.3
92
4.9
300
59
3.7
81
3.5
88
3.6
86
4.5
87
5.2
400
53
4.2
76
3.8
84
3.7
81
4.7
82
5.4
500
48
4.6
71
4.0
79
3.9
77
5.0
75'
5.8
600
45
4.8
67
4.2
76
4.1
73
5.3
72
6.1
700
41
5.2
64
4.4
72
4.2
69
5.6
68
6.4
800
39
5.3
62
4.7
69
4.4
66
5.9
65
6.8
900
38
5.5
59
5.0
67
4.7
63
6.1
62
6.9
1000
37
5.7
56
5.3
64
5.0
60
6.3
60
7.0
1100
36
5.7
53
6.0
62
5.4
58
6.5
58
7.1
1200
35
5.8
50
6.3
59
5.6
46
6.7
56
7.1
Distribution of JLig-Int by Incandescent X<am»s.
The best form of lighting interiors is to have single lamps uniformly dis-
tributed over the ceiling ; unless the room has been especially designed
with this in view, it is sometimes difficult to accomplish.
Another method giving most excellent results, but requiring more candle-
power, is the arrangement of lamps around the sides of the room close to
the ceiling. If the walls and ceiling are of a light color, this method is
quite satisfactory, and easier to wire.
If the chandeliers, or more correctly in this case, electroliers, are used,
it is best to have but one main or largo one in the room, balancing the light
by side brackets.
All such suspended lights should be above the line of vision as far as con-
venient.
The most economical distribution as far as candle-power necessary is the
first mentioned, where lights are evenly distributed over the ceiling, to
IXCANDESCENT LAMPS.
413
obtain the same luminosity by using clusters of lamps more widely distrib-
uted instead of single ones, will require much more candle-power.
The 16 candle-power lamp is the universal standard in the United States
when rating lumps or illumination, and the following table gives the basis
on which illumination of different classes of buildings is figured.
Ordinary illumination, 1 lamp, 8 feet from floor for 100 square feet, as in
sbeds, depots, walks, etc.
In waiting-rooms, ferry-houses, etc., 1 lamp for 75 square feet.
In stores, offices, etc., 1 lamp for 60 square feet.
Of course the above must be varied to suit the circumstances, such as dark
walls or other surroundings requiring more light, as the walls reflect little
of that furnished ; and in rooms with dead white walls the reflection ap-
proaches 90 per cent and less lamps would be required than in interiors
Laving worse reflecting surfaces.
A very ingenious and satisfactory method of illuminating high arched
and vaulted interiors, developed first by Mr. I. R. Prentiss of the Brush
Company, is to place a number of lamps around the lower edge of the arch
or dome, with reflectors under them, and so located behind the cornice as
to be invisible to the eye from the floor.
The dome or arch will reflect a large part of the light so placed, giving a
very fine even illumination to the whole interior, without shadows, and very
restful to the eye.
Of course the arch must be of good color for reflecting the light, or much
of it will be wasted.
Ska u a via! t*i»t Hates for Iiacawclesiceiit JLigliting*.
(Buckley.)
Without Lamp Renewals.
Including Renewals.
Gas per
5
<D
xteen
indie-Power
amp, per
our.
o>
1000 Cubic
Feet.
p u ■
g£ft
53 * -^
Ills
St
* c 1 0
c3
8%
OQOniW
ffiOHrt
Sfl
CCOi-^W
oqoi-^S
SM
$1.00
$0,005
$0.42
$0.10
$0.0056
$0.47
$0.12
1.20
.006
.50
.12
.0066
.55
.14
1.40
.007
.58
.14
.0076
.63
.16
1.50
.0075
.63
.15
.0081
.68
.17
1.60
.008
.67
.16
.0086
.72
.18
1.80
.009
.75
.18
.0096
.80
.20
2.00
.01
.83
.20
.0106
.88
.22
2.20
.011
.92
.22
.0116
.97
.24
2.40
.012
1.00
.24
.0126
1.05
.26
2.50
.0125
1.04
.25
.0131
1.09
.27
2.60
.013
1.08
.26
.0136
1.13
.28
2.80
.014
1.17
.28
.0146
1.22
.30
3.00
.015
1.25
.30
.0156
1.27
.32
3.20
.016
1.34
.32
.0166
1.30
.34
3-40
.017
1.42
.34
.0176
1.39
.36
3.50
.0175
1.46
.35
.0181
1.47
.37
3.60
.018
1.50
.36
.0186
1.55
.38
3.80
.019
1.58
.38
.0196
1.63
.40
4.00
.02
1.67
.40
.0206
1.72
.42
4.50
.0225
1.88
.45
.0231
1.93
.47
5.00
.025
2.08
.50
.0256
,14
■M
414
ELECTRIC LIGHTING.
Cost of Producing- Electric Eight.
No very general investigation has yet been made on this subject in the
United States, and few outside the Edison Companies have good facilities
for determining the cost. Buckley gives the following :
" The profits on electric lighting depend primarily on the average number
of hours the lamps burn. Under usual conditions (supplying incandescent
current through meter including lamp renewals) the cost per lamp per hour
averages as follows :
Average Cost of Arc and Incandescent Eamps per Hour.
Cost 16 Candle-
Cost 2000 Can-
Cost 1200 Can-
Length Time Burning.
Power Lamp,
dle-power Arc,
dle-power Arc,
per Hour.
per Hour.
per Hour,
\ Hour each day ....
$.02
$0.16
$0.14
1 Hour each day . .
.0112
•08J
.07}
2 Hours each day .
.0062
.05
.04}
3 Hours each day .
.0046
.04
•03|
4 Houi-s each day .
.0037
.03J
.03
5 Hours each day .
.0032
.03
.02*
6 Hours each day .
.0028
.02f
.02}
7 Hours each day .
.0026
m\
.024
8 Hours each day .
.0025
.02}
.021
.02
9 Hours each day .
.0024
.013
.01f
10 Hours each day .
.0022
.02
UTotes : —
An incandescent lamp gives off from \ to ^ the heat of an equivalent
gas-jet.
An arc lamp gives off from £$ to ^o as much heat as gas-jets producing an
equal light.
A 5-foot (16 c.p.) gas-jet vitiates as much air as four men.
IIGHTL\(; ICHEDl'LES.
General Rule for Construction Schedules.
Moonlight Schedules. — Start lamps one half hour after sunset
until fourth night of new moon ; start lamps one hour before moonset.
Extinguish lamps one hour before sunrise, or one hour after moonrise.
No light the night before, the night of, and the night after full moon.
During summer months there will be found nights near that of full moon
when, under the rule, the time of lighting would be very short. It may not
be positively necessary to light up during such times.
If better service be desired, but not full every night and all-night service;
lamps can be started at sunset and run to 12 or 1 o'clock on full-time sched-
ule, and after 12 or 1 on the moonlight basis.
The above rules by Alex. C. Humphreys, M.E., have been modified by
Frund as follows : Light every night from dusk to 12 o'clock ; after 12
o'clock follow Humphrey's rule for moonlight schedule, excepting there
will be no light after 12 o'clock during the three nights immediately pre-
ceding full moon.
All-Might. Ever j- Wight Schedule. — Start lamps one half hour
after sunset, and extinguish them one half hour before sunrise every day in
the year. Full schedule commonly called 4000 hours for the year.
All the above rules serve to make schedules for any locality, and such
schedules must be based on sun time for the locality, and not on standard
time.
Permanent average schedules are used in New York City, but for other
cities they are usually made up fresh every year.
Following will be found New York City time tables, also another set by
Humphreys that is a good average for sun time in any locality.
LIGHTING TABLE.
415
•Sat
■nana
etuii,
•qsmS
utQ.xa
jSoooqoSSSoioiomiooiqoiqioioiiJiqiq'Oioiqiniq
«r^r/(»Q0Q600l>l>l>l>t^t>t>t^t-t-t>t-t>L-»t-l>l>l>t-t-t-
essggss?
JSSS^feS^^iSEci'-^^i^ii^ccici
•Sai
91UJX
•qsin§
■uiq!xa
I "TO§n
•gai
-u.mgi
B.S2-2S2SSS52S22222SSS^««!oo«xodo6«6»od«6
^§SS^i2SSS3?JSS228qqqq81qqqqo
£ cn <N CN 01 CO CO 00 CO CO CO CO CO CO CO •* -* •* ^_ "* <* -d
ses^sss
SgSSSSri'^^^^-^^MScooiciii^-^HHqqq .
■qsmS
■atixa:
gSHriqqoqqLOioo lo iq ' - l . -r -r -i
fi -« -f -tl CO CO CO 00 CO o
■wsn
•Sat
-tuna
auitx
•qsmS
-ut;xg[
"W%\1
9UIIX
•qsmj
-ui^xa;
,_ _. O 1-H <M CO -t< L0 -
SOoSSSooqqqqqqqOHrHHHH^r
i ,-~ ~ » - - c 3 ;
?"* CN "
H"cd«Jicidioioicioiau;
didididididididididioicioiaioiro-
SSSfifS
;o»tsddtodddffldddtdofflffloo»»®«®(D(OCOtoffltBt£
-^Ni^iMHHrtrtqqq^
Jhoo»cohoniomo
glO-#-*Tt<-#COCOCOCOCO
,j oi oi e>i o i '^^^^^^S^S^^^l^^^^'-'^'-'
si— <oocot-^co--<oa
docdcDcddcdcddcddsdoooc
•mSlTE
•Sat
-UJU! '
9UIIX
ttt r:omcoi^oic^cocqo<^co»^^c>'i^22^;32^§§§§oS51?oS
g S"#eOCO ^^^^^^-^^^^^^^^cO^CO^COOO^O^COCOCNCNCNOa
•qsm§
^cddcdcddcdyscdo^oyscoo
*q • X Ld id id id id id id id 10 id is «5 «o >o « io io « io io »o w »o o »
rri«5t!>5Se£:2S§5)§^q?^5;
id id id id id ia ia
JOW8iK I -x^* — *
_
416
ELECTRIC LIGHTING.
O
•Sat
h.m.
13.32
13.33
13.34
13.36
13.37
13.38
13.39
13.40
13.41
13.42
13.43
13.44
13.45
13.45
13.45
13.45
13.46
13.46
13.46
13.46
13.46
13.46
13.45
13.45
13.45
13.45
13.44
13.44
13.44
13.43
13.42
0_1
•qsmg
-niqixg;
r:»t-ccoO'-iNco'#Lotot>ooccoQOOHHOi(NMwnn«m'*T)i'*
£ co :o co co -r -f -p -p -r -r -r -r -P ~v -r -p in iq in lO lO in in lO lo in LO in in in in
•;q§JT[
^"^■f-t<nc-3-OCOCOCOCOmcOMcO-t,-t<-tl-t,l-OLOOtONl>00(»C)0>Oi-i!N
- q q q q q q q q q q q q q q q q q q q ioccocccohhth
-' in i in m- m' in in in in in in in in in in m" in in m' m' m' in in in in in in in in in" in in
«
o
525
"§ur
-nmg
SMMW'ttttCLOOLOCOOOOrirlHTHrlflCjC-lCKjqC'lWW .
^ oi oi c-5 ci oi oi ci oi oi oi ci co co co co' co" co' co' co' co' co' co" co co co co co co co co .
LO
■qstnS
HT-INMlO(OXmOffim*«Ot-00»OH«mr|(iaQOO)OrtNNM^lO •
"g
•^§71
rN©LO'*OHOfflCOI>OLO'*M(NHOOOOOXNtO'fflmL0 1ClflTtl^ •
;:i:icici:i:i:iHHHrHHHnHHHr-qqqoqqcocooq .
jinmmmininominmminminmin'ininin'minmmininmininmm .
e
i
CO
o
H
O
o
■Sui
8UIl£
^•ft^onaooHMcoffiHijKooHTfMonuot-ow'tt'CC'i'ft-oci
Cr<H OI C] OI 01 CO CO CO CO -t> -V -t ~H m LO m = — O O O i-i — i-< i-H C4 05 OI CO CO
^rtrtrtHrtHHn'HrirtHrtHHrtM Cl" OI (N CI 01 Cl' CI CN CN iH oi oi c4 oi
5
co
g
•qsin§
-ui^xg;
r.'NWOwc-in-fiLowt-ooaoHiMcoiocoNMoO'Hcico-fincNffiO
- oi oi cq co co co o; co ct co co cq -r -r -r; -p -r -h -r_ -t -h in lo in in in in in in in q
^laiQ^inVn^ia^iQ^io^iQ^in^inoiniQ^iA^iA^iQiQiQiaiQco
s
h
wan
^'MHOXt-CMClOCONLl-lfNHQNO-jiniMwr x VC LO CO M O OJ CO
SH«p-qq q q q q ,q iq m_ in in ^■ftltltt ". ::. ". :". ". :". c/5 ~: ^2
j®«»66»«6»iaidioioioiQiaidioioioioidiooio«ioioioioio
I
ft
1
*
H
H
•Sui
-u.mg
HffiffioddoddododddddccodcddocHHHTHH •
OC'
•qsinS
-ui^xa;
r:MC50-HMM-fiO(0|>MO!OHCin-|H-*LOtOt>a300rtlSMrJnn» •
;i-.i-.qooq;;c;:ocHrHrtHHrt«HrirHr;c-ici«iicioiC)N .
H
'%^11
r-'nHOi»0"*nHOiN<OTiimHffiNiO'*iMHoano'!i,M'-|ffioofflio ■
g q q q m m lo m m -+ -f •* -t< -r -r co co co co co co co 01 oi 01 oi 01 h t-h h h .
br
^t>L-t-O»O»WW«0«OOO«>OOOOO«5i»OM5C0C0O«D«)tt> .
a
5
•SlTI
-u.ing
• Qtuix
r.'OCl'f®CC)HCOOCCOCl-CNffiN-*ll»QC10CllONOni>C5H<*l»aCl
^c©!»c©cdcx3o6aJa3cocscic»cscsc»cscimc»Gsc>
to
CI
ci
•qsmS
J cj i_- » o o w 01 n * 10 » i> » « o w ci m ^ a a n cc o o -H f i « -J 10 1-
•*q§n:
-gL'5'tiMrt005l»a>lO-liMHO!»NOiO'*«rtOCO«P3iM'Hg>OOglO
- 1 "t t "*i 1 1 c/? c-. t:. "c cc. :". :". ::. ~\ C1. T.' -; °\ 7>. 'i c! *■: t "i 'i1-: R^0. ^
^L^t^lc^t^l^t^t^tc^L^t^t>^»c^t^Ic^L^t~t^lc^tc^tc^lc^Jc^t^Ic^tc^tc^^
^
•Sut
-ixjiiai
^-t^[>^c^odco"ccco*c<jc»c»ocde/oajodajo6oo"c^
OI
ci
01
•qsm§
-tn^'xa
- 01 c: co -t 10 in -o n k co o o o w 01 co -f 10 m co i> co o o ^ « co ^ ■+ 10 to
- q q q q q q q qc ^ q - « ^ « ,— — i -h ^_ i-h r-< — < — i oi oi oi ci oi oi oi oi
^ •* ■* "*' -* -*' ■* Tj<" T)5 ■*" Tfi -*' ■*' -*' rj< -#" -#" -*H ■* "* ■* ■* •* •*" ^* Tt< ■* •* -^H •>#' ^ ■*"
•(UlSiT
■"2J225Swnf'f'tl-<'Hcaeoai(»(>offlL0')|«cirto»!»«)i>
- ~. — . °. °. ^ c. °. —. — . °. q — . q q '-~ >-^ '^ >~ Lq '-"? '-. i~. i-~ u" ,-~. '" l^ *t ■* ■* ■*
^"oooo"cdcooo'c/5cc'cococcc>Dcocdc/>t^L~t^t^t>t^i>^L^i>^t^
JO
iqSjK
rHO<JCO^inWt^G0050^C'lCO'*iniCDt^OOC50^01CO-tlin«Ot^<X)050r-l
f-llHrtrHi-lrtr-iT-lTHr^<NCNC>)CN(NCNCNCNCNl0qCOCO
LIGHTING TABLE.
417
Summary of New York City JLig-hting- Xahle.
Average.
Average
Day.
January .
February
March . .
April . .
May . .
June . .
July . .
August .
September
October .
November
December
413.10
355.27
341.29
290.17
264.39
238.51
256.12
286.26
316.48
368.50
392.59
424.52
13.19
12.15
11.01
9.40
8.32
7.57
8.16
9.14
10.33
11.54
13.05
13.42
18th
15th
16th
16th
15th
12th
17th
16th
15th
16th
14th
10th
Shortest
Longest .
Average
June 21
Dec. 21
Mar. 21 &
Sept. 21
7.54
13.46
Note. — Lights started 30 minutes after sunset. Lights stopped 30 min-
utes before sunrise.
For commercial lighting : add 1 hour for part night lights, add 2 hours for
all night lights to above schedule.
Tahie Snowing- Hours of Lighting- throughout a Year of
§«00 Uoui'N.
Daily Lighting.
03
to
o3
a,
<
6
p
is
>-»
bo
P
53
&
5
<v
w
E
O
53
>
53
CD ■
89
117
145
173
201
257
313
92
64
36
67
98
129
160
191
253
315
69
38
36
66
96
126
156
216
276
32
2
6
37
68
99
130
192
254
3
21
52
83
114
145
207
269
24
54
84
114
144
174
234
294
51
21
57
118
149
180
211
273
335
75
44
13
117
147
177
207
237
297
357
103
73
43
140
171
202
233
264
326
3SS
154
123
63
742
1091
1456
1821
2186
2916
3646
728
459
" 9 " .
"10 " .
"11 " .
" " " midnight
" " " 2 a.m. „
"4 " .
From 4 a.m. to sunrise
" 5 " "
15G
187
218
249
311
373
125
04
63
20
50
80
110
170
230
25
56
87
118
180
242
254
1
418
ELECTRIC LIGHTING.
IS
li.m.
11.40
11.40
11.40
11.40
11.30
11.20
11.20
11.20
11.20
11.20
11.20
11.20
11.10 '
11.00
11.00
11.00
11.00
11.00
10.50
10.50
10.50
10.50
10.50
10.40
10.30
10.30
10.30
10.30
10.30
10.30
10.20
5,
0
,0
0
^ ?
li.m.
5.30
5.30
5.30
5.30
5.30
5.20
5.20
5.20
5.20
5.20
5.20
5.20
5.10
5.10
5.10
5.10
5.10
5.10
5.00
5.00
5.00
5.00
5.00
5.00
4.50
4.50
4.50
4.50
4.50
4.50
4.40
to
S3
<
2
if'
p 0000000000000000000000000000000
G iq lOiOiOOC = - Z SOOO rH r«rHr-HHHHrtHCj <N C-l O-l CI <N CI CN
^z\ 10 10 0 10 CO 0 0 0 0 0 0 0 0 0 0 0 O CO 0 0 0 0 co co co to eo'co to CO CO
— S
rtiMMTHciOfooooHrin-fiooNccc.CHCKo^ijoNcooo^
11
h.m.
12.50
12.50
12.50
12.50
12.50
12.40
12.40
12.30
12.30
12.30
12.30
12.30
12.30
12.20
12.20
12.10
12.10
12.10
12.10
12.10
12.00
12.00
12.00
12.00
11.50
11.50
11.50
11.40
id
0
A
O
£
s
H
p
.2 ■- ■
^ i/_
li.m.
6.10
6.10
6.10
6.10
6.10
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
5.50
5.50
5.50
5.50
5.50
5.50
5.50
5.40
5.40
5.40
5.40
5.40
5.40
5.40
5.30
si
SB
3
li.m.
5.20
5.20
5.20
5.20
5.20
5.20
5.20
5.30
5.30
5.30
5.30
5.30
5.30
5.30
5.30
5.40
5.40
5.40
5.40
5.40
5.40
5.40
5.40
5.40
5.50
5.50
5.50
5.50
5 5
Q1^
HNMTfio»NO)050-Hwn^oot-»c;Orjn«^offlNoo
i.m.
3.50
3.50
3.50
3.40
3.40
3.30
3.30
3.30
3.30
3.30
3.30
3.30
3.30
3.20
3.20
3.20
3.20
3.20
3.20
3.20
3.20
3.10
3.10
3.10
3.10
3.10
3.00
3.00
3.00
3.00
2.50
0
£<g
3
0
3
c
5
3
&
h5
3^
h.m.
6.30
6.30
6.30
6.30
6.30
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.20
6.10
6.10
6.10
6.10
6.10
'5b
5
h.m.
4.40
4.40
4.40
4.50
4.50
4,50
4.50
4.50
4.50
4.50
4.50
4.50
4.50
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.10
5.10
5.10
5.10
5.10
5.10
5.10
5.10
5.10
5.20
nPieOTjdOCr-OOOSOHWCO'JIiOONOOCSOHIMCO^lOffl^OOcSOH
LIGHTING TABLE.
419
11
as
h.m.
8.10
8.10
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
8.00
0
©
0
0
z:
A
c
H
x'5
c'ooOOOOOOOOOOOOOOOOOOOOOOOOOOOO
S CO CO CO CO CO 00 CO CO CO CO O0 CO CO CO OO CO CO CO CO CO CO 00 O] CO CO CO CO CO CO CO
►3
3
soooooooooooooooooooooooooooooo
Z 01 CN CO CO CO OO 00 CO CO CO CO CO CO CO 00 CO CO CO CO 00 CO CO 00 CO OO CO CO CO 00 CO
ft
HCqcOi<ia01>OOS50HlMW#lCH01>00»OHtlM^10(DI>COOO
HHHHr(HHrlHHN(NN(MNN(NNNNn
5' b
zooooooooooooooooooooooooooooooo
Sqqio lo iq 5 i ■ ■ ' -r- -+ oo co co co co co co co oi oi c-5 ci -r* i-< r-j <-; ^ t-j h
^OTosodcoo6o6ododo6o6o6odo6o6o6o6odo6o6cocxjo6o6coo6o6odod
z
3
c
-a
£
=
z
3^
a 5c
='0000000000000000000000000000000
SooiottL: ■ ■-. > - 1 .0 -+ -H -t •* -f< -f_ -+ -+ -h ■* •* -H 00 00 co 00 00 00 co
^'^Ttico^cocococo^co^cococococo'co'co'coco'co'co'co'coco'coco'cocococo
3
S888888S888SSSSSSSyS2'SSgSSSSSSgg
M 3-
HNM^WCONCOQOHfinjwONWOOwcJ^OONgOOOjH
c 000000000000000000000000000000
■ - :-. CO CO CN CI C\ ClrtHHrirt
,£] ©v© © O O O © O O O O CS OS OS OS OS OS OS OS OS C O OS OS OS OS OS OS OS OS
0
— '
5
0
rZ
s
H
<l
c 000000000000000000000000000000
^ "* "*. ** "*. t " :". :" :: " " ' I ~ ! - ! - ! - ! ~ ! : : ". "": ^ '""! ^ rt. '""! R 9 °. °. ^
,3 -* ^ -# ■*" rji tF •*" rj< ■* -# <* -# ■*' ■* •* <# -*" *#" -*" •<* tjJ *# -^ t1< tJh" -^ Tin ■*' ■* -#
1
3
coooooooooooooooooooooooooooooo
o4
3£
HC1CO*U5tO!><»lSOH«W-*LOOI>COOOH«M^LOffl^OOaO
<rYJ
420
ELECTRIC LIGHTING.
I ■ •§ r"^
Ill
Si
53 u
a'gSS22ooooooc>0ooooooooooooooooo
goqqoo«riCi:i:icic-:cMo:M:c lo lo i- lo lo lo © © © © t-h-i <n
s
3S
,j5 © © © © © © © © © © © © © © © © © © © O © © © — i — < h ri — t-i th
g
x'5
poooooooooooooo©ooooooooooooooo
~ m co m oo « ?o :o -t< -c -t< -i< -f -c -t -f •+ -t l- i~ .-. i - i - ,-. )-. i.o lo o © © ©
^ -#-*•*' •* •# x* tJh •#" •# -# ■*' f° -^ ^3 «# •# rj5 ■># "#' ■* -#" rj< -#' -(< ■#" r)H "* lO lO lO
£
fr>
or©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©
C CO CO CO M CO Ol C! Ol 01 Ol 0) « r- ^ rn rn rt O O O O O C LO LO LO LO LO Of
o
Hi
z
iHc<iecT^iooi>cooi©i-ic^co-*KOj©t-co©©^o'ico-#«i?ot-ooc50
«S
H
n »
6 £
s ©©©©©©©©©©©©©©©©©© ©©©©©©©©©©©©©
S m io lo lo lo lo lo lo o rn h ri rn h ^ ^ : i : i •; :: :: :: CO -t f f f f LO LO o
§
h»00C0CCC0»»00OQOOOOOOCSOOOOC)CSQC»OCBOO05O
01
Jl
SO©©©©©©©©©©©©©©©©©©©©©©©©©©©©©©
W M
^ff^Th^fffffffffffTh^ffffffffffff-*
0
s
2S22SS2222SS§8S88Sgggggg?^?5§^^^
o
3
,^C-l>l>r>t>t-t-t>t-t-t-t-t-t-t-t>CO<»0?0«Ci«0«i«0?D5DO<10CCOCO
,0
3
1-1 rt
>."£
ris»*ioot-»nO'-i;in-tiL03t-cooo^:icoi<isjpNoonOH
03
G£
H
5 -~
3 O
pooooooooooo©©©©©©© pccoppopcjoooo
—
5
~W
^0O00O0O0CO00COO0CCCO0OC»0OC«COCOCOCO00COCOC«COCOCCCOCOCOO0C»CC
^ o
O'l
jrd
a o © o © © © © © © © © © © © © © © © © © © © © © © © © © © © ©
E^§o
^nWCOMcOmMmMMMCCCOMMncOMcOMCOncOMCOMCOMM*'*
o
b0
c©©©©©©©©©©©© ©©©©©©©©©©©©©©©©©©©
C CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO 01 01 01 01 Ol Ol 01 Ol C-l CI
hI
^I>Nl-l>t>l>t-t>l>t-t-l>Nt-t-l>t>t»t-l>«>Nt-t>t>t>t-t^t-l>N
g
°5
HIMCOflOfflt-OOOOWClCO-f LOONKCC^OlCO^lOCKODOO-l
AS
H
LIGHTING TABLE.
421
h.m.
13.40
13.40
13.40
13.40
13.40
13.40
13.40
13.40
13.40
13.40
13.50
13.50
13.50
13.50
13.50
13.50
13.50
13.50
13.50
13.40
13.40
13.40
13.40
13.40
13.40
13.40
13.40
13.40
13.40
13.40
13.40
o
ol
2
o
"o
J:
"ci
H
3
-o
CO
r^OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
fl r- f r- < tH t—i t— 1 r-< i-H r— ( t— ' r-1 C} CI CI C} CI CI CI CI CI CI CI 0 1 CI CI oj CI Cl 01 CI CI CI
o
fi
i
3
C992SSSS920020SOOOOOOQOOOOOOQOOO
£COCOCOCOCOCOCOCOCOCOCOCOCOCOCOOOCOCOCO-tH-1H--f*--f-t<-f,r-t<^t,-3H.^-^iT3H
co
p
o^3
TH<^Otl^lO»I^OOC50^C1CO-*lOCOt-OOCipT-IC1Cp-f<ipCpt~00050'i-l
1
1 1
3> ~'
^oooooooooooooooooooooooooooooo
gwco^ffliBioiqiqoioiqrHHrtHHrtHrtHt] c; c; ci ci co co cq cq ^
« ci ci ci ci ci ci ci ci ci ci ci co co ci co co co ci ci co co co" co co co' co" co co co' co
K5 M
^"oooooooooooooooooooooooooooooo
5 CO CO CO •*"*■***"*•*•* t »" ' ' - ~ q O © H
^'ifiicoo'ioKiiriiriioicinioioic'^^^o^iriQScD^cocs'ocdcocdcd
ho
3
^oooooooooooooooooooooooooooooo
Sqquo uq o lo uq o lo lo o ** ^ -# -# **-*-# -# -* -* -h ~r -v -t< cq cq co cq co
5 ^
a w
- :
fig
HiMCO'tLOONOOCiOHClcO-tO'-Ot-COr. e — < ~ 1 co ;: ■' i_rON00C5O
s
•ooooooooooooooooooooooooooooooo
C ci ci ci ci o i : : t - - -,- Lq iq uq uq io © q r-j ^h h ih r-j th th cq co cq co co co
o
8
CO
c
©
H
«
H
ffl
O
H
O
O
3|
rjooooooooooooooooooooooooooooooo
H.OOOOOOOHHrtHHHHHrH | | !N CO CO CO CO CO CO
^"uoiriioioicioiduo^uoouoiouooo'icuo'iriioirio
^lOioooioioioioioioioioioioioioioioioioioioioiOL'jioL'jioaiaio
c ~
fig
i-icqcO'#io«oi>GOo;0'rMCJco-tiio^cit^cooO'-jcico-+iio«ot-oociO'rH
422 ELECTRIC LIGHTING.
Hours of Lighting* per Annum Uy Different Schedule.*.
Regular all-night schedule 4000 hours
New York City schedule « . . . 3950 hours
Philadelphia schedule 4288 hours
Providence schedule ........... 4012 hours
Philadelphia moonlight schedule ..... t 2190 Lours
Frund schedule ............. 3000 hours
Hours of Burning- Commercial 'Lights.
Time of Sunrise and Sunsets.
o
o
nfl
o^
All night
"3 «3
X X
PX
P
Poo
Pes
03o
PS
<£o
PS
41 O
P0^
S 03
x£
lights.
^ o 2
P bco
"uarH bo
P'Sfl
h.ni
ll.IIl
h.m.
h.m.
h.m.
h.m.
h.m.
h.m.
h.m.
1
Jan. 15
4.55
4.30
3.30
4.30
5.00
5.30
6.30
7.30
7.25
8.00
15.30
Feb. 15
;>.;n
5.0(1
3.00
4.00
4.30
5.00
6.00
7.00
6.56
7.30
14 30
Mar. 15
<;.<><;
5.30
2.30
3.30
4.00
4.30
5.30
6.30
6.12
6.45
April 15
6.41
(i.15
1.45
2.45
3.15
3.45
4.45
5.45
5.16
5.45
11.30
May 15
7.13
6.45
1.15
2.15
2.45
3.15
4.15
5.15
4.39
5.15
10.30
June 15
,..H
7.00
1.00
2.00
2.30
3.00
4.00
5.00
4.24
5.00
10.00
July 15
'/.:;■_'
7.00
1.00
2.00
2.30
3.00
4.00
5.00
4.39
5.15
10.45
Aug. 15
,.00
(1.30
1.30
2.30
3.00
3.30
4.30
5.30
5.08
5.45
11.45
Sept. 15
<;.()!»
5.30
2.30
3.30
4.00
4.30
5.30
6.30
5.40
6.15
12.45
Oct. 15
!>.!!)
4.45
3.15
4.15
4.45
5.15
6.15
7.15
6.13
6.45
14.00
Nov. 15
4.:;:)
4.00
4.00
5.00
5.30
6.00
7.00
8.00
6.52
7.15
15.45
Dec. 15
4.31
6.06
4.00
5.30
4.00
5.00
5.30
6.00
7.00
8.00
7.20
7.45
15.45
Aver'ge )*
for y'r )
1.30
3.30
4.00
4.30
5.30
6.30
5.54
6.26
13.00
Graphic Lighting Schedule for London, England.
r—
3 6
1
fri-
'"""'"'""i ; i r
ijfllfi
\H
I 1 . : I
AHH.
\\ !
\\ \ {
1
//\' ■ 1 1 \]\ 1
•£■' |s\
SE. .
jA''' ! 11'^
/
'' 1 ■ 1 ! ■
%
DEC.
/
v
Uii:.!:.:,h;: 1 i i ! : .
k
Fig. 7. — The shaded area represents the time during which light is
required. The horizontal lines show the months of the year. The vertical
lines show the hours of the day and night. The inner dotted lines show the
time of sunset and sunrise. The outer lines show the time of lighting up
and extinguishing. Each square is an hour month, i.e., 30.4 hours.
ELECTRIC STREET RAILWAYS.
CARS, MOTORS, AID GRIDES.
(From Pamphlet by S. H. Short, issued by Walker Company.)
Grades and sharp curves should of course be avoided as much as possible,
but when unavoidable, the ascent of a 10 per cent or even a 12 per cent
grade is possible to a car fitted with a double 15 h. p. or 20 h. p. equipment,
and pulling no trailer. The grip of the wheels on the rails may be depended
upon, with the aid of sand, to give from 250 to 300 pounds pull for each ton
of weight upon them, in even the worst weather. On nearly level roads
(having nothing steeper than a 2 per cent grade;, a single 25 h. p. equipment
will handle a car, and in a pinch pull a trailer. Ordinarily, however, it is
not advisable to use a trail car with a single 20 h. p. equipment, as it makes
a slow start and a slow maximum speed. A single 30 h. p. equipment should
be able to handle a short car and trailer satisfactorily on roads with noth-
ing greater than 2 per cent grades. While the power of a 30 h. p. motor
could be depended upon to climb steeper grades, the adhesion of the wheels
in bad weather cannot be. Siu.gle 20 or 30 h. p. equipments will handle 20
ft. or 22 ft. cars nicely, when no trailer is used, on as high as 4 per cent
grades, and even steeper in good weather, the failure being, as previously
explained, not in the power of the motor, but in the adhesion of the wheels
to the rails. The 30 h. p. motor has the advantage of the 20 h. p. in giving
a quicker start and higher speed on grades. Single motor equipments are,
however, not advisable, on account of the liability of a single pair of drivers
to slip in bad weather. They will prove especially annoying where snow-
storms are of frequent occurrence, or where the track is liable to become
icy. All long double-truck cars should have double equipments, as their
greater weight requires greater power to bring them up to speed quickly,
even on a level. On roads with over 4 per cent grades, whether it is pro-
posed to haul trail cars or not, double equipments should be installed. A
double 25 or 30 h. p. equipment will handle a trail car on a 6 per cent or 7
per cent grade, the advantage of the 30 h. p. motors again being the higher
speed on grades and quicker start. On roads where the traffic is sufficient
to warrant the use of trailers with short cars, but the grades exceed 7 per
cent, long cars on double trucks, or radial trucks, with double-motor equip-
ments should be substituted. These will climb nearly as steep grades as
the smaller cars, without trailers. Long cars are not advisable except in
the case just named, and on long runs where the stops are few, as the time
required for the letting off and taking on of passengers is excessive.
Finally, on roads where traffic, such as fairs, base-ball games, etc., has to
be handled, giving light loads most of the time, but few exceedingly heavy
ones, the most economical arrangement is that of 30 h. p. double equip-
ments, hauling two trailers, when the heavy traffic is to be handled. This
combination can be depended upon for grades not exceeding 3 per cent in
bad and 4 per cent in good weather.
CURVES.
A 30 ft. radius curve on grade adds about as much to the resistance of a
car as 4 per cent additional grade. It will consequently be frequently
found impossible to start on such a curve on grade in bad weather without
sand. Sand boxes should, then, be a part of every car's equipment. Sharp
curves on grade should always be avoided if possible, as they are the cause
of great annoyance on wet or icy days.
423
424 ELECTRIC STREET RAILWAYS.
§TATIOHf.
A station should never contain less than two dynamos. It is desirable
also for the steam plant to be composed of two or more units if possible ;
but on very small roads, say under five cars, this is of course impracticable.
The general plan of a station should be such that the disabling of one dyna-
mo or engine could not cause a shut-down on the road. For roads of 15 cars
or less, where the fluctuations of load are exceedingly violent, simple high-
speed engines are undoubtedly to be preferred. As the road grows larger
and the load more steady, simple Corliss engines will give a somewhat better
steam consumption. On a road of 40 cars or more, compound condensing
engines, of either the Corliss or high-speed type, in units of such size that
at least one can be kept fairly loaded at all times, will be economical.
Always condense either simple or compound engines when water for that
purpose can be had plenty and cheap. Never use compound engines non-
condensing. Considering the increased expense and complication, together
with the difficulty in regulating under widely and suddenly varying loads,
the economy of triple-expansion engines in railway work is doubtful.
The size of the engine should be always such as to give the maximum
average efficiency with the variations of load in question. It should be
noted here that this is not the same size engine which will give the maxi-
mum efficiency at the average load.
Where it is possible, belt directly from fly-wheels of engines to generator
pulleys. Counter shafts give flexibility and make possible the use of larger
steam units, but they consume a very appreciable amount of power, and are
liable to give trouble otherwise.
Concerning the amount of power per car in generators and engines, no
general rule can be laid down, as three variables, viz., grade resistances,
curve resistances, and traffic, must be considered in this connection. 25
h. p. (rated at J-i cut off), and 30 amperes per car for roads of 5 to 10 cars,
and. 20 h. p. with 25 amperes per car for larger roads, would probably cover
the demands. This, hoAvever, should be considered only as a rough esti-
mate. The question of the amount, character, and location of power should
be settled for each road separately by a thoroughly competent engineer, as
a small variation from correct principles and design in this respect is liable
to considerably increase the running expenses. The whole design should
be based on Sir Wm. Thomson's principle, namely, that " The interest on
the investment and the cost of such losses as could have been avoided by
larger investment should be equal."
SPECIFICATIONS vs. STA1¥I>JLI6» TYM3S.
The series motor can easily be designed to fill two conditions as to
speed and power in the same machine, provided always that the condition
for the lesser power calls also for the greater speed, and that these two
requirements are not too near alike in speed when the powers called for
vary widely or vice versa — too near alike in phase when the speed varies
widely.
Standard motors for street-railway work are now designed to give a 20-ft.
loaded car a speed of from 20 to 22 miles per hour on a level, and to develop
NOTE. — In the selection of engines for electrical railway work, the best
practice of to-day is to choose the engines in the same manner as for any
other commercial manufacturing plant. For large installations, or where
storage batteries are used for regulating the load, and so retaining fairly
constant power requirements, the size and arrangement of the plant will
determine whether the engines should be simple, compound, or triple expansion,
and whether they should be run condensing or not, if water is a callable
Engines should be designed with all shafts, pins, wearing surface, etc.,
heavy enough for the maximum loads or brer loads, but their cylinders
should be so proportioned that the average loads be secured at the most
economical point of cut-off. This gives strength for heavy load and economy
for average conditions.
Countershafts with friction clutches and pulleys are seldom installed
to-day. Either direct-belted or direct-connected engines and dynamos are
belter, rc(/uiring less engine-room area, expense for real estate, building, etc.,
and reduce friction losses aud cost of repairs. J- S. G.
MOTORS AND TAX EQUIPMENT. 425
their full rated capacity (of 20 h.p., 25 h.p., etc.), at a speed of 10 miles per
hour, when mounted upon wheels of a specified diameter (generally 33 inch).
The voltage being kept the same, each speed corresponds to a certain
horizontal effort or thrust at the circumference of the wheel, this horizontal
effort increasing as the speed decreases. Therefore, for each different
tractive resistance, he it due tc the condition of the track, to grade or
curve, or to whatever cause, has for a given weight of car and load, a given
speed which cannot be altered wi tin >ut altering at the same time the two
speeds which the motor was originally designed to give. These speeds are
most easily altered by changing the diameter of the wheel to a larger or
smaller size than the standard, according as it is desired to increase or
decrease the speed, or in S. R motors by changing the ratio of the gearing.
In asking for designs for special motors, the weight of the maximum train
and the maximum speed on level, together with the weight of the maximum
train and the highest speed on the maximum grade, should be given. As
before stated, within limits, any conditions as to speed on level and on
grade can be approximated by special design.
DESIRABLE POINTS I1V MOTORS AITD TAX
EO.UIPMEIST.
It is desirable that motors should be electrically sound, i.e., that their
insulation should be high, mechanically strong, and waterproof. It is of
great advantage in this connection if the entire frame of the motor can be
insulated from the car truck and consequently from the ground, thus re-
lieving the insulation of the armature and fields of half the strain. The
mechanical difficulties in the way of accomplishing this, however, go a great
way towards counterbalancing the advantage gained.
A high average efficiency between three h.p. and full load should be ob-
tained if possible, but mechanical points should not be neglected to obtain
this.
A motor should run practically sparkless up to § of its rated capacity. A
low starting current is especially desirable, and for obtaining this nothing
can equal a multiple series controlling device, which cuts the starting cur-
rent actually in half. This device also enables cars to run at a slow speed
with far greater efficiency than any other method.
Mechanically, the motor should be simple. The fewer the parts, and es-
pecially the wearing parts, the better, It should be well encased in a cover-
ing strong enough not only to keep out water, pebbles, bits of wire, etc.,
encountered on the track, but to shove aside or slide over an obstruction
too high to be cleared. At the same time, the case should be hinged so
that by the removal of a few bolts access can be had to the whole interior
of the motor. The brush holders and commutator should be easily accessi-
ble through the traps in the car floor at ail times. As much of the weight
of the motor as possible should be carried by the truck on springs ; if
practicable, all of it. This arrangement saves much of the wear and tear
on the tracks.
A switch in addition to the controlling stand should always be provided,
by which the motorman himself can cut off the trolley current, in case of
accident to the controlling apparatus.
Roads having; long, steep grades should have their cars provided with a
device for using the motors as a brake in case the wheel brake gives out.
There are several methods of accomplishing this, but limited space pro-
hibits any description of them.
Last, but by no means least, all wearing parts should be capable of being
easily and cheaply replaced.
NOTE. — Double brakes or track brakes should be used on roads with
steep grades. Power brakes a,re seldom, used on ordinary cars. With the
increase in the length, and weight of cars they will probably come into more
general use, and orders hare been issued by the Railroad Commission of the
State of New York that all street cars must be equipped ivith power brakes.
426
ELECTRIC STREET RAILWAYS.
WEIGHTS OF BAILN.
Pounds per
"Weight per Mile.
Weight per 1000'.
Yard.
Long Tons.
Long Tons.
640
^986.7
25
392240
320
39.286
7~2240
2080
7.441
30
472240
47.143
82240
8.929
35
55
1920
55
933.3
10 2240
2026.6
10.417
40
622240
1600
62.587
11 2240
880
11.905
45
702240
960
70.714
132240
635.5
13.393
48
742240
1280
74.428
14 2240
1973.3
14.284
50
782240
1600
78.571
14 2240
1066.7
14.881
52
812240
960
81.714
15 2240
826.6
15.477
55
862240
86.428
16 2240
16.369
56
88
320
88
1604.4
16 2240 .
586.7
16.667
58
2240
2080
91.143
17 2240
1920
17.262
58J
912240
640
91.928
172240
920
17.411
60
942240
960
94.286
172240
1013.3
17.857
62
972240
97.428
18 2240
1680
18.452
63
99
1760
99
182240
2013.3
18.75
63£
992240
1ftJ20
99.785
18 "2240
773.3
18.899
65
102
U 2240
in„1600
102.143
19 2240
1440
19.245
66
103
2240
103.714
192240
1773.3
19.643
66|
1042240
1ftK640
104.5
19 2240
2106
19.792
67
1 05 — —
2240
1920
105.286
2240
533.3
19.940
68
1062240
106.857
20 2240
2000
20.238
70
110
111280
2240
110
202240
293.3
20.833
71
111.125
21 2240
21.131
WEIGHTS OF RAILS. 427
WFICJHTS OF M AIL§ — Continued.
Pounds pei-
"Weight per Mile.
Weight per 1000 '.
Yard.
Long Tons.
Long Tons.
320
960
72
11322io"
1920
113.143
212240
720.2
21.429
75
1172^40
117.857
22^240
2053.3
22.322
77
121
«™ 320
121
22 2240
480
22.917
78
122 ■
2210
1600
122.143
232240
1813.3
23.214
80
1252240
1920
125.714
23 2240
906.6
23.810
82
1292240
1280
129.857
24 2240
666.6
24.405
85
2240
960
133.571
25 2240
1760
25.298
90
1412249
141.428
262240
186.6
26.786
91
143
143
27 2240
373.3
27.083
98
154
320
154
29^240
1706.7
29.167
100
1572240
157.143
29~2240~
29.762
For iron or steel weighing 480 lbs. per cubic foot : Cross-section in square
inches = weight in lbs. per yard -J- 10.
For iron or steel having J conductivity of copper : Weight in lbs. per yard
-^-11.6333 = number of 0000 B. & S. copper wires with combined equivalent
carrying capacity. Also, weight in lbs. per yard X 18189.1 = C. M. of equiva-
lent copper wire.
KJLDIXJS OF CURVE! FOR DIFFEREJX CJI8ABES
OF CXTRVATURF.
3
0
© ^
1
■S 3
<v
.
a>
ri
b£
£1
b£>
bo
bo
©■d
bD
£1
ft
«
ft
«
ft
«
A
&
A
«
11
1
5730
12
521
21
273
31
185
41
139
2
2865
13
477
22
260
32
179
42
136
3
1910
14
441
23
249
33
174
43
133
4
1432
15
409
24
238
34
169
44
130
5
1146
16
382
25
229
35
163
45
127
6
955
17
358
26
220
36
159
46
125
7
818
18
337
27
212
37
155
47
122
8
716
19
318
28
206
38
150
48
119
9
636
20
301
29
197
39
147
49
117
10
573
21
286
30
191
40
143
50
114
Note No. 1. — A 1° curve has a radius of 5730 feet; 2° curve, ^this;
curve, I this, etc.
428
ELECTRIC STREET RAILWAYS.
GRADES
Iltf PER CEUfT AUD RISE IN FEET.
Rise in Feet at Given Distances.
Per Cent Grade.
500 Eeet.
1000 Feet.
5,280 Feet (1 Mile).
i
2.5
5
26.4
1
5
10
52.8
1.5
7.5
15
79.2
2
10
20
105.6
2.5
12.5
25
132
3
15
30
158.4
3.5
17.5
35
184.8
4
20
40
211.2
4.5
22.5
45
237.6
5
25
50
204
5.5
27.5
55
290.4
6
30
60
216.8
6.5
32.5
65
343.2
7
35
70
369.6
7.5
37.5
75
396
8
40
80
422.4
8.5
42.5
85
448.8
9
45
90
475.2
9.5
47.5
95
501.6
10
50
100
528
11
55
110
580.8
12
60
120
633.6
13
65
130
686.4
14
70
140
739.2
15
75
150
792
Note No. 1. — For other distances interpolate the table by direct multi-
plication or division.
EIEVATIOlf OE OUTER RAIL OK CURVES.
o .
Speed in Miles per
Hour
10
15
20 25
30 35
40
45 1 50
60
ob
a
A
Elevation of Outer Rai
in Inches.
1
5730
ft
i
til
1ft
If
It*
24
2
2865
*
ft
ft
*
H
it*
2ft
2*
2ft
411
3
1910
*
t*
Aft
1*
24
3ft
4*
58
V*
4
1432
J ft
A+*
21
3S
4*
4ft
«t*
y*
5
1146
#
|
i#
2#
3ft
4ft
<*
84
12ft
6
955
tfr
i*
2ft
3H
6ft
«*
10*
7
818
HI
3
4ft
5f
u*
yft
11*
8
716
5ft
2i3g
3ft
4+ft
6t*
8i-i-
10*
9
636
8
2|
3x1
54
y*
iat*
10
573
t*
2f
4|
H
8ft
101
11
521
*
H*
3
4nf
6i
y*
lit*
12
477
t»
3ft
5*
»ta
12 J|
14
409
2ft
3x1
5tt
«T9TT
n+
16
358
lis
24
4#
fitf
9xs
18
20
318
286
W
2|
3ft
4«
5ft
8*
10|
12
Note No. 1.
— Wli
enE =
: elevation ir
i inches of o
uter r
ail above th(
s hori-
zo
ntal p
Lane:
V = velocity of car in feet per second ;
R = radius of curve in feet ;
V2
Therefore E =1.7879 —when gauge of track is 4/-8£//
429
SPIKE§.
Size.
N0-2P^Sg0f ^-Per Spike.
Spikes per Lb.
4§ Xi
533
3752
2.66
5 X/5
650
3077
3.25
5 X|
520
3846
2.6
5 XT96
393
50S9
1.96
5| x h
4G6
4292
2.33
5§ X r96
384
5208
1.92
6 XT9s
350
5714
1.75
6 X|
260
7692
1.3
SPIKES PER lOOO' AUTR PEB flttHE SIT¥€nLE
IBACK, WITH FOUR SPIRES PER TIE.
Spacing of Ties.
Per 1000'.
Per Mile.
10 ties to 30' rail
13334
7040
11 " " " "
1466|
7744
12 " " " "
1600
8448
13 ■"■"■"■ «
1733^
8152
14 " " " "
1866|-
I 9856
15 " " " "
2000
10560
16 " " " "
2133-J
11264
JOINTS
PER
MILE
OE SIltfCilE
TRACK.
Per 1000'.
Per Mile.
Joints
Angle
Bolts
— 30' rails
66§
133J
266§
400
533J
800
352
704
— 4 hole bar
6 "
8 "
12 " "
1408
2112
<(
2816
"
4224
TIES PER I©©©/
AITS PER IffflEE.
Spacing.
Per 1000'.
Per Mile.
10 ties to 30' rail
11 " " " "
12 " " " "
13 " " " "
14 " " " "
15 " " " "
16 " " " "
333i
366|
400
433J
463§
500
533i
1760
1936
2112
2288
2464
2640
2816
BOARD EEET, CUBIC FEET, AID SQUARE FEET
OE BEARIH& SURFACE PER TIE.
Size.
Board Feet.
Cubic Feet.
Bearing Surface
5" X 5" X 7/
14.56
1.213
2.91
5" X 6" X 7'
17.5
1.458
3.5
5" X 7" X 7'
20.41
1.7
4.08
5" X 8" X 7/
23.33
1.944
4.66
6" X 6" X V
21
1.75
3.5
6" X 7" X V
24.5
2.041
4.08
6" X 8" X 7'
28
2.333
4.66
6" X 9" X V
31.5
2.625
5.25
6"X10" X7/
35
2.916
5.83
6" X 8" X 8'
32
2.666
5.33
6" X 9" X 8'
36
3
6
6"X10" X 8'
40
3.333
6.66
430
ELECTRIC STREET RAILWAYS.
REPORT OF E. S. DEPARTMEJIT OF ACiRICEE-
1URE OJT DUKABIMTY OF RAILROAD TIES.
White oak 8 years.
Chestnut 8 "
Black locust 10 "
Cherry, black walnut, locust 7 "
Elm 0 to 7 "
Red and black oaks 4 to 5 "
Ash, beech, and maple 4 "
Redwood 12 "
Cypress and red cedar 10 "
Tamarack 7 to 8 "
Longleaf pine 6 "
Hemlock 4 to 6 "
Spruce 5 "
PAVIHTG.
Paving prices vary so that it is difficult to state even an approximate cost
that will not be dangerous to use. Prices are not at all alike for asphalt,
even in cities in tbe same localities ; other styles vary according to prox-
imity of material, cost of labor, and amount of competition.
Square yards of paving between rails, 4' 8|" gauge, less 4// for width of
carriage tread :
' Per 10007 run = 485.89
Per mile run z= 25G5.5
Square yards paving for 18" outside both rails :
Per 10u0' run = 333§
Per mile run = 1760
Approximate Cost of Pavin
§•• (D
ivis,
>
PAVEMENT.
Cost of all Material
and Labor.
Cost of
Tearing up
Existing
Pavement
and Repla-
cing as
Found.
6*
xix
<o
ft
O cS
5
ft
o o
ft -2
ft
£.3
Granite blocks on gravel foundation
Gravel blocks on concrete foundation .
Asphalt on concrete foundation . . .
Vitrified brick on broken stone ....
Wood without concrete
Cobble without concrete
Macadam
%
2.80
3.60
3.80
2.15
1.50
2.00
1.00
$
2.24
2.88
3.04
1.72
1.20
1.60
.80
$
12000
15500
16000
9000
8000
8500
4500
$
.35
.45
.49
.30
.50
$
1900
2400
2400
1600
2700
ESTIMATE OE TRACK IAYIIG FORCE.
One engineer, 1 rodman, 1 foreman of diggers, 1 foreman of track-layers,
4 spikers, 20 laborers, 2 general helpers. Such a gang can lay from 400 to
900 feet of single track per day.
In case it is desired to proceed more rapidly, the above number of men
PAVING. 431
should be increased proportionately, omitting the engineer and rodman, as
these two will be able to handle any ordinary number of gangs, no matter
how widely scattered, if a horse and buggy is placed at their disposal.
Tools For Track Crang- as Above.
One portable tool-box padlocked, 1 small flat car, 1 portable forge, 4 cold
chisels, 2 ball pein hammers, 6 lbs. ; 1 sledge, 12 lbs. ; 2 axes, 2 adzes, 1 cross-
cut saw, 1 large double-handled saw, 6 track wrenches, 2 monkey wrenches
1 complete ratchet track drill with bits, 1 track " Jimmy " for bending rails'
1 reel line cord, braided : 30 picks, 15 extra pick- handles, 25 long -hand led,'
roundnose shovels, 6 short handled, square-nose shovels, 10 tampers, 5
wheelbarrows, 2 track gauges, 1 level, 1 straight-edge, 4 pair rail tongs G
spiking hammers, 3 crow-bars, one end sharp, the other end chisel-pohfted
2 spike claw-bars, 1 engineer's transit, 1 leveling-rod, 10 surveyor's marking-
pins, 1 steel tape, 10 red lanterns, 1 box lump chalk, 1 squirt oil-can, 1 quart
black oil , 5 gals, kerosene, 1 flag-rod, 1 paper of tacks, 1 broad blade hatchet
RHIWAT TURJfOlJTS.
By W. E. Harrington, B. S.
For example, assume a railway to operate 4 cars, the distance between
terminals four miles, the time of round trips 60 minutes, and the headway
15 minutes, with a lay over at each end of five minutes. Take a piece of
cross-section paper, and make the
vertical lines represent distance,
and the horizontal lines represent
time.
The time necessary to run from
terminus to terminus is half of 60
minutes, less \ of ten minutes (the
layover time), "or 25 minutes. Let
each division on the ordinate axis
represent the distance traversed by
a car in one minute, which in the
above case is 844.8 feet per minute, as-
suming that the car is to run at the
average speed of 9.6 miles per hour.
Let each division on the axis of ab-
scissas represent five minutes. The
first car will travel from terminus to
terminus as represented by the diag-
onal line OA. Tllis lirie shows the
car's position at any instant of
time, assuming, of course, that the
car is running at a uniform rate of
speed. The car upon its arrival at
the other terminus will have a lay-
over of five minutes as repre-
sented bv the horizontal space AB.
Upon the expiration of the time of lay-over the car starts upon its return
run. This determines the locus of the several turnouts, as the car has to
pass each of the remaining cars. The line of the return run is represented
by the line BC. Upon the arrival of the car at the original terminus and a
lay-over of five minutes, the cycle of trips will be repeated. During the
time the first car is running its round trip the other cars are leaving at in-
tervals of 15 minutes, as represented by the lines DE, FG, and HI. Where
these three lines intersect the line BC turnouts must be located, as the cars
meet and pass at these points. The distance apart of the turnouts, as well as
their distance from the starting terminus O, may be readily determined by
projecting the intersections on the axis of ordinates OY.
1. The number of turnouts for a given number of cars is one less than the
number of cars running. . • .
Eig. 1.
Location of Street Bailway
Turnouts.
432 ELECTRIC STREET RAILWAYS.
2. The time consumed running between turnouts must be the same
between all the turnouts. For instance, if it is found necessary to irregu-
larly locate turnouts for any reason, then the time consumed by a car run-
ning between these two turnouts farthest apart determines the time the
cars must run between the remaining turnouts, even though two or more of
the turnouts be only a slight fraction of the distance apart of the two
greater ones.
3. The time consumed running between two consecutive turnouts is one-
half the running time between cars.
For determining the distance apart of turnouts without the aid of graph-
ical methods :
Rule. — To the length of the railway from terminus to terminus add the
distance a car would travel running at the same rate of speed as running on
the main line, for the time of lay-over at one terminus. Divide the above
result by the number of cars desired to be run, the result is the distance
between turnouts. Multiply this latter result by two less than the number
of cars, and deduct the result obtained from the length of the line from ter-
minus to terminus, and divide by two. The result is the distance from
either terminus and the first adjacent turnout.
To operate more or less cars on a railway than it is designed for is a ques-
tion most frequently met in railway practice.
Rule 1 tells us that Ave must have one turnout less than the number of
cars running. In Fig. 1 we have four cars and three turnouts. If we pro-
pose running three cars we would use two turnouts, by omitting the middle
turnout. The result is at once apparent ; for according to Rule 2, the time
to run between turnouts is determined by the time consumed in running
between those two turnouts farthest apart. Since the distance is doubled,
the time consumed is doubled. Where with four cars, with fifteen minutes
between cars, and sixty minutes for the round trip, with three cars the time
between cars as by Rule 2 is thirty minutes, and the time of round trip is
ninety minutes, making at once a very pronounced loss.
The better plan, and the one usually pursued by railway managers, is to
run the lesser number of cars on the same trip time as the railway was
designed for. In our example above, the three cars would be run as if the
four cars were running, with the exception that the space which the car
should be running in will be omitted, leaving an interval between two of
the cars of thirty minutes, giving only the loss occasioned by the omission
of one car.
Another method to pursue, especially so where additional cars will be
run at times, such as holidays, excursions, and other times of travel requir-
ing more than the regular number of cars to accommodate the travel, is to
provide and locate more turnouts. The expense of doubling the number of
turnouts, while they would be a great convenience, would not be warranted
without the railway were doing a large and growing business, Avith a fluctu-
ating number of cars in service. Two cases should be considered.
First — If a certain fixed number of cars are to be operated for the greater
portion of time and the extra cars for odd and infrequent intervals, locate
the turnouts to suit the regular business.
Second — In the case of a railway running an irregular number of cars —
for instance, a railway running a heavy business at certain times of the day
— as the lesser number of cars are subordinate to the greater number,
locate the turnouts to run the greater number of cars the most efficiently.
In conclusion, we might state that the grades, the running through
crowded business streets, stoppages occasioned by grade railroad crossings,
and varying business, all enter in and must be considered while designing.
Block Signal for Single-Track Roads or for Itridg*es, etc.
M. S. Wightman has designed a system which is operated automatically
by the passage of the trolley wheel along the wire, as follows :
Suppose a car passing south from the north siding, its trolley makes con-
tact at " make hanger a'," current passes through magnet A/, white lamps
W/, plunger contacts RS — AVSR — red lamps R' to ground. Plunger is then
raised connecting contacts TM. Current then flows from trolley through
contacts TM, magnet A', white lamps W, contacts WSM — L, — line, con-
RAILWAY TURNOUTS.
433
tacts in box at south switch, L — WSM, contacts WSB — RS, through the
red lights to ground. This condition remains until the car passes "break
hanger" contact a2 ; the trolley while striking the " break hanger a2" mo-
mentarily excites magnet B, raising the plunger and breaking the signal
WIGHTMAN BLOCK SIGNAL
Fig. 2.
circuit at WSM — L, this in turn de-energizes magnet A/, its plunger drops
to its normal position, breaking the circuit at TM, and the signal is " off."
The same action in a reverse direction takes place when a car passes out of
the south siding going north.
Another method, a manual one, is in use by the Lehigh Valley Traction
Co. on all the street railways in and about Allentown and Bethlehem, Penn.
One advantage claimed for this system over an automatic method is, that
the conductor is responsible for maintaining his own right of way.
The system is operated as follows : A conductor before entering a section
between switches pushes a switch-rod, which sets a signal at the turnout
SIGNAL SETTING BOX
Fig. 3.
ahead, a magnet operating a red semaphore and incandescent lamps be-
hind a red glass disk. This makes the signal visible both night and day.
This semaphore stays set until he reaches the switch ahead ; then the con-
ductor opens the circuit which sets the track behind him to safety. If on
reaching the switch he finds the semaphore is set to danger, he has to wait
434
ELECTRIC STREET RAILWAYS.
on switch until ear passes. Conductors only set semaphores ahead of them
and release those behind ; the car is controlled by semaphores operated by
the conductors of cars passing it at the switches, and the signal systems for
cars operating in opposite direction are entirely independent. In each
signal box there is also a pilot lamp which is extinguished when the section
of track is opened, and illuminated when the section is closed ; this gives
RAILWAY TURNOUTS.
435
the conductor knowledge that his signals have operated properly at the
distant switch. As the first signal set gives the right of way, there is no
meeting between switches. The detailed description is given below.
There are three separate operating parts, — a signal setting-box, a signal
releasing-box, and the semaphore box.
The signal setting-box is shown with details in Fig. 3. The magnets are
11 in. x 1\ in. winding-space with fiber heads, and | in. core ; the end of the
iron cores exposed to the armature are tipped with platinum or silver, and
the armature B is also faced as these surfaces come together and complete
>\
Ti
j
1
I
^T
J_
up
N WIND WITH
20 O.C. COVERED
Fig. 6.
the circuit and are held in contact by this current also passing through the
magnets. The armature B normally rests out of the influence of its magnet.
A rod entering from the bottom of this box shoves the armature up into con-
tact with the ends of the magnet, and is held in this position until the circuit
is broken.
The current from the trolley enters first through a lamp, then through
the magnet-winding to the frame. When the armature is up the current
passes down the arm holding the armature, and then through the signal line
to the distant semaphore box.
The semaphore box contains a pair of solenoid magnets, which set the
semaphore disk and light the lamps. These lamps are arranged behind a
red glass disk inserted in the semaphore box. The disk is set by means of a
solenoid operating a bell crank and link, which turns the semaphore rod
and displays the red disk. The dimensions and methods of general con-
struction employed are shown in Fig. 6. The circuit first passes through
three lamps, then through the solenoid, and out to the signal releasing-box.
The construction of this box is shown in Fig. 5, and consists of a switch and
a lamp in circuit with this switch. It is operated by pushing up the rod,
and when the rod is released the blade falls back into position, but it will
not close the circuit iioav ; for on opening the circuit, the magnet in the cir-
cuit-making box dropped its armature, and opened the current at the dis-
tant switch, which can now only be closed by the conductor on the car
following. The diagram of connections is given in Fig. 4. Covered No. 10
iron wire can be used. Robert Doumblaser developed all the details.
436
ELECTRIC STREET RAILWAYS.
EIST OE MATERIAL 1SE(41"IKEI» EOR (tt'B MTEE
OE OVERHEAD OAE FOR ELECTRIC
STREET RAILWAY.
1 Mile Overhead.
Curve Overhead
Material.
Anchor-
Material for
Railway
Construction.
Cross
Suspen-
sion.
Bracket
Suspen-
sion.
Main
Line.
Branch
Line.
i
o
age.
H
M
33
■ H
P
o
H
3d
33
H
la
o
ft
'3d
33
H
3
o
ft
33
H
a?
O
A
33
O
ft
u
No. 0 B. & S.
H. D. Trolley
Ft.
Lb.
-,1'SO
10560
3369
52S0
ION,")
10560
3369
250
80
o
O
No. OB. &S.
S.D. F'd'rT'ps
Ft.
Lb.
400
154
500
192
90
35
180
69
3
7 strand
No. 12 span
Ft.
Lb.
:;<;oo
756
3600
756
800
168
koo
168
soo
168
KOI)
168
200
42
400
84
600
122
>
1
7 strand
No. 15 guy
Ft.
Lb.
;;ooo
300
4500
450
1500
150
2000
200
100
10
100
10
100
10
100
10
Plain ears ....
Strain ears ....
Splicing ears . . .
Feeder ears ....
45
1
10
45
45
90
2
20
45
1
10
45
45
90
2
20
5
2
7
10
4
4
4
5
1
6
6
15
2
"If
17
4
4
4
—
Insulating caps . .
Insulating cones . .
90
90
90
90
M O
w
Straight line . .
Single curve . .
Double curve
Bracket . . .
45
90
45
90
3
4
3
11
3
12
4
2
2
i
Stra
Tur
Sect
Froj
Fro
Har
Eye
Cas1
Gas
Cros
in insulators . .
abuckles . . .
ion insulators
90
90
2
45
90
45
90
90
4
45
90
45
45
45
48
4
90
90
48
4
4
2
4
4
2
2
2
1
2
2
1
2
2
2
y crossings . . .
dwood pins . .
2
-iron brackets .
pipe arms . . .
s arms (l^'-lS) .
Cros
&
Boll
r("
Lag
et
Lag
ar
Lag
s-arm braces
'X8")
s for brackets
'X4")
90
45
144
90
45
144
45
45
90
90
screws for brack-
3 (i"X7'0 . . .
screws for cross
ms(!"x3") . .
screws for braces
Poles, 125-ft. apart .
90
90
45
45
2
2
2
2
2
2
Cha
Bon
Ligfc
anel pins . . .
ds
800
400
1600
800
KOI)
400
1600
800
tning arresters .
3
3
3
3
Section switch boxes
2
2
2
2
PLATE BOX POLES.
437
Plate Box Poles.
BY BUFFALO BRIDGE AND IRON WORKS
=LO=L SCREW PIN:
M
438
ELECTRIC STREET RAILWAYS.
TUBULAR IRON OR STEEL POLES.
By Morris, Tasker, & Co. (Inc.).
Size.
Wrought Iron or
Steel.
Length.
Weight.
No. 1, light .
No. 1, heavy
No. 2, light „
No. 2, heavy
No. 3, light .
No. 3, heavy
No. 4, light .
No. 4, heavy
5 in., 4 in., 3 in.
5 in., 4 in., 3 in.
6 in., 5 in., 4 in.
6 in., 5 in., 4 in.
7 in., 6 in., 5 in.
7 in., 6 in., 5 in.
8 in., 7 in., 6 in.
8 in., 7 in., 6 in.
27 ft.
27 ft
28 ft.
28 ft.
30 ft.
30 ft.
30 ft.
30 ft.
350 lbs
500 lbs
475 lbs
700 lbs
600 lbs
1000 lbs
825 lbs
1300 lbs
POLES.
Dimensions and W^eig-hts W^roug-ht-Iron and Steel Poles.
Length.
Diameter.
Weights.
27 ft.
28 ft.
30 ft.
30 ft.
28 ft.
30 ft.
5 in., 4 in., 3 in.
6 in., 5 in., 4 in.
6 in., 5 in., 4 in.
7 in., 6 in., 5 in.
8 in., 7 in., 6 in.
8 in., 7 in., 6 in.
350 lbs. to 515 lbs.
475 lbs. to 725 lbs.
510 lbs. to 775 lbs.
600 lbs. to 1000 lbs.
775 lbs. to 1260 lbs.
825 lbs. to 1350 lbs.
Cubic Contents of Wooden Poles, in Eeet.
Length.
Diameter.
Section.
Cubic Feet.
27 ft.
6 in. X 8 in.
Circular
7.36
27 ft.
7 in. X 9 in.
Circular
9.56
27 ft.
7 in. X 9 in.
Octagonal
10.1
28 ft.
7 in. x 9 in.
Circular
9.92
28 ft.
6 in. X 9 in.
Octagonal
10.46
28 ft.
8 in. x 10 in.
Circular
12.52
28 ft.
8 in. x 10 in.
Octagonal
13.2
30 ft.
7 in. x 9 in.
Circular
10.63
30 ft.
7 in. x 9 in.
Octagonal
11.21
30 ft.
8 in. x 10 in.
Circular
13.41
30 ft.
8 in. X 10 in.
Octagonal
14.15
30 ft.
9 in. X 12 in.
Octagonal
19.06
Rake of Poles.
Wooden poles should be given a rake of 9 to 18 inches away from the
street. Iron or steel poles set in concrete need be given but 6 to 9 inches
rake. Corner poles, and those supporting curves, should be given additional
rake or be securely guyed.
AVERAGE WEIGHTS OF WOOD.
439
AVERAGE WEIGHTS ©IT VADIOUS WOODS, IJ¥
POUUfBS.
osa? isl
Live oak
White oak ....
Red oak
Chestnut
Southern yellow pine
Northern yellow pine
Long-leaf yellow pine
Norway pine . . .
Spruce
Hemlock
Perfectly dry
Perfectly dry
Perfectly dry
Perfectly dry
Perfectly dry
Perfectly dry
Unseasoned
Perfectly dry
Perfectly dry
Perfectly dry
The weight of green woods may he from one-fifth to one-half greater than
the weight when perfectly dry.
DIP Il¥ SPAUT WIRE.
(Merrill.)
The following tables give the dip of the span wire in inches under the
combined weight of span wire and trolley wire, for various spans and strains.
Length of trolley wire between supports, 125 feet. Weight of trolley
wire, 319 lbs. per 1000 feet. Weight of span wire, 210 lbs. per 1000 feet.
Single Trolley "Wire.
Spans in
Strain on Poles, in Pounds.
Eeet.
500
800
1000
1500
2000
2500
3000
30
7.8
4.9
3.9
2.6
1.9
40
10.6
6.5
5.3
3.5
2.7
50
13.6
8.5
6.8
4.5
3.4
2.7
60
16.7
10.4
8.3
5.6
4.2
3.3
2.8
70
19.9
12.4
9.9
6.6
4.9
4
3.3
80
23.2
14.5
11.6
7.7
5.6
4.6
3.9
90
26.7
16.7
13.4
8.9
6.6
5.3
4.5
100
30.3
18.9
15.2
10.1
7.6
6.1
5.1
110
34
21.3
17
11.3
8.5
6.8
5.7
125
37.9
23.7
18.9
12.6
9.5
7.6
6.3
Two Trolley Wires, 1© Feet
Apart.
Span in
Strain on Poles, in Pounds.
Feet.
500
800
1000
1500
2000
2500
3000
3500
40
15.4
9.6
7.7
5.1
3.9
3.1
50
20.8
13.
10.4
6.9
5.2
4.2
60
26.3
16.4
13.1
8.8
6.6
5.3
4.4
70
31.9
19.9
15.9
10.6
8.
6.4
5.3
80
37.6
23.5
18.8
12.5
9.4
7.5
6.3
5.4
90
43.5
27.2
21.8
14.5
10.9
8.7
7.3
6.2
100
49.5
30.9
24.8
16.5
12.4
9.9
8.3
7.1
110
55.6
34.7
27.8
18.5
13.9
11.1
9.3
7.9
120
61.9
38.7
30.9
20.6
15.5
12.4
10.3
8.7
Note. — See also chapter on Conductors.
For table of stranded wire for spans and guys see page h 18, Properties
of Conductors.
440
ELECTRIC STREET RAILWAYS.
Span wires should be stranded galvanized iron or steel, sizes J inch
diameter &, J, or § inch according to the weight of trolley wire, etc., to be
supported. Where wooden poles are used it is not necessary to provide
other insulation for the span wire, and the wire can be secured to the loop
Fig. 8. Section of Track and Overhead Construction in Broad Streets,
showing Double Overhead Wires and Underground Feeder Conduits.
Section of Track and Overhead Construction in Narrow Streets,
showing Overhead Pipe Brace.
Trolley Suspension for Havana Streets, as developed by
F. S. Pearson.
SIDE BRACKETS.
441
of an eye-bolt that is long enough to pass through the pole at a point from
twelve to eighteen inches below the top, and that has a long thread to allow
taking up slack. On many roads in the country the span wire is simply
wrapped around the pole top, using a number of feet more wire, making it
difficult to take up slack, and presenting a slovenly appearance. Where
metal poles are used it is necessary to insulate the span wire from the pole
This has been done in some cases" by inserting a long wooden plug in the
top of tubular poles, capping it with iron, the wooden plug then being pro-
vided with the regular eye-bolt. The most modern way is to provide a good
anchor bolt or clasp on the pole, then insert between the span wire and this
bolt one of the numerous forms of line or circuit-breaking insulators devised
for the purpose. If the anchor bolt is not made for taking up slack, the insu-
lating device can be so designed as to be used as a turnbuckle. Of course
insulation must be provided for both ends of the span wire.
Span wire must be pulled very taut when erected so that the sag under
load will be a minimum. Height above rail surface should be at least 18
feet after the trolley-wires are in place. This height is regulated by statute
in some States, and runs all the Avay from IS to 21 feet.
Figures 8, 9, and 10 illustrate one of the most modern installations, that
at Havana, Cuba, as designed by Mr. F. S. Pearson for double trolley.
\feh
*0 COPPER1. 'galv.iron
STRETCHED
FIG. 10. Views of Trolley Spans with Plus and Minus Feeder connections
and Plan of Double Track Y, showing Location of Insulators.
SI»E BRACKETS.
Along country roads and in such places as the track is along the side of
the roadway or street, it is customary to use single poles with side brackets
to support the trolley wire.
Where side brackets are used it is not safe to place the pole less than four
feet away from the nearest rail, and to give flexibility to the stranded sup-
porting wire, now always provided for the trolley wire, the bracket should
be long enough to reach the distant rail, thus giving a little more than two
feet of cable for flexibility. A common length of bracket is 9 feet.
Figures 11 and 13 show the simple form of side bracket in most general
use, and Figs. 12 and 14 show variations of the same. It is obvious that this
method of support may be made as elaborate and ornamental as may be
desired.
On double-track roads center-pole construction is sometimes used, in
which poles are placed along the center line between the two tracks, and
brackets are erected on each side of the poles overhanging the tracks.
Where wooden poles are vised a good form of construction is to bore the pole
at the proper height and run through it the tube for the arms, this long
tube being properly stayed on both sides of the pole by irons from the pole-
top to the bracket ends, or by braces against the pole. The trolley support-
ing wire can extend from end to end of the brackets through the pole, or
442
ELECTRIC STREET RAILWAYS.
can be cut at the pole, and eye-bolts be used, as in tbe side-bracket construc-
tion shown by Eig. 11.
Fig. 11. Single Suspension.
For Wood Poles.
Figures 15 and 16 illustrate simple forms of center-pole brackets.
Fig. 12. Single Suspension.
For Wood Poles.
Center-pole construction is quite often used on boulevards in cities where
tbe brackets and poles can be made quite ornamental.
Fig. 13. Single Suspension.
For Iron Poles.
TROLLEY WIRE SUSPENSION.
443
Fig. 15. Double Suspension. For Wood Poles.
FiG. 16. Double Suspension. For Iron Poles.
TROLLEY WIBE SUSJPEWSIOW.
The support of the trolley wire along straight lines
is a. simple matter and needs no explanation ; at
curves and ends there have been some simple forms
developed in practice that are handy to have at
hand. FolloAving are some of the points :
Terminal anchorag-e. — Single track. See
Fig. 17.
Line anchorag'e.-See Figs. 18 and 19. To be
placed at the foot of all grades, at the top of hills,
and at tangents, three (3) per mile is good practice ;
where curves are frequent they will afford all the
anchorage necessary.
444
ELECTRIC STREET RAILWAYS.
Fig. 18. Single Track.
Fig. 19. Double Track.
Turnout and Siding* Suspension. — Following is a sketch of a
very simple arrangement of suspension and guys for a single-track turn-out.
Fig. 20.
Curves, Suspension, and Ours. — The suspension of the trolley wire
at curves is complicated or simple, according as the track may be single or
double, or the curve may be at a crossing or a simple curve. Below are
sketches of several types of suspension for different forms of curves, for
single and double track, for cross suspension, and for center-pole construc-
tion.
Fig. 21. Simple Right-angle
Curve, Single Track.
Fig. 23. Double Track, Right-angle Fig. 24. Double Track, Right-
Turn, Cross Suspension. angle Turn, Center Pole.
Crossing's, Suspension, and Guys. — Simple crossings of tracks
make no complication in the suspension of the trolley wires. When curves
are added to connect one track with the other, complications begin, and
GUARD WIRES.
445
where double tracks cross double tracks, aud each is connected to the other
by curves each way, the network of trolley wires becomes very complicated.
Following are sketches of a couple of simple crossings which will clearly
enough illustrate the methods of suspension commonly used.
L
Fig. 25. Single-Track Cross- Fig. 26. Single-Track Crossing,
ing, Cross Suspension. Cross Suspension.
€HJAIt» WIRE§.
Where trolley Avires are used in cities or in any location where there are
other overhead conductors liable to fall across the trolley wire, it is custom-
ary to place guard wires parallel with but above the trolley wire, as shown
in the following sketch. A piece of No. 6 B. & S. galvanized iron or steel
CROSS SUSPENSION WITH GUARDS
FOR TROLLEY^WIRE
Fig. 27.
wire is drawn taut above the regular suspension wire ; porcelain insulators
are secured to the same at a point about a foot or 18 inches either side of the
trolley wire, and through these insulators is threaded and tied a No. 10 gal-
vanized iron wire. This guard should be broken at least every half-mile
where it is in any great length, as it is not advisable to have it a continuous
conductor for any great distance, and it is advisable to avoid its use wher-
ever possible.
IBMETEJtlMlSATTOlSr OF MOST ECOlVOlfllCAI, »«]¥-
SIXT OF CrRBEIl O STREET RAILWAY
COWBXCTOItS.
(See Chapter on " Conductors," also paper by Mr. H. M. Sayers.*)
Wherever there is danger of interference with other properties from elec-
trolysis it is desirable to have the drop in rails quite low, the B.T. regula-
* See Trans I. E. E. for July, 1900.
446 ELECTRIC STREET RAILWAYS.
tions being 7 volts between points on rails. This of course means track
return feeders, and in some cases "negative boosters," or boosters on the
track feeders.
The formula was developed by Professor Perry from Kelvin's law, and
following is Mr. Sayers's application of it to tramway work : —
formula for Determining- tlie Most Economical Current
Density and Drop in Conductors for Tramway Lines.
R =. percentage or rate to be charged on complete cost of cables laid ready
for use, representing interest and depreciation and maintenance, say
7 per cent.
Hours run per year, at 15 hours per day, for 365 days = 5475.
w= number of watts continuously wasted in distributing system, that
would cost one dollar, at a rate of 1.5 cents per k.w.
100 cents 10 1Er ...... , __
— £^i — ; — tit- = 12. 15 watts for one dollar.
5475 X 1.5
1000
p = cost of copper per ton of 2000 lbs. @ 30 c. per lb. laid complete readv
for use = $600.
m= tons (2000 lbs.) copper per mile fori square inch cross-section = 10.2
tons.
r = resistance per mile of copper of 1 square inchcross-section= .0455 ohms.
t= most economical drop per mile in volts.
then ^jR.w.p.m.r. _ -\/7 X 12.15 X 600 X 10-2 X -0155
_ 100 100
t — V 236.8 = 15.37 volts per mile.
t— — = — — — =z 388 amperes per square inch.
.0455 .0455
It is obvious that the distance that the current can be transmitted at the
economical density is limited by the permissible drop in the distributing
system. The total drop is usually divided somewhat as follows, and is
varied to suit conditions.
Drop in feeders 50 volts.
Drop in trolley 5 "
Drop in track return 5 "
Drop in return feeders (boosted) .... booster.
Thus the distance over which an unboosted feeder will carry current with-
out exceeding the drop is determined as follows :
50 volts drop in feeder „ __ „ . ...
— — -— .^ ., rr- = 3.25 miles, m this case.
t =z 15.3* volts drop per mile
Where feeders are " boosted" it is necessary to introduce in the formula,
the factors of the cost of the booster and its losses, changing the value of
" w " and therefore that of " t" let
a =z cost per annum per k.w. for interest and depreciation on cost of
booster, say $7.50.
b = cost per annum for supplies and maintenance of booster, say $2.50,
say the efficiency of the booster is 75 per cent,
100
and w = — „nopT , ^ „ — - — — = 8.37 watts for 1 dollar.
/.1827 + 1.5 X 100\ 5475
\ 75 )X 1000
Using the same values as in the first equation,
. _ / 7 X 8.37 X 600 X 10.2 X .0455 ,
f — 4 / Job" — Vi63 — 12.76 volts per mile.
t 12 76
and -ttjv^ = ri = 281 amperes per square inch as the most economical cur-
rent density for boosted feeders.
Determination of the most economical drop, or limiting distance on the
track may be made by the above formulae, but calculations may be expe-
dited by use of a constant, as follows. Let
HORSE-POWER OF ACCELERATION.
447
c = constant for ampere miles.
«.= resistance of track per mile, say .03 ohms.
d = limit of drop permitted in rails, say 5 volts. Then
c = — = — =166 ampere miles.
Thus, if each car requires an average of 20 amperes the limit in miles of
track for a drop of 5 volts would be for the above values, 166 — (20 x no. of
cars, say 5) = 1.66 miles, provided all tbe cars were bunched at the end, or
that one or two cars were ascending a heavy grade, requiring the same
amount of current. To determine the greatest length of track that can be
economically used without feeders, Adhere cars are scattered along a line,
the distances intervening between the power-house, or other power or feed-
ing center, and each car, are multiplied by the amperes required per car,
and the sum of these products must not exceed the value of " C," as follows :
1 car .5 miles from power-house, 20 amperes c = 10
1 " 1.5 " " " " 20 " c= 30
1 " 3. " " « " 20 '• c= 60
1 " 5. " " " " 20 " c = 100
Total c = 200
In this case c = 200, or more than the limit of 166 ; therefore tbe feeder
point must be between the third and fourth cars, and the distance will be
governed much by the grade between these points, for it is obvious thai;
each of the above cars will take a much larger current than stated when
ascending grades, and the value of this extra current must be carefully
determined before making the calculations.
HORSE-POWER ©JF ACCEIERATIO]¥.
The following diagram shows the power required to accelerate one ton,
when running at any speed, to the next higher speed in miles per hour.
HORSE-POWER EXERTED FOR EACH TIME.
1
5
—10
1
5
20
25
3
5
35
4
3
-4
5
50
/
/
j
/
/
/
/
/
/
/
/
1
/
1
/
/
/
/
/
gJ_
1
/
1
U\
/
/
/
/
w
£
1
t
/
/
/
y
§1
ih
-■?/
/
/
/
j\
/
« *
it!/
,*7
\i i
-A
?/
*>/
/
/
r_5M7
o/
i/\J/
2zz:
i
r~T
/
r$~i
W& -
8
?/
//
j
I
*w
HORSE
PO
WEF
*
/
7
■/
ffs
Ly
1/
NECESS
!E-tERA-T
1 B
AKY
:-on
(
TO
E-TC
~T
/
/
1 1
/
/ /
>
_f
/
'/
i
//
/
u
/
C
HARLES HENRY DAVIS
C.
I.
T
//
>/
//
'/.
/
CONSULTING
ENC
IN.EE
R.
_T
'/
//
//
//
/
/
//
//
'A
/
NOT
3TH
>. NE
;ess
RY T
0 AC
:ele
^ATE
OTH
:r
///
///
w
T.HI
S, MULTIP
! DIAGRAM
1
?ED IN TO
LY T
BY T
E H.
HE W
200
P. FOR Q\
:iGHT;-TO
1 LBS-, TH
E TON AS
iE ACCEL
JS: FOR 2
FOU
RAT
0 —
///
^
/
§
/
M
JLTI
! 2;
OR 3
TONS
BY :
1 ET
7
-
Fig. 28. Copyrighted, 1901, by Charles Henry Davis. All rights reserved*
448
ELECTRIC STREET RAILWAYS.
Power Curves. — For convenience in quickly ascertaining the horse-
power required to propel a car of known weight under known conditions of
speed and grade, the curves shown below have been calculated.
The quantities which the various lines represent are clearly marked in
the cut, but for the benefit of those who may be unfamiliar with such dia-
grams, the following explanatior /.-■ inserted: The left-hand portion of the
lower horizontal line represents t_ie speed in miles per hour ; the right-hand
portion of same line, the h. p. per car ; the oblique lines in left-hand side of
cut, the per cent grade as marked on each line ; the oblique lines on right-
hand side of cut, the weight of car as marked ; while the vertical line in
centre of cut represents the h. p. per ton.
\
\
\
<N
o
\
\
\
\
\
\
\
o
K
\
o
<
\
<N
Ki
\
CO
\
\
\
o
s.
\
\
\
V\
0
o
\
N
X
%.
z
<
S
t
•*£
>
■ A
\
i\
\
c:
z
-v?
4 <7
\
V
s
%
fc\
I
°
u*
o>
'S
r
o
>
*\
\
\
*"
a
<*\?o
N
\
* 0
^
\
\
\
5,
\ \
0
CO
7p-
~^
N
\
\
g
>i
\
>
\
h
s^
jjj
NC
1
JJ.
■H
-s^
O
t
J
M
w
o
D
AY/
IO.
E
^
//a
/ 1
a
/
f ,
/
/
/
/
-
cc
/
/
/
1
/
S
^
y
/
7^
A
/
-
o
o.1:
GP
/
/"
A
•
/
V
/
/
/
a
*
'r
/
A
^
/
o
I-
<M.
o
•^
-
ty"
A
/
/
%
^
/
/
/
&f
8'
M
p
' l->
,«f
/
»*
/I
A
/
%J
x
w/
u
/
^c
CO
<
1
/
7
in
O
/
/
w
£
S
<*
y
V-
/
/
/
/
<
/
/
/
3
O
s
'
/\
/
/
/
IO
>
/
/
/
/
/
o
/
y
../.
/
/
/
1
HORSE-POWER OP CONSTANTS.
449
*
e
=
=
$
N ~
fc • sa
«B s
S«1
<*© I
£*£
0
p
h
N
-
H
N^
1^
82 883S
ooo oo o
COCOCO -#'#^
53j cno
oo* ot^
■-T C -
oi-* ~
~. x. -
co'cori
ooo
oScnI
ooffl coco
^ oi oi oi oi oi
(COM CSO
OOOlO <MO
TM-* CO OlO
■* ■* ■** in ia
§??§
no® co o
o; oi ■* t- o
oi co co co •*'
I If
ooo
■* to o
oioi oi
111
<N CO^
cogo moo
CO -tf rf 10 O O
wot- cooo
n = = ~ 23 -i
M OI OI OI CO
383
HI |8£
-*LO© l> CO c
MOO COO
OCN^ ooo
oi oi oi oi oi
5?S
ooo oc
ri o o7 — -" t5 ciico to
- Z, X -. O rH OI CN CO -* 0_ t^RO CO "*
03H l-J 05
CO O O CO o o
CO o o woe
co_ ^ -^ in o o
co o 2 ro c co
CI O 0_ rH CI CO
^ CO o o
? -2 —
c o q
sgco5 si-
O 01 I- 0 1 -r :-
Oi ro :o -f -h i0
§§3 888
23 3 35 co cm o
23 S3?
c 2 c
coots
883
§s sss
CO O O CO o o
O O CO o o
SS3
§ss
r-i^cq OI CO CO rP^uO :
OOO HUM
H. P. =z-^=- CST+2000 sin 0). Wr=Load in tons. n= Speed in miles per hour,
.AT
= Wn X .0026§ (K ± 2000 sin 0). K— Resistance in lbs. per ton. K'=Tq
E~= Constants of power required to move one ton on level at speeds in
table with K= 10.
5/= Constants of additional powee required to raise ONE TON ON
grades and at speeds given.
77" X WK/=.'R. P. required on levels alone for speeds given.
IZ'X JF = H. P. additional on grades alone for speeds and % given.
W(K'H± RO = total H. P. required.
F\ami)l«' : Given a motor car, total Aveight 9 tons, to ascend a 7 per
cent grade at a speed of six miles per hour. What is the estimated horse-
power required, with K= 30 lbs. ?
450
ELECTRIC STREET RAILWAYS.
30
muuipnea Dy y ; '
overcoming the track resistances alone.
#'=2.240, which, multiplied by 9, = 20.16. The sum of the two will give
the total theoretical, i.e., 24.48 h. p. required. Allowing 50 per cent as the
combined efficiency of motors and gearing, to operate this car would require
a draft of 48.96 h. p. upon the line.
HORSE - POWER
OF TRACTIOIf.
(Davis.)
<D
c8
Speed in Miles per Hour.
"3
o
4
6
8
10
12
15
20
25
30
35
40
50
60
Horse-Power Required to Propel One Ton at Various Speeds up
P4
Various Grades.
0
.32
.48
.64
.80
.96
1.20
1.60
2.00
2.40
2.1 so
3.20
4.00
4.80
1
.53
.80
1.07
1.33
1.60
2.00
2.66
3.33
4.00
4.66
2
.74
1.12
1.49
1.87
2.24
2. SO
3.63
4.(50
5.60
3
.93
1.44
1.92
2.40
2.88
3. 00
4.80
6.00
4
1.17
1.76
2.34
2.03
3.52
4.40
5.47
5
1.39
2. OS
2.77
3.46
4.16
5.20
6
1.60
2.40
3.20
4,00
4.80
7
1.88
2.72
3.62
4.53
8
2.02
3.04
4.05
9
2.24
:;.:;<;
4.48
10
2.47
3. ox
4.90
11
2.67
4,00
12
2.88
4.32
13
3.09
14
3.29
15
3.52
Note No. 1. — The h. p. required to propel a car equals the total weight
of car plus its load (in tons) multiplied by the h. p. in table corresponding
to assumed grade and speed.
STREET RAILWAY.
Tractive Force.
E. E. Idell, M. E.
On Good Track. -To start car 116 lbs. per ton.
To keep in motion at 6 miles per hr. 15.6" " "
On Bad Track. — To start car 135 " " "
To keep in motion 32 " " "
On Curves. — To start car from 0 to 6 miles per hour . 284 " " "
average, 264 feet per minute.
APPROXIMATE INDICATED HOR§E - POTTER
PER CAR. (Dawson.)
Number Cars.
1
to 5
5
" 10
10
" 15
15
" 25
25
" 50
I. H. P.
25
20
15
I. H. P. per car in large city systems varies from 18 to 23.
^^IHHI
TRACTION.
451
TRACTION.
(Davis.)
Load of Trailer Cars in Tons
which a Motor
Per cent
Grade.
Tractive Force
in Pounds
per Ton.
Car of one Ton will Haul.
Snowy
Rail. Wei Rail.
Dry Rail.
0
30
8.5C
12.33
16.00
1
50
4.7(
7.00
9.00
2
70
3.07
4.21
6.14
3
90
2.17
3.44
4.55
4
110
1.6C
2.63
3.54
5
130
1.1!
2.07
2.84
6
150
0.9C
1.66
2.33
7
170
0.7(
1.35
2.00
8
190
0.5(
1.10
1.63
9
210
0.35
0.90
1.38
10
230
0.2^
0.74
1.17
11
250
0.14
0.60
1.00
12
270
0.05
0.48
0.85
13
290
Wheels
slip. 0.38
0.77
14
310
0.30
0.61
15
330
0.21
0.51
16
350
0.14
0.43
17
370
0.08
0.35
18
390
0.02
0.28
19
410
Wheels slip.
0.22
20
430
0.16
21
450
0.11
22
470
0.06
23
490
Wheels slip.
Note No. 1. — Multiply figures in table by weight of motor car (in tons)
to get weight of trailer (in tons) that said motor car will haul up corre-
sponding grades.
revolutions per juiwumj of various sized
wheels to make various speeds.
Miles per Hour.
2
4
6
8
10
15
20
30
40
Diameter
of
Wheel.
Feet per Minute.
176
352
528
704
880
1320
1760
2200
2640
3520
24 in.
28
56
84
112
140
210
280
350
420
560
26 in.
26
52
78
103
129
194
258
323
388
517
28 in.
24
48
72
96
120
180
240
300
360
480
30 in.
22
45
67
90
112
168
224
280
336
448
33 in.
20
41
61
82
102
153
204
255
306
408
36 in.
19
37
56
75
93
140
187
234
280
374
42 in.
16
32
48
64
80
120
160
200
240
320
452
ELECTRIC STREET RAILWAYS.
THACTIOJ1.
Theoretical Horse-Power per Ton of 3000 i,l»s. and per
mile per Hour with Various Grades and
Coefficients of Traction.
(Merrill.)
1
Coefficient of Traction.
12
13.5
15
18
20
25
30
35
40
50
CO
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
.032
.1383
.192
.245,,
■2!»8i
.352
.4( ).-»:-;
.458 1
.512
.5(552
x>m
.672
.7253
.778L
.832
.036
.0891
.1423
.196
.249i
.302^
.356
.4091
.462s
.516
.5694
.0223
.676
.7291
.782§
.836
.04
•094
.143
.20
•251
.30f
.36
•41*
.46f
.52
•571
•62|
.68
n
.84
.048
.1014
.1543
.208
.261A
.3143
.368
.4211
•4743
.528
.r,s\y
• 6>iH
.688
.7411
.7943
.848
.051
.103
.16
.211
.263
!S74
.42f
.48
•534
•58f
.64
.694
•74§
■84
•854
•061
.12
.173
!'283
.333
.384
.44
.49|
.603
•653
.704
.76
.813
•861
.08
.134
.183
.24
i43
.40
•454
.503
.56
•614
.66f
1774-
•82|
.88
.091
.143
.20
.254
.303
.36
.411
•46f
.52
.574
.623
.68
.534
•783
.84
•S94
•104
.16
.21|
.264
.32
'424
.48
.533
.584
.64
.693
•744
.80
•853
•904
• 134
.183
.24
.294
.343
.40
.454
.503
.56
.614
.663
'774
.823
.88
•934
.16
•214
•26|
.423
48
.534
•583
.64
c|
.80
.854
.96
HOR§E-POWER. SPJEEB, AHI> HORIZONTAL
ETJFOKT O POVKD8.
Miles Per Hour.
Mecli.
2
4
6
8
10
15
20
25
30
40
H. P.
Feet
Per Minute.
176
352
528
704
880
1320
1760
2200
2640
3520
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
2
375.0
187.0
125.0
93.7
75.0
50.0
37.5
30.0
25.0
18.7
4
750.0
375.0
250.0
187.5
150.0
100.0
75.C
60.C
50.C
37.5
6
1125.0
562.0
375.0
281.2
225.0
150.0
112.5
90.C
75.C
56.2
8
1500.0
750.0
500.0
375.0
300.0
200.0
150.0
120.0
100.0
75.0
10
1875.0
937.0
625.0
468.7
375.0
250.0
187.5
150.C
125.C
93.7
15
2812.0
1406.0
937.0
703.1
562.5
375.0
281.2
225.C
187.5
140.6
20
3750.0
1870.0
1250.0
937.2
750.0
500.0
375.0
300.0
250.C
187.5
25
4687.0
2343.0
1562.0
1172.0
937.5
625.0
468.7
375.0
312.5
234.4
30
5625.0
2812.0
1875.0
14(i(i.ll
1125.0
750.0
562.5
450.0
375.0
3S1.2
40
7500.0
3750.0
2500.0
1875.0
1500.0
1000.0
750.C
600.0
500.0
375.0
50
9372.0
4687.0
3125.0
2344.0
1875.0
1250.0
•937.5
750.0
625.0
468.7
POWER REQUIRED FOR TRUCK CARS.
453
POWER REailRED FOR DOVBIE **■» SIXGEE
TRUCK CARS.
Wattmeter placed on car. (McCulloch.)
£$
Double-truck car. Seats
36; weight, 11.75, tons ;•
average for entire day
Same as above. Average
for heaviest trip . . .
Single-truck car, no
trailer. Seats 28;
weight, 8 tons ....
Single-truck car. Trail-
ers operated 26% of the
time. Average for the
entire day
Si-igle-truck motor and
open trailer. Seats,
63 ; weight, 10.5 tons.
Average for heaviest
trip
MORIZO^TAE EFFORT EXERTED Oltf CURVES.
Pounds Per Ton.
Feet.
Length of
Wheel
Base, Feet.
25
30
40
50
60
70
80
100
3.5
88.6
73.9
55.4
44.3
36.9
31.7
27.7
22"
4
94.0
7S.4
58.8
47.0
39.2
33.6
29.4
23.5
4.5
99.4
82.9
62.2
49.7
41.4
35.5
31.1
24.9
6
115.6
96.4
72.3
57.8
48.2
41.3
36.1
28.9
6.5
121.0
100.9
75.7
60.5
50.4
43.2
37.9
30.3
7
126.4
105.2
79.0
63.2
52.7
45.2
39.5
31.6
Assumed — 3 miles per hour speed on curve, 4 ft. 8J in. gauge.
454
ELECTRIC STREET RAILWAYS.
Formula from Molesworth :
Let W = weight on wheels in lbs.
A' = coefficient, in this case .27.
G = gauge of track = 4/ — 8|" =: feet.
B = rigid wheel base in feet.
/i=r radius of curves in feet.
Tractive force or resistance per ton =
W X K X (G + £)
HORIZONTAL EFFORT ON C^nADEM.
Ponuds per Ton.
Speed
— Miles per Hour.
Grade.
Per Ct.
2
4
6
8
10
12
14
16
18
20
0
15.03
15.11
15.24
15.42
15.66
15.95
16.29
16.69
17.14
17.64
1
35.03
35.11
35.24
35.42
35.60
35.95
36.29
36.69
37.14
37.64
n
45.03
45.11
45.24
45.42
45.66
45.95
46.29
46.69
47.14
47.64
2
55 03
55.11
55.24
55.42
55.66
55.95
56.29
56.69
57.14
57.64
2i
65.03
G5.ll
65.24
65.42
65.66
65.95
66.26
66.69
67.14
67.64
3
75.03
75.11
75.24
75.42
75.66
75.95
76.29
76.69
77.14
77.64
3*
85.03
85.11
85.24
85.42
85.66
85.95
86.20
86.69
87.14
87.64
4
95.03
95.11
95.24
95.42
95.66
9555
96.29
96.69
97.14
97.64
5
115.03
115.11
115.24
115.42
115.66
115.95
116.20
116.69
117.14
117.64
6
135.03
135.11
135.24
135.42
135.66
135.95
136.29
136.69
137.14
137.64
7
i.-,r,.o:;
155.11
155.24
155.42
155.66
155.! (5
156.29
156.69
157.14
157.64
8
175.02
175.11
175.24
175.42
175.66
175.95
176.29
176.69
177.14
177.64
9
195.03
195.11
195.24
l!»r> .42
195.66
195.95
196.29
196.69
197.14
197.24
19
215.03
215.11
215.24
215.42
215.66
215.95
216.29
216.69
217.14
217.64
APPROXIMATE CURRENT CONSUMPTION PER
CAR.
Two 35-H.P., S. R. Ct. Motors.
Diameter
Horizontal Effort -
- Pounds.
Inches.
100
200
400
600
800
1000
1200
1400
30
33
25.8
26.6
32.8
34.0
44.6
47.0
54.6
57.6
63.8 72.6
67.4 77.6
82.6
88.4
92.0
98.2
Two 30-H.P., S. R. Ct. Motors.
Diameter
Wheels.
Inches.
Horizontal Effort —
Pounds.
100
250
500
750
1000
1250
1500
2000
2500
3000
30
33
28.6
29.4
38.8
40.0
51.4
54.0
63.0
65.8
73.2
77.0
84.2
88.8
93.4
98.8
111.8
119.2
130.0
138.4
147.6
158.0
AXLE SPEED.
455
AXIS SPEED PER CAR WITH DOUBIE MOTOR
EaUIPME^T - RE V§. PER MOTIE.
Averag-e of Several Types 25»-H.P. Motors.
Diameter
Wheels.
Inches.
Horizontal Effort —
Pounds.
100
200
400
600
800
1000
1200
1400
30
33
308
300
253
248
195
189
170
165
153
149
141
136
131
126
122
119
Average of Several Types of 30 H. P. Motors.
Diameter
Wheels.
Horizontal Effort —
Pounds.
Inches.
100
250
500
750
1000
1250
1500
2000
2500
3000
30
33
282
272
260
252
202
194
173
166
153
148
139
134
130
125
117
113
107
103
100
95
Formula for close approximation of current required to propel a given car.
No. tons in train x [( (% grade -J- 1) 20) + (curve resistance per ton)] =
Pounds Horizontal Effort.
TMO. OF CARS OJ¥ TES MILEi OE TRACK, VARI-
OUS SPEEDS AHT» HEADWAYS.
Minutes
Average Speed in Miles per Hour.
Apart
or
H'dway.
6
7
8
9
10
12
15
20
25
30
1
100
86
75
67
60
50
40
30
24
20
2
50
44
38
33
30
25
20
15
12
10
3
33
29
25
22
20
17
13
10
8
7
4
25
22
19
14
15
13
10
8
6
5
5
20
17
15
13
12
10
8
6
5
4
6
17
14
13
11
10
8
7
5
4
3
7
14
12
11
10
9
7
6
4
3
3
8
13
11
9
8
8
6
5
4
3
3
10
10
9
8
7
6
5
4
3
2
2
15
7
6
5
4
4
3
3
2
2
1
20
5
4
4
3
3
3
2
2
1
1
30
3
3
3
2
2
2
1
1
1
1
Note. — Fractions above one-half are considered whole numbers, and
fractions below one-half are neglected.
456
ELECTRIC STREET RAILWAYS.
To obtain the number of cars required to operate any length road, divide
the number found in the table under the desired average speed and head-
way by ten, and multiply by the length of the road in question. Should it
PRESSURE IN POUND PER SQUARE FOOT OF CROSS SECTION.
880
NS
s?
j\
!
^
NA
S
\
0
^
§
\
\
4
\
\
a
^4
£o
i/,
A'
$
£\
\
K
\
^
^
t
Vn
^
-^
3>v
?
3
#
»
\
\
\
K
V
£/
^i
V£
H
-«-
?
V
?
v
\
\
\
<*
*
_,
s
~%
Li
V
\\
\
&\
>
^
>
\
?
-f
3
I
&
\\
w>
\<
\
"
I
I
o
\
%'
\
^
'
\4
0
D
*
\
m
°
M
\
$
$
w
\
x"
,
%'
\%
"3
j
$\
\
\
X
\
t\
^
v
N
\
\
>^
°
\
ui
\
&
^
\
\
?
>^
^~^
°
\
"-
\
ft
V
\
\
\
^*
^'-
\
\
\
,?
^S
\
_
\
>/
1
\
^
\
M
>,
\
\
\
\
Fig. 30. " Effect of Shape of Moving Body on Air Resistance," Crosby's
Experiments.
be desired to run at different average speeds on various portions of the road,
treat each portion as a separate road, and add the results together. To the
number of cars thus obtained should be added 20 per cent for reserve for
roads under 20 cars. For roads over 20 cars, 10 per cent reserve will be
enough.
RATING STREET-RAILWAY MOTORS.
457
Formula : —
Let n = number of cars required.
m — miles of track.
S = average speeds in miles per bour.
/= interval or headway in minutes.
Tben, m x 60
n = r •
SX I
HEADWAY,
IPEED, AUTR TOTAL IVIMHER OF
CAMS.
Total number of cars on a given lengtb of street on whicb cars are run-
ning botb ways = (lengtb of street X 120) -~ (headway in minutes X speed
in miles per bour).
MIXES PER HOUR I]tf FEET PER HLWEI
Aar» per lEcoxn.
(Merrill.)
Miles
Feet
Feet
Miles
Feet
Feet
per
per
per
per
per
per
Hour.
Minute.
Second.
Hour.
Minute.
Second.
1
88
1.46
16
1408
23.47
2
176
2.94
17
1496
24.93
3
264
4.4
18
1584
36.4
4
352
5.87
16
1672
27.86
5
440
7.33
20
1760
29.33
6
548
8.8
21
1848
30.8
7
616
10.26
22
1936
32.26
8
704
11.73
23
2024
33.72
9
792
13.2
24
2112
35.2
10
880
14.67
25
2200
36.67
11
968
16.13
26
2288
38.14
12
1056
17.6
27
2376
39.6
13
1144
19.07
28
2464
41.04
14
1232
20.52
29
2552
42.50
15
1320
22
30
2640
44
RATHfG STREET-RAILWAY MOTORS.
(Condensed from W. B. Potter in Street Railway Journal.)
Rise of temperature after one hour's run under rated full load not to ex-
ceed 75° C. ; room being assumed at 25° C. Average load for a day's run
should not exceed 30 per cent of its rated full load, Avhich will give a rise of
temperature of about 60° C.
The above ratings are based on aline potential of 500 volts, but the aver-
age performance can generally be increased in proportion to the increase in
line voltage ; that is, a motor will do approximately 10 per cent heavier
service for the same temperature rise when operated at 550 volts.
With electric brakes, motors must have increased capacity, as heating
increases 20 to 25 per cent. The 20 per cent increase is on roads having few
grades and stops, while the 25 per cent is on hilly roads with frequent stops.
Approximate rated horse-power of motors =
(total weight of car in tons) X (max. speed in miles per hour on level).
_
458 ELECTRIC STREET RAILWAYS.
For equipments with electric brakes, divide by 4 instead of 5. When
maximum speed is not known, it may be assumed as twice the schedule
Example 1:
20 ton car (loaded) X 50 m. p. h. „^ , ^ „ ,
~ - = 200 h. p., or four 50 h. p. motors. In
this case, if the line pressure were raised to 600 volts, electric brakes could
be used on the equipment by changing the gear ratio so as to have the same
maximum speed.
Example 3 :
11 ton car (loaded) X 25 m. p. h.
p = 55 h. p., or two 30 h. p. motors,
These rules indicate minimum capacity under ordinary conditions.
Tractive Effort.
Tractive effort is dependent on the rate of acceleration, grade, car fric-
tion, and air resistance, which latter is ordinarily included in friction.
Acceleration is expressed in miles an hour per sec. 1 mile per hour per sec.
= 1.466 feet per sec. Excluding car friction, a tractive effort of 92§ lbs. per
ton (2000) will produce an acceleration of 1 mile per hour per sec. on a level
track, and the rate of acceleration will vary in direct proportion to the
amount of tractive effort. On ordinary street cars, tractive effort during
acceleration often rises to 200 or 300 lbs. per ton.
On elevated or suburban roads the maximum tractive effort is generally
100 to 150 lbs. per ton. For heavy freight work with slow speeds, the trac-
tive effort seldom exceeds 30 to 40 lbs. per ton.
Grades are commonly expressed in percentage of feet rise in 100 feet of
distance, and tractive effort for a grade is the same percentage of the
weight to be drawn as the rise is of the length of 100 feet. For instance,
the tractive effort for a weight of one ton (2000 lbs.) up a grade of 3 per
cent would be 3 per cent of 2000 lbs., or 60 lbs. For the total tractive effort
there must be added to this, the effort for overcoming the car, wind, and
rolling friction on a level.
Maximum tractive efforts from numerous tests are shown in the following
table :
Tractive effort in
lbs. per ton.
15 ton car, up to 25 m, p. h 25
'" " " " " 50 " " " 50
25 " " " " 25 " " " 20
" " " " " 50 " » " 25
100 "train" " 25 " " " 15
Heavy freight train up to 25 m. p. h 6 to 10.
The above figures have to be increased for snow and ice on the track.
Tractive Coefficient.
This coefficient is usually expressed as the ratio between the weight on
the driving-wheels and the tractive effort, and varies largely with the con-
dition of the rails.
In train work, the weight on drivers should be six times the tractive
effort.
Example:— Required the weight of a locomotive to draw a 100-ton
train up a 2 per cent grade.
For train.
100 tons x 15 lbs. for friction = 1500 lbs.
" " X 40 " " grade = 4000 "
5500 lbs.
RATING STREET-RAILWAY MOTORS. 459
Assume a 20-ton locomotive.
20 tons X 15 lbs. for friction = 300 lbs.
20 " X 40 " " grade = 800 "
6600 lbs.
6600 lbs. equals 16.5 per cent of 20 tons, or a tractive coefficient of 16.5 per
cent. Starting the train on a 2 per cent grade with acceleration of J m. p. h.
per sec. would mean additional tractive effort equivalent to — ^— = 30.8 lbs.
per ton.
This would add to the requirements as follows :
Train 100 tons, for friction and grade as above . . . 5500 lbs.
" " " at 30.8 lbs. for acceleration 3080 "
Total for train 8580 lbs.
Assume 35-ton locomotive with motors on all axles.
35 tons at 15 lbs. for friction 525 lbs.
" " " 40 " " grade 1400 "
" " " 30.8 for acceleration 1078 "
Total tractive effort . . . 11583 lbs.
or a tractive coefficient of 16.5 per cent for the 35-ton locomotive.
Tests show the following tractive coefficients :
Sanded
per cent. per cent.
Dry rail 28 30
Thoroughly wet rail 20 25
Greasy moist rail . 15 25
"With ice and snow on the track, the coefficient is lower, and the rolling-
friction higher.
JLverag-e energy. — Approximate capacity of a power station may be
assumed as about 100 watt-hours per ton mile of schedule speed for ordinary
conditions of city and suburban service.
Example : — 15-ton car, 12 miles per hour schedule,
k.w. at station = 100 x 15 X 12 = 18 k.w.
If stops are a mile or more apart, only 60 to 70 watt-hours may be neces-
sary.
Frequent stops and high schedule speeds take 120 or more watt-hours.
The following table of efficiencies Avill be found convenient in estimating
the power required for operation of motor cars, using three-phase trans-
mission and direct current motors. The efficiencies would vary somewhat
with the load factor, but can be taken as generally applicable.
Considering the I.H.P. of the engine as a basis, for the
Average efficiency of engine 90 per cent.
" " generator 94 " "
" " high potential lines .... 95 " "
" " substations 90 " "
" " direct current lines .... 92 " "
" " motors, including losses of
control 72 " "
Combined efficiency of the motors and series parallel
control during period of cutting out the controller
may be taken as 63 " "
Efficiency of motors after cutting out the controller,
depending on size of motors 80 to 85 per cent.
460
ELECTRIC STREET RAILWAYS.
©
03
•sptreg; jo ok
o
5
o
<M
•sa^jf
<#
**H
■*
<+
8
CO
,_,
,_,
fr-
C75 UO
jo^nuuuof)
CO
^
s
m
UU
■*oiS
--
Si
+
CO
oo
00
<M
<m
-+l
00
.iod sao^onpuoo
CO
cf
"
'o.m^uuv
ui s;o[s
s
3
3
CO
i
CO
i
-r
:o
CD
eo ic
CO OS
lO
HO
•sujnx
1
eo
-#
CO
o
V\z\£ 1*6*0,1,
3
'.SHOO
<M
,_,
^
<M
CM
■*
(M
(N
"#
Tt<
<# ■*
PPM JO -OJs[
•S810J JO 'OK
CI
c<j
(M
<M
«
-*
*
■*
*#
•#
Tjt ^*
fcJO
•.n?Q*)
b.
^
,,
^
,,
^
T*
f_
t- ^1
e3
co
to
CO
CO
CO
CP
co
iO
IO
•"IJ
■#
3
-r
■*
3
t>
£
t>
£
-r
00 00
CO
oo
00
oo
eo
co
-k
oo
fN ^
cS
•oi^y; uoi^onpoy;
03
-#
■*
■<*
rH
UJ
•pi30T[
8
to
. o
Xin^; ^ poods
. %
C
PI
0,
6
o
6
O
6
a
o
O
6
o
6
O
° 6
O 03
©
•2W .
O
O
o
=5
o
£
£
£
■S
£
•S
s
W
w
w
w
-2
03
03
V
03
03
03 P.
r^
pj
PI
Pi
g
H
y
H
H
H
H
«i^
S
-
O
■a.gg
1*
-
OS
S3
c«
o
«1
o
o
o
©
03
1=1
a)
a
s
03
H
H
H
H
3
©
0
V
a
0
ops
9
o
IM
lO
3
CO
00
co
§
oo
t>
CM ^) z>
LOc ^o
>>
t>>
!>>
>»
>.
o5
%
as
cS
%
cti
1
cS
c«
te
03 ci
>
Eh
rt
5
§3
Ph
«
w
PI
0=i
c3
<5
©
M
co
CO
CO
CO
CO
CO
1-1
M
CO
H
.2
So
o
d
CO
Ph
S
Ph
g
r/i
d
6
d
d
in
d
d
t-
"O CO
W 6
d ^
A
•ofi
rH
CN
eo
<*
ia
CO
t-
OO
OS
c
s s
DIMENSIONS, WEIGHTS, ETC., OF MOTORS.
461
o w
s
o
~
o?
lO
o
t-
lO
2
on
%
CO
to
o
00
oo
CO
co
">*
CO
2
o
CO
CO
-* ■*
*
fr-
|
to
to
CO
1
in
o
lO
CM
rt< tH
<#
rH
■*
-*
«
*#
"#
«
ON
+
co
00
^
■*
■*
«
CM
"# •*
"*
«
-*
*#
"*
«
<*
■*
■tf
-*
CO
-*
rh
■<:»
?
"*
^*
§33
f.
,.
r.
ro
_^
fn
^
.
CO CO
m
o>
yj
lO
>o
UJ
co
-# -#
<*
£
3
-f
OS
£
ce
s
>#
3
eg
00
■ -.
Tf
■* ■*
<M CO-#
CO
-#
lO
rj<
•*
CO
CO
CO
T*
lO
^
iC
IO
•<*
^
to O
8 22
JO
50
£
s
CO
|
o
I
1
o
o
s
s
1
o
lO lO
6 d
CD CD
CD
1%8
n
6
O
d
t
S
J
^
6
o
6
o
s6s^
o wot
m
o
o
o
O
o
O
O
o
O
o
O
o
8
<s
■2
d
6
3
H
43
S
Sjjg iJl^ acg
CD
9
^
"3
jM
"3
2
s
o
o
5^5^5=3
"3
£
£
£
£
£
£
£
£
■»
•«
^
O
CD <U
^
o
02
o
02
S
CD
o
CD
C
H
§
o o
8 8
o
g3
^
a
8
8
o
1-
in
|
©
s
o
rt
o
CO
lO
>, >>
>v
CD
.
^
fl
Q
>>
>->
>»
^
>i
oS os
S3
e3
S3
c3
o3
crt
cS
C5
O
,e
,c
1*
^
£
2
^
^
03
c3
fS
r
=
'?
cS
r^
J3
c3
« g
CD
«
p
£
M
«
,0
33
CD
B
«
«
-
«
M
P^
5
02 02
M
02
£
32
02
M
M
M
O.
02
02
02
tt!
02
02
u
"eS
d
S ^
n
3s^
02
02
«!
P
6
©
d
1?
|
02
O
M
l
£ o
£
o
^
*!
13
£
'A
ki
O
O
O
O
o
m
02
^
£
02
~'
462
ELECTRIC STREET RAILWAYS.
rt M ci cS c$ cj cS g
2 2 2 2 S£ 3£ 3^
1 >** S al
M w>*» M+l
£ "3 ±! 5 ^3 "oS r^ 'S 43 §"« fS^ 3 "£
3 £ 3 s 3 ,3 3 £ .S" a .S° a .&» a c
•ajiAvojn^'BiujY
•sap a
•O.IIA1 ppi^
•9jm+«ra.TY
C- iH OS
O CS <N
•9.IXX+X2XU.XY
jo jajQimjxd
-In | hh
ci co <M co co
„
CO
co
&
«o
co
*
*
'cb*
r*
«,
; #
5
*
*
ff
co
co
cY
*
Sf
Sxns'BQpxre sjr8£)
1
1
1
s
eo
1
1
'tf
1
m
co
-raof) 8.xn4i?xnJY
1
1ft
m
I
8
CO
IQ
os
o
1
1
1
•S.XX?9f)
q+xAV a+axdxuoQ
lO
OS
o
1
1
1
CI
1
1
CO
1Q
1
O
O
OS © rH
DIMENSIONS, WEIGHTS, ETC., OF MOTORS.
463
©
-d
cr!
CJ
d
53
O
en
tn
M
to
bn
bn
2
0
s
fl
0
d
d
'-=
Ti
d
'•&
bn
bb
Tl
d
=]
rt
fl
3
s
a
s
01
o
rt
g
£
£
F=
p
£
*
U
'£
a-
?
d
d
crt
2
pi
P3
o
O
O
O
O
£
'o
o
o
So
>>
©
2
S
a
s
2
A
£
P
cS
1=1
bo
b£
bo
bfl
Tj
d
0)
X
^
-
cS
r1
Bj
cci
c3
O
A
H
H
s
cc
02
X
M
cc
0Q
W
03
S
s
d
0
CO
^
CO
53
s
ej
si
crt
d
ft
y
d
1
©
d*
6
5^
X
1
X
©
X
lO
3
X
q
x ;
d
g
g
s
S
g
B.
cS
oi
<M
o
gd?o
d
d
d
d
©^
• ©
d
6
6
1
1
ib
o
fc
6
ot5" 6
1
\ S?
CO
V
s
Oi
os
o
*
CO
J
TJH
lO
§"
lO
rt
LO
1
11
05
OJ
<N
CO CO
O
«
co
OS
CO
ta co
IQ
■a
CO
co
CO
"
CO*
<N <M
eo
co
§
lO
£]
s
~p
©
IS
CO
CO
CI
rH
<#
<#
$
«
£
O
ss
R
»c
lO
-t<
-H
o
CO
o
—
©
1
|
1
©
1
o
—
I
1
o *#
1 1
O -H
LI CO
© t-
© ©
Si §
<M i-l
c_
tH
lO
cc
s
23
©
8
<M
S3
8
s
8
8 &
S 8
eo co
464
ELECTRIC STREET RAILWAYS.
8 8 8
§88
-
H
S
§^
© g
P
ft "'
0
H
=
M
H
Boh-;
S
111
io IO T*
o o o
§ S 8
t- 00 b-
8 8
| 8
CO CO
I |-s 8-S 8-3
co co ^ c-i a) co ©
£ £
88
§5 9'
« c3 g
•5 * =
WEIGHT OF TRUCKS. 465
APPROXIHATE WEIGHTS OF TRUCKS.
Kind.
Weight.
Single truck for motor car
Maximum traction . . .
Pivotal, motor car . . .
" trail car . . .
Radial
Running gear
3900
1500
3700
1500
lORaVE A^TI> HORIE-POWER.
H. P.
per Lb. Applied at Periphery at 100 Rev. per Min.
Diameter
Wheel.
26"
28"
30"
33"
36"
H. P.
.02062
.02221
-0238
.02618
.02656
Pounds at Periphery per H.
P. at 100 Rev. per Min
Diameter
Wheel.
26"
28"
30"
33"
36"
Lbs.
48.481
45.018
42.017
38.197
35.014
Lbs.
126050.9 X H. P.
Diam. x Rev.
H. P. = .00000793 X diam. wheel x rev. x lbs. at periphery.
H. P. per lb. at periphery at one mile per hour = .002867.
Lbs. at periphery per H. P. at one mile per hour = 374.9.
iiVote on Emergency Braking* of Cars.
In case of emergency, motormen often reverse the motors, which brings
the car up with a severe jerk, and is quite apt to strip gears. This is
not necessary, and should never be done unless the canopy switch is first
thrown off, then when the motors are reversed and the controller handle
thrown around to parallel, the motors will act as generators and will bring
the car to an easy stop with no harm to the apparatus. In case circuit
breakers are used in place of the plain canopy switches, the reversal of the
motors will draw so much current from the line that the circuit breakers,
if properly adjusted, will open the circuit and the controller can then be
used as suggested above.
COPPEB WIRE FUSES FOR RAIIWA1 CIRCUITS.
B. &S.
Gauges.
17
16
15
14
13
12
11
10
9
390
8
450
7
Fuse Point
in
Amperes.
100
120
140
166
200
235
280
335
520
466
ELECTRIC STREET RAILWAYS.
J3
1
8 feet high in Center
Vestibules.
Vestibules.
Vestibules.
Vestibules.
Total Weight, 27860
" 23750
I
CP
CD
a
o
<1
•sqq;
if 1 1 | 1 1 1 1 II II 1 II 1
•sqT
4800
4800
4800
4800
4800
4800
3000
3200
3200
3200
5200
5200
m
•sqT
'Xpoa
4500
4000
5000
4600
4300
4800
4800
5100
5250
7400
6000
6000
5850
6050
6200
6200
w
•UOSJ8J.T8d -lit H @
<M CN <M CI ci CI CI CI CI CO CO CO CO 00 § 4< ^ "#
Si
N *i
8*
8e
*§
£
15 cc
7 ft. 6 in.
7 " 6 "
7 « 6 "
7 " 6 "
7 " 7 "
8 " 0 "
7 " 6 "
7 " 6 "
7 " 6 . "
8 "
7 " 6 "
7 " 6 "
7 " 6 "
7 " 6 "
7 " 10 "
8 " 0 "
8 " 0 "
O 02
a .. ..
<N I CO I 1 iNCTN 1 CD CO CO O 1 |Q
CO CO CD CD CD CD CD CD t- t-
sac
ID
•suuoj^x<I
^^rin ^ THTh^Thv? S? iP^fTH^ tH ^H 1 1
H
Over All.
(Bumpers.)
25 ft. 6 in.
25 " 6 "
25 " 6 "
26 " 3 "
27 " 2 "
26 " 8 "
27 " 8 "
27 " 8 "
29 " 8 "
30 " 8 "
30 " 8 "
33 " 8 "
34 " 8 "
34 " 8 "
35 " 2 "
37 " 2 "
42 " 0 "
38 " 8 "
f§
15 ft. 10 in.
15 " 10 '•'
15 " 10 "
16 " 7 "
17 " 6 "
17" 0"'
18 " 0 "
18 " 0 "
21 " 0 "
22 » 0 "
22 " 0 "
24 " 0 "
25 " 0 "
25 " 0 "
25 " 6 "
27 " 6 "
31 " 10 "
29 " 0 "
cS
o
O
©
.2
16 foot closed ....
16 " trailer . . .
16 " storage battery
Convertible summer
and winter trailer .
do. do.
17 foot closed . . .
18 " " ...
18 " " ...
21 " " ...
Convertible winter and
summer trailer . .
22 foot closed trailer .
24 " closed . . .
25 " " ...
Convertible summer
and winter ....
do. do.
Akron, Bedford & CI.
Buffalo & Niagara Falls
DIMENSIONS OF BRILL CARS.
467
$%3
•sqq;
•sqi;
•sq^
sSooooo IOOOOG
OlOCOCO© lO
0©©©©©©©©=©©©© o
©000 = .".-: ~ - © © © 10
m -f © -+ o < - ' '-.-;; - ■
C0C0t)<'#©tH t-rH^Ui© O©© 10
■suosjaj
nOrHOOC^OiO
Si s
n 1
© © © © ^|N© -*1© © 05 0
o©©©t~©t-t-t-t-i>
« I |«« I I I s °>
6S
Tt< Th TJ< Tt< ^t< Tf Tt< -^ C
12 I'-IS I I
0 O©00 ©© •# ©-*C0©©00 © ©
1 CI oi ci ci 01 01 CO 01 CO CO CI Tt< ■* CO CO
i-H CN CO <M
g.- Oh ^ ° go g fl S3
•§„ „° lis sis I If
468
ELECTRIC STREET RAILWAYS.
c
-
©
a
8
o
s
o
O
o
o
$
R
•sqrj 'Apog;
*!£
tt
3
o
LO
JO ^qSpAi
O
o
.— -.
— *-,
—
—
■*co
LO
CO
"S ««
<N
s
eo
S
as,
°-
8
o
o o,
>co
o A
go*
d-d
°r2
fit^
-SB
-^
■—
-v~
tn
ea
cS
©
cc
-o
o
o
,d
-d
bo
-
5
X
co
©
PES
&
•s^as
<N
e,
<M
IN
00
t.
c
t.
jo aequiiiii
rt
v
v
*
-
'mPLA!
— *-s
*""
t-
CO
L~
CO
t~
i
•episui !)q§iaH
5d^
■V
"
V ^
•sieaq^ jo ozig
CO o
-
"
-
-
-
-
-
v V
„
•nv
J8AO *qSpH
© o
2
2
~
^
=
2
-
ib
LO
•suuo;^!,!
— v—
V
V
jo q^Suaq:
^M
Th
^
*
5,
■*
v
v
•sjsoj
J8AO q^Sueq;
CO
2h
^
8
*
o
lO
„
x
v
•suijoj^u
CO
J8AO mSua^i
tH
<N
CO
8
OS
CO
Sq
CO
H
&
_/ .
,— A_
•
, — ■ — .
, . ,
£
3 .
-d
r2
•d
co
-d'- •
§ *
o .
T)
CO
co
o
•o '
13
c
c
n:
c
O
cp ©
33 £
5^
.go
lo-d
CO
O
O
d
1
-d
9
CO
d,
o<
1
sf
ft
CD
-d
~£>
d S
o
,2 ?
So
;-
C
u
O
o
-
o
:
P
Q
APPROXIMATE DIMENSIONS.
469
S 8
1
o
©
o
S
o
8
o
8
O
§
8
8©
<M
^3
GQ
,o
CO
^
&
o
§{
a &
r-H O
If
©
o
8
,-*-,
.—— s
,-*- ,
CD
■§,-§
M
t3
CD CD (jj
ca
cd >>
H«Wfo3
,0 c$
-2 *
CD
§ a 2
53.2 3
>.2
"So a
53 •£
£8
CD .g
CD "3
-so
5
>"cl «
ta
oocn
^CN
CD
Sh
o m
i-i 50
^_
a
o
o
a
s
t-
t-
*"
^
CO
^
ti"
CO
l"
^
3o2»
-
-
-
-
b-
CO
&
fc- *>
«,
CO
v
v
CO
CO
V ;.
x
CO QCO
CO
tH rl
1-1
v
?H
co
CO
CO
CO
lb
b
<N
<M
CO
lO
CO
1-1
O
*
CO
CO
c5>
8
£_
CO
cq
1-1
CO
(M
rH
v
V
o
N
CO
&
cn
CI
■*
cq
£
ct
sy
IO
3
,— *_
,— *_
.— *_s
— ■— ,
o
CD
a .
o
13 *
■d" •
CD
S •
^ •
cd 53
3"S
o
CD .
O
,0
'o
o
tin
cl
o
^2
cf
,0-
cS
'3 '
s
t:£
0 >s
v%
,2 CD
'ol
m
§c
a
a
a
a
3 O
-go
^
fe
a
N
O
C
O
C
o
Q
ft
ft
4
4
E
470
ELECTRIC STREET RAILWAYS.
o
0
o ©
O
•p^oq; noisanoxg;
o
1
o o
1 1
o
§
8 8
H
•puoq; ^j^nipjo
2
CO
00 n
3
3
•saGguassBj; ^noi^i^
1
8
1 1
o
CO
t~
s s
o
"P^ot; uoismoxg;
o
o
|
8 |
O lO
o
CI
CO CO
-S
2
1
•p'BOT; jfj'BUtpJO
1
o
1 1
lO
i-
Ah
<»
ft
<M tN
2
"55
o
o
•saaguessB,! ;not[^TAi
o
o
8
8 8
CO CO
o o
-2
ui ■
•<TH OS 'siqnoa
8 8
c3
O-S'-S
io \a
s
z$z
o
Shs
• J'H SI 'aiqnoa
s
8
3
ft
«!
|lfj
•(S^DIU^ z) I^oaij
© o
8 8
CO CO
•froiu; i) piSig;
8
o
o
w
CI
03 03
•(speqAi. 8 'S5[0tij^ z)
8 8
ipiUJ, {T^OAIJ
3 3
•sieaqAV f 'jpnj;; j)
©
o
1
5i»nJX piSiH
•Apog; jbq
I
1
8 8
<*
£>,
•uoisanoxg;
in
8
§ §
Ah
|-3
•Supveag
s
§ 8
•q^Suaq; itJ^oj,
CJ
&
co co
d
_
-
G
■*
o
o o
•qipi^i i«*ojd
eo
t- ©
tA
A
T3
-o
o
o „_
pq
e3
<*h a>
o
a>
m w
a
<N CO
v5
CO
"O 1
s
fl
S fl
o
ft
J ft
5
O
o o
ELEVATED RAILWAY TRAIN PERFORMANCE. 471
ihtiewioy* ojp itaidird - peckh in
TRIJCK§.
Style.
Lengths.
Top
Frame.
Spring
base.
Wheel
Base.
Height of
Truck,
30 in.
Wheels.
Weight
Complete
Pounds.
8 Standard, for open cars
8A " " "
9 A Extra long, for open
cars
7 D Excelsior ....
7B "
7 A "
7 Excelsior trailer truck
Extra strong storage bat-
tery
Extra long, with regular
and emergency brake
Extra long, with track
brake '.
Electric mining truck .
14 ft. :
14 " !
7 in.
7 "
3 ft. 6 in.
7 ft.
7 "
7 "
3 ft. 6 in.
27^ in.
27* "
5000
4500
4000
5000
5000
5000
4500
IVote on motors.
It had been the author's intention to include in this chapter cuts and di-
mensions of the standard motors and generators ; but it was found that the
standards changed so rapidly, and practice demanded so many and diversi-
fied forms of motor and equipment, that it Avas impracticable to include
such cuts without danger of misleading the engineer.
ELEVATED MJLIJLWAY TJRAIH PEREORMA3FCE.
(S. H. Short.)
Data Sheet of Train Ho. 1.
Elevated Railway Service
Number of cars in train 3
Full speed of train on level track (miles per hour) . . 31
Average speed, stops one-third mile apart (miles per
hour) 16.5
Motor Car.
Weight of motor car body 10 Tons.
Weight of both trucks 10 "
Weight of two motors 7 "
Weight of seventy-five passengers 5 "
Total weight of loaded motor car 32 "
Number of motors on motor car 2 "
*Commercial rated power of each 200 H.P.
Safe constant load for each 100 "
Safe temporary tractive effort of equipment 10,000 Lbs.
Safe constant tractive effort of equipment 3,500 "
Weight on drivers 19.5 Tons.
Ratio of weight on drivers to total weight 26%
Adhesive power 9,750 Lbs.
Ratio of safe temporary tractive effort to adhesion .... 100%
Ratio of safe constant tractive effort to adhesion 36%
* This motor will deliver the commercial rated output for one hour with-
out heating more than 75° C. above the surrounding air.
472
ELECTRIC STREET RAILWAYS.
Complete Train.
Total weight of loaded motor car 32 Tons.
Weight of two coaches 32 "
Weight of 150 passengers in coaches 10 "
Total weight of loaded train 74~ «<
Maximum horizontal effort in accelerating train 9,750 Lbs.
Horizontal effort per ton during acceleration 132 "
Maximum power in accelerating uniformly to full speed . . 412 H. P
Maximum current at 500 volts accelerating train uniformly
to full speed 780 Amp.
Time required in accelerating uniformly to full speed ... 34 Sec.
Distance in which train will acquire full speed 900 Ft.
Horizontal effort, train running uniform speed 1,300 Lbs.
Power consumed, train running uniform speed 106 H. P.
Tractive effort per ton 18.25 Lbs.
Maximum practical negative horizontal effort in braking . 13,800 "
Time required to bring train to full stop 16 Sec.
Distance traversed by train during braking 370 Pt.
Train Performance.
Track.
Horse
Power.
Current at
500 Volts.
Speed Miles
per Hour.
Horizontal
Effort.
Level . . .
1% grade . .
2% grade . .
3% grade . .
106
170
235
295
190 amperes.
290 "
400 "
505 "
32
22
20.8
19
1300 lbs.
2780 "
4260 "
5740 "
Bala Sheet of Train ]Vo. 2.
Character of Service ; Elevated Railway.
Number of cars in train 2
Full speed of train on level track (miles per hour) . . 31
Average speed, stops one-third mile apart 15.8
Motor Car.
Weight of motor car body 10 Tons.
Weight or both trucks ♦ . . . . 10 "
Weight of two motors 5.5 "
Weight of 75 passengers 5 "
Total weight of loaded motor car 30.5 "
Number of motors on motor car 2
♦Commercial rated power of each 125 H. P.
Safe constant load for each 60
Safe temporary tractive effort of equipment 5,600 Lbs.
Safe constant tractive effort of equipment 1,600 "
Weight on drivers 18 Tons.
Ratio of weight on drivers to total weight 35%
Adhesive power 9,000 Lbs.
Ratio safe temporary tractive effort to adhesion 62%
Ratio safe constant tractive effort to adhesion 18%
Complete Train.
Total weight of loaded motor car 30.5 Tons.
Weight of one coach 19 "
Weight of 75 passengers in coach _5_ "
51.5
* This motor will deliver the commercial rated output for one hour with-
out heating more than 75° C. above the surrounding air.
ELEVATED RAILWAY TRAIN PERFORMANCE.
473
Maximum horizontal effort in accelerating train 5,640 Lbs.
Horizontal effort per ton during acceleration 109 "
Maximum power in accelerating uniformly to full speed . . 280 H. P.
Maximum current at 500 volts accelerating uniformly to full
speed 500 Amp.
Time required in accelerating uniformly to full speed . . . 37.5 Sec.
Distance in which train will acquire full speed 953 Ft.
Horizontal effort, train running uniform speed 1,000 Lbs.
Power consumed, train running uniform speed 115 H. P.
Tractive effort per ton, train running uniform speed . . . 19.7 Lbs.
Maximum practical negative horizontal effort in braking . . 11,000 Lbs.
Time required to bring train to full stop 16 Sec.
Distance traversed by train during braking 390 Ft.
Train Performance.
Track.
Horse
Power.
Current at
500 Volts.
Speed Miles
per Hour.
Horizontal
Effort.
Level . . .
1% grade . .
2% grade . .
3% grade . .
92
135
176
220
175 amperes
550
320
390
31
24.8
21.3
19.9
1,013 lbs.
2043 "
3073 "
4103 "
Data Sheet of Train Wo. 3.
Elevated Railway Service.
N umber of cars in train 1
Full speed of train on level track (miles per hour) . . 36
Average speed, stops one-third mile apart (miles per
hour) 15
Motor Car.
Weight of motor car body 10 Tons.
Weight of both trucks 10
Weight of two motors 3.5 "
Weight of 75 passengers 5 "
Total weight of loaded motor car "2875 "
Number of motors on motor car 2
♦Commercial rated power of each 60 .H.P.
Safe constant load for each 25 "
Safe temporary tractive effort of equipment 3,300 Lbs.
Safe constant tractive effort of equipment 700 "
Weight on drivers 16 Tons.
Ratio of weight on drivers to weight . 56%
Adhesive power 8,000 Lbs.
Ratio safe temporary tractive effort to adhesion 41%
Ratio safe constant tractive effort to adhesion 8%
Complete Train.
Total weight of loaded train 28.5 Tons.
Maximum horizontal effort in accelerating train 2,600 Lbs.
Horizontal effort per ton during acceleration 91.5 "
Maximum power in accelerating uniformly to full speed . . 122 H.P.
Maximum current at 550 volts, accelerating uniformly to full
speed 220 Amp.
Time required in accelerating uniformly to full speed . . . 36.5 Sec.
Distance in wiiich train will acquire full speed 810 Ft.
Horizontal effort, train running uniform speed 712 Lbs.
Power consumed, train running uniform speed 51 H.P.
* This motor will deliver the commercial rated output for one hour with-
out heating more than 75° C. above the surrounding air.
474
ELECTRIC STREET RAILWAYS.
Tractive effort per ton, train running uniform speed . .
Maximum practical negative horizontal effort in braking .
Time required to bring train to full stop
Distance traversed by train during braking .......
25 Lbs.
5,300
14.5 Sec.
305 Ft.
Train Performance.
Track.
Horse
Power.
Current at
500 Volts.
Speed Miles
per Hour.
Horizontal
Effort.
Level . . .
1% grade . .
2% grade . .
3% grade . .
51
63
85
101
90 amperes.
124 "
154 "
182
26
19.9
17.2
15.5
712 lbs.
1282 •'
1832 "
2422 "
ISSTALLATI^l OX1 iTREET CAR MOTORS.
(General Electric Company.)
In Creneral.
In locating the various parts of the equipment and in wiring the car, par-
ticular attention should be taken to secure the following results :
1. Maintenance of high insulation.
2. Exclusion of all foreign material, particularly grease, dirt, and water,
from the electrical equipment.
3. The avoiding of fire from arcs, naturally occurring at fuse-box, light-
ning arrester, etc.
4. The prevention of mechanical injury to the parts.
5. The placing of the parts so as to be accessible for operation and inspec-
tion, and yet out of the way of passengers.
Preparation of the Car Body.
The floor should be provided with a trap-door of such size as to allow as
free access as possible to the motors. Particular attention is called to the
advisability of having the bar across the car between the trap-doors remov-
able, in order that the top of either motor can be thrown back.
The roof should be provided with a trolley board which strengthens it,
and protects in case the trolley is thrown off ; it also deadens the noise.
A firm support should be provided for the light clusters. Grooves should
be cut for the leading wires in the roof moulding, and also in two of the
corner posts, one for the trolley wire, the other for the ground wire of the
lighting circuit.
On a closed car four 2 in. holes should be bored through the car floor under
the seats, one as near each corner of the car as possible.
On one side of the car, four § in. holes should be bored in a line, and 4 in.
apart, to receive the taps from the cable to the leads of motor No. 1. The
exact location of these holes depends on the type of motor used. The dis-
tance from the center of the axle to the center of this group of holes should
be about two and one-half feet for GE motors. On the same side of the car,
and in the same line, four other f in. holes should be bored 4 in. apart, to
receive the taps from the cable to the resistance boxes. On the other side
of the car three § in. holes in a line and 4 inches apart, should be bored
to receive the taps from the cable to the leads of motor No. 2, and on
same side of car and in the same line five other § in. holes 4 inches apart
should be bored to receive the taps for the trolley, resistance, and shunt for
IVTotor No 2.
Reference should be made to diagram in order that each set of holes shall
be on the proper side of the car, and at such a distance from side-sills as to
be out of the way of wheel throw.
INSTALLATION OF STREET CAR MOTORS. 47£
Measuring about 38 inches from the brake-staff and a suitable distance
inside of the dash rail, an oval hole 5 in. x 2| in. should be cut in each plat-
form, to receive the cables.
On an open car no holes need be bored for the floor wiring except those
through the platform.
Installing1 Controllers.
In the standard car equipment one controller is placed on each platform
on the side opposite the brake handle, in such a position that the controller
spindle and the brake-staff shall not be less than 36 inches, nor more than
40 inches apart. The exact position depends somewhat on the location of
the sills sustaining the platform. The feet of the controller are designed to
allow a slight rocking with the spring of the dasher. Two one-half inch
bolts secure the feet to the platform. An adjustable angle iron is furnished
to be used in securing the controller to the dash-rail. A. wire guard is also
furnished, to be secured to the platform in such a position that the cables
pass through it into the controller. A rubber gasket is furnished with each
controller, to be placed between the wire guard and the platform, to exclude
water. For dimensions of controller, see Figs. 25 and 26.
Wiring-.
This work can be conveniently divided into two parts ; namely, roof
wiring- and floor wiring.
Roof wiring includes the running of the main circuit wire from the
trolley through both main motor SAvitches down the corner posts of the car
to a suitable location for connecting to the lightning arrester and fuse box ;
also wiring the lamp circuit complete, leaving an end to be attached to the
ground. Whenever wires lie on the top of the roof, they need not be
covered with canvas or moulding, except to exclude water where they
pass through the roof. In such cases a strip of canvas the width of the
moulding, painted with white lead, should be laid under the wire, and over
this and the wire should be placed a piece of moulding extending far enough
in either direction to exclude water. The moulding should be firmly
screwed down and well painted.
The above wiring should be done if possible while the cars are being
built.
floor wiring may be done after the car is completed without injuring
the finish.
Made op cables give far better protection to the wiring, and are
easier to install than separate wires, and should be used in the floor wiring
if possible. The simplest way of installing them on box cars seems to be as
follows :
After the car bodies are prepared according to the above instructions, the
cables (one on each side of the car) should be run through holes in the plat-
form, and the connections made to the motors and controllers.
After making connection to the controllers, all slack should be pulled up
inside of the car under the seats, and held in place, preferably against the
side of the car, by canvas or leather straps. Motor taps should project
through the sills for attachment to the flexible motor leads just far enough
to permit easy connection, leaving as little chance as possible for vibration.
No rubber tubing will be required on taps, as they all have a weather-proof,
triple-braided cotton covering outside of the rubber insulation to prevent
abrasion. All joints should be thoroughly soldered and well taped. The
portions of the cables passing under the platforms should be supported by
leather straps screwed to the floors or sills. Cables should never be bent
at a sharp angle. The ground wire should run under the car floor rather
than under the seats.
On open cars all wires and cables must be run under the car, and should
be well secured to the floor with cleats or straps.
A good joint can be made by separating the strands of the tap-wire, and
476 ELECTRIC STREET RAILWAYS.
wrapping the two parts in opposite directions around the main wire. Both
Okonite and rubber tape are furnished. It is desirable that Okonite should
be used first and rubber tape put over it, as the latter will not loosen and
unwrap as Okonite will. All openings in the hose should be sewed up as
tightly as possible around the wires.
Separate wires can be installed if necessary, observing the following
directions :
The floor wires on box cars should be placed under the seats as much as
possible. In the few places where it is necessary for wires to cross, wood
should intervene in preference to a piece of rubber tubing or loop in the
air. This rubber tubing is not necessary where wire is cleated under the
floor (as on open cars), if it does not pass over iron work, or is not ex-
posed to mud and water. Where so exposed, it should be covered with
moulding, but where moulding is used it should be carefully painted inside
and out with good insulating compound to exclude water. The wire passing
to the fuse box should be looped downward to prevent water running along
the wire and into the box. Care should be taken to avoid metal work about
the car in running the wires, and that nails or screws are not driven into
the insulation.
In general it is not desirable to use metallic staples and cleats for car-
wiring, except about the roof, or inside the car. Where wires are subject
to vibration, as between the car bodies and motors, flexible cable must al-
ways be used. A certain amount of slack should be left in the leads from
the motor to the car body, depending on their length. On cars with swivel-
ing trucks a greater amount of slack is necessary. As slack gives greater
opportunity for abrasion, care should be taken to leave only what is abso-
lutely necessary.
Operation and Care of Controller.
When starting, regulate the movement of the handle from point to point
so as to secure a smooth acceleration of the car.
Do not run between points.
The resistance points 1st, 2d, 3d, 6th, and 7th, are intended only for the
purpose of giving a smooth acceleration, and should not be used contin
uously.
Eor continuous running, use the 4th, 5th, 8th, and 9th points, which are
shown by the longest bars on the dial.
When using the motor cut-out switches be sure that they are thrown up
as far up as they will go.
In case the trolley is off and the hand-brakes do not hold the car, an
emergency stop may be accomplished by reversing the motors, and turning
the power-handle to the full speed, or next to full speed point.
To examine the controller, which should be done regularly, open the
cover, remove the bolt with wrench attached, and swing back the pole-piece
of the magnet.
The contact surfaces and fingers should be kept smooth, and occasionally
treated with a small amount of vaseline to prevent cutting.
All bearings should be regularly oiled.
A repellent compound, paraffine, rosin, and vaseline, equal parts by
weight, placed in the water-caps of the power and reversing shaft, is an
efficient protection against Avater.
Dirt must not be allowed to collect inside of the controller.
No diagrams of wiring are included here as there are now a large number
of different combinations of motors, and sizes and diagrams are always to
be procured from the builders.
Diagrams of Car Wiring.
In general car wiring is carried out in about the same manner for all
styles and sizes of car, more particular description being given above. Wil-
ing differs mainly in details, governed by the number, style and horsepower
of motors used.
INSTALLATION OF STREET CAR MOTORS.
477
Diagrams of standard wiring for two motors per car and for four motors
per car follow, in Figs. 31, 32, 33, 34. They are all from the G. E. Co. lists, as
controllers made by that Company are almost universally used, although
many of older design by other companies are still in the held.
jo"
iHtJsiiSsr^ g:
S = "> 5. 5 HvnO °a o 3 s
478
ELECTRIC STREET RAILWAYS.
INSTALLATION OF STREET CAR MOTORS.
479
m z»*
°UJ
480
ELECTRIC STREET RAILWAYS.
° i S5
Equipment Iiists.
The following is a list of material required for the electrical equipment
of one car fitted with two motors :
■■^^■■^M^^Hi
CONTROLLERS. 481
QUANTITY.
1 Trolley pole.
1 Trolley base.
2 Motor circuit switches.
1 Lightning arrester.
1 150 ami M-e magnetic cut-out (fuse-box).
1 Resistai. ue box.
1 Resistance box.
1 Core for kicking coil.
2 Controllers (includes wire guard and gasket, supporting bracket,
cap screws, and washers for fastening to dasher).
1 Controlling handle.
1 Reversing handle.
One of each of these handles is always shipped with each pair of
controllers unless specified to the contrary.
75 ft No. 6 B. & S. strand wire (7-.061 in.) for roof-wiring.
20 100 or 150 ampere fuses.
10 Two-way connectors, J in. hole, No. 6.
30 Brass corner cleats, {B in. slot.
25 Brass flat cleats, T7B in. slot.
110 J in. No. 4 R. H. brass wood screws for brass cleats.
25 Wood cleats, £ in. slot.
25 "Wood cleats, f in. slot.
100 1J in. No. 8 R. H. blued wood screws for wood cleats.
1 lb. Solder.
1 lb. | in. Okonite tape.
1 lb. 1 in. adhesive tape.
Material for set of cables as follows :
4S0 ft. No. 6 B. & S strand wire (7-.0G4 in.), single braid.
100 ft. No. 6 B. & S. strand wire (7-.064 in.), triple braid for taps.
41 Brass marking-tags.
64 ft. 1£ in. cotton hose.
1J lbs. Rubber tape.
4 lbs. Paragon tape.
li lbs. Solder.
This material can be procured made into a " set of cables " with-
out extra cost.
1 Car-lighting equipment.
Under this heading are included all that type of appliance used for start-
ing and stopping the motors and controlling tbe speed of the same. As
almost all the old forms of rheostat with different steps have been aban-
doned for the so-called series- parallel controller, it is not necessary to de-
scribe any other here, nor will any detailed description of tbose now in use
be attempted.
Two distinct forms are now mostly in use ; one, the magnetic blow-out type,
made by tbe General Electric Company and used by the Westinghouse Elec-
tric and Manufacturing Company ; the other the so-called solenoid blow-out
type, made by the Wafker Company, of Cleveland, Ohio.
The principle of the magnetic blow-out type was first developed by Prof.
Elihu Thomson, i. e., that an electric arc in a strong magnetic field is
blown out of line and extinguished or cut in two. Tbis fact is taken ad-
vantage of in the controller of the General Electric Company by using a
strong electro-magnet to extinguish the arcs formed at the contact-points,
when the circuits are broken. The construction is shown in the cut of
Series-parallel controller, form K2, following.
The theory of the solenoid blow-out of the Walker Company is said to be
that the arc is lifted out of place, and eases down the current, thus cutting
it off easily, and' without bad inductive effects. The following cut shows
482
ELECTRIC STREET RAILWAYS.
the connection and supposed action, and further along will be found cuts
showing the assembled controller, the same developed, and a diagram
showing general dimensions.
ElG. 35. Enlarged diagram showing theory of
Solenoid Blow-out Controller of Walker
Company.
Controllers are now made in so many forms and varieties that it is im-
possible to give more than a few of the combinations which are practi-
cally the same everywhere in the United States.
Fig. 36. Series-Parallel Controller, Form K2.
General Electrie Company.
Used also by theWestinghouse Electric and Manufacturing Company, and
others.
CONTROLLERS.
483
The General Electric Company manufactures controllers for all condi-
tions of electric railway service. They are divided for convenience in desig-
nation into four general classes, each designated by an arbitrary letter.
Type IS. Controllers are of the series parallel type, and include the
feature of shunting or short circuiting one of the motors when changing
from series to parallel connection.
Type Ii Con* rollers are also of the series-parallel type, but com-
pletely open the power circuit when changing from series to parallel.
Type B Controllers may be either the series-parallel or rheostatic
type, but always include the necessary contacts and connections for operat-
ing electric brakes.
Type II Controllers are of the rheostatic type and are designed to
control one or more motors by means of resistance only.
Fig. 37. " R " Type of Rheostatic Controller.
Rheostatic Controllers.
It 11 Controller.
Designed for one 50 h.p. motor.
Can be wired for use with motors using either shunted or full field.
Total number of notches, six.
(The Rll controller has been known as the KR controller.)
R 13 Controller.
Designed for two 50 h.p. motors.
Same as Rll controllers with exception that magnet-coils and contact-
fingers are of greater capacity, and reversing-switch is arranged
for two motors.
484
ELECTRIC STREET RAILWAYS.
ISeries Parallel Controllers.
Title.
Capacity.
Controlling
Points.
Remarks.
K
Two 35 h.p.
Motors.
4 Series.
3 Parallel.
For motors using loop or shunted field.
K-2
Two 35 h.p.
Motors.
5 Series.
4 Parallel.
For motors using loop or shunted field.
K-4
Four 30 h.p.
Motors.
5 Series.
4 Parallel.
For motors using loop or shunted field.
K-6
Two 80 h.p.
Motors or
Four 40 h.p.
Motors.
6 Series.
5 Parallel.
Connection board so arranged that con-
troller may be used for two or four motors
on grounded or metallic circuit.
K-7
Four 30 h.p.
Motors.
5 Series.
4 Parallel.
Similar to K-12, but arranged for metallic
circuit system.
K-8
Two 50 h.p.
Motors.
5 Series.
4 Parallel.
Similar to K-ll, but arranged for metallic
circuit system.
K-9
Two 35 h.p.
Motors.
5 Series.
4 Parallel.
Similar to K-8, but has connecting wires
and blow-out coil of smaller capacity.
K 10 .Two 35 h.p.
lv 1U Motors.
5 Series.
4 Parallel.
K-ll
Two 50 h.p.
Motors.
5 Series.
4 Parallel.
Similar to K-10, but has connecting wires
and blow-out coil of larger capacity.
K-12
Four 30 h.p.
Motors.
5 Seines.
4 Parallel.
The K-12 is a K-ll with reversing switch
arranged for four motors.
K-13
Two 125
h.p. Motors
7 Series.
6 Parallel.
K-14
Four 60 h.p.
Motors.
7 Series.
6 Parallel.
L-2
Two 175h.p.
Motors.
7 Series.
7 Parallel.
L-3
Four 175
h.p. Motors
9 Series.
7 Parallel.
L-4
Four 100
h.p. Motors
7 Series.
7 Parallel.
Similar to the L-2, but with additional re-
versing switch parts for four motors.
L-6
Four 200
h.p. Motors
9 Series.
6 Parallel.
Special for Central London Locomot ves.
Handle moves in counter-clockwise direc-
tion for turning on power.
L-7
Four 200
h.p. Motors
9 Series.
6 Parallel.
Differs from the L-6 in the direction cf ro-
tation of the operating handle.
Electric Brake Controllers.
Title.
Capacity.
Controlling
Points.
Remarks.
BA
Two 35 h.p.
Motors.
5 Series.
4 Parallel.
6 Brake.
Power connections same as K-2. For mo-
tors using shunted field for running
points.
B-3
Two 35 h.p.
Motors.
4 Series.
4 Parallel.
6 Brake.
Has no points for shunting motor fields.
Superseded for general use by the B-13.
B-5
Two 50 h.p.
Motors.
4 Series.
4 Parallel.
6 Brake.
Similar to B-3, but has heavier connecting
wires and blow-out coil. Superseded for
general use by the B-23.
B-6
Four
30 h.p.
Motors.
4 Series.
4 Parallel.
6 Brake.
Similar to B-3, but has reversing switch and
brake contacts arranged for four motors.
Superseded for general use by the B-19.
CONTROLLERS.
485
Electric Brake Controllers. — Continued.
Title.
Capacity.
Controlling
Points.
Remarks.
B-7
Two 100
h.p.
Motors.
6 Series.
5 Parallel.
6 Brake.
Has separate brake handle.
B-8
Four
50 h.p.
Motors.
6 Series.
5 Parallel.
7 Brake.
Has separate brake handle.
B-13
Two
40 h.p.
Motors.
5 Series.
4 Parallel.
7 Brake.
Supersedes the B-3, from which it differs in
having contacts for connecting motor
armature in series with their respective
brake shoes.
B-16
Two
50 h.p.
Motors.
5 Series.
4 Parallel.
7 Brake.
Similar to B-23, but has special connections
for the surface contact system.
B-18
Two
35 h.p.
Motors.
4 Series.
4 Parallel.
6 Brake.
Differs from the B-3 in that it has an extra
cut-out switch blade, and connection board
arranged for motors using metallic or
grounded circuit.
B-19
Four
40 h.p.
Motors.
6 Series.
5 Parallel.
7 Brake.
Similar to B-8, having separate handles for
power and brake. Supersedes B-6.
B-23
Two
50 h.p.
Motors.
5 Series.
4 Parallel.
7 Brake.
Supersedes the B-5. Similar to the B-13,
but has connecting wire and blow-out coil
of larger capacity.
B-24
Two
40 h.p.
Motors.
5 Series.
4 Parallel.
7 Brake.
Similar to B-13, but has cut-out switches
arranged for metallic circuit systems.
B-25
Two
50 h.p.
Motors.
5 Series.
4 Parallel.
7 Brake.
Similar to B-24, but has connecting wire
and blow-out coil of larger capacity.
B-29
Two
50 h.p.
Motors.
5 Series.
4 Parallel.
7 Brake.
Similar to B-23, but has separate brake
handle.
Stlaeostatfc Controllers.
Title.
Capacity.
Controlling
Points.
Remarks.
11-11
One 50 h.p.
Motor.
6
For motors using either full or shunted
fields for running points.
R-12
Two 50 h.p.
Motors.
6
Motors are connected permanently in par-
allel.
R-14
Two 35 h.p.
Motors.
*
Very short and specially adapted to mining
locomotives. Motors are connected per-
manently in parallel.
R-15
Two 75 h.p.
Motors.
G
Motors are connected permanently in par-
allel.
R-16
Four 35 h.p.
Motors.
6
Similar to R-15, but has reversing switch
arranged for four motors.
11-17
One
Motor.
6
Similar to R-ll. but has resistance on the
trolley side of the motor instead of on the
ground side.
11-19
Two 50 h.p.
Motors.
6
Similar to R-17. Motors are connected
permanently in parallel.
R-22
Two 50 h.
Motors.
5
Shape like R-14, others same as R-12. Mo-
tors are connected permanently in parallel.
486
ELECTRIC STREET RAILWAYS.
MOTOR COMBINATIONS
RES. MOTOR 1 MOT OR 2
rmirO^IHKJ-W-,
-KIIIHIo^w-J-^^^- _
XnTh-T0_AMA/^ur°^wWH—
|-T^ri pO-WA^-. r-O-^MA-i
— Hini|[!0-jfA^rC^AAw^'
CONTROLLERS.
487
-fc-H,
?! LJ
An
! Lc*
f
__,
f
-B-
G
*■ — L--*
M"*oT-»i
I'
'" °(fe^P
1;
Figs. 40 and 41. Diagrams for Dimensions of Controllers.
Dimensions of Controllers.
Type K.
I
Type L.
33T35
w
IN
35 Jg
35ft
38|
33ft
33ft
t, -
33A
0
gig
33T3H
M
33ft
33ft
M
■ -■J
39
381
Hi
3
&
A
401
451
401
B
1?%
7t3b
7ft
8ft
'l6
7ft
7ft
7ft
7ft
7ft
10
10
101
13
101
C
2i
2|
2J
3ft
21
21
21
21
21
21
5|
5|
8|
6i
84
D
4£
3i
4J
1
43i
4i
1
3J
43J
3i
47
41
41
4J
1
31
4J
1
42J
4*
4i
I
31
F,
1
3*
42£
1
3i
1
3+
F
G
42J
42i
42J
42i
46x§
461
46i|
531
47i|
H
"<1
291
291
25f
16§
33§
28f
16J
29
29
29
29
29
29
K
24§
16f
241
24+
24+
24+
24i
241
L
16|
16|
16f
16f
16f
16|
16f
19
22|
25}
281
251
M
17|
m
171
17i
17*
17J
17*
17i
17$
m
20
23|
27|
29
32ft
0
5|
5|
5|
5|
5|
5|
5|
5|
5|
5|
8|
8|
5i-5
P
8
8
8
9
8
8
8
8
8
8
Si-
9J
9§
13
9*
R
8T3*
8t3b
8ft
9+
8ft
8ft
St3*
8ft
8ft
8ft
ll
11
HI
14
HI
fl
U
5i
6i
5i
4i
5i
5£
5i
5i
5J
5i
4
4
3i
V
7/5
7f
7ft
7|
7ft
7ft
7ft
7ft
7/5
7ft
10|
I0|
151
w
6H
5i§
6T5
'"'IS
6M
6tt
Hh
w
6H
6X5
5
8|
9
X
4ft
4ft
4ft
4f
4ft
4ft
4ft
4ft
4ft
4ft
5i
6i
10
Y
488
ELECTRIC STREET RAILWAYS.
CD
ft
>>
H
CM
aw
gco
Ht^N CO COt-lOCOCClQt-C©^
OS
3
g«
:-f L-"Vi'^>— To — "— ^'trT-uo co x u~ i> co%t< * *
CO -*NNHH • •
P3
go
co^cf^'i-i To'^H— , ^'coT-iooo coin l~- co1'*' ' •
CO rf CM CM rH rH . .
CO
3
3W
f^CO
C5 t- CM £- CO L~ LO 00 00 IC t~ CO "*
m
iw
^CO
CO t- CM r-j CO L— LO CO CO LO L- CO Tt* ' *
2
bi> .
Rco
r-|t-<M ^ 00 COt>0»COON»t • •
gcb
« t>N t H CO iH r. J "J l- C X CO L- L- to tP " "
i
r"i6
co t- ci -t" " :o — : re ^ co i - i- x x TV i -co"'-* • •
CD
w
.Sfco
f^CO
cooocot'h:o»dp:i:i co x re l- co o ■* io ob
gcO
r-Wrtbi ~;:i-::i.c ?- /-;i-rsn rclx-Hfrir-feo "°|H
CO CJ T»H -# i-l CO CO CD CO rH oi o <r. cs lo CI lO O * *
CO TJH CO CO CM <M T-l . .
CO
gw
00 C5 •* -C* -^ CO CO O CO -. J 1 . - C. C. i- - > l-. o * *
CO ■* CO CM CM CM i-l . .
«
.^co
^co
O 05 CO •* r- CO CO p CO o O O CO O LC CO o UO 00 CO
CO
ieuo
^co
00 05 ■* -* ^H -fi S5 O CO r-i CI IC CO. C5 O 01 UO o
CO
f^CO
CO G5 ■* ■* rH CO CO O CO i-; CI O O ©5 LO CI LO O ' "
CO ■* CO CM CM CM rH . .
W
.^00
^co
3310 . - .g . .g>g^O>^^C005C5
w
^co
cr"- ^? * ' *J0 ' ' L- ^O Cj rnP^L- CO co ao°05
CO
g$g | gcoco^co^co^nooicocooc^ ; ;
CO
fr
CO CO' CO -t — :o -+■ p "O C^ -~- »o O. COOCOCOHI "
gco
co co' co ^r ^h co ^t" p cp — re ih cr. x- co — co •#
|
<l«OflH^OWW^gOPH^H)r*^MrHSJ
THE SPRAGUE MULTIPLE UNIT SYSTEM.
489
I" V
Figs. 42 and 43. Diagrams for Dimensions of Controllers.
THE iPRAGUE MULTIPLE V]¥IT SYSTEM.
BY FRANK J. SPRAGCTE IN STREET RAILWAY JOURNAL, MAY, 1901.
This system, briefly defined, is a system of control of railway motor con-
trollers, whatever their number and wherever situated in a train, through a
secondary electric circuit common to all the cars from or through which it
is desired to exercise control. The number and position of equipped or
unequipped units, and to a certain extent the character of these units, iz
immaterial, and variation in end relation is likewise a matter of indifference.
The system covers the entire range of service from a single car operated
as an independent unit to a train of any length equipped with as much or
little power as required.
In General.
Each motor car is equipped with complete power operated apparatus for
its motors, and has in addition an independent train line by means of which
it can be operated from other cars, as well s operate other cars. This train
line terminates in shrouded couplers under the platform at each end of the
car. The train lines on different cars, whether equipped with motors or
not. are joined by detachable reversible jumpers.
The train line is especially designed to secure reliability. To insure this
it carries only small currents, and has but four or five controlling wires
There is no ground wire carried through the train line. Provision is made
for a ralay line to be carried in the common cable for the operation of the
air compressors. The wires are each thoroughly insulate! and the cable is
protected from mechanical injury. The train line is completely isolated
from the local circuits on each car. The operating: relays, energized from
the train line on each car, are each separately protected so that their fail-
are cannot interfere with the operation of unaffected cars. The operation
is in no way affected by changes in the sequence of cars
The train line can be readily cut off from the local circuits on any car
The local pilot motor circuit and main motor circuits are independent of
the train line, so that no derangement of main circuits or apparatus can be
communicated to it.
Each pair of motors is controlled by the joint operation of a speed con-
troller and reverser. The main circuit is opened independently by each.
Any derangement of either renders that car inoperative. This is secured by
interconnection of operating circuits, so that current cannot be continued
through motors.
Each car automatically governs the current input in the car, and insures
the most efficient acceleration and operation independent of the motorman.
Means are also provided to restrain the current input at will by manipula-
tion of the master switch.
Protection is automatically provided against any improper operation at
the master switch, or misplacement or failure of any part of the system.
In any case, the indicated result will follow a movement of the master
switch, or the main circuit will be opened and the apparatus rendered
inoperative.
490
ELECTRIC STREET RAILWAYS.
The system is
circuit diagrams.
Circuits.
illustrated by an elemental diagram, Fig. 44, two typical
Figs. 45 and 47, with and without the coast relay, showing
also the development of the appara-
tus, and two corresponding schematic
diagrams, Figs. 4G and 48, showing con-
trolling circuits only for single cars.
Reference to the diagrams shows that
on a fully equipped car there are four
distinct circuits, which are shown by
distinguishing lines. These are :
( iii-iiiotor Circuit. — This in-
cludes the main motors, the contacts
with the supply circuit, and the re-
verser, rheostat and motor grouping
contacts which are in the circuit of
the main motors.
JLockb & Operative or Control-
ling- Circuit. — This includes the
relay or magnet coils, pilot motors, or
whatever directly moves or controls
the main motor controllers, or actu-
ates main controlling contacts when
the system is, as here shown, entirely
electric, or controls the pilot mechan-
ism if some other power than electri-
city is used to move the main con-
trollers.
Platform-switch Line. — This
on a single car becomes a part of the
local operative circuit, and on a train
energizes all the local operative or
controlling circuits through the inter-
mediary of the particular platform-
switch in use, and the electrical train
or governing lines on it and the other
cars.
Train ©r Governing- line. —
This is the continuing cable running
from one car to another, which at one
or more points is connected, on the
one hand to the platform-switch line,
and on the other to the local operative
circuits. It is made up of the per-
manently placed train line on the sev-
eral cars' and the couplers or jumpers
connecting them together. It may evi-
dently be common to cars which are
equipped with and to cars which are
not equipped with motors. It is the
independent means of transmitting an
initial and governing impulse from any
one of a number of points.
Operation.
The specific operation of the appa-
ratus controlled by these circuits is as
follows :
On each of the fully equipped cars
there are two main motors. Each mo-
tor has a single unchangeable set of
field coils and an armature. The mo-
tor connections and the current flow-
ing therein are determined by three
principal switches. There is a reverser
for changing the armature connections
HM^HB^^^MI^H
THE SPRAGUE MULTIPLE UXIT SYSTEM.
491
492
ELECTRIC STREET RAILWAYS.
of tlie two motors, a rheostat for varying the resistance in the circuit
with them, and a motor switch for effecting series or parallel relation.
These three pieces of apparatus can be physically separate, or any two or
all three can be combined in one structure. * As here shown, the two switches
which determine speed form one structure, termed the main controller, and
the reverser the other.
These main switches are primarily controlled from a master switch on
each platform of any equipped car, through a train line and suitable relays
and a pilot motor. This master switch is a multiple circuit maker, a means
for closing the line supply to one or more independent train wires, each of
which operates a relay. This switch has neither mechanical nor electrical
connection of any kind with the motor circuits, nor, although it has certain
corresponding position, is its movement necessarily coincident with, nor
proportional to, the movement of any of the main switches.
In ordinary operation, the two motors are first put in series with each
other with suitable resistance, which is cut out until the full half potential
FlG. 46. Schematic Diagram of Control Circuits Only, Sprague System.
is supplied to each motor, which is the half-speed combination. In going
thence to full speed, the main circuits are first opened instantly at the main
controller, or, if desired, progressively through resistances and independent
main contacts, or they can be opened at the reverser.
The motors are then thrown into multiple relation with a resistance in
circuit of about one-quarter that used in the first series position, which is
progressively cut out until the motors have full potential, and run at their
full capacity and speed. The quartering of the resistances on the first
position is effected by using independent resistances in each motor, throw-
ing them in series and parallel relation the same as the motors, and using
the same progressive steps.
In any position of the controller the current can be cut off either instantly
by the reversers, which have independent main-line contacts, or progies-
sively at the main controller.
The reverser contacts for the armatures of the two motors, as well as two
extra " line" contacts, are for convenience mounted on a common spindle.
The cylinder of the reverser is normally retracted to a middle or open
THE SPRAGUE MULTIPLE UNIT SYSTEM.
498
circuit position, and there are two solenoids, one for pulling the cylinder
one way for ahead movement of the train, and the other for pulling it the
opposite way for backward movement.
Provision is made for dead-beat movement, and also for inter-connection
of controlling circuits by contacts on the same cylinder as the main
contacts.
The circuit for the reverser passes through the automatic stop coil, and
is completed through a by-pass on the controller in the first contact 'posi-
tion, or through a contact made by the automatic, so that once opened it
cannot be operated unless the controller is in a safe position for the
motors.
The cylinder of the main controller is driven with an intermittent motion
by a pilot motor through a powerful locked spring, so that the armature of
the pilot motor and the spindle of the cylinder do not move either in
synchronism or to an exactly like extent. This is necessary to insure free-
dom from hot contacts and dragging of arcs.
"ft G Fuses
a! i r~7u<n ; .-s?<Ki :
■ a a e!3^— -; M~* Coils
CliD3 on Reve
'^.iszsxisj
|1400 |l000 Pilot So Brake
* | 70 ohms.fo
| Grouud J
FlG. 47. Schematic Diagram, Control Circuits Only, Without Coast Relay.
The pilot motor is governed by either four or five relays called, respec-
tively, the "coast," "series," and "multiple" relays, the "automatic
stop" and the "throttle." Since the "automatic stop" also has coast
relay contacts, the separate coast relay may be discarded.
There are three allowable running positions for a pair of motors, — the
coast or open circuit position, the series position, wrhen the two motors are
in series without any resistance in circuit, and the multiple position, when
the two motors are independently across the line without any resistance*
In addition, the motors can be run temporarily with more or less of the
resistance in circuit for the purpose of switching. On heavy railroad work,
such as on elevated and suburban roads, minor variation of running speed
in either the series or the multiple relation of the motors by the use of
resistances is rarely practiced, and is never necessary save in starting. The
494
ELECTRIC STREET RAILWAYS.
apparatus is especially constructed to discourage any such variation of
running speed.
The circuit which operates tlie pilot motor on each car is a purely local
circuit, coming from the car shoes and returning to the track, just as the
main circuit of the motor does. It is not connected to the train line or the
master switches in any way. Its path is through the field magnets, hreak
THE SPRAGUE MULTIPLE UNIT SYSTEM.
495
of current, it can become
of acceleration. It does
and armature of the pilot
motor, through the contacts
of the coast, series, or
multiple relays, and also
through the contacts of the
throttle and automatic stop.
If either the throttle or the
automatic stop are in an
open circuit position it is
impossible for the pilot mo-
tor to move in one direction,
and it is hence impossible
for the controller to be ad-
vanced, although if in an
advanced position it can be
moved backward. The cir-
cuits through the relay con-
tacts and the pilot motor
also pass through limit
switches on the controller
cylinder. If this control
cylinder is in "off" posi-
tion, and the throttle and
automatic stop are in proper
positions, closure of the
coasting relay would not
cause any movement what-
ever, but closure of the
series relay will allow the
pilot, if otherwise uninter-
rupted, to move the con-
troller^ the series position,
Avhere it will automatically
stop. In the same way clos-
ure of the multiple relay
will move the controller
either from the coast posi-
tion or from the series posi-
tion to the full multiple
position, where it will be au-
tomatically stopped. Open-
ing the throttle, however,
will either arrest or retard
the rotation of the pilot
motor and the progression
of the controller, and drop-
ping of the automatic stop
or opening of the reverser,
which is also provided with
a coasting contact, will at
once return the controller
to an open circuit or any
other determined position,
regardless of the motorman.
The throttle is operated
automatically by the cur-
rent in one of the motors,
and serves a double pur-
pose.
It retards or stops the
forward movement of the
main controller at any de-
sired current increment,
and, since it responds to
a determinate rise and fall
m automatic switch for providing a definite rate
lot prevent any desired slower rate of accel-
496 ELECTRIC STREET RAILWAYS.
eration, or in any way remove from the motorman the positive operation
of the main controller at will within the limits of safe and desirable current
inputs. Further reference to its action will be made.
It will be seen, therefore, that the physical operation of the controller is
intermittent in character, and certain automatic controlling devices are
provided which modify its operation.
A single car will first be considered. The coast, series and multiple relays
are energized by platform-switch circuits, which terminate in a master
switch or controller at the platform, at which a connection to the supply
circuit is also made. To this same master switch are brought also the
terminal wires of the solenoids operating the reverser. This master switch
is the apparatus manipulated by the motorman, and except as he is limited
by the automatic features, or hindered by circumstances which he cannot,
and is not intended to, control, all operation either of the particular car or
the train is initiated at this point.
The master switch consists of a cylinder with suitable contacts operated
by a handle interlocked with the top of the switch. Against the cylinder
rest a set of fingers, and between each pair of the fingers is an insulating
shield or separator, the separators being mounted on a common spindle.
The speed and direction of car movement are initiated at this master switcb
by the movement of a single handle. The switch has (1) the off or normal
position, to which the handle is spring retracted in case the operator lets
go of it, (2) for ahead movement, three running positions, coast, series and
multiple or full speed, with no contacts between, and (3) for the back move-
ment, two running positions, coast and series or half-speed position. The
car can be stopped and reversed by a single throw of the handle of the
operator's or master switch from one side of the open position to the other.
It will be noted that there is no physical, nor even any electrical, con-
nection whatever betAveen the master switch and the main controller. There
is simply an electrical connection with the three relays spoken of, and with
the solenoids of the reverser which form a part of the main control system.
Movement, therefore, of this handle only indirectly affects operation of the
main parts of the apparatus under certain conditions and when certain
circuits permit such operation.
The ordinary operation is that when a motorman wishes to go ahead at
half-speed he moves the master controller to the series position. The
reverser is instantly set for movement ahead, the series relay is closed, the
pilot motor starts up, the driving spring is put under tension, and the con-
troller spindle moves forward intermittently until the pilot limits stop it at
the half-speed position. If during this operation the throttle should lift,
this advance of the controller cylinder will be retarded or stopped. If the
automatic stop should drop, the advance not only will be stopped, but the
controller will at once run backward to an open circuit or other determined
position without regard to the set of the series relay, or. what is the wish of
the man at the master switch.
Being at the series position, if the motorman wishes to go at full speed,
the handle of the master switch is moved to that position, when similar
operations take place at the relays and pilot motor.
Or the operator may move his switch handle at once from the open circuit
to the multiple position without any regard to the series position, and the
main controller, controlled by the throttle, will advance to full-speed
position. Of course the advance of the main controller may be made at
will, step by step, by touch-and-go contact at the master switch, and its
advance can be arrested instantly. If desirable, when a coast relay is used
its connection can be changed so as to, at will, throw the throttle out of
action, although this is not desirable.
By minor changes in the controlled circuits they can be arranged so that
the operator can operate entirely with the motor's in series or entirely in
multiple, or either at will. This is because the controller has two circuit
positions, one at the beginning of the series combination and one at the
beginning of the multiple combination. It is what is known as an open-
circuit controller, and provision is made for not only opening circuit in two
places on its cylinder, but also independently on the reverser.
Comparison of the movements of the master switch and the main con-
troller illustrate very clearly the inter-connection of controlling circuits
and their utility, and how they are intended to provide for every emergency.
The master switch has two running advance positions and one running
THE SPRAGUE MULTIPLE UNIT SYSTEM. 497
back position, and movement of its handle between those two points in no
Avay affects the main controller ; the latter has several positions where it
can rest with identically the same position of the master switch handle pro-
vided its motion is arrested before it has reached one of its limits ; under
certain conditions the controller will not make any motion whatever in
response to a master switch ; under certain other conditions, it will make
a partial response, then automatically stop, and without any change of
movement of the master switch go ahead again and automatically stop ;
the controller, under other circumstances, will respond to the master
switch, then stop, and immediately, or after an interval, go back to an open
circuit or any other predetermined position ; under changed circumstances
it will advance intermittently to, or toward, some determined position
indicated by the master switch, then stop, go backward to some other
position, and then go forward again ; or in passing from a coast or open
circuit to a multiple position, the controller may or may not respond to
closure of the series contact." If the inotorman wishes to reverse the car
while going ahead, with the motors in either the series or the multiple
position, the mister switch can be instantly thrown to the reverse series
position, and the controller while immediately responding, will not in like
degree, for as the master switch passes the off position the reversers will
open, the main circuit of the motors will be instantly interrupted, the
automatic stop, on each car will run the controller back to some other
determined position, the reversers will then close, and the series relay,
which, although set by the master switch, has, up to that moment, been
entirely inoperative, will now allow the pilot motor, controlled by the
throttle, to intermittently move the controller to the reverse half-speed
position.
If the by-pass on the controller is of proper length the reverser will close
circuit as soon as the controller has returned to, say, the first resistance
position, and it will remain there until the current has dropped below the
safe amount.
In short, to all apparent intents and purposes, the controller seems pos-
sessed of an independent intelligence, because the relay system and the
inter-connection of circuits is such that all local emergencies are provided
for, as they must be, without regard to the wishes, intents or carelessness
of an operator.
To connect two or more cars together, and to provide for the initiation of
the operation of the controllers on such other cars as may be fully equipped
from one or more of the master switches, an independent train line is
provided, which is the extension of the platform-switch circuit from car to
car, through fixed train cables on each car terminating in couplers at the
ends of the cars, and flexible and reversible train cables, or jumpers, ter-
minating in couplers with complementary contacts joining the several train
cables together at the ends of the cars. These train lines and jumpers are
so connected to the coupling heads that the controlling circuits are auto-
matically paired to insure proper operation of the various main controllers
from any master switch without regard to what are the abutting ends of
the cars, or what is their number or sequence, or how the jumpers are
reversed, or whether, as in practice, they are coupled indifferently on one
side or other on the cars.
All roads, of course, do not change their sequence in the make-up of
trains, but on many the cars are reversed, as in the operation of open-end
relays, cross-overs and loops and yards. It follows that not only must
there be a pairing of the sets of speed and direction circuits, but the
individual speed circuits must always be paired alike, while the individual
direction circuits must at times be changed in connection. These conditions
have developed an invariable law of connections for the master and train
line and jumper connections to get proper co-operation of the motor and
like relative directional and hand movements under all circumstances.
The platform-switch circuits, the local operating or relay circuits, and the
train-line circuits are joined together by switches which permit such inde-
pendent connection on each car that controllers on any car can be operated
from the master switch on its car, no matter how a train is made up, with-
out the controllers on other cars being affected, or the controllers on as
many cars as are desired can be operated from the master switch on another
car without the controller on that car being operated, as well as the normal
operation of all controllers from any master switch.
498 ELECTRIC STREET RAILWAYS.
Normally, movement then of any master switch (the others for the time
being inoperative and held at open circuit) closes like relays on each car,
and starts the sequence of operations which 1 have indicated above for a
single car.
ilere again, however, the automatic variation of movement already
described in regard to a particular controller, takes place independently on
each car, and different kinds and degrees of movements of the controllers
on different cars could take place sinuiltaneously if necessary.
Not only that, but to provide for difference of wheel diameters, difference
of tractive co-efficients on different wheels, and to provide also against any
irregular condition on any car, similar movements may be differently timed,
and different controllers may take different relative' positions when meas-
ured by time, each accommodating itself to the limiting current input
determined for itself.
It therefore becomes possible, by this combination of positive and semi-
automatic control, to combine cars having controllers of different sizes,
motors of different capacities, resistances of different gradations, gears of
different ratios, and wheels of different diameters, and to successfully
operate them all from one or more controlling points. The total weight of
equipment per car other than the motors, platform switches, and train
cables, is 1,072 pounds. At the time of going to press, both the Westinghouse
Electric & Manufacturing Company and the General Electric Company had
developed modified forms of multiple control, but few cars equipped with
them had been put in actual commercial use.
APPROXUfATE MATES OE DEPRECIATION OUT
ELECTRIC STREET RAlIWATi.
(Dawson.)
Buildings 1 to 2 % Feeder cables . . . . 3 to 5 %
Turbines 7 " 9 " Lightning and current
Boilers 8 " 10 " meters 8 " 10"
Dynamos and Engines, Cars 4 " 6"
belted plants . . . 5 " 10 " Repair shop and test-
Belts 25 " 30." room fittings . . .12 " 15"
Large, slow-speed steam Motors 5 " 8"
engines 4 " 6 " Rotary transformers . . 8 "10"
Large, slow-speed direct- Boilers and engines . . 6 "10"
driven plants . . . 4 " 8 " Spare parts l£ " 2"
Stationary transformers, 5 " 6 " Track work 7 " 13"
Storage batteries in cen- Bonding 6 " 10"
tral stations . ... 9 " 11 " On remaining capital ex-
Trolley line 4 " 8 " penditure 4 " 6"
If interest rate is 5 per cent, and plant has to be renewed at the end of 20
years, 3 per cent of original outlay must be reserved annually to provide for
renewal.
DEPRECIATION OE STREET RAILWAY MA-
CHINERY AID EftEIPMENT.
Rates Stated l>y Chicag-o City Railway in 'Street Railway
Journal," »ec, 1SOS.
Power-Station. Engines, 8 per cent; Boilers, 8 per cent; Gene-
rators, 3 per cent ; Buildings. 5 per cent.
CaMe Machinery. Cable machinery, 10 per cent ; Cables, 175 per cent.
RoadUed. Rails, 5.5 per cent ; Ties, 7 per cent.
Paving-. Granite, 5 per cent ; Cedar blocks, 16 per cent ;
Brick, 7 per cent ; Asphalt, 7 per cent ; Macadam,
6 per cent.
Car*. Car bodies. 7 per cent ; Trucks. 8 per cent.
Rolling- Stock. Armatures. 33 per cent ; Fields, 12 per cent ; Gear
cases, 20 per cent ; Controllers, 4 per cent ; Com-
mutators, 33 per cent.
Wiring and other electrical equipment, 8 per cent.
Eine Equipment. Iron poles, 4 per cent ; Wood poles, 8 per cent ; In-
sulation, 12 per cent; Trolley-wire, 5 percent;
Trolley insulation, 7 per cent ; Bonding, 8 per
cent.
All based upon renewals and per cent of wear.
TRACK RETURN CIRCUIT.
499
CAR HEATIIG BY ELECTRICITY.
Test on Atlantic Avenue Railway, Brooklyn.
Cars.
Temperature F.
Watts
Consumed.
Doors.
Windows.
Contents,
Cu. ft.
Outside.
Average
in car.
2
12
850*
28
55
2295
2
12
850i
7
39
2325
2
12
808£
28
49
2180
2
12
913£
35
52
2745
4
16
1012
7
46
3038
4
16
1012
28
54
3160
TRACK RETITRI CIRCUIT.
It goes without saying that the return circuit, however made, whether
through track alone or in connection with return feeders, should he thehest
possible under the circumstances. Few of the older roads still retain the
bonds and returns formerly considered ample and good enough.
Electrolysis and loss of power have compelled many companies to replace
bonds and return circuits by much better types. The British Board of Trade
paid especial attention to the return circuit in the rules gotten out by them
(see page m67), and many American railroads would have been much
in pocket to-day if such rules had been promulgated in the United States at
the beginning of the trolley development.
With few exceptions the practice of engineers has been to connect the
rail joints by bomls, both rails of a track together at intervals, and both
tracks of a double-track road together. To this has sometimes been added
track return wires laid between the rails, and in other cases return feeders
from sections of track have been run to the power-house on pole lines.
The writer favors the full connection return with frequent insulated
overhead return feeders where there may be danger from electrolysis of
water and gas pipes ; in fact, ample return circuit has been proved time and
again to be the only preventive of that trouble.
Careful and continuous attention should be given to bonds from the
moment cars are started on a line.
Dr. Bell gives the following ratios of track return circuit to overhead sys-
tem as being average conditions.
Let Ry — resistance of track return circuit, and
R =. resistance of overhead system ;
Then
Ry = .1 to .2R. Exceedingly good track and very light load.
R, = .2 to .3R. Good track and moderate load.
Ry = A to .6R. Fair track, moderate load.
Ry = .2 to .3R. Exceptional track and large system.
Ry — .3 to J1R. Good track, large system.
Ry = .7 to I.O.K. Poor track, large system.
In exceptional cases track resistance may exceed that of overhead system.
It is sometimes assumed that R, = .25R, but this is rather better than
usual.
Under ordinary conditions R, = AR is nearer correct.
If formula for copper circuit = cm. = then for Ry = 4R, the
constant 11 should be increased to between 14 and 15 in order that copper
drop may bear correct proportion to that of the ground return.
Some forms of rail bond are shown on the following pages ; most of these
are applied to the rail by pressure or hammer riveting, but some of our bet-
ter road managements are now soldering all bonds by strong heat.
500
ELECTRIC STREET RAILWAYS.
A few roads still use wire secured in the web of the rail by steel channel
pins, which is about the easiest and cheapest, as well as the least efficient
form of bonding.
As copper bonds have a high value as junk, many of the long type are now
stolen from suburban railways, and the tendency is strongly in favor of the
concealed or protected bond which is so designed as to go in the space back
of the first piate against the web. For a time these protected bonds were
made very short, and no very great attention paid to their flexibility but
experience has proved that no bond of less tnan eight or nine inches' will
last well, no matter how flexible. Solid conductor bonds are only available
for the outside of fish plates, and not less than two feet in length. In applv-
ing tin copper bonds to the rails, it is necessary to apply them immediately
after drilling the web, unless holes are made at the rail mill and carefully
oiled, in which case the oil should be very carefully lemoved before apply-
ing the bond.
Bonds are best applied by a medium using heavy pressure, either by
screw or hydraulic pressure, rather than by hammer riveting.
On many of the systems, in large cities, rails are made practically continu-
ous now by use of electrically welded joints or cast weld joints.
In the electrically welded system a piece of wire about nine inches long,
two inches wide and an inch thick is welded across the joint on each side of
the rail web by means of a heavy current of electricity applied by special
machinery, taking its power from the trolley system. After the straps are
welded in position, the tops of the rail ends are carefully ground to an even
surface. Contrary to the ordinary ideas of the results of expansion and
contraction, but little trouble is experienced by broken joints or bent rails,
and in most places, where the method is in use, it has been quite successful.
The system is controlled by the Johnson Steel Co. of Cleveland, Ohio.
The cast weld joint is simply a bunch of cast iron cast about the joint
after it has been cleaned and prepared by placing a mold under it. The
Falk Company of Milwaukee makes a specialty of bonding street railway
systems in this manner, and the results seem to have been good.
Several forms of plastic bond have been devised and used to some extent.
They all consist of some form of plastic metal held in position between the
fish plate and the rail Aveb, the surfaces of both being treated chemically
or otherwise, so as to remove scale and oxide so that the plastic material
may be applied directly against the wire.
Solid Bonds. — This type is simply a heavy copper bar, say No. 0000
B. & S. gauge, with the ends compressed to form a collar, and bent to fit
the holes in the rails, and their hammer riveted to place.
A good example is that made by Messrs. Benedict and Burnham, and
shown in Fig. 50 ; the first three cuts showing a side view of the bonds and
rails, the next three cuts showing cross sections of rails with bonds applied.
Benedict and Burnham Solid One-Piece Rail-Bond.
Fig 50. Short thick Bond applied to " Tram " of Girder
Rail, allowing constant inspection.
O O O O O O I
Fig. 51. Short thick Bond applied to Base of either
Girder or T Rail.
TRACK RETURN CIRCUIT.
501
O O O O O O
Fig. 52. Solid long Bond clearing the Fish-plate in either
Girder or T Rail.
.Protected Bonds. — Good examples of these are exhibited in Figs.
53, 54, 55, 56, which show the type of protected bond sold by the Mayer
& "Eriglund Co. of Philadelphia. They are applied by a special hydraulic
press, and many variations of form are made to fit special cases.
FlG. 53. Showing 7-inch Girder Rail, bonded with one Bond.
Fig. 54. Showing 7-inch Girder Rail, double bonded with two
Bonds, one on each side of rail. Electrical connection
of 425,000 cm.
Fig. 55. Showing 9-inch Grooved Girder Rail double bonded
with two Bonds, one in each chamber and both on same
side of rail. Electrical connection of 425,000 cm.
502
ELECTRIC STREET RAILWAYS.
Fig. 56. Showing 9-inch Girder Rail quadruple bonded with
four Bonds, two in each chamber, on both sides of rail.
Electrical connection of 850,000 cm.
Another form of this type of bond is that shown in Fig. 57, as made by the
Forest City Electric Co. of Cleveland.
^TrY
^
Fig. 57.
Still another form of concealed bond is shown in Fig. 58, and made by
I. M. Atkinson & Co., Chicago.
Rail Bond of J. WE. Atkinson & Company, Chicag-o.
1P§
Fig. 58. Applied either single or double under fish-plate.
TRACK RETURN CIRCUIT.
503
In some types of bond the plug has a hole through it, and after placing
it in the hole in the web of the rail a steel mandrel is driven through to
expand the copper outwardly to fill the hole.
forest City Electric Company Short Bond.
This bond is applied underneath the fish-plate, and secured by a special
tool. ,
504
ELECTRIC STREET RAILWAYS.
In numerous tests of rail bonds, Mr. W. C. Burton, of the J. G. White Co.,
says it was found that where the copper plug was well pressed home the
resistance of the joint between rail and bond did not exceed that of three-
eighths inch of the bond itself, even after a year or more of use : and that
short bonds, especially those that could be covered by the 'fish-plate
made rail-joint resistance a very small percentage of the total track resist-
ance. He had never found tinned copper any better than the bare metal,
and when pressed tight had not noticed any effect whatever from local action.
Table Showing- Sectional Areas of Various Rails, tSae
Equivalents in Circular Mils, and tlie Equivalent Cir-
cular Jlils of Copper living- Same Conductivity.
(Figures on rails are for one side of a single track.)
Weight
Per Yard.
Area of
Single Rail.
Sq. in.
Circular Mils of
Single Rail.
Equivalent Circular
Mils of Copper for
Same Conductivity.
45
50
56
60
65
70
80
4.4095
4.8994
5.4874
5.8794
6.3693
6.8592
7.8392
5,614,400
6,238,200
6,986,700
7,485,800
8,109,600
8.733,400
9,981,100
997,200
1,108,000
1,241,000
1,329,500
1,440,400
1,551,200
1,772,800
Area in Cir. Mils :
_ 1,000,000 x wgt. per yard
10.2052 X .7854
Area in cir. mils
Equivalent Cir. Mils of Copper
Mr. W. C. Burton, of J. G-. White Co., found a very considerable difference
in rail resistivity, and numerous tests of modern steel rails showed the spe-
cific resistance to be from six to twelve times that of copper, where six has
been the factor frequently used. In his own practice Mr. Burton uses a
factor dependent upon the chemical properties and the physical treatment
of the rail in the rolling-mill.
BOABD ©E TRADE REGULATIONS.
For Great Rritain.
Regulations prescribed bv the Board of Trade under the provisions of
Section of the Tramways Act, 189—, for regulating the emplov-
ment of insulated returns, or of uninsulated metallic returns of low resist-
ance ; for preventing fusion or injurious electrolytic action of or on o-as or
water pipes, or other metallic pipes, structures, or substances ; and for min-
imizing, as far as is reasonably practicable, injurious interference with the
electric wires, lines, and apparatus of parties other than the company, and
the currents therein, whether such lines do or do not use the earth as a
return.
Definitions.
In the following regulations : —
The expression " energy " means electrical energy.
The expression " generator " means the dynamo or dynamos or other
electrical apparatus used for the generation of energy.
BOARD OF TRADE REGULATIONS. 505
The expression "motor" means any electric motor carried on a car and
used for the conversion of energy.
The expression "pipe" means any gas or water pipe, or other metallic
pipe, structure, or substance.
The expression "wire" means any wire apparatus used for telegraphic,
telephonic, electrical signaling, or other similar purposes.
The expression "current" means an electric current exceeding one-
thousandth part of one ampere.
The expression " the company " has the same meaning or meanings as in
the Tramways Act. 189—.
Reg-iilations.
1. Any dynamo used as a generator shall be of such pattern and con-
struction as to be capable of producing a continuous current without appre-
ciable pulsation.
2. One of the two conductors used for transmitting energy from the gen-
erator to the motors shall be in every case insulated from earth, and is
hereinafter referred to as the " line"; the other may be insulated through-
out or may be insulated in such parts and to sucb extent as is provided in
the' following regulations, and is hereinafter referred to as the " return." .
3 Where any rails on which cars run, or any conductors laid between or
within three feet of such rails, form any part of a return, such part may be
uninsulated. All other returns or parts of a return shall be insulated,
unless of such sectional area as will reduce the difference of potential be-
tween the ends of the uninsulated portion of the return below the limit
laid down in Regulation 7. .„..'.« f * *
4 When any uninsulated conductor laid between or within three feet of
the rails forms any part of a return, it shall be electrically connected to
the rails at distances apart not exceeding 100 feet, by means of copper
strips having a sectional area of at least one-sixteenth of a square inch, or
by other means of equal conductivity.
5. When any part of a return is uninsulated it shall be connected with
the' negative terminal of the generator, and in such case the negative termi-
nal of the generator shall also be directly connected, through the current-
indicator hereinafter mentioned, to two separate earth connections, which
shall be placed not less than twenty yards apart.
Provided that in place of such two earth connections the company may
make one connection to a main for water supply of not less than three
inches internal diameter, with the consent of the owner thereof, and of the
person supplying the water ; and provided that where, from the nature of
the soil or for other reasons, the company can show to the satisfaction of an
inspecting officer of the Board of Trade that the earth connections herein
specified cannot be constructed and maintained without undue expense, the
provisions of this regulation shall not apply.
The earth connections referred to in this regulation shall be constructed,
laid, and maintained so as to secure electrical contact with the general
mass of earth, and so that an electromotive force not exceeding four volts
shall suffice to produce a current of at least two amperes from one earth
connection to the other through the earth, and a test shall be made at least
once in every month to ascertain whether this requirement is complied
with.
No portion of either earth connection shall be placed within six feet of
any pipe, except a main for water supply of not less than three inches in-
ternal diameter, which is metallically connected to the earth connections
with the consents hereinbefore specified.
6. When the return is partly or entirely uninsulated, the company shall,
in the construction and maintenance of the tramway (a), so separate the
uninsulated return from the general mass of earth, and from any pipe in
the vicinity ; (b) so connect together tbe several lengths of the rails ; (c)
adopt such means for reducing tbe difference produced by the current be-
tween the potential of the uninsulated return at any one point and the po-
tential of the uninsulated return at any other point ; and (cl) so maintain
the efficiency of tbe earth connections specified in the preceding regulations
as to fulfill the following conditions, viz.:
506 ELECTRIC STREET RAILWAYS.
(1.) That the current passing from the earth connections through the in-
dicator to the generator shall not at any time exceed either two amperes
per mile of single tramway line, or 5 per cent of the total current output of
the station.
(2) That if at any time and at any place a test be made by connecting a
galvanometer or other current indicator to the uninsulated return, and to
any pipe in the vicinity, it shall always be possible to reverse the direction
of any current indicated by interposing a battery of three Leclanche cells
connected in series, if the direction of the current is from the return to the
pipe, or by interposing one Leclanche cell, if the direction of the current is
from the pipe to the return.
In order to provide a continuous indication that the condition (1) is com-
plied with, the company shall place in a conspicuous position a suitable,
properly connected, and correctly marked current indicator, and shall keep
it connected during the whole time that the line is charged.
The owner of any such pipe may require the company to permit him at
reasonable times and intervals to ascertain by test that the conditions
specified in (2) are complied with as regards his pipe.
7. When the return is partly or entirely uninsulated, a continuous record
shall be kept by the company of the difference of potential during the work-
ing of the tramway between the points of the uninsulated return furthest
from and nearest to the generating station. If at any time such difference )
of potential exceeds the limit of seven volts, the company shall take imme-
diate steps to reduce it below that limit.
8. Every electrical connection with any pipe shall be so arranged as to
admit of easy examination, and shall be tested by the company at least once
in every three months.
9. Every line and every insulated return or part of a return, except any
feeder, shall be constructed in sections not exceeding one half of a mile iii
length, and means shall be provided for insulating each such section for
purposes of testing.
10. The insulation of the line and of the return when insulated, and of all
feeders and other conductors, shall be so maintained that the leakage cur-
rent shall not exceed one-hundredth of an ampere per mile of tramway.
The leakage current shall be ascertained daily, before or after the hours of
running, when the line is fully charged. If at any time it should be found
that the leakage current exceeds one-half of an ampere per mile of tram-
way, the leak shall be localized and removed as soon as practicable, and the
running of the cars shall be stopped unless the leak is localized and removed
within twenty-four hours. Provided, that where both line and return are
placed within a conduit this regulation shall not apply.
11. The insulation resistance of all continuously insulated cables used for
lines, for insulated returns, for feeders, or for other purposes, and laid be-
low the surface of the ground, shall not be permitted to fall below the
equivalent of 10 megohms for a length of one mile. A test of the insulation
resistance of all such cables shall be made at least once in each month.
12. Where in any case in any part of the tramway the line is erected over-
head and the return is laid on or under the ground, and where any wires
have been erected or laid before the construction of the tramway, in the
same or nearly the same direction as such part of the tramway, the com-
pany shall, if required to do so by the owners of such wires or any of them,
permit such owners to insert and maintain in the company's line one or
more induction coils, or other apparatus approved by the company for the
purpose of preventing disturbance by electric induction. In any case m
which the company withhold their approval of any such apparatus, the
owners may appeal to the Board of Trade, who may, if they thmk fit, dis-
dispense with such approval.
13. Any insulated return shall be placed parallel to, and at a distance not
exceeding three feet from, the line, when the line and return are both
erected overhead, or 18 inches when they are both laid underground.
14. In the disposition, connections, and working of feeders, the company
shall take all reasonable precautions to avoid injurious interference with
any existing wires.
15. The company shall so construct and maintain their systems as to
secure good contact between the motors, and the line and return respec-
tively.
BOARD OF TRADE REGULATIONS. 507
16. The company shall adopt the best means available to prevent the oc-
urrence of undue sparking at the rubbing or rolling contacts in any place,
and in the construction and use of their generator and motors.
17. In working the cars the current shall be varied as required by means
of a rheostat containing at least twenty sections, or by some other equally
ifftcient method of gradually varying resistance.
18. Where the line or return or both are laid in a conduit, the following
Conditions shall be complied with in the construction and maintenance of
iuch conduit :
[a) The conduit shall be so constructed as to admit of easy examination of,
and access to, the conductors contained therein, and their insulators
and supports.
'b) It shall be so constructed as to be readily cleared of accumulation of
dust or other debris, and no such accumulation shall be permitted to
remain.
(c) It shall be laid to such falls, and so connected to sumps or other means
of drainage as to automatically clear itself of water without danger
of the water reaching the level of the conductors.
(d) If the conduit is formed of metal, all separate lengths shall be so jointed
as to secure efficient metallic continuity for the passage of electric
currents. Where, the rails are used to form any part of the return,
they shall be electrically connected to the conduit by means of cop-
per strips having a sectional area of at least one-sixteenth of a square
inch, or other means of equal conductivity, at distances apart not ex-
ceeding 100 feet. Where the return is wholly insulated and contained
within the conduit, the latter shall be connected to earth at the gen-
erating station through a high resistance galvanometer, suitable for
the indication of any or partial contact of either the line or the return
with the conduit.
(e) If the conduit is formed of any non-metallic material not being of high
insulating quality and impervious to moisture throughout, and is
placed within six feet of any pipe, a non-conducting screen shall be
interposed between the conduit and the pipe, of such material and
dimensions as shall provide that no current can pass between them
without traversing at least six feet of earth ; or the circuit itself shall
in such case be lined with bitumen or other non-conducting damp-
resisting material in all cases where it is placed within six feet of any
pipe.
(/) The leakage ciirrent shall be ascertained daily before or after the hours
of running, when the line is fully charged, and if at any time it shall
be found to exceed half an ampere per mile of tramway, the leak shall
be localized and removed as soon as practicable, and the running of
the cars shall be stopped unless the leak is localized and removed
within 24 hours.
19. The company shall, so far as may be applicable to their system of
working, keep records as specified below.' These records shall, if and when
required, be forwarded for the information of the Board of Trade.
Daily Records.
Number of cars running.
Maximum working current.
Maximum working pressure.
Maximum current from earth connections (vide Regulation 6 (1) ).
Leakage current (vide Regulation 10 and 18/.).
Fall of potential in return (vide Regulation 7).
Monthly Records.
Condition of earth connections (vide Regulation 5).
Insulation resistance of insulated cables (vide Regulation 11).
Quarterly Records.
Conductance of joints to pipes (vide Regulation 8).
508 ELECTRIC STREET RAILWAYS.
Occasional Records.
Any tests made under provisions of Regulation 6 (2) ).
Localization and removal of leakage, stating time occupied.
Particulars of any abnormal occurrence affecting the electric working
of the tramway.
Signed by order of the Board of Trade this day of 189
Assistant Secretary, Board of Trade.
OVERHEAD SYSTEM FOR EIEC1RIC STREET
RAILROAD!.
1. Ladder system, shown in the following cut, formerly somewhat used on
small roads, where both feeder and trolley wire of the same size would carry
the load. Feeder in this case is simply an enlargement of the trolley wire,
and as used might have better been one large trolley wire.
TROLLEY WIRE
2. A modification of the above system is the folloAving. In this second
system the trolley wire is cut into sections, and while losing the extra con-
ductivity of the continuous trolley, by placing fuse and switch at the junc-
tion of each sub-feeder Avith the main feeder, each such section may be cut
out in case of trouble without depriving the remainder of the system of
current.
FIG. 61.
Both above systems are now somewhat out of date, although occasion-
ally used on the smaller roads.
3. The system shown in the following cut is more of a real feeding system
than either of the previous two.
The trolley wire is connected directly to the dynamo, but is also fed at
various points, as at a, b, c, by larger wires tapped into it.
A load at d would thus receive current from both feeders b and c, and the
pressure can be more evenly maintained than by either of the previous
methods. By making the trolley wire of larger cross-section than is usual
in the previous systems, it is possible to have fewer sections and yet main-
tain a fairly even voltage.
OVERHEAD SYSTEM.
509
4. An obvious modification of the above is shown in the following cut.
In this system the trolley wire is again divided into sections, but each sec-
tion is supplied from its own separate feeder, the size of which may be so
calculated as to keep a very even pressure at all points on the line, especially
so if the trolley wire be not too small and the sections not too long. It is
of course, subject to the objection that the sections receive no help from the
remainder of the circuit, but has the advantage that each section maybe,
(controlled by switch and circuit-breaker at the station, and if at any part of
[the system, as at d, there is a heavy grade or a heavy massing of cars, cross
^connection can be made to the feeder c, either by switch or by permanent
tie. Another method of tying that has been used in some localities is that
of connecting the ends of trolley sections together with a small copper wire,
say No. 12 B". & S., and thus getting part current both ways ; and in case of
heavy overload oi short circuit on a section the tie-wires will burn off, leaving
all other sections free as before. This method is said to be of consider-
able advantage.
5. The following cut shows a combination of the previous methods, such
as results from experience in operating larger systems of roads. The
principal feeder C is tapped at intervals to feed the short and long sections,
and in order to maintain even voltage at its distant end, is reinforced at
d and e by the feeders E and F, while the still farther distant trolley-line
sections are fed by the long feeders G and H, which can be joined as at/, if
the circumstances call for it.
_ As mentioned above, this method is the result of actual experience on a
line after it has been run, and the loads have developed the points where
current is most needed. While systems of overhead lines are always laid out
with more or less care, traffic often takes the most erratic changes in direc-
tion, and changes its call for load to such an extent that feeders often have
to be run to new points, sections have to be joined or new divisions made,
or feeders have to be tied ; and this cut shows the general result of such
actual experience. As a general thing it is not good practice to cut the
trolley into any more sections than necessary for safety ; and even then a
separable line, that is, one that can be cut into sections by switches, is bet-
ter than separate sections.
510
ELECTRIC STREET RAILWAYS.
6. For long roads the system shown in the following cut may be used
with advantage, as, with heavy trolley wire such as should always be used
on long lines, the trolley wire can be reinforced by the feeders as shown,
Fig. 65.
as to maintain a fairly constant pressure, and advantage be taken of all the
conductivity of the system. On double-track roads all the trolley system
should be united and at frequent intervals, so that advantage may be taken
of the full conductivity installed.
7. A system sometimes used on small single-track lines, A\rhere feeders are
not entirely necessary, but a single trolley Avire may be too small, is to run
two trolley Avires side by side, and at all sidings the Avire nearest the siding
is run around it, and the cars can pass and the trolleys follow each its own
wire without troublesome switches.
CAECUI^TIMCJ THE COlfDITCTIH-G- SYSTEM.
Dr. Louis Bell gives the following steps as the best to be followed in
entering upon the calculation of the conducting system of a trolley road :
1. Extent of lines.
2. Average load on each line.
3. Center of distribution.
4. Maximum loads.
5. Trolley wire and track return.
6. General feeding system.
7. Reinforcement at special points.
It must be said at once that experience, skill, and good judgment are far
better than any amount of theory in laying out the conducting system of
any road.
Much depends upon the character of the load factor, i. e., the ratio of
average to maximum out-put ; and this, varying from .3 to .6, can only be
guessed at by a study of the particular locality, the nature of its industries
and working people, the shape of the territory, and the nature of the sur-
rounding country.
CALCULATING CONDUCTING SYSTEM. 511
1. Map out the track to scale, noting all distances carefully, and dot in
any contemplated extensions, so that adequate provision may be made in
the conducting system for them. Note all grades, giving their length, gra-
dient, and direction. Divide the road into sections such as may best sug-
gest themselves by reason of the local requirements, but such as will make
the service under ordinary conditions fairly constant.
2 The average load on each section will depend, of course, upon the
number of cars, and the number of cars upon the traffic. This can only be
arrived at by a comparison with similar localities already equipped with
street railway and even then considerable experience and keen judgment
of the general nature of the towns are necessary in arriving at anything like
a correct result. ' .
3 If the road has been correctly laid out as to sections, the load on each
will he uniform and may be considered as concentrated at a point midway
in each section. Now, if a street railway were to be laid down on a perfectly
level plain where the cost of real estate was the same at all points, and
wires could he run directly to the points best suited ; then it would only be
necessary to locate the center of gravity of the entire system, and build the
power station at that point, sending out feeders to the center of each sec-
tion. Unfortunately for theory, such is never the case ; and cost of real
estate, availability of the same, convenience of fuel, water, and supplies
will govern very largely the selection of a location for the power-house.
Evenwhen all the above points necessitate the placing of the power-house
far from the center of gravity of a system, it may be possible to use such
center as the distributing point for feeder systems, and even where this is
not possible, it is well to keep in mind the center, and arrange the distribut-
ing system as nearly as possible to fit it.
All this relates, however, to preliminary determinations for the system as
determined at the time, and in large systems will invariably be supplemented
by feeders, run to such points as the nature of the traffic demands. A base-
ball field newly located at some point on the line not known to the engineer
previous to the installation, will require reinforcement of that particular
section ; and often after a road has been running for some time, the entire
location of traffic changes, due to change in facilities, and feeder systems
then have to be changed to meet the new conditions, so that after all, loca-
tion of the center of distribution depends largely on judgment.
4. The predetermination of the maximum or average load is another mat-
ter for experienced guessing, as it will depend altogether upon the nature
of the traffic, how many people patronize the line, and how often the cars
are run.
If the weight of the car and its load be known it is an easy matter to de-
termine the power necessary to propel it ; and tables will be found in this
section showing the tractive effort necessary, and all other data for such
determination .
Bell gives the following formula for the horse-power necessary at the
wheel of a ear.
Let P = total horse-power.
W= weight of car and load in tons.
.43 — h.p. per ton required at wheel at 20 lbs. per ton for a
speed of 8 miles per hour.
G = per cent grade.
?hen
P = W(.43 + A3G).
This applies to straight tracks only, and at a speed of 8 miles per hour,
which is often exceeded.
The same authority also states that allowing an efficiency between trolley
and car- wheel of 66f per cent, and voltage at the car of 500, 1-i amperes per
ton plus 1J amperes per ton for each per cent of grade will be approximately
correct. This means an average of about 15 amperes per car, throughout
the day, for the ordinary car and road. Long double-truck cars will take
nearer 25 amperes, and in the writer's judgment this last is a good average
to use for all traffic on ordinary street railways.
The maximum current will rise to four or five times the average where
but one or two cars are in use ; will easily be three times the average on
512 ELECTRIC STREET RAILWAYS.
roads of medium size, while on very large systems it may not be more than
double the average. If speeds are maintained on heavy grades the maxi-
mum is still further liable to increase.
Another point to be considered in connection with maximum load, is the
location, not only of heavy grades, but of parks, ball-grounds, athletic
fields, cemeteries, and other such places for large gatherings of people that
are liable to call for heavy massing of cars, many of which must be started
practically at the same time, and tor which extra feeder, and in some cases
extra trolley capacity, must be provided.
Having determined the average current per section of track, the maximum
for the same, and the extraordinary maximum for ends, park locations etc
as well as the distances, all data are obtained necessary lor the determinal
tion of sizes of feeders.
5. The selection of the proper size of trolley is somewhat empirical, but
the size may be g< .yerned by the amount of current that is to be carried. It
is obvious tliat with given conditions the larger the trolley wire the fewer
feeders will be necessary, and yet with few feeders the voltage is liable to
vary considerably. In ordinary practice of to-day No. 0 B. & S. and No. 00
B. & S. gauge, hard-drawn copper are the sizes mostly in use, the latter on
those roads having heavier traffic or liable to massing of cars at certain
localities. On suburban roads using two trolley wires in place of feeders,
0000 B. & S. gauge will probably be best.
Track return circuit has been treated fully in a previous chapter; and all
that is needed to say here is, that some skill in judgment is necessary in
settling on the value of the particular track return that may be under con-
sideration, in order to determine the value of the constant to be used in the
formula for computing the size of wire or overhead circuit. In ordinary
good practice this value may be taken as 13, 14, or 15, according as the bond-
ing and rail dimensions are of good type and large.
6. Feeder-points should, in a general way, be so located as to allow no
drop in a section of trolley wire exceeding 5 per cent or 25 volts under nor-
mal load. This drop is easily determined by the regular formula :
Let D = distance from feeding point to end of the trolley section,
cm. — circular mils of the trolley,
E = drop in volts,
13 = constant for circuit in connection with a well bonded heavy
track,
/= current required per car, usually taken as 15 amperes under
running conditions, but more safely taken as 25 amperes.
Then
_ cm. E
—'~l3~T »
and if the trolley wire selected be No. 00 B. & S. cm. = 133,600, and as the
• •-, , • +1 * ii • • or 1+ ;n 133,000 X 25
maximum drop permissible in the trolley wire is 25 volts D = g —
— longest section of trolley wire for one car, or 10,231 feet. If two cars are
bunched at the end of the section the drop will be twice as great, or the
length of section can be but 5,115 ft.; for 3 cars the lengtb Avill be 3,410 ft.;
for 4 cars the length will be 2,558 ft.; and for five cars the length will be
2,046 feet.
The above calculation will be correct for level roads and where the load is
well distributed ; but the trolley-wire sections must necessarily be shortened
up for grades or at such points in the line as heavy massing of cars is liable
to take place, as at ball-parks, etc., where people all want to get home at
once, and all available cars are started from that point.
In such cases it will probably be safe to allow 50 amperes per car for the
section of trolley wire on which the park is located, and the result is then
D — ' A = 5,115 ft. for one car, and for n cars the greatest length
of section would be 5,115 -j- n.
CALCULATING CONDUCTING SYSTEM.
513
Having calculated all the points on the trolley line at which it should be
fed, it remains to calculate the size of feeder for the purpose.
As to the allowable drop in feeders, it is not well to have over 100 volts
total drop at the car and 75 volts total drop is better under maximum load,
as low voltage at the motors tends to over-heat them to a dangerous degree.
Much of the regular drop can be overcome by over-compounding the gene-
rators for a rise of potential of about 50 volts.
It is decidedly better practice to make feeder determinations based on the
maximum load, as the average load will easily care for itself, but during
times of extraordinary crowds, or snow-storms, if the line has not been cal-
culated for such heavy loads, all the motors will heat, and much trouble
is liable all along the line.
The writer considers 75 volts drop in feeders under maximum load condi-
tions a safe basis, together with 35 amperes per car for all those liable to
be on the section at once. Over-compounding will make up for 50 volts of
the drop at the motors at times of heaviest distributed load, so there will
be no danger. Feeder calculation will then be
. . , 13 x D X 35 » cars
cm. of feeder = =-
to
It is quite obvious that the current-carrying capacity of the feeder must
be taken into consideration, in spite of any determination of drop ; and this
can be found in the chapter on Conductors. Sizes of conductors are also
governed to some extent by convenience in handling, and it is found that
1,000,000 c. m. is about the largest that can be safely handled for under-
ground work, while anything larger than 500,000 c. m. for overhead circuits
is found to be difficult to handle.
7. In cases where it is necessary to feed the trolley wire in short sections,
in order to reinforce the trolley wire for heavy grades, sub-feeders are often
used, the main feeder being tapped into its center, or at such point in its
length as will give the best distribution, as shown in the following cut.
SUB-FEEDER
Fig. 66.
For lines having parks at the end, or in fact for any such section, it is
perhaps best to run a feeder nearly to the end of the section, then take the
trolley line to the feeder at various points comparatively short distances
apart, as shown in the following cut; and if the loads are at times especially
heavy, the next feeder can be made to assist by cross-connecting, as at d.
a
BALL PARK AT END OF LINE
TRACK RETURN
CIRCUIT
Fig. 67.
In this connection it must be remembered that heavy loads from parks,
as well as on grades, do not often come at the same time as heavy loads on
other sections, and therefore that the over-compounding may not be but a
514
ELECTRIC STREET RAILWAYS.
part of the full-load rise, and it is best under the circumstances to calculate
the sizes of such feeders for a smaller drop, say 50 volts maximum instead
of 75.
In general it may be said that it is now tbe usual practice to use a few
standard sizes of feeder wire, such as 100,000 cm., 200,000, 250,000, 500,000,
and so connect them as to produce the required results, rather than to
carry a large number of various sizes of wire in stock. In fact, this same
practice is now carried out in large lighting installations as well, and in
those constant pressure is much more needed than in railway circuits.
Special HKethods of Distribution.
For cases requiring excessively large currents carried a considerable dis-
tance, or for ordinary currents carried excessive distances, it is usually
economy to adopt some special method ; and among those most commonly
mentioned are : the three- wire system, the booster system, the substation
system.
Three-Wire System. This system, patented some time ago by the I
General Electric Company, has been seldom used, and where used has met
with little success, owing to the difficulty met in keeping the system bal-
anced.
The diagram below will assist in making the method plain. Two 500-volt
generators are used, as in the lighting system of the same type. The rail
return is used as the neutral conductor; and if both trolley wires could be
made to carry the same loads, and to remain balanced, then the rail return
7 °
1 J
;
i
THREE WIRE SYSTEM
Fig. 68. Three-Wire System.
would carry no current, and no trouble would occur from electrolysis. The
overhead conductors could also be very much smaller, as currents would
be halved, and the full voltage would be practically 1000.
The Booster System.— Where current must be conveyed a long
distance, say five to ten miles, and be delivered at 500 volts, it is hardly
good economy to install copper enough to prevent the drop; and if the volt-
age of the generator be raised sufficiently to deliver the required voltage,
the variations due to change of load will be prohibitive.
In such cases a "booster" can be connected in series with the feeder,
and automatically keep the pressure at the required point, as long as the
generator delivers the normal pressure.
The "booster" is nothing more than a series-wound dvnamo, connected
so that all the current of the feeder to which it is attached flows through
both field and armature coils, and the voltage produced at the armature
terminals is added to that of the line, and as the voltage so produced is in
proportion to the current flowing, it will be seen that the pressure will rise
i^^HH
CALCULATING CONDUCTING SYSTEM.
515
and fall with the current. This is now used in many instances, both in
lighting and for railway feeders, and especially in feeding storage batteries,
and has met with entire success. The following cut is a diagram of the
connections.
6 TO 10 MILES
I MOTOR
\ TO DRIVE
generatofl\eoostep.
OVERHEAD RETURN
BOOSTER SYSTEM
Beturn Feeder Booster. —Major Cardew, Electrical Engineer for
the Board of Trade, some time ago devised a method of overcoming exces-
sive drop in track return circuits by the use of insulated return feeders, in
series with which he placed a booster.
The booster draws current back toward the station, adding its E.M.F. to
that in the feeder. Cardew used a motor generator, the series field of
which was separately excited by the outgoing feeder for the same section of
road. Thus the volts "boosted" were indirect proportion to the current
flowing. H. F. Parshall, in adopting the return feeder booster for some of
his work in England, used a generator in place of the motor-generator of
Major Cardew, exciting the field by the current flowing out on the trolley
feeder, thus producing volts in the armature in proportion to the current
flowing. The following diagram shows Parshall's arrangement.
GENERATORS
Fig. 70. Modification of Major Cardew's System of Track Return
Booster for Preventing Excessive Drop in Bail Return Circuits.
516
ELECTRIC STREET RAILWAYS.
Sul»-Station System. — Where traffic is especially heavy, and a rail-
way system widespread, it is now the practice to use one large and very
economical power station with high-pressure generators, now invariably
polyphase alternators, and to distribute this high-pressure alternating
current to small sub-stations centrally located for feeding their districts,
and there changing the current by means of static and rotary transformers
into continuous current of the requisite pressure, in the case of railways
500 or 550 volts. Such systems have already been mapped out for the Man-
hattan Elevated Railway, and for the Metropolitan Traction Company of
New York, and are now in operation, as well as on the Central Underground
Railway of London.
The following diagrams will assist in making the system plain.
6UBSTATION|
no. 1
DISTRIBUTION FROM
SUB-STATIONS
Fig. 71.
TESTS ©JF STREET RAILWAY CIRCUITS.
The following tests are condensed from an article by A. B. Herrick in the
Street Railway Journal, April, 1899.
The following instruments will be required :
A barrel water rheostat to take say 100 amperes.
A voltmeter reading to GOO volts.
A voltmeter reading to 125 volts.
An ammeter reading to say 150 amperes.
A pole long enough to reach the trolley wire, with a wire running along it
having a hook to make contact.
Use one generator at the station, and have the attendant keep pressure
constant.
Test for Drop and Resistance in Overhead lines an;3
Returns.
The car containing the above equipment of instruments is run to the end
of the section of conductor which it is desired to test, where a line circuit-
breaker divides the sections.
The instruments are then connected as shown in Fig. 72.
It is clear now that if the switch G be closed, current will flow through
the rheostat and be measured by the ammeter. We now have the trolley
and feeder B for a pressure wire back to the station, and the readin<>- of
voltmeter C therefore gives the drop between the station and the point A
^HHiH^
TESTS OF STREET RAILWAY CIRCUITS.
517
518
ELECTRIC STREET RAILWAYS.
in the feeder and trolley carrying the load. Voltmeter D shows the drop
across the rheostat ; and if the sum of readings C and!) be deducted from the
station pressure, the difference will be the drop in the ground return.
Fig. 73.
The station pressure can be taken by changing the lead of voltmeter C
down to F as shown by the dotted line.
The drop on A and its resistance having been found, the trolley-pole can
be swung around and the same data be determined for the circuit B.
To Stead the Ground Return Drop Directly.
Open the station switch on that feeder that is being used as pressure wire,
and ground the feeder to the ground bus through a fuse for safety.
Connect the instruments as shown in the following cut ; then when the
switch G is closed and current flows, the drop from A to F read on voltmeter
C will be the drop in the ground return from F to X.
j FEEDER
1
A
B
TROLLEY
TROL
c
LEY
p.
<
w
D
p
SiMMETE
Ft
-AW
RHEOSTAT
\>G
o
RAML V
>
^
TESTS OF STREET RAILWAY CIRCUITS.
To Determine Drop at JEnd of line.
519
For use on double-track lines only, unless a pressure wire can be run to
the end of line from the last line circuit-breaker.
Break all cross connections from feeder to trolley-wire for one track, as
at n ; connect this idle trolley to the next one back toward the station, as
at C, then make the tests as in the two methods described above, connections
being shown in the following cut.
FFEDER
TROLLEY
TROLLEY
A
TROLl EY
n
C TROLLEY
S^^ B
"V s
1 ^
/
/
Vi:
Iw.
>
o
■*^G
/
M
. / RHEOSTAT
RAIL
1
To Determine the Condition of Track Donding-, and the
Division of Return Current throug-h Mails, Water
or Gas Pipes, and Ground.
The cut below shows the connections for this test as applied to a single
track, or to one track of a double-track road.
Ground the feeder A at the station, or rather connect it to the ground bus
through a fuse. Then connect the track at C to A by the pole E through
the ammeter M. The drop between points F and D will be the drop through
the rail circuit between C and D, due to the current flowing.
If connection be made to a hydrant, or other water connection, and to a
gas-pipe, as at X, still retaining the rail connection at C, more current will
520
ELECTRIC STREET RAILWAYS.
flow through ammeter M, due to providing the metallic return through A
for the water-pipe, and the first reading of the ammeter M is to the second
reading as the resistance of the water-pipe is to that of the rail return, and
the current returning to the station will distribute itself between the two
paths in proportion to the readings mentioned. If ammeter G be read at the
same time, the difference between its reading and the sum of the other
two readings will be the amount of current returning by other paths than
the rail and water-pipe. If C is near the station it may be necessary to
break the ground connection between rails and bus, so that all current may
return over the metallic circuit A.
To determine condition of bonds, move the contact C back towards D, and
the decrease in drop as shown by the vm. will be very nearly proportional
to the length of track, except where a bad or broken bond may be located,
when the change will be sudden.
TESTING RAIL BOIDS.
It is not commercially practicable to measxire the exact resistance of rail
joints, as such resistance is small under ordinary circumstances, and all the
conditions vary so much as to prevent accurate measurement being made.
The resistance of rail joints is therefore measured in terms of length of the
rail itself, and there are numerous instruments devised for the purpose,
nearly all being based upon the principle of the wheatstone bridge, the
resistance of the rail joint being balanced against a section of the rail, as in
the following diagram.
Fig. 77. Diagram of Method of Testing Rail Joints.
A "Weston or other reliable milli-voltmeter, with the zero point in the mid-
dle of the scale, is the handiest instrument for making these tests. The
points b and c are fixed usually at a distance of 12 inches apart, the point a
is then moved along- the rail until there is no deflection of the needle when
both switches are closed. The resistance of the joint or the portion between
the points b and c is to that of the length, x, inversely as the length of the
former is to that of the latter, all being in terms of the length of rail, or,
Let
x rr distance in inches between points a and c,
y = distance between the points c and b,
v =r resistance of joint in terms of length of rail,
TESTING RAIL JOINTS.
521
and if x — 36 inches and y z
then
12 inches,
Another scheme for testing rail joints is pointed out by W. N. Walmsley
in the " Electrical Engineer," December 23, 1897.
In the following cut, the instrument is a specially designed, double milli-
voltmeter, both pointers having the same axis, and indicating on the same
scale.
DOUBLE
MILIVOLTMETER
<p ' l Q
c
- x -X~
I
* '\P V
WALMSLEY'S RAIL TESTER
FIG. 78.
The points ab are at a fixed distance d, the point c being movable along
the rail. Points a and b are set on the rail astride the joint, as shown ; the
point c is then moved along the rail until the pointers on the instrument
coincide, indicating the same drop. Then the resistance of x is the same
as d, in terms of the size of rail used.
Harold P. Brown has devised an instrument for testing rail joints with
little preparation. It consists of two specially shielded milli-voltmeters of
the Weston Company's make, put up in a substantial wooden case, the top
of which is made up in part of two folding legs which, when unfolded, cover
six feet of rail. These legs form one length, which is divided by slots into
two lengths, one of one foot, the other five feet long. The instrument is
placed alongside the track in such position that the leg rests on the rail, and
the joint to be tested is between the ends of the shorter branch ot leg, while
five feet of clear rail are included between the ends of the longer leg.
The instrument terminals are connected to small horseshoe magnets, that
fit into the slots in each leg, and when rested on the rail always make the
same pressure of contact, the poles being amalgamated and coated with a
special soft amalgam, called Edison Flexible Solder.
With the five feet of rail as a shunt, the instrument will read to 1500 am-
peres.
There are several separate resistance coils and binding-posts supplied for
different sizes of rail in common use, so that the dial of the milli-voltmeter
needs but one scale.
The second milli-voltmeter measures the drop around the one foot of
joint, and has coils so arranged to permit of reading .15, 1.5, 15. volts.
A reading of the current value is taken from the five feet of rail, and a
simultaneous reading of the drop across the joint and one foot of rail is also
made. The resistance of the latter is then found by ohm's law,
522
ELECTRIC STREET RAILWAYS.
Fig. 79. Brown's Rail-bond Testing Instrument.
Street Railway motor Vesting*.
Barn test for efficiency : —
Put a double-flange pulley on tbe car axle for tbe application of a prony
brake, pour water inside tbe pulley to keep it cool. Use common platform
scale, as shown in cut.
Fig. 80.
Then let D — distance from center of axle to point on scales in feet,
measured horizontally.
7T = 3.1416,
R = revolutions per minute,
E = voltage at motor,
1= amperes at motor,
T— force applied to balance scales, in pounds.
B. H. P. at 500 volts =
EI
.P.
(2 7!
2tt DR T
33,000
500
DR XE )T
746
500 I
33,000
— E.H.P. supplied to motor.
= E.H.P. supplied to motor at 500 volts.
^ . M B.H.P. B.H.P. at 500 volts
Efficiency of motor =lorp- X v„„ a, fino -tt--
Draw-bar Pull and Efficiency Test Without Removing-
Motor from Car.
Rig up lever as shown in cut, being sure the fulcrum A is strong enough
to stand the pull. Posts, as shown, make good fulcrum ; have turn buckle
F for taking up any weakness.
FAULTS AND REMEDIES.
Fig. 81.
Let D = diameter of car wheel in feet.
■k = 3.1416,
T= force on scale in pounds,
L = length of long arm of lever,
L, =. length of short arm of lever,
li = revolutions per minute.
Place a jack-screw under each side of the car, and lift the body until there
is only friction enough between wheels and rail to keep the speed of revolu-
tions down to the normal rate.
Then
Draw-bar pull = T --- ,
and the efficiency is the same as before,
B.H.P.
E.H.P.
rz efficiency.
Mr. A. B. Herrick has devised a testing-board for street-railway repair
shops that will greatly assist in making all inspection tests, and which is
described in the " Street Railway Journal " for January, 1898, pages 11
and 12.
FAUIIi JLM» REMEOIEi.
Car Will not Start :
a. Turn on lamps ; if they burn, trolley and ground wires are all right
and current is on line.
b. If lights die down when controller is thrown on, trouble may be poor
contact between rails and wheels, or car may be on " dead" track.
c. If car works all right with one controller, fault may be open circuit, or
poor contact in the other. Throw current off at canopy, or pull down the
trolley and examine the controller.
d. See that both motor ctit-outs are in place.
e. Fuse may be blown ; throw canopy switch and replace.
/. See that motor brushes are in place and intact, and make good contact.
g. Car maybe standing on "dead" or dirty rail ; in either case connect
wheels to next rail by wire. It is better to open canopy switch while con-
necting wire to wheels, or a shock may be felt.
h. Ice on trolley wheel or wire will prevent starting.
Sparking- at Commutator Srushes:
a. Brushes may be too loose ; tighten pressure spring.
b. Brushes may be badly burned or broken, and therefore make poor con-
tact on the commutator. Replace brushes with new set, and sandpaper
commutator surface smooth.
524 ELECTRIC STREET RAILWAYS.
c. Brushes may be welded to holder, and thus not work freely on commu-
tator surface.
d. Commutator may be badly worn and need renewing.
e. Commutator may have a flat bar, or one projecting above the general
surface ; commutator must then be turned true in lathe.
/. Dirt or oil on commutator may produce sparking ; clean well.
flame at the commutator may be produced by : —
a. Broken lead wire or coil, producing a greenish flame, and burning two
bars usually diametrically opposite each other. If left too long the two
bars will be'badly burned, as will also the insulation between.
Temporary relief can be had by putting a jumper of solder or of small
wire across the burned bar, connecting the two adjacent bars to each other ;
one jumper is enough.
b. A short-circuited field coil, or a field coil improperly connected, will
produce flare at commutator. Short-circuited coil can be found by volt-
meter test across terminals showing drop in coil. Wrong connection can be
detected by pocket compass.
Incandescent Lamps sometimes burn out or break. Replace with
new ones. If they do not burn when switch is on,
a. Examine each for broken filament.
b. Examine for poor contact in socket.
c. Examine SAvitch for poor contact or broken blades.
d. Examine each part of circuit, switches, line, and sockets with magnets,
which will locate opening. The wire may be broken at ground or trolley
connections.
IS rakes fail to Operate:
In great emergency only, throw controller handle to off, reverse reversing-
switch, and turn controller handle to first or second notch.
In sliding down grades, or when there is time, proceed as follows :
a. Throw controller handle to off point.
b. Throw canopy switch off.
c. Reverse reversing-switch.
d. Throw controller handle around to last notch. Both methods are
more or less strain on the motors, but the second is somewhat less so than
the first.
Grounds: Either on field or armature coils will nearly always blow
fuse ; it can then be tested out. »
Bricking-: When running along smoothly, a car will sometimes com-
mence jerky, bucking motions, and should be thoroughly examined at once.
It may be due to a ground of field or armature that may short-circuit one or
the other, either fully or intermittently. Injured motor may usually be
located by smell of burning shellac, and can be cut out at the controller,
and the car run in with the good motor.
Mud and water splashing on commutator will sometimes produce bucking,
and often a piece of wire caught up from the track may do the same.
EEECTHOSyfiTSIJi Of WATER JLSTD OTHER
PIPES.
(From Report of the Electrical Bureau of the National Board of Fire Under-
writers, on Electrolytic Deterioration of Water Pipes.)
Recent reports show that the destructive effects of electrical currents on
subterranean metal pipes are becoming sufficiently marked in many parts
of the country to seriously interfere with the service the pipes are intended
to perform.
Underground water mains have broken down, because of faults unques-
tionably due to electrolytic action ; and smaller service pipes have been
Aveakened to such an extent as to break at critical moments, Avhen excess
pressure is put upon them at inteiwals during a fire. Measurements show
that conditions unquestionably exist in nearly eveiy district in the United
States covered by a trolley road, Avhich are favorable for destructive action
REPORT OF THE ELECTRICAL BUREAU. 525
on the subterranean metal work in the vicinity, and pipes taken up in many
of these districts show unmistakable signs of harmful effects. The general
nature of this action, and the causes which bring it about, are too often
seen to need elaborate description. Briefly it may be compared to the
action which takes place in an electro-plating bath.
The current which enters the bath through the nickel or silver metal sus-
pended therein, flowing through the bath and out through the object to be
plated, ultimately brings about the destruction of the suspended piece of
metal. Similarly the current from a grounded trolley system floAving
through the earth in its course from the cars back to the generating station
selects the path of least resistance, which is generally for the whole or a
part of the way the underground water mains, and at points where it leaves
the pipes to reach the station the iron of the pipe wastes away until at
points the walls become too thin to withstand the pressure of the water,
and a breakdown ensues. The difference of potential necessary to bring
about this action is very small, — a fraction of a volt, — and consequently
in all districts where potential differences are found between water-pipes
and the surrounding earth, such actions can be assumed to betaking place;
for dampness, and the salts necessary to produce electrolysis, are present in
all common soils.
Whenever, then, a reading is shown by an ordinary portable voltmeter
registering tenths of a volt with the positive binding-post in electrical con-
nection with a water-pipe or hydrant, and the negative binding-post in elec-
trical connection with an adjacent lamp post, car track, or metal rod driven
in the earth, electrolytic action will be found upon examination to be tak- .
ing place at that point which will ultimately result in the destruction of the
water-pipe.
The only certain remedies for this evil are obviously to keep the current
from using the pipes as a conductor, or to keep it from flowing from the
pipes through the surrounding soil. The first remedy necessitates a com-
plete metallic circuit for the railway, and the second a joining of pipes by
wires wherever potential differences are found. Trolley roads having abso-
lutely no ground connections will not be installed as long as the present
trend of practice prevails, and consequently an absolutely complete metal-
lic circuit for such roads cannot be secured. Bonding all underground
pipes together with wires of sufficient carrying capacity to prevent current
flow through the earth would also be obviously impossible. By a judicious
employment of part of each remedy, however, it has been demonstrated
that the evil can be so largely reduced as to be practically negligible ; and it
is to securing these improvements in the numerous trolley districts of the
country that the energies of everyone interested should be devoted.
Referring to the diagram shown in Fig. 59, it is seen that the current will
pass from the generator out over the trolley line, through the motor to rail.
Through rails and wire the current flows back to the power-house. There
♦jOj-
"^^---.-^ i y'"i I" jT^ j& I fB i^i
Fig. 82.
are obviously two paths open for the current. One a return through the
rail, the other a return through the earth and any existing gas-pipes, water-
mains, or other metallic structures that may be in its path in the earth. The
current flowing through these two paths in parallel is plainly inversely propor-
tional to the resistance of these two paths. Therefore, in a general way the
current will leave the rails at A, flowing into the Avater-pipe at B, and Avill
again leave the Avater-rrpe at C and enter the rails. Here, then, is an elec-
tric current flowing between metallic structures that may be called elec-
trodes at places in the return path from the motor to station. All that
remains, then, to promote electrolytic action is the presence of some solu-
tion which will act as an electrolyte.
526
ELECTRIC STREET RAILWAYS.
Observation has shown that the earth, especially in the larger cities, con-
tains a large percentage of metallic salts in solution, which will readily act
as electrolytes upon the passage of electric current. It can he seen, then,
referring to this diagram, that if there exists in the ground sufiicient moist-
ure of some metallic salt, electrolytic action will take place between the
electrodes A and B, and between the electrodes C and the rails. The metals
of this electrolyte will be deposited at B and on the rails, while the active
part of the electrolyte will be found at A and C. Consequently, corrosion
of the metallic structure may be expected at A and 0, and at all points
where current is found leaving the metallic structure. Such conditions as
are shown in Fig. 82 exist in practically all of the railroads in this country.
The rail and feeder returns offer one path for the flow of current ; and as the
earth with its water-pipes and gas-pipes offers a parallel path, the amount
of current flowing through the earth will then depend upon the resistance
of the return path in the track and feeders. If, at a point in the track re-
turn there exists a joint of somewhat high resistance, this high resistance
will tend to prevent the current nowing back through the rails. The other
return path of the current' offered is through the earth and water-pipe.
Con&equently, electrolytic action in any metallic structure which may occur
in the earth path of the return current is practically almost directly "propor-
tional to the faultiness cf the construction in the rail return. In the earlier
electric roads the positive terminals of the generators were connected to
ground. This arrangement of the polarity of the street railway has a
tendency to distribute the points of danger on water-pipes, gas-pipes, cable-
sheathing, or any other underground metallic structure throughout a large
and extended territory. By reversing the polarity of the railway generator,
bringing the positive terminal to line and negative to ground, the points
where the current leaves these metallic structures will be brought much
nearer the power station, and will be localized in a much smaller area. At
the same time that these danger points or points of positive potential are
brought closely to the power station, it can be seen that the volume of cur-
rent flowing from these danger points has been proportionally increased, and
with it the amount of electrolytic action or corrosion.
On the whole, the placing of the current positive to line appears to be a
material advantage. Corrosive action is very much enhanced in a limited
area, but being in a limited area and definitely located, it may be easily
watched and remedies applied. With the current negative to line, the ac-
tion at a given danger point may be considerably less than under the other
condition ; but as the danger district is widespread, and as the conditions are
continually changing, it would be very difficult to locate precisely the dan-
ger points. Consequently the results of electrolytic action are likely to ap-
pear at unexpected points.
REPORT OF THE ELECTRICAL BUREAU.
527
From the electric railway standpoint, the prohibitive expense of the
requisite addition of copper to make a complete circuit is advanced, to-
gether with the impracticability of a double-trolley system that is appar-
ently a necessary concomitant of the metallic return ; and these arguments
have a certain weight. There is no question but that the complete metallic
return is in the beginning a more expensive installation, but per contra few
railway companies have any idea of the energy now expended in returning
the energy delivered by the power station through the poor conductivity of
the average railway track with its surrounding earth.
It has been suggested that corrosion from the underground current could
be avoided by operating the railway as a three-wire system in which the
trolley wires would form the two sides, and the ground play the part of a
neutral wire. The feasibility of a three-wire system depends upon the abil-
ity to obtain a double track through the entire railway territory, and the
adoption of such a car schedule as to render the loading of the two sides of
the system essentially equal. Such a railway could rarely be successfully
operated excepting in cities that are essentially level, and in which the
traffic was exceedingly uniform. The probability is that in practice elec-
trolytic action would not be wholly avoided ; and due to inequality in car
loading and car scheduling it would be impossible to locate the danger
points in the system, and therefore impracticable to employ methods of
correction.
Harold P. Brown has proposed an arrangement which is diagrammati-
cally outlined in Fig. 77. At the station at least two or more generators are
required, the division of units being such that there is at least one special
generator of about one-quarter the total capacity of the station, which is to
be connected, as indicated in the diagram, directly to the pipe structures in
45il
lOf
□□□□
BTT
"Tj
T7?
the street. The remainder of the station generators are, as usual, connected
to the rails or to the return feeds. If, now, the special machine be operated
at a few volts higher potential than the rest of the station, it is quite evi-
dent that its action Avill be to render the pipe structures to which the nega-
tive pole of the special generator is connected electro-negative to the rest
of the system, thus obviating electrolytic action. Such an arrangement of
station machinery is undoubtedly a palliative. It is by no means a cure,
for in case in any part of the pipe system there happens to be a high resist-
ance joint, such a joint would become a point of inflection in the current,
being electro-positive on one side and electro-negative on the other side.
It is, perhaps, possible to locate such joints by means of a careful voltmeter
survey, but only at the expense of considerable time and trouble ; and when
dangerous spots of this kind are determined, the resistance of the joint must
be obviated either by some form of bond or other device. It will be readily
perceived that in many instances pipe structures will not return near
enough to the station to render such an action as is outlined in the diagram
possible, and frequently the pipe lines may be parallel to the railway track
for a considerable distance, and then lead away from the station in such a
way as to render the application of this method impractical. Under these
circumstances it will be necessary to determine by means of a voltmeter
528 ELECTRIC STREET RAILWAYS.
survey the condition of the underground structures, and run to the danger
points a special conductor.
Very recently Mr. Farnham has proposed an additional solution of the
electrolytic problem, which appears to be one of considerable merit. The
usual conditions, together with the remedy proposed, are outlined in Figs.
82 and 8G. Under ordinary circumstances, the railway system is operated
as shown in Fig. 82.
The positive pole of the generator is connected to the trolley wire, and
current passes from the station over the trolley wire, and then to the rails.
From this point it returns to the station by the route of least resistance,
whether through the ground, the rails, or a neighboring pipe line, as the
case may be. At all points where the current leaves the pipe line or other
underground structure, the line becomes electro-positive to its surround-
ings and affords points of danger, as is indicated in the diagram.
Suppose the circuit to be arranged as shown in Fig. 78. Here, as in the
.
/
A
JoJ-
STATION
Jt J-
t It J* It
- 1 _y?°E°y f
% . !□□□□! <
-t=dt=^t=it
:=£==8==l£=3==fl==l)
Fig. 86.
previous case, the positive pole of the generator is connected to the trolley
wire, but the negative pole is not connected to ground in any way. On the
contrary, the generating station is carefully insulated from earth, the nega-
tive pole being connected to a set of return feeds that may be strung along
the route of the railway on the same poles that carry the positive feeds. At
frequent intervals, say at every pole, or every other pole, the return feed,
Avdiich is otherwise carefully insulated, is connected to the rails only through
sets of variable resistances, as indicated on the diagram. These resistances
are proportioned in such a manner as to render all paths from and to the
station of precisely the same resistance — that is to say, from the station
the resistance of the circuit to the farthest car and back to the station will
be the same as the resistance from the station to the nearest car and back
to the station.
A consideration of the diagram will render it quite evident that as the
generators at the station are entirely insulated, and as the return feeds are
connected at frequent intervals to the rails in such a manner as to render
all the paths of equal resistance, no current will flow from the rails, except-
ing such as passes from any car to the two nearest points of return to the
return feeds ; and under these circumstances there is little or no tendency
for the current to leave the rails and pass to any adjacent underground
structures. It is, of course, conceivable that a pipe line may be so near
the rails — within a few inches of them, perhaps — that a slight amount
of electricity may escape to the pipe line for a few feet. Such cases would
have to be particularly guarded, but would form an exceedingly infrequent
exception to the general rule.
The objection to be urged against this expedient will inevitably be the
additional expense required in the erection and maintenance of the return
feeds, for this expedient amounts to giving the railway a complete metallic
circuit ; only using the rails to carry current between the adjacent poles.
I. IE. Fitmnm in a paper R»efore tlae A.IJE.I3. gives the follow-
ing conclusion, viz.,
First — All single-trolley railways employing the rails as a portion of the
circuit cause electrolytic action, and consequent corrosion of pipes in their
immediate vicinity, unless special provision is made to prevent it.
Second — A fraction of a volt difference of potential between pipes and
the damp earth surrounding them is sufficient to induce the action.
Third — Bonding of rails or providing a metallic return conductor equal
in sectional area and conductivity to the outgoing wires is insufficient to
wholly prevent damage to pipes.
THIRD-RAIL SYSTEM.
529
Fourth — Insulating pipes sufficiently to prevent the trouble is imprac-
ticable.
Fifth — Breaking the metallic continuity of pipes at sufficiently frequent
intervals is impracticable.
Sixth — It is advisable to connect the positive pole of the dynamo to the
trolley lines.
Seventh — A large conductor extending from the grounded side of the
dynamo entirely through the danger territory, and connected at every few
hundred feet to such pipes as are in danger, will usually insure their pro-
tection.
Eighth — It is better to use a separate conductor for each set of pipes to
be protected.
Ninth— Connection only at the power station to water or gas pipes will
not insure their safety.
Tenth — Connection between the pipes and rail, or rail return wires out-
side of the danger district, should be carefully avoided.
Eleventh — Frequent voltage measurements between pipes and earth
should be obtained, and such changes in return conductors made as the
measurements indicate.
TNIItlMtlli SITSTJEMS.
FiG. 87. Trolley, Metropolitan West Side
Elevated Railway, Chicago, 1895.
The use of an insulated rail
alongside of or between the rails
of the regular track, for carrying
the current for the motors, was
one of the earliest forms used for
electric railroads ; but until its
use on the Intramural Railway
at the World's Fair, Chicago, in
1898, demonstrated its success
and reliability when well laid
down, there had been so many
defects in the construction, and
faults from its use, that the over-
head trolley wire was substan-
tially the only method given any
attention. The complete success
of the system as laid down at
the Fair resulted in the installa-
tion of the third or conducting
rail on three of the Chicago
elevated railways during the
years 1895-1896 ; and being con-
structed in a rational and me-
chanical manner, the success
has been complete and continu-
ous.
The Metropolitan West Side
Elevated Railway started the
use of the third rail in 1895.
This rail is of steel T, supported
upon wooden blocks placed at
one side of the tracks, and the
current is collected from this
rail by four iron brushes suspended from each car.
The Lake Street Elevated Railway laid down a third-rail system in 1896.
This rail is supported upon pillar insulators six feet apart, and is protected
by wooden guard rails.
The Northwestern Elevated Railway started its use of a third-rail system
in 1896.
All the above-named roads make use of the track and structure for return
circuit, and the electrical pressure used is about 500 volts.
330
ELECTRIC STREET RAILWAYS.
Elec. World Engineer.
Fig. 88. Diagrams of Truck, Showing Shoe-Lifting Mechanism.
CONDUIT SYSTEMS OF ELECTRIC RAILWAYS. 531
Tn Fie 88 is shown a very good form of attachment for third-rail contact-
shoe as used on the Albany and Hudson Railway and Rower Company line
This'shoe can be turned up out of the way when entering city streets, and
the regular overhead trolley that is hooked down on the top of the car
"wZJ&i^™!™*^'^*1* of the use of the third rail
is'thatfd the N^ntasfet branch of the New York, New Haven, and Hartford
Railroad, which was equipped in 1896. The voltage used is 500.
Fig. 89. Section of Third Rail at Joint, Nantasket
Branch N. Y., N. H., & H. R. R., 1896.
The rail section used is inverted V in form, weighs 93 pounds per yard,
and is supported without fastening on wooden blocks tenoned into the
ties. There is a contact shoe weighing 25 lbs. hanging loosely from the
motor trucks at either end of the cars, and making contact by its weight.
As there is a break in the conducting rail at all crossings and turnouts, the
shoe at the front end always makes contact before the rear shoe leaves the
last rail.
As the conducting rail is but five-eighths inch above the ties and earth
lightning jumps to ground freely ; and experience shows that the distance of
this rail above the ground is scarcely wide enough, as the power current
also frequently jumps over.
Where the third rail breaks at crossings, etc.. the ends are connected by
well-insulated cable laid in wooden duct underground. Sloped wooden ap-
proaches are placed at the ends of the third rail at these breaks in order
that the contact shoe may ride up onto the rail easily.
The third-rail system as used on the above-named railroad is said to be
inexpensive of construction and quickly laid. There is little wear and tear
on the rail or contact shoe, and large amounts of current can be collected
without danger.
Other examples of the use of the third rail are the New Britain and Hart-
ford, Conn., branch of the N. Y. & N. H. Railroad, the New York and
Brooklyn Bridge, and the Brooklyn Elevated Railways.
CO]¥I>"Ui:T SYSTEMS OF ELECTRIC RAIIWATi.
Previous to 1893 hundreds of patents were granted on conduit and other
sub-surface systems of carrying the conductors for electric railways, and
hundreds of experiments were carried on ; but it has been only since that
year that capitalists have had the necessary courage to expend enough
money to make a really successfully operating road. The work was put
into the hands of competent mechanical engineers, who perfected and im-
proved the mechanical details, and the electrical part of the problem was
by that means rendered very simple.
532 ELECTRIC STREET RAILWAYS.
The Metropolitan Street Railway Company of New York, and the Metro-
politan Railroad Company of Washington, decided, in 1894, that,.hy build-
ing a conduit more nearly approaching cable construction, the underground
electric system could be made a success. The former contracted for its
Lenux Avenue line, and the latter for its Ninth Street line. The New York
road was in operation by June, 1895; the Washington road by August of
the same year ; and they continue to run successfully. While modifications
have been made in some details since these roads were started, yet the
present construction is substantially the same. These roads were the first
to avoid the almost universal mistake of spending too little and building
unsubstantially where new enterprises are undertaken. The history, in
these particulars, of the development of overhead trolley and conduit roads
is to-day repeating itself in the third-rail equipment of branch and local
steam roads.
The Metropolitan Railroad, in Washington, used yokes of cast iron placed
on concrete foundations, and carrying the track and slot rails. The slot
rails had deep inner flanges, with water lips to prevent dripping on con-
ductors. The conductor rails were T bars 4 inches deep, 13 feet 6 inches
long, 6 inches apart, and were suspended from double porcelain corrugated
insulators filled with lead and mounted on cast-iron handholes. A sliding
plow of soft cast iron collected the current. During the first few months of
its operation there were but few delays, mostly due to causes other than
electrical defects. Some trouble came from short-circuiting of plows, which
was remedied by fuses on plow leads, and a water rheostat at the power-
house. The flooding of conduits did not stop the road, although the
leakage was 300 to 550 amperes. Under such circumstances the voltage was
reduced from 500 to about 300. The average leakage on minus side, when
tested with plus side grounded, was one ampere over 6,500 insulators. The
positive side always showed higher insulation than the negative, possibly
due to electrolytic action causing deposits on the negative pole.
The Lenox Avenue line of the Metropolitan Street Railway was the first
permanently successful underground conduit line in the United States.
The cast-iron yokes were similar to those used on their cable lines, placed
5 feet apart. Manholes were 30 feet apart, with soapstone and sulphur ped-
estal insulators located under each, carrying channel beam conductors,
making a metallic circuit. At first the voltage was 350, but it was gradually
raised to 500. The pedestal support was afterwards abandoned, and sus-
pended insulators used every 15 feet, at handholes. At one time iron-tube
contact conductors were tried, but they proved unsatisfactory.
The details of track construction for underground or sub-surface trolley
railroads are essentially of a special nature, and are determined in every
case by the local conditions and requirements. They belong to the civil en-
gineering class entirely, and will not be treated here in any way other than
to show cuts of the yokes and general construction.
The requirements' of the conduit for sub-surface trolley conductors are
first, that it shall be perfectly drained, and second, that it be so designed
that the metallic conductors are out of reach from the surface, of any-
thing but the plow and its contacts. Another requisite is that the conduct-
ing rails and their insulated supports shall be strong and easily reached for
repairs or improvement of insulation.
The conducting rails must be secured to their insulating supports in such
a manner as to provide for expansion and contraction. This can be done by
fastening the center of each section of bar solid to an insulated support at
that point, and then slotting the ends of the bar where they are supported
on insulators. The ends of the bars will be bonded in a manner somewhat
similar to the ordinary rail bonding.
The trolley circuit of the sub-surface railway differs from the ordinary
overhead trolley system in that while the latter has a single insulated con-
ductor, and return is made by the regular running rails, the former has a
complete metallic circuit, local, and disconnected in every way from track
return.
The contact rails must be treated like a double-trolley wire, and calculations
for feeders and feeding in points can be made after the methods explained
for overhead circuits and feeders earlier in this chapter. Feeders and mains
are usually laid in underground conduits for this work, and the contact rails
may be kept continuous or may be divided into as many sections as the ser-
vice may demand, taps from the mains or feeders being made to the contact
CONDUIT SYSTEMS OF ELECTRIC RAILWAYS.
534
ELECTRIC STREET RAILWAYS.
FlG. 92. Drainage at Manhole of Conduit, Metropolitan Railroad,
Washington, 1895.
PLAN OF CLIP
Fig. 93. Clip and Ear for Conduit. Metropolitan Railroad, Washington,
1895.
rails at such points as may be determined as necessary. All the insulated
conductors should be of the highest class ; may be insulated with rubber or
paper, but should in any case be covered with lead. Especial care should
be taken in making joints between the conducting rail and copper conductor
so that jarring will not disturb the contact.
Other than the above few general facts it is difficult to say much regard-
ing this type of electric railway, for it is so expensive to install that it can
be used in but a few of the largest cities, and in every case will be special,
and require special study to determine and meet the local conditions. The
reader is referred to the files of the street railway journals for complete
descriptions of the few installations of this type of electric railway.
CONDUIT SYSTEMS OF ELECTRIC RAILWAYS.
535
Following are a number of cuts showing the standard construction of
electric conduits as designed and built by the Metropolitan Street Railway
Company, of New York. The system of railway may be said to use all the
latest methods, including wire-carrying conduits along side or under the
tracks, as will be seen by the next cut.
The porcelain insulator here shown for supporting the contact rails is
very substantial in design and construction, and by its location at a hand-
hole is easily reached for cleaning, repairs, and replacement. The jjIoiv has
also received careful attention, and those now used as standard by the Met-
ropolitan Company leave little to be desired.
Fig. 94. Section of Conduit, Metropolitan Street Railway, New York. -
Standard Work, 1897-98.
Section, Side and End Elevation of Plow, Metropolitan Street
Railway, New York. — Standard Work, 1897-99.
536
ELECTRIC STREET RAILWAYS.
Fig. 96. Plan and Elevation of Plow Suspension
from Truck, Metropolitan Street Railway, New
York. — Standard Work, 1897-98.
Fig. 97. Section and Elevation of Insulator, Metropolitan Street Railway,
New York. — Standard Work, 1897-98.
SVRFACi! CONTACT Oil EJLECOrKO-lflACHtfETIC
SYSTEMS.
The development of surface contact systems began even earlier than the
use of the overhead-trolley wire, and many patents have been issued on the
WESTINGHOUSE SYSTEM. 537
same. Most of these failed through ignorance of the requirements, and
timidity of capital in taking up a new device answers for others.
The Westinghouse Electric and Manufacturing Company and the General
Electric Company finally took the matter up, and being equipped Avith vast
experience of the requirements, and the necessary engineering talent and
apparatus, have each developed a system that is simple to a degree, and is
said to cost hut half as much to install as the conduit system, and to offer
advantages not known to that or other systems.
I quote as follows from a bulletin issued by the Westinghouse Electric
and Manufacturing Company.
Some Advantages of the System.
No poles, overhead wires, or troublesome switches are employed. The
streets, yards, and buildings are left free of all obstructions.
The facility with which freight cars can be drilled in yards and through
buildings, without turning the trolley whenever the direction of a motor
car or locomotive is reversed, and the absence of the necessity of guiding
the trolley through the multiplicity of switches usually found in factory
yards and buildings, is of great advantage, permitting, in fact, the use of
electric locomotives where otherwise electricity could not be used.
The only visible parts of the system, when installed for street railway
work, are a row of switch boxes between the tracks, flush with the pave-
ment, and a double row of small contact buttons which project slightly
above the pavement, and do not impede traffic in any way.
This system can be used in cities where the use of the overhead trolley is
not permitted, and if desired the continuation of the road in the suburbs
can be operated by the cheaper overhead system. It would only be neces-
sary to have a trolley base and pole mounted on the car, the pole being
kept down when not in use.
There are no deep excavations to make. The system can be installed on
any road already in operation without tearing up the ties.
The cost is only about one-half that of a cable or open conduit road.
The insulation of all parts of the line, the switches, and the contact but-
tons is such that the possibility of grounds and short circuits is reduced to a
minimum.
The system is easy to install, simple in operation, and reliable under all
conditions of track and climate.
Finally, the system is absolutely safe. It is impossible for anyone on the
street to receive a shock, as all the contact buttons are " dead " except-
ing those directly underneath the car.
Requirements.
In devising this system the following requirements of successful working
were carefully considered.
The insulation must be sufficient to prevent any abnormal leakage of
current.
The means for supplying the current to the car must be infallible.
The apparatus must be simple, so that inexperienced men may operate it
without difficulty.
The system must operate under various climatic conditions.
Finally, absolute safety must be assured.
WESTOGHOVSE SYSTEM.
This system includes the following elements.
First. Electro-magnetic switches, inclosed in moisture-proof iron cases.
Each switch is permanently connected to the positive main or feeder which
is laid parallel to the track.
Second. Cast-iron contact plates or buttons, two in each group, placed
between the rails and electrically connected to the switches. A separate
switch is provided for each group of buttons.
Third. The conductor forming the positive main or feeder. This is com-
pletely inclosed in wrought-iron pipe, and is connected to the various
switches.
538
ELECTRIC STREET RAILWAYS.
Fourth. Metal contact shoes or hars, suspended from the car trucks ;
two bars on each car.
Fifth. A small storage battery carried upon the car.
The operation of the system is described as follows, and is illustrated by
cuts making plain the text.
H— SHUNT COIL
I— SERIES COIL
Fig. 98. Diagram of Switch Connections.
CAR WIRING
D =. STORAGE BATTERY'
Fig. 99. Diagram of Car Connections.
Electro-magnetic switches, Xl5 X2, X3., inclosed in water-tight casings,
are installed at intervals of about 15 feet along the track to be operated.
Each switch is provided with two windings, I and H, which are connected
by the wires N and M to two cast-iron contact buttons, 1 and 2, which are
mounted on suitable insulators and placed between the rails.
Each car to be operated on this system is provided with two spring-
mounted T steel contact bars, Q3 and Q2, and a few cells of storage battery
in addition to the usual controllers and motors. The contact bars are
mounted at the same distance apart as the contact pins, 1 and 2, so that as
the cars advance along the track the bars will always be in contact with at
least one pair, as the length of the bar exceeds the distance between any
two pairs by several feet.
Suppose a car is standing on the track over the switch X2, the contact
bars, Qx and Q2, being then in connection with the buttons 1 and 2 respec-
tively. The first step is to "pickup" the current, i.e., render the buttons
1 and 2 alive.
Switch A is first closed ; this completes the circuit from the storage bat-
tery, D, through the wiring, R, contact shoe, Q15 button No. 1, and shunt
coil, H, to the ground. The current passing through H magnetizes the
core, S, which in turn attracts the armature, P, closing the switch and es-
tablishing connection between the 500-V main feeder K, and button No. 2,
through the contacts, JJ, coil I, and wiring N. Switch C is noAV closed and
switch A opened ; the switch X, is kept closed, however, by the current
flowing from button No. 2 through bar Q2, connection T, resistance L, con-
nection R, bar Qlt button No. 1, connection M, coil H to ground.
The car now proceeds on its way, current from the main passing through
connection T, to the controller and motors. When the car has advanced a
short distance the contact bars make connection with the pair of buttons
connected to switch X3. Current then passes from bar Q, through the
shunt coil of this switch. The operation described above is then repeated.
As soon as the bars leave the buttons 1 and 2, current ceases to pass through
the coils I and H of switch X2, and this switch immediately opens by grav-
WESTINGHOTJSE SYSTEM.
539
ity, leaving the buttons connected to it dead and harmless. As connection
with the main has already been established through switch X3, there will
be a continuous flow of current from the feeder, and no flash will occur
either at the button or the switch.
It will be observed that all the current passing to the car from the main
through switch contacts J J passes through the series coil, I, holding the
switch firmly closed and precluding all possibility of its opening while cur-
rent is passing through the contacts, even should the circuit through coil H
be interrupted. Although the act of "picking up the current " requires
some time to describe, it takes in practice only a few seconds.
Two separate switches, A and C, are shown in the diagram; but in practice
one special switch of circular form is provided, and the necessary combina-
tions required for " picking up the current " are made by one revolution of
the switch handle.
The battery need only be employed to lift the first switch; for after that
has been closed, the contact shoes bridge the main voltage over from one set
of pins to another, as described, thus closing the successive switches, with-
out further attention from the motorman.
The battery is charged by leaving switches A and C closed at the same
time.
The Switch.
Fig. 100 shows the general arrangement of switch, bell, and pan. The
switch and magnet are mounted upon a marble slab, which is secured in
the bell by means of screws to the bosses, B B.
The switch magnet, M, is of the iron-clad type. It is secured to the upper
Fig 100. Section of Switch, Bell, and Pan.
side of the marble base, and is provided with a fine (shunt) winding for the
" pick up " current, and a coarse (series) winding through which the work-
ing current passes.
When magnetized the poles attract an armature attached to a bridge piece,
J, each end of which carries a carbon disk, N. R, R, are guides for the bridge
piece, J. Directly above each of the carbon disks, N, is a stationary disk,
O, mounted upon a marble base. One of the disks, O, is permanently con-
nected by means of one of the contact cups, G1} as explained later, to the
positive main cable, and the other, through the series coil and cup, G2, to
the positive contact button.
540
ELECTRIC STREET RAILWAYS.
The pan, C, is provided with four bosses, S, to support the vertical split
pins, F, which are insulated from the pan. These pins slide into recepta-
cles, G, on the switch base. The pins, F, are provided with connectors, I,
for the purpose of making connection with the several cables, H, which pass
through the holes in the under side of the pan. The pan is completely filled
with paraffine after the connections are made, thus effectually keeping out
all moisture.
The object of the bell, A, and the pan, C, with the split pins, F, and the
cups, G, is to provide a ready means of examination of the switch without
disconnecting the wires. The bell can be lifted entirely free of the pan.
In replacing it, it is only necessary to see that a lug, T, on the side of the
cover, fits into a slide, U, on the frame. When in this position the split
pins make connections with their corresponding cups, G.
The bell, A, is provided with lugs, L, to facilitate handling ; and also a
double lip, W. The inner portion of this lip fits into and over the annular
groove, D, of pan C. This groove is filled with a heavy non-vaporizing oil.
The outer portion of lip, W, prevents Avater from entering the groove. The
object of the groove, D, and the lip, W, is to make a waterproof joint to pro-
tect the switch and cable terminals without the necessity of screw joints or
gaskets. The bells are all tested with 25 pounds air pressure ; they may be
entirely submerged in several feet of water without affecting the operation
of the system.
Xlie Contact Kuttons are made of cast iron. They are about 4J inches
in diameter, and, when installed on paved streets, project about five-eighths
of an inch above the pavement and offer no obstruction to traffic. This is
sufficiently high to enable the collector-bars to make contact, and at the
same time to entirely clear the pavement. For open-track installations they
are substantially mounted in a combination unit as described below.
Fig. 101. Section of Combination Unit.
The Combination Units.
The bell and pan are entirely inclosed in a cast-iron switch-box. This box
and the contact buttons are made into a complete unit as shown in Fig 20.
Each unit consists of three separate castings. The cylindrical cast-iron
box, which incloses the switch, bell, and pan, is bolted into a recess provided
for that purpose in the bottom of the spider-like structure, Avhich is a sep-
arate casting, consisting of box rim, receptacles for the button insulators,
and supporting arms. The removable lid is the third casting.
The insulators, A, Fig. 100, are made of a special composition, and are ce-
mented into the tapered cups, B, and supported by the iron plates, C. The
contact buttons, E, are mounted on top of these insulators and stand, when
installed, about one inch above the rail.
The four arms, G, are secured to the ties by means of the bosses, H, thus
reducing to a minimum the labor of leveling the boxes and avoiding the
necessity of special ties.
WESTINGHOUSE SYSTEM.
541
Mains and Wiring-.
The positive main or feeder is incased in a 1^-inch iron pipe, and passes
directly through each switch-box, and a tap is made to each switch, the
switch-boxes being all connected by the iron pipe, as per cut below.
ruu u u uuu-u
Fig. 102. Track Equipped for Track Return Circuit.
No additional wires are used to interconnect the coils or contacts of ad-
jacent switches.
The Contact Bars are of steel, of ordinary T section. They are sup-
ported from the car trucks by two flat steel springs and adjustable links.
These bars are inclined at the ends so that they may readily slide over the
buttons and over any ordinary obstacle.
Insulated Return line.
In case it is considered best not to use the rails as the return line, insu-
lated mains for this purpose may be included in the system. It is only
necessary to install another row of contact buttons, another collecting bar,
n r
i r
n r
n r
pi, j§) Jc
qI @ Jq
T -
i
_J ■■ 'i
;■
^®Y
'wWf
U L
U L
U L
Fig. 103. Track Equipped for Insulating Return Circuit.
and to use double-pole switches. Fig. 103 illustrates an installation of this
kind. For all ordinary work, however, the ground return is satisfactory.
Modifications of the System.
The description given on the preceding pages applies to the system as in-
stalled for yard and similar work. Modifications can be made and detail
matters arranged according to the requirements of each case.
Street Railway Work.
The foregoing description applies to installations where the track is open
(unpaved),and where it is unnecessary to make provision for traffic crossing
the tracks except at certain points. For street railway work, the switch-
boxes are preferable installed outside the track, Avhile the buttons are
placed between the rails and mounted on a light metal tie, as shown in Fig.
542
ELECTRIC STREET RAILWAYS.
The operation of the system is exactly the same as in open-track work.
Connecting wires pass from the buttons under the tie to the switch-boxes.
For double-track work the switches are installed between the two tracks,
and the boxes may be built to hold two switches, one for each track.
NE or_PAVING
CHANNEL IRON
Fig. 104. Section of Track Equipped for Street Railway Service.
When, as is sometimes necessary, the buttons are placed in a single row,
it is necessary that the "pick-up" current should be of the same voltage
as that of the main circuit, and consequently the car-wiring indicated in
Fig. 96 is used, instead of that shown in Fig. 99.
Fig. 105. Diagram of Car-Wiring.
Referring to Fig. 105, the method of "picking up" the current is as fol-
lows : Switch A is first closed ; this completes the circuit from a storage
battery D, through a small 500-volt motor-generator F, which immediately
starts. As soon as it is up to speed, which only requires a few seconds,
switch B is closed ; current then passes from F through the wiring R, to
contact shoe Q, and then through the switch magnet, as explained on page
530. Switches A and B are then opened, thus stopping tbe motor-generator,
which need only be used to operate the first switch. The successive
switches are closed, as described on page 527.
This arrangement of a high-voltage " pick-up " may also be used advan-
tageously with two rows of buttons where the track is liable to be obstructed
by mud or snow.
Sectional Mail Construction.
For suburban railway or similar service two light rails may be substituted
for the two rows of contact buttons, as shown in Fig. 90. The cars are
then equipped with contact shoes instead of bars. These rails are insulated
from the ground, and may also be insulated from each other wherever
desirable, thus breaking them up into sections, which are each controlled by
a single switch. The sections may be made of any desired length to suit the
conditions. For example, between stations they may be 500 or more feet
long, while near stations or crossings, where anyone is liable to come in
contact with the rail, the length of a section may be reduced to 50 feet or
less. The electrical operation of two-rail installations is the same as when
two rows of buttons are used. The sectional switches along the tracks are
entirely under the control of the motorman, and the rails may be rendered
" dead" at any moment should occasion arise.
GENERAL ELECTRIC COMPANY.
543
The Westinghouse Company use a system of surface contact all oyer its
large works at East Pittsburg, and another plant has been in operation for
some time at Indian Head, Md.
Fig. 106. Sectional Rail Installation.
«EXEHAI ELECTRIC SITSTJEM: OI1 S1J1IFACE
CONTACT RAILWAY.
Following is a description of the surface contact system, as developed by
the General Electric Company, and practical application of it has been
made at Monte Carlo, and at the company's works at Schenectady. The
description is from a report made by W. B. Potter, Cf . Eng. of the Railway
Department, and written by Mr. S. B. Stewart, Jr.
In the operation of electric cars, by tbe closed conduit surface plate con-
tact system of the General Electric Company, the current is collected for
the motor service by means of two light steel shoes carried under the car,
making contact with a series of metal plates, introduced along the track
between the rails, automatically and alternately energized or de-energized
by means of switches grouped at convenient places along the line ; the
method of the switch control being such that in the passage of the car, in
either direction, it is impossible for any plate to become alive except when
directly under the car body.
In ordinary street car practice, the contact plates are spaced approxi-
mately ten feet apart, positive and negative plates being staggered, as
shown in Fig. 106, which admits of but three plates ever being covered at any
one time by the shoes, which are so designed as not to span more than two
plates of the same polarity.
In grouping the switches it is customary to locate them either in vaults
constructed between or near the tracks, or in accessible places along the
side of the street, the location and spacing of groups and number of
switches in each group being based upon a comparative cost between the
style of vault or other receptacle, and the amount of wire with ducts be-
tween the contact plates and their corresponding switches.
The main generator feeder is carried to each vault or group, and auxiliary
feeders from it are distributed to each switch, the track rail being utilized
for the return circuit.
544
ELECTRIC STREET RAILWAYS.
The operation or performance of this system can be readily traced out bv
reference to Fig. 107. It will be seen that the current in its passage to the
motor from the positive generator conductor passes to contact A of switch
No. 2 through the carbons on its magnet armature (which has been lifted
by the energized coilG) to contact plates B and C, through the contact shoe
D to the controller and motor, coming out at contact shoe E to the contact
plate F, when it passes through the coil of the automatic sAvitch G, ener-
gizing it and returning by the track-rail H ; thus maintaining contact at
switch No. 2 armature carbons as long as the shoes remain on the contact
plates C and F. It should now be noted that contact plate B is energized
MOTOR <^n /^^
-|QIIMil|^
Fig. 107. Diagram of Connections for Surface Contact Railway Plate
System, General Electric Co.
as stated above. As the car proceeds, the shoe D spans the plates B and d
thereby keeping the coil of switch No. 2 energized after shoe has left plate
C, and until shoe E comes in contact with plate J, which immediately ener-
gizes coil No. 1, thus making the preceding contact plate energized, prepara-
tory to the further advance of the car. It will be noted in the above
description of the performance of the system, that we have assumed switch
No. 2 on Fig. 107 as closed; it should therefore be understood that an aux-
iliary battery circuit is necessary in starting or raising a first switch, pre-
paratory to its armature being held in contact position by the generator
current, which current energizes the preceding contact plates consecutively
as described above.
The battery current is brought into the automatic switch circuit momen-
tarily during the period of first movement of handle of the controller in
starting a car, the transition of the controller cylinder also bringing the
generator current in connection with the battery for a short period of time,
thus replenishing the elements sufficiently to operate the switches. The
battery is also used to supply current for lighting the car, the generator
circuit being disconnected while the car is at rest.
Surface Cobs tact .Plates.
The surface contact plates are made of cast iron, with wearing surfaces
well chilled, designed to be leaded into cast-iron seats in such "a manner
that they are thoroughly secure, but can be readily removed by special
tongs for the purpose. The seat is imbedded in a wooden or composition
block set into a cast-iron box, the latter being spiked or screwed to the tie.
A brass terminal is fastened to the seat for the reception of the connecting
wire from the switch. See Fig. 106.
GENERAL ELECTRIC COMPANY.
545
As stated above, the plates are usually located 10 feet apart for straight
line work, but somewhat closer on curves, depending upon the radius of the
curve and length of contact shoe. The negative and positive contact plates
are staggered with a uniform angular distance between them, situated not
less than 10 inches from the track rails.
Fig. 108. Plan and Section of Track, Monte Carlo, Europe.
General Electric Company's Surface Contact System, 1898.
Surface Contact Switch.
The automatic switches are constructed on the solenoid principle, the
armature or core of which is employed in closing the contacts as shown in
Fig. 109. Automatic Switch for Open Conduit, Surface Plate Contact System.
546 ELECTRIC STREET RAILWAYS.
Fig. 109. The end of the armature core is provided with a pressed sheet-
steel carbon-holder, for the purpose of supporting the carbon contacts which
are held in place by bronze clips and cotter pins which can easily be re-
moved. The pressed-steel carbon-holder can also be detached with little
trouble by removing the end holding it to the core. Copper plates are se-
cured to the slate base for contact surfaces and the attachment of feeder-
wires. The wire of the solenoid is wound on a copper spool and placed in
a bell-shaped magnet frame, and a pole-piece, slightly recessed to receive
the end of the armature core when the switch is in a closed position, is at-
tached to the top cover, and extends part way down through the winding.
The recess in the armature increases the range of the magnet, making the
attraction uniform except at the point of contact where the power increases
rapidly, thus securing an excellent contact. A blow-out magnet coil is con-
nected in series with the feeder current, and so situated that the influence
of its poles is used to rupture any arc that might be formed while the switch
is opening ; however, this blow-out magnet is used simply as a precaution-
ary device, as under ordinary conditions there is no arcing, the succeeding
automatic switch closing the circuit before it is opened by the preceding one.
Each vault or group of switches should be provided with cut-outs or an
automatic circuit breaker to protect them in the event of short circuits.
Surface Contact Shoes.
The contact shoes are made of " T " steel of light section, the suspension
for which is an iron channel beam extending longitudinally with the truck
frame directly under the motors, with a substantial wooden cross-arm at-
tached to each end for the shoe-supporting casting, the shoes being attached
to these supporting castings by a spring equalizing device for maintaining
the shoes at the proper height, and also for making them flexible enough to
meet any slight variations in the contact plates and track rails. The shoes
when in their correct position should never drop over one-fourth inch below
the surface contact plates, and are designed so that they may raise three-
fourths of an inch or more above them. See Fig. 109.
Fig. 110. Collecting Shoes, Monte Carlo, Europe.
General Electric Company's Surface Contact System, 1898.
A screw adjustment is provided to lower the shoes as they wear away, or
to take care of any other discrepancies due to wear of parts, etc. ; if they
are allowed to drop too low they will interfere with rail crossings, causing
short circuits.
Storagre Batteries.
_ It requires for closing the first automatic switch when starting, and for
lighting the car approximately, ten storage battery elements capable of 35
amperes rate of discharge for five hours.
GENERAL ELECTRIC COMPANY. 547
The batteries are only slightly exhausted in making the initial connec-
tions through the automatic switch, as it only takes approximately 15 am-
peres momentarily to perform this work, the battery is immediately
recharged by current which has passed through the motors. The battery
serving as a rheostatic step, this momentary cnarging does not represent
any extra loss of energy.
The circuit connections of the battery are accomplished in the controller,
and require no attention on the part of the motorman.
Car JLigliting-.
The amount of recharging derived from the motor circuits is sufficient to
operate the automatic switches, but where lighting of the car is done from
the same battery, an additional recharge is required.
Assuming that 10 20-volt lamps are used for lighting a car, the batteries
will need to be recharged every night about five hours, at an approximate
rate of 25 amperes.
It is customary to run leads from both the positive and negative terminals
of the batteries to charging-sockets attached to the under side of one of
the car sills in a convenient place for connection to the charging-wire.
A small generator of low potential (30 volts) driven by a motor or other
method is required for supplying current for recharging the batteries where
the desired low-potential current is not accessible, and the wiring from the
charging source should be run to a location in the car-house most convenient
for connections to the battery sockets. These locations may be fixed either
in the pits or on posts at the nearest point to Avhere the cars will be sta-
tioned, and there should be flexible lead wires attached to plugs for connect-
ing to the battery circuit on the car. In wiring the car-house for the
battery connections, it would be found convenient to designate the polarity
of the various wires either by different colored insulation or tags, and the
plugs at the ends of the flexible leads should be marked plus and minus to
avoid mistakes in making connections with the car battery receptacle.
Motors and Controllers.
The motor and controller equipment used with the surface plate contact
system is standard apparatus as ordinarily employed for electric car service,
with the exception that provision is made in the controller for cutting in
and out the storage battery while starting the car.
Care of Apparatus.
As success in the operation of the contact plate system depends largely
on the care of the apparatus, a few general remarks on the subject will not
be out of place here.
Care should be taken that the contact plates are kept clean, and they
should be frequently inspected, the roadbed being well drained. Any small
quantity of water temporarily standing over the tracks, however, would do
little harm, as the leakage through the water would not be sufficient to
create a short circuit, although this condition should not be allowed to
exist any length of time.
The automatic switches should be carefully inspected and all cast-iron
parts thoroughly coated with heavy insulating paint, and a test for insula-
tion or grounds be made frequently, and all the parts kept clean and free
from moisture.
The contact shoes, in order to prevent leakage, should have their wooden
supports well protected with a coating of an insulating paint, and should
also be occasionally cleaned.
The storage batteries should be properly boxed and should have the cus-
tomary care which is necessary to keep them in good working order.
TRANSMISSION OP POWER.
The term " Transmission of Power," as used by electrical engineers, lias
come to have a conventional meaning which differentiates it from what
must be considered its full meaning. Any transmission of electric current,
for whatever practical purpose, whether for lighting, heating, traction, or
power-driving, must of course be a transmission of power ; but the conven-
tional meaning of the term as now used by electrical engineers and others
eliminates many of these objects, and is held to mean simply the trans-
mission of electric current from a more or less distant point or station to a
center from which the power is distributed, or to power motors at different
points in a factory or other installation. While the distances over which
electric current is transmitted for arc lighting in some large cities and in
many small places far exceeds the length of line of the ordinary or average
power transmission, yet the former is never alluded to as transmission of
power. The same condition obtains with traction, the transmission of cur-
rent covering miles of territory, and yet it is only alluded to as power
transmission when the current is transmitted from a central point to vari-
ous sub-stations from which it is distributed.
The engineering features of transmission of power will all be found
treated under the separate heads in their respective chapters, and the fol-
lowing is a short resume, of the subject matter.
Building- :
Structural conditions and material.
JHotive Power:
"Water power : Turbines, etc.
Steam power : Boilers and appliances.
Engines and appliances.
Shafting and pulleys.
Belting and rope drive.
Generators:
Dynamos : direct current.
alternating current,
double current.
Transmitting- Appliances :
Switchboards.
Transformers, step up.
Botaries.
Cables and pole lines.
Conduits, etc.
Distributing- Appliances;
Sub-stations and terminal houses.
Transformers, step down.
Switchboards, high tension and secondary.
Botary converters.
Direct current motors.
Synchronous motors.
Induction motors.
Frequency changers.
Distributing circuits.
548
DISTRIBUTING APPLIANCES.
549
Much has been written regarding the relative values of the different
methods of transmitting power, and comparison is often made between the
following types, i.e.,
a. Wire rope transmission.
b. Hydraulic transmission, high pressure.
c. Hydraulic transmission, low pressure.
d. Compressed air transmission.
e. Steam distribution for power.
/. Gas transmission.
g. Electrical transmission.
All of the first six methods listed have so many limitations as to distance,
efficiency, adaptability, elasticity, etc., that electricity is fast becoming the
standard method. The matter of efficiency alone is 'one of the best argu-
ments in its favor, and I take from Dr. Bell's book, " Electric Power Trans-
mission" the following table of the efficiencies such as have been found in
practice.
System.
Per Cent Efficiency ;
Wire rope
Hydraulic high pressure
Hydraulic low pressure
Pneumatic
Pneumatic reheated, virtual efiiciency
Electric
45
50
50
65
For short distances out of doors, transmission by wire rope is much used
both in the United States and Europe, and where but few spans are neces-
sary, say less than four, the efficiency is very high.
Hydraulic transmission is in considerable'use in England, but except for
elevator (lift) service is in little use in the United States.
Pneumatic transmission is in wide use in Paris, but not so for general
distribution in the United States, although for shop transmissions for use
on small cranes and special tools is making good progress.
Electrical transmission is so elastic and so adaptable to varied uses, and has
been pushed forward by so good talent, a not small factor, that its progress
and growth have been simply phenomenal. In one place alone, that of
traveling cranes for machine shops, it has revolutionized tbe handling of
material, and has cheapened the product by enabling more work to be done
by the same help.
Electric Power Transmission may be divided into two classes, i.e., long
distance for which high tension alternating current is exclusively used ;
and local or short distance transmission for which either direct current or
polyphase alternating current are both adapted, with the use of the former
largely predominating, owing perhaps to two factors, a, the much earlier
development of direct current machinery, and b, to the fact that a large
number of manufacturers are engaged in the building of direct current
machinery. Both types of current have their special advantages, and
engineering opinion is, and will probably remain, divided as to which has the
greater value.
Long distance transmission is now accomplished by both three-phase three-
wire, and by the two-phase four-wire systems, with the former predoni-
550 TRANSMISSION OF POWER.
mating for the greatest distances, owing to economy of copper. Each sys-
tem lias certain advantages over the other, and both have strong advocates
among engineers. For the distribution of very large amounts of power the
three-phase system presents a strong point in its economy of copper, and
another in simplicity of switching appliances.
Every case of electric transmission presents its own problem, and needs
thorough engineering study to decide what system is best adapted for the
particular case. It is, therefore useless to enter into any detailed discus-
sion here, as all the engineering details are treated of elsewhere in the book
under the respective departments. The economic discussion does not enter
into the engineering problem except in the preliminary study, which has
presumably been satisfactory before reference is necessary to this book.
Limitations of Voltage.— While 10,000 volts pressure was used with some
distrust for a time previous to 1898, since that time 15,000, 20,000, 25,000, and
40,000 volts have been and are still in use with substantial satisfaction.
Properly designed glass or porcelain insulators, made of the proper
material, and tested under high pressure conditions, cause little trouble
from puncture or leakage. The latter is its own cure, for the reason that
the leakage of current over the surface of the insulator dries up the mois-
ture. Dry air, snow, and rain-water are fairly good insulators, and offer no
difficulties for the ordinary high voltages. Dirt, carbon from locomotive
smoke, dust from the earth, and such foreign material that may be lodged
on the insulators, are sure to cause trouble. In the West and some sections
of the East many insulators are broken by bullets fired by the omnipresent
marksman.
Oil insulators have proved worse than useless, as dirt and dust, to say
nothing of bugs, are gathered by the oil, and produce very bad results';
they were introduced in the United States in some of the early high-voltage
installations, but after a short time the cups holding the oil had to be
broken off.
Glass makes the surest insulator, as the eye can make all necessary
tests ; but it is so fragile that porcelain is more commonly used. It is not
safe to accept a single porcelain insulator without a test with a pressure at
least twice as great as that to be used. The interior of the porcelain
should be perfectly vitreous, and should not absorb red ink so that it can-
not be wiped off perfectly clean.
A convenient way of testing such insulators is to invert a number, say a
dozen, in a pan of salt water ; fill the pinhole with more water of the same
kind. Connect the pan with one terminal of a high potential transformer,
and use as the other terminal a piece of metal, say a spike or old battery
zinc pencil which will be connected to the opposite terminal of the trans-
former, and inserted in the pinhole of each insulator. A double-pole switch
should be used to open and close the low-pressure side of the testing trans-
former. Under these conditions one insulator is tested at a time, and good
porcelain will stand very high pressure before a breakdown. Heavy sea-fog
is about as bad a condition as can be assumed for high voltage trans-
mission. Mr. Ralph D. Mershon of the Westinghouse E. & M'fg. Co. made
a long series of tests at Telluride, Col., on the high-pressure lines in use
there.
At 50,000 volts there will be a brush discharge or leakage from one wire
to the next that can be seen at night, and makes a hissing noise
that can be heard a hundred feet or more. This brush discharge
begins to show at about 20,000 volts, on dark nights, and increases
very rapidly, as does also the power loss at 50,000 volts and higher.
This loss depends upon the distance apart of the conductors and their
size. Above 50,000 volts the losses become serious, the discharge dis-
posing of a large amount of energy. For these reasons, wires should be
kept well apart~and be of as small size as other properties will allow.
The wave form of E. M. F. used also influences the brush discharge, being
the least in effect for sine wave curves of E. M. F., and being much in-
creased by the use of the sharp, high forms of curve.
Line inductance, capacity, and resonance, unbalancing of phases, etc.,
have caused little trouble in practice, although they should be given serious
consideration, especially for lines carrying heavy currents.
In regard to the frequency to be adopted for power transmission, one has
to be governed by the case in hand, and the commercial frequencies avail-
able at economical cost.
LIMITATIONS OF VOLTAGE. 551
Since the success of the Niagara plant the frequency used there, 25 per
second, has become a standard for power transmission purposes, but should
be avoided if much arc or incandescent lighting is to be done. Other fre-
quencies, such as 30 and 60, are in common use, the latter being the favorite
for plants having a mixed output of power and lighting.
It must be remembered that the higher the frequency, the more trouble-
some are the rotary converters that may be connected to the system.
Induction motors and synchronous motors of the revolving field type are
now almost perfection, and are useful to counteract each other's effects on
lines, and both give their best results at low frequencies. Alternating arc
lamps cannot be used with any satisfaction on a frequency less than 40.
STORAGE BATTERIES.
ELECTRIC STORAGE BATTERIES.
Partly condensed from articles by Joseph Appleton in " Electrical
Engineer."
An electric storage battery, or accumulator, is a combination of cells, each
of which is a unit.
In the ordinary lead, sulphuric acid type, a cell is made up of three parts
— the jar, or box, the plates, and the electrolyte.
Thenar, or containing-box , may be of any good non-conducting and acid-
proof material of sufficient strength and rigidity to support the plates and the
electrolyte. In the smaller stationary types the jar is of tenest made of glass
or of hard rubber, the latter especially for portable cells where lightness is
of moment. Portable cells are now often made of hard wood lined with
lead. Large cells for central-station work are made of heavy planks, well
jointed, and lined with five-pound sheet lead.
Stationary cells should always be supported upon some well-designed in-
sulator, such as porcelain, so constructed as to have a retaining-cup of oil,
in order to maintain a high degree of insulation. They are also generally
set up from the floor a short distance, most often on stringers of well dried
and filled hard wood.
The plates are of two kinds, positive and negative, arranged alternately,
there always being one more negative than positive, A set or group of these
plates is commonly known as an element. All positive plates are connected
together, as are also all negative plates, but the positives and negatives are
separated from each other by insulating strips of some kind.
The electrolyte used with all lead batteries — and no others are in exten-
sive use at the present time — is sulphuric acid diluted with water to a s.g.
of 1.15 to 1.30 according to the type. The acid must be free from impurities,
such as arsenic, nitric or hydrochloric acid, and the water must be distilled.
Storage or secondary batteries of the ordinary lead, sulphuric acid type
may be divided into two classes, the Plants and the Faure. Both are lead
elements in dilute sulphuric acid, but are formed differently.
The Plante type is constructed of lead plates so designed as to present a
large surface area to the action of the electrolyte, the active material being
formed on the plates, either electrically, by charging and discharging, com-
monly called " forming," or chemically.
In the Faure, commonly known as the pasted, type the active material is
applied mechanically to a lead conducting-plate or grid. Tbe material may
be active Avhen applied, or may be such that it can be converted into active
material by electrical or chemical formation.
Tlates.
The positive plate is of lead, upon which a coating of peroxide of lead has
been formed or mechanically applied.
The negative plate is of pure lead, the surface of which is spongy or porous
in its formation.
The peroxide and spongy lead are the portions of the plates which are sub-
jected to the chemical action, and are called the active material, the lead
body of the plates serving practically as a support for the active material.
The chemical condition of the plates and acid differs when charged and
discharged. At full charge the positive plate has a dark brown coating of
peroxide of lead, the negative plates having the porous or spongy condition
above described, of dark slate color, and the electrolyte being of full specfic
gravity and strength. In this condition, when the positive and negative
poles are connected through an external circuit an E.M.F. is set up in the
cell, a current flowing through the circuit from the positive plate. When
discharged, the positive plates have a chocolate, and the negative a light
slate color. A drab color on the positive indicates sulphating or an over dis-
charge.
552
ELECTRIC STORAGE BATTERIES. 553
Chemical Action.
The chemical action taking place during charging is as follows : the cur-
rent enters at the positive pole, passing through the acid to the negative.
Both plates contain sulphate of lead, due to the preceding discharge, and
the net result of the passage of the current is to decompose this sulphate,
and at the same time to transfer all the oxygen from the negative to the
positive. At the completion of the charge, the negative is entirely free from
oxide, and the positive contains no oxide lower than the peroxide, though
it may still contain some sulphate. The reduction of the sulphate of lead
forms free sulphuric acid, and, of course, increases the density of the elec-
trolyte. The complete account of the chemical reactions in charging is too
extensive to be given here.
If charging is continued after all the active material has been converted
to peroxide of lead and spongy lead, oxygen and hydrogen gas will be given
off in bubbles.
In discharging, the sulphur radical in the acid combines with the active
material on both plates, forming sulphate of lead, the specific gravity of the
electrolyte being reduced. When all the active material has been acted
upon, the cell is discharged, as an equilibrium has been created between the
positive and negative plates, and the E.M.F. set up by the chemical action
has been reduced to zero. In practice the E.M.F. is never allowed to fall
below 1.8 volts.
The chemical reactions are given as follows, by Frankland.
If the buff lead salt be the active material of the battery plates, the fol-
lowing equations express the electrolytic reactions taking place in the
cell : —
I. In charging —
(a.) Positive Plates.
S3Pb,014 + 30H2 + 05 = 5Pb02 + 3S04A2.
Buff load Water. Lead Sulphuric
Water. Peroxide. Acid.
(b.) Negative Plates.
S3Pb5014 + 5H2 = 5Pb + 3S04A2+20H2.
II. In discharging —
(a.) Positive Plates.
5Pb02 -f 3S04H2+5H2 = S3Pb5014 + 80H2.
(b.) Negative Plates.
5Pb + 3S04H2 + 05 = S3Pb5014 + 30H2.
If the red lead salt be the active material, then the following equations
express the same electrolytic reactions : —
I. In charging —
(a.) Positive Plates.
S2Pb,O10 + 02 + 20H2 = 3Pb02 + 2S04H2.
Red lead Lead Sulphuric
Salt. Peroxide. Acid.
(b.) Negative Plates.
S2Pb3O10 + 4H2 =: 3Pb + 2S04H2 + 20H2.
II. In discharging —
(a.) Positive Plates.
3Pb02 + 2S04H2 + 2H2 = S2Pb3O10 + 40H2.
(b.) Negative Plates.
3Pb + 2S04H2 + 202 = S2P3O10 + 2H2.
554 STORAGE BATTERIES.
It is, however, very questionable whether these salts play any important
role in the normal reaction of the cell.
The various oxides of lead are as follows : —
Plumbous or sub-oxide Ph>0.
Plumbic oxide, litharge PbO.
Triplumbic oxide, or red lead miniuin Pb304.
Diplumbic oxide Pb203.
Monoplumbic dioxide, or peroxide PbU2.
CALCriATIOlf OF E.M.F. OF STORAGE BATTERY,
Streintz.
Let JE=E.M.E. required.
S = Specific gravity of the electrolyte.
s = Specific gravity of water at the temperature of observation.
Then JS= 1.850+ .917 (S — s).
Wade.
7F=work in joules.
Q= coulombs of electricity passed through the electrolyte.
H= number of calories liberated by the recombination of a unit
weight of one of the decomposed ions.
e = its electro-chemical equivalent.
c = its chemical equivalent.
h = electro-chemical equivalent of hydrogen = -00001038.
J = Joule's coefficient = 4.2.
E = E.M.~F. required.
Then W— QE— QJeH.
E = JeH.
e = hc.
E = JhcH=4t.2x. 0000 038 cH= .0000436 cH.
heat of formation
valency
.0000436 X heat of formation
valency
.0000436x46,000
CALCFIATIOir OF THE CAPACITY OF A
STORAGE BATTERY IW AMPEfiE HOURS.
The current in ampere hours maintained by the consumption of any given
chemical substance varies with the change of valence and inversely with
the molecular weights of the transforming substance. The combustion
of liberation of 1 pound of hydrogen corresponds to 12,160 ampere hours.
The theoretical capacity in ampere hours may be calculated as follows : —
F= change of valence of the ions.
JF=the sum of the molecular weights affected.
12,160 = capacity per pound of hydrogen.
„. n , 12,160 X V
Then Capacity per pound =
In lead-lead-sulphuric acid cells the above formula gives 40.24 ampere hours
as the capacity per pound of lead sulphate.
The above formula is based on the supposition that the entire material of
both plates is transformed into lead sulphate. This is never accomplished,
and Fitzgerald gives as a safe rule :
.53 oz. lead peroxide and the same Aveight of spongy lead per
ampere hour for a 10-hour rate of discharge,
.62 oz. for a 5-hour rate,
.70 oz. for a 3-hour rate,
1 oz. for a 1-hour rate.
All above for the ordinary thickness and an electrolytic density of 1,200.
CALCULATION OF E.M.F. OF STORAGE BATTERIES. 555
IHH Hl'DRO^ETEll.
The hydrometer is an instrument for determining the density of liquids.
It is usually made of glass, and consists of three parts: (1) the upper part,
a graduated stem or fine tube of uniform diameter ; (2) a bulb, or enlarge-
ment of the tube, containing air ; and (3) a small bulb at the bottom, con-
taining shot or mercury, which causes the instrument to float in a vertical
position. The graduations are figures, representing either specific gravities
or the numbers of an arbitrary scale, as in Beaume's, TwaddelFs, Beck's, and
other hydrometers.
There is a tendency to discard all hydrometers with arbitrary scales, and
to use only those which read in terms of specific gravity directly. This ten-
dency is all the more to be indorsed, as there are considerable discrepancies
in the different tables professing to give the Beaume scale, the following one
being, perhaps, as much quoted as any.
Deaume's Hydrometer and Specific Grat
Sties Compared.
Liquids
Liquid
s •
Liquids
Liquids
TS2-C
Liquids
Liquids
Heavier
Lighte
r % d
Heavier
Lighter
than
Heavier
Lighter
* =
than
than
£ §
than
than
than
rcr-
Water,
Water
iacce
Water,
Water,
CX-
Water,
Water,
2,'A
sp. gr.
sp. gr
• AS
sp. gr.
sp. gr.
£::
sp. gr.
sp.gr..
0
1.000
19
1.143
.942
38
1.333
.839
1
1.007
20
1.152
.936
39
1.345
.834
2
1.013
21
1.160
.930
4!)
1.357
.830
3
1.020
22
1.169
.924
41
1.369
.825
4
1.027
23
1.178
.918
42
1.382
.820
5
1.034
24
1.188
.913
44
1.407
.811
fi
1.041
25
1.197
.907
46
1.434
.802
7
1.048
26
1.206
.901
48
1.462
.794
8
1.056
27
1.216
.896
50
1.490
.785
9
1.063
28
1.226
.890
52
1.520
.777
10
1.070
1.000
29
1.236
.885
54
1.551
.768
11
1.078
.993
30
1.246
.880
56
1.583
.760
12
1.086
.986
31
1.256
.874
58
1.617
.753
13
1.094
.980
32
1.267
.869
60
1.652
.745
14
1.101
.973
33
1.277
.864
65
1.747
15
1.109
.967
34
1.288
.859
70
1.854
16
1.118
.960
35
1.299
.854
75
1.974
17
1.126
.954
36
1.310
.849
76
2.000
18
1.134
.948
37
1.322
.884
Streng-th of IMlute Sulphuric Acid of Different Densities
at 15° C. (50° F0. (Otto.)
Per Cent.
Specific
Per Cent.
Per Cent.
Specific
Per Cent.
of H2S04.
Gravity.
of S03.
of H,S04.
Gravity.
of S03
100
1842
81.63
23
1167
18.77
40
1306
32.65
22
1159
17.95
31
1231
25.30
21
1151
17.40
30
1223
24.49
20
1144
16.32
29
1215
23.67
19
1136
15.51
28
1206
22.85
18
1129
14.69
27
1198
22.03
17
1121
13.87
26
1190
21.22
16
1116
13.06
25
1182
20.40
15
1106
12.24
24
1172
19.58
14
1098
11.42
Ordinarily in Accumulators the densities of the Dilute Acid vary between
1150 and 1230.
556
STORAGE BATTERIES.
Conducting* Power of Dilate Sulphuric
Acid of Various Strengths. (Matthiessen).
Sulphuric
Relative
Specific
Acid in
Temperature.
Resistances.
Gravity.
100 parts
C.°
Ohms per
by Weight.
cub. centim.
1.003
0.5
16.1
16.01
1.018
2.2
15.2
5.47
1.058
7.9
13.7
1.884
1.080
12.0
12.8
1.363
1.147
20.8
13.6
.960
1.190
26.4
13.0
.871
1.215
29.6
12.3
.830
1.225
30.9
13.6
.862
1.252
34.3
13.5
.874
1.277
37.3
.930
1.348
45.4
17.9
.973
1.303
50.5
14.5
1.086
1.492
60.6
13.8
1.549
1.638
73.7
14.3
2.786
1.726
81.2
16.3
4.337
1.827
92.7
14.3
5.320
1.838
100.0
Conducting- Power of Acid and Saline
Solutions.
Copper (Metallic) at 66° F 100,000,000.
Sulphuric Acid 1 Measure "^
Water 11 Measures lQQ n „^„^4™„+Q
(Equal to 14.32 parts by weight of Acid fy8,u approximate.
in 100 parts of the mixture), at 66° F. . .J
Sulphate of Copper, saturated solution at ) a . ..
66° F | b'*
Chloride of Sodium, saturated solution at \ R 1 ,,
66° F J bl
Sulphate of Zinc, saturated solution at ) QK n ,,
6$F }35<0
(\
MOTAtlLATlOM AID CARS.
Fig. 2.
Standard
Hydrom-
eter.
8§ inches
long.
In small batteries, in which the cells are small enough to be
handled Avhen assembled, the cells may all be assembled before
placing. Large cells have to be assembled in place, as they will
seldom permit change of position without considerable incon-
venience.
The battery-room should be dry, well lighted and ventilated, and
of moderate temperature, as the evaporation of electrolyte is apt to be
troublesome in heated rooms.
All exposed iron work should be painted with an acid-proof paint; in fact,
all metal work exposed to the acid fumes should be painted for its protection.
The floor of the battery room is preferably of brick, tile, or cement, laid
so it will drain easily to some common outlet. Wooden floors should never
be used unless protected by lead trays to catch any stray acid.
The battery room should preferably be located as near the power-house as
possible, thus reducing the cost of connecting conductors, and possibly using
the same attendants.
INSTALLATION AND CAKE. 557
Cells should be arranged so as to be easily accessible for examination and
repairs. Large cells are seldom placed in more than one tier, but the smaller
ones can be erected in two or three tiers.
Where cells are of glass they may be conveniently set in trays on a bed of
sand, and the trays be set on insulators. Wooden tanks are set directly on
insulators, as they are always built of sufficient strength to support their
weight and contents.
Cell Connections.
In small cells the plates of one polarity are usually connected by a lead
strap that is cast on the plates in a bunch, the strap of one cell being con-
nected to that of the next by a bolt or screw clamp or weld. All battery con-
nections should be of ample sectional area to avoid loss, and, as lead is the
metal mostly used for such purposes, and as compared with copper has
about seven times the resistance, it is especially important that its area
be large.
The best method of connecting the positive group of plates to the adjacent
group of negative plates in the next cell is to bum or weld the two to a lead
strap of large cross-section ; and, in case of very heavy currents, a copper
conductor may be embedded in this lead strap.
.Lead-Burning- Apparatus.
The hydrogen flame has the special property of not oxidizing, or otherwise
soiling the lead, and is therefore used for melting together two lead surfaces,
notably that between cells and the sheet lead lining of the tanks.
Hydrogen gas is generated in a vessel from sulphuric acid and zinc. The
gas is collected and passed through a water bottle to a burner, where it is
mixed with air that has been forced into the burner by a pump or bellows,
the mixture being ignited for the welding.
The use of this burner requires some skill and practice, especially in join-
ing the edges of sheet lead, as it is very apt to burn away. All plate ter-
minals, and all lead connections of any kind, must be scraped clean before
connecting up.
Acid.
Sulphuric acid made from pyrites is not suitable for storage battery use ;
only that made from sulphur should be used. Ordinary sulphuric acid con-
tains many impurities that are apt to be injurious to the plates, notably,
copper, iron, arsenic, nitric and hydrochloric acids.
The acid should only be diluted with pure distilled water, and the acid
should always he poured into the water, and never vice versa. Mix carefully,
as much heat is generated.
Tests for Impurities.
Conner and Arsenic. —To a fresh solution of hydrogen sulphide,
H S add an equal quantity of the diluted electrolyte, which must be diluted
far enough so that no white precipitate is thrown down A black precipi-
tate generally shows presence of copper, although it may be lead, if the acid
has already been used in batteries ; a yellow precipitate shows presence of
"iron -To a small quantity of the diluted electrolyte add a few drops of
nitric acid, HNO„ and heat; when cold add a few drops of solution of potas-
sium -sulphocyanide, KCNS; the presence of iron will be shown by a deep
red color. . „„,„„> no fril
Citric Acid. -Make up a solution or diphenylarmne. * R_ (C, ;H3), as , to£
lows : h gm. NH(CRH02, 100 cc. strong sulphuric acid. H2S04, 20 cc. ot water
H,0; to a small quantity of this solution, in a test tube, add a small quantity
of the diluted electrolyte, which must not have been in use; the pie»ence
of nitric acid will be indicated by the appearance of a blue color.
Hydrochloric Acid. — To a small quantity of the proposed diluted
electrolyte add two or three drops of nitric acid, HNO„ heat this in a test
tube then let it cool; now add two or three drops of nitrate of silver, AgNOv
The presence of hydrochloric acid will be indicated by precipitated or
cloudy appearance.
558
STORAGE BATTERIES.
JFirst Charge.
Charging current should always be ready for application when the electro-
lyte is put in the cells, as it injures plates to stand in the acid without being
charged.
The first charge should be carried on for a much longer period than any
of the subsequent or working charges, as it virtually completes the forma-
tion of the plates.
See that the positive pole of the charging dynamo is connected to the posi-
tive pole of the battery.
The voltage of charging commences at about 2 volts per cell, and rises to
2.6 volts at the full charge while taking current at the normal rate shown
on the maker's lists.
The curves in Fig. 3 show the voltage of a cell during charge and discharge
at the normal rate.
Continue the first charge for at least 10 consecutive hours, and 20 or 30
would be preferable. The first charge is usually about twice the capacity of
a battery, and should be made at the normal rate.
This cut shows the general forms of the charge and discharge curves at
any rate; but in commercial use cells are almost always worked at much
higher rate than shown in the cut, and give lower efficiencies. For exam-
ple, a five-hour rate of discharge is quite usual, and in some cases even
higher rates. Some of the larger users of the Electric Storage Battery
Company's cells usually overcharge 15 per cent. So the ampere efficiency is
85 per cent, and the watt efficiency about 72 per cent.
The specific gravity of the electrolyte will drop during the first few hours
of the first charge, but will rise again, as the process continues, until its
maximum point is reached at full charge. If the s. g. be 1.000 at the start
it will decrease to about J .180, and rise again to about 1.210 at full charge.
As the charge nears completion, bubbles of gas will rise from both plates,
and the charging current should then be reduced, as the active material is
becoming fully formed, and cannot take up all the gas set free from the de-
composition of the acid. As the amount of gas li Iterated is in proportion to
the current flowing gasing will decrease as the current is decreased.
It is especially important with the pasted plates that charging be com-
menced immediately after the electrolyte is put in, as the plates are apt to
sulphate otherwise, sulphating being the formation of a coating of sulphate
of lead between the grid and the active material, which practically insulates
the two from each other, and is very difficult to reduce. Sulphating will also
occur with pasted plates if discharged too low. The plante form of plate is
not so susceptible to injury from sulphating.
INSTALLATION AND CARE.
559
It will take 20 or 30 discharges to fit a new battery to give its full ca-
pacity, and it is well to charge for 25 per cent longer time at normal rate
for the first few months. In ordinary work the battery will retain its nor-
mal condition with a charge of 10 per cent in excess of the discharge.
General Charging-.
During ordinary charging of the battery keep in view the following
points : —
Charge at normal rate, or lower, except in emergency.
Under normal charging conditions 2.5 volts may be considered full charge,
although it can be charged higher than this on an over-charge.
The specific gravity of the electrolyte is a good indication of the condition
of the cell; but care must be taken that it is of uniform density throughout,
as during charging the electrolyte at the bottom of the cell will become
denser unless agitated, as the sulphuric acid liberated from the active mate-
rial falls to the bottom.
The water in the electrolyte will evaporate, exposing the top of the plates,
unless replaced, Avhich should be done through a hose or tube reaching to the
bottom of the cell, as water added- otherwise will stay on top, being lighter
than the acid.
The specific gravity of its electrolyte is the best possible guide to the con-
dition of a cell, as it may appear fully charged by gasing and by the voltage,
and yet its condition be such as to cause these appearances when only partly
charged. As the hydrometer measures the density of the liquid in the
upper part of the cell only, care must be taken that the electrolyte be
stirred up so that the density will be the same throughout the cell, or nearly
AMPERE HOURS
AMPERE HOURS
: '".""".".; ' a::.
A /
y ^
A '
Z /
/- Vi
A- -V
2- A~
/- z ±
2 X
/
4 ± ■
y \
/
A X-
A X-
J
f * ?
/ .■"
/ yS*
n - J-*.*—- - .
0 ■* ii O CO <0 rf.
oiocoto^- «gm co^caococo
SPECIFIC GRAVITY
Fig. 4. Curve of Specific Gravity at Charge and Discharge.
so : of course the difference will be greater in the deeper cells. As the den-
sity of the electrolyte is due to the sulphuric acid in it, and the sulphuric
acid is liberated from the active material in proportion to the charge given,
the s. g is always a true indication of the condition of the cell as to its
charge.
Although not always the most economical, the highest efficiency and
longest life are obtained when the battery is charged slowly, never exceeding
the normal rate. Conditions of plant operation will determine the most
economical method for each installation.
560
STORAGE BATTERIES.
Each cell should be tested with a voltmeter and hydrometer once a week.
Any cell found with voltage low should he examined thoroughly for any
foreign substance that may have short-circuited it. This Avill be indicated
by low specific gravity and lack of gas given off, and voltage rising slowly
at the end of a charge, when it should rise quickly.
Always reduce charging current near the end of charging, so as not to
waste energy by escape of gas.
4000 «=T
^
4i!
;::
:
■
,.
..
-
R--
a.
--T-
: ■ :
O 3000 \\
■
>-~
dr.:
.™i
:::
<2000 ;;
0 .-
>-■-■:
..,_
-
":■
1
^
zz
"-■:
AMPERES
1000 1200 1400 1600
AMI
CAPACITY CURVE
Fig. 5. Curve of Variation of Capacity.
When discharging at normal rates, never discharge a battery below 1.8
volt. In discharging at high rates 1.8 volt will be reached before the bat-
tery is discharged to the same condition as at normal discharge owing to
the internal resistance, producing a greater fall of potential in accordance
with the IR law.
Capacity at Different Kates of IMscharg-e.
The output capacity of a battery will decrease as the rate of discharge
increases; but the efficiency will not, as commonly supposed, decrease in
the same degree, as the decrease in capacity is due to the fact that at
high discharge rates the point is soon reached where the cell is unable to
maintain the rate of discharge. But when apparently completely exhausted
at a high rate, a cell will still furnish current at a lower rate, and on re-
charging it will be found that only the amount taken out, plus the usual
excess, is necessary to recover the full capacity. The internal losses, how-
ever, are greater at high rates, which reduces the efficiency to some extent.
If cells are given short periods of time to recuperate, during excessive dis-
charge, they will give practically the same capacity as at normal discharge.
The General Electric Company is now making a recording wattmeter, es-
pecially adapted for storage batteries, that will show at all times the amount
of energy in the battery, as its reading will decrease with discharge and in-
crease as a charge is put in.
Never allow a battery to stand without charge ; even half charge is better
than none, and full charge is much the best.
SOME OF THE ADVAMTACJES OF STOWAGE
BATTERIES.
For Central Station.
The chief points of advantage are :
(1.) Reduction in coal consumption and general operating expenses, due to
the generating machinery being run at point of greatest economy while in
service, and being shut down entirely during hours of light load, the bat-
tery supplying the whole of the current.
(2.) The possibility of obtaining good regulation in pressure during fluc-
tuations in load, especially when the day load consists largely of elevators,
and similar disturbing elements.
(3.) To meet sudden demands which arise unexpectedly, as in the case of
UNPACKING, SETTING UP, AND USING. 561
darkness caused by storm or thunder showers ; also in case of emergency
due to accident or stoppage of generating plant.
(4.) Smaller generating plant required where the battery takes the peak of
the load, which usually only lasts for a few hours, and yet where no battery
is used, necessitates sufficient generators, etc., being installed to provide for
the maximum output Avhich, in many cases, is about double the normal
output.
All the above advantages apply quite as well to batteries in the power-
house of street railways, and for maintaining the voltage at or near the end
of a branch they are of inestimable benefit.
They can be so installed as to take care of both railway and lighting load,
as is done at Easton, Pa.
For Uarg-e Office XKuilding-s.
Many of the same advantages mentioned in the above paragraphs apply
quite as well to large isolated plants ; some of those in the modern office-
building being much more extensive than a large proportion of the central
stations throughout the country.
In many such plants the night operatives can be dispensed with, as the
battery will take all the lighting load.
The load-peak on most office buildings is pretty heavy between four and
six o'clock in the winter afternoons, and will run up very rapidly if a
shower comes up in summer, sometimes getting ahead of extra engines. The
storage battery can always take the load until new generators can be started.
Running the dynamos at a more even load is also more economical.
for Sniall Isolated Plants.
For country residences and the like,Avhere buildings are far from any cen-
tral supply, a dynamo or two run by a gas or oil engine, with batteries used
for storing the output, enables one to have all the advantages of the current,
and with compai-atively little care, as the plant need be run but once or
twice per week in order to keep the battery stored. This is of especial ad-
vantage when there is a small water-power.
Telephone and Telegraph.
Many storage cells are now in use in telegraph and telephone work, where
they have replaced many hundreds, if not thousands, of gravity cells.
miscellaneous Uses.
For the horseless or motor carriage storage batteries are well adapted,
and are in considerable use.
Train-lighting is done to a small extent by storage batteries.
Launches for lakes and rivers are now often propelled by storage bat-
teries.
Street-cars are occasionally equipped with storage batteries, and in some
localities have had a precarious success.
:orSTIMTCTI©]¥!S FOR UUfPACKIIG, §ETTI]¥CJ UP,
ATITD I7SIMG- STORAGE KATTEK IE*.
(By the Electric Storage Battery Company.)
1. The elements are packed in the following way : one set of each positive
and negative plates, i.e., a complete element, are packed together in posi-
tion with sheets of paper and pieces of wood between the plates. A piece
of string is tied around same to keep it compact and tight (see illustration,
Fig. 6). Take the elements out of the packing cases carefully, and see
that they are free from all dirt and foreign material. Place each element
on a piece of wood, as shown in Fig. 7; cut the string and take out
the paper and wood. Space the plates so that the separating rings can be
placed in position on the positive plates, two to each positive plate. Be sure
562
STORAGE BATTERIES.
that the containing jar is clean before placing the element in it. In setting
up the larger elements it is advisable to tie a piece of string around the ele-
ment after all the rubber separating rings are in position to prevent the
plates and rings shifting while being placed in the contain ing-jar. The
string must, of course, be removed as soon as the element is in the contain-
ing-] ar.
2. Place cells in position on battery stands.
3. Scrape the lead lugs before connecting up, so that both surfaces pre-
sent a bright metallic appearance.
4. See that all bolt connectors are well screwed up, otherwise resistance
and consequent heating Avill result. Always be sure that the cells are con-
nected up in series ; i.e., positive of one cell to negative of the next.
Figs. 6 and 7.
one or more negative plate than positive in every cell.
The negative (pole) plates are of a grayish color, and the positives are gen-
erally light brown when new. The free pole at one end of the series will, in
consequence of this, be a positive, that of the other end being a negative.
5. When all the cells are connected up in this manner, the electrolyte may
be added, provided the charging current is available. The electrolyte mm t
never be allowed to stand for more than two (2) hours in new cells before
the charging is started.
To make .Acid.
6. " Oil of Vitriol "is of much higher specific gravity than that required
for the cells, and must never be used unless diluted. It must be free from
impurities, such as arsenic, nitric or hydrochloric acid, and must be diluted
with pure water to a specific gravity of twelve hundred (1,200), or 25° Baume,
as shown by the hydrometer at a temperature of 60° Fahrenheit. In mix-
ing the electrolyte, the acid must always be poured into the water, and never
the water into the acid.
7. Always see that the electrolyte is cold before pouring into the cells.
It is advisable to mix it at least twelve (12) hours before using.
8. The initial charge must be commenced immediately the cells are filled
at about one-third Q) of the normal rating for four (4) hours, then increased
to the normal current, at which it should be continued for twenty (20) con-
secutive hours, if not longer, until the positive plates are of a dark brown
color, and the voltage of the cells are 2.6 volts per cell while charging at
the normal rate. If possible do not stop charging at the above period, but
continue at a lower rate, gradually reducing the charging current until one-
fourth (I) of the normal rate is reached, at which rate it should be continued
until the cells reach a voltage of 2.6 volts per cell.
9. In subsequent charges and in general use, it is only necessary to charge
until the voltage is 2.5 per cell while charging. It is advisable to charge
the cells once a week until the voltage per cell is 2.5 volts on about one-
third (i) the normal charging rate.
10. The cells maybe discharged down to 1.8 volt per cell, on closed cir-
cuit at normal rate ; but their efficiency and life will be improved if the
discharge is not regularly carried to thi's point, but is stopped before the
UNPACKING, SETTING UP, AND USING. 563
cells become so nearly emptied. The cells must never be allowed to stand
idle if more than seventy-five (75) per cent of their capacity has been used.
11. If a battery is to remain idle for a long time, it should first he fully
charged and then given a recharge, enough to bring it to a boil, at least once
a week. If, for any reason, this weekly charge is impossible, the battery
should be thoroughly charged ; then syphon the electrolyte from each cell,
heing sure to refill each cell with water immediately thereafter. Then start
discharging the battery at its normal rate, which will only last a few hours ;
then decrease the resistance in the battery circuit until it is almost short-
circuited. The battery should be in the water about thirty-six (36) hours,
the acidulated water being then drawn off.
12. To put the cells in commission again, replace the electrolyte, and pro-
ceed as per instructions for first charge. '
13. The specific gravity of the electrolyte should be twelve hundred (1,200),
'or 25° Baume, when the'cells are fully charged.
14. Always see that the plates are well covered with electrolyte.
15. The cells should be individually tested at regular intervals with a low-
reading voltmeter and a hydrometer. It is very essential that the voltage
of each cell should be recorded at the end of every charge and discbarge. If
any cell reads low, give it immediate attention, as otherwise serious results
may ensue.
Partial list of Manufacturers of Storag-e Batteries.
United States.
Electric Storage Battery Company, Philadelphia, Pa.
Electro-chemical Storage Battery Company, New York, N. Y .
American Battery Company, Chicago, 111.
Willard Electric and Battery Company, Cleveland, O.
Gould Storage Battery Company, Depew, N. Y.
England.
The Electrical Power Storage Company.
Chloride Electrical Storage Syndicate.
D. P. Accumulator Company.
Crompton & Howell.
Epstein Company.
France.
Societe Anonyme pour le Travail Electrique des Meteaux.
Germany.
The Tudor Company.
Battery for Private Residence.
The battery should have a capacity to supply one-half the lamps wired for
eight or ten hours on one charge. The average use is much less, and the
battery will supply ordinary calls for two or three days on a charge.
The 'capacity of the engine and dynamo should be equal to that ol the bat-
tery at the eight-hour discharge rate, so that on special occasions, when all
the lamps are needed, both dvnamo and battery can supply current together.
The best method of installation Avill be dictated by local conditions, but,
up to 200 lamps capacity, a shunt-wound dynamo that will give 150 volts
pressure is probably the best.
The best method of regulating a plant of this small capacity is by counter
E.M.F. cells, placed in series between the battery and lamps, being all in
when the battery is fully charged, and cut out one at a time as the pressure
falls.
Counter E.M.E. cells are simply unformed lead plates, mounted in the
same manner as are the regular plates, and placed in opposition to the regu-
aThe use'of counter E.M.F. cells enables one to charge the battery at the
same time that lights are being supplied from it, as the counter E.M.* . cells
will absorb the extra pressure necessary for charging.
564
STORAGE BATTERIES.
"Where it is desired to charge the hattery at the same time that lamps are
operated, 18 counter E.M.E. cells are necessary; hut where the hattery can
he charged when lights are not in use, as is easily done in the ordinary
house, hut 7 counter E.M.F. cells are necessary.
The cuts following show two methods of controlling the pressure, the first
diagram being with the use of counter E.M.F. cells as described above, while
VOLTMETER
<1 T
6 6
DYNAMO RHEOSTAT
Jl!L.
A
oL-96Q \
0---0 l-^I O P ° O?"
* B
-°l£%o£>' ° °
L*sC
— o 9 p^p— -p
-oLiv6o o o o
L*6D
-- Q-? p 9 o- — e
fW
o ■; o>J
54^i!
DIAGRAM of CONNECTIONS
FOR THE
PEQUOT LIBRARY,
SOUTHPORT, CONN.
THE E.S.B.Co. PHILA, PA.
Fig. 8.
BATTERY FOR PRIVATE RESIDENCE.
565
tlie second is done by cutting in and out the end cells. Both diagrams show
the proper arrangement of all controlling and indicating appliances for a
switchboard.
D CELLS BATTERY
The method of regulating by cutting in and out end cells is used only in
plants large enough to afford an attendant, as the end cells are charged and
discharged to different degrees, and need attention to keep in normal con-
dition.
Useful appliances for isolated batteries are underload switches, for auto-
matically cutting out the battery when it has discharged as low as is safe,
and overload switches for preventing discharge at greater than a safe rate,
say in case of a short-circuit on the line. Both devices open the main bat-
tery circuit and prevent trouble.
506
STORAGE BATTERIES.
Storage Battery in I^arge Isolated Plants.
A large isolated plant, such as is now used in large office buildings, is prac-
tically a central station with a prescribed territory; and the battery is, in
this case, an auxiliary, and used for furnishing the peak of the load, and in
some cases all the load, during such periods of the run as it is within the
capacity of the battery.
Experienced judgment is necessary in properly proportioning a storage
battery to any plant; and it is necessary to know a number of points regard-
ing its particular features, such as the following ; viz.: —
1. Nature of load and duration.
2. Maximum, minimum, and average loads.
3. Size and type of generating units.
21000
20000
!-
._.
■ -"/■ \ 1
19000
13000
17000
16000
rn ;i i
—
14000
13000
-
-A
-
f
"S
12000
; ■;
/
t
—A
1 0000
9000
8000
7000
t
■
1
I
p
h
■
\7
'"7
/
' -1 '-
5000
4000
3000
2000
1000
-
0
1
/ ..
-■
-.
:
_■■:■
0
...
'■
■
i
WEEK DAY LOAD
Fig. io.
Where it is possible to do so, a load diagram constructed from actual
records of output is in all ways the best, as it will include the information
necessary, excepting data as to generators and voltage.
Even in new plants it is nearly always possible for the designing engineer
to construct a load diagram that will serve well for proportioning the battery.
6000
:::
1 ■
-1 — 1
5000
-
—
^"T
!
-b_:
4000
-'■
| ■■
■ 1
■ 1
it :
3000
-{-
r~
|
—
^
.
1000
-f
—
8
^
-'|_!l_
"
4
-rr
'■■'■
0
: :
"
' \-
' ■ '
1" ■
i
i i
1 1<
5
6
1
0
SUNDAY LOAD
Fig. 11.
STORAGE BATTERY IX ISOLATED PLANTS.
•567
Advantages of a, Battery in an Isolated Plant.
1. Generator capacity for the average load is all that is necessary, the bat-
tery taking the peak ; and if the low load is within the capacity of the bat-
tery, the generating plant may be run at economical loads only, and shut
down entirely during the time of low load, providing the battery is then
fully charged, thus saving fuel.
2. Lamps may be run on the same lines with elevators or other variable
load, the battery providing instantaneous regulation.
3. Greater reliability of plant, and provision for quick supply in case of
storms and other sudden calls.
4. Possibility of reduction in pay-roll due to use of battery instead of
steam plant and generators.
"jr
BUS BARS
«
PROPOSED ARRANGEMENT
FOR BELTED BOOSTER,
WITH END CELL REGULATION
THE ELECTRIC STORAGE B
Battery Cliarg-e and Control.
In the large isolated plant and in the central lighting station there are a
number of methods in common use for operating the battery and controlling
its output and pressure.
568
STORAGE BATTERIES.
In such plants the dynamos are seldom designed with large enough range
in voltage to permit of charging the battery direct to its full pressure, and
recourse is then had to the " booster ; " a belt or motor driven dynamo,
with its armature in the battery-charging circuit, and its fields being excited
from the bus bars, which may be used to supply the excess pressure neces-
sary to produce the proper rise of voltage in the line to overcome the
counter E.M.F. of the batteries.
The booster must have a capacity for the full charging current, and a
range of pressure from ten to fifty volts.
Following are a number of diagrams of arrangements of batteries in
actual use, the diagrams showing relative location of all appliances for
switchboards and battery. These diagrams are furnished by the courtesy
of the Electric Storage Battery Company of Philadelphia, Pa.
Belted Booster; End Cell Regulation.
The preceding diagram, Fig. 12, is one of the simplest forms for a plant
with no special complications, and explains itself.
Belted Booster; Regulation Itj Counter J2.]fl.l?. Cells.
The following diagram shows the relative location and arrangement of all
controlling and indicating appliances for a battery using a belted booster,
and the regulation being accomplished by counter E. M. F. cells as pre-
viously described.
Fig. 13. Diagram of Connections for Plant consisting of Storage Battery,
C.E.M.F. Cells, Compound Wound Dynamo and Belt-driven Booster.
TheE. S. B. Co.
BELTED BOOSTER.
569
switch board panel for motor driven booster
with end cell regulation,
for storage battery in large public building
note:-
on fifteen point voltmeter switch points numbered 58, 59, 60, etc. connect with
CORRESPONDINGLY NUMBERED POINTS OF END CELL SWITCH. ON END CELL SWITCH POINT8
NUMBERED 57, 58, 59, ETC. CONNECT WITH CORRESPONDINGLY NUMBERED POINTS OF END CELLS.
Fig. 14.
570
STORAGE BATTERIES.
Motor- BE riven Booster; End Cell Regulation.
Tlie preceding diagram (Fig. 14) gives the layout of the switchboard and
all connections for a storage battery in a large public building.
DIAGRAM OF CONNECTIONS
FOR BATTERY BOOSTER AND BOOSTER DYNAMO IN
CONNECTION WITH C. E. M. F. CELLS AS AN AUXILIARY TO AN
EXISTING SWITCHBOARD FOR COMPOUND WOUND DYNAMOS.
FIG. 15.
MOTOB-DBIVEN BOOSTER.
571
Motor-driven Booster; Counter B.M.F. Cell Regulation.
The Dreceding diagram shows connections and relative location of appli-
ances for the slitchloard for connection to an existing switchboard ; coun-
terE m" F cells being used for regulation, with a motor-driven booster for
^NoSg-On Fifteen Point Voltmeter Switch Point s ^^^Mi^'
etc connect with correspondingly numbered Points of End Cell Switch.
On End Cell Switch Points numbered 57, 58, 59, etc., connect with corre-
spondingly numbered Points of End Cells.
Yacht Plant.
Yachts cannot carry any surplus weight of machinery ; and in order to
chlr|fthe Stery^t7s often cut in tWo and the twohalves charged in par-
DIAGRAM OF CONNECTIONS OF SWITCHBOARD,
FOR PLANT CONSISTING OF STORAGE BATTERIES
WITH C.E.M.F. CELLS, AND SHUNT OR
COMPOUND GENERATOR. BATTERY IN TWO PARTS,
CHARGED AND DISCHARED IN PARALLEL.
note: on c. e. m. f. cell SWITCH POINTS NUMBERED 1, 2, 3, 4,
ETC. CONNECT CORRESPONDENT NUMBERED POINTS OF C. E. M. F. CELLS.
Fig. 16.
572
STORAGE BATTERIES.
allel from the regular lighting dynamos, counter E. M. F. cells being inserted
to take up the extra voltage of the dynamo, and to be used for regulation
when in use on the bus bars. For discharge the cells are again all connected
in series, and run as usual.
Note. — On C.E.M.F. Cell Switch Points numbered 1, 2, 3, 4, etc., Gonnect
with correspondingly numbered points of C.E.M.F. Cells.
.AMMETER ' AMMETER i "VOLTMETER AMMETER | j AMMETER |
H^SFJ/
-^>'f", "^
a53e D|8CH"AR6E I CHARGE DISOHARS
™3
BBEQ9TM DYNAMO
Fig. 17. Diagram of Connections of Storage Battery Switchboard Panel for
Yacht " Niagara." The E.S.B. Co., Phila.
Plant for Ifaclit Niag-ara.
Preceding is the diagram for the connections of battery and switchboard
for the above-named yacht. This battery is also charged in parallel and dis-
charged in series, as was the last ; but rheostats are here used for equalizing
the charging current to the different legs of the battery.
FLUCTUATING POWER LOAD AID LIGHTS OUT
THE SAME Ol'IAMO CIRCUIT.
ky
GENERATOR
CONSTANT
CURRENT BOOSTER,
ADJUSTED FOR AVERAGE
LOAD ON MOTORS AND
ELEVATORS.. SHUNT BOOSTER
WITH BEVERSED SERIES WINDING '
Fig. 18. Arrangement of Storage Battery and Booster for Circuits having
a Widely Varying Power Load in Connection with Lighting.
FLUCTUATING POWER LOAD.
573
"When electric elevators or other appliances taking current intermittently
are connected to circuits furnishing current for incandescent lamps, there
BATTERY END CELLS
STARTING ao.x
CONNECTIONS FOR
BATTERY, DYNAMO AND BOOSTER
FOR FLUCTUATING LOAD.
E-S.BX0.
Fig. 19.
574
STORAGE BATTERIES.
will be a very considerable fluctuation in the ligbt unless means are fur-
nished for preventing it. This does not permit of using one dynamo for
both services unless a storage battery be connected as a regulator.
The diagram on p. 572 (Fig. 18) shows the scheme of such a connection of
battery; and the more complete diagram following that gives the actual con-
nections and diagram of panel board for an existing plant now being worked
in this manner.
J
3
/ 3'
0 STORAGE BATTERY
1 (
pi
TROLLEY WIRE
_^/°
Hiiiiniiim
STORAGE BATTERY
O £=
>
r*
500 VOLTS
o
J
I W M
RAIL RETURN
Fig. 20. Arrangement of Battery for Street Railway Circuits where Refine-
ment of Regulation is not necessary.
r
[VOLTMETER]
!\ >
ST
T
CIRCUIT BREAKER
STORAGE BATTERY REGULATION
AT DISTANT POINT ON LINE.
E.S.B. Co.
STORAGE BATTERY FOR STREET RAILWAYS.
SlORAfiE BATIERl AS AUXIIIARI FOR
POWER PIMX FOB STREET RAILWAYS.
Owing to great fluctuations of load on the power-plant of street railways,
a storage battery of the proper size and properly connected can be made
to assist greatly in the economy of the station.
It will maintain a much evener pressure on the circuits.
Will take on all overload ; and at the low demand between one and six
o'clock a.m. will take all the load on all but special occasions, thus relieving
the steam plant and attendant labor.
On such occasions, as it may be necessary to shut down the power-plant for
a short time, the battery Avill take the entire load for a short period.
Battery used for Simple Reg-ulation.
The two preceding diagrams illustrate the simplest form of application of
a storage battery to street railway circuits. The first is when the battery is
placed in the power-house, and in connection with a compound-wound gen-
erator ; the two cells shown in shunt to the series winding are needed to
prevent the main battery reacting on the generator.
The second diagram shows the use of a battery at some distant point
on the line where it acts as a regulator of pressure, and at the same time a
regulator of load on the engine.
Close Reg-ulation, with Battery and Booster.
The following diagram is a sketch of an arrangment of a storage battery
in connection with a differentially wound booster that will maintain a very
close pressure on the lines at all times.
With this arrangement, when a heavy load comes on the circuit the cur-
rent through the series field of the booster increases the pressure from the
battery to the line, thus compelling the battery to assist. As the load de-
creases the series field is overbalanced by the shunt field, and the generator
then feeds directly into the battery.
GENERATOR
IUNT
FIELD
SHUNT FIELD IS
CONNECTED IN OPPOSITION TO
SERIES FIELD, IN BOOSTER .
Fig. 22. Differential Booster for Maintaining Constant Voltage on Rail-
way Circuits.
Battery for Reg-ulation of Pressure at tRe End of a
Long1 Railway Feeder.
The following diagram illustrates the use of a storage battery in main-
taining a constant pressure at the end of a long railway line, as is done on
one of the Philadelphia lines at Chestnut Hill. In this case the booster is
located in the main power-house and charges the battery, which is located a
number of miles away, through a special feeder at such times as the load is
light and power is available at the power-house.
576
STORAGE BATTERIES.
BATTERY STATION
Fig. 23. Diagram Showing Application of Storage Battery to Electric
Traction, Battery Located at a Distant Substation and Acting as a Load
Regulator.
Generator and Battery can feed the system either separately or in com-
bination through main feeder No. 1, a special feeder No. 2 with Booster
being used as an adjunct to main feeder, or for independent charging of
Battery. The E. S. B. Co., Philadelphia, Pa.
STORAGE BATTERY FOR CEXTRAI-STATIOUT USE.
All the advantages recited in the preceding paragraphs relating to the use
of batteries in small and large isolated plants, and in street railway power,
apply equally well to. their use in central lighting stations ; and with some
refinements not necessary in railway work, they have been found to make
for increased economy of working in every case where they have been in-
telligently applied.
The Edison Illuminating Companies were the first to develop their use on
this side the Atlantic ; and the growth of such use has been steady, and the
capacity of batteries has increased to a very great extent since the first
Tudor battery was installed in the station of the Boston Edison Company.
Different methods of Application of Battery to Central
Station Practice.
Fig. 24. Circuits of Storage Batteries in Connection with Three-Wire
System, Philadelphia Edison Station.
STORAGE BATTERY FOR CENTRAL STATION.
577
The three diagrams, Figs. 24, 25, 26, illustrate the straight application of a
storage battery to use in a central lighting station for all the regular uses
of regulation of pressure and load, etc.
The first is the sketch of connections of the plant used in the station of
the Philadelphia Edison Company ; the second, that of the plant for the
San Francisco Edison station ; the third, that of the recently installed plant
of the Chicago Edison Company, the largest by far yet constructed.
m
Fig. 25. Storage Batteries in Connection with Three-Wire System as used
at San Francisco Gas and Electric Co., San Francisco, Cal. The E. S. B.
Co., Phila.
J
+ Auxiliary Bus
1 -1- Charging Bus
hrt
~:
rtit
— Charging Bus
m
Switches C^A. CJ^A <1
1 "jAmmJeters |
Fig. 26. Diagram of Connections of Storage Battery for Chicago Edison Co.
E. S. B. Co.
The two diagrams, Figs. 27 and 28, show the circuits and connections of
batteries in the two large substations of the New York Edison Company ;
the first is the station at Bowling Green, and the second at 12th Street.
The second of these substations is right in the heart of the city, and feeds
in all directions into the heart of the network of conductors.
The first-mentioned station, that at Bowling Green, is in the lower part of
the city, and feeds a large district occupied by the large office buildings, and
keeps up pressure at what was practically the lower end of the network.
578
STORAGE BATTERIES.
Fig. 27. Battery, Booster, and Feeder Connections, Bowling Green Storage
Battery Station.
Fig. 28. Battery, Booster, and Line Connections of the 12th Street Station
of the New York Edison Company.
STORAGE BATTERY FOR CENTRAL STATION.
579
The diagram, Fig. 20, illustrates the method of connecting a storage bat-
tery to a three-wire system with the dynamos of full pressure and connected
directly across the outside conductors. This method has been in use abroad
by the Siemens-Halske Company to some extent, and will make a satisfac-
tory three-wire system from one dynamo or more.
] .£^1 J©-, i
BOOSTER > ^
„ oQo-^sll-Or. =
Fig. 29. Diagram of Connections Showing Application of Storage Battery
to Three Wire System with Generators across Outside Wires Only. The
E. S. B. Co., Phila., Pa.
The diagram, Fig. 30, shows one of the newer applications of the storage
battery for use in connection with long-distance transmission, and it is quite
similar to the preceding application with the exception that in this case a
rotary converter is used in place of the regular generator.
The diagrams, Figs. 31, 32, of the Hartford Electric Lighting Company's
plant, show a very clever method of using a rotary converter and storage
battery on a three-wire direct current system.
Fig. 30. Diagram of Connections for the General Electric Co.'s Exhibit,
Omaha, Nebraska, Showing Applications of Storage Battery to Three
Wire System with Generator across Outside Wires Only. The E. S. B.
Co., Phila.
The terminals of the direct current side of the rotary are connected to the
outside wires of the three-wire circuits, and the neutral is carried back of
the rotary, and connected to the middle of the secondary on each of the
two or three static transformers. This method works well whether the
battery is connected or not.
TESTES^ STORAGE BATTERIES.
Condensed and rearranged from Article by Carl Hering in
"Electrical World."
An intelligent test of storage batteries requires a considerable knowledge
of such batteries, in addition to the mere capacity to make the proper con-
nections and to read the instruments accurately. The conditions of the test
are also highly important, and must be well understood if the results are to
be reliable.
Storage battery tests may in general be separated into two classes; viz. : —
580
STORAGE BATTERIES.
FARMINGION RIVER POWER STATION
600 K.W. TWO PHASE
500-VOLT ALTERNATORS
A. AMMETER
V. VOLTMETER
C..B, AUTOMATIC CIRCUIT BREAKER
8, .SWITCHES,
Figs. 31 and 32. Connections of Machines and Circuits of Hartford Electric
Light Company, showing Special Connection of the Storage Batteiy to
Rotary Converters.
a. To determine for a purchaser if the hattery fulfills the specifications
under which it was furnished.
TESTING STORAGE BATTERIES. 581
b. To determine for a maker or prospective investor all the qualities of a
battery, including its capacity, efficiency, maximum, minimum, and normal
or best rate of working, both as to charge and discharge.
The first test should really be included in the second; or, when making it,
it will he Avell to carry out as much of the routine of the second test as can
be done without excessive cost to the client, and anyway as much as may be
necessary to determine the prescribed results.
In the second test the operator will necessarily have to determine the con-
ditions; and it is therefore highly important that he fully understand the
peculiarities of storage batteries and their behavior and working, especially
so where two batteries of different makes are to be compared.
Following are some of the points to be determined.
1. Whether the battery is for stationary or for portable purposes.
2. Weight of plates, of acid, of containing-cell, of one coupling.
3. Floor space, accessibility for inspection and repairs.
4. Size of plates.
5. Dimensions of containing-cell or box.
6. Rate of charge, — maximum, best, normal.
7. Rate of discharge, — maximum, best, normal.
8. Efficiency at all rates of charge and discharge.
9. Normal rate of charge per unit of plate surface.
10. Normal rate of charge per pound of plates, and per pound of cell total.
11. Normal rate of discharge per unit of plate surface.
12. Normal rate of discharge per pound of plates and per pound of cell
total.
13. Curve of rise of voltage at different rates of charge.
14. Curve of fall of voltage at different rates of discharge.
15. Kilowatts capacity at different rates of charging.
1(3. Kilowatts capacity at different rates of discharge.
17. Curve of load value when charging at constant potential.
18. Curve of load value when charging at constant current.
1J. Curve of specific gravity of acid by hydrometer during charge and dis-
charge.
1. The specifications of the manufacturer will essentially determine whether
the battery is for stationary or portable purposes, except in trials of new
ones, in which case the person making the test will be in position to say
from his trials for which purpose the battery may be best adapted.
Batteries for stationary purposes may, in general, be chosen regardless of
weight and dimensions, but for portable purposes size and weight must, of a
necessity, be the smallest commensurate with the service demanded.
2. A knowledge of the weight of plates, acid, containing-cell, and one
coupling is useful in comparing output per unit of weight with other makes
of battery.
3. The floor space required, and accessibility for repairs, often govern the
selection of batteries for special purposes ; and good practice would dictate
that the cell occupying the least space per unit of output, and the one that
was repaired with the least trouble, be selected.
4. The size of plates will determine the output per unit of surface.
5. Dimensions of the containing jar or box must be known, in order that
proper space may be laid out for its installation.
6. In order to adapt a battery to the purposes of its use it is highly impor-
tant that the maximum and normal rate of charge be known, as the battery
is most frequently charged during the idle time, or time of lowest output of
some operating electrical plant. It is sufficiently obvious that where a plant
is available for but a short time, a battery admitting of a high rate of char-
ging is desirable, although not always the most efficient in all ways; whereas,
if there is plenty of time, during which the charging may be done, then the
battery may be charged at a slower and more efficient rate.
7. A full knowledge of the maximum and normal rates of discharge is of
the very highest importance, as on this depends the capacity and good work-
in? of the battery.
The capacity of • all lead batteries is reduced by hastening the discharge,
and this is especially so for batteries having the active material in thick
masses, or so disposed that the acid has not free access to it. In batteries
having the active material disposed in thin layers, and freely exposed to the
action of the acid, the reduction of capacity is not so great.
582 STORAGE BATTERIES.
While it may be true that a battery maybe constructed for less cost if made
for low rates of discharge, the capacity is so much reduced when dis-
charged at high rates, that it seems better policy to construct for high rates
of discharge, in which case the battery may be equally well used for dis-
charges at low rates, but will not hold a charge quite so long as will the slow
discharge battery. Treadwell says 8 amperes per square foot of positive
plate is a good rate of discharge.
Theoretically, the capacity of a battery depends upon the amount of
active material, while the rate of discharge depends upon the amount of
surface acted upon by the acid.
In most installations where a storage battery is used, it is essential that the
battery be capable of a high rate of discharge for a short time, say an hour
or two, and it is this fact that governs the selection rather than its capacity,
although this latter condition must receive due attention after the rate of
discharge is settled.
In the United States it is now customary to designate the capacity of a ,
storage battery by a time rate ; viz., a given battery has a certain capacity,
at a full discharge in three hours, and such a capacity at a discharge in five
hours, etc., 8 to 19 inclusive. Nearly all these items are determined by cal-
culations from the readings of the instruments in use, and need no further
explanation here.
The following named readings may be taken as the routine of a test.
Charge.
Time.
Amperes input.
Volts of charging circuit.
Specific gravity of acid by hydrometer.
Temperature of room.
Temperature of acid.
Statement of gasing.
Discharge.
Time.
Amperes output.
Volts at cell terminals.
Specific gravity of acid by hydrometer.
Temperature of room.
Temperature of acid.
Statement of gasing.
General Conditions.
Insulation resistance of cell from ground.
Resistance of cell between terminals when fully charged and when
fully discharged.
If there is a storage battery recording wattmeter available it will be use-
ful in connection with the readings mentioned above.
§OVRCE§ OV CURBEflfT FOR CHARGOO.
Current from a battery of storage cells will be found by far the best for
testing a cell or cells. Where one cell is under test, four others of similar
size connected, two in multiple and two in series, will be found to give good
results.
Tf current from public circuits, or from a dynamo, is to be used, it should
be as steady as possible, of considerably higher voltage, and have a large
resistance capable of carrying indefinitely the maximum current in series
with the cell.
Before starting a test, it is necessary to decide the points at which the
battery may be considered charged and discharged, as overcharging and
undercharging and light and full discharge make much difference in the
results.
It is difficult to predetermine a rate at Avhich the battery will be fully
discharged in a certain time, and the only way is by trial rates. Even
SOURCES OF CURRENT FOR CHARGING. 583
then, no rate can be taken as reliable unless it can be repeated under
the same conditions, any variation in result showing that the battery had
not recovered from its previous discharge.
Charging too long at a high rate will injure the plates, but moderate over-
charging with a small current is beneficial to the plates, though it, of course,
reduces the efficiency.
Charging too little results in increased efficiency but less capacity.
Discharging too far increases the capacity, reduces the efficiency, and re-
sults in great variations in voltage and a tendency to increase the destructive
action on the plates.
Discharging too little increases the efficiency but reduces the capacity.
Destructive action on the plates determines the limits of charge and dis-
charge and inside the safe limits the points of stopping charge and discharge
will depend on whether high efficiency or high capacity is deemed the most
desirable under the special conditions. The proper stopping point is deter-
mined by a preliminary test for a curve of voltage, then the points may be
selected between the points of rapid change in pressure.
Slow discharge Avill take out more of the charge than a rapid discharge,
the latter condition leaving some of the charge in the battery, which may
show in the next discharge, and make the results erroneous.
If a rapid discharge be followed by a slow one, the capacity for the second
test will indicate higher than it ought, in some cases showing an efficiency ex-
ceeding 100 per cent.
If a slow discharge be followed by a rapid one, then the capacity of the
second test will indicate lower than will be the correct result.
Destructive action on the plates can only be determined by inspection,
which will show other than normal colors, sulphating, buckling, loosening
of the active material, etc. A number of discharges may be necessai'y to
determine if a certain rate is deleterious.
In stating the limiting voltages, it is most correct to state the rise or fall
of voltage in percentage of the initial pressure, taking as such initial pressure
the reading of voltage a short time after the start to charge or discharge,
and when it has become constant. The percentage is not always the same
for charge and discharge.
For the sake of uniformity, especially in comparing cells, it is best to make
all tests with continuous discharge without stop.
It is considered best to charge, with constant voltage, but is very difficult
to do, as the current varies greatly, starting in at a large amount and reducing
to a small amount at the end of the charge. The current may vary through
wide limits without much effect on the charging voltage. Varying the
charging current by steps will be found to result in more nearly constant
voltage, reducing to a lower value when the voltage indicates a ranid rise.
Take the time of charge at each rate in order to compute the capacity of
charge.
It is best to make the discharge at constant current, as that more nearly
approaches actual practice. If 'this is not practicable in the circumstances,
then the best method is to discharge through a constant resistance.
Discharge at a constant current will require the use of a rheostat that can
be changed by very small increments, such as a Avater box or carbon plate
resistance. The readings will then be the voltage at the cell terminals and
the constant amperes, and with a proper rheostat the test is very simple.
Discharge through a constant resistance, which, by the way, is seldom an
actual condition, owing to heat variations, the calculations become tedious,
as they have to be made for each reading, and a careful record kept of the
time.
A discharge at constant watts would be the most correct method for bat-
teries that were to be used for traction, but the calculations and adjust-
ments are so troublesome and difficult as to add to the liability to error.
In comparing two cells connect them in series for charge or discharge, cut-
ting out each one as its work is completed, measuring the voltage at the cell
terminals.
In a comparison of different cells it is necessary to base the comparison
on some common factor, such as the following items, the selection depend-
ing on the special conditions to be filled: —
Ampere-hours per pound.
Watt-hours per pound.
Charge and discharge rate in hours.
584 STORAGE BATTERIES.
Discharge in watt-hours per pound.
Discharge in ampere-hours per dollar of cost.
Discharge in watt-hours per dollar of cost.
Readings of instruments will he governed as to time by the circumstances
of the test and the quality of the apparatus. If the source of current or the
rate of discharge is variable, many more readings will be necessary than
if they are steady. If the instruments do not respond freely to changes
of current many readings will also be necessary on that account. If all the
conditions are favorable 15 to 25 readings will he sufficient to give a good
average.
Betore starting test, take the voltage of the cell on open circuit, as it is
some indication of the condition of the cell.
During test take occasional readings of voltage from which to calculate
the internal resistance of the cell, as follows: first take the voltage of the
cell while connected in circuit and working, then take the cell out of circuit
and take voltage on open circuit.
Connect voltmeter terminals to the lead terminals of the cell, not to the
circuit or the couplers.
Connect the amperemeter as close as possible to one terminal of the cell,
so as to include any leakage.
Leakage may he found by connecting one leg of the voltmeter to ground
and the other to one terminal of the cell and then the other. The leak, if
any, will be found nearest the terminal indicating the least deflection of the
voltmeter.
Where the circuit is merely switched from the charging source to the dis-
charging circuit, it is necessary to reverse the ammeter leads.
Calculate efficiencies for ampere-hours and watt-hours, and for mean' volts,
as follows: —
. . „ . „ Discharge in ampere-hours X 100
Ampere-hour efficiency % = -^ : :
Charge in ampere-hours
m- ,, , ,„. . ,„ Discharge in watt- hours X 100
Watt -hour efficiency % = 7^r- - : =
Charge in watt-hours
_„ . .. .. „ Mean volts of discharge x 100
Efficiency of mean volts % = ^ rr — * i_
Mean volts of charge
„. „. „. . „ Mean volt efficiency x ampere-hour efficiency
Watt-hour efficiency % = — -•
Comparing ampere-hour efficiency with mean-volt-efficiency Avill show
whether loss in watt-hours is due to polarization and internal resistance,
or to leakage and gasing or lack of retaining power of the active material.
SWITCHBOARDS.
There are two general types of modern switchboards :
(1) Those in which all the switching and indicating apparatus is mounted
directly on switchboards.
(2) Those in which the main current carrying parts are separate or at a
distance from the controlling and indicating apparatus. Both of these can
be further divided into Direct Current and Alternating Current, and there
are numerous and distinct classes under these.
Modern switchboards are made of slate or marble panels, each having a
definite function.
LAYOUT OF SWITCHBOARMS.
In laying out buildings for central stations or isolated plants, the switch-
board should be located in an accessible place, and have plenty of room
both back and in front. In many cases the switchboard can be placed
advantageously on a gallery overlooking the machinery. If due considera-
tion be given ito the location of switchboard with respect to the machines
and feeders which it controls, unnecessary complications and expense can
be avoided.
Switchboards are now standardized, covering a large range of D.C. and
A.C. generators and feeders, although, of course, it is often necessary to
meet special conditions, which, however, can be met usually by slight modi-
fications from standard.
Unnecessary complications and extra flexibility being at the expense of
simplicity, are always to be avoided. It would seem unnecessary, for in-
stance, in the great majority of cases to have more than one set of bus bars.
Plainness, combined with neatness, and symmetry, is much to be preferred,
and nothing should be placed on a switchboard which has no other function
than ornamentation.
If extensions to switchboards are expected, which is usually the case,
panels controlling generators should be together at one end of the switch-
board, and those controlling feeders at the other end. When total output
panels are used, they are placed between the generator and feeder sections.
Of course, where switches are controlled at a distance, this rule need not
be followed ; but, on the other hand, it is often advisable, in order to sim-
plify station wiring, and to save copper in the busses, to intermingle the
generator and feeder switches. Even in this case it is desirable to group
the generator controlling and indicating devices together and likewise those
for the feeders. For ordinary D.C. switchboards 4 feet is little enough
behind the panel. In any case, there ought to be a clear space between
connections on panels and wall, of 2£ to 3 feet. For large work and most
A.C. work it is very often necessary to have 6 to 8 feet behind panels.
In the high-tension work of 5000 volts and above, the General Electric
Company remove all high-tension apparatus from the face of the board ;
the switches being placed in fire-proof compartments of brick or soapstone,
and operated mechanically through bell cranks and levers by means of a
handle on the panel, or electrically by means of a controlling switch. The
instruments are connected to secondaries of current or potential transform-
ers, which are placed in some convenient place in connection with the high-
tension wiring. This, of course, necessitates more room than the ordinary
switchboards require. The main current carrying apparatus can be placed
directly behind the controlling board, below in a basement, or under a
gallery ; or above in a gallery ; or, if switches are electrically or electro-
pneumatically controlled, they can be placed in any convenient place.
In locating switches and other appliances, it is usually assumed that
dynamo leads come from below, and that feeder wires go out overhead,
except in the case of underground feeders, which naturally go out below.
COBflTBUCTIOI.
Central station switchboards are usually composed of panels about 90"
high and 1" thick, and varying in width from 167/ to 36". The panels are
585
5S(5
SWITCHBOARDS.
generally in two sections ; the top varying from 60" to 65", and the lower
from 25" to 30". The General Electric Company's Standard is 62" and 28"
respectively for top and lower part ; the Westinghouse Standard is 65" and
25". The General Electric Company also makes panels 76" high, \\" thick
for isolated plants. Each panel is beveled all around on the front edges
with a \" to \" bevel.
"Where a well finished switchboard is desired, black enameled slate is
recommended for circuits of less than 1100 volts. The main current carry-
1. Method of Joining
Adjacent Panels.
Channel Foot for Switch-
board Frame.
ing parts are mounted directly on the panel. For higher voltages it is
necessary to use marble on account of its higher insulating qualities. Plain
slate can be used where a low-priced switchboard is
desired for low voltages.
There are several different varieties of marble used
for switchboards, viz. : blue or white Vermont, pink
or gray Tennessee, and white Italian. Marble being
a natural product cannot always be matched in shade
or markings. The colored marbles do not show so
readily as white marbles the effect of oil or grease,
and therefore are more suitable for switchboards.
Of the colored varieties, the blue Vermont marble
can be obtained in the most uniform color.
Steel angle bars varying from 1\" x 1£" x \'' to 3"
x 2" x \", are ordinarily used for supporting the
panels, although in some cases for heavy work, steel
channels, tees, or "I" beams are used. The angle
bars stand on the floor, to which they are fastened by
means of a small foot iron. The panels are bolted to
the narrow web of angle bars, and adjacent angles
are bolted together through their wide webs (Fig. 1).
The panels should be set up on a level strip, which
can be of either hard wood, " I " beams, or an inverted
channel.
The frame-work of all switchboards should be in-
sulated from ground when used on circuits of 600
volts or less. In high tension A.C. systems it is neces-
sary to ground all frame-work to carry off static
discharge and in order to get rid of danger to the
Fig. 3. Showing operator should he accidentally touch the frame-
Method of Bracing work. For securing the structure in a vertical posi-
Switchboard Panel tion, rods with turn buckles for adjustment of length
to Wall. are run from the back wall to the angle frame, at
or near the top. A " Y " connection can be made to
straddle the two angles, and a bolt be put through the whole. The wall
end can be secured by expansion bolts or other means.
CONSTRUCTION.
587
Circuit breakers should, be placed, if possible, near tbe top of the panel,
so that there will be no apparatus above them. Instruments should be
placed within convenient view of attendant, and switches and rheostat
hand wheels should be located within easy reach.
It is recommended that illuminating lamps be left off of switchboards,
and that instruments be illuminated from ligbts on the front of the
switchboard.
The copper bus-bars and connections on the back of switcb boards need
careful laying out, with a view to carrying the current economically and
without overheating, and above all, in order that there will be no undue
crowding, and that they will present a neat and workmanlike appearance.
The tendency has been of late to place the busses toward the top of panels,
except in the case of small isolated plant switchboards. The switches, cir-
cuit breakers, and instruments are connected to busses by means of bare
copper strips or insulated wire, bent in the most convenient shape to suit
the case. It is not recommended, as a rule, to have long studs on the appara-
tus projecting out far enough to connect direct to busses, as the strain on the
switch, due to weight of busses, is likely to affect the adjustment of switch
contacts. Very often the connection strips are sufficient to rigidly support
the busses, but in some cases it becomes necessary to provide insulated
supports for carrying them. Copper bars, flat or round, are now practically
universal on low-potential boards. Owing to the greater ease in making
attachments and in adding capacity the flat bar is to be preferred, and a
thickness of g", \", and \" ', with width according to the current carrying
capacity required, is convenient. The size of copper bus-bars and connec-
tion strips is usually figured on the basis of 1000 amperes per square inch of
cross-section. By properly laminating the bars, it is safe to use this basis
even for very heavy current. Contact surface should be figured anywhere
from 100 to 200 amperes per square inch, according to the method of clamp-
ing, bolting, or soldering. In clamping or bolting, steel bolts should be
used.
Herrick gives the following table as embodying the current practice for
central stations, based upon a load factor not exceeding 50%. If figuring on
a 100% load factor, the following amperes must be cut in half : —
COPPER BAR DATA.
From " Modern Switchboards," by A. B. Herrick.
Dimensions.
Amps.
Cir. Mils.
Sq. Mils.
Ohms
per Foot.
Weight,
per Foot.
l xf
433
318,310
250,000
.0000336
.97
li x \"
530
397,290
312,000
.0000269
1.21
H x \"
626
477,465
375.000
.0000223
1.45
if x \"
725
556,400
437,000
.0000192
1.70
li x i"
676
596,830
468,750
.0000179
1.82
H x f"
798
716,200
562,500
.0000149
2.18
if x f"
916
835,600
656,250
.0000128
2.54
2 x t"
1035
954,930
750,000
.0000112
2.92
2i X §"
1154
1,074,300
843,750
.00000995
3.27
2 x¥/
1222
1,273.240
1,000,000
.00000840
3.89
2J X \"
% x f"
1500
1,591,550
1,250,000
.00000672
4.86
1715
1,989,440
1,562,500
.00000537
6.07
0000 B. & S.
257
211,600
.0000505
.64
\" round
305
250,000
.0000428
.76
\" round
426
390,625
.0000273
1.18
\" round
560
562,500
.0000190
1.71
\" round
861
1,000,000
.0000107
3.05
For the sake of securing the best conductivity, as far as possible, all
switchboard connections should be worked out of rolled copper ; but it is
588
SWITCHBOARDS.
occasionally necessary to use copper or brass castings, although their use
should he avoided as far as possible, as the conductivity is always low, vary-
ing from 12% to 60% according to mixture. Where necessary to use cast-
ings, they should be made of new metal only, and care should be taken to
insist upon a standard of conductivity in each piece if it is to be used where
such a condition counts. A conductivity of 50% may be considered high
and sufficient.
The following table from " Modern Switchboards," by A.B. Herrick, gives
percentages of mixtures with resulting conductivity as compared with 100%
copper : —
%
%
Conduc-
%
%
Conduc-
Copper.
tivity.
Copper.
Tin.
tivity.
98.44
1.56
46.88
98.59
1.41
62.46
94.49
5.51
33.32
93.98
6.02
19.68
88.89
11.11
25.50
90.30
9.70
12.19
86.67
13.33
30.90
89.70
10.30
10.21
82.54
17.50
29.20
88.39
11.61
12.10
75.00
25.00
22.08
87.65
12.35
10.15
73.30
36.70
22.27
85.09
14.91
8.82
67.74
32.26
25.40
16.40
83.60
12.76
100.00
27.39
100.00
11.45
All minor connections to bus-bars such as switch leads, feeder ends, or in
fact any attachments whatsoever, whether bolted to, clamped against, or
soldered, should have ample surface contact, not less than ten (10) times (and
twenty (20) times is better), the cross-section of the smaller of the two
conductors connected, and where the sub-connection is of round-section it
should be cup-soldered or " sweated " into a flat lug having the proper
amount of surface contact for bolting or clamping to the bus-bar.
Cup-soldered conductors should enter the socket from two to three
diameters. While all permanent joints of this nature should be soldered,
it is sometimes necessary
equalizer bus *° make joints that can
be easily disconnected, in
which case the old-style
socket with binding screws
may be used, but the con-
ductor should be entered
from four (4) to ten (10)
diameters to make a secure
connection.
BUS EXCITES*
DYNAMOS.
The diagram ^ig. 4) and
text on a method of ex-
citing dynamos from the
bus-bars, in starting, was
published by W. B. Potter,
in the " Electrical Engi-
neer." Besides being a
very simple method of bus-
connecting for excitation,
if the equalizing switch,
E.S., and positive switch,
P.S., are left closed all the
time, which can be done
without harm excepting
when some repairs or changes may be wanted in the dynamo, all equalizing
connections are left in circuit all the time, and any dynamo that may be
Fig. 4. Excitation of Generators.
*i
BUS EXCITED DYNAMOS.
589
Fig. 5. Connections of Generator Panels for Direct Current. 300-1800
Amp. G. E. Co.
590
SWITCHBOARDS.
t-1
Fig. 6. Switchboard Panel for One Three-phase Alternating Current Gen-
erator, to 2500 volts. G. E. Co.
wh — 1
0=3
m 1
(fl II
w~~
HI
ORMER I
tia
~r
Fig. 7. Switchboard Panel for One Single-phase Alternating Current Gen-
erator, to 2500 volts. G. E. Co.
BUS EXCITED DYNAMOS.
591
| IffjOjl
§ 5s I
Fig. 8. Diagram of connections for switchboard of main power station
Manhattan Railway Co., L. B. Stillwell, Cons. Engr.
592 SWITCHBOARDS.
running will then take its proper amount of current through its series coils
and will, therefore, compound more nearly as it was designed to do, than
if all the load is on the series coil of the running dynamo. If greater sim-
plicity is desired, the equalizing switch, E.S., and positive switch, P.S., can
be one double-pole switch, and the negative switch, N.S., a single pole.
Leave the double-pole switch closed all the time, and throw the machine
in and out with N.S.
Mr. Potter says : —
By reference to the accompanying diagram, it will be seen that by closing
the positive switch, F.S. (the equalizer switch, E.S., being closed), the series
coil of the generator to be started is connected in parallel with the series
coils of generatoi's in operation, thus separately exciting the field of the
generator to be started.
The field switch, F.S., being closed, the voltage is then adjusted by the
field resistance to correspond with that of tbe bus, and the more easily so,
as by this method there is secured a variation of voltage corresponding to
that due to changes of load on the over-compounded generators in operation.
This method also insures the polarity being at all times the same as the
other generators. On closing the negative switch, N.S., and reducing the
resistance in the shunt field, the generator takes up its load smoothly
and without the violent fluctuation usually caused by connecting the series
coils after the full potential has been developed by the shunt field only.
It is not necessary to show here all the standard forms of switchboard, or
the appliances that are used with them, as changes take place so often that
any article pictured or described is apt to be out of date in a very short
time. A few diagrams showing standard arrangements that are not subject
to much change follow. 1 have included the diagram of general arrange-
ment of switchboard connections of the great plant of the Manhattan
Elevated Railway of New York, as being very simple and of considerable
interest.
-A.MC SWITCHSOAIlI>S.
This line of switchboards represents an entirely different construction
from that of ordinary switchboards.
Extra flexibility makes it desirable, and small currents make it possible,
to use plug connections instead of the ordinary type of switches.
The function of arc switchboards is to enable the transfer of one or more
arc light circuits to and from any of a number of generators. This trans-
ferring is sometimes accomplished by means of a pair of plugs connected
with insulated flexible cable; sometimes by plugs without cables, which
bridge two contacts back of the board, or by a combination of cable plugs
and plugs without cables. The type using plugs without cables is pref-
erable, because danger is eliminated, which would otherwise be possible to
attendant, due to contact with exposed or abraded cables carrying high-
potential current.
Below is a cut of the G. E. Co. Standard Carrier bus type of Arc Board
with description.
The accompanying illustration shows an arc switchboard of the General
Electric panel type, arranged for three machines and three circuits. The
vertical rows of sockets are lettered and the horizontal numbered. The
ends of the vertical bars are connected to the machines and circuits. Each
of the bars is broken in three places, and the machine may be connected to
its circuit by plugging across these breaks, thus making the bar continuous ;
by removing any pair of plugs the machine may be disconnected.
Cll, Ell and Gil are ammeter jacks, and are used in connection with two
plugs connected with a twin cable, for placing an ammeter in. the circuit.
The six horizontal bars are for the purpose of transferring a machine or
a feeder to some circuit other than its own. Each horizontal bar is pro-
vided, at one side of the panel, with a socket (A3, A4, A5, A7, A8, and A9)
by means of which it can be connected with the horizontal bar on the
adjoining panel. All ordinary combinations can be made by means of the
bars and plugs ; but cable plugs are provided with each panel, so that when
necessary, machines and feeders can be transferred without the use of the
bar. These plugs and cables are intended for use only in case of an
emergencv.
To run machine No. 1 on feeder No. 1, insert plugs in BIO, CIO, B6, C6,
SWITCHING DEVICES.
593
B2, and C2. To shut down machine No. 2, and run feeders Nos. 1 and 2 in
series on machine No. 1, insert a plug at C5, D5, C7, and D7, and remove
plugs at C6 and DG ; this leaves two circuits and two machines in series.
Short circuit machine No. 2 by inserting the plug at E7. Cut out machine
No. 2 by removing the plug at D10 and E10. Take out plug at D7.
SWITCHOG DEVICES.
Switching devices in connection with switchboards can be divided gener-
ally into two classes, viz. :
1. Switches.
2. Automatic circuit breakers.
594
SWITCHBOARDS.
Pig. 10. Gen. Elec. Oil Break Switch, 5000 volts, 300 amcs
Opened and Closed by Hand. <*IUPS.,
CASE REMOVEI
Fig. 11. Gen. Elec. Co. Oil Break Switch Opened and Closed by Hand,
SWITCHBOARD DEVICES.
595
Switches for low voltage and small current are of the same general form,
though differing in details. In the main they consist of a blade of copper
hinged at one end between two parallel clips, the other end of blade sliding
into and out of two parallel clips. The clips are joined to copper or brass
blocks to which the circuit is connected.
There seems to be little uniformity among manufacturers regarding
the cross-section of metal and surface of contact to be used. Perhaps a
cross-section of metal of one square inch per 1000 amperes of current
capacity is as near to the common practice as any, and a contact surface of
at least one inch per 100 amperes or ten times the cross-section of metal is
also common practice, but will depend somewhat on the pressure between
surfaces.
Auxiliary breaks are demanded by the National Code for currents
exceeding 100 amperes at 300 volts, and "quick-break" switches are now
quite common for pressure as low as 110 volts, although not in any way more
necessary for that pressure than should be " quick-make" switches.
596
SWITCHBOARDS.
The rules on switch design issued by the National Code cover the require-
ments well, and they must be followed in order to obtain or retain low
insurance rates ; all switches must meet the requirements. See index for
" National Code," and refer to section on " Switches."
Blades, jaws, and contacts should be so constructed as to give an even
and uniform pressure all over the surface, and no part of the surfaces in
contact should cut, grind, or bind when the blade is moved. The workman-
ship should be such that the blade can be moved with a perfectly uniform
motion and pressure, and the clips and jaws should be retained so perfectly
in line that the blades will enter without the slightest stoppage.
For pressures above 1000 volts, practice varies among the different manu-
facturers. The General Electric Company makes a switch in which the cir-
cuit is ruptured in oil. In the type designed by the Westinghouse Co. de-
pendence is placed upon the arc being ruptured in open air by drawing
it through a wide break. The Stanlay Co. has devised a switch which is
designed to rupture the arc by means of a sliding shutter, Avhich intercepts i
the arc when the contact is broken.
For non-inductive loads of small power and up to 2500 volts, any good
form of quick-break switch can be satisfactorily used.
Attached are shown a few types of high-potential switches.
AUTOMATIC CIMCXJIT BMEAKEIl§.
Automatic breakers are devices which have as an integral part an auto-
matic trip which opens the circuit when the flow of current exceeds a pre-
AMPERES
A
B | C
D
E
-^d^oir-
-£-
~~"~C
J:i_
28 2]4
+ '«
Fig. 13. One Form of Circuit Breaker. 1800 to 10000 Amperes. G. E. Co.
determined limit. Many types are now made, some with carbon secondary
breaks ; but a very successful type is one early introduced by the G. E. Co.,
with the magnetic blow-out principle applied to extinguish the arc. Illus-
trations follow of one of the main sizes and a table for the various adjust-
ments of the same.
For mean high potential circuits the Westinghouse Electric & Mfg. Co.
has devised the instrument shown in the following cuts and diagrams (Figs.
15 and 16) : —
The circuit-breaker consists of two hardwood poles, one being longer
than the other, mounted upon a marble base, to which are secured the
terminals to which the main leads or wires are connected. The poles are
connected by a hinge, so that their extremities are in line at the upper end.
On the upper end of each pole is mounted a copper sleeve supporting a round
carbon contact block with a hole through its center. The longer pole is
provided with spring jaws or clips so that it may be quickly and easily
attached to, or detached from, the terminals on the marble base. The short
pole has a flexible wire running through its interior ; this wire is connected
to the copper sleeve at the upper end of the short pole and to the lower clip
terminal on the long pole. The sleeve at the upper end of the long pole is
AUTOMATI C CIRCUIT BREAKERS.
597
Amperes.
AVide Open.
Closed.
When See.
Contacts
Touch.
A
2
§
b'o
!
TlT
8 32
7B!T
77
D
E
r3e
F
D
150- 2000
ftof
1
i7sto£
1800- 3000
11
Stoi
1
2000- 6000
1*
|to*
1
2000-10000
I
Mi
H
1 to |
1
NOTE — B is dimension when parts are new.
First, Adjust E.
Second, Adjust Brush Tension.
Third, Adjust C.
FIG. 14. Dimensions for Adjusting Mlv Circuit Breakers.
connected to the upper clip terminal. Thus, these connections practically
make the sleeves at the upper ends of the two poles the terminals of the
apparatus.
The poles being removed from the base, a wire is inserted through the
hole in the carbon tip at the upper end of the short pole, and secured to the
High Potential Circuit Breakers, Made by Westinghouse
Electric and Manufacturing Company.
Fig. 15.
) to 15000 Volts.
Fig. 16. 20000 to 40000 Volts.
copper sleeve by a screw and washer. The other end of the fuse is p„.
through the carbon tip on the long pole, and secured to the copper sleeve by
a cam-shaped lock. The length of the fuse should be from 6 to 10 inches.
The poles, after being fused, are placed in position by taking hold of the
lower end of the long pole. When the fuse blows, the short pole is released
by the action of the spring at the lower end, and falls away from the station-
598
SWITCHBOARDS.
High Potential Circuit Breakers Made by Westinghouse
Electrical and Manufacturing Company.
SK,
'•A
^
a
^rv.
~:-
M
;«y
J PRINCIPAL DIMENSIONS,
6000-15000 VOLTS
Figs. 17 and 18.
Figs. 19 and 20.
ary pole, thus making a very long break'. The lock cam has a long string
attached to it, by means of which the fuse can be released if desired, thus
causing the short pole to drop in the same manner as when the fuse blows.
This feature permits the device to be used as a switch.
REVERiffi CUK«E1¥T CIRCUIT BREAKER§.
For large installations of electrical transmission, where it is highly im-
portant that continuity of service shall be maintained, it is good engineering
to use two separate lines of conductors. In such cases it is usual to keep
both circuits connected so that in case of trouble on one of them its fuses or
circuit breaking devices will cut it out, leaving the clear line to carry the
load. An examination of the following diagram Avill explain the utility of
the reverse current circuit breaker. Let a and ax be circuit breakers at the
dynamo end of the two lines, and b and bY reverse current circuit breakers
at the far end of the same. Should a short circuit occur as at x on the
main line, it is plain that current will rush in both directions from the
dynamo, by way of the main line and by way of the auxiliary line and the far
end of the main line, in which portion the direction of the current will
be the reverse of what it was ordinarily. Under this condition it is obvious
that all the circuit opening devices would operate, and the auxiliary line
would be of no effect in maintaining continuity of current. Now, if circuit
breakers of such a design that they will open on a reversal of the direction
.-..k
REVERSE CURRENT CIRCUIT BREAKERS.
599
b , [
7>
-Q-J
-B—
Pig. 21. Diagram Showing Use of Reverse Current Circuit Breaker.
of the current through them, be placed at the far end, as at b and bx then the
main circuit breakers, a, a, will open, as Avill also the reverse current circuit
breakers, b, b, thus leaving the auxiliary line intact. Of course a short
circuit on tbe auxiliary line will operate in a similar manner.
The following diagram shows the connections of the reverse current
circuit breaker at Buffalo as designed by the General Electric Co. An
Pig. 22. The Circuits of a Reverse
Current Circuit Breaker Set
Showing How a Direct Current
Motor is Used with Alternating
Currents to Distinguish between
Power Passing in One Direction
and Power Passing in the Other
Direction in the Line.
Fig. 23. The Circuits of a Time
Element Relay Circuit-break-
ing Set.
600 SWITCHBOARDS.
ordinary fan motor is introduced by means of a transformer into the line,
and acts to operate a relay on the shunted circuit breaker, a reversal of the
current reversing the motion (or pull) of the fan motor armature, and closes
the relay contacts as shown.
Inline El«*iii«*Mt for Circuit J$r«>ak<»rs. — Where circuits are loaded
with large synchronous or induction motors and other devices liable to
produce short circuits on the system when out of step or started too sud-
denly, it is not only necessary to protect the local or feeder circuit with
circuit breakers, but in order to prevent the operation of all the protecting
devices between the one in trouble and the dynamo itself, it is found advis-
able to introduce a time element or adjustable delay on all the main circuit
breakers. This device must allow the circuit breakers farthest from the
station to be adjusted so they will open first, and all the intermediate
devices must have variable or graduated adjustments, say for opening after
three seconds, and the main circuit breaker at the power house itself will
open last of all, say in five seconds.
Mr. L. B. Stillwell devised an instrument for this purpose, and it has been
widely adopted. Both the Westinghouse Co. and General Electric Co. have
adapted this time element device to the circuit breakers in use at Niagara
Falls, and the following cut shows the arrangement by General Electric
Co. diagramatically. The instrument is composed of a simple clock move-
ment, the wheels of which are prevented from turning by a pawl which
may be lifted out of place by either one of two relay magnets connected by
transformer in the main line. The lifting of the pawl allows the clock
wheels to revolve and close a relay circuit connected with the circuit
breakers which promptly open. The clock movement can be adjusted to
close the local circuit in any desired time ; and in case the clock is started
on a short circuit, which is off before the lapsing of the time period, the
pawl drops, and the movement returns to its original position.
LIGHTNING ARRESTERS.
IIGHTIU'U AKHESTEM« IX GEItERAI.
(From pamphlet by Westinghouse Electric & Manufacturing Company.)
Tlie Timction of liig-litiiiitg* Arresters.- — The function of a
lightning arrester is two-fold. It should provide a path to earth offering
the least possible resistance to the passage of static discharges, and it
should avoid interruption of the service. The latter, though a negative
function, is one of primary importance.
In the early days of electrical industry it was found that lightning dis-
charges from overhead wires would pass more readily to ground over a
small air gap than through coils or even long lengths of straight wire.
Numerous arresters based upon this principle were constructed and
placed in practical use. The simplest form of these is the old saw-tooth
spark-gap arrester which is still used for protecting telegraph and telephone
lines. But a great difficulty arose with gap arresters when used on electric
lighting, railway or power circuits, owing to the fact that the dynamo cur-
rent followed the lightning discharge, establishing thereby a short circuit
which would melt the dynamo fuses" and thus interrupt the service.
With the object of overcoming this trouble various arresters were der
vised that would automatically interrupt the dynamo short circuit. At
first this interruption was accomplished by simply placing fuses in the
lightning arrester circuit, thus making it necessary to renew the fuses after
each discharge. This method was obviously unsatisfactory. Arresters
were then devised which would automatically interrupt the arc and then
immediately adjust themselves for another discharge by means of moving
parts ; the latter, however, proved to be the cause of considerable annoy-
ance, and experience demonstrated that the arc rupturing arresters were
uncertain in action and hence unreliable.
Recognizing the importance of the problem the Westinghouse Electric
& Manufacturing Company undertook a series of extensive theoretical and
practical investigations, with the object of devising arresters which would
offer a low resistance path to ground for disruptive discharges, and at the
same time operate automatically and repeatedly without moving parts and
without interrupting the service.
— PI A-
,-p, n — ,
11111111
' y
LINE
iiiiiiii;
u
GROUND
Of
LINE
Fig. 1. Diagram Showing Electrical Connections for A. C. Lightning
Arresters.
The results of these investigations, which extended over a period of sev-
eral years, are embodied in the Wurts Non-arcing Lightning Arresters.
With a non-arcing arrester the dynamo current does not continue to fol-
low the discharge ; the apparatus is not left unprotected for an instant ;
the instrument does not deteriorate ; it is entirely automatic in action, and
will handle frequent and persistent discharges with perfect facility.
For systems of distribution, with their various motors, converters, and
other appliances, a liberal allowance of line arresters judiciously distributed
over the lines is essential for securing adequate protection. Much, how-
601
602
LIGHTXIXG ARRESTERS.
ever, depends upon the local conditions, such as the character of the soil
with reference to the ground connections, and severity of lightning dis-
turbances, the grade of insulation to be protected, the voltage of the circuit
and the surroundings with reference to telegraph and telephone wires.
EiG. 2. Double-Pole Non-Arcing Metal Lightning Arrester. Type " A."
(For Station Use.)
Fig. 3. Unit Lightning Arrester, Type
THE ]\OI¥.
' C," Showing Cylinders in Place.
-arcihtg metal
ARRE§fEll.
The non-arcing metal lightning arrester for alternating current circuits is
based upon the discovery made by Mr. A. J. Wurts that an alternating
current arc cannot be maintained over a short air-gap when the electrodes
consist of certain metals and alloys thereof. Types " A " and " C " arresters,
described below, are of the non-arcing metal type.
THE NON-AROIXG METAL LIGHTNING ARRESTER. 603
The Type "A" Arrester. — The construction of this arrester can
be best understood by reference to Fig. 2.
It will be noted that there are seven independent cylinders of non-arcing
[metal placed side by side and separated by air-gaps. The cylinders, which
are mounted on a marble base, are knurled, thus presenting hundreds of
confronting points for the discharge. The dynamo terminals are connected
I I
Figs. 4, 5. Double-Pole Non-Arcing Metal Line Arrester — Type " C."
to the end cylinders, and the middle cylinder is connected to the ground.
The arrester is, therefore, double pole, that is, one arrester protects both
sides of the circuit. When the lines become statically charged the dis-
charge spark passes across between the cylinders from the line terminals to
the ground. The non-arcing metal will not sustain an arc or become fused
by it ; hence with an arrester constructed of this material all possibility of
vicious arcing and short circuits is avoided. There are no moving parts,
no coils to impede the passage of the lightning discharge, and in fact
nothing that requires either adjustment or inspection. These arresters are
made in units for 1000 volts ; for 2000 volts two units are connected in
series, and for 3000 volts three are connected in series, as indicated in the
diagram, Fig. 7.
GROUPS—
Fig. 6. Lightning Arrester for 15,000 Volt Circuit — Type " R
604
LIGHTNING ARRESTERS.
Tlie Type " C " Arrester. — This is similar to type "A," but instead
of being mounted on marble it is inclosed in a weather-proof iron case for
line use. The cylinders are placed in porcelain holders, as shown in Figs. 3
and 4. The arrester complete in the iron case is shown in Fig. 5. The!
method of connecting type " C " arresters to circuits of different voltage is
also shown in Fig. 1.
The Type " JR. " Arrester. — Our standard form of arresters for pro-
tecting alternating current high potential power transmission circuits is
shown in Fig. G. A diagram illustrating the method of connecting the
arresters and choke coils for various voltages is given in Fig. 7.
FIG. 1
DYN. LINE
Fig. 2
I
3,000 VOLTS
1
5,000 VOLT8 -=±=-
Fig. 5
DYN. LINE
o r^ r^ o o o
u u o
i
Fig. 3
DYN. LINE
FlG. 4
DYN. LINE
i1 ■?
Y ■?
8,000 VOLTS
i
10,000 VOLTS
FlG. 7. Diagram Showing Pyramidal Form of Connecting Lightning
Arresters and Choke Coils for Various Voltages.
Explanatory Note — Each circle represents a choke coil. Each rect-
angle represents one unit (type " C ") non-arcing metal lightning arrester.
.
CHOKE COILS FOR A. C. CIRCUITS.
605
Sub-Fig. 1, four coils in series and one and one-half unit arresters between
line and ground. Sub-Fig. 2, live coils in series and two and one-half unit
arresters between line and ground. Sub-Fig. 3, six coils in series and four
unit arresters between line and ground. Sub-Fig. 4, six coils in series and
five unit arresters between line and ground. Sub-Fig. 5, six coils in series
and seven unit arresters between line and ground.
Plan View of Lightning Arrester Racks, Showing Unit Lightning
Arresters and the Connections for Each Voltage.
CHOKE COE3LS JOB A. C. CIMCUITi.
A lightning discharge is of an oscillatory character and possesses the
property of self-induction ; it consequently passes with difficulty through
coils of wire. Moreover, the frequency of oscillation of a lightning dis-
charge being much greater than that of commercial alternating currents, a
coil can readily be constructed which will offer a relatively high resistance
to the passage of lightning and at the same time allow free passage to all
ordinary electric currents.
Any coil will afford a certain amount of impedance to a disruptive dis-
charge. Experience has shown, however, that there is one form which
offers at once the maximum impedance to the discharge with the minimum
resistance to the generator current.
Choke coils of this type connected in the circui*, when used in connec-
tion with non-arcing lightning arresters, offer a very reliable means of pro-
tecting well-insulated apparatus against lightning. This arrangement is
particularly suited for protecting station apparatus in power transmission
systems. Coils can, however, be used to advantage on the line for the pro-
tection of the more expensive translating devices.
606
LIGHTNING ARRESTERS.
Tests made under actual working conditions indicate that for ordinary
commercial voltages effective protection is obtained with four choke coils
in series in each wire, with four lightning arresters intervening, as shown
in Fig. 10. This diagram also shows the method of connecting the coils and
arresters to one end of a three- wire transmission system.
Fig. 9. A. C. Choke Coil.
Fig. 10. One end of a 2000-Volt 3-Wire Power Transmission System
Showing Bank of Choke Coils and Lightning Arresters.
GROUND CONNECTIONS.
607
AMBEITEBS JOB ». C. CIBCUIT§.
The non-arcing metal arresters described above are not suitable for use
on D. C. circuits, but a non-arcing D. C. arrester has been devised bv Mr.
. J. Wurts.
The principles upon which this arrester is designed are based upon the
following facts : —
First. A discharge will pass over a non-conducting surface, such as
glass or wood, more readily than through an equal air-gap.
Second. The discharge will take place still more readily if a pencil or
carbon mark be drawn over the non-conducting surface.
Third. In order to maintain a dynamo arc, fumes or vapors of the elec-
trodes must be present ; consequently if means are provided to prevent the
formation of these vapors there will be no arc.
0 ^-ttv e
•
•e
o
•
o
9
o
fill
o
o
•
•
o
9
J
0
m
i
0
b
Fig. 11. Non-Arcing Railway Lightning Arrester, Type " K."
(For Station Use.)
TJie Type " BL " .Ai'restier. — The illustration, Fig. 11, shows the
type "K" arrester for station use on D. C. circuits up to 700 volts. The
instrument is single pole, and consists of two metal electrodes mounted
upon a iiguum-vitge block, flush with its surface. Charred or carbonized
grooves provide a ready path for the discharge. A second lignum-vitse
block fits closely upon the first block, completely covering the grooves and
electrodes. Disruptive discharges will pass readily between the electrodes
over the charred grooves, which act simply as an electrical crack through
the air, providing an easy path.
The resistance between the electrodes is more than 50.000 ohms, so that
there is, of course, no current leakage, but it should not be understood that
the lightning discharge passes through this high resistance — it leaps over
the surface of the charred grooves from one electrode to the other exactly
as it would if there were but a simple air-gap. The presence of the charred
grooves simply makes the path easier.
There being no room for vapor between the two tightly fitting blocks, no
arc can be formed, hence the arrester is non-arcing.
GROMD COMECTIOIS W&M. JL. C. JkJ¥l> I>. C.
Too much importance cannot be attached to the making of proper con-
nections from the arrester to ground, which should be as short and straight
as possible.
It is obvious that a poor ground connection will render inefficient every
608
LIGHTNING ARRESTERS.
3rs to drive the static elec-
t that we not only should
sction, but also thoroughly
latural conditions.
11 lightning arresters may
'le six feet square directly
s been reached ; second,
ushed coke or charcoal
of No. 1G tinned copper
No. 0 copper, securely
ver the ground plate
effort made with choke coils and lightning
tricity into the earth. It is, therefore, im
understand how to construct a good groum
appreciate the necessity of avoiding unfavorable n
A good ground connection for a bank of station
he made in the following manner : First, dig a ho]
under the arrester until permanently damp earth h
cover the bottom of this hole with two feet of <
(about pea size) ; third, over this lav 25 square fee
plate; fourth, solder the ground wire, preferabl
across the entire surface of the ground plate; fift
with two feet of crushed coke or charcoal ; and sixth, till in the holewith
earth, using running water to settle.
The above method of making a ground connection is simple, and has
been found to give excellent results, and yet, if not made in proper soil, it
would prove of little value. Where a mountain stream is conveniently near,
it is not uncommon to throw the ground plate into the bed of the stream.
This, however, makes a poor ground connection, owing to the high resist-'
ance of the pure water and the rocky bottom of the stream. Clay, even
when wet, rock sand, gravel, dry earth and pure water are not suitable
materials in which to bury the ground plate of a bank of lightning arresters.
Rich soil is the best. It is therefore advisable before installing a bank of
choke coils and lightning arresters to select the best possible site for the
lightning arrester installation, with reference to a good ground connection.
This may often be at some little distance from the station, in which case it
is of course necessary to construct a lightning arrester house. Where per-
manent dampness cannot be reached, it is recommended that water be sup-
plied to the ground through a pipe from some convenient source.
jLicjHTnriarc} arresters eom direct cerrest.
(From pamphlet by General Electric Company.)
Some years ago Prof. Elihu Thomson devised a lightning arrester based
on the principle that an electric arc may be repelled by a magnetic field.
In this device, the air-gap, across which the lightning discharges to reach
Fig. 12. Type "A" Arc Station Arrester.
the ground, is placed in the field of a strong electro-magnet. When the
generator current attempts to follow the high potential discharge, it is
instantly repelled to a position on the diverging contacts where it cannot be
maintained by the generator.
LIGHTNING ARRESTERS FOR DIRECT CURRENT. 609
The magnetic blow-out principle has been employed in the construction
of a complete line of lightning arresters for all direct current installations,
and in more than ten years of service magnetic blow-out arresters have
always been effective in affording protection to electrical apparatus.
In designing lightning arresters for the protection of bigh-voltage alter-
nating current circuits, however, different conditions have to be met, since
high-voltage arcs are not readily extinguished by a magnetic blow-out. In
a recently designed lightning arrester for alternating current circuits,
metallic cylinders with large radiating surfaces are found to so lower the
temperature of the arc that volatilization of the metal ceases and the arc is
extinguished.
Fig. 13. Type " AA" Arc Station Arrester.
The variety of these lightning arresters provides for the protection of all
forms of electrical apparatus and circuits.
The Type "A" Arrester is manufactured for the protection of arc lighting
circuits, and is in extensive use throughout the world. Its construction
includes a pair of diverging terminals mounted on a slate base with an
electro-magnet connected in series with the line. The magnet windings are
Fig. 14. Type "A," Form " C," Lightning Arrester,
in Iron Box for Line Use
610
LIGHTNING ARRESTERS.
of low resistance, and therefore consume an inappreciable amount of energy
with the small current used for arc lighting, although they are always in
circuit.
The single Type "A" Arrester is suitable for circuits of any number of
series arc lamps not exceeding seven ty-nve. For circuits of higher voltage,
a double arrester known as the type l,AA" is made by mounting two
arresters on one base and connecting them in series. One arrester should
be installed on each side of the circuit, as shown in the Diagram of Con-
nections.
For use in places exposed to weather, the Type "A" Arrester is furnished
inclosed in an iron case, and designated Type "A," Form " C."
Connections for Type
'A" Arresters.
Fig. 16. Type " B " Incandescent
Station Arrester 300 Volts or Less.
The construction of the Type " B " Arrester is similar to that of the Type
"A," but its magnet windings are excited only when a discharge takes place
across the air-gap. A supplementary gap is provided in the Type "B"
Arrester, in shunt with the magnets, thus providing a relief for the coils
from excessive static charge without affecting their action upon the main
gap. The magnet coils, carrying current only momentarily, allow the same
arrester to be used on circuits of large and small ampere capacity. The
Type "B" can also be furnished with weatherproof case similar to that
used with Type "A."
FlG. 17. Type " MB " for Direct
CurrentCircuits up to 850 Volts.
Fig. 18. Connections for
Type " B " Arresters.
LIGHTNING ARRESTEES FOR DIRECT CURRENT. 611
The Type " MD" Lightning Arrester has been designed for use on direct
current circuits up to 850 volts. While similar to Type"M," Form " C "
Arrester, it is considerably smaller, and is inclosed in a compact porcelain
box measuring 1\ inches x 5 inches x 4£ inches. For street car and line use,
Fig. 19.
-n r—
' MD" Lightning Arrester in "Wood Box.
the arrester is furnished in an additional box of iron or wood, as shown by
Fig. 19.
This arrester has been adopted as standard for railway and all direct
current 500-volt circuits. It has a short spark gap, a magnetic blow-out,
and a non-inductive resistance.
CONNECTIONS OF
MAGNETIC BLOW-OUT LIGHTNING ARRESTERS TYPE MD.
FOR DIRECT CURRENT CIRCUITS UP TO 850 VOLTS.
CONNECTIONS FOR LIGHTING OR POWER CIRCUITS.
(METALIC CIRCBITS)
T
CONNECTIONS FOR RAILWAY
CIRCUIT
(ONE SIDE GROUNDED)
REACTANCE COIL JS COMPOSED
25 FT. OF CONDUCTOR WOUND IN
COIL OF TWO OR MORE TURNS
AS CONVENIENT.
Fig. 20. Connections of Magnetic Blow-out Lightning Arresters,
Type " MD " for Direct Current Circuits up to 850 Volts.
612
LIGHTNING ARRESTERS.
LIGHTSIMCJ ARKESTERM FOR AJLTFRUrATIXC*
CUIIRE1IT.
The G. E. Alternating Current Arresters bave been designed to operate
properly with very small gap spaces. The arrester for 1000-volt circuity has
two metal cylinders 2 inches in diameter and 2 inches long, separated by a
spark gap of about J-5 inch. One cylinder is connected to the overhead
line and the other cylinder to the ground, and a low non-inductive graphite
resistance is placed in circuit. The large radiating surface of the metal
cylinders combined with the effect of the non-inductive resistance prevents
heating at the time the lightning discharge passes across the gap, and the
formation of vapor which enables the current to maintain an arc is thus
avoided.
ALTERNATOR
ALTERNATOR
10000 V. ARRESTER CONSISTS OF FOUR 2000 V.
O.P. ARRESTERS CONNECTED IN SERIES.
- GROUND
15000 V. ARRESTER CONSISTS OF SIX. 2000 V.
D.P. ARRESTERS CONNECTED INSERIES.
FIG. 21. Connections of Wirt or G. E. Alternating Current Short Gap
Lightning Arresters, 5000 to 10,500 volts.
The arrester under normal action shows a small arc about as large as a
pin-head between the cylinders.
The arrester for 2000-volt circuits is designed with two gaps of approxi-
mately 3V inch each and a low non-inductive resistance.
The G. E. Arresters are now furnished by the General Electric Company
for use on all alternating current circuits at practically any potential. For
circuits above 2000 volts, the standard 2000-volt double-pole arrester has
been adopted as a unit, and several of these are connected in series to give
the necessary number of spark gaps.
LIGHTNING ARRESTERS FOR ALTERNATING CURRENT. 613
FlG.22. G. E. Alternating Current
Lightning Arresters.
ALTERNATOR
FIG. 24. Connections of Wirt
or G. E. Alternating Current
Short Gap Lightning Arresters,
1000 to 3000 Volts.
ALTERNATOR
GROUND
1000 V.S. P. 1000 V.D. P.,
GROUND
2000 V.S..P, 2000 V.D. P.
614
LIGHTNING ARRESTERS.
Fig. 25.
THE GARIODT ARREiTER.
In Fig. 25 a cross-section view is shown of the
Garton Arrester.
The discharge enters the Arrester by the bind-
ing post A, thence across non-inductive resistance
B, which is in multiple with the coil F, through
conductors imbedded in the base of the Arrester,
to flexible cord C, to guide rod D and armature
E, which is normally in contact with and rest-
ing upon carbon H, thence across the air-gap to
lower carbon J, which is held in position by
bracket K. This bracket also forms the ground
connection through which the discharge reaches
the earth.
We have noted that the discharge took its
path through the non-inductive resistance in
multiple with the coil. This path is, however,
of high ohmic resistance, and tbe normal cur-
rent is shunted through the coil F, which is
thereby energized, drawing the iron armature
E upward instantly. This forms an arc between
the lower end of the armature and the upper
carbon H. As this arc is formed inside the
tube G, which is practically air-tight, the oxygen
is consumed, the current ceases', and the coil
loses its power, allowing the armature to drop
of its own Aveight to its normal position on
the upper carbon. The arrester is again ready for another discharge.
ELECTRICITY METERS.
Meters for measuring the amount of electrical energy furnished to cus-
tomers are commercially called wattmeters or recording wattmeters,
whereas they are really measurers or meters of watt-hours. The Edison
chemical meter, in which a shunted definite portion of the current supplied
to the customer is made to deposit zinc upon an electrode of an electrolytic
cell, is properly a coulomb meter, or ampere hour meter, which becomes a
watt-hour meter if the pressure be maintained constant.
This last meter is rapidly going out of use. The Thomson watt-hour
meter, which is replacing it, can be used upon either direct or alternating
circuits. It consists of a motor whose armature is connected in series with
a resistance to the two mains, and whose field coils are in series with the
supply circuit. The armature in rotating moves a recording mechanism.
The rapidity of rotation is regulated by a copper disk connected to the
armature shaft and moving between the poles of adjustable permanent
magnets. It is made for use on two or three wire circuits, arc circuits,
single phase or three phase a. c. circuits, and for recording input and output
of storage batteries. The following diagrams show some of the principal
uses to which it is put with the scheme of the connections to the circuits.
There are many other purposes to which it is put, but the reader is referred
to the instruction books accompanying the meters for further information
on the subject.
Fig. 1, Two-wire Meter.
(Small Capacity.)
615
Fig. 2. Two-wire Meter.
(Large Capacity.)
616
ELECTRICITY METERS.
Fig. 3. Three-wire Meter. (High
Efficiency Type).
Fig. 4. Primary Meter.
Fig. 5. Arc Circuit Meter.
Fig. 6. Station Arc Meter.
ELECTRICITY METERS.
617
Fig. 7. Balanced Three-phase Secondary Meter.
Eig. 8. Balanced Three-phase Primary Meter.
618
ELECTRICITY METERS.
Fig. 9. Two- wire Meters from
75 Amperes to 1200 Amperes.
Fig. 10. Two Meters on Mono-
cyclic System.
Fig. 11. Balanced Three-phase
Meter.
Fig. 12. Three-wire High
Efficiency Meter.
PNT TUBE
Fig. 13. Arc Circuit Meter. Fig. 14. Single-phase Primary Meter
ELECTRICITY METERS.
619
Fig. 15. Large Capacity Station
Meter Form G,.
Fig. 16. Station Arc Meter.
Fig. 16a. For Storage Battery 25 and 50 Amperes. 100 volts.
OEIXRAI HTOT£§ CO!¥CI!Jl]¥I]¥« THOMSON
In case a new jewel is inserted in the meter it is advisable to put in a
new shaft end, as the point on the old one will probably be injured,
more particularly if the meter has been running on the broken jewel.
Just before inserting a new jewel in a meter, it is well to place a drop of
fine watch oil on the jewel.
Oil must not l»e used in the top bearing under any circumstances.
Oil or dirt on the commutator will cause the meter to register less than
the correct number of watt hours.
If no " constant" is marked on the dial, the meter reads directly in watt
hours.
See that the disk and armature move freely, and that no dirt collects on
the magnets in such a way as to touch the disk.
Install the meter in a dry place, as far away from any heavy vibration as
possible.
When it is necessary to install a meter near a railroad, or in any place
where the vibration is sufficient to cause sparking at the brushes, the ten-
sion of the brushes upon the commutator should be slightly increased. This
will do away with the sparking, and ensure greater accuracy.
In case of severe jar, it is advantageous to place a number of soft rubber
washers under the heads of the screws which bind the meter to the wall and
between the meter and the wall itself at each screw.
The disk will always rotate to the right when the meter is properly
connected.
620 ELECTRICITY METERS.
Testing- of Thomson Recording' Wattmeters.
Most companies find it desirable to test meters on their lines from time to
time, not so much to check the accuracy of the meters as to be able to state
to the customer how the meter is operating. If only a rough test be required,
it can be made by turning on a specified number of lights, multiplying the
number of lights by the average watts per lamp, and using the following
standard formula : —
3600 x Constant (if meter has one; „ , . .. _,/,
,,_ ^ . =r Seconds per revolution of disk.
Watts m use ^
By using a stop watch, meters can be tested in this way, and the only in-
accuracy is the difference between the estimated and actual watts per lamp.
If a more accurate test be required, there are two methods, both of which
are simple, and obviate the necessity of taking down the meter.
A portable indicating wattmeter may be connected in series with the
meter to be measured. The portable instrument will read directly in watts,
and with the above formula give an absolute test.
Another method is to have half a dozen high candle-power lamps, which
have been tested at the station so that their wattage at all voltages is abso-
lutely known. These lamps can be connected as the only load on the meter.
By reading the voltage at the point of test with a portable voltmeter, and
noting the watts recorded by the meter for the group of lamps, a direct
comparison can be made.
Calibration of Thomson Recording* "Wattmeters.
Meters which have been neglected, misused, or very much worn, should
be taken down, and brought into the station for repair and recalibration.
In modern meters the speed can be increased or retarded about 16% by
moving the magnets. On older meters having only one movable magnet,
the variation obtainable by moving the magnet is considerably less. Meters
which cannot be properly calibrated by moving the magnets can be roughly
corrected by changing the resistance in series with the armature. Meters
which are slow on light loads can be speeded without affecting the accuracy
on high loads by increasing the shunt field coil, which is the fine winding.
Meters Avhich show a tendency to creep, that is, to move slightly without
any load, have too many turns in the shunt field coil. Creeping is almost
invariably traceable to vibration, which aids the meter to overcome friction
on very light loads. It can be corrected by removing turns from the shunt
field coil until the meter disk just barely fails to move on no load.
ALTERIATIHG CURRENT METERS.
In addition to the Thomson watt-hour meter, which is used on either a.c.
or d.c. circuits there is a class of induction meters used only on the a.c.
circuits. The Schallenberger meter is of this type, and is made by the
Westinghouse Electric and Manufacturing Company in several designs, such
as Watt-hour meters, ampere-hour meters, and the first mentioned are also
made in two- and three-phase meters.
All of these meters depend in some way on the rotating of a disk or cyl-
inder by means of induction coils properly placed in relation thereto.
The Duncan integrating meter is another of the class, and one formerly
made by the Fort Wayne Electric Corporation was very similar to the
Schallenberger ampere-hour meter. Some of these meters are regulated as
to speed by small fans placed on the armature shaft, and are hardly as
accurate as those having a retarding disk betAveen magnets.
THE STAIIEY METER.
The Stanley manufacturing Company has recently (January, 1899) brought
out an a.c. meter that is sealed and Avarranted to remain accurate within a
very small percent for a period of 3 years, provided it is properly installed
and the seals are not broken. This meter is of the induction type, and the
disk upon which the coils act is held in suspension, and at the same time
retarded by tAvo permanent magnets. The disk is so adjusted as to remain
suspended midAvay between the poles of the magnets, and there is no other
gearing for friction.
THE STANLEY METER
The following two cuts show its construction : —
621
Figs. 17 and 18.
Directions for Installing- Stanley Meters.
Place the instrument on a secure support in as nearly a vertical position
as can be judged by the eye. Open one of the mains in the circuit to be
metered, and connect the heavy black terminal of the meter to the main
leading to the transformer or current generator, and connect the white ter-
minal toward the lamp circuit or current consuming device. Connect the
small shunt wire directly across the mains to the opposite side of the circuit
so that the shunt connection of the meter will receive the full working
pressure of the circuit at approximately the voltage indicated on the case
cover. See cuts No. 19 and No. 20 for diagrams of connections.
Figs. 19 and 20.
Directions for Reading*.
Kilo-watt hours are recorded directly on the dial without the use of a con-
stant, unless otherwise marked on the case cover. The first right-hand
pointer on the dial indicates 1,000 Watt hours, or 1 K. W. H. for one com-
plete revolution of the pointer, and each unit indicated by this pointer rep-
resents 100 Watt hours. The other pointers, taken in order from right to
left, record successively 10 K. W. H., 100 K. W. H., 1,000 K. W. H., and
10,000 K. W. H. for one complete revolution of the pointer.
622
ELECTRICITY METERS.
DIAGRAMS OF CO!¥l¥FCXIOI¥S OF SHAILE]».
JIERttER II¥XEGRAXII^ WATTMETERS
XO VARIOUS STYIES OF CIRCUITS
Fig. 21. Connections for Single-Phase Circuits ; Current not exceeding 100
Amperes, Potential not exceeding 500 Volts.
The illustration above shows the method of connecting a meter to a single-
SKSSKr™* not exceedin§ io° ~ and at a ^
Fig. 22. Connections for Single-Phase Circuit; Current exceeding 100
Amperes, Potential not exceeding 500 ^olts.
The illustration herewith shows the method of connection to a single-
P^lV^rnn ^J^? a ^rrent exceedi"§" 100 amperes at a potential not
exceeding 500 volts. In this case a series transformer is used, the current
to be measured passing through the primary coil of the transformer while
the meter receives from the secondary coil of the transformer current bear-
ing a fixed ratio to the primary current.
DIAGRAMS OF CONNECTIONS.
623
Fig. 23. Connections for Single-Phase Circuit ; Potential exceeding 500
Volts.
The illustration shows the method of connecting the meter to a single-
phase circuit carrying current at a potential exceeding 500 volts. To keep
the high potential current out of the meter, hoth a series and a shunt trans-
former are used, even for currents not exceeding 100 amperes.
Fig, 24. Connections for Polyphase Circuits ; Current not exceeding 100
Amperes, Potential not exceeding 500 Volts.
The illustration above shows the method of connecting two meters to a
three-wire polyphase circuit, in which the current traversing each of the out-
side wires does not exceed 100 amperes, while the potential between either
of the outside conductors and the middle conductor does not exceed 500
volts. This connection is correct for a three-wire, two-phase system, and
also for a three-wire three-phase system.
624
ELECTRICITY METERS.
Fig. 25. Connections for Polyphase Circuits ; Current exceeding 100
Amperes, Potential not exceeding 500 Volts.
The illustration herewith shows the method of connecting two of these
meters to a three-wire polyphase circuit, where the current in each of the
outside wires exceeds 100 amperes, while the potential between each of the
outside wires and the middle wire does not exceed 500 volts. Series trans-
formers are used to reduce the current to the meter. This arrangement is
correct for either a three-wire two-phase or a three-wire three-phase system.
Fig. 26. Connections for Polyphase Circuit ; Potential exceeding 500 Volts.
The illustration shows the method of connecting two meters to a poly-
phase three-wire system carrying currents at a potential exceeding 500 volts.
It will be noted that both series transformers and shunt transformers are
used. This connection is correct for either a three-wire two-phase or a
three- wire three-phase system,
WESTLN"GHOTJSE INTEGRATING WATTMETERS. 625
WESTIHrCJHOUSU IjITEGRATIHG wattmeter§,
Two-Wire, Single-Phase. — The two-wire single-phase meter is
rated for the average load of the installation, this being permissible on
account of its ability to safely carry a load fifty per cent in excess of its
rated capacity. It registers in International Watts the true energy deliv-
ered to the circuit, and it is said to be correct for all power factors. The
counter reads directly in watts or kilowatt hours. Series transformers are
used on all circuits carrying more than 80 amperes, and for voltages above
500 volts shunt transformers are also used. These meters are connected to
two-wire, single-phase circuits, as shown in Figs. 21, 22 and 23.
TIiree-VTire, §>iiig-le-I*liase. — This meter is made to register the
energy delivered by a three- wire circuit, through the medium of a specially
designed series transformer, having two primary coils and one secondary
coil.
One of these primary coils is connected in series with one of the outside
ires of the three-wire circuit, and the other primary coil is connected in
[series with the other outside wire of the three-wire circuit. The secondary
icoil, in which the current is proportional to the sum of the currents in the
two primary coils, is connected to the wattmeter. The shunt circuit of the
wattmeter is connected between the neutral and one of the outside wires.
The current capacity, marked on the counter of the three-wire Westing-
house wattmeter, represents the current in each of the outside wires of the •
three-wire circuit. The voltage marked on the counter is that between one
of the outside wires and the neutral wire.
Fig. 27. Diagram of Connections of Westinghouse Three-Wire, Single-
Phase Integrating Wattmeter.
The total current capacity of a three-wire wattmeter is, therefore, twice
that marked on the counter, which represents the capacity of one side only.
The counter records, hoAvever, the total energy supplied to both sides of
the three-wire installation ; and the watt hours recorded on the counter in
one hour, when the meter is running at full load, will be twice the product
of the current and the voltage marked on the face of the counter.
626
ELECTRICITY METERS.
Two- or Three-I*hase Meters.
The "Westinghouse polyphase meter records on a single dial the total
energy delivered in all the phases of a two or three-phase circuit under all
conditions of balance and of power factor.
The current capacity marked on the counter of the polyphase wattmeter
is the current in each wire of the circuit ; the voltage is that across a phase.
No constant or factor is used.
Instructions for Checking- and Testing- Westing-house
Integrating Wattmeters.
Registration. — These meters as shipped are ready for use, and are
accurate -within the limits specified on the tag attached to them.
The disk revolves 50 times per minute at full load; the direction of rota-
tion being from left to right. The unit of power is the international watt,
and all Avattmeters register directly in watts or kilowatt hours without the
use of constants.
Methods of Checking. — One of the two methods mentioned below
are recommended, circumstances dictating which of the two is the better.
First method is to compare the instrument to be checked with a standard
indicating wattmeter, and timing the disk.
Second method is by comparing with a standard integrating wattmeter.
JFirst Method — Two-Wire, Single-I*hase Wattmeter. —
Connect the instrument to be compared in circuit with a standard indicat-
ing wattmeter, as shown in the following diagram.
STANDARD INDICATING WATTMETER
Fig. 28.
Load the circuit until the desired reading is obtained on the indicating
wattmeter, and keep it at a constant value while the integrating wattmeter
is being read. Time the revolutions of the disk with a stop-watch, com-
mencing to count when the spot on the disk has made one revolution (after
the watch has started), and counting the revolutions for at least a minute.
To arrive at the number of watts registered by the wattmeter, use the
following formula :
"Watts = -ThK. In this formula, R= complete number of revolutions of
the disk in time T.
T — time in seconds of revolutions B.
K= constant.
For wattmeters that are used without transformers, X = volts multiplied
by amperes (as marked on the counter), multiplied by 1.2. For wattmeters
that are used Avith series transformers (but checked without them), K =
volts, as marked on the counter, multiplied by 6. For Avattmeters that are
used with both shunt and series transformers (but checked Avithout them),
A'=G00.
In this way a wattmeter can be compared with a standard, and by varying
the number of Avatts can be checked through its entire range.
WESTINGHOTTSE INTEGRATING WATTMETERS.
627
All wattmeters for circuits exceeding 80 amperes are wound for 5 am-
peres, and are made to register the energy delivered by the main circuit by
means of series transformers. The primary coils of these transformers,
which are of heavy capacity, are connected in the main circuits, while the
secondary coil, in which the current is proportional to the current in the
primary windings, is connected to the wattmeter. These wattmeters can
be tested without the series transformers, but should be connected as in
Fig. 31 above, and the test made in the manner indicated. The full load is,
however, the product of the voltage marked as the counter multiplied by 5,
and not by the current indicated on the counter. A', in this case, = volts,
as marked' in the counter, x 6.
All wattmeters of voltages exceeding 400 volts are provided with 100-volt
shunt-coils and 5 ampere series-coils, and are connected to the main circuit
through shunt and series transformers of the proper ratio. In checking,
connect without the series or shunt transformers to 100-volt circuit, as
shown in Fig. 28, and proceed as indicated above, remembering that full
load is 500 watts, and that in the formula X= 600.
Three-Wire, Single-Phase. —These wattmeters are all 5-ampere,
single-phase instruments, and the method of connecting them for the first
method of test is shown in Fig. 29.
WESTINGHOUSE
WATTMETER
*J
ICATING WATTMETERS
Fig. 29.
A. Comiect two standard indicating wattmeters, one into each side of
the three-wire circuit, being careful to have the connections of these stand-
ard wattmeters made on the supply side of the integrating wattmeter, as
shown, so that it will not measure the energy used by them. Load the cir-
cuit until the desired readings are obtained on the indicating wattmeters,
and keep at a constant value while the integrating wattmeter is being read.
Time the number of revolutions of the disk as before. To arrive at the
number of watts registered by the wattmeter, use the following formula :
Watts =r ~K.
R = number of complete revolutions in time T.
T =r time in seconds required for revolutions R.
K= constant (volts times amperes, as marked on the counter, multiplied
by 2.4).
The reading of the integrating wattmeter should equal the sum of the
readings of the two standard indicating wattmeters.
B. A simpler method is to check the wattmeter without the series trans-
former. As previously mentioned, all these wattmeters are 5-ampere, 100-
volt, single-phase, two-wire instruments. For purposes of test it is neces-
sary only to connect them, as shown in Fig. 31, into a single-phase, two-wire
circuit, with a standard indicating wattmeter, and proceed in the same
manner as for two-wire wattmeters of this capacity.
Polyphase Wattmeter. — To compare a polyphase wattmeter with
the standard, check each side separately on a single-phase circuit. Where
transformers are not used in connection with the wattmeters, the full-load
rating for each circuit of the wattmeter is the number of watts obtained by
multiplying the current by the voltage marked upon the dial of the watt-
meter.
628
ELECTRICITY METERS.
If a series transformer is used with the Avattmeter, full load in each cir-
cuit is the number of Avatts obtained by multiplying the voltage marked
upon the dial by 5, as all Avattmeters used Avith series transformers are
wound for 5 amperes.
In testing, connect the polyphase Avattmeter as shoAvn in Fig. 30. Both
shunt circuits of the integrating Avattmeter are connected. The main cur-
rent, however, is passed through only one series coil at a time, by connect-
ing " C " to "A" or to " B." "When one circuit of the wattmeter is fully
loaded the rotating element makes 25 revolutions per minute, and 50 revolu-
tions AvLen both phases are fully loaded.
Fig. 30.
Load the circuit until the desired reading is obtained on the indicating
wattmeter, and keep it at a constant value AVhile the integrating wattmeter
is being read. Time the revolutions of the aluminium disk for at least one
minute.
To arrive at the number of watts registered by the Avattmeter, use the fol-
loAving formula :
Watts —-?pK- Where
R =r complete number of revolutions of the disk in time T.
T= time in seconds of revolutions 1L
K = constant. (For Avattmeters Avhich are used Avith both series and
shunt transformers, but checked Avithout them, K = 1200.)
"Always be sure to have both shunts connected when testing.
Second Method: With Standard Xnteg-rating- Wattmeter.
Single-Phase Wattmeters. — When using integrating Avattmeters
STANDARD WESTINGHOUSE
WESTINGHOUSE INTEGRATING
INTEGRATING WATTMETER,
WATTMETER
Fig. 31.
as standards, use one of same capacity and voltage as those under test.
Load the circuit into Avhich the Avattmeter is connected. If the disk of the
instrument under test runs in synchronism with the standard Avattmeter it
is in correct calibration. Repeat for several different loads. Another
method is to alloAv the instrument under test to run Avith the standard for
several hours under full load. A comparison of the amount registered
urn
WESTINGHOUSE INTEGRATING WATTMETERS.
629
will show the difference between the two, or the error of the instrument
tested.
When but a single wattmeter is to be checked against the standard, it
should be connected as shown in Fig. 31.
When more than one wattmeter is to be checked against the standard,
they should be connected as indicated in Fig. 32.
Referring to Fig. 32 : If a short run is to be made, but one meter should
be run with the standard at a time, otherwise the meter near the line con-
nection will measure the energy taken by the shunts of those near the
standard. If, however, the test is to be made by allowing the wattmeters to
STANDARD WESTINGHOUSE
AVESTINGHOUSE INTEGRATING
INTEGRATING WATTMETERS
WATTMETER
run with the standard for several hours they can all be run together, as the
amount of energy used by the wattmeters themselves will be so small a per-
centage of the total readings that it will not be noticeable.
l*olyi»Iiase Wattmeters. —Polyphase wattmeters should be checked
against single-phase standards. The standard used, however, should be of
twice the current capacity marked on the counters of the polyphase watt-
meters. Connect as shown in Fig. 33.
The wire at " A" is connected first to the upper phase of the meter and
then to the lower phase, proceeding in the same manner as with single-
phase meters, noting, however, that the full-load speed of the disk will be
25 r.p.m., as only one phase Avill be on at a time.
Be sure to always have both shunts connected when making a test. In
meters Avhich do not use series transformers there is only one shunt termi-
nal (the other wire of the shunt being connected to the right-hand series
terminal inside the meter).
Fig. 33*
Fig. 34.
Fig. 31 shoAVs the method of connecting three-wire, single-phase Westing-
house Avattmeters to three-Avire circuits.
All three-Avire, single-phase Westinghouse Avattmeters, for circuits ex-
ceeding 400 amperes per side, are connected in this manner.
Fig. 35 shows the method of connecting polyphase Westinghouse watt-
meters to two-phase circuits.
630
ELECTRICITY METERS.
All polyphase Westinghouse wattmeters for two-phase circuits of 400
volts or less, and of 80 amperes or less, are connected in this manner.
The following illustration shows the method of connecting polyphase
Westinghouse wattmeters to three-phase circuits.
All polyphase Westinghouse wattmeters for three-wire, three-phase
circuits of 400 volts or less, and of 80 amperes or less, are connected in this
manner.
Fig. 36.
The following illustration, Fig. 37, shows the method of connecting poly-
phase Westinghouse wattmeters to two-phase circuits.
All polyphase Westinghouse wattmeters for two-phase circuits of 400 volts
or less, and greater than 80 amperes capacity, are connected with series
transformers in this manner.
Fig. 38 shows the method of connecting polyphase Westinghouse watt-
meters to three-phase circuits.
All polyphase Westinghouse wattmeters for three-phase circuits of 400
volts or less, and of greater than 80 amperes capacity, are connected Avith
series transformers in this manner.
WESTINGHOUSE INTEGRATING WATTMETERS.
631
Fig. 39 shows the method of connecting polyphase "Westinghouse watt-
neters to two-phase circuits.
All polyphase Westinghouse wattmeters for two-phase circuits of all
jurrent capacities, and for more than 400 volts, are connected with shunt
ind series transformers in this manner.
Fig. 40 shows the method of connecting polyphase Westinghouse watt-
meters to three-phase circuits.
All polyphase Westinghouse wattmeters for three phase circuits of all
current capacities, and for more than 400 volts, are connected with shunt
and series transformers in this manner.
632
ELECTRICITY METERS.
To Tell the Exact Current blowing- at Any Time in a
Scliallenuerg-er JfEeter.
Note the number of revolutions made by tbe small " tell-tale" index on
the top of the movement, in a number of seconds equal to the constant o;
the meter. The number of revolutions noted will correspond to the number
of amperes passing through the meter. For example : the 20 ampere metei
constant is 63.3 ; if the index makes ten revolutions in 63.3 seconds, 10
amperes are passing through the meter. In order to avoid errors in reading
it is customary to take the number of revolutions during a longer time, say
120 seconds ; then as a formula, we have :
Number of revolutions x meter constant _
Number of seconds
§8©
§S©
OOKSO xtfrnpcre-houra.
«*«?■*»—*-«
"WS®
"(§©0
Fig. 41. Dials showing Sample
Readings.
Fig. 42. Difficult Meter Readings.
THE SCHEEFER WATT-METER. 633
THE iCHEErfER watt-hleter.
This meter, made by the Diamond Meter Co., Peoria, 111., is another of
the induction type, used for alternating currents, and has some special
features. The two following cuts illustrate its latest development.
Fig. 43. Round Pattern, Type D.
Scheeffer Watt-Meter Closed.
Fig. 44. Round Pattern, Type D.
Scheeffer Watt-meter Open.
A very ingenious device is used for sensitive adjustment, and the follow-
ing cut and description taken from the Company's catalogue is sufficiently
clear to indicate its use.
FlG. 45. Meter Core. Showing Shields for Sensitive Adjustment.
There are two knurled posts, A and B, secured to the meter core by screw
clamps as shown in the cut. These posts carry iron shields that" can he
made to embrace more or less of the disk by turning the posts.
" When the iron piece or shield embraces the disk it exerts an influence
indixctively on the disks so as to give it a torque, and will catise it to revolve
slightly. The left-hand piece (looking at the meter in front) will cause a
torque towards the right, and the right hand piece toward the left. If the
two pieces equally embrace the disk they will balance each other, and no
movement will result. By throwing one out the other will prevail, and cause
634
ELECTRICITY METERS.
it to revolve. Thus the two pieces can he adj usted towards each other so that
the meter is always balanced and just on the point of turning, and is highly
sensitive to extremely small loads. Great care must be taken so the balance
is perfect, as otherwise the meter will be overcompensated, and will slowly
run on pressure, and record when no load is on. When this adjustment is
made, a good way to establish a balance is to keep tapping the meter when
adjustment is made, as this will give a better adjustment for the meter, as a
meter will often not run on pressure wben quiet, but run slowly when sub-
jected to vibrations. A very good way to calibrate a meter is to adjust the
full load, and then adjust tbe knurled brass posts, so that by tapping a bal-
ance of the meter is effected so as not to run on pressure. This condition
will leave the meter highly sensitive and correct, as it is not necessary that
the lower loads be calibrated by a Watt-meter. When the posts have been
properly adjusted, they must then be fastened securely by screwing the
clamp which holds them tight, so that they will not be distured."
In testing or calibrating " Seheefl'er " meters, use a stop-watch for timing
and the following formulae for determinations.
MEIER CAICULATIOHTi.
w _ B x 3,600 X C
B — revolutions.
W — watts.
C — constant on meter dial.
S — second.
Wx S
B-
3,600 X C
B x 3,600 X C
METER PRICE CHART.
The General Electric Company furnishes a large price-chart for facilitat-
ing the making of bills from meter readings. The above cut is a reduced
facsimile of the chart. The figures at the bottom are kilowatt-hours ; those
at the left are the amounts of bills in dollars and cents. The diagonals are
different rates per kilowatt-hour. Selecting the diagonal having the rate at
which charges are to be made, a point is found on it directly over the num-
ber of kilowatt hours shown by the meter ; in the column at the left, on a
horizontal line from the same point, will be found the amount of bill. For
exar. pie, take 50 kilowatt hours at 10 cents per kilowatt hour, the amount of
bill shown at the left is $5.00.
313.00 -
1 1 1 1 1 1 1 1 1 1 1 1 1 1
r
V
V
p
y
1 | 1 1 1 II 1 II II M
-IdA-
^
y
•
PRICE CHART
i
/
AP/
y
' Ay
y
y
^ti^k
,'
y
PER 1000 W
<:9<M'&
y
3^3.
V
y
9.00 -
c >
'
/
<&
/
— 0
/,
b
/
;•;
•
:*>
/
v>
^
/
'
'
y
Y
/ /
•
■
/
y
T,
7
/
>
y
Jr
<9 -
7 z
/
y
'
:
V
'/'■//
y
v.
/ ///
V
_//
/
/■
///,
'//
>A^
1.00 -
:
i^^
MA
ES = AMOUNT OF BILLS IN DOLLARS AND CENTS
AGSC
SSAE^THOUSANDSOF WATT-HOURS
1 1 1 1
0
i
8 12
0 20
I
2?
.;>
a
■
-1
8 5
;u
6
1
6
a 7.
Fig. 49. Meter Price Chart.
WRIGHT DISCOUNT METER.
635
WRIGHT MiCOUST METER.
This instrument is for use in connection with a watt hour meter for de-
terming the maximum use of current during any given period; or may be
used without the watt-hour meter in connection with any electrical device
for which it is desired to know the maximum use of current, either direct or
alternating.
It is slow acting so as to take no account of momentary spurts, such as
starting an elevator or street car, and is rated to record as follows :
If the maximum load lasts 5 minutes, 80 % will register ;
If the maximum load lasts 10 minutes, 95 % will register ;
If the maximum load lasts 30 minutes, 100 </0 will register.
The following figure shows the working parts in theory, which, being of
u!ass and liquid, are placed in a cast-iron case, with a glass front to permit
reading. As shown, one leg of the circuit passes around a glass bulb which
is hermetically sealed, and connected to a glass tube holding a suitable
liquid.
T, Terminals.
H w, House wires.
R w, Resistance wire.
H B, Heated bulb.
A b, Air Bulb.
I T, Indicating tube.
L, Liquid.
^> Direction.
Fig. 47. Wright Discount Meter.
The heat due to the current passing in the circuit expands the air in the
bulb, which forces the liquid down in the left column and up in the right.
Should the quantity of heat be such as to force some of the liquid high enough,
it will fall over into the central tube, where it must stay until the instru-
ment is readjusted. The scale back of the central tube is calibrated in am-
peres on the left and in watts on the right. After reading and recording
the indication for any period of time, the liquid is returned to the outer
tubes by simply tipping up the tubes, etc., which are hinged at the top
connections for the purpose.
The readings of the demand meter or discount meter, either of which names
are used, together with those of the watt-hour recording meter, furnish a
basis for a more rational system of charging for electricity than has been
customary. This subject is being taken up by many of the larger electricity
supply companies.
The instrument is handy to use in circuit with a transformer to show how
the maximum demand compares with the transformer capacity ; also on
feeders and mains to show how heavily they may be loaded.
TELEGRAPHY.
In this chapter only the instruments used in telegraphy will be noticed
and these, Avith their connections, in theoretical diagrams only. For th
various details, whose presentation would defeat the purpose of clearness
in this compilation, readers are referred to various works on telegraphy
Lines, batteries, etc., are each treated in other chapters.
AMERICAN, or CUOKER CIRCUIT METHOD.
The following diagram shows the connections of the Morse system of
single telegraphy, as used in the United States. The terminal stations only
are shown, and in one case the local circuit is omitted. Several interme-
LINE TO TERMINAL
ft
1
±
Fig. 1.
diate stations (in practice 25 is not unusual) may be cut in on one circuit ;
all the instruments working in unison, in response to one key only.
In Fig. 1 at either end is a key which, when open, allows the now un-
attracted armatures to be withdrawn by the retractile spring, S. Closing
the key restores the current to the relays, attracts the armatures to the.
front stop ; the local circuit through the relay points is closed, and the
signal is heard on the sounder. The attracting force of spring, S, is less than
that of the relay cores as energized by the current from the battery used
for a given circuit. It can, by "pulling up " on the spring, be made greater ;
in which case the given current is ineffective to close the relays, and if the
tension of spring, S, is maintained, battery must be added to close the relays.
It is possible, therefore, by means of spring, S, to make a comparatively
weak current ineffective to close the relay points. The significance of this
will appear later in connection with the quadruplex.
EUROPEAN, or OPES CIRCUIT METHOD.
The following diagram shows the connections of one terminal station with
the line connecting to the next. The ground plates may be dispensed with
if a return wire from the next station is used, thus forming a metallic cir-
cuit.
This method of connecting Morse apparatus is used mostly in Europe, and
has two advantages over the American method .
a. The battery is not in circuit except when signals are being sent.
b. When the key is closed and the current admitted to line, the coils of
the relay are cut but of the circuit, thus lessening the hindrance to the flow
of current.
636
lift
TELEGRAPHY.
637
NE TO NEXT STATION KEY
REPEATERS.
In practical telegraphy, the high resistance of the line wire between the
terminal stations, and imperfect insulation permitting leakage in damp
weather, make it inexpedient to attempt to transmit signals over circuits
whose lengths have well-defined limits. But a circuit may be extended,
and messages exchanged over longer distances by making the receiving
instrument at the distant terminal of one circuit do the work of a transmit-
ting key in the next. The apparatus used for this purpose is called a re-
peater,*and is usually automatic, in a sense Avhich will appear later on.
From among the scores of repeaters, selection must be made of repre-
sentative types, — the two in most general use.
MilBiken Repeater.
The following diagram illustrates the theory of the Milliken repeater,
which is in general use in the United States and Canada. The essential
feature of every form of automatic repeater is some device by which the
circuit into Avhich the sender is repeating not only opens when he opens, but
closes when he c'
638
TELEGRAPHY.
In the diagram is represented the apparatus of a repeating station
which appear the instruments and three distinct circuits in duplicate, viz.
the east and west main line ; east and west local (dotted) ; east and west
extra local (dash and dot). Starting' with both "east" and " w est" keys
closed and the line at rest, battery//, whose circuit (dash and dot) is com-
plete through transmitter, T/, energizes extra magnet. E', attracts the pen-
dent armature, P', leaving the upright armature tree, the pendent armature,
.
P, being similarly held by battery, b. In
his key, relay, E, opens, then transmitter,
passes the west line, which opens, and wc
transmitter, T' ; but at the moment Iran
circuit (dash and dot) opens, releasing pel
by its soring against the upright armature
W, and transmitter, T', and therefore th
its tongue and post. When the distant 1
begins with the west relay instead of east.
the distant east opens
X, through whose tongue and post
uld open relay, W, and therefore
smitter, T, opens, the extra local
dent armature, P, which is drawn
holding closed the points of relay.
■ east line, which passes through
vest breaks and sends, the action
and follows the same course,
Weiny-Pliillips Repeater.
A theoretical diagram of the Weiny-Phillips repeater is given herewith.
It is in general use by one of the principal telegraph companies, and is
introduced here because it involves the principle of differentiation in mag-
net coils, which plays so important a part in duplex telegraphy. As in the
Milliken, there are three distinct circuits in duplicate ; and in the diaj
the parts performing like functions in the twro types of repeater
larky lettered. The connections and functions of the main line (solid I
Milli-
tical with those of the
1 pendent armature of the latter,
•aight iron core and its -windings,
performing the same tunc '
circuits and of local (dotted) circuit
ken. But instead of the extra magnets
we have a tubular iron shell inclosing s
the combination of shell and straight i
as the usual horse-shoe core. The turns of wire around the core of the
extra magnet are equally divided, and the current traverses the two halves
in opposite directions. Such a core is said to be differentially wound, be-
cause the core is energized by the difference in strength of the currents in
the coils; but when the coils are equal in resistance, the equal currents,
passing in opposite directions around the core, neutralize each other. If
one of the coils is opened, the core at once becomes a magnet capable of
holding the armature at the moment when, the repeater in operation, the
" east "" station opens his key, opening relay, E ; then transmitter, T ; then
opening the " west" wire, which would open relay, AV, transmitter, T', and
therefore the east wire ; but the opening of transmitter, T', is prevented by
the energizing at the critical moment of core W one coil of which is opened
DUPLEX TELEGRAPHY.
639
when transmitter, T, opens. When the distant west breaks and sends, the
action begins with the west relay instead of the east, and follows the same
course.
DO>IEX VELEGHAPHY.
That method of telegraphy by which messages can be sent and received
over one wire at the same time is called duplex ; and the system in general
use, known as the polar duplex, is illustrated in the accompanying diagram.
In single telegraphy all the relays in the circuit, including the home one,
respond to the movements of the key ; the duplex system implies a heme
relay and sounder unresponsive, but a distant relay responsive to the move-
ments of the home key ; and this result is effected by a differential arrange-
ment of magnet coils, of which the extra magnet coils in the Weiny-Phillips
repeater furnished an example. A current dividing between two coils and
their connecting wires of equal resistance will divide equally, and passing
round the cores, will produce no magnetic effect in them. This condition
WEST C
it--
EAST
THEORETICAL DIAGRAM OF POLAR DUPLEX
balancing switch omitted
Fig. 5.
is established when tbe resistance of the wire marked — > < — in the diagram
is balanced by the resistance of a set of adjustable coils in a rheostat marked
R. This is called the ohmic balance (from ohm, the unit of resistance) ; and
the static balance is effected by neutralizing the static discharge on long
lines by means of an adjustable condenser, C, and retardation coil, r, shunt-
ing the rheostat as shown. In the single line relay the movement of the
armature is effected by the help of a retractile spring in combination with
alternating conditions of current and no current on the line. In the polar
relay the spring is dispensed Avith, and the backward movement of the arm-
ature is effected, not by a spring, but by means of a current in a direction
opposite to that wbich determined the forward movement. This reversal
of the direction of the current is effected by means of a pole-changer, PC,
whose lever, T, connected with the main and artificial lines, makes contact,
by means of a local circuit and key, K, with the zinc ( — ) and copper (-J-)
terminal of a battery alternately. The usage in practice is zinc to the line
when the key is closed ; copper, when open. The law for the production of
magnetic poles by a current is this: When a core is looked at "end on"
a current passing round it in the direction of the hands of a clock produces
south-seeking magnetism, S ; in the opposite direction, north-seeking mag-
netism, marked N. A springless armature, permanently magnetized and
640 TELEGRAPHY.
pivoted, as shown in the drawing, will, if its free end is placed between S and
N magnetic poles, be moved in obedience to the well-known law that like
poles repel, while unlike poles attract each other. The" east" and" Avest "
terminal is each a duplicate of the other in every respect ; and a description
of the operation at one terminal will answer for both.
Under the conditions shown, the keys are open ; and the batteries, which
have the same E.M.F. oppose their copper (+) poles to each other, so that
no current flows in t Lie main line. But in the artificial line the current
flows round the core in such direction as, according to the rule just given,
to produce N and S polarities as marked, opening the sounder circuits at
both terminals. If, by means of key, K', the pole-changer, PC, of " east "'
station is closed, the connections ot battery, IV, are changed ; it is said to
be reversed ; and it now adds its E.M.F. to that <>1 battery B, the current
flowing in a direction from " west" to " east " ; i.e., from' copper to zinc.
But the current in the main line is to that in the artificial as 2 to 1 ; and if
the relative strength of the resultant magnetic poles is represented by small
type for that produced by the current in the artificial line, and by large type
for the main, the magnetic conditions can be graphically shown, as they are
produced on each side of the permanently magnetized armatures marked
(X) and (X'). In relay, PR7, it is Sn (S/) sX, causing it to remain open ; in
relay PR it has changed to Xs (X) nS — just the reverse of that shown in
the diagram — the relay therefore closes, and the sounder also. If key, K,
of the west station is closed at the same time, the batteries are again placed
in opposition, but with zinc ( — ) poles to the line, instead of, as in the first
instance, copper (-)-) poles. The result is no current on the main line ; but
the current in the artificial lines, flowing in the direction from the ground
(whose potential is 0) to the zinc (— ) of the batteries, the magnetic condi-
tion at " east" station is represented by n (X') s, which closes relay, PR';
and at " west " station by n (X) s, which closes relay PR. The conditions
necessary to duplex work, viz., that the movement of key, K7, should have
no effect on relay, PR', but should operate the distant relay, PR, are thus
fulfilled, and the transmission of messages in opposite directions at the same
time is made practicable. In the case of the Wheatstone Automatic duplex
this exchange goes on at high rate of speed, the maximum rate being 250
words a minute.
Duplex Repeater.
In wires worked in the duplex or quadruplex system, the static capacity
of the wire, which plays little if any part in the operation of circuits by the
single method, places a limit on the length of the continuous circuit. But
the distance between working stations can be greatly extended by the use
of repeaters in which, by an arrangement perfectly simple, the pole-changer
of a second circuit is controlled by the relay points of the first. The long-
est regular circuit in the United States is that worked between Xew York
and San Francisco, with six repeaters.
ftUADRHPLEX.
The quadruplex system of telegraphy allows of two messages being sent
in either direction, over the same wire, and at the same time. In theory it
is an arrangement of two duplexes, so different in principle as to permit
of their combination for the purpose designated. If the accompanying dia-
gram of the quadruplex is examined, there will be noticed in it the pole-
changer, polar relay, and all the apparatus of the polar duplex. The polar
relay at the " east" station (not shown) will respond to signals sent by the
pole-changer, PC, at the " west " in the manner described in the paragraph on
the Polar Duplex, so long as the working minimum of current is main-
tained. This working minimum can be doubled, trebled, or quadrupled
without appreciable difference to the polar relays. In the paragraph on
Single Telegraphy, the operation of the single relay, fitted with a retractile
spring, Avas effected by opening and closing the key ; or, in other words, by
alternating periods of "no current" and "current "on the wire. It was
further stated, in anticipation of its introduction at this point, that the
spring could be so adjusted that a weak current, though flowing all the
time through the coils, would not close it. To effect the closing an increase
THE STEARNS DUPLEX.
641
of battery, and therefore of current strength is necessary, so that the relay,
instead of, as in the first instance, responding to alternating periods of " no
current " and " current" could be operated by alternating periods of " weak
current" and "strong." In the diagram, transmitter T, when its key is
open, admits to the line a current sufficient to operate the polar side ; and
THE QUADRUPLEX (one terminal)
Fig. 6.
at the " east" station (not shown) there is a differentially wound relay, M',
the duplicate of relay M in the diagram, the tension of A\Those spring makes
it unresponsive. But when all the battery is on, a condition which obtains
when the key closes transmitter, T, the distant relay, M/, is closed. In short,
there is in the quadruplex a pair of polar relays which respond to changes
in the direction, not in the strength of the current ; and a pair of neutral
relays, which respond to changes in the strength, not to the direction of the
current. The diagram shows the apparatus in its simplest form ; there are
a number of details in connection with its operation, the complete connec-
tions for which are rather too complicated for this book. On page 199 of
Mavers's American Telegraphy will be found a diagram embodying the full
scheme of connections ; "ami Thorn and Jones' Telegraphic Connections con-
tains diagrams and detailed descriptions of the systems in general use.
THE STEARH'S BlPtEX.
The operation of differential relays like M in the diagram of the quadru-
plex, by alternations of "no battery" and "battery," is the principle of
the Stearns duplex which, as the first condenser-using, and therefore static-
eliminating duplex in the world, has a certain historic interest. In Febru-
ary, 1868, there were in use by the Franklin Telegraph Company a duplex,
set New York to Philadelphia, and another to Boston ; and in August, 1871,
STEARNS DUPLEX
(ONE TERMINAL)
642 TELEGRAPHY.
by the Western Union Telegraph Company, a duplex, New York to Albany
— all without condensers. In March, 1872, the Stearns Duplex, with con-
denser, went into operation between New York and Chicago, but it has been
superseded by the polar system.
Reverting to the diagram, the pole-changer with its adjuncts, and the
polar relay of the quadruples, are omitted; one pole of the battery is
grounded, and the lever of transmitter, T, is grounded through a resistance
equal to that of battery, B. This grounds the line through tongue, T, and
leaves the battery open at the post, P. The " east" station (not shown) is a
duplicate of the " west," and the control of relay, D, by the distant trans-
mitter, T', may be traced as follows. Suppose distant transmitter, T', sends
copper to the line when closed, the current dividing equally between the
main and artificial lines in distant relay, D', has no effect upon it ; but at the
Avest station there is no current in the artificial line in relay, D, so that
the current in the main line closes it. Open the key, K/, and the line is
grounded through the lever of transmitter, T'; battery P/is open, and there
being no current on the wire, relay, D, is open in response to the opening of
distant key, K'. Let transmitter, T, now be closed, and trace the control of
relay, D, by the distant key, K'. The current, which now flows from the
ground through the lever of open transmitter, T', to the zinc pole of battery,
B, is neutralized in relay, D, by an equal current flowing from the ground
through its artificial line in the opposite direction around its cores, so
that relay, D, remains open. Now close distant transmitter, T', and the
current in the artificial line (i.e., through the rheostat, R) of relay D is over-
powered as to its effects by a current on the main line of twice its strength,
and relay D is closed. It 'is thus shown to be controlled by the distant key,
K7, irrespective of the position of home key, K, and the conditions necessary
to duplex telegraphy are met.
TELEGRAPH CODES.
THorse, used in the United States and Canada.
Continental, used in Europe and elsewhere.
l*hiliij»M, used in the United States for " press " work.
Dash — 2 dots.
Long dash = 4 dots.
Space between elements of a letter = 1 dot.
Space between letters of a word = 2 dots.
Interval in spaced letters = 2 dots.
Space between words = 3 dots.
JDetters.
Morse. Continental.
E — —
I
M
N
P
TELEGRAPH CODES. 643
Morse.
T
U
V
w
X
Y
Z
Numerals.
Morse. Continent c
2
6
0
Punctuations, etc.
Morse. Continental.
: Colon
: — Colon dash
; Semi-colon
? Interrogation
! Exclamation
Fraction line —
— Dash
- Hyphen
' Apostrophe —
£ Pound Sterling
/ Shilling mark
$ Dollar mark
d pence
Capitalized letter
Colon followed )
by quotation :" J
c cents
. Decimal point
If Paragraph
Italics or underline
( ) Parentheses
[ ] Brackets
""Quotation )
marks. J
Quotation within j
a quotation |
Phillips.
. Period
: Colon — —
: — Colon dash
; Semi-colon
, Comma
' ? Interrogation
644 TELEGRAPHY.
! Exclamation
Fraction line
— Dash
- Hyphen
' Apostrophe
€ Pound Sterling
/ Shilling mark
$ Dollar mark
<l Pence
Capitalized letter
Colon followed by quo- )
tation : " j
c cents
. Decimal point
1[ Paragraph
Italics or underline
( ) Parentheses
[ ] Brackets
" " Quotation marks . -
Quotation within a ) _
quotation " ' ' " j
Abbreviations in Common "Use.
Min. Minute. Bn. Been.
Msgr. Messenger. Bat. Battery.
Msk. Mistake. Bbl. Barrel.'
No. Number. Col. Collect.
Ntg. Nothing. Ck. Check.
N.M. No more. Co. Company.
O.K. All right. D.H. Free.
Ofs. Office. Ex. Express.
Opr. Operator. Frt. Freight.
Sig. Signature. Fr. From.
Pd. Paid. G.A. Go ahead.
Qk. Quick. P.O. Post Office.
G.B.A. Give better address. Ii.li. Repeat.
TELEPHONY.
THIOKY OF THE MACHTET TEIEPHOXE.
Fig.
Field of Bell Telephone.
Tlte Receiver. — Tlie following cnt is meant to illustrate in a simple
manner about all that is known of the theory of the magnet or Bell tele-phone.
It is well known that the lines of force in a bar magnet curve backward and
around from one end or pole to the other. If a piece of iron, or say a dia-
phragm, be placed across one end of the bar, but not touching it, many of
the lines will traverse the diaphragm, as the path so provided "is magnetic-
ally easier than air. Now, if the diaphragm be moved backward and forward,
or to and from the end of the bar, a change will take place in the position
and condition of the lines of force surrounding that end of the magnet ; and
if a coil of fine wire be placed on the end of the bar close up to the dia-
phragm, then the changes produced in the lines of force will react on the
coil of wire (as in a dynamo when the amiature is moved across the lines
of force), and an E.M.F. will be produced in the coil. This is the exact
condition found in the cut below.
Now, if the ends of the wire of the coil be extended, and connected to the
terminals of an exactly similar instrument, any movement of the diaphragm
of one will be exactly reproduced in the other
instrument ; and, therefore, if one talks against
and so vibrates one diaphragm, the other will
be vibrated, and speech will thus be repeated.
"While authorities seem to think that this simple
theory is scarcely enough to account for all the
results found in a telephone receiver, yet it
apparently covers the greater part.
Based on the above theory, good transmission
of sound needs :
A powerful magnet and magnetic field.
A diaphragm that will vibrate freely.
A wide, shallow coil, in order to take in as many lines of force as
possible. The permanent magnet is essential to reproduce the pitch.
'jf lie Transmitter. — Although the Bell receiver proved to be an in-
strument of the most extraordinary sensitiveness, and as a receiver has
never been superseded, yet as a transmitter its range is extremely limited,
and much time has been spent by many minds in developing instruments
to extend the range of telephonic transmission.
While many inventors have tried to design a
transmitter in which the circuit is broken at
each and every vibration of the receiving dia-
phragm, yet none have succeeded; and success-
ful telephones are based in principle on the
change of resistance in a circuit, which produces
undulatory curents, and that is exactly the point
patented by Professor Bell.
Edison, taking up the principle, devised the
transmitter known by his name, in which, to pro-
duce the undulatory currents, he utilized the
change in resistance of carbon under varying
pressure.
The cut herewith shows the design of the Edi-
son Carbon Transmitter, which was quite a suc-
cess as a loud-speaking instrument, and was
doubtless the forerunner of the modern trans-
mitters. The instrument consists of a button
of lamp-black, compressed between two metal
plates to which the conductors are connected,
Fia. 2. Edison Carbon with a battery in circuit. An ivory button
Transmitter. C, Carbon presses against the cake of lamp-black, or carbon,
Disk ; B, Button ; Dt and is in turn pressed by the diaphragm.
Diaphragm. ■ Hughes next determined, by his experiments
645
646
TELEPHONY.
with the microphone, that the maximum effect is produced when the contact
with or between the particles of the carbon is a loose one. He showed many
beautiful experiments with that crudely made instrument which is shown
in principle and as used in the following cuts.
r
=a
B'l
Fig. 3. Hughes Car- Fig. 4. Diagram of simple telephone circuit for trans-
bon Microphone. mitting in one direction. C, pressure button ; IJ, dia-
phragm ; T, loose carbon contacts ; B, battery ; P, pri-
mary of induction coil ; S, secondary ; It, bell receiver.
The well known principle of the induction coil was then utilized to mag-
nify the effects of the undulations ; and thus were devised all the essential
features of the modern telephone transmitter, Avhich are in use to-day in
every commercial instrument. The following cuts show the simple form in
which all the above mentioned principles are connected to form a practical
telephone.
The principles are :
The diaphragm, operated by sound vibrations, varying the pressure on
loose carbon contacts, and varying the resistance in the local circuit so as to
produce undulatory currents, which are reproduced in the secondary cir-
T
T
H«
Fig. 5. Diagram of simple telephone circuit for conversing, or transmitting
in both directions. Letters all the same as in previous cut.
cuit of the induction coil, transmitted over the line circuit to the receiver,
where the undulatory currents cut the lines of force surrounding the coil,
and produce exactly similar vibrations in the diaphragm adjacent to it,
thus vibrating the surrounding air, and producing sound waves identical
with those directed at the diaphragm of the transmitter.
Receivers. — The Bell receiver is almost universally used to-day. It
varies in its construction only in using a single-pole magnet for ordinary
work, a double-pole magnet for long-distance circuits, and the watch-case
receiver for desk, speaking-tube and operators' sets. All are shown in the
accompanying cuts.
It has been found that a very narrow air-chamber between the diaphragm
and mouth-piece produces the best results, and that a small hole through
the rubber of the cap helps also.
Few if any improvements have been made excepting in the use of better
quality of materials and better construction.
The reader is referred to the " Telephone Hand Book " by Herbert Laws
Webb (Electrician Publishing Co., Chicago), for description of foreign and
other instruments.
THEORY OF THE MAGNET TELEPHONE.
647
Fig. 6. Magnet Fig. 7. Sin-
of Single Pole gle Pole
Receiver. Receiver.
Fig. 8. Double
Pole Receiver.
Fig. 9. Watch
Receiver.
Transmitters. — After Edison designed his carbon transmitter, and
Hughes made the microphone experiments, the Bell receiver was no longer
used for transmitting purposes, and numerous forms of battery transmitters
were designed. To-day they are legion, and differ, generally speaking, only
in inessential details. Only those forms mostly in use will be described here,
as they illustrate in principle nearly all others.
None but carbon transmitters are used to-day, and these are in three prin-
cipal forms or classes ; the first using single contacts, of carbon for varying
the resistance, as in the Blake ; the second using several contacts ; and the
third class, known as the Hunning type, using granulated carbon. Granu-
lar carbon transmitters are more used than any other type.
Transmitters of the second class are not used to any great extent in the
United States. The Blake, of the first class, and the " solid back," of the third
class, are the forms most used by American companies, the latter largely
predominating since the extensive adoption of metallic circuits.
I can do no better than quote, in describing these instruments, from
"Webb's " Telephone Hand-Book."
Blake Transmitter. — For lines of moderate length, the Blake trans-
mitter will give good service if kept in good adjustment. It is of simple con-
struction, low first cost, and requires but little battery power. It has the
disadvantage of needing careful adjustment when set up, and frequent in-
spection and adjustment while in service.
Each of the parts has an important function to perform, and on all being
in good condition depends the efficient working of the instrument. See Figs.
10 and 11.
The variable resistance is made in the
following way : A slender spring, carry-
ing a platinum contact point, bears on
the centre of the diaphragm. A second
spring carries a button of compressed
carbon let into a rather heavy socket of
brass. The face of the carbon button
presses lightly on the platinum contact
point of the first spring. The vibrations
of the diaphragm cause the pressure of
the platinum point on the carbon button
to vary, resulting in a variation of the
resistance at the contact. The secret of
the good working of the instrument is
that the two sides of the contact have no
rigid bearing. In Edison's first trans-
mitter he made one carbon contact solid with the case, and the other solid
Fig. 10. Blake transmitter. I), Dia-
phragm ; B, rubber band; C, clip ;
A, damper ; L, iron bracket ; F,
adjusting-screw.
648
TELEPHONY.
with the diaphragm. Consequently, the variable contact was not sufficiently
" sympathetic," as it were, with the vibrations of the diaphragm, and the
instrument did not work well. Blake discovered the reason of the defect,
and applied the remedy.
In the Blake transmitter the carbon button " stands up" to the platinum
contact, securing the full effect of the variations in pressure, because of the
weight of the brass socket ; that is, because of its inertia, or resistance to be
set in motion. The platinum contact is held against the diaphragm by the car-
bon button, but the normal set of its spring is toward
the button and aivay from the diaphragm. Conse-
quently we have a delicately balanced arrangement,
susceptible to change by the least vibration com-
municated by the diaphragm to the platinum point.
The arrangement of the parts to allow of proper
adjustment of the springs is very ingenious. An iron
ring is attached to the inside of the case, this ring
having a bracket, or projection, top and bottom. To
the top bracket is attached a piece of angle iron bent
at its upper part to a right angle, at the lower part
to an obtuse angle. The lower bracket serves as a
bearing for the screw by which the iron support may
be adjusted. The top part of the support carries the
two springs, which are insulated from each other by
hard-rubber washers. The carbon spring is sheathed
Fig. 11. Section of with a rubber sleeve, the diaphragm (generally of
Blake transmitter, iron) is clamped over a rubber gasket, and is pro-
D,diapliragm; S,car- vided Avith a damper, consisting of a metal spring
bon spring ; S', plat- screwed to the inside of the case. This damper is
inum spring ; L, iron rubber-covered, and has a little cloth pad that presses
bracket ; F, adjust- Gn the diaphragm near its centre. The damper
ing-screw. checks the vibrations of the diaphragm as quickly as
they have done their work, preventing continued
vibrations that would interfere with those following. The adjustment of
the springs is effected by means of the screw bearing on the obtuse angle of
the iron support. Turning the screw upward forces the support, and con-
sequently the carbon button, toward the diaphragm, increasing the pressure
between the button and the platinum contact. A reverse action of the screw
allows the support to come away, by reason of the outward set of the spring
by which it is attached to the iron frame, resulting in a decrease of the
pressure between the button and the platinum contact. The normal set of
the spring with the platinum contact gives it a tendency to follow the car-
bon button, and, if the button is pulled back, the platinum contact should
follow it nearly half an inch. The best adjustment is when the pressure of
the carbon button on the platinum contact just holds it lightly against the
diaphragm, not so lightly as to allow of any separation or break when the
diaphragm is vibrated by the voice. The two springs of the transmitter
are, of course, connected in circuit with the primary wire of the induction
coil and with the battery. The induction coil generally used in the Blake
transmitter has a resistance in the primary of half an ohm and in the sec-
ondary of about 250 ohms.
Tin* "Solid-Back" Transmitter. — The transmitter case is of
metal, and has much the form of the gong of an electric bell ; it is enclosed
by a perforated metal lid or cover, to which is attached the mouthpiece.
The cover carries the entire transmitter, which consists of two small carbon
disks enclosed in a metal chamber having an insulating lining ; between the
disks is a layer of finely granulated carbon, and the disks being slightly
smaller than the containing chamber, the surrounding space between the
edges ot the disks and the side of the chamber is also filled with carbon
granules. The back electrode is in metallic connection with the containing
chamber, a little pin in the brass backing of the carbon disk fitting into a
recess in the chamber, and holding it firmly seated. The front electrode is
insulated from the chamber by the insulating lining of varnished paper and
by a mica disk or washer, which encloses the chamber when the front elec-
trode is placed in position. The front electrode is secured to the vibrating
diaphragm of the transmitter by means of a pin, which extends from its
brass backing through a hole in the centre of the diaphragm. This pin has
two threads, one for a nut that clamps the mica washer over the end of the
__
THEORY OF THE MAGNET TELEPHONE.
649
chamber containing the two electrodes, and a finer one for two small nuts
that clamp the electrode to the diaphragm.
The mica washer is held against the little chamber by a brass collar,
which screws on the brass chamber itself, and secures the mica washer to it
around its edge. The mica washer being clamped to the chamber at its peri-
phery, and to the front electrode at the centre, has sufficient elasticity to
allow of the electrode responding to the vibrations of the diaphragm, and at
the same time the transmitter chamber is effectually closed. The chamber
has a projecting stud at the back which
fits into a hole in a stout brass bridge, and
is there secured by a set screw. The metal
bridge is screwed to the cover of the trans-
mitter case. The diaphragm, which is of
metal, is secured to the cover, and is pro-
vided with the usual clip and padded
dampening spring. One end of the brass
bridge carries a block of insulating mate-
rial, and to a small binding-post on this
block a fine wire, attached to the front -p,
p.lpp.trrxip is prmnpctpfl. Tbfi rp.nr pi p.p.- tr
12. Section of Solid-Back
Transmitter. M, mouthpiece ;
D, diaphragm ; E, front elec-
trode ; B, back electrode ; W,
electrode chamber ; P, metal
bridge piece ; d, set screw ; m,
micawasher;;j,threadedpinon
front electrode ; e, rubber band;
/, damper ; C, case ; E, cover.
electrode, is connected. The rear elec-
trode, being in metallic contact with the
bridge and through it with the case of the
transmitter and the supporting arm, needs
no special connection, one side of the pri-
mary circuit being connected to the arm of
the transmitter. The other side is con-
nected by a cord, which passes through a
hole in the bell-shaped transmitter-case to
the binding-post on the insulating block.
The vibrations of the diaphragm are communicated to the front electrode
by the pin, which forms a rigid connection between them. The electrode,
having a certain freedom of movement within the little chamber, varies the
pressure on the layer of carbon granules between it and the back electrode,
thereby setting up the usual variation of resistance required in a carbon
transmitter. The design of the instrument is very good. The two elec-
trodes, being of carbon, make excellent contact with the carbon granules,
thus affording the best opportunity for wide variation of resistance under
vibration, while the carbon electrodes, being soldered to brass disks, good
metallic contact is obtained with the two sides of the primary circuit. The
"packing" difficulty is, to a consid-
erable extent, obviated by this form
a,r,r- u. c of transmitter. The space in the cham-
ber around the edges of the electrodes
contains a certain quantity of granu-
lated cai'bon, which is not directly in
the circuit, and does not become heated
up rapidly by the current ; and any ex-
pansion of the granules immediately
oetAveen the electrodes through heating
causes a displacement of part of the
heated carbon into the cooler. When
the transmitter is out of circuit and
cools off, the granules tend to resettle
into their original position.
The chamber containing the working-
parts of the instrument is extremely
small, and forms a sort of button at-
tached to the front cover of the case.
By unfastening the screws which hold the cover, the entire transmitter can
be Avithdrawn, the connecting cord joined to the insulated binding-post
having first been disconnected. On account of the smallness and delicacy
of the parts, great care is required in handling the transmitter when assem-
bling or taking apart. When properly set up, it needs no adjustment ; and
indeed there is nothing that can be adjusted unless some radical defect
exists. Figs. 12 and 13 shoAV the details of construction by means of a sec-
tion of the transmitter mounted, and a section of the various parts of the
chamber, and a front view of the chamber
Fig. 13. Details of Solid-Back
Transmitter. TV, electrodecham-
ber; i, insulating lining; B, back
electrode ; a, brass backing ; E,
front electrode ; b, brass back-
ing; p, thread for nut U; in, mica
washer ; u, nut for clamping m
in place ; p', thread for t and V ;
c, cover of TV; TT, nuts for
clamping front electrode to dia-
phragm.
650
TELEPHONY.
^flag-net© Generator and Bell. — Tlie magneto generator has, in
the United States, displaced every other device for a calling signal for use
with telephones.
It is simply a crude form of alternating-current dynamo having permanent
magnet fields, and but one armature coil with its terminals led out. through
the shaft, and one contact. To this dynamo circuit is joined a polarized
bell or ringer. It is made up of a small electro-magnet that is connected in
circuit with the wires from the small dynamo; and when that instrument
is brought into action by revolving its armature, current is sent through
the coils of the electro-magnet, thus energizing it alternately, first in one
direction, then in the other, and throwing its armature, or keeper, which is
pivoted opposite the poles, back and forth, and so vibrating the hammer
attached to the armature between the two gongs mounted above. The polar-
ized bell has a small permanent magnet fixed to the frame carrying the
e.fcctro-magnet, which tends to keep the armature pressed over in one direc-
tion. Owing to the high resistance of the generator armature, this, when
not in use, is cut out of circuit, and only the bell coils left connected to the
line. There are many ways of effecting this change in the circuits automat-
ically, but the devices employed are so varied that no description will be
attempted here. The cuts shown embody the theories and general methods
of connection.
An extension bell should only be connected in the ringing-circuit, as shown
in the cut. An extension bell is simply the ringing-portion of a magneto
separated from the dynamo part, in order that it may be placed in some
distant location, where it is necessary to get a signal from the telephone.
Magneto-Generator and
Bell.
Complete Magneto-Bell.
Post Pattern.
Automatic Switches. — In a complete telephone set or instrument
there are several circuits, or parts of circuits, each having its own applica-
tion.
The ringing-circuit consists of the magneto-bell and generator, the arma-
ture of the latter being individually controlled by an automatic device.
The talking -circuit, consisting of the secondary of the induction coil, and
the receiver.
The primary circuit, consisting of the battery, the variable resistance of
the transmitter, and the primarv of the induction coil.
The automatic switch must be so designed as to connect the ringing-cir-
cuit to the line when the instrument is not in use, so that signals may be
received from other telephones or from the exchange, and to cut out the
ringing -circuit, and connect the line to the talking-circuit, and close the
primary circuit when one wishes to talk.
THEORY OF THE MAGNET TELEPHONE.
651
This is almost always done by using the weight of the receiver to hold
down a switch that will make all the necessary contacts for cutting the
ringing circuit in when the instrument is not in use. When the weight of
the receiver is removed, a spring lifts the switch to an upper position, in
which it closes another set of contacts through the talking ami primary cir-
cuits, and leaves the ringing circuit either open or short-circuited.
There are so many of these switches that only a diagram of a standard
plan can be included here. A second diagram shows the proper connection
for an extension bell.
Fig. 16. Diagram of Connections Fig. 17. Diagram showing proper
of Series Magneto Bell and Connections of Extension Bell.
Telephone Set.
Requirements of JfSetallic Circuits. — Metallic circuit telephone
lines must fulfil the following conditions : —
a. Both wires of the circuit must have substantially the same resistance.
b. Both wires must have substantially the same electrostatic capacity.
c. Both wires must have substantially the same insulation resistance.
Overhead Circuits on JPoles. — The above three requirements mean
practically that both wires must be of the same material, the same length,
have the same methods of insulation, be carried on the same poles (or in the
same cable), and in most cases should be on the same cross-arm, and always
adjacent to each other.
Electrostatic capacity is treated in the chapter on conductors.
Mutual- and self-induction are also treated in the chapter on conductors,
but there are some points applying especially to telephone circuits that will
be mentioned here.
The telephone is so sensitive that unless care be taken to prevent it,
the induction from neighboring lines will produce noise and " cross-talk."
Therefore, both lines of the circuit must be balanced in relation to adjacent
lines, so that induction from them may be neutralized.
This is usually accomplished by transposing the two wires of a circuit at
certain intervals along the line, the frequency of such transposition varying
according to the number of circuits on the line and the length of line. On
the main long-distance lines it is usually done every quarter of a mile.
The following cuts show the methods of transposition used in the United
States and in England.
Fig. 19. Transposition of
Metallic Circuit.
Fig. 18.
In American practice if more than two cross-arms are used, odd-numbered
arms are transposed as the upper arm in Fig. 18, and even-numbered arms
are transposed as the lower arm in Fig. 19.
In England it is sometimes the practice to change the position of the wires
652 TELEPHONY.
at each cross-arm, so that in four spans two wires of a circuit make a com-
plete twist about each other.
Aerial cables for telephone circuits are generally made up of No. 18 B.
and S. copper wire, insulated with rubber to ^" .
The wires are twisted in pairs, and laid up into a cable containing the
number of wires required. Each layer is taped, and the whole is wrapped
with two strong tapes impregnated with a preservative compound, and laid
on in reverse layers.
In modern practice lead-covered dry-core cable is frequently used for aerial
cable with very successful results. The lower cost and improved electrical
conditions are substantial arguments in its favor. The chief disadvantage
is the weight of lead-covered cable as compared with rubber.
Underground Circuit*. — For many years after the introduction of
the telephone the dime ul ties of working thro u gh
underground wires seemed insurmountable.
The electrostatic capacity of the underground
wires of early days was so much greater tban
that of overhead circuits as to materially in-
terfere with telephonic transmission. In late
years, however, the methods of insulation have
been so much improved that many thousands
of miles of telephone wire are now under
Fig. 20. English method of ground ; and it may be said that underground
of Transposing Metallic construction of telephone circuits is the gen-
Circuit, eral rule in large cities, and is rapidly being
adopted even in small towns.
The electrostatic capacity of a submarine conductor is twenty times that
of an overhead copper wire of equal resistance ; and the etectrostatic capa-
city of the early forms of paraffined-cotton insulated cable was about twelve
times as high as that of an overhead copper conductor, 104 mils diameter ;
but the underground conductor, being of much smaller cross-section, has a
higher resistance, about seven times that of the overhead wire in the case
above cited.
I'ndrrii -round Cables. — The standard type of cables for telephone
work contains four hundred insulated wires, twisted in pairs with about
three-inch lay ; and the pairs are cabled in reversed layers, forming a cable
about 2 inches diameter. The cable is always enclosed in a lead pipe Avith
walls | inch thick, and for the size here under consideration about 2\ to 1\
inches diameter. 100-pair and 50-pair cable, and various smaller sizes, are
used for distribution. Originally 50-pair was the standard size ; it was later
replaced by 100-pair, and now 200-pair has practically become the standard
cable for main routes.
Cables are often made of other sizes, sometimes of 500 and even of 600
wires ; but such large cables are difficult to handle, and 100-pair is the size
most generally used in large cities.
The insulation of cables is nowmostlyof drypaper loosely wound on thewire.
This method of construction secures a low capacity and a high insulation as
long as the lead covering remains intact, preserving the dryness of the paper.
The standard size of copper wire for telephone cables is now No. 19 B. and
S., which has a resistance of about forty-five ohms per mile.
The average mutual electrostatic capacity is about .085 microfarad per
mile, and runs as low as .07 microfarad per mile.
The insulation resistance of ail conductors should exceed five hundred
megohms per mile, after being laid and connected to the cable heads ; and
in practice this resistance is nearly always much higher, often several thou-
sand megohms per mile.
The lead covering of underground cables is nearly always alloyed with
three per cent of tin ; and in many cities where the gases are destructive to
the lead, a covering of asphalted jute is served outside the lead.
Submarine telephone cables are usually made up of stranded conductors,
seven No. 22 B. and S. wires, insulated with rubber compound to s% inch.
The cores are twisted in pairs the same as the paper insulated underground
conductors, and cabled together much in the same way. Ten pairs of con-
ductors is the usual limit for a submarine telephone cable. The cable
formed by the cores is served with hemp, and armored with galvanized iron
wires, the iron being protected by a layer of hemp soaked in a pitch com-
pound. In situations where the risk of damage by anchors, etc., is not great
dry core cables are now used for river crossing. The cable is iron-armored
over the lead sheathing.
THEORY OF THE MAGNET TELEPHONE.
653
lightning' and Current Arresters.— Telephone lines need pro-
tection from :
a. Lightning.
b. Crossing with heavy currents that will immediately hum out the in-
struments.
c. Crossing with " sneak " currents, or currents feeble enough not to burn
out at once, but by gradual or slow heating cause the destruction of the
instruments or parts of them.
A simple fuse wire Avould afford ample protection in most cases but for
the danger that it will be replaced, when blown, by a copper wire.
The fuse at the outer terminal of an underground cable is usually set to
blow at eight amperes.
A style of protector now extensively used, especially to protect the central-
station instruments, is the one shown in the following cut. It has an air-
space cut-out that blows if pressure on the circuit reaches 300 volts ; and a
"sneak" current arrester that will ground the line within thirty seconds,
under a steady current of .3 ampere.
The air-space cut-out consists of two blocks of carbon, separated by a thin
strip of mica, with a perforation in the centre. The upper carbon block has
a drop of fuse-metal let into its lower face, which completes the short circuit
when the current sparks across the space.
The lower block rests on a metal strip that is grounded, and the upper
carbon block is held in position by a spring connected to the line.
The sneak current-arrester is a small spool of fine German-silver wire,
having a resistance of 28 ohms.
In the centre of this spool is a metal pin, which is normally prevented from
passing clear through by a drop of fuse-metal, but which is released when
Plan of Combination Pro-
tector.
Fig. 21. Combination protector,
line-post ; F, instrument post ; B,
German-silver spring ; CC, carbon
blocks ; M, mica sheet ; S C, sneak
coil ; P, releasing-pin ; G, ground-
ing-strip ; D, ground wire.
the drop of fuse is melted by the heating of the coil by a foreign current, and
allows the lower spring connected with line to fly up, and make contact with
a ground strip.
Notes on the Installation and Maintenance of Tele-
phones.—The subscriber's telephone should be placed in some location
out of the usual route of office traffic, and on a solid wall or where it may be
free from vibration.
Use No. 38 B. and S. rubber-covered wire for connection to outer circuits,
unless wires are to be much exposed, when it is better to use No. 16 B. and S.
The rubber on No. 18 should be at least ^ thick, and on No. 16 at least ^.
Following the rules of the National Conference of Underwriters (see index
for insurance rules) will insure a good job ; and as they must be followed,
it is hardly necessary to give other directions.
Instruments should be periodically inspected, and all parts should be kept
clean and bright.
Go over all connections and binding-posts and see that all are tight, also
that all screws are tight.
Dirty contacts and frayed cords often cause much trouble.
Examine the receiver by unscrewing the ear-piece. The diaphragm should
not be bent or dirty or rusty ; the pole-piece should be clean, and the top
should be -^ inch from the diaphragm, no more, no less ; if it is farther
away from the diaphragm, the field will be too weak, whereas if much
nearer, the diaphragm is liable to stick. A good test for strength of magnet
is to see if it will hold up the diaphragm by its edge.
(354 TELEPHONY.
In the magneto bell keep all contacts clean and bright, especial attention
being given to those of the automatic switch and shunt.
Gearing and armature bearings should work freely and be occasionally
oiled.
The bells should ring clearly, and when ringing dull are probably loose at
centre.
Short circuit the bell binding-posts and turn the crank ; the bell should
ring. Place a resistance of several thousand ohms between bell and gen-
erator, and the bell should then ring when crank is turned. A generator
may be strong enough to ring its own bell on short circuit, and yet not do it
through resistance.
It is, hoAvever, of the most importance that the generator be capable of
ringing the distant bell, or of throwing the drop at the central station.
If the bell is known to be all right, and will not ring on short circuit, then
the fault will be in the generator armature, and may be caused by a broken
wire or a bad contact. If its contacts are platinized, clean with unglazed
writing-paper ; if not platinized, use emery paper.
Short circuit the binding-posts of the transmitter, then tap on the mouth-
piece or diaphragm of the transmitter, and notice quality of the " side-tone,"
which will enable the inspector with some practice to judge of the condition
of the transmitter and battery.
In the Blake transmitter, the rubber band under the diaphragm, the pad,
and the sleeve must be soft and elastic, and the rubber ring encircling the
diaphragm must not stick to the casting.
The platinum spring should touch the diaphragm only with its point.
The platinum spring and that carrying the carbon should both be tightly
clamped to the support.
The contact between the platinum point and the carbon button must be
clean ; and, as the platinum tends to dig into the carbon and to roughen
itself, it is highly important that the platinum point be smoothed and bur-
nished, and that the carbon be rubbed down with emery paper, giving the
final polish with a clean piece of paper. The platinum point, if not too
rough, can be polished with unglazed writing-paper.
Make final adjustment Avith the bottom screw on the iron support. Test
results Avith side tone until the talk is clear.
If the talk has a hollow sound, weaken the damper and slip.
If the volume is poor, loosen the adjusting-screw, stiffen the damper, and
see that the platinum point rests well against the diaphragm.
If the sound is broken and confused, give the platinum spring more " fol-
Ioav " to the carbon button, and see that the diaphragm is firmly clamped
on the rubber ring, and that there are no inequalities in the ring. If the
sound is scratchy, clean the platinum and carbon, and see that the platinum
spring is not twisted.
A weak battery Avill give a weak transmission, as will also a high resist-
ance in the primary circuit.
Frying and buzzing sounds maybe caused by loose battery connections or
dirt on the carbon button.
A bent diaphragm will give a metallic sound to the transmission.
There is no adjustment to the solid-back; and its efficiency depends on its
having been properly set up at first, and on the condition of the battery and
its circuit.
The good working of granular-carbon transmitters depends mainly on the
battery. If the battery poAver be too low, the transmission will, of course,
be Aveak ; but if it be too high, the transmitter may be overheated, which
Avill injure it.
Tavo cells of Fuller battery giving about 4.2 volts, or two cells of storage
battery giving about 4 volts, are generally used Avith the solid-back instru-
ments.
The resistance of the primary circuit is very low when the transmitter is
at rest, being for the transmitter itself about i ohm ; the current may then
be 2 J to 3 amperes, and the heating may produce packing.
When the transmitter is spoken into, the resistance immediately rises to
about 10 ohms, and the current decreases to .G amperes or less.
Below is quoted from " Webb " the methods of locating trouble in a
telephone.
" When a telephone Avill not work, the trouble may be either in the line,
the inside Aviring, or in the instrument and its connections. If, on short-
SWITCHBOARDS. 655
circuiting the instrument at the top binding-posts the bell rings and side
tone is obtained, the instrument is all right. The inside wiring should
then be tested by short-circuiting the wires if a metallic circuit, or attach-
ing a temporary ground if a grounded circuit, at the point where the line
enters the building ; if the bell then rings, the trouble is in the line, and
muit be found in the ordinary way. If the bell does not ring, the fault is
in the inside wiring, and can soon be traced out. If no side-tone is obtained
at the first test, the instrument is at fault. Either the receiver or a detector
gilvanometer may be used in locating the defect. The receiver is most
convenient, and it should be tested first by connecting it directly to the bat-
tery ; if a good click is heard, it is all right ; if not, there may be a broken
wire in the receiver, or the diaphragm may be out of order. If the receiver
is good, the primary circuit should be tested by opening it at one of the con-
nections, the automatic switch being up, and trying for current either with
the receiver or by testing. If no current is found, the trouble may be a
broken or disconnected wire, loose binding-post, corroded connection, bat-
tery dry or zinc eaten off ; the automatic sv\ itch may have a bad contact
through rust or dirt, or bent or loose springs, or broken wire ; the transmit-
ter may have a broken wire or cord, or may be open at the variable resist-
ance through bad adjustment or lack of carbon. All the various paths for
the current in the primary circuit should be traced out from one pole of the
battery back to the other, and the trouble will quickly be found. If the
primary circuit tests O.K., the trouble must be in the secondary circuit ;
and this can be tested by connecting one terminal of the battery to one bind-
ing-post of the telephone and touching the end of a wire joined to the other
terminal to various points in the secondary circuit, beginning with the second
binding-post of the telephone. When a click is heard in the receiver, the
trouble lies between the point just touched with the wire and the second
binding-post of the instrument.
The inspector's kit should contain the following tools and material :
Pair cutting pliers,
Pair long-nose pliers,
Warner Battery gauge,
Tack-hammer,
Screw-driver,
Soldering lamp and iron,
File,
Dusting brush,
Coil of insulated wire,
Rubber tape for covering joints,
Candle for examining instruments,
Solder and soldering fluid,
Small bottle of oil,
Trimming-knife,
Box containing screws, staples, washers, nuts, etc.,
Chamois skin, cloth, and polishing paste,
Spare parts of instruments, such as transmitter and receiver diaphragms,
cords, hinges, bell-cranks, gongs, rubber bands, dampers, clips and springs,
carbon buttons, and granulated carbon.
The small articles are conveniently carried and kept in good order by using
small round tin boxes to contain them. A separate stout bag should be
used for battery material, and should contain a number of spare zincs and
carbon plates or porous cups complete, a supply of sal-ammoniac, etc., a
strong knife, a sponge, and a quantity of cotton rags or waste.
The author feels it is necessary to offer some apology for having confined
the foregoing text so largely to telephone instruments used by the Bell Com-
pany only ; but principles only are meant to be treated, and" there is little
available" data that would serve to make those principles plainer. Many of
the so-called independent instruments are Avell designed and constructed,
and are gradually making headway. The same methods of test and connec-
tion in general apply to one as well as to the other.
SWITCHBOAIIȤ.
The subject of switchboards will be treated only as to diagrams showing
the general principles on which they are constructed. They differ much in
details, and one company at least is carrying on a quite extensive business
656
TELEPHONY.
with an automatic switchboard having no operator whatever. No descrip-
tion is at this time available which does justice to the exceedingly ingenious
instrument that makes the connections automatically between any two sub-
scribers.
Many improvements in detail have been introduced, and are continually
being brought out, such as sell-restoring drops, luminous indicators in place
of drops, and various other devices which cannot be mentioned here.
Multiple Switchboard. — The multiple switchboard is in use in most
of the large offices, and, while very complicated in practice, is simple in
theory, and is designed to enable the operator to be independent of other
operators, and to reach each subscriber's line without excessively long cords.
The board is divided into sections, each being of such a size that an operator
can reach either end, and yet three operators may work at the board with-
out inconvenience.
Every subscriber's line has a spring-jack at every section, but the drop or
other visual signal is on one section only. There are usually 200 drops on a
section; therefore when a subscriber calls " central," the operator inserts
her plug in the spring-jack of the subscriber, learns with what number he
wants to be connected, then connects one end of a cord from the calling
subscriber's jack to the one he called, as the number called for has a jack
on every section. The following diagram shows in simple form the connec-
tions for three subscribers' circuits for three sections of a multiple circuit
board. This diagram (Fig. 22a), as are those following, is from an article
in the American Electrician by Kernpster B. Miller.
Line J.
Of
b
This form of board is open to many
defects, and is being replaced by an-
other form to be next described. The
series multiple board, as the above is
sometimes called, has all the spring-
jacks of a subscriber's line in series,
and a weak spring or a particle of
dust may open-circuit one of the
jacks and put the line out of use.
The circuits are also liable to unbal-
ancing.
RrasBt-Ba T'ernainiil THultiple-
Jloarel. — This is a multiple-board
devised to overcome the defects of the series multiple-board previously de-
scribed. The general distribution of circuits is the same, but the spring-
jacks are connected to the subscriber's line in multi]ile instead of in series.
There is a common ground-wire for all sections, and there is also a third
wire through each section for each circuit of a subscriber. This line is so
connected through the drop magnet as to automatically restore the shutter
when connection is made to tlie calling subscriber's jack.
The following diagrams (Figs. 226, 22c) give the scheme of the connec-
tions.
Express S.rstem. — As the number of subscribers increases, the multi-
plicity of circuits, jacks, and connections increase as the square of the num-
ber on all multiple-boards.
Messrs. Sabin & Hampton of San Francisco devised a system that has
been in use several years in the San Francisco office. It is much simpler
than the multiple system, but not so handy to operate. Each subscriber's
SWITCHBOARDS.
657
line has one line-jack which is on a section of board which may be termed
B boards. Ihe < B boards are divided into sections of 100 lines each,
with an operator for each section. Another set of boards, called "A"
boards, are used as a sort of clearing-house, through which all connections
from suDscriber to subscriber are made. Trunk-lines lead from the "B"
boards to the "A" boards, and an order-wire connects the "A" board
operator with the " B " board operators. When a subscriber calls, the " B "
operator on the section on which the calling subscriber's line-drop happens
to be situated merely plugs a trunk-line into the subscriber's spring-iack
The "A" operator inserts her listening-plug in the trunk-line iust con-
nected, and asks what number is wanted. She then calls through the order-
wire to the " B " section on which the required number is situated, asking
. Line I.
Fig. 22c,
I W
P'-HH'I'i Subscribers' Lines.
a*
:7Tb °
that operator to plug a trunk-line in on the number required, which she
does, and answers back giving the number of the trunk-line she proposes to
use ; and the " A " operator then connects the ends of the two trunk-lines
by a multiple cord, as on the multiple-board. The process would seem to
be complicated, but is said not to cause unusual delays.
No magneto bell is used ; the subscriber merely removing his telephone
from its hook operates the calling drop, which immediately restores itself
when the trunk-line is plugged
in or the subscriber hangs up
his telephone. The drop signal
also operates at once, should the
"B" operator pull the trunk-
line plug before the subscriber
has finished. One small storage
battery is sufficient for a large
exchange; and the entire plant,
— boards, subscribers' instru-
ments, and all, — is much less
expensive than those of the or-
dinary multiple type.
The diagrams (Figs. 22c?, 22e)
show the scheme of connections
in the Express System; the first
one showing the subscribers'
lines and their connections to
the "B" boards, while the
second diagram shows the ' ' cen-
tral" connections.
If— ir=i+*r
o?l
j[~ ir^
4?i
FL
■*L.
GD8
COMMOH-KATTEIIY system:.
The common-battery system, as its name implies, is a centralized energy
system ; i.e., the transmitter and signalling batteries, or sources of energy,
are all located at the central office or exchange. This centralization has
numerous advantages: batteries at each station are done away with, thus
lessening the inspection and maintenance charges ; hand generators are not
required at each station, thus decreasing the investment ; and the apparatus
at stations is made much more compact and neater. The power-plant at
the central office is, however, more expensive to instal and maintain than
in the magneto system. The service is quickened, and the labor on the part
of the subscriber is diminished.
The underlying principle of the common-battery system is the insertion of
a battery into the line connecting two stations, the battery being a part of
the cord circuit completing the connection, between the stations, at the
exchange.
The line from the station enters the exchange, passes through the contacts
of a cut-off relay, then one side of the line passes directly to ground, while
the other side passes through a line relay, and battery to ground. A line
lamp signal, an auxiliary relay and battery, are connected through the con-
tacts of the line relay, the auxiliary relay controlling a pilot lamp signal.
The cord circuit contains a repeating coil and battery. Supervisory rebus,
controlling lamp signals, are placed in both the answering and the calling
sides of the cord circuit at the exchange. The calling side also contains a
combined ringing and listening key, or separate keys.
The operation of this system is briefly as follows : Nominally the receiv-
ers are on the hooks, and the line-circuits are open. Removing the receiver
from the hooks closes the line circuits through the contact of the hook-
switch, current then flowing through the line from the central office. This
flow of current energizes the line relay, closes its contact, thus lighting the
PARTY LINES. 659
line lamp signal, and closing the contacts of the auxiliary relay which in
turn lights the pilot lamp. The pilot lamp acts as a safeguard in case the
line lamp is broken, and also gives the supervising operator an indication as
to the line operators' punctuality in answering calls. The lighting of the
line lamp indicates that a station is calling. The operator takes the answer-
ing plug of the cord circuit and inserts it into the jack of the calling line.
This introduces grounded battery through the sleeve of the plug, energizes
the cut-off relay, opens the circuit of the line relay, and thus extinguishes
the line and pilot lamp signals. Having ascertained the number called for,
the operator inserts the calling-plug into the proper jack, and rings the called
for station. As long as the receiver at the called-for station remains on the
hook the supervisory relay in the calling side of the cord circuit is not en-
ergized, and the supervisory lamp is lighted. As soon as the receiver is
removed from the hook the supervisory relay is energized, and the lamp is
shunted out by a low resistance, and thus extinguished.
When neither of the supervisory lamp signals in the cord circuit glows,
the operator knows that both receivers are off the hooks. The operator
can supervise the conversation, if necessary, by means of the listening-key.
If neither station hangs up its receiver, the supervisory relay armature is
released, and the corresponding lamp signal glows. When both lamps glow,
the operator knows that both stations have hung up their receivers and that
the connection is at an end, whereupon she disconnects by removing the two
plugs from their jacks. If during the connection one station wishes to
attract the attention of the operator, he can do so by moving the receiver
hook up and down, thus causing the supervisory lamp signal to flash.
Lamp signals as above described are much used in the larger exchanges,
and are rapidly coming into more extended use. The magnetic signals are,
however, largely employed in the smaller exchanges.
In furnishing many lines with currents from the same battery, precautions
must be taken to eliminate cross-talk. This is accomplished by using sto-
rage-batteries of large capacity and very low internal resistance, and of cop-
per bus-bars of large cross-section. The multiple board is largely used,
usually of the divided type. A good description of the common-battery
system is to be found in Miller's " American Telephone Practice."
PARTY MUHES.
Until 1896 or 1897 no party-line system seems to have been invented that
was at all satisfactory for regular use ; but the advent of the " B.W. 0." sys-
tem, put forward by the Bell Co.'s, has changed all that, so that in residence
districts lines with six or more subscribers are becoming very common ; and,
as the charge for such installations is materially less than for the direct
line-system, and only the latest and best instruments with metallic circuit
are used, the service is equal to the best.
A good description of the " B. W. C." (Barrett, Whittemore, Craft) system
has been published in the American Electrician for January and February,
1899.
No special systems can be described here except in illustration of prin-
ciples of working.
As the telephonic current is undulatory, it is retarded by coils of wire
having self-induction ; and all such coils connected into the line hinder the
good working of its instruments. For this reason but few telephones can
be connected in series and work with any kind of satisfaction, as the self-
induction of the bell-magnets soon cuts down the transmission below the
working-point. In practice, telephones for party lines are connected in
multiple ; and J. J. Carty, of the New York Telephone Co., invented the so-
called bridging-bell, which enables us to couple up ten to thirty stations in
parallel.
The magnet-coils of the bridging-bell are wound with a large number of
turns of No. 33 B. and S. wire, and measure 1000 ohms resistance.
The magnets, therefore, have high self-induction, which stops off tele-
phone cm-rents, but does not prevent the bell ringing. The disadvantage is
that all the bells ring when any one of them is started ; and it is necessary,
therefore, to have some code of signals by which calls for different stations
may be distinguished.
660
TELEPHONY.
The generator armature of the bridging-bell is wound with low resistance,
jo as to give plenty of current for ringing the bells.
The following three diagrams show the bridging-bell and its connections.
Fig. 24. Polarized Bell with long core
for Ringer of Bridging-Bell.
NUT
Fig. 23. The Bridging-Bell
Fig. 25. Diagram of Connections of
Bridging-Bell.
I,OT¥0-I»ISXA]¥CI3 HIES.
In American telephone parlance the term " long distance" has come to
mean lines of the very best construction, and instruments of the latest and
best pattern.
The standard size of wire used on long distance lines is No. 12 N. B. S. G.,
104 mils, hard-drawn copper, weighing 172 pounds to the mile. On the longer
lines No. 8 wire, 165 mils, weighing 435 pounds to the mile, is used. 30-ft.
poles are used, set 130 feet apart and 6 feet in the ground.
Fig. 26. Standard Repeating-Coil.
Fig. 27. Diagram of Connections
of Repeating-Coil.
Cross-arms are 10 feet long, 3| x 4 J inches. They are placed 12 inches
apart, secured to the poles by bolts, and supported by iron braces.
Double cross-arms and transposition insulators are provided on every
tenth pole ; and at each such pole some of the circuits are transposed in
order to avoid inductive disturbance.
DUPLEX AND MULTIPLEX TELEPHONY.
661
Great care is taken to keep each side of long-distance circuits balanced ;
and for this reason all central-office appliances are connected in " bridge."
Eor joining local or grounded lines to the long-distance so as not to dis-
turb the balance, the circuits are connected through a repeater, which is an
induction coil, well made, and proportioned for the purpose.
Eigs. 26 and 27 show the standard repeating coils, as connected and as
made up. There is a closed core of fine iron wire, with its ends interwoven
and spliced after the two coils are wound on as shown. There are 10,000
turns of No. 30 B. and S. wire wound in four coils, one-half of one circuit
being the inner half of each coil, the two being connected in series. The
other circuit is wound outside of these coils, one-half over each side.
The following diagrams show the method of connecting grounded, local,
and long-distance lines together through repeaters.
y=*\
GROUNDED LINE
FlQ. 28. Long-distance circuit connected to grounded circuit through
repeater coil A.
Fig. 29. Two distant grounded circuits connected through repeating coils
A and B to a long-distance metallic circuit.
I*=*C
J*=®
Local metallic and long-distance metallic circuits connected
through repeating coil A.
»UJPI,EX A3W* 9EIJLTIPLEX TEIEPHOIY.
The following diagrams show a method of duplexing and multiplexing tel-
ephone lines invented by Frank Jacobs. They are interesting, but have not
yet proved to be of great practical use.
The duplex system is an arrangement by Wheatstone bridge, with resis-
tances Rl, R>, R3, R4, connected as shown. Those at either end must be
equal to each other, but the two ends need not be the same.
These resistances must be greater than that of the line in order that the
currents from T3 and T4 may pass along the line rather than around the
coils. The condensers C may be placed in shunt to the coils in order not to
retard the current, so that 1\ and T2 may work better.
. . ... __ - R<t
Fig. 31. Duplex Telephony.
062
TELEPHONY.
The second diagram shows the method of multiplexing; but it is easily
seen that T\, T2, T3, T4, will not work well owing to the resistances interposed.
Multiplex Telephony.
8IMrLTA]¥EOlJ§
TELEGRAPHY
AID TEL-
A system of simultaneous telephony and telegraphy is extensively em-
ployed in the United States, and is an improvement upon' the system invented
by Van Rysselberghe of Belgium, the system being often culled by his name.
Tbe figure, taken from Maver's "American Telegraphy," gives a genera]
idea of the working of the system.
Fig 33.
It consists of a combination of telephone and telegraph apparatus with
condensers and retardation or impedance coils so arranged that the Morse
signals do not react upon the telephone apparatus and the telephone cur-
rents do not react upon the telegraph apparatus. The letters attached to
the component parts of the figure are self-explanatory. The retardation
coils in the line circuit keep back the telephone currents, and the condensers
in the telephone legs keep back the Morse currents.
INTERIOR TELEPHONE SYSTEMS.
663
ISTERIOR IEIEPH091E SYSTEUIS.
Condensed from articles by W. S. Henry in Am. Elec. — 1900.
The systems considered may be divided into series party lines, bridging
' party lines, intercommunicating systems, and small central switchboard
systems. As the last system differs practically only in size from the regular
central station system no description of it will be undertaken here. In
these systems either magneto or microphone transmitters may be used, and
the signaling apparatus may be either magneto bells and generators or the
common vibrating bell and battery.
Where microphone transmitters or vibrating bells are employed, the
batteries may be distributed at the various stations or, in some cases, all
concentrated at one place. It is generally desirable, although not really
necessary, so to arrange the circuits that the bell at the calling station, or
the home bell as it is called, should ring when calling up another station.
This assures the person signaling that his own circuit and probably the
whole system is in working order, and that his call is being transmitted to
the desired station.
One of the simplest telephone systems comprises magneto instruments
connected in series in one line. Fig. 34 shows an arrangement of tbis kind
requiring at each station two magneto instruments ; T is the transmitter
and 72 is the receiver. An ordinary vibrating battery bell, V, a battery, B,
of two or more cells, and a hook switch, If, complete the equipment. When
the receiver, B, is hanging on the hook, the line is connected to the lower
contact ; when the receiver is removed, a spring pulls the lever up against
the contact, b. The smaller auxiliary switch, I, is arranged to normally
rest on the contact, c. It may be pressed down upon d, but when released
it should be returned to c by a stiff spring.
Fig. 34. Series System with Magneto Transmitters and Signaling
Batteries.
In Fig. 35 a very similar arrangement is shown, the only difference being
the use of magneto generators, G, in the place of the signaling batteries,
B, of Fig. 34, and the substitution of magneto bells for the simple bells used
in the first system. The signalling key. K, has only the upper contact, to
normally short-circuit the generator, G, as indicated in the sketch. Some
magneto generators are provided with an automatic arrangement on the
Fig. 35. Series System with Magneto Transmitters and Generators.
spindle which short-circuits the armature of the magneto whenever the
spindle is at rest. The act of turning the handle of the magneto removes
the short-circuit and allows the induced current to pass out to the line.
When this type of magneto is used, the push button, K, is, of course,
unnecessary.
664
TELEPHONY.
The arrangements described are known as series party lines, meaning that
all of the stations connected up are in series with each other. As intimated
above, when this arrangement is used even for a small number of stations,
the bell magnets should have as low resistance and as few turns of wire on
them as possible, in order to reduce the impedance of the circuit; and the
generators should be wound with rather fine wire, because the current gen-
erated must pass through all of the bells in series.
In order to avoid forcing the talking current through the magnets of the
signaling bells, the latter may be " bridged " directly across the circuit, as
shown in Fig. 30, in which case the bells may be wound for high resistance
and impedance so that the talking currents will be turned past them.
Fig. 36. Bridging System, with Magneto Transmitters and Generators.
In Fig. 3fi, three different methods of bridging are shown. At Station 1
the bell is removed entirely from the circuit when the receiver hook is up ;
at Station 2 the bell remains constantly across the circuit in series with the
transmitter and receiver, but when the hook is up it is short-circuited by
the hook and its upper contact through the wire, a ; at Station 3 the bell
remains permanently connected across the circuit, and when the receiver
hook is up the transmitter and receiver are connected in parallel with it.
Fig. 37. Series Systems with Microphones and Batteries.
Fig. 37 shows the simplest method of using microphone transmitters. The
instruments are a transmitter, T; an ordinary receiver, R; a vibrating
bell, V, and one or two separate batteries at each station. The battery, B,
is used only for ringing the bells ; the battery 31. B., only for operating the
microphone transmitters, and the battery I), for both purposes. In this
>
STATION »
Hfjr-j
Fig. 38. Series System with Microphones and Magnetos.
INTERIOR TELEPHONE SYSTEMS.
665.
arrangement, as well as in the one shown by Fig. 38, the microphones,
receivers, and microphone batteries are directly in series with the line, no
induction coils being used.
Instead of vibrating bells and batteries for ringing, we may use a polar-
ized bell, C, and a generator, G, as shown in Fig. 3S. In such an arrange-
ment the talking current must pass through all the polarized bells except
those at the stations where the receivers are removed from the hooks.
Fig. 39. Bridging System with Microphones and Magnetos.
A better arrangement is to use high-impedance bells bridged across the
two-line wires, as shown in Fig. 39. The generator, as explained in connec-
tion with Fig. 36, is normally on open circuit.
Three bridging methods are shown. At Station 1 some of the current
from the battery, M.B., can flow through the bell when the receiver is off
the hook, but this will do no harm ; in fact, it may be beneficial, for it
allows a larger direct steady current to flow through the microphone. The
fluctuations in the current produced by the microphone cannot pass
through the bell-magnet coils, but will pass through the line circuit on
account of the lower impedance of the latter. At Station 3 the bell is cut
out when the hook switch is raised, and at Station 2 both the generator and
bell circuits are cut off by raising the hook. An extra contact, d, is
required at these two stations, but on the other hand, there are two bells
less across the circuit to form shunts or leaks for the current when two
parties are conversing. On the whole, the arrangement at Station 3 is the
best of the three.
Fig. 40 represents a series party system (corresponding with that which
was shown at Station 1 in Fig. 37) in which a battery, £, and vibrating bell,
V, are used for signaling, and an induction coil, 1, is added to the speaking
apparatus. The primary of the induction coil is in series with the micro-
phone transmitter, T, and its battery, MB., and the secondary is in series
with the telephone receiver and the line.
The connections at Stations 1 and 2 are identical ; when the receiver
hook, H, is down the talking instruments are entirely cut out, and when it
FlG. 40. Series Party System, with Induction Coils and Signaling
Batteries.
is up the signaling key, battery and bell are thrown out of circuit and the
main circuit passes through only the telephone receiver and the secondary
of the induction coil. At Station 3 the connections are different ; when the
receiver hook is down the telephone receiver and secondary of the induc-
tion coil are merely short-circuited, while the transmitter, its battery, and
666
TELEPHONY.
the primary of the induction coil are open-circuited. When the hook is up,
the talking instruments are connected up for service and the signaling part
of the apparatus is short-circuited. Fig. 41 corresponds with Fig. 40, except
that magneto-generators, G, and magneto bells, C, have been substituted in
the place of the signaling battery and vibrating bells shown in Fig. 40. The
station connections correspond also, the receiver hook, H, at Stations 1
and 2 being arranged to throw in and out of circuit the talking apparatus
and the signaling apparatus, while the hook at Station 3 merely short-
circuits the signaling apparatus or the receiver circuit, according to its
position. This arrangement is the preferable one of the two, for the reason
that faulty switch contacts at the receiver hook will not open the circuit,
so that there will always be a continuous line through which one may
signal.
Fig. 41. Series Party System Using Induction Coils and Signaling
Magnetos.
A simple system installed where there was considerable noise, dirt, and
vibration, is represented diagrammatically by Fig. 42. Here, there are three
line wires, a, b, and c, the line c forming a common return for both the
signalling and the talking circuits, a and b, on which the apparatus is ar-
ranged in series. In this system the talking line is never open-circuited, the
telephone hook, JJ, serving to merely short-circuit the receiver and the
secondary of the induction coil when down, and to remove the short-circuit
and close the local circuit of the transmitter and induction coil primary
when up. It is obvious that the middle line wire, c, gives a free path to the
talking current, instead of its being forced through the signaling bells. Such
an arrangement facilitates the separation of the signaling and talking ap-
paratus, so that the call bells can be located where they can be easily heard,
while the transmitter and receiver may be put in a sound-proof closet. The
disagreeable noises due to induction from lighting or power circuits may be
overcome by using a twisted three-conductor cable between stations. Such
an installation is greatly superior to the series system shown by Figs. 40
and 41.
H'M-
HiM-
"t^^ * W-W
Fig. 42. Three-wire Series Party System.
Fig. 43 shows a series system in which one battery is used both for signal-
ling and for talking. In this system the connections are alike at all stations ;
Avhen the receiver hook, H, is down and the signaling key, /, is up, there are
included in the line circuit only the vibrating bells. Depressing the signal-
INTERIOR TELEPHONE SYSTEMS.
667
ing key I, puts the battery in the line and causes all the bells to ring. It is
preferable to have the batteries so connected up that if two or more signal-
ing keys should be depressed at once the batteries will agree in polarity.
When the receiver hook is up the battery is connected in series with the
transmitter and the primary of the induction coil, wbile the signaling key
and bells are thrown out of circuit and the telephone receiver and secondary
winding of the induction coil are included in the line, as shown at Station 3.
Fig. 43. Series Party System using only Battery at each Station for both
Talking and Signaling.
In this, as in previous series systems, with the exception of Fig. 42, the
talking current must flow through the signaling bells at idle stations. The
advantage of the system is obviously that it eliminates half the batteries,
only the one battery being used at each station for both signaling and talk-
ing. As in all series systems where vibrating bells are used, the vibrators,
should be short-circuited on all bells except one.
The best method for connecting a large number of telephones on a single
system where only two line wires may be used is to bridge them, as shown
in Fig. 44. The dots A and A', represent the binding-posts of each complete
outfit. The bells are permanently bridged between the two line wires at
Stations 1, 2, and 4, irrespective of the position of the receiver hooks. The
magneto generator is also bridged across the two line wires in an independ-
ent circuit, which is normally kept open either by a push-button, k, or by an
automatic device on the magneto spindle.
Fig. 44. Bridging Party-Line System ; Three Arrangements of Station
Instruments.
At Station 3 the magneto generator is bridged permanently across[the line
as in Stations 1, 2, and 3, but the bell is connected across only when the re-
ceiver hook is down, being thrown out when the hook is up. At Station 5
the bell and generator are bridged across the line wires when the receiver
hook is down, and are cut out entirely when it is up. At all of the stations
a third bridging circuit includes the receiver and the secondary winding
of the induction coil in series, this circuit being open when the receiver
hook is down, and closed when it is up. The hook also closes the local
transmitter circuit in the usual way Avhen it is up, and opens it when it is
down. The connections shown at Stations 3 and 5 possess the advantage of
cutting out their signaling bells entirely when the receiver hooks are up,
instead of leaving the bells shunted across the line continuously, as is the
case at Stations 1, 2, and 3.
668
TELEPHONY,
intercommunicating systems.
An intercommunicating system may be denned as a system having thre
or more telephones connected to the same system of wiring in such a maniie
that one may from any station call up and converse with any other station
without requiring any central-station switchboard whatever. Intercofl
municating systems require one wire from each station to every other statio
and at least one more wire running through all the stations. "Where vibr,
ing bells and one common ringing battery are employed, at least two more
wires than there are stations are necessary. At each station there must b
a switch of some kind whereby the telephone at each station may be con
nected to any one of the wires belonging to the other stations. Intercom
municating systems are very practical and satisfactory up to fifteen or even
twenty stations ; beyond that, the large number of wires running through
all stations makes the cost of the system increase rapidly, especially when
the stations are some distance apart. For a large number of stations well
scattered, a simple central-station switchboard system is preferable.
Fig. 45 shows a very common but not a good method of interconnecting a
number of telephones, where each station is equipped with ordinary series
bells and magneto generators. Theoretically any number of telephones may
be connected on such a system, but practical consideration would place the
limit at about twenty. In this figure there are four stations ; at Kos. 1, 2,
and 4 the telephone connections are drawn in full, while at No. 3 is shown
the telephone outfit as it usually appears. There are four individual line
wires, numbered 1, 2, 3, and 4, and a common return wire. Thus there is
one more wire than there are stations, and all these wires run through all
the stations, each wire being tapped at each station and not cut. At each
station there is one ordinary telephone instrument consisting of the usual I
talking apparatus, magneto-generators and polarized bells. Below each I
telephone there is an intercommunicating switch, the buttons of which are i
connected to the respective line wires, and the common return wire. When
not in use the switch at each station should remain on the home button.
liii
It"
Fig. 45. Intercommunicating System, with Magneto Signaling Gener-
ators and Polarized Bells.
"With all the levers in this position, a person at any station can call up
any other station by moving the switch lever to the button connected with
the individual line of the station desired, and turning the generator
handle ; only the bells at the home station and at the station called up will
ring. The ringing and talking currents pass through only the instruments
at the stations in communication. After finishing the conversation, the
switch lever at the home station must be returned to its home position,
otherwise the system will be crippled.
INTERCOMMUNICATING SYSTEMS.
669
In Fig. 46 is shown a method of wiring the intercommunicating switch
hat avoids the principal objection mentioned in connection with Fig. 18;
hat is, the failure to return the switch to the Lome position does not leave
he station so that it cannot be called up. Only four stations are shown,
»ut the system can be extended to include as large a number as may be
lesirable. The usual telephone sets, consisting of a microphone trans-
mitter, induction coil, receiver, hook switch, two cells of battery, a series
nagne'to-generator and polarized bell, are included in the outfits indicated
>y Tlt T2, etc. The inside connections of these telephones are the same as
ihown in the preceding figure.
Fig. 46.
In Fig. 46 one binding-post of each telephone is connected to the common
return wire, and the other binding-post is connected to both the lever arm,
s, and the individual line wire belonging to that particular station.
The home button in this last system is the first on the left and is not con-
nected to anything ; it is really a dummy button, but it should be there by
all means, for the lever, s, of the switch should always be returned to it
when the original calling party leaves the telephone. If all switch arms, s,
are on the home buttons it will be found that the circuits of all instru-
ments are open and no bell will ring, no matter what generator is turned.
If Station 2 desires to call Station 1 it will be necessary to first move the
switch arm, s, at Station 2 to button 1.
Fig. 47 is a system similar to that shown in Fig. 46, but arranged for vi-
brating bells and one common calling battery, CB, in place of magneto-
FiG. 47. Common Signaling-Battery System.
670
TELEPHONY.
generators and polarized bells. A battery is used at each station for oper-
ating the transmitter. This is probably the best arrangement of batteries
for such a system where vibrating bells are used. This system requires one
more wire than that shown in Figs. 45 and 46 where magneto-calling ap-
paratus is employed; thus there are two more wires throughout than there
are stations. The calling battery, CB, must be connected to the two wires
shown, but it may be located at any convenient place. In this arrangement
only the bell at the station called will ring, the bell at the calling station
remaining silent. If the bells are not arranged in this manner, the vibra-
tors on the two bells that happens to be connected in series when making a
call might interfere more or less Avith good ringing. Furthermore, it would
not do to short-circuit any of the vibrators, because there is no telling which
two stations may be connected together in making a call.
-j^T
Fig. 48. Common Signaling-Battery System.
Trouble is experienced with intercommunicating systems similar to that
of Fig. 47 by reason of the user carelessly leaving the selective switch S, off
the home button after using the telephone. Fig. 48 shows a method of wir-
ing such a system which obviates to a considerable extent this trouble.
Here, the vibrating bell is permanently connected to the home button, and
the pivot of the switch, S, is connected to the arm of the push-switch, Iv.
Any station can still be called up, no matter on what button its switch, S,
may be left.
The same system of wiring employed in Fig. 48 is applied to the system
shown in Fig. 49, in which magneto-generators, G. and polarized bells, C,
are used in place of the battery and vibrating bells. There is no need of
having a push button or automatic shunt on the generator, although it will
do no harm. The generator is normally on open circuit because one of its
terminals is connected to the under contact of the push switch, Iv. In order
to call up a station, the switch, S, is placed on the button belonging to the
station desired, the push switch, K, depressed, and the generator handle
turned. Since no common battery is employed for ringing, this system
requires one less wire through all the stations than the preceding arrange-
ment.
INTERCOMMUNICATING SYSTEMS.
671
In Fig. 50 is shown an arrangement in which one conveniently located
common battery, C B, supplies current for ringing and also for all trans-
mitters. No matter where the lever of the selective switch is left, the bell
can still be rung, but conversation cannot be carried on until the switch at
the station called is returned to the home button. This system includes a
piece of apparatus at each station that has not been required in any of the
systems previously described, to-wit : the impedance coil E. Where a
common battery supplies all the local microphone circuits with current in
systems of this kind, there is very apt to be cross talk between two pairs of
telephones that may be in use at the same time, in which case the battery
will be supplying current to four microphones.
BATTERY WIRE
Fig. 50. Common Battery System with Impedance Coils.
The cross talk is due to the variation in the fall of potential along the
battery and common return wires.
The cross talk may be greatly reduced by using batteries of very low in-
ternal resistance, such as storage cells, and making the common return
and battery wires extra large, that is, small in resistance, so that the vari-
able fall of potential through the battery and in these two wires may be
small. However, it is impractical to make the resistance of these two
wires low enough, especially where they are of considerable length, to
eliminate all cross talk.
Another way to reduce the trouble from cross talk is to insert an impe-
dance coil in each microphone circuit, as shown in Fig. 50. This makes
the impedance of each microphone circuit large compared to that of the
two lines and battery, and in order to get the same current as before in
each microphone the e. m. f . of the battery must be increased. These im-
pedance coils reduce the efficiency of the system, but the reduction in
cross talk compensates for this loss to a great extent.
-#-
~ir
Fig. 51. Radial System ; Selective at One Station Only.
672
TELEPHONY.
It sometimes occurs that a system is required to be so arranged that one
station can call up any one of the others, but the others can call up and
converse with the first station only. Fig. 51 is a diagram of such a system;
Station No. 1 or No. 2 can call up station C by merely depressing the push
switch Kl or K2, but they cannot call up or converse with each other.
Station C by means of the switch, S, and push, K, can call up either
Station No. 1 or No. 2. There are only two wires that must run through all
the stations. There is one Avire, however, from Station C to each one of
the other stations. These wires, Call Wire No 1 and Call Wire No. 2, are
used only when Station C calls up one of the other stations. One wire
could be made to answer if there was no objection to having all but the
home bell ring when Station C makes a call. In this case a certain num-
ber of rings would be necessary for each station except C, and the one
common call wire would be connected to the signaling key at a, Station C,
and there would be no need of the switch, S.
As arranged in the diagram, the push switch, K, is normally open. When
Station C desires to call Station No. 2, for instance, the switch, S, must be
turned to button 2 and the push switch, K, depressed. The one common
battery, B, furnishes current for all ringing and talking. At each station
there is an ordinary receiver, microphone transmitter, and vibrating bell.
There is only one bell in circuit when a call is made so that each bell must
have a vibrator. It makes no difference upon what button the switch, S,
is left.
In the systems so far described there is nothing to prevent the intercom-
municating switch from being left off the home button when the conversa-
tion is finished and the receivers hung up.
Fig. 52. Ness Automatic Switch.
An example of a device obviating this trouble is the Ness automatic
switch, illustrated by Fig. 52, arranged so that the replacing of the re-
ceiver upon the hook causes the switch to fly back to its home position.
In the engraving S is the lever of the selective switch, adapted to be ro-
tated over the various contact buttons, 1, 2, 3, etc. It is mounted upon a
shaft, A, passing through the front board of the box and carrying a ratchet-
wheel, E, inside the box. This ratchet-wheel is held in any position to
Avhich it may be rotated by a pawl, F, and thus prevents the lever S, from
turning backward. Upon the short arm of the hook lever, H, is pivoted a
dog, G, adapted, when the receiver is removed from the hook, to engage a
notch in the pawl, F; when the receiver is replaced, the dog, G, is pulled
upwards and lifts the pawl out of the engagement with the ratchet-wheel,
allowing a spiral spring around the shaft, A, to return the switch lever, S, to
the home button. After raising the pawl out of the notch on the ratchet-
wheel the dog slips out of the notch on the pawl, thus allowing the latter to
return into contact with the ratchet-wheel in order to be ready for the next
use of the telephone. In order, however, that the pawl may not engage the
ratchet-wheel before the lever, S, has fully returned to its normal position,
INTERCOMMUNICATING SYSTEMS.
673
a second dog, J, is provided which is pressed by a spring so as to occupy a
position under the pin,p, carried on the pawl, F, thus holding it out of
engagement with the ratchet-Avheel until the rotation of the lever is com-
pleted. At this point a pin on the farther side of the ratchet-wheel pushes
the dog, Jy out of engagement Avith the pin, p, and allows the pawl, F, to
drop into contact with the ratchet-wheel.
Fig. 53. Common Signaling Battery System ; Individual Talking
Batteries.
In Fig. 53 are shown the circuits of a four-station system using one com-
mon battery, CB, for ringing up the various stations, each station having
an ordinary vibrating bell, C. The circuits of Stations 1 and 4 are shown in
full, while those of the intermediate stations, being exactly the same, are
partially omitted. It will be noticed that the switch lever, S, at each
station is connected with the line wire bearing the same number as that
station, by means of the Avire, d. Each line wire is also connected at each
of the stations not bearing its own number with a button on the switch of
System having Common Talking and Signaling Battery.
674 TELEPHONY.
that station which does hear the same number in the manner pre-
viously described, by means of tbe wire, e. In this common-battery call
system two additional wires are run, one being termed the " call wire " and
the other the " common talking wire." The call wire and the talking wire
are connected through tbe calling battery CB, as shown. It is evident that
the number of wires passing through all the stations will be two more than
the number of stations, irrespective of that number.
If Station 4 desires to call up Station 1, for example, No. 4 will turn his
switch lever until it rests upon button 1, then a slight pressure upon the
switch knob causes the switch lever, S, to touch the contact strip, D, com-
pleting a circuit from the battery, CB, to contact strip, D, lever, S, and
button, 1, at Station 4; line wire, 1, wire, d, switch, H, and bell, C, at
Station 1, and back to the battery through the common talking wire.
"When both subscribers remove their receivers from the hooks, the circuits
are completed over line wire 1 with the common talking wire as a return.
At tbe close of the conversation the receiver is simply hung upon the hook,
and the automatic mechanical device returns the lever to the home po-
sition.
Fig. 54 shows the application of the Ness automatic switch to an inter-
commuicating system, using one common and centrally located battery for
supplying both the ringing and talking current. The section, TB, of the
battery supplies all the microphone transmitter circuits, and the whole
battery, KB, supplies tbe current for ringing the ordinary vibrating bells
that are used in this system. In this arrangement it is evident that the
number of wires passing through all tbe stations will in any size of system
be three in excess of the number of stations.
ELECTRO-CHEMISTRY. - ELECTRO-
METALLURGY.
ELECTRO-CHEMIiTRY.
Electrolysis.
The separation of a chemical compound into its constituents by means of
an electric current. Faraday gave the nomenclature relating to electroly-
sis, tie called the compound to be decomposed the Electiolyte; and the pro-
cess Electrolysis. The plates or poles of the battery he called Electrodes.
The plate where the greatest potential exists he called the Anode, and the
other pole the Cathode. The products of decomposition he called Ions.
Lord liayleigh found that a current of one ampere Avill deposit 0.017253
grain, or 0.001118 gramme, of silver per second on one of the plates of a sil-
ver voltameter, the liquid employed being a solution of silver nitrate con-
taining from 15 per cent to 20 per cent of the salt.
The weight of hydrogen similarly set free by a current of one ampere is
.00001014 gramme per second.
Knowing the amount of hydrogen thus set free, and the chemical equiva-
lents of the constituents of other substances, Ave can calculate what weight
of their elements will be set free or deposited in a given time by a given
current.
Thus the current that liberates 1 gramme of hydrogen will liberate 7.94
grammes of oxygen, or 107.11 grammes of silver, these numbers being the
chemical equivalents for oxygen and silver respectively.
To find the weight of metal deposited by a given current in a given time,
find the weight of hydrogen liberated by the given current in the given
time, and multiply by the chemical equivalent of the metal.
Thus: Weight of silver deposited in 10 seconds by a current of 10 amperes
= weight of hydrogen liberated per second X number seconds X current
strength x 107.11 = .00001044 X 10 X 10 X 107.11 = .1118 gramme.
Weight of copper deposited in 1 hour by a current of 10 amperes =
.00001044 X 3600 X 10 X 31.55 = 11.86 grammes.
Since 1 ampere per second liberates .00001044 gramme of hydrogen,
strength of current in amperes
_ weight in grammes of H. liberated per second
.00001044
weight of element liberated per second
~~ .00001044 X chemical equivalent of element
Resistances of Dilute Sulphuric Acid.
(Jamin and Bouty.)
Ohms per c.c. at
Ohms pei
Cu. In.
at
Density.
ofc
Sh
0&H
o .
oP^
°fc '
°fc
o?
d^
Do
Co
d^
o'2m
Do
Co
© CO
o ©*
S8
3£
©CO
oo-tf
ss
cn£
1 1
1.37
1.04
.845
.737
.540
.409
.333
.290
1.2
1.33
.926
.666
.4S6
.524
.364
.262
.191
1.25
1.31
.896
.624
.434
.516
.353
.246
.171
1.3
1.36
.940
.662
.472
.535
.370
.260
.186
1.4
1.69
1.30
1.05
.896
.666
.512
.413
.353
1.5
2.74
2.13
1.72
1.52
1.16
.838
.677
.598
1.6
4.82
3.62
2.75
2.21
1.90
143
1.08
.870
1.7
9.41
6.25
4.23
3 07
3.71
2.46
1.67
1.21
675
676 ELECTRO-CHEMISTRY. ELECTRO- METALLURGY.
CD a g
•^ cog
P-S-
- '
KjJ
-: .
y,-
b:.i
s, ~
- 2.
^ -
- ^
EN
•-< -
-.r-
WJJ
;~
02&
o
33
F
OT3
co
Aluminiumf . .
Antimony . . .
Bromine ....
Calcium ....
Carbon ....
Chlorine ....
Copper (cupric)
Copper (cupreus) .
Gold
Hydrogen . . .
Iodine
Iron (ferric)t . .
Iron (ferrous) . .
Lead .....
Magnesium . . .
Manganese . . .
Mercury (mercuric)
Mercury (mercurous
Nitrogen ....
Oxygen ....
Platinum (platinie)
Platinum (platinous
Potassium . . .
Silver .....
Sodium ....
Tin (stannic) . .
Tin (stannous) . .
2
P P ~< gs orq «• «■ i— aq r/Q w crc; C CO CO £ £ C — ^ >-. & ~
2 53
CS P-C
S 1
26.9
119.5
79.34
39.8
11.9
35.18
63.1
63.1
195.7
1.000
125.89
55.6*
55.6
205.36
24.1
54.6
198.5
198.5
58.25
13.93
15.88
193.4
193.4
38.82
107.11
22.88
118.1
118.1
64.9
os P
CO E.
8.965
39.83
79.34
19.90
2.975
35.18
31.55
63.10
65.23
1.000
125.89
18.53
27.80
102.68
12.05
27.30
99.25
198.50
29.125
4.64
7.94
48.35
96.70
38.82
107.11
22.88
29.525
59.05
32.45
Is. i
T ? |
Electro-Chemi-
cal Equiva-
lents.
Grammes per
Coulomb.
0000936
0004157
0008281
0002077
0000310
0003672
0003293
0006586
0006809
00001044
0013140
0001934
0002902
0010718
0001258
0002850
0010360 •
0020719
0003040
0000484
0000829
0005047
0010094
0004052
0011180
0002388
0003082
0006164
0003387
0.3370
1.4965
2.9812
0.7477
0.1116
1.3219
1.1855
2.3710
2.4512
0.0376
4.7304
0.6962
1.0447
3.8585
0.4529
1.0260
3.7296
7.4588
1.0944
0.1742
0.2984
1.8169
3.6338
1.4587
4.0248
0.8597
1.1095
2.2190
1.2193
►1
2.9674
0.6682
0.3354
1.3374
8.9606
0.7565
0.8435
0,4218
0.4080
26.5957
0.2114
1.4364
0.9576
0.2592
2.2080
0.9747
0.2681
0.1340
0.9137
5.7405
3.3512
0.5504
0.2752
0.6855
0.2485
1.1632
0.9013
0.4506
0.8201
|S,3
g|1
co ft co
►0
O p N
S^ o-
000743
003299
006572
001648
000246
002914
002614
005228
005404
000083
010429
001535
002302
008506
000998
002262
008222
016444
002413
000384
000658
004006
008012
003216
008873
001895
002446
004892
002688
1346.0
303.1
152.1
606.6
4064.5
343.1
382.6
191.3
185.1
12063.6
95.9
051.5
434.4
117.6
1001.5
442.1
121.6
60.8
414.4
2603.8
1520.1
249.7
124.8
310.9
112.7
527.6
408.8
204.4
37'\0
Ph~ CO
ELECTRO-CHEMISTRY.
677
Resistances of Sulphate of Copper at 10° C1. or 50° tP.
(Ewing and MacGregor.)
Ohms per
Ohms per
Density.
c.c.
Cu. In.
c.c.
Cu. In.
1.0167
164.4
64.8
1.1386
35.0
13.8
1.0216
134.8
53.1
1.1432
34.1
13.4
1.0318
98.7
38.8
1.1679
31.7
12.5
1.0622
59.0
23.2
1.1829
30.6
12.0
1.0858
47.3
18.6
1.2051 |
29.3
11.5
1.1174
38.1
15.0
Saturated )
Resistances of Sulphate of Zinc at 10° C or 500 V.
Ohms per
Ohms per
Density.
Density.
c.c.
Cu. In.
c.c.
Cu. In.
1.0140
182.9
72.0
1.2709
28.5
11.2
1.0187
140.5
55.3
1.2891
28.3
11.1
1.0278
111.1
43.7
1.2895
28.5
11.2
1.0540
63.8
25.1
1.2987
28.7
11.3
1.0760
50.8
20.0
1.3288
29.2
11.5
1.1019
42.1
16.6
1.3530
31.0
12.2
1.1582
33.7
13.3
1.4053
32.1
12.6
1.1845
32.1
12.6
1.4174
33.4
13.2
1.2186
30.3
11.9
1.4220 |
33.7
13.3
1.2562
29.2
11.5
Saturated j
Specific resistance of fused sodium chloride (common salt) at various
temperatures.
Temperature Cent. 720° 740° 750° 770° 780°
Ohms per cu. cm. .348 .310 .294 .265 :247
Application of Electro-Chemistry.
The various forms of primary and secondary batteries may be regarded
as applications of electro-chemistry, but they are treated as special subjects
in other parts of this book. Other important practical applications are the
processes for producing chemicals by electrolysis or by electrical heating.
Among the materials thus produced in large quantities are caustic soda,
carbonate of soda, chlorine, bleaching powder, chlorate of potash, calcium
carbide, phosphorus, cyanide of potassium, etc.
The production of caustic soda may be effected by electrolysing a solution
of common salt tlie reaction being NaClx H20=NaOHx Hx CI the products
being caustic soda {NaOH) which remains in solution, hydrogen and
chlorine that pass off as gases the latter being collected and used for mak-
ing bleaching powder.
There is a tendency to form a mixed product of caustic soda and salt and
a certain amount of hypochlorite of soda. These difficulties are avoided
by separating the caustic soda from the rest of the solution either by a
porous diaphragm or by drawing it off as fast as produced. In the Castner
process, mercury is used as the cathode and absorbs the metallic sodium
deposited upon it. In another chamber the sodium decomposes water and
forms caustic soda.
678 ELECTRO-CHEMISTRY. ELECTRO-METALLURGY.
Calcium Carbide is produced by heating a mixture of burnt lime and
pulverized coke or anthracite coal in an electric furnace, the reaction being:
CaO-\-3C=CaC2+CO
The carbonic oxide (CO) passes off as a gas and the calcium carbide after
cooling is a solid grayish mass which is broken up for use. A rotary form
of furnace is used at the large works of the Carbide Company at Niagara
Falls, the material being fed in at one side and the calcium carbide being
taken out at the other.
ELECTRO-METALLURGY.
Electro-metallurgy may be defined as that branch of science which re-
lates to the electrical reduction or treatment of metals.
The subject may be divided into three important and quite distinct
branches, as follows:
1. Electrolytic Metallurgy, which consists in reducing or separat-
ing metals by the decomposing effect which occurs when an electric current
is passed through their compounds while in the liquid state. These com-
pounds may be rendered liquid either by dissolving or fusing them; hence
there are:
(a.) Wet methods with solutions.
(b.) Dry methods with fused materials.
Electrolytic metallurgy is applied to the following purposes:
(c.) Electrotyping, which is the art of reproducing the exact form of
type, engravings, medals or other articles by electrodepositing metal on the
article itself or on a mould obtained from it.
(d.) Electroplating, Avhich is the art of coating articles with an adherent
layer of metal by ele'ctrodeposition.
(e.) Electrolytic reduction of metals, which is the art of obtaining metals
from their ores or compounds by electrically decomposing such ore or
compound in the state of solution or fusion.
(/.) Electrolytic refining of metals, which is the art of eliminating im-
purities by electrodepositing the metal itself, the foreign substances being
left in the anode or liquid, or vice versa.
2. Electrical smelting*, which consists in reducing metallic oxides
by carbon at a high temperature produced by the passage of an electric
current.
3. Electrical working- of metals, which consists in treating
metals mechanically with the aid of heat generated by electric currents.
Various mechanical processes which are facilitated by softening or fusing
the metal may be effected in this way, the principal ones being: welding,
forging, rolling, casting.
Electrotyping.— To reproduce an engraving, typographical composition,
or other object, a mould of gutta percha, wax, piaster or fusible alloy is
made from the object. If it is not a conductor it is coated with graphite
to start the action, connection being made to it by a wire or clamp put
around it. It is used as the cathode in a bath consisting of a saturated
solution of copper sulphate acidulated with sulphuric acid. The anode is a
plate of copper. The ordinary thickness of deposit is .01 to .02 inch. The
" shell" thus formed is separated from the mould and backed by a filling of
type metal.
Electroplating an article with an adherent coating of metal requires the
article to be thoroughly cleaned mechanically and chemically.
Cleaning. — Solutions for cleaning Gold, Silver, Copper, Brass and Zinc
are prepared as follows:
Water.
Nitric
Acid.
Sulphu-
ric.
Hydro-
chloric.
For copper and brass
Silver
100
100
100
100
100
50
10
3
100
10
8
12
2
Zinc
Iron, wrought
Iron, cast
2
3
ELECTRO-METALLURGY. 679
Lead, Tin, Pewter, are cleaned in a solution of caustic soda.
Objects to be plated witb gold or silver must be carefully and thoroughly
freed from acids before transfer to the solutions. Objects cleaned in soda
or those cleaned in acid for transfer to acid coppering solutions may be
rinsed in clean water, after which they should be transferred immediately
to the depositing solution.
Baths for plating:.— The reader is referred to the various books on
electroplating for particulars, as but few, and those the most used solutions
can be referred to here.
Solutions should be adapted to the particular object to be plated, and
must have little if any action upon it. Cyanide of gold and silver act chemi-
cally upon copper to a slight extent and the objects should be connected to
the electrical circuit before being immersed.
Solutions are best made chemically, but can be made by passing a current
through a plate of the required metal into the solvent.
Copper. —A good solution for plating objects with copper is made by
dissolving in a gallon of water 10 ounces potassium cyanide, 5 ounces copper
carbonate, and 2 ounces potassium carbonate.
The rate of deposit should be varied to suit the nature and form of the
surface of the object, large smooth surfaces taking the greatest rate of
deposit. Electrotype plates must be worked at a slow rate, owing to the
rough and irregular surface.
Non-metallic Surfaces may be plated by first providing a conducting sur-
face of the best black lead or finely ground gas coke. Care is required in
starting objects of this sort, to obtain an even distribution of the metal, and
hollow places may be temporarily connected by the use of fine copper wire.
Copper on iron or on any metal that is attacked by copper sulphate is
effected by an alkaline solution. One which can be worked cold is made
up of \ ounce of copper sulphate to a pint of water. Dissolve the copper
sulphate in a half pint of water, add ammonia until all the first formed
precipitate re-dissolves, forming a deep blue solution, then add cyanide of
potassium until the blue color disappears. A heavy current is required with
this solution, enough to give off gas from the surface. This solution will
deposit at a high rate but ordinarily leaves a rough and crystalline surface,
and will not do good work on steel.
A cyanide solution is the most used, takes well on steelpr brass, as well as
on iron, and permits of many variations.
For each gallon of water use :
Copper carbonate 5 ozs.
Carbonate of potash 2 ozs.
Potassium cyanide, chem. pure 10 ozs.
Dissolve about nine-tenths of the potassium cyanide in a portion of the
water then add nearly all the copper carbonate, Avhich has also been dis-
solved in a part of the water: dissolve the carbonate of potash in water and
add slowly to the above solution stirring slowly until thoroughly mixed.
Test the solution with a small object, adding copper or cyanide until the
deposit is uniform and strong. For coppering before nickel plating, the
coating of copper must be made thick enough to stand hard buffing, and for
this reason the coppering solution must be rich in cyanide and have just
enough copper to give a free deposit. Use electrolytically deposited copper
for anodes, as it gives off copper more freely. Regulate the current for the
work in the tanks, and it should be rather weak for working this solution.
Brass Solutions of any color may be made by adding carbonate of zinc in
various quantities to the copper solution. The zinc should be dissolved in
water with two pai'ts, by weight, of potassium cyanide, and the mixture
should then be added to the copper bath. A piece of work in the tank at
the time will indicate the change in color of the deposit. Two parts copper
to one zinc gives a yellow brass color. For the color of light brass add a
little carbonate of ammonia to the brass solution. To darken the color
add copper carbonate. Varying the amount of current will also change
the color, a strong current depositing a greater amount of zinc, thus pro-
ducing a lighter color.
Silver. — The standard solution for silver plating is chloride of silver
dissolved in potassium cyanide. This solution consists of 3 ounces silver
chloride with 9 to 12 ounces of 98 percent potassium cyanide per gallon of
water. Rub the silver chloride to a thin paste with water, dissolve 9
680 ELECTRO-CHEMISTRY. ELECTRO-METALLURGY.
ounces potassium cyanide in a gallon of water and add the paste, stirring
until dissolved. Add more cyanide until the solution works freely. The
bath should be cleaned by filtering. Great care should be taken to keep
the proper proportions between current, silver and cyanide. A weak cui'-
rent requires more free cyanide than a strong one, and too much cyanide
prevents the work plating readily, and gives it a yellowish or brownish
color. If there is not enough cyanide in the solution the resistance to the
current is increased and the plating becomes irregular.
The most suitable current for silver plating seems to De about one ampere
for each sixty (60) inches of surface coated.
Gold. — Cyanide of gold and potassium cyanide make the best solution
for plating with gold. The solution is prepared in the same manner as the
silver solution just described, using chloride of gold in place of chloride of
silver. The electrical resistance of the bath ic controlled by the quantity
of cyanide, the more cyanide the less the resistance, cut an excess of
cyanide produces a pale color. Hot baths for hot gilding require from 11 to
20 grains of gold per quart of solution and a considerable excess of cyanide.
Baths for cold gilding and for plating should have not less than 60 grains
per quart and may have as much as 320 grains, this quantity being used with
a dynamo current for quick dipping.
Wickel. —The solution now almost universally used for nickel plating
is made up from the double sulphate of nickel and ammonia, with the
addition of a little boracic acid under certain conditions.
The double salt is dissolved by boiling, using 12 to 14 ounces of the salts
to a gallon of water, the bath is then diluted with water until a hydrometer
shows a density of 6.5° to 7° Baume.
Oast anodes «.re to be preferred as they give up the metal to the solution
more freely. Anodes should be long enough to reach to the bottom of the
work and should have a surface greater than that of the objects being plated.
Current strength should be moderate, for if excessive the work is apt to
be rough, soft or crystalline, voltage may vary from 3.5 to 6 volts and the
most suitable current is from .4 to .8 ampere per 15 square inches surface
of the object. Zinc is the only metal requiring more current than this, and
takes about double the amount named.
A nickel bath should be slightly acid in order that the work may have a
suitable color. An excess of alkali darkens the work and an excess of acid
causes " peeling."
Iron. — A hard Avhite film of iron can he deposited from the double
chloride of iron and ammonia, which can be prepared by the current
process. It is somewhat used for coating copper plates to make them
wear a long time, the covering being renewed occasionally.
The Electro-motive Forces suited to the different metals are : —
Copper in sulphate, Volt, ^-l*
" cyanide, . . 4* - 6-
Silver in " 1- -2-
Gold in " -5-3-
Nickel in sulphate, "5-1"
The Resistance will depend on the nature of the surface. "Work is
best effected with about equal surface of anode and objects, and the coating
will be more even, the greater the distance between them, especially where
there are projecting points or rough surfaces.
Copper and silver should never show any sign of hydrogen being given off
at the objects; gold may show a few bubbles if deep color is wanted.
Nickel is always accompanied with evolution of hydrogen, but the bath
should not be allowed to froth.
The Rate of Deposit is proportional to current, as described under
the head of " Electrolysis," in the proportions given in the table of electro-
chemical equivalents except in the case of gold, the equivalent of which in
combination with cyanogen is 195.7, but subject to modifications dependent
upon the hydrogen action just described; there is also a partial solution of
the metal, so that there is always a deduction to be made from the theoret-
ical value. Thus : —
Gold gives about 80 to 90 per cent.
Nickel " 80 to 95
Silver " 90 to 95
Copper "98 "
ELECTROLYTIC REFINING OP COPPER. 681
An ampere of current maintained for one hour, which serves as a unit of
quantity called the " ampere hour," represents
Gramme 0376 Grain 58
Ounce Troy 00121 Ounce Avoir. . . .00132
which multiplied by the chemical equivalent will furnish the weight of any
substance deposited.
Separation of jfletals.
Aluminum. — There are several successful processes in use. HaWs
process is operated on a large scale at Niagara Falls. The cell is an iron
vessel lined with carbon, which forms the cathode, and contains molten
cryolite (sodium and aluminum double fluoride), into which is fed the
alumina, Al20-6, ; this is electrolysed, the oxygen passes oft as C02 at the
anode, which is a carbon cylinder. The aluminum having a higher specitic
gravity than the fluoride, settles at the bottom of the bath, from which it is
tapped or ladled off. The temperature of the bath is 1,600° to 1,800° Fahr.,
while from 7 to 8 volts are required, and a current of 5,000 amperes is used,
producing 1 pound of metal per 10 K. W. - hours. About 1 pound of carbon
electrode is consumed per 1 pound of aluminum produced.
The Cow les process is chiefly for producing alloys of aluminum and sili-
con with copper and iron. Corundum (aluminum oxide) or bauxite is mixed
with iron tilings or granulated copper, and is smelted in a furnace as fol-
lows : — The furnace pit is built of fire brick with holes in the ends for
admitting the carbon electrodes ; the furnace is lined internally with limed
charcoal, the lime keeping apart the carbon particles, which would other-
wise connect and make a short circuit. The carbon electrodes are brought
together and the charge of corundum, &c, is put in, the furnace is then
covered, and the current is gradually started. The electrodes are then
gradually separated, and the current is increased and maintained for about
an hour, when the reduced metal is drawn from the bottom of the furnace.
\Vith the cupro-aluminum process the current is easily maintained steady,
but with the ferro-aluminum process the conductivity of the charge varies
greatly during the process, and regulation of current is very difficult.
Electrolytic Refining- of Copper.
The most important application of electrolytic metallurgy is the refining
of copper which is carried on at many places in this country and abroad on
a very large scale. The crude copper obtained from the smelting furnaces
is cast or rolled in the form of plates which are used as anodes in electro-
lytic cells. Theelectrolyte is a solution of copper sulphate acidulated with
sulphuric acid to increase its conductivity. The cathodes are usually thin
sheets of pure copper upon which the refined copper is electrodeposited,
the impurities are left behind in the anodes or solution, or as a scum or
sediment. In some cases the plates are arranged in series and in others in
parallel. The former has the advantage of requiring electrical contracts
to be made to the first and last plates only, whereas the parallel plan re-
quires connection to each plate; but in the series arrangement there is a
considerable leakage of current amounting to about 15 or 20 per cent. The
pressure required is from .2 to .4 volt per cell with a current density of 10 to
15 amperes per square foot. It requires in practice 400 to 475 ampere-hours
per pound of copper, the theoretical amount being 382.6 ampere-hours.
About 8 or 9 pounds of copper are produced per kiloAvatt-hour at about .3
volt which is the ordinary value. The cost of the process is about .7 cent
per pound of copper. A great advantage of the electrolytic method of refin-
ing copper is the fact that the silver and gold contained in the copper is left
behind in the sediment, from which it is extracted afterward usually by
electrolysis. The silver and gold thus recovered constitute an important
item in the output of an electrolytic refinery.
The Elmore process consists in depositing the copper on a revolving iron
mandrel which forms the cathode ; an agate burnisher travels along the
mandrel and presses the crystals of metal into a fibrous form which is said
to account for the superior strength of the metal deposited by this process.
The copper is removed from the mandrel by expansion, for which purpose
682 ELECTRO-CHEMISTRY. ELECTRO-METALLURGY.
steam is used. Specimens tested by Prof . Kennedy have broken at 27 to 41
tons per square inch with an extension of 5 to 1\ per cent. Tbe tubes may
be cut into sheets or strips for drawing into wire. The conductivity is very
high, being sometimes 2 or 3 per cent above Matthiessen's standard.
Silver is refined from copper bullion by taking anodes of the bullion \
inch thick and 14 inches square, and cathodes of sheet silver slightly oiled.
The electrolyte consists of water with 1 per cent of nitric acid. When the
current is started the copper and silver form nitrates of copper and silver
and free nitric acid from which the silver is deposited, leaving the copper
in solution. Trays are placed under the cathode for catching the deposited
silver, and if there is any copper deposited owing to the solution contain-
ing too little silver or a superabundance of copper, the copper falls into the
trays and is re-dissolved.
In the Moebius process the deposit is continually removed from tbe cath-
ode by means of a mechanical arrangement of brushes, and falls into the
trays above mentioned.
ELECTRIC HEATING, COOKING AND
WELDING.
HEAl UMTS AND EftUIVALEXTi.
The unit of heat in mechanics is the " calorie" or " lesser calorie," which
is the heat necessary to raise one cubic centimeter of water from 4° to 5°
Centigrade in one second.
The British Heat Unit, known as the " British Thermal Unit," or " B.T.U.,"
is the quantity of heat necessary to raise one pound of water from 60° to 61°
Fahrenheit, and is equal to 778 foot pounds, or 1055 Joules. The Joule is
the heat generated by a watt in a second.
Joule's Law shows that the heat generated in a conductor is directly
proportional to :
Its resistance, the square of the current strength, and the time during
which the current flows, or,
H— c2m.
According to Ohm's law, C= E -f- B, hence,
C*Et = J Gilt = EC't = ~
And calling Q the quantity of electricity flowing, then
and H= EQ or the heat = E.M.F. X Quantity,
in which E.M.F. is the difference of potential between the end of the
conductor.
The table on the following page clearly shows the equivalent values
of the electrical and mechanical units.
VAHIOUi METHODS OF UTILIZING THE HEAT
GENERATED BY THE EIECTSIC CERHEHT.
I. Metallic Conductors (Uninterrupted Circuit).
1. Exposed coils of wire or strips.
(a) Entirely surrounded by air.
(b) Wound around insulating material.
2. Wire or strips of metal imbedded in enamel.
(a) In the form of coils. { Leonard, Carpenter, Crompton, and
(b) In flat layers. j others.
3. Wire or strips of metal imbedded in asbestos.
(a) In the form of coils.
(6) In flat layers.
4. Wire imbedded in various insulating compounds.
(a) Crystallized acetate of sodium, etc. Tommasi.
5. A Film of metal.
(a) Rare metal fired on enamel. ) Prntnptllw1,
(6) Rare metal fired on mica. f Riometheus.
(c) Silver deposited on glass. Reed.
6. Sticks of metal.
(a) Crystallized silicon in tubes of glass. Le Roy.
(b) Metallic powder mixed with clay and compressed- Parville\
684 ELECTRIC HEATING, COOKING, AND WELDING.
£
.1
A
,_;
1
O o3
P
rt • • 2
©
So
N
ft
^=H
S JS ft
§
1
1 '8S1
do «i;bos
3 £ 22l©
{ft
o 0
O
3
^ ^ ^ a; • -?
3
t ■"! 3 ^ "- £ - ~
■~ a ~
t lo ci «
^38§
•+1 ^ N ^J ^mM^'J^
1-1 th c-icq^io^rt
t"i ':: ~ - "'S'j
p
w|
© . .
5 El
i = ll
al^ll
0 £+-l 0
IT
© 2
-H i
5
ft 0
p
ft G
• ■'^'g S3
©
5 aa^S »
p . fe ©
^ ft
o
SgS. t,o > 0
O m
0 . b
o~ p,-S
3 ft "S
g
<* £
^^§
a ^S % ^
H
• © "3 ft" •"£ 'r2 *"- 3 "
£ .S^ 2 % %£ & x, 2
.- co c 2: -f ~r 1- 1- 2 -* .£
t> l . CO tQ CI ■■# L . . <>J t
5 -' ©ft
S{£ aft-*
-; 23 4 <■- +"
12 7"; - -
2 fcicco ^ 0
^2888
P '2 ft!» '?
iJ0H S^ sj
^P©i^i
P CO <M CO lO Tj<
•^O -fMO ;
^*=>co^-=3
a" co rt.
p
II
P
©
-111
ha
II
t^ ©_a
ffl
^ ^ H
5 "2 ft
,- CO
■ u
(§
^ ^ «H
©-P
5
o
a" © P, ©
'S 0 s
N ^ P
^ . ^
© . Oh^
2 5 a 2 -3 ° 2 •
f1 -a 3 7" 2 ;3J2 -"■'-
1
so2> 9
g £ . £ g pj © ® "§
© .s^,«rtaH, ci
!>
©
"3
2 2-9 2 &§££ ^0
+5 T • «* © >fe rife
^"Sj? "S lo *o
|i-*r^|i2«|s3
&2?'2!-£J22;2f^2
s^ -h-h coct^'^ m1-1 ?
--+:,- :, ■ _ ~ x !- ■'- ~
0:0 co _^ ££ -^._- -t -;1 •"
rHH Cl" -# t- MIO °? ^ CO
HHNMMM-: CO (M
L~ i-Tcf<N *"2 OJ tH
s
*u
fl;11
oJJ
**,.&
iH '. fl
p
W O
^,
If
ELECTRIC COOKING. 685
II. Heat of the Electric Arc (Interrupted Circuit).
1. The Electric Furnace. Siemens, Cowles, Parker, and others.
2. Heat of Arc acting upon material, producing local fusion.
Meritens, Werdemann, Bernardos, Howells, and others.
3. Welding by bringing metals in contact. Thomson.
4. Deflecting Arc by Magnet. Zerener.
III. Hyflro-electrotliermic System, or Water-Pail JT©rge.
Burton, Hoho and Lagrange.
Referring to the above classification, Section I., the methods referred to
under subhead 1 and 3 require no further explanation. The method under
subhead 2 consists in imbedding the resistance wire in some fireproof insu-
lation such as enamel or glass. This insulation is of comparatively poor
quality as a conductor of heat, and so thin that it affords the least possible
resistance to the flux of heat from the heated resistance.
GFomnaasi (subhead 4) imbeds the coil of wire in a material having great
latent heat of fusion, such as crystallized acetate of sodium, hyposulphide of
sodium, etc., the principle being that the material acts as a reservoir of
heat. The heaters, it is claimed, are first heated by immersion in. hot
water, then the current is turned on, and after they have been brought
to the desired temperature, the current is cut off, and the heaters remain
active for about four hours more.
The Prometlieus System (subhead 5) is extensively used in Ger-
many, and consists of firing a broad strip of rare metal on to an enamel,
which forms the outside of the vessel. The efficiency of this apparatus has
been found by Prof. Dr. Kittler to be between 84 and 87 per cent.
The Meed method of depositing a layer of silver on glass was described
in the Electrical World, June 5, 1895.
The method employed by JLe SSoy (subhead 6) consists of inclosing
sticks of crystallized carbon, having a specific resistance 1333 as high as that
of ordinary arc light carbon, in glass tubes. For 110 volts rods are ICO mm.
long, 10 mm. wide, and 3 mm. thick. This takes about 150 watts ; and
having a surface of 26 sq. cm., the dissipation of heat is at the rate of about
5 kg. calories per sq. cm. of surface, or an absorption of electrical energy of
6 watts per sq. cm. of surface.
Parrille (VEclairage Elec, Jan. 28, 1899) uses rods of metallic
(quartz, kaolin) powder, mixed with fusible clay, compressed under a press-
ure of 2000 kg. per sq. cm., and baked at a temperature of 1350° C. A rod 5
cm. long, 1 cm. wide, 0.3 cm. thick, has a resistance of 100 ohms, and absorbs
16500 watts per kg. One quart of water boils in 5 minutes with 15 amp. and
110 volts.
The above methods are utilized in the construction of electric cooking and
heating apparatus, while those enumerated under sections II. and III. are
employed for purposes of welding, smelting, and forging.
EIECTRIC COOKIIG.
Cost of Operating- Electric Cooking- utensils.
On account of the number of variables which enter into the determination
of the cost of electric heating and cooking, it is impossible to present any
general data. These variables mav be classified as follows :
1. Cost of current. 2. The skill of the operator from the cooking stand-
point. 3. The skill of the operator from the standpoint of using the elec-
trical apparatus economicallv. 4. The type of apparatus employed.
It is possible, however, by assuming an arbitrary cost for current, to
calculate the cost of heating a given quantity of water. Let it be required
to heat one gallon of water at a temperature of 50° F. (10° C), without
actually boiling it, to the boiling-point, or 100° C. ; it would then be elevateu
90° C. Hence 3786 cubic centimeters would be raised 90° C. or 3786 x 90 = o40,-
740 water-gramme-degrees-centigrade of heat are produced. The unit cor-
686 ELECTRIC HEATING, COOKING, AND WELDING.
responding to a water-gramme-degree-centigrade is the calorie, which
requires an expenditure of 4.18 joules, so that the work required to be done
in raising a gallon of water to the temperature of 100° C. is equal to 340,-
740 X 4.18= 1,424, 293 joules. Assuming the cost of electric current, in large
quantities, to be 5 cts. per kilowatt-hour (which is equal to 3,600,000 joules,
as 1 joule = 1 watt per second), the cost of raising one gallon of water to
the boiling-point is approximately 2 cents. If we assume the current to cost
15 cts. per kilowatt-hour, then the cost would be 6 cents.
This calculation, however, is strictly theoretical, as the assumption is
made that all the heat generated is utilized in raising the temperature of
the water. This, of course, is not the case, as a certain amount of the heat is
transmitted to the metal vessel and the air during the time of the opera-
tion (about 15 minutes). Assuming the efficiency of the vessel to be 70 per
cent, which represents the ratio between the useful and the total developed
heat, then the actual cost of heating a gallon of water from 10° to 100° C. at
a cost for current of 5 cts. per kilowatt-hour would be 2 x -V0op- = 2.86 cents,
or at 15 cents per kilowatt-hour would be 3 X 2.86 = 8.58 cents.
Before proceeding to cite actual results achieved with electric cooking
apparatus, the following table, furnished by the American Electric Heating
Corporation, may be of value :
Time .Required.
Stoves and griddles are ready for use, i.e., have reached a temperature for
cooking, in from 5 to 8 minutes from time current is turned on. Broiler, 12
to 14 minutes ; Oven, 20 minutes ; Farina Boilers, 6 to 8 minutes ; Chafing-
dishes, 10 minutes ; Stew-pan, 5 minutes ; Laundry-irons, 8 to 10 minutes
very hot ; Tailor's Irons, 6 to 12 minutes ; Foot-warmers, 5 to 15 minutes ;
Curling-iron Heater, 6 to 8 minutes ; Plate-Avarmer, 10 minutes ; Soldering-
iron, 5 to 8 minutes ; Glue-pots, 15 to 30 minutes.
To boil water, starting with water and heater cold, Stew-pan, 1 pint 16
minutes ; small Teakettle, 1 pint 15 minutes ; Five O'clock, 1 quart 18
minutes ; 6 inch stoves (using suitable flat-bottom vessel), 1 quart 18 min-
utes ; Teakettle, 1 quart 15 minutes, 2 quarts 28 minutes ; Hot-water Urns,
1 gallon, one-half full in 35 minutes, full in one hour ; 2 gallons, one-half
full in 50 minutes, full in 1 hour 20 minutes ; three gallons, one-half full in
37 minutes, full in 60 minutes ; 5 gallons, one-half full in 30 minutes, full in
55 minutes. Very hot water, about 175 degrees F., can be had in about two-
thirds the time stated for boiling. Water-heaters can be made to boil the
quantities mentioned in about half the time, but the current required
would be nearly double that mentioned for any standard articles. Coil-
heaters when immersed in a covered vessel give the following results, using
maximum current, and after water boils will maintain it at the boiling-
point with one-fourth of the maximum.
(400 Watts) 1 pt., 10 minutes ; 1 qt., 19 minutes ; 2 qts., 35 minutes.
(660 " ) 1 pt., 7 minutes; 1 qt., 12 minutes; 2 qts., 21 minutes;
3 qts., 28 minutes.
(880 " ) 1 pt., 5 minutes ; 1 qt., 8 minutes ; 2 qts., 15 minutes ; 1
gal., 28 minutes.
(1100 " ) 1 qt., 6 minutes ; 1 gal., 18 minutes ; 2 gals., 35 minutes ;
3 gals., 45 minutes.
(1650 " ) 2 qts., 8 minutes ; 1 gal., 14 minutes ; 2 gals., 26 minutes ;
3 gals., 35 minutes.
Practically the same results are obtained with immersion disk-heaters of
the same Avatt capacity.
Mr. Colin (Bui. Soc. Int. des Elec, Feb., 1897) found that the surface tem-
perature of a broiler should be from 270° to 280° C. The total heat emitted
will then be 11922 calories per hour. The surface of such a broiler 20 cm. by
14 cm., will require 140 watts per sq. decimeter for ordinary heating ; 120
watts will give the best results.
C. O. Grimshaw (Lnnd. Elec, Dec. 23, 1898) estimates the cost of electric
cooking, based on 8 cts. per kilowatt-hour, as follows : —
ELECTRIC COOKING.
687
Apparatus.
Capacity.
Cost per Hour
in Cents.
Cost for One
Operation from
Cold in Cents.
Kettle
Griller
Saucepan ....
Fish kettle . . .
l£ pints
2 chops
2 quarts
16 quarts
2.56
4.48
3.2
9.12
0.96
1.06
1.6
At the Carmelite Hospice, Victoria Free Park, Niagara, an electric range
has a heating surface of 6 sq. ft., each square foot consuming 15 amp. at 110
volts. The two small ovens consume 23 amp. each, the large one 50 amp.
The oven equipment is designed for four 25 lb. roasts at one time. In the
small ovens bread is baked in IS minutes. The current for water heating,
cooking, and lights costs $25 per H. P., while the 75 H. P. used in heating
the corridor and bedrooms is secured at about one-fifth this price per H. P.
Mr. Dowsing, in the London Electrical Revieiv, refers to a trial with a gas
oven in which it was found that out of a total of over 13,000 heat units
required in roasting a joint of 8.5 lbs. 2,203 units were actually used in the
food itself, or about 16 'per cent.
In a lecture before the A. I. E. E. in 1897, Prof. J. P. Jackson made the
following statement :
To determine the relative cost of cooking with electricity and coal, the
same foods were cooked on the No. 8 Othello coal stove ordinarily used by
the family. The coal was carefully weighed. The results gave an average
of 12.6 pounds per meal, which at $5.00 per ton gives a cost of 3.15 cents per
meal. The results show the cost of cooking by coal to be about 19 per cent
of the cost of cooking by electricity.
Prof . Dr. Kittler made a series of tests of the " Prometheus " cooking
apparatus, and from a table prepared by him the following data are taken:
Quantity of
Water Heated.
Time
required,
Seconds.
Energy con-
sumed,
Watt Seconds
Temp.
Incr.
Fahr.
Efficiency
of
Apparatus.
300 grams
400 grams
255
327
131,835
169,400
191.3
191.3
83.9%
87.1%
Mr. P. E. Crompton accurately measured the temperature of a number of
electric heating utensils, and utilized the facts obtained in the compilation
of the following table :
Time
Energy
Cost at
Temp
m
in
8 cts. per
Fahr.
Minutes.
K.W. hrs.
K.W. hr.
Scale
50
10
0.116
.92
257
14
0.164
1.34
332
21
0.248
2.00
337
30
0.404
3.22
400
Table I. — Showing en-
ergy required to raise a
heater plate from 50° F.
to 400° F. in half an
hour.
688
ELECTRIC HEATING, COOKING, AND WELDING.
Time
in
Minutes.
Energy
in
K.W.hrs.
Cost at
8 cts. per
K.W. his.
Temp.
Fahr.
Scale.
Table II. — Shows the
energy required for a
radiator plate such as
is used for heating the
air of a room.
10
30
40
50
60
0.091 '
0.277
0.350
0.430
0.500
0J728
2.8 '
3.44
4.00
50
171
240
257
2G1
264
Table III. — Shovrs the
energy required to boil
1 lb. of water in a kettle.
18
'0.675'
0.64 '
50
212
Table IV. — Shows en-
ergy required by a
smaller kettle contain-
ing | lb. of water, i.e.,
sufficient for two cups
of tea.
12
O.651'
0.4
50
212
This sIioavs that the efficiency of the operation in Table III. is 63 per
cent, and that in Table IV. is 71.5 per cent.
The following curves shoAV the rise of temperature in the case of a heater
plate and a radiator and also the energy consumed:
1/
-O^,
J^**:
f
^
&
*>
<^
^<^^'
^
;
TIME IN MINUTES
Fig. 1.
Efficiency of Heating- Apparatus.
In the foregoing references it Avill be seen that the efficiency of electric
cooking apparatus varies from about 63 per cent to 90 per cent (for ovens),
depending upon a number of variable conditions, such as time, size, quantity
to be heated, temperature rise, etc.
According to Mr. Crompton, the efficiency of an ordinary cooking-stove
using solid fuel is only about 2 per cent, 12 per cent being wasted in obtain-
ELECTRIC CAR HEATING. 689
ing a glowing fire, 70 per cent going up the chimney, and 16 per cent being
radiated into the room.
In a gas-stove, considering that the number of heat units obtainable from
the gas at a certain price is but small compared with solid fuel, the venti-
lating current required for the operation alone consumes at least 80 per
cent of the heat units obtained by burning the gas.
In the case of an electrical oven, more than 90 per cent of the heat energy
can be utilized ; and thus, although possibly 5 to 6 per cent only of the heat
energy of tbe fuel is present in the electrical energy, 90 per cent of this, or
4£ per cent of the whole energy, actually goes into the food, and thus the
electrical oven is practically twice as economical as any other oven, whether
heated by solid fuel or by gas.
ELECTRIC RAUIATORi,
Unless electricity is produced at a very low cost it is not commercially
practicable to heat residences or large buildings. While this is true, the
electric heater still has a field of application, in heating small offices,
bathrooms, snuggeries, cold corners of rooms, street railway waiting
rooms, the summer villa on cool evenings, and in mild climates a still
wider range. It has the peculiar advantage of being instantly available,
and the amount of heat is regulated at will. The heaters are perfectly
clean, do not vitiate the atmosphere, and are portable.
According to Houston and Kennelly, one joule of work expended in
producing heat will raise the temperature of a cubic foot of air about
is ° F-
The amount of power required for electrically heating a room depends
greatly upon the amount of glass surface in the room, as well as upon
the draughts and admission of cold air.
In order to make a comparison between heating an ordinary city house
by means of coal burnt in a furnace and by electricity furnished by a cen-
tral station, let it be assumed that 100 lbs. of coal are consumed per day in
the furnace. Assuming the furnace to have an efficiency of 50 per cent,
50 lbs. of coal are utilized throughout the building in the form of heat.
Reducing this to actual horse-power we have
700,000
700,000 X 778 = 544,600,000 ft.-lbs.
544,600,000 _
33,000
16,503
: 16,503 H.-P. minutes.
- = 275 H.-P. hours.
Assuming that a H.-P. hour is furnished at 5 cents the cost would be
275 X .05 = $13.75.
ELECTRIC CAM HEiTIAG.
At the Montreal meeting of the American Street Railway Association in
1895, Mr. J. F. McElroy read an exhaustive paper on the subject of car-
heating, from which the following abstracts are taken :
In practice it is found that 20,000 B. T. U. are necessary to heat an 18 to
20 foot car in zero weather. When the outside temperature is 12J- ° F.
only 16,000 B. T. U. are required, etc., which shows the necessity of hav-
ing electric heaters adjustable.
The amount of heat necessary in a car to maintain a given inside tem-
perature, depends on : 1. The amount of artificial beat which is given to it.
2. The number of passengers carried. The average person is capable of
giving out an amount of heat in 24 hours which is equal to 191 B. T. TJ.
690 ELECTRIC HEATING, COOKING, AND WELDING.
Cost of Car Heating-.
The following table was compiled by Mr. McElroy from the reply re-
ceived from the Albany Railway Company :
Average fuel cost on Albany Railway, per amp. hour = .241 cent.
Average total cost for fuel, labor, oils, waste, and packings per amp.
hour = .423 cent.
Cost of fuel per hour for heating a car
with electric beaters with coal at
$2.00 per 2000 lbs.
Position of Switch.
Amperes equal.
2.88
6.88
8.09
cts.
cts.
cts.
.58
1.40
1.62
.54
1.30
1.51
.52
1.27
1.47
.48
1.17
1.36
Simple high speed condensing . .
Simple low speed condensing . .
Compound high speed condensing
Compound low speed condensing
2.41
2.24
2.20
2.03
Average Cost Per Dav for Stores.
33 lbs. of coal at $4.55 per ton $.075
Repairs 005
Dumping and removing coal and ashes, coaling up
and kindling fire, including cost of kindling,
and part of cleaning car 100
Removing stoves for summer, installing for win-
ter, repairing head linings, repainting, etc.,
average per day 0125
Total $.1925
ELECTKIC WELDIKG.
691
EIECTKIC IROXS EOIft DOMESTIC AEf» ODUII-
TBIAI PURPOSES.
Comparing the hand-irons heated by gas with those heated electrically, it
is claimed that if gas can be purchased at 81.25 per 1000 cu. It., and the
cost of electricity is about 1 cent per H. P., the two systems are about on a
par, as far as cost only is concerned.
According to the American Electric Heating Corporation, the power con-
sumption for the various types of irons is as follows : —
Watts
4 lbs. Troy Polishing, diamond face 330
Q lbs. Small Seaming (can be connected to lamp socket) . . . 200
4 lbs. Gentleman's Small Hat Iron 200
5£ lbs. Light Domestic 500
5A- lbs. Light Domestic, round nose ; . . 500
7 "lbs. Domestic 600
9 lbs. Heavy Laundry 680
9 lbs. Hatters' 550
9 lbs. Corset 500
15 lbs. Hatters' Factory 550
5£ lbs. Morocco Bottom 500
Morocco Bottom, round nose 500
XIECTRIC WELDHfG JLND FOR^OG.
The current employed in electric welding may be either continuous or
alternating. By the use of alternating currents, a slightly more uniform
heating of the contact surfaces is obtained, because alternating currents
tend to develop a greater heat at the surface of a large mass than at the
central portions.
Thomson Electric Welding* Process.
The principle involved in the system of electric welding, invented by
Prof. Elihu Thomson, is that of causing currents of electricity to pass
through the abutting ends of the pieces of metal which are to be welded,
thereby generating heat at the point of contact, which also becomes the
point of greatest resistance, while at the same time mechanical pressure is
applied to force the parts together. As the current heats the metal at the
junction to the welding temperature, the pressure follows up the softening
surface until a complete union or weld is effected ; and, as the heat is first
developed in the interior of the parts to be welded, the interior of the joint
is as efficiently united as the visible exterior.
Horse-Power Used in Electric "Welding.
The power required for the different sizes varies nearly as the cross sec-
tional area of the material at the joint where the weld is to be made.
Within certain limits, the greater the power, the shorter the time ; and
vice versa.
The following tables are based upon actual experience in various works,
and from very careful electrical and mechanical tests made by reliable
experts. The time given is that required for the application of the current
only.
Round Iron or Steel.
Diameter.
Area.
H.-P. Applied
to Dynamo.
Time in
Seconds.
iin.
.05
2.0
10
IS:
.10
4.2
15
.22
6.5
20
fin.
.30
9.0
25
Jin.
.45
13.3
30
692 ELECTRIC HEATING, COOKING, AND WELDING.
Extra, Heavy Iron JPipe.
Inside
Area.
H.-P. applied
Time in
Diameter.
to Dynamo.
Seconds.
i in.
.30
8.9
33
f in
.40
10.5
40
1 in
.60
16.4
47
li in
.79
22.0
53
1J in
1.10
32.3
70
2 in
1.G5
42.0
84
2h in
2.25
63.7
93
3 in
3.00
96.2
106
General Table.
Iron and Steel.
Copper.
Area in
Time in
H.-P. applied
Area in
Time in
H.-P. applied
sq. m.
Seconds.
to Dynamos.
sq. in.
Seconds.
Dynamos.
0.5
33
14.4
.125
8
10.0
1.0
45
28.0
.25
11
23.4
1.5
55
39.4
.375
13
31.8
2.0
65
48.6
.5
16
42.0
2.5
70
57.0
.625
18
51.9
3.0
78
65.4
.75
21
61.2
3.5
85
73.7
.875
22
72.9
4.0
90
83.8
1.0
23
82.1
Axle Welding-.
V round axle requires 25 Horse-power for 45 seconds.
\" square "
\\" round "
30
" 35
\\" square "
2// round "
40
75
2" square "
90
The slightly increased time and power required for welding the square
axle is not only due to the extra metal in it, but in part to the care which it
is best to use to secure a perfect alignment.
\\" x §"
2" xf
2" xf
Tire "Welding-.
tire requires 11 Horse-power for 15 seconds.
23 "
23 "
62
ictual
The time above given for welding is of course that required for the a
application of the current only, and does not include that consumed ny
placing the axles or tires in the machine, the removal of the upset, and
other finishing processes.
From the data thus submitted, the cost of welding can be readily figured
for any locality where the price of fuel and cost of labor are known.
HYDRO— ELECTROTHERMIC SYSTEMS. 693
HYDBO-E&ECTIIOTHERMIC SYSTEMS.
XSolio and Eagrange System.
In this system an electrolytic bath is employed, into which an electric
current of considerable E.M.F. is led, passing from the positive pole which
forms the boundaries of the bath and presents a large surface to the elec-
trolyte and thence to the negative pole, consisting of the metal or other
material to be treated, and which is of relatively small dimensions.
Through the electrolytic action hydrogen is rapidly evolved at the nega-
tive pole and forms a gaseous envelope around the pole ; as the gas is
a very poor conductor of electricity, a large resistance is thus introduced
in the circuit, entirely surrounding the object to be treated. The current in
passing through this resistance develops thermal energy, and this is com-
municated to the metal or other object which forms the negative pole.
This system has been extensively used in England, and is described in
The Electrical World, Dec. 7, 1895.
ISurton Electric Eorge.
In a patent granted to George D. Burton on an electrolytic forge, the
portion to be heated is placed in a bath consisting of a solution of sal soda,
or water, carbonate of soda, and borax. The tank is preferably made of
porcelain or fire-clay. The anode plate has a contact surface with the
liquid much greater than the area of contact of the article to be heated.
This plate is composed of lead, copper, carbon, or other suitable conducting
material.
Zerener System.
In this system an arc is used in combination with a magnet which deflects
the arc, making a flame similar to that of a blow-pipe, but having the tem-
perature of the arc. The apparatus contains a self-regulating device
which is driven by a small electric motor ; for welding iron a current of 40 to
50 amperes at 40 volts will suffice for strips of metal three mm. thick.
Hernardos System.
In this system the article to be operated upon is made to constitute one
pole of the electric circuit, while a carbon pencil attached to a portable
insulated holder, and held by the workman, constitutes the other pole, the
electx-ic arc — which is the heating agent of the process — being struck
between the two poles thus formed. This system has been used extensively
in England for the repair of machinery. The Barrbeat-Strange Patent
Barrel Syndicate use this system for the welding of the seams of sheet-
steel barrels.
Voltex Process for "Welding- and Brazing-
Consists in the use of an electric arc formed between two special carbon
rods inclined to each other at an angle of about 90°. The whole apparatus
can generally be held in one hand. With gas and coke, gas costing only
70 cents per 1000 cubic feet, it is claimed the complete cost of brazing and
filling up a bicycle frame is $1.43, while with the Voltex process, at 6 cents
per kilowatt hour, it is only 46 cents.
Stassano Process of Electric Smelting
Consists of heating, in an arc furnace, briquettes composed of iron ore,
carbon, and lime made into a paste with tar. The smelting process occurs
in a blast furnace, the iron being reduced, and the siliceous matter of the
ore slagged off.
Annealing- of Armor JPlate.
The spot to be treated is brought to a temperature of about 1000 ° F.
The current used is equivalent to 40,000 amperes per square inch, a density
which is only possible by the use of cooling by water circulation. The
operation generally takes seven minutes.
694 ELECTRIC HEATING, COOKING, AND WELDING.
Electric Mail Welding-.
The " Electric " joint, applied by the Lorain Steel Co., is made by welding
plates {on both sides of the web of the rail. The plates shown in Fig. 4
are 1 inch by 3 inches, by 18 inches, and have three bosses, three welds
OIAGRAM OF CONNECTIONS OF RAIL WELDER
(^T
t • trolley
c . b • circuit breahir
r.r-rheostats
m • icotqr
b - booster
RT' ROTARY TRANSFORMER
W.T WELDING TRANSFORMER
3 Vf; SWITCH
SKETCH OF BAR.
USED IN WELDING
o
<3
... *&■,
8'
1
¥
, X
|
(«0i) * ' "
Web Plates
Figs. 3 and 4. — The Lorain Steel Company Method of Electric Welding.
being made at each joint. Great pressure up to 35 tons is maintained on
the joint whilst making and cooling. The welding current runs as high as
25,000 amperes. The connections are shown in Fig. 3.
FT§E DATA.
In a lecture on " The Eating and Behavior of Fuse Wires," before the
A. I. E. E., in October, 1895, Messrs. Stine, Gaytes, and Freeman arrived at
the following conclusions :
1. Covered fuses are more sensitive than open ones.
2. Fuse wire should be rated for its carrying capacity for the ordi-
nary lengths employed.
2 (a). When fusing a circuit, the distance between the terminals
should be considered.
FUSE DATA. 695
On important circuits, fuses should be frequently renewed.
The inertia of a fuse for high currents must be considered when
protecting special devices.
Fuses should be operated under normal conditions to ensure cer-
tainty of results.
Fuses up to five amperes should be at least 1| inch long, one-
half inch to be added for each increment of five amperes
capacity.
Round fuse wire should not be employed in excess of 30 amperes
capacity. For higher currents flat ribbons exceeding four
inches in length should be employed.
(For additional data on Fuses see p. h60.)
SOME NOTES ON THE
OPERATION OP ELECTRIC MINING PLANTS.
From Pamphlet by General Electric Company.
Mr. F. J. Piatt of the Scranton Electric Construction Company, Scranton,
Pa., gives some figures on electric haulage. They are from plants which
have been in operation for one year or longer. The expenses given are the
actual figures for labor, oil, repairs, etc.
In figuring the cost of mule-power, the cost per mule has been taken at
50 cents per working-day, which includes feed, attendance, medicine, shoe-
ing, harness, and the item of mortality. Depreciation on the electric plant
is figured at 5%, and is given per working-day.
The first plant on whicli Mr. Piatt presents figures is the Green Ridge
Colliery, installed in March, 1895, for Mr. O. S. Johnson, in the city of
Scranton.
The Green Ridge Colliery.
The Green Ridge Colliery plant consists of one 100 H.P. automatic, high-
speed engine, and one 75 H.P. dynamo, with switchboard and station
equipment, all of which are installed in a frame building 30 feet by 45 feet.
From the dynamo a feeder wire is run down the slope 1,000 feet to the
main gangway, where a 6g- ton electric locomotive is in operation over about
1\ miles of trolley road. This locomotive gathers trips from three different
points in the mines, and delivers them to the foot of the outside slope.
The main gangway, whiuh is very crooked, is about 3,100 feet long, and
branching from it are two other roads, one of which is 1,000 feet and the
other 2,100 feet in length. For the past year this locomotive has made a
daily average of twenty trips, each trip consisting of eight cars, which is
very much below its capacity.
The grades on the main roads are about 1% in favor of the loaded and
ag mist the empty cars. On the 1,000 foot branch the locomotive has about
500 feet of 3% and 500 feet of \% grade against the empty cars. On the 2,100
foot branch the grades are very uneven, and most of them are against the
loaded cars. The grades of this road, against the loaded cars, consist ap-
proximately of 150 feet of 7% grade, 500 feet of 2% grade, 350 feet of 5£%
grade, and 450 feet of 3i-% grade.
This 6£ ton locomotive has been hauling trips of four cars up these grades
ever since it was installed, and on some days has hauled trips of five cars.
The roof of the mine is very low, being about five feet in the highest
places ; and as this height was obtained by blowing the roof over the center
of the road, the height on the main road will not average much over four
feet. This is one difficulty which would have been met had a steam loco-
motive been introduced instead of an electric locomotive.
Cost of Haulage at the Green Ridg-e Colliery.
After very carefully going over all the expenses connected Avith this
plant, the following results were obtained :
The plant cost .$7,625.18. Depreciation at 5% per year would amount to
$381.25, or taking 200 working-days per year the depreciation per working-
day would be $1.90.
Cost of operation per day is as follows :
Station Engineer $1.75
Motorman 1.75
Helper 1.60
Repairs 76
Depreciation 1.90
Oil and waste 20
Total $7.96
OPERATION OF ELECTRIC MINING PLANTS. 697
The coal hauled per day by the electric locomotive is 288 tons, at a cost
per ton, as shown above, of 2.76 cents.
To haul this coal by mule-power would require
Seventeen mules at 50 cents each $8.50
Three drivers at $1.45 each 4.35
Three drivers at $1.25 each 3.75
Four boys at $1.00 each 4.00
Total $20.60
This shows a cost for haulage by mule-power of 7.15 cents per ton, and a
saving by electric haulage of 4.39 cents per ton. On the 2S8 tons hauled per
day the saving is $12.64, and for a year of 200 working-days it amounts to
$2,528.00.
This locomotive has averaged 30 miles per day, making a total of about
12,700 miles since it was installed.
The expense of repairs taken on the basis of mileage is a trifle over two
cents per mile.
This statement shows the actual results at this particular plant, and
what is being saved per day. The number of mules saved in the above case,
is the number that it would require to haul an amount equal to the output
of the locomotive on any one day ; but it is doubtful if seventeen mules
would be able to do this work continually, as they would interfere with
each other on the main roads, and would not deliver the coal as regularly as
does the locomotive.
Among others referred to are the two electric haulage plants at the mines
of the New York and Scranton Coal Company, at Peckvilie, Pa. The
figures given are based on the expenses, of the year 1896.
The Hew York and Scranton Coal Company.
One of the mines operated by the New York and Scranton Coal Company
is known as The Sturges Shaft. The plant consists of a 160 H.P. engine and.
generator and a 6£ ton locomotive, operating over 4,500 feet of trolley road.
The cost of the plant was $6,103.00. The depreciation per year at 5% would
amount to $305.15, or for 200»wor king-days, $1.52 per day.
Cost of operation per day is as follows :
Motorman $1.75
Helper 1.25
Electrician .78
Repairs 1.03
Depreciation 1.52
Oil 24
Total $6.57
The coal hauled per day is 250 tons, at a cost per ton, as shown above, of
2.62 cents.
To haul this coal by mule-power would require
Fourteen mules at 50 cents each $7.00
Seven boys at $1.35 each 9.45
Total $16.45
This shows a cost for haulage by mule-power of 6.58 cents per ton, and a
saving by electric haulage of 3.96 cents per ton. On the 250 tons hauled per
day the saving is $9.90, and for a year of 200 working-days it amounts to
$1,980.00.
698 ELECTRICITY IN MINES.
The locomotive runs about 32 miles per day, and up to tbis time has
covered about 7,800 miles, with a cost for repairs of 2.7 cents per mile.
The otlier haulage plant operated by the New York and Scranton Coal
Company is located at the tunnel opening.
The cost of the plant was $7,039.00. The depreciation per year at 5%
would amount to $351.95, or for 200 working-days $1.75 per day.
Cost of operation per day is as follows :
Motorman $1.75
Helper 1.25
Electrician .78
Repairs .65
Depi-eciation 1.75
Oil 24
Total $6.42
The coal hauled per day is 600 tons, at a cost per ton as shown above, of
1.07 cents.
To haul this coal by mule-power would require
Twelve mules at 50 cents each $6.00
Six boys at $1.35 each 8.10
Total $14.10
This shows a cost for haulage by mule-power of 2.35 cents, and a saving by
electric haulage of 1.28 cents per ton. On the 600 tons hauled per day the
saving is $7.68, and for a year of 200 working-days it amounts to $1,536.00. ■»
The Hillside Coal and Iron Company.
The Hillside Coal and Iron Company was one of the first companies to
install electric haulage. At Forest City, Pa., they have two openings
operated by electric haulage from one power-house. The power-house con-
tains about 150 Kw. direct connected generators and one 62 Kw. belt driven
machine. At what is known as the "No. 2 Shaft" they have one twenty-
ton, eight-wheel locomotive, one twelve-ton single motor locomotive, and
one six-ton locomotive. At the Forest City Slope there is a twelve-ton
single motor locomotive. In addition to this, they have two electric pumps.
The plant here has been in operation since 1891, although the power-house
has been increased and rebuilt since the original plant was installed.
Mr. W. A. May, Superintendent, very kindly furnished the following
figures, which are on exactly the same basis as the figures in Mr. Piatt's
paper.
Cost of operation per day is as follows :
No. 2 Shaft. Forest City Slope.
Engineer of power-house . . . $1.20 $0.60
Motormen 4.23 2.11
Helpers (Brakemen) 3.20 1.60
Electrician 1.67 .83
Repairs to motors 5.95 4.09
Depreciation, 5% ..... . 5.20 2.60
Oil and waste .22 .14
Total $21.67 $11.97
Coal hauled per day — tons . . 989 541
Cost per ton $.0219 $.0221
This plant has never been operated with mules, but the mine foreman has
gone over the matter very carefully, and has made up the following estimate
of the number of mules it would require to do the work. He finds that it
would take fifty-three mules in the shaft and twenty-four in the slope.
Again using Mr. Piatt's figures, we get the folloAving cost per day for haul-
age by mule-power in No. 2 Shaft.
OPERATION OF ELECTRIC MINING PLANTS. 699
Fifty-three mules at 50 cents each $26.50
Twenty-four drivers at $1.48 each 35.52
Twenty-four team leaders at $1.04 each .... 24.96
Total $86.98
This shows a cost for haulage by mule-power of 8.79 cents per ton and a
saving by electric haulage of 6.60 cents per ton. On the 989 tons hauled per
day the saving is $65.27, and for a year of 200 working-days it amounts to
$13,054.00.
In the Forest City Slope the cost per day for haulage by mule-power is as
follows :
Twenty-four mules at 50 cents each $12.00
Ten drivers at $1.48 each 14.80
Ten team leaders at $1.04 each 10.40
Two runners at $1.59 each 3.18
Total • • • $40-38
This shows a cost for haulage by mule-power of 7.47 cents per ton, and a
saving by electric haulage of 5.26 cents per ton. On the 541 tons hauled per
day the saving is $28.46, and for a year of 200 working-days it amounts to
$5,692.00.
Mr. May remarks that in their particular case this estimate is not entirely
correct, as the expenses of the engineer, motormen, helpers, etc., are steady
expenses, their time on idle days being occupied with more or less running
around and making repairs about the mines. They have therefore made an
additional set of figures, using the actual number of days that the mines
were running, with the actual cost. The No. 2 Shaft ran 141J days, and the
Forest City Slope 138| days. Under these circumstances the cost of oper-
ation per day is as follows :
No. 2 Shaft. Forest City Slope.
Engineer of power-house . . . $2.84 $1.45
Motormen
Helpers (Brakemen) ....
Electrician
Repairs to motors
Repairs to line
Repairs to generators . . .
Fireman .
Depreciation, 5%
Oil and waste for motors . .
Oil and waste for generators
Interest on plant at 3% . .
Total
Coal hauled per day— tons .
Cost per ton
Then, again, taking their own figures on the cost of keeping Avhat mules
they have, they obtained the following cost per working-day for haulage in
No. 2 Shaft :
The depreciation on 53 mules, at $1.67 each per month, is $88.51, and for 12
working-days per month the depreciation per day is $7.38.
Depreciation on 53 mules $7.38
Feed for 53 mules (at 25 cents each per day per month) 33.12
Shoeing and harness 1.59
Care of mules 3.97
Forty-eight drivers and team-leaders 60.48
Total ,,,",. , , o $106.54
9.31
4.76
3.61
2.63
3.68
1.87
8.42
5.89
.46
.03
.61
.30
2.50
1.26
8.17
4.16
.35
.21
.74
.37
4.41
2.25
$45.10
$25.18
989
541
$.0456
$.0465
700 ELECTRICITY IN MINES.
This shows a cost for haulage by mule-power of 10.77 cents per ton, and a
saving by electric haulage of 6.21 cents per ton. On the 989 tons hauled per
day the saving is $61.42, and for a year of 141^ days it amounts to $8,615.75.
In the Forest City Slope the depreciation ligured as above on 24 mules is
$3.34, and the detailed cost of haulage by mule-power is as follows :
Depreciation on 24 mules $3.34
Feed for 24 mules (at 25 cents each per day per month) 15.00
Shoeing and harness .72
Care of mules 1.80
Twenty-two drivers, leaders, and runners . . . 28.38
Total $49.24
This shows a cost for haulage of mule-power of 9.10 cents per ton, and a
saving by electric haulage of 4.45 cents per ton. On the 541 tons hauled per
day the saving is $24.07, and for a year of 138| days it amounts to $3,339.71.
To the cost of the msle-power might yet be added interest at 3% on the
value of the mules and harness, but as it has not heretofore been included,
it has been left out here.
From the foregoing it will be seen that in either case there is a consider-
able saving in favor of electric haulage, and that this saving will increase
as the number of idle days increases and with the increase in tonnage in the
colliery.
LIGHTNING CONDUCTORS.
Views concerning the proper function and value of lightning rods, con-
ductors, arresters and all protective devices have undergone considerable
modification during the past ten years. There may he said to be four
periods in the history of the development of the lightning protector. The
first embraces the discovery of the identity of lightning with the disruptive
discharge of electrical machines and Franklin's clear conception of the
dual function of the rod as a conductor and the point as a discharger. The
second begins with the experimental researches of Faraday and the minia-
ture house some twelve feet high, which he built and lived in while testing
the effects of external discharges. Maxwell's suggestion to the British
Association, in 187(5, embodies a plan based upon Faraday's experiments, for
protecting a building from the effects of lightning by surrounding it with a
cage of rods or stout wires. The third period begins with the experiments
of Hertz upon the propagation of electro-magnetic waves, and finds its most
brilliant expositor in Dr. Oliver J. Lodge, of University College, Liverpool,
whose experiments made plain the important part which the momentum
of an electric current plays, especially in discharges like those of the
lightning flash, and all discharges that are of very high potential and oscilla-
tory in character. The fourth period is that of the present time, when
individual Hashes are studied ; and protection entirely adequate for the
particular exposure is devised, based upon some knowledge of the electrical
energy of the flash, and the impedance offered by appropriate choke coils
or other devices. For example, under actual working conditions, with
ordinary commercial voltages, effective protection to electrical machinery
connected to external conductors may be had with a few choke coils in
series with intervening arresters.
A good idea of the growth of our knowledge of the nature and behavior
of the lightning flash may be obtained from the following publications :
Franklin's letters.
Experimental Researches. . . . Faraday.
Report of the Lightning Rod Conference, 1882.
Lodge's "Lightning Conductors and Lightning Guards," 1892.
"Lightning and the Electricity of the Air." . . . McAdie and Henry,
FIG. 1 EFFECT OF THE ACTION OF LIGHTNING
UPON A ROD.
That a lightning rod is called upon to carry safely to earth the discharge
from a cloud was made plain by Franklin, and the effect of the passage of
the current very prettily shown in the melting of the rod and the point
(aigrette).
Here indeed was a clew to the measurement of the energy of the lightning
flash. W. Kohlrausch in 1890 estimated that a normal lightning discharge
would melt a copper conductor 5 mm square, with a mean resistance of 0.01
ohm in from .03 to .001 second. Koppe in 1895 from measurements of two
nails 4 mm in diameter fused by lightning, determined the current to be
about 200 amperes and the voltage about 20,000 volts. The energy of the
flash, if the time be considered as 0.1 second, would be about 70,000 horse
power, or about 52,240 kilowatts.
Statistics show plainly that buildings with conductors when struck by
lightning suffer comparatively little damage compared with those not pro-
vided with conductors. The same rod, however, cannot be expected to
serve equally well for every flash of lightning. There is> great need of a
classification of discharges based less upon the appearance of the flash than
upon, its electrical energy. Dr. Oliver J. Lodge has made a beginning with
701
702 LIGHTNING CONDUCTORS.
liis study of steady strain and impulsive rush discharges. " The energy
of an ordinary flash," says Lodge, " can he accounted for by the discharge
of a very small portion of a charged cloud, for an area of ten yards square
at the height of a mile would give a discharge of over 2,000 foot-tons
energy."
We must get clearly in our minds then the idea that the cloud, the air,
and the earth constitute together a large air condenser, and that when the
strain in the dielectric exceeds a tension of \ gramme weight per square
centimeter, there will be a discharge probably of an oscillatory character.
And as the electric strain varies, the character of the discharge Avill vary.
Remember too that the air is constantly varying in density, humidity and
purity. We should therefore expect to find, and in fact do, every type of
discharge from the feeble brush to the sudden and terrific break. Recent
experiments indicate that after the breaking-down of the air and the pas-
sage of the first spark or flash, subsequent discharges are more easily ac-
complished ; and this is why a very brilliant flash of lightning is often
followed almost immediately by a number of similar flashes of diminishing
brightness. The heated or incandescent air we call lightning, and these lines
of fracture of the dielectric can be photographed ; but the electrical waves or
oscillations in the ether are extremely rapid, and are beyond the limits of
the most rapid shutter and most rapid plate. Dr. Lodge has calculated the
rapidity of these oscillations to be several hundred thousand per second.
Lodge has also demonstrated experimentally that the secondary or induced
electrical surgings in any metallic train cannot be disregarded ; and, as in
the case of the Hotel de Ville at Brussels Avhich was most elaborately
pi'otected by a network, these surgings may spark at nodal points, and ignite
inflammable material close by.
While therefore it cannot be said that any known system of rods, wires,
or points affords complete and absolute protection, it can be said with con-
fidence that we now understand why " spitting-off " and " side " discharges
occur ; and furthermore, to quote the words of Lord Kelvin, that " there is
a very comfortable degree of security . . . when lightning conductors are
made according to the present and orthodox rules,"
Selection and. Installation of Rods. — The old belief that a
copper rod an inch in diameter could carry safely any flash of lightning is
perhaps true, but we now know that the core of such a rod would have little
to do in carrying such a current as a lightning flash, or, for that matter, any
high frequency currents. Therefore, since it is a matter of surface area
rather than of cubic contents, and a problem of inductance rather than of
simple conductivity, tape or cable made of twisted small wires can be used
to advantage and at a diminished expense.
All barns and exposed buildinr/s should hare lif/htninr/ rods with the neces-
sary points and earth connections. Ordinary dwelling-houses in city blocks
well built up have less need for lightning conductors. Scattered or isolated
houses in the country, and especially if on hillsides, should have rods. All
protective trains, including terminals, rods, and earth connections, should
be tested occasionally by an experienced electrician, and the total resist-
ance of every hundred feet of conductor should not greatly exceed one ohm.
Use a good iron or copper conductor. If copper, the conductor should
weigh about six ounces per linear foot ; if iron, the weight should be about
two pounds per foot. A sheet of copper, a sheet of iron, a tin roof, if with-
out breaks, and fully connected by well soldered joints, can be utilized to
advantage.
b
FIG. 2 AND 3 APPROVED CONDUCTORS AND FASTENINGS.
PERSONAL SAFETY DURING THUNDER-STORMS. 703
In a recently published* set of Rules for the Protection of Buildings from
Lightning, issued by the Electro-Technical Society of Berlin, Dr. Slaby gives
the results of the work of various committees for the past sixteen years
studying this question. The lightning conductor is divided into three parts,
— the terminal points or collectors, the rod or conductor proper attached to
the building, and the earth plates or ground. All projecting metallic sur-
faces should be connected with the conductors, whicb, if made of iron,
should have a cross section of not less than 50 mm square (1.9 sq. inches) ;
copper, about half of these dimensions, zinc about one and a half, and
lead about three times these dimensions. All fastenings must be secure and
lasting. The best ground which can be had is none too good for the light-
ning conductor. For many flashes an ordinary ground will suffice, but there
Avill come occasional flashes when even the small resistance of ^ ohm may
count. Bury the earth plates in damp earth or running water. The plates
should be of metal at least three feet square.
" If the conductor at any part of the course goes near water or gas mains,
it is best to connect it to them. Wherever one metal ramification ap-
proaches another, connect them metallically. The neighborhood of small
bore fusible gas pipes, and indoor gas pipes in general, should be avoided."
— Db. Lodge.
FIG, 4 CONDUCTORS AND FASTENINGS..
(FROM ANDERSON, AND LIGHTNING ROD CONFERENCE.)
The top of the rod and all projecting terminal points should be plated, or
otherwise protected from corrosion and rust.
Independent grounds are preferable to water and gas mains. Clusters of
points or groups of two or three along the ridge rod are good. Chain or
linked conductors should not be used.
It is not true that the area protected by any one rod has a radius equal
to twice the height of the conductor. Buildings are sometimes, for reasons
which we understand, damaged within this area. All connections should
be of clean well-scraped surfaces properly soldered. A few wrappings of
wire around a dirty water or gas pipe does not make a good ground. It is
not necessary to insulate the conductor from the building.
BIIIECTIOAS FOR PEKSO^AL iAfETI D1IRIHG
IHVIKDEn STORMS
Do not stand under trees or near wire fences ; neither in the doorways of
barns, close to cattle, near chimneys or fireplaces. Lightning does not, as
a rule, kill. If you are near a person who has been struck do not give him up.
Ztschrift, 1901, May 29, ei
704
LIGHTNING CONDUCTORS.
as beyond recovery, even if seemingly dead. Stimulate respiration and
circulation as best you can. Keep the body warm ; rub the limbs energet-
ically, give water, wine, or warm coffee. Send for a physician.
TESTS Of L1&HTX1AG RODS.
To make the test, first determine the resistance of the lead wire lx and call
it lv Then connect E{ and E2 as shown in the diagram, call the result lix ;
then connect Ex and EM call the result Ji2 ; connect E2 and E3 and call the
result JRS.
TESTS OF LIGHTNING RODS.
THIS LEAD MUST BE
SOLDFRED TO THE PIPE
OR OTHER EARTH SO AS
E NO RESISTANCE
AT THIS JOINT.
FIG, 6 DIAGRAM OF CONNECTIONS FOR TEST OF LIGHTNING RODS.
Now, Rx = lx-\-Ex-\-E2 and Es=E1—l1 — E1
Jti = l1-\-Ex-\-E« and j0, = i?2 — I, — JE.
XSi = E2-t-Es '
solving, we have
All lightning rods should be tested for continuity and for resistance of
ground plate each year, and the total resistance of the whole conductor and
ground plate should never exceed an ohm.
DETERMINATION OF WAVE FORM OF CUR-
RENT AND ELECTRO MOTIVE FORCE.
^^
There are numerous methods of determining wave form, those used in
laboratory experiments commonly making use of the ballistic galvanometer.
Of the simple methods used in shop practice, R. D. Mershon, of the West-
inghouse Electric and Manufacturing Co., has applied the telephone to an
old ballistic method in such a manner as to make it quite accurate and
readily applied.
Jtlershon's Method.— The following cut shows the connections. A
telephone receiver, shunted with a condenser, is connected in the line from
the source of current, the wave form of which it is wished to determine. A
contact-maker is placed in the other leg, and an external source of steady
current, as from a storage battery, is opposed to the alternating current, as
shown. The pressure of the external current is then varied until there is
no sound in the telephone, when the
pressures are equal and can be read a.c. terminals
from the voltmeter. The contact-
maker being revolved by successive
steps, points may be determined for an
entire cycle.
Duncan's Method. — Where it
is desirable to make simultaneous de-
terminations it will ordinarily require
several contact-makers, as Avell as full
sets of instruments. Dr. Louis Dun-
can has devised a method by which one
contact-maker in connection with a
dynamometer for each curve will ena-
ble all readings to be taken at once.
The following cut shows the connec-
tions. The fixed coils of all the dy-
namometers are connected to their
respective circuits, and the fine wire Fig.
movable coils of about 1,000 ohms each,
are connected in series with a contact-
maker and small storage battery. The contact-maker is made to revolve in
synchronism with the alternating current source. Now, if alternating cur-
rents from the different sources are passed through the fixed coils, and at
intervals of the same frequency current from
the battery is passed through the movable coils,
the deflection or impulse will be in proportion
to the instantaneous value of the currents
flowing in the fixed coils, and the deflections of
the movable coils will take permanent position
indicating that value, if the contact-maker and
sources of alternating current are revolved in
unison.
The dynamometers are calibrated first by
passing continuous currents of known value
through the fixed coils, while the regular in-
terrupted current from the battery is being
massed through the movable coils.
Ryan's Method. — Prof. Harris J. Ryan,
of Cornell University, designed a special elec-
trometer for use in connection with a very fine
series of transformer tests. This instrument
Avill be found described and illustrated in the
chapter on description of instruments.
The method of using it is shown in the cut below, in which the contact-
maker shown is made to revolve in synchronism with the source of alter-
705
MershOn's method of de-
termining Wave Form.
Fig. 2. Duncan's method
of determining curves
of several circuits at the
same time.
706
WAVE FORM.
TRANSFORMER
nating current. The terminals, d dt, of the indicating instruments can be
connected to anyone of the three sets of terminals, a ax b 6X c clm
The terminals, a ar, are for reading
the instantaneous; value of the pri-
mary impressed E.M.F. ; b bu the
same value of the current flowing
through the small non-inductive re-
sistance, R ; and c ct the same value
of the secondary impressed E.M.F. ;
the secondary current being read
from the ammeter shown. Of course
if the contact-maker be cut out, then
all the above values will be Vmean2.
UK
aafifyee, ™
WAVE METER.
The instrument illustrated and de-
scribed in the following pages has been
in use in the laboratory of the General
Electric Company at Schenectady,
since early in 1896, and is, I think, the simplest form of apparatus yet sug-
gested for determining wave forms in alternating currents.
The General Electric Company very kindly furnished the following de-
scription, and the diagrams and illustrations accompanying it.
Fig. 3. Prof. Ryan's method of ob-
taining curves of wave form for
studying transformers.
Fig. 4.
This device consists of a synchronous motor intended to run in synchro-
nism with the machine under test. On the shaft of the motor is placed a
contact device similar to the contact device usually placed directly on the
shaft of the generator. By the use of a synchronous motor, the device be-
comes much more flexible, and enables the Avave to be taken on any part
of any alternating current circuit by merely attaching a pair of lead wires,
thus doing away with all mechanical attachments to the generator.
Since the advent of alternators with a considerable number of poles, the
old method of mechanical connection has been found to be unsuitable on
account of the great degree of accuracy required in dividing a cycle into the
requisite number of degrees, owing to the fact that a complete cycle of 360°
forms such a small part of the arc of the armature.
The operation of the machine in detail is as follows : —
The field requires about 1.35 amperes I). C, and the armature about 4
amperes for starting. The machine should then be started by means of the
crank (marked A in Fig. 4) until it has been brought up to the frequency of
the A. C. circuit, which a\ ill be indicated by tachometer (mai-ked H). At 60
cycles the speed is 900 R. P. M. As soon as it is in synchronism (which can
be easily told by the running of the machine) the lever (marked B) on the
crank standard should be pressed, which releases the gear mechanism and
allows the motor to run free. After the machine is running, current in the
armature should be reduced to 3 amperes.
WAVE METER.
The following precautions are necessary in order to procure satisfactory
working of the apparatus : —
1. The resistance in all the circuits must be unvarying ; the contact,
therefore, must be perfect.
2. The E.M.F. of the A. C. and D. C. circuits must be steady and unchan-
ging. Complying with No. 1 and No. 2 secures steady currents in all the
circuits.
3 Above all, the speed of the source must be kept constant ; and if this is
not possible, readings must be taken only at a certain speed, that speed
being preferred to which the generator most frequently returns.
4. Avoid any leads other than shown on the diagram coming in contact
with the terminals of the D. C. voltmeter. It will be noticed that a con-
nection between the large and small segments will cause alternating cur-
rent to flow through the direct current voltmeter.
5. The tension on the contact spring " F" must be stiff enough to insure
a good contact. If the brush does not make an even contact on the contact-
disk, it can be remedied by placing a piece of emery cloth on the contact-
disk and revolving the brush over the rough side of the emery cloth by
hand.
G. The carbon brushes must make as perfect contact on collector rings as
possible.
7. In taking a wave, it is recommended that the voltmeter reading should
vary from a minimum of zero to a maximum of nearly a full scale deflection.
Fig. 5.
This absolute zero can be obtained by loosening the set screw (marked C)
on the end of index lever " D." The contact disk, " G," can then be rotated
on the shaft until the voltmeter reading is at zero, with index pointer set
on zero degrees. In case the maximum deflection is too low, it can be in-
creased by either inserting more capacity in the circuit or by using a higher
voltage on the condenser circuit ; this would be accomplished by using a
small step-up transformer or compensator at the point marked T in Curve
Sheet IN o. 8. The transformer voltage should not exceed 150 volts at this
point.
8. In case the voltage is too low to give a readable deflection on the volt-
meter, a DArsonval galvanometer can be used in place of the voltmeter.
9. The oil-cups (marked E) should be kept full of oil, as a thorough lubri-
cation is found necessary to procure perfect results.
10. If the machine sparks at contact disk, that is, if spark causes arcing
from one segment to the following one, it will be necessary to rub the sur-
face of the disk with fine sandpaper.
The external wiring connections of the machine are shown on Curve Sheet
A attached. The connections of the contact device are also shown. This
consists of a contact-disk with 4 large and 4 small segments. The 4 large
segments are connected to the inner copper ring on the side of the contact-
disk. By means of a spring contact and leads the latter is connected to the
terminal V. Similarly the smaller segments are connected through the
outer ring and spring contact and leads to the terminal T.
708
WAVE FORM.
The revolving brush is in contact by means of brush and contact ring as
seen on the end of the shaft (marked 1) to the frame, and from the latter by
means of wire under the base to the terminal C.
The principle on which the method is based is the following : When the
revolving brush, F, leaves the small segment of tbe contact disk, U, and
breaks the contact between the condenser and the E.M.F. to be measured,
it leaves the condenser charged with the potential difference which oc-
curred at that instant. As soon as the revolving brush touches the large
segment, the condenser discharges into the voltmeter until the brush leaves
it. As the speed is constant, the time of discharge is constant, and as the
discharging circuit is unaltered during the test, the instantaneous E.M.F's
cause proportional deflections ; the latter follow so quickly as to give steady
deflections.
Reading', Plotting, and Calculating-. — The movable index
pointer is turned till the spring-actuated pin drops into the small hole above
zero on the fixed scale, and the deflection of the voltmeter noted on a sheet
of paper having two parallel columns counting the degrees from zero to 360,
as indicated below : —
DEFLECTION.
DEFLECTION.
180
185
190
195
etc.
180
355
360
After taking the reading at zero, the pointer is moved to 5, then to 10, and
so on. If after finishing this series of readings a marked difference is noted
between corresponding deflections in the left and right hand columns, such
points must be taken over again.
The average of the two corresponding deflections is taken, and the results
are then multiplied by such a constant as to make the maximum = 10.
These values are plotted as Ordinates, and the corresponding degrees are
abscissae. See sample test and Curve Sheet B.
To find the average E.M.F. , divide the area
in terms of squares of the paper used, by 10
times the actual length of one cycle in terms of
one side of the same squares, as the maximum
is plotted to a scale of 10 instead of one. On
Curve Sheet B the length of the half -cycle = 9
units, and therefore the area must be divided
by 90.
The effective E.M.F., or Vmean square
J\
the square root of the mean squares of the
same instantaneous values used before. The
simplest method of obtaining this is the fol-
lowing : Plot the same deflections on polar co-
ordinate paper similar to that used in Curve
Sheet C, and find the area of the resulting
curve.
The effective E.M.F. is then equal to the
radius of a semi-circle whose area expressed
in terms of squares of the rectilinear co-ordi-
nate paper, is equal to the area enclosed by
the wave plotted on . the polar co-ordinate
paper after being reduced to the same dimensions by multiplying by the
ratio of ^2^2
EXPERIMENTAL ALTERNATOR
FIG. 6. Curve Sheet B.
'(f)*
To find the area a planimeter is used, or the curve is traced or copied by
means of carbon paper on paper of uniform thickness, which is then weighed
on a chemical balance, or in case neither of the above methods is avail-
SAMPLE TEST.
709
able, the area can be found by actually counting the number of squares it
contains.
The form factor is the
ratio of the effective to
the mean E.M.F. The
form factor of a sine
wave is 1.11.
The amplitude factor
is the ratio of the max-
imum to the effective
E.M.F., which, as the
maximum is one, is
equal to the reciprocal
of the effective E.M.F.
The amplitude factor
of a sine wave is 1.414.
These values are to
be used in making cal-
culations for alternat-
ing currents whose
wave shapes have been
determined by means
of the wave meter in-
stead of employing the usual values based on the sine curve. The accom-
panying record sheets give the results obtained with an actual E.M.F. wave
taken with the machine. In the sample test, columns 2 and 4 give the read-
ings obtained for the different angular deflections. Column 5 is the average
of the readings obtained. These values are then multiplied by a constant,
which in this case is .1127, to give a maximum of 10. The resultant values
plotted in rectilinear and polar co-ordinates are shown on curve sheets B
and C.
^ — /—+— i— i_^ 1 III
— /\ W X r~-4-^.fe — 1^\ a A/ /\-
Fig.
Curve Sheet C.
SAIKPIE TEST.
(Nov. 21, 1897.)
JS.M.IT. Wave of Experimental Alternator.
Ko. 1.
No. 2.
No. 3.
No. 4.
No. 5.
No. 6.
Degrees.
0
—4.5
180
—4.5
—4.5
— .507
175
5
+2.5
185
+2.5
+2.5
+ .28
0
10
190
7.
+7-
.79
5
15
11.
195
11.
+11.
1.24
10
20
21.
200
19.5
+19.75
2.23
15
25
29.5
205
29.5
29.5
3.32
20
30
30.
210
29.5
29.75
3.35
25
35
29.5
215
29.5
29.5
3.32
30
40
36.
220
36.
36.
4.06
35
45
51.
225
50.
50.5
5.695
40
50
71.
230
72.
71.5
8.05
45
55
72.5
235
71.5
72.
8.12
50
60
66.
240
66.
66.
7.44
55
65
70.
245
71.
70.5
7.95
60
70
85.
250
85.
85.
9.58
65
75
89.
255
88.5
88.75
10.
70
80
75.5
260
73.5
74.5
8.4
75
85
68.5
265
67.5
68.
7.66
80
90
61.5
270
60.5
61.
6.87
85
95
59.5
275
60.
59.75
6.73
90
100
72.
280
72.5
72.25
8.15
95
105
81.
285
81.
81.
9.13
100
110
87.
290
87.5
87.25
9.82
105
710 WAVE FORM.
SAMPLE TEST — (Continued).
Mo. 1.
No. 2.
No. 3.
No. 4.
No. 5.
No. 6.
Degrees.
J 15
84.
295
83.
83.5
9.40
110
120
72.5
300
73.
72.75
8.2
115
125
67.5
305
68.
67.75
7.63
120
130
77.
310
77.5
78.25
8.81
125
135
82.5
315
82.5
82.5
9.3
130
140
60.
320
59.5
59.25
6.68
135
145
41.
325
41.5
41.25
4.65
140
150
32.
330
32.5
32.25
3.64
145
155
30.5
335
30.5
30.5
3.44
150
160
37.5
340
37.
37.25
4.2
155
165
30.
345
30.5
30.25
3.31
160
170
16.
350
15.5
15.25
1.775
165
175
8.5
355
9.0
8.75
.98
170
The different constants of this wave are given below in "Method of De-
termining Constants of E.M.F. Curve." This also gives the constants for a
sine wave for comparison.
SPECEAE DATA ©]¥ THE MOTOR IILISTRATED.
Resistance of field = 10.87 ohm.
Resistance armature and brushes = 2.055 ohm.
Armature alone = .560 ohm.
Armature winding — 14 turns of No. 28 D. C. C. copper wire doubled in
each slot.
Field frame consists of Txff H.P. U. I. Fan Motor — 125 cycles, 104 volts.
METHOD OE »ETEI»]fII]¥I]¥« COISTAHiTS OE
E.M.E. CURVE.
Area Rect. Co-ord. Curve " B " = 51.32.
Mean E.M.F. = ^^5 = -571.
Polar Area = 4,062, which must be multiplied by I ' ) to be com-
parable to the area in rectilinear co-ordinates. 11.33 is the maximum ordi-
nate of the rectilinear co-ordinate in centimeters, and 8.95 is the maximum
ordinate of the polar co-ordinate curve ; therefore the corrected polar area
= 40.62 X 1.6 = 64.992.
Now ^nr* = 64.992, therefore r = .643, which is the effective E.M.F.
The form factor being therefore
The amplitude factor :
effective
mean
maximum
.643 _
^571"
1.127.
For comparison the constants of a sine wave are also given in the recapit-
ulation below.
Mean
E.M.F.
Rect. Co-ord. Curve B 51.32 | _—
Polar " " C 40.62 { ■i3il
Sine Wave 637
Effect.
E.M.F.
.643
.707
Form
factor.
1.127
1.110
Amp.
factor.
1.554
1.414
CERTAIN USES OP ELECTRICITY IN THE
UNITED STATES ARMY.
Electricity enters into nearly every branch of the military art, being used
for the operation of searchlights, turret-turning, manipulation of coast-de-
fense guns, ammunition hoists, range and position tinders; for firing sub-
marine mines ; field and fortress telephones and telegraphs ; firing devices
for guns, ground mines ; in tide gauges ; submarine boats and dirigible tor-
pedoes ; while electrically operated chronographs are employed in the solu-
tion of ballistic problems.
SEARCHLIGHTS.
Searchlights are used both as offensive and defensive auxiliaries ; defen-
sive when used by shore fortifications to light channels or by a vessel to
discover the approach of torpedo boats ; offensive when used as " blinding-
lights " to smother the light of an approa ching vessel and confuse her pilot.
The accompanying illustrations show the searchlight manufactured by
Schuckert & Go. of Nurnberg, Germany.
The lamp is placed on top of the two lowest longitudinal rods of the cas-
ing, and is held in place by four lugs, two on each side. The carbon holders
reach upward through a slit in the casing, and there is a small wheel in rear
for moving the light parallel to the axis of the reflector, for the purpose of
focusing it. The trunnions of the casing are fastened to two longitudinal
rods on each side, parallel to the axis of the cylinder, and can be moved for-
ward or back so that the casing and what is carried with it will have no pre-
ponderance. The trunnions are supported in trunnion beds in the ends of
supports which project upwards from the racer.
The elevating arc is attached to another longitudinal rod beneath the
cylindrical casing and is capable of adjustment on this rod. Engaging in
this arc is a small gear attached to a horizontal shaft passing through the
right trunnion support and carrying a small hand wheel. This small hand
wheel is for the purpose of elevating or depressing the light rapidly.
The light may be elevated or depressed slowly by means of a small hand
wheel attached to another horizontal shaft in front of the one just described.
This shaft near its center carries a worm, engaging in a worm wheel on a
vertical shaft, to which is also attached a bevel gear. This gear engages in
another, which is attached to the quick- motion shaft, but is free to turn
about it until it is connected with the elevating gear wheel by means of a
friction clamp. The relation between the worm and worm wheel is such
that a slow motion is obtained.
The racer rests upon live rollers and is joined by a pintle to the base ring.
Attached to the base ring is a toothed circular rack, into which on the
outside a gear wheel attached to a vertical shaft engages. This vertical
shaft projects upward through the racer and carries a worm wheel, which
engages in a worm carried on a horizontal shaft having a hand wheel. The
worm wheel is entirely independent of its vertical shaft, except when con-
nected with it by means of a friction clamp. When so connected, by turn-
ing the hand wheel the light is traversed by a slow motion. To traverse
the light rapidly, the friction clamp is released and the light turned by
hand, taking hold of the trunnion supports. One of the ends of the slow
motion elevating and traversing shafts is connected with a small electric-
motor, which is encased in a box on top of the racer. By means of these
motors the motion of the searchlight can be controlled from a distant point.
A switch is provided with contacts so arranged that the current can be
passed into the armatures of the motors in either direction, so as to obtain
any movement the operator may desire. The current needed for the move-
ment is obtained from the lines supplying the current used in the light itself.
The current is brought to the motors by means of contact points, bearing
on circular contact pieces attached to the racer.
The reflector is a parabolic mirror embedded in asbestos in a cast-iron
frame, and is held in place by a number of brass springs. The frame of the
reflector is fastened to the overhanging rear ring of the casing with studs
and nuts, the overhanging part of the ring protecting the reflector from
711
712 CERTAIN USES OF ELECTRICITY IN U.S. ARMS".
Fig. 1. Schuckert Searchlight as used in U. S. army,
moisture. In order to enable the operator to observe the position of the
carbons and the form of the crater while the apparatus is in use small
optical projectors are arranged at the side and on top of the casing, which
enables images of the arc as seen from above and from the side to be
observed. When the light is properly focused the positive carbon reaches
a line on the glass on top of the casing.
There are two screws on the positive carbon holder which enable the end
of this carbon to be moved vertically or horizontally to bring it to a proper
adjustment.
In consequence of the ascending heat the carbons have a tendency to be
consumed on top ; and to avoid this there is placed just back of the arc and
concentric with the positive carbon a centering segment of iron, attached to
the casing, which, becoming magnetic, so attracts the current as to equalize
Searchlights.
713
the upward burning of the carbons. In taking the light out of the casing
this centering segment must be unfastened, and swung to the side on its
hinge.
SAFETY FUSE
Fig. 2. Diagram showing Searchlight Connections.
An example of the method of calculating the intensity of the light sent out
by the mirror follows : —
Diameter of parabolic mirror, 59.05 inches.
Diameter of positive carbon, 1.5 incbes.
Diameter of negative carbon, 1 inch.
Power consumed, 150 amperes x 59 volts.
Maximum intensity of rays impinging upon tbe mirror, 57,000 candle-
power.
714 CERTAIN USES OF ELECTRICITY IN U.S. ARMY.
•iu in -ui 0001 W
uopimiumni J° PPki
L11C* Tt< -* L
333
Ci CO -* t- 00 LO
•aoisjadsiQ;
X — co o :- ~l X O i-
lO IQ •<* •* ■* lO i-< CO -*
OOO OOO OOO
«N« NIMO) Ci CO <N
rhrf 00
(MC1C0
•IUUI TIT JOJ
-jij\[ jo oouuiisiq'tijoo^
MaAVod-axpu^o in
iqSiq; joAu^jjOiCiisuaiui
OOO OOO OOO OOO OOO o
OOO OOO OOO OOO OOO o
O O O O O O OOO' O O O OOO o
M CI Hrtrl CO O
zU
JO J9AY0J 3in£jISU8}UI
•UUU UT
p .io^bjq jo jo:i8urei<I
6H t-c CO t- in
ooo ooo o o : i
;33 S3 S3
•j9Avod-9xpxre9
pxepiTB^s ui .io.i.iij\[
Aq pa^oano^r sAt^
JO AjTSU9:iUI 9§'8J8AY
88f ||S
c5 ^f o co oo ^
DO O O
2 £3
i-i LO O CO c
osuS
OOO OOO
op o o ooo
88S 8
i-H i-l i-l <M <N CO •* "#
OOO
CO LOCO
4 - -
lO-Tof
CO -* ic m o
'WBAY 9^0 ui
J9AVod-8ipui30 pjuput^s
o3 288
io LO o CD co o CO
°as 888
'S!|[OA Ut l'BI^U8^0<I
CO-*-* CO -* lO LOCOt-
-*-*■* Tt<-*T* T*-*-"
Tjl ■* LO LO LO LO
8 8
•saaadiuy
ut :iu8.i.mo jo q^Suej^s
•uiui ui
(J J0JJIJ\[ JO JQ^eiUBIQ
OiOO OOO OOO OLOO
<N CJ CO <M CO ■* -* IO CO COt^Ol
888 g
8 8
CHRONOGRAPHS.
715
Average intensity of rays impinging upon mirror, 45,600 candle-power.
Diameter of crater, 0.905 inch.
Intensifying power of the mirror,
J» _ (59.05)2 _
tf2 - (0.905)2 - %^6-
Total intensity of light ->ent out by
mirror, 45,600x4,253 = 194,000,000 can-
dle-power.
The focal distance of the mirror is 25.5 *
inches.
The dispersion angle of the concen-
trated beam is 2° 2'.
The diameter of the illuminated area
at a distance of 1,111 yards is 84 yards.
The resistance Rm on the switchboard
at the light is in series with the main
current for the purpose of regulating
the amperage at the lamp. The volt-
meter at the lamp should indicate about
60 volts. The connection of the dis-
tance governor with the two motors for
elevating and traversing is also shown.
The largest searchlight so far built is
the one that was on exhibition at the
Paris Exposition of 1900 in the section
" Navigation de Commerce et Armees
de Terre et de Mer," which is 6 feet 6
inches in diameter, and gives a beam of
316.000,000 candles.
The table on preceding page gives
data in regard to searchlights of various
sizes.
CHROIOGRlPH§.
In the experimental work of testing
guns, etc., it becomes necessary to ascer-
tain the velocity of projectiles both
while passing through the bore of the
gun and during flight. Chronographs of
various sorts are used for this purpose.
In order to ascertain the velocity of a
projectile during flight, two screens or
targets are set up in the course of the
projectile, generally 100 feet apart.
These screens ordinarily consist of a
frame of wood carrying a number of
small parallel copper wires. The break-
ing of the wires in the successive frames
by the projectile causes the interruption
of the current through the instrument,
and thus registers the time of flight
between the screens.
Probably the best-known instrument
of this class is the one invented by Cap-
tain Le Boulenge of the Belgian artil-
lery, which was afterwards modified by
Captain Breger.
Bouleng-e Chronograph.
This instrument depends for its accu-
racy upon the law of falling bodies or the
acceleration due to gravity, namely 32
feet per second.
It consists of a vertical column (Fig. 3 ) to which are affixed two electro-
magnets ; the right-hand one, A , is actuated by the current of the first frame
716 CERTAIN USES OF ELECTRICITY IN U.S. ARMY.
and supports an armature called the chronometer ; the left-hand magnet,
jB, is actuated by the current of the second frame, and supports an ai ma-
ture, D, called the registrar.
The chronometer, C, is a long, cylindrical brass tube terminating at its
upper extremity in a piece of soft iron, and bearing at its lower extremity a
steel bob. It is surrounded by a zinc or copper cylinder called the recorder.
The rupture of the first target causes the demagnetization of the magnet A,
releasing the rod C. The registrar is of the same weight as the chronome-
ter, and is a tube with soft iron and* bob. The cores of the electro-magnets
and the soft iron of the armatures terminate in cones slightly rounded at
their vertices in order that the armatures when suspended can take a verti-
cal position.
When the registrar is set free by the rupture of the second target it
strikes a horizontal plate («), which turns upon its axis (c) and releases the
spring (d). The spring is furnished with a square knife (<?), which strikes
the recorder and leaves an indentation upon it.
If the two currents be ruptured simultaneously the indentation is found
upon the recorder at a height h, indicating that since the chronometer
commenced to fall the time t has elapsed. t=z l/ — * .
* <J
It is evident that t is the time required for the apparatus to operate ; it
is a systematic retardation inherent in the instrument.
A special device, called the disjunctor, permits the simultaneous rupture
of the circuits to be produced, so that the time t is always known.
A very simple device is resorted to in order to render it constant. If the
current of the registrar is not ruptured until after that of the chronometer,
and if an interval T has elapsed between these ruptures, the time during
which the chronometer will fall before receiving the indentation of the
knife will simply be augmented by t, and calling H the height of the inden-
tation, we will have ,jr-=.
t+T=J!E.
▼ 9
Thus the determination of an interval T always comprises two opera-
tions : the measurement of the time (t) required for the instrument to
operate, and that of the time t + T. The difference of these two measure-
ments gives the time sought. This indirect method of ascertaining the
result is the characteristic of the instrument and explains its accuracy.
When the rupture of the currents is produced by the projectile the portion
(D) of the trajectory between the targets is regarded as rectilinear and the
mean velocity V is jy
V—
VF
h)
The arrangement of the circuit must vary according to circumstances,
and no particular system can be prescribed. The general arrangement,
however, is shown in the sketch
FlG. 4. Connections of Boulenge" Chronograph.
CHRONOGRAPHS.
717
Schultz Chronoscope.
The Boulenge chronograph measures velocity at one point only, but it is
frequently necessary to measure the velocity of the same projectile at
different points as in determining the laws of the resistance of the air to its
motion, or in ascertaining the velocity of a projectile at different points in
the bore.
FlG. 5. Schultz Chronoscope.
For such purposes an instrument must be used which will give a scale of
time of such length that all the phenomena may be registered upon it.
There are several instruments of this class, of which the best known is the
Schultz chronoscope. In this instrument a drum (a), one meter in circum-
ference, and covered with a coating of lamp-black, is driven by the means
of a clock movement and weight, so as to revolve once per second and
at the same time slowly advance longitudinally. In front of the drum,
mounted on a support and actuated by two magnets, is a standard tuning-
fork (c), vibrating 250 times a second ; on one link of this fork is a quill (b)
which traces aline on the blackened surface of the drum, and therefore
will record 250 complete vibrations for every revolution of the drum.
A telescope with micrometer (not shown in drawing) is also attached to
the support fork ; and each vibration of the fork, traced on the drum in form
of a curve, can be subdivided in 1000 parts, thus allowing readings to be
made to 35^00 of one second. On the support with the tuning-fork is a
small pointer which traces a straight line on the drum. This pointer has an
electrical connection with an accurate chronometer which at every half-
second closes the circuit and causes the pointer to make a succession of
records on the revolving drum. These marks serve as starting-points to
count the number of vibrations of the tuning-fork, and to check them up
every half-second.
In order to measure the velocity of projectiles, the gun must be fitted
along its bore with special electrical circuit breakers, usually placed one
foot apart. Each circuit breaker is so constructed that the current is
interrupted as the projectile passes, hut is made again before the projectile
reaches the next breaker one foot farther on. ♦
These breakers, with appropriate battery, are all in one circuit with the
primary of an induction coil. One terminal of the secondary of the coil is
grounded to the frame of the chronoscope, vhile the other terminal con-
sists of a fine point near the blackened surface of the drum. Therefore,
718 CERTAIN USES OF ELECTRICITY IN U.S. ARMY,
when the primary circuit is opened by the first circuit breaker along the
bore of the gun, the spark induced in the secondary of the induction coil
jumps from the points to the revoking drum, leaving a distinct mark on
tbe blackened surface As the next circuit breakei in the gun is passed,
the spark again passes to the drum, and this operation is repeated for every
breaker along the gun bore. Thus on the drum, alongside of the indications
made by tbe tuning-fork, will be recorded a succession of spots at certain
distances from each other. The time elapsing between any two of these
spots can be calculated directly from the record which the tuning-fork
made, and thus the time (measured to the ssi/orto part of a second) taken by
the projectile in passing a known distance, along the gun barrel calculated.
— Electrical World and Engineer, June 23, 1900.
Schmidt Chronograph.
This is a portable instrument, and while probably not so accurate as the
Boulenge instrument is sufficiently so for the every-day work of the proving-
ground.
The chronograph is composed of the following principal parts (see Figs.
6 and 7) :
Fig. 6. Connections of Schmidt Chronograph.
The balance-wheel A with its spring and needle.
The electro-magnet B, which holds the balance-wheel at the starting-
position and releases it the instant the first current is broken.
The electro-magnet C, with its mechanism, which stops the balance-wheel
the instant the second current is broken.^
The dial I), graduated for velocity readings.
A circular frame E, for setting the instrument at zero.
The button E, reestablishing the current in the magnet C.
The rheostats G and G', with their resistance coils for regulating the .
currents.
The balance-wheel, made of nonmagnetic metal, is about 2£ inches in
diameter and mounted on the axis o, which is held by two strongly made
bridges fastened to the face plate of the instrument. The pivots of the
axis are set in jeweled bearings. The spiral spring i/is fastened to the
bridge and axis as in ordinary chronometers.
The needle, /, is composed of two parts, as shown in Fig. 8. One part, a, of
bronze, is fastened rigidly to the axis; the other, l>, a steel spring, is
fastened at one end to a, the free end being limited in its motion by, two
small pins set into a.
The electro-magnet B, Avhich holds the balance-wheel at the starting-
CHRONOGRAPHS.
719
point, is operated by the current passing through the first screen, and is
mounted on the face piate so that the core is radial with reference to the
balance-wheel. Tbe core of the magnet projects beyond the coil and acts
upon the small armature c, mounted on the rim of the balance-wheel.
The electro-magnet C, with its mechanism operated by the current pass-
ing through the second screen, stops the balance-wheel the instant the
current is broken. This magnet is somewhat larger than the other, and is
Fig. 7. Interior Schimdt Chronograph.
placed tangentially with reference to the balance-wheel. It acts upon the
two armatures d, d', placed opposite the extremities of the core. These
armatures are fastened to the ends of the two levers K, K', which are
mounted on the axis e, e', parallel to the axis of the balance-wheel and
Fig. 8. Construction of Needle.
similarly supported. The other ends of the levers are joined by the coiled
spring L with its adjusting-screw. Set in the levers near this end are four
pins, /,/,/',/', that ordinarily, due to the tension of the spring, bear against
720 CERTAIN USES OF ELECTRICITY IN U.S. ARMY.
the rim of the balance-wheel, holding it fast. "When the current passes
through this magnet, the armatures on the levers are attracted by the
core, the spring is elongated, and the pressure of the pins upon the balance-
wheel is released. When the current is broken the armatures are released,
and the tension of the spring closes the pins upon the wheel. To insure
effective action the pins are accurately set and the rim of the wheel is
The face of the chronograph is a graduated dial concentric with the
balance-wheel axis. When the wheel is held at its starting-point the needle
points at the zero of the graduation. The scale in black indicates the time
in thousandths and two-ten-thousandths of a second. Another scale, in red,
gives the velocity directly in meters per second when the screens are placed
50 meters apart. . . . .
The dial is covered with glass inclosed m the circular metal frame E.
A pin, g, fixed in the glass, is used to set the. needle at zero by turning the
frame, to which is also fastened the lens h, to facilitate reading. This lens
is provided with two pointers so placed that the reading is always taken in
the vertical plane.
The button F is for the purpose of reestablishing the current through
the magnet C after it has once been broken. Pressing the button closes
the circuit ; the magnet then attracts the armatures d, d', fixed to the ends
of the levers X, K'. This motion of "he levers brings the small spring I,
mounted on K', in contact with the projection k, thus forming a circuit
through which the current continues to flow after the pressure on F has
been released. This contact is broken by the motion of the lever when the
current is interrupted by the shot. This arrangement prevents the current
from passing through the magnet and releasing the balance-wheel before
the circuit is closed by pressing the button F, even though the broken screen
is repaired, and gives the operator time to take the reading and prepare for
the next shot. This is especially important when targets that close the
circuit automatically are used.
The rheostats for regulating the currents are placed above the dial, their
resistance coils being inside the case. One binding-post of each rheostat is
provided with a circuit closer for passing the currents through the resis-
tance coils or directly into the rheostats.
The Squire-Creliore Photo-Chronograph.
This instrument was designed to overcome the minute errors inherent in
other forms of chronographs, such as the inertia of the amature, the time
required to magnetize iron, or in instruments employing a sparking de-
vice, the fact that successive sparks do not proceed from the same point by
identically the same path.
The agents employed in this instrument are light and electricity. Briefly
stated, a ray of light from an electric arc is reflected upon a revolving
photographic plate. The interposition of a tuning-fork gives on the plate
a curve which is used as a scale of time.
In the path of the beam of white light is placed a Nicol prism in order to
obtain a beam of plane polarized light. This prism is made of two crystals
of Iceland spar, which are cemented together by Canada balsam in such a
way as to obtain only a single beam of polarized light. The crystal is a
doubly refracting medium ; that is, a light beam entering it is in general
divided into two separate beams which are polarized and have different
directions. One of these beams in the Nicol prism is disposed of by total
reflection from the surface where the Canada balsam is located, and the
other emerges a completely polarized beam ready for use.
A second Nicol prism exactly like the first is iiow placed in the path of
the polarized beam. This second prism is called the " analyzer," and is
set so that its plane is just perpendicular to that of the first prism, called
the "polarizer," so that all the light vibrations not sorted out by the one
prism will be by the second. In this position, the planes being just perpen-
dicular to each other, the prisms are said to be " crossed," and an observer
looking through the analyzer finds the light totally extinguished as though
a shutter interrupted the beam.
By turning the analyzer ever so little from the crossed position, light
passes through it, and its intensity increases until the planes of the prisms
are parallel, when it again diminishes ; and if one of the prisms is rotated
MANIPULATION OF COAST-DEFENSE GUNS. 721
there will be darkness twice every revolution. In order to accomplish this
same end without actually rotating the analyzer a transparent medium
which can rotate the plane of polarization of the light subject to the con-
trol of an electric current is placed between the two prisms. The medium
used is carbon bisulphide contained in a glass tube. To produce a mag-
netic field in the carbon bisulphide a coil of wire through which passes an
electric current, is wound around the glass tube. When the current ceases
the carbon bisulphide instantly loses its rotatory power, and the ray of
light is free to pass tiirough the prisms.
Breaks in the current are made in the same way as in other ballistic
chronographs. For a complete description of this instrument, with an
account of experiments, see The Polarizing Photo-Chronograph, John
Wiley & Sons, New York.
MiAHfUPUI-ATIOlir Of COASI-DEFEVSE CJUWS.
Until recently all gun carriages installed in the coast fortifications of the
United States were designed for the use of hand power iu their manipula-
tion. Tests, however, having demonstrated the adaptability of electrical
power for this purpose, such guns are now being equipped with electric
motors.
The following data is taken from recent tests of the equipment of a 10-
inch disappearing carriage.
The equipment installed consists of :
One 3 h.p. motor connected directly by spur gearing to the crank shaft of
the traversing mechanism.
One 5 h.p. motor for operating both the elevating mechanism and the
retraction gear.
A hand brake applied to a drum on main crank shaft of traversing gear.
Control switches, wiring, etc.
The iron-clad motors and switch boxes are water and dust tight. The
mechanical hand brake is used to overcome the tendency of the carriage to
settle back when stopped quickly at a particular point, due to the great
weight and inertia.
The weight of the gun is 67,000 pounds, and moving parts of carriage,
approximately 170,000 pounds, a total of 237,000 pounds.
TRAVERSING MOTOR. -
S&esults.
130 volts.
At full speed, Jg-^g-tortgt
1.1.8 effective H.P.
H19 volts.
A t h a 1 f sinppd J 23 amPeres to start.
At halt speed. ^ 22 it running.
^2.9 effective H.P.
(120 volts.
«,„„„. „„„„ A J 23 amperes to start.
Slowest speed. ^ 20 am^eres rurming.
(.2.4 effective H.P.
Time required to traverse through entire field of fire, 106° 30/ twenty-five
seconds [of time].
ELEYATING AND RETRACTING MOTOR.—
f 128 volts full speed.
In depressing through extreme J 13 amperes full speed,
range, + 15° to — 5°. 1 1.8 effective H.P.
(^Time, 22 seconds.
( 122 volts full speed.
In elevating gun through ex- J 20 amperes, full speed,
treme range. | 1.8 effective H.P.
^Time, 22 seconds.
ill CERTAIN USES OF ELECTRICITY IN U.S. ARMY.
RETKACTION.-
{ 120 volts full speed.
■'. 20 amperes full speed.
( Time, 2 min. 2 sec.
To bring gun from firing
loading position.
A more complete description of this apparatus may be found in the
Electrical World and Engineer, January 19, 1901.
ELECTRIC FUSES.
It is often necessary to fire at a distance from the gun, as in experiments,
and for this purpose electric fuses are used.
The fuse consists of a ^-inch length of tine wire of platinum-iridium alloy,
called the bridge, surrounded by a little gun-cotton or powder ; next to this
c\/c
FiCx. 11. Firing Key.
A, copper case.
B, hollow wood cap.
CC, wires, .035 inch.
D, bridge, .0025 inch.
F, priming.
H, fulminate of mercury,
10 to 24 grains.
1, paper discs held by
drop of collodion.
K, plug of beechwood.
A, copper case.
B, plug (beechwood).
C, insulated wires.
D, bridge.
F, gun-cotton priming.
H, rifle powder.
I, cotton string.
K, tin foil cap.
Figs. 9 and 10. Electric Fuses.
is placed, when required for detonating, a few grains of fulminate of mer-
cury. The whole is usually fixed inside a copper case. The bridge being
inserted in an electrical circuit is heated by the current which ignites the
gun-cotton and fires the fuse.
Fig. 9 shows a gun-fuse. Fig. 10 is a mine-fuse, which is similar in con-
struction, and is used in firing high explosives, or where it is desired to
DEFENSIVE MINES. 723
ignite several charges simultaneously, as in a group of submarine mines.
Fig. 11 shows the tiring-key, in which T is a turnbuckle of ebonite which
prevents accidental closing of the circuit.
DEF1LYM1YK M L\EM.
A mine is a charge of explosive contained in a case which is moored be-
neath the surface of the land or water. The mines laid and operated in and
around seacoast fortifications are for the most part defensive in their char-
acter, fixed in position, and hidden.
A defensive mine is either self-acting, — a mine which, once placed, ceases
to be under control, and is tired by means within itself, mechanical or elec-
trical,—or controlled, a mine fitted with electrical apparatus, which ena-
bles a distant operator to ascertain its condition, and to fire it at any time ;
it may also be tired automatically.
A controlled mine may be fired in four different ways : (a) by contact with
the mine only ; (b) at will of the operator only ; (c) by contact and will, both
of which are necessary ; (</) by observation from two stations.
A controlled sea mine may be either a buoyant mine whose case floats 3
or 4 feet beneath the surface, and contains both the charge and electrical
apparatus, or aground mine. The latter is in two parts: one a case contain-
ing the charge and fuse, rests on the bottom ; the other, containing the elec-
trical apparatus, floats 3 or 4 feet beneath the surface.
Copper wires lead to two or three Sampson-Leclanche cells, which are
put in circuit with the torpedo casemates of the fortification.
Jill'-- SU. %, \\l/,^>4=/r> ^^
SPRING BOARD
3C
Fig. 12. Electrical Land Mine.
The sketch shows a self-acting electrical land mine, and is self-explana-
tory. By using three lead wires the mine may be fired by the enemy's con-
tact with it, or by the operator at the station.
Circuit Closer or Torpedo.
NS, circular permanent magnet with attached electro-magnets N and S.
A, armature whose adjusting spring near K holds it away from the mag-
net, while a weak current flows in through the electro-magnet coils in a
direction to assist the permanent magnet. But if a stronger current flows,
the armature is attracted, and sticks to the magnet, until a reverse current is
sent in. The spring then draws the armature away, and breaks the contact
of the circuit closer K on W.
B, a brass ball f inch diameter, held by spiral S.
T, a silk thread running through the vertical axis of the ball from adjust-
ing screw to the armature. When the vessel strikes the mine the brass ball
being knocked sidewise pulls, by means of the sti'ing, the armature against
the poles where it sticks.
R, 1000-ohm resistance coil, which is cut out of the mine circuit by the
contact of K on W.
PC, priming-charge.
F, fuse.
724 CERTAIN USES OF ELECTRICITY IN U.S. ARMY.
Operating-Box on Shore.
WB', watching-battery of gravity cells and brass bar.
FB', tiring-battery of Sampson cells and brass bar.
P', firing-plug.
M'M', ordinary electro-magnet, 100 ohms. (See Relay No. 7.)
A7, armature pivoted at the center. (See Relay No. 7.)
S', spring holding armature back against a weak current. (Relay No. 7.)
I/, shutter arm pivoted above its center of gravity. When set as in relay
No. 1, shutter-arm 1/ makes electrical connection with the armature at N' ;
when armature is attracted it releases L/, whose lower end strikes a bell, and
makes electrical contact with the firing-bar at B'.
b, terminal of mine circuit which may be plugged to WB'.
a, terminal for testing-set.
o, o, two reversing-keys.
Xand Y are two stations, 1 to 3 miles apart, each having a key and an ob-
server of the mine field.
Operation.
The torpedo having been planted and connected with its relay, whose
shutter-arm L' is set as in relay No 1, a small steady watching-current Hows
through G', WB', b, M'M', H, NT/, J', O', V, coil S, cod, N, W, K (1,000 ohms),
G to G' again. The direction of the current is such as to preserve the mag-
netism of the magnet. If the circuit closer is accidentally closed (indicated
by a change of the resistance in the circuit) it can be opened by using the
reversing-key from shore.
The fuse F may be tired in four ways : —
(a) By contact with the mine only. Insert firing-plug P'. When a vessel
strikes a mine the brass ball B in the circuit-closer is thrown aside, closing
K on W and thus short circuiting R. The watching-current, thus made
stronger, flows from coil N through K, A, Z, fuse, &„ to G'. Coming from
gravity cells it cannot fire the fuse, but is strong enough to operate the relay
and drop L/, which throws in the firing-battery. A strong current now flows
through G", FB', P', B', J', O', V, coil S, coil N, W, K, A, Z, F, G„ to G"
again, and fires the fuse.
(b) At will of_ operator only, who may at any time drop the shutter arm 1/
by hand and insert the firing-plug. The firing-current is strong enough,
even through R in the torpedo, to close K, short-circuiting R, and to fire
the fuse.
(c) By contact with the mine and at operator's will. Remove firing-plug
P'. The watching-current flows as above in (a). When the vessel strikes
the mine 1/ drops, striking the bell, when the operator inserts P', throwing
in the firing-current which fires the mine.
(d) By observation from two stations ; shutter arm L/ set, and firing-plug
P' in. When a hostile vessel appears over the mine from the position of X
the observer closes his key. Y has like instructions. When both keys are
closed the main part of the current from WB' flows through G', WB', b,
M'M', H, Q', X, Y, G, to G' again, drops the shutter-arm and fires the mine.
For obvious reasons the foregoing is not a description of the service cir-
cuit closer, but the principle of construction and operation of the mines of
all countries are much alike.
MISCELIAHEOUS.
Fortress Telephones and Telegraphs.
Covering as it does a considerable area, the modern fortification must have
its several units within instant communication, in order to insure that con-
cert of action so necessary to a successful command. The fort commander
must communicate his orders to the battery commanders, and they in turn
transmit the necessary commands to the gun commanders ; and while much
time and ingenuity has been spent in devising means of communication
through the medium of printing and dial telegraphs, the telephone is to-day
practically the universal method of communication from one part of a fire
command to another. As ordinary commercial telephones are employed, no
special description of them need be given in this section. The telephone is,
however, at best, but an unsatisfactory method of communication, and will
be rendered more so by the noise and confusion of battle.
DEFENSIVE MINES.
725
CIRCUIT CLOSER
IN TORPEDO
OPERATING BOX ON SHORE
Fig. 13. Diagram of torpedo circuit closer and connections.
G*3
726 CERTAIN USES OF ELECTRICITY IN U.S. ARMY.
field Telephones and Telegraphs.
But little is to be said of field telephones and telegraphs, as they do not
differ from commercial instruments except in their portability. The wire
is carried on reels mounted on wheeled trucks, and may or may not be
strung on poles as the occasion demands. Light reels are also provided
which may be strapped to a man's back to run wires to places otherwise in-
accessible. The work to be done by field telegraphers is, however, an im-
portant one in keeping a commander constantly in touch with his outposts.
ELECTRICITY IN THE UNITED STATES
NAVY.
The application of electricity in ships in the United States Navy at the
tresent time (July, 1901) is as follows : —
All ship's lights, searchlights, and signal lights are entirely electric.
Of power appliances the turret turning, elevating and loading of big guns,
and hoisting ammunition, are always done electrically ; ship's ventilation
is partly steam and partly electric, Avith the practice rapidly going to
complete electric ; deck winches and boat cranes are usually steam, but
very successful electric ones are in use ; steering-gear is entirely steam,
hydraulically or mechanically controlled, and electric appliances are in the
experimental stage ; an electric system of opening and closing water-tight
doors is now in progress of development ; anchor-handling gear is entirely
steam.
Interior communication appliances are almost entirely electric, but are
in some cases paralleled with mechanical equivalents, as for example voice
tubes paralleling telephones.
uvx.tno ROOM.
The generating plant is located in a compartment called the " Dynamo
Room," which is under the protective deck and adjacent to the boiler
rooms, so as to secure a direct lead of steam pipes.
«EATERATI9[G-§ETS.
The following are the principal requirements contained in the standard
specifications for generating-sets : —
Generators.
Generators to be of the direct current compound-wound multipolar type,
giving 80 volts at the terminals. The compounding to be such that at the
designed normal speed the voltage shall at no point of the external char-
acteristic curve vary more than 1.5 volts from SO volts.
There shall be no sparking whatever at the brushes when the generator
is in operation with a constant load, nor shall there be any detrimental
sparking with a change of one-half load, the brushes not being moved.
The allowable temperature rises above the air after a four-hour run at
full load are : —
Field and armature windings 60° F.
Commutator 72° F.
The temperature of windings to be calculated from their resistance rise,
and of the commutator to be measured by thermometer.
Generator to stand an over-load of 33 per cent for two hours without
injury, and the engine to be able to produce normal voltage with this over-
load.
Insulation resistance to be one megohm, tested with a pressure not greater
than 1000 volts.
The change of voltage at the terminals of the generator as measured on a
dead-beat voltmeter not to exceed 10 volts, when full load is suddenly
thrown on or off.
External magnetic field to be inappreciable at a distance of 15 feet.
Insulating substance used not to be injured by a temperature of 200° F.
Engines.
Engines to work most economically at 100 pounds steam pressure if com-
pound, and 80 pounds if simple, vacuum being 25 inches ; but they must be
able to work with pressure 20 pounds above and below these normal
pressures. _~_
728 ELECTRICITY IN THE UNITED STATES NAVY.
Cylinders to be of hard cast iron cross-heads connecting rods, shafts,
pistons and valve rods all nuts bolts, etc., to be of best forged steel.
The design must be such that all parts subject to wear shall be accessible
for adjustment and repair, especially those parts which by reason of wear
would affect the alignment of the engine.
Cylinders must be fitted with relief valves, arranged to work automati-
cally, in addition to the usual drain cocks.
All parts must be able to bear without injury the throwing on or off of
the entire load by quickly making or breaking the external circuit of the
generator.
The governor must control the speed automatically, the throttle being
wide open, within the following limits :
Variation of Load.
Variation of Steam Pressure.
Allowed
Speed
Variation.
Full load to 20% load .
Constant normal
1\%
Constant load ....
20 lbs. above to 20 lbs. below normal
3h%
Full load to no load .
20 lbs. above to 20 lbs. below normal
Wo
If engines have more than one cylinder, the work done in each cyclinder
must be practically equal at full load and normal pressure.
Cylinders and valve chests must be covered with suitable non-conducting
material. Cylinders must be fitted with indicator motions.
It is very desirable that engines shall be capable of continuous running,
without the use of lubricants in steam spaces.
The gross weight of complete sets not to exceed one-third of a pound per
watt of rated capacity. Generator and engine to be mounted on a common
bed-plate and direct connected.
The style of sets installed on the latest ships is a tandem compound
engine with a six-pole generator, manufactured by the General Electric
Company. The sizes used are 32 k.w. and 50 k.w.
The two cylinders are cast together, the L.P. on top, and separated by a
hollow cast-iron head, which forms the stuffing-box for the L.P. piston rod.
The engine is entirely inclosed, and is provided with forced oil lubrica-
tion for the main bearings, crank pin, wrist pin, and cross-head guides.
Rocker arms, governor and valve stems are provided with automatic grease
cups. A cylinder lubricator is provided, but is only used a few minutes
before shutting down, so that the cylinders will be coated with a film of oil
while standing idle. United States Metallic packing is used.
32 k.w. size runs at 400 r.p.m. and the 50 k.w. size at 310 r.p.m.
Tests.
The 50 k.w. sets of the U.S.S. " Kearsarge" and " Kentucky" gave the
following average results on tests :
STEAM CONSUMPTION AT FULL LOAD.
Steam pressure 100 pounds
Vacuum 24 inches
Steam per I.H.P. per hour 21 pounds
Steam per K.W 35.2 pounds
Combined efficiency of set 80 %
KEGULATION.
Normal speed 310 r.p.m.
Steam constant 100 pounds, full load to 20% load, gives
variation of 1.56 %
SWITCHBOARDS. 729
Constant full load steam 120 pounds to 80 pounds gives
variation of 1.5%
No load with 120 pounds to full load with 80 pounds
gives variation of 3.85 %
Normal voltage 80 volts
Throw off full load suddenly gives total fluctuation of 9.6 volts
Throw on full load suddenly gives total fluctuation of 6.9 volts
HEATIXG AFTER FOUR HOURS FULL LOAD.
Armature core surface 21° C rise
Commutator bars 28 "
Shunt-field spool surface 11.4 "
Outboard bearing 7. "
Armature conductors, by resistance 23.4 "
Field conductors, by resistance ......... 17.7 "
Engine has L.P. cylinder 18 inches diameter, H.P. 10£ incbes diameter,
with stroke of 8 incbes. Clearance in H.P. cylinders is 7£%, in L.P.
cylinder is 7i%. Weigbt of complete set is 15,000 pounds.
STEAM-pipiarG.
The dynamo room is supplied by a special steam pipe which usually is so
connected that it can take steam direct from any boiler or from the auxil-
iary steam pipe, it passes into a steam separator from which branches lead
to each of the generating-sets in the dynamo room. This separator is
drained by a steam trap which sends the water back to the hot well in the
main engine room.
The exhaust pipe from each set joins a common exhaust which connects
with the auxiliary exhaust service of the ship. If the sets are located
below the level of the ship's auxiliary exhaust pipe, a separator is placed in
the common exhaust pipe before it goes up and joins the ship's auxiliary
exhaust. This separator is drained by a small steam pump, which is
automatically started and stopped by means of a float in the body of the
separator, which float starts the pump when the separator is full and stops
it when empty.
SWITCHBOARDS.
The general problem of the design of a generator switchboard for a naval
vessel is to be able to connect any number of generators to any set of bus-
bars. There are usually four separate sets of busbars, one for the lighting
system, one for the power system, and one for the turning-gear of
each turret. The Ward-Leonard system of motor control being used for
turning the turrets, it is necessary to use a separate generator for each
turret. Separate equalizer buses are provided for both the lighting and
power systems.
Current is supplied to the different appliances by means of distribution
switchboards, which have two sets of busbars, one for lighting and one for
power, and are connected directly to the corresponding busbars on the
main generator board. Feeders run direct from these distribution boards,
each feeder being provided with a fused switch. Distribution boards are
sometimes located at various parts of the ship and sometimes made con-
tinuous with the main board.
The diagram of generator switchboard and turret turning system on page
12w shows connections as made on the U. S. S. " Illinois," except there are
four more generators connected on exactly like the four shown. Each
generator has a headboard carrying a double-pole circuit breaker, and clips
for a series field short circuiting shunt used for turret turning. The diagram
shows generators Nos. 1 and 2 operating in parallel on the power system,
No. 3 alone on the light system, and No. 4 operating the after turret turning
motors. It is to be noted that the three generators on the power and light-
ing systems have the right-hand blades of their triple pole field switches
closed, giving self-excitation through the field rheostat, while the machine
for turret turning has the middle blades closed, giving separate field excita-
tion from the power bus-bars and through the field resistance attached to
the controller in the turret.
730 ELECTRICITY IN THE UNITED STATES NAVY.
■
WIRING.
Specifications.
The principal requirements of the Navy standard specifications for light
and power conductors are : —
All layers of pure Para rubber must contain at least ninety-eight (98)
per cent of pure Para rubber ; must be of uniform thickness, elastic, tough,
and free from Haws and holes.
All layers of vulcanized rubber must contain not less than forty (40) per
cent nor more than fifty (50) per cent of pure Para rubber ; must be concen-
tric, continuous, and free from flaws or holes ; must have a smooth surface
and circular section ; and must be made to a diameter in the finished con-
ductor that will be in exact conformity with the diameter as tabulated.
All layers of cotton tape must be filled with a rubber insulating com-
pound, the tape to be of the width best adapted to the diameter of that
part o'f the conductor which is intended to bind. The tape must lay one-
half (i) its width, and be so worked as to insure a smooth surface and
circular section of that part of the finished conductor which is beneath it.
All exterior braid must be closely woven ; and all, except silk braid,
must be thoroughly saturated with an insulating waterproof compound
which will neither be injuriously affected, nor have any injurious effect on
the braid, at a temperature of '200° F. (dry heat), or at any stage of test, the
conductor being sharply bent. "Wherever a diameter over vulcanized
rubber or outside braid is tabulated or specified, it is intended to secure a
neat working-fit in a standard rubber gasket of that diameter for the pur-
pose of insuring water-tightness of the joint, and no departure from such
tabulated or specified diameter will be permitted.
All conductors to be of soft annealed pure copper wire.
No single wire larger than No. 14 B. & S. G. to be used.
"When greater conducting area than that of No. 14 B. & S. G. is required,
the conductor shall be stranded in a series of 7, 10, 37, 61,91 or 127 wires, as
may be required ; the strand consisting of one central wire, the remainder
laid around it concentrically, each layer to be twisted in the opposite di-
rection from the preceding, and all single wires forming the strand must be
of the diameter given in the American wire gauge table as adopted by the
American Institute of Electric Engineers, October, 1893.
The material and manufacture of the strand must be such that the
measured conductivity of each single wire forming the strand shall not be
less than ninety-eight (98) per cent of that of pure copper of the same
number of circular mills, the measured conductivity of the conductor as a
whole to be not less than ninety-five (95) per cent of that of pure copper of
the same number of circular mills.
Each wire to be thoroughly and evenly tinned.
All conductors shall be insulated as follows : —
First. — A layer of pure Para rubber, not less than one sixty-fourth (^)
of an inch in thickness taped or rolled on; if lapped, the tape to lap one-
half of its width.
Second. — A layer of vulcanized rubber, of exact diameter as tabulated.
Third. — A layer of commercial cotton tape, lapped to about one thirty-
second (Jj) of an inch in thickness.
Fourth.— A close braid to be made of No. 20 2-ply cotton thread, braided
with three (3) ends for all conductors under 60,000 circular mills, and of No.
16 3-ply cotton thread braided with four (4) ends for all conductors of and
above 60,000 circular mills. The outside diameter over the braid to be in
exact conformity with that tabulated.
Tests. Two samples, each 500 feet long, will be selected by the Bureau
from the coils of wire to be supplied, and must be sent by the Contractors
to the New York Navy Yard for test.
(a) Both samples, after 24 hours imersion in sea water, must have an
insulation resistance of not less than 1,000 megohms per nautical mile.
(b) Test to be at 72° F.
(c) To be tested by the direct deflection method at a potential of not less
than 200 volts.
(d) Both samples will be tested for a conductivity of not less than 96
per cent of that of pure copper, having a cross-section of the specified num-
ber of circular mills.
LIGHTING— SYSTEM.
731
(e) Chemical tests will be made to determine the constituents of the
different layers of the insulation.
(f) Braid will be tested for water-proof qualities.
(g) Physical tests will be first made for qualities of strength, toughness,
dimensions, etc.
(h) The physical and electrical characteristics of the insulation under
change of temperature will be tested by exposing the finished conductor for
several hours at a time, alternately, to a temperature of 200° F. (dry heat)
and the temperature of the atmospere, during a period of three days.
(i) The tests for characteristics of the insulation will then be repeated
and must show no practical deterioration on the results of the former
tests.
Methods of Insulating- Conductors.
Three methods of insulating conductors are used.
1. Conduit ; 2. Molding ; and 3. Porcelain supports
1. Conduit is the principal method, being used in almost all spaces below
the protective deck, and wherever wiring is exposed to mechanical injury
or the weather. Iron-armored insulated conduit is used, except in maga-
zines, and within 12-feet of the standard compass, where brass is used.
Conduit passing through water-tight bulkheads is made water-tight by
means of stuffing-boxes and hemp-packing. Water-tightness is provided
at the ends of conduit by a stuffing-box and a soft-rubber gasket, through
which the conductor passes. Long lines of conduit passing through several
water-tight compartments are provided with gland couplings at proper
intervals, which divide the run into water-tight sections, thus preventing
an injury in a flooded compartment from allowing the water to run through
the conduit into another compartment. These gland couplings are also
used where conduit passes vertically through decks, and all vertical leads
are run in conduit.
2. Wood molding is generally used in living spaces. It consists of a
backing piece fastened to the iron work of the ship, to which the molding
proper is secured by screws and covered with a wooden capping-piece.
Where leads installed in molding pass through water-tight bulkheads, a
bulkhead stuffing-box is provided for water-tightness.
3. Porcelain supports are used in dynamo rooms and for the long feeders
which are run in the wing passages where there is no danger of interference.
Stuffing-tubes are used where the wires pass through bulkheads, the same
as with molding.
Connection Boxes.
All conductors are branched by being run into standard connection boxes,
which are usually provided with fuses. Where conduit is used these boxes
are tapped, to have the conduit screwed into them ; where molding or
porcelain is used the boxes are provided with stuffing-tubes. The box covers
are made water-tight with rubber gaskets ; inside the fuses and connection
strips are mounted on porcelain bases.
IIGHTI5fC.§T8TEl[.
"Wiring1.
The maximum drop allowed on any main is 3 per cent at the farthest
lamp. Mains are required to be of the same size throughout, and to be of
1000 circular mills per ampere of normal load.
fixtures. '
Most incandescent lamps are installed in air-tight glass globes of different
shapes, depending upon position or location. Magazines are lighted by
"Magazine Light Boxes," which are water-tight metal boxes set into the
magazines through one of its walls, and provided with a water-tight door
opening into the adjacent compartment, so that the interior of the box is
accessible without entering the magazine. The sides of the boxes have
732 ELECTRICITY IN THE UNITED STATES NAVY.
j
glass windows, and each box is fitted with two incandescent lamps, each
lamp having its own separate fused branch to the main, so that one lamp
can be used as a spare.
. " Switch Receptacles " containing a snap switch and a plug socket are I;
provided for attaching portable lamps.
Lamps.
The principal requirements of the standard Navy specifications are : —
They must be of the best quality and finish, and uniform size ; the bases
must fit and be interchangeable in the standard socket.
All leading-in wires and anchors must be fused in the glass ; all anchors
must be made of metal.
The filaments must be centered in the bulb, and must not drop when the
lamps are run in a horizontal position.
Each lamp must be marked on the inside of the bulb Avith the date of
manufacture, and must have its rated candle-power, the voltage necessary
to give this candle-power, and the name of the manufacturer conspicuously
labeled on the outside of the bulb.
The material used for cementing the bases to the bulb must be so treated
as to insure against danger of short circuiting the lamp when exposed to
moisture. When porcelain is used all holes must be filled.
They must be designed for 80 volts, the rated candle-powei to be given at
not less than 78 nor more tnan 82 volts. No fraction of a volt beyond these
limits will be permitted.
The efficiency of all 16 c. p. and 32 c. p. lamps must be not less than 3 j6n,
nor more than 4 watts per candle-power, and that of 150 c.p. lamps not less
than 3 f$ nor more than 3 ^ watts per candle-power, the efficiency to be
measured when the lamps are new. The contractors shall guarantee that
all lamps supplied will have an average life of at least 600 hours, and that
the rated candle-power shall not have decreased more than 20 per cent after
burning for this length of time at the initial potential.
Before acceptance a test lot will be selected at random from the lot of
each type of lamp delivered as follows ; —
From lots not exceeding 50 lamps, all lamps.
From lots exceeding 50 but not exceeding 500, 50 lamps.
From lots exceeding 500 lamps, 10 per cent of the lot.
The test lot will be subject to the following tests: —
(a) For design, dimensions, and construction.
(6) For vacuum, by trembling of filament and spark.
(c) For voltage and efficiency when rotating at a speed of 180 revolutions
per minute.
(d) For rated candle-power by standard photometer.
A secondary standard lamp, standardized from the Bureau's standards,
will be used in the tests.
A failure of 30 per cent of the test lot to comply with foregoing specifica-
tions will cause rejection of the lot represented by that test lot.
Divingr-ljanterns.
Diving-lanterns consist of a glass cylinder closed at each end with a metal
cap, having the joint between the glass and metal packed with a soft-rubber
gasket. On the inside of one of the caps is provided a standard marine
lamp-socket for 100 candle-power incandescent lamp, to which is connected
100 feet of twin conductor cable, at the other end of which is connected a
double pole plug for a standard marine receptacle.
When first submerged a considerable amount of moisture is deposited in
the inside, which is drawn out through a small hole made water-tight by a
screw with a rubber gasket.
Searchlig-lats.
The requirements of the standard Navy specifications are : —
It shall, in general, consist of a fixed pedestal or base, surmounted by a
turntable carrying a drum. The base shall contain the turning mechanism
and the electric connections, and be so arranged that it can be bolted
securely to a deck or platform.
LIGHTING-SYSTEM. 733
The turntable to be so designed tbat it can be revolved in a horizontal
plane freely and indefinitely in either direction, both regularly and gradu-
ally by means of a suitable gearing, and rapidly by hand, the gearing being
thrown out of action.
The drum to be trunnioned on two arms bolted to tbe turntable, so as to
have a free movement in a vertical plane, and to contain the lamp and re-
flecting mirror. The drum to be rotated on its trunnions, both regularly
and gradually by means of suitable gearing, and rapidly by hand ; the gear-
ing being thrown out of action. The axis of the drum to be capable of a
movement of not less than 70° above and 30° below the horizontal.
The drum to be thoroughly ventilated and well-balanced ; to be fitted with
peep sights for observing the arc in two planes, and with hand holes to give
access to the lamp. It must be so designed that eitber a Mangin or a para-
bolic mirror can be used, and means for balancing it with either mirror
must be provided.
The mirror to be made of glass of the best quality, free from flaws and
holes, and having its surface ground to exact dimensions, perfectly smooth
and highly polished. Its back to be silvered in the most durable manner ;
the silvering to be unaffected by heat. To be mounted in a separate metal
frame lined with a non-conducting material, in such a manner as to allow
for expansion due to heat and to prevent injury to it from concussion.
The lamp to be of the horizontal carbon type, and designed for both hand
and automatic feed. The feeding of the carbons must be effected by a posi-
tive mechanical action, and not by spring or gravitation. It must burn
quietly and steadily on an 80-volt circuit in series Avith a regulating rheostat,
and shall be capable of burning for about six hours without removing the
carbons.
The front of the drum to be provided with two glass doors, one composed
of strips of clear plate glass, and the other of strips of plano-concave glass
lenses, so designed as to give the beam of light projected from the mirror a
horizontal divergence of at least 20°. The doors to be interchangeable, and
to be so arranged that either can be put in place on the drum easily and
quickly.
Electrically Controlled Projector.
To be in all respects similar to the hand controlled, with the addition of
two shunt motors, each with a train of gears ; one motor for giving the ver-
tical and the other the horizontal movement of the projector. The motors
and gears to be contained in the fixed base, and to be well protected from
moisture and mechanical injury. A means to be provided for quickly
throwing out or in the motor gears, so that the projector can be operated.
! either by hand or by motor, as desired.
The motors to be operated by means of a compact, ligbt, and water-tight
I controller, which can be located in any desired position away from the pro-
i jector. The design of the controller to be such that the movement of a
| single handle or lever, in the direction it is wished to cause the beam of
I light to move, will cause the current to flow through the proper motor in the
I proper direction to produce such movement. The rapidity of movement of
! the projector to be governed by the extent of the throw of the handle or
j lever. A suitable device to be included whereby the movement of the pro-
jector can be instantly arrested when so desired.
All projectors to be finished in a dead-black color throughout, excepting
the working-parts, Avhicb shall be bright.
The lamps to be designed to produce the best results when taking current
as follows : 18-inch, 30 to 35 amperes ; 24-inch, 50 to 60 amperes ; 30-inch,
75 to 90 amperes.
The 18-incb projector shall project a beam of light of sufficient density to
render plainly discernible, on a clear, dark night, a light-colored object 10
by 20 feet in size, at a distance of not less than 4,000 yards ; the 24-inch pro-
jector, at a distance of not less than 5,000 yards ; and the 30-inch projector,
at a distance of not less than 6,000 yards.
The connections for the electrically controlled projectors as manufactured
by the General Electric Company are shown in the diagram. The fields of
the two training motors an in series with each other and connected across
the 80-volt circuit. Both horizontal and vertical training can be simultane-
ously produced. The controller-handle when released, is brought to the off
734 ELECTRICITY IN THE UNITED STATES NAVY.
POWER SYSTEM. 735
position by springs and short circuits both motor armatures thus stopping
all movement.
The horizontal training motor drives through a worm gear, and the verti-
cal motor through a revolving nut on a vertical screw shaft : all gearing
can be easily thrown out for quick hand control.
The highest speeds are 360° in 30 seconds horizontally, and 100° in 60
seconds vertically. The motors may also be operated at four lower speeds.
The lamp has a striking magnet in series with the arc and feeding
magnet in shunt with the arc. When the arc becomes too long, sufficient
current is forced through the shunt feeding magnet to cause it to make its
armature vibrate back and forth, and thus move the carbons together
through a ratchet which turns the feed screws. The point at which the
magnet Avill begin to feed is adjustable by means of a spring attached to
armature. The feed screws are so proportioned that the positive and
negative carbons are each fed together at the same rate that they are con-
sumed, thus keeping the arc always in the focus of the mirror. Sight
holes are provided through which the arc may be watched. A permanent
magnet, fastened to the inside of the projector and surrounding the arc on
all sides but the top, causes the arc to burn steadily near the upper edge of
the carbons and in focus with the mirror.
The rheostat is located near the switchboard, and after being once set
for proper working does not need to be again changed. Double-pole circuit
breakers are used at the switchboards for switches.
SIGXAX. EIGHTS.
Ardois Signals.
The Ardois signals consist of four double lanterns, each containing a red
and a white light, which are hung from the top of the mast, one under the
other and several feet apart. By means of a special controller any number
of lanterns may have either their red or white lamps lighted, thus producing
combinations by which any code can be signaled. The lamps used are
clear, and the color is produced by having the upper lens which forms the
body of the lantern colored red ; the lower lens is clear.
The controller consists of eight semi-circular plates, with pieces of hard
rubber set in the inner edges where needed, and a rotating center stud
with eight plunger contacts rubbing on the edges of the plates. By suita-
bly placing the pieces of hard rubber for any given position of the
contacts, any desired combination of lights can be produced.
The operation consists in moving the arm carrying the contacts to the
position desired (as shown by a pointer on an indicating dial; and closing
the operating switch, when the proper lamps will light.
Truck Xiig-lsfs.
The truck lights are lanterns of construction similar to the Ardois
lanterns, mounted, one on the top of both the fore and main masts. By
means of a special controller the red or white light in either lantern can be
lighted.
POWJEK SYSTEM.
Motors are kept entirely separate from lights by the use of different
bus-bars on the generator switchboard and distribution boards. Each
motor or group of motors is supplied by its own feeder running from the
distribution board, where it has its own fused switch. A maximum drop of
5 per cent is allowed.
Principal Requirements of Specifications for Motors.
Motors to be wound for 80 volts direct current.
Sizes above 4 H. P. to be multipolar ; 4 H. P. and below may be bipolar.
Armatures to be of iron-clad type, and coils preferably to be separately
Wound and easily removable.
736 ELECTRICITY IN THE UNITED STATES NAVY.
Band wires to be of non-magnetic material, and not more than three to
be used under poles.
Commutator segments to be of pure copper, insulated with mica of such
quality that it will wear evenly with the«copper.
Carbon brushes to be used carrying not more than 30 amperes per square
inch at full load.
PILOT LAMP
Fig. 2. Diagram of Ardois Signal Set.
POWER SYSTEM. 737
No sparking to occur up to full load with no shifting of the brushes.
To prevent deterioration from rust and corrosion, such parts as holts,
nuts, screws, pins, and fittings of a light character, which if rusted or
corroded would injure the operation, strength, ease of adjustment or taking
apart, or appearance, are to be made of tobin bronze, or similar metal, and
not of iron or steel.
No insulating substances to be used that can be injured by a temperature
of 94° 0. Test for dielectric strength to be made with a pressure of 1500
volts alternating for 60 seconds, using a transformer and generator of at
least 5 k. w. capacity.
Allowed temperature rises above surrounding air are : —
Continuous running motors, open type, windings 35° C, commutator 40°
C, after eight hour full-load run.
Same as above, but closed type, 50° C, for both winding and com-
mutator.
Intermittent running motors have special requirements depending upon
use ; but nearly all require 45° C. for all parts after one hour at constant
full-load.
Bearings of all motors 40° C.
Lubrication of continuous running motors is by oil rings or slight feed
cups, the intermittent running motors by grease pockets.
Every motor to be protected by an automatic circuit-breaking device,
capable of being set to 50 % above the normal full load.
Turret-Turning* Gear.
The motors are controlled by the Ward-Leonard system, the principle of
operation of which is illustrated by the elementary diagram on the diagram
of generator switchboard and turret-turning system, page 12w.
The motors are shunt wound, and have the fields constantly separately
excited from the bus-bars of the ship's power system. A separate generator
is required which cannot be used for any other purpose when used with the
turret. The generator is also separately excited from the power bus-bars;
but a variable rheostat, located in the turret, is connected in the shunt-
field circuit. The brushes of the motor are directly connected to the
brushes of the generator, and the generator is kept running at constant
speed by its driving-engine. It is now evident that by varying the rheostat
in the turret, the held excitation, and consequently the voltage produced
by the generator, will be varied ; and any variation in the voltage of the
generator will produce a corresponding variation in the speed of the motor,
which has a constant field from separate excitation. The direction of rota-
tion of the motor is reversed by reversing the leads to the armature. The
actual connections for the application of the above principles are shown in
the main part of the diagram. Generator No. 4 is shown connected for
operating the after-turret.
Closing the after-turret field switch and the center blades of the generator
field switch, separately excites the fields of the motors and generator from
the power bus-bars. The regular field rheostat of the generator is entirely
disconnected, and a rheostat located in the turret and operated by the tur-
ret turning controller is used instead.
Closing the positive and negative single-pole switches on the after-turret
bus-bars connects the generator armature to the motor armatures, through
a circuit breaker, the reversing contacts of the controller, and separate
armature switches for each of the two motors, which are operated in
parallel.
The controller has one shaft, at the top of which are located the con-
nections for the generator field rheostat, so arranged that as the controller
is turned either way from the off position the rheostat is gradually cut out ;
below are located the reversing contacts, which reverse the connections
between the generator armature and the motor armatures ; ■ these contacts
are so arranged that at the off position the motor armatures are entirely
disconnected from the generator, and are short-circuited through a low
resistance called the " Brake resistance." The effect of this brake resist-
ance is to bring the turret to a quick stop when the controller is brought
to the off position, as the motor armatures revolving in a separately excited
field generate a large current, which passes through the braking resist-
ance, and thus absorbs the kinetic energy of the turret, giving a quick and
738 ELECTRICITY IN THE UNITED STATES NAVY.
POWER SYSTEM. 739
smooth stop. In parallel with each of the large main fingers of the re-
versing contacts is a small auxiliary finger and an auxiliary resistance
connected to it. This auxiliary finger makes contact a little before and
breaks it a little after the main linger, and thus reduces the sparking.
The controller is also provided with a magnetic blow-out for reducing
sparking at contacts.
When used on this system for operating a turret the generator has its
series coil short circuited by a very low resistance shunt, so that it has very
little effect on the field excitation, but this resistance is so proportioned
that enough of the total current generated by the generator will pass
through the series coil to give a quick and positive start of the turret ; be-
cause if the series coil is absolutely short circuited, and only the separately
excited shunt coil used, the time required for the held to build up is suffi-
cient to make the starting of the turret very sluggish and irregular, and pre-
vents very tine training from being obtained.
On the U.S.S. " Kearsarge " and " Kentucky," two 50 H. P. motors of 400
r.p.in. are used to turn each double turret, which weighs 710 tons and is
mounted on 32-rlanged conical rollers, 15|-inches diameter, running on a
track 21 feet in diameter. Each motor drives through a worm and wheel,
connected to a spur pinion meshing into a stationary circular rack. The
motors are geared together by a cross shaft. Friction clutches are inserted
in the transmission gearing to prevent sudden stops, firing the guns, or im-
pact of shot, from breaking the gearing. Full speed of the turret is at the
rate of one revolution per minute. The controller is provided with a me-
chanical automatic stop which brings it to the off position when the turret
reaches the limit of its train at either side.
The following results were obtained on test of the four turrets of the two
ships. The friction varied considerably for different turrets.
Forward turret of the " Kearsarge " gave : —
Turning at constant full speed,
Input of motors 22 E.H.P.
Output of motors 13 H.P.
Maximum when accelerating at rate of attaining
full speed in 10 seconds,
Input of motors 44.5 E.H.P.
Output of motors 36.3 H.P.
This was the easiest running of the four turrets.
The hardest running gave,
Turning at constant full speed,
Imput of motors 41 E.H.P.
The motors are seen to be greatly over-powered for the work, this to
allow for overcoming any deformation of track, rollers, etc., which might
occur during action.
Fineness of train obtained : —
The turrets were easily started and stopped with a resulting movement of
10 seconds of arc, which equals a movement of about 2 inches at 1,000 yards
range.
This is a movement much smaller than the visual angle covered by the
cross hair of the sighting telescope, so that the fineness of train is much
greater than that of sighting.
A turret was turned thro ugh its extreme train from one side to the other
48 times in one hour, with a stop being made at each beam position during
each trip.
The motors used were entirely inclosed and weighed 5,700 pounds.
JLoading* and Training: Gear for Guns.
Guns of 12-inch and over are elevated and rammed by power, smaller guns
have hand gear.
The elevating gear for 12-inch and 13-inch guns consists of a 2J H.P., SO-volt,
300 r.p.m. series motor, geared to a revolving screw which raises or lowers a
nut crosshead from which connecting rods go to the gun.
Ordinary rheostatic control is used with no braking appliance. To train a
13-inch gun at the rate of 30° per minute, an armature input of from 1.5 to
740 ELECTRICITY IN THE UNITED STATES NAVY.
3 E.H.P. is required, depending npon the condition of the load and whether
elevating or depressing. The motors used are entirely inclosed and weigh
550 pounds.
Rammers consist of a telescopic tube worked through spur and chain-
gearing by a 5 H.P., 80-volt, 775 r.p.m. series motor. A friction slip clutch
is inserted in the gearing to prevent damage when the shell seats itself in
the breach. Ordinary rheostatic control is used.
When ramming a shell but little power is required, as the shell slides
along the breech, but as it is being forced to its seat at the end of the breech
chamber a sudden rush of current of from two to three times the full-load
current of the motor is produced.
The motors used are similar to the elevating motors, except wound for
higher speed.
AUKmUNITIOlV HOISTS.
Power ammunition hoists are of two kinds ; first, those in which a car
or cage is hoisted up and down by a line wound on a drum on the motor
counter-shaft ; and second, those in which the motor runs an endless chain
provided with toes or buckets on which the ammunition is placed and con-
veyed up through a trunk.
Hoists for 13-inch and 13-inch Ammunition.
These hoists are of the first kind. The motor frame is provided with
bearings for a counter-shaft, geared by a spur-gear and pinion to the arma-
ture shaft; on the counter-shaft is mounted a grooved drum for the hoisting-
cable.
On the armature shaft is mounted a solenoid band-brake. The cores of
the solenoid are weighted and attached to the brake-setting lever so that
when free their weight is sufficient to hold the loaded car from falling;
when the solenoids are energized the cores are drawn up and the brake re-
leased.
The controller is constructed so that on the off position the solenoids are
not energized and the brake is set ; but at all other points, both hoisting and
lowering, the solenoids are energized and the brake released.
Shunt motors are used, and the control for hoisting is ordinary rheostatic ;
the resistance being put in series with the armature and gradually cut out,
the field is always constantly excited as soon as the feeder-switch is closed.
For lowering, the entire rheostat is thrown directly across the line, one
armature lead connecting to one side of the line and the other lead gradu-
ally moved (as the motor is brought to full speed) from the condition of a
short-circuited armature at the off position to direct connection to the other
side of the line at the full on position ; in all intermediate positions the
armature is in shunt with a part of the rheostat. The object of this is to
cause the armature to take current from the line and run as a motor when
lowering a light load which will not overhaul, but to run as a generator and
send current through the rheostat if the load is very heavy and overhauls
the motor and gearing. In either case the speed will depend upon the
amount of the rheostat that is in shunt across the armature. The off posi-
tion of the controller short-circuits the armature, and since the fields are
always excited, this gives a quick stop and also holds the load.
The 13-inch hoists of the tJ.S.S. "Kearsarge" and "Kentucky" used 20
H.P. motors running at 350 r.p.m., with a gearing ratio of 6.43 from arma-
ture to counter-shaft.
The load was, empty car 1,846 pounds, and full charge 1,628 pounds, or a
total of 3,474 pounds.
The following average results were obtained when testing at hoisting full
charge : —
Hoisting-speed, feet per minute 180
Mechanical H.P. in load 18.96
Input of motor, E.H.P . 28.5
Total efficiency 66.6%
Motors were designed to be suspended under the turret, were entirely
inclosed, and weighed 3,000 pounds complete with brake.
AMMUNITION HOISTS
741
Hoists for 8-inch Ammunition.
Hoists for smaller ammunition are made and controlled in a similar
manner as the above, except the solenoid brakes are replaced with an ordi-
nary band-brake, operated by a foot or hand lever.
The 8-inch hoists used a 6 H.P.,375 r.p.m. shunt motor to hoist a total load
of 910 pounds at 163 feet per minute.
Tests gave average results of, —
Mechanical H.P. in load 4.5
Input of motor, E.H.P 7.4
Total efficiency . [ 60.8%
742 ELECTRICITY IX THE UNITED STATES NAVY.
Endless Chain Auimuuitioii Hoists.
These hoists run continuously, the ammunition being fed in as desired.
The motor is geared to the chain sprockets by spur gearing, is shunt wound,
and is started and stopped by a controlling panel, which is provided with no
voltage and overload release, a held rheostat fur varying the speed of the
motor, and a reversing-switch.
A solenoid brake, similar to the one above described for the 13-inch
hoist, is mounted on the armature shaft, and is set when the starting-arm
is in the off position, but has its coils energized and is released when the
arm makes the first contact in starting. At the full on position, part of the
starting rheostat is in series with the brake, thus cutting down the current
consumed by it. This does not affect the reliability of the brake, since the
current required to hold up the cores is much less than that required to
first start them, and at the start the full-line voltage is on the coils.
To lower ammunition the reversing-switch is thrown down, which re-
verses the connections to the motor armature, and puts in the armature
circuit a safety switch. This safety switch is attached to the lever which
operates the catch pawls in the hoist trunk. These pawls will allow am-
munition to go up, but will catch and prevent it from going down, and are
used to keep the ammunition from falling in case any part of the hoist
should be shot away. When the pawl lever is thrown down it throws the
pawls out of action, and allows ammunition to be lowered by reversing the
motor ; it also closes the safety switch which completes the armature cir-
cuit for the lowering position of the reversing-switch.
This style of hoist is used for all kinds of ammunition up to and includ-
ing 6-inch. Packages are so made that they weigh about 100 pounds each.
Motors rated at 3| H.P., continuous running, with speed variation of 360 to
475 r.p.m. are used ; power required varies greatly with kind and style of
hoist. Motors are entirely inclosed and weigh 980 pounds.
BOAT CRAIES.
For handling steam cutters and other boats a revolving crane having the
general shape of a davit is used ; it extends down to the protective deck,
and has a steady bearing at each deck passed through, and the weight is
carried by a roller thrust bearing. The operating machinery is carried on
a circular platform fastened to the crane.
The cranes for the U.S.S. "Kearsarge" and "Kentucky" have two
motions ; namely, rotating the entire crane, and raising or lowering the
hook. One motor only is used for both motions, clutches and gearing being
used to produce either at will. Two counter-shafts are driven by the
motor, each having a worm at the end, one driving a worm wheel on the
hoisting-drum and the other a worm wheel on the shaft of the rotating
pinion. Each of the counter-shafts contains a friction clutch, so that it can
be disconnected from its worm at will.
A band-brake is provided on the rotating-worm to hold the crane from
rotating. A strap brake is provided on the hoisting-drum, which consists
of a wrought-iron strap, one end of Avhich is permanently fastened to the
platform, wound three times around the hoisting-drum and the free end
attached to a weighted lever which pulls it taut. This strap is wound
around the drum in the direction it turns when lowering, so that any
motion in this direction causes the friction to make the strap bind tighter
and hold the drum from turning ; but rotation of the drum in the hoisting
direction causes the friction to make the strap loosen up and allow the drum
to continue rotating. Thus the brake automatically holds the load from
over-hauling the drum when the motor is disconnected. For lowering, the
brake has its free end raised by a hand lever, thus loosening it, and allow-
ing the drum to turn in the lowering direction.
The motor is shunt wound with field constantly excited as soon as the
feeder switch is closed at the distribution board.
The controller cylinder gives ordinary rheostatic control with resistance
in series with the armature, but there is a commutating switch which when
closed gives the same kind of control as used for lowering with the 13-inch
ammunition hoist described above ; this control is used for lowering and
BOAT CRANES.
743
rotating, since it gives a smoother stop, and the rheostatic control is used
for hoisting. The off position of the controller short circuits the arma-
ture, giving a quick and positive stop.
A 40-foot steam cutter is the largest boat handled, and weighs complete
16,000 pounds.
Fig. 5. Diagrams of Connections for Boat Crane Motors
The weight of the complete crane is 54,000 pounds.
Motor is 50 H.P,, 400 r.p.m., is entirely inclosed and water-tight, and
weighs 5,890 pounds. Current is supplied through collector rings mounted
on the cranes. The controller is water-tight, and the circuit breaker is
744 ELECTRICITY IN THE UNITED STATES NAVY.
mounted in a water-tight iron box ; all were tested for water-tightness by
playing a stream of salt water on them from the fire-hose.
The following results were obtained on test : —
Load of 16,000 pounds
Hoisting-speed, feet per minute ... 25
Mechanical H.P. in load 13.64 H.P.
Input of motor to hoist ...... 30.6 E.H.P.
Total efficiency 44.5 %
Rotating speed 1 r.p.m.
Imput of motor to rotate 14.8 E.H.P.
EMPTY HOOK.
Input of motor to hoist 7.3 E.H.P.
Input of motor to rotate 8.9 E.H.P.
It is seen that the motor is very much overpowered for the ordinary work
required, but this is done to have a large margin to be able to handle boats
in rough weather when the ship is rolling. Especial strain will be pro-
duced when rotating a boat in when the ship is heeled over, and also from
the inertia effect of rolling.
DECK WIWCHES.
The electric deck winches of the U.S.S. "Kearsarge" and "Kentucky"
consist of a series motor geared through a system of spur-gearing to the
shaft carrying the winch heads.
The control is ordinary rheostatic, with the controller suspended horizon-
tally from the deck underneath the winch and operated by a vertical shaft
and a pair of bevel gears. Braking is accomplished by a foot lever, operat-
ing a brake-band. For ordinary working the controller is turned to the
full speed and the winch allowed to run continuously, the load being con-
trolled by taking several turns of the hoisting-rope around the winch
head. The maximum load can be very nicely controlled in this manner.
The capacity of the winches is 2,200 pounds at 300 feet per minute ; and
two winches are provided with a compound gear which can be thrown in to
give a speed of 50 feet per minute with a corresponding pull of 13,000
pounds. The motors are 25 H.P., with a full-load speed of 320 r.p.m., but
when the winch is allowed to run without load the speed of the motor
increases to about 900 r.p.m.
When hoisting 2,200 pounds at 300 feet per minute, the average test
results were : —
Mechanical H.P. in load 20 H.P.
Input of motor 34.3 E.H.P.
Total efficiency 58.4%
Motors are entirely inclosed and water-tight, and were tested for water-
tightness by playing a stream of salt water from the fire-hose on them
without any water entering.
ViafTILATIOHr FAlfS.
Nearly all compartments of a ship have artificial ventilation by power
fans ; both exhaust and pressure systems being employed. Both steam and
electric drive is used, steam being used almost entirely for forced draught
in the boiler rooms, while electric predominates for all other places.
Shunt motors are used, started, and stopped by a controlling panel having
" no voltage"' and "overload" release. Speed variation is obtained by a
field rheostat.
The following table gives results of tests on different sizes and styles of
fans when run at full load and speed :
STEERING-GEAR.
745
Fan.
03
5
o
03
03
<D N
§1s
£ 03 y
Hi
& .
^^03
53 rt
Steel plate . .
Blower
50"
500
IS
12500
11.1
300
No. 6 Monogram,
Sturtevant .
Ex-
hauster
27£"
1030
1J
2580
2.7
810
No. 5 Monogram,
Sturtevant .
Ex-
hauster
24"
1220
*5
1460
1.43
910
No. 3 Monogram,
Sturtevant .
Ex-
hauster
14J"
1650
1*
835
.77
1196
ITEEROG-GEAR.
Electrical steering-gears are not at present used in the United States
Navy, but are somewhat used in foreign navies. One method used is
shown in the diagram of connections in which M is a shunt motor oper-
ated from the ship's mains and running continuously at constant speed ;
its shaft is directly coupled to G, a shunt generator, the two forming a
SHIPS MAINS
v Fig. 6. Diagram of Steering-Gear.
motor generator set and located at any desired place, most conveniently in
the dynamo room. P is a shunt motor geared by suitable gearing to the
rudder post, and has its field constantly excited from the ship's mains, its
brushes are directly connected to the brushes of the constantly running
generator G. R and R' are two equal and symmetrical rheostats, the con-
tact arm of R being attached to the rudder post or any part of its gearing
which has a similar rotation, and the contact arm R' being attached by
suitable gearing to the steering-wheel. The ends of the field of G are con-
nected to these two contact arms, and the two rheostats are connected
across the ship's mains.
It is now seen that the two rheostats and the field of G form a Wheat-
stone's bridge, the parts of the rheostat on each side of the contact arms
being the four resistances, the field of G taking the place of the galvanom-
eter and the line being the battery. This bridge is in balance, and no
746 ELECTRICITY IN THE UNITED STATES NAVY.
current will flow through the field of G whenever the two rheostant arms
occupy similar positions on their respective rheostats ; hut if they do not
occupy similar positions, then the bridge will be out of balance and current
will flow through the field of G.
The operation is as follows : Starting with everything central as shown
in the diagram, if the steering-wheel is turned, moving the arm of K/ a
certain distance, the balance will be disturbed and current will flow through
the field of G, causing it to generate an E.M.E. and start the motor P, which
will continue to run until the arm of R has been moved a distance equal to
the original movement made by the arm of IV, when the balance will be
restored, no current will flow through the field of G, which will then
develop noE.M.F., and the motor P will consequently stop. The gearing
between P and the contact arm of R is so arranged "hat the movement of
the arm will be in the proper direction to restore the balance. The direction
of current flow in the field of G, and consequently the polarity of G and
direction of rotation of P, will depend upon the direction of movement of
the arm of R/. It is thus seen that the arm of R is given an exact copying
motion of the arm of R/, both for distance moved and direction of rotation.
Instead of actually turning the rudder, the motor P can be made, it
desired, to only operate the valve of a steam-steering engine ; when this is
done the device is called a " Telemotor."
Another method (which has only been applied for use as a telemotor) has
the first movement of the steering-wheel connect the operating motor
directly to the ship's mains, and the motion of the motor causes a step by
step mechanism to disconnect it when it has moved the engine valve a
distance proportional to the original movement of the steering-wheel. Both
connection and disconnection of the operating motor are made by a switch
at the steering-wheel, the interrupter of the step-by-step mechanism is at
the operating motor and the mechanism itself at the steering-wheel. The
mechanical arrangements are quite complicated.
Several ships of the Russian Navy have been fitted with direct acting
steering-gears by the Electro-Dynamic Company, of Philadelphia. Pa.,
and work on the above first described bridge principle, with the addition
of a small exciter for the generator mounted on the generator shaft, and
the field of this exciter is connected with the bridge rheostats, instead of
the main generator field itself. The motor of the motor-generator is rated
at 70 H.P., the generator at 500 amperes and 100 volts, and the rudder
motor at 50 H.P. ; all being easily capable of standing 50% overloads for
short periods of time. The motor-generator runs at 650 r.p.m. and weighs
11,000 pounds ; the rudder motor runs at 400 r.p.m. and weighs 5,500 pounds ;
the accessory appliances weigh 1,500 pounds, making a total weight of
18,000 pounds.
Tests made on the Russian Cruiser " Variag" took 150 H.P. to move the
rudder from hard-a-port to hard-a-starboard in 20 seconds, while going at a
speed of 23 knots an hour. For ordinary steering at about 19 knots, readings
taken every time the rudder was moved gave the following results : —
Amperes.
Volts.
K.W.
250
4
1.
250
10
2,5
150
14
2.1
180
30
5.4
200
40
8.
100
50
5.
100
55
5.5
50
5
.25
50
25
1.25
60
40
2.
100
22
2.2
100
25
2.5
50
15
.75
200
26
5.2
100
18
1.8
100
20
2.
WATER-TIGHT DOOR GEAR. 747
Readings were taken for every movement occurring for a period of J hour,
rudder was never moved more than 15 degrees.
WATER-TIGHT DOOR GEAR.
An arrangement for electrically operating sliding water-tight bulk-head
doors has been experimentally tried and has given good results. The sliding
door is provided with a rack and pinion, the shaft of the pinion being con-
nected through a worm gear witb a 1 H,P. motor, compound wound, of
the short shunt type, the shunt coils being relatively weak. The circuits
are so arranged that for raising the door, only the series coils are in circuit,
giving quick and easy starting, while for closing the door where it may be
necessary to cut through coal, the shunt and series coils are both in circuit.
The door can be opened or closed by a switch having a handle on both
sides of the bulkhead. A limit switch is provided, which is opened by a
bell crank when the door reaches either of its extreme positions. An
emergency control is also provided by means of which all doors in the ship
can be closed at the same time from any desired place, such as the conning-
tower.
The diagram on the next page shows the connections for the control of
one door, and the parts are as follows : —
S and S' are two separate solenoids having attached to their cores, by
insulating washers, cross contact arms, which make and break contact
across the contact clips 1, 2, 3, 4, etc. When a solenoid is energized it draws
up its core and the arms make contact across the two upper pairs of clips,
and when it is not energized the weight of the core will cause it to drop and
the arms make contact across the two lower pairs of clips.
L and 1/ are the limit switches. 1/ is opened when the door reaches its
upper limit of travel, but is closed at all other positions. L opens its left
hand pair of contacts and closes its right-hand pair of contacts at the
extreme down position, but at all other positions it is closed at the left
and open at the right. The left-hand contacts form the limit switch, the
right-hand ones being used for signal connections described later
C is the local control switch at the door, and can be operated from either
side of tne bulkhead. It is provided with a spring which keeps it on the
middle point when released.
E is the emergency control switch, and is located at any desired point on
the ship. ^ L _
D is a signal lamp located near E at the emergency station.
A and B are the ship's mains.
The operation is as follows : — _ ,
To Open Door. — Move local control switch C to its right-nand con-
tact which will energize solenoid S', the circuit being from main A through
arm' of C throuoh I/, through S', across contacts 2, to main B. This will
raise the 'core ofs' and the arms will connect across contacts 5 and 7, and
the motor will be connected to the mains as a series motor, the shunt coils
beino- idle. The circuit is from main A through contacts 5, through the
armature, across contact 7, through the series field to main B, and the
' motor will run in the raising direction until the switch C is released, or
until the door reaches its upper limit and opens the limit switch I/, which
will open the solenoid circuit and allow the core to fall, thus cutting off the
motor. , , . , ...
To close Boor.— Move switch C to its left-hand contact, which will
energize solenoid S, the circuit being from main A through arm of C,
through L, across contacts 8. through series field coil to mam B. 11ns will
raise the core of S and connect across contacts 1 and 3, ana the motor will
be connected to the mains with both the shunt and series coils in use. Ihe
circuit is from main A through contacts 1, through armature through con-
tacts 3, through series coil to main B ; and for the shunt field is from mam
A through shunt field to side of armature which connects to the series coil
and through it to main B, giving a short shunt connection. This will cause
the motor tc run in the lowering direction until C is released and the limit
Whenever the motor is stopped both solenoids are released as drawn in the
diagram, and the armature is short circuited through its series field, thus
giving an electrical braking effect which absorbs the kinetic energy of the
748 ELECTRICITY IN THE UNITED STATES NAVY.
W- ^5
^rn^i^=^
-oa
r
Q— 1— Q
i—Qi
-snti^i-^nns-
'Q-^tf
7Qn
o
Fig. 7. Diagram of Connections for Electric Control of Watertight
Sliding Doors.
INTERIOR COMMUNICATION SYSTEM. 749
armature and other moving parts, and gives a smooth and quick stop. The
circuit is from right brush, through contacts 6 and 2, through series field,
through contacts 8 and 4 to left brush.
The door can be closed from the distant emergency station by closing the
switch E, which gives the same result as moving switch C to its left-hand
point, since closing E connects the pivot of C to the left point, the circuit
being through the center point on which C normally rests. It is thus seen
that the closing of E does not affect the action of C, since as soon as C is
moved from its center point E is cut out.
If the door is closed at the emergency station by means of E, the lamp D
will light up as soon as the door is completely closed, for the closing of the
door operates the lower limit switch L and closes its right-hand contacts.
The circuit is from main B through lamp, through right ciontacts of L,
through E, through C, to main A.
If desired all doors in the ship can be closed by one emergency switch, by
having that switch operate a solenoid having a pair of contacts for each
door, or the doors may be divided into sections, each section having a sepa-
rate emergency switch and solenoid.
Since the motor takes its maximum current just at the instant of final
closing of the door, the speed of the different motors on any one section is
so adjusted that the doors will reach the end of their travel one after the
other with a small time interval between each, thus preventing the sudden
drain of current from the ship's generators that would occur if all shut ex-
actly at the same instant. One-third k.w. of generator capacity is allowed
per door for a system. This system is made by the "Long Arm" System
Company, Cleveland, O.
The following results were obtained on test: —
Amperes. Volts.
To start the door down 13* 115
Steadying while closing at ... 3\ 113
To start the door up 22 115
Steadying while opening at 11 113
With fine bituminous coal heaped against the back of the door to within
six inches of the top : —
Amperes. Volts.
To start the door up ...... 24§ 115
Steadying while opening at ll" 113
On opening the door wide the coal ran through the doorway, and the door
was then closed through this coal lying eleven inches deep on the sill : —
Amperes. Volts,
To start the door down 14 115
13.5 115
Cutting through coal and within an inch of seat-
ing, steadied at 3 113
3 113
While driving loose coal through the hollow sill
the ammeter jumped to 52 115
49 113
INTERIOR COMMIJiriC AVION §YSTEM.
The interior communication system of a ship consists of, as the name
implies, the appliances for transmitting signals of all kinds from one part
of the ship to another.
Order a sad Position Indicators.
Many devices have been tried for the electrical transmission of pre-
arranged orders, or the position of a moving body, such as a rudder-head ;
but the most successful and the one generally installed consists at the re-
ceiving end of a number of small incandescent lamps, each mounted in a
small separate light tight cell with a glass front, and the whole inclosed in
a suitable case On the glass front of each light cell is marked an order or
number, or whatever particular information the particular device is to in-
dicate. This receiver is connected to the transmitter by a cable having a
50 ELECTRICITY IX THE UNITED STATES NAVY.
separate Avire for each lamp, and one wire for a common return. The trans-
mitter consists of a switching device, by means of which any lamp or lamps
in the receiver may be lighted, the current being taken from the lighting
mains As many receivers as desired can be operated from one transmitter,
the receivers being connected in parallel.
Melna Angle Indicator.
When the above-described device is used to indicate in different parts of
the ship the angle that the helm is turned, the transmitter switch consists
of an arm, as shown in diagram No. 8 on the next page, fastened to the
rudder stuck, and moving over a series of contact pieces arranged in an arc-
in the same manner as an ordinary held rheostat, Each ot the contact
pieces is connected, through one wire of an interior communication table, to
one side of one ot the receiver lamps, which lamp has marked on its front
the number of degrees that the given contact is situated from the center-line
ot the ship ; the other side of the lamp is connected to the common return
wire, which goes to the source of current and then to the contact arm.
As the rudder turns, the contact arm makes connection with the different
contact pieces, and as it touches each piece the corresponding lamp in the
receiver lights up and indicates its position within the limits shown ; when
it is just midway between any two pieces it will touch both and light both
corresponding lamps, which doubles the closeness with which the position
is indicated.
As many receivers can be connected on as desired, all being operated in
parallel,
Engine Telegraphs.
When used for engine order telegraphs the contact arm is mounted in a
metal case and operated by a hand lever of the same construction as the
hand lever of an ordinary mechanical ship's engine telegraph The case
contains indicator lamps in parallel with the lamps of the receiver at the
engine-room, so that the operator on the bridge has visual evidence of the
order sent. A small magnetto is geared to the transmitter handle, and rings
a bell at the receiver whenever the handle is moved, thus calling attention
to the change of order.
Itattle Order Indicators.
The receiving indicators are of the same construction as above described
for the Helm Indicators, but the transmitter consists of single-pole snap
switches, connected up exactly like the lamps of the indicator, so that by
turning the proper switches any desired number of lamps can be lighted,
and of course any desired order can be marked in front of any lamp. Sev-
eral indicators, located in different parts of the ship, are usually worked by
each transmitter, all being connected in parallel.
The case which contains the transmitter switches also contains an indica-
tor, thus always showing what orders are being indicated on the system.
llang-e Indicators.
Range indicators are exactly like the Battle Order Indicators, except that
instead of having different orders marked before each lamp, a number rep-
resenting the range in yards is marked.
A range indicator and a battle-order indicator are usually mounted to-
gether at desired stations, thus showing what kind of firing is to be done,
and at what range.
Hevolution Indicators.
To show on the bridge the direction and speed of rotation of the engines,
several appliances have been devised. The one most generally used is shown
in Fiy. 0, and consists at the transmitter of a small gear E, mounted eccen-
trically upon the propeller shaft S, and meshing with a pinion P, which is
carried on the lower end of an arm A. The arm A is slotted and mounted
on a pivot as shown, and when S is rotating, A will be turned to one side or
the other, defending upon the direction of rotation of S, until it hits on the
stop B, and will then remain against the stop and reciprocate up and down
from the eccentric actior of E ; on each up movement it will make contact
with clip Cor (7, depending upon which side it is turned.
■M^HHIi^M
INTERIOR COMMUNICATION SYSTEM.
CONTACT ARM FASTENED TO RUDDER POST
751
The receiver consists of two pivoted pointers, connected as shown to two
electro-magnets and marked "Astern " and " Ahead."
From the connections shown, it is seen that at each rotation of the pro-
peller shaft the pointer corresponding to the direction of rotation will make
a movement, and at the same time the magnet armature will make a plainly
audible click, thus indicating both visually and audibly the rotation. The
other pointer corresponding to the direction in the opposite rotation will
752 ELECTRICITY IN THE UNITED STATES NAVY.
remain still. For twin screws a separate transmitter and receiver is in
stalled for each.
A separate mechanical indicator is also usually installed, consisting of {
small shaft geared to the propeller shaft, and running to the bridge (angles
being turned by bevel gears) , where it drives a pointer at the same rate a;
the main shaft.
mm^—m—m^—^^^m^^^
MISCELLANEOUS. 753
Telephones.
In the telephone system used there is no "Central" station; but each
telephone is provided with a transfer switch, by means of which it can be
directly connected with the other telephones. An annunciator is provided
to show what station has made the call. The ringing and talking circuits
are entirely separate, and ringing is done by battery current.
To make a call, the transfer switch is turned so that the pointer is over
the name of the station desired, and a push-button pressed. This rings the
bell, and causes the annunciator at the desired station to indicate the name
of the station calling ; then the person called turns his transfer switch to
agree with the indication of the annunciator, which connects the two tele-
phones directly with each other, and allows talking to proceed.
Bell Company's telephones are used, and are mounted in water-tight
cases ; all accessories are made water-tight.
fire Alarms.
The fire-alarm system consists of mercurial thermostats, located in all
parts of the ship, and connected to an annunciator in the captain's office.
The thermostats consist of a hermetically sealed metal tube containing
mercury, and provided with an insulated platinum point, so adjusted that
at a temperature of 200° F. the mercury will have expanded sufficiently to
make contact with the platinum, thus completing the circuit, and indicat-
ing at the annunciator the location of the heated thermostat. The annun-
ciator is provided with a bell which will ring continuously until a switch
corresponding to the indicating drop is opened. Battery current is used.
Water-tig-ht Boor Alarms.
To give a general signal for the closing of all water-tight doors, a system
of alarm whistles is used. The whistle consists of a solenoid which pulls
its core down into an air chamber, and thus forces the air out through a
small shrill whistle. The core is restored by spiral springs. Ail whistles
are connected in parallel, and are operated by a make and break mechan-
ism, which by the pulling of a lever will interrupt the circuit continuously'
for about 30 seconds, each interruption giving a blast from each whistle.
Current from the lightning mains is used.
SOLENOID ALARM WHISTLE.
The construction is shown in Fig. 12. The clockworks for operating the
contact maker is constructed so that by rotating an operating lever it is
wound up, and upon releasing the lever it vibrates the contact while running
down, thus giving periodical signals.
Call Bells.
An elaborate system of call bells, annunciators, electro-mechanical signal
gongs, etc., is installed on all large ships. The main difference from ordi-
nary commercial work is that all appliances are made water-tight.
MISCELLAIirEOlJS.
Bang-e-Finder.
The following is a brief outline of the principles employed in the instru-
ment designed by Lieutenant Bradely Fiske of the United States Navy.
In Fig. 10 let A represent the target and BC a known base. Then
AC : BC : : sin ABC : sin BAG.
sin BAC '
The angle A BC can be readily measured. The angle BAC =
line BE being parallel to AC.
fo4 ELECTRICITY IN THE UNITED STATES NAVY.
The Fiske range-finder measures the angle DBE by the use of the Wheat-
stone bridge, as follows :
Suppose tbe two semi-circles in Fig 10 replaced by two metallic arcs (Fig.
11). At the center of each of these arcs is pivoted a teiescope. tbe pivot of
which is connected to a battery B The telescopes are in electrical contact
with the arcs. These metallic arcs are connected at their extremities with
a galvanometer, c, the whole forming a Wheatstone bridge, whose arms are
aa bb.
When the telescopes are pointed at the object A, it is evident that the
arms of the bridge are unequal, and hence do not balance ; and this fact i
indicated by the deflection of the needle of the galvanometer. The arc FD
Fig. 10.
Fig. 11.
is noted. By swinging the telescope at F around till the needle of the
galvanometer indicates zero, the bridge balances, tbe telescope being
parallel to the one at C, and the arc or angle DF — FE is equal to the
angle at A. From this the distance AC can be calculated, or read oft'
directly on a properly constructed scale.
Generally, in using the instrument, the telescopes are mounted at a
distance from the battery, where the view is uninterrupted, while the gal-
vanometer is at the gun. The observers keep the telescopes constantly
directed on the target, and the man at the gun balances the bridge by in-
troducing a variable resistance into the circuit till the needle stands at
zero This variable resistance is graduated so as to indicate the range
corresponding to the resistance introduced
firing' Guns.
Large guns are arranged to use both percussion and electric primers for
firing The electric primer is of tbe same external shape as the percussion
primers, and is exploded by a fine platinum wire, heated by current from
the cells of a dry battery mounted near the gun A ground'return is used,
and a safety switch is fastened to the breech plug, so that the circuit can-
not be completed until the breech plug is closed, A push-button is used to
complete the circuit and fire tbe gun,
Speed Recorder.
An instrument called the "Weaver Speed Recorder" is somewhat used
for measuring the speed of ships when run on tbe measured mile, and while
being Jaunched ; also to measure the acceleration of turrets during test
it consists essentially of a clock-works, which drives a paper tape over a
set of five pens operated by electro-magnets, so that when any magnet is
MISCELLANEOUS.
755
excited it pulls its pen against the moving paper tape, and makes a dot
thereon The connecting levers between the "magnet and pen are arranged
something like a piano finger action, so that no matter how long the magnet
is kept excited, the pen will only make a quick, short dot All pens are
located side by side in the same line, so that if they were all operated at
the same instant, the result would be a line of dots across the tape.
When used for measuring mile runs, one pen is connected to a make and
brake chronometer, so that it makes a dot on the tape every second ; an-
other pen is connected to a hand push-button, so that a dot can be made at
the start and finish of the run, and at as many intermediate points as de-
756 ELECTRICITY IN THE UNITED STATES NAVY.
sired ; the other three pens arc connected to contact makers on the shafts
of the main engines, so that a dot is made for every revolution of the en-
gine. (If the ship has twin screws, of course only two of the remaining
pens are used ; and if single screw, only one.)
It is thus seen that by counting the number of second dots between the
start and hnish dots, the length of time to make the run is given, and fey
counting the number of revolution dots in any desired space, the speed of
the engine is given. Fractional seconds or revolutions can easily be scaled.
"When used to obtain launching curves, a long steel wire wound on a drum
has one end attached to the ship, and a contact maker is fastened to this
drum. As the ship slides out the drum is revolved and dots made on the
tape at each revolution ; knowing the diameter of the drum, the speed at
any instant is found by comparison of the revolution dots with the second
dots. The hand-push is used to mark the start, finish, instant of pivoting,
and any other desired matters.
When used for acceleration runs on turrets, the same procedure as for
launching curves is followed, except the contact maker is attached to some
rotating part of the turret mechanism.
MISCELLANEOUS.
757
MISCELLANEOUS.
THERUIO-JEIvECTRIC SCALE.
With respect to lead, at a mean temperature of 20° C. (Matthiessen.)
The E.M.F.s are in micro-volts per degree centigrade :
Bismuth of commerce in wire +97.0
" pure " +89.0
" crystallized along axis +G5.0
" " normal to
axis
Cobalt
German Silver ....
Mercury ......
Lead
Tin
Copper of commerce . .
Platinum
Gold
-22.0
11.75
0.418
(i.l
Antimony, pure, in wire .
Silver * " "
Zinc " "
Copper, galvano-plastic
Antimony of commerce in
Arsenic
Iron, piano wire . .
Antimony, crystallized along
axis .......
Antimony, normal to axis .
Phosphorus (red) ....
Tellurium
Selenium
3.7
3.S
6.0
13.56
17.50
— 22.60
— 26.40
— 29.70
—502.00
—807.00
conutectio]!^ of ihductiou con,
(Ruhinkoff' s.)
I, T2
Index to Figure.
TXT2 = Terminals to which wires from
B = Battery are attached.
Ji =. Revers'er or commutator for removing or cutting off current.
C£= Contact screw platinum-pointed (in primary circuit).
H— Hammer (soft iron), the movement of which completes and
breaks circuit at CS.
C = Condenser for arresting the momentary direct induced current in
PC=z Primary coil of thick wire, through which battery current
passes.
SC= Secondary coil of fine wire (well insulated) in which sparking
currents are induced.
DXD2— Spark dischargers fitted to ends of secondary coil.
IC = Iron core, being a bundle of very soft iron wires.
POWER REQVIRED FOR iEWIIVG-IVACHI^ES.
Light-running 20 machines to 1 h.p.
Heavy work on same 15 " " "
Leather-sewing , . . 12 " " "
Button-hole machines . ... 8 to 12 " " "
758
MISCELLANEOUS.
^M«]¥Y BRAKE.
Fig. 2.
Constant
then
.0001904.
Horse-power.
'ci
6
>
>
£
a
H
H
Kind
-d >-
-8.5
3
o
!W
*w
Name of Firm.
of
— ._
J) •
Work.
l~
T.r=
■2«S
u
£w
c3
g,00 i g^j
0^2
s
o
°
CO
©
H
M
W
^
ft
fc
,4
Lane & Bodley ....
E. & W.W.
58
132
2.27
J. A. Fay & Co
W. W.
100
15
85
15
300
M.I Hi
3.53
Union Iron Works . .
E.,M. M.
400
95
305
23
1G00
4.0ii
5.24
Frontier Iron &Brass W'ks
M.E.,etc.
25
8
17
32
150
i ;.oi)
8.82
Taylor Mfg. Co
E.
95
230
'1.42
Baldwin Loco. Works
L.
2500
2000
500
80
4100
1.64
S.20
W. Sellers & Co. (one de-
partment)
H.M.
102
41
61
40
300
2.93
4.87
Pond Machine Tool Co. .
M. T.
180
75
105
41
432
•'.40
4.11
Pratt & Whitney Co. . .
"
120
725
6.04
Brown & Sharpe Co. . .
230
900
3.91
33000 "
Horse-power = .0001904 x d X w x revolutions per minute.
POWJEH lTSE» BY MlCHIi\E-T«OI§.
(K-. E. Dinsmore, from the Electrical World.)
1. Shop shafting 2T35 in. x 180 ft. at 160 revs., carrying 20 pulleys
from 6 in. diam. to 36 in., and running 20 idle machine belts . 1.32 H. P
2. Lodge-Davis upright back-geared drill-press with table, 28 in.
swing, drilling § in. hole in cast iron, with a feed of 1 in. per
minute 0.78 H. P,
3. Morse twist-drill grinder No. 2, carrying 26 in. wheels at 3200
revs ' 0.29 H. P.
4. Pease planer 30 in. x 36 in., table 6 ft., planing cast iron, cut
\ in. deep, planing 6 sq. in. per minute, at 9 reversals .... 1.06 H. P.
5. Shaping-machine 22 in. stroke, cutting steel die, G in. stroke, \
in. deep, shaping at rate of 1.7 square inch per minute . . . 0.37 H. P.
6. Engine-lathe 17 in. swing, turning steel shaft 2| in. diam., cut
T3g deep, feeding 7.92 in. per minute 0.43 H. P.
7. Engine lathe 21 in. swing, boring cast-iron hole 5 in. diam., cut
j3s diam., feeding 0.3 in. per minute 0.23 H. P.
8. Sturtevant No. 2, monogram blower at 1800 revs, per minute,
no piping 0.8 H. P.
9. Heavy planer 28 in. X 28 in. X 14 ft. bed, stroke 8 in., cutting
steel, 22 reversals per minute 3.2 H. P.
Horse-power in Machine-shops; friction; Men Employed.
(Flather.)
MISCELLANEOUS.
759
Horse-power in Machine-shops.
Horse-power.
cS
§
©
<o
EH
Kind
o?
-3 £
- V
°.3
««2
S
ft .
a cm
Name of Firm.
of
Work.
"ei
•5 ^
o
s
O
6
4) ©
O
6
H
d
Ph
£
14
A
Yale & Towne Co. . . .
C. & L.
135
67
68
49
700
5.11
10.25
Ferracute Machine Cu. .
P. &D.
35
11
24
31
90
2.57
3.75
T. B. Wood's Sons . . .
P. & S.
12
30
'J. 50
Bridgeport Forge Co. .
H. F.
150
75
75
50
130
.86
1.73
Singer Mfg. Co
S.M.
1300
3500
2.69
Howe Mfg. Co
"
350
1500
4.28
"Worcester Mach. Screw Co.
M. S.
40
80
2.00
Hartford " " "
"
400
100
300
25
250
0.02
0.83
Nicholson File Co. . .
Averages
F.
350
400
1.14
346.4
38.6%
818.3
2.1)(
5.13
Abbreviations: E., engine; W.W., wood-working machinery; M. M.,
mining machinery ; M. E., marine engines ; L., locomotives ; H. M., heavy
machinery; M. T., machine-tools; C. &L,, cranes and locks; P. & D.,
presses and dies; P. & S., pulleys and shafting; H. F., heavy f orgings ;
S. M., sewing-machines ; M. S., machine-screws ; F., tiles.
DYIAMOS.
1 Tool chest.
1 Magneto and cable.
1 Speed indicator.
1 Tape line, 75 ft.
1 Rule, 2 ft.
1 Scraper, for bearings.
1 Blow lamp.
1 Clawhammer, No. 13.
1 Ball pein hammer, No. 24.
1 B. & S. pocket wrench, No. 4.
1 Monkey wrench, 10 inch.
1 Set (2) Champion screw-drivers.
1 Large screw-driver, 12-inch.
1 Off-set screw-driver.
1 Ratchet brace, No. 33.
Bits, i, §, h f , I, h 1 inch.
1 Clarke Expansive bit, £ to 3 inch.
1 Screw-driver bit.
1 Gimlet bit.
1 Wood countersink.
1 Extension drill, § in. length, 24 in.
1 Long or extension gimlet.
1 Cold chisel, f inch.
1 Half round cold chisel.
1 Cape chisel.
1 Wood chisel, firmer paring, f inch.
1 Brick drill.
Files, one each : round, flat, half-
round and three-square.
1 Saw, 20 inch.
1 Hack-saw, 10 inch.
10 Extra saw blades.
1 Plumb bob.
1 Brad awl.
1 Pair carbon tongs.
1 Soldering copper, No. 3.
1 Pound of solder.
1 Pair of climbers.
1 Come-along.
1 Splicing-clamp.
1 Strap and vise.
1 Pair line pliers, 8 inch.
1 Pair of side-cutting pliers, 5 inch.
1 Pair of diagonal-cutting pliers, 5 in.
1 Pair of round-nose pliers, 5 inch.
1 Pair of flat-nose pliers, 5 inch.
1 Pair of burner pliers, 7 inch.
6 Sheets of emery cloth.
6 Sheets of crocus cloth.
2 Gross of assorted machine screws.
2 Gross of assorted wood screws.
150 Special screws.
Taps, 6-30, 10-24, 12-24, 18-18.
Brills, 34, 21, 9, 15-64.
Tap wrench.
760
MISCELLANEOUS.
TOOLS III «M ■ It • l>
The followiug-named tools will probably be required in constructing lines
for city or commercial ligbting :
(Davis.)
Stubs' pliers, plain
Climbers and straps
Pulley-block and ecc. clamp
Come-along and strap . . . .
Splicing-clamps
Linemen's tool-bag and strap .
Soldering-furnace
Gasoline blow-pipes
Soldering coppers
Pole-bole sbovels
Pole-bole spoon, regular . . .
Octagon digging-bars . . . .
Tamping-bars
Crowbar ,
Pick-axe
Carrying-hook, beavy . . . ,
Cant-hook
Pike-poles
Pole-supporter
Comb, pay-out reel and straps .
Nail-hammer
Linemen's broad hatchets . .
Drawing-knives
Hand-saw
Ratchet-brace, bits
Screw-drivers
Wrench
Bastard file
Size.
Cost
about
8 in.
$2.00
3.00
( To
8.00
\ No. 3
2.25
(B. &S.
2.50
4.80
6.00
6.00
2 1b.
.95
8 ft.
1.50
7 ft.
1.25
8 ft.
3.50
7 ft.
2.60
10 1b.
.90
.75
6.00
4 ft.
2.00
16 ft.
2.40
6 ft.
12.00
20.00
lib.
1.00
6 in.
1.50
12 in.
2.10
26 in.
1.50
10 in.
3.00
8 in.
.80
12 in.
1.25
12 in.
.30
APPROXIMATE LliT OF SUPPHIS
REQUIRED IN INSTALLING 15 CITY LAMPS AND 20 COMMERCIAL LAMPS
ON A FIVE-MILE CIRCUIT, SETTING POLES 132 FEET APART.
(Davis.)
Size or
Diameter.
Price
about
Quantity.
Electric-light poles
Electric-light poles
Electric-light poles
Cross-arms, 4-pin .
Painted oak pins .
Oak pins and bolts
Iron break-arms .
Lag-screws and washer
Glass insulators, D. G.
Pole steps ....
Guy stranded cable .
Cross-arm brace and bolts
Line wire
30 ft.,
35 ft.,
40 ft.,
4 ft.
ljin.
l£in.
7 in.
7 in.
£X71
f X 8*i
$2.40 each
4.15
5.50
.07
.75
.04
■n
.05
.07 lb.
.20 each
125.00 mi.
40
200
800
24
25
400
850
2500
500 lbs.
40
6 miles
MISCELLANEOUS.
761
MATERIAL HE«V1 1 IIK1> FOR CONITOCTIIYC} IN
1AOTP§.
Sleet-proof pulleys . .
Street-lamp cleats, iron
Arc-lamp cordage .
Suspension cable .
Hard-rubber tube .
Soft-rubber tubing
Arc cut-out . . .
Porcelain insulators
, Oak brackets and spikes
(Davis.)
£in.
$0.75 eacb.
30
.25 "
15
1.25 bd. ft.
25
.02i ft.
3000 ft.
1.50 lb.
5 lbs
.20 ft.
200 ft.
3.50 eacb
20
2.40 bd.
400
2.50 "
150.
'NATIONAL ELECTRICAL CODE.'
RULES AND REQUIREMENTS OF THE NATIONAL BOARD OF
FIRE UNDERWRITERS FOR THE INSTALLATION OF WIRINHi
AND APPARATUS FOR ELECTRIC LIGHT, HEAT, AND POWER
AS RECOMMENDED BY THE UNDERWRITERS' NATIONAL
ELECTRIC ASSOCIATION.
EDITION OF 1901.
The National Electrical Code, as it is here presented, is the result of the
united efforts of the various Electrical, Insurance, Architectural, and allied
interests which have, through the National Conference on Standard Elec-
trical Rules, composed of delegates from various National Associations,
unanimously voted to recommend it to their respective Associations for
approval or adoption.
The following is a list of the Associations represented in the Conference,
all of which have approved of the Code :
American Institute of Architects.
American Institute of Electrical Engineers
American Society of Mechanical Engineers
American Street Railway Association
Factory Mutual Fire Insurance Companies
National Association of Fire Engineers
National Board of Fire Underwriters
National Electric Light Association
Underwriters' National Electric Association
OE^fRAL M,A]¥ «OVERJI\C THE ARRAK^E-
ittEarx of rilei.
CLASS A. — Central Stations, Dynamo, Motor, and Storag-e-
Battery-Rooms, Transformer Substations, etc. Rules 1
toll.
CLASS B. — Outside Work, all systems and voltages. Rules 12 and 13.
CLASS C — Inside Work. Rules 14 to 39. Subdivided as follows :
General Mules, applying to all systems and voltages. Rules 14 to 17.
Constant-Current systems. Rules 18 to 20.
Constant-I*otentiai systems.
All voltages. Rules 21 to 23.
Voltage not over 550. Rules 24 to 31.
Aroltage between 550 and 3,500. Rules 32 to 37.
Voltage over 3,500. Rules 38 and 39.
CLASS D. — Specification for Wires and Fitting's. Rules 40 to 63.
CLASS E. — Miscellaneous. Rules 64 to 67.
CLASS F. —Marine Wiring-. Rules 68 to 80.
CIASS A.-§TATIOS§ AVD DYKAMO ROOMS.
INCLUDES CENTRAL STATIONS, DYNAMO, MOTOR, AND STORAGE-BATTERY
ROOMS, TRANSFORMER SUBSTATIONS, ETC.
1. Generators —
a. Must be located in a dry place.
b. Must never be placed in a room where any hazardous process is carried
on, nor in places where they would be exposed to inflammable gases or
flyings of combustible materials.
762
CLASS A. STATIONS AND DYNAMO IIOOMS. 763
; c. Must be insulated on floors or base frames, which must be kept filled
;o prevent absorption of moisture, and also kept clean and dry. Where
Erame insulation is impracticable, the Inspection Department having juris-
diction may, in writing, permit its omission, in which case the frame must
jDe permanently and effectively grounded.
! A high-potential machine which, on account of great weight or for other
reasons, cannot have its frame insulated from the ground, should be sur-
rounded with an insulated, platform. This may be made of wood, mounted
jn insulating supports, and so arranged that a man must always stand upon
lit in order to touch any part of the machine.
I In case of a machine having an insulated frame, if there is trouble from
static electricity due to belt friction, it should be overcome by placing near
the belt a metallic comb connected with the earth, or by grounding the
frame through a very high resistance of not less than 200 ohms per volt
generated by the machine.
i d. Every constant-potential generator must be protected from excessive
current by a safety fuse, or equivalent device, of approved design in each
lead wire.
These devices should be placed on the machine or as near it as possible.
;, Where the needs of the service make these devices impracticable, the '
Inspection Department having jurisdiction may, in writing, modify the
requirements.
e. Must each be provided with a waterproof cover.
I /. Must each be provided with a name-plate, giving the maker's name,
the capacity in volts and amperes, and the normal speed in revolutions per
minute.
2. Conductors —
] From generators to switchboards, rheostats, or other instruments, and
jthence to outside lines.
! a. Must be in plain sight or readily accessible.
b. Must have an approved insulating covering as called for by rules in
Class "0" for similar work, except that in central stations, on exposed
circuits, the wire which is used must have a heavy braided non-combustible
outer covering.
Bus bars may be made of bare metal.
c. Must be kept so rigidly in place that they cannot come in contact.
d. Must in all other respects be installed under the same precautions as
required by rules in Class " C " for wires carrying a current of the same
volume and potential.
3. $w*tcnt>oards —
a. Must be so placed as to reduce to a minimum the danger of communi-
cating fire to adjacent combustible material.
Special attention is called to the fact that switchboards should not be
built down to the floor, nor up to the ceiling, but a space of at least ten
or twelve inches should be left between the floor and the board, and from
eighteen to twenty-four inches between the ceiling and the board in order
to prevent fire from communicating from the switchboard to the floor or
ceiling, and also to prevent the forming of a partially concealed space very
liable to be used for storage of rubbish and oily waste.
b. Must be made of non-combustible material or of hardwood in skeleton
form filled to prevent absorption of moisture.
c. Must be accessible from all sides when the connections are on the back,
but may be placed against a brick or stone wall when the wiring is entirely
on the face.
d. Must be kept free from moisture.
e. Bus bars must be equipped in accordance with rules for placing
conductors.
4. Resistance Boxes and Equalizers —
{For construction rules, see No. 60.)
a. Must be placed on a switchboard or, if not thereon, at a distance of a
a foot from combustible material, or separated therefrom by a non-inflam-
mable, non-absorptive3 insulating material.
764 NATIONAL ELECTRICAL CODE.
5. Lightning- Arresters —
{For construction rules see No, 63.)
a. Must be attached to each side of every overhead circuit connected with
the station.
It is recommended to all electric lightand power companies that arresters
be connected at intervals over systems in such numbers and so located as to
pi event ordinary discharges entering (over the wires) buildings connected
to the lines.
b. Must be located in readily accessible places away from combustible
materials, and as near as practicable to the point where the wires enter the
building.
Station arresters should generally be placed in plain sight on the switch
board.
In all cases, kinks, coils, and sharp bends in the wires between the
airesters and the outdoor lines must be avoided as far as possible.
c. Must be connected with a thoroughly good and permanent ground con-
nection by metallic strips or wires having a conductivity not less than that
of a No. 6 B. & S. copper wire, which must be run as nearly in a straight
line as possible from the arresters to the earth connection.
Ground wires for lightning arresters must not be attached to gas-pipes
within the buildings.
It is often desirable to introduce a choke coil in circuit between the
arresters and the dynamo. In no case should the ground wire from
lightning arrester be put into iron pipes, as these Avould tend to impede the
discharge.
G. Care and Attendance.
a. A competent man must be kept on duty where generators are operating.
b. Oily waste must be kept in approved metal cans and removed daily.
Approved waste cans shall be made of metal, with legs raising can three
inches from the floor, and with self-closing covers.
1. Testing" of Insulation Resistance.
a. All circuits, except such as are permanently grounded in accordance
with Rule 13 A, must be provided with reliable ground detectors. Detectors
which indicate continuously, and give an instant and permanent indication
of a ground, are preferable. Ground wires from detectors must nut be
attached to gas-pipes within the building.
b. Where continuously indicating detectors are not feasible, the circuits
should be tested at least once per day, and preferably oftener.
c. Data obtained from all tests must be preserved for examination by tli
Inspection Deptrtment having jurisdiction.
These rules on testing to be applied at such places as may be designated
by the Inspection Department having jurisdiction.
H. Motors —
a Must be insulated on floors or base frames, which must be kept filled
to prevent absorption of moisture ; and must be kept clean and dry. Where
frame insulation is impracticable the Inspection Department having juris-
diction may, in writing, permit its omission, in which case the frame must
be permanently and effectively grounded.
A high-potential machine which, on account of great weight or for other
reasons, cannot have its frame insulated, should be surrounded with an
insulated platform. This may be made of wood mounted on insulating
supports, and so arranged that a man must stand upon it in order to touch
any part of the machine.
In case of a machine having an insulated frame, if there is trouble from
static electricitv due to belt friction, it should be overcome by placing near
the belt a metallic comb connected to the earth, or by grounding the frame
through a very high resistance of not less than 200 ohms per volt generated
by the machine.
b. Must be wired under the same precautions as required by rules in class
" C," for wires carrying a current of the same volume and potential.
The leads or branch circuits should be designed to carry a current at least
iifty per cent greater than that required by the rated capacity of the motor
■BOHH^BIB^
CLASS A. STATIONS AND DYNAMO ROOMS. 765
to provide for the inevitable overloading of the motor at times without
overf using the wires.
c. The motor and resistance box must be protected by a cutout and con-
trolled by a switch (see No. 17 a), said switch plainly indicating whether
"on" or "off." Where one-fourth horse-power or less is used on low-
tension circuits a single-pole switch will be accepted. The switch and
rheostat must be located within sight of the motor, except in such cases
where special permission to locate them elsewhere is given in writing by
the Inspection Department having jurisdiction.
d. Must have their rheostats or starting-boxes located as to conform to
the requirements of No. 4.
In connection with motors the use of circuit-breakers, automatic start-
ing-boxes and automatic under-load switches is recommended, and they
must be used when required.
e. Must not be run in series-multiple or multiple-series, except on con-
stant-potential systems, and then only by special permission of the Inspec-
tion Department having jurisdiction.
/. Must be covered with a waterproof cover when not in use, and, if
deemed necessary by the Inspection Department having jurisdiction, must
be inclosed in an approved case.
From the nature of the question the decision as to what is an approved
case must be left to the Inspection Department having jurisdiction to de-
* "mine in each instance.
/. Must, when combined with ceiling fans, be hung from insulated hooks,
or else there must be an insulator interposed between the motor and its
support.
h. Must each be provided with a name-plate, giving the maker's name,
the capacity in volts and amperes, and the normal speed in revolutions
per minute.
©. Maihvaj Power Plants*.
i. Must be equipped in each feed wire before it leaves the station with
an approved automatic circuit-breaker (see No. 52) or other device, which
will immediately cut oft the current in case of an accidental ground. This
device must be mounted on a fireproof base, and in full view and reach of
the attendant.
1©. Storage or Primary Hatteries.
(. When current for light and power is taken from primary or secondary
batteries, the same general regulations must be observed as applied to
similar apparatus fed from dynamo generators developing the same differ-
ence of potential.
b. Storage battery rooms must be thoroughly ventilated.
c. Special attention is directed to the rules for rooms where acid fumes
exist (see No. 24, j and k).
d. All secondary batteries must be mounted on non-absorptive, non-
combustible insulators, such as glass or thoroughly vitritied and glazed
porcelain.
e. The use of any metal liable to corrosion must be avoided in cell con-
nections of secondary batteries.
11. Transformers.
{For construction rules, see No. 62.)
i. In central or substations the transformers must be so placed that
. smoke from the burning out of the coils or the boiling over of the oil
(where oil-filled cases are used) could do no harm.
CliJLSS B. — ©XJXSII9E WORK.
ALL, SYSTEMS ASD VOLTAGES.
13. Wires.
t,. Service wires must have an approved rubber insulating covering (see
No. 41). Line wires, other than services, must have an approved weather-
proof, or rubber insulating covering (Nos. 41 and 44). All the wires must
have an insulation equal to that of the conductors they confine.
7C6 NATIONAL ELECTRICAL CODE,
b. Must be so placed tliat moisture caunot form a cross connection be-
tween tliem, not less than a foot apart, and not in contact with any sub-
stance other than their insulating supports. Service blocks must be covered
over their entire surface with at least two coats of waterprool paint.
c Must be at least seven feet above the highest point of flat roofs, and
at least one foot above the ridge of pitched roofs over which they pass or to
which they are attached. .
il Must be protected by dead insulated guard iron or wires from pos-
sibility of contact with other conducting wires or substances to which cur-
rent may leak. Special precautions of this kind must be taken where sharp
angles occur, or where any wires might possibly come in contact with
electric light or power wires. .
e. Must be provided with petticoat insulators of glass or porcelain. For-
celain knobs or cleats and rubber hooks will not be approved.
f Must be so spliced or joined as to be both mechanically and electri-
cs il'lv secure without solder. The joints must then be soldered, to insure ,
preservation, and covered with an insulation equal to that on the con-
AlMomts must be soldered, even if made with some form of patent spli-
cing device. This ruling applies to joints and splices in all classes of wiring
covered by these rules. , , . , . , , ..
a Must, where they enter buildings, have drip loops outside, and the
holes through which the conductors must be bushed with non-conibustible,
non-absorptive insulating tubes slanting upward toward the inside.
h Telegraph, telephone, and similar wires must not be placed on the
same cross-arm with electric light or power wires ; and when placed on the
same pole with such wires the distance between the two inside pins of each
cross-arm must not be less than twenty-six inches.
i. The metallic sheaths to cables must be permanently and effectively
connected to " earth."
TROLLEY WIRES.
j. Must not be smaller than No. 0 B. & S. copper or No. 4 B. & S. silicon
bronze, and must readily stand the strain put upon them when muse.
le Must have a double insulation from the ground. In wooden-pole con-
struction the pole will be considered as one insulation.
I Must be capable of being disconnected at the power plant, or of being
divided into sections, so that, in case of fire on the railway route, .he cur-
rent may be shut off from the particular section and not interfere with the
work of 'tin* firemen. This rule also applies to feeders.
m. Must be safely protected against accidental contact where crossed by
other conductors. , , , , , , , , .
Guard wires should be insulated from the ground, and should be electric-
ally disconnected in sections of not more than 300 feet in length.
GROUND RETURN WIRES.
n. For the diminution of electrolytic corrosion of underground metal g
work, ground return wires must be so arranged that the diilerence oi '
potential between the grounded dynamo terminal and any point on the
return circuit will not exceed twenty -five volts. J
It is suggested that the positive pole of the dynamo be connected t<> tin
trolly line,' and that whenever pipes or other underground metal work an
found to be electrically positive to the rails or surrounding earth, that thej
be connected by conductors arranged so as to prevent as far as possible
current flow from the pipes into the ground.
13. Transformers —
(For construction rules, see No. 62.)
a. Must not be placed inside of any building, excepting central station!-
unless by special permission of the Inspection Department having juris
T^Must not be attached to the outside walls of buildings, unless ser
arated therefrom by substantial supports.
CLASS B. OUTSIDE WORK. 767
13. A. Grounding- JLow Potential Circuits.
The grounding of low potential circuits under the following regulations is
only allowed when so arranged that under normal conditions there will be no
flow of current through the ground wire.
Direct Current 3 -Wire Systems.
a. Neutral wire may be grounded, and when grounded the following
rules must be complied with : —
1. Must be grounded at the Central Station on a metal plate buried in
coke beneath permanent moisture level, and also through all available
underground water- and gas-pipe systems.
2. In underground systems the neutral wire must also be grounded at
each distributing-box through the box.
3. In overhead systems the neutral wire must be grounded every 500 feets
as provided in Sections c, e, and/.
The Inspection Department having jurisdiction may require grounding if
they deem it necessary.
Two-wire direct current systems having no accessible neutral point are
not to be grounded.
Alternating' Current Secondary Systems.
b. The neutral point of transformers, or the neutral wire of distributing
systems, may be grounded, and when grounded the following rules must be
complied with : —
1. Transformers feeding 2-wire systems must be grounded at the center
of the secondary coils.
2. Transformers feeding systems with a neutral wire must have the
neutral wire grounded at the trausformer and at least every 250 feel
beyond.
Inspection Department having jurisdiction may require grounding if they
deem it necessary.
Ground Connections.
c. The ground wire in D. C. 3-wire systems must not at Central Stations
be smaller than the neutral wire and not smaller than No. 6 B. & S. else-
where.
d. The ground wire in A. C. systems must never be less than No. 6 B. &
S., and must always have equal carrying capacity to the secondary lead of
the transformer, or the combined leads where transformers are banked.
e. The ground wire must be kept outside of buildings, but may be di-
rectly attached to the building or pole. The wire must be carried in as
nearly a straight line as possible, and kinks, coils and sharp bends must be
avoided.
f. The ground connections for Central Stations, transformer sub-
stations, and banks of transformers must be made through metal plates
buried in coke below permanent moisture level, and connections should also
be made to all available underground piping systems. For individual
transformers and building services the ground connection may be made as
above, or may be made to water or other piping systems running into the
buildings. This connection may be made by carrying the ground wire into
the cellar and connecting on the street side of meters, main clocks, etc._
In connecting ground wires to piping systems, where possible the wires
should be soldered into one or more brass plugs and the plugs forcibly
screwed into a pipe-fitting, or where the pipes are cast iron into a hole
tapped to the pipe itself. For large stations, where connecting to under-
ground pipes with bell and spigot joints, it is well to connect to several
lengths, as the pipe joints may be of rather high resistance. Where such
plugs cannot be used the surface of the pipe may be filed or scraped bright.
the wire wound around it, and a strong clamp put over the wire and firmly
bolted together.
Where ground plates are used a No. 16 copperplate, about 3 x 6 feet in
size, with about two feet of crushed coke or charcoal about pea size both
under and over it, would make aground of sufficient capacity for a mod-
erate size station, and would probably answer for the ordinary sub-station
768 NATIONAL ELECTRICAL CODE.
or bank of transformers. For a large Central Station considerable more
area might be necessary, depending upon the other unground connections
available. The ground wire should be riveted to such a plate in a number
of places, and soldered for its whole length. Perhaps even better than a
copperplate is a cast-iron plate with projecting forks, the idea of the fork
being to distribute the connection to the ground over a fairly broad area,
and to give a large surface contact. The ground wire can probably best be
connected to such a cast-iron plate by brass plugs screwed into the plate to
which the wire is soldered. In all cases the joint between the plate and
the ground wire should be thoroughly protected against corrosion by suit-
able painting with waterproof paint or some equivalent.
CLASS C. — 1\SII)E WORK.
ALL SYSTEMS AND VOLTAGES.
« EX 12 It A JL RELE§ — ALL lYiTKIUS VX I> VOLTAGES.
14. Wires.
(For special rules, See Nos. 18, 24, 32, 38, and 39.)
a. Must not be of smaller size than No. 14 B. & S., except as allowed
under Rules 24 t and 45 b,
b. Tie wires must have an insulation equal to that of the conductors they
confine.
c. Must be so spliced or joined as to both mechanically and electrically
secure without solder ; they must be then soldered to insure preservation,
and the joint covered with an insulation jqual to that on the conductors.
Standard wires must be soldered before being fastened under clamps or
binding screws ; and, when they have a conductivity greater than No. 10 B.
& S. copper wire, they will be soldered into lugs.
All joints must be soldered, even if made with some form of patent
splicing device. This ruling applies to joints and splices in all classes of
wiring covered by these rules.
d. Must be separated from contact with walls, floors, timbers, or parti-
tions through which they may pass by non-combustible, non-absorptive
insulating tubes, such as glass or porcelain.
Bushings must be long enough to bush the entire length of the hole in one
continuous piece, or else the hole must first be bushed by a continuous
waterproof tube, which may be a conductor, such as iron pipe ; the tube
then is to have a non-conducting bushing pushed in at each end so as to
keep the wire absolutely out of contact with the conducting pipe.
e. Must be kept free from contact with gas, water, or other metallic
piping, or any other conductors or conducting material which they may
cross, by some continuous and firmly fixed non-conductor, creating a sepa-
ration of at least one inch. Deviations from this rule may sometimes be
allowed by special permission.
/. Must be so placed in wet places that an air space will be left between
conductors and pipes in crossing, and the former must be run in such a way
that they cannot come in contact with the pipe accidentally. Wires should
be run over, rather than under, pipes upon which moisture is likely to
gather or Avhich, by leaking, might cause trouble on a circuit.
15. Underground Conductors —
a. Must be protected, when brought into a building, against moisture and
mechanical injury, and all combustible material must be kept removed
from the immediate vicinity.
b. Must not be so arranged as to shunt the current through a building
around any catch-box.
1©. Table Carrying- Capacity of Wires.
Below is a table which must be followed in placing interior conductors,
showing the allowable carrying capacity of wires and cables of ninety-eight
per cent conductivity, according to the standard adopted by the American
Institute of Electrical Engineers.
-INSIDE WORK.
769
Table A.
Table B.
Table A.
Table B.
6
Rubber-
Weather-
Rubber-
Weather-
Cfi
Covered
proof
Covered
proof
Wires.
Wires.
Circular
Circular
Wires.
Wires.
^3
See No. 41.
See No.
Mills.
Mills.
See No. 41.
See No.
W
42 to 44.
42 to 44.
Amperes.
Amperes.
Amperes.
Amperes.
18
3
5
1,624
200,000
200
300
16
6
8
2,583
300,000
270
400
14
12
16
4,107
400,000
330
500
12
17
23
6,530
500,000
390
590
10
24
32
10,380
600,000
450
680
8
33
46
16,510
700,000
500
760
6
46
65
26,250
800,000
550
840
5
54
77
33,100
900,000
600
920
4
65
92
41,740
1,000,000
650
1,000
3
76
110
52,630
1,100,000
690
1,080
2
90
131
66,370
1,200,000
730
1,150
1
107
156
83,690
1,300,000
770
1,220
0
127
185
105,500
1,400,000
810
1,290
00
150
220
133,100
1,500 000
850
1,360
000
177
262
167,800
1,600,000
890
1,430
0000
210
312
211,600
1,700,009
1.800,000
1,900.000
2,000,000
930
970
1,010
1,050
1,490
1,550
1,610
1,670
The lower limit is specified for rubber-covered wires to prevent gradual
deterioration of the high insulations by the heat of the wires, but not from
fear of igniting the insulation. The question of drop is not taken into con-
sideration in the above tables.
The carrying capacity of sixteen and eighteen wire is given, but no
smaller than fourteen is to be used, except as allowed under Rules 2it
and 45 b.
Iff. Switches. Cutouts, Circuit-Breakers, etc. —
(For construction rules, see Nos. 51, 52, and 53.)
a. Must, whenever called for, unless otherwise provided (for exceptions,
see No. 8 c and No. 22 c), be so arranged that the cutouts will protect, and
the opening of the switch or circuit-breaker will disconnect, all of the
wires ; that is, in a two-wire system the two wires, and in a three-wire
• system the three wires, must be protected by the cutout, and disconnected
by the operation of the switch or circuit-breaker.
b. Must not be placed in the immediate vicinity of easily ignitible stuff or
where exposed to inflammable gases or dust or to flyings of combustible
material.
c. Must, when exposed to dampness, either be inclosed in a waterproof
box or mounted on porcelain knobs.
COMSTA]¥T CURKEIT SYSTEMS.
PRINCIPALLY SERIES ARC LIGHTING.
IS. Wires —
(See also ATos. 14, 15, and 16.)
a. Must have an approved rubber insulating covering (see No. 41).
b. Must be arranged to enter and leave the building through an approved
double-contact service switch (see No. 51), mounted in a non-combustible
case, kept free from moisture, and easy of access to police or firemen. So-
called " snap switches " must not be used on high-potential circuits.
770 NATIONAL ELECTRICAL CODE.
c. Must always be in plain sight, and never incased, except when required
by the Inspection Department having jurisdiction.
d. Must be supported on glass or porcelain insulators, which separate the
wire at least one inch from the surface wired over, and must be kept rigidly
at least eight incbes from each other, except within the structure of lamps,
on hanger-boards, in cutout boxes, or like places, where a less distance is
necessary.
e. Must, on side walls, be protected from mechanical injury by a sub-
stantial boxing, retaining an air space of one inch around tbe conductors,
closed at the top (the wires passing through busbed holes), and extending
not less tban seven feet from the floor. When crossing floor-timbers in
cellars or in rooms, where they might be exposed to injury, wires must be
attached by their insulating supports to the underside of a wooden strip not
less than one-half an inch in thickness.
lO. Arc Lampo —
{For construction rules, see No. 57.)
a. Must be carefully isolated from inflammable material.
b. Must be provided at all times with a glass globe surrounding the arc,
securely fastened upon a closed base. No broken or cracked globes to be
used.
c. Must be provided with a wire netting (having a mesh not exceeding one
and one-fourth inches) around the globe, and an approved spark arrester
(see No. 58), when readily inflammable material is in the vicinity of the
lamps, to prevent escape of sparks, melted copper or carbon. It is recom-
mended that plain carbons, not copper-plated, be used for lamps in such
places.
Arc lamps, when used in places where they are exposed to flyings of easily
inflammable material, should have the carbons inclosed completely in a
globe in such manner as to avoid the necessity for spark arresters.
For the present, globe and spark arresters will not be required on so-
called " inverted arc" lamps, but this type of lamp must not be used where
exposed to flyings of easily inflammable materials.
d. "Where hanger-boards (see No. 56) are not used, lamps must be hung
from insulating supports other than their conductors.
30. Incandescent Stamps in Series Circuits —
a. Must have the conductors installed as provided in No. 18, and each
lamp must be provided with an automatic cutout.
b. Must have each lamp suspended from a hanger-board by means of rigid
tube.
c. No electro-magnetic device for switches and no system of multiple-
series or series-multiple lighting will be approved.
d. Under no circumstances can they be attached to gas fixtures.
COHSTAJtfT potential systems.
GENERAL RULES, ALL VOLTAGES.
81. Automatic Cutouts (Fuses and Circuit-Breakers).
(See No. 17, and for construction Nos. 52 and 53.)
a. Must be placed on all service wires, either overhead or underground,
as near as possible to the point where they enter the building and inside
the walls, and arranged to cut off the entire current from the building.
Where the switch required by rule No. 22 is inside the building, the cut-
out required by this section must be placed so as to protect it.
b. Must be placed at every point where a change is made in the size of
wire [unless the cutout in the larger wire will protect the smaller (see
No. 16)].
c. Must be in plain sight, or inclosed in an approved box (see No. 54) and
readily accessible. They must not be placed in the canopies or shells of
fixtures.
CONSTANT POTENTIAL SYSTEMS. 771
d . Must be so placed that bo set of incandescent lamps, whether grouped
on one fixture or several fixtures or pendants, requiring more than 660
watts, shall be dependent upon one cutout. Special permission may be given
in writing by the Inspection Department having jurisdiction for departure
from this rule in case of large chandeliers, stage borders, and illuminated
signs.
e. Must be provided with fuses, the rated capacity of which does not
exceed the allowable carrying capacity of the wire ; and, when circuit-
breakers are used, they must not be set more than about thirty per cent
above the allowable carrying capacity of the wire, unless a fusible cutout
is also installed in the circuit (see No. 16).
22. Switches —
(See No. 17, and for construction No. 51.)
a. Must be placed on all service wires, either overhead or underground,
in a readily accessible place, as near as possible to the point where the
wires enter the building, and arranged to cut off the entire current.
6. Must always be placed in dry, accessible places, and be grouped as far
as possible. Knife switches must be so placed that gravity will tend to open
rather than close the switch.
c. Must not be single -pole, except when the circuits which they control
supply not more than six 16-candle power lamps or their equivalent.
d. Where flush-switches are used, whether with conduit systems or not,
the switches must be inclosed in boxes constructed of or lined with fire-
resisting material. No push-buttons for bells, gas-lighting circuits or the
like shall be placed in the same wall-plate with switches controlling elec-
tric light or power wiring.
23. Electric Heaters —
a. Must, if stationary, be placed in a safe situation, isolated from inflam-
mable materials, and be treated as sources of heat.
b. Must each have a cutout and indicating -switch, (see No. 17 a).
c. Must have the attachments of feed wires to the heaters in plain sight,
easily accessible, and protected from interference, accidental or otherwise.
d. The flexible conductors for portable apparatus, such as irons, etc.,
must have an approved insulating covering (see No. 45 h).
e. Must each be provided with name-plate, giving the maker's name and
the normal capacity in volts and amperes.
EOW POTEUJTIAE SYSTEMS.
550 VOLTS OR LESS.
Any circuit attached to any machine, or combination of machines, which
develops a difference of potential, between any tivo wires, of over ten
volts and less than 550 volts, shall be considered as a low-potential
circuit, and as coming under this class, unless an approved transform-
ing device is used, which cuts the difference of potential down to ten
volts or less. The primary circuit not to exceed a potential of 3,500
volts.
24. Wires —
GEXERAL RULES.
(See also Nos. 14, 15, and 16.)
jt. Must not be laid in plaster, cement, or similar finish.
b. Must never be fastened with staples.
c. Must not be fished for any great distance, and only in places where the
inspector can satisfy himself that the rules have been complied with.
d Twin wires must never be used, except in conduits, or where flexible
conductors are necessary.
c. Must be protected on side walls from mechanical injury. When cross-
ing floor-timbers in cellars or in rooms, where they might be exposed to
injury, wires must be attached by their insulating supports to the under
side of a wooden strip, not less than one-half inch in thickness, and not less
than three inches in width.
772 NATIONAL ELECTRICAL CODE.
Suitable protection on side walls may be secured by a substantial boxing,
retaining an air space of one inch around the conductor, closed at the top
(the wires passing through bushed holes), and extending not less than live
feet from the floor ; or by an iron-armored or metal-sheathed insulating
conduit sufficiently strong to withstand the strain it will be subjected to ;
or plain metal pipe, lined with insulating tubing which must extend one-
half inch beyond the end of the metal tube.
The pipe must extend not less than five feet above the floor, and may
extend through the floor in place of a floor bushing.
If iron pipes are used with alternating currents, the two or more wires of
a circuit must be placed in the same conduit. In this case the insulation of
each wire must be reinforced by a tough conduit tubing projecting beyond
the ends of the iron pipe at least two inches.
/. When run immediately under roofs, or in proximity to water tanks or
pipes, will be considered as exposed to moisture.
SPECIAL RULES.
For open work :
In dry places :
g. Must have an approved rubber or " slow-burning" waterproof insula-
tion (see Nos. 41 and 42).
h. Must be rigidly supported on non-combustible, non-absorptive insula-
tors, which separate the wires from each other and from the surface wired
over in accordance with following table :
VOLTAGE. DISTANCE FROM SURFACE. DISTANCE BETWEEN WIRES.
0 to 225 I inch. 1\ inches.
225 "550 1 " 4 "
Rigid supporting requires under ordinary conditions, where wiringalong
flat surfaces, supports at least every four and one-half feet. If the wires are
liable to be disturbed, the distance between supports should be shortened.
In buildings of mill construction, mains of No. 8 B. & S. wire or over,
where not liable to be disturbed, may be separated about four inches, and
run from timber to timber, not breaking around, and may be supported at
each timber only.
This rule will not be interpreted to forbid the placing of the neutral of a
three-wire system in the center of a three-wire cleat, provided the outside
wires are separated in accordance with above table.
In damp places, such as Breweries, Sugar Houses, Packing Houses, Stables,
Dye Houses, Paper or Pulp Mills, or buildings specially liable to
moisture, or acid, or other fumes liable to injure the wires or their insu-
lation, except tvhere used for pendants :
i. Must have an approved rubber insulating covering (see No. 41).
j. Must be rigidly supported on non-combustible, non-absorptive in; -t. la-
tors, which separate the wire at least one inch from the surface wired over,
and they must be kept apart at least two and one-halt inches.
Rigid supporting requires under ordinary conditions, where wiring over
flat surfaces, supports at least every four and one-half feet. If the wires
are liable to be disturbed, the distance between supports should be
shortened. In buildings of mill construction, mains of No. 8 B. & S. wire or
over, where not liable to be disturbed, may bf> separated about four inches,
and run from timber to timber, not breaking around, and may be supported
at each timber only.
k. Must have no joints or splices.
JFor molding- work :
I. Must have approved rubber insulation covering (see No. 41).
m. Must never be placed in molding in concealed or damp places.
Cor conduit work :
n. Must have an approved rubber insulating covering (see No. 47).
o. Must not be drawn in until all mechanical work on the building has
been, as far as possible, completed.
LOW POTENTIAL SYSTEMS. 773
p. Must, for alternating systems, have the two or more wires of a circuit
drawn in the same conduit.
It is advised that this be done for direct-current systems also, so that
they may be changed to alternating systems at any time, induction troubles
preventing such a change unless this construction is followed.
Tor concealed 4i knob and tube " work:
q. Must have an approved rubber insulating covering (see No. 41).
r. Must be rigidly supported on non-combustible, non-absorptive insula-
tors which separate the Avire at least one inch from the service wired over,
and must be kept at least ten inches apart, and, when possible, should be
run singly on separate timbers or studding.
Kigid supporting requires under ordinary conditions, where wiring along
flat surfaces, supports at least every four and one-half feet. If the wires are
liable to be disturbed, the distance between supports shoxild be shortened.
s. When, from the nature of the case, it is impossible to place concealed
wiring on non-conbustible, insulating supports of glass or porcelain, an ap-
proved armored cable with single or twin conductors (see No. 48) may be
used where the difference of potential between wires is not over 300 volts,
provided it is installed without joints between outlets, and the cable armor
properly enters all fittings and is rigidly secured in place ; or, if the differ-
ence of potential between wires is not over 300 volts, and if wires are not
exposed to moisture, they may be fished on the loop system if separately
incased throughout in approved flexible tubing or conduits.
Tor fixture work :
t. Must have an approved rubber insulating covering (see No. 46), and
shall not be less in size than No. 18 B. & S.
u. Supply conductors, and especially the splices to fixtures wires, must
be kept clear of the grounded part of gas-pipes ; and, where shells are used,
the latter must be constructed in a manner affording sufficient area to
allow this requirement.
r. Must, Avhen fixtures are wired outside, be so secured as not to be cut
or abraded by the pressure of the fastenings or motion of the fixture.
35. Interior Conduits.
(See also Nos. 24 n top, and 49.)
The object of a tube or conduit is to facilitate the insertion or extraction
of the conductors to protect them from mechanical injury and, as far as
possible, from moisture. Tubes or conduits are to be considered merely as
raceways, and are not to be relied upon for insulation between wire and
wire, or between the wire and the ground.
a. No conduit tube having an internal diameter of less than five-eights
of an inch shall be used. (If conduit is lined, measurement to be taken
inside of lining.)
b. Must be continuous from one junction box to another or to fixtures,
and the conduit tube must properly enter all fittings.
c. Must be first installed as a complete conduit system, without the con-
ductors.
d. Must be equipped at every outlet with an approved outlet box.
e. Metal conduits, where they enter junction boxes, and at all other out-
lets, etc., must be fitted with a capping of approved insulating material,
fitted so as to protect wire from abrasion.
/. Must have the metal of the conduit permanently and effectively
grounded.
SO. Fixtures —
(See also No. 24 t to v.)
a. Must, when supported from the gas-piping of a building, be insulated
from the gas-pipe system by means of approved insulating joints (see No.
59) placed as close as possible to the ceiling.
It is recommended that the gas outlet pipe be protected above the insulat-
ing joint by a non-combustible, non-absorptive insulating tube, having a
flange at the lower end where it comes in contact with the insulating joint ;
774 NATIONAL ELECTRICAL CODE.
and that, where outlet tubes are used, they be of sufficient length to extend
below the insulating joint, and that they be so secured that they will not be
pushed back when the canopy is put in place. Where iron ceilings are
used, care must be taken to see that the canopy is thoroughly and perma-
nently insulated from the ceiling.
b. Must have all burs, or tins, removed before the conductors are drawn
into the fixture.
c. The tendency to condensation within the pipes should be guarded
against by sealing the upper end of the fixture.
d. No combination fixture in which the conductors are concealed in a
space less than one-fourth inch between the inside pipe and the outside
casing will be approved.
e. Must be tested for " contacts " between conductors and fixture, for
" short circuits," and for ground connections before it is connected to its
supply conductors.
/. Ceiling blocks for fixtures should be made of insulating material ; if
not the wires in passing through the plate must be surrounded with nun-
combustible non-absorptive, insulating material, such as glass or porcelain.
g. Under no conditions shall there be a difference of potential of more
than 300 volts between wires contained in or attached to the same fixture.
2?. Sockets.
(For construction rules, see No. 55.)
a. In rooms where inflammable gases may exist the incandescent lamp
and socket must be inclosed in a vapor-tight globe, and supported on a pipe
hanger, wired with approved rubber-covered wire (see No. 41) soldered
directly to the circuit.
b. In damp or wet places, or over specially inflammable stuff, waterproof
sockets must be used.
When waterproof sockets are used, they should be hung by separate
stranded rubber-covered wires, not smaller than No. 14 B. & S., which
should preferably be twisted together when the drop is over three feet.
These wires should be soldered direct to the circuit wires, but supported
independently of them.
28. Flexible Cord —
a. Must have an approved, insulation and covering (see No. 45).
b. Must not be used where the difference of potential between the two
wires is over 300 volts.
c. Must not be used as a support for clusters.
d. Must not be used except for pendants, wiring of fixtures, and port-
able lamps or motors.
e. Must not be used in show windows.
/. Must be protected by insulating bushings where the cord enters the
socket.
g. Must be so suspended that the entire weight of the socket and lamp
will be born by knots under the bushing in the socket, and above the point
where the cord comes through the ceiling-block or rosette, in order that
the strain may be taken from the joints and binding screws.
20. Arc trig-lit* on tow-Potential Circuits —
a. Must have a cutout (see No. 17a) for each lamp of each series of
lamps.
The branch conductors should have a carrying capacity about fifty per
cent in excess of the normal current required by the lamp to provide for
heavy current required when lamp is started or when carbons become stuck
without overfusing the wires.
b. Must only be furnished with such resistances or regulators as are in-
closed in non-combustible material, such resistances being treated as
sources of heat. Incandescent lamps must not be used for resistance de-
vices.
c Must be supplied witn globes and protected by spark arresters and wire
netting around globe, as in the case of arc lights on high-potential circuits
(see Nos. 19 and 58).
LOW POTENTIAL SYSTEMS. 775
30. Economy Coils.
a. Economy and compensator coils for arc lamps must be mounted on
non-conbustible, non-absorptive insulating supports, such as glass or porce-
lain, allowing an air space of at least one inch between frame and support,
and in general to be treated like sources of beat.
31. Decorative Series JLaiiips.
a. Incandescent lamps run in series sball not be used for decorative pur-
poses inside of buildings, except by special permission in writing from tbe
Inspection Department baving jurisdiction.
33. Car- Wiring- —
a. Must be always run out of reach of tbe passengers, and must have an
approved rubber-insulating covering (see No. 41).
33. Car-Houses —
a. Must have the trolley wires securely supported on insulating hangers.
6.' Must have the trolley hangers placed at such distance apart that, in
case of a break in tbe trolley wire, contact cannot be made with the floor.
c. Must have cutout switch located at a proper place outside of the
building, so that all trolley circuits in tbe building can be cut out at one
point and line circuit-breakers must be installed, so that when this cutout
switch is open the trolley wire will be dead at all points within 100 feet of
the building. The current must be cut out of the building whenever the
same is not in use or the road not in operation.
d. Must have all lamps and stationary motors installed in such a way
that one main switch can control the whole of each installation — lighting
or power— independently of main feeder-switch. No portable incandes-
cent lamps or twin wire allowed, except that portable incandescent lamps
may be used in the pits, connections to be made by two approved rubber-
covered flexible wires (see No. 41), properly protected against mechanical
injury ; the circuit to be controlled by a switch placed outside of the pit.
e. Must have all wiring and apparatus installed in accordance with rules
under Class " C " for constant potential systems.
/. Must not have any system of feeder distribution centering in the
building.
g. Must have the rails bonded at each joint with no less than No. 2 B.
& S. annealed copper wire, also a supplementary wire to be run for each
track.
h. Must not have cars left with trolley in electrical connection with the
trolley wire.
34. Ug-fitiiis* and Power from Railway "Wires —
a. Must not be permitted, under any pretense, in the same circuit with
trolley wires with a ground return, except in electric railway cars, electric
car houses and their power stations ; nor shall the same dynamo be used
for both purposes.
HICJKf-T»©TE]¥TIAE SYSTEMS.
550 TO 3,500 Volts.
Any circuit attached to any machine, or combination of machines, which de-
velops a difference of potential , between any two wires, of over 300 volts
and less than 3,500 volts, shall be considered as a high-potential cir-
tuit, and as coming under that class, unless an approved transforming
device is used, which cuts the difference of potential down to 300 volts
or less.
35. Wires —
{See also Nos. 14, 15, and 16.)
a. Must have an approved rubber-insulating covering (see No. 41).
6. Must be always in plain sight and never incased, except Avhere re-
quired by the Inspection Department having jurisdiction
776 NATIONAL ELECTRICAL CODE,
c. Must be rigidly supported on glass or porcelain insulators, which raise
the wire at least one inch from the surface wired over, and must be kept
apart at least four inches for voltages up to 750 and at least eight inches for
voltages over 750.
Rigid supporting requires under ordinary conditions, where wiring along
flat surfaces, supports at least about every four and one-half feet. If the
wires are unusually liable to be disturbed, the distance between supports
should be shortened.
In buildings of mill construction, mains of No. 8 B. & S. wire or over,
where not liable to be disturbed, may be separated about six inches for
voltages up to 750 and about ten inches f or voltages above 750 ; and run
from timber to timber, not breaking around, and may be supported at each
timber only.
d. Must be protected on side walls from mechanical injury by a substan-
tial boxing, retaining an air space of one inch around the conductors,
closed at the top (the wires passing through bushed holes) and extending
not less than seven feet from the floor. When crossing floor-timbers, in
cellars or in rooms, where they might be exposed to injury, wires must be
attached by their insulating supports to the under side of a wooden strip
not less than one-half an inch in tbickness.
3G. Xraiasformei-s (when permitted inside buildings, see No. 13) —
(For construction rules, see No. 62.)
a. Must be located at a point as near as possible to that at which the
primary wires enter the building.
b. Must be placed in an inclosure constructed of or lined with fire-
resisting material : the inclosure to be used only for this purpose, and to be
kept securely locked, and access to the same allowed only to responsible
persons.
c. Must be effectually insulated from the ground, and the inclosure Li
which they are placed must be practically air-tight, except that it shall be
thoroughly ventilated to the outdoor air, if possible, through a chimney or
flue. There should be at least six inches air space on all sides of the trans-
former.
31. Series lamps.
a. No system of multiple-series or series-multiple for light or power will
be approved.
b. Under no circumstances can lamps be attached to gas fixtures.
EXTRA HlftH 1POTE1* TIJUL SYSTJEMS.
Ovek 3,500 Volts.
Ami circuit attached to any machine or combination of machines , which de-
velops a difference of potential, between any two wires, of over 3,500
volts shall be considered as an extra high-potential circuit, and as
cominq under that class, unless an approved transforming device is
used, which cuts the difference of p>otential down to 3,500 volts or less.
3S. Primary Wires —
a. Must not be brought into or over building, except power and sub-
stations. ___.
30. Secondary Wires —
a Must be installed under rules for high-potential systems, when their
immediate primary wires carry a current of oyer 3,500 volts, unless the
primary wires are entirely underground, within city and village limits.
The presence of wires carrying a current with a potential of over 3,500
volts in the streets of cities, towns, and villages is considered to increase
the. fire hazard. Extra high potential circuits are also objectionable in any
location where telephone, telegraph, and similar circuits run in proximity
to them. As the underwriters have no jurisdiction over streets and roads
they can only take this indirect way of discouraging such systems ; but fur-
ther, it is strongly urged that municipal authorities absolutely refuse to
grant any franchise for right of way for overhead wires carrying a current
of extra high potential through streets or roads which are used to any great
extent for public travel or for trunk-line, telephone, or telegraph circuits.
CLASS D. FITTINGS, MATERIALS, AND DETAILS. 777
CJ.JLSS ». JTITTI^OS, MATEKIAIS, .AJtfl* DETAILS
o*1 coj*s>xucTioar.
All Systems and Voltages. Insulated Wires — Rules 40 to 48.
40. General Rules.
a. Copper for insulated conductors must never vary in diameter so as to
be more than two one- thousandths of an inch less than the specihed size.
b. Wires and cables of all kinds designed to meet the following speciiica
tions must be plainly tanked or marked as follows :
1. The maximum voltage at which the wire is designed to be used.
2. The words " National Electrical Code Standard."
3. Name of the manufacturing company, and, if desired, trade-name of
the wire.
4. Month and year when manufactured.
41. Bnblier-Covered.
a. Copper for conductors must be thoroughly tinned.
Insulation for voltag-es between © and GOO.
b. Must be of rubber or other approved substance, and be of a thickness
not less than that given in the following table for B. & S. gauge sizes :
rom 18 to
16, inclusive, ^
14 to
8, " B34
7 to
" 1 to
0000, " BV
" 0000 to
500,000, c. m. gy
" 500,000 to
1,000,000, " BV
Larger than
1,000,000, " i'
Measurements of insulating wall are to be made at the thinnest portion
of the dielectric.
c. The completed coverings must show an insulation resistance of at
least 100 megohms per mile during thirty days' immersion in water at
seventy degrees Fahrenheit.
d. Each foot of the completed covering must show a dieletric strength
sufficient to resist throughout five minutes the application of an electro-
motive force of 3,000 volts per one-sixty-fourth of an inch thickness of in-
sulation under the following conditions :
The source of alternating electro-motive force shall be a transformer of at
least one kilowatt capacity. The application of the electro-motive force
shall first be made at 4,000' volts for five minutes, and then the voltage in-
creased by steps of not over 3,000 volts, each held for five minutes, until
the rupture of the insulation occurs. The tests for dielectric strength shall
be made on a sample of wire which has been immersed for seventy-two
hours in water, one foot of which is submerged in a conducting liquid" held
in a metal trough, one of the transformer terminals being connected to the
wire and the other to the metal of the trough.
Insulations for voltag-es between 600 and 3.5»©0:
e. The thickness of the insulating walls must not be less than those given
in the following table for B. & S. gauge sizes :
From 14 to 1, inclusive, gV
From 0 to 500,000, C. M., ^" covered by a tape or a braid.
Larger than 500,000, C. M., ^" covered by a tape or a braid
/. The requirements as to insulation and break-down resistance for wires
for low potential systems shall apply, with the exception that an insulation
resistance of not less than 300 megohms per mile shall be required.
g. Wire for arc-light circuits exceeding 3,500 volts potential shall have
an insulating wall not less than six-thirty-seconds of an inch in thickness,
and shall withstand a break-down test of at least 30,000 volts, and have an
insulation of at least 500 megohms per mile.
The tests on this wire to be made under the same conditions as for low-
potential wires.
Specifications for insulations for alternating currents exceeding 3,500
( id NATIONAL ELECTRICAL CODE.
volts have been considered, but on account of tbe somewhat complex con-
ditions in such work it has so far been deemed inexpedient to specify gen-
eral insulations for this use.
h. All of the above insulations must be protected by a substantial
braided covering properly saturated with a preservative compound and suffi-
ciently strong to withstand all t,he abrasion likely to be met with in prac-
tice, and sufficiently elastic to permit all wires smaller than No. 7 B. & S.
gauge to be bent around a cylinder with twice the diameter of the wire,
without injury to the braid.
42. Slow-lrarning- Weatherproof.
a. The insulatioi shall consist of two coatings, the inner one to be fire-
proof in character, the outer to be weatherproof. The inner fireproof coat-
ing must comprise at least six-tenths of the total thickness of the wall.
The completed covering must be of a thickness not less than that given in
the following table for 13. & S. gauge sizes :
rorn 14 to
8, inclusive, &ri
7 to
2, A"
" 2 to
oooo, By
" 0000 to
500,000, CM., 5y'
" 500,000 to
1,000,000, '• B'4y/
arger than
1,000,000, " i"
Measurements of insulating wall are to be made at the thinnest portion
of the dielectric.
b. The inner fireproof coating shall be layers of cotton or other thread,
the outer one of which must be braided. All the interstices of these layers
are to be filled with the fireproofing compound. This is to be material whose
solid constituent is not susceptible to moisture, and which will not burn
even when ground in an oxidizable oil, making a compound which, while
proof against fire and moisture, at same time has considerable elasti-
city, and which when dry will suffer no change at a temperature of 250
degrees Fahrenheit, and which will not burn at even higher temperature.
c. The weatherproof coating shall be a stout braid thoroughly satu-
rated with a dense moistureproof compound thoroughly slicked down,
applied in such manner as to drive any atmospheric moisture from the
cotton braiding, thereby securing a covering to a greater degree waterproof
and of high insulating power. This compound to retain its elasticity at
zero Fahrenheit, and not to drip at 160 degrees Fahrenheit.
This wire is not as burnable as the old " weatherproof," nor as subject to
softening under heat, but still is able to repel the ordinary amount of
moisture found indoors. It would not usually be used for outside work.
43. Slow-burning-.
a. The insulation shall be the same as the " slow-burning weatherproof,"
except that the outer braiding shall be impregnated with a fireproofing
compound similar to that required for the interior layers, and with the
outer surface finished smooth and hard.
This " slow-burning" wire shall only be used with special permission of
the Inspection Department having jurisdiction.
This is practically the old " Underwriters' " insulation. It is specially
useful in hot, dry places where ordinary insulations would perish, also
where wires are bunched, as on the back of a large switchboard or in a
wire tower so that the accumulation of rubber or weatherproof insulation
would result in an objectionably large mass of highly inflammable material.
Its use is restricted, as its insulating qualities are not high and are dam-
aged by moisture.
44. Weatherproof.
a. The insulating covering shall consist of at least three braids thoroughly
impregnated with a dense moisture repellent, which will not drip at a tem-
perature lower than 180 degrees Fahrenheit. The thickness of insulation
shall be not less than that of "slow-burning weatherproof." The outer
surface shall be thoroughly slicked down."
This wire is for outdoor use where moisture is certain and where fireproof
qualities are not necessary.
CLASS D. FITTINGS, MATERIALS, AND DETAILS. 779
45. flexible Cord —
a. Must be made of stranded copper conductors, each strand to be not
larger than No. 26 or smaller than No. 30 B. & S. gauge, and each stranded
conductor must be covered by an approved insulation and protected from
mechanical injury by a tougb braided outer covering.
For pendent lamps:
In this class is to be included all flexible cord which under usual condi-
tions bangs freely in air, and whicb is not likely to be moved sufficiently to
come in contact with surrounding objects.
b. Each stranded conductor must have a carrying capacity equivalent to
not less than a No. 18 B. & S. gauge wire.
c. The covering of each stranded conductor must be made up as follows :
1. A tight, close wind of fine cotton.
2. The insulation proper, which shall be either waterproof or slow-
burning.
3. An outer cover of silk or cotton.
The wind of cotton tends to prevent a broken strand puncturing the insu-
lation and causing a short circuit. It also keeps the rubber from corroding
the coppei
d. Waterproof insulation must be solid, at least one-thirty-second of an
inch thick, and must show an insulation resistance of fifty megohms per
mile throughout two weeks' immersion in water at 70 degrees Fahrenheit,
and stand the test prescribed for low-tension wires as far as they apply.
e. Slow-burning insulation must be at least one-thirty-second of an inch
in thickness, and composed of substantial, elastic, slow-burning materials,
which will suffer no damage at a temperature of 250 degrees Fahrenheit.
/. The outer protecting braiding should be so put on and sealed in place
that when cut it will not fray out, and where cotton is used, it should be
impregnated with a flameproof paint, which will not have an injurious
effect on the insulation.
For portables:
In this class is included all cord used on portable lamps, small portable
motors, etc.
g. Flexible cord for portable use must have waterproof insulation as
re'quired in section d for pendent cord, and in addition be provided with a
reinforcing cover especially designed to withstand the abrasion it will be
subject to in the uses to which it is to be put.
For portable beating* apparatus:
h. Must be made up as follows : —
1. A tight, close wind of fine cotton.
2. A thin layer of rubber about one-one-hundredth of an inch thick, or
other cementing material. _
3. A layer of asbestos insulation at least three-sixty-fourths of an inch
thick.
4. A stout braid of cotton.
5. An outer reinforcing cover especially designed to withstand abrasion.
This cord is in no sense waterproof, the thin layer of rubber being speci-
fied in order that it may serve merely as a seal to help hold in place the fine
cotton and asbestos, and it should be so put on as to accomplish this.
4©. Fixture Wire —
a. Must have a solid insulation, with a slow-burning, tough, outer cover-
ing, the whole to be at one-thirty-second of an inch in thickness, and show
an insulation resistance between conductors, and between either conductor
and the ground, of at least one megohm per mile, after one week s submer-
sion in water at seventy degrees Fahrenheit, and after three minutes
electrification with 550 volts.
4*. Conduit Wire —
Must complv with the following specifications :
a. For metal conduits, having a lining of insulating material, single wires
780 NATIONAL ELECTRICAL CODE.
must comply with Xn. 41, and all duplex, twin, and concentric conductors
must comply with No. 41, and must also have each conductor separately
braided or taped and a substantial braid covering the whole.
b. For unlined metal conduits, conductors must conform to the specifica-
tions given for lined conduits, and in addition have a second outer fibrous
covering at least one-thirty-second of an inch in thickness, and sufficiently
tenacious to withstand tlie abrasion of being hauled through the metal
conduit.
The braid required around each conductor in duplex, twin, and concen-
tric cables is to hold the rubber insulation in place and prevent jamming
and flattening.
48. .Armored Cable.
a. The armor of such cables must be at least equal in thickness and of
equal strength to resist penetration by nails, etc., as the armor of metal
covering of metal conduits (see No. 49 b).
b. The conductors in same, single wire or twin conductors, must have an
insulating covering as required by No. 41, any filler used to secure a round
exterior must be impregnated with a moisture repellent, and the whole
bunch of conductors and fillers must have a separate exterior covering of
insulating material at least one-thirty-second of an inch in thickness, con-
forming to the insulation standard given in No. 41, and covered with a sub-
stantial braid.
Very reliable insulation is specified, as such cables are liable to hard
usage, and in part of their length may be subject to moisture, while they
may not be easily removable, so that a breakdown of insulation is likely to
be expensive.
-!■«>. Interior Conduits.
{For wiring rules, see Nos. 24 and 25.)
a. Each length of conduit, whether insulated or uninsulated, must have
the maker's name or initials stamped in the metal or attached thereto in a
satisfactory manner, so that the inspectors can readily see the same.
METAL CONDUITS WITH LINING OF INSULATING MATERIAL.
b. The metal covering or pipe must be equal in strength to the ordinary
commercial forms of gas-pipe of the same size, and its thickness must be not
less than that of standard gas-pipe, as shown by the following table :
Size,
nches.
Thickness of
Wall — Inches.
Size.
Inches.
Thickness of
Wall — Inches.
h
1
1
.109
.111
.113
if
2"
.140
.145
.154
1 -.134
An allowance, of two one-hundredths of an inch for variation in manu-
facturing and loss of thickness by cleaning will be permitted.
c. Must not be seriously affected externally by burning out a wire inside
the tube when the iron pipe is connected to one side of the circuit.
d. Must have the insulating lining firmly secured to the pipe.
e. The insulating lining must not crack or break when a length of the
conduit is uniformly bent at temperature of 212 degrees Fahrenheit to an
angle of ninety degrees, with a curve having a radius of fifteen inches, for
pipes of one inch and less, and fifteen times the diameter of pipe for larger
pipes.
/. The insulating lining must not soften injuriously at a temperature
below 212 degrees Fahrenheit, and must leave water in which it is boiled
practically neutral.
(j. The insulating lining must be at least one-thirty-second of an inch in
thickness ; and the materials of which it is composed must be of such a
nature as will not have a deteriorating effect on the insulation of the con-
ductor, and be sufficiently tough and tenacious to withstand the abrasion
test of drawing long lengths of conductors in and out of same.
CLASS D. FITTINGS, MATERIALS, AND DETAILS. 781
h. The insulating lining must not be mechanically weak after three days'
submersion in water, and when removed from the pipe entire must not
absorb more than ten per cent of its weight of water during 100 hours of
submersion.
*. All elbows or bends must be so made that the conduit or lining of same
will not be injured. The radius of the curve of the inner edge of any elbow
not to be less than three and one-half inches. Must have not more than the
equivalent of four quarter bends from outlet to outlet, the bends at the
outlets not being counted.
UXLIXED METAL CONDUITS.
?". Plain iron or steel pipes of equal thickness and strengths specified for
lined conduits in No. 49 b may be used as conduits, provided their interior
surfaces are smooth and free from burs ; pipe to be galvanized, or the
interior surfaces coated or enameled, to prevent oxidation, with some sub-
stance which will not soften so as to become sticky and prevent wire from
being withdrawn from the pipe.
k. All elbows or bends must be so made that the conduit will not be
injured. The radius of the curve of the inner edge of any elbow not to be
less than three and one-half inches. Must have not more than the equiva-
lent of four quarter bends from outlet to outlet, the bends at the outlet not
being counted.
5©. Wooden Moldiiag-s —
(For wiring rules, see No. 24.)
a. Must have, both outside and inside, at least two coats of waterproof
paint, or be impregnated with a moisture repellent.
b. Must be made of two pieces, a backing and capping, so constructed as
to thoroughly incase the wire, and provide a one-half inch tongue between
the conductors, and a solid backing, which, under grooves, shall not be less
than three-eighths of an inch in thickness, and must afford suitable protec-
tion from abrasion.
It is recommended that only hardwood molding be used.
51. Switches —
(See Nos. 17 and 22.)
a. Must be mounted on non-combustible, non-absorptive, insulating bases,
such as slate or porcelain.
b. Must have carrying capacity sufficient to prevent undue heating,
c. Must, when used for service switches, indicate, on inspection, whether
the current be " on " or " off."
d. Must be plainly marked, Avhere it will always be visible, with the name
of the maker and the current and voltage for which the switch is designed.
e. Must, for constant potential systems, operate successfully at fifty per
cent overload in amperes, Avith twenty-rive per cent excess voltage under
the most severe conditions they are liable to meet with in practice.
/. Must, for constant potential systems, have a firm and secure contact ;
must make and break readily, and not stop when motion has once been
imparted by the handle.
g. Must, for constant current systems, close the main circuit and discon-
nect the branch wires when turned" off " ; must be so constructed that they
shall be automatic in action, not stopping between points when started, and
must prevent an arc between the points under all circumstances. They
must indicate, upon inspection, whether the currents be " on " or " off."
52. Cutouts and Circuit-Breakers —
(For installation rules, see Nos. 17 and. 21.)
a. Must be supported on bases of non-combustible, non-absorptive insu-
lating material.
b. Cutouts must be provided with covers, when not arranged in approved
cabinets, so as to obviate any danger of the melted fuse metal coming in
contact with any substance which might be ignited thereby.
t OJ NATIONAL ELECTRICAL CODE.
c. Cutouts must operate successfully, under the most severe conditions
they are liable to meet with in practice, on short circuits with fuses rated at
fifty per cent above, and Avith a voltage twenty-five per cent above the
current and voltage for which they are designed.
d. Circuit-breakers must operate successfully, under the most severe
conditions they are liable to meet with in practice, on short circuits when
set at fifty per cent above the current, and with a voltage twenty-five per
cent above that for which they are designed.
e. Must be plainly marked, where it will always be visible, with the
name of the maker, and current and voltage for which the device is de-
signed.
53. fuses —
(For installation rules, see Kos. 17 and 21.)
a. Must have contact surfaces or tips of harder metal having perfect
electrical connection with the fusible part of the strip.
b. Must be stamped with about eighty per cent of the maximum current
they can carry indefinitely, thus allowing about twenty-five per cent over-
load before fuse melts.
With naked open fuses, of ordinary shapes and not over 500 amperes
capacity, the maximum current which will melt them in about five minutes
may be safely taken as the melting point, as the fuse practically reaches its
maximum temperature in this time. With larger fuses a longer time is
necessary.
Inclosed fuses where the fuse is often in contact with substances having
good conductivity to heat and often of considerable volume, require a
much longer time to reach a maximum temperature, on account of the
surrounding material which heats up slowly.
These data are given to facilitate testing.
c. Fuse terminals must be stamped with the maker's name, initials, or
some known trade-mark.
54. Cutout Caliiuets —
a. Must be so constructed, and cutouts so arranged, as to obviate any
danger of the melted fuse metal coming in contact with any substance
which might be ignited thereby.
A suitable box can be made of marble, slate, or wood, strongly put
together, the door to close against a rabbet so as to be perfectly dust-tight ;
and it should be hung on strong hinges, and held closed by a strong hook or
catch. If the box is wood, the inside should be lined with sheets of asbestos
board about one-sixteenth of an inch in thickness, neatly put on, and
firmly secured in place by shellac and tacks. The wire should enter
through holes bushed with porcelain bushings ; the bushings tightly fitting
the holes in the box, and the wires tightly fitting the bushings (using
tape to build up the wire, if necessary) so as to keep out the dust.
55. Sockets.
(See No. 27.)
Sockets of all kinds, including wall receptacles, must be constructed in
accordance with the following specifications : —
a. Standard Sizes. — The standard lamp socket shall be suitable for
use on any voltage not exceeding 250 and with any size lamp up to fifty
candle-power. For lamps larger than fifty candle-power a standard keyless
socket may be used ; or if a key is required, a special socket designed for
the current to be used must be made. Any special sockets must follow the
general spirit of these specifications.
b. Marking. — The standard socket must be plainly marked fifty candle-
power, 250 volts, and with either the manufacturer's name or registered
trademark. Special large sockets must be marked Avith the current and
voltage for which they are designed.
c. Shell. — Metal used for shells 'must be moderately hard, but not
hard enough to be brittle or so soft as to be easily dented or knocked out of
place. Brass shells must be at least 0.013 inch in thickness, and shells of
any other material must be thick enough to give the same stiffness and
strength of brass.
CLASS D. — FITTINGS, MATERIALS, AND DETAILS. 78o
d. Lining. — The inside of the shells must he lined with insulating
material, which shall absolutely prevent the shell from becoming a part
of the circuit, even though the wires inside the socket should start from
their position under binding screws.
The material used for lining must be at least one thirty-second of an
inch in thickness, and must be tough and tenacious. It must not be in-
juriously affected by the heat from the largest lamp permitted in the
socket, and must leave the water in which it is boiled practically neutral.
It must be so firmly secured to the shell that it will not fall out with
ordinary handling of the socket. It is preferable to have the lining in one
piece.
e. Cap. — Caps when of sheet brass 'must be at least 0.013 inch in thick-
ness, and when cast or made of other metals must be of equivalent
strength. The inlet piece, except for special sockets, must be tapped and
threaded for ordinary one-eight-inch pipe. It must contain sufficient metal
for a full, strong thread, and, when not of the same piece as the cap, must
be joined to it in a way to give the strength of a single piece.
There must be sufficient room in the cap to enable the ordinary wireman
to easily and quickly make a knot in the cord, and push it into place in cap
without crowding. All parts of the cap upon which the knot is likely to
bear must be smooth and well insulated.
/. Frame and Screws. — The frame holding moving parts must be
sufficiently heavy to give ample strength and stiffness.
Brass pieces containing screw threads must be at least 0.06 of an inch in
thickness.
Binding-post screws must not be smaller than No. 5 wire and about forty
threads per inch.
g. Spacing. —Points of opposite polarity must everywhere be kept
not less than three sixty-fourths of an inch apart unless separated by a
reliable insulation.
h. Connections. — The connecting points for the flexible cord must be
made to very securely grip a No. 16 or 18 B. & S. conductor. A turned-up
lug, arranged so that the cord may be gripped between the screw and the
lug in such a way that it cannot possibly come out, is strongly advised.
i. Lamp-Holder. — The socket must firmly hold the lamp in place so
that it cannot be easily jarred out, and must provide a contact good enough
to prevent undue heating with maximum current allowed. The holding-
pieces, springs and the like, if a part of the circuit, must not be sufficiently
exposed to allow them to be brought in contact with anything outside of
lamp and socket.
j. Base. —The inside parts of the socket, which are of insulating
material, except the lining, must be made of porcelain.
k. Key. — The socket key-handle must be of such a material that it will
not soften from the heat of a fifty candle-power lamp hanging downwards
in air at seventy degrees Fahrenheit from the socket, and must be securely,
but not necessarily" rigidly, attached to the metal spindle it is designed to
turn.
/. Sealing. — All screws in porcelain pieces, which can be firmly sealed
in place, must be so sealed by a waterproof compound which will not melt
below 200 degrees Fahrenheit.
to. Putting Together. — The socket must, as a whole, be so put
together that it will not rattle to pieces. Bayonet joints or equivalent are
recommended. *
n. Test. — The socket when slowly turned "on and off," at the rate of
about two or three times per minute, must " make and break " the circuit
6,000 times before failing, when carrying a load of one ampere at 220 volts.
o. Keyless Sockets.— Keyless sockets of all kinds must comply with
requirements for key sockets as far as they apply.
p. Sockets of Insulating Materials. — Sockets made of porcelain
or other insulating material must conform to the above requirements as
far as they apply, and all parts must be strong enough to withstand a
moderate amount of hard usage without breaking.
q. Inlet Bushing. — When the socket is not attached to fixtures the
threaded inlet must be provided with a strong insulating bushing, having a
smooth hole of at least fifteen sixty-fourths of an inch in diameter. The
corners of the bushing must be rounded, and all inside fins removed, so that
in no place will the cord be subjected to the cutting or wearing action of a
sharp edge.
784 NATIONAL ELECTRICAL CODE.
5G. Hanger-boards.
a. Hanger-boards must be so constructed that all wires and current-
carrying devices thereon shall be exposed to view, and thoroughly insu-
lated by being mounted on a non-combustible, non-absorptive insulating
substance. All switches attached to the same must be so constructed that
they shall be automatic in their action, cutting off both poles to the lamp,
not stopping between points when started, and preventing an arc betwesn
points under all circumstances.
»?. Arc liamps.
(For installation rules, see No. 19.)
a. Must be provided with reliable stops to prevent carbons from falling
out in case the clamps become loose.
b. Must be carefully insulated from the circuit in all their exposed
parts.
c. Must, for constant-current systems, be provided with an approved
hand switch, also an automatic switch that will shunt the current around
the carbons, should they fail to feed properly.
The hand switch to be approved, if placed anywhere except on the lamp
itself, must comply with requirements for switches on hanger-boards as
laid down in No. 56.
58. Spark Arresters.
(See No. 19c.)
a. Spark arresters must so close the upper orifice of the globe that it
will be impossible for any sparks thrown off by the carbons to escape.
50. Insulating1 Joints -
(See No. 26 a.)
a. Must be entirely made of material that will resist the action of illumi-
nating gases, and will not give way or soften under the heat of an ordinary
gas-flame, or leak under a moderate pressure. They shall be so arranged
that a deposit of moisture will not destroy the insulating effect, and shall
have an insulating resistance of at least 250,000 ohms between the gas-pipe
attachments, and be sufficiently strong to resist the strain they will be
liable to be subjected to in being installed.
Insulating Joint for Gas Pipes.
b. Insulating joints having soft rubber in their construction will not be
approved.
GO. Resistance Boxes and Equalizers —
(For installation rules, see No. 4.)
a. Must be equipped with metal or with other non-combustible frames.
The word " frame " in this section relates to the entire case and sur-
roundings of the rheostat, and not alone to the upholding supports.
CLASS D. FITTINGS, MATERIALS, AND DETAILS. 785
Gl. Reactive Coils and Condensers.
a. Reactive coils must be made of non-combustible material, mounted
on non-combustible bases, and treated, in general, like sources of heat.
b. Condensers must be treated like apparatus operating with equivalent
voltage and currents. They must have non-combustible cases and supports,
and must be isolated from all combustible materials, and, in general,
treated like sources of heat.
G2. Transformers —
(For installation rules, see Nos. 11, 13, and 33.)
a. Must not be placed in any but metallic or other non-combustible cases.
b. Must be constructed to comply with the following tests :
1. Shall be run for eight consecutive hours at a full load in watts
under conditions of service, and at the end of that time the rise in
temperature, as measured by the increase of resistance of the
primary coil, shall not exceed 135 degrees Fahrenheit.
2. The insulation of transformers when heated shall withstand con-
tinuously for five minutes a difference of potential of 10,000 volts
(alternating) between primary and secondary coils and core, and
between the primary coils and core and a no-load " run " at double
voltage for thirty minutes.
G3. liig-litning; Arresters.
(For installation rules, see No. 5.)
a. Must be mounted on non-combustible bases, and must be so con-
structed as not to maintain an arc after the discharge has passed, and must
have no moving parts.
CLA§i E. — JfEISCEIiEiAMEOUS.
G4. Sig-naling- Systems (governing wiring for telephone, telegraph,
district messenger, and call-bell circuits, fire and burglar alarms, and all
similar systems) —
a. Outside wires should be run in undergrouna ducts or strung on poles
and, as far as possible, kept off of buildings, and must not be placed on the
same cross-arm with electric light or power wires.
b. When outside wires are run on same pole with electric light or power
wires, the distance between the two inside pins of each cross-arm must not
be less than twenty-six inches.
c. All aerial conductors and underground conductors which are directly
connected to aerial wires must be provided with some approved protective
device, which shall be located as near their point of entrance to the build-
ing as possible, and not less than six inches from curtains or other inflam-
mable material.
d. If the protector is placed inside of building, wires, from outside sup-
ports to binding-posts of protector, shall comply with the following require-
ments :
1. Must be of copper, and not smaller than ISio. 16 B. & S. gauge.
2. Must have an approved rubber insulating covering (see No. 41). ,
3. Must have drip loops in each wire immediately outside the building.
4. Must enter buildings through separate holes sloping upward from the
outside ; when practicable, holes to be bushed with non-absorptive,
non-combustible insulating tubes extending through their entire
length. Where tubing is not practicable, the wires shall be wrapped
with two layers of insulating tape.
5. Must be supported on porcelain insulators, so that they will not come
in contact with anything other than their designed supports.
6. A separation between wires of at least two and one-half inches must
'"be maintained.
In case of crosses these wires may become a part of a high-voltage circuit,
so that similar care to that given high-voltage circuits is needed in placing
them. Reliable porcelain bushings at the entrance holes are desirable, and
are only waved under adverse conditions, because the state of the art in
this type of wiring makes an absolute requirement inadvisable.
78G NATIONAL ELECTRICAL CODE.
e. The ground wire of the protective device shall be run in accordance
with the following requii ements :
1. Shall be of copper, and not smaller than No. 16 B. & S.
2. Must have an approved rubber insulating covering (See No. 41).
3. Shall run in as straight a line as possible to a good permanent
ground, to be made by connecting to water- or gas-pipe, preferably
water-pipe. If gas-pipe is used, the connection, in all cases, must
be made between the meter and service pipes. In the absence of
other good ground, the ground shall be made by means ol a metallic
plate or bunch of wires buried in permanently moist earth.
4. Shall be kept at least three inches from all other conductors, and sup-
ported on porcelain insulators so as not to come in contact with
anything other than its designated supports.
In attaching a ground wire to a pipe, it is often difficult to make a
thoroughly reliable solder joint. It is better, therefore, where possible, to
carefully solder the wire to a brass plug, which may then be firmly screwed
into a pipe fitting.
Where such joints are made under ground, they should be thoroughly
painted and taped to prevent corrosion.
f. The protector to be approved must comply with the following require-
ments :
1. Must be mounted on non-combustible, non-absorptive insulating
bases, so designed that when the protector is in place, all parts
which may be alive will be thoroughly insulated from the wall
holding the protector.
2. Must have the following parts :
A lightning arrester which will operate with a difference of potential
between wires of not over 500 volts, and so arranged that the
chance of accidental grounding is reduced to a minimum.
A fuse designed to open the circuit in case the wires become crossed
with light or power circuits. The fuse must be able to open the
circuit without arcing or serious flashing -"'hen crossed with any
ordinary commercial light or power circuit.
A heat coil which will operate before a sneak current can damage the
instrument the protector is guarding.
The heat coil is designed to warm up and melt out with a current
large enough to endanger the instruments if continued for a long
time, but so small that it would not blow the fuses ordinarily found
necessary for such instruments. These smaller currents are often
called " sneak " currents.
3. The fuses must be so placed as to protect the arrester and heat coils,
and the protector terminals must be plainly marked "line," "in-
strument," " ground."
g. Wires beyond the protector, except where bunched, must be neatly
arranged and securely fastened in place in any convenient, workmanlike
manner. They must not come nearer than six inches to any electric light
or power wire in the building, unless incased in approved tubing so secured
as to prevent its slipping out of place.
The wires would ordinarily be insulated, but the kind of insulation is not
specified, as the protector is relied upon to stop all dangerous currents.
Porcelain tubing or circular loom conduit may be used for incasing wires
where required as above.
h. Wires connected with outside circuits, where bunched together within
any building, or inside wires, where laid in conduits or ducts, with electric
light or power wires, must have fire-resisting coverings, or else must be
inclosed in an air-tight tube or duct.
It is feared that if a burnable insulation were used, a chance spark might
ignite it and cause a serious fire, for many installations contain a large
amount of very readily burnable matter.
G;1. Electric *-ii«. lag-hting-.
Where electric gas lighting is to be used on the same fixture with the
electric light :
a. No part of the gas-piping or fixture shall be in electric connection with
the gas-lighting circuit.
CLASS E. MISCELLANEOUS. 787
b. The wires used with the fixtures must have a non-inflammable insula-
tion, or, where concealed between the pipe and shell of the fixture, the
insulation must be such as required for fixture wiring for the electric light.
c. The whole installation must test free from " grounds."
d. The two installations must test perfectly free from connection with
each other.
OO. Insulation .Resistance.
The wiring in any building must test free from grounds ; i. e., the com-
plete installation must have an insulation between conductors and between
all conductors and the ground (not including attachments, sockets, recep-.
tacles, etc.) of not less than the following :
Up to 5 ampere:
10
25
50
100
200
400
" 800
" 1,600 "
4,000,000 ohms
2,000,000
4
800,000
4
400,000
4
200,000
4
100,000
4
25,000
'
25,000
4
12,500
4
All cutouts and safety devices in place in the above.
Where lamp sockets, receptacles, and electroliers, etc., are connected,
one-half of the above will be required.
tit. Soldering- Fluid.
a. The following formula for soldering fluid is suggested :
Saturated solution of zinc chloride 5 parts
Alcohol 4 parts
Glycerine . 1 part
CLAS§ F.— BEARIIVi: WOJtlfc.
ft§. Generators —
a. Must be located in a dry place.
ft. Must have their frames insulated from their bed-plates.
c. Must each be provided with a waterproof cover.
(I. Must each be provided with a name-plate, giving the maker's name,
the capacity in voltage and amperes and normal speed in revolutions per
minute —
«©. Wires —
a. Must have an approved insulating covering.
The insulation for all conductors, except for portables, to be approved,
i must be at least one-eighth-inch in thickness and be covered with a substan-
I tial waterproof and flameproof braid. The physical characteristics shall
> not be affected by any change in temperature up to 200 degrees Fahrenheit.
After two weeks' submersion in salt water at seventy degrees Fahrenheit it
must show an insulation resistance of one megohm per mile after three
minutes' electrification, with 550 volts.
b. Must have no single wire larger than No. 12 B. & S. "Wires to be
1 stranded when greater carrying capacity is required. No single solid wire
smaller than No. 14 B. & S. /except in fixture wiring, to be used.
; Stranded wires must be soldered before being fastened under clamps or
binding screws, and when they have a conductivity greater than No. 10
B. & S. copper wire they must be soldered into Ligs.
c. Must be supported in approved molding, except at switchboards and
portables.
Special permission may be given for deviation from this rule in dynamo-
rooms.
d. Must be bushed with hard-rubber tubing one-eighth of an inch in
thickness when passing through beams and non-water-tight bulkheads.
788
NATIONAL ELECTRICAL CODE.
e. Must have, when passing through water-tight bulkheads and through
all decks, a metallic stuffing-tube lined with hard rubber. In case of deck
tubes they shall be boxed near deck to prevent mechanical injury.
f. Splices or taps in conductors must be avoided as far as possible. Where
it is necessary to make them they must be so spliced or joined as to be both
mechanically and electrically secure without solder. They must then be
soldered, to insure preservation, covered with an insulating compound equal
to the insulation of the wire, and further protected by a waterproof tape.
The joint must then be coated or painted with a waterproof compound.
a©. Portable Conductors —
a. Must be made of two stranded conductors, each having a carrying
capacity equivalent to not less than No. 14 B. & S. wire, and each covered
with an approved insulation and covering.
Where not exposed to moisture or severe mechanical injury, each stranded
conductor must have a solid insulation at leas! one-thirty-second of an inch
in thickness, and must show an insulation resistance between conductors,
and between either conductor and the ground, of at least one megohm per
mile after one week's submersion in water at seventy degrees Fahrenheit
and after three minutes' electrification, with 590 volts, and be protected by
a slow-burning, tough-braided outer covering,
Where exposed to moisture and mechanical injury — a? for use on decks,
holds, and fire-rooms — each stranded conductor shall have a solid insula-
tion to be approved, of at least one-thirty-second of an inch in thickness
and protected by a tough braid. The two conductors shall then be stranded
together, using a jute filling. The whole shall then be covered with a layer
of flax, either woven or braided, at least one-thirty-second of an inch' in
thickness, and treated with a non-inflammable waterproof compound.
After one week's submersion in water at seventy degrees Fahrenheit, at 55C
volts and a three minutes' electrification, must show an insulation between
the two conductors, or between either conductor and the ground, of one
megohm per mile.
91. Bell or Other Wires —
a. Shall never run in same duct with lightning or power wires.
ll
as. Tal»le of Capacity of Wires.
t:
B. & S. G.
Area Actual
No. of
Size of Strands
CM.
Strands.
B. &S. G.
Amperes.
L
19
1,288
-
18
1,624
3
in
17
2,048
;'
16
2,583
*6
?i
15
3,257
!
14
4,107
12
£'
12
6,530
17
i
9,016
i
19
21
H
11,368
7
18
25
i,
14,336
7
17
30
::t
18,081
7
16
35
(,
22,799
7
15
40
K.
30,856
19
18
50
"Il
38,912
19
17
60
If
49,077
19
16
70
•'
60,088
37
18
85
k
75,776
37
17
100
iiiii
99,064
61
18
120
i
124,928
61
17
145
his
157,563
61
16
170
198,677
61
15
200
250,527
61
14
235
296,387
91
15
270
J,
373,737
91
14
320
■>
413,639
127
15
340
1,
CLASS F. MARINE WORK. 789
"When greater conducting area than that of a single wire is required, the
conductor shall be stranded in a series of *, lO, 31, Ol, Ol, or 12*,
vires as may be required ; the strand consisting of one central wire, the
remainder laid around it concentrically, each layer to be twisted in the
opposite direction from the preceding
73. Switchboard's —
a. Must be made of non-combustible, non-absorbtive insulating material,
such as marble or slate.
6. Must be kept free from moisture, and must be located so as to be
accessible from all sides.
c. Must have a main switch, main cutout, and ammeter for each gen-
erator.
Must also have a voltmeter and ground detector.
d. Must have a cutout and switch for each side of each circuit leading
from board.
"S4r. [Resistance Boxes —
a. Must be made of non-combustible material.
b. Must be located on switchboard or away from combustible material.
When not placed on switchboard they must be mounted on non-inflam-
mable, non-absorptive insulating material.
c. Must be so constructed as to allow sufficient ventilation for the uses
to which they are put.
"33. Switches —
a. Must have non-combustible, non-absorptive insulating bases.
b. Must operate successfully at fifty per cent overload in amperes with
twenty-five per cent excess voltage under the most severe conditions they
are liable to meet with in practice, and must be plainly marked, where
they will always be visible, with the name of the maker and the current
and voltage for which the switch is designed.
c Must be double pole when circuits which they control supply more
than six sixteen-candle-power lamps or their equivalent.
d. When exposed to dampness, they must be inclosed in a water-tight
?G. Cutouts —
a. Must have non-combustible, non-absorptive insulating bases.
b. Must operate successfully, under the most severe conditions they are
liable to meet with in practice, on short circuit with fuse rated at fifty per
cent above, and with a voltage twenty-five per cent above the current and
voltage they are designed for, and must be plainly marked, where they will
always be visible, with the name of the maker and current and voltage for
which the device is designed.
c. Must be placed at every point where a change is made in the size of
the wire (unless the cutout in the larger wire will protect the smaller).
d. In places such as upper decks, holds, cargo spaces, and fire-rooms a
water-tight and fireproof cutout may be used, connecting directly to mains
when such cutout supplies circuits requiring not more than' 660 watts
energy.
e. Wben placed anywhere except on switchboards and certain places, as
cargo spaces, holds, fire-rooms, etc., where it is impossible to run from
center of distribution, they shall be in a cabinet lined with fire-resisting
material.
/. Except for motors, searchlights, and diving-lamps shall be so placed
that no group of lamps, requiring a current of more than six amperes, sball
ultimately be dependent upon one cutout.
A single-pole covered cutout may be placed in the molding when same con-
tains conductor supplying circuits requiring not more than 220 watts energy.
•J1?. [Fixtures —
. Shall be mounted on blocks made from Avail-seasoned lumber treated
with two coats of white lead or shellac.
b. Where exposed to dampness, the lamp must be surrounded by a vapor-
proof globe.
790 NATIONAL ELECTRICAL CODE.
e. Where exposed to mechanical injury the lamp must he surrounded
hy a glohe protected by a stout wire guard.
cL Shall be wired -with, same grade of insulation as portable conductors
which are not exposed to moisture or mechanical injury.
«•*». Sockets.
a. No portion of the lamp socket or lamp base exposed to contact with
outside objects shall be allowed to come into electrical contact with either
of the conductors.
tO. Wooden HEoulding-s —
a. Must be made of well-seasoned lumber and be treated inside and out
with at least two coats of white lead or shellac.
b. Must be made of two pieces, a backing and a capping, so constructed
as to thoroughly incase the wire, and provide a one-half inch tongue
between the conductors, and a solid backing which, under grooves, shall
not be less than three-eighths of an inch in thickness.
c. Where molding is run over rivets, beams, etc., a backing strip must
first be put up and the molding secured to this.
d. Capping must be secured by brass screws.
$©. Motors —
a. Must be wired under the same precautions as with a current of same
volume and potential for lighting. The motor and resistance box must be
protected by a double-pole cutout, and controlled by a double-pole switch,
except in cases where one-quarter horse-power or less is used.
The leads or branch circuits should be designed to carry a current at
least fifty per cent greater than that required by the rated capacity of the
motor to provide for the inevitable overloading of the motor at times.
b. Must be thoroughly insulated. Where possible, should be set on base
frames made from filled, hard, dry, wood, and raised above surrounding
deck. On hoists and winches they shall be insulated from bed-plates by
hard rubber, fiber, or similar insulating material.
c. Shall be covered with a waterproof cover when not in use.
d. Must each be provided with a name-plate giving maker's name, the
capacity in volts and amperes, and the normal speed in revolutions per
minute.
GMERAI fcl'CiGJESTIOJfS.
In all electric work conductors, however well insulated, should always be
treated as bare, to the end that under no conditions, existing or likely to
exist, can a grounding or short circuit occur, and so that all leakage from
conductor to conductor, or between conductor and ground, may be reduced
to the minimum.
In all wiring special attention must be paid to the mechanical execution
of the work. Careful and neat running, connecting, soldering, taping of
conductors and securing and attaching of fittings, are specially conducive
to security and efficiency, and will be strongly insisted on.
In laying out an installation, except for constant-current systems, the
work should, if possible, be started from a center of distribution, and
the switches and cutouts, controlling and connected with the several
branches, be grouped together in a safe and easily accessible place, where
they can be readily got at for attention or repairs. The load should be
divided as evenly as possible among the branches, and all complicated and
unnecessary wiring avoided.
The use of wire-ways for rendering concealed wiring permanently acces-
sible is most heartily indorsed and recommended ; and this method of
accessible concealed construction is advised for general use.
Architects are urged, when drawing plans and specifications, to make pro-
vision for the channeling and pocketing of buildings for electric light or
power wires, and in specifications for electric gas lighting to require a two-
wire circuit, whether the building is to be wired for electric lighting or not,
so that no part of the gas fixtures or gas-piping be allowed to be used for
the gas-lighting circuit.
FOUNDATIONS AND STRUCTURAL
MATERIALS.
rOWEH 8IATIOI COflfSlRrCTIOHf.
Chart.
(By E. P. Roberts & Co.)
fFoundafcion
(A Setting
[.Stack
Sta-
tion
Steam
Plant
Link y
En-
gines j
^Source
J Pumps and injectors, valves
] and gauges
(^Heaters
fSediment ( Blow off
I Mud drum
{Steam pipe and
valve to heater
Entrained water,
separator
Placing in building
Placing in boiler
Removal of coke and ashes
^Removal of soot
Supply to surface
Piping and valves
Coverings
Drains and drips
^Supports
'Foundation .
Steam to cylinder
Oil to cylinder
Steam from cylinder
Water from cylinder
Oil to engine
Oil from engine
Engine indicator
( Steam to condenser
■{ Water to condenser
I^Water from condenser
| Foundations
( Lubrication
f Belts
^Connecting links . . . -< Shafts
* ^Pulleys
("Foundation
I Lubrication
Insulation
Governing devices
Measuring devices
[Safety devices
Elec- [Dynamos to switchboard
trical -i Wire <; Switchboards to line
plant I Track to dynamo
[Distribution devices
I Dynamo governing devices
J Dynamo measuring devices
^Switchboard 1 Feeder to measuring devices
I Safety devices
'^Cut-out and lightning arrester
( Weatherproof
| Fireproof
Build- J. Ventilated
ing Light
(^Provisions for cranes or other strains foreign to its func-
tions as a shelter.
791
792 FOUNDATIONS AND STRUCTURAL MATERIALS.
FOUNDATIONS.
The term foundation designates the portion of a structure used as a base
on which to erect the superstructure, and must be so solid that no move-
ment of the superstructure can take place after its erection.
As all foundations or structures of coarse masonry, whether of brick or
stone, will settle to some extent, and as nearly all soils are compressible
under heavy weight, care must be taken that the settlement be even all
over the structure in order to avoid cracks or other haws. Although it is
quite general to make the excavation for all the sub-foundation without
predetermining in mure than a general way the nature of the subsoil, and
then adapting the base of the foundation to the nature of soil found ; yet in
large undertakings, where there may be question as to the bearing, borings
are made and samples brought up in order to determine the different strata
and distance of rock below the surface. Where foundations are not to be
deep, or the soil is of good quality, a trench or pit is often sunk alongside
the location of the proposed foundation, and the quality of the soil deter-
mined in that way.
Foundations on Rock.
The surface of rock should be cleaned and dressed, all decayed portions
removed, crevices filled with grouting or concrete, and where the surface
is inclined, it should be cut into a series of level steps before commencing
the structure In such cases of irregular levels, all mortar joints must be
kept as close as possible, iu order to prevent unequal settlement. A still
better way is to bring all such uneven surfaces to a common level with a
good thick bed of concrete, which, if properly made, will become as incom-
pressible as stone or brick.
The load on rock foundation should never exceed one-eighth its crushing-
load. Baker says " the safe bearing power of rock is certainly not less than
one-tenth of the ultimate crushing strength of cubes. That is to say, the
safe bearing power of solid rock is not less than 18 tons per square foot for
the softest rock, and 180 for the strongest. It is safe to say that almost any
rock, from the hardness of granite to that of a soft crumbling stone easily
worn by exposure to the weather or to running water, when well bedded
will bear the heaviest load that can be brought upon it by any masonry
construction." Rankine gives the average of ordinary cases as 20,000
pounds per square foot on rock foundations. Later in this chapter will be
found a table that gives the crushing load in pounds per square inch for
most of the substances used in foundations and building-walls.
Foundations on Sand or Gravel.
Strong gravel makes one of the best bottoms to build on; it is easily leveled,
is almost incompressible, and is not affected by exposure to the atmosphere.
Sand confined so that it cannot escape forms an excellent foundation, and
is nearly incompressible. It has no cohesion, and great care must be used
in preparing it for a foundation. Surface water must be kept from running
into earth foundation beds, and the beds themselves must be well-drained
and below frost-line. Baker says that a rather thick bed of sand or gravel,
well protected from running water, will safely bear a load of 8 to 10 tons per
square foot. Of course the area of the surface must be proportioned to the
weight of the superstructure, and to the bearing resistance of the material,
and for this reason it is common practice to spread the subfoundation to
give it the proper area. Rankine sjives 2,500 to 3,500 lbs. per square foot as
the greatest allowable pressure on firm earths.
Foundation on Clay.
A good stiff clay makes a very good foundation bed, and will support
great Aveight if care is taken in its preparation. Water must be kept away
from it, and the foundation level must be below the frost-line. The less
clay is exposed to the atmosphere the better will be the result. Baker
gives as safe bearing power for clay 3,000 or 4,000 pounds per square foot.
Gaudard says a stiff clay will support in safety 5,500 to 11,000 pounds per
square foot.
FOUNDATIONS. 793
foundation on Soft Earth*
Where the earth is too soft to support the superstructure, the trench is
; excavated to a considerable width, and to a considerable depth below the
frost-line ; then a bed is prepared of stones, sand, or concrete, the latter
1 being most in use to-day. In fact, it is a common thing to cover the whole
.; area of the basement of large power stations with a heavy layer of concrete
'I of a thickness sufficient to sustain not only the building-walls, but all ma^
1. chine foundations.
I Sand makes a good foundation bed over soft earth, if the earth is of a
.quality that will retain the sand in position. Sand may be rammed in
19-mcli layers in a soft earth trench, or it can be used as piles instead of
,1 wooden ones, by boring holes 6 or 8 inches in diameter and say six feet deep
■ and ramming the sand in wet. It is necessary to cover the surface with
.1 planking or concrete to prevent the earth pressing upward. Alluvial soils
J are considered by Baker safe under a load of one-half to one ton per square
J foot. M-
! foundation on files.
When the earth is unsuitable in nature to support foundations, it is com-
Imon to drive piles, on the tops of which the foundation is then built.
II When possible the piles are driven to bed rock, otherwise they are made of
fcsuch length and used in such number as to support the superstructure by
■ reason of the friction of their surfaces in the soil. Where the soil is quite
iisoft it is also common to drive piles in large number all over the basement
I area iu order to consolidate the earth, and make all parts of a better bearing
I" quality.
Piles must be driven and cut off below the water level, and a grillage of
heavy timbers or a layer of broken stone and a capping of concrete must be
placed on top of them for supporting the foundation.
■ The woods most used for piles are spruce and hemlock in soft or medium-
§ soft soils, or when they are to be always under water, hard pine, elm, and
I beech in firmer soils, and oak in compact soils. When piles are liable to be
I alternately wet and dry, white oak or yellow pine should be employed.
I Piles should not be less than 10 inches in diameter at the small end, nor
l| more than 14 inches at the large end. They should be straight-grained, and
have the bark removed. The point is frequently shod with an iron shoe, to
prevent the pile from splitting, and the head is hooped with an iron band to
prevent splitting or brooming.
Safe load on Piles.
Rankine gives as safe loads on piles 1,000 pounds per square inch of head,
If driven to firm ground; 200 pounds, if in soft earth, and supported by
friction.
Major Sanders, IT. S. Engineers, gives the following rule for finding the
safe load for a wooden pile driven until each blow drives it short and nearly
equal distances:
c, - , , . , Weight of hammer in pounds x fall in inches
Safe load m pounds = — ^ : — = 5— = , — ; — rrr,
^ 8 X inches driven by last blow
Trautwine's rule is as follows :
_ 3VFall in feet x Lbs. wgt. of hammer x .023
Extreme load in gross tons = -
inches driven by last blow -4- 1
He recommends as safe load one-half the extreme load where driven in
firm soils, and one-sixth when driven in soft earths or mud. The last blow
should be delivered on solid wood, and not on the " broomed " head.
Piles under Trinity Church, Boston, support two tons each.
Piles under the bridge over the Missouri River at Bismarck, Dakota, were
driven into sand to a depth of 32 feet, and each sustained a load of 20 tons.
A pile under an elevator at Buffalo, N. Y., driven into the soil to a depth
of 18 feet, sustained a load of 35 tons.
794 FOUNDATIONS AND STRUCTURAL MATERIALS.
Arrangement of Piles.
Under walls of a building piles are arranged in rows of two or three,
spaced 24 inches or 30 inches on centers. Under piers or machine founda-
tions they are arranged in groups, the distance apart being determined by
the weight to be supported, but usually, as above, from two to three feet
apart on centers.
Concrete foundation Bed.
As mentioned in a previous paragraph, concrete is now used to a very
great extent for foundation beds, not only in soft earths, but to level up all
kinds of foundation beds.
Good proportions are by measure, using Portland cement:
Cement, 1 part,
Coarse sand, 2 parts,
Broken stone, 5 parts.
Only hard and sharp broken stone that will pass through a 1£- or 2-inch
ring should be used ; and the ingredients should be thoroughly mixed dry,
and after mixing, add just as little water as will fully wet the material.
Concrete should be placed carefully. It is never at its best when dropped
any distance into place. It should be thoroughly rammed in six- or nine-
inch layers, and after setting the top of each layer should be cleaned, wet,
and roughened before depositing another layer over it. It is common prac-
tice to place side-hoards in trenches and foundation excavations in order to
save concrete.- This is economical, but not good practice, if the earth is
even moderately firm, as filling out the inequalities makes the foundation
much firmer and steady in place. Weight of good concrete per cubic foot
is 130 to 160 lbs. dry.
Permissible JLoadw on foundation Beds.
Piles, in firm soil, each pile 30,000 to 140,000 lbs.
Piles in made ground, each pile, 4,000 "
Clay, 4,000 "
Coarse gravel and sand, 2,500 to 3,500 "
Rock foundations, average, 20,000 "
Concrete, 8,000 "
New York City laws, no pile to be
weighted with a load exceeding, 40,000 "
New York City rule for solid nat-
ural earth per superficial foot, 8,000 "
Concrete foundations.
One of the best foundations for engines or other heavy machinery is con
structed wholly of concrete, rammed in a mold of planking. The mould
can be made of any desired shape; the holding-down bolts placed by tem-
plate, and the material rammed in layers not exceeding 12 inches thick.
Brick foundations.
Only the best hard-burned brick should be used for foundations, and they
should be thoroughly wet before laying. To insure a thorough wetting, the
bricks should be deposited in a tub of water. Bricks should be push placed
in a good rich cement mortar. Grouting should never be used, as it takes
too long to dry. Joints should be very small. A well constructed brick
foundation will break as easily in the brick as at the joints after it has been
built for some time.
Stone foundations.
Rubble stone foundations should start with large flat stones on the bot-
tom. Care must be taken that all are well bedded in mortar, and that the
work is well tied together by headers.
MORTARS. 795
Dimension stone foundations are always laid out with the heavy and thick
stones at the bottom, and gradually decreasing in height, layer by layer, to
the top. A large cap-stone, or several if the size is too great for one, is
often placed on top of the foundation. Care must be taken to bed each stone
in cement mortar, so that the joints will be thin and yet leave all the spaces
between the stones completely tilled with mortar to prevent any unequal
strains on the stone. In all large foundations use plenty of headers; and if
the backing or center is of rubble, see that all stones are well bedded, and
the crevices rilled with spawls and cement.
I-Beam Foundations.
One of the best and now most common methods of constructing founda-
tions for piers, walls, columus, etc., is the use of steel I-beams set in con-
crete. Knowing the weight to be supported and the bearing value of the
soil, excavation is made of the right dimensions to get the proper area of
bearing, then I-beams of predetermined dimensions are laid parallel along
the bottom, and beld in place with bolts from one beam to the next. Con-
crete is rammed in all the spaces to a level with the top of the beams. An-
other similar layer of beams is then laid on top of the first, and at right
angles thereto, and the spaces also tilled with concrete. The column base,
or footing course, is then set on the structure ready to receive the column.
For method of calculation of dimensions of I-beams for use in foundations
for piers and walls, the reader can consult the hand-book of the Carnegie
Steel Company.
;viomt Alt*.
lime JtEortar.
Good proportions are : 1 measure or part quicklime, 3 measures of sand,
well mixed, or tempered with clean water.
Quantity required". — Trautwine. 20 cu. ft. sand and 4 cu. ft. of
lime, making about 22J cu. ft. mortar, will lay 1,000 bricks with average
coarse joints.
Weig-lit. — 1 bbl. weighs 230 lbs. net, or 250 lbs. gross; 1 heaped bushel
of lump lime weighs about 75 lbs.; 1 struck bushel ground quick lime, loose,
weighs about 70 lbs. Average hardened mortar weighs about 105 to 115 lbs.
per cu. ft.
Tenacity. —Ordinary good lime mortar 6 months old has cohesive
strength of from 15 to 30 lbs. per square inch.
Adhesion to common l»ricks or rubble.- At 6 months old, 12
to 24 lbs. per sq. inch.
Cement Mortar.
Good proportions are: 1 measure cement, 2 measures sand, h measure
water. The above is rich and strong, and for ordinary work will allow in-
crease of sand to 3 or 4 measures.
Quantity required. — Trautwine. 1 bbl. cement, 2 bbls. sand, will
lay 1 cu. yd. of bricks with § inch joints or 1 cu. yard rubble masonry.
WeigTit. —
American Rosendale, ground, loose, average, 56 lbs. per cu. ft.
" " U. S. struck bushel, 70 " " " "
English Portland, 81 to 102 " " " "
per struck bushel, 100 to 128 " " " "
" " per bbl., 400 to 430 " " " "
796 FOUNDATIONS AND STRUCTURAL MATERIALS.
Average Streng-th of Heat Cement after © I>ays in
Water.
Tensile, Lbs.
per sq. in.
Compress, Lbs,
per sq. in.
Compress,
Tons per sq. ft.
Portland, artificial . . .
" Saylor's natural
U. S. common hydraulic .
200 to 350
170 to 370
40 to 70
1400 to 2400
1100 to 1700
250 to 450
90 to 154
70 to 10 9
16 to 29
Cements are weakened by the addition of sand somewhat as shown in the
following table : calling neat cement 1.
Sand.
0
h
1
1*
2
3
4
5
6
Strength.
1
*
\
.4
i
.3
1
5
i
JLdraesion to Bricks or Rul»l»le.
Adhesion of cement, either neat or mixed with sand, will average about
three-fourths the tensile strength of the mortar at the same age.
S.OD A]V» CEMEHTT.
Recommendations of Am. Soc. Civil Engineers.
(Sand. — To be crushed quartz only. To pass,
1st sieve, 400 meshes per square inch.
2d " 900
Sand to pass the 400 mesh, but be caught by the 900 mesh, all finer parti-
cles to be rejected.
Portland. Cement. — For fineness, to pass,
1st sieve, 2500 meshes per square inch.
2d " 5476
3d " 10000 " "
Should be stored in bulk for at least 21 days to air-slake and free it from
lime, as lime swells the bulk, and if not removed is apt to crack the work.
IMOJV AJ¥I» §TEEL.
Iron, weig-lit of: cu. in.
Cast, .2604 Lbs.
Wrought^ .'2777 "
a = sectional area wrought-iron bar.
x =r weight per foot "
cu. ft.
450 Lbs.
3x
Steel, weig-lit of:
_10rt
X— g ■
cu. in.
cu. ft.
.2831 Lbs.
489.3 Lbs
Cast Iron. Test.
Bar an inch square, supported on edges 1 foot apart, must sustain 1 ton at
center.
WEIGHT OF FLAT ROLLED IRON.
797
h r,
; * S
0B -d
fl .■s
ft s 3
ft - •
N .3 o
1 »_ N •"
i ^ « w
© s 3
S2 ^
W- -
2 a
s£ g
H 5~
M *> g
M ^ "*
© 3"
P &
^ s
! M £
1
.3
.990
1.98
2.97
3.96
4.95
5.94
6.93
7.92
8.91
9.90
10.89
11.88
12.86
13.85
14.84
15.83
16.82
17.81
18.80
19.79
20.78
21.77
22.76
23.75
24.74
25.73
26.72
27.71
28.70
30^68
31.67
3
5
.938
1.88
2.81
3.75
4.69
5.63
6.56
7.50
8.44
9.38
10.31
11.25
12.19
13.13
14.06
15.00
15.94
16.88
17.81
18.75
19.69
20.63
21.56
22.50
23.44
24.38
25.31
26.25
27.19
28.13
29.06
30.00
d
.885
1.77
2.66
3.54
4.43
5.31
6.20
7.08
7.78
8.85
9.74
10.63
11.51
12.40
13.28
14.17
15.05
15.94
16.88
17.71
18.59
19.48
20.36
21.25
22.14
23.02
23.91
24.79
25. (IS
26.56
27.45
28.33
■*
.833
1.67
2.50
3.33
4.17
5.00
5.83
6.67
7.50
8.33
9.17
10.00
10.83
11.67
12.50
13.33
14.17
15.00
15.83
16.67
17.50
18.33
19.17
20.00
20.83
21.67
22.50
23.33
24.17
25.00
25.83
26.67
CO
.781
1.56
2.34
3.13
3.91
4.69
5.47
6.25
7.03
7.81
8.59
9.38
10.16
10.94
11.72
12.50
13.28
14.06
14.84
15.63
16.41
17.19
17.97
18.75
19.53
20.31
21.09
21.88
22.66
23.44
24.22
25.00
5
.729
1.46
2.19
2.92
3.65
4.38
5.10
5.83
6.56
7.29
8.02
8.75
9.48
10.21
10.94
11.67
12.40
13.13
13.85
14.58
15.31
16.04
16.77
17.50
18.23
18.96
19.69
20.42
21.15
21.88
22.60
23.33
s*
.677
1.35
2.03
2.71
3.39
4.06
4.74
5.42
6.09
6.77
7.45
8.13
8.80
9.48
0.16
0.83
1.51
2.19
2.86
L3.54
4.22
L4.90
5.57
16.25
6.93
7.60
18.28
18.96
19.64
20.31
20.99
21.67
i
.625
1.25
1.88
2.50
3.13
3.75
4.38
5.00
5.63
6.25
6.88
7.50
8.13
8.75
9.38
0.00
0.63
1.25
1.88
2.50
3.13
3.75
4.38
5.00
5.63
6.25
6.88
7.50
8.13
18.75
9.38
20.00
.3
.573
1.15
1.72
2.29
2.86
3.44
4.01
4.58
5.16
5.73
6.30
6.88
7.45
8.02
8.59
9.17
9.74
10.31
10.89
11.46
12.03
12.60
13.18
13.75
14.32
14.90
15.47
16.04
16.61
17.19
17.76
18.33
n
.521
1.04
1.56
2.08
2.60
3.13
3.65
4.17
4.69
5.21
5.73
6.25
6.77
7.29
7.81
8.33
8.85
9.38
9.90
10.42
10.94
11.46
11.98
12.50
13.02
13.54
14.06
14.58
15.10
15.63
16.15
16.67
|
.469
.938
1.41
1.88
2.34
2.81
3.28
3.75
4.22
4.69
5.16
5.63
6.09
6.56
7.03
7.50
7.97
8.44
8.91
9.38
9.84
10.31
10.78
11.25
1.1.72
12.19
12.66
13.13
13.59
14.06
14.53
15.00
<N
.417
.833
1.25
1.67
2.08
2.50
2.92
3.33
3.75
4.17
4.58
5.00
•5.42
5.83
6.25
6,67
7.08
7.50
7.92
8.33
8.75
9.17
9.58
10.00
10.42
10.83
11.25
11.67
12.08
12.50
12.92
13.33
|
.365
.729
1.09
1.46
1.82
2.19
2.55
2.92
3.28
3.65
4.01
4.38
4.74
5.10
5.47
5.83
6.20
6.56
6.93
7.29
7.66
8.02
8.39
8.75
9.11
9.48
9.84
10.21
10.57
10.94
11.30
11.67
*
.313
.625
.938
1.25
1.56
1.88
2.19
2.50
2.81
3.13
3.44
3.75
4.06
4.38
4.69
5.00
5.31
5.63
5.94
6.25
6.56
6.88
7.19
7.50
7.81
8.13
8.44
8.75
9.06
9.38
9.69
10.00
.260
.521
.781
1.04
1.30
1.56
1.82
2.08
2.34
2.60
2.86
3.13
3.39
3.65
3.91
4.17
4.43
4.69
4.95
5.21
5.47
5.73
5.99
6.25
6.51
6.77
7.03
7.29
7.55
7.81
8.07
8.33
-
.208
.417
.625
.823
1.04
1.25
1.46
1.67
1.88
2.08
2.29
2.50
2.71
2.92
3.13
3.33
3.54
3.75
3.96
4.17
4.37
4.58
4.79
5.00
5.21
5.42
5.63
5.83
6.04
6.25
6.46
6.67
V
1$
r '3
; 3
rt|2H^nHrfWuHnlffl^Hrt|sa!ScixrtS«H'2Hc*02H rtHHlnHH^^5:-:x''^':,"-,-l-2.x4.2'2tix2H
798 FOUNDATIONS AND STRUCTURAL MATERIALS.
'■'- - '-'-. - ''. -. u~: ~. ^. ^ ul =. L~' — . ul
_ooooooooo
qpppppppp©
<5 in t^ © ci '0 : i- - '■ I* t" 1_- — ':} J.~ Lr — '- ~ K- --? ' 5' ^ L~' ®
rtnrir-INlNOKNCO?;
0 ■* rfi ia o » «;
- x x t- © 1- -t- :■-. :: - 1 — © © x x l- m 00 01 c x l- 10 c
■ ' ' ~ ''-""ti- ■-. : • — . © - i ' "- L~ O co © ci x ■* p in t-h 1^ c
S "* © ©' rH •"' - x" © 0 i 1-' t- ©i CI -* OrllOO in ci •# x c
rH 1-1 rt rH 0-1 OI C I C 1 O-l CO 00 CO T ■* 1C O O © © t-
00 [> ifl W Cl O '/. 1- C " : 1 O X i- l". " C [- :o o t> » o t-
p !-h c 1 co ^ 5 in p 1^ x p p p — 0 1 : : p p x p r-< co in p
us^rS^<THi-ir-ioioioioiricococo-*'*miSioo«>
x m co o x 1- co © x ■ >n co — x 1- co o n c c © m o m c
x 1- p p co ci t-h p x L- p in co 0 1 1—, p l- p ci p 1- in oi o
r-5 cb in 1-- ci r-5 oo m' ©' x ©' ci-t'o x' o w t- h l* cc 010c
— -H S i-h th 01 oi ci ci oi co co co -* ■* ** m m «
t- -+< t-h 00 m co © 1- -t< h x 10 oi 0-.. ocooofiBO-joont;
t- in co © x © -r — - 1 - -r 0 1 © 1 - >o co x -1- © m oohb
r-5 cd id t-: 06 © ci -r o t- © ~ co -3 © x j-j £ x ci o 0 co jo
o co ^ -* •# m m
t> co o n n © t- co 00 t- co © t- co © t- © co i~ o co c- © co
p co © p co 0; p :: © © :: © © co © © © co p © co p p co
r-5 cd in © 00 © -5 co in © x ©' -^ co m" © © co © ©' co' © © co
©co©mi-HX-H©©co©in^x-+(©coinx©coin'X©
in th © -oi co cc © o © p -h i-.«co-i;oh 01 co p © l- x ©
r-5 cd "*' © t>5 ci © oi -+' in t- x ~ -- co' 1 0' x — -+ t- © co' © ©
HriHHHr- 1 CI 0)01 01 01 00 CO CO ■"■f^^lO
© cm x cc © m »h t^ co x -t< © © 0 1 x co 10 t- x © 01 co m t-
•+ © co x 01 1- 01 © — m co in © -+- x co oi — © © © co l- p
i-< ci <# in t^ 00 © t-h 00 -+ ©' 1- co © 1-^ 00' © ©' 0 i lol^ © co ©
rlHrlHHHHCltlClflCl CO CO CC ■* ■* ■*
1-1 oi t-h co co -p -f m © © t>- x x © © © 1-1 co "**! in
i* CO CI © © •* CO 01 p © -+ CO CI tSOlOtOnOl-;
r-i ci -* in l- 06 ci T-.' oi -P m' © x © -5 ci m' «'
i-icc-*in©x©©
00: 1^ c
o cc 00 co ■* -#
o©i*©in©©iHt-xx©©T-icicccc
<=> © j— 1 i-H 1-1 ih i-( ci ci ci ci 00 00 cc co co -t< -+i m m m © © t-
cc p © ci m co i-j ■# t>; © co © p 01 1.0 x -h © © 01 x -t< © ©
i-5 ci cd in" © t^ ci © i-H cc •* in © co ci © cd ©' 06 1-5 cd ©' ci 1 "
M Cl CO CC CO CC Td
m © m © m © in © m © 0 © m © m © © © © © © © © ©
ci m l- © 01 m t- © ci 101-0:1 p 1- © m © m © un m m ©
i-5 ci cd in © t^-' cd ©' ih ci cd in © t-^ 00 ©' ci in t- © ci in t~ ©"
rH ri r->. rH HrtHH(Md(M!M«MWm-#
OOOfflQC.OWOOCOCCOOt-t-Nt-tOOl-Ol.OOif-fM
ci -fiqi-OH^ p t- p rH co p l- © t-h m p 00 i~ hoqw
i-5 ci ci tj5 un t- cd ci © i-5 cd -r in ©' 1 - © r-' 00 ©' x -5 cc in cd
T-H lH l-H rH l-H 1-1 1-H T-H ci ci oi 01 co co :: ::
O CO 00 Ol N H O O l-O O i)
OtlHOOfflCCh
rH CI -t LO L-_ X © H :o -+ © t'-^ © © rH 00 p ci ci p f^ C
i-5 ci cd "*" in © 00 ci ©' ri ci co -r" © 1--' cd © ci in t-^ ci ci -f <x
HHrtHHHHHOlCKMClNMWK
© © x x t- © © in -* -h co. 00 01 -h t-h © © x © m -t< co i-H ©
© i-j ci co -* 1.0 © 1- x © ©.-h:i co -1- m © x © ci -t © x ©
-h ci cd ■* in © l^ 00 ci © ci n tj5 in ©' t-^ ci h -f ©' cc ©' ci in
o©-HHXcct-inccci©xt-inco
■rrxcot~-Hin©cox .. -
© © H rH 01 CI Cl p CO -*H -t in 1.0 I 0 © © I - X ©. © © l-H CI CO
r-5 ci cc -* in © t^ co ci ©' —^ 0 i :d -+ id © x' ©> oi in t-^ ci 1-"
TH^HTjn^h-a^r.^i-'^-.iu.^c;!^;
WEIGHT OF BARS OF IRON.
799
WEIGHTS
OF
lariBE AID HOOD BARS ©J?
WROIGHT JLR09T I]¥ POmiDi
raja
JLJOTEAI, JFOOT.
Iron weighing 480 lbs. per
cubic foot. For steel add 2 per cent.
©
s
U
ID
cS
u
03
3
u
s
.5 •
03&P
^ si
-3 fl
jL
A •
Mi
03
3 .
a .
2^
12 8
A «
II
§a
A $
S o
SA
SJ
cS O
PA
C O
gA
«1
S3
co o
M
9
co o
Ao
°1
tf o
o£
|£
ei-i O
oA
03 fl
<H,°
So
.SPo
.S°o
.SPO
2 fl
.£Po
ll
3
03
03
3
H
'S
^
H
03
£
0 -
ii
24.08
18.91
1
96.30
75.64
A
.013
.010
I
25.21
19.80
98.55
77.40
i
.052
.041
26.37
20.71
100.8
79.19
f
.117
.092
?
27.55
21.64
I
103.1
81.00
.208
.164
tI
28.76
22.59
i6
105.5
82.83
f
.326
.256
3
30.00
23.56
¥
107.8
84.69
,469
.368
JL
31.26
24.55
110.2
86.56
f
.638
.501
¥
32.55
25.57
it
112.6
88.45
.833
.654
$
33.87
26.60
X
115.1
90.36
f
1.055
.828
35.21
27.65
AS
117.5
92.29
1.302
1.023
t
36.58
28.73
61
120.0
94.25
¥
1.576
1.237
37.97
29.82
i
125.1
98.22
1.875
1.473
A
39.39
30.94
i
130.2
102.3
f
2.201
1.728
40.83
32.07
|
135.5
106.4
2.552
2.004
A
42.30
33.23
140.8
110.6
if
2.930
2.301
43.80
34.40
1
146.3
114.9
l
3.333
2.618
t
45.33
35.60
|
151.9
119.3
A
3.763
2.955
46.88
36.82
§
157.6
123.7
i
4.219
3.313
48.45
38.05
7
163.3
128.3
A
4.701
3.692
50.05
39.31
i
169.2
132.9
|
5.208
4.091
51.68
40.59
i
175.2
137.6
5.742
4.510
53.33
41.89
181.3
142.4
¥
6.302
4.950
i
55.01
43.21
i
187.5
147.3
t
6.888
5.410
?
56.72
44.55
i
193.8
152.2
7.500
5.890
58.45
45.91
1
200.2
157.2
A
8.138
6.392
1
60.21
47.29
206.7
162.4
f
8.802
6.913
61.99
48.69
88
213.3
167.6
tt
9.492
7.455
^
63.80
50.11
i
226.9
178.2
1
10.21
8.018
I
65.64
51.55
i
240.8
189.2
H
10.95
8.601
Vs
67.50
53.01
I
255.2
200.4
?
11.72
9.204
1
69.39
54.50
9
270.0
212.1
12.51
9.828
I
71.30
56.00
I
285.2
224.0
216
13.33
10.47
73.24
57.52
300.8
236.3
t
14.18
11.14
I
75.21
59.07
I
316.9
248.9
15.05
11.82
77.20
60.63
10
333.3
261.8
t
15.95
12.53
?
79.22
62.22
|
350.2
275.1
16.88
13.25
81.26
63.82
367.5
288.6
17.83
14.00
57
83.33
65.45
t
385.2
302.5
X3g
18.80
14.77
85.43
67.10
11
403.3
316.8
_z_
19.80
15.55
16
87.55
68.76
i
421.9
331.3
1
20.83
16.36
8
89.70
70.45
I
440.8
346.2
f
21.89
17.19
16
|
16
91.88
72.16
460.2
361.4
22.97
18.04
94.08
73.89
12
480,
377.
800 FOUNDATIONS AND STRUCTURAL MATERIALS.
© CO t~ © CO t- © CO t~ © CO t^ © CO t~ © © t-
- :o © © q q q :: q q q © © q © © q © © tr~ © © i>. © © b- © © b- cq © t>- co C
1 © © co d © co d © d d d d d © d d © d ::' © d ::' ©' d d d d c: © © © :
I -C LO LO LO © © © L- L- I- X X -X © © © © © i-i 01 01 CO -* -V LO © © I- X X © C
- — - .'J — — . .' w -^ - I l.
5 -*-*•* LO LO 1.0 LO © ©
?J V3 % ~ P «
d©looo©©loco©©©o:
-M - © ::" ©' d oi x i.o — ft d © d oi x
£ X © © © © ,-h i-i o 1 CO CO -)' ) - i 0 © -
© : i :o iO i - © © — © io t - © © — co uo i - © © co c-
© © 00 t-; q 10 q q q ci q © q © x . q q q cmhown W
CO CO ■*"*'* ^ i'O i.0 l© © © © ft L- ft L~^ X X X © cK © 2S?
-I 01 CO © LO 1-0 LO t~ CO CO ©
I © © CO © I- q rH 00 q CO
©©CI ©•#
© -f 10 i-
q x 1 0 0
o ro -tf •* -t< ■* ir
ooLodddftftftft^cc-Sb©;-:-?;
)©©©©©©© ©©©©©©©©©©©OO©
> q © q © q © q © q © q © q © q © q © © © ©
0 CO CO -# -* "#
i~~ © ci lo h c oi i o i ~ © oi rdi'idi^oiA
•# o o lo lo © © © © ft ft ft x x © © 5 ©
©©©©©©©©©
© d ~ o"i © ':: © d i"o
3 © CO 00 t— © 1-0 -t1 CO CO 01 — © © X X I- © 10 CO -h © © c~ lo
o i- © q © © oi q q q q q © oi q q q q q co © o © © oi <x
CC :ilO t-Ort-H'OC/
*i i.O 10 10 1.0 lo © —
: ft l- -x »cv£Sd-HH o
JWWHHHrtHH^rtH
*
25.00
27.08
29.17
31.25
33.33
35.42
37.50
39.58
41.67
43.75
45.83
47.92
50.00
52.08
54.17
56.25
58.33
60.42
62.50
66.67
70.83
75.00
79.17
83.33
87.50
91.67
95.S3
100.0 .
104.2
108.3
112.5
116.7
120.8
125.0
ffiM
22.50
24.38
2d. 25
28.13
30.00
31.88
33.75
35.67
37.50
39.38
41.25
43.13
45.00
46.88
48.75
50.63
52.50
54.38
56.25
60.00
63.75
67.50
71.25
75.00
78.75
82.50
86.25
90.00
93.75
97.50
101.3
105.0
108.8
112.5
To.oo
21.67
23.33
25.00
26.67
28.33
30.00
31.67
33.33
35.00
36.67
38.33
40.00
41.67
43.33
45.00
46.67
48.33
50.00
53.33
56.67
60.00
63.33
66.67
70.00
73.33
76.67
80.00
83.33
86.67
90.00
93.33
96.67
100.00
o -t< © © oi eg
© © oi oo co © lO i-H c-
I q © q oq q l- o i i - q © © lo ©_ q ©
n © oi co d d ft © d
t- 00 © i-l CO -JH © t-
i-H i-l 01 OI OI CI CO 01 i
CO © LO t- 00 © C
oq oi t-_ q lo lo -*
CO Th "f -f1 •* d LO LO IO © © — 1- ft ft
t- 00 © i-< CO LO © CO ©
q © © © q i- q lo lo
-*" ft © oi lo cc d q ft
S >~ q I" © q © io © io o lo © io © io © lo © © © © © © © © © 5 © 5 9 2 2 =
_ o i q q q : i i- i - q oi io i- © oi lo i- © oi lo © lo © lo © lo © lo © lo © lo — l. ,
_ q ft © oi lo ft © o t lo © lo © lo ©
2 " 2 i d d d Lo d © — 3 oi co lo d ft © ci
i o" oi co
rJH Tfi •* LO LO LO LO © © W © b- t- t-
2 "2 -2 .:2 Jr rn lo © co
oi © © -h oo co i- -< 10 co oi © ©. i- ;-
q © © © © i-i i-i oi oi q q lo lo_ © t-
©' i-H Oi CO lO* ©' I - d © © — ' CO 10 ft © rH o-
01 01 01 01 0 1 0 1 M 0 1 0 1 CO CO CO CO CO © i* Ti
+< 01 © 00 t^ LO CO 01 ©
o © © © q o i co q lo
o ft © oi d © x b o_i
ti -r< i.O LO i.O LO LO © ©
- ^ :" '.: 2 !2 '~ S c-
OI>-©t— CO©t— CO©t-
o — oo © co © © q © «
v io © d © ih d lo c:
■ i ; i : i oi :0 co co CO c
0 00 t- CO © t- CO ©
: © © o © © co ©
c © — d 1.0 d x ©
o co © © © ^h -r-i oi © d -+i lo io © ©
© lo © ip © lo © in ©
ft oJOH oi d lo d ft
oioqeococococococc
© 0 ! CO lO t- CO © O
© q q oi q - io r
lo lo d d © ft ft t-
0 C- CO © 01 OO IO t~ 00 © CO t- OtONO
- q lo © q q oi © © io_ co q © oq © lo
o © © © © © -3 -^ oi oi co tjh lo
qq©q©Loqq©
OA Ol Ol ?1 01 OI 01
u © ^H Ol © CO •* LO © t- CO CO © © — 0 I CO -o -n LO t- 0O O Ol CO LO C- CO © OI CO IO C- CO ©
„to j lo l- © q co i.o i - © i-h co lo l- © oi -t* © x © oi © © i o © co t ; lo © q oq oi © © q
' © © © © © i-3 --< oi oi
c © © i-i oi co -I
lo © r- oo © © oi -t< co co © oi ■* ©
OI Ol Ol 01 Ol CO CO © © © tP tJ< •* ^
© oo © oi -f cc:
GAUGE FOR SHEET AND PLATE IRON.
801
HT.OUARD «A.UCJE EOR SHEET -AJ¥»
PJLAXJE IROI AID STEEJL. 1S03.
6
«H
^
^
^;
M
CD *- «
O
H "-* "£ •
l| I
0*03.2
"II
^3*
co S
Pi
t per
Meter
unds
upois.
X xn ee
<2.J
•3 *<
m£,2
CO .3
1
H*3
0
F
*
f
0000000
1-2
0.5
12.7
320
20.
9.072
97.65
215.28
000000
15-32
0.46875
11.90625
300
18.75
8.505
91.55
201.82
00000
7-16
0.4375
11.1125
280
17.50
7.938
85.44
188.37
0000
13-32
0.40625
10.31875
260
16.25
7.371
79.33
174.91
000
3-8
0.375
9.525
240
15.
6.804
73.24
161.46
00
11-32
0.34375
8.73125
220
13.75
6.237
67.13
148.00
0
5-16
0.3125
7.9375
200
12.50
5.67
61.03
134.55
1
9-32
0.28125
7.14375
180
11.25
5.103
54.93
121.09
2
17-64
0.265625
6.746875
170
10.625
4.819
51.88
114.37
3
1-4
0.25
6.35
160
10.
4.536
48.82
107.64
4
15-64
0.234375
5.953125
150
9.375
4.252
45.77
100.91
5
7-32
0.21875
5.55625
140
8.75
3.969
42.72
94.18
6
12-64
0.203125
5.159375
130
8.125
3.685
39.67
87.45
7
3-16
0.1875
4.7625
120
7.5
3.402
36.62
80.72
8
11-64
0.171875
4.365625
110
6.875
3.118
33.57
74.00
9
5-32
0.15625
3.96875
100
6.25
2.835
30.52
67.27
10
9-64
0.140625
3.571875
90
5.625
2.552
27.46
60.55
11
1-8
0.125
3.175
80
5.
2.268
24.41
53.82
12
7-64
0.109375
2.778125
70
4.375
1.984
21.36
47.09
13
3-32
0.09375
2.38125
60
3,75
1.701
18.31
40.36
14
5-64
0.078125
1.984375
50
3.125 •
1.417
15.26
33.64
15
9-128
0.0703125
1.7859375
45
2.8125
1.276
13.73
30.27
16
1-16
0.0625
1.5875
40
2.5
1.134
12.21
26.91
17
9-160
0.05625
1.42875
36
2.25
1.021
10.99
24.22
18
1-20
0.05
1.27
32
2.
0.9072
9.765
21.53
19
7-160
0.04375
1.11125
28
1.75
0.7938
8.544
18.84
20
3-80
0.0375
0.9525
24
1.50
0.0804
7.324
16.15
21
11-320
0.034375
0.873125
22
1.375
0.6237
6.713
14.80
22
1-32
0.03125
0.793750
20
1.25
0.567
6.103
13.46
23
9-320
0.028125
0.714375
18
1.125
0.5103
5.493
12.11
24
1-10
0.025
0.635
16
1.
0.4536
4.882
10.76
25
7-320
0.021875
0.555625
14
0.875
(i.. •;:»<;<)
4.272
9.42
26
3-160
0.01875
0.47625
12
0.75
0.3402
3.662
8.07
27
11-640
0.0171875
0.4365625
11
0.6875
0.3119
3.357
7.40
28
1-64
0.015625
0.396875
10
0.625
0.2835
3.052
6.73
29
9-640
0.0140625
0.3571875
9
0.5625
0.2551
2.746
6.05
30
1-80
0.0125
0.3175
8
0.5
0.2268
2.441
5.38
31
7-640
0.0109375
0.2778125
7
0.4375
0.1984
2.136
4.71
32
13-1280
0.01015625
0.25796875
6*
0.40625
0.1843
1.983
4.37
33
3-320
0.009375
0.238125
6
0.375
0.1701
1.831
4.04
34
11-1280
0.00859375
0.21828125
5}
0.34375
0.1559
1.678
3.70
35
5-640
0.0078125
0.1984375
5
0.3125
0.1417
1.526
3.36
36
9-1280
0.00703125
0.17859375
ih
0.28125
0.1276
1.373
3.03
37
17-2560
0.006640625
0.168671875
4
0.2(55625
0.1205
1.297
2.87
38
1-160
0.00625
0.15875
4
0.25
0.1134
1.221
2.69
802 FOUNDATIONS AND STRUCTURAL MATERIALS.
COLUMlfi, PILLARN, Oil STJRUTS.
Hodgfkinson'ii Formula for Columns,
P = crushing weight in pounds ; d = exterior diameter in inches ; dl -
interior diameter in inches ; L = length in feet.
Kind of Columns.
Both ends rounded, the
length of the column
exceeding 15 times its
diameter.
Both ends flat, the
length of the column
exceeding 30 times its
diameter.
Solid cylindrical col-
umns of cast iron .
Hollow cylindrical
columns of cast
Solid cylindrical col- :
unms of wrought
iron '
Solid square pillar of ]
Dantzic oak (dry) . J
P = 33,380
P = 29,120
P = 95,850 -
$3.76 (J 3.70
P — 98,920 -
rf3.5S _ rfi3.B
$3.55
W-
These formula? apply only to cases of breakage caused by bending rather
than mere crushing. Where the column is short, or say five times its diam-
eter in length, then the following formula applies.
Let
P z= value given in preceding formulae,
K— transverse section of column in square inches,
C= ultimate compressive resistance of the material,
W = crushing strength of the column.
Then
P CK
P + l CK'
Hodgkinson's experiments were made upon columns the longest of which
for cast iron was 60^ inches, and for wrought iron 90| inches.
The following are some of his conclusions :
1. In all long pillars of the same dimensions, when the force is applied in
the direction of the axis, the strength of one which has Hat ends is about
three times as great as one with rounded ends.
2. The strength of a pillar with one end rounded and the other flat is an
arithmetical mean between the two given in the preceding case of the same
dimensions.
3. The strength of a pillar having both ends firmly fixed is the same as
one of half the length with both ends rounded.
4. The strength of a pillar is not increased more than one-seventh by en-
larging it at the middle.
Gordon's formulae, deduced from Hodgkinson's experiments, are
more generally used than Hodgkinson's own. They are :
Columns with both ends fixed or flat P —
P'
1 + a-
Columns with one end flat, the other end round, P =z
fS
72
Columns with both ends round or hinged, P -
Z2'
1+ 4a -£
STRENGTH OF MATERIALS. 803
S= area of cross-section in inches ;
P = ultimate resistance of column in pounds ;
f zz crushing strength of the material in pounds per square inch ;
. . ,. ,. ,. . . . , Moment of inertia
r =s least radius or gyration, in inches, r2 = — : :
area of section
I = length of column in inches ;
a = a coefficient depending upon the material ;
/ and a are usually taken as constants ; they are really empirical varia-
bles, dependent upon the dimensions and character of the column as well as
upon the material. (Burr.)
For solid wrought-iron columns, values commonly taken are : /= 36,000
to 40,000 ; a r-
New York City Building Laws 1897-1898 give the following values for/:
Cast iron f — 80,000 lbs.
Rolled steel .... f = 48,000 lbs.
Wrought or rolled iron / = 40,000 lbs.
American oak . . . f= 6,000 lbs.
Pitch or Georgia pine . /■=. 5,000 lbs.
White pine and spruce f = 3,500 lbs.
For solid cast-iron column s,/ = 80,000, a =
0400*
80 000
For hollow cast-iron columns, fixed ends, p = j9, I = length and
1 + 800 -j
d =r diameter in the same unit, andp = strength in lbs. per square inch.
Sir Benjamin Baker gives,
For mild steel / = 67,000 lbs., a = .
For strong steel /= 114,000 lbs., a — tt-ttja-
STRENGTH OF IHATERUI§.
The terms stress and strain are generally used synonymously, authorities
differing as to which is the proper use. Merriman defines st?-ess as a force
which acts in the interior of a body, and resists the external forces which
tend to change its shape. A deformation is the amount of change of shape
of a body caused by the stress. * The word strain is often used as synony-
mous with stress, and sometimes it is also used to designate the deforma-
tion. Merriman gives the following general laws for simple tension or
compression, as having been established by experiment.
a. When a small stress is applied to a body, a small deformation is pro-
duced, and on the removal of the stress the body springs back to its original
form. For small stresses, then, materials may be regarded as perfectly
elastic.
b. Under small stresses the deformations are approximately proportional
to the forces or stresses which produce them, and also approximately pro-
portional to the length of the bar or body.
c. When the stress is great enough, a deformation is produced which is
partly permanent; that is, the body does not spring back entirely to its
original form on removal of the stress. This permanent part is termed a
set. In such cases the deformations are not proportional to the stress.
d. When the stress is greater still, the deformation rapidly increases, and
the body finally ruptures.
e. A sudden shock or stress is more injurious than a steady stress, or than
a stress gradually applied.
804 FOUNDATIONS AND STRUCTURAL MATERIALS.
.Elastic liimit.
The elastic limit of a material under test for tensile strength is defined as
the point where the rate of stretch begins to increase, or where the defor-
mations cease to be proportional to the stresses, and the body loses its
power to return completely to its former dimensions when the stress is re-
moved.
Modulus of Elasticity.
The modulus or coefficient of elasticity is the term expressing the relation
of the amount of extension or compression of a material under stress to the
load producing that stress or deformation. It is the load per unit of section
divided by the extension per unit of length.
If P == applied load,
k = sectional area of piece,
I = length of the part extended,
A. = amount of extension,
M = modulus of elasticity,
M- P ' k— Pl
k ' l~ kk
Following are the Moduli of elasticity for various materials.
Brass, cast 9,170,000
wire 14,230,000
Copper 15,000,000 to 18,000,000.
Lead 1,000,000
Tin, cast 4,600,000
Iron, cast 12,000,000 to 27,000,000 (?)
Iron, wrought 22,000,000 to 29,000,000
Steel 26,000,000 to 32,000,000
Marble 25,000,000
Slate 14,500,000
Glass 8,000,000
Ash 1,600,000
Beech 1,300,000
Birch 1,250,000 to 1,500,000
Fir 869,000 to 2,191,000
Oak 974,000 to 2,283,000
Teak 2,414,000
Walnut 306,000
Pine, long-leaf (butt-logs) . . 1,119,200 to 3,117,000 Average, 1,926,00
Factor of Safety.
This may be defined as the factor by which the breaking strength of a
material is divided to obtain a safe working-stress. The factor of safety is
sometimes a rather indefinite quantity, owing to lack of information as to
the strength of materials, and it is now becoming common to name a defi-
nite stress which is substantially the result of dividing the average strengths
by a factor.
The following factors are found in the " Laws Relating to Building in
New York City," 1897-1898.
For beams, girders, and pieces subject to transverse strains, factor of
safety — 4.
For wrought-iron or rolled-steel posts, columns, or other vertical sup-
ports, 4.
For other materials subject to a compressive stx-ain, 5.
For tie-rods, tie-beams, and other pieces subject to tensile strain, 6.
MOMEUfT OF IHfEMTIA.
The moment of inertia of a body about any axis, is the sum of the products
of the mass of each particle of the body, into the square of its (least) dis-
tance from the axis.
MOMENT OF INERTIA. 805
radius or cnritATi:©]*.
The radius of gyration of a section is the square root of the quotient of
the moment of inertia, divided by the area of the section, or
Radius of gyrations /Moment of inertia
V Area of section.
The radius of gyration of a solid about an axis is equal to the
. /Moment of Inertia
V Mass of the Solid
Use in the formulae for Streng-th of Girders and
Columns.
The strength of sections to resist strains, either as girders or as
columns, depends on the form of the section and its area, and the property
of the section which forms the basis of the constants used in the formulae
for strength of girders and columns to express the effect of the form, is its
moment of inertia about its neiitral axis. Thus the moment of resistance
of any section to transverse bending is its moment of inertia divided by the
distance from the neutral axis to the fibers farthest removed from the axis ;
or
...- .:, . , Moment of inertia ., i"
Moment of resistance r= •
Distance of extreme fiber from axis" e '
moment of Inertia of Compound Shapes.
(Pencoyd Iron "Works.)
The moment of inertia of any section about any axis is equal to the I about
a parallel axis passing through its center of gravity -f- (the area of the sec-
tion X the square of the distance between the axes).
By this rule, the moments of inertia or radii of gyration of any single sec-
tions being known, corresponding values may be obtained for any combina-
tion of these sections.
Radius of gyration of Compound Shapes.
In the case of a pair of any shape without a web the value of R can always
be found without considering the moment of inertia.
The radius of gyration for any section round an axis parallel to another
axis passing through its center of gravity is found as follows :
Let r = radius of gyration around axis through center of gravity ; R =:
radius of gyration around another axis parallel to above ; d =. distance be-
tween axes :
R — Vrf2 + r
When r is small, R may be taken as equal to d without material error.
ELEHXWTI OF USUAX SECTIONS.
Moments refer to horizontal axis through center of gravity. This table is
intended for convenient application where extreme accuracy is not impor-
tant. Some of the terms are only approximate ; those marked * are cor-
rect. Values for radius of gyration in flanged beams apply to standard
miiiimum sections only.
A = area of section ;
b = breadth ;
h = depth ;
D = diameter.
806
FOUNDATIONS AND STRUCTURAL MATERIALS.
Shape of Section.
Moment of
Inertia.
Moment
of
Resistance.
Square of
Least
Radius of
Gyration.
Least
Radius of
Gyration.
bh**
12
bh**
6
/Least \2*
V Side )
*""
Solid Rect-
angle.
Least side*
fc
12
F
e-6— »
Hollow Rect-
angle.
bW—bJtf *
bW — bJi**
h* + V *
_.
h+h1
12
6h
12
4.89
-&-*
Solid Circle.
AD**
16
AD*
8
D**
"16"
D*
4
- - D- -H
Hollow Circle
A, area of
large section ;
a, area of
small section.
AD*— ad*
AD*— ad*
Z>2+rt2*
16
D + d
16
8D
5.64
->
/ \_ "^
Solid
Triangle.
bhs
36
bh*
24
The least
of the two:
h2 b*
18 °r 24
The leist
of the two :
h b
-6— H
IM °r 479
Even Angle.
Ah*
10.2
Ah
7.2
63
25
b
~5~
-rft —
o
Uneven Angle
Ah*
9.5
Ah
6.5
(hb)*
/t6
fcr-
13(/i2+62)
2.6 (h -4- 6)
HB
Even Cross.
Ah*
19
Ah
9.5
/t2
22.5
ft
4.74
M
Even Tee.
Ah*
ILT
8
b*
22.5
6
4J4
^m
I-Beam.
Ah*
6.66
3.2
62
21
b
4.58
f i
Channel.
Ah*
7.34
Ah
3.67
62
12.5
3.54
.^
11
I
4
fe)
Deck Beam.
Ah*
6.9
4
b*
36.5
6
6
Distance of base from center of gravity, solid trii
-— — ; uneven angle, -— ; even tee, -^; deck beam,
given in the table, ^ or ~z ■
even angle,
3.3'
ELEMENTS OF USUAL SECTIONS. 807
Solid Cast-iron Columns.
Table, based on Hodgkinson's formula (gross tons).
The figures are one-tenth of the breaking weight in tons, for solid col-
umns, ends flat and fixed.
.5
S3
Length of Column
n Feet.
6.
8.
10.
12.
14.
16.
18.
20.
25.
ii
.82
.50
.34
.25
.19
.15
.13
.11
.07
if
1.43
.87
.60
.44
.34
.27
.22
.18
.13
2
2.31
1.41
.97
.71
.55
.44
.36
.30
.20
21
1
3.52
2.16
1.48
1.08
.83
.67
.54
.46
.31
5.15
3.16
2.16
1.58
1.22
.97
.80
.66
.56
7.26
4.45
3.05
2.23
1.72
1.37
1.12
.94
.64
3
9.93
6.09
4.17
3.06
2.35
1.87
1.53
1.28
.88
3J
17.29
10.60
7.26
5.32
4.10
3.26
2.67
2.23
1.53
4
27.96
17.15
11.73
8.61
6.62
5.28
4.32
3.61
2.47
4*
42.73
26.20
17.93
13.15
10.12
8.07
6.60
5.52
3.78
5
62.44
38.29
26.20
19.22
14.79
11.79
9.65
8.06
5.52
5*
88.00
53.97
36.93
27.09
20.84
16.61
13.60
11.37
7.78
6"
120.4
73.82
50.51
37.05
28.51
22.72
18.60
15.55
10.64
6J
160.6
98.47
67.38
49.43
38.03
30.31
24.81
20.74
14.19
7
209.7
128.6
87.98
64.53
49.66
39.57
32.30
27.08
18.53
7i
268.8
164.8
112.8
82.73 .
63.66
50.73
41.53
34.72
23.76
8
339.1
207.9
142.3
104.4
80.31
64.00
52.39
43.80
29.97
8i
421.8
258.6
177.0
129.8
99.90
79.61
65.16
54.48
37.28
9
518.2
317.7
217.4
159.5
122.7
97.80
80.05
66.92
45.80
9*
629.5
386.0
264.2
193.8
149.1
118.8
97.25
81.70
55.64
10
757.2
464.3
317.7
233.1
179.3
142.9
117.0
97.79
66.92
lOJ
902.6
553.5
378.7
277.8
213.8
170.3
139.4
116.6
79.77
11
1067.1
654.4
447.8
328.5
252.7
201.4
164.9
137.8
94.31
11*
1252.3
767.9
525.5
385.4
296.6
236.4
193.5
161.7
110.7
12
1459.6
895.1
612.5
449.3
345.7
275.5
225.5
188.5
129.0
Where the length is less than 30 diameters,
Strength in tons of short columns =
SC
10£+fC"
S being the strength given in the above table, and C= 49 times the sec-
tional area of the metal in inches.
Hollow Columns.
The strength nearly equals the difference between that of two solid col-
umns, the diameters of which are equal to the external and internal diam-
eters of the hollow one.
More recent experiments carried out by tbe Building Department of New
York City on full-size cast-iron columns, and other tests made at the
Watertown Arsenal on cast-iron mill columns, show Gordon's formula,
based on Hodgkinson's experiments, to give altogether too high results.
The following table, from results of the New York Building Department
tests, as published in the Engineering N'eics, January 13-20, 1898, sIioav actual
results on columns such as* are constantly used in buildings. Applying
Gordon's formula to the same columns gives the following as the breaking
load per square inch. For 15-inch columns, 57,000 lbs.; for 8-inch and 6-inch
columns, 40,000 lbs., all of Avhich are much too high, as shown by the table.
Prof. Lanza gives the average of 11 columns in the Watertown tests as
29,600 pounds per square inch, and recommends that 5,000 pounds per square
inch be used as the maximum safe load for crushing strength.
808 FOUNDATIONS AND STRUCTURAL MATERIALS.
Tests of
Cast-iron Colun
I11S.
Thickness.
Breaking Load.
Diam.
Inches.
Max.
Min.
Average.
Pounds.
Pounds
per sq. in.
1
15
1
1
1,356,000
30,8300
2
15
Its
1
li
1,330,000
27,700
3
15
1
li
1,198,000
24,900
4
15|
1
li
1,246,000
25,200
5
15
3*
1
itt
1,632,000
32,100
6
15
li
1t3S
2,082,000+
40,400+
7
7| to 81
li
f
1
651,00
31,900
8
8
1*
1
l£
612,800
26,800
9
6A
1*
H
1&
400,000
22,700
10
653s
^1
1A
1*
455,200
26,300
Ultimate Streng-th of Hollow, Cylindrical VTroug-ht and
Cast-iron Columns, when fixed at the Ends.
(Pottsville Iron and Steel Co.)
f
Computed by Gordon's formula, p ■=. — - — -
1 + Cl
p = Ultimate strength in lbs. per square inch ;
I = Length of column, * ) , ,, . xmita-
h = Diameter of column, \ both m same umt8»
f f 40,000 lbs. for wrought iron; )
J ~~ \ 80,000 lbs. for cast iron; }
C = 1/3000 for wrought iron, and 1/800 for cast iron.
_ . . 80.000
For cast iron, p —
1 +
For wrought iron, p =
40,000
800 V h )
+— i-V
^ 3,000 V hj
Hollow Cylindrical Columns.
Ratio of
Maximum Load per sq. in.
Safe Load pei
• Square Inch.
Length to
Diameter.
Z
h
Cast Iron.
Wrought Iron.
Cast Iron,
Factor of 6.
Wrought Iron,
Factor of 4.
8
74075
39164
12346
9791
10
71110
38710
11851
9677
12
67796
38168
11299
9542
14
64256
37546
10709
9386
16
60606
36854
10101
9213
18
56938
36100
9489
9025
20
53332
35294
8889
8823
22
49845
34442
8307
8610
24
46510
33556
7751
8389
26
43360
32642
7226
8161
28
40404
31712
6734
7928
30
37646
30768
6274
7692
ELEMENTS OF USUAL SECTIONS.
809
Hollow Cylindrical Columns.-
Ratio of
Maximum Load per Sq. In.
Safe Load pei
Square Inch.
Length to
Diameter.
1
h
Cast Iron.
Wrought Iron.
Cast Iron,
Factor of 6.
Wrought Iron,
Factor of 4.
32
35088
29820
5848
7455
34
32718
2S874
5453
7218
36
30584
27932
5097
6983
38
28520
27002
4753
6750
40
26666
26086
4444
6522
42
21962
25188
41G0
6297
44
23396
24310
3899
6077
46
21946
23454
3658
5863
48
2061S
22620
3430
5655
50
19392
21818
3262
5454
52
18282
21036
3047
5259
54
17222
20284
2S70
5071
56
16260
19556
2710
4889
58
153G8
18856
2361
4714
60
14544
181S0
2424
4545
intimate Streng-tla of Wroug^ht-iron ColunniM.
p — ultimate strength per square inch;
I— length of column in inches;
r — least radius of gyration in inches.
For square end-bearings, p =-
1 +
mo\rJ
For one pin and one square bearing,
For two pin bearings,
40000
40000
T 30000 V*"/
40000
1-
/ I \
20000 \rj
For safe working-load on these columns use a factor of 4 when used in
buildings, or when subjected to dead load only; but wben used in bridges
the factor should be 5.
Wrought-Iron Columns.
Ultimate Strength
in Lbs.
Safe Strength in
Lbs. per
1
per Square In
ch.
I
r
Square Inch — Factor of 5.
r
Square
Pin and
Pin
Square
Pin and
Pin
Ends.
Sq. End.
Ends.
Ends.
7888
Sq.End.
Ends.
10
39944
39866
39800
10
7973
7960
15
39776
39702
39554
15
7955
7940
7911
20
39604
39472
39214
20
7021
7894
7843
25
39384
39182
38788
25
7887
7836
7758
30
39118
38S34
38278
30
7821
7767
7656
35
38810
38430
37690
35
7762
7686
7538
40
38460
37974
37036
40
7692
7595
7407
45
38072
37470
36322
45
7614
7494
7264
50
37646
36928
35525
50
7529
7386
7105
55
37186
36336
34744
55
7437
7267
6949
60
36697
35714
33898
60
7339
7143
6780
65
3bl82
34478
33024
65
7236
6896
6605
70
3o634
34384
32128
70
7127
6877
6426
75
350^6
33682
31218
75
7015
6736
6244
80
3*482
32066
30288
80
6896
6593
6058
85
33883
32236
29384
85
6777
6447
5877
90
33264
31496
28470
90
6653
6299
5694
95
32636
30750
27562
95
6527
6150
5512
100
32000
30U00
2b666
100
6400
6000
5333
105
31357
29250
25786
105
6271
5850
5157
810 FOUNDATIONS AND STRUCTURAL MATERIALS.
TMASrSVEMSE S1REXGTH.
Transverse strength of bars of rectangular section is found to vary di-
rectly as the breadth of the specimen tested, as the square of its depth, and
inversely as its length. The deflection under load varies as the cube of the
length, and inversely as the breadth and as the cube of the depth. Alge-
braically, if S = the strength and D the deflection, I the length, b the
breadth, and d the depth,
S varies as —r- and JJ varies as j-^t.
I bd3
To reduce the strength of pieces of various sizes to a common standard,
the term modulus of rupture (li) is used. Its value is obtained by experi-
ment on a bar of rectangular section supported at the ends and loaded in
the middle, and substituting numerical values in the following formula :
2 bd*
in which P = the breaking load in pounds, I = the length in inches, b the
breadth, and d the depth.
fundamental Forinnla' for flexure of ISeain*.
(Merriman.)
Resisting shear ~ vertical shear ;
Resisting moment = bending moment ;
Sum of tensile stresses = sum of compressive stresses ;
Resisting shear = algebraic sum of all the vertical components of the in-
ternal stresses at any section of the beam.
If A be the area of the section and ,S'S the shearing unit stress, then resist-
ing shear = ASs ; and if the vertical shear = V, then V— ASa.
The vertical shear is the algebraic sum of all the external vertical forces
on one side of the section considered. It is equal to the reaction of one sup-
port, considered as a force acting upward, minus the sum of all the vertical
downward forces acting between the support and the section.
The resistiug moment = algebraic sum of all the moments of the inter-
nal horizontal' stresses at any section with reference to a point in that sec-
tion, = — , in which S = the horizontal unit stress, tensile or compressive
as the case may be, upon the fiber most remote from the neutral axis, c =
the shortest distance from that fiber to said axis, and /= the moment of
inertia of the cross-section with reference to that axis.
The bending moment Mis, the algebraic sum of the moment of the external
forces on one side of the section with reference to a point in that section =
moment of the reaction of one support minus sum of moments of loads be-
tween the support and the section considered.
The bending moment is a compound quantity — product of a force by the
distance of its point of application from the section considered, the distance
being measured on a line drawn from tbe section perpendicular to the direc-
tion of the action of the force.
Concerning the above formula, Prof. Merriman, Eng. News, July 21, 1894,
says : The formula just quoted is true when the unit-stress S on tlie part of
the beam farthest from the neutral axis is within the elastic limit of the
material. It is not true when this limit is exceeded, because then the neutral
axis does not pass through the center of gravity of the cross-section, and
because also the different longitudinal stresses are not proportional to their
distances from that axis, these two requirements being involved in the de-
duction of the formula. But in all cases of design the permissible unit-
stresses should not exceed the elastic limit, and hence the formula applies
rationally, without regarding the ultimate strength of the material or any
of the circumstances regarding rupture. Indeed, so great reliance is placed
upon this formula that tlie practice of testing beams by rupture has been
almost entirely abandoned, and the allowable unit-stresses are mainly de-
rived from tensile and compressive tests.
TRANSVERSE STRENGTH.
811
=
*fi
o
© 0
si^l^^K^
^lfe]-lf*:
g& hi5
p
p
,-mco-uco-I^io|* + fijc?
mini
2^|§ 2
1
^
CO
. O i .
p-e £<£
Sl,,S|,,Si.1^i„N| ,,Si,,S
£
g§||
fci|«ft;|»ft3.|0ftq|ttfcj|cfi;|«ft5
o«^loft?h
51°
o
1
2
II II II II II II
1 II II
11
P
go
,-^s
A
£> £=. ^ £> u
*2£
oS OCC
A s- 5; fe ^7«> ^ S^ & |
L.
^,^,^■00 + rt,C0^
i»~|S iA
1-1 100
^S
A.
i-i I-*
CO 100
*"bJ
l§
2
oS
w
oS
o o
£3
^co « l^«|g + ^|S
^I8~
%
5
<=>l
ii i-*
bJO
-d
oS
ce
o
hi
B;| 03 | ft3| 0=| C3| C=| |
1-1 icoth i coin ico-* ico-t< in-t ico^
05 1
03 1
TfH ICO
P
bfi
II II II II Jl II 1
II
II
s
A L. ft, t^ ^ ft, ft
U
oS
+
P
A
• T5
-p
O
a •
0
0
s
'2
■a
p
0
73 (D
^3 OP
0)
^ s
■> ^
p= T3
a
•2 =2 3
0 '3 2
® ^ p
0 -s
OS JH y
c3
-P
OS
•S ^
£ Tl P
0>
43 0) -p g © *
P
^ 1 ■§ >, OT 1 1
'P eve
® as
-a
C3 •£ O P 'P 5 C.
3 Pa.
■p
-;§»*" <s a •§ £
§ 3 * ■§ 5- ■■§ 5
0 5 ^ "P 1i -° Js
os £ "S 0 -2 tl »
S 2 1
1 !!
OS
2
>>
2
0
P "oS^
P
® ■ § 1 § § © i
<D "P50
af
1 S'S
2
■1 oS 3 oS oS -_P oS
fc
CO CO CO
CO W CO
CO
ft
CO
812 FOUNDATIONS AND STRUCTURAL MATERIALS.
formulae for Transverse Strength of Beams.
(Referring to table on preceding page.)
P = load at middle ;
W = total load, distributed uniformly;
I =z lengtb ; b — breadth ; d — depth, in inches ;
E =z modulus of elasticity ;
B — modulus of rupture, or stress per square inch of extreme fiber ;
/=: moment of inertia ;
c =z distance between neutral axis and extreme fiber.
For breaking-load of circular section, replace bd- by 0.59tf3.
For good wrought iron the value of li is about 80,000, for steel about
120,000, the percentage of carbon apparently having no influence. (Tburs-
ton, " Iron and Steel," p. 491.)
For cast iron the value of li varies greatly according to quality. Thurston
found 45,740 and 07,980 in No. 2 and No. 4 cast iron, respectively.
For beams fixed at both ends and loaded in the middle, Barlow, bv experi-
ment, found the maximum moment of stress = \Pl instead of \lh, the re-
sult given by theory. Prof. Wood (" Resistance Materials," p. 155j.says of this
case, " The phenomena are of too complex a character to admit of a thorough
and exact analysis, and it is probably safer to accept the results of Mr. Bar-
low in practice than to depend upon theoretical results."
APPROXIMATE GREATEiT SAFE LOAD X5i
LB§. OUT STEEL BEAMS.
(Pencoyd Iron Works.)
Based on fiber strains of 16,800 lbs. for steel. (For iron the loads should be
one-sixth less, corresponding to a fiber strain of 14,000 lbs. per square inch.)
L ■=. length in feet between supports ;
A = sectional area of beam in square inches ;
D = depth of beam in inches ;
a = interior area in square inches ;
d — interior depth in inches ;
w r= working-load in net tons.
Shape
Greatest Safe Load in Lbs.
Deflection in Inches.
of
Section.
Load in
Middle.
Load
Distributed.
Load in
Middle.
Load
Distributed.
Solid
Rectangle.
940^iZ>
L
1880^Z>
L
2,2 AD2
mA&
Hollow
940 (AD — ad)
L
lS80(AD—ad)
L
wLs
wL*
Rectangle.
32(AD2—ad2)
52(AD2—ad2)
Solid
Cylinder.
700AB
L
1400.4/)
L
2AAD2
wL3
38AD2
Hollow
700 (AD — ad)
L
1400(AD—ad)
L
wL*
wlfl
Cylinder.
2\(AD2—ad2)
3S(AD2—ad2)
APPROXIMATE GREATEST SAFE LOAD IN LBS.
813
Shape
Greatest Safe Load, in Lbs.
Deflection in Inches.
of
Section.
Load in
Middle.
Load
Distributed.
Load
in Middle.
Load
Distributed.
Even-
legged
Angle 01-
Tee.
930 AD
L
1860 A D
L
wL3
32Alf-
wL3
52AD*
Channel or
Z Bar.
160(U£>
L
3200AD
L
wL3
53AD2
wL3
85AD2
Deck
Beam.
145fUZ>
290(U D
L
Eoaip
ivL3
80ZD2
I-Beam.
1780AD
L
3560AD
L
ioL3
58ZZJ2
wL3
93ZD2
I
II
III
IV
Y
The rules for rectangular and circular sections are correct, while those for
the flanged sections are approximate, and limited in their application to the
standard shapes as given in the Pencoyd tables.
The calculated safe loads will be approximately one-half of loads that
"would injure the elasticity of the materials.
The rules for deflection apply to any load below the elastic limit, or less
than double the greatest safe load by the rules.
If the beams are long, without lateral support, reduce the loads for the
ratios of width to span as follows :
Length of Beam.
Proportion of Calculated Load
forming Greatest Safe Load.
20 times flange width.
60
70
Whole calculated load.
9-10
8-10 " "
7-10 "
6-10 " "
5-10 "
These rules apply to beams supported at each end. For beams supported
otherwise, alter the coefficients of the table as described below, referring to
the respective'columns indicated by number.
Changes of Coefficients for Special Forms of Beams.
Kind of Beam.
Coefficient for Safe
Load.
Coefficient for Deflec-
tion.
Fxed at one end, loaded
at the other.
One-fourth of the coeffi-
cient of col. II.
One-sixteenth of the co-
efficient of col. IY.
814 FOUNDATIONS AND STRUCTURAL MATERIALS.
Changres of Coefficients — Continued.
Kind of Beam.
Coefficient for Safe
Load.
Coefficient of Deflec-
tion.
Fixed at one end, load
evenly distributed.
One-fourth of the coeffi-
cient of col. 111.
Five forty-eighths of the
coefficient of col. V.
Both ends rigidly fixed,
or a continuous beam,
with a load in middle.
Twice the coefficient of
col. IE.
Four times the coeffi-
cient of col. IV.
Both ends rigidly fixed,
or a continuous beam,
with load evenly dis-
tributed.
One and a half times
the coefficient of col.
III.
Five times the coeffi-
cient of col. V.
Modulus of Elasticity and Elastic Resistance.
P = tensile stress in pounds per square inch at the elastic limit
e = elongation per unit of length at the elastic unit ;
E = modulus of elasticity = P -f- e ; e = P -j- E. j pi
Then elasticity resilience per cubic inch = \Pe =
2 E'
THRODGHOIT
BEAMS OE MIFORM STBEI^TH
THEIR LEHGTH.
The section is supposed in all cases to be rectangular throughout. The
beams shown in plan are of uniform depth throughout. Those shown in
elevation are of uniform breadth throughout.
B = breadth of beam. D = depth of beam.
Fixed at one end, loaded at the other ;
curve parabola, vertex at loaded end ; BD2
proportional to distance from loaded end.
The beam may be reversed so that the up-
per edge is parabolic, or both edges may be
parabolic.
Fixed at one end, loaded at the other ; tri-
angle, apex at loaded end ; BD2 proportional
to the distance from the loaded end.
Fixed at one end ; load distributed ; tri-
angle, apex at unsupported end ; BD2 pro-
portional to square of distance from unsup-
ported end.
Fixed at one end ; load distributed ; curves
two parabolas, vertices touching each other,
at unsupported end ; BD2 proportional to dis-
tance from unsupported end.
Supported at both ends ; load at any one
point ; two parabolas, vertices at the points
of support, bases at point loaded ; BJJ2 pro-
portional to distance from nearest point of
support. The upper edge or both edges may
also be parabolic.
Supported at both ends ; load at any one
point ; two triangles, apices at points of sup-
port, bases at point loaded ; BD2 propor-
tional to distance from the nearest point of
support.
Supported at both ends ; load distributed ;
curves two parabolas, vertices at the middle
of the beam ; bases center line of beam ; BD2
proportional to product of distances from
points of support.
Supported at both ends ; load distributed ;
curve semi-ellipse ; BD2 proportional to the
product of the distances from the points of
support.
TRENTON BEAMS AND CHANNELS.
815
XUJEJffTOJtf BEAMS AJD CHA^aTEES.
(Trenton Iron Works.)
To find which beam, supported at both ends, will be required to support
with safety a given ■uniformly distributed load :
Multiply the load in pounds by the span in feet, and take the beam whose
" Coefficient for Strength " is nearest to and exceeds the number so found.
The weight of the beam itself should be included in the load.
The deflection in inches for such distributed load will be found by divid-
ing the square of the span taken in feet, by seventy (70) times the depth of
the beam taken in inches for iron beams, and by 52.5 times the depth for
steel.
Example. — Which beam will be required to support a uniformly distrib-
uted load of 12 tons (= 24,000 lbs.) on a span of 15 feet ?
2-±,O0O X 15= 360,000, which is less than the coefficient of the 12i-inch 125-
lb. iron beam. The weight of the beam itself would be 625 lbs., which,
added to the load and multiplied by the span, would still give a product less
than the coefficient; thus,
The deflection will be :
24,625 X 15=369,375.
z 0.26 inch.
70 X T2i
The safe distributed load for each beam can be found by dividing the
coefficient by the span in feet, and subtracting the weight of the beam.
When the load is concentrated entirely at the center of the span, one-half
of this amount must be taken.
The beams must be secured against yielding sideways, or the safe loads will
be much less.
TREITOH ROLLED STEEL BEAMS.
Designation of
Beam.
12
10
10
10
2
Weight per
Yard in Lbs.
150
123
120
96
39
30
190
160
150
125
160
125
100
105
85
Width of
Flanges in
Inches.
5.5
5.25
5.25
5.0
4.75
4.75
2.75
2.62
.75
1.50
Thickness
of Stem.
.45
.37
Coefficient for
Strength in
Lbs., Minimum
Weight.
753,000
603,000
500,000
407,000
461,000
344,000
264,000
232,000
200,000
192,000
154,000
151,000
118,000
104,000
83,300
67,000
52,900
41,200
31,400
2,660
2,300
816
FOUNDATIONS AND STRUCTURAL MATERIALS.
TBE]¥TO]¥ IROJY JlKATlft
A]¥» CHAHrHEl§.
.3
I
W
2J=
ah
3|
oj
Coefficient
in Lbs. for
Transverse
Strength.
a
.5
W
2-S
^ !h 5?
m an
<h a
^ <S m
— if. -
Coefficient
in Lbs. for
Transverse
Strength.
I-Beams.
Channels.
20
272
6!
tt
1,320,000
15
190
4|
1
625,000
20
200
6
A
990,000
15
120
4
J
401,000
15i-
200
5|
.6
748,000
121
140
4
B
3S1,000
15r3B
150
5
i
551,000
12i
70
3
.33
200,100
15§
125
5
.42
460,000
ioi
GO
21
1
134,750
12i5s
170
5£
.6
511,000
10
48
2}
i3s
102,000
12i
125
4.8
.47
377,000
9
70
3^
IB
146,000
12
120
5J
.39
375,000
9
50
2£
.33
104,000
10
96
5i
.32
306,000
8
45
2*
.26
88,950
m
135
5
.47
360,000
8
33
2.2
.20
65,800
10|
105
4^
I
286,000
7
36
2J
i
62,000
io£-
90
4^
iss
250,000
7
25i
2
.20
39,500
9
125
4^
.57
268,000
6
45
2i
.40
58,300
9
85
4^
I
199,000
G
33
2i
.28
45,700
9
70
4
.3
167,000
G
22i
15
.18
33,680
8
80
4-i
|
168,000
5
19
If
.20
22,800
8
65
4
.3
135,000
4
ICi
If
.20
15,700
7
55
120
6i
.3
101,000
172,000
3
15
if
.20
10,500
6
G
90
50
5
.3
132,000
76,800
Deck Beams
G
8
65
4^
|
91,800
G
40
3
t
62,600
7
55
4A-
is
63,500
5
40
3
IB
49,100
5
4
30
37
2f
3
*
38,700
36,800
Strut Bars.
16B
4
30
2|
3
30,100
5
22
Wb
A
11,900
4
IS
2
A
18,000
5
16
1A
I
9,100
TBENTON BEAMS AND CHANNELS.
817
o
sS
o.
lap
FEET.
3.2
3.9
3.3
4.4
3.0
3.8
3.3
4.2
3.6
4.8
3.6
3.7
3.0
4.4
3.3
3.6
3.0
4.1
3.5
4.7
3.9
5.3
3.4
4.6
<s>% ft.1*
J OOlOLOlOOlOOLOlOlOLOLOCOOOOOOOHOM
M ^iniQOtst-coo2:u::i:ii: i- i- L- — co — ■ — i^- — t-
oiot-ooMOOci^^irii^utc^occooo
M " »
o
o
u
si
ft
c3
O
S »>oq»iocoqccco-*LOoqq©cooociLoa)rt>a
j^ co •* CO -# CO -<# CO id CO •#" CO -#' CO ■* CO CO CO 00 CO -# CO ■* ■*" id
to
by
j OOOIOLOOOOOOC IO l- ■ o io uO o O O O O O O <M
o w » t> oo os o co o c co oi ' o i o i ' o i io o'V lo lo lo lo © © o
£
O
o
ft
■2s
a; co
ft
1
o
® -2 •
3* Jo
^ ©coot^^iqcor^t^-t^c^cq^iqi^-iqoioccoi^ococ^
H CO^COCO00ri<00^CO^^^c6^C0^00-^CO»l0^cdc6lO
to
■Sfe: ►*
S- 8§§S!S88g8§8§S8ia88§g88888
i-l rtrlHr-rirlrlClClfllMOl
lQffltoONoocoocc c^icci^ii.t :u*i-i:i-'30ioo
^ ,-^^^^^^c,^,
o
o
©
M
ft1-1
e3
O
« 3 •
lis!
H
to '""' ^ 'I * "? <°. °7. L~ ,;r- - ] ~: —. L~ ~. °. °> ,~i ^ n. r1 ^ °5 ^ 1
H co^^iCCO^cOT^co^co^^O^^^ior^iO^OCOiJO
05 -3, H v
S-Sft^
J O00cooioioi0iocioc->oio:oi0i0'0>ocooooo
w co co -1- 10 10 io io — — l- x co co oi co oi oi o I : i io '0 r 10 -
Tt* ia CD «o co t- 1- -o CO CO CO co C 0 I 01 O I 0 1 10 10 10 10 LO LO LO
Szi
o
o
M
si
■03
c3
O
O _; ^ ■ h
J ?-§ -
fcj CD O CO 00 03 OI O t^ © CO CO CO O ■OOOHH 1 LO | CO |
W "*ioc6^-*iaicc5iocDrtii6cD *'i6i-OC5lo 'irj ' lo
, -i o o c o o o io io io © o io o "oisoioia no " o
1-1 CO CO CO ^5 ^ io LO cs vr L- l- CO - _ - - r. 0101 _oi _S
■* io ia ia c- co n co oo o o o c oocici'ci i« io
03
0)
5
3 c"§
02 ^
O01-*C0C0OCM-*C000O
00 t-i, rH H rH iH, <M <N <N <N <N CO
818
FOUNDATIONS A2sTL>
STRUCTURAL
MATERIALS.
•" ^ ~£
c
5
o
o
in
g
-
c
c
o
O
c
o
o
P4;£J o
1
c
1
L-j
oo
1
rS M
+= 03
1
1
8
CO
IQ
rh
i^s-s
o
OS
o
o
o
O
■Stofi'S?
00
<M
in
eo
CO
^fl-sa
§
f?
lO
05
CO
m
CM
£ M
5 o
M S
§ no MM
©
3
CO
S3
W
o
b-
c
OS
©
C
+3 o "5 2
C<
S
o
-2 S
o
eo
o
o
c
o
O
|
o
o
® . ©Pn
p
o
m
CD
I
<N
o;
o
2o^5
o
o
OS
CO
oo
rt £
£
CO
8
1
1
8
OS
o
o
o
I
a
8
"d
in
m
2
13 S"^
c
O
m
o
o
8
m
o
c
os
o
o
1
o
o
o
o
g
B
1
4
1
1
o
8
eo
co
i
o
i
o
8
$
"S
lO
W
W
CO
OS
in
m
m
*
$ •
1
1
§
01
8
3
8
3
1
|
o
o
|
8
o
2
9
c
OS
CO
c
o
o
o
o
o
8
O
CN
o
o
o
o
o
o
&
©
0
H S° ~
1
8
I
~
©
o
o
%
©
c
c
3
©
§
I
§
CO
fc
o
c
c
©
c
OS
12
7-1
'""'
1-1
rt
(N
1-1
1-1
1-1
rH
©.« SB
a . cS
OS
in
o
©s
t.
,_,
oo
in
CO
m
fwl
T*
*
oi
oi
CO
Tt
■*
in
CN
oi
co-
tt£
*§»
•*
CO
t_
m
it
s
CO
-+
3©a
c
in
o
CO
o
^
1
m
o
©
o
CO
o
rn
M£ rt
CO
o
•*
"2
^ °
T*
■-#
W
CO
■*
=3
O
^
©
©
$
a
cS
s
s
1
"O a
1 cp
o
0
12
a
1 ^
3
©
©
©
a
<
w
© r^
Q C
5 o
s
w
s
o
Hi
i
c$
O
cS
o
£
s
f
WOOD.
Tests of Americau Woodi,
819
In all cases a large number of tests were made of each wood. Minimum
and maximum results only are given. All of the test specimens had a sec-
tional area of 1.575 x 1.575 inches. The transverse test specimens were
39.37 inches between supports, and the compressive test specimens were
12.60 inches long. Modulus of rupture calculated from formula li —
= load in pounds at the middle, I = length in inches, b :
= depth :
" 2 brP '
: breadth,
Name of Wood.
Transverse
Tests,
Modulus of
Rupture.
Compression
Parallel to
Grain, pounds
per sq. in.
Cucumber tree
Yellow poplar, white wood
White wood, Bass wood
Sugar maple, Rock maple
Red maple
Locust
Wild cherry
Sweet gum
Dogwood
Sour gum, pepperidge . .
Persimmon
White ash
Slippery elm ......
White elm ,
Sycamore, Buttonwood ,
Butternut, white walnut .
Black walnut
Shellbark hickory . . .
Pignut
White oak
Red oak
Black oak
Chestnut
Beech
Canoe birch, paper birch .
Cottonwood
White cedar
Red cedar
Cypress
White
pine
Spruce pine
Long-leaved pine, Southern pine
White spruce
Hemlock
Red fir, yellow fir
Tamarack
7400
6560
6720
9680
8610
12200
8310
7470
10190
9830
18500
5950
5180
10220
8250
6720
4700
8400
14870
11560
7010
9760
7900
5950
13850
11710
8390
6310
5640
9530
5610
3780
9220
9900
7590
8220
10080
120'n
11756
11530
20130
13450
21730
16800
11130
14560
14300
10290
15800
10150
13952
15070
11360
11740
16320
20710
19430
18360
18370
18420
12870
18840
17610
13430
9530
15100
10030
11530
10980
21060
11650
14680
17920
16770
4150
3810
7460
6010
8330
5830
5630
6250
6240
6650
4520
4050
6980
4960
4960
54S0
6940
7650
7460
5810
4960
4540
3680
5770
5770
3790
2660
4400
5060
3750
25S0
4010
4150
4500
4880
6810
7410
5790
6480
9940
7500
11940
9120
7620
9400
7480
5970
8790
8040
7340
6810
8850
10280
8470
9070
8970
8550
6650
7840
8590
6510
5810
7040
7140
5600
4680
10600
5300
7420
9800
10700
820 FOUNDATIONS AND STRUCTURAL MATERIALS.
HOnaoOfflH
lco cm oo co lo -f o i :: co -Mr tier: o i i - - x :h ^ohiohOi
cm rH o o oi r -o >o -- r : i o SrH-t i- ,-, co o i oo -t< i-> t- u".(MOt-
o oo cm en h o n ci t~ o •* co n h c g a » co t- i» t» » to to ;o io
Ot-LOCOCOCMCM--
rH CO t- CO CM CI -+ ^ CM i-l L- -+i I- CM I- t-h i-< CO CO i-l OO CI CM t- ^ -# rf «
— r : : r : : ■ - -t- r — co c-. :: — i - r i- ~ > - -- x -t — c re -+ o i r v.
CO X lO -f l- CM CI t- lO CO CM t* O CS CI OO OO L~ L- CD CO CO' LO ICO LO LO LO -I
CO CO-* CO CMC-
Hori««'riHHrHHrid6666666dd6d666o'6o'd
0 CO CO i-l CO CM OO IO CM O L- lei CO 5- ~ l&~ C^\:'-f- £
o q co in q q -ch c; --i q q oo l - l- q q q q q q •* -p -ch -t; -+ co co co co co
didco'ciciHHririrHodoooodddddddddddddd
5 q q co t- t^ q q q lco ^ --ch -ch -oh *-h co co co co co 'c6 co cm t>.
CCTFcicMTMi--5-MT--10©©0©0©d©ddddddddddddd
f CM LCi CO CS C~ CM OO CM -J 1-1 cs -J CO co -ch CO CO W t— i-l H CM cs 00 r> t— 00 OS iH
v i - .— co x o cs co l- cs co l- co cs co co r X or; ~\- -- ,-- — rr , r. — J>. rY K rr
r. -r :o l- -o v-, q x . - q q q q -i- -r -f -# q q co co co co cm cm ci ci oi ci oi
onciHriHooooododdddddddddddddddd
lONOfflocogngWHoncjL'jNHMtoHajtoioitioteojHto
o i i— l- r o i co o o cm -co i-i co co o l~ i~ co i-H cs oo co lo -f cc- ^ i r; — - -
co x x -tHOco l- q q q -ch -ch -h co q co co ci oi cm cm ci ci 6i cm oi cm S
^c4rHiHrHOOOOOOOOOCDOoooOo^^^<='C'C'<='G'
hi tredg
-h cm i-h i-i x — i r; lo -h -h -ch o oi t- co oo i-i tr- -ck oi o i oi co t-cfrtirca •
-*C}rHT--i ©©©©©©©©©© ©'©©©©©©©©©©©©© •
_ l-HCO
co co co oi oj oi 6
DOCOLOOt-NClX'OI-COClC.t-Ot-OCl LO K-tC-fOtO
o io co o i r i- io v-; i- io oi o co l- co lo -f co co oi i-i i-i cD r r cs
OClCOOlOtWCOClClCKIHrtHHHrtHHHrtHrfHO
spiddoddddddddoddddddooe'ddo
tHOOOOOOOOOOOOOOOOOOOOOOOO
c To co o i — cd ccs co t- i.
ICO OI OO CO ICO -H CS OO CS 01 I- 01 X I- 01 CS I- ICO CO r- CCO N
oi holociO coi-cocoi-c i~ -k -* -h co co co co ro re oi oi
oMNrtHiHoqc o cccqcccccccc r
do'ddddo'dddcdcddcddddccc
^ ~ ^ ,~ -5 — C= l-O —-< -v- i - -- .1 C Cl f» CC LO LO -H CO CO -
ci h q q q cq c q q q q cbooooo qq q q
dddddo'ddddddddddoddddd "
qdqcqc q q q q q q occoceoq " *
o o d d d cd cd cd d cd d o" r c r" r" cd r d d ' '
3 t» 00 CS O i-< fl « "f LO C3 N CO CS D "-< Ol CC •+ l' CC
HMHrtrtHHrtHlCKMClClClClC
wood. 821
Rule. — To find the safe uniformly distributed load in tons for white pine
or spruce beams, multiply the number given in the above table by the thick-
ness of the beam in inches. For beams of other wood, multiply also by the
following numbers :
White Oak. Hemlock. White Cedar. Yellow Pine. Chestnut.
1.45 .99 .60 1.50 1.08
Formula' for White JPine Beams.
Subject to vibration from live loads.
w = safe load in pounds, less weight of beam.
I = length of beam in inches.
d = depth of beam in inches.
b = breadth of beam in inches.
For a beam fixed at one end and loaded at the other:
1000 6rf2
w=— 6T—
For a beam fixed at one end and' uniformly loaded :
1000 bd2
W=-JT—
For a beam supported at both ends and loaded at the middle:
2000 bd*
W=—3f—
For a beam supported at both ends and uniformly loaded:
4000 bd2
w = —sr-
Note. — In placing very heavy loads upon short, but deep and strong
beams, care should be taken that the beams rest for a sufficient distance on
their supports to prevent all danger from crushing or shearing at the ends.
Ordinary timbers crush under 6,000 lbs. per square inch. To assure a safety
of beam against crushing at the end, divide half of the load by 1000; the
quotient will be the least number of square inches of base that should be
allowed for each end to rest on.
Table of Safe Load for Moderately Seasoned White JPine
Struts or I*illars.
The following table, exhibiting the approximate strength of white pine
struts or pillars, with flat ends, is outlined and interpolated from the rule
of Rondolet, that the safe load upon a cube of the material being regarded
as unity, the safe load upon a post whose height is,
12 times the side will be I
60
72
700 pounds per square inch is assumed as the safe load upon a cube of
white pine.
The strength of each strut is considered with reference to the first-named
dimension of its cross-section, so that if the second dimension is less than
the first, the strut must be supported in that direction, to fulfill the condi-
tions of the computation.
The strength of pillars, as well as of beams of timber, depends much on
their degree of seasoning. Hodgkinson found that perfectly seasoned blocks
2 diameters long, required in many cases twice as great a load to crush
them as when only moderately dry. This should be borne in mind when
building with green timber.
822 FOUNDATIONS AND STRUCTURAL MATERIALS.
I. Safe Distributed Xioads upon Southern Pine Beams
One Inch in Width.
(C. J. H. Woodbury.)
(If the load is concentrated at the center of the span, the beams will sus-
tain half the amount as given in the table.)
CD
Depth of
Beam in
Inches.
fc
i|s|«
*
• | T| 8
9
10
11 | 12 |
13 1
"1
,5 |
16
Load in Founds per Foot of Span.
5
38
86
154
240
34fi
470
614
778
960
6
27
60
107
L67
240
327
427
540
0(17
807
7
20
44
78
122
176
240
314
397
41)0
593
705
828
8
15
34
60
94
135
1S4
240
304
375
454
540
634
735
9
27
47
74
107
145
190
240
296
359
427
501
581
667
759
10
22
38
60
86
11«
154
194
240
290
34! ;
40(1
470
540
614
11
32
50
71
97
127
161
HIS
240
286
335
38!)
446
508
12
27
42
60
82
107
135
1(17
202
240
282
327
375
474
13
36
51
70
90
115
142
172
205
240
278
320
364
14
31
44
60
78
99
123
148
176
207
240
276
314
15
27
38
52
68
86
107
129
154
ISO
209
240
273
16
34
46
CO
76
94
113
135
158
184
211
240
17
30
41
53
67
83
101
120
140
163
187
217
18
36
47
60
74
90
107
125
145
167
190
19
43
54
66
80
96
112
130
150
170
20
38
49
60
73
86
101
118
135
154
21
44
54
06
78
92
107
122
139
22
50
60
71
84
97
112
127
23
45
55
65
77
89
102
116
24
50
60
70
82
94
107
25
46
55
65
75
86
98
DiNtrihuted Load* upon Southern Pine Beams Suf-
ficient to Produce Standard Limit of Betlection.
(0. J. H. Woodbury.)
%
Depth of Beam
in Inches.
£
fr
p-
2 3 4 5
6 7 8 9 10
11 12 13 14 15 16
* o
Load in Founds per Foot of Span.
5
3
10
23
44
77
122
182
259
.0300
6
2
7
16
31
53
85
126
180
247
.0432
7
5
12
23
39
62
93
132
181
241
.0588
8
4
9
17
30
48
71
101
139
185
240
305
.0768
9
7
14
24
38
56
80
110
146
190
24!
301
.0972
10
6
11
19
30
46
65
89
118
154
195
244
300
.1200
11
9
16
25
38
54
73
98
127
161
202
248
301
.1452
12
13
21
32
45
62
82
197
136
10!)
208
253
.1728
13
11
18
27
38
53
70
91
116
144
178
215
.2028
14
16
23
33
45
60
78
100
124
153
186
.2352
15
14
20
29
40
53
68
87
108
133
162
.2700
16
18
25
35
46
60
76
95
117
147
.3,072
17
16
' 22
31
41
53
68
84
104
126
.3468
18
20
27
37
47
60
75
93
112
.3888
19
18
25
33
43
54
68
83
101
.433,2
20
22
30
38
49
61
75
91
.4800
21
20
27
35
44
55
68
83
.5292
22
24
32
40
50
62
75
.5808
23
22
29
37
46
57
69
.6348
24
27
34
42
52
63
.6912
25
••
.. | ..
25
31
39
48
58
.7500
823
MASONRY.
Brick work is generally measured by 1000 bricks laid in the wall. In con-
sequence of variations in size of bricks, no rule for volume of laid brick can
be exact. Tbe following scale is, bowever, a fair average.
7 common bricks to a super, ft. 4-incb wall.
14 " " " " 9-incb "
24 " " " " 13-incb "
28 " " " " 18-incb "
35 " " " " 22-incb "
Corners are not measured twice, as in stone- work. Openings over 2 feet
square are deducted. Arcbes are counted from tbe spring. Fancy work
counted l£ bricks for 1. Pillars are measured on tbeir face only.
One tbousand bricks, closely stacked, occupy about 56 cubic feet.
One tbousand old bricks, cleaned and loosely stacked, occupy about 72 cu-
bic feet.
One cubic foot of foundation, with one-fourtb inch joints, contains 21
bricks. In some localities 24 bricks are counted as equal to a cubic foot.
One superficial foot of gaviged arches requires 10 bricks.
Stock bricks commonly measure 8| inches by 4^ incbes by 2| inches, and
weigh from 5 to 6 lbs. each.
Paving bricks should measure 9 inches by 4i inches by If inches, and
weigh about 4i lbs. each.
One yard of paving requires 36 stock bricks, of above dimensions, laid flat,
or 52 on edge^ and 35 paving bricks, laid flat, or 82 on edge.
The following table gives the usual dimensions of the bricks of some of
the principal makers.
Description.
Inches.
Description.
Inches.
Baltimore front .
Philadelphia front
Wilmington front
Trenton front
Croton ....
Colabaugh . . .
>- 8i X 4i X 2f
8J X 4 X 1\
8i X 3f X 2§
Maine ....
Milwaukee . .
North River .
Trenton . . .
Ordinary . . .
7\ X 3f X 21
%\ X 4i X 2f
8 X Sk X 2J
8 X 4 X21
( 7f X 3f X 2\
{ 8 X 4i X 2i
( Valentine's (Woodbridge, N. J.)
( Downing's (Allentown, Pa.) . .
8| X 4f X 2|- inches
9 X 4J X 2| inches
To compute the number of bricks in a square foot of wall. — To the face
dimensions of the bricks used, add the thickness"of one joint of mortar, and
multiply these together to obtain the area. Divide 144 square inches by
this area, and multiply by the number of times which the dimension of the
brick, at right angles to its face, is contained in the thickness of the wall.
Example. — How many Trenton bricks in a square foot of 12-inch wall,
the joints being J inch thick ?
8-4-J X 2J + \ — 20.62 ; 144 -=- 20.62 = 7 ; 7 X 3 = 21 bricks per square ft.
S24
FOUNDATIONS AND STRUCTURAL MATERIALS.
W^igli* and Bulk of It rick*.
Number of Bricks,
by itself.
in wall w
Tons.
Pounds.
Cu. ft.
C. Brick.
F. Brick.
C. Brick.
1
2240
22.4
448
416.6
381
0.044.64
100
1
20
18.6
17
2.23
5000
50.00
lOOO
930
850
2.4
5376
53.76
1075
lOOO
914
2.62
5872
58.72
1130
1100
lOOO
2.88
6451
64.51
1240
1200
1100
One perch of stone is 24.75 cubic feet.
In New York City laws a cubic foot of brick-work is deemed to weigh
115 lbs.
Building-stone is deemed to weigh 160 lbs. per cubic foot.
The safe load for brick-work according to the New York City Laws is as
folio \vs : —
In tons per superficial foot,
For good lime mortar 8 tons.
For good lime and cement mortar mixed . ll£ tons.
For good cement mortar 15 tons.
Average Ultimate Crushing--Uoad in Pounds per Square
Inch for Jtricks, Stones, mortars, and Cements.
Lbs. per
Sq. In.
Brick, common (Eastern)
Brick, best pressed
Brick (Trautwine)
Brick, paving, average of 10 varieties (Western)
Brick-work, ordinary
Brick-work, in good cement
Brick-work, first-class, in cement
Concrete (1 part lime, 3 parts gravel, 3 weeks old)
Lime mortar, common
Portland cement, best English,
Pure, three months old
Pure, nine months old
1 part sand, 1 part cement,
Three months old
Nine months old
Granites, 7750 to 22,750
Blue granite, Fox Island, Me
Blue granite, Staten Island, N. Y
Gray granite, Stony Creek, Conn
North River (N. Y.) flagging
Limestones, 11,000 to 25,000
Limestone from Glen's Falls, N. Y. ...
Lake limestone, Lake Champlain, N. Y. . .
White limestone, Marblehead, O
White limestone from Joliet, 111
Marbles,
From East Chester, N. Y
Common Italian
Vermont (Souther! and Falls Co.) . . . .
Vermont, Dorset, Vt
Drab, North Bay Quarry, Wis
10000
12000
770 to 4660
7150
300 to 500
450 to 1000
930
620
770
3760
5960
2480
4520
12000
14875
22250
15750
13425
12000
11475
25000
11225
12775
12950
11250
10750
7612
20025
MISCELLANEOUS MATERIALS.
825
Average Ultimate Crushing-- JLoad — Continued.
Lbs. per
Sq. In.
Sandstones
Brown, Little Falls, N. Y
Brown, Middletown, Conn
Red, Haverstraw, N. Y
Red-brown, Seneca freestone, Obio . . .
Freestone, Dorcbester, N. B
Longmeadow sandstone, Springfield, Mass.
6000
9850
6950
4350
9687
9150
8000 to 14000
lEKSOBULAjrBOlJS MATERIALi.
freight of Hound Bolt Copper Per Foot.
Incbes.
Pounds.
Incbes.
Pounds.
Inches.
Pounds.
t
.425
3.02
If
7.99
.756
l-i
3.83
If
9.27
f
1.18
li
4.72
H
10.64
1
1.70
If
5.72
2
12.10
3
2.31
li
6.81
Weight of Sheet and Bar Brass.
Thick-
Sheets
Square •
Round
Thick-
Sheets
Square
Round
ness.
per
Bars
Bars
ness.
per
Bars
Bars
Incbes.
sq. ft.
1 ft. long.
1 ft. long.
Inches.
sq. ft.
1 ft. long.
1 ft. long.
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
?
2.7
.015
.011
1A
45.95
4.08
3.20
5.41
.055
.045
li
48.69
4.55
3.57
f
8.12
.125
.1
if
51.4
5.08
3.97
10.76
.225
.175
54.18
5.65
4.41
y
13.48
.350
.275
li5s
56.85
6.22
4.86
16.25
.51
.395
It
59.55
6.81
5.35
19.
.69
.54
1ft
62.25
7.45
5.85
f
21.65
.905
.71
n
65.
8.13
6.37
24.3
1.15
.9
ii9s
67.75
8.83
6.92
§
27.12
1.4
1.1
if
70.35
9.55
7.48
¥
29.77
1.72
1.35
it'
73.
10.27
8.05
32.46
2.05
1.66
75.86
11.
8.65
if
35.18
2.4
1.85
78.55
11.82
9.29
i
37.85
2.75
2.15
H
81.25
12.68
9.95
40.55
3.15
2.48
HI
84.
13.5
10.58
l
43.29
3.65
2.85
2
86.75
14.35
11.25
Composition of Various Oracles of Boiled Brass.
Trade Name.
Copper.
Zinc.
Tin.
Lead.
Nickel.
Common high brass
Yellow metal
Cartridge brass
61.5
60
66|
80
60
60
66f
61*
38.5
40
331
20
40
40
33J
20*
1
'lV
l*to2
*18
Clock brass
Drill rod
Spring brass
18 per cent German silver . . .
826 FOUNDATIONS AND STRUCTURAL MATERIALS.
So
O 3
w
Lbs.
1.22
1.08
.966
.860
.766
.682
.608
.541
.482
.429
.382
.340
.303
.270
.240
.214
.191
.170
.151
.135
53
o
a
-CMC- /.i--i:c-f-)< :o co cicicic-iHrtrt
A^AA
ft©
© CD
O 3
c3
• lis lis t> o t— w
* C- CO I- 10 CO t- Cl-C-lt-QOHnfHH CO 10 .0 CO
^ _ -c ,- ,-^cii- ,o CO CO 01 CO' -fTHC. 1-10 -f CO - l
^ CO CO -P H Ci L- liS -tn COCNC-li-HrHrH©©©©©©
©
ft
Q
• cscio-f co-t«HHCioc: So oi~l- re
a? ii5 -H -t< Ol — , co ■ —. x co — -f ~ i0 o i - r - co -p co oi
,o -p q lo o i co L- co -h co sciHHrtoqqooo
.WNHOO Oi-iNLOCCOO-t-tOCOiOH-f
_-< CO -+i 1- © O -V CO -+i i.O 0 1 0 1 10) CO CO — ~ liS. © 00 -f
cr-t cci-ricc-H-ocic: : - -i- co lo . i-i
-cic!Cici-Hrfrt-.rt^_ : - -
HOOOCOCCCCOOOOCCOOOOO
°8)
o"g
HNOS-PLOCCNOOCjOHSlCO-fLOONCCCSO
(M <M CI 0 1 0 1 0 1 0 1 0 1 0 1 CC. CO CO CO CO CO CO 00 CO co. -*
IN
eg O
£*
rfl a*
• c; co rt o co co si f cs co cc o o co co o co -f ■+» -n oi ^ t-
ct CO L0 CO ~ CO CO CO !-l--HOQCOOO-tOl-:-t,HOt>LO»
'j05^ocooi^csooi>0{oid^^eoeoeco^<N(Ni-<rHTHTH
ft
ft
o
O
• ^iooioiot^ciiis-t<-t<--fHoicooii--ico)co>oc50iiSoocoin
ct X 1.0 liS I- H CO CO 0] 01 00 1.0 -X r- CO i-< CO 01 CO liS CO © CO © -ch
£ ©
^ eg
b/JO
• CO H t- CI i.O 01 01 CO 1 - CO liS 01 -+l CO liS CO -H lis C} SS CO lis 00 OCI
cc oi co l- co -t; co in -+ cq © uo c; -# co lo q co l- q lo co q © q
oiisddrtdoioc!^ id re! i - i -' — ' co co' -v A co t^ id -#° oo oi
-Ol-X O :-•/. I0HCC L- LO -P CO 01 Ol tH i-l i-l
CO ■* CO OS Ol ^ rl i-l
o
O
OHCC+COtlNlO-fONOClOO
• lo q q lo co — cq -v o i -r q q q -p q i- q -p x co. oi q q q
- co' CO 0 i CO CO CO CO CO © CO CO CO CO i-H -f' CO L0 0 i CO t>l CO •# OS 00
^-t;-:;o.csi.ociot-cs-*cocoisiHHH
4-1 °"
o£
A o -f< o co o co oi rn -ti oi co co oo co cc^ o co co co c~i lis ci r. vr
"- -f -f ., 1 - CO -t< ^h 0 1 -ti CO -f i-i ■_■ ■_ — ( -t 1 _ LO CO LO — i
- co co co oi co. io oi co co -otsiiH co — x l- ■- •'. i.O -t -+ c- CO
H ^ -t 00 CO 01 01 CI C) H H h H H rt .;. o c c o o o o o o
OOgOHCMCO^LOCSt-COCOOi-IOlM'flOCDNCOCBO
go
MISCELLANEOUS MATERIAL.
827
Galvanized Iron Wire Rope.
For Ships' Rigging and Guys for Derricks.
CHARCOAL ROPE.
CP
3.3
III
Cir. of New
Manila Rop
of Equal
Strengtli.
tes'*-' •
•c - °^
11 So
!-. j3 o °
a! S
Cir. of New
Manila Ropt
of Equal
Strengtli.
|||
U
O
5i
23}
11
43
21
51
5
9
5i
24V
10}
40
2i
4}
4f
8
5
22
10
35
2
3}
3|
7
4f
21
9}
33
H
2.T
5
4*
19
9
30
1}
2
3
3}
4i
16}
8}
26
U
If
21
2}
4
i*i
8
23
H
11
3|
12J
7*
20
l
*
21
3}
10|
6k
1G
1
If
1
3i
9}
G
14
f
i
1}
3
8
5f
12
§
§
H
1
2|
6i
Si-
10
}
5
if
Transmission an<8 Standing* Rope.
With 6 Strands of 7 Wires Each.
IROIf.
2
6
&
?
O
0 s> a
O A 03
.5 0
•31 .
03 ~ oa
Proper Work-
ing Load in
Tons of 2000
Lbs.
Circumference
of new Manila
Rope of Equal
Strength.
05
CG g 0)
ri 3fr
§3.3
11
1}
4f
3.37
36
9
10
13
12
4i
3|
2.77
30
7*
9
12
13
1+
2.28
25
6i
8}
10|
14
3|
1.82
20
n
9}
15
3
1.50
16
4
6}
8*
1G
2|
1.12
12.3
3
5f
n
17
*
3
0.S8
8.8
-i
4}
6f
18
0.70
7.6
2
4}
6
19
11
0.57
5.8
1*
4
5i
20
TI
if
0.41
4.1
1
3?
4*
21
if
0.31
2.83
f
93
4
22
li
0.23
2.13
2}
3i
23
H
0.19
1.65
2i
24
156
0.16
1.38
2
2}
25
32
i
0.125
1.03
if
2i
C
VST STEEL.
11
ji
4f
3.37
62
13
13
8}
12
If
4^
2.77
52
10
12
8
13
If
%
2.28
44
9
11
11
14
1.82
36
7}
10
64
15
3
1.50
30
6
9
5f
16
f
2f
1.12
22
4}
8
5
828 FOUNDATIONS AND STRUCTURAL MATERIALS.
Transmission and Standing- Rope. — Continued.
CAST STEEL.
©
©"
o
O © s
0 a®
ft 5°
•is
X3g
in
S5|
> 1
<w ©
©
02 <H
O CN
&
1
£
a'o «
boo
. 0 0
©^
■2op 1
-d
2
|
S 5W
rt S .
a 2 •
S £ O bJQ
5 oj o> g
«J _, © 1
. 5 ® 1
H
5
5
p: s'> ©
©EH«
m.5m
O - Q,©
17
1
2|
0.88
17
3£
7
4+
18
*t
2i
0.70
14
3
6
4"
19
s
11
0.57
11
2:1
5n-
3i
20
1
If
0.41
8
11
4f
3
21
if
0.31
6
n
4
2A
22
11
0.23
4J
it
3:7
21
23
if
0.19
4
1
3|
24
1
0.16
3
j
11
25
3%
i
0.12
2
j
21
li
Pliable
Hoisting- It ope.
Wit
b. 6 strar
ids of 19 Wii
es Each
(Trenton Iron Works.)
IKON.
5
©
©J
®tf|
O CO
3 s^°
|^8
05 $ c3
g ^ o&o
3a8fl
§P©
©
2
5m
"bif^ * ^
^•5 5
5 © © 5
5
2^ s §
p.5 ?o
Woqo
fl © ©
1
21
6i
8.00
74
15
14
13
2
2
6
6.30
65
13
13
12
3
If
5i
5.25
54
11
12
10
4
If
5"
4.10
44
9
11
8J
5
n
44
3.65
39
8
10
7i
5;V
if
4i
3.00
33
6J-
9i
7^
G
U
4
2.50
27
5i
■ 8h
(U-
7
if
3£
2.00
20
4"
n
6"
8
i
3I
1.58
16
3
6|
51
9
I
93
1.20
11.50
2*
5|
4
10
0.88
8.64
lf
4-1
4
101
|
2
0.60
5.13
11
3|
3£
10*
f
If
0.44
4.27
f
3i
2f
10|
1*
0.35
3.48
3
21
10<x
IS
0.29
3.00
n
2|
2
10£
1
1*
0.26
2.50
1
4
2i
H
CAST S'J'KKL.
1
6}
8.00
155
31
8|
2
2
6
6.30
125
25
8
3
If
51.
5.25
106
21
71
61
4
If
5
4.10
86
17
15
5
l|
4f
3.65
77
15
14
a
5.V
IS
4S
3.00
63
12
13
5£
6
H
4
2.50
52
10
12
5
7
14
3i
2.00
42
8
11
4*
8
1
3£
1.58
33
6
9i
4
9
1
21
1.20
25
5
Sh
3£
10
21
0.88
18
3h
7
3
io|
ft
0.60
12
2A
5f
21
^r
If
0.44
9
U
5
if
10$
li
0.35
7
1
4*
10a
1
If
0.29
5'r
f
2
3J
11
m
H
0.26
4|
8*
1
STEAM BOILERS. 829
STEAM.
• STEAM BOILERS.
Points to Reinvnibvi' in Selecting- a Boiler.
(a) Suitability of furnace and boiler to kind of fuel.
(b) Efficiency as to evaporative results.
(c) Rapidity of steaming including
(I.) Mass of water for given power.
(II.) Water surface for given power.
(d) Steam keeping qualities.
(e) Safety from explosion.
(/) Floor space required.
(g) Portability, and ease witb which boiler can be removed when old, for
replacement by a new boiler.
(h) Amount of, ease of, and rapidity of repairs.
(i) Simplicity and fewness of parts.
(J) Ability to stand forcing in case of necessity.
(k) Price, including cost of freight and setting.
(I) Durability and reliability.
(to) Ease of cleaning and inspection both inside and outside.
(n) Freedom from excessive strains due to unequal expansion and ability
i to withstand same.
| (o) Efficient natural circulation of water.
| (p) Absence of joints or seams where flames may impinge.
| For central stations it is necessary to arrange for a number of boilers
•rather than one or two large ones. The size of unit adopted will depend
;to some extent on the character of the expected load diagram. With a
number of boilers the cost of the reserve plant is reduced, though beyond,
isay six, there is less object in increasing the number on this account.
Types.
Horizontal Return Tulmlar. — More generally used in United
States than any other. Fire first passes under the shell, returns to front
through tubes, thence up the chimney, except in some cases gases are again
returned over top of the shell. Limited as to size and pressures carried by
reason of external firing.
> "Water-tune. — Very largely used where high steam pressures or
safety from explosion are desirable. Fire passes about the exterior of tubes
and in most cases under about one-half the circumference of the steam
:drums. Can be built for any size or pressure. Tubes are generally placed
in a slanting position, from one set of headers to another, as in the Babcock
& Wilcox, Heine & Go. ; or vertically, as in the Sterling and Cahall.
> Vertical Fire Tube. — Used considerably in New England. Spe-
cial design by Captain Manning; tubes 15 feet long 2£ inches diameter,
arranged in vertical shell with large combustion chamber surrounded by a
water leg. Gases mingle in combustion chamber, and in passing through the
long narrow tubes give up nearly all the heat, practicably leaving flue gases
450° to 500° F. By controlling height of water steam can be superheated.
Can be built for high pressures and of large size.
a^iwfr0?' Marine Boilers. — Not much used for electrical purposes,
bneii or thick material, short in length and large in diameter. Furnaces
: internal, with return tubes from combustion chamber to uptake.
i fi /Sf are the finder boiler, of small diameter and considerable
lengtn uu to 35 feet). Fired externally, and gases pass under full length to
cmniney._ Flue boiler, has two or three large tubes running full length of
snen, which is long and of small diameter. Fired externally under the shell,
gases return through the flues to uptake. Neither of these types is now
jused for electrical purposes.
The Horse-Power of Steam Boiler.
The committee of the A. S. M. E. on "Trials of Steam Boilers in 1884"
(Trans., vol. vi. p. 265), discussed the question of the horse-power of boilers :
830 STEAM.
The Committee) A.S.M.E. see Trans, vol. xxi.) approves the conclusions of
the 1885 Code to the effect that the standard " unit of evaporation " should
be one pound of water at '212° F. evaporated into dry steam of the same
temperature. This unit is equivalent to 965.7 British thermal units.
The committee recommends that, as far as possible, the capacity of a
boiler be expressed in terms of the " number of pounds of water evaporated
per hour from and at 212°." It does not seem expedient, however, to aban-
don the widely recognized measure of capacity of stationary or land boilers
expressed in terms of " boiler horse-power."
The unit of commercial boiler horse-power, adopted by the Committee of
1885 was the same as that used in the reports of the boiler tests made at the
Centennial Exhibition in 1876. The Committee of 1885 reported in favor of
this standard in language of which the following is an extract :
" Your Committee, after due consideration, has determined to accept the
Centennial standard, and to recommend that in all standard trials the com-
mercial horse-power be taken as an evaporation of 30 pounds of water per
hour from a feed-water temperature of 100° F. into steam at 70 pounds gauge
pressure, which shall be considered to be equal to 34| units of evaporation ;
that is, to 34£ pounds of water evaporated from a feed-water temper-
ature of 212° F. into steam at the same temperature. This standard is
equal to 33,305 thermal units per hour."
The present Committee accepts the same standard, but reverses the order
of two clauses in the statement, and slightly modifies them to read as follows :
The unit of commercial horse-power developed by a boiler shall be taken
as 34£ units of evaporation per hour ; that is, 34^ pounds of water evaporated
per hour from a feed-water temperature of 212° F. into dry steam of the
same temperature. This standard is equal to 33,317 BritislTthermal units
per hour. It is also practically equivalent to an evaporation of 30 pounds
of water from a feed-water temperature of 100° F. into steam at 70 pounds
gauge pressure.*
The Committee also indorses the statement of the Committee of 1885 con-
cerning the commercial rating of boilers, changing somewhat its wording, so
as to read as follows :
A boiler rated at any stated capacity should develop that capacity when
using the best coal ordinarily sold in the market where the boiler is located,
when fired by an ordinary fireman, without forcing the fires, while exhibit-
ing good economy ; and, further, the boiler should delelop at least one-
third more than the stated capacity when using the same fuel and operated
by the same fireman, the full draft being employed and the fires being
crowded ; the available draft at the damper, unless otherwise understood,
being not less than J inch water column.
Heating- Surface of Boilers.
Although authorities disagree on what is to be considered the heating
surface of boilers, it is generally taken as all surfaces that transmit heat
from the flame or gases to the water. The outside surface of all tubes is
used in calculations.
Kent gives the following rule for finding the heating surface of
Vertical Tubular ISoilers. — Multiply the circumference of the fire-
box (in inches') by its height above the grate. Multiply the combined circum-
ference of all the tubes by their length, and to these two products add the area
of the lower tube sheet ; from this sum subtract the area of all the tubes,
and divide by 144 : the quotient is the area of heating surface in square feet.
Horizontal Return Tubular Boiler*. — (Christie). Multiply the
length of that part of circumference of the shell (in inches) exposed to the
fire by its length ; multiply the circumferences of the tubes by their num-
ber, by their length in inches ; to the sum of these products add two-thirds
of the' area of both tube sheets less twice the area of tubes, and divide the
remainder by 144. The result is the herting surface in square feet.
Heating* Surface of Tubes. — Multiply the number of tubes by the
diameter of a tube in inches, by its length in feet, and by .2618. The diam-
eter used should be that of the 'fire side of the tube.
* According to the tables in Porter's Treatise on the Richards Steam, En-
gine Indicator, an evaporation of 30 pounds of water from 100° F. into steam
at 70 pounds pressure is equal to an evaporation of 34.488 pounds from and
at 212° ; and an evaporation of 34h pounds from and at 212° F. is equal to
30.010 pounds from 100° F. into steam at 70 pounds pressure.
The " unit of evaporation" being equivalent to 965.7 thermal units, the
commercial horse-power = 34.5 X 965.7 = 33,317 thermal units.
STEAM BOILERS.
831
, Heating* Surface per Horse-power. — There is little uniformity
of practice among builders as to the amount of heating surface per horse-
power, but 12 square feet maybe taken as a fair average. Babcock <fe Wil-
cox ordinarily allow 10 square feet, but usually specify the number of
square feet of heating surface. The Heine Boiler Company allow Ih square
feet, and the water-tube type in general will develop a horse-power for that
amount of surface.
Specifications for boilers should always clearly state the amount of heating
surface required.
•Grate Surface. — The amount of grate surface per horse-power varies
with the character of fuel used and the draught that is available. With
good quality of coal about equal results can be obtained with strong draught
and small grate surface, and with large grate surface and light draught.
Pittsburg coal gives best results with strong draught and a small grate sur-
face. The following table shows the usual requirements, but in general
grate surface should be liberal in size, and a rate of combustion of about
10 lbs. per hour will be found good practice.
Grate Surface per Horse-Power. (Kent.)
<a ~ £
Pounds of Coal burned per square foot
of Grate per hour.
8
10
19
15
20
25
30
35 40
^■Sw
(10
3.45
Square Feet Grate per H.P.
Good coal and
.43
.35
.28
.23
.17
.14
.11
.10
.09
boiler . . .
1 9
3.83
.48
.38
.32
.25
M
.15
.13
.11
10
Fair coal or
boiler . . .
( 8.61
8
4.
4.31
.50
.54
.40
.4:;
.33
.36
.26
.29
.20
.17
.13
.14
.12
.13
.10
11
( 7
4.93
.62
.4!)
.41
.33
.24
.20
.17
.14
.12
Poor coal or
boiler . . .
( 6.9
6
5.
5.75
.63
.50
.58
.42
.4«
.34
.38
.25
.29
.20
.23
.17
.1!)
.15
.17
.13
.14
( 5
6.9
.86
.69
.58
.4!
.35
.28
.93
.?,?,
.17
Lignite and
poor boiler .
{ 3.45
10.
1.25
1.00
.83
.67
.50
.40
.33
.29
.25
Area of Gas-Passag-es and flues.
This is commonly stated in a ratio to the grate area. Mr. Barrus says the
highest efficiency for anthracite coal, when burning 10 to 12 lbs. per s'quare
foot of grate per hour, is with tube area a to rxa of grate surface ; and for soft
coal the tube area should be i to } of the grate surface.
Other rules in common use are to make the area over bridge walls (for
horizontal return tubular boilers) \ the grate surface ; tube area£ andchim-
ney area \.
Air-space in Grates. — Usual practice is 30% to 50% area of grate for
air space. If fuel clinkers easily, use the largest air space available. With
coal free from clinker smaller air space may be used.
Distance between Under Side of Boiler and Top of Grate.
(For Horizontal Tubular Boiler.)
For anthracite coal this should be 24 inches for the larger sizes, and can
be 20 inches for the smaller sizes, such as pea, buckwheat, and rice. For
bituminous coals non-caking, the grate should be about 30 inches below the
boiler, and for fatty or gaseous coals from 36 to 48 inches. For average
bituminous coals the distance can be 36 inches. Anthracite and bituminous
coals cannot be economically burned in the same furnace.
Steam Boiler Efficiency.
The ratio of the heat units utilized in making steam in a boiler, to the
total heat units in the coal used is called the efficiency of the boiler, and is
8.32
rated in per cent. For example, the heating value of good anthracite coal
is about 14.500 B. T. U., and will evaporate from and at 212° 15 lbs. watei
(14,500 ~ 9(36). If a boiler under test evaporates 12 lbs. water per pound of
combustible, the efficiency will be — = 80%, a figure not often ob-
tained, but possible uuder special conditions. The heating value of bitumi-
nous coals varies so much that it is necessary to determine it by a co; "
calorimeter before it is possible to determine the boiler efficiency.
Strength of Riveted Shell.
(Abridged from Barr on " Boilers and Furnaces.")
Wrought-iron boiler-plates should average 45,000 lbs., and mild steel 55,U.
lbs., tensile strength per square inch of section ; but the gross strength oi
plate is lessened by the amount which has been taken out of it for the inser-
tion of rivets.
The following tables give the calculated working pressure for doubb
riveted and triple-riveted lap joints, and for butt-joints triple riveted, th
factor of safety being 5. The rule for calculating the safe working pressun
is : Multiply together the tensile strength of the plate, the thickness of th
plate in parts of an inch, and the efficiency of the joint (see Riveting) ; divide
the product by one-half the diameter of the boiler multiplied by the factor
of safety.
Working- Pressure for Cylindrical Shells of Steam Boilers.
Factor of Safety, 5. (Barr.)
Thick-
ness in
Lap-joints, Double-Riveted.
Lap-Joints, Triple
-Riveted.
Diam-
eter
Inches.
16ths
of an
Inch.
Iron
Steel
Steel
Iron
Steel
Steel
Shell,
Shell,
Shell,
Shell,
Shell,
Shell,
Iron
Iron
Steel
Iron
Iron
Steel
Rivets.
Rivets.
Rivets.
Rivets.
Rivets.
Rivets.
36
4
91
Ill
Ill
100
121
123
5
112
128
137
124
139
151
40
4
82
100
100
90
109
110
5
101
115
123
112
125
136
44
4
74
91
91
83
99
100
5
91
105
112
101
114
124
48
5
84
96
102
93
104
114
6
99
107
121
110
118
135
r9
5
77
89
95
86
96
105
°"
6
92
99
112
102
109
124
54
5
75
85
91
83
93
101
6
88
96
108
98
105
120
56
5
72
82
88
80
89
97
6
85
92
104
95
101
116
60
5
67
77
82
74
83
91
6
79
85
97
8S
95
108
62
6
77
83
94
85
92
104
7
88
92
108
98
103
120
64
6
74
81
91
83
89
101
7
86
89
105
95
100
117
66
6
72
78
88
80
86
98
7
S3
87
102
93
97
113
68
6
70
76
86
78
84
95
7
81
80
99
90
94
110
70
6
68
74
83
76
81
• 92
7
78
82
96
'87
91
107
72
7
76
79
93
85
89
104
8
85
89
104
97
98
117
STEAM BOILERS.
833
Working- Pressure for Cylindrical Shells of
Steam floilers. (Ban-.)
Butt Joints, Triple Riveted. Factor of Safety, 5.
Diameter
Inches.
Thick-
ness in
16ths of
an inch.
Iron
Shell,
Iron
Rivets.
Steel
Shell,
Iron or
Steel
Rivets.
Diam-
eter,
Inches.
Thick-
ness in
16ths of
an inch.
Iron
Shell.
Iron
Rivets.-
Steel
Shell,
Iron or
Steel
Rivets.
4
108
134
6
83
102
36
5
135
165
70
7
97
118
6
161
197
8
110
134
4
102
127
9
123
151
38
5
128
156
6
80
99
6
152
187
7
94
115
4
97
120
IZ
8
107
131
40
5
121
148
9
120
147
6
145
178
7
90
110
4
93
115
75
8
102
125
42
5
116
141
9
115
141
6
138
169
10
128
157
4
89
109
7
87
106
44
5
110
135
78
8
99
121
6
132
161
9
111
135
4
85
105
10
123
151
46
5
106
129
8
92
112
6
126
154
9
103
126
5
101
124
84
10
115
140
48
6
121
148
11
126
158
7
141
172
12
137
167
5
97
119
8
86
105
50
6
116
142
9
96
117
7
135
165
90
10
107
131
5
93
114
11
117
143
52
6
111
137
12
128
156
7
130
159
8
80
98
5
90
110
9
90
110
54
6
107
132
96
10
100
123
7
125
153
11
110
134
5
87
106
12
120
146
56
6
103
127
8
75
92
7
121
148
9
85
104
5
S4
102
102
10
94
115
58
6
100
123
11
104
127
7
117
142
12
113
138
6
97
118
8
71
87
60
7
111
138
9
80
98
8
128
157
108
10
89
109
6
93
115
11
98
120
62
7
109
133
12
107
130
8
124
152
8
68
83
6
90
111
9
76
93
64
7
106
129
114
10
84
103
8
120
147
11
93
113
9
135
165
12
101
123
6
88
108
8
64
78
66
7
102
125
9
71
88
8
117
143
120
10
80
98
9
131
160
11
88
108
6
85
105
12
96
117
68
7
8
9
99
113
127
121
138
155
834
Safe Working- Pressure for Shell Plate.
I" . *. Statutes. —
d = diameter of boiler in inches.
iJ= safe working pressure, lbs. per square inch.
t = thickness of metal in inches.
w ■=. tensile strength of metal.
k = factor of safety = 6 for U. S. and 4.5 for Great Britain.
P = " — for single-riveted. For double-riveted, add 20%.
Board of Trade.—
w X B X t X 2
— d X tc X 100
where the notation is the same as in U". S. rule, and B =z percentage of
strength of joint as compared with solid plate.
Rules Governing- Inspection of Boilers in Philadelphia.
In estimating the strength of the longitudinal seams in the cylindrical
shells of boilers, the inspector shall apply two formulae, A and B :
j Pitch of rivets— diameter of holes punched to receive tbe rivets _
' ( pitch of rivets
percentage of strength of the sheet at the seam.
( Area of hole filled by rivet x No. of rows of rivets in seam x shear-
B, ] ing strength of rivet _
( pitch of rivets X thickness of sheet X tensile strength of sheet
percentage of strength of the rivets in the seam.
Take the lowest of the percentages as found by formuhe A and B, and
apply that percentage as the " strength of the seam" in the following for-
mula, C, which determines the strength of the longitudinal seams :
( Thickness of sheet in parts of inch X strength of seam as obtained
q < by formula A or B x ultimate strength of iron stamped on plates
' internal radius of boiler in inches X 5 as a factor of safety
safe working pressure.
Safe Working- Pressure for Flat Plates.
U. S. Statutes. —
P = safe working pressure.
S = surface supported, square inches.
t — thickness of metal in sixteenths of an inch.
Tc = constant for plates of different thickness, and for various condi-
tions.
p = greatest pitch in inches.
p=tyjc
p2
K— 112 for -/g-inch plates and less, fitted with screw stay bolts and nuts, or
plain bolt fitted with single nut and socket, or riveted head and
socket.
K= 120 for plates more than T7g inch thick, under same conditions.
K=z 140 for fiat surfaces where the stays are fitted with nuts inside and out.
K = 200 for flat surfaces under same conditions, bnt with washer riveted to
plate, washer to be one-half as thick as plate, and of a diameter §
pitch.
STEAM BOIBF/RS. 835
No brace or stay on marine boilers to bave a greater pitch than 10£
inches on fire boxes and back connections. Plates fitted, witn double-angle
irons riveted to plate, and with leaf at least two-thirds thickness of plate,
and depth at least one-fourth of pitch, allowed the same pressure as plate
with washer riveted on.
Board of Trade. — Using same notation as in U. S. rules :
£ — 6
if =125 for plates not exposed to beat or flame, the stays fitted with nuts
and washers, the latter at least three times the diameter of tbe stay
and § the thickness of the plate ;
7il":= 187.5 for the same condition, but the washers § the pitch of stays in
diameter, and thickness not less than plate ;
K = 200 for the same condition, but doubling plates in place of washers, the
width of which is f the pitch, and thickness the same as the plate ;
K— 112.5 for the same condition, but the stays with nuts only ;
K = 75 when exposed to impact of beat or flame and steam in contact with
the plates, and tbe stays fitted with nuts and washers three times
the diameter of tbe stay, and § the plate's thickness ;
K = 67.5 for the same condition, but stays fitted with nuts only ;
A' = 100 when exposed to heat or flame, and water in contact with the
plates, and stays screwed into the plates, and fltted with nuts ;
K— 66 for the same condition, but stays with riveted heads.
Buctility of Boiler Plate. — U. S. Inspectors of Steam Vessels.
In test for tensile strength, sample shall show reduction of area of cross-
section not less than the following percentages :
Iron.
45,000 lbs. tensile strength and under 15 per cent.
For each additional 1000 t. s. up to 55,000 t. s. add . 1 "
55,000 lbs. tensile strength, and above 25 "
Steel.
All steel plates h inch thick and under 50 per cent.
" " " J to J inch 45 "
" " " | inch and above 40 "
Boiler Head Stays.
The United States Regulations on braces are : " No braces or stays here-
after employed in the construction of boilers shall be allowed a greater
strain than 6,000 lbs. per square inch of section. Braces must be put in suf-
ficiently thick so that the area in inches which each has to support, multi-
plied by the pressure per square inch, will not exceed 6,000 when divided by
the cross-sectional area of the brace or stay.
" Steel stay-bolts exceeding a diameter 'of 1J inches, and not exceeding a
diameter of 1\ inches at the bottom of the thread may be allowed a strain
not exceeding 8,000 lbs. per square inch of cross-section ; steel stay bolts
exceeding a diameter of 2# inches at bottom of thread may be allowed a
strain not exceeding 9,000 lbs. per square inch of cross-section ; but no
forged or welded steel stays will be allowed.
"Tbe ends of such stay may be upset to a sufficient thickness to allow
for truing up, and including the depth of the thread. And all such stays
after being upset, shall be thoroughly annealed."
836
Direct Braces. — The following table is given by Mr. Wm.M. Barr
in " Boilers and Furnaces," p. 122. The working strength assumes an ulti-
mate strength of 6000 lbs. per square inch of section.
Diam-
eter of
Wrought Iron
Stays.
Inches square each Brace will Support for
Pressures per Square Inch.
Brace
Inches.
Area
sq. in.
Working
Strength
Pounds.
75
Pounds.
100
Pounds.
125
Pounds.
150
Pounds.
1
1
u
if
.60
.78
.99
1.23
1.48
1.77
3600
4712
5964
7362
8880
10620
7.0
7.9
8.9
9.9
10.7
11.9
6.0
6.9
7.7
8.6
9.5
10.4
5.4
6.1
6.9
7.7
8.5
9.2
4.9
5.0
6.4
7.0
8.5
Diag-onal Braces.
calculated separately.
- (" Boilers and Furnaces," p. 129.) These must be
A = surface to be supported in square inches.
B = working pressure in lbs.
H= length of diagonal stay in inches.
L — length of line drawn at right angles from surface, to be sup-
ported to end of diagonal stay in inches.
S = working stress per square inch on stay in lbs.
a =z area required for direct stay in square inches,
a, = area of diagonal stay in square inches.
T= diameter of diagonal stay in square inches.
a, = a x H~ L ;
H=:alX L -^- a.
T .7854 V .7
.7854 X T72 X Sx L
Boiler Setting's.
Water tube and special types of boilers require special settings largely
controlled by local conditions, location of flues, etc., and cannot be tabulated
here.
The setting of horizontal return tubular boilers has become so nearly
standardized that the table following, taken in connection with the cuts,
will give all the general dimensions of brick-work required.
For all special boiler settings, furnaces, etc., the reader is referred to the
makers of each.
STEAM BOILERS.
837
a
£
•dox *« HT?A1
espug jo sseui[oii[x
0
CD
,oj m m m m m m m m m m m m m m in
«
•aioj^og ye ip?AY
eSpiajj jo ssgujpiqx
fe
_q ci cm co co co co co co co co o o co © ©
r3coeocococococococo-*Tti^Tt<-*^
•joo^ jo dox
uioij sn«Ai jo ;q§PH
n
Ft. In.
7- 0
7- 0
7- 7
7- 7
7-10
8- 0
8- 1
8- 6
8- 6
8-11
8-11
8-11
9- 8
9- 8
10- 1
'IF
j9ao sn^W J° *WPJAY
h9
Ft. In.
6- 8
G- 8
7- 4
7- 8
7-10
8- 2
8- 2
9- 4
9- 4
9- 4
9-10
9-10
10- 4
•S[[RAV ©PIS JOJ
uoij^puno^ jo qijSaai
M
n. In.
1- 7
3- 7
3- 7
5- 7
5- 7
5- 7
6- 7
5- 9
8- 9
7-11
8-11
9-11
9- 3
0- 3
0- 5
•mojjoa: j^ tp?ay
;uoj & jo sseujprqx
b
^ co co co co co r-V-TrrT-T-'.-'r-l'i-'I-'-.o
R
•aa-edS .iiy
qoup-g qjiAV 4si[BAV
a^a: 5 jo ssaiupiqx
M
CD
^- CO X CO CO CO CO CO X CO CO CO CO CO X CO
R
•ajvedg jiy
tpur-g txjiav 'S[IBAV
9PIS 5 jo ssaujppix
H
^ IM tl CI Cl CI CI CI CI CI CD CD CD CO CO CD
o <N C-l CI CI CI 01 CI CI CI CI CI CI CI CI CI
•S[IBAV»P!S
apisui jo ssgujpiqx
0
cc
^ CI CI CI CI CI CI CI CI CI CO CO CO CO CO CO
S3
•S[[T?AV aPTS
apis^no J0 ssatopufx
*
^OOOOOOCOCOOOGOCOCOOOCOOOCOCOCO
a5
a
o
Q
\i9liog; jo JHO.I.J
OJ eiUOQ JO J9JU9Q
s
CD
j a rt - '/ x — j -. r. t - c i x -f x -r m
w w lo -t t- 1- i» » i- o n c- o o o o
•91U0(I UO'9§aT3[^[ JO
dox oj .xatiog jo dox
ft
6
JCJ Cl Cl co -o X CO C 1 C 1 Cl C 1 T 1 X X X CO
^ Cl Cl Cl Cl 01 CO CO :-. CO CO CO CO CO CO CO
'o
fastis
nre^ino jo mSuaq;
o
2 _| ,-4 Cl Cl Cl -f -f -+ -f CO CO CO t~ t~ 00
«riH,Hrt
ssat .lajiog; jo qjSu9rj
PQ
cu co o co ci ci ci co ci in -p m co m co co
En
M9nog; JO J9J9lU'BICI
^
— CO CO Cl Cl -f CO o -f -f © © O CO CO Cl
73 co co -p -+ •+ -* m m m co co co co co i~
S§8§8§3i§gg}2§gfg
STEAM BOILERS.
839
•5[0tJe: 9JT.t[ JO "OR
888888388888888
®ot-f»Mooososooo««*ia
•quit; .ioot^
aAoqt? jpijg; uouuuoq jo #ojsi;
6250
7100
8200
8750
9250
10700
11700
14450
17680
16600
17900
19000
19600
21550
22500
CO
•apig aqj ^t? n^Ai
pire .i8{toa; uga.wjgq aoudg
N
(M(M<M(NC^(M<M(M(MC^(M(MC<I(M<M
neaAvjeq .reag hi ooBdg
H
CI CJ CI CM CI CI CI CI CI CI Ol 04 <M CJ CO
•jerrag joapjs japufi
<n ifav ssp'i-ia i° d°x
M
O O O O O O CM 31 <M CI CI <N ■* -f •*
•arao(j no aStrtq^
jo dox oj jooi^ jo dox
£
^ c» cs © © o '-' rt ^' ~> ci ci co co co •*
^ _,H_irH^rH_rt,HrH,-,THrH
■jBaji jt? jra[iog J°
9pjS Jtapun oj .iooii jo dox
ti-
-"©'©Vi .Vl'ci'co
"3 lfl O IS lO ul LO O lO 13 O 13 lO » (O ffl
•juojjj ye J9[iog jo
9piS Japan o; .ioot^ jo dox
ts
rtHHCOMMOOOOOOOOOCOW-*
3 13 13 13 13 13 13 13 13 13 CO CO © CO CO CO
6
•somunji jo qjpiAS.
H
r^COCOTt<-t<-#THl3 13l3COCOCOCOCOt~
■aotjiuriji jo qjSnax
w
3 CO ^ ^ •? T^ -# -# 13 CO CO CO CO CO CO t-
•JQlJog jo ©pis
jspufi oj saj^j*) jo dox
ti
2 CO CO CO CO CO CO CO CO CO O O © O CO o
3 CI CI CI CI CI CI CI CI CI CO CO CO CO CO 00
•xeeg aqj jb saj^jQ
jo dox °^ 9un -tooiil
c*
- r:'::\o^>-^c'-.o co oo co cc co co •-h *-i cn
3 CI CI CI CI CI CI CI 01 CI CI CI 0! CO COCO
'JTtOJ^ 9qj JT? S9JT?jr)
jo dox OJ 9HJX JOOT^
Ph
2l3l3C-t-t~©©©©O©©C0C0TH
3 CI CI CI CI CI CO CO CO 00 CO CO CO CO CO CO
Pi
fcd
13©13©13©13©©©10 0©©13
rtUNKM-t<^inOt-t-M»0 CI
840
The draught power of a chimney varies as the square root of the
height.
The retarding friction of the chimney may be taken as equivalent to a
diminution of its actual area by a layer of gas two inches thick all the way
around the perimeter of its hue.
A = actual area of flue in square feet.
E — effective area of flue in square feet.
H= height in feet.
1) = diameter of hue in feet.
Dx = side of a square chimney equivalent to A.
Then: E=A— O.&^A. (l)
£)1 = "V ' E 4- 4 inches. (2)
Horse-power = 3.33 E^H. (3)
The above formulae are by Kent, and are based on a consumption of 5
lbs. coal per h. p. per hour. W. W. Christie, in a paper read before the
A.S.M.E., Trans., vol. xviii., p. 387, gives as his opinion that all chimneys
should be compared and rated by using coal capacity as a basis, not horse-
poAver. In the following table, coal capacity can be found by multiplying
h.p. by 4.
Size of Chimneys for Steam-Boilers.
(W. W. Christie.)
A
Height of Chimney.
a
50
60
70
80
90
100
110
125
150
175
200
225
250
300
£
csS
Q
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
ft.
Boiler Horse-power=3.25 E^H; 4 lbs. of coal burned considered 1 H.P.
18
42
46
49
52
1 1
21
55
62
65
68
24
72
78
85
91
98
27
91
101
107
114
124
30
114
124
133
143
153
159
33
36
39
14!)
179
163
192
2<>4
172
lS'J
192
201
ior,
241
•J IS
257
22.S
••70
241
283
257
302
42
263
:;:;''
351
•;<k
364
:;s7
410
4"!i
458
r»h
54
60
66
491
517
-.4';
">7'i
047
683
cor,
637
774
00!)
715
797
845
809
865
965
1021
1092
72
920
1)0"
nr.i
1147
1215
1300
1378
78
1131
1206
134!)
1459
1524
1619
1706
84
1310
1401
1503
1654
1768
1875
1976
2165
90
1009
1794
1898
2031
2155
2269
2486
96
ix:;o
'04 1
2161
2311
2451
2584
2831
10<>
1007
'3li4
2434
2607
2766
2915
3195
108
2314
1.-S4
2734
2925
3101
3269
3578
114
■,.s79
3045
3257
3455
3643
3991
120
:1!)1
3374
3611
3829
4037
4420
13?
;s01
4082
4368
4631
4882
5350
144
•'
4596
4859
5200
5515
5811
6367
841
The following table* will prove useful to those having to do with electric
installations, and gives the horse-power of chimneys to be used in power
plants having very efficient engines, such as compound or triple expansion
engines, when 2 lbs. of coal burned under the boiler produce one horse-
power at the engine.
Size of Chimney for Steam Boilers.
(W. W. Christie.)
Height of Chimney
S
50'
6C
70/
807
90'
100
110'
125'
150'
175'
200'
225'
250'
300'
5
H(
rse-power = G.5 Ay H. When 2 lbs
coal burned per hour rr 1 H.P.
18
84
f
92
98
,04,'..
1 1
21
110
124
130
13(3
24
144
156
170
182
19fi
27
182
202
214
228
248
30
228
24S
266
286
301
318
33
298
358
32 s
384
448
52.3
344
410
4S2
554
728
364
431
514
592
774
384
456
540
624
S20
1034
404
482
566
662
858
10X6
36
514
604
702
916
1 158
39
4?
780
1020
1"94
48
54
1366
60
1210
1274
1548
1338
1618
1430
1730
1594
1930
1690
2042
68
2184
72
1840
1924
2102
2294
2430
2600
2756
78
2262
'412
26! ).S
2918
3048
3238
3412
84
2620
2802
3126
3308
3536
3750
3952
4330
90
5218
■:r>sx
3796
4062
4310
4538
4972
91>
3660
4082
4322
4622
4902
5168
5662
102
. .
4134
460S
4868
5214
5532
5830
6360
108
4628
5168
5468
5850
6202
6538
7156
114
->7.-»x
6090
6514
6910
7286
7982
12)
....
5382
6748
7222
7658
8074
8840
132
...
7722
8164
8736
9262
9764
10700
144
"I "
)192
9718
10400
11030
11622
12734
Chimney Construction.
A brick chimney shaft is made up of a series of steps, each of which is of
uniform thickness, but as we ascend each succeeding step is thinner than
the one it rests upon. These bed joints at which the "thickness changes are
the joints of least stability. The joints and the one at the ground line
are the only ones to Avhich it is necessary to apply the formulas for deter-
mining the stability of the stack.
The height of the different steps of uniform thickness varies greatly, ac-
cording to the judgment of the engineer, but 170 feet is, approximately, the
extreme height that any one section should be made. This length is seldom
approached even in the tallest chimneys, as the brick-work has to bear, in
addition to its weight, that due to the pressure of the wind. The steps
should not exceed about 90 feet, unless the chimney stack is inside a tower
which protects it from the wind. In chimneys from 90 to 120 feet high the
steps vary from 17 to 25 feet, the top step being one brick thick ; in chim-
* " Chimney Design and Theory," W. W.Christie, D. VanNoslrand Company.
842
: ^, J=i 'Tl° PLAN OF BRICK CHIMNEY
?\%% FOR M.H. BIRGE S
'ALL PAPER FACTORY
A MARYLANO 8TS.
^-J/mZ/y ? i ~' 2 I g GREEN & WICKS-j *R^"
Fig. 4.
843
neys from 130 to 150 feet the steps vary from 25 to 35 feet ; in chimneys from
150 to 200 feet the steps vary from 35 to 50 feet ; in chimneys from 200 to 300 feet
and over, the steps vary from 50 to 90 feet, the top step being one and one-
half bricks thick. The outside dimensions of a chimney at the base should
generally not be less than one-tenth of the height of the stack for square
chimneys ; one-eleventh for octagonal, and one-twelfth for round. The bat-
ter may be 2£ inches for every 10 feet.
The foundation of a chimney is one of the most important points to be
considered. When this is upon solid rock it is only necessary to excavate
to a depth sufficient to prevent the heat of the gases from materially affect-
ing the natural stone, and to secure the spread of the base. In cases where
chimneys are to be built upon alluvial clays or made ground, it is necessary
to excavate until a good stiff clay, hard sand, or rock bottom is reached.
The excavation is filled with concrete in various ways, or filled according
to the judgment of the engineer, so as to economize material without en-
dangering the structure.
Babcock and Wilcox give the following formula for the ability of brick
chimneys to withstand wind pressure.
w = weight of chimney in lbs. (brickwork — 100 to 130 lbs. per cubic foot.)
d = average diameter' in feet, or width if square.
h = height in feet.
b = width of base.
k = constant, for square chimneys = 56.
for round chimneys — 28.
for octagonal chimneys = 35.
c = k and w = k —r—.
w o
Thin Shell IS rick Chimneys. — While the steel-plate lined stack
is considerably cheaper than the ordinary heavy brick chimney, there is a
design of brick chimney used by Messrs. Green & Wicks, architects, of
Buffalo, N. Y., that has all the durability of the brick stack, and costs less
than one of the same capacity in steel plate. The bricks must all be spe-
cially selected, hard burned, laid in rich Portland cement. By courtesy of
the architects we are able to show drawings of such a chimney, that was
erected by them for a wall-paper factory in Buffalo, and which has success-
fully withstood the most severe winds of the region (Figs. 4 and 5).
Note on Thin Shell Brick Chimneys. — The fire-brick core must be kept
free from the outer shell, not being tied or bonded to it in any manner.
The bricks are circular, with inside diameter laid up to 4 feet.
The galvanized iron-wire cables shown in the plans are for lightning protec-
tion. They are soldered and bolted to the iron cap, and after passing
down through staples built into the walls for the purpose, are grounded on
20-oz. copper plates 3 feet by \\ feet, set on edge ten feet away from the
foot of the stack. The cables are to be soldered and riveted to the plates,
and all the plates must be connected together by a f-inch galvanized iron
cable soldered to all the plates,
The chimney shown in the plans cost about $ 2,000, and can be built for
PLAN AND SECTION
SHOWING LOCATION
OF CHIMNEY
BIRGE FACTORY
844
Draft Power for Combustion of fuels.
(R. H.Thurston.)
Draft of Chim
ney in Indies
of Water.
Draft in Ins.
of Water.
Wood. . . .
Sawdust . .
Sawdust mixed with
small coal . . .
Steam coal . . .
Slack, ordinary .
Slack, very small .
0.20 to 0.25
0.35 " 0.50
0.60 " 0.75
0.40
0.60
I
0.90
1.25
Coal-dust
Semi Anthracite coal
Mixture of breeze and
slack
Anthracite . . .
Mixture of breeze and
coal-dust ....
Anthracite slack . .
0.80 to 1.25
0.90 " 1.25
1.00 '
1.25 '
1.33
1.50
1.75
1.80
Height of Chimney for Burning- Given Amounts of Coal.
Professor Wood (Trans. A. S. M. E., vol. xi.) derives a formula from
which he calculates the height of chimney necessary to burn stated quan-
tity of coal per square foot of grate per hour, for certain temperatures of
the chimney gas.
Pounds of Coal per Square Foot Grate Area.
Temp.
Absolute
Outside
Temp. Chim-
16 20 24
Air.
ney Gases.
Height of Chimney, Feet.
-
700
67.8
157.6
250.9
■g .
800
55.7
115.8
172.4
7! .3
1000
48.7
100.0
149.1
1100
48.2
98.9
148.8
1200
49.1
100.9
152.0
1400
51.2
105.6
159.9
©£
ss
1600
53.5
110.9
168.8
2000
63.0
132.2
206.5
Rate of Combustion Due to Height of Chimney.
Prof. Trowbridge (" Heat and Heat Engines," p. 153) gives the following
table, showing the heights of chimneys for producing certain rates of com-
bustion per square foot of area of section of the chimney. The ratio of the
grate to the chimney section being 8 to 1.
Lbs. Coal
burned per
Lbs. Coal
burned per
Hour per
sq. ft. of
Grate.
Lbs. Coal
burned per
Lbs. Coal
Height
Hour per
Height in
Hour per
burned per
in Feet.
sq. ft. of
Feet.
sq. ft. Sec-
Hour per
Section of
tion of
sq. ft. Grate.
Chimney.
Chimney.
25
68
8.5
70
126
15.8
30
76
9.5
75
131
16.4
35
84
10.5
80
135
16.9
40
93
11.6
85
139
17.4
45
99
12.4
90
144
18.0
50
105
13.1
95
148
18.5
55
111
13.8
100
152
19.0
60
116
14.5
105
156
19.5
65
121
15.1
110
160
20.0
845
Dimensions and Cost of Brick Chimneys.
(Buckley.)
I.
fa
2
fa
Outside Wall.
£.2
o >?
tt o
5
ts
®»£
— rti«
Q^
og
<
5M
No.
Brick.
C( >st us
.$14 per
M.
Ofa
if .5
HO
85
80
25 in.
7 ft. 5 in.
32,000
$ 448.00
$ 60.00
$ 90.00
$ 598.00
135
90
30 in.
8 " 3 "
40,000
560.00
82.00
144.00
786.00
200
100
35 in.
9 "10 "
65,000
910.00
118.00
198.00
1,226.00
300
110
43 in.
10 " 2 "
75,000
1,050.00
190.00
252.00
1,492.00
450
120
51 in.
11 " 2 "
87,000
1,218.00
261.00
306.00
1,785.00
750
130
61 in.
12 " 6 lk
131,000
1,834.00
334.00
360.00
2,528.00
1000
140
74 in.
13 " 11 "
151,000
2,114.00
432.00
414.00
3,060.00
1650
150
8S in.
15 " 1 "
200,000
2,800.00
482.00
468.00
3,750.00
2500
160
110 in.
17 " 10 "
275,000
3,850.00
720.00
525.00
5,095.00
Steel Plate Chimneys have long been used in the iron and coal re-
gions, but have only recently come into use in the East, except in the old
style thin sheet iron guyed stack, which lasts but a short time.
Many of the manufacturers of steel structures are now erecting very sub-
stantial steel-plate stacks lined with fire bricks, that are of artistic outline,
strong, and when kept well painted are durable and need no guys, as they
are spread at the base, and bolted to a heavy foundation. They are usually
designed to stand a wind pressure of 50 lbs. per square foot.
Sizes of foundations for Steel Chimney.
(Selected from Circular of Philadelphia Engineering Works.)
Half-Lined Chimneys.
Diameter, clear, feet . . .
Height, feet
Least diameter foundation .
Least depth foundation . .
Height, feet
Least diameter foundation .
Least depth foundation . .
3
4
5
3
7
9
100
100
150
150
150
150
15'9"
i6'4"
20'4"
21'IC
22/7//
23/8/-
6'
6'
9'
8'
9/
10'
125
200
200
250
275
18'5"
23'8"
25'
29'8''
33'6"
r
10'
W
12'
12''
11
150
24/8//
W
300
36'
14'
Brick Lining' for Steel Stacks.
Allowing 1| inches air space between stack and lining :
Bricks 8\ X 4 X 2 inches, laid without mortar ;
Lining B\ inches (one brick) thick ;
Number of bricks per foot in diameter of stack, and per foot of height
= 47.
Allowing 1 inch air space between stack and lining :
" Bricks 8J x 4 X 2 inches, laid without mortar ;
Lining 4 inches (one brick) thick ;
Number of bricks per foot in diameter of stack, and per foot of height
= 25.
846
l*i mention* and Cost of Iron Stacks. (Guyed.)
(Buckley.)
Horse-
Height,
Diameter,
Number of
Price Stack
Price
Power.
Feet.
Inches.
Iron.
Complete.
per Foot.
25
40
16
12 and 14
$ 61.00
$ 1.52
40
18
12 and 14
71.00
1.78
50
18
12 and 14
84.00
1.68
'75'
50
20
12 and 14
87.00
1.75
50
26
12 and 14
105.00
2.10
60
22
12 and 14
111.00
1.85
160'
60
24
12 and 14
125.00
2.08
60
26
12 and 14
133.00
2.22
60
28
12 and 14
148.00
2.45
125
60
28
10 and 12
190.00
3.18
60
32
10 and 12
203.00
3.38
'l50
60
34
12 and 14
165.00
2.75
200
60
36
10 and 12
215.00
3.58
225
60
38
10 and 12
228.00
3.80
2o0
60
42
10 and 11
257.00
4.28
300
60
46
10 and 12
286.00
4.76
400
60
52
10 and 12
340.00
5.66
For general details of construction of the various types of chimneys used
in the U. S. the reader is referred to " Chimney Design and Theory," by
W. Wallace Christie, published by D. Van Nostrand Co.
Kinds and Ingredients of fuels.
The substances which we call fuel are : wood, charcoal, coal, coke, peat,
certain combustible gases, and liquid hydrocarbons.
Combustion or burning is a rapid chemical combination.
The imperfect combustion of carbon produces carbonic oxide (CO), and
carbonic acid or dioxide (CO,).
From certain experiments and comparisons Rankine concludes "that the
total heat of combustion of any compound of hydrogen and carbon is nearly
the sum of the quantities of heat which the hydrogen and carbon contained
in it would produce separately by their combustion (CH4 — marsh gas or
fire-damp excepted)."
In computing the total heat of combustion of a compound, it is conven-
ient to substitute for the hydrogen a quantity of carbon which would give
the same quantity of heat ; this is accomplished by multiplying the weight
of hydrogen by 62032 -f- 14500 = 4.28.
From experiments by Dulong, Despretz, and others, " when hydrogen and
oxygen exist in a compound in the proper proportion to form water (by
weight nearly 1 part H to 8 parts O), these constituents have no effect on
the total heat of combustion.
" If hydrogen exists in a greater proportion, take into the heat account
only the surplus."
Dulong's formula for the total heat of combustion of carbon, hydrogen,
oxygen, and sulphur, where C,H,0,and S refer to the tractions of one
pound of the compound, the remainder being ash, etc. Let h = total heat
of combustion in B.T.U. per pound of compound.
h — 14600 C+ 62000 (h— Q\ -f 4000 S. (A.S.M.E. Trans, vol. xxi.)
Rankine says : " The ingredients of every kind of fuel commonly used may
be thus classed : (1) Fixed or free carbon, which is left in the form of char-
coal or coke after the volatile ingredients of the fuel have been distilled
away. These ingredients burn either wholly in the solid state, or part in
the solid state and part in the gaseous state, the latter part being first
dissolved by previously formed carbonic acid.
"(2) Hydrocarbons, such as olefiant gas, pitch, tar, naphtha, etc., all of
which must pass into the gaseous state before being burned.
847
" If mixed on their first issuing from amongst the burning carbon with a
large quantity of air, these inflammable gases are completely burned with
a transparent blue flame, producing carbonic acid and steam. When raised
to a red heat, or thereabouts, before being mixed with a sufficient quantity
of air for perfect combustion, they disengage carbon in fine powder, and.
pass to the condition partly of marsh gas, and partly of free hydrogen ; and
the higher the temperature, the greater is the proportion of carbon thus
dis "ngaged.
" If the disengaged carbon is cooled below the temperature of ignition be-
fore coming in contact with oxygen, it constitutes, while floating in the gas,
smoke, and when deposited on solid bodies, soot.
" But if the disengaged carbon is maintained at the temperature of ignition,
and supplied with oxygen sufficient for its combustion, it burns while float-
ing in the inflammable gas, and forms red, yellow, or white flame. The
flame from fuel is the larger the more slowly its combustion is effected.
" (3) Oxygen or hydrogen either actually forming water, or existing in com-
bination with the other constituents in the proportions which form water.
Such quantities of oxygen and hydrogen are to be left out of account in de-
termining the heat generated by the combustion. If the quantity of water
actually or virtually present in each pound of fuel is so great as to make its
latent heat of evaporation worth considering, that heat is to be deducted
from the total heat of combustion of the fuel. The presence of water or its
constituents in fuel promotes the formation of smoke, or of the carbona-
ceous flame, which is ignited smoke, as the case may be, probably by
mechanically sweeping along fine particles of carbon.
" (4) Nitrogen, either free or in combination with other constituents. This
substance is simply inert.
" (5) Sulphuret of iron, which exists in coal and is detrimental, as tending to
cause spontaneous combustion.
" (6) Other mineral compounds of various kinds, which are also inert, and
form the ash left after complete combustion of the fuel, and also the clinker
or glassy material produced by fusion of the ash, which tends to choke the
grate."
Total Heat of CoiulmMtion of JFuel». (D. K. Clark.)
The following table gives the total heat evolved by combustibles and their
equivalent evaporative power, with the weight of oxygen and volume of air
chemically consumed.
Combustibles.
Quantity of Air
Consumed per
Pound of Com-
bustible.
Cu. Ft.
at 62°F,
O oh
Hydrogen
Carbon making CO ......
Carbon making CO.,
Carbonic oxide .
Light Carbureted Hydrogen . .
Olefiant Gas
Coal (adopted average desiccated)
Coke(adopted average desiccated)
Lignite, perfect
Wood, desiccated
Wood, 25 per cent moisture . .
Petroleum
Petroleum oils
Sulphur
4.00
3.43
2.45
2.49
2.04
1.40
1.05
3.29
34.8
5.8
11.6
2.48
17.4
15.0
10.7
10.81
8.85
6.09
4.57
14.33
17.93
4.35
229
196
140
142
62000
4452
14&00
4325
23513
213-13
14^00
13548
13108
10974
7951
20411
27531
4000
5.00
1.48
848
-is- i''3
'oOSC su*)
'o09 J« .ny jo Apldns
•JJBJQ Aauunqo *mAi
Tj* OfflOONd
aiqi^Stiquioo -q] ] qgiAV
'oolo W !>«« uicij pajuuo
■d'BAa jag's AV jo spunoj uj
?. § S S § £ g g
i-' d i-" ci d l- t^ 10
•apq^stiquioo
jo punoj jad oi pasnu
jaj'BAi jo spunoj uj
-jj - i- -^
■jiy
jo ^[ddng ji?oija.ioaqx
aqj saiujx aaaqx tW!A\
38 3
\ny jo X[ddng t^oi
-jajoaqx aqj sox-^X miA\
2 oooooo
\iiy jo j?[ddns j-koijo.t
-oaqx 8<IJ sauiix fl q^A\
CO 00 CO CO CO CO CO CO (M O
••xiy jo
j£pidng i^oijojoaqx qi!A\
^ooooc o
JlOOt-OOOO
O OC
•©[qijsnquioo
jo punoj jaj spunod uj
ONOOffltBOO
- S3twpq
S o o j. -a
^OU^^i
FUEL.
Temperature of Fire.
849
By reference to the table of combustibles, it will be seen that the temper-
ature of the fire is nearly the same for all kinds of combustibles, under sim-
ilar conditions. If the temperature is known, the conditions of combustion
may be inferred. The following table, from M. Pouillet, will enable the
temperature to be judged by the appearance of the fire :
Appearance.
Temp. F.
Appearance.
Temp. F.
Red, just visible . .
" dull
" cherry, dull . .
full . .
" " clear .
977°
1290
1470
1650
1830
Orange, deep . . .
" clear . . .
White heat ....
bright . . .
" dazzling . .
2010
2190
2370
2550
2730
Xo determine Temperature l»y Fusion of jffetalw, etc.
Substance.
Tem.F.
Metal.
Tern. F.
Metal.
Tem. F.
Tallow . . .
Spermaceti .
Wax, white .
Sulphur . .
Tin ....
92°
120
154
2.39
455
Bismuth .
Lead . . .
Zinc . . .
Antimony .
Brass . .
518°
630
793
810
1650
Silver, pure . .
Gold, coin . .
Iron, cast, med.
Steel ....
Wrought iron .
1830°
2156
2010
2550
2910
American Woods.
Kind of Wood.
Hickory — Shell bark.
White oak ....
Hickery — Bed heart
Southern pine . . . .
Red oak
Beech
Hard maple . . .
Virginia pine . . .
Spruce
New Jersey pine . .
Yellow pine . . . ,
White pine . . . .
Weight
per Cord.
4469
3821
3705
3375
3254
3126
2878
2680
2325
1904
1868
Value in Tons Coal.
Anthracite | Bituminous
.504
.459
.443
.425
.391
.364
.316
.291
.259
.254
.563
.481
.467
.425
.41
.394
.363
.338
.293
.24
.235
850
STEAM.
A in e' 1*1 can Coal
Coal.
Per Cent
of
Ash.
Theoretical Value.
State. Kind of Coal.
In Heat
Units.
Pounds of
Water
Evap.
Pennsylvania. Anthracite ....
" Cannel
" Connellsville ....
Semi-bituminous . .
" Stone's Gas ....
" Youghiogheny . . .
" Brown
Kentucky. Coking ......
" Cannel ......
" Lignite
Illinois. Bureau Co . . . .
" Mercer Co.. ....
" Montauk
Indiana. Block ......
" . Coking ......
" Cannel
Maryland. Cumberland ....
Arkansas. Lignite
Colorado. " ......
Texas. " ......
Washington Ter. " .....
Pennsylvania. Petroleum .....
3.49
6.13
2.90
15.02
6.50
10.70
5.00
5.60
9.50
2.75
2.00
14.80
7.00
5.20
5.60
5.50
2.50
5.66
6.00
13.88
5.00
9.25
4.50
4.50
3.40
14,199
13,535
14,221
13,143
13,368
13,155
14,021
14,265
12,324
14,391
15,198
13,360
9,326
13,025
13,123
12,659
13,588
14,146
13,097
12,226
9,215
13.562
13,866
12,962
11,551
20,746
14.70
14.01
14.72
13.60
13.84
13.62
14.51
14.76
12.75
14,89
16.76
13.84
9.65
13.48
13.58
13.10
14.38
14.64
13.56
12.65
9.54
14.04
14.35
13.41
11.96
21.47
The weight of solid coal varies from 80 lbs. to 100 lbs. per cubic foot.
The Heating- Value of Coals.
On page r61 are given the results (Sibley, Journal of Engineering) of some
experiments made at Cornell University with a coal calorimeter devised by
Prof. R. C. Carpenter. It consists of two cylindrical chambers, in the inner
one of which the sample of coal is burned in oxygen. The heated gases pass
through a coiled copper tube about 10 feet long contained in the outer cham-
ber. The coil is surrounded by water which expands, the expansion being
measured in a finely graduated glass tube, thus giving the heat units in the
coal. The calorimeter is calibrated by burning it in pure carbon. Follow-
ing are the tables :
851
EH
all
11801
12036
12149
12294
12307
12-123
12903
12934
12943
13051
13254
13324
13723
33 <b
33 w.
9.75
9.80
2.51
6.2
0.162
8.21
3.54
0.589
5.48
0.228
0.11
0.00
0.63
*
cC-^5
in in m m
co ^ ■>* -t< ^ in ->* ^ -o -v -+ in o
3
i.
s
©
*
76.94
71.68
79.23
84.46
80.54
75.2
83.98
85.7
83.13
86.68
91.45
87.96
89.19
4
15.3
10.84
13.71
9.2
10.65
16.00
9.91
7.31
9.62
6.15
2.17
6.77
5.23
1
s
©
z
£
£
sIS
6.42
5.78
3.73
5.37
7.54
7.36
4.99
5.95
5.98
5.89
5.03
2.3
1.96
CD
o
1.34
1.7
3.33
.97
1.27
1.44
1.12
1.04
1.27
1.28
1.35
2.97
3.62
©
o
hi
W.-Barre, Pa.
Scliuyl. Co., Pa.
Scranton, Pa.
Scranton, Pa.
Scranton, Pa.
L. V. Region .
Scranton, Pa.
Scranton, Pa.
Scranton, Pa.
Avondale, Pa.
Scranton, Pa.
Drit'ton, Pa. .
Cross Creek, Pa
L. V. Buckwheat
Jermyn . .
Woodward . .
Cayuga . . .
Mt. Pleasant .
Ii. V. Pea . .
Forty Foot . .
Manville Shaft
Continental .
Avondale . .
Oxford . . .
Mammoth . .
Buck Mountain
(3
cq
3
° CD
„£ '£ £
^11
13700
12043
12724
10899
11827
11231
12217
12855
15255
11959
Pounds
Combustible
Matter in
Smoke from
1 Ton Coal.
11.8
20.94
5.29
8.63
6.12
5.33
6.53
18.25
4.00
9.88
i
9
3
CP
cfP
0506
L3126
3528
13756
L4150
14864
4971
5005
5094
15266
3-"S
CD cS
PyjJ
I
275
42
32
28
31
34
34
345
$
HrtrtHHHHrir
CD o
49.55
58.61
69.3
69.69
59.45
61.71
69.21
63.26
77.48
64.44
1
«i
11.74
7.83
10.9
5.73
4.22
3.80
5.3
6.1
3.65
4.03
34.94
31.29
18.51
23.55
34.22
31.41
21.4
28.71
17.62
30.42
0
m
3
s
to
1
o
3.77
2.27
1.23
1.03
2.11
3.08
1.09
1.93
1.25
1.11
"c8
o
o
a
"z
£
33
«
13
Clearfield Co., Pa. . .
Monongaliela River, Pa.
No. 2 Slope, Nova Scotia
lleynold'sville, Pa. . .
Conneilsville ....
New River, Va. . . .
fl
§
o
.2 2
a: £
- '- '-
Eureka . . .
Turtle Creek .
Nova Scotia .
Reynold's ville
Leisenring . .
Pocahontas
H
i
852
Proximate A imli -sis of Coal.
(Power.)
Designation of Coal.
ANTHRACITE.
Beaver Meadow, Penn
Peach Mountain, Penn
Lackawanna, Penn. .
Lehigh, Penn
AVelsh, Wales
SEMI-ANTHRACITE.
Natural Coke, Virginia
Cardiff, Wales
Lycoming Creek, Penn
Arkansas, No. 16 Geol. Survey ....
SEMI-BIT 0 M1N0U S .
Blossburg, Penn
Mexican
Port Smith, Arkansas
Cliff, New South Wales, Australia . .
Skagit River, State of Washington . .
Cumberland, Maryland
Cambria County, Penn
Mount Kembla, New South Wales, Aus.
Fire Creek, West Virginia
Arkansas, No. 12 Geol. Survey ....
BITUMINOUS.
Wilkeson, Pierce County, Washington .
Cowlitz, Washington
New River, West Virginia
Pictou, Nova Scotia
Big Muddy, Illinois
Bellinghain Bay, Washington ....
Midlothian, Virginia
Connellsville, Penn
Illinois, Average
Carbon Hill, Washington
Clover Hill, Virginia
Wellington, Vancouver Island, B.C. . .
Franklin, Washington
Rocky Mountains
Newcastle, England
Mokihinui, Westport, New Zealand . .
Brunner Mine, Greymouth, New Zealand
Pittsburg, Penn
Nanaimo, Vancouver Island, B.C. . . .
Hocking Valley, Ohio
Pleasant Valley, Utah
Kentucky
Ellensburg, Washington
Olympic Mountains, Washington . . .
Scotch, Scotland
Roslyn, Washington
Cook's Inlet, Alaska
Kootznahoo Inlet, Admiralty I., Alaska
Liverpool, England
Calispel. Washington
Carbonado, Washington
Upper Yakima, Washington
MethoAV, Washington
2.96
3.91
3.28
6.25
12.44
12.: *5
13.S4
14.93
14.78
14.86
17.2
17.7
18.8
19.87
20.52
2.46
1.26
8.93
2.16
1.34
2,15
1.59
1.7
2.25
6.95
5.43
1.25
3.74
2H.9:',
22.42
24.66
26.12
26.64
27. S3
29.5
29. r»4
29. S6
30.10
30.14
31.73
32.21
34.15
34.27
34.65
34.7
34.94
35.68
36.
36.05
36.15
37.73
37.89
39.1
39.15
39.19
39.7
39.87
37.02
39.96
41.1S
42.27
42.47
43.71
NX. 94
89.02
87.74
75. 1 is
81.9
71.53
74.06
73.11
55.7
73.05
71.8
71.66
69.37
66.96
66.75
61.9
70.66
56.98
54.64
59.9
53.01
59.61
45.93
55.8
56.83
54.85
54.23
42.85
59.3
57.92
56.62
55.
51.95
51.3
49.40
50.01
54.4
47.01
48.81
52.65
49.89
45.15
54.9
42.92
52.11
52.21
49.27
853
"£■§
^
6-g
^S
1*
4.
£ 3
^kH
Eii
<j
fcS
f»-w
"o
2.12
46.7
43.9
7.15
3.11
47.19
45.11
4.58
14.69
33.89
46.84
4.58
19.61
37.25
39.41
3.73
4.8
47.07
37.19
10.06
15.45
41.55
34.95
8.05
14.6
44.85
31.2
9.35
11.7
51.73
19.65
16.94
42.58
34.88
17.42
5.12
Proximate .Analysis of Coal— Continued.
Designation of Coal.
Newcastle, King County, Washington
Black Diamond, King County, Washington
Black Diamond, Mt. Diablo, California
LIGNITES.
Otago (Kaitangata Cr.), New Zealand
Gilman, Washington
Coos Bay (Newport Mine), Oregon . . 15.45 41.55 34.95 8.05 2.53
Alaska 14.6 44.85 31.2 9.35 1.15
Huron, Fresno County, California . . 11.7 51.73 19.65 16.94 2.73
lone, Amador County, California . . . 42.58 34.8S 17.42 5.12 Trace.
Space ltequiretl to Stow a Ton (3"-J-40 H»s.) of Various
Kinds of Coal.
ANTHRACITE.
Welsh, Wales 39 cubic feet.
Peach Mountain, Penn 41.6 " "
Beaver Meadow, Penn 40.2 " "
Lehigh, Penn 40.5 " "
Lackawanna, Penn 45.8 " "
SEMI-ASTHEACITE.
Cardiff, Wales 38.3 cubic feet.
Natural Coke, Virginia 50.2 " "
SEMI-BITUMINOUS.
Cumberland, Virginia 41.7 cubic feet.
Blossburgh, Penn 42.2 " "
Mt. Kembla, Australia 37.7 " "
Mexican 36.7 " "
BITUMINOUS.
New River, Virginia 46 cubic feet.
Wellington, Vancouver Island, B.C 41.8 " "
Midlothian, Virginia 41.4 " "
Newcastle, England 44 " "
Pictou, Nova Scotia .... 45 " "
Scotch Splint, Fordel 40.7 •« "
Pleasant Valley, Utah 42.3 " "
Sydney, N. S. W., Australia 47.2 " "
Takasima, Japan 46.4 " "
Pittsburgh. Penn 47.8 " "
Liverpool, England 46.7 " "
Scotch, Dalkeith 43.8 " "
Carbon Hill, Washington 36.9 « "
Clover Hill, Virginia 49.2 " "
Rocky Mountain 41.2 " "
LIGNITE.
Alaska 41.8 cubic feet.
WOOD.
Dry pine wood 107 cubic feet.
Coke. — Coke from ovens, preferred to gas coke as fuel, weighs with
few exceptions about 40 lbs. per bushel. Light coke will weigh 33 to 38 lbs.
Heavy coke, 42 to 50 lbs.
Analysis of Coke.
(From report of John R. Procter, Kentucky Geological Survey.)
Where Made.
Fixed
Carbon
Ash.
Sul-
phur.
Connellsville, Pa. (Average of 3 samples)
Chattanocga, Tenn. " " 4
Birmingham, Ala. " "4
Pocahontas, Va. " "3
New River, W. Va. " " 8
Big Stone Gap, Ky. " "7
88.96
80.51
87.29
92.53
92.38
93.23
9.74
16.34
10.54
5.74
7.21
5.69
0.810
1.595
1.195
0.597
0.562
0.749
m
854
Wood as Fuel.
Green wood contains from 30 to 50 per cent of moisture. After about a
year in open air the moisture is 20 to 25 per cent.
The woods of various trees are nearly identical in chemical composition,
which is practically as follows, showing the composition of perfectly dry
wood, and of ordinary firewood holding hygroscopic moisture :
Desiccated Wood. Ordinary Firewood.
Carbon 50 per cent . . . 37.5 per cent
Hydrogen 6 per cent . . . 4.5 per cent
Oxygen 41 per cent . . . 30.75 per cent
Nitrogen 1 per cent . . . 0.75 per cent
Ash 2 per cent ... 1.5 per cent
100 per cent 75.0 per cent
Hygrometric water 25.0 per cent
100.0
Some of the pines and others of the coniferous family contain hydrocar-
bons (turpentine). Ash varies in American woods from .03 per cent to 1.20
per cent.
In steam boiler tests wood is assumed as 0.4 the value of the same w eight of
coal.
The fuel value of the same weights of wood of all kinds is practically the
same ; and it is important that the wood be dry.
WvtighLt of Wood per Cord.
Weighs per Equal in value to Coal,
Cord, Lbs. in Lbs.
Average pine ....
Poplar, chestnut, elm .
Beech, red and black oak
White oak
Hickory and hard maple
2000
2350
3250
3850
4500
800 to 925
940 to 1050
1300 to 1459
1540 to 1715
1800 to 2000
A cord of wood = 4 x 4 x 8 = 128 cubic feet. About 5G per cent is solid
wood, and 44 per cent spaces.
liiquid fuels.
Petroleum is a hydrocarbon liquid which is found in abundance in Amer-
ica and Europe. According to the analysis of M. Sainte-Claire Deville, the
composition of 15 petroleums from different sources was found to be practi-
cally the same. The average specific gravity was .870. The extreme and the
average elementary compositions were as follows :
Chemical Composition of 3*etroleum.
Carbon 82.0 to 87.1 per cent. Average, S4.7 per cent.
Hydrogen 11.2 to 14.8 per cent. Average, 13.1 per cent.
Oxygen 0.5 to 5.7 per cent. Average, 2.2 per cent.
100.0
The total heating and evaporative powers of one pound of petroleum hav-
ing this average composition are as follows :
Total heating power = 145 [84.7 + (4.28 X 13.1)] = 20411 units.
Evaporative power : evaporating at 212°, Avater supplied at 62° = 18.29 lbs.
Evaporative power : evaporating at 212°, water supplied at 212° = 21.13 lbs.
Petroleum oils are obtained in great variety by distillation from petro-
leum. They are compounds of carbon and hydrogen, ranging from C10 H24
to C32 HlU ; or, in weight ;
855
Chemical Composition of Petroleum Oils.
Mean.
( 71.42 Carbon \
( 28.58 Hydrogen )
100.00
f 73.77 Carbon .
( 2G.23 Hydrogen
100.00
, 27.40
100.00
The specific gravity ranges from .62S to .792. The boiling point ranges
from 86° to 495° F. The total heating power ranges from 2.so.-w t< > '_'<i975 units
of heat ; equivalent to the evaporation, at 212°, of from 25.17 to 24.17 lbs.
of water supplied at 62°, or from 29.0S lbs. to 27.92 lbs. of water supplied
at 212°.
furnaces for the combustion of oil fuel need not be as large as when
burning coal, as the latter, being solid matter, requires more time for de-
composition, and the elimination of the products and supporters of com-
bustion. Coal fuel requires a large fire chamber and the means for the
introduction of air beneath the grate-bars to aid combustion. Compared
with oil, the combustion of coal is tardy, and requires some aid by Avay of
a strong draft. Oil having no ash or refuse, when properly burned, requires
much less space for combustion, for the reason that, being a liquid, and the
compound of gases that are highly inflammable when united in proper pro-
portions, it gives off heat witb the utmost rapidity, and at the point of igni-
tion is all ready for consumption.
Gaseous Fuels. — Mr. Emerson McMillin (Am. Gas. Lt. Asso., 1887)
made an exhaustive investigation of the subject of fuel gas ; he states that
the relative values of these gases, considering that of natural gas as of unit
value, are :
By Volume.
Natural gas
Coal gas . .
"Water gas .
Producer gas
1000
G6G
292
130
The water gas rated in the above table is the gas obtained in the decom-
position of steam by incandescent carbon, and does not attempt to fix the
caloi'ific value of illuminating Avater gas, which may be carbureted so as to
exceed, when compared by volume, the value of coal gas.
Composition of Gases.
Natural
Gas.
Coal
Gas.
Water
Gas.
Producer
Gas.
Hydrogen . . .
'Marsh gas . .
j Carbonic oxide
defiant gas . .
Carbonic acid .
Nitrogen . . .
| Oxygen . . .
j "Water vapor
jSulphydric acid
2.18
92.60
0.50
0.31
0.26
3.61
0.34
0.00
0.20
100.00
46.00
40.00
6.00
4.00
0.50
1.50
0.50
1.50
45.00
2.00
45.00
0.00
4.00
2.00
0.50
1.50
6.00
3.00
23.50
0.00
1.50
65.00
0.00
1.00
100.00
856
Mechanical Stoking*.
In boiler installations that can be conveniently bandied by one man it is
doubtful if we can improve on tlie best band tiring ; but wbere good firemen
are scarce, or the installation is of considerable size, there can be no doubt
that the use of some form of mechanical stoker will result in economy, and
especially Ln the prevention of large quantities of smoke, as the combustion
is gradual and more nearly perfect.
The types may perhaps be limited to three : the straight feed, as the Mur-
phy, Koney, Wilkinson, and Brightman ; the under-feed of which the
" American " is a good representative; and the chain stoker, by Coxe and
the B. & W. Co.
Mechanical draught is generally used with the two last-mentioned types,
and sometimes with the lust.
Mr. Eckley B. (Joxe developed the chain stoker in the most scientific man-
by Mr. J.
Advantat
2. A40p<
M. Wi
."5-10 per sq
with souk
the power
ningthest
Tins is abi
ton. 5. ('
whenever
requires constant attention.
lisadvantages of mechanical stokers are stated
nan (Trans. A.S.M.E., vol. xvii. p. 558) to be as follows:
laptability 1<» the burning of the cheapest grades of fuel,
or saving in plaids of HOOor more li. p., when provided with
linery. 3. Economy in combustion, even under forced
management. 4. Constancy and uniformity of furnace
3 being <dean at all times, and responding to sudden de-
ower. This should result in prolonged life of boilers.
Disadvantages. 1. High first cost, varying from .$25 to
of grate area. 2. High cost of repairs per year, Avhich,
is as much as $5 per square foot. 3. The dependence of
un the stoker engine's working. 4. Steam cost of run-
n e, which is from £ to § of 1 per cent of the steam generated.
year on a 10-hour basis for 1000 h. p., where fuel is $2 per
jam used for a steam blast, or for driving a fan blast,
used. This, lor a steam blast, is from 5 per cent to 11
un generated by the boilers, and from 3 per cent to 5 per
t. Tins amounts to about #1000 per year for asteam blast,
fuel for a fan blast, for a 1000 h. p. plant on a 10-hour
3 $2 per ton. 6. Skill required to operate the stoker,
ent causes either loss of fuel in the ash, or loss due to
:ien the coal is too soon burned out on the grate, thus per-
freely pass through the ash. 7. The stoker is a machine
like any other machine, wears out and
WATER.
Weig-ht of Water per Culiic Foot, from 32° to 212° F., and heat-
units per pound, reckoned above 32° F. (Wm. Kent, Trans. A. S. M. F.,
vi. 90.)
-a .2
&
J; O
i
<-*'£
i
,
'£ 2
i
^o^
p
3
1 ^
+?0
0
2 fa
2 °+»
%
Si;
| ftcg
5-5^
03
S-5^
« Ph<h
H
w
H
^
w
H
P>
w
H
r*
w
32
G2.42
0.
41
62.42
9.
50
62.41
18.
59
62.38
27.01
'.',.',
62.42
l.
42
62 42
10.
51
62.41
1!).
60
G2.37
28.01
34
62.42
2.
4:5
62.42
11.
52
62.40
20.
Gl
G2.37
29.01
35
62.42
3.
44
62.42
12.
53
62.40
21.01
62
G2.36
30.01
36
62.42
4.
45
62.42
13.
54
02.40
22.1 H
G3
62.36
31.01
3V
62.42
5.
41 ;
62.42
14.
55
62.39
23,01
64
62.35
32.01
38
62.42
6.
47
62.42
15.
56
62.39
24.01
65
62.34
33.01
39
02.42
7.
48
64.41
16.
57
62.39
25.01
66
62.34
34.02
40
62.42
8.
49
62.41
17.
58
62.38
2G.01
67
62.33
35.02
857
Weight of Water — Continued.
is
CO
Ms
to
-a .2
MS
no
~&
^6
^,0
~&
rfe
#o+±
3
S°-^
%
« P
P
I >
3©^
B
ft iij
bDu O
■otsu O
— i iJQ
•HJ)0
•X dj o
■~ v z
® ft^
o>
g-is-d
gftk
<v
©-tJ't!
i® ft^
©
£ a^
©
H
^
H
H
"
w
H
^
H
H
w
08
62.33
36.02
105
61.96
73.10
141
61.36
109.25
177
60.62
145.52
61)
62.32
37.02
100
61.95
74.10
142
61.34
110.20
178
00.59
146.52
70
62.31
38.02
107
61.93
75.10
143
61.32
111.26
179
00.57
14', .53
71 | 62.31
39.02
108
61.92
76.10
144
61.30
112.27
180
00.55
148.54
72
62.20
40.02
109
61.91
77.11
145
61.28
113.28
181
00.53
149.55
73
62.29
41.02
110
61.89
78.11
146
61.26
114.28
182
00.50
150.56
74
62.28
42.03
111
61.88
79.11
147
61.24
115.29
183
60.48
151.57
75
62.28
43.03
112
61.86
80.12
148
61.22
110.29
184
60.46
152.58
76
62.27
44.03
113
61.85
81.12
149
61.20
117.30
185
60.44
153.59
77
62.26
45.03
114
61.83
82.13
150
61.18
118.31
186
60.41
154.60
78
62.25
46.03
115
61.82
83.13
151
61.16
119.31
187
60.39
155.61
79
62.24
47.03
116
61.80
84.13
152
61.14
120.32
188
60.37
156.62
80
62.23
48.04
117
61.78
85.14
153
61.12
121.33
189
60.34
157.63
81
62.22
49.04
118
61.77
86.14
154
61.10
122.33
190
60.32
158.64
82
62.21
50.04
119
61.75
87.15
155
61.08
123.34
191
00.29
159.65
83
62.20
51.04
120
61.74
88.15
156
61.06
124.35
192
60.27
160.67
84
62.19
52.04
121
61.72
89.15
157
61.04
125.: {5
193
60.25
161.68
85
62.18
53.05
122
61.70
90.16
158
61.02
120.30
194
60.22
162.69
86
62.17
54.05
123
61.68
91.16
159
61.00
127.37
195
00.20
163.70
87
62.16
55.05
124
61.67
92.17
160
00.98
128.37
196
00.17
164.71
88
62.15
56.05
125
61.65
93.17
161
00.96
12!). 3*
197
60.15
165.72
89
62.14
57.05
126
61.63
94.17
162
60.94
130.39
198
60.12
166.73
90
62.13
58.06
127
61.61
95.18
163
00.92
131.40
199
60.10
167.74
91
62.12
59.06
128
61.60
96.18
164
00.90
132.41
200
60.07
168.75
92
62.11
60.06
129
61.58
97.19
165
00.87
133.41
201
60.05
169.77
93
62.10
61.06
130
61.50
98.19
166
00.85
134.42
202
60.02
170.78
94
62.09
62.06
131
01.54
99.20
167
60.83
135.43
203.
oo.oo
171.79
95
62.08
63.07
132
61.52
100.20
168
60.81
130.44
204
59.97
172,80
96
62.07
64.07
133
61.51
101.21
169
60.79
137.45
205
59.95
173.81
97
62.06
65.07
134
61.49
102.21
170
60.77
138.45
206
59.92
174.83
98
02.05
66.07
135
61.47
103.22
171
60.75
139.40
207
59. SO
175.84
99
02.03
07.08
136
61.45
104.22
172
60.73
140.47
208
59.S7
176.85
100
02.02
08.08
137
61.43
105.2:;
173
00.70
141.48
209
59.84
177.86
101
02.01
09.08
188
61.41
106. 22,
174
00.08
142.49
210
59. S2
178.87
102
62.00
70.09
139
61.39
107 24
175
00. 0(5
143.50
211
59.79
179.89
103
61.99
71.09
140
61.37
108.25
176
60.64
144.51
212
59.76
180.90
104
61.92
72.09
WeigTit of Water at Temperatures Above 312° JF.
(Dr. R. H. Thurston, " Engine and Boiler Trials," p. 548.)
©
c3
Srr.^
k .
k ^
-^LO'Q
oS
-^ rr,'^
k .
-^OD^
& ©f^
3 -3*
Srgp
A%*
© ©-ft
A%2
©©-ft
-^P .
ftp; jjj
8 fi
'53 P '~ §
z?b ■;>.
'33 3 u o
ft ~ -.1-
"Z P u s
pp^
p*p ^
'53 P n §
£&§* s^p
l> ft ftf^
©^Q
H
t> ftftfr
r* ftftft
g~Q
j£ ftftft
212
59.71
280
57.90
350
55.52
420
52.86
490
50.03
220
59.64
290
57.59
360
55.16
430
52.47
500
49.61
230
59.37
300
57.26
370
54.79
440
52.07
510
49.20
240
59.10
310
56.93
380
54.41
450
51.66
520
48.78
250
58.81
32Q
56.58
390
54.03
460
51.26
530
48.36
260
58.52
330
56.24
400
53.64
470
50.85
5*0
47.94
270
58.21
340
55.88
410
53.26
480
50.44
550
47.52
858
STEAM.
Expansion of "Water.
(Kopp : corrected by Porter.)
Cent.
Fahr.
Volume.
Cent.
Fahr.
Volume.
Cent.
Fahr.
Volume.
40
39.2°
1.00000
35°
95°
1.00586
70°
158°
1.02241
5
41
1.00001
40
104
1.00767
75
167
1.02548
10
50
1.00025
45
113
1.00967
80
176
1.02872
15
59
1.00083
50
122
1.01186
85
185
1.03213
20
68
1.00171
55
131
1.01423
90
194
1.03570
25
77
1.00286
60
140
1.01678
95
203
1.03943
30
86
1.00425
65
149
1.01951
100
212
1.04332
Water for Boiler Feed.
(Hunt and Clapp, A. I. M. E., 188S.)
Water containing more than 5 parts per 100,000 of free sulphuric or nitric
acid is liable to cause serious corrosion, not only of the metal of the boiler
itself, but of the pipes, cylinders, pistons, and valves with which the steam
comes in contact.
The total residue in water used for making steam causes the interior lin-
ings of boilers to become coated, and often produces a dangerous hard scale,
which prevents the cooling action of the water from protecting the metal
against burning.
Lime and magnesia bicarbonates in water lose their excess of carbonic
acid on boiling, and often, especially when the water contains sulphuric
acid, produce, with the other solid residues constantly being formed by the
evaporation, a very hard and insoluble scale. A larger amount than 100
parts per 100,000 of total solid residue will ordinarily cause troublesome
scale, and should condemn the water for use in steam boilers, unless a bet-
ter supply can be obtained.
The following is a tabulated form of the causes of trouble with water for
steam purposes, and the proposed remedies, given by Prof. L. M. Norton.
CAUSES OF INCRUSTATION.
1. Deposition of suspended matter.
2. Deposition of deposed salts from concentration.
3. Deposition of carbonates of lime and magnesia by boiling off carbonic
acid, which holds them in solution.
4. Deposition of sulphates of lime, because sulphate of /ime is but slightly
soluble in cold water, less soluble in hot water, insoluble above 270° F.
5 Deposition of magnesia, because magnesium salts decompose at high
temperature.
6. Deposition of lime soap, iron soap, etc., formed by saponification of
grease.
MEANS FOR PREVENTING INCRUSTATION.
1. Filtration.
2. Blowing off.
3. Use of internal collecting apparatus or devices for directing the circu-
lation.
4. Heating feed-water.
859
5. Chemical or other treatment of water in boiler.
6. Introduction of zinc into boiler.
7. Chemical treatment of water outside of boiier.
TABULAR VIEW.
Trouble.
Incrustation.
Troublesome Substance.
Sediment, mud, clay, etc.
Readily soluble salts.
Bicarbonates of lime, magnesia,
iron.
Sulphate of lime. "
Chloride and sulphate of magne- ) „
sium. 8 } Corrosion.
Carbonate of soda in large )
amounts. )
Acid (in mine waters).
Dissolved carbonic acid and oxy-
gen.
Grease (from condensed water).
Organic matter (sewage).
Organic matter.
Priming.
Corrosion.
Priming.
Corrosion.
Remedy or Palliation.
Filtration, Blowing off.
Blowing off.
( Heating feed. Addition of
\ caustic soda, lime, or
^ magnesia, etc.
| Addition of carb. soda,
{ barium chloride, etc.
( Addition of carbonate of
( soda, etc.
(Addition of barium chlo-
( ride, etc.
("Heating feed. Addition
< of caustic soda, slacked
[_ lime, etc.
f Slacked lime and filtering,
-{ Carbonate of soda.
L. Substitute mineral oil.
( Precipitate with alum or
( ferric chloride and filter.
Solubilities of Scale-making- Materials.
(" Boiler Incrustation," F. J. Bowan.)
The salts of lime and magnesia are the most common of the impurities
found in water. Carbonate of lime is held in solution in fresh water by an
excess of carbonic acid. By heating the water the excess of carbonic acid
is driven off and the greater part of the carbonate precipitated. At ordi-
nary temperatures carbonate of lime is soluble in from 16,000 to '24,000 times
its volume of water ; at 212° F. it is but slightly soluble, and at 290° F. (43
lbs. pressure) it is insoluble.
The solubility of sulphate of lime is also affected by the temperature ;
according to Kegnault, its greatest solubility is at 95° F., where it dissolves
in 393 times its weight of water ; at 212: F. it is only soluble in 460 times its
weight of water, and according to M. Coute, it is insoluble at 290° F.
Carbonate of magnesia usnally exists in much smaller quantity than the
salts of lime. The effect of temperature on its solubility is similar to that
of carbonate of lime.
Prof. R. H. Thurston, in his " Manual of Steam Boilers," p. 261, states
that:
The temperatures at which calcareous matters are precipitated are :
Carbonate of lime betAveen 176° and 248° F.
Sulphate of lime between 284c and 424° F.
Chloride of magnesium between 212° and 257° F.
Chloride of sodium between 324° and 304° F.
860
" Incrustation and sediment," Prof. Thurston says, " are deposited in
boilers, the one by the precipitation of mineral or other salts previously
held in solution in the feed-water, the other by the deposition of mineral
insoluble matters, usually earths, carried into it in suspension or me-
chanical admixture. Occasionally also vegetable matter of a glutinous
nature is held in solution in the feed-water, and, precipitated by heat or
concentration, covers the heating-surfaces with a coating almost impermea-
ble to heat, and hence liable to cause an over-heating that may be very dan-
gerous to the structure. A powdery mineral deposit sometimes met with is
equally dangerous, and for the same reason. The animal and vegetable oils
and greases carried over from the condenser or feed-water heater are also
very likely to cause trouble. Only mineral oils should be permitted to be
thus introduced, and that in minimum quantity. Both the efficiency and
the safety of the boiler are endangered by any of these deposits.
"The only positive and certain remedy for incrustation and sediment
once deposited is periodical removal by mechanical means, at sufficiently
frequent intervals to insure against injury by too great accumulation. Be-
tween times, some good may be done by special expedients suited to the
individual case. No one process and no one antidote will suffice for all
cases.
" Where carbonate of lime exists, sal-ammoniac may be used as a pre-
ventive of incrustation, a double decomposition occurring, resulting in the
production of ammonium carbonate and calcium chloride — both of which
are soluble, and the first of which is volatile. The bicarbonate may be in
part precipitated before use by heating to the boiling-point, and thus break-
ing up the salt and precipitating the insoluble carbonate. Solutions of
caustic lime and metallic zinc act in the same manner. Waters containing
tannic acid and the acid juices of oak, sumach, logwood, hemlock, and other
woods, are sometimes employed, but are apt to injure the iron of the boiler,
as may acetic or other acid contained in the various saccharine matters
often introduced into the boiler to prevent scale, and which also make the
lime-sulphate scale more troublesome than when clean. Organic matters
should never be used.
"The sulphate scale is sometimes attacked by the carbonate of soda, the
products being a soluble sodium sulphate and a pulverulent insoluble cal-
cium carbonate, which settles to the bottom like other sediments and is
easily washed off the heating-surfaces. Barium chloride acts similarly,
producing barium sulphate and calcium chloride. All the alkalies are used
at times to reduce incrustations of calcium sulphate, as is pure crude petro-
leum, the tannate of soda, and other chemicals.
" The effect of incrustation and of deposits of various kinds is to enor-
mously reduce the conducting power of beat inn-surfaces ; so much so, that
the power, as well as the economic efficiency of a boiler, may become very
greatly reduced below that for which it is rated, and the supply of steam
furnished by it may become wholly inadequate to the requirements of the
case.
" It is estimated that a sixteenth of an inch thickness of hard ' scale' on
the heating-surface of a boiler will cause a waste of nearly one-eighth its
efficiency, and the waste increases as the square of its thickness. The boil-
ers of steam vessels are peculiarly liable to injury from this cause where
using salt water, and the introduction of the surface-condenser has been
thus brought about as a remedy. Land boilers are subject to incrustation
by the carbonate and other salts of lime, and by tbe deposit of sand or mud
mechanically suspended in the feed-water."
Kerosene oil ("Boiler Incrustation," KoAvan) has been used to advantage in
removing and preventing incrustation. From extended experiments made
on a 100 h. p. water tube boiler, fed with water containing 6.5 grains of
solid matter per gallon, it Avas found that one quart kerosene oil per day
was sufficient to keep the boiler entirely free from scale. Prior to the in-
troduction of the kerosene oil, the Avater had a corrosive action upon some
of the fittings attached to the boiler ; but after the oil had been used for a
feAV months it Avas found that the corrosive action had ceased.
It should be stated, however, tbat objection has been made to the intro-
duction of kerosene oil into a boiler for the purpose of preventing incrusta-
861
tion, on account of the possibility of some of the oil passing with the steam
into the cylinder of the engine, and neutralizing the effect of the lubricant
in the cylinder.
When oil is used to remove scale from steam-boilers, too much care can-
not be exercised to make sure that it is free from grease or animal oil.
Nothing but pure mineral oil should be used. Crude petroleum is one
thing ; black oil, which may mean almost anything, is very likely to be
something quite different.
The action of grease in a boiler is peculiar. It does not dissolve in the
water, nor does it decompose, neither does it remain on top of the water ;
but it seems to form itself into " slugs," which at first seem to be slightly
lighter than the water, so that the circulation of the water carries them
about at will. After a short season of boiling, these " slugs," or suspended
drops, acquire a certain degree of " stickiness," so that Avhen they come in
contact Avith shell and flues of the boiler, they begin to adhere thereto.
Then under the action of heat they begin the process of " varnishing " the
interior of the boiler. The thinnest possible coating of this varnish is suf-
ficient to bring about over-heating of the plates.
The time when damage is most likely to occur is after the fires are banked,
for then, the formation of steam being checked, the circulation of Avater
stops, and the grease thus has an opportunity to settle on the bottom of the
boiler and preA-ent contact of the Avater Avith the fire-sheets. Under these
circmnstances, a very low degree of heat in the furnace is sufficient to over-
heat the plates to such an extent that bulging is sure to occur.
Zinc as a Scale Preventive. — Dr. Corbigny gives the folloAAdng hypoth-
esis : he says that " the tAvo metals, iron and zinc, surrounded by AA^ater at a
high temperature, form a A'oltaic pile with a single liquid, which sloAvly
decomposes the water. The liberated oxygen combines Avith the most oxy-
dizable metal, the zinc, and its hydrogen equiATalent is disengaged at the
surface of the iron. There is thus generated over the AArhole extent of the
iron influenced a very feeble but continuous current of hydrogen, and
the bubbles of this gas isolate at each instant the metallic surface from the
scale-forming substance. If there is but little of the latter, it is penetrated
by these bubbles and reduced to mud ; if there is more, coherent scale is
produced, Avhich, being kept off by the intervening stratum of hydrogen,
takes the form of the iron surface Avithout adhering to it."
Zinc, in the shape of blocks, slabs, or as shaATings inclosed in a perforated
vessel, should be suspended throughout the Avater space of a boiler, care
being used in getting perfect metallic contact betAveen the zinc and the
boiler. It should not be suspended directly over the furnace, as the oxide
might fall upon the surface and be the cause of the plate being over-heated.
The quantity placed in a boiler should vary Avith the hardness of the Avater,
and the amount used, and should be measttred by the surface presented.
Generally one square inch of surface for every 50 lbs. Avater in the boiler is
sufficient. The British Admiralty recommends the reneAving of the blocks
Avkenever the decay of the zinc has penetrated the slab to a depth of \ inch
beloAV the surface.
Purification of IVed- Water Ity Boiling-.
Sulphates can be largely removed from feed-water by heating it to the tem-
perature due to boiler pressure in a feed-Avater heater, or " live steam puri-
fier " before introduction to boiler. This precipitates those salts in the heater
and the water can then if necessary be pumped through a filter into the boiler.
The feed-Avater i.3 first heated as hot as possible in the ordinary exhaust
feed-water heater in Avhich the carbonates are precipitated, and then run
through the purifier, Avhich is most generally a receptacle containing a
number of shalloAv pans, that can be removed for cleaning, over which the
feed-Avater is allowed to flow from one to the other in a thin sheet. Live
steam at boiler-pressure is introduced into the purifier, heating the water
to a temperature high enough to precipitate the salts Avhich form scale on
the pans. This method of treating feed-Avater is said to largely increase the
efficiency of a boiler plant by the almost complete avoidance of scale.
Purification of f eed-AArater by filtration before introduction to the system is
often practised Avith good results.
862
STEAM.
Xal»l<* of Water Analyses.
Grains per U. S. Gallon of 231 Cubic Inches.
Where From.
Buffalo, N. Y., Lake Erie ....
Pittsburgh, Allegheny River . .
Pittsburgh, Mononga'hela River .
Pittsburgh, Pa., artesian well . .
Milwaukee, Wisconsin River . . .
Galveston, Texas, 1
Galveston, Texas, 2
Columbus, Ohio
Washington, D. C, city supply . .
Baltimore, Md., city supply . . .
Sioux City, la., city supply ....
Los Angeles, Cal., 1
Los Angeles, Cal., 2
Bay City, Michigan, Bay
Bay City, Michigan, River ....
Cincinnati, Ohio River
Watertown, Conn
Fort Wayne, Ind
Wilmington, Del
Wichita, Kansas
Springfield, 111., 1
Springfield, 111., 2
Hillsboro, 111
Pueblo, Colo
Long Island City, L. I
Mississippi River, above Missouri
River
Mississippi River, below mouth of
Missouri River
Mississippi River at St. Louis, W. W.
Hudson River, above Poughkeepsie,
N. Y
5.66
0.37
1.06
23.45
6.23
13.68
21.79
20.76
2.87
2.77
19.76
10.12
3.72
8.47
4.84
3.88
1.47
8.78
10.04
14.14
12.99
5.47
14.56
4.32
4.0
Croton River, above Croton Dam
N. Y
Croton River water from service
pipes in New York City. . . .
Schuylkill River, above Philadelphia,
Pa
3.32
3.78
5.12
5.71
4.67
13.52
29.15
11.74
3.27
0.65
1.24
5.84
12.59
10.36
33.06
0.78
4.51
6.22
6.02
25.91
7.40
4.31
2.97
16.15
28.0
7.41
6.94
0.58
0 58
0.64
18.41
1.76
326. 04
39S.99
7.02
Trace
Trace
1.17
3.51
20*.48
120.78
1.79
1.76
3.51
4.29
24.34
1.97
1.56
2.39
1.20
16.0
0.50
1.36
1.54
0.37
0.78
1.04
20.14
Trace
V.58
0.36
0.10
1.03
2.63
0.76
1.15
3.00
Trace
1.59
2.19
4.2
1.63
1.97
0.18
1.50
3.20
0.82
6.50
Trace
4.00
6.50
2.10
3.80
4.40
4.10
6.00
8.74
10.92
Trace
1.78
10.98
6.17
2.00
S.62
'..S3
1.22
1.57
10.76
1.92
1.36
1.30
15.86
9.85
39.31
353.8-
453.93
46.60
8.60
7.30
27.60
26.20
23.07
49.20
179.20
6.73
9.52
31.08
35.00
66.39
33.17
21.45
21.55
28.76
39.0
15.01
36.49
29.54
12.70
7.72
3.72 j
4.24 I
863
Feed-Pumps.
These should be at least double the capacity found by calculation from
tbe amount of water required for the engines, to allow for blowing off, leak-
age, slip in the pumps themselves, etc., and to enable the pump to keep
[down steam in case of sudden stoppage of the engines when the tires hap-
pen to be brisk, and in fact should be large enough to supply the boilers
when run at their full capacity. In addition, for all important plants, there
[should be either a duplicate feed-pump or an injector to act as stand-by in
case of accident. The speed of the plunger or piston may be 50 feet per
minute and should never exceed 100 feet per minute, else undue wear and
tear of the valves results, and the efficiency is reduced. If the pump be re-
quired to stand idle without continually working, the plunger or piston and
rod should be of brass.
If
D = diameter of barrel in inches,
S = stroke in inches,
n =z number of useful strokes per minute,
w = cubic feet of water pumped per hour,
W= lbs. of water pumped per hour ;
w = 1.7 D2S n.
n ~ 36.6 '
If S n = 50,
fF =1.361)2,
. and
D=VZ.
Rubber valves may be used for cold water, but brass, rubber composition,
or other suitable material is required for hot water or oil.
If a new pump will not start, it may be due to its imperfect connections or
temporary stiffness of pump.
Unless the suction lift and length of supply pipe be moderate, a foot-valve,
a charging connection, and a vacuum chamber are desirable. The suction-
pipe must be entirely free from air leakage. If the pump refuses to start
lifting water with full pressure on, on account of the air in the pump-cham-
ber not being dislodged, but only compressed each stroke, arrange for run-
ning without pressure until the air is expelled and water flows. This is
done with a check-valve in the delivery-pipe, and a waste delivery which
may be closed when water flows.
Pumping- Mot Water. — With a free suction-pipe, any good pump
fitted with metal valves and with hot-water packing will pump water hav-
ing a temperature of 212°, or higher, if so placed that the water will flow
into it.
Robert D. Kinney, in " Power," gives the following formula for deter-
i?11?.1]1^ ,to AVnat height water of temperatures below the boiling point can
be lifted by suction.
D — lift in feet,
A ■= absolute pressure on surface of water ; if open to air = 14.7 lbs.
B and W= constants. See table.
864
Water Temp.
B
Water Temp.
B
W.
Degrees F.
Degrees F.
40
0.122
62.42
130
2.215
61.56
50
0.178
62.41
140
2.879
61.37
60
0.254
62.37
150
3.708
61.18
70
0.360
62.31
160
4.731
60.98
80
0.503
62.23
170
5.985
60.77
90
0.693
62.13
180
7.511
60.55
100
0.942
62.02
190
9.335
60.32
110
1.267
61.89
200
11.526
60.07
120
1.6S5
61.74
210
14.127
59.82
Speed of Witter through Pump-Passages and Valves.
The speed of water flowing through pipes and passages in pumps varies
from 100 to 200 feet per minute. The loss from friction will be considerable
if the higher speed is exceeded.
The area of valves should be sufficient to permit the water to pass at a
speed hot exceeding 250 feet per minute.
The amount of steam which an average engine will require per indicated
horse-power is usually taken at 30 pounds. It varies widely, however, from
about 12 pounds in the best class of triple expansion condensing engines up
to considerably over 90 pounds in many direct-acting pumps. Where an
engine is overloaded or underloaded more water per horse-power will be re-
quired than when operated at rated capacity. Horizontal tubular boilers
will evaporate on an average from 2 to 3 pounds of water per square foot
heating-surface per hour, but may be forced up to 6 pounds if the grate sur-
face is too large or the draught too great for economical working.
Sizes of Direct-acting- Pumps.
The two following tables are selected as representing the two common
types of direct-acting pump, viz., the single-cylinder and the duplex.
Efficiency of Small Direct-acting- Pumps.
In "Reports of Judges of Philadelphia Exhibition," 1876, Group xx.,
Chas. E. Emery says : " Experiments made with steam-pumps at the Amer-
ican Institute Exhibition of 1867 showed that average size steam-pumps do
not, on the average, utilize more than 50 per cent of the indicated power in
the steam cylinders, the remainder being absorbed in the friction of the en-
gine, but more particularly in the passage of the water through the pump.
Again, all ordinary steam-pumps for miscellaneous use, require that the
steam-cylinder shall have three to four times the area of the water-cylinder
to give sufficient power when the steam is accidentally low ; hence, as such
pumps usually work against the atmospheric pressure, the net or effective
pressure forms a small percentage of the total pressure, which, with the
lame extent of radiating surface exposed and the total absence of expansion,
makes the expenditure of steam very large. One pump tested required 120
pounds weight of steam per indicated horse-power per hour, and it is be-
lieved that the cost will rarely fall below 60 pounds; and as only 50 per
cent of the indicated power is utilized, it may be safely stated that ordinary
steam pumps rarely require less than 120 pounds of steam per hour for each
horse-power utilized in raising water, equivalent to a duty of only 15,000.000
foot pounds per 100 pounds of coal. With larger steam-pumps, particularly
when they are proportioned for the work to be done, the duty will be mate-
rially increased.
865
Single-Cylinder ^Direct-acting- Pump.
(Standard Sizes for ordinary service.)
.3
,
©
ft
Diameter of
.9
-a
1
p
Capacity
©
©
o
O
a
per
Minute
£
A
3
©
©
©
at
Given
.3
.3
©
O
® ©
>
o
p
O
A
ft
£
Speed.
M O
"Si
a
©
p
©
©
ft
5
©
ft
©
bo
jt =
©
^
MB
o3 &
p p*
M
x
©
rf
M
©
O
P
ft
^
6
%
OQ O
H
H
OQ
P
02
s
4
3J
5
.14
300
130 18
33
9h
|
|
2
1J
4
4
5
.27
300
130 35
33
9h
2
li
5
4
7
.39
300
125 49
45J
15
s
1
3
2*
5}
5
7
.51
275
125 64
45J-
15
3
1
3
2J
5£
5*
7
.72
275
125 90
45J
15
|
1
3
2*
7
7
10
1.64
250
110 180
58
17
1
1*
5
4
7£
^2
10
1.91
250
110 210
58
17
n
5
4
7*
8
10
2.17
250
110 239
58
17
n
5
4
8
6
12
1.47
250
100 147
67
20i
n
4
4
8
7
12
2.00
250
100 200
67
20i
H
5
4
8
8
12
2.61
250
100 261
68
30'
n
5
5
8
10
12
4.08
250
100 408
68
20J
ij
8
8
10
8
L2
2.61
250
100 261
68i
30
1*
2*
2
5
5
10
10
12
4.08
250
100 408
68*
30
2
8
8
10
12
12
5.87
250
100 587
68*
30
2
8
8
12
10
12
4.08
250
100 408
64
24
21
8
8
12
10
18
6.12
200
70 428
"6Si
30
2
21
8
8
12
12
12
5.87
250
100 587
64
28*
2
2}
8
8
12
12
18
8.80
175
70 616
88
28i
2
2*
8
8
12
14
18
12.00
175
70 840
88
28l-
2
2J
8
8
14
10
12
4.08
250
100 408
69
30"
2
2*
8
8
14
10
18
6.12
175
70 428
93
25
2
2j
8
8
14
10
24
8.16
150
50 408
112
26
2
2i
2i
8
8
14
12
12
5.87
250
100 587
69
30
2
8
8
14
12
18
8.80
175
70 616
88
28J
2
2J
8
8
14
12
24
11.75
150
50 587
112
26"
2
2*
10
8
14
14
24
15.99
150
50 800
112
34
2
2J
12
10
14
16
16
13.92
175
80 1114
84
34
2
2*
12
10
14
16
24
20.88
150
50 1044
112
38
2
2*
12
10
16
14
IS
12.00
175
70 840
89
27
2
2j
8
8
16
14
24
15.99
150
50 800
109
34
2
2i
12
10
16
16
16
13.92
175
80 1114
85
34
2
24
12
10
16
16
24
20.88
150
50 1044
115
34
2
2*
12
10
16
18
24
26.43
125
50 1322
115
40
2
2}
14
12
18
16
24
20.88
125
50 1044
118 .
38
3
3*
12
10
18
18
24
26.43
125
50 1322
118
40
3
31
14
12
18
20
24
32.64
125
50 1632
118
40
3
3*
16
14
20
18
24
26.43
125
50 1322
118
40
3
3*
14
12
20
20
24
32.64
125
50 1632
118
40
3
3*
16
14
20
22
24
39.50
125
50 1975
120
40
3
3*
18
14
866
Duplex-Cylinder Direct-acting* Pump,
(Standard sizes for ordinary service.)
53
I
a>
£
o
-W M
cc
s o
o
a> a)
§5
be
.22 co
A
A
i-l
A
3
2
3
.04
4*
2f
4
.10
5*
3*
5
.20
6
4
6
.33
7*
7*
4*
6
.42
b
6
.51
it
10
.69
9
10
.93
10
6
10
1.22
10
7
10
1.66
12
7
10
1.66
14
7
10
1.66
12
8*
10
2.45
14
8*
10
2.45
16
8*
10
2.45
18*
8*
10
2.45
20
8*
10
2.45
12
10}
10
3.57
14
10*
10}
10
3.57
16
10
3.57
18*
KM-
10
3.57
20
io|-
10
3.57
14
12
10
4.89
16
12
10
4.89
18*
12
10
4.89
20
12
10
4.89
18*
14
10
6.66
20
14
10
6.60
17
10
15
5.10
20
L2
15
7.34
20
15
15
11.47
25
15
15
11.47
J2 ® o
2 5^
100 to 250
100 " 200
100 " 200
100 " 150
100 " 150
100 " 150
75 " 125
75 '
125
75 " 125
125
125
125
125
125
125
77
75 " 125
75 "• 125
75 " 125
75 " 125
75 " 125
75 " 125
75 " 125
100
£i
_ o .
0> d
•d = t
tjfc
:- ~ -
a-d
- = f:
"H
£*3
a?cc
P.43
■d *
bt^t
® 5° 0Q
53 33 S
> -on*
So|
~~Lv
^s
O
53 ■- 5
50
a3
S ^"D
rt^
- _ —
a
A
8 to
20
2-i
20"
40
4
40"
80
5
70"
100
5f
85"
125
6|
100"
150
7
100"
170
6|
135"
230
7*
180"
300
8*
245"
410
94
245 "
410
9£
245"
410
9*
365"
610
12
365"
610
12
365"
610
12
365"
610
12
365"
610
12
530"
890
141
14}
530"
S90
530"
890
14}
530"
890
14}
530"
890
14}
730"
1220
17
730"
1220
17
730"
1220
17
730"
1220
17
990"
1060
19|
990"
KifiO
19|
510"
1020
14
730"
1460
17
1145 "
2290
21
1145 "
2290
21
Sizes of Pipes for
Short Lengths.
To be Increased as
Length Increases.
INJECTORS.
Live Steam Injectors.
W= water injected in pounds her hour.
P = steam pressure in pounds per square inch.
Z> = diameter of throat in inches.
T= diameter of throat in millimeters.
INJECTORS.
867
Then W= 1280 D*Vp
= 1 .98 cP Vp
The rule given by Rankine, " Steam Engine," p. 477, for finding the proper
sectional area in square inches for the narrowest part of the nozzle is as
follows :
cubic feet per hour gross feed-water
area = .
800 » pressure m atmospheres
The expenditure of steam is about fourteen times the volume of water
injected.
The following table gives the water delivered for different sizes of injec-
tors at different pressures ; but when the injector has to lift its water a de-
duction must be made varying from 10 to 30 per cent according to the lift.
Deliveries for Iiive Steam Injectors.
o
Pressure of Steam.
1
•%,$>
ao5
M <S
30 lbs.
60 lbs.
80 lbs.
100 lbs.
120 lbs.
140 lbs.
fL, bj)
<S*~*
(D-'S
lS
Delivery in Gallons per B
our.
N —
In.
2
43
61
71
80
87
93
a
3
97
138
160
178
196
211
4
173
246
285
317
348
376
1
5
272
385
445
496
545
587
1
G
392
555
640
715
783
846
H
7
533
755
871
973
1067
1152
li
8
696
985
1137
1272
1393
1505
H
9
882
1247
1440
1610
1763
1905
H
10
1088
1540
1777
1987
2177
2352
2
11
1317
1863
2150
2405
2633
2846
2
12
1567
2217
2560
2861
3136
3387
2^
13
1840
2602
3005
3358
3680
3975
2}
14
2133
3018
3485
3895
4267
4610
15
2450
3465
4000
4471
4900
5292
2h
16
2787
3942
4551
5087
5575
6022
2|
17
3146
4450
5138
5713
6291
6798
oa
18
3527
4990
5760
6438
7055
7633
2|
19
3930
5560
6418
7175
7861
8492
93
20
4355
6160
7110
7950
8710
9410
3
5 inch, nearly.
As the vertical distance the injector lifts is increased, a greater steam
pressure is required to start the injector, and the highest steam pressure at
which it will work is gradually decreased.
If the feed-water is heated a greater steam pressure is required to start
the injector, and it will not work with as high steam pressure.
The'capacity of an injector is decreased as the lift is increased or the feed-
water heated.
.Performance of Injectors. — W. Sellers & Co. state that one of
their injectors delivered 25.5 lbs. water to a boiler per pound of steam ;
steam pressure G5 lbs.; temperature of feed, 64° F.
Schaeffer & Budenberg state that their injectors will deliver 1 gallon
water to a boiler for from 0.4 to 0.8 lbs. steam. Thev also state that the
temperatures of feed-water taken by their injector, if non-lifting or at a
low lift, can be as follows :
868 STEAM.
Pressure, lbs. . 35 to 45, 50 to 85, 90,105, 120, 135, 150.
Temperature, °F., 144 to 136, 133 to 130, 129, 122, 118 to 113, 109 to 105, 104 to 100.
The Haydeii & Derby Mfg. Co. state that the results given below are from
actual tests of Metropolitan Double-Tube Injectors.
With Cold Feed- Water.
n„ „ 9 f „At nft . I Starts with 14 lbs. steam pressure.
un a --ioor. nit . ^ Works up to 250 lbs. steam pressure.
On in s fnnt lift • i Starts with 23 lbs. steam pressure.
On an 8-ioot lift . j Workg up tQ 22Q lbg_ ^^ presgure>
On a 14-foot lift : j ^ai'ts with, 2? ">f: stefm pressure.
( Works up to 175 lbs. steam pressure.
On a 20-foot lift : j l^8 with, 42, "»• ste»m Pressure.
( Works up to 135 lbs. steam pressure.
Whpri nnt lifHno- • i Starts with 14 lbs. steam pressure.
When not lifting . j Workg up tQ 25Q lbg> gtea]£ pressure>
Witli reed-Water at 100° F.
On a 2-foot lift :
On an 8-foot lift :
Starts with 15 lbs. steam pressure.
Works up to 210 lbs. steam pressure.
Starts with 26 lbs. steam pressure.
Works up to 160 lbs. steam pressure.
r»„ ., i/i ts ~+ -\ivt- . ( Starts with 37 lbs. steam pressure.
On a 14-toot lift . j Workg up to 120 lbs> gteam presSure.
l Starts with 46 lbs. steam pressure.
{ Works up to 70 lbs. steam pressure.
On a 20-foot lift :
wv.™ r^*- nw„„ . S Starts witb 15 lbs. steam pressure.
When not lifting : -j Workg up to 210 lbg_ gteam pressurep
With Feed- Water at 130° F.
/-> o -p t-Tfi- ( Starts Avith 20 lbs. steam pressure.
On a 2-foot lift : j Works up to 185 lbs. steam pressure.
r> a * 4- v*+ S Starts with 30 lbs. steam pressure.
On an 8-toot lift : ^ Works up to 120 lbs. steam pressure.
/~w ,. . .,... ( Starts with 42 lbs. steam pressure.
On a 14-toot lift : j Works up to 75 lbs. steam pressure.
.„ri ...... ( Starts with 20 lbs. steam pressure.
When not lifting : j Works up to 185 lbs. steam pressure.
WTi*li Feed- Water at 140° F.
On a short lift or when not lifting, this injector will work with steam
pressures from 20 'lbs. to 120 lbs., and on an 8-foot lift with steam pressures
from 35 lbs. to 70 lbs. .
Fxhanst Inf ectors working with exhaust steam from an engine, at
about atmospheric pressure will deliver water against boiler pressure not
exceeding 80 lbs. per square inch. The temperature of the Avater may I e as
high as 190° F., while 12 per cent of the water delivered will be condensed
steam. For pressures over 80 lbs. it is necessary to supplement the exhaust
steam with a jet of live steam.
Injector vs. Pump for Feeding- Boilers.
The relative value of injectors, direct-acting steam pumps, and pumps
driven from the engine, is a question of importance to all steam-users. The
following table (" Stevens Indicator," 1888) has been calculated by D. S.
Jacobs, M. F., from data obtained by experiment. It will be noticed that
when feeding cold water direct to boilers, the injector has a slight economy,
but when feeding through a heater a pump is much the most economical.
INJECTORS.
869
Method of Supplying Feed-Water
to Boiler.
Relative Amount
Saving of Fuel
of Coal Required
over the
per Unit of Time,
Amount
Temperature of Feed-Water as
the Amount for a
Required
delivered to the Pump or to the
Direct-Acting
when the
Injector, 60° F. Rate of Evap-
Pump, Feeding
Boiler is Fed by
oration of Boiler, 10 lbs. of
Water at 6<P, with-
a Direct-
Water per pound of (Joai from
out a Heater, being
Acting Pump
and at 212° F.
taken as Unity.
without Heater.
Direct-acting pump feeding water
at 60°, without a heater ....
1.000
.0
Injector feeding water at 150°,
without a heater
.985
1.5 per cent.
Injector feeding through a heater
in which the water is heated
from 150° to 200°
.938
6.2
Direct-acting pump feeding water
through a heater, in which it is
heated from 60° to 200° ....
.879
12.1 "
Geared pump, run from the engine,
feeding Abater through a heater,
in which it is heated from 60° to
200°
.868
13.2 "
Sizes for Feed-loafer JPipes.
Three and six-tenths gallons of feed-water are required for each h. p. per
hour. This makes 6 gallons per minute for a 100 h. p. boiler. In proportion-
ing Dipes, however, it is well to remember that boiler-work is seldom per-
fectly steady, and that as the engine cuts off just as much steam as the work
demands at each stroke, all the discrepancies of demand and supply have to
be equalized in the boiler. Therefore we may often have to evaporate dur-
ing one-half hour 50 to 75 per cent more than the normal requirements. For
this reason it is sound policy to arrange the feed-pipes so that 10 gallons
per minute may flow through them, without undue speed or friction, for
each 100 h. p. of boiler capacity. The following tables will facilitate this
Avork.
TaMe Giving- Hate of Flow of Water, in Feet per Minute,
Through I*ipes of "Various Sizes, for \ arring-
(Quantities of Flow.
Gallons
per Min. ~4
in. 1 in.
liin.
l*in.
2 in.
2* in.
3 m.
4 in.
5
218 122*
78*
54*
30*
19*
13*
n
10
436 245
157
109
61
38
27
15*
15
653 367*
235*
163*
91*
58*
40*
23
20
872 490
314
218
122
78
54
30f
25
090 612*
392*
272J
152*
97*
67*
384
30
735
451
327
183
117
81
46
35
857*
549*
381*.
213*
136*
94*
53§
40
980
628
436
244
156
108
61*
45
. . 1102*
706*
490*
274*
175*
121*
69
50
785
545
305
195
135
76§
75
1177*
817*
457*
292*
202*
115
100
1090
610
380
270
153*
125
762*
487*
337*
191f
150
915
585
405
230
175
1067*
682*
472*
268*
200
1220
780
540
306|
870
Table Grivingr l,o^ in Pressure due to Friction, in Pounds
per Square Inch, for Pipe lOO JFeet long-.
(ByG. A.Ellis, C.E.)
Gallons
Dis-
charged
| in.
lin.
11 in.
1J in.
2 in.
21 in.
3 in.
4 in.
per Min.
5
3.3
0.84
0.31
0.12
10
13.0
3.16
1.05
0.47
0.12
15
28.7
6.98
2.38
0.97
20
50.4
12.3
4.07
1.66
0.42
25
78.0
19.0
6.40
2.62
0.21
0.10
30
27.5
9.15
3.75
0.91
35
37.0
12.4
5.05
40
48.0
16.1
6.52
1.60
45
20.2
8.15
50
24.9
10.0
2.44
0.81
0.35
0.09
75
56.1
22.4
5.32
1.80
0.74
100
39.0
9.46
3.20
1.31
0.33
125
14.9
4.89
1.99
150
21.2
7.0
2.85
0.69
175
28.1
9.46
3.85
200
37.5
12.47
5.02
1.22
JLoss of Head due to Bends.
Bends produce a loss of head in the flow of water in pipes. Weishach
gives the following formula for this loss :
H-=f — where H= loss of head in feet, / = coefficient of friction, v = ve-
locity of flow in feet per second, g r= 32.2.
As the loss of head or pressure is inmost cases more conveniently stated in
pounds per square inch, we may change this formula by multiplying by
0.433, which is the equivalent in pounds per square inch for one foot head.
If P = loss in pressure in pounds per square inch, F = coefficient of fric-
tion.
3 before.
From this formula has been calculated the following table of values for F,
corresponding to various exterior angles, A.
130°
0.934
This applies to such short bends as are found in ordinary fittings, such as
90° and 45° Ells, Tees, etc.
A globe valve will produce a loss about equal to two 90° bends, a straight-
way valve about equal to one 45° bend. To use the above formula find the
speed p. second, being one-sixtieth of t hat found in Table Xo. 35 ; square this
speed, and divide the result by 64.4; mhltiplg the quotient by the tabular
value ofk F corresponding to the angle of the turn, A.
For instance, a 400 h.p. battery of boilers is to be fed through a 2-inch pipe.
Allowing for fluctuations we figure 40 gallons per minute, making 244 feet
per minute speed, equal to a velocity of 4.6 per second. Suppose our pipe is
in all 75 feet long ; we have from Table No, 36, for 40 gallons per minute,
1.60 pounds loss ; for 75 feet we have only 75 per cent of this = 1.20 pounds.
Suppose Ave have 6 right-angled ells, each' giving F= 0.426. We have then
4.06 X 4.06= 16.48; divide this by 64.4 = 0,256. Multiply this by ^=0.420
A —
20°
40°
45°
60°
80°
90°
100°
110°
120°
f =
0.020
0.060
0.079
0.158
0.320
0.426
0.546
0.674
0,806
INJECTORS. 871
pounds, and as there are 6 ells, multiply again by 6, and we have 6 x 0.420 x
0.256 = 0.654. The total friction in the pipe is therefore 1.20 -4- 0.654 = 1.854
pounds per square inch. If the boiler pressure is 100 pounds and the water
level in the boiler is 8 feet higher than the pump suction level, we have first
8 X 0.433 = 3.464 pounds. The total pressure on the pump plunger then is
100+3.464 + 1.854= 105.32 pounds per square inch. If in place of 6 right-
angled ells we had used three 45° ells, they would have cost us only 3 X
0.079 = 0.237 pounds ; 0.237 X 0.256 = 0.061.
The total friction head would have been 1.20 + 0.061 = 1.261, ami the total
pressure on the plunger 100+ 3.464 + 1.261 = 104.73 pounds per square inch,
a saving over the other plan of nearly 0.6 pounds.
To be accurate, Ave ought to add a certain head in either case, "to produce
the velocity." But this is very small, being for velocities of :
2 ; 3 ; 4 ; 5 ; 6 ; 8 ; 10 ; 12 and 18 feet per sec.
0.027; 0.061; 0.108; 0.168 ; 0.244 ; 0.433; 0.672 ; 0.970 and 2.18 lbs. per sq. in.
Our results should therefore have been increased by about 0.11 pounds.
It is usual, however, to use larger pipes, and thus to materially reduce the
frictional losses.
yeed- Water Heaters are of the " open" or "closed" type.
The open heater is usually made of cast iron, as this material will with-
stand the corrosive action of acids found in feed-waters better than any
other metal. In this tvpe of heater the exhaust steam from engines and
pumps, and the feed-water broken up into drops by suitable means, are
brought into immediate contact, and the steam not condensed in heating
the water passes off to the atmosphere. The quantity of water that can be
heated is only limited by the amount of steam and water that can be
brought together. The steam condensed in heating the water is saved and
utilized for boiler feed. An open heater should be provided with an effi-
cient oil-separator, a large settling-chamber or hot well in which, if desired,
a filtering bed of suitable material can be placed to insure the removal from
the water, of all the impurities held in suspension, a device for skim-
ming the surface of the water to remove the impurities floating on the water,
and a large blow-off opening placed at the lowest point in the heater.
The closed heater is made with a wrought-iron or steel cylindrical shell
and cast- or wrought-iron heads, having iron or brass tubes inside, set in
tube plates so as to make steam- and water-tight joints, provision being made
for the expansion and contraction of the tubes. According to the particular
design of the heater, the exhaust steam passes through or around the tubes,
the water being on the opposite of the walls of the tubes. The steam and
water are separated by metal through which the heat of the exhaust steam
is transmitted to the water. As an oil-separator is very seldom attached to
a closed heater, the steam condensed in heating the water is wasted. The
quantity of water that can be heated is limited by the amount of heat that
can be transmitted through the tubes. The efficiency of heat transmission
is decreased by the coating of oil that covers the steam side, and the crust
of scale that coats the water side of the tubes. No provision can be made
for purifying the water in a closed heater, as the constant circulation of the
water prevents the impurities from settling. The impurities that are in the
water pass on into the boiler. Purification must be done by means of an
auxiliary apparatus.
Saving- \>y Heating- Teed-"Water.
(W. W. Christie.)
In converting water at 32° F. into steam at atmospheric pressure, it must
be raised to 212° F., the boiling point.
The specific heat of water varies somewhat with its temperature, so that to
raise a pound of water from 32° to 212° F. or 180° F., requires 180.8 heat
units.
To convert it into steam, after it has reached 212° F., requires 965.8 heat
units, or in all 180.8 + 965.8 == 1146.6 units of heat, thermal units.
The saving to be obtained by the use of waste heat, as exhaust steam,
heating the water by transfer of some of its heat through metal walls, is
calculated by this formula :
»
872
r, ■ • « 100 (ft, — ft,) 100 (t2 — ty) ,
Gam m per cent = — r, , — - =r _r ; , ol, very nearly,
ri — II i ii — f i ~r" 3-s
in which H= total heat in steam at boiler pressure (above that in water at
32° F.) in B. T. U.
h2 = heat in feed-water (above 32° F.) after heating.
hx = heat in feed- water (above 32° F.) before beating.
t2 = temperature of feed-water after heating °F.
t^ =z temperature of feed-water before heating °F.
given H= 1146.6, t2 = 212, fx = 112, or a difference of 100°; and we obtain by
use of the above formula, gain in per cent = 9.37, or for 10° approximately
.937 per cent, for 11° 1.03 per cent, so we may say that for every 11° F. added
to the feed-water temperature by use of the exhaust steam, 1 per cent of
fuel saving results.
The table which follows is taken from " Power."
Percentag-e of Saving- in Fuel tor Heating- feed-Water toy
V^aste Steam, Steam at SO Pound!* Oaug-e Pressure.
- o
•2 3
= S
■ v
Temperature of Water Entering Boiler,
120:
V.HP
140°
150°
160°
170°
180°
190°
200°
210°
220°
250°
35°
7.24
8.09
8.95
9.89
10.66
11.52
12.38
13.24
14.09
14.95
15.81
19.40
40°
0.X4
7.6:)
8.56
9.42
10.28
11.14
12.00
12.87
13.73
14.59
15.45
18.89
45°
6.44
7.31)
8.16
9.03
9.90
10.76
11.62
12.49
13.36
14.22
15.09
18.37
50°
(5.03
6.8!)
7.76
8.64
9.51
10.38
11.24
12.11
12.98
13.85
14.72
17.87
55°
5.63
6.4!)
7.37
8.24
9.11
9.99
10.85
11.73
12.60
13.48
14.35
17.38
60°
5.21
COS
6.96
7.84
8.72
9.60
10.47
11.34
12.22
13.10
13.98
16.8G
65°
4.80
5.(!7
6.56
7.44
8.32
9.20
10.08
10.96
11.84
12.72
13.60
16.35
70J
4.38
5.21)
6.15
7.03
7.92
8.80
9.68
10.57
11.45
12.34
13.22
15.84
75°
3.1)6
4.S4
5.73
6.62
7.51
8.40
9.28
10.17
11.06
11.95
12.84
15.33
80°
3.54
4.42
5.32
6.21
7.11
8.00
8.88
9.78
10.67
11.57
12.46
14.82
85°
3.11
4.00
4.90
5.80
6.70
7.59
8.48
9.38
10.28
11.18
12.07
14.32
90°
2. (IS
3.5S
4.48
5.38
6.28
7.18
8.07
8.98
9.88
10.78
11.68
13.81
95°
2.25
3.15
4.05
4.96
5.86
6.77
7.66
8.57
9.47
10.38
11.29
13.31
100°
1.81
2.71
3.62
4.53
5.44
6.35
7.25
8.16
9.07
9.98
10.88
12.80
Pump Exhaust.
In many plants the only available exhaust steam comes from the steam
pumps used for elevator service, boiler-feeding, etc. ; or in condensing plants
from the air-pumps, water-supply, and boiler feed-pumps. It should also be
remembered that all direct-acting steam pumps are large consumers of
steam, taking several boiler h.p. for each indicated h. p., and that the ex-
haust steam from them will heat about six times the same quantity by weight
of cold water, from 50° to 212° F., and that these pumps, or the independent
condenser pumps, are more economical when all the exhaust from them is
used for heating feed-water than the best kind of triple expansion condens-
ing engines. With the pumps all the heat not used in doing work can be
conserved and returned to the boiler in the feed-water, whereas even with
triple expansion engines at least 80 per cent of the total heat in the steam is
carried away in the condensing water.
While the supply of exhaust from these pumps may not be sufficient to
raise the temperature to the highest point, yet the saving is large and con-
stant.
These results do not take any account of the purifying action in the
"open" heaters on the feed-water, the improved condition of which, by di-
minishing the average deposit within the boiler, materially increases both
the boiler capacity and the economy ; while the more uniform temperature
FUEL ECONOMIZER.
873
accompanying the use of a hot feed reduces the repairs and lengthens the
life of all boilers.
If the quantity of water passing through the heater is only what is re-
quired to furnish steam for the engine from which the exhaust comes, more
than four-fifths of this exhaust steam will remain uncondensed, and Avill
thus become available for other purposes, such as heating buildings, dryer
systems, etc. ; in which case the returns can be sent back to the boiler by
suitable means.
Fl'El ECOaiOMIZERS.
Performance of a Green Economizer with a Smoky Coal.
(D. K. Clark, S. E., p, 286.)
From tests by M. W. Grosseteste, covering a period of three weeks on a
Green economizer, using a smoke-making coal, with a constant rate of com-
bustion under the boilers, it is apparent that there is a great advantage in
cleaning the pipes daily — the elevation of temperature having been in-
creased by it from 88° to 153°. In the third week, without cleaning, the ele-
vation of temperature relapsed in three days to the level of tbe first week ;
even on the first day it was quickly reduced by as much as half the extent
of relapse. By cleaning the pipes daily an increased elevation of tempera-
ture of 65° F. was obtained, whilst a gain of 6% was effected in the evapora-
tive efficiency.
The action of Green's economizer was tested by M. W. Grosseteste for a
period of three weeks. The apparatus consists of four ranges of vertical
pipes, 6i feet high, 3f inches in diameter outside, nine pipes in each range,
connected at top and bottom by horizontal pipes. The water enters all the
tubes from below, and leaves them from above. The system of pipes is
enveloped in a brick casing, into which the gaseous products of combustion
are introduced from above, and which they leave from below. The pipes
are cleared of soot externally by automatic scrapers. The capacity for
water is 24 cubic feet, and the total external heating-surface is 290 square
feet. The apparatus is placed in connection witb a boiler having 355 square
feet of surface.
Green's Economizer. — Results of Experiments on its Efficiency as Affected
by the State of the Surface.
(W. Grosseteste.)
Temperature of Feed-
Temperatnre of Gas-
water.
eous Products.
Time.
February and March.
Enter-
Leav-
Enter-
Leav-
ing
Feed-
ing
Differ-
ing
ing
Differ-
Feed-
ence.
Feed-
Feed-
ence.
heater.
heater.
heater.
heater.
Fahr.
Fahr.
Fahr.
Fahr.
Fahr.
Fahr.
1st Week
73.5°
161.5°
88.0°
849°
261°
588°
2d Week
77.0
230.0
153.0
882
297
585
3d Week — Monday . .
73.4
196.0
122.6
831
284
547
Tuesday . .
73.4
181.4
108.0
871
309
562
Wednesday
79.0
178.0
99.0
Thursday .
80.6
170.6
90.0
952
329
623
Friday . .
80.6
169.0
88.4
889
338
551
Saturday
79.0
172.4
93.4
901
351
550
1st Week.
Coal consumed per hour 214 lbs.
Water evaporated from 32° F. per hour 1424
Water per pound of coal ...... 6.65
2d Week. 3d Week.
216 lbs. 213 lbs.
1525 1428
7.06 6.70
874
The Fuel Economizer Company, Matteawan, N.Y., describe the construc-
tion of Green's economizer, thus: The economizer consists of a series of sets
of cast-iron tubes about 4 inches in diameter and 9 feet in length, made in
sections (of various widths) and connected by " top " and " bottom headers,"
these again being coupled by " top " and " bottom branch pipes " running
lengthwise, one at the top and the other at the bottom, on opposite sides
and outside the brick chamber which encloses the apparatus. The waste
gases are led to the economizer by the ordinary flue from the boilers to the
chimney.
The feed-water is forced into the economizer by the boiler pump or in-
jector, at the lower branch pipe nearest the point of exit of gases, and
emerges from the economizer at the upper branch pipe nearest the point
where the gases enter.
Each tube is provided with a geared scraper, which travels continuously
up and down the tubes at a slow rate of speed, the object being to keep the
external surface clean and free from soot, a non-conductor of heat.
The mechanism for working the scrapers is placed on the top of the econ-
omizer, outside the chamber, and the motive power is supplied either by a
belt from some convenient shaft or small independent engine or motor.
The power required for operating the gearing, however, is very small.
The apparatus is fitted with blow-off and safety valves, and a space is pro-
vided at the bottom of the chamber for the collection of the soot, which is
removed by the scrapers.
One boiler plant equipped with the Green economizer gave, under test,
these results.
The total area of heating surface in the plant was 3,126 square feet, and
the number of tubes in the economizer 160. The results were as follows: —
Particulars of Test.
Econo-
mizer
working,
Dec. 15.
Econo-
mizer not
working,
Dec. 16.
Duration of test hours
Weight of dry coal consumed lbs.
Percentage of' ash and refuse . . . per cent
"Weight of coal consumed per hour per square
foot grate surface lbs.
Weight of water evaporated lbs.
Horse-power developed on basis of 30 lbs. per
h.p. fed at 100° and evaporated at 70 lbs., h.p.
Average boiler pressure (above atmosphere),
lbs.
Average temperature of feed-water entering
economizer deg. Fahr.
Average temperature of feed-water entering
boilers deg. Fahr.
Number of degrees feed-water was heated by
economizer deg. Fahr.
Average temperature of flue gases entering
economizer deg. Fahr.
Average temperature of flue gases entering
chimney deg. Fahr.
Number degrees flue gases were cooled by econ-
omizer deg. Fahr.
Lbs. water evaporated per lb. of coal, as ob-
served
Equivalent evaporation per lb. of coal from
and at 212°
Percentage gained by using the economizer
per cent
11.5
8,743
15.2
84,078
11.5
,694
7.7
16.8
82,725
84.2
196.2
82.0
112.
435.
279.
452.0
156.
9.617
8.533
11.204
9.955
12.5
The steam in this test contained 1.3 per cent of moisture.
I UEL ECONOMIZERS,
875
M. W. S. Hutton gives the following results of tests of a steam boiler
with and without an economizer.
With Econ-
omizer.
Without
Econo-
mizer.
Duration of test, hours
Weight of coal, pounds
Steam pressure, pounds
Temp, water entering economizer, degrees . . .
" " " boiler, degrees
Degrees feed-water heated by economizer . . .
Temp, gases entering economizer, degrees . . .
" " " chimney, degrees ....
Degrees gases cooled by economizer
Evaporation per lb. coal, from and at 212°, pounds
Saving by economizer, per cent
HI
7856
58
88
225
137
618
365
253
10.613
28.9
10282
57
Green's Fuel Economizer, — Clark gives the following average re-
sults of comparative trials of three boilers at Wigan used with and without
economizers :
Coal per square foot of grate per hour .
Water at 100° evaporated per hour . .
Water at 212° per pound of coal . . .
Without
Economizers.
. . 21.6
. . 73.55
. . 9.60
With
Economizers.
. 79.32
10.56
Showing that in burning equal quantities of coal per hour the rapidity of
evaporation is increased 9.3% and the efficiency of evaporation 10% by the
addition of the economizer.
The average temperature of the gases and of the feed-water before and
after passing the economizer were as follows :
With 6-f t. grate. With 4-ft. grate.
Before. After. Before. After.
Average temperature of gases . . • 649 340 501 312
Average temperature of feed-water . 47 157 41 137
Taking averages of the two grates, to raise the temperature of the feed-
water 100°, the gases were cooled down 250°.
§EPARATORS.
Carefully conducted experiments have shown that water, oil, or other
liquids passing through pipes along with steam do not remain thoroughly
mixed with the steam itself, but that the major portion of these liquids fol-
lows the inner contour of the pipe, especially in the case of horizontal
pipes.
From this it would necessarily follow that a rightly designed separator to
meet these conditions must interrupt the run of the liquid by breaking the
continuity of the pipe, and offering a receptacle into which the liquid will
flow freeiv, or fall bv gravity — that this appliance must further offer the
opportunity for the liquid to come to rest out of the current of steam, for it
is not enough to simplv provide a well or a tee in the pipe, since the current
would jump or draw the liquid over this opening, especially if the velocity
was high.
It is also evident that means must be provided in this appliance for inter-
rupting the progress of those particles of the liquid which are traveling in
the current of the steam, and do this in such a way that these particles will
876
also be detained and allowed to fall into the receptacle provided, which
receptacle must be fully protected from the action of the current of the
steam ; otherwise, the separated particles of water or oil will be picked
up and carried on past the separator.
To prevent the current from jumping the liquid over the well, and to
interrupt the forward movement of those particles traveling in or with the
current, it follows that some obstruction must be interposed in the path of
the current.
Steam separators should always be placed as near as possible to the steam
inlet to the cylinder of the engine. Oil separators are placed in the run of
the exhaust pipe from engines and pumps, for the purpose of removing the
oil from the steam before it is used in any way where the presence of oil
would cause trouble.
Prof. R. C. Carpenter conducted a series of tests on separators of several
makes in 1891. The following table shows results under various conditions
of moisture :
A.
Test with Steam of about 10%
of Moisture.
Tests with Varying Moisture.
i
Quality of
Steam
Before.
Quality of
Steam
After.
Efficiency
per cent.
Quality of
Steam
Before.
Quality of
Steam
After.
Average
Efficiency.
B
A
D
C
E
F
87.0%
90.1
89.6
90.6
88.4
88.9
98.8%
98.0
95.8
93.7
90.2
92.1
90.8
80.0
59.6
33.0
15.5
28.8
66.1 to 97.5%
51.9 " 98
72.2 " 96.1
67.1 " 96.8
68.6 " 98.1
70.4 " 97.7
97.8 to 99 %
97.9 " 99.1
95.5 " 98.2
93.7 " 98.4
79.3 " 98.5
84.1 " 97.9
87.6
76.4
71.7
63.4
36.9
28.4
Conclusions from the tests were : 1. That no relation existed between the
volume of the several separators and their efficiency.
2. No marked decrease in pressure was shown by any of the separators,
the most being 1.7 lbs. in E.
3. Although changed direction, reduced velocity, and perhaps centrifugal
force are necessary for good separation, still some means must be provided
to lead the water out of the current of the steam.
A test on a different separator from those given above was made by Mr.
Charles H. Parker, at the Boston Edison Company's plant, in November,
1897, and the following results obtained :
Length of run 3-4 hrs.
Average pressure of steam 158 lbs. per sq. in.
Temperature of upper thermometer in calorimeter on
outlet of separator 368.5° F.
Temperature of lower thermometer in calorimeter on
outlet of separator 291.7° F.
Normal temperature of lower thermometer, when steam
is at rest 292.9° F.
Degrees cooling as shown by lower thermometer . . . 1.2° F.
Moisture in steam delivered by separator as shown by
cooling of lower thermometer 06 per cent.
"Water discharged from separator per hour 52 lbs.
Steam and entrained water passing through engine, as
shown by discharge from air pump of surface con-
denser 7359 lbs.
Steam and entrained water entering separator .... 7411 lbs.
Moisture taken out by separator 72
Total moisture in steam (.06 plus .72) 78 per cent.
Efficiency of separator 92.3 per cent.
SAFETY VALVES. Oil
SAFETY VALVES.
Calculation of Weight, etc., for lever Safety- Valve.
Let JF= weight of ball at end of lever, in pounds ;
■w = weight of lever itself, in pounds ;
V=: weight of valve and spindle, in pounds ;
L = distance between fulcrum and center of ball, in inches ;
I =z distance between fulcrum and center of valve, m inches ;
g — distance between fulcrum and center of gravity of lever, in inches;
A = area of valve, in square inches ; .
P = pressure of steam, in pounds per square inch at whicU valve will
open.
Then PAxl = W X L 4- w X g + VXl;
whence P -
WL + wg +
VI
Al
PAl-
-wg —
VI
L
PAl-
-tog —
VI
Example. — Diameter of valve, 4 inches ; distance from fulcrum to center
of ball, 36 inches ; to center of valve, 4 inches ; to center of gravity of lever,
16 inches ; weight of valve and spindle, 6 lbs. ; weight of lever, 10 lbs. ; re-
quired the weight of ball to make the blowing-olf pressure 100 lbs. per
square inch ; area of 4-inch valve = 12.566 square inches. Then
Pjjl — tyg— VI _ 100 X 12.566 X4— 10x16 — 6x4 _
134.5 lbs.
Rules Governing- Safety- Valves.
(Rule of U. S. Supervising Inspectors of Steam-vessels as amended 1894.)
The distance from the fulcrum to the valve-stem must in no case be less
than the diameter of the valve-opening ; the length of the lever must not be
more than ten times the distance from the fulcrum to the valve-stem ; the
width of the bearings of the fulcrum must not be less than three-quarters
of an inch ; the length of the fulcrum-link must not be less than four inches;
the lever and fulcrum-link must be made of wrought iron or steel, and the
knife-edged fulcrum points and the bearings for these points must be made
of steel and hardened ; the valve must be guided by its spindle, both above
and below the ground seat and above the lever, through supports either
made of composition (gun-metal) or bushed with it ; and the spindle must
fit loosely in the bearings or supports.
Lever safety-valves to be attached to marine boilers shall have an area of
not less than 1 square inch to 2 square feet of the grate surface in the
boiler, and the seats of all such safety-valves shall have an angle of inclina-
tion of 45° to the center line of their axes.
Spring-loaded safety-valves shall be required to have an area of not less
than 1 square inch to 3 square feet of grate surface of the boiler, except as
hereinafter otherwise provided for water-tube or coil and sectional boilers,
and each spring-loaded valve shall be supplied with a lever that will raise the
valve from its seat a distance of not less than that equal to one-eighth the
diameter of the valve-opening, and the seats of all such safety-valves shall
have an angle of inclination to the center line of their axes af 45°. All
spring-loaded safety-valves for water-tube or coil and sectional boilers
required to carry a steam-pressure exceeding 175 lbs. per square inch shall
be required to have an area of not less than 1 square inch to 6 square feet
of the grate surface of the boiler. Nothing herein shall be construed so as to
prohibit the use of two safety-values on one water-tube or coil and sectional
boiler, provided the combined area of such valves is equal to that required
by rule for one such valve.
Rule on Safety- Valves in Philadelphia Ordinances.—
Every boiler when tired separately, and every set or series of boilers when
placed over one tire, shall have attached thereto, without the interposition
of any other valve, two or more safety-valves, the aggregate area of which
shall have such relations to the area of the grate and the pressure within
the boiler as is expressed in schedule A.
Schedule A. — Least aggregate area of safety-valve (being the least sec-
tional area for the discharge of steam) to be placed upon all stationary
boilers with natural or chimney draught (see note a).
A- 22-5g
P + 8.62'
in which A is area of combined safety-valves in inches ; G is area of grate in
square feet ; P is pressure of steam in pounds per square inch to be carried
in the boiler above the atmosphere.
The following table gives the results of the formula for one square foot of
grate, as applied to boilers used at different pressures :
Pressures per square inch :
10 20 30 40 50 60 70 80 90 100 110 120 150 175
Valve area in square inches corresponding to one square foot of grate :
1.2 .79 .58 .46 .38 .33 .29 .25 .23 .21 .19 .17 .14 .12
[Note a.] — Where boilers have a forced or artificial draught, the inspec-
tor must estimate the area of grate at the rate of one square foot of grate
surface for each 16 lbs. of fuel burned on the average per hour.
The various rules given to determine the proper area of a safety-valve do
not take into account the effective discharge area of the valve. A correct
rule should make the product of the diameter and lift proportional to the
weight, of steam to be discharged.
Mr. A. G. Brown (The Indicator and its Practical Working) gives the fol-
lowing as the lift of the lever safety-valve for 100 lbs. gauge 'pressure. Tak-
ing the effective area of opening at 70 per cent of the product of the rise and
the circumference
Diameter of valve, inches 2 1\ 3 Zl 4 4J 5 6
Rise of valve, inches . . .0583 .0523 .0507 .0492 .0478 .0462 .0446 .043
For " pop " safety-valves, Mr. BroAvn gives the following table for the
rise, effective area, "and quantity of steam discharged per hour, taking the
effective area at 50 per cent of the actual on account of the obstruction
which the lip of the valve offers to the escape of the steam.
Dia. value,
in Lift,
Inches.
Area, sq.in.
1
n
2
21
3
3£
4
H
5
6
.125
.150
.175
.200
.225
.250
.275
.300
.325
.375
.196
.354
.550
.785
1.061
1.375
1.728
2.121
2.553
3.535
Gauge-
press.
Steam discharged per hour, lbs.
30 lbs.
474
856
1330
1897
2563
3325
4178
5128
6173
8578
50
669
1209
1878
2680
3620
4695
5901
7242
8718
120/0
70
861
1556
2417
3450
4660
6144
7596
9324
11220
15535
90
1050
1897
2947
4207
5680
7370
9260
11365
13685
18945
100
1144
2065
3208
4580
6185
8322
10080
12375
14895
20625
120
1332
2405
3736
5332
7202
9342
11735
14410
17340
24015
140
1516
2738
4254
6070
8200
10635
13365
16405
19745
27340
160
1696
3064
4760
6794
9175
11900
14955
18355
22095
30595
180
1883
3400
5283
7540
10180
l :;•_';-,()
16595
20370
2*520
33950
200
2062
3724
5786
8258
11150
14465
18175
22310
26855
37185
If we also take 30 lbs. of steam per hour, at 100 lbs. gauge-pressure =
h. p., we have from the above table :
Diameter inches . 1 l£- 2 2£ 3 ft . 4 4£ 5 6
Horse-power . . 38 69 107 153 206 277 336 412 496 687
RULES FOR CONDUCTING BOILER TESTS.
879
A boiler having ample grate surface and strong draft may generate
double the quantity of steam its rating calls for ; therefore in determining
the proper size of safety-valve for a boiler this fact should be taken into
consideration and the effective discharge of the valve be double the rated
steam-producing capacity of the boiler.
The Consolidated Safety-valve Co.'s circular gives the following rated
capacity of its nickel-seat " pop " safety-valves :
Size, in . .
1
H
1*
2
2h
3
3*
4
Q
5
5i
Boiler f from
8
10
20
35
60
75
100
125
150
175
200
H.P. | to
10
15
30
50
75
100
125
150
175
200
275
BUIE8 JPOK COHDUCTIJIG BOILER TESTS.
The Committee of the A. S. M. E. on Boiler-tests recommended the fol-
lowing revised code of rules for conducting boiler trials. (Trans, vol. xx.)
Code of 1897.
Preliminaries to a Trial.
I. Determine at the outset the specific object of the proposed trial, whether
it be to ascertain the capacity of the boiler, its efficiency as a steam gener-
ator, its efficiency and its defects under usual working conditions, the econ-.
omy of some particular kind of fuel, or the effect of changes of design,
proportion, or operation ; and prepare for the trial accordingly.
II. Examine the boiler, both outside and inside ; ascertain the dimensions
of grates, heating surfaces, and all important parts ; and make a full
record, describing the same, and illustrating special features by sketches.
The area of heating surfaces is to be computed from the outside diameter of
water-tubes and the inside diameter of fire-tubes. All surfaces below the
mean water level Avhichhave water on one side and products of combustion
on the other are to be considered water-heating surface, and all surfaces
above the mean water level which have steam on one side and products of
combustion on the other are to be considered as superheating surface.
III. Notice the general condition of the boiler and its equipment, and
record such facts in relation thereto as bear upon the objects in view.
If the object of the trial is to ascertain the maximum economy or capa-
city of the boiler as a steam generator, the boiler and all its appurtenances
should be put in first-class condition. Clean the heating surface inside and
outside, remove clinkers from grates and from sides of the furnace. Re-
move all dust, soot, and ashes from the chambers, smoke connections, and
flues. Close air leaks in the masonry and poorly-fitted cleaning-doors. See
that the damper will open wide and close tight. Test for air leaks by firing
a few shovels of smoky fuel and immediately closing the damper, observing
the escape of smoke through the crevices, or by passing the flame of a can-
dle over cracks in the brickwork.
IV. Determine the character of the coal to be used. For tests of the effi-
ciency or capacity of the boiler for comparison with other boilers the coal
should, if possible, be of some kind which is commercially regarded as a stan-
dard. For New England and that portion of the countrv east of the Allegheny
Mountains, good anthracite egg coal, containing not over 10 per cent of ash,
and semi-bituminous Clearfield (Pa.), Cumberland (Md.), and Pocahontas
(Va.) coals are thus regarded. West of the Allegheny Mountains, Poca-
hontas (Va.), and New River (W. Va.) semi-bituminous,' and Youghiogheny
or Pittsburg bituminous coals are recognized as standards.* Thereds no
special grade of coal mined in the Western States which is widely recog-
nized as of superior quality or considered as a standard coal for boiler test-
ing. Big Muddy Lump, an Illinois coal mined in Jackson County, 111., is
* These coals are selected because they are about the only coals which con-
tain the essentials of excellence of quality, adaptability to various kinds of
furnaces, grates, boilers, and methods of firing, and icide distribution and
general accessibility in the markets.
880
sug.sje.sted as being of sufficiently high grade to answer the requirements in
districts where it is more conveniently obtainable than the other coals men-
tioned above.
For tests made to determine the performance of a boiler with a particular
kind of coal, such as may be specified in a contract for the sale of a boiler,
the coal used should not be higher in ash and in moisture than that speoi-
fied, since increase in ash and moisture above a stated amount is apt to
cause a falling off of both capacity and economy in greater proportion than
the proportion of such increase.
V. Establish the correctness of all apparatus used in the test for weighing
and measuring. These are :
1. Scales for weighing coal, ashes, and water.
2. Tanks, or water meters for measuring water. Water meters, as a rule,
should only be used as a check on other measurements. For accurate work,
the water should be weighed or measured in a tank.
3. Thermometers and pyrometers for taking temperatures of air, steam,
feed-water, waste gases, etc.
4. Pressure gauges, draft gauges, etc.
The kind and location of the various pieces of testing apparatus must be
left to the judgment of the person conducting the test; always keeping in
mind the main object, i.e., to obtain authentic data.
VI. See that the boiler is thoroughly heated before the trial to its usual
working temperature. If the boiler is new and of a form provided with a
brick setting, it should be in regular use at least a week before the trial,
so as to dry and heat the walls. If it has been laid off and become cold, it
should be worked before the trial until the walls are well heated.
VII. The boiler and connections should be proved to be free from leaks
before beginning a test, and all water connections, including blow and extra
feed pipes, should be disconnected, stopped with blank flanges, or bled '
through special openings beyond the valves, except the particular pipe
through which water is to be fed to the boiler during the trial. During the
test the blow-off and feed-pipes should remain exposed.
If an injector is used, it should receive steam directly through a felted
pipe from the boiler being tested.*
If the water is metered after it passes the injector, its temperature should
be taken at the point at which it enters the boiler. If the quantity is deter-
mined before it goes to the injector, the temperature should be determined
on the suction side of the injector, and if no change of temperature occurs
other than that due to the injector, the temperature thus determined is
properly that of the feed-water. When the temperature changes between
the injector and the boiler, as by the use of a heater or by radiation, the
temperature at which the water enters and leaves the injector and that at
which it enters the boiler should all be taken. The final temperature cor-
rected for the heat received from the injector will be the true feed-water
temperature. Thus if the injector receives water at 50° and delivers it at
12u° into a heater which raises it to 210°, the corrected temperature is 210 —
(120 — 50)= 140°.
See that the steam main is so arranged that water of condensation can-
not run back into the boiler.
VIII. Starting and Stopping a Test. — A test should last at least ten hours
of continuous running, but, if the rate of combustion exceeds 25 pounds of
coal per square foot of grate per hour it may be stopped when a total of 250
pounds of coal has been burned per square foot of grate surface. A longer
test may be made when it is desired to ascertain the effect of widely vary-
ing conditions, or the performance of a boiler under the working conditions
of a prolonged run. The conditions of the boiler and furnace in all respects
should be, as nearly as possible, the same at the end as at the beginning of
the test. The steam pressure should be the same ; the water level the
* In feeding a. boiler undergoing test with an injector talcing steam from
another boiler, or the main steam pipe from several boilers, the evaporative,
results may be modified by a difference in the quality of the steam from such
source compared with that supplied by the boiler being tested, and in some
cases the connection to the injector may act as a drip for the main steam pipe.
If it is known that the steam' from the main pipe is of the same quality as that
furnished by the boiler undergoing the test, the steam may be taken from such
main pipe.
RULES FOR CONDUCTING BOILER TESTS. 881
same ; the fire upon the grates should he the same in quantity and condi-
tion ; and the walls, flues, etc., should be of the same temperature. Two
methods of obtaining the desired equality of conditions of the fire may be
used, viz. : those which were called in the Code of 1885 " the standard
method " and " the alternate method," the latter being employed where it
is inconvenient to make use of the standard method.
IX. Standard Method. — Steam being raised to the working pressure,
remove rapidly all the fire from the grate, close the damper, clean the ash-
pit, and as quickly as possible start a new fire with weighed wood and coal,
noting the time and the water level while the water is in a quiescent state,
just before lighting the fire.
At the end of the test remove the whole fire, which has been burned low,
clean the grates and ash-pit, and note the water level when the water is in
a quiescent state, and record the time of hauling the fire. The water level
shuuld be as nearly as possible tbe same as at the beginning of the test.
If it is not the same, a correction should be made by computation, and not
by operating the pump after the test is completed.
X. Alternate Method. — The boiler being thoroughly heated by a prelimi-
nary run, the fires are to be burned low and well cleaned. Note the amount
of coal left on the grate as nearly as it can be estimated ; note the pressure
of steam and the water level, and note this time as the time of starting the
test. Fresh coal which has been weighed should now be fired. The ash-
pits should be thoroughly cleaned at once after starting. Before the end of
the test the fires should be burned low, just as before the start, and the
fires cleaned in such a manner as to leave the bed of coal of the same
depth, and in the same condition, on the grates, as at the start. The
water level and steam pressures should previously be brought as nearly as
possible to the same point as at the start, and the time of ending of the test
should be noted just before fresh coal is fired. If the water level is not the
same as at. the start, a correction should be made by computation, and not
by operating the pump after the test is completed.
XI. Uniformity of Conditions. — In all trials made to ascertain maximum
economy or capacity, the conditions should be maintained uniformly con-
stant. Arrangements should be made to dispose of the steam so that the
rate of evaporation may be kept the same from beginning to end. This
may be accomplished in a single boiler by carrying the steam through a
waste steam pipe, the discharge from which can be regulated as desired.
In a battery of boilers, in which only one is tested, the draft can be regu-
lated on the remaining boilers, leaving the test boiler to work under a con-
stant rate of production.
Uniformity of conditions should prevail as to the pressure of steam, the
height of water, the rate of evaporation, the thickness of fire, the times of
firing and quantity of coal fired at one time, and as to the intervals between
the times of cleaning the fires.
XII. Keeping the Heco?-ds. — Take note of every event connected with the
progress of the trial, however unimportant it may appear. Record the
time of every occurrence and the time of taking every weight and every
observation.
The coal should be weighed and delivered to the fireman in equal propor-
tions, each sufficient for not more than one hour's run, and a fresh portion
should not be delivered until the previous one has all been fired. The time
required to consume each portion should be noted, the time being recorded
at the instant of firing the last of each portion. It is desirable that at the
same time the amount of water fed into the boiler should be accurately
noted and recorded, including the height of the water in the boiler, and the
average pressure of steam and temperature of feed during the time. By
thus recording the amount of water evaporated by successive portions of
coal, the test may be divided into several periods if desired, and the degree
of uniformity of combustion, evaporation, and economy analyzed for each
period. In addition to these records of the coal and the feed-water, half
hourly observations should be made of the temperature of the feed-water,
of the flue gases, of the external air in the boiler-room, of the temperature
of the furnace when a furnace pyrometer is used, also of the pressure of
steam, and of the readings of the* instruments for determining the moisture
in the steam. A log should be kept on properly prepared blanks containing
columns for record of the various observations.
When the " standard method " of starting and stopping the test is used,
882
the hourly rate of combustion and of evaporation and the horse-power may-
be computed from the records taken during the time when the tires are in
active condition. This time is somewhat less than the actual time which
elapses between the beginning and end of the run. This method of
computation is necessary, owing to the loss of time due to kindling the fire
at the beginning and burning it out at the end.
XIII. Quality of Steam. — The percentage of moisture in the steam should
be determined by the use of either a throttling or a separating steam calor-
imeter. The sampling nozzle should be placed in the vertical steam pipe
rising from the boiler. It should be made of J-inch pipe, and should extend
across the diameter of the steam pipe to within half an inch of the opposite
side, being closed at the end and perforated with not less than twenty £-inch
holes equally distributed along and around its cylindrical surface, but none
of these holes should be nearer than \ inch to the inner side of the steam
pipe. The calorimeter and the pipe leading to it should be well covered
with felting. Whenever the indications of the throttling or separating
calorimeter show that the percentage of moisture is irregular, or occasion-
ally in excess of three per cent, the results should be checked by a steam
separator placed in the steam pipe as close to the boiler as convenient, with
a calorimeter in the steam pipe just beyond the outlet from the separator.
The drip from the separator should be caught and weighed, and the per-
centage of moisture computed therefrom added to that shown by the
calorimeter.
Superheating should be determined by means of a thermometer placed in
a mercury well inserted in the steam pipe. The degree of superheating
should be taken as the difference between the reading of the thermometer
for superheated steam and the readings of the same thermometer for satu-
rated steam at the same pressure as determined by a special experiment,
and not by reference to steam tables.
XIV. Sampling the Coal and Determining its Moisture. — As each barrow
load or fresh portion of coal is taken from the coal pile, a representative
shovelful is selected from it and placed in a barrel or box in a cool place
and kept until the end of the trial. The samples are then mixed and
broken into pieces not exceeding one inch in diameter, and reduced by the
process of repeated quartering and crushing until a final sample weighing
about five pounds is obtained, and the size of the larger pieces is such that
they will pass through a sieve with J-inch, meshes. From this sample two
one-quart, air-tight glass preserving jars, or other air-tight vessels which
will prevent the escape of moisture from the sample, are to be promptly
filled, and these samples are to be kept for subsequent determinations of
moisture and of heating value, and for chemical analyses. During the
process of quartering, when the sample has been reduced to about 100
pounds, a quarter to a half of it may be taken for an approximate determi-
nation of moisture. This may be made by placing it in a shallow iron pan, not
over three inches deep, carefully weighing it, and setting the pan in the
hottest place that can be found on the brickwork of the boiler setting or
flues, keeping it there for at least twelve hours, and then weighing it.
The determination of moisture thus made is believed to be approximately
accurate for anthracite and semi-bituminous coals, and also for Pittsburg
or Youghiogheny coal ; but it cannot be relied upon for coals mined west of
Pittsburg, or for other coals containing inherent moisture. For these latter
coals it is important that a more accurate method be adopted. The method
recommended by the Committee for all accurate tests, whatever the char-
acter of the coal, is described as follows :
Take one of the samples contained in the glass jars, and subject it to a
thorough air-drying in a warm room, weighing it before and after, thereby
determining the quantity of surface moisture it contains. Then crush the
whole of it by running it through an ordinary coffee mill, adjusted so as to
produce somewhat coarse grains (less than Jginch), thoroughly mix the
crushed sample, select from it a portion of from 10 to 50 grams, weigh it in
a balance Avhich will easily show a variation as small as 1 part in 1,000, and
drv it in an air or sand bath at a temperature between 240 and 280 degrees
Fahr. for one hour. Weigh it and record the loss, then heat and weigh it
again repeatedly, at intervals of an hour or less, until the minimum weight
has been reached and the weight begins to increase by oxidation of a por-
tion of the coal. The difference between the original and the minimum
weight is taken as the moisture in the air-dried coal. This moisture should
RULES FOE CONDUCTING BOILER TESTS. 883
preferably be made on duplicate samples, and the results should agree
within 0.3 to 0.4 of one per cent, the mean of the two determinations being
taken as the correct result. The sum of the percentage of moisture thus
found and the percentage of surface moisture previously determined is the
total moisture.
XV. Treatment of Ashes and Refuse. — The ashes and refuse are to be
weighed in a dry state. For elaborate trials a sample of the same should
be procured and analyzed.
XVI. Calorific Tests and Analysis of Coal. — The quality of the fuel
should be determined either by heat test or by analysis, or by both.
The rational method of determining the total heat of combustion is to
burn the sample of coal in an atmosphere of oxygen gas, the coal to be
sampled as directed in Article XIV. of this code.
The chemical analysis of the coal should be made only by an expert
chemist. The total heat of combustion computed from the results of the
ultimate analysis may be obtained by the use of Dulong's formula (with
constants modified by recent determinations), viz. : 14,600 C -f- 62,000
f H— ^ ) + 4,000 S, in which C, H, 0, and S refer to the proportions of
carbon, hydrogen, oxygen, and sulphur respectively, as determined by the
ultimate analysis.*
It is recommended that the analysis and the heat test be each made by
two independent laboratories, and the mean of the two results, if there is
any difference, be adopted as the correct figures.
it is desirable that a proximate analysis should also be made to determine
the relative proportions of volatile matter and fixed carbon in the coal.
XVII. Analysis of Flue Gases.— The analysis of the flue gases is an espe-
cially valuable method of determining the relative value of different meth-
ods of firing, or of different kinds of furnaces. In making these analyses,
great care should be taken to procure average samples — since the compo-
sition is apt to vary at different points of the flue. The composition is also
apt to vary from minute to minute, and for this reason the drawings of gas
should last a considerable period of time. Where complete determinations
are desired, the analyses should be intrusted to an expert chemist. For
approximate determinations the Orsat or the Hempel apparatus may be
used by the engineer.
XVIII. Smoke Observations. — It is desirable to have a uniform system of
determining and recording the quantity of smoke produced Avhere bitumi-
nous coal is used. The system commonly employed is to express the degree
of smokiness by means of percentages dependent upon the judgment of the
observer. The Committee does not place much value upon a percentage
method, because it depends so largely upon the personal element, but if
this method is used, it is desirable that, so far as possible, a definition be
given in explicit terms as to the basis and method employed in arriving at
the percentage.
XIX. Miscellaneous. — In tests for purposes of scientific research, in
which the determination of all the variables entering into the test is de-
sired, certain observations should be made which are in general unneces-
sary for ordinary tests. These are the measurement of the air supply, the
determination of its contained moisture, the determination of the amount
of heat lost by radiation, of the amount of infiltration of air through the
setting, and (by condensation of all the steam made by the boiler) of the
total heat imparted to the water.
As these determinations are not likely to be undertaken except by engi-
neers of high scientific attainments, it is not deemed advisable to give
directions for making them.
XX. Calculations of Efficiency. — Two methods of defining and calculat-
ing the efficiency of a* boiler are'recommended. They are :
-. -i-^ • * j.-, x. -i Heat absorbed per lb. combustible
1. Efficiency of the boiler = — — * — -—- ■
Heating value of 1 lb. combustible
o ua: • * ., t, ., j . Heat absorbed per lb. coal
2. Efficiency of the boiler and grate = — : -. = „ „ .,, =•
Heating value of 1 lb. coal
* Favre and Silberman give 14,544 B.T.U. per pound carbon; Berthelot
14,647 B.T. U. Favre and Silberman give 62,032 B.T. U. per pound hydro-
gen; Thomson 61,816 B.T.U.
884
The first of these is sometimes called the efficiency based on combustible,
and the second the efficiency based on coal. The first ifi recommended as a
standard of comparison for all tests, and this is the one which is understood
to be referred to when the word " efficiency " alone is used without qualifi-
cation. The second, however, should be included in a report of a test,
together with the first, whenever the object of the test is to determine the
efficiency of the boiler and furnace together with the grate (or mechanical
stoker), or to compare different furnaces, grates, fuels, or methods of firing.
The heat absorbed per pound of combustible (or per pound coal) is to be
calculated by multiplying the equivalent evaporation from and at 212°
per pound combustible (or coal) by 965.7. (Appendix XXI.)
XXI. The Heat Balance. — An approximate " heat balance," or statement
of the distribution of the heating value of the coal among the several items
of heat utilized and heat lost, may be included in the report of a test when
analyses of the fuel and of the chimney gases have been made. It should
be reported in the following form :
Heat Balance, or Distribution of the Heating Value of the Combustible.
Total Heat Value of 1 lb. of Combustible B. T. U.
1. Heat absorbed by the boiler = evaporation from and at
212° per pound of combustible x 965.7.
2. Loss due to moisture in coal = per cent of moisture re-
ferred to combustible -f 100 X [(212 — /) + 966 + 0.48
(T — 212)] (t z= temperature of air in theboi.er-room,
T= that of the flue gases).
3. Loss due to moisture formed by the burning of hydro-
gen zr per cent of hydrogen to combustible -f- 100 X 9
X [(212 — t) + 966 + 0.48 (T — 212)].
4.* Loss due to heat carried away in the dry chimney gases
rr weight of gas per pound of combustible x 0.24 x
(T-t).
CO
5.f Loss due to incomplete combustion of carbon:
~C02-\-CO
per cent Cin combustible
100
X 10,150.
Loss due to unconsuined hydrogen and hydrocarbons, to
heating the moisture in the air, to radiation, and un-
accounted for. (Some of these losses may be sepa-
rately itemized if data are obtained from which they
may be calculated.)
Totals
* The weight of gas per pound of carbon burned may be calculated from
the gas analysis as follows :
Dry gas per pound carbon =
11 CO.,
' in which C02,
CO, O, and N are the percentage* by
sampling and analyses of the gases i,
to considerable errors, the result of this
imateone. The heat balance itself is <
as well as for the fact that it is not p<
centage of unburned hydrogen orhyart
The weight of dry gas per pound of
the dry gas per pound of carbon by tht
ble. and di riding hg 100.
t CO, and CO are respect, rely the
and carbonic oxide in the fine gases.
generated by burning to carbonic acid
Ionic oxide.
+ 8 0+7(C0+N), .„
3 (C02 + CO)
rolumc of the several gases. Js the
.i the present slate of the art are liable
calculation is usually only an approx-
%lso only approximate for this reason,
ossible in determine accurately theper-
ncarbons in the flue gases.
combustible is found by multiplying
" percentage of carbon in the combusti-
percentage by volume of carbonic acid
The quantity 10,150 =z No. heat units
one pound of carbon contained in car-
RULES FOR CONDUCTING BOILER TESTS. 885
XXII. Report of the Trial. — The data and results should be reported in
the manner given in either one of the two following tables, omitting lines
where the tests have not been made as elaborately as provided for in such
tables. Additional lines may be added for data relating to the specific
object of the test. The extra lines should be classified under the headings
provided in the tables, and numbered, as per preceding line, witb sub let-
ters, a, b, etc. The Short Form of Report, Table No. 2, is recommended
for commercial tests and as a convenient form of abridging the longer form
for publication when saving of space is desirable.
Table Wo. 1.
Data and Results of Evaporative Test.
Arranged in accordance with the complete form advised by the Boiler
! Test Committee of the American Society of Mechanical Engineers.
I Made by of boiler at to
determine
Principal conditions| governing the trial
Kind of fuel
i Kind of furnace
State of the weather ,
1. Date of trial
2. Duration of trial hours
Dimensions and Proportions.
(A complete description of the boiler should be given on an annexed sheet.)
Grate surface . . . width . . . length . . . area . . sq. ft.
Water-heating surface "
5. Superheating surface "
6. Ratio of water-heating surface to grate surface
7. Ratio of minimum draft area to grate surface
Average Pressures.
8. Steam pressure by gauge lbs.
9. Force of draft between damper and boiler ins. of water
10. Force of draft in furnace " "
11. Force of draft or blast in ash-pit " "
Average Temperatures.
12. Of external air
13. Offireroom
14. Of steam
15. Of feed- water entering heater . .
; 16. Of feed-water entering economizer .
j 17. Of feed-water entering boiler . . .
;18. Of escaping gases from boiler. . .
i|19. Of escaping gases from economizer
20. Size and condition
21. Weight of wood used in lighting fire
22. Weight of coal as fired*
I * Including equivalent of wood used in lighting the fire, not including un-
burnt coal iritlulrairn from furnace at times of cleaning and at end of test. One
pound 'of wood is taken to 'be equal to 0.4 pound of coal , or, in case greater
accuracy is desired, as having a heat value equivalent to the evaporation of
6 pounds of xoater from and at 212° per pound (6 x 965.7 = 5,794 B.T.UJ.
886
23. Percentage of moisture in coal * ... per cent.
24. Total weight of dry coal consumed ... lbs.
25. Total ash and refuse lbs.
2(3. Total combustible consumed
27. Percentage of ash and refuse in dry coal per cent
Proximate Analysis of Coal.
Of Coal. Of Combustible.
28. Fixed carbon per cent. per cent.
29. Volatile matter " "
30. Moisture "
31. Ash "
100 per cent 100 per cent.
32. Sulphur, separately determined " "
Ultimate Analysis of Dry Coal.
33. Carbon (C) per cent.
34. Hydrogen (R) "
35. Oxygen (O)
36. Nitrogen (N) "
37. Sulphur (S)
100 per cent.
38. Moisture in sample of coal as received "
Analysis of Ash and Refuse.
39. Carbon per cent.
40. Earthy matter ... "
Fuel per Hour.
41. Dry coal consumed per hour lbs.
42. Combustible consumed per hour "
43. Dry coal per square foot of grate surface per hour ... "
44. Combustible per square foot of water-heating surface per
hour "
Calorific Value of Fuel.
45. Calorific value by oxygen calorimeter, per lb. of dry coal . B. T. U.
46. Calorific value by oxygen calorimeter, per lb. of combustible "
47. Calorific value by analysis, per lb. of dry coalt "
48. Calorific value by analysis, per lb. of combustible .... "
Quality of Steam.
49. Percentage of moisture in steam per cent,
50. Number of degrees of superheating deg.
51. Quality of steam (dry steam = unity)
Water.
52. Total weight of water fed to boiler t lbs.
53. Equivalent water fed to boiler from and at 212° ....
54. Water actually evaporated, corrected for quality of steam
55. Factor of evaporation §
56. Equivalent water evaporated into dry steam from and at
212°. (Item 54 -f Item 55) "
* This is the total moisture in the coal as found by drying it artificially.
t See formula for calorific value under Article XVI. of Code.
% Corrected for inequality of water level and of steam pressure at begin-
ging and end of test.
§ Factor of evaporation = ~ ' in which H and h are respectively the
total heat in steam of the average observed pressure, and in water of the aver- !
age observed temperature of the feed.
RULES FOR CONDUCTING BOILER TESTS. 887
Water per Hour
57. Water evaporated per hour, corrected for quality of steam lbs.
58. Equivalent evaporation per hour from and at 212° .... "
59. Equivalent evaporation per hour from and at 212° per
square foot of water-heating surface "
Horse-Power.
60. Horse-power developed. (34£ lbs. of water evaporated per
hour into dry steam from and at 212° equals one horse-
power) * H.P.
61. Builders' rated horse-power "
62. Percentage of builders' rated horse-power developed . . . per cent.
Economic Results.
63. Water apparently evaporated per lb. of coal under actual
conditions. (Item 53 -j- Item 22) lbs.
64. Equivalent evaporation from and at 212° per lb. of coal
(including moisture). (Item 56 -f- Item 22) "
65. Equivalent evaporation from and at 212° per lb. of dry
coal. (Item 56 -f- Item 24) "
66. Equivalent evaporation from and at 212° per lb. of combus-
tible. (Item 56 -± Item 26) "
(If the equivalent evaporation, Items 64, 65, and 66, is
not corrected for the quality of steam, the fact should
be stated.)
Efficiency.
67. Efficiency of the boiler ; heat absorbed by the boiler per
lb. of combustible divided by the beat value of one lb.
of combustible t per cent.
68. Efficiency of boiler, including the grate ; heat absorbed by
the boiler, per lb. of dry coal fired, divided by the heat
value of one lb. of dry coal %
Cost of Evaporation.
69. Cost of coal per ton of 2,240 lbs. delivered in boiler room . $
70. Cost of fuel for evaporating 1,000 lbs. of water under ob-
served conditions $
71. Cost of fuel used for evaporating 1,000 lbs. of water from
and at 212° $
Smoke Observations.
72. Percentage of smoke as observed
73. Weight of soot j>er hour obtained from smoke meter . . .
74. Volume of soot obtained from smoke meter per hour . .
Table Ufo. 3.
Data and Results of Evaporative Test.
Arranged in accordance with the Short Form advised by the Boiler Test
Committee of the American Society of Mechanical Engineers.
Made by on
determine
* Held to be the equivalent of 30 lbs. of water per hour evaporated from
100° Fahr. into dry steam at 70 lbs. gauge pressure.
t In all cases where the word " combustible " is used, it means the coal with-
out moisture and ash, but including all other constituents. It is the same as
what is called in Europe " coal dry and free from ash."
t The heat value of the coal is to be determined either by an oxygen calorim-
eter or by calculation from ultimate analysis. When both methods are
used the mean value is to be taken.
Grate surface sq.ft.
Water-heating surface "
Superheating surface "
Kind of fuel "
Kind of furnace "
Total Quantities.
1. Date of trial
2. Duration of trial hours.
3. Weight of coal as fired lbs.
4. Percentage of moisture in coal per cent.
5. Total weight of dry coal consumed lbs.
6. Total ash and refuse "
7. Percentage of ash and refuse in dry coal per cent.
8. Total weight of water fed to the boiler lbs.
9. Water actually evaporated, corrected for moisture or super-
heat in steam "
Hourly Quantities.
10. Dry coal consumed per hour lbs.
11. Dry coal per hour per square foot of grate surface ... "
12. Water fed per hour "
13. Equivalent water evaporated per hour from and at 212°
corrected for quality of steam "
14. Equivalent water evaporated per square foot of water-
heating hour "
Average Pressures, Temperatures, etc.
15. Average boiler pressure lbs. per sq. ii\
16. Average temperature of feed-water deg.
17. Average temperature of escaping gases "
18. Average force of draft between damper and boiler . . . ins. of watei1
19. Percentage of moisture in steam, or number of degrees of
superheating
Horse-Power.
20. Horse-power developed (Item 13 -^ 3U) H.P.
21. Builders' rated horse-power "
22. Percentage of builders' rated horse-power per cent.
Economic Besults.
23. Water apparently evaporated per pound of coal under
actual conditions. (Item 8 -=- Item 3) lbs.
24. Equivalent water actually evaporated from and at 212° per
pound of coal as fired. (Item 9 -f- Item 3) "
25. Equivalent evaporation from and at 212° per pound of dry
coal. (Item 9 -f- Item 5) "
26. Equivalent evaporation from and at 212° per pound of
combustible. [Item 9 -)- (Item 5 — Item 6)] "
(If Items 23, 24, and 25 are not corrected for quality of
steam, the fact should be stated.)
Efficiency .
27. Heating value of the coal per pound . B. T. U.
28. Efficiency of boiler (based on combustible) "
29. Efficiency of boiler, including grate (based on coal) ... "
Cost of Evaporation.
30. Cost of coal per ton of 2,240 pounds delivered in boiler-room $
31. Cost of coal required for evaporation of 1,000 pounds of
water from and at 212° $
DETERMINATION OF MOISTURE.
889
DETEIlMiarATIOar OP THE MOISTURE I1V
SKE1A
The determination of the quality of steam supplied by a boiler is one of
the most important items in a boiler test. The three conditions to be de-
termined are :
a. If the steam is saturated, i.e., contains the quantity of heat due to the
pressure.
b. If the steam is wet, i.e., contains less than the amount of heat due to the
pressure.
c. If the steam is superheated, i.e., contains more than the amount of heat
due to the pressure.
There are several methods of determining the quality of steam ; one being
to condense all the steam evaporated by a boiler in a surface condenser, and
weigh the condensing water, taking the temperature at its entrance to and
exit from the condenser. Another is by use of a barrel calorimeter, in
which a sample of the steam is condensed directly in a barrel partly filled
with cold water, the added weight and temperature taken, and by use of a
formula the quality of steam can be determined.
Both the above-named methods are now practically obsolete, as their place
has been taken by the throttling calorimeter, used for steam in which the
moisture does not exceed 3 per cent, and the separating calorimeter, for
steam containing a greater amount of moisture.
Throttling- Calorimeter.
In its simplest form this instrument can be made up from pipe fittings,
the only special parts necessary being the throttling nozzle, which is readily
made by boring out a piece of brass rod that is the same diameter as a half-
inch steam pipe, leaving a small hole in one end, say Jg inch diameter. The
inside end of the small hole should be tapered with the end of a drill so as
not to cause eddies ; and the thermometer well, which is a small piece of
brass pipe, plugged at one end, and fitted into a half-inch brushing to fit
into place. The following cut hows the instrument as made up from fittings.
The whole must be carefully covered with some non-conductor, as hair felt.
Fig. 6.
For more accurate work the instruments designed by George H. Barrus,
M.E., and Prof. R. C. Carpenter, are to be preferred. Professor Carpenter's
instrument is shown in the following cut, and differs from the primitive
instrument previously described only by the addition of the manometer,
890
which determines the pressure of the steam above the atmosphere in the
body of the calorimeter. With a free exit to the air the pressure in the
calorimeter may be taken as that of the atmosphere.
Carpenter's Throttling- Calorimeter.
(\ size. Schaeffer & Budenberg.)
Fig. 7.
The perforated pipe for obtaining the sample of steam to be tested should
preferably be inserted in a vertical pipe, and should reach nearly across
its diameter.
IHrections for "Use. — Connect as shown in the preceding cuts, till
the thermometer cup with cylinder oil and insert the thermometer. Turn
on the Globe valve for ten minutes or more in order to bring the tempera-
ture of the instrument to full heat, after which note the reading of the ther-
mometer in the calorimeter, and of the attached manometer or of a barometer.
The steam gauge should be carefully calebrated to see that it is correct.
A barometer reading taken at the time the calorimeter is in use, gives
greater accuracy in working up the results than taking the average
atmospheric pressure as 14.65 pounds. Pressure in pounds may be deter-
mined from the mercury column of the barometer and manometer by divid-
ing the inches rise by 2.03, or taking one pound for each two inches of
mercury.
Following is the formula for determining the quality of steam by use of
the throttlihy calorimeter. ■
U= total heat in a pound of steam at the pressure in the pipe.
h = total heat in a pound of steam at the pressure in the calorimeter.
L = latent heat in a pound of steam at the pressure in the pipe.
t = temperature in the calorimeter.
b = temperature of boiling point at calorimeter pressure (taken as
212° with the " fittings" instrument).
0.48 = specific heat of superheated steam.
x = quality of the steam.
y z= percentage of moisture in the steam.
„ = "-"- f«-»y.m.
x — 100 — y.
DETERMINATION OF MOISTURE.
891
If h be taken as 212°, as it can be with but slight error, then
II — 1146.6 — .48 (t — 212)
Following are tables calculated from the above formula.
X 100.
Moisture in Steam.
Determinations by Throttling Calorimeter.
Gauge-pressures.
5
10
20
30
40
50
60
70
75
80
85
90
Per Cent of Moisture in
Steam
0°
0.51
0.90
1.54
2.06
2.50
2.90
3.24
3.56
3.71
3.86
3.99
4.13
UF
0.01
0.39
1.02
1.54
1.97
2.36
2.71
3.02
3.17
3.32
3.45
3.58
20°
.51
1.02
1.45
1.83
2.17
2.48
2.63
2.77
2.90
3.03
30°
.00
.50
.92
1.30
1.64
1.94
2.09
2.23
2.35
2.49
40°
.39
.77
.24
1.10
.57
.03
1.40
.87
.33
1.55
1.01
.47
l!l5
.60
.06
1.80
1.26
.72
.17
1.94
50°
1.40
fin0
.85
70°
.31
Gauge-pressure.
I
100
110
120
130
140
150
160
170
180
190
200
250
Per Cent of Moisture in
Steam
0°
4.39
4.63
4.85
5.08
5.29
5.49
5.68
5.87
6.05
6.22
6.39
7.16
10u
3.84
4.08
4.29
4.52
4.73
4.93
5.12
5.30
5.48
5.65
5. 8L
6.58
20u
3.29
3.52
3.74
3.96
4.17
4.37
4.56
4.74
4.91
5.08
5.25
6.00
30°
2.74
2.97
3.18
3.41
3.61
3.80
3.99
4.17
4.34
4.51
4.67
5.41
40°
2.19
2.42
2.63
2.85
3.05
3.24
3.43
3.61
3.78
3.94
4.10
4.83
50°
1.64
1.87
2.08
2.29
2.49
2.68
2.87
3.04
3.21
3.37
3.5o
4.25
60°
1.09
1.32
1.52
1.74
1.93
2.12
2.30
2.48
2.64
2.8(
2.96
3.67
70u
.55
.77
.97
1.18
1.38
1.56
1.74
1.91
2.07
2.23
2.3f-
3.09
80-'
.00
.22
.42
.63
.82
1.00
1.18
1.34
1.50
1.66
1.8'
2.51
90°
.07
.26
.44
.61
.78
.94
1.09
1.2-
1.93
Kill'
.05
.21
.37
.52
.67
.1C
1.34
110°
.76
The easiest method of making the determinations from the observations
is by use of the following diagram, prepared by Professor Carpenter.
Find in the vertical column at the left the pressure observed in the
main pipe -4- atmospheric pressure (the absolute pressure), then move hori-
zontally to the right until over the line giving the degree of superheat
(t — b), and the quality of steam will be found in a curve corresponding to
one of those shown, and which may be interpolated where results do not
come on one of the lines laid down.
«y
892
180
170
160
150
140
/
/
*
/
/
l
/
/
/
/
/
/
)
/
/
7
1
/
i
/
/
i
/
1
/
I
/
/
/
/
1
/
/
/
/
/
/
/
/
1
1
,
/
'
/
I
/
/
/
A>
/
/
/
/
/
/
1
/
*l
/
/'
/
1
/
/
j
'
/
/
/
/
1
j
I
1
'
1
!
/
/
1
/
1
/
/
k//
;
/
/
/
i
/
/
1
/
/'
/
/
/
/
j
/
j
/
«;
l
/
'
i
/
/
i
i
~l
/
/
/
'-/
/
i
1
/
/
/
/
/
1
7
7
»\7
/
/
/
/
>
*/
/
/
/
g/
f
1
/
/
/
/
/
/
V
/
1
/
/
t
/
f
.it
/
/
1
/
/
/
N.
/
/
I
/
/
/
/
i
/
L"4/
/
/
/
/
/
/
/
'
?
'
j/
/
/
f
/
/
ft
/
/
4/
/
/
/
/
/
£/
?/
/
/
t
l_
/
/
£
<o /
*
h
/
/
1
A
/
?y
/
c
V
/
4
/
/
/
/
/
/
/
/
$
y
/
/
/
/
/
/
7
\/
/
/
/
/
/
7
/
/
/
/
/
/
/
/
,'
/
/
/
/
/
/
y
/
/
/
y
,'
,
/
set
kl_C
UL/
TIC
)N C
;ur
VE
3
„'
■'
/'
y'
FOH
^'
-"
,'
''
Th
1ROTTLING C
\LO
Rirv
ET
ER
.--
'"
.„-
'"
1. 1;
OF
ATI/
jsp
HERI
C PF
EtS
RE
„,-
--'
) 10 20 30 .40 50 60 70 80 90
DEGREES OF SUPERHEAT IN THE CALORIMETER
diagram giving results from throttling calorimeter without computation
Fig 8.
DETERMINATION OF MOISTURE. 893
By putting a valve in the discharge pipe of the calorimeter, being careful
that when open it offers no obstruction to a free passage of the steam, de-
terminations may be make from temperatures without reference to a steam
table, and by using the following diagram by Professor Carpenter no calcu-
lation is necessary.
a. Determine the boiling-point of the instrument by opening supply and
discharge valves, and showering the instrument with cold water to
produce moisture in the calorimeter, in which case the boilins-noint
will be 212° or thereabouts.
6. Determine temperature due to the boiler pressure by closing the dis-
charge-valve, leaving the supply-valve open, and obtain the full boiler
pressure in the calorimeter.
c. Open the discharge-valve and let the thermometer settle to the tempera-
ture due to the superheat.
Deduct the temperature of the boiling-point from this last temperature to
obtain the degrees superheat.
Suppose the boiling-point of the calorimeter to be 213°, the following dia-
gram will give the result directlv from the temperatures.
To use the diagram Avhen the boiling-point differs from 212°, add to the
temperature of superheat the difference between the true boiling-point and
212°, if less than 212° ; and subtract the difference if the true boiling-point
be greater than 212 ; use the result as before.
{Separating- Calorimeter.
This instrument separates the moisture from the sample of steam, and the
percentage is then found by the ordinary formula.
amount of moisture X 100 , . „
— per cent moisture.
total steam discharged as sample
One of the most convenient forms of this type of calorimeter is the one
designed by Professor Carpenter, and shown in Fig. 10.
The sample of steam is let into the instrument through the angle valve
6, the moisture gathers in the inner chamber, its weight in pounds and
hundredths being shown on the scale 12, and the dry steam flows out through
the small calibrated orifice 8.
By Napier's law the flow of steam through an orifice is proportional to
the absolute pressure, until the back pressure equals .58 that of the supply.
The gauge 9 at the right shows in the outer scale the flow of steam
through the orifice 8 in a period of 10 minutes' time.
After attaching the instrument to the pipe from which sample is taken
through a perforated pipe as with the throttling or other instrument, it
must be thoroughly wrapped with hair, felt, or other insulator. Steam is
then turned on through the angle valve, and time enough allowed to thor-
oughly heat the instrument.
In taking an observation, first observe and record height of water on
scale 12, then let the steam flow for 10 minutes, observing the average posi-
tion of the pointer on the flow-gauge ; at the end of 10 minutes observe
the height of water in gauge 12, and the difference between this and the
first observation will be the amount of moisture in the sample ; the percent-
age of moisture will then be found as follows :
difference in scale 12 x 100
difference on scale 12 4- average for 10 minutes on the flow-gauge
■=.% moisture.
For tests and data on " Calorimeters," see papers in Trans. A.S.M.E., by
Messrs G. H. Barrus, A. A. Goubert, and Professors Carpenter, Denton,
Jacobus, and Peabody.
894 STEAM.
TEMPERATURE IN CALORIMETER
220 230 240 250 260 270 280 290 300 310 320 330 340
/
/
/
/
/
/
/
/
/
/
/
/
_/
/
/
400
1°,
/
/
/
/
/
/
/
/
/
/
/
/
/
*Yi
/
/
/
7
/
/
/
/
/
/
/
/
390
/
y
S
/
. /
/
/
/
/
/
/
-1
/
/
/
z
/
/
/
/
«
?
y
,V
/
/
/
/ /
/
/
/
/
380
/
/
/
/
P
V
•\
/
\»/
/
/
/
/
/
/
/
/
/
/
/
*/
*V
&/
/
/
/
/
/
/
/
7
:«i>
/
/
/
/
/
/
/
4*
7
10
/
/
/
/
/
'
/
/
/
/
/
w
,1<V
'
/
/
/
300
/
/
/
/
/
sv
/
/
/
w
,
/
/
/
/
7
/
c
V
s<V
<?/
/
^
350
/
r^
/
/
/
/
/
/
*/
-'-
/
<.
V
/
/
/
/
/
/
z
/
/
7
jf/
s/o
/
/
/
/
/
/
/
/
i
/
/
/
T
/
/
/
/
/
/
/
y.
330
/
/
/
/
/
/
f
/
/
/
_l!
/
/
/
/
/
/
/
/
/
-0
320
/
/
7
/
/
/
/
&/
J.
D
/
/
/
/
/
7
/
f */
jj
310
/
/
/
/
/
/
,y
D
/
/
/
/
f
/
/
/
7
f
<
800
/
/
/
/
/
/
-Ll
/
/
7
/
/
/
E
2'JC
/
/
*
/
T^
/
'
/
h
/
/
/
/
/
/
'280
/
/
7
/
/
/
f
V
/
r~
/
/
870
/
/
/
/
/
/
~t
/
/
/
/
/
/
/
/
/
/
25(
/
/
~t
/
/
/
/
1
/
/
/
CURVES OF QUALITY
FOR USE WITH
/
/
/
/
CARPENT
ER'S THROTTLING CALC
RIMETE
/
22<
/
;:]<
D
AG
20
RA
2
M
30
"OF
2i
I C
to
DM
21
TE
PU
>0
MP
TIN
2
ER
Q F
>o
AT
^E£
2
UR
UL
Fj
0
E
TS
G.
2
N
W
30
CA
TH
2
LO
T
J0
RIIV
HR
3
El
OT
)0
"ER
TL
3
NG
L0
C/
■i
0
)RI
3
ME
$0
TE
340
R.
DETERMINATION OF MOISTURE. 895
duality of Steam Shown l*y Color of Issuing- Jet.
Prof. J. E. Denton (Trans. A. S.
M. E., vol. x.,p. 349) lias demon-
strated that jets of steam escaping
from an orifice in a boiler or steam
reservoir snow unmistakable
change of appearance to the eye
■when the steam varies less than
one per cent from the condition of
saturation either in the direction of
"wetness or superheating. Conse-
quently if a jet of steam flow from
a boiler into the atmosphere under
circumstances such that very lit-
tle loss of heat occurs through
radiation, etc., and the jet be
transparent close to the orifice, of
be even a grayish white color,
the steam may be assumed to be
so nearly dry that no portable
condensing calorimeter will be
capable of measuring the amount
of water therein. If the jet be
strongly white, the amount of
water maybe roughly judged up
to about 2 per cent, but beyond
this a calorimeter only can deter-
mine tbe exact amount of moist-
ure. With a little experience any
one may determine by this meth-
od the conditions of steam within
the above limits. A common
brass pet cock may be used as an
orifice, but it should, if possible,
be set into the steam drum of the
boiler and never be placed farther
away from the latter than four
feet, and then only when the in-
termediate reservoir or pipe is
well covered, for a very short
travel of dry steam through a
naked pipe will cause it to become
perceptibly moist.
FACTORS &W EVAPO-
Fig. 10. Carpenter's New Evaporat- RA1IOI.
ing Calorimeter. (Schaeffer & Bu-
denberg.) In order to facilitate the calcu-
lation of reducing the actual rate
of evaporation of water from a certain temperature into steam of a cer-
tain pressure, into the rate from water at 212° F. into steam of 212° a
table of factors of evaporation is made up from the formula where
965.7
His the total heat of steam at the observed pressure, and h the total heat
of feed-water of the observed temperature.
896
Table of factor* of Evaporation.
(Compiled by W. Wallace Christie.)
Gauge
Pressure.
0
10
20
30
40
45
50
52
54
Temp, of
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
lbs.
Feed.
212° F.
1.0003
1.0088
1.0149
1.0197
1.0237
1.0254
1.0271
1.0277
1.0283
209
1.0035
1.0120
1.0180
1.0228
1.026X
1.0286
1.0301'
1.0309
1.0315
206
1.0066
1.0151
1.0212
1.0260
1.0299
1.0317
1.0334
1.0340
1.0346
203
1.0098
1.0183
1.0243
1.0291
1.0331
1.0349
1.0365
1.0372
1.0378
200
1.0129
1.0214
1.0275
1.0323
1.0362
1.0380
1.03! 17
1.0403
1.0409
197
1.0160
1.0246
1.0306
1.0354
1.0394
1.0412
1.0-128
1.0434
1.0441
194
1.0192
1.0277
1.0338
1.0385
1.0425
1.0443
1.0460
1.0466
1.0472
191
1.0223
1.0308
1.0369
1.0417
1.0457
1.0474
1.0491
1.0497
1.0503
188
1.0255
1.0340
1/M00
1.0448
1.0488
1.0506
1.0522
1.0528
1.0535
185
1.0286
1.0371
1.0432
1.0480
1.0519
1.0537
1.0554
1.0560
1.0566
182
1.0317
1.0403
1.0463
1.0511
1.0551
1.0568
1.05X5
1.0591
1.05! IS
179
1.0349
1.0434
1.0495
1.0542
1.0582
1.0600
1.0616
1.0623
1.0629
17G
1.03S0
1.0465
1.0526
1.0574
1.0613
1.0631
1.0648
1.0654
1.0660
173
1.0411
1.0497
1.0557
1.0605
1.0645
1.0663
1.0679
1.0685
1.0692
170
1.0443
1.0528
1.0589
1.0636
1.0676
1.0694
1.0710
1.0717
1.0723
167
1.0474
1.0559
1.0620
1.0668
1.0707
1.0725
1.0742
1.0748
1.0754
164
1.0505
1.0591
1.0651
1.0699
1.0739
1.0756
1.0773
1.0780
1.0786
161
1.0537
1.0622
1.0682
1.0730
1.0770
1.0788
1.0804
1.0811
1.0817
158
1.0568
1.0653
1.0714
1.0762
1.0801
1.0819
1.0S36
2.0842
1.0848
155
1.0599
1.0684
1.0745
1.0793
1.0833
1.0850
1.0867
1.0873
1.0880
152
1.0631
1.0716
1.0776
1.0824
1.0864
1.0882
1.0898
1.0905
1.0911
149
1.0662
1.0747
1.0808
1.0855
1.0*95
1.0913
1.0930
1.0936
1.0942
146
1.0693
1.0778
1.0839
1.0887
1.0926
1.0944
1.0961
1.0967
1.0973
143
1.0724
1.0810
1.0870
1.0918
1.0958
1.0975
1.0992
1.0998
1.1005
140
1.0756
1.0841
1.0901
1.0949
1.0989
1.1007
1.1023
1.1030
1.1036
137
1.0787
1.0872
1.0933
1.0980
1.1020
1.1038
1.1055
1.1061
1.1067
134
1.0818
1.0903
1.0964
1.1012
1.1051
1.1069
1.1086
1.1092
1.1098
131
1.0849
1.0934
1.0995
1.1043
1.1083
1.1100
1.1117
1.1123
1.1130
128
1.0881
1.0966
1.1026
1.1074
1.1114
1.1132
1.1148
1.1155
1.1161
125
1.0912
1.0997
1.10o7
1.1105
1.1145
1.1163
1.1179
1.1186
1.1192
122
1.0943
1.1028
1.1089
1.1136
1.1176
1.1194
1.1211
1.1217
1.1223
119
1.0974
1.1059
1.1120
1.1168
1.1207
1.1225
1.1242
1.1248
1.1254
116
1.1005
1.1090
1.1151
1.1199
1.1239
1.1256
1.1273
1.1279
1.1286
113
1.1036
1.1122
1.1182
1.1230
1.1270
1.1288
1.1304
1.1310
1.1317
110
1.1068
1.1153
1.1213
1.1261
1.1301
1.1319
1.1335
1.1342
1.1348
107
1.1099
1.1184
1.1245
1.1292
1.1332
1.1350
1.1366
1.1373
1.1379
104
1.1130
1.1215
1.1276
1.1323
1.1 30:;
1.1381
1.1398
1.1404
1.1410
101
1.1161
1.1246
1.1307
1.1355
1.1394
1.1412
1.1429
1.1435
1.1441
98
1.1192
1.1277
1.1338
1.1386
1.1426
1.1443
1.1460
1.1466
1.1473
95
1.1223
1.1309
1.1369
1.1417
1.1457
1.1475
1.1491
1.1497
1 1504
92
1.1255
1.1340
1.1400
1.1448
1.1488
1.1506
1.1522
1.1529
1.1535
89
1.1286
1.1371
1.1431
1.1479
1.1519
1.1537
1.1553
1.1560
1.1506
86
1.1317
1.1402
1.1463
1.1510
1.1550
1.1568
1.1584
1.1591
1.1597
83
1.1348
11433
1.1494
1.1541
1.1581
1.1599
1.1616
1.1622
1.1628
80
1.1379
1.1464
1.1525
1.1573
1.1612
1.1630
1.1647
1.1653
1.1659
77
1.1410
1.1495
1.1556
1.1604
1.1(344
1.1661
1.1678
1.1684
1.1690
74
1.1441
1.1526
1.1587
1.1635
1.1675
1.1692
1.1709
1.1715
1.1722
71
1.1472
1.1558
1.1618
1.1666
1.1706
1.1723
1.1740
1.1746
1.1753
68
1.1504
1.1589
1.1649
1.1697
1.1737
1.1755
1.1771
1.1778
1.1784
65
1.1535
1.1620
1.1680
1.1728
1.1768
1.1786
1.1802
1.1809
1.1815
62
1.1566
1.1651
1.1711
T 1759
1.1799
1.1817
1.1833
1.1840
1.1846
59
1.1597
1.1682
1.1743
1.1790
1.1830
1.1848
1.1864
1.1871
1.1877
56
1.1628
1.1713
1.1774
1.1821
1.1861
1.1879
1.1896
1.1902
1.1908
53
1.1659
1.1744
1.1805
1.1852
1.1892
1.1910
1.1927
1.1933
1.1939
50
1.1690
1.1775
1.1836
1.18S4
1.1923
1.1941
1.1958
1.1964
1.1970
47
1.1721
1.1806
1.1867
1.1915
1.1954
1.1972
1.1989
1.1995
1.2001
44
1.1752
1.1837
1.1898
1.1946
1.1986
1.2003
1.2020
1.2026
1.2032
41
1.1783
1.1868
1.1929
1.1977
1.2017
1.2034
1.2051
1.2057
1.2064
38
1.1814
1.1900
1.1960
1.2008
1.204s
1.2065
1.2082
1.2088
1.2095
35
1.1845
1.1931
1.1991
1.2039
1.2079
1.20!)6
1.2113
1.2119
1.2126
' 32
1.1876
1.1962
1.2022
1.2070
1.2110
1.2128
1.2144
1.2151
1.2157
FACTORS OF EVAPORATION.
897
Table of factors of Evaporation.
Gauge
Pressure.
56
58
60
65
70
75
80
85
90
95
Temp, of
Feed.
lbs.
lbs.
lbs.
lbs.
11)315
lbs.
lbs.
lbs.
1~X)353
lbs.
lbs.
lbs.
212° F.
1.0290
1.0295
1.0301
1.0329
1.0341
1.0365
1.0376
1.0387
209
1.0321
1.0327
1.0333
1.0346
1.0360
1.0372
1.0385
1.0397
1.0408
1.0419
206
1.0352
1.0358
1.0364
1.0378
1.0391
1.0403
1.C416
1.0428
1.0439
1.0450
203
1.0384
1.0390
1.0396
1.0464
1.0423
1.0435
1.0448
1.0460
1.0471
1.0482
200
1.0415
1.0421
1.0427
1.0441
1.0454
1.0466
1.0479
1.0491
1.0502
1.0513
197
1.0447
1.0453
1.0458
1.0477
1.0486
1.0498
1.0511
1 .0522
1.0533
1.0544
194
1.0478
1.0484
1.0490
1.0504
1.0517
1.0529
1.0542
1.0553
1.0565
1.0576
191
1.0510
1.0515
1.0521
1.0535
1.0549
1.0561
1.0573
1.0585
1.0596
1.0607
188
1.0541
1.0547
1.0553
1.0566
1.0580
1.0592
1.0605
1.0616
1.0628
1.0639
185
1.0572
1.0578
1.0584
1.0598
1.0611
1.0623
1.0636
1.0648
1.0659
1.0670
182
1.0604
1.0610
1.0615
1.0629
1.0643
1.0655
1.0668
1.0679
1.0090
1.0701
179
1.0635
1.0641
1.0647
1.0660
1.0674
1.0686
1.0699
1.0710
1.0722
1.0733
176
1.0666
1.0672
1.0678
1.0092
1.0705
1.0717
1.0730
1.0742
1.0753
1.0764
173
1.0698
1.0704
1.0709
1.0723
1.0737
1.0749
1.0762
1.0773
1.0784
1.0795
170
1.0729
1.0735
1.0741
1.0754
1.0768
1.0780
1.0793
1.0804
1.0816
1.0827
167
1.0760
1.0766
1.0772
1.0786
1.0799
1.0811
1.0824
1.0836
1.0847
1.0858
164
1.0792
1.0798
1.0803
1.0817
1.0831
1.0843
1.0S5C
1.0867
1.0878
1.0889
161
1.0823
1.0829
1.0835
1.0848
1.0862
1.0874
1.0887
1.089S
1.0910
1.0921
158
1.0854
1.0860
1.0866
1.0880
1.0893
1.0905
1.0916
1.0929
1.0941
1.0952
155
1.0886
1.0892
1.0897
1.0911
1.0925
1.0937
1.0941
1.0961
1.0972
1.0983
152
1.0917
1.0923
1.0929
1.0942
1.0956
1.0968
1.0981
1.0992
1.1004
1.1015
149
1.0948
1.0954
1.0960
1.0974
1.0987
1.0999
1.1011
1.102;
1.1035
1.1046
146
1.0979
1.0985
1.0991
1.1005
1.1018
1.1030
1.1043
1.1055
1.1066
1.1077
143
1.1011
1.1017
1.1022
1.1036
1.1050
1.1062
1.1074
1.1086
1.1097
1.1108
140
1.1042
1.1048
1.1054
1.1067
1.1081
1.1093
1.1HK
1.1117
1.1129
1.1140
137
1.1073
1.1079
1.1085
1.1099
1.1112
1.1124
1.1137
1.1148
1.1160
1.1171
134
1.1104
1.1110
1.1116
1.1130
1.1143
1.1155
1.1168
1.1180
1.1191
1.1202
131
1.1136
1.1142
1.1147
1.1161
1.1175
1.1187
1.119S
1.1210
1.1222
1.1233
128
1.1167
1.1173
1.1179
1.1192
1.1206
1.1218
1.1231
1.1242
1.1253
1.1264
125
1.1198
1.1204
1.1210
1.1223
1.1237
1.1249
1.1261
1.1273
1.1285
1.1296
122
1.1229
1.1235
1.1241
1.1255
1.1268
1.1280
1.1293
1.1294
1.1316
1.1327
119
1.1260
1.1266
1.1272
1.1286
1.1299
1.1311
1.1324
1.1336
1.1347
1.1358
116
1.1292
1.1298
1.1303
1.1317
1.1331
1.1343
1.135E
1.1366
1.1378
1.1389
113
1.1323
1.1329
1.1334
1.1348
1.1362
1.1374
1.1387
1.1398
1.1409
1.1420
110
1.1354
1.1360
1.1366
1.1374
1.1393
1.1405
1.1418
1.1429
1.1441
1.1452
107
1.1385
1.1391
11397
1.1411
1.1424
1.1436
1.1448
1.1460
1.1472
1.1483
104
1.1416
1.1422
1.1428
1.1442
1.1455
1.1467
1.148C
1.1491
1.1503
1.1514
101
1.1447
1.1453
1.1459
1.1473
1.1486
1.1498
1.1511
1.1523
1.1534
1.1545
98
1.1479
1.1485
1.1490
1.1504
1.1518
1.1530
1.1541
1.1554
1.1565
1.1576
95
1.1510
1.1516
1.1521
1.1535
1.1549
1.1561
1.1574
1.1583
1.1596
1.1607
92
1.1541
1.1547
1.1553
1.1566
1.1580
1.1592
1.1605
1.1616
1.1628
1.1639
89
1.1572
1.1578
1.1584
1.1598
1.1611
1,1623
1.163C
1.1647
1.1659
1.1670
86
1.1603
1.1609
1.1615
1.1629
1.1642
1.1654
1.1667
1.1678
1.1690
1.1701
83
1.1634
1.1640
1.1646
1.1660
1.1673
1.1685
1.1698
1.1709
1.1721
1.1732
80
1.1665
1.1671
1.1677
1.1691
1.1704
1.1716
1.1729
1.1741
1.1752
1.1763
77
1.1696
1.1702
1.1708
1.1722
1.1735
1.1747
1.176C
1.1772
1.1783
1.1794
74
1.1728
1.1734
1.1739
1.1753
1.1767
1.1779
1.1791
1.1803
1.1814
1.1825
71
1.1759
1.1765
1.1770
1.1784
1.1798
1.1810
1.1823
1.1834
1.1845
1.1856
68
1.1790
1.1796
1.1802
1.1815
1.1829
1.1841
1.1854
1.1865
1.1877
1.1888
65
1.1821
1.1827
1.1833
1.1846
1.1860
1.1872
1.1885
1.1S96
1.1908
1.1919
62
1.1852
1.1858
1.1864
1.1877
1.1891
1.1903
1.1916
1.1927
1.1939
1.1950
59
1.1883
1.1889
1.1895
1.1909
1.1922
1.1934
1.1947
1.1958
1.1970
1,2981
56
1.1914
1.1920
1.1926
1.1940
1.1953
1.1965
1.1978
1.1989
1.2001
1.2012
53
1.1945
1.1951
1.1957
1.1971
1.1984
1.1996
1.2009
1.2020
1.2032
1.2043
50
1.1976
1.1982
1.1988
1.2002
1.2015
1.2027
1.2040
1.2052
1.2063
1.2074
47
1.2007
1.2013
1.2019
1.2033
1.2046
1.2058
1.2071
1.2083
1.2094
1.2105
44
1.2039
1.2044
1.2050
1.2064
1.2078
1.2090
1.2102
1.2114
1.2125
1.2136
41
1.2070
1.2076
1.2081
1.2095
1.2109
1.2121
1.2133
1.2145
1.2156
1.2167
38
1.2101
1.2107
1.2112
1.2126
1.2140
1.2162
1.2164
1.2176
1.2187
1.2198
35
1.2132
1.2138
1.2143
1.2157
1.2171
1.21831 1.2196
1.2207
1.2218
1.2229
32
1.2163
1.2169
1.2175
1.2188
1.221)2
1.2214| 1.2227
1.2239
1.2249
1.2260
898
Table of
factors of Evaporation.
Gauge
Pressure.
100
105
115
125
135
145
155
165
185
Temp, of
Feed.
Lbs.
Lbs.
Lbs.
Lbs.
Lbs.
Lbs.
Lbs.
Lbs.
Lbs.
212° F,
1.0397
1.0407
1.0427
1.0445
1 0462
1.0478
1.0493
1.0509
1.0536
209
1.0420
1.0438
1.0458
1.0476
1.0403
1.0509
1.0524
1.0540
1.0567
20G
1.0460
1.0470
1.0489
1.0510
1.0527
1.0543
1.0558
1.0574
1.0601
203
1.0192
1.0502
1.0521
1.0540
1 0557
1.0573
1.0588
1.0604
1.0631
200
1.0523
1.0533
1.0552
1.0571
1.05X8
1.0604
1.0619
1.0035
1.0062
197
1.0555
1.0565
1.0584
1.0602
1.0619
1.0635
1.0650
1.0666
1 .0093
194
1.0586
1.0596
1.0615
1.0635
1.0052
1.066S
1.0683
1.6699
1.0726
191
1.0617
1.0627
1.0647
1.0665
1.0082
1.069S
1.0713
1.0729
1.0756
188
1.0649
1.0659
1.0678
1.0696
1.0713
1.0729
1.0744
1.0760
1.0787
185
1.0680
1.0690
1.0709
1.0728
1.0745
1.0761
1.0776
1.0792
1.0819
182
1.0712
1.0722
1.0741
1.0759
1.0776
1.0792
1-0807
1.0823
1.0850
170
1.0743
1.0753
1.0772
1-0790
1.1 IS07
1.0823
1.0838
1.0854
1.0881
176
1.0774
1.0784
1.0803
1.0822
1.0839
1.0855
1-0870
1.0886
1.0913
173
1.0806
1.0816
1.0835
1.0S53
1.0870
1.0886
1.0901
1.0917
1.0944
170
1.0837
1.0847
1.0866
1.0884
1.0901
1.0917
1-0932
1.0948
1.0980
1.0975
167
1.0868
1.0S78
1.0897
10916
1.0933
1.0949
1.0964
1.1007
164
1.0900
1.0910
1.0929
1.0946
l .()!)(;:;
1.0979
1.0994
1.1010
1.1037
161
1.0031
1.0941
1.0960
1.0979
1.0996
1.1012
1.1027
1.1043
1.1070
158
1.0962
1.0972
1.0991
1.1010
1.1027
1.1043
1-1058
1.1074
1.1101
155
1.0993
1.1003
1.1023
1.1041
1.1058
1.1074
1.1089
1.1105
1.1132
152
1.1025
1.1035
1.1054
1.1073
1.1090
1.1107
1.1122
1.1138
1.1165
149
1.1056
1.1066
1.1085
1.1103
1.1120
1.1136
1.1151
1.1167
1.1194
146
1.1087
1.1097
1.1116
1.1135
1.1152
1.1168
1.1183
1.1199 1.1226
143
1.1118
1.1129
1.1148
1.1166
1.1183
1.1199
1.1214
1.1230 1.1257
140
1.1150
1.1160
1.1179
1.1197
1.1214
1.1230
1.1245
1.1261 1.1288
137
1.1181
1.1191
1.1210
1.1228
1.1245
11262
1.1277
1.1293 1.1320
134
1.1212
1.1222
1.1241
1.1260
1.1277
1.1293
1.1308
1.1324 1.1351
131
1.1243
L1253
1.1273
1.1291
1.1303
1.1324
1.1339
1.1355 1.1382
128
1.1275
1.1285
1.1304
1.1322
1,1339
1.1355
1.1370
1.1386 1.1413
125
1.1306
1.1316
1.1335
1.1353
1.1370
1.1386
1.1401
1.1417
1.1444
122
11337
1.1347
1.1366
1.1384
1.1401
1.1417
1.1438
1.1448
1.1475
119
1.1368
1.1378
1.1397
1.1415
1.1432
1.1449
1.1464
1.1480
1.1507
116
1.1399
1.1409
1.1429
1.1447
1.1464
1.1480
1.1495
1.1511
1.1538
113
1.1431
1.1441
1.1460
1.1478
1.1495
1.1511
1.1526
1.1542
1.1569
110
1.1462
1.1472
1.1491
1.1509
1.1516
1.1542
1.1557
1.1573
1.1600
107
1.1493
1.1503
1.1522
1.1540
1.1557
1.1573
1.1588
1.1604
1.1631
104
1.1524
1.1534
1.1553
1.1571
1.1588
1.1605
1.161!
1.1635
1.1062
101
1.1555
1.1565
1.1584
1.1602
1.1620
1.1636
1.1652
1.1668
1.1095
98
1.1586
1.1596
1.1616
1.1634
1.1651
1.1667
1.168:
1.1699
1.1726
95
1.1618
1.1628
1.1647
1.1665
1.1682
1.1698
1.1713
1.1729
1.1756
92
1.1640
1.1660
1.1678
1.1696
1.1713
1.1729
1.1744
1.1760
1.1787
89
1.1680
1.1690
1.1709
1.1727
1.1744
1.1760
1.1775
1.1791
1.1818
86
1.1711
1.1721
1.1740
1.1758
1.1775
1.1791
1.18(11
1.1822
1.1849
83
1.1742
1.1752
1.1771
1.1789
1.1800
1.1823
1.1837
1.1853
1.1880
80
1.1773
1.1783
1.1802
1.1820
1.1837
1.1854
1.1869
1.1885
1.1912
77
1.1804
1.1814
1.1834
1.1852
1.1869
1.1885
1.1900
1.1916
1.1913
74
1.1835
1.1845
1.1865
1.1883
1.1900
1.1916
1.1932
1.1948
1.1975
71
1.1867
1.1877
1.1896
1.1914
1.1931
1.1947
1.1961
1.1977
1.2004
68
1.1898
1.1908
1.1927
1.1945
1.1962
1.1978
1.1993
1.200!
1.2036
65
1.1929
1.1939
1.1958
1.1976
1.1993
1.2009
1.2024
1.2040
1.2067
62
1.1960
1.1970
1.1989
1.2007
1.2024
1.2040
1.2055
1.2071
1.2098
59
1.1991
1.2001
1.2020
1.2038
1.2055
1.2071
1.20X1
1.2102
1.2129
56
1.2022
1.2032
1.2051
1.2069
1.2086
1.2102
1.2117
1.2133
1.2160
53
1.2053
1.2063
1.2082
1.2100
1.2117
1.2134
1.2148
1.2164
1.2191
50
1.2084
1.2094
1.2113
1.2131
1.2148
1.2165
1.2180
1.2196
1.2223
47
1.2115
1.2125
1.2144
1.2163
1.2180
1.2196
1.2211
1.2227
1.2254
44
1.2146
1.2156
1.2176
1.2194
1.2211
1.2227
1.2242
1 .2258
1.2285
41
1.2177
1.2187
1.2207
1.2225
1.2242
1.2258
1.2273
1 .228!
1.2316
38
1.2208
1.2219
1 2238
1.2256
1.2273
1.2289
1.2304
1.2521
1.2347
35
1.2240
1.2250
1 2269
1.2287
1.2304
1,2320
1.2335
1.2351
1.2378
32
1.2271
1.2281
1.2300
1.2318
1.2335
1.2351
1.2566
1 .2382
1.2409
PROPERTIES OP SATURATED STEAM.
899
PKOPEHTIES OF SATTJUATKI* STEAM.
(Compiled by W. W. Christie.)
Pounds per
Square Inch.
, • a3
Heat Units in one
Pound above 32° F.
Volume.
jo
6
6
'c 2
<j
¥
111!
IIhWoo
Rela-
tive
Specific
OH •
|;| %
§1 J>
Cu. Ft.
in 1 Cu.
Ft. of
Water.
Cu. Ft,
in one
Lb. of
Steam.
1
2
4
102.
12G.2
141.6
153.0
70.1
94.4
109.8
121.4
1042.9
102G.0
1015.2
1007.2
1113.0
1120.4
1125.1
1128. G
20G20
10720
732G
5G00
319.600
172.417
117.723
89.799
.0030
.0058
.0085
.0112
5
6
7
8
1G2.3
170.1
176.9
182.9
130.7
138.5
145.4
151.4
1000.7
995.2
990.4
986.2
1131.4
1133.8
1135.8
1137.7
4535
3814
3300
2910
72.792
61.311
53.000
46.771
.0137
.0163
.0189
.0214
9
10
11
12
188.3
193.2
197.7
201.9
156.9
161.9
1G6.5
170.7
982.4
978.9
975.7
972.8
1139.3
1140.8
1142.2
1143.5
2G07
2360
2157
19S8
41.858
37.904
34.G59
31.932
.0239
.0264
.0289
.0313
' .304
1.3
13
14
15
1G
205.8
209.5
213.0
216.3
174.7
178.4
181.9
185.2
970.0
967.4
964.9
962.6
1144.7
1145.8
114G.9
1147.9
1846
1722
1012
1514
29.593
27.G24
25.858
24.335
.0337
.0362
.0387
.0413
2.3
3.3
4.3
5.3
17
18
19
20
219.4
222.3
225.2
227.9
188.4
191.4
194.2
197.0
960.4
958.3
956.3
954.4
1148.8
1149.7
1150.6
1151.4
1427
1350.6
1282.1
1220.3
22.985
21.781
20.701
19.725
.0437
.0462
.0487
.0511
G.3
7.3
8.3
9.3
21
22
23
24
230.5
233.0
235.4
237.7
199.6
202.2
204.6
207.0
952.5
950.8
949.0
947.4
1152.2
1153.0
1153.7
1154.4
1164.4
1113.5
10GG.9
1024.1
18.839
18.033
17.293
16.615
.0536
.05G1
.0585
.0G10
10.3
11.3
12.3
13.3
25
26
27
28
240.0
242.1
244.2
246.3
209.3
211.5
213. G
215.7
945.8
944.2
942.7
941.3
1155.1
1155.8
115G.4
1157.0
984.8
948.4
914.6
883.2
15.9S8
15.409
14.871
14.371
.0034
.0G58
.0G83
.0707
14.3
15.3
1G.3
17.3
29
30
31
32
248.3
250.2
252.1
253.9
217.7
219.7
221. G
223.5
939.9
938.9
937.1
935.9
1157.6
1158.2
1158.8
1159.3
854.0
82G.8
801.2
777.2
13.904
13.4(57
13.058
12.674
.0731
.0755
.0779
.0803
18.3
19.3
20.3
21.3
33
34
35
36
255.7
257.4
259.1
260.8
225.3
227.1
228.8
230.5
934.6
933.3
932.1
931.0
1159.9
1160.4
11G0.9
1161.5
754.7
733.5
713.4
694.5
12.312
11.971
11.649
11.344
.0827
.0851
.0875
.0899
22.3
23 3
24.3
25.3
37
38
39
40
262.4
264.0
265.6
267.1
232.1
233.8
235.3
236.9
929.8
928.6
927.5
926.4
1161.9
11G2.4
11G2.9
1163.4
676.6
659.7
643.6
628.2
11.055
10.756
10.521
10.259
.0922
.0946
.0970
.0994
20.3
27.3
41
42
2G8.6
270.0
238.4
239.9
925.4
924.3
1163.8
11G4.3
G13.4
599.3
10.037
9.811
.1017
.1041
900
PROPERTIES OF SATURATED STEAM — Gmtinued.
Pounds per
Heat Units in one
Yol
line.
Square Inch.
Pound above
32° F.
© 0
* c o
0
2 33
Sta
itent
sat of
ipori-
tion.
+gi|
Rela-
tive
Specific
§D«
Cu. Ft.
Cu. Ft.
%Z
J£
££
s>
^X> S3
HhkJ
in 1 Cu.
in one
geS
o
<i
H
rC-
A
K
Ft. of
Lb. of
Water.
Steam.
28.3
43
271.5
241.4
923.3
1164.7
586 1
9.596
.1064
29.3
44
272.9
242.8
922.3
1165.1
573.7
9.391
.1088
30.3
45
274.3
244.2
921.3
1165.6
561.8
9.196
.1111
31.3
46
275.6
245.6
920.3
1166.0
550.4
9.006
.1134
32.3
47
276.9
247.0
919.4
1166.4
539.5
8.826
.1158
33.3
58
278.2
248.3
918.4
1166.8
529.0
8.653
.1181
34.3
49
279.5
249.6
917.5
1167.2
518.6
8.487
.1204
35.3
50
280.8
250.9
916.6
1167.6
508.5
8.326
.1227
36.3
51
282.1
252.2
915.7
1167.9
499.1
8.173
.1251
37.3
52
283.3
253.5
914.8
1168.3
490.1
8.025
.1274
38.3
53
284.5
254.7
913.9
1168.7
481.4
7.882
.1297
39.3
54
285.7
255.9
913.1
1169.0
472.9
7.745
.1320
40.3
55
286.9
257.1
912.2
1169.4
464.7
7.612
.1343
41.3
56
288 0
258.3
911.4
1169.7
457.0
7.484
.1366
42.3
57
289.1
259.5
910.6
1170.1
449.6
7.360
.1388
43.3
58
290.3
260.6
909.8
1170.4
442.4
7.241
.1411
44.3
59
291.4
261.7
909.0
1170.8
435.3
7.125
.1434
45.3
60
292.5
262.9
908.2
1171.1
428.5
7.013
.1457
46.3
61
293.6
264.0
907.4
1171.4
422.0
6.905
.1479
47.3
62
294.6
265.1
906.7
1171.8
415.6
6.800
.1502
48.3
63
295.7
266.1
905.9
1172.1
409.4
6.699
.1524
49.3
64
296.7
267.2
905.2
1172.4
403.5
6.600
.1547
50.3
65
297.7
268.3
904.4
1172.7
397.7
6.505
.1569
51.3
66
298.7
269.3
903.7
1173.0
392.1
6.412
.1592
52.3
67
299.7
270.3
903.0
1173.3
386.6
6.322
.1614
53.3
68
300.7
271.3
902.3
1173.6
381.3
6.234
.1637
54.3
69
301.7
272.3
901.5
1173.9
376.1
6.149
.1059
55.3
70
302.7
273.3
900.9
1174.2
371.2
6.066
.1681
56.3
71
303.6
274.3
900.2
1174.5
366.4
5.986
.1703
57.3
72
304.6
275.3
899.5
1174.8
361.7
5.907
.1725
58.3
73
305.5
276.2
898.8
1175.1
357.1
5.831
.1748
59.3
74
306.4
277.2
898.1
1175.4
352.6
5.757
.1770
60.3
75
307.3
278.1
897.5
1175.3
348.3
5.684
.1792
61.3
76
308.2
279.0
896.8
1175.9
344.1
5.614
.1814
62.3
77
309.1
280.0
896.2
1176.2
340.0
5.546
•1836
63.3
78
310.0
280.9
895.5
1176.5
336.0
5.479
.1857
64.3
79
310.9
281.8
894.9
1176.7
332.1
5.413
.1879
65.3
80
311.8
282.7
894.3
1177.0
328.3
5.342
.1901
66.3
81
312.6
283.5
893.7
1177.3
324.6
5.287
.1923
67.3
82
313.5
284.4
893.1
1177.5
320.9
5.227
.1945
68.3
83
314.3
285.3
802.4
1177.8
317.3
5.167
.1967
69.3
84
315.1
286.1
S91.8
1178.0
313.9
5.110
1988
PROPERTIES OF SATURATED STEAM.
901
PROPERTIES OF SATIRATED §TE Am — Continued.
Pounds per
Square Inch.
11 .
Heat Units in one
Pounds above 32° F.
Volume.
0>°
3
6
3 ?
<
M'i
3*1.1
7i ^ ® 3
Rela-
tive
Specific
c2§
g.2 «
b0?
0
Cu. Ft.
in lCu.
Ft. of
Water.
Cu. Ft.
n lLb.
of
Steam.
>
70.3
71.3
72.3
73.3
85
86
87
88
316.0
316.8
317.6
318.4
287.0
287.8
288.7
'289.5
891.2
890.6
890.1
889.5
1178.3
1178.5
1178.8
1179.0
310.5
307.2
304.0
300.8
5.053
4.998
4.943
4.891
.2010
.2032
.2053
.2075
74.3
75.3
76.3
77.3
89
90
91
92
319.2
320.0
320.8
321.6
290.3
291.1
291.9
292.7
888.9
888.3
887.8
887.2
1179.3
1179.5
1179.8
1180.0
297.7
294.7
291.8
288.9
4.839
4.788
4.739
4.690
.2097
.2118
.2139
.2160
78.3
70.3
80.3
81.3
93
94
95
96
322.3
323.1
323.8
324.6
293.5
294.3
295.1
295.9
886.6
886.1
885.5
885.0
1180.2
1180.4
1180.7
1180.9
286.1
283.3
280.6
278.0
4.643
4.596
4.551
4.506
.2182
.2204
.2224
.2245
82.3
83.3
81.3
85.3
97
98
99
100
325.3
326.1
326.8
327.5
296.6
297.4
298.1
298.9
884.5
883.9
883.4
882.9
1181.1
1181.4
1181.6
1181.8
275.4
272.8
270.3
267.9
4.462
4.419
4.377
4.336
.2266
.2288
.2309
.2330
80.3
87.3
8S.3
89.3
101
102
103
104
328.2
329.0
329.7
330.4
299.6
300.4
301.1
301.8
882.3
881.8
881.3
880.8
1182.0
1182.2
1182.5
1182.7
265.5
263.2
260.9
258.7
4.296
4.256
4.217
4.179
.2351
.2371
.2392
.2413
90.3
91.3
92.3
9J.3
105
106
107
108
331.1
331.8
332.4
333.1
302.5
303.3
304.0
304.7
880.3
879.8
879.3
878.8
1182.9
1183.1
1183.3
1183.5
256.5
254.3
252.2
250.1
4.142
4.105
4.069
4.033
.2434
.2454
.2475
.2496
94.3
95.3
93.3
97.3
109
110
111
112
333.8
334.5
335.1
335.8
305.4
306.1
306.8
307.4
878.3
877.8
877.3
876.9
1183.7
1183.9
1184.1
1184.3
248.0
246.0
244.0
242.0
3.998
3.964
3.931
3.897
.2516
.2537
.2558
.2578
98.3
99.3
100.3
1C1.3
113
114
115
116
336.5
337.1
337.8
338.4
308.1
308.8
309.5
310.1
876.4
875.9
875.4
875.0
1184.5
11S4.7
1184.9
1185.1
240.1
238.2
236.3
234.5
3.865
3.833
3.802
3.771
.2599
.2619
.2640
.2661
102.3
103.3
101.3
105.3
117
118
119
120
339.1
339.7
340.3
340.9
310.8
311.4
312.1
312.7
874.5
874.0
873.6
873.1
1185.3
1185.5
1185.7
1185.9
232.7
231.0
229.3
227.6
3.740
3.711
3.681
3.652
.2681
.2707
.2722
.2742
10'3.3
107.3
1013
109.3
121
122
123
124
341.6
342.2
342.8
343.4
313.4
314.0
314.7
315.3
872.7
872.5
871.8
871.3
1186.1
1186.3
1186.5
1186.6
226.0
224.4
222.8
221.2
3 624
3.596
3.568
3.541
.2762
.2782
.2802
.2822
110.3
111.3
125
126
344.0
344.6
315.9
316.6
870.9
870.4
1186.8
1187.0
219.7
218.2
3.515
3.488
.2842
.28o2
902
PHOMJIITIES OF SATURATED STEAM- Continued.
Pounds per
Square Inch.
? P
11
<V '-1
S3 a
H
Heat Units in one
Pound above 32° F.
Volume.
© o
6
B
6
<
^-2
53 « o z
Z 71 z,~
7t o - 1:
Rela-
tive
"CuTFt.
in 1 Cu
Ft. of
Water.
Specific
®O02
Cu. Ft.
in 1 Lb.
of
Steam.
112.3
113.3
114.3
115.3
127
128
129
130
345.2
345.8
346.4
347.0
317.2
317.8
318.4
319.0
870.0
869.6
869.1
868.7
1187.2
1187.4
1187.6
1187.8
216.7
215.2
213.7
212.3
3.463
3.437
3.412
3.387
.2882
.2902
.2922
.2942
116.3
117.3
118.3
119.3
131
132
133
134
347.6
348.2
348.8
349.3
319.6
320.2
320.8
321.4
868.3
867.8
867.4
867.0
1187.9
1188.1
1188.3
1188.5
210.9
209.5
208.1
206.7
3.363
3.339
3.315
3.292
.2961
.2981
.3001
.3020
120.3
121.3
122.3
123.3
135
136
137
138
349.9
350.5
351.0
351.7
322.0
322.6
323.2
323.8
866.6
866.2
865.7
865.3
1188.6
1188.8
1189.0
1189.1
205.4
204.1
202.8
201.5
3.269
3.247
3.224
3.202
.3040
.3060
.3079
.3099
124.3
125.3
126.3
127.3
139
140
141
142
352.2
352.7
353.3
353.8
324.3
324.9
325.5
326.1
864.9
864.5
864.1
863.7
1189.3
1189.5
1189.7
1189.8
200.2
199.0
197.8
196.6
3.180
3.159
3.138
3.117
.3118
.3138
.3158
.3178
128.3
129.3
130.3
131.3
143
144
145
146
354.4
354.9
355.5
356.0
326.8
327.2
327.8
328.3
863.3
862.9
862.5
862.1
1190.0
1190.2
1190.3
1190.4
195.4
194.2
193.0
191.9
3.097
3.076
3.056
3.037
.3199
.3219
.3239
.3259
132.3
133.3
134.3
135.3
147
148
149
150
356.5
357.1
357.6
358.1
328.9
329.4
330.0
330.5
861.7
861.4
861.0
860.6
1190.6
1190.8
1191.0
1191.1
190.8
189.7
188.6
187.5
3.017
2.998
2.980
2.961
.3279
.3299
.3319
.3340
136.3
137.3
138.3
139.3
151
152
153
154
358.6
359.2
359.7
360.2
331.1
331.6
332.2
332.7
860.2
859.8
859.4
859.1
1191.3
1191.4
1191.6
1191.8
186.4
185.3
184.3
183.3
2.942
2.924
2.906
2.888
.3358
.3376
.3394
.3412
140.3
141.3
142.3
143.3
155
156
157
158
360.7
361.2
361.7
362.2
333.2
333.7
334.3
334.8
858.7
85S.3
857.9
857.6
1191.9
1192.1
1192.2
1192.4
182.3
181.3
180.3
179.3
2.871
2.853
2.837
2.819
.3430
.3448
.3466
.3484
144.3
145.3
146.3
147.3
159
160
161
162
362.7
363.2
363.7
364.2
335.3
335.8
336.3
336.9
857 2
856.8
856.5
856.1
1192.5
1192.7
1192.8
1193.0
178.3
177.3
176.4
175.5
2.804
2.787
2.770
.3502
.3520
.3539
.3558
148.3
149.3
150.3
151.3
163
164
165
166
364.7
365.2
365.7
366.2
337.4
337.9
338.4
338.9
855.7
855.4
855.0
854.7
1193.1
1193.3
1193.5
1193.6
174.6
173.7
172.8
171.9
2.737
2.722
2.706
2.691
.3577
.3596
.3614
.3633
152.3
153.3
167
168
366.7
367.1
339.4
339.9
854.3
853.9
1193.7
1193.9
171.0
170.1
2.676
2.661
.3652
.3671
CONDENSATION IN STEAM-PIPES.
903
PROPERTIES OJP §ATIJBATED STEAM -
Pounds per
Square Inch.
p o3
EH
Heat Units in One
Pound above 32° F.
Volume.
S v
■**%
&
d ° * a
SpOo
asm
ii " "-> i
HhWm
w
Rela-
tive
Specific
beg
Cu. Ft.
in 1 Cu.
Ft. of
Water.
Cu. Ft.
in 1 Lb.
of
Steam.
154.3
155.3
156.3
157.3
169
170
171
172
367.6
368.1
368.6
369.1
340.4
340.9
341.4
341.9
853.6
853.2
852.9
852.6
1194.0
1194.2
1194 3
1194.5
169.2
168.4
167.6
166.8
2.646
2.633
2.617
2.603
158.3
159.3
160.3
161.3
173
174
175
176
369.5
370.0
370.5
370.9
342.4
342.8
343.3
343.8
852.2
S51.9
851.5
851.2
1194.6
1194.8
1194.9
1195.0
166.0
165.2
164.4
163.6
2.589
2.575
2.561
2.547
162.3
163.3
164.3
165.3
177
178
180
371.4
371.9
372.3
372.8
344.3
344.8
345.3
345.7
850.8
850.5
850.2
849.8
1195.2
1195.3
1195.5
1195.6
162.8
162.0
161.2
160.4
2.533
2.521
2.507
2.494
166.3
167.3
168.3
169.3
181
182
183
1S4
373.2
373.7
374.1
374.6
346.2
346.7
347.1
347.6
849.5
849.2
848.8
848.5
1195.7
1195.9
1196.0
1196.2
159.7
159.0
158.3
157.6
2.480
2.468
2.455
2.443
170.3
171.3
172.3
173.3
185
186
187
188
375.0
375.5
375.9
376.4
348.1
348.6
349.0
349.5
848.2
847.8
847.5
847.2
1196.3
1196.4
1196.6
1196.7
156.9
156.2
155.5
154.8
2.430
2.418
2.406
2.394
174.3
175.3
176.3
177.3
189
190
191
192
376.8
377.2
377.7
378.1
349.9
350.4
350.8
351.3
846.9
846.5
846.2
845.9
1196.8
1197.0
1197.1
1197.2
154.1
153.4
152.7
152.0
2.382
2.370
2.358
2.347
178.3
179.3
180.3
181.3
193
194
195
196
378.5
379.0
379.4
379.9
351.7
352.2
352.6
353.1
845.6
845.3
845.0
844.6
1197.4
1197.5
1197.6
1197.8
151.3
150.7
150.1
149.5
2.335
2.324
2.312
2.302
182.3
183.3
184.3
185.3
197
198
199
200
380.3
380.7
381.1
381.5
353.5
354.0
354.4
354.8
844.3
844.0
843.7
843.4
1197.9
1198.0
1198.1
1198.3
148.9
148.3
147.7
147.1
2.290
2.279
2.269
2.258
186.3
187.3
188.3
• 189.3
201
202
203
204
381.9
382.4
382.8
383.2
355.3
355.7
356.1
356.6
843.1
842.8
842.5
842.2
1198.4
1198.5
1198.7
1198.8
146.5
145.9
145.3
144.7
2.248
2.238
2.227
2.216
190.3
191.3
192.3
193.3
205
206
207
208
383.6
384.0
384.4
384.8
357.0
357.4
357.9
358.3
841.8
841.5
841.2
841.0
1198.9
1199.0
1199.2
1199.3
144.1
143.5
1*2.9
142.3
2.204
2.196
2.186
2.176
194.3
195.3
209
210
385.2
385.6
358.7
359.1
840.7
840.4
1199 4
1199.5
141.8
141.3
2.166
2.1o7
904
CO»I>EI¥!iATi:01¥ Mf STIAM.PIPES.
(w. w. c.)
No very satisfactory figures are found for the absolute condensation
losses in steam pipes, most of reported tests being compared with hair felt.
0.012 lbs. per 24 hours per sq. ft. of pipe per degree Fahr., difference in
temperature of steam and external air, which may be used in calculations,
is based on the following :
Lbs. of Water.
d>
u ^
Sq. ft.
Sur-
face.
0> 3
is*
2. & •
5 ate
&3
u o
"el**
■ p
Jd So
Test by.
in 24
hrs.
per
sq. ft.
in 24
hrs.
Covering.
Bedle & Bauer.
4130
11315
2.74
262
.0104
Asbestos.
Norris.
3892
9360
2.40
234
.0103
Asbestos.
Brill.
308
.0105
Magnesia sect'l.
Norton.
315
.0125
Magnesia.
The last test by C. L. Norton (Trans. A. S. M. E., 1898) was made with the
utmost care. Mr. Norton found that a pipe boxed in with charcoal 1 inch
minimum thickness Avas 20 per cent better insulated than when magnesia
was used, corroborating Mr. Reinhart's statements concerning his experi-
ence using flue dust to insulate pipes.
Aboard Ship. — The battleship "Shikishima" carries 25 Belleville
boilers capable under full steam of developing 15,000 I.H.P. in the main
engines besides working the auxiliaries, each boiler supplying steam for
150 I.H.P. When at anchor, one boiler under easy steam, i.e., evaporating
from 9 lb. to 10 lbs. of water from and at 212° F., per pound of coal — was
just able to work one 48 K.W. steam dynamo at about half power, together
with one feed pump, and the air and ciroulating pumps connected with the
auxiliary condenser, into which the dynamo engine exhausted, besides
working a fire and bilge pump occasionally.
The dynamo was about 160 ft. of pipe length away from the boiler, the
total range of steam pipe length connected being 500-600 ft.
Performing the first-mentioned service with only one boiler under steam,
the coal burned varied from 3h to 5 tons per day of 18 hours, for about 65
I.H.P., or about 7 lbs. per indicated horse-power at the best to 10 lbs. at the
worst, an average of 8 lbs. and over, which shows that more than half the
fuel must have been expended in keeping the pipes warm. All pipes were
well covered and below decks, and machinery in first-class condition.
(London-Engr.)
Heating* JPipes. — To determine the boiler H.P. necessary for heating,
it maybe assumed that each sq. ft. of radiating surface will condense about
0.3 lbs. of steam per hour as a maximum when in active service ; thus 20,000
sq. ft. times 0.3=6000 lbs. of condensation, which divided by 30 gives 200
boiler horse-power.
Condensed steam in which there is no oil may be returned to the boiler
with the feed-water to be re-evaporated.
OUTFLOW OF STEAM.
905
OCTFIOW OF STEAM FROM A 6ITM OITI.1I
PR£^lTRE IUTO VARIOUS LOWER PRESSURES.
(D. K. Clark.)
Absolute
Outside
Velocity of
Actual Ve-
Weight Dis-
Pressure in
Pressure
Ratio of
Outflow at
locity of
charged per Sq.
Boiler per
per Sq.
Expansion.
Constant
Outflow
In. of Orifice
Sq. Inch.
Inch.
Density.
Expanded.
per Minute.
Lbs.
Lbs.
Ratio.
Ft. per Sec.
Ft. per Sec.
Lbs.
75
74
1.012
227.5
230
16.68
75
72
1.037
386.7
401
28.35
75
70
1.063
400
521
35.93
75
65
1.136
660
749
48.38
75
61.62
1.198
736
876
53.97
75
60
1.219
765
933
56.12
75
50
1.434
873
1252
64.
75
45
1.575
890
1401
65.24
75
43.46, 58 %
1.624
890.6
1446.5
65.3
75
15
1.624
890.6
1446.5
65.3
75
0
1.624
890.6
1446.5
65.3
When, however, steam of varying initial pressure is discharged into the
atmosphere — pressures of which the atmospheric pressure is not more
than 58 per cent — the velocity of outflow at constant density, that is, sup-
posing the initial density to be maintained, is given by the formula —
V— 3.5953 yfh,
where V= the velocity of outflow in feet per minute, as for steam of the
j initial density, h = tlie height in feet of a column of steam of the given
absolute initial pressure of uniform density, the weight of which is equal to
| the pressure on the unit of base.
The following table is calculated from this formula :
OUTEUOW OF STEAM INTO THE ATMOSPHERE.
(D. K. Clark.)
Absolute
Initial
Outside
Ratio of
Velocity of
Actual Ve-
Weight Dis-
Pressure in
Pressure
Expansion
Outflow at
locity of
charged per
Boiler in
in Lbs. per
in
Constant
Outflow,
Sq. Inch of
Lbs. per
Sq. Inch.
Sq. Inch.
Nozzle.
Density.
Expanded.
Orifice per Min.
Lbs.
Lbs.
Ratio.
Ft. per Sec.
Ft. per Sec.
Lbs.
25.37
14.7
1.624
863
1401
22.81
30
14.7
1.624
867
1408
26.84
40
14.7
1.624
874
1419
35.18
45
14.7
1.624
877
1424
39.78
50
14.7
1.624
880
1429
44.06
60
14.7
1.624
8S5
1437
52.59
70
14.7
1.624
889
1444
61.07
75
14.7
1.624
891
1447
65.30
90
14.7
1.624
895
1454
77.94
100
14.7
1.624
898
1459
86.34
115
14.7
1.624 .
902
1466
98.76
135
14.7
1.624
906
1472
115.61
155
14.7
1.624
910
1478
132.21
165
14.7
1.624
912
1481
140.46
215
14.7
1.624
919
1493
181.58
906
STEAM PIPES.
Rankine says the velocity of steam flow in pipes should not exceed 6000
feet per minute (100 feet per second). As increased size of pipe means in-
creased loss by radiation, care should be taken that in order to decrease the
velocity of flow, the losses by radiation do not become considerable.
The quantity discharged per minute may be approximately found by
JRankine's formula (" Steam Engine," p. 298;, W = 00 ap -j- 70 — Gajj-f 7, in
which W = Aveight in pounds, a = area of orifice in square inches, and p ■=
absolute pressure. The results must be multiplied by lc = 0.93 for a short,
pipe, and by lc = 0.63 for their openings as in a safety valve.
Where steam flows into a pressure greater than two-thirds the pressure in ;
the boiler, W = 1.9 ak^(p — d) d, in which d = difference in pressure in
pounds per square inch between the two sides, and a,p, and A; as above.
Multiply the results by 2 to reduce to h.p. To determine the necessary dif-
ference in pressure where a given h.p. is required to flow through a given
opening,
(L - 2 V 4 14 aVc
Flow of Steam Tliroug-li Pipes.
(G. H. Babcock in " Steam.")
The approximate weight of any fluid which will flow in a minute through
any given pipe with a given head or pressure may be found by the formula
r=87t /:
D (Pi — Pi) d5
3.6\
*+¥)
in which W= weight in pounds, d = diameter in inches, D =. density or
weight per cubic foot, ^ = initial pressure, p2 — pressure at the end of the
pipe, and L = length in feet.
The following table gives, approximately, the weight of steam per minute
which will flow from various initial pressures, with one pound loss of pres-
sure through straight smooth pipes, each having a length of 240 times its
own diameter. For sizes below 6 inches, the flow is calculated from the
actual areas of " standard " pipe of such nominal diameters.
For h.p. multiply the figures in the table by two. For any other loss of
pressure, multiply by the square root of the given loss. For any other
length of pipe, divide 240 by the given length expressed in diameters, and
multiply the figures in the table by the square root of this quotient, which
will give the flow for 1 pound loss of pressure. Conversely dividing the
given length by 240 will give the loss of pressure for the flow given in the
table.
Table of Flow of Steam Tliroug-li Pipes.
Initial Pres-
sure by
Gauge.
Lbs. per Sq.
Inch.
10
20
30
40
50
60
70
Diameter of Pipe in Inches. Length of each — 240 Diameters.
Weight of Steam per Min. in Lbs., with 1 Lb. Loss of Pressure.
1.16
2.07
5.7
10.27
15.45
25.38
46.85
1.44
2.57
7.1
12.72
19.15
31.45
58.05
1.70
3.02
8.3
14.94
22.49
36.94
68.20
1.91
3.40
9.4
16.84
25.35
41.63
76.84
2.10
3.74
10.3
18.51
27.87
45.77
84.49
2.27
4.04
11.2
20.01
30.13
49.48
91.34
2.43
4.32
11.9
21.38
32.19
52.87
97.60
2.57
4.58
12.6
22.65
34.10
56.00
103.37
2.71
4.82
13.3
23.82
35. S7
58.91
108.74
2.83
5.04
13.9
24.92
37.52
61.62
113.74
2.95
5.25
14.5
25.96
39.07
64.18
118.47
3.16
5.63
15.5
27.85
41.93
68.87
127.12
3.45
6.14
17.0
30.37
45.72
75.09
138.61
STEAM PIPES.
907
Table of Plow of Steam Xliroug-ti I*ipe«.— Continued.
Initial Pres-
sure by
Gauge.
Lbs.' per Sq
Inch.
Diameter of Pipe in Inches. Length of Each = 240 Diameters.
I
Weight of Steam per Min. in Lbs., with 1 Lb. Loss of Pressure.
10
20
40
50
100
120
150
95.8
112.6
126.9
139.5
150.8
161.1
170.7
179.5
187.8
195.6
209.9
115.9
211.4
341.1
143.6
262.0
422.7
168.7
307.8
496.5
190.1
346.8
559.5
209.0
381.3
615.3
226.0
412.2
665.0
241.5
440.5
710.6
255.8
466.5
752.7
269.0
490.7
791.7
281.4
513.3
828.1
293.1
534.6
862.6
314.5
573.7
925.6
343.0
625.5
1009.2
502.4
622.5
731.3
824.1
906.0
979.5
1046.7
1108.5
1166.1
1219.8
1270.1
1363.3
1486.5
804
1177
996
1458
1170
1713
131 S
1930
1450
2122
1567
2294
1675
2451
1774
2596
1866
2731
1951
2856
2032
2975
21S1
3193
2378
3481
The loss of head due to getting up the velocity, to the friction of the
steam entering the pipe and passing elbows and valves, will reduce the
"~-y given in the table. The resistance at the opening and that at a
be valve are each about the same as that for a length of pipe equal to
114 diameters divided by a number represented by 1 -f- -j- ■ For the sizes of
pipes given in the table these corresponding lengths are :
20 1 25 1 34 | 41 I 47 j 52 | 60 |
71
79
84
92
95
The resistance at an elbow is equal to § that of a globe valve. These
equivalents — for opening, fur elbows, and for valves —must be added in
each instance to the actual length of pipe. Thus a 4-inch pipe, 120 diame-
ters M0 feet) long, with a globe valve and three elbows, would be equivalent
to 120 + 60 + 60 4- (3 X 40) = 360 diameters long ; and 360 -f 240 = 1±-. It
would therefore have 1£ ibs. loss of pressure at the flow given in the table,
or deliver (1 ~ Vf| — 8.16), 81.6 per cent of the steam with the same (1 lb.)
loss of pressure.
^Equation of Pipes (Steam).
It is frequently desirable to know what number of one size of pipes will
equal in capacity another given pipe for delivery of steam or water. At
the same velocity of flow two pipes deliver as the squares of their internal
diameters, but the same head will not produce the same velocity in pipes of
different sizes or lengths, the difference being usually stated to vary as the
square root of the fifth power of the diameter. The friction of a fluid
within itself is very slight, and therefore the main resistance to flow is the
friction upon the sides of the conduit. This extends to a limited distance,
and is, of course, greater in proportion to the contents of a small pipe than
ol a large. It may be approximated in a given pipe by a constant multi-
plied by the diameter, or the ratio of flow found bv dividm*? some power of
the diameter by the diameter increased by a constant. Careful compari-
sons of a large number of experiments, bv different investigators, has de-
Vf ?PJ? the followin.g as a close approximation to the relative flow in pipes
of different sizes under similar conditions :
W oo
V d + 3.6
W being the weight of fluid delivered in a given time, and d being the
internal diameter in inches.
908
The diameters of " standard " steam and gas pipe, however, vary from the
nominal diameters, and in applying this rule it is necessary to take the true
measurements, which are given in the following table :
Tal>le of Standard Sizes Steam and GaN Pipes,
s
<s
3
Diameter.
o
o
"3
M
KH
^
1
<S
Inter-
Exter-
®
Inter-
Exter-
of
Inter-
Exter-
.2
nal.
nal.
N
nal.
nal.
N
nal.
nal.
CO
co
CO
i
.27
.40
21
2.47
2.87
9
8.94
9.62
\
.36
.54
3
3.07
3.5
10
10.02
10.75
!
.49
.67
3^
3.55
4
11
11
11.75
.62
.84
4
4.03
4.5
12
12
12.75
#
.82
1.05
4i
4.51
5
13
13.25
14
l
1.05
1.31
5
5.04
5.56
14
14.25
15
H
1.38
1.06
6
6.06
6.62
15
15.43
16
H
1.61
1.90
7
7.02
7.62
16
16.4
17
2
2.07
2.37
8
7.98
8.62
17
17.32
18
The following table gives the number of pipes of one size required to
equal in delivery other larger pipes of the same length and under the same
conditions. The upper portion above the diagonal line of blanks pertains to
" standard " steam and gas pipes, while the lower portion is for pipe of the
actual internal diameters given. The figures given in the table opposite the
intersection of any two sizes is the number of the smaller-sized pipes
required to equal one of the larger.
DIAGRAM GIVING
DIAMETER OF STEAM AND EXHAUST PIPES
\k. F°R ENG'NE CYLINDERS FROM 5 TO 40 INCHES DIAMETER,
AT PISTON SPEEDS UP TO 1,000
FEET PER MINUTE
FROM "POWER"
16-
14-
15-
13-
14-
12-
13-
11-
12-
11-
10-
10-
9-
ffi 9-
8-
2 8-
S7-
E 7-
K3 6-
3 b-
?5-
3 5-
H
* 4-
£ 4-
<£
S 3~
H 3-
1-
la-
12-
0 1-
0 0-
%o-
-
5^
"
40 35 an «k oh J- J,
25 20
Fig. 11.
STEAM PIPES.
909
°«tci
HH^JiCO'^mOt'COOHrtMrtHHH
1
£
9717
42S2
2092
614
307
184
100
47.4
25.8
15.6
10.6
7.52
5.50
3.91
3.22
2.58
1.98
1.64
1.35
1.14
1.16
1.52
2.43
4.30
6.85
10.1
14.2
t-
S
8535
3761
1837
539
269
161
88.0
41.6
22.6
13.8
9.31
6.60
4.83
3.43
2.83
2.26
1.74
1.44
117
1.17
1.36
1.78
2.84
5,03
8.01
11.9
16.6
1"
S
7321
3226
1576
463
231
138
75.5
35.7
19.4
11.8
7.97
5.67
4.14
2.94
2.43
1.93
1.49
1.24
1.18
1.37
1.59
2.08
3.32
5.88
9.37
13.9
19.4
s
3
5927
2615
1263
375
187
112
61.1
28.9
15.7
9.56
6.45
4.57
3.35
2.38
1.88
1.57
1.21
1.21
1.42
1.66
1.92
2.52
4.02
7.14
11.3
16.8
23.5
2
4904
2161
1070
310
155
92.6
50.6
23.9
13.0
7.91
5.34
3.79
2.77
1.97
1.03
1.30
1.22
1.48
1.73
2.03
2.35
3.08
4.92
8.72
13.9
20.5
28.8
s
a
3786
1668
815
239
119
71.5
39.1
18.5
10.0
6.11
4.12
2.92
2.14
1.52
1.26
1.22
1.50
1.81
2.12
2.47
2.87
3.76
6.01
10.7
16.9
25.1
35.2
1 M
a
s
3014
132S
649
190
95.1
56.9
31.2
14.7
8.00
4.86
3.2s
2.33
1.71
1.21
1.26
1.53
1.88
2.27
2.66
3.11
3.60
4.73
7.55
13.4
21.3
31.5
44.2
fl
o
2488
1096
536
157
78.5
47.0
23.7
12.1
6.60
4.02
2.71
1.93
1.41
1.28
1.61
1.98
2.41
2.92
3.41
4.63
6.07
9.70
17.2
27.3
40.5
56.8
*
C5
1767
779
380
112
55.8
33.4
20.9
8.61
4.69
2.85
1.93
1.35
1.32
1.70
2.13
2.60
3.18
4.51
5.27
6.11
S.02
12.8
22.7
36.1
53.4
75.0
i.
6
P.
s
CO
1292
569
278
81.7
40.8
24.4
13.3
6.30
3.43
2.09
1.41
1.37
1.80
2.32
2.91
3.56
4.35
5.27
6.15
7 20
8.35
10.9
17.5
31.0
49.3
73.0
102
„
r.
-
918
405
198
58.1
29.0
17.4
9.48
4.48
2.44
1.48
1.43
1.95
2.57
3.31
4.15
5.07
621
7.52
8J8
10.3
11.9
15.6
25.0
41.2
70.4
104
146
«>
C
£
CO
620
273
133
39.2
19.6
11.7
6.39
3.02
1.65
1.51
2.18
2.98
3.93
5.05
6.34
7.75
9.48
11.5
13.4
15.7
1S.2 ■
23.9
38.2
67.6
108
159
CO
cc
1Q
377
166
81.1
23.8
11.9
7.12
3.89
1.84
1.63
2.49
3.54
4.85
6.40
8.22
10.3
12.6
15.4
18.7
21.8
25.6
29.6
38.9
62.1
110
175
259
363
io
c
<-
-
205
90.4
44.1
13.0
6.47
3.87
2.12
1.83
2.97
4.54
6.48
8.85
11.7
15.0
18.8
23.0
28.2
34.1
39.9
46.6
54.1
70.9
113
201
319
473
663
*#
CO
96.9
42.5
20.9
6.13
3.06
1.83
2.21
4.03
6.56
10.0
14.3
19.5
25.8
33.1
41.6
50.7
62.2
75.3
88.0
103
119
157
250
443
705
1044
1465
-
a
52.9
23.3
11.4
3.34
1.67
1.66
3.67
6.70
10.9
16.6
23.8
32.5
42.9
55.1
69.2
84.5
103
125
146
171
198
260
416
736
1172
1734
2434
5?
«
31.7
14.0
6.82
1.26
1.87
3.11
6.87
12.5
20.4
31.2
44.5
60.8
80.4
103
129
158
193
234
274
320
371
487
778
1378
2193
3245
4554
CO
*
15.8
6.97
3.45
2.26
4.23
7.03
15.5
28.3
46.0
70.5
101
137
181
233
293
358
438
530
619
724
840
1102
1761
3117
4961
7341
10301
*
-
4.88
2.05
3.20
7.25
13.6
22.6
49.8
90.9
148
226
322
440
582
747
938
1146
1403
1098
1984
2322
2691
3532
5644
9990
15902
23531
33020
~
-
2.27
2.90
9.30
21.0
39.4
65.4
144
263
429
656
936
1281
1688
2168
2723
3326
4070
4927
5758
6738
7810
10249
16376
2X91)0
46143
6S282
95818
*
*
2.60
7.55
24.2
54.8
102
170
376
686
1116
1707
2435
3335
4393
5612
7087
8657
10600
12824
14978
17537
'20327
26676
42621
75453
120100
177724
249351
-ma
rtiNsi-*^ "^Kt m'co ^iocot>.<x>c^0"HC<'M'r*lli:5':ot:~coo~l''0':oc':iC0
•VIQ
910
ft »
« 1
o
ft 1
H 2
ft S
si :
ft 2 >, £
2 o o
H e8
3
o
a
S
3
o
s
rH ■* CiOCOlO
CO rH L- -fl 10 CO
•ssoq; jo opu'a;
1.000
.280
.172
.091
.056
.042
•jnou isd imfi
joo^ .i8d sjuifi ui ssoq;
1077.4
301.7
185.3
98.0
60.3
45.2
.5
•jsoq;
'd "H a9d q^SuQT ui %dd£
rH 63 -t< f- C5
■ssoq; jo opi:^
1.000
.301
.170
.103
.063
.047
mtioh J9c[ tttl'St
joojj jad s^iufi ui ssot;
729.8
219.6
128.3
46.0
34.3
_cB
CO
•;soq;
•<I -H J9d txjSuoT: ai ;a'8j[
co t- 0 -¥ co a
10 t- 0 — 0 X
rHCOiOCOO
•ssoq; jo 017133;
1.000
.300
.178
.106
.066
.054
•.inoH -lad un>i
^00,3; .I8d SiJIUfl tii ssori
624.1
187.2
111.0
66.2
41.2
33.7
3
•iso-j
"<I TI -T9CT u^Sus^ ui 788^
86
182
284
451
745
1186
1424
■ssori jo otjb'h;
1.00
.46
.30
.18
.11
.07
.06
muoh -I9d unjj
joo^j aad sjiuq, ui ssorj
390.8
180.9
117.2
73.9
44.7
28.1
23.4
s
•jsoq-
152
331
507
761
1173
1683
•sso't; jo oiji3>j
1.00
.46
.30
.20
.13
.09
muoh; .T8d mi-j-x
700j[ .I8d S'HUQ ui ssorx
219.0
100.7
65.7
43.8
28.4
19.8
•sanou
J UI §lII.I8AOQ JO SS8U5[0iqX
©~ """i-H <M ■<* CO
STEAM PIPES.
911
In a paper read before the A. S. M. E. in June, 1898, Prof. C. L. Norton of
the Massachusetts Institute Technology, gave a series of tables showing the
results of tests. For the sake of brevity the descriptions of the different
materials are omitted. The tables follow :
Specimen.
•
0§3
wA
O tD 03 ?
2.20
15.9
1.00
2.38
17.2
.80
2.38
17.2
1.25
2.-15
17.7
1.12
2.49
18.0
1.12
2.62
18.9
1.12
2.77
20.0
1.12
2.80
20.2
1.50
2.87
20.7
1.25
2.88
20.8
1.50
2.91
21.0
1.12
3.00
21.7
1.12
3.33
24.1
1.12
3.61
26.1
1.12
13.84
100.
Nonpareil Cork Standard
Nonpareil Cork Octagonal
Manville High Pressure .
Magnesia
Imperial Asbestos . . .
" B.
Asbestos Air Cell . . .
Manville Infusorial Earth
Manville Low Pressure .
Manville Magnesia Asbestos
Magnabestos ....
Molded Sectional . .
Asbestos Fire Board .
Calcite
Bare Pipe
Specimen.
miscellaneous !§>uostances.
B.T.U. per
Specimens.
sq. ft. per
min.
at 200 lbs
. 3.18
Box A, 1 with sand . .
2 with cork, powdered . . 1.75
3 with cork and infusorial 1.90
earth . .
4 with sawdust 2.15
5 with charcoal 2.00
6 with ashes 2.46
Brick wall 4 inches thick . . 5.18
Pine wood 1 inch thick
Hair felt 1 inch thick .
Cabot's seaweed quilt .
Spruce 1 inch thick . .
Spruce 2 inches thick .
Spruce 3 inches thick .
Oak 1 inch thick . . .
Hard pine 1 inch thick .
B.T.U. per
sq. ft. per
min.
at 200 lbs.
. 3.56
. 2.51
. 2.78
. 3.40
2.31
. 2.02
. 3.65
. 3.72
Prof. B,. C. Carpenter says that there is great difference in the flow of heat
through a metal plate between different media. In discussing Professor
Norton's paper he gave the values as shown in the following table as the
result of experiments conducted in his laboratory.
Heat transmitted, in Thermal "Units Through Clean Cast-
iron T»late T7g Inch Thick. (Carpenter.)
Difference
of
Temperature.
Degrees F.
Steam to Water.
Lard Oil to Water.
Air to Water.
Per Square Foot.
Per Square Foot.
Per Squ
are Foot.
Per Deg
Total per
Per Deg.
Total per
Per Deg.
Total per
per hour
mimne
per hour
minute
per hour
minute
B. T. U
B. T. U.
B. T. U.
B. T. IT.
B. T. U.
B. T. IT.
25
21
8.8
6.5
2.7
1.2
0.5
50
48
40
13
10.8
2.5
2.7
75
84
110
19.5
24.5
3.7
5.8
100
127
211
26
43.3
5.0
8.3
125
185
375
31.5
65.5
6.2
13
150
255
637
39
72.5
7.5
18.7
175
45.5
132
8.7
25.4
200
52
173
10
33
300
78
390
15
75
400
20
133
500
25
208
The above investigation indicates that the substance which surrenders the
heat is of material importance, as is also the temperature of the surrounding
media.
912
jo qouj
jod syedjqx
jo aequmsj
t^COCO-^-tlT^^r-i^OOOOCOOOOOOOOOOOOOOOCOCOOOOOOOOO
t
s
PS
s
H
II
4
.241
.42
.559
.837
1.115
1.668
'2.244
2.678
3.609
5.739
7.536
9.001
10.665
12.34
14.502
18.762
23.271
28.177
33.701
40.065
45.95
48.985
53.921
57.893
61.77
69.66
77.57
85.47
93.37
^"3
so .
crjS o
2513.
1383.3
751.2
472.4
270.
166.9
96.25
70.66
42.91
30.1
19.5
14.57
11.31
9.02
7.2
4.98
3.72
2.88
2.29
1.82
1.456
1.27
1.04
.903
.788
.616
.495
.406
.339
o £,+=
"So 53^
§ ft
M xi
3
14.15
10.49
7.73
6.13
4.635
3.645
2.768
2.371
1.848
1.547
1.245
1.077
.949
.848
.757
.63
.544
.478
.427
.382
.339
.319
.288
.268
.250
.221
.198
.179
.164
1 ^
3,— i rt
^ x
CD
9.44
7.075
5.657
4.547
3.637
2.904
2.301
2.01
1.608
1.328
1.091
.955
.849
.764
.687
!501
.443
.397
.355
.318
.299
.273
.255
.239
.212
.191
.174
.159
B3
*■ s
s
<
CD
l>
'S
1
.0717
.1249
.1663
.2492
.3327
.4954
.668
.797
1.074
1.708
2.243
2.679
3.174
3.674
4.316
5.584
6.926
8.386
10.03
11.924
13.696
14.579
16.051
17.23
18.407
20.764
23.12
25.477
27.832
CD
X'
.0573
.1041
.1917
.3048
.5333
.8626
1.496
2.038
3.356
4.784
7.388
9.887
12.73
15.961
19.99
28.888
38.738
50.04
62.73
78.839
99.402
113.098
137.887
159.485
182.655
233.706
291.04
354.657
424.558
CD
=
X
.129
.229
.358
.554
.866
1.358
2.164
2.835
4.43
6.492
9.621
12.566
15.904
19.635
24.306
34.472
45.664
58.426
72.76
90.763
113.098
127.677
153.938
176.715
201.062
254.47
314.16
380.134
452.39
03
3
o
"3
el
CD
CD
.848
1.144
1.552
1.957
2*589
3.292
4.335
5.061
6.494
7.753
9.636
11.146
12.648
14.162
15.849
19.054
22.003
25.076
28.076
31.477
35.343
37.7
41.626
44.768
47.909
54.192
60.476
66.759
73.042
to
e
B
N
H
N
"eg
PI
CD
|
1.272
1.696
2.121
2.639
3.299
4.131
5.215
5.969
7.461
9.032
10.996
12.566
14.137
15.708
17.477
20.813
23.955
27.096
30.238
33.772
37.699
40.055
43.982
47.124
50.265
56.549
62.832
69.115
75.398
•ssan5[oiqx
o
PI
.068
.088
.091
.109
.113
.134
.14
.145
.154
.204
.217
.226
.237
.246
.259
.28
.301
.322
.344
.366
.375
.375
.375
.375
.375
.375
.375
.375
.375
0
CD
s
5
!&3
i
.27
.364
.494
.623
.824
1.048
1.38
1.611
2.067
2.468
3.067
3.548
4.026
4.508
5.045
6.065
7.023
7.9S2
8.937
10.019
11.25
12.
13.25
14.25
15.25
17.25
19.25
21.25
23.25
4jH "
C
.405
.54
.675
.84
1.05
1.315
1.66
1.9
2.375
2.875
3.5
4.
4.5
5.
5.563
6.625
7.625
8.625
9.625
10.75
12.
12.75
14.
15.
16.
18.
20.
22.
24.
III
J
rtlXriWKII-fcw** WW-4N ~bl ~fa Pta
.
STEAM PIPES.
913
.i8d ^qSta^ I^uiuioj^;
a
o
Ph
.29
54
74
1.09
1.39
2.17
3.
3.63
5.02
7.67
10.25
12.47
14.97
20.54
28.58
o 33^
"So e8
G 3
F c«
CP
OP
18.632
12.986
9.07
7.046
5.109
4.016
3.003
2.556
1.975
1.649
1.328
1.137
1.
.793
.664
£
9.433
7.075
5.657
4.547
3.637
2.904
2.301
2.01
1.608
1.328
1.091
.955
.849
.687
.577
s
a
H
"3
CD
m
.086
.161
.219
.323
.414
.648
.893
1.082
1.495
2.283
3.052
3.71
4.455
6.12
8.505
5 ^
a
a1
02
.033
.068
.139
.231
.452
.71
1.271
1.753
2.935
4.209
6.569
8.856
11.449
18.193
25.967
3 ^
GO
.129
.229
.358
.554
.866
1.358
2.164
2.835
4.43
6.492
9.621
12.566
15.904
24.306
34.472
a5
a
?
a
5
a a
a?
a
a
.644
.924
1.323
1.703
2.312
2.988
3.996
4.694
6.073
7.273
9.085
10.549
11.995
15.120
18.064
CD
O
1.272
1.696
2.121
2.639
3.299
4.131
5.215
5.969
7.461
9.032
10.996
12.566
14.137
17.477
20.813
•aStVBf) 8JT^
& !JS9J'B8_JJ
6
h* .*, * * 08
ClHOG>»t»fflOiO«rtOOOO
•sson^oiqx
s
cot^cst-ci^fcoT-i rn y-t i-H in t>
Cl CI -V l- x — o CI CC O CI -f t- CO
HrlHrtHHHflCMtlMMnW-*
co
B
s
"^ G
<5
1
.205
.294
.421
.542
.736
.951
1.272
1.494
1.933
2.315
2.892
3.358
3.818
4.813
5.75
s ?
+s cu
o
.405
.54
.075
.84
1.05
1.315
1.66
1.9
2.375
2.875
3.5
4.
4.5
5.563
6.625
'3'^
si
a
rH ?h 7-t <m cf co c^V io co
1
914
2 *y 1 1
pH*CON«(N«HHrtrtHr;
iJ P-l r/5 ^
W) 2 £ ji cS
n
\£*
STKAM.
CO COO
co io i-
coco-*
LO CO —
ooio
o i -* --.
7 ! ::. ~K
t- ci oi
? ^ © o5 2? r1 - 3 2? 2.1 ° o> w -+<
o - 1 i - O' o i © © i- © -r< ©' ©
-i oi oi ci co ro -r -f -r i o lo o;
© ~ L~ 'j;.«::-tC2;:: : • ~ '" — — — © -f rH -+ -* Ci t- x ci x lo re ro -H
i::L-OH-i-c-tci:i:-i: x i - x lo © x ro — io oi © l- i- -ti o i tA © ~i x
«n«l>MOL-tttC0 01 t- © © X I- ttCTt CO CO CO 04 CM 01 01 01 0 1 ~l — rn
+-> © 10 t- CO © X 'X O CO LO rH X LO © -f t- L0 CO -+i 01 t- CO CO Ol •* CO -P CI O O rH
iHC.-fcoco:ic[-i-o-i-.-r-::-fi-:ixTHC,t- io co oi h — ■ © x
CD X O O i-i © © LO CO 0! i-H © O © X I- © L0 -r -r CO CO CO 01 01 01 01 01 Ol CM rH rH
IMCOCllMHHHHHHr
poLOcowcooncfjMccHccnHoo-t'O'fOHOiaeint'Wot-b
O © 1.0 — -+ i-i 10 L- CO i~ © L- X 01 C; ~ /. © ~r :0 i-H © c
cd -r -f x -h i-h x cq 10 co Cjwqcqoqffl lo lo -h co cr> co co ei ei 01 :i:i:i-
&-! t* CO Ol 01 01 rH rH rH i-i i-H rH i-i rH
' 10 1-0 CO L- X CO rH 01 rH CO CO t- 01 -H -H re CO O X -HH rH -HH CO
, iTi ft* ro rr, _H r. ■* - - | .. -C O I- C O' O [- O H 1". O r ^
.,.:-*-* io co i - x i-h co r.cc-H-t<-f-j-/jcrooixi- co co x co"
^O O O O 3 O © O CO © O © © rH rH rH 01 CO ~H L0 CO L- © © 01 rH LO L- © rH -HH
, . J ~ - C I - X ~ r- .
■ Co ? ■ £ tr S rr : s
rH ' ^ th CN CO CO •# IO O
UOH«
a ih n w o » » o n co uj n ci co o n o -f n -f '»'
rH rH rH rH 01 CO L0 CO L~ Ci rH CO L0 I- CO 01 >l X — -
rH rH r-, rn 01 01 0 1 01 CO C-
t~ t- CO lC- © ■* OlirSCOCOrHVOlrHt- CO « LO « "t W 00 C-l 00 Mm M C<
■ ~f CO — CO I - CO X 10 01 Ci X t- CO X Hl-H X -+• Ci L- CO 1.0 -f CO CO CO -« CO -H 0
. © © © rn rn oi oi co -t -t- io -o i- r- oi c- -+ •- co c. © oi lo cc •+ co i- lo -r -I lo
1 © © ~ © © © © © © © © © © © rH H 01 CO -+ -H CO L- X © -H CO -r CO X © 0
l-< LO © CO t-< CO -t< -H CO CO IO r- Lo JJ '© t Ci L0 L0 rH ,- O O I- O X t-N-* CO«H
rH L- CO © rH L0 rH — CO X 01 L0 X © 01 C. © © © © L- l~ -f X X rH CO Ol 01 © L- rn
. lo Ci cq © lo co r q ;«:•. -q z. — -+ 1.0 xi-ci © -i-_ t - — — i - © 01 01 © co co
COT1 " ' i-i i-i oi co' -* LO) CO t-" CO ©J © -f' I- LO* -t' lo' X r^ t^ CO CO co" -+ [ - 0 i X ) o -+ -t-
X rH rH rH 01 CO -H L0 L^ X © 01 -H © X rH CO © © 01
-R Ol IC- CM X CO © -H © 1 0 CO 1 0 r- CO I - X © rH 01 -H CO O © © 01 -H L0 l>- 00 © 03 CO
Oi -c" oi rn ci x co , o cc o i — ro x © co © -+< © co t- — ,- c. ^ x 01 © © -r © co i-
flnqtH-jHC, © x © -t o i oq i - lq - i - co © — o i -+ i o © x © — J i * lo cq cq ©
r^ CO CO -rJH LO CO t^ t-^ 00 Ci ©" ©' i-H Ol' -"" lo" 00 -H L0 CO rj -jH t^ © CO t^' ©
OCOCOrH-J<rriLOLf
)£ © -H rH i-H t^ -t1 01 t- CO 01 X CO CO CO X ~H -H © L0 -H LO L0 "t1 © 01 Ol •* LO rH t-
0- X L- © © © X L- 10 -r" © -f CO 10 01 rH o rn X 1.0 I- t- © -* ri. © © CO — 00 0 1 CO
^ © ■-? rn cq cq -+ h © i - -h o 1 1 © i - co x © ©. © ©_ © ~ oi co -+ -'r i.o © L-cqccq
2 01 CO r)3 rj< LO CO t^ [-' 00* Ci © l-H rH CO ~V t-' ©" CO* t^ ©" Co' ©' ©' 01 10 x' H -+( t-^ O CO
!-c rH rH rH rH rH rH Ol 01 Ol CO CO CO CO -* -H -H LO LO L0 © ©
Jl* 3 '-
:l 0 1 01 01 01 01 01 CO cc
CO © © -+l © -+ -H rO CO CO Ol 01 01 rH hH o © h- © L0 CO © 01 -H -H 01 X CM © © © c
•J lo © ro © © io x ro X r- © ■ h -+ o ) © io co — i - -o -h- : i ~ x i o co — © © :
- X — CO 10 X © 0 I i 0 I - © 0 I i 0 I - 0 1 I - © 'O © © i O i 0 i 0 i.O LO -fi -+i -f -+< -H CO c
o •* -J< LO © E- X © ©'-hOI CO -t' 10 © t-^ X © ©
oi'oTc
rH t-fr-i r-H 01 01 Oi 01 CO CO CO CO •# rp LO © t- CO O O rH CM CO TP lO CO t- CO © © r-
STANDARD PIPE FLANGES.
915
In estimating the effective steam-heating or boiler surface of tubes, the
surface in contact with air or gases of combustion (whether internal or
external to the tubes) is to be taken.
For heating liquids by steam, superheating steam, or transferring heat
from one liquid or gas to another, the mean surface of the tubes is to be
taken.
Collapsing- Pressure in Cylindrical Boiler-flues.
P = collapsing pressure in pounds per square inch.
t = thickness of iron plate in inches.
L — length of tube or flue in feet.
D— diameter of tube or flue in inches.
Then P = S06.300 ^-~ (Fairbairn.)
Approximately P -.
\00inl inch ; 810 in .
n ^g inch ; and 860 ii
. w
in which Jc is a constant = 790 in T3g inch plate ;
820 in | inch ; 8343 in T7S inch ; 840 in *. inch ; 850
inch plate.
LD
. inch
STA^foAKB PIPE fXAIfOES.
A. S. M. E. and Master Steam and Hot Water Fitters' Association stan-
dard, adopted July 18, 1894. Medium pressure includes pressures ranging
below 75 pounds. High pressure ranges up to 200 pounds per square inch.
■^ lo
£
§
<D
8
^3
^11
A
~ Z. ;
Er
o1
1
£
<d
1
'S
©
513
A
V
B
33
a
ft
1 *
3
\
h
P
S ■
~ i
3 tc
©ft
02
5
o
3
©
c3
ft
bD
©
o3
ft g
3
ft
ft
ft
o
3
2
B
3
o3
ft
o
ft
a
©
ft
3«o
- "75
■3-3®
Sftl
s © ^
32
2
.409
ft
460
A
6
1
2
4!
4
f
2
825
2*
.429
IS
550
i
7
ii
5i
4
t
21
1050
3
.448
f
690
1
7*
la
6
4
f
2*
1330
3i
.466
700
1
8*
2i
6*
4
1
2*
2530
4"
.486
i
800
1
9"
16
2f
21
71
4
2!
2100
*i
.498
i
900
J
9i
3
8
!
3
1430
5
.525
I
1000
*
10
T6
2*
8
!
3
1630
6
.563
i>_
1060
1
11
1
2f
9|
8
!
3
2360
7
.60
f
1120
*,
12i
It
2f
10!
8
1
31
3200
S
.639
1
1280
1
13*
2|
ii!
8
1
3*
4190
9
.6^8
ii
1310
ft
15
li
2|
13
12
i
3*
3610
10
•713
3
1330
16
ll36
3
14i
12
£
3f
2970
12
.79
if
1470
135
19
li
3i
16i-
12
1
3!
4280
14
.864
§
1600
T36
21
If
3*
18!
12
l
H
4280
15
.904
F
1600
T36
22J
If
3f
3|
20
16
l
3660
16
.946
1600
ft
23A-
llB
21J
16
l
1
4210
18
1.02
1690
25
ll96
3*
22!
16
H
4540
20
1.09
1780
¥
27i
1*4
3f
25
20
H
5
4490
2 '2
1.18
1850
29*
lit
3f
27i
20
ii
5J
4320
24
1.25
1920
l
31* 32"
li 1|
3f 4
291 29*
20
ii
5*
5130
26
1.30
1980
33| 341
36 36*
1| 2
3£ 4*
311 31!
24
H
5!
5030
28
1.38
!'
2040
J
Mfi-,,1n
4 4133* 34
28
H
6
5000
30
1.48
2000
38 38f
1* 21-
4 4|35* 36
28
if
61
4590
36
1.71
1*
1920
I
4U 4f>3r
51 52|
15 2^
4J 4^42" 42f
j.i r,« 4si 49A
32
if
6*
5790
42
1.87
2100
1
15 ^0
36
i*
71
5700
48
2.17
2J
2130
57* 59^
282|
4| 5!|54| 56"
44
i*
n
6090
916 STEAM.
NOTES. — Sizes up to 24 inches are designed for 200 lbs. or less.
Sizes from 24 to 48 inches are divided into two scales, one for 200 lbs., the
other for less.
The sizes of bolts given are for high pressure. For medium pressures the
diameters are & inch less for pipes 2 to 20 inches diameter inclusive, and 4
inch less for larger sizes, except 48-inch pipe, for which the size of bolt is If
inches.
When tAvo lines of figures occur under one heading, the single columns up
to 24 inches are for botb medium and high pressures. Beginning with 24
inches, the left-hand columns are for medium and the right-hand lines are
for high pressures.
The sudden increase in diameters at 16 inches is due to the possible inser-
tion of wrought-iron pipe, making Avith a nearly constant Avidth of gasket a
greater diameter desirable.
When wrought-iron pipe is used, if thinner flanges than those given are
sufficient, it is proposed that bosses be used to bring the bolts up to the
standard lengths. This avoids the use of a reinforcement around the pipe.
Figures in the third, fourth, fifth, and last columns refer only to pipe for
200 lbs. pressure.
In drilling valve flanges a vertical line parallel to the spindles should be
midway between tAvo poles on the upper side of the flanges.
steam: EaroiwES.
Steam engines are often classed according to the number of cylinders the
steam passes in succession, and which are different in size,
Simple expansion,
Compound,
Triple,
Quadruple.
Any one of the above classes, if run non-condensing, is called low-pres-
sure, or non-condensing ; and if run with condenser is called high-pressure,
or condensing.
Nowadays the above classes are made in two types : high speed, including
all engines running above, say, 150 revolutions per minute ; and low speed,
all those running at less than 150 revolutions.
This division is scarcely correct, as some of the long-stroke engines run-
ning at 125 revolutions have more than 1000 feet piston speed, Avliile few
of the so-called high speed machines exceed 600 feet per minute piston
speed.
in selecting an engine for electrical work it is necessary to see that the
machine is extra heavy in all its parts ; especially so for electric railway
work, as the changes in load are often great and sudden, and in case of
short circuit, engines are liable to be called on for tremendous increase in
output, and should have no weak parts. This especially applies to fly-
wheels, of which a large number have burst on the large, slow-running
engines used in railway power-houses.
Bearings should all be of extra large size, especially so on the main shaft
journals of large direct-connected units.
The selection of size (horse-power) depends largely upon the rating of the
connected electrical machinery and the number of hours it runs, much being
left to the judgment of the advising engineer. For direct-connected units
it is not necessary to install an engine of greater rated capacity than the
rated output of the generator, as the engine Avill easily care for overload on
the generator if rated at \ cut-off, as is usual.
Some builders of engines rate their sizes for connections to dynamos so as
to supply \\ h. p per k.AV. capacity of the dynamo.
The selection of condensing or high-pressure engines has in the past de-
pended largely on availability of an adequate supply of water for condens-
ing purposes ; but to-day the cooling toAver Avith water enough to fill a
supply-tank once, and a regular supply for boiler-feed, is a very satis-
factory arrangement.
STEAM ENGINES.
917
Summary of Tests of Steam Engines of Various Types.
By Prof. R. C. Carpenter.
%0*u
f*o>-
I SS9
Style of
Engine.
Boiler
Eva p. p
lb. Comb
B.&A.2
Kind of
Coal.
Simple non-
G
200
34.S
4.47
110
55
11.50
Pea A.
condensing
1
405
34.5
6.54
257
63.4
9.11
Culm
slide valve.
7
107r,
35.7
4.60
862
51.
9.46
Soft Pa.
11
300
37.3
4.49
90
44.
12.20
" "
11
300
34.3
4.72
95
46.7
10.20
" 111.
24
1000
31.8
5.38
717
71.7
9.15
"
31
270
41.5
5.50
126
47.5
10.60
Hard, Buck
33
270
31.6
4.61
147
54.5
10.70
Pea
Average.
35.1
5.07
54.2
10.24
Simple non-
17
30(
30.1
3.09
139
46
11.45
Clearfield
condensing
19
150
26.9
3.5
90
60
9.73
Hard, Buck
Corliss.
22
350
28.
3.77
153
44.7
S.55
Soft, Ohio
Average.
28.3
3.45
50.3
Compound
2
1000
30.5
4.22
603.5
60.3
9.03
1 Soft, 3 Hard
non-con-
4
1250
36.8
4.33
674
53.8
9.92
Culm and slack
densing.'
21
400
34.20
4.17
203
51.
10.23
Soft, Pa.
24
1200
30.37
4.93
754
62.7
9.01
" 111.
Average of.
32.28
4.55
Compound
3a
600
29.4
4.43
174
29
10.38
1 Soft, 3 hard
condensing
high-speed
3
(',00
23.2
3.50
190
32
9.93
" "
8
400
20.2
3.14
154
3S
8.29
Soft, Ohio
automatic.
86
400
16.7
2.40
180
45
7.75
" "
13
250
24.6
2.95
86
34.5
10.51
" Pa.
16
350
22.7
3.41
164
47
9.50
Hard pea
18
1200
25.6
3.61
904
75
10.58
" "
21
400
29.3
3.81
188
47
10.23
Soft
Average.
23.96
3.41
9.64
Compound
10
825
22.7
4.06
482
58.2
8.29
Culm & Slack
condensing
14
looo
21.9
2.56
277
27.7
10.96
" "
Corliss,
14
1000
20.
314
31.4
10.96
" "
Greene,
28
350
16.64
2.10
182
52.2
11.80
Soft
Mcintosh &
27
500
16.90
2.61
290
58.
9.36
"
Seymour,
30
2000
14.5
1.80
814
40.7
10.7
"
etc., etc.
34
200
17.3
2.91
145
72.
11.14
«
35
1600
20.5
2.18
11.14
Average.
18.8
2.60
10.54
918 STEAM.
Hoi'ie-power of Steam Engines.
Xominal Horse-power. — Now very little used.
D = dia. cyl. in inches.
A — area of piston in sq. inches.
L = length of stroke in feet.
Boulton & Watt, nominal H.P. = — - •
Kent gives as handy rule for estimating the h.p. of a single cylinder engine,
— . This rule is correct when the product of the in.e.p. and piston speed =
21,000.
The above rule also applies to compound triple and quadruple engines, and
is referred to the diameter of the low-pressure cylinder, and the h.p. of such
an engine then becomes
(dia. low-pres. cyl.)2 TT _ , , . .
i 1 ^^ = H.P. (roughly.)
Indicated Horse Power : 1. 12.1*. — The power developed in
the cylinder of a steam engine is correctly determined only by use of the
indicator, and comparisons and steam consumption are always calculated
on that basis.
M.E.P. = mean pressure in pounds per square inch, as shown by the
indicator card.
L= stroke of piston in feet.
n = number of revolutions per min.
a — effective area of head side of piston.
a, = effective area of crank side of piston.
_ [(a x in.e.p.) + (a, X m.e.p.)] X Ln
' — 33,000
For multiple cylinder engines, compute I. H.P. for each cylinder, and add
results together for total power.
Brake Morse-power.— The brake horse-power (B. H.P.) of an engine
is the actual or available horse-power at the engine pulley ; at any given
speed and given brake-load, the B.H.P is less than the corresponding I. H.P.
by the horse-power required to drive the engine itself at the given speed,
and with the pressures at the bearings, guides, etc., corresponding to the
given brake-load.
If W= load. in lbs. on brake lever or rope,
/= distance in feet of center of brake-wheel from line of action
of brake-load,
]¥= revolutions per minute ;
tlienB-HP = flr
The mechanical efficiency of any given engine is less the greater the
expansion ratio employed, and of two engines of the same type, developing
the same power at the same speed, that which uses the higher degree of
expansion will have the lower mechanical efficiency. The effect of this,
though not usually important, is to make the best ratio of expansion in any
given case somewhat less than that Avhich makes the steam consumption
per I. H.P. -hour a minimum.
The mechanical efficiencies on full load of modern engines range from 80
to 95 per cent. Large engines have, of course, higher mechanical efficien-
cies than small ones (a very small engine may have as low a mechanical
efficiency as 40 to 50 per cent, but this is generally due to bad design and
insufficient care being taken of the engine), simple than compound engines,
and compound than triple engines — at any rate when not very large.
Prof. Thurston estimates that the total mechanical loss in non-condensing
engines having balanced valves may be apportioned as follows : — main
bearings 40 to 47 per cent, pistons and rods 33 per cent, crank-pins 5* per cent
slide-valves and rolls 2£ per cent, and eccentric straps 5 per cent. An unbal-
anced slide-valve may absorb 2G per cent, and in a condensing engine the
air-pump 12 % of the total mechanical loss.
STEAM ENGINES.
Cylinder Ratios iu Compound Eng-ines.
919
The object of building multiple cylinder engines is,
a, to use high steam pressure,
b, to get the greatest number of expansions from the steam,
c, to reduce the cylinder condensation.
Prof. Thurston says : " Maximum expansion, as nearly adiabatic as prac-
ticable, is the secret of maximum efficiency."
Although the theory of determining the sizes of cylinders is perfectly
understood, yet there are so many causes for varying the results that prac-
tically to-day but little attention is given to calculations, the plan being to
use dimensions such as have proved best practice in the past.
The proportions of cylinders are supposed to be such as to equally divide
the number of expansions and work among tliem, and these dimensions
have to be varied somewhat to meet the experience of the engineer.
Given the initial pressure (absolute) i.P. and the terminal pressure (abso-
i P.
lute) t.P., then the total number of expansions is E =—:— ^ , and the num-
ber of expansions for each cylinder is as follows :
For compound ^E,
For triple expansion 3"^E,
For quadruple expansion "VE.
Better results are often obtained by cutting off a trifle earlier in the high-
pressure cylinder ; and this fact, in connection with the extent of reheaters
and receivers, changes the actual ratios from the ideal to the practical ones
shown in the following table :
IVumBicr of ExpanMons for Condensing* £ng-in«s.
i.P.
Abso-
lute.
Total
Expan-
sions.
Expansions in
Each Cylinder.
Type.
1st.
2d.
3d.
4th.
Single cylinder ....
Compound ......
Triple compound . . .
Quadruple compound
65
145
185
265
7
30
48
7.
4.8
3.2
2.7
4.6
3.1
2.65
3.0
2.6
2.55
For tri
sizes
r triple engines, Jay M. Whitham* recommends the following relative
of cylinders when the piston-speed is from 750 to 1,000 ft. per minute :
Boiler Pressure
(above
Atmosphere).
High-Pressure
Cylinder.
Intermediate
Cylinder.
LoAv-Pressure
Cylinder.
130
140
150
160
1
1
1
1
2.25
2.40
2.55
2.70
5.00
5.85
6.90
7.25
The following are the maximum, average, and minimum values of the
relative cylinder volumes of triple-expansion condensing engines, working
with boiler pressures of 150 or 160 lbs. per square inch above atmosphere, on
board 65 boats launched within the last three or four years : —
Maximum value
Average "
Minimum "
High-Pressure
Cylinder.
Intermediate
Cylinder.
Low-Pressure
Cylinder.
2.84
2.58
1.89
* American Society of Mechanical Engineers, 1889.
920
«*§[$
*
CO
©
©
s
os
3
°5
CO
os
©
©
©
CD
©
o
os
CO
8
©
co
©
©
©
c^
B
©
©
<M
<o^.
2
1
©
pa
us
OS
<5
US
cz
8
co
US
US
us
|
o
us
os
us
os
s
s
e*s g CO
us
t-
§
©
c
©
©_
OS
OS
3
3
OS
~;
^
os
CO
©
3?
■*
**$
CO
©
OS
o
OS
OS
i>
OS
us
OS
us
us
OS
CO
OS
os
©
os
cl
OS
co
I
©
*s«
-3
CO
c
1
a
OS
*#
OS
OS
s
OS
OS
'-0
©
OS
c^
OS
%
os
H"g'«3
«
CO
1
§
s
i
%
©
CO
oq
co
00
co
-#
£
1
©
00
CO
1
1
""Oi;
p
c
g
co
©
00
t-;
1
<->eo
co
§
t-
o
s
co
1-
©
co
us
00
«>;
(M
■*
©
[^
1
s
H«~ CO
eo
©
—
00
©
CI
CO
1
1
00
g
g
g
|
g
CD
©
CI
CO
CO
co
CO
CD
co
co
CO
CO
i
©
CO
co
§
©
1
1
©
g
CD
©
•*
US
1
CO
us
co
CO
cp
@
CO
s
»
^
us
©
§
CO
«
o<yq
us
CO
us
'~
us
us
S3
us
©
us
©
§
1
co
CO
ci
§
CO
us
1
us
US
us
us
us
us
US
us
us
us
CO
CD
«M^o0
US
^
^.
us
g
8
us
us
©
us
co
T
us
co
s
us
©
co
us
us
oo
us
us
9?
©
us
-*oS
©
CO
US
t
■^
CO
CI
c
o
us
us
us
oo
§
H
©
us
o
us
us
2
j*
CO
"*
©
©
©
us
us
us
o:
us
us
CO
us
©
LO
I
1
s* ©
-
§
CO
*t
"t
c
-r_
us
1
©
us
us
us
us
CO
3
us
«fi§S
us
o
CO
SI
3
<#
<#
■*
us
CO
<*
o
CO
co
s
•*
©
l£S
©
c
us
©
us
CO
CI
us
©
CN
US
-*»&§
00
US
CO
©
OS
cl
©
CO
oo
3
CO
©
-H
s
CO
"I^o^
US
1
CO
CO
§
co
"*
CD
3
s
3
us
-M
cs
CO
r)J
©
1
rt|°Ort
©
8.
00
CO
os
©
1
co
8
8
^
^
1
©
©
CO
5?
-H
•es§
US
OS
us
CD
CO
©
CO
(M
CI
3
•*
■*
CO
§
"*
©
<*
1
©
TH
HHO,~i
o
1
■^
*
8
©
CD
co
1
1
1
<dj
CO
CI
3
-
oo
1
5
nj
4s rt
£-2g
o .
o
-
(M
co
*
us
.
-
-
©
o
a
a
M
3
2
STEAM ENGINES. 921
Receiver Capacity. — In compound engines with cranks at right
angles the receiver capacity should be from 1 to 1.5 times that of the
high-pressure cylinder (Seaton), or not less than the capacity of the low-
pressure cylinder (" Practical Engineer ")• When the cranks are oppo-
site, the receiver capacity need not exceed that of the steam passage from
the high-pressure to the low-pressure cylinder. The general effect of large
receiver capacity is to cause a drop between the pressure at the end of the
high-pressure expansion stroke and the beginning of the high-pressure ex-
haust stroke and low-pressure admission, thus increasing the power devel-
oped in the high-pressure, and decreasing the power developed in the low-
pressure cylinder ; this leads to a loss of power in the engine, and one
which — at any rate in engines with cranks at right angles — is greater the
more the receiver capacity exceeds that necessary for free passage of the
steam.
Steam Ports and Passag-es. — The areas of these should be such
that the mean linear velocity of the steam does not exceed 5,000 to 6,000 feet
per minute ; hence, if
D zr diameter of cylinder in inches,
A = area of cylinder in square inches,
a = area of port or passage in square inches,
S = piston-speed in feet per minute ;
_AS__ E2S
a ~ 6,000 — 7,640
for mean velocity of steam 6,000 feet per minute ;
_ AS _ £2S
a ~ 5,000 ~~ 6,370
for mean velocity of steam 5,000 feet per minute.
The lengths of the steam passages between the cylinders and valves
should be as small as possible, in order to minimize clearance and resist-
ance to flow of steam.
Condensers and Pumps.
Condensers are principally of two types, viz., Jet Condensers, in which
the steam and condensing water mix in a common vessel, from which both
are pumped by the air-pump ; and Surface Condensers, in which the steam
generally passes into a chamber containing a number of brass tubes, through
which the condensing water is made to circulate. The latter form is usually
adopted where water is bad, as it enables the same feed-water to be passed,
through the boiler over and over again.
The capacity of a jet condenser should not be less than one-fourth of the
low-pressure cylinder, but need not exceed one-half, unless the engines are
very quick running ; one-third is a good average ratio. Large condensers
require more time for forming the vacuum, while small condensers are
liable to flood and overflow back to the cylinders. The amount of condens-
ing water required per pound of steam condensed varies with the tempera-
ture of the exhaust, of the " hot-well," and of the condensing water. (The
"hot-well "is the receptacle into which the air-pump delivers the water
from the condenser.) The feed-water is obtained from the "hot-well,"
which should be maintained at 110° to 120° F. Sometimes even 130° E. can be
obtained Avith care.
The amount of cooling or tube surface depends upon the difference be-
tween the temperature of the exhaust steam and the average temperature
of the cooling water, and on the thermal conductivity and thickness of the
metal tubes. For copper and brass tubes in good condition the rate of
transmission is about 1,000 units (equivalent to about 1 lb. of steam con-
densed) per square foot per 1° F. difference of temperature per hour. With
the hot-Avell at 110° and the cooling water at 60°, the average difference is
25°, and 25 lbs. of steam should be condensed per hour per square foot. In
practice allowance must be made for the working conditions of the ttibes,
and half the above, i.e., £lb. of steam per 1°F. difference is nearer the usual
allowance ; and under the above conditions about 12.5 lbs. of steam would be
condensed per square foot per hour, which is considered very fair work.
The tubes are generally of brass, No. 18 S.W.G. thick, and from h to 1 in.
diameter, according to the length of the tubes ; they are usually | in. in
922
diameter, and spaced at a pitch of \\ in., while the tube-plates, which are
also of brass, are 1^ to 1\ in. thick for J in tubes. The length of the tubes.
Avhen unsupported between plates, should not exceed 120 diameters.
If H= total heat of 1 lb. of exhaust steam in B. T.U.,
t — temperature F.° of hot-well,
ty — temperature F.° of cooling Avater on entering,
t.2 = temperature F.° of cooling water on leaving,
Ql = quantity in lbs. of cooling" water per lb. of steam for jet condenser,
Q., = ditto for surface condenser ;
t — -Tl1- for jet condenser,
1 + Vi
t = H— Q2 (t2 — t-i), for surface condensers.
N.B. II — £==1,050 approximately.
Values of QL and Q.-, for different temperatures of cooling Avater, wheni/=
1150, t = 110, and U == 100 in case of Q.2 : —
Values of tx
40
50
GO
70
80
Q1. . . .
15
17
21
26
35
Q,. . . .
17
21
26
35
52
Area of injection orifice should be such as to alloAv a velocity of flow of
water not exceeding 1,500 feet per minute. It is better to have a large ori-
fice and to control the flow of water by an injection valve.
Area of orifice in square inches.
= lbs. Avater per minute -f- 650 to 750.
= area of piston ±- 250.
The cooling or circulating water in surface condensers should travel some
20 ft. lineally through the tubes. In small condensers, Avhere this is not
convenient, and the water only circulates twice through short tubes, the
rate of flow must be reduced.
A replenishing cock should be fitted to allow of the passage of part of the
circulating water into the air-pump suction to provide for water lost in
drains, bloAving off, leakage, etc. This may have one-tenth the area of the
feed-pipe.
A cock should be fitted close to the exhaust inlet for introducing caustic
soda Avhen required to dissolve grease off the tubes.
Assume yoitr engine to require 20 pounds of steam per horse-power per
hour, or one-third of a pound per minute, and to exhaust at atmospheric
pressure. One pound of steam at atmospheric pressure contains 1146.1 heat
units aboA'e 32°. One pound of Avater at this temperature contains approxi-
mately 120 — 32 = 88 heat units above 32°, so that to change a pound oi steam
at atmospheric pressure into water at 120°, Ave should have to take from it
1146.1 — 88 = 1058.1 heat units, and for one-third of a pound, 1058.1 -£- 3 =
352.7 heat units. Suppose the injection water to be 60°. In heating to 120°
each pound Avill absorb approximately 60 heat units, so that it would take
352.7 -f- 60 = 5.88 pounds of injection water per minute per horse-power
under" the assumed conditions'. A higher terminal pressure, higher tem-
perature of injection, less efficiency in the engine, or loAver hot-well
temperature, w'ill increase this figure.
In order to cover all conditions, makers and dealers figure that a con-
denser should be able to supply from a gallon to a gallon and a half of in-
STEAM ENGINES. 923
jection water per minute for each indicated horse-power developed. The
capacity of a single-acting vertical air-pump should be from one-tenth to
one-twelfth that of the cylinder ; of a double-acting horizontal pump, from
one-sixteenth to one-nineteenth.
Ejector Condensers are made on the principle of steam injectors except
that the action is reversed, the cooling water taking the place of the steam
in the injector, and the exhaust steam that of the feed-water. In order to
ensure their successful working, the cooling water should be supplied at a
head of 15 feet to 25 feet, either from a tank above or from a centrifugal or
other pump. The amount of cooling water required is about the same as for
jet condensing ; the vacuum is from 20 in. to 25 in.
Air-pumps) are used to draw the condensed water from the condenser to
the hot-well, together with the air originally contained in the water, or
which may find its Avay in through glands, etc., and with jet condensers
\ they also draw the cooling water. A cubic foot of ordinary water contains
about .05 cubic foot of air at atmospheric pressure, which expands in the
condenser to about .4 cubic foot of air ; hence the term air-pump.
The efficiency of a single-acting air-pump may be taken at .6 to .4, and
1 generally .5, while that of the double-acting pump may be .5 to .3, say .4 on
average. For jet condensing, the volume of the air-pump should be theo-
retically 1.4 times the volume of condensed -4- cooling water ; for good
working it should be from twice to thrice that required by theory. Or if
v =z volume of condensed Avater per minute in cubic feet,
V= volume of cooling water per minute in cubic feet,
n = number of strokes (useful) of air-pump per minute,
A == volume of air-pump in cubic feet ;
— 3.5 — - — for double-acting pumps.
Since, for surface condensing, the air-pump does not draw the cooling
water, and as the feed-water, being used over again, should not contain so
much air, it would appear that the air-pump might be much smaller
th?n for jet condensing. However, surface condensers are frequently
arranged for use as jet condensers in case of mishap, and with surface con-
densing a better vacuum is expected, so that for surface condensing the air-
pump is only slightly less than for jet condensing. In actual practice the
air-pump is made from one-tenth to one-twenty-fifth the capacity of
the low-pressure cylinder, according to the number of expansions and
nature of condenser, while a comparison of a number of marine engines by
different makers shows a ratio of one-sixteenth to one twenty-first.
If expansion joints are used in the exhaust pipe, a copper bellows joint is
better than the ordinary gland and stuffing-box type, through which air is
apt to leak.
Air-pump valves should have sufficient area that the full quantity of cool-
ing and condensed water in jet condensation in passing does not exceed a
velocity of 400 feet per minute ; in practice the area is larger than this. A
large number of small valves is perhaps better than one or two large valves
which are sluggish, owing to their inertia. The clearance space between
head and foot valves should not exceed one-fifteenth the capacity of the
pump as ordinarily constructed.
If a = area through foot valves in square inches,
a, ■=. area through head valves in square inches,
d = diameter of discharge pipe in inches,
D = diameter of the air-pump in inches,
S =. speed (useful) in feet per minute ;
If there be no air vessel or receiver, d should be 10 per cent larger.
924
An air-pipe should be fitted to the hot-well one-fourth the diameter of
the discharge pipe.
Circulating- Pumps. — The size of these depend chiefly on conditions
mentioned for air-pumps, and they may hear a constant relation to the air-
pump as to size, or to the L.P. cylinders.
Air-pump. Circulating Pump. Ratio.
Single acting ' Single acting .6
Single acting Double acting .31
Double acting Double acting .52
or if V =. volume of cooling water in cubic feet per minute,
S =. length of stroke in feet,
n= number of strokes (useful) per minute,
C= capacity of pump in cubic feet,
D = diameter of pump in inches ;
D= 13.55 1—5-
Circulating pump valves should be of sufficient area that the mean velo-
city of flow does not exceed 3 or 4 feet per sec. High velocities tend to
wear out the valves, and cause undue resistance in the pump. In the suc-
tion and delivery pipes the velocity should not exceed 500 feet per minute,
or for large and easy leads 600 feet per minute. Better results, however,
will be obtained by using larger pipes, so as to reduce the velocity, espe-
cially if the pipes are long. For single-acting pumps the suction may be
smaller than the delivery, if the pump be below the water-level.
If a = minimum area through valves in square inches,
d = minimum diameter of pipe in inches,
A = area of pump in square inches,
D = diameter of pump in inches,
S = mean speed (useful) of pump in feet per minute ;
AS
a = l80'
*■=?-*"
where jST varies from 22 for small pumps to 25 for large pumps, while for the
suction of single-acting pumps it may be 27.
Air chambers should always be fitted, which for single-acting pumps may
be twice the capacity of the pump. An air-pipe should be fitted to the
highest points of the water passages for escape of air to enable the con-
denser and pipes to run full. If the speed of the circulating pump cannot
be varied independently, it is advisable to fit a water valve between the two
ends of the pump, so that the discharge may be varied to suit the require-
ments.
Strainers should be fitted to the inlet of the suction pipe, and the aggre-
gate area of the passages should be from two to four times the area of the
pipe, according to the velocity of flow in the pipe. Owing to difficulty ex-
perienced in cleaning strainers when under water, they are sometimes fixed
in a cast-iron vessel near the suction entrances to the pump, with a door
arranged in some convenient position for cleaning.
foot Valve. — When the water level is below that of the pump, a foot
valve should be fitted just above the surface of the water. A door should
be provided for examining the valve Avithout disturbing the suction pipe.
Or an air ejector may be used to charge the pump.
STEAM ENGINES.
925
"-1 i-i t-3 to (ji CO "n Ji
CO O Oi O CT o W H C
°
. p --=== — -
^-~~Z~~~—Zi-~—
^" ^-"" ^"^~ t~-"'"^ 'j.-
h"L ^^ ^^^ t^""^ ■"'*'*" *a.'~''~"
O / «> .^ <^°* x"1*" ^^=°" --'"="
/^ .-<r /'^ s'^ <*"" ^"^- -""-
y* ? /^v^ *?* r'*'* *'~ t^*'**
s - - A z»S-S* SzsUK'<<<>*
V i t £ ? *' ^ s^ ^t't-Z'
Af- -t 7- A- y ^^' S s*s+*£*
- 7^ * /v _/ /Vv^<^ - -
s""===|fe?=7 ?^-^"pPP-""""
:::: :J:i?lfc^:^;$?:^z^^:±~ : ±
-hi 3: €z/z^ ^gr
S i fnpj? ^^^7,,Z/^+
fl ez \^%t/ Wilder
° ■, hi i i A t f J kY /^
' A A / / /*'-/ A/m
- ^-tt-h-fyl¥m- -4=
i=:==|EEi-te^
= iffi?L-S|s$m== == =p== == = ==
- ii-hH Wft¥A
fe : -^hThWf :
8 - -HiHhtffttt
- Miliz-Em
\WttT4-iTtttt
& tttttllAttw
- fr-thhtPRiFt
- EttctSpr +
±jj±jj#:g
s III l\ III III II
WHEEL. OR PULLEY DIAMETER IN FEET
926 WATER-POWER.
WATER-POWER.
IN determining the feasibility of utilizing water-power to operate electri
cally the industries of any particular town or city, careful consideration
must be given to the following points, viz. : 1. The amount of water-power
permanently available. 2. The cost of developing this power. 3. The in-
terest on this amount. 4. The total demand for power. 5. The amounts
and relative locations of the various kinds of power. 6. The cost of steam
plants now in operation. 7. The interest on this amount. 8. Cost of fuel
for plants now in operation. 9. Cost of operating present plants. Labor.
10. Cost of maintenance of present plants. 11. The amounts and kinds of
electric power already in operation. 12. The distance of transmission.
13. The estimated cost of the hydraulic machinery. 14. The guaranteed
efficiency and regulation of the hydraulic machinery. 15. Estimated cost of
electric machinery. 16. Estimated cost of line construction. 17. Total cost
of operating hydraulic and electric machinery. 18. Total cost of mainte-
nance of hydraulic and electric plants. 19. The interest on the total esti-
mated cost of proposed plant. 20. The estimated gross income.
Charles T. Main makes the following general statements as to the value
of a water-power : " The value of an undeveloped variable power is usually
nothing if its variation is great, unless it is to be supplemented by a steam-
plant. It is of value then only when the cost per horse-power for the doubie-
plantis less than the cost of steam-power under the same conditions as
mentioned for a permanent power, and its value can be represented in the
same manner as the value of a permanent poAver has been represented.
" The value of a developed power is as follows : If the power can be run
cheaper than steam, the value is that of the power, plus the cost of plant,
less depreciation. If it cannot be run as cheaply as steam, considering its
cost, etc., the value of the power itself is nothing, but the value of the plant
is such as could be paid for it new, which would bring the total cost of run-
ning down to the cost of steam-power, less depreciation."
Mr. Samuel Webber, Iron Age, Feb. and March, 1893, criticises the state-
ments of Mr. Main and others who have made comparisons of costs of steam
and of water-power unfavorable to the latter. He says : " They have based
their calculations on the cost of steam, on large compound engines of 1000
or more h. p. and 120 pounds pressure of steam in their boilers, and by care-
ful 10-hour trials succeeded in figuring down steam to a cost of about §20
per h. p., ignoring the well-known fact that its average cost in practical use,
except near the coal mines, is from §40 to $50. In many instances dams,
canals, and modern turbines can be all completed at a cost of $100 per h. p.;
and the interest on that, and the cost of attendance and oil, will bring
water-power up to but about $10 or $12 r>er annum ; and with a man compe-
tent to attend the dynamo in attendance, it can probably be safely estimated
at not over $15 per h. p.
SYNOPSIS OF REPOBT HKQrittED OS
WATEH-POWEH JPHOrJEMTY.
JLocation.
Geographical, etc.
Sketch of river and its tributaries.
Surrounding country and physical features.
Sources ; lakes, springs, etc.
Water's head; area drained, nature of, whether forest, swamp, snow-
covered mountains, etc.
Elevation of head waters and of mouth.
Length from main source to mouth.
Accessibility ; how and by what routes.
Meports.
Reports of IT. S. Coast or Geological Survey.
Reports of Engineers IT. S. Army.
Any other reports.
Any estimate by engineers and for what purpose.
When it first attracted attention and for what reason.
History.
REPORT ON WATER-POWER PROPERTY. 927
Rainfall.
Average for several years for the drainage area. Maximum, what month.
Minimum, what month. Comparison with other similar localities.
Volume of Water.
Gauging of river if possible. Reports by other engineers.
Cubic feet per second flow.
Cubic feet per second per mile of watershed = say .2 to .3 cubic feet of
total rainfall and a available as water-power.
Comparison with other rivers.
Reservoirs.
Possibility of storing water for dry time.
Available Fall.
Location of ; accessibility, by what routes.
Can power be used locally, or would it be necessary to transmit it, and if
so, where to, and distances ? Nature of country over which it would have to
be carried.
Volume of water in cubic feet per second.
Note. — 12 cubic feet falling one foot per second = 1 h.p. (approximate).
Horse-Power of River.
Calculated from available fall and volume.
Horse-power for each fall or dam.
Location of dams, dimensions, length, and height, best method of con-
struction, estimated cost.
Backwater ; volume, andhow far ; what interests disturbed by it ; benefits,
if any.
Compare power with that of similar rivers.
Probable cost of power at clams and transmitted.
Applications PossiS»le.
Near by ; at distance, stating when and for what. Note industries appli-
cable to ; comparison with other applications.
Bifew Industries Suggested,
and old industries already going to Avhich power is applicable.
Cost to these, and comparison with cost of other forms of power already
in use.
Property of the Company.
Land, buildings, water rights, flowage rights, franchises, lines, rights of
way. Character of deeds. Probable value.
Comparison with other similar properties.
Other resources.
liabilities.
Stocks, bonds, floating debt, other.
Earning- Capacity.
Probable cost of power per h. p. at power-house.
Probable cost of power per h. p. delivered or transmitted.
Price for which it can be sold at power-house, and price transmitted or
delivered.
General Features.
Surrounding country, its characteristics, people, cities, and towns, indus-
tries, condition of finances.
Facilities for transportation, water and rail.
Nearness of sources of supplies and sales of products.
Horse-Power of a Waterfall.
The horse-power of a waterfall is expressed in the following formula :
Q = quantity of water in cubic feet flowing over the fall in 1 minute.
H— total head in feet, i.e., the distance between the surface of the water at
the top of the fall, and that at its foot. In a water-power the head is
the distance between the surface of the water in the head-race, and that
of the water in the tail-race.
928 WATER-POWER.
w — weight of water per cubic foot = 62.36 lbs. at 60° F.
Gross horse-power of waterfall = X,.ifJ? ™ or .00189 OH.
ooOOO
Loss of head at the entrance to and exit from a water-wheel, together witi
the friction of the water passing through, reduces the power to the fall that
can be developed to about 70 per cent of the gross power of the fall.
Horse-Power of a Running- Stream.
The power is calculated by the same formula as for a fall, but in this case
H=. theoretical head due to the velocity of the water in the stream
v2
— where
v = velocity of water in feet per second.
Q = the cubic feet of water actually impinging against the bucket per
minute.
Gross horse-power =r .00189 QH.
Wheels for use in the current of a stream realize only about .4 of the gross
theoretical power.
Current motors are often developed to operate in strong currents, such as
that of the Niagara River opposite Buffalo, but are of little use excepting
for small powers. Such a small fraction of the current velocity can be
made use of that a current motor is extremely inefficient. In order to
realize power from a current it is necessary to reduce its velocity in taking
the power, and to get the full power would necessitate the backing up of the
whole stream until the actual head equaled the theoretical.
Power of Water Howing- in a Pipe.
v2 v2
Hdue to velocity = — - = — - where v = velocity in feet per second.
f
Hx due to pressure — -, where /= pressure in lbs. per square foot.
and w = 62.36 lbs. = weight 1 cubic foot of water.
H^ distance above datum line in feet.
v2 f
Total H— °—+J-+Hi.
In hydraulic transmission the work or energy of a given quantity of water
under pressure is the volume in cubic feet x lbs. pressure per square foot.
Q = cubic feet per second.
P = pressure in lbs. per square inch.
144 PO
Horse-power = 55Q v = .2618 PQ.
Mill-Power.
It has been customary in the past to lease water-power in units larger
than the horse-power, and the term mill-power has been used to designate
the unit. The term has no uniform value, but is different in all localities.
Emerson gives the following values for the seven more important water-
power.
Holyoke, Mass. — Each mill-power at the respective falls is declared to have
the right during 16 hours in a day to draw 38 cubic feet of water per second
at the upper fall when the head there is 20 feet, or a quantity proportionate
to the height at the falls. This is equal to 86.2 horse-power as a maximum.
Lowell, Mass, — The right to draw during 15 hours in the day so much
water as shall give a power equal to 25 cubic feet a second at the great fall,
when the fall there is 30 feet. Equal to 85 h. p. maximum.
Lawrence, Mass. — The right to draw during 16 hours in a day so much
water as shall give a horse-power equal to 30 cubic feet per second when the
head is 25 feet. Equal to 85 h. p. maximum.
Minneapolis, Minn. — 30 cubic feet of water per second with head of 22
feet. Equal to 74.8 h. p.
COMPARISON OF COLUMNS.
929
Manchester, N. H. — Divide 725 by the number of feet of fall minus 1, and
tbe quotient will be the number of cubic feet per second in that fall. For 20
feet fall this equals 38.1 cubic feet, equal to 86.4 h. p. maximum.
Cohoes, N.Y. — "Mill-power" equivalent to the power given by 6 cubic
feet per second, when the fall is 20 feet. Equal to 13.6 b. p. maximum.
Passaic, A". /. — Mill-power : The right to draw 8£ cubic feet of water per
second, fall of 22 feet, equal to 21.2 horse-power. Maximum rental, $700 per
year for each mill-power = $33.00 per h. p.
The horse-power maximum above given is that due theoretically to the
weight of water and the height of the fall, assuming the water-wheel to have
perfect efficiency. It should be multiplied by the efficiency of the wheel,
say 75 per cent for good turbines, to obtain the h.p. delivered by the wheel.
At Niagara power has in all cases been sold by the horse-power delivered
to the Avheels if of water, and to the building-line if electrical.
Charges for water in Manchester, Lowell, and Lawrence, are as follows :
About $300 per year per mill-power for original purchases.
$2 per day per mill-power for surplus.
Lowell.
About $300 per year per mill-power for original purchases.
$2 per day per mill-power during " back-water."
$4 per day per mill-power for surplus under 40 per cent.
$10 per day per mill-power for surplus over 40 per cent and under 50 per cent.
$20 per day per mill-power for surplus over 50 per cent.
$75 per day per mill-power for any excess over limitation.
Lawrence.
About $300 per year per mill-power for original purchases.
About $1200 per year per mill-power for new leases at present.
$4 per day per mill-power fur surplus up to 20 per cent.
$8 per day per mill-power for surplus over 20 and under 50 per cent.
$4 per day per mill-power for surplus under 50 per cent.
comparison of coifUnara of wateb ins
Mercury in Inches, and Pressure in U»s., per &quai
FEET,
■e Inch.
Lbs.
Water. 1
Merc'ry
Water.
Merc'ry
Lbs.
Merc'ry
Water.
Lbs.
Press.
1
Press.
Press.
Sq. In.
Feet.
Inches.
Feet.
Inches.
Sq. In.
Inches.
Feet.
Sq. In.
1
2.311
2.046
1
0.8853
0.4327
1
1.1295
0.4S87
2
4.622
4.092
2
1.7706
0.8654
2
2.2590
0.9775
3
6.933
6.138
3
2.6560
1.2981
3
3.3885
1.4662
4
9.244
8.184
4
3.5413
1.7308
4
4,5181
1.9550
5
11.555
10.230
5
4.4266
2.1635
5
5.6476
2.4437
G
13.866
12.2276
6
5.3120
2.5962
6
6.7771
2.9325
7
16.177
14.322
7
6.1973
3.0289
7
7.9066
3.4212
8
18.488
16.368
8
7.0826
3.4616
8
9.0361
3.9100
9
20.800
18.414
9
7.9680
3.8942
9
10.165
4.3987
10
23.111
20.462
10
8.8533
4.3273
10
11.295
4.8875
11
25.422
22.508
11
9.7386
4.7600
11
12.424
5.3762
12
27.733
24.554
12
10.624
5.1927
12
13.554
5.8650
13
30.044
26.600
13
11.509
5.6255
13
14.683
6.3537
14
32.355
28.646
14
12.394
6.0582
14
15.813
6.8425
15
34.666
30.692
15
13.280
6.4909
15
16.942
7.3312
16
36.977
32.738
16
14.165
6.9236
16
18.072
7.8200
17
39.288
34.784
17
15.050
7.3563
17
19.201
8.3087
18
41.599
36.830
18
15.936
7.7890
18
20.331
8.7975
19
43.910
38.876
19
16.821
8.2217
19
21.460
9.2862
20
46.221
40.922
20
17.706
8.6544
20
22.590
9.7750
21
48.532
42.968
21
18.591
9.0871
21
23.719
10.264
22
50.843
45.014
22
19.477
9.5198
22
24,849
10.752
23
53.154
47.060
23
20.382
9.9525
23
25.978
11.241
24
55.465
49.106
24
21.247
10.385
24
27.108
11.7300
25
57.776
51.152
25
22.133
10.818
25
28.237
12.219
26
60.087
53.198
26
23.018
11.251
26
29.367
12.707
27
62.398
55.244
27
23.903
11.683
27
30.496
13.196
28
64.709
57.290
28
24.789
12 116
28
31.626
13.685
39
67.020
59.336
29
25.674
12.549
29
32.755
14.174
30
69.331
61.386
30
26.560
12.981
30
33.885
14.662
930
WATER-POWER.
©
&
X
>>
o
o
O
£
o
o
o
95=
$15.49
23.18
20.35
29.83
48.79
58.27
105.67
O
H=
$14.47
22.16
19.33
28.81
47.77
57.25
104.65
$13.46
21.15
18.32
27.80
46.76
56.24
103.64
©
95
$12.45
20.14
17.31
26.79
45.75
55.23
102.63
o
95=
$11.44
19.13
16.30
25.78
44.74
54.22
101.62
©
m
$10.42
18.il
15.28
24.76
43.72
53.20
100.60
o
o
O
o
bo
o3
O
•d
3
5
o
o
O
95=
$10.15
©
o
95=
CO
95=
o
95=
95=
O
95=
95=
o
CO
95=
O
CO
95
g
95=
00
in
95=
•0^9
'sgijddns 'xio
;90irepu9wy
d
95=
O
o
$4.62
12.31
9.48
18.96
37.92
47.40
94.80
S
£
O
1)
(a
$300 per year I
2 per day . .
4 " " . .
8 " " . .
10 " " . .
20 " " . .
1 3s is
PRESSURE OF WATER.
931
PRESSURE OF WATER.
The pressure of water in pounds per square inch for every foot in height
to 300 feet ; and then by intervals to 1000 feet head.
Feet
Press.,
Feet
Press.,
Feet
Press.,
Feet
Press.,
Feet
Press.,
He'd.
Sq. In.
He'd.
Sq. In.
He'd.
Sq. In.
Head.
Sq. In.
Head.
Sq. In.
1
0.43
65
28.15
129
55.88
193
83.60
257
111.32
2
0.86
66
28.58
130
56.31
194
84.03
258
111.76
3
1.30
67
29.02
131
56.74
195
84.47
259
112.19
4
1.73
68
29.45
132
57.18
196
84.90
260
112.62
5
2.16
69
29.88
133
57.61
197
85.33
261
113.06
6
2.59
70
30.32
134
58.04
198
85.76
262
113.49
7
3.03
71
30.75
135
58.48
199
86.20
263
113.92
8
3.46
72
31.18
136
58.91
200
86.63
264
114.36
9
3.89
73
31.62
137
59.34
201
87.07
265
114.79
10
4.33
74
32.05
138
59.77
202
87.50
266
115.22
11
4.76
75
32.48
139
60.21
203
87.93
267
115.66
12
5.20
76
32.92
140
60.64
204
88.36
268
116.09
13
5.63
77
33.35
141
61.07
205
88.80
269
116.52
14
6.06
78
33.78
142
61.51
206
89.23
270
116.96
15
6.49
79
34.21
143
61.94
207
89.66
271
117.39
16
6.93
80
34.65
144
62.37
208
90.10
272
117.J2
17
7.36
81
35.08
145
62.81
209
90.53
273
118.26
18
7.79
82
35.52
146
63.24
210
90.96
274
118.69
19
8.22
83
35.95
147
63.67
211
91.39
275
119.12
20
8.66
84
36.39
148
64.10
212
91.83
276
119.56
21
9.09
85
36.82
149
64.54
213
92.26
277
119.99
22
9.53
86
37.25
150
64.97
214
92.69
278
120.42
23
9.96
87
37.68
151
65.40
215
93.13
279
120.85
24
10.39
88
38.12
152
65.84
216
93.56
2S0
121.29
25
10.82
89
38.55
153
66.27
217
93.99
281
121.72
26
11.26
90
38.98
154
66.70
218
94.43
282
122.15
27
11.69
91
39.42
155
67.14
219
94.86
283
122.59
28
12.12
92
39.85
156
67.57
220
95.30
284
123.02
29
12.55
93
40.28
157
68.00
221
£5.73
285
123.45
30
12.99
94
40.72
158
68.43
222
96.16
286
123.89
31
13.42
95
41.15
159
68.87
223
96.60
287
124.32
32
13.86
96
41.58
160
69.31
224
97.03
288
124.75
33
14.29
97
42.01
161
69.74
225
97.46
289
125.18
34
14.72
98
42.45
162
70.17
226
97.90
290
125.62
35
15.16
99
42.88
163
70.61
227
98.33
291
126.05
36
15.59
100
43.31
164
71.04
228
98.76
292
126.48
37
16.02
101
43.75
165
71.47
229
99.20
293
12692
38
16.45
102
44.18
166
71.91
230
99.63
294
127.35
39
16.89
103
44.61
167
72.34
231
160.06
295
127.78
40
17.32
104
45.05
168
72.77
232
100.49
296
128.22
41
17.75
105
45.48
169
73.20
233
100.93
297
128.65
42
18.19
106
45.91
170
73.64
234
101.36
298
129.08
43
18.62
107
46.34
171
74.07
235
101.79
299
129.51
44
19.05
108
46.78
172
74.50
236
102.23
300
129.95
45
19.49
109
47.21
173
74.94
237
102.66
310
134.28
46
19.92
110
47.64
174
75.37
238
103.09
320
138.62
47
20.35
111
48.98
175
75.80
239
103.53
330
142.95
48
20.79
112
48.51
176
76.23
240
103.80
340
147.28
49
21.22
113
48.94
177
76.67
241
104.39
350
151.61
50
21.65
114
49.38
178
77.10
242
104.83
360
155.94
51
22.09
115
49.81
179
77.53
243
105.26
370
160.27
52
22.52
116
50.24
180
77.97
244
105.69
380
164.61
53
22.95
117
50.68
181
78.40
245
106.13
390
168.94
54
23.39
118
51.11
182
78.84
246
106.56
400
173.27
55
23.82
119
51.54
183
79.27
247
1C6.99
500
216.58
56
24.26
120
51.98
184
79.70
248
107.43
600
259.90
57
24.69
121
52.41
185
80.14
249
107.86
700
303.22
58
25.12
122
52.84
186
80.57
250
108.29
800
346.54
59
25.55
123
53.28
187
81.00
251
108.73
900
389.86
60
25.99
124
53.71
188
81.43
252
109.16
1000
433.18
61
26.42
125
54.15
189
81.87
253
109.59
62
26.85
126
54.58
190
82.30
254
110.03
63
27.29
127
55.01
191
82.73
255
110.46
64
27.72
128
55.44
192
83.17
256
110.89
932 WATER-POWER.
RITE1ED STEEL PIPES.
Riveted sheet steel pipe is much used on the Pacific Coast for conveying
water for considerable distances under high heads, say as much as 1700 feet.
Corrosion of iron and steel pipe has always been an argument against its
use, but for about thirty years such pipe has been in use in California; and
a life of twenty-five years' is not considered the limit, when both inside and
outside of the pipe are treated with a coating of asphalt.
The method of covering with asphalt referred to affords perfect protec-
tion against corrosion, and so long as the coating is intact, makes it practi-
cally indestructible so far as all ordinary wear is concerned. The conditions
which interfere with the best service are where the coating is worn off by
abrasion in transportation, or Avhere the pipe is subject to severe shock by
the presence of air, or by a sudden closing of tbe gates, or where the service
is intermittent, causing contraction and expansion, which opens the joints
and breaks the covering. With ordinary care these objections can mostly
be overcome. While the primary object of coating pipe in this way is to
prevent oxidization, and thus insure its durability, it is incidentally an ad-
vantage in providing a smooth surface on the inside, which reduces the fric-
tion of water in its passage.
The Coast method of laying pipe is to take tbe shortest practicable dis-
tance that the ground will permit, placing the pipe on the surface and con-
necting directly from ditch, flume, or other source of supply to the wheel.
Avoid short turns or acute angles, as they lessen the head and produce shock.
The ordinary method of jointing is the slip joint, made up in much the
same way as stove-pipe. Of course this is only adapted to comparatively
low heads, special riveted-joint construction being necessary for the higher
falls. In laying such pipe where the lengths come together at an angle, a
lead joint should be made. This is done by putting on a sleeve, allowing a
space, say three-eighths of an inch, for running in lead. With a heavy
pressure, and especially on steep grades, the lengths should be wired
together, lugs being put on the sections forming the joints for this purpose;
and where the grade is very steep, the pipe should be securely anchored
with wire cable.
In laying the pipe line it is customary to commence at the wheel, and with
slip joint the lower end of each length should be wrapped with cotton drill-
ing or burlaps to prevent leaking ; care being taken in driving the joints
together not to move the gate and nozzle from their position. Some tempo-
rary bracing may be necessary to provide against this.
Where several wheels are to be supplied from one pipe line, a branch
from the main in the form of the letter Y is preferable to a right angle out-
let. When taken from the main at a right angle, the tap-hole should be
nearly as large as the main, reducing by taper joint to the size of pipe
attached to the wheel gate.
It is advised where practicable to lay the pipe in a trench, covering it
with earth. Even in warm climates, where this is not necessary as protec-
tion from frost, it is desirable to prevent contraction and expansion by
variations of temperature, a? well as to afford security against accident.
When laid over a rocky surface a covering of straw or manure will protect
it from the sun, and generally prevent freezing ; as where kept in motion,
water under pressure will stand a great degree of cold without giving
trouble in this way. After connections are made, it should be tested before
covering to see that the joints are tight.
Care should be taken when the pipes are first filled to see that the air is
entirely expelled, the use of air valves being necessary in long lines laid
over undulating surfaces. Care should also be taken before starting to see
that there are no obstructions in the pipe or connections to wheel, and that
there are no leaks to reduce the pressure. Pipe lines of any considerable
length should be graduated as to size, being larger near the top and reduced
toward the lower end, the thickness of iron for various sizes being deter-
mined by the pressure it is to carry. This is a saving in first cost, and
facilitates transportation by admitting of length, being run inside of each
other.
When used near railroad stations, pipe is generally made in 27 ft. lengths
for purpose of economizing freight, this being the length of a car. When
transported long distances by wagon, it is usually made in about 20 ft.
lengths. For pipe of large diameter, or for transportation over long: dis-
tances, as also for mule packing, it is made in sections or joints of 24 to 30
inches in length, rolled and punched, with rivets furnished to put together
WOODEN-STAVE PIPE. 933
on the ground where laid. Pipe of this character, being cold riveted, is
easily put together with the ordinary tools for the purpose. In such case,
preparation should be made for coating with asphalt before laying.
In many cases much expense may be saved in pipe by conveying the
water in a flume or ditch along the hillside, covering in this way a large
part of the distance, then piping it down to the power station by a short
line. This is more especially applicable to large plants, where the cost of
the pipe is an important item.
DATA JPOM WWJbM]E& AWM DITCHES.
To give a general idea as to the capacity of flumes and ditches for carry-
ing water, the following data is submitted :
The greatest safe velocity for a wooden flume is about 7 or 8 feet per second
For an earth ditch this should not exceed about 2 feet per second. In Califor-
nia it is the general practice to lay a flume on a grade of about £ inch to the
rod, or often 2 inches tothelOOfeet, dependingon the existing conditions.
Assuming a rectangular flume 3 feet wide, running 18 inches deep, its
velocity and capacity would be as shown below : —
Grade. Vel. in Ft. per Sec. Quantity Cu. Ft. Min.
| inch to rod 2.6 702
1 " " " 3.7 999
\ " " " 5.3 1,431
As the velocity of a flume or ditch is dependent largely on its size and
character of formation, no more specific data than the above can be given.
It is not safe to run either ditch or flume more than about f or | full.
WOODEflfSTAVE PIPE.
Although wooden-stave pipe has been in use for years on old water powers
for penstocks, etc., it seems to have been given but little study until late
years, when it has been used to some extent on the Pacific Coast for con-
veying water long distances under heads not much exceeding 200 feet. Al-
though the construction of wooden-stave pipe is quite simple, yet consider-
able skill and care are necessary to make water-tight work. One of the
latest pieces of work employing this type of pipe is the plant of the San
Gabriel Los Angeles Transmission, California, — where several miles of
wooden-stave pipe, 48 ins. diameter, are used. The pipe is laid uniformly ten
feet below hydraulic grade ; and the wood is of such thickness as to be always
water-soaked, and will thus outlast almost any other form of construction.
The staves are placed so as to break joints, the flat sides are dressed to a
true circle, and the edges to radial planes. The staves are cut off square at
the ends, and the ends slotted, a tight-fitting metallic tongue being used to
make the joint.
The pipe depends upon steel bands for its strength, and in the case above
mentioned they are of round steel rod placed ten inches apart from center
to center. "Where the pressures vary along the line, bands can be spaced
closer or wider apart to make the necessary strength. The preference is
given round bands over flat ones, on account of their embedding themselves
in the wood better as it swells. They also expose less surface to rust than
would flat ones of the same strength. The ends of the bands are secured
together through a malleable iron shoe, having an interior shoulder for the
head of the bolt, and an exterior shoulder for the nut, the whole band thus
being at right angles to the line of the pipe. Where curves are not too
sharp, they can easily be made in the wooden pipe ; but for shore turns, sec-
tions of steel-riveted pipe of somewhat larger internal diameter than that
of the wooden pipe are introduced. The joints between wood and steel are
made by a bell on the steel pipe that is larger than the outside diameter of
the wooden pipe. After partly filling the space between bell and Avood with
oakum packed hard, for the remainder use neat Portland cement.
Advantages claimed for this type are that it costs less than any other
form, and especially so where transportation is over the rugged country
where it is most liable to be used ; great length of life, and greater capacity
than either cast-iron or steel-riveted. Compared with new riveted pipe, the
carrying capacity of stave pipe is said to be from 10 to 40 % more, and this
difference increases with age as the wooden pipe gets smoother, while the
friction of the metal pipe increases to a considerable degree.
As compared with open flumes, the life is so much greater and repairs so
much less as to considerably more than counterbalance the first cost. For
detailed information on wooden-stave pipe, see papers by A. L. Adams,
September, 1898, Am. Soc. C. E.
934
WATER-POWER.
TAJBI,E Ol RIVETED HYDRAUIIC JPIP£.
(Pelton Water Wheels Co.)
Showing weight, with safe head for various sizes of double-riveted pipe.
05
ft
£
°J
!£.a«
55 .S
Ift
ft
*S2
l?-d
05 .3
ft .
ft .
00 ^
g«Seo
a«- P
ft
00 P
""' " 5
0 W Sco73
o 2
2 a
3.2
n '-
a ^
2, "~ i
- _ u
— z z
■rt ft to
-a ft£-
EC 5
£ ? ft? ®
. ® ^ "*
3.2^55
3*" P J
z 'z.
2^05
r-i.a so
a ~^
W5£
5 u • c~
£ £ a? |
pj ft>» ^
Oa>sa
Mis
"5 05 .
3
18
400
9
2
18
254
16
165
320
16*
4
12
18
350
16
5**
18
"54
14
252
320
27*
4
12
16
525
16
3
18
18
254
254
12
11
385
424
320
320
5
20
18
325
25
3*
30
5
20
20
16
14
500
675
25
25
4
5
18
254
10
505
320
34
5
20
20
314
314
16
14
148
227
400
400
18
6
28
18
296
36
4i
22*
fi
28
16
487
36
5|
7*
20
314
12
346
400
30
6
28
14
743
36
20
20
314
344
11
10
380
456
400
400
32*
36*
7
38
38
18
16
254
419
50
50
1
8*
7
22
380
16
135
480
20
7
38
14
640
50
22
22
22
22
3SO
3S0
3X0
380
14
206
316
347
415
480
480
480
480
24|
32}
35}
40
8
8
8
50
50
50
16
14
12
367
560
854
63
63
63
9*
13
11
10
9
9
9
63"
63
63
78
78
78
78
78
16
14
12
16
14
12
11
10
327
499
761
80
80
80
8*
lOf
14*
24
24
24
24
24
452
452
452
452
452
14
12
11
10
8
188
290
318
379
466
570
570
570
570
570
271
35*
39
43*
53
10
10
10
10
10
295
450
687
754
900
100
100
100
100
100
91
Hf
15|
17*
19i
26
26
26
26
26
530
530
530
530
530
14
12
11
10
8
175
267
294
352
432
670
670
670
670
670
29*
38*
42"
47
11
95
95
95
95
95
16
14
12
11
10
269
412
626
687
820
120
120
120
120
120
9|
57i
11
11
11
17*
181
21
28
28
28
28
615
615
615
615
14
12
11
10
102
247
273
327
775
775
775
775
31i
41J
45
501
611
12
12
12
12
12
113
113
113
113
113
132
132
132
132
132
16
14
12
11
10
16_
14
12
11
10
246
377
574
630
753
228
348
530
583
696
142
142
142
142
142
111
2S
615
8
400
775
181
19|
22|
30
30
30
30
30
Tor;
706
706
706
70(]
12
11
10
8
7
231
254
304
375
425
890
890
890
890
890
44
48
54
65
13
13
13
13
13
170
170
170
170
170
12
74
15
20
22
24*
36
36
36
36
1017
1017
1017
017
11
10
8
7
141
155
192
210
1300
1300
1300
1300
58
67
78
88
14
14
14
14
14
153
153
153
153
153
16
14
12
11
10
211
324
494
543
648
200
200
200
200
200
13
16
2H
23i
26
~~ 13f
17
23
24*
28
40
40
40
40
40
42
42
42
42
42
42
1256
256
256
256
1256
3N5
:;s5
3X5
::x5
13S5
3X5
10
8
7
6
4
10
8
7
6
4
1
141
174
189
213
250
1600
1600
1600
1600
1600
71
86
97
108
126
176
176
176
J76
176
201
16
14
12
11
10
~16~
197
302
460
507
606
225
225
225
225
225
15
15
15
15
15
135
165
180
210
240
270
1760
1760
1660
1760
1760
1760
74*
91
102
114
133
16
185
255
14*
137
16
201
14
283
255
17|
42
3X5
3
300
1760
145
16
20.1
12
432
255
24*
42
3X5
J>
321
1760
177
16
201
11
474
2*5
2(U
42
::^>
I
363
1760
216
16
201 1
10 I
567
255
29*
FLOW OF WATER.
Cubic Feet of Water per Ulinute Discharged Through an
Orifice 1 Square Inch in Area.
For any other size oj
orifice, multiply by its area in square inches.
^ ©
^3 o5
© ®
"■3 <D
73 ©
© ®
© ®
- -i =
© bCS
i* ;/, s
^ S.2
A
£ g.S
A
fc =8.3
A
fn « .2
A
f=H ~-~
A
A
frjs-5
-§ c
- 1~ ^
J£ 5
J*s
B a
©^
~ =i
■--*
3 s
©^
2 S
v'Zrt
-j. ~
gw.fg
ce1-1
-~
^.i r
T.~~
— .£ r
eSH
1*1
6-~ z
5Pa
^•«a5
W-pH
griS,
5^
"23"
gM&
W*
opft
43
8*
53
-P'A
3
1.12
2.20
2.90
33
3.47
3.95
4.39
63
4.78
4
1.27
14
2.28
•24
2.97
34
3.52
44
4.00
54
4.42
(14
4.81
5
1.40
15
2.36
25
3 03
35
3.57
45
4.05
55
4.46
a5
4.85
6
1.52
lfi
2.43
2(5
3.08
36
3.62
46
4.09
56
4.52
66
4.89
7
1.64
17
2.51
27
3.14
37
3.67
47
4.12
57
4.55
67
4.92
8
1.75
18
2.58
28
3.20
38
3.72
48
4.18
58
4.58
68
4.97
9
1.84
19
2.64
29
3.25
39
3.77
49
4.21
59
4.63
69
5.00
10
1.94
20
2.71
3D
3.31
40
3.81
50
4.27
60
4.65
70
5.03
11
2.03
21
2.78
31
3.36
41
3.86
51
4.30
61
4.72
71
5.07
12
2.12
22
2.84
32
3.41
42
3.91
52
4.34
62
4.74
72
5.09
Table Showing- the Theoretical "Velocity and. Discharge an
Cubic JFeet Through an Orifice of 1 (Square Inch Issu-
ing Under Heads Varying from 1 to lOO feet.
Theoreti-
Theoret-
Theoreti-
Theoret-
Theoreti-
Theoret-
.5 •
cal Dis-
ical
.9 ■
cal Dis-
ical
a .
cal Dis-
ical
-C! g
charge in
Velocity
charge in
Velocity
rs ®
charge in
Velocity
tfr
Cu. Ft.
in Feet
Cu. Ft.
in Feet
©6
Cu. Ft.
in Feet
£
per Min.
per Min.
"2
per Min.
per Min.
w
per Min.
per Min.
1
3.34
481.2
35
19.77
2847.6
69
27.74
3997.1
2
4.73
680.4
36
20.05
2887.2
70
27.94
4021.1
3
5.79
833.4
37
20.33
2926.8
71
28.14
4054.5
4
6.68
962.4
38
20.60
2966.4
72
28.34
4283.0
5
7.47
1075.8
39
20.87
3004.8
73
28.53
4111.3
6
8.18
1178.4
40
21.13
3043.2
74
28.73
4139.4
7
8.84
1273.2
41
21.38
3081.1
75
28.93
4165.2
8
9.45
1360.8
42
21.64
3118.5
76
29.11
4194.9
9
10.02
1443.6
43
21.90
3156.4
77
29.30
4222.4
10
10.57
1521.6
44
22.15
3191.8
78
29.49
4249.8
11
11.08
1596.0
45
22.40
3227.8
79
29.68
4265.9
12
11.57
1666.8
40
22.65
3263.6
80
29.87
4303.6
13
12.05
1734.6
47
22.89
3298.9
81
30.06
4330.8
14
12.50
1800.6
48
23.14
3333.8
82
30.24
4357.4
15
12.94
1863.6
49
23.38
3368.4
83
30.42
4383.6
16
13.37
1924.8
50
23.61
3402.5
84
30.61
4410.2
17
13.78
1984.2
51
23.85
3436.4
85
30.79
4436.4
18
14.18
2041.8
52
24.08
3469.9
86
30.97
4462.4
19
14.57
2097.6
53
24.31
3503.1
87
31.15
4488.2
20
14.95
2152.2
54
24.54
3536.0
88
31.33
4514.0
21
15.31
2205.0
55
24.76
3568.6
89
31.50
4539.5
22
15.67
2256.6
56
24.99
3600.9
90
31.68
4565.0
23
16.02
2307.6
57
25.21
3632.9
91
31.86
4590.3
24
16.37
2357.4
58
25.43
3664.6
92
32.04
4615.4
25
16.71
2406.0
59
25.65
3696.1
93
32.20
4640.5
26
17.04
2453.4
60
25.87
3727.3
94
32.38
4665.3
27
17 36
2500.2
61
26.08
3758.2
95
32.55
4690.1
2S
17.68
2545.8
62
26.29
3788.9
96
32.72
4714.7
29
17.99
2590.8
63
26.51
3819.3
97
32.89
4739.2
30
18.30
2635.8
64
26.72
3849.6
98
33.06
4763.5
31
18.60
2679.0
65
26.92
3879.5
99
33.23
4787.8
32
18.90
2722.2
66
27.13
3909.2
100
33.40
4812.0
33
19.20
2764.2
67
27.33
3938.7
34
19.49
2806.2
GS
27.54
3968.4
936
WATER-POWER.
flow of Water Through an Orifice.
a= area of orifice in square inches.
Q = cubic feet discharged per minute.
h =z head in inches.
Q = M±>/h x a.
The best form of aperture for giving the greatest flow of water is a coni-
cal aperture whose greater base is the aperture, the height or length of the
section of cone being half the diameter of aperture, and the area of the
small opening to the area of the large opening as 10 to 16 ; there will be no
contraction of the vein, and consequently the greatest attainable discharge
will be the result.
JIHAHi I' J I E 31 E2I" T
OF FLOW OF
STllEAJfl.
WATJEM O A.
The quantity of water flowing in a stream may be roughly estimated as
follows :
Find the mean depth of the stream by taking measurements at 10 or 12
or more equal distances across. Multiply this mean depth by the width of
the stream, which will give the total cross-section of the prism.
Find the velocity of the flow in feet per minute, by timing a float over a
measured distance, several times to get a fair average. Use a thin float,
such as a shingle, so that it may not be influenced by the wind.
Fig. 13.
The area or cross-section of the prism multiplied by the velocity per min-
ute will give the quantity per minute in cubic feet.
Owing to friction of the bed and banks the actual flow is reduced to about
83 per cent of the calculated flow as above.
HORSE-POWER OF AVATER.
937
miners' Inch Measurements.
(Pelton Water Wheel Co.)
Miners' inch is a term much in use on the Pacific Coast and in the mining
regions, and is described as the amount of water flowing through a hole 1
inch square in a 2-inch plank under a head of 6 inches to the top of the
orifice.
Fig. 13 shows the form of measuring-box ordinarily used ; and the follow-
ing table gives the discharge in cubic feet per minute of a miners' inch
of water, as measured under the various heads and different lengths and
heights of apertures used in California.
.5
Openings 2 Inches High.
Openings 4 Inches High.
Itj
Head to
Head to
Head to
Head to
Head to
Head to
3&a
Center,
Center,
Center,
Center,
Center,
Center, .
5 Ins.
6 Inches.
7 Inches.
5 Inches.
6 Inches.
7 Inches.
Cu.Ft.
Cu. Ft.
Cu. Ft.
Cu. Ft.
Cu. Ft.
Cu. Ft.
4
1.348
1.473
1.589
1.320
1.450
1.570
6
1.355
1.480
1.596
1.336
1.470
1.595
8
1.359
1.484
1.600
1.344
1.481
1.608
10
1.361
1.485
1.602
1.349
1.487
1.615
12
1.363
1.487
1.604
1.352
1.491
1.620
14
1.364
1.488
1.604
1.354
1.494
1.623
16
1.365
1.489
1.605
1.356
1.496
1.626
18
1.365
1.489
1.606
1.357
1.498
1.628
20
1.365
1.490
1.606
1.359
1.499
1.630
22
1.366
1.490
1.607
1.359
1.500
1.631
24
1.366
1.490
1.607
1.360
1.501
1.632
26
1.366
1.490
1.607
1.361
1.502
1.633
28
1.367
1.491
1.607
1.361
1.503
1.634
30
1.367
1.491
1.608
1.362
1.503
1.635
40
1.367
1.492
1.608
1.363
1.505
1.637
50
1.368
1.493
1.609
1.364
1.507
1.639
60
1.368
1.493
1.609
1.365
1.508
1.640
70
1.368
1.493
1.609
1.365
1.508
1.641
80
1.368
1.493
1.609
1.366
1.509
1.641
90
1.369
1.493
1.610
1.366
1.509
1.641
100
1.369
1.494
1.610
1.366
1.509
1.642
Note. — The apertures from which the above measurements were obtained
were through material 1\ inches thick, and the loicer edge 2 inches above the
bottom of the measuring-box, thus giving full contraction.
FLOW OF WATER OVER WEIRS.
IVeir Dam Measurement.
(Pelton Water Wheel Co.)
Place a board or plank in the stream, as shown in Fig. 14, at some point
where a pond will form above. The length of the notch in the dam should
be from two to four times its depth for small quantities, and longer for
large quantities. The edges of the notch should be beveled toward the
intake side as shown. The overfall below the notch should not be less than
twice its depth, that is, 12 inches if the notch is 6 inches deep, and so on.
In the pond, about 6 feet above the dam, drive a stake, and then obstruct
the water until it rises precisely to the bottom of the notch, and mark the
stake at this level. Then complete the dam so as to cause all the water to
flow through the notch, and, after time for the water to settle, mark the
stake again for this new level. If preferred, the stake can be driven with
its top precisely level with the bottom of the notch, and the depth of the
water be measured with a rule after the water is flowing free, but the marks
938
WATER-POWER.
are preferable in most cases. The stake can then be withdrawn ; and the
distance between the marks is the theoretical depth of flow corresponding
to the quantities in the table.
JFrancis's formulae for Weirs.
As given by
Francis.
Weirs with both end contractions )
suppressed j
Weirs with one end contraction )
suppressed J
Weirs with full contraction . .
Q — 3.33111*
Q — 3.33(1 —
Q = 3.33(1 -
As modified by
Smith.
3.29 (l + J-) ft1
.lft) ft* 3.29lh
:llnlr
3.29 l — ^\ ft2
The greatest variation of the Francis formube from the value of c given
oy Smith amounts to 3* per cent. The modified Francis formulae, says Smith,
will give results sufficiently exact, when great accuracy is not required,
Within the limits of ft, from .5 feet to 2 feet, I being not less than 3 ft.
Q = discharge in cubic feet per second, / = length of weir in feet, h =
effective head in feet, measured from the level of the crest to the level of
still water above the weir.
If Qf = discharge in cubic feet per minute, and V and ft' are taken in inches,
the first of the above formulae reduces to Q' — QAl'h'* • The values are suf-
ficiently accurate for ordinary computations of water-power for weirs
without end contraction, that is, for a weir the full width of the channel
of approach, and are approximate also for weirs with end contraction when
I = at least 10ft, but about 6 per cent in excess of the truth when / = 4ft.
Weir 'Fable.
Table Showing the Quantity of Water Passing over Weirs in Cubic Feet
per Minute,
d
_j^
© ^
. s,q
«|S°1
a&
-t^o
© .- y
T! 3 Tj fa -3
-2 U MO d"<5
d © cS cS ^>
o o -
d 53 3 2 © ►?>
q aaW?
0 0 s
5 © ^
fa.S=V-
0 yd fa !§ .
1 1-d^-l
d S | § © g
0 0 -h
"B © u
III
H£~£#
&u K ©<{-r©
6&a©3^
1
4.85
4f
50.20
8*
120.18
12*
214.32
H
5.78
*t
52.18
8f
122.82
12|
220.76
n
6.68
5
54.22
8|
125.52
13
227.30
if
7.80
5|
56.25
82
128.14
13i
233.92
1*
8.90
5i
58.33
9
130.93
13*
240/4
if
if
10.00
5|
60.42
94
91
133.65
13|
247.22
11.23
5*
62.55
136.43
14
254.03
if
12.45
5f
64.68
91
139.18
14i
260.83
2
13.72
5|
66.86
9*
141.99
14*
267.77
2*
15.02
5£
68.98
9|
144.80
14|
274.70
21
16.36
6
71.27
9|
147.64
15
281.72
2|
17.75
6*
73.45
n
150.47
15i
15*
288.82
2*
19.17
6|
75.77
10
153.35
295.93
2f
2|
20.63
6|
78.04
10*
15G.20
15|
303.10
22.11
6*
80.36
104
159.14
16
310.36
2£
23.63
6f
82.63
10-1
162.07
16i
317.69
3
25.20
6|
85.04
10*
164.99
16*
325.03
3!
26.78
6|
87.43
lOf
167.89
16|
332.42
28.43
7
89.82
101
169.92
17
339.91
3§
30.06
71
92 16
10J
173.90
171
17*
347.45
&h
31.75
7|
94.67
11
176.92
355.02
3f
33.45
97.11
114
179.94
17|
362.77
3|
35.22
7?
99.50
111
182.99
18
370.34
3£
36.98
74
102.10
111
186.03
ISi
378.12
4
38.80
7|
104.63
11*
189.13
18*
385.87
a
40.63
7|
107.13
lit
192.20
18|
393.66
42.49
8
109.74
111
195.32
19
401.63
4f
44.39
8*
112.31
112
198.47
19*
409.58
4£
46.29
1
114.91
12
201.59
19*
417.48
4f
48.22
117.51
12i
207.94
19|
425.68
HORSE-POWER OF WATER.
939
TABLE! FOR CAICIIATIJG TH11 HORiE-POWER
OJP WATE1*.
(Pelton Wheel Co.)
Miners' Inch T
able.
Cubic JFeet Table.
The following table gives
the horse-
The following table gives the
powei
of one miners' inch of water
hor
e-power of
one cubic foot of
under heads from one up
hundred feet. This inch
to eleven
water per minute under heads from
equals 1J
one
up to eleven hundred feet.
cubic feet per minute.
'" _^
Horse-
.5
Horse-
-§ CD
Horse-
■rt ^j
Horse-
s£
Power.
"31
0>R
Power.
Power.
!l
Power.
M
w
w
w
1
.0024147
320
.772704
1
.0016098
320
.515136
20
.0482294
330
.796851
20
.032196
330
.531234
30
.072441
340
.820998
30
.048294
340
.547332
40
.096588
350
.845145
40
.064392
350
.563430
50
.120735
360
.869292
50
.080490
360
.579528
60
.144882
370
.893439
60
.096588
370
.595626
70
.169029
380
.917586
70
.112686
380
.611724
80
.193176
390
.941733
80
.128784
390
.627822
90
.217323
400
.965880
90
.144892
400
.643920
100
.241470
410
.990027
100
.160980
410
.660018
110
.265617
420
1.014174
110
.177078
420
.676116
120
.289764
430
1.038321
120
.193176
430
.692214
130
.313911
440
1.062468
130
.209274
440
.708312
140
.338058
450
1.086615
140
.225372
450
.724410
150
.362205
460
1.110762
150
.241470
460
.740508
160
.386352
470
1.134909
160
.257568
470
.756606
170
.410499
480
1.159056
170
.273666
480
.772704
180
.434646
490
1.183206
180
.289764
490
.788802
190
.458793
500
1.207350
190
.305862
500
.804900
200
.482940
520
1.255644
200
.321960
520
.837096
210
.507087
540
1.303938
210
.338058
540
.869292
220
.531234
560
1.352232
220
.354156
560
.901488
230
.555381
580
1.400526
230
.370254
580
.933684
240
.579528
60)
1.448820
240
.386352
600
.965880
250
.603675
650
1.569555
250
.402450
650
1 .046370
260
.627822
700
1.690290
260
.418548
700
1.126860
270
.651969
750
1.811025
270
.434646
750
1.207350
280
.676116
800
1.931760
280
.450744
800
1.287840
290
.700263
900
2.173230
290
.466842
900
1.448820
300
.724410
1000
2.414700
300
.482940
1000
1.609800
310
.748557
1100
2.656170
310
.499038
1100
1.770780
When the Exact Head is found in Above Table.
Example.— Have 100 foot head and 50 inches of water. How many
horse-power ?
By reference to above table the horse-power of 1 inch under 100 feet
head is .241470. The amount multiplied by the number of inches, 50, will
give 12.07 horse-power.
When Exact Head is not found in Table.
Take the horse-power of 1 inch under 1 foot head, and multiply by the
number of inches, and then by number of feet head. The product will be
the required horse-power.
The above formula will answer for the cubic-feet table, by substituting
the equivalents therein for those of miners' inches.
Note. — The above tables are based upon an efficiency of 85 percent.
940
WATER-POWER.
WATER.WHEELi.
Undershot TO'heels, in which the water passes under acting by im-
pulse, when constructed in the old-fashioned way with flat boards as floats,
have a maximum theoretical efficiency of 50 per cent ; but Avith curved floats,
as in Poncelet's wheel, which are arranged so that the water enters without
shock and drops from the floats into the tail-race without horizontal velo-
city, the maximum efficiency is as great as for overshot wheels, and the
available efficiency is found to be about (30 per cent. The velocity of the
periphery should be about .5 of the theoretical velocity of the water due to
the head.
.Breast and Overshot Wheels.
The best peripheral velocity is about 6 feet per second, and for the water
supplied to it about 12 feet per second, which is the velocity due to a fall of
about 2J feet ; therefore, the point at which the water strikes the wheel
should be 2\ feet below the top-water level. The chief cause of loss in over-
shot wheels is the velocity which the water possesses at the moment it falls
from the float or bucket ; overshot wheels are good for falls of 13 feet to 20
feet ; below that breast wheels are preferable. The capacity of the buckets
should be three times the volume of water held in each. The distance apart
of the buckets may be 12 inches in high-breast and overshot wheels, or 18
inches in low-breast wheels, while the opening of buckets may be 6 to 8
inches in high-breast, and 9 inches to 12 inches in low-breast wheels.
TUHJBEMElS.
These may be divided into two main classes, viz., pressure and impulse
turbines. The former may be again divided into the following : parallel-
flow, outward-flow, and inward-flow turbines, according to the direction in
which the water flows through the turbine in relation to its axis.
IParallel-flow turbines, sometimes called downward-floAV, are best
suited for low falls, not exceeding say 30 feet. Fontaine's turbine is of this
class, the wheel being placed at the bottom of the water-pipe or flume, just
above the level of the tail-race. The water passes through guide blades and
strikes the curved floats of the wheel. Jonval's turbine is of similar type,
but is arranged to work partly by suction, and may be placed above the
level of the tail-race Avithout loss of power, Avhich is often more convenient
for Avorking. The efficiency is from 70 to 72 per cent Avith well-designed
wheels of this type.
Fig. 15. Victor Wheel set in ordinary Flume.
Outward-flow Turbines have a somewhat higher efficiency than the
parallel-floAv — as much as 88 per cent has been realized by Boyden's tur-
bine ; Fourneyron's has given a maximum of 79 per cent.
Inward-flow Turbines have been designed by SAvain and others.
Tests made on a SAvain turbine by J. B. Francis gave a maximum effi-
ciency of 84 per cent Avith full supply, and with the gate a quarter open 61
per cent, the circumferential velocity of the Avheel ranging from 80 to 60
per cent of the theoretical velocity due to the head of Avater. In Swain's
turbine the edges of the floats are vertical and opposite the guide blades,
DIMENSIONS OK TURBINES.
941
the edges towards the bottom of the floats being bent into a quadrant form.
The Victor turbine is claimed to give 88 per cent under favorable conditions.
It receives the water upon the outside, and discharges it downward and out-
ward, the lines of discharge occupying the entire diameter of the lower portion
of the wheel, excepting only the space tilled by the lower end of the shaft.
Impulse Turbines are suitable for very high falls. The Girard and
Pelton are both of this type. It is advised that pressure turbines be used
on heads of 80 feet or 100 feet, but above this an impulse turbine is best.
A Girard turbine is working under a fall of 650 feet.
Installing* Turbines.
Particular attention must be paid to the designing and construction of
water-courses. The forebay leading to the flume should be of such size that
the velocity of the water never exceeds 1^ feet per second, and should be
free from abrupt turns or other defects likely to cause eddies. The tail-race
should have similar capacity and sufficient depth below the surface of the
stream to allow at least 2 feet of dead water standing when the wheels are
not in motion, and with large wheels, 3 feet to 4 feet ; after extending sev-
eral feet beyond the flume, this may be gradually sloped up to the level of
the stream. It is not uncommon to see 2 feet or 3 feet of head lost in
defective races.
When setting turbines some distance above the tail-race, the mouth of the
draft-tube must be 2 inches to 4 inches below the lowest level of the stand-
ing tail-water. Theoretically draft-tubes may be 30 feet long ; but 20 feet
is as long as is desirable on account of the difficulty of keeping air-tight ;
they should be made as short as possible by placing the turbine at the
bottom of the fall.
Particulars of the setting recommended for Victor turbines are given
below, as an example.
Table of Dimensions of Victor Turbine.
A.
B.
C.
D.
E.
F.
K.
"3
01
o
Diameter of
Cylinder pass-
ing through
Floor of Flume.
0
fl 2 2
S S S
5SS
Length of Shaft
from Flange
Resting on
Floor of Flume
to Center of
Coupling.
Diameter of
Bore of Upper
Half of Coup-
ling.
^ 5,2
0 |^ 6
S 55^
Depth of Pit
from End of
Cylinder to
Bottom of
Wheel-Pit.
4)
2 0 6
^•3 2
In.
In.
In.
Ft.
In.
In.
In.
2&£:i
Lbs.
6
10
131
20J
2
12
1
5i
•cDrt.g-S
165
8
10
13£
16
2*
3
19H
22$
1/s
lis
n
l£11
260
350
12
18i3s
23&
31
28i
lit
9§
ga_g*
500
15
fi
28 &
4
33|
Vb
11
g >>'-?S $
830
m
31i
35*
5
351
m
12|
rt-S s 2
1125
20"
30J
6
37j
3&
13i
as^ 3
1475
22J
33|
35i
38£
6i
42
h%
14*-
2s'ofl
1900
25
40f
6*
43f
3/1
15|
« ^Bro
2335
27J
38i
43|
7l
48i|
4|
16i
S a © «
3225
30
40!
46
8
50!
a
3540
321
43!
49i
9
55f
n
W^^'-P
4500
35
46i
53"
9
59
H
20
3 2-d§
5450
40
52i
60^
10
64f
5|
22
^ % go-S
7500
44
48
56J
60J
65J
70i
11
12
67J
74f
1
24
26
ool 0 A
9380
11700
55
68
80
14
85J
28
r" O O ° ^
N N 2 C 2
19000
69
80i
92
16
96i
'~g
32
'S-So^
BUJIEjYSI©]*® ©JP TI'ItBJIlHrES.
Tables of sizes of turbine wheels vary so much under different makers,
and are so extensive, as not to permit their insertion here, but through the
kindness of Mr. Axel Ekstrom of the General Electric Company I am per-
mitted to print the following sheets of curves for the McCormick type
turbine and the Pelton impulse wheel. From them may be made deter-
minations of dimensions in much shorter time than is necessary by use of
tables.
942
WATER-POWER.
§
LL
c
> s g
3
z •§ 5
£ r-V-
o CO « g
^A
H i W X
Ji V co
£ " ui g
3 *-£ X Hiu
£ S S
r\ \ UJ a.
OT h 5
-VVX zif
< 3
°v^\ §^g
J g 0
-£-\-m sSl
Z H '"
S^V^ £z§
J o o
^
SvxXV s§
w 3 °
^"
, \SvV\i ^^
Ig„Q
y
\Niva 2
Ts'*i ^
<v
\ K N YV; H
£ g. 4 ± 4^
s*
sv rvS5 j
aS "** ffi -ot-^
VS \X\5v-
^v
s^v\^v5X
"^?K'
VxV^SSSv
z°o6 ,«m/
<?^>^
§V\SV\^T .
°-':°- ±z in
V<J>
N,^v^VO^\
-:s0hJ ^te/ t-
o^pj
«^ sX^Njv, -
x s « t y _ ^
*1^
o xN^sVsss*
So ^ ^Pffl
raN0*.X^Sv&\
sOvJn^n^sSSS
g * y cd^4^ ■
s:>^^^555$§
a ^*^2>^^§§S
IS^ s-4 77- '
» ^-^-^^r^SS
^^ -' 7 ti>'
^r7r
" ~~~~" — --^rlpfe^is
^ ±
s-s-^-^-s-^fffl3
— || 1 — ] — | — a va h|---j
2 ° co-o . o —- -,j-~ ^ -- ■" 2 o gJ ^ j
rJ-| — |— | | |
y*"^=—
7S0G3"-:>!|E^- — EjE-
====-=i
J<s£« ffl ^^^"^r- ~~~^- — ■ _
~=~- — -___
^ T ^5^>--
^£0ii
i2>v7x/t =~r T\X ^ ^
""■=» "°
//L/Z/V,-0'!0'' \\V H. ■>-.
"^r^-i,^
£ ■—^^-^^^^-^^'^.^'^^
^y// = i \\,xv\ >^
""»«*<,
S ^-'Z^-'^^'^ ^^ <^fs'' /'*
yy/7th^^ hX \\^ s ^s. "s
Xs, ^-^^
'/iJ-LLzJLit xsW ^^
.** *" ' ^^Z^'^'l''^'' ^ s /
7/7S^T^ ^ v^ v
»* ""--"".a;^' ^ ^ t^_ /
/ t±p°±^ NNC^ s^ ^
§ ^^ ^^ ^ y^ 7 .
'/ .rfz*Tl± K\^T\ ^
^^^ ^-
« ^ -" ^ y y
/' A J so „LT s \ \ s v 'v
s^ ^ ^7 * S-,
' ' iS d0,09T l > \ N N.
"a-^ *>' *' 7-7
^_,/ -SooU1^ ^XvN^ ^
^^ "^
*' 7 7 7
""N ^^
"s^ ^ ^ Z ^
' |o 1 .3 > \\ ^
Sy "**.
^ ^ ^ 7
"7 x « ot|00i' ° v ^ >. >^
\ ^^
\^ 7 7 A
> = 1 ^ ^ a v 2
■N "s.
^ -7 7
^ i- m 00|0c"|• j. S; ^
^ ^7 ^ v
H ^;-
'a' ^ -^ ^
v- ^ s-
^ ^ 7
K > oil g j
^^ ^N
-*' ^ -V
■ 7 7 -f
nP oil <
^. "n
53 7 ^
^v
^ /
a 2 =,11 ; .-. -
s^
W^ -/
""1 f 5
"n
V Zt
bIt r-
DIMENSIONS OF TURBINES.
943
|-i g OO00T
> s §1
J
* i
z '° 3 0<]0?l
- 4-
A 4
^
V V v
S S S g <Kj»T
: rfe
X A ti
^^
4-V -t *
i?i S< 3
X t z i
V A °^
A,
H X V ^
ujg 1 j-
>
"/
V -X s^
5- T1^
A
y
X 3
\ \ _
e> -'
\ ^tX A i
o e oooc °f ^
i£y
V X d£ 4
m,=>\ y £y
c^
*r
S v 3
a S 00|0" "- d/
- "S-
'A 5 V
| g 00'0i h <y
\ ^3
- - 1 /
foyT
\ V V
j^oV-
S S 3
rt
^ s \
o 1 /
^
N- -N S__
\ S oopsr-
4$/\
'<*
L t \ \
V o 1/
ot/Co
^ N
\ ?°°f
si -fe
S V g'T! ^
s\v * ^jjk
^J^ZK± S nroTi^
~"-"~~--~^--
j- i r"~5~~5^ "xfs
= ^Tf^> T ~i — 5 — 5~
_g
-S s
0V3H *ld
~TTT++#ff
S "S "§
^T"-
^z.^m%\^
^.^■^
>^A*isX- v^
^-""^^^
^--^-few--^
L o
^-""*~ ^^
i^ SrA
— — ■"" ,-»''
^ V '!§ A ^
^«<
*>■*. y
Z / B2 v s
""* ^
7 ZHg.§. V
"*•> >
/ ^J£° S
^s'
^ 1 Zg.guj \
^■S
>'*" X
Z -h_2 g z <_ ^^
:^s^ :
^
/ JuirocoS
N
' ^4.
/_
-v Zfc; g g s
\
>^^
7
7- £iSS£
\
yS
;/ y s g g ,_: ^
V
x
^ >s
^ ~~ 'S g g 2 °
-N^s -
* *=/
1 >. s - 5 Jfc
_ N^ _
/ |ss°
X
* Za
A *3 3 ^
vv
Z£> IF
y gg £
_X
ZIfgl
"N-
Z "p
2 it SS <
2 <S
r s 2 5
7^ S 2
7 sg <
3 2 $
«o 2
s.s
944 WATER-POWER.
THE IJtEPUIiSE WAIER-WHEEI.
Mr. Ross E. Browne states that " The functions of a water-wheel, operated
by a jet of water escaping from a nozzle, is to convert the energy of the jet,
due to its velocity, into useful work. In order to utilize this energy fully,
the wheel bucket, after catching the jet, must bring it to rest before dis-
charging it, without inducing turbulence or agitation of the particles. This
c innot be fully effected, and unavoidable difficulties necessitate the loss of
a portion of the energy. The principal losses occur as follows :
" First : In sharp or angular diversion of the jet in entering, or in its
course through the bucket, causing impact, or the conversion of a portion of
the energy into heat instead of useful work.
" Second : In the so-called frictional resistance offered to the motion of
the water by the wetted surfaces of the buckets, causing also the conver-
sion of a portion of the energy into heat instead of useful work.
"Third: In the velocity of the water as it leaves the bucket, represent-
ing energy which has not been converted into work.
'••Hence, in seeking a high efficiency, there are presented the following
considerations :
" 1st. The bucket surface at the entrance should be approximately paral-
lel to the relative course of the jet, and the bucket should be curved in such
a manner as to avoid sharp angular deflection of the stream. If, for exam-
ple, a jet strikes a surface at an angle and is sharply deflected, a portion of
the water is backed, the smoothness of the stream is disturbed, and there
results considerable loss by impact and otherwise.
2d. The number of buckets should be small, and the path of the jet in the
bucket short ; in other words, the total wetted surface should be small, as
the loss by friction will be proportional to this.
" A small number of buckets is made possible by applying the jet tangen-
tially to the periphery of the wheel.
" 3d. The discharge end of the bucket should be as nearly tangential to
the wheel-periphery, as compatible with the clearance of the bucket which
follows ; and great differences of velocity in the parts of the escaping
water should be avoided. In order to bring the water to rest at the dis-
charge end of the bucket, it is easily shown mathematically that the velo-
city of the bucket should be one-half the velocity of the jet.
" An ordinary curved or cup bucket will cause the heaping of more or less
dead or turbulent water in the bottom of the bucket. This dead water is
subsequently thrown from the wheel with considerable velocity, and repre-
sents a large loss of energy.
" The introduction of the wedge in the bucket is an efficient means of
avoiding this loss."
Wheels of this type are very efficient under high heads of water, and have
been used to a great extent in the extreme Avestern parts of the United
States, where the fall is in hundreds of feet. It is difficult to say at what
point of head the efficiency becomes such as to induce the use of some other
form of wheel; but at 200 feet head the efficiencies of both impulse and tur-
bine will be so much alike that selection must be governed by other factors.
Tests of one of the leading impulse wheels show efficiencies varying from
80 % to 86 % according to head and size of jet. However, many factors
besides the efficiency enter into selection of water-wheels, which must be
subject to local conditions, and as in most water-power plants, each is a
special case by itself, and selection of apparatus best fitted in all ways must
govern.
SHAFTING, PULLEYS, BELTING, ROPE-
DRIVING.
SHAFTIUC.
TTiurston gives the following formulae for calculating power and size of
shafting.
H.P. = horse-power transmitted.
d = diameter of shaft in inches.
r = revolutions per minute.
( dh- 3/
For head shafts well For iron> Hp- = ^ d = \
4
125 H.P.
supported against^ For cold. 8/
springing. r>lled iron jyp. _ «£. d_ i / <& ^ -f-
L ' - 75 '
* = $?
}^^n,H.P. = ^,d = ^
L 55 T
For line shafting i For iron, H.P.= — \
hangers 8 feet
apart.
For transmission
H.P.
(Foriron,H.P. = ^,d = ^^
simply, no pul- J F ld_ ^ S/z^HP,
ieys- r'lld iron, H.P.= — — ; d = V
35 ' " r
35 '
Jones and Laughlin's use the same formulae, with the following excep-
tions :
~ 50'
For transmission and for short-counters,
_ ^/50 H.r
Turned iron H.P. = -c— ; d=y
d3r , t3/3(
Cold-rolled iron H.P.
Pulleys should be placed as near to hearings as practicable, but care
should be taken that oil does not drip from the box into the pulley.
The diameter of a shaft safe to carry the main pulley at the center of a
bay may be found by multiplying the fourth power of the diameter obtained
by the formulae above given, by the length of the bay, and dividing the pro-
duct by the distance between centers of bearings. The fourth root of the
quotient will be the required diameter.
The following table is based upon the above rule, and is substantially
correct :
945
946
SHAFTING, PULLEYS, BELTING, ETC.
° § o . i
Diame
er of Shaft necessary to carry the Load at the Center of
% ~ *•
a Bay, which is from Center to Center of Bearings.
S^'^ii'S
2} ft,
3 ft.
3i ft.
4 ft.
5 ft.
6 ft.
8 ft.
10 ft.
S 32 .0 s w
in.
in.
in.
in.
in.
in.
in.
in.
in."
2
2i
24
2f
2i
2f
2|
^
3
2i
2i
2|
21
■ 2|
3
3i
3f
3f
3
3
31
34
3§
3*
3|
4
44
3*
3i
3|
3|
4
4|
4*
4|
4
4
4i
44
4i
4f
5i
5|
a
4£
4f
4f
5|
5£
a
5
5
5i
5§
*t
6
5i
6i
3
6
<%
6f
6
6
6f
u
7l
Should the load be placed near one end of the bay, multiply the fourth
power of the diameter of shaft necessary to safely carry the load at the cen-
ter of the bay (see above table) by the product of the two ends of the shaft,
and divide this product by the product of the two ends of the shaft where
the pulley is placed in the center. The fourth root of this quotient will be
the required diameter.
A shaft carrying both receiving and driving pulleys should be figured as
a head-shaft.
Reflection of Shafting*.
(Pencoyd Iron Works.)
As the deflection of steel and iron is practically alike under similar con-
ditions of dimensions and loads, and as shafting is usually determined by
its transverse stiffness rather than its ultimate strength, nearly the same
dimensions should be used for steel as for iron.
For continuous line-shafting it is considered good practice to limit the
deflection to a maximum of Tiff of an inch per foot of length. The weight
of bare shafting in pounds — 2.6 d2L = W, or when as fully loaded with
pulleys as is customary in practice, and allowing 40 lbs. per inch of width
for the vertical pull of the belts, experience shows the load in pounds to be
about 13 (PL = W. Taking the modulus of transverse elasticity at 26,000,000
lbs., we derive from authoritative formulas the following :
L — ^873 d2, d — V -jSL for bare shafting;
L—^j 175 d2, d -.
175
, for shafting carrying pulleys, etc.;
L being the maximum distance in feet between bearings for continuous
shafting subjected to bending stress alone, d = diam. in inches.
The torsional stress is inversely proportional to the velocity of rotation,
while the bending stress will not be reduced in the same ratio. It is there-
fore impossible to Avrite a formula covering the whole problem and suffi-
ciently simple for practical application, but the following rules are correct
within the range of velocities usual in practice.
For continuous shafting so proportioned as to deflect not more than T^j
of an inch per foot of length, allowance being made for the weakening
effect of key-seats,
,$
50 H. P.
~,L— ^700rf2 for bare shafts ;
SHAFTING.
947
, L — %J 140rf2, for shafts carrying pulleys, etc.
d =r diam. in inches, L = length in feet, r = revols. per minute.
The following table (by J. B. Francis) gives the greatest admissible dis-
tances between the bearings of continuous shafts subject to no transverse
strain, except from their own weight.
Distance between
Bearings in ft.
Distance between
Bearings in ft.
iam. of Shaft,
Wrought-iron
Shafts.
Steel
in inches.
Shafts
6
22.30
22.92
7
23.48
24.13
8
24.55
25.23
9
25.53
26.24
Diam. of Shaft, Wrought-iron Steel
in inches Shafts. Shafts
2 15.46 15.89
3 17.70 18.19
4 19.48 20.02
5 20.99 21.57
The writer prefers to apply a formula in all cases rather than use tables,
as shafting is nearly always one-sixteenth inch less in diameter than the
sizes quoted. The following tables are made up from the formulae first
given in this chapter.
Horse-f»o*ver Transmitted oy Turned Iron Shafting-.
As Prime Mover or Head Shaft well Supported by Bearings.
s=
Revolutions per Minute.
5
60
80
100
125
150
175
200
225
250
275
300
Ins.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
I*
2.6
3.4
4.3
5.4
6.4
7.5
8.6
9.7
10.7
11.8
12.9
2
3.8
5.1
64
8
9.6
11.2
12.8
14.4
16
17.6
19.2
2+
5.4
7.3
8.1
10
12
14
16
18
20
22
24
2\
7.5
10
12.5
15
18
22
25
28
31
34
37
2*
10
13
16
20
24
28
32
36
40
44
48
3
13
17
20
25
30
35
40
45
50
55
60
34
3i
16
22
27
34
40
47
54
61
67
74
81
20
27
34
42
51
59
68
76
85
93
102
m
25
33
42
52
63
73
84
94
105
115
126
4
30
41
51
64
76
89
102
115
127
140
153
U
43
58
72
90
108
126
144
162
180
198
216
5
60
80
100
125
150
175
200
225
250
275
300
H
80
106
133
166
199
233
266
299
333
366
400
Approximate Centers of Bearing's for ^Wrought Iron Line
Shafts Carrying- a fair Proportion of I*ulleys.
Shaft, Diameter Inches . .
1J
If
2
2|
2J
2|
3
3i
4
4
c. to c. Bearings — Feet . .
7
7J
8
84
9
9i
10
11
12
13
Shaft, Diameter Inches . .
5
5i
6
6J
7
1\
8
9
10
c. to c. Bearings — Feet . .
13£
14
15
15|
16
17
18
19
20
948
SHAFTING, PULLEYS, BELTING, ETC.
Line-shafting, Bearings 8 ft. Apart.
5
Revolutions per Minute.
100
125
150
175
200
225
250
275
300
H.P.
325
H.P.
350
Ins.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
1*
6
7.4
8.9
10.4
11.9
13.4
14.9
16.4
17.9
19.4
20.9
1*
7.3
9.1
10.9
12.7
14.5
16.3
18.2
20
21.8
23.6
25.4
2
8.9
11.1
13.3
15.5
17.7
20
22.2
24.4
26.6
28.8
31
2£
10.6
13.2
15.9
18.5
21.2
23.8
26.5
29.1
31.8
34.4
37
2i
12.6
15.8
19
22
25
28
31
35
38
41
44
1
15
18
22
26
29
33
37
41
44
48
52
17
21
26
30
34
39
43
47
52
56
60
2|
23
29
34
40
46
52
58
64
69
75
81
3
30
37
45
52
60
67
75
82
90
97
105
3i
38
47
57
66
76
85
95
104
114
123
133
34
47
59
71
83
95
107
119
131
143
155
167
3*
58
73
88
102
117
132
146
162
176
190
205
4
71
89
107
125
142
160
178
196
213
231
249
POWER TRANSMISSION ONLY.
a
Revolutions per Minute.
3
100
125
150
175
200
233
267
300
333
367
400
Ins.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
:i
6.7
8.4
10.1
11.8
13.5
15.7
17.9
20.3
22.5
24.8
27.0
8.6
10.7
12.8
15
17.1
20
22.8
25.8
28.6
31.5
34.3
if
10.7
13.4
16
18.7
21.5
25
28
32
36
39
43
i*
13.2
16.5
19.7
23
26.4
31
35
39
44
48
52
2
16
20
24
28
32
37
42
48
53
58
64
t
19
24
29
33
38
44
51
57
63
70
76
22
28
34
39
45
52
60
68
75
83
90
2|
27
33
40
47
53
62
70
79
88
96
105
1
31
39
47
54
62
73
83
93
104
114
125
41
52
62
73
83
97
111
125
139
153
167
3
54
67
81
94
108
126
144
162
180
198
216
3i
68
86
103
120
137
160
182
205
228
250
273
3*
85
107
128
150
171
200
228
257
285
313
342
Horse-power Transmitted \ry Cold-rolled Iron Shafting-.
AS PRIME MOVER OR HEAD SHAFT WELL SUPPORTED BY BEARINGS.
g
Revolutions pei
Minute.
s
60
80
100
125
150
175
200
225
250
275
300
Ins.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H
2.7
3.6
4.5
5.6
6.7
7.9
9.0
10
11
12
13
if
4.3
5.6
7.1
8.9
10.6
12.4
14.2
16
18
19
21
2
6.4
8.5
10.7
13
16
19
21
24
26
29
32
1
9
12
15
19
23
26
30
34
38
42
46
12
17
21
26
31
36
41
47
52
57
62
2f
16
22
27
35
41
48
55
62
70
76
82
3
21
29
36
45
54
63
72
81
90
98
108
3
27
36
45
57
68
80
91
103
114
126
136
34
45
57
71
86
100
114
129
142
157
172
3|
42
56
70
87
105
123
140
158
174
193
2i0
4
51
69
85
106
128
149
170
192
212
244
256
^
73
97
121
151
182
212
243
273
302
333
364
SHAFTIXG.
949
LINE-SHAFTING, BEARINGS 8 FT. APART.
Kevolutions per Minute.
&
s
100
125
150
175
200
225
250
275
300
325
350
Ins.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
n
6.7
8.4
10.1
11.8
13.5
15.2
16.8
18.5
20.2
21.9
23.6
n
8.6
10.7
12.8
15
17.1
19.3
21.5
23.6
25.7
28.9
31
if
10.7
13.4
16
18.7
21.5
24.2
26.8
29.5
32.1
34.8
39
n
13.2
16.5
19.7
23
26.4
29.6
32.9
36.2
39.5
42.8
46
16
20
24
28
32
36
40
44
48
52
56
^
19
24
29
33
38
43
48
52
57
62
67
a
22
28
34
39
45
50
56
61
68
74
80
27
33
40
47
53
60
67
73
80
86
94
2h
31
39
47
54
62
69
78
86
93
101
109
2f
41
52
62
73
83
93
104
114
125
135
145
3
54
67
81
94
108
121
134
148
162
175
189
3k
68
86
103
120
137
154
172
188
205
222
240
'3k
85
107
128
150
171
192
214
235
257
278
300
POWER TRANSMISSION AND SHORT COUNTERS.
s
Kevolutions pei
Minute.
S
100
125
150
175
200
233
267
300
333
367
400
Ins.
H.P.
H.P.
H
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H.P.
H
6.5
8.1
9.7
11.3
13
15.2
17.4
19.5
21.7
23.9
26
1*
8.5
10.7
12.8
15
17
19.8
22.7
25.5
28.4
31
34
1*
11.2
14
16.8
19.6
22.5
26
30
33
37
41
45
1*
14.2
17.7
21.2
24.8
28.4
33
38
42
47
52
57
lif
18
22
27
31
35
41
47
53
59
65
71
H
22
27
33
38
44
51
58
65
72
79
87
2
26
33
40
46
53
62
71
80
88
97
106
2ft
32
40
47
55
63
73
84
95
105
116
127
2*
38
47
57
66
76
89
101
114
127
139
152
n
44
55
66
77
88
103
118
133
148
163
178
ih
52
65
78
91
104
121
138
155
172
190
207
2^
69
84
99
113
138
161
184
207
231
254
277
3
90
112
135
157
180
210
240
270
300
330
360
Hollow Shafts.
Let d be the diameter of a solid shaft, and dxd2 the external and internal
diameters of a hollow shaft of the same material. Then the shafts will be
of equal torsional strength when d3 = 1 - • A 10-inch hollow shaft with
internal diameter of 4 inches will weigh 16% less than a solid 10-inch shaft,
but its strength will be only 2.56 % less. If the hole were increased to 5
inches diameter the Aveight would be 25 % less than that of the solid shaft,
and the strength 4.25 % less.
Table for JLaying- Out Shafting-.
The table on the following page is used by ¥m. Sellers & Co. for the lay-
ing out of shafting.
950
SHAFTING, PULLEYS, BELTING, ETC.
I Si t
»t t
2a M
•saqoiq
jejaureia
W "*< i5 iO SO t-t-aO©5©*-C-)c5-*i~i>C:a5
•saqouj
S^ffS^Ojjgjw^aoebsSjgg^g'
•ant 'xog jo Sui
-jrea'g jo q^3u9T;
<Df »0)OHNM*»00C
?S«5^^® o
lb
c
c3
oT
§0
E
«5
49
CD
ti
fl
"ft
a
o
©
o
a
W
o
s
8
05
s
9
£
o
49
fl
s
Use of Table. — Look for size of first shaft in left-hand col-
umn, under the head of size of first shaft, and in the top line
of table marked size of second shaft, find the size of the shaft
to be coupled to it. The intersection gives the length B ; this
added to the length A, or distance fr< m center to center of
bearing, and in cases similar to Fig. 19, to the length C, gives
the length of the first shaft, thus : as in Fig. 18, B + A + B =
length ; Fig. 19, C -f- A + B = length.
Make bearings at equal
distances from each
other when practicable;
always put 2 bearings on
first, which is collared
shaft. See Figs. 18 & 19.
8
p?
s$
I;
isfo
Sr
!« si
1,
sg&saS
3?
38$'?38Jo
«£
ib
slffaSsa
£
|
$%$&$'£&$
«
-^
ssfusj^si'
it
S
^SSsff^f
re
#
2'^2S5?!fa
£3 2 £2 2=1% d
It
■*3FlOW!ONtS,O0
a
ir
2 M t -*<& ttt-00
In coupling shafts of different
sizes either reduce the end o4
the large shaft in diameter and
use a small coupling, or use a c
ling to suit the larger shaft,
1 cone bored for smaller nomin;
I?
unm "$*r $"o' «r
S.
•*iir„ja,«fc,«i.a
1?
S'iV-s
1?
*•*
|gOT.S
Hnmw -w-tortrr *-w-»l« -4n -In -in -in
fc
***««««
*t» r- ST© <■» cTcOTt^uTsS'c^'
951
PlILEli.
Unwin says the number of arms is arbitrary, and gives the following
values :
a = Number of arms = for a single set = 3 -f- — — •
d — diameter pulley.
t = thickness of edge of rim of pulley = .75 inches + .005d.
J1^ thickness of middle of rim of pulley = It -f- c.
b f= breadth of rim of pulley = | (JS + 0.4j.
B = breadth of belt.
| for single belt = .6337 \ —
h = breadth of arm at hub -i a
for double belt
" a
ht = breadth of arm at rim = § h.
e = thickness of arm at hub = 0.4 h.
ex — thickness of arm at rim = 0.4 hv
c = crowning = ^ b.
L rr length of hub — about f b.
Reuleaux says pulleys of more than one set of arms may be considered
as separate pulleys, except proportions of arms may be 0.8 to 0.7 that of
single-arm pulleys.
To find Size of Pulley.
D =z diameter of driver, or No. teeth in gear.
d = diameter of driven, or No. teeth in pinion.
Rev =i revolutions per minute of driver.
rev = revolutions per minute of driven.
d x rev d x rev
Jiev —
Rev D
D X Rev B x
The coefficient of friction of belts on pulleys varies greatly, and it is there
fore customary to use some arbitrary formula that has proved safe in
practice.
d =± diameter pulley in inches.
«-rf = circumference.
v = velocity of belt (or pulley face) in feet per minute.
a = angle of arc of contact, commonly assumed as 180°.
I = length of arc of contact in feet = —t^tt-
F= tractive force per square inch cross-section of belt.
w = width of belt in inches.
t = thickness of belt in inches.
F
S — tractive force per inch of width =z — .
rpm — revolutions per minute.
v = ~ x rpm.
v iv S d w S X rpm
' ' ~ 33000 — 126050
A rule in common use for approximate determination of the H.P. of belts
is, that a single belt 1 inch wide, traveling 1000 feet per minute, will trans-
mit 1 horse-power. This corresponds to a strain on the belt of 33 lbs. per
inch of width.
952
SHAFTING, PULLEYS, BELTING, ETC.
Authorities say single belts can be safely worked at 45 lbs. strain per
square inch, and on this basis
TT P — ^-^ — ^ w X rpm
' '~ 733 — 2800
Double belts are said to be able to transmit power in the ratio of 10 to 7
for single belts.
H. P. of double belts = - ^ = 19(/ •
If the double belt is twice the thickness of the single belt, then it is fair
to assume that it will transmit twice the power, and
v w d to x rpm
1400
A. JP. IVag-le (Trans. A. S. M. E., vol. ii. 1881) gives the following
formula
=■*■ = <"* £=^)-
Where C = 1 — io--00758^.
f— coefficient of friction.
Hoi-se-Powerofa Belt one Inch Wide, Arc of Contact ISO0.
Comparison of Different Formulse.
a
a
*; ©
Form. 5
Nagle's
Form.
>~u
^^
fr A
Form. 1
Form. 2
Form. 3 Form. 5
Double.
&" single
."£ -r:
H.P. =
wv
550'
H.P. —
wv
lioo
H.P. =
wv
1000
H.P. =
wv
733'
Belt
H.P. —
wv
Belt.
® © J)
Laced.
Riveted
r*fc<Xl
513
10
600
50
1.09
.55
.60
.82
1.17
.73
1.14
20
1200
100
2.18
1.09
1.20
1.64
2.34
1.54
2.24
30
1800
150
3.27
1.64
1.80
2.46
3.51
2.25
3.31
40
2400
200
4.36
2.18
2.40
3.27
4.68
2.90
4.33
50
3000
250
5.45
2.73
3.00
4.09
5.85
3.48
5.26
60
3600
300
6.55
3.27
3.60
4.91
7.02
3.95
6.09
70
4200
350
7.63
3.82
4.20
5.73
8.19
4.29
6.78
80
4800
400
8.73
4.36
4.80
6.55
9.36
4.50
7.36
90
5400
450
9.82
4.91
5.40
7.37
10.53
4.55
7.74
100
6000
500
10.91
5.45
6.00
8.18
11.70
4.41
7.96
110
6600
550
4.05
7.97
120
7200
600
3.49
7.75
Width of Belt for a g-iven Hoi'se-Power.
The width of belt required for any given horse-power may be obtained
by transposing the formulse for horse-power so as to give the value of w.
Thus :
From formula (1), w =
From formula (2), w =
From formula (3), w =
From formula (4), w =r
From formula (5),* w =
550 H. P.
9.17 H.P.
2101 H. P.
275 H. P.
V
V
~ d x rpm
L x rpm
1100 H. P.
18.33 H. P.
4202 H. P.
530 H. P.
V
V
~ d X rpm
L x rpm
1000 H. P.
16.67 H. P.
38.20 H. P.
500 H. P.
V
733 H. P.
V
12.22 H. P.
~ d x rpm
2800 H. P.
~ L x rpm
360 H.P.
V
513 H. P.
~~ V
8.56 H. P.
— d x rpm
1960 H. P.
~ L x rpm
257 H. P.
V
* For
V
double belts.
— d x rpm
L x rpm
953
Length of Belt.
[~ / Diat -4- Dia2
\ X 3.14161 + [2
Approximate rule ; two pulleys I I
between centers] = length of belt.
Length of Belt in Boll.
Outside diameter roll in inches 4- diameter bole X number turns x .1309
= length of belt in inches for double belt.
'Weight of Belt {approximate).
Length in feet x width in inches . ,, „ . . , ,, _^. . , , 0 .
s _ — weight of single belt. Divide by 8 for
Horse-Power Transmitted by Light, Bouhle Endless
.Leather Belting*.
(Buckley.)
Width,
Inches.
4
6
8
10
12
14
16
18
20
22
24
■9 2000
14
22
29
36
43
50
58
65
72
80
87
H 2400
17
26
35
44
52
60
70
78
88
96
105
b 2800
20
30
40
51
61
71
81
91
102
112
122
a 3000
22
33
44
54
65
76
87
98
108
120
131
•g 3500
25
38
50
63
76
89
101
114
127
140
153
® 4000
29
43
58
73
87
101
116
131
145
160
174
d 4500
•- 5000
32
49
65
82
98
114
131
147
163
180
196
36
55
73
91
109
127
145
163
182
200
218
*2 5500
40
60
80
100
120
140
160
180
200
220
240
S 6000
XJl
44
65
87
109
130
153
175
200
218
240
260
(Speed X width -f-550 = horse-power, light, double.)
(Horse-power X 550 -f- speed = width, light, double.)
Horse- Power Transmitted by Heavy, Double Endless
Leather Belting*.
Width,
Inches.
4
6
8
10
12
14
16
18
20
22
24
M 2000
18
27
36
43
51
60
70
80
86
96
104
a 2400
21
31
42
53
62
72
83
94
105
115
120
35 2800
24
36
48
61
73
85
96
109
122
135
146
a 3000
27
40
53
65
78
90
104
118
129
344
157
-§ 3500
30
45
60
75
91
106
121
137
152
168
184
« 4000
35
52
70
88
104
121
139
157
174
192
209
t* 4500
■? 5000
38
59
78
98
118
137
157
176
196
216
235
43
66
87
110
130
152
174
196
218
240
262
^ 5500
48
72
96
120
144
168
192
216
240
264
288
» 6000
CO
52
78
104
122
153
1S3
210
240
262
288
312
(Speed X width -f- 460 =r horse-power, heavy, double.)
(Horse-power x 460 4- speed = width, heavy, double.)
954
SHAFTING, PULLEYS, BELTING, ETC.
KOPJE DBIVOG.
C'= Circumference of rope in inches.
Dz= Diameter of pulley in feet.
Jl= Involutions per minute.
200
or, Half the diameter of rope multiplied by the hundreds of feet per min-
ute traveled. (L. I. Seymour.)
Breaking strength of manila rope in pounds = C2 X coefficient. The
coefficient varies from 900 for |-inch to 700 for 2-inch diameter rope. The
following is a reliable table prepared by T. Spencer Miller, M.E. (See En-
gineering News, December 6, 1890.)
Diameter.
Circumference.
Ultimate Strength.
Coefficient.
i
1*
2,000
900
f
2
3,250
845
1
2i
4,000
820
1
2f
6,000
790
1
3
7,000
780
li-
3i
9,350
765
lt
3|
10,000
760
4}
13,500
745
n
4i
15,000
735
if
5
18,200
725
if
5i
21,750
712
2
6
25,000
700
This table was compiled by averaging and graduating results of tests at
the Watertown Arsenal and Laboratory of Riehle Brothers, in Philadelphia.
Weight of manila rope in pounds per foot = .032 (Circumference in
inches)2. (C. W. Hunt.)
or, diameter of rope in inches squared = weight in pounds per yard ap-
proximately.
The coefficient of friction on a rope working on a cast-iron pulley = 0.28 ;
when Avorking in an ungreased groove it is increased about three times, or
from 0.57 to 0.84. If the pulleys are greased, the coefficient is reduced
about one-half. It has been found by experiment that a rope 6 inches cir-
cumference in a grooved pulley possesses four times the adhesive resistance
to slipping, exhibited by a half-worn, ungreased 4-inch single belt.
The length of splice should be 72 times the diameter of rope. The strength
of a rope containing a properly made " long splice" was found to be 7,000
pounds per square inch of section.
A mixture of molasses and plumbago makes an excellent dope for trans-
mitting ropes. Grease and oils of all kinds should be kept from transmis-
sion ropes, since, as a rule, they are injurious.
Following is another formula for horse-power of manila rope :
H. P.
_(77n— QV
' 33000 '
ln which h.p. is the horse-power transmitted by one rope, V the velocity in
feet per minute, T0 the maximum working stress, and Cthe centrifugal
tension, so that (T — C) is the net tension available for the transmission of
power. Taking the total maximum stress at 200<72 and allow 20 % of this
for slack side tension, we have TQ = 160r/2, so that H.P. =- ^tkkft — ■•
33,000
A table has been calculated by this rule, giving the horse-power per rope,
transmitted at various speeds.
ROPE DRIVING.
955
C= Centrifugal, Tension in Manila Ropes-
- Pounds.
•jo*
Nominal Diameter of Rope
n Inches.
£o3§
h
f
1
I
1
1ft
11
If
u
if
If
2
1000
0.7
1.1
1.5
2.1
2.7
3.4
4.3
5.1
6.2
7.2
8.3
11
1500
1.5
<>.4
3.4
4.7
6.2
7.6
9.7
11
13
16
18
25
2000
2.7
4..°.
6.1
8.2
11
13
17
20
24
28
33
44
2500
4.3
6.7
9.6
13
17
21
27
32
38
45
52
69
3000
6.2
9.7
13
18
24
30
39
45
55
64
74
100
3500
X.4
13
19
25
r34
42
53
63
75
89
102
136
4000
11
17
24
33
44
54
69
82
98
116
133
177
4500
14
22
31
42
55
69
87
103
125
146
168
223
5000
17
27
39
52
69
86
109
129
156
183
210
275
5500
21
33
47
63
83
104
132
156
189
221
254
332
6000
24
39
56
75
99
125
157
188
225
257
303
396
6500
39
45
65
88
116
145
183
217
261
307
353
462
Horse-Power of Manila. Ropes.
£gs
Nominal
Diameter of Rope in Inches.
£ o£i
ft
f
1
1
1
9.08
1ft
U
If
H
If
23.8
If
27.5
2
2000
2.25
3.51
5.14
6.84
11.5
14.0
17.0
20.3
36.1
2100
2.35
3.67
5.27
7.15
9.40
11.8
14.7
17.8
21.1
24.8
28.8
37.6
2200
2.45
3.82
5.48
7.45
9.80
12.3
15.3
18.5
22.0
25.9
30.0
39.2
2300
2.55
3.98
5.71
7.75
10.2
12.8
15.9
19.3
22.9
26.9
31.2
40.8
2400
2.62
4.10
5.89
7.98
10.5
13.2
16.4
19.8
23.6
27.7
32.2
42.0
2500
2.70
4.21
6.05
8.21
10.8
13.6
16.8
20.4
24.3
28.5
33.1
43.2
2600
2.78
4.33
6.21
8.43
11.1
14.0
17.3
21.0
25.0
29.3
34.0
44.4
2700
2.85
4.45
6.39
8.67
11.4
14.4
17.8
21.5
25.6
30.5
35.0
45.6
2800
2.94
4.59
6.59
8.93
11.75
14.8
18.3
22.2
26.4
31.0
36.0
47.0
2900
3.00
4.68
6.73
9.13
12.0
15.1
18.7
22.7
27.0
31.6
36.8
48.0
3000
3.06
4.78
6.87
9.32
12.3
15.4
19.1
23.2
27.6
32.3
37.6
49.1
3100
3.12
4.87
7.01
9.50
12.5
15.7
19.5
23.6
28.2
33.0
38.3
50.0
3200
3.18
4.97
7.14
9.70
12.7
16.0
19.9
24.0
28.7
33.7
39.0
51.0
3300
3.25
5.07
7.27
9.89
13.0
16.3
20.3
24.5
29.2
34.3
39.8
52.0
3400
3.30
5.15
7.39
10.0
13.2
16.6
20.6
25.0
29.7
34.8
40.4
52.8
3500
3.35
5.22
7.50
10.2
13.4
16.9
20.9
25.3
30.1
35.4
41.0
53.6
3600
3.40
5.30
7.61
10.3
13.6
17.1
21.2
25.7
30.6
35.9
41.6
54.4
3700
3.44
5.36
7.70
10.4
13.7
17.3
21.5
26.0
30.0
36.3
42.1
55.0
3800
3.46
5.40
7.76
10.5
13.8
17.4
21.6
26.2
31.1
36.6
42.4
55.4
3900
3.49
5.45
7.81
10.6
13.9
17.6
21.8
26.4
31.4
36.9
42.7
55.8
4000
3.51
5.49
7.86
10.6
14.0
17.7
21.9
26.5
31.6
37.1
43.0
56.1
4100
3.53
5.52
7.92
10.7
14.1
17.8
22.0
26.7
31.8
37.3
43.2
56.4
4200
3.55
5.54
7.95
10.8
14.2
17.9
22.1
26.8
31.9
37.5
43.4
56.8
4300
3.56
5.55
7.98
10.8
14.2
17.9
21.2
26.9
32.0
37.6
43.6
56.9
4400
3.57
5.56
7.99
10.8
14.2
18.0
22.2
27.0
32.1
37.6
43.6
57.0
4500
3.56
5.55
7.96
10.8
14.2
17.9
22.2
26.9
32.0
37.6
43.5
56.9
4600
3.55
5.54
7-95
10.8
14.2
17.9
22.1
26.S
31.9
37.5
43.4
56.8
4700
3.53
5.50
7.90
10.7
14.1
17.8
22.0
26.6
31.7
37.2
43.1
56.4
4800
3.51
5.48
7.86
10.7
14.0
17.7
21.9
26.5
31.6
37.1
43.0
56.2
4900
3.49
5.45
7.81
10.6
13.9
17.6
21.8
26.4
31.4
36.9
42.7
55.8
5000
3.45
5.38
7.73
10.5
13.8
17.4
21.5
26.1
31.0
36.4
42.2
55.2
5100
3.43
5.35
7.67
10.4
13.7
17.2
21.3
25.9
30.8
36.2
41.9
54.8
5200
3.38
5.26
7.56
10.2
13.5
17.0
21.0
25.5
30.4
35.6
41.3
54.0
5300
3.34
5.20
7.47
10.1
13.3
16.8
20.8
25.2
30.0
35.2
40.8
53.4
5400
3.28
5.11
7.34
9.95
13.1
16.5
20.4
24.8
29.4
34.6
40.1
52.5
5500
3.21
5.00
7.20
9.75
12.8
16.2
20.0
24.2
28.9
33.9
39.3
51.4
6000
2.78
4.33
6.21
8.43
11.1
14.0
17.3
21.0
25.0
29.3
34.0
44.4
6500
2.17
3.38
4.85
6.60
8.6
10.9
13.5
16.4
19.5
22.9
26.5
34.7
956
SHAFTING, PULLEYS, BELTING, ETC.
HORSE POWER
1*
^^
1 1 1 1 1 1 1 1
ROPE DRIVING
HORSE POWER OF MANILLA ROPE
AT VARIOUS SPEEDS
Vj^|<f^s^
'^iSSFv-
\ ^f x >T
\ V \^ "^
\ \ \ X
^ v v ^t
3 S V \
V- V V
I 5 S .
> ■A_ . \
r \ \_
V V . 5
\.
4 4 \
\
- 4
\
1
i
t I
r
4 -4 J-
i-j 7-
--/ z /
/
_i f~ / y
T / 7 y^
Z/ / ^
//_ ^ ^
// /^/^
J& -
p>
Mit^OJCOOKftO
g§§£
CO CO rfx
ROPE DRIVING.
957
Horse«Power of " Stevedore " Transmission Rope at
Various Speeds.
In this table the effect of the centrifugal force has been taken into con-
sideration, and the strain on the fibers of the rope is the same at all
speeds when transmitting the horse-power given in the table. When more
than one rope is used, multiply the tabular number by tbe number of the
ropes. At a speed of 8.400 per minute the centrifugal force absorbs all the
allowable tension tbe rope should bear, and no power will be transmitted.
Table of the Horse-Power of Transmission Rope.
(Hunt's Formula.)
o
Speed of the Rope in Feet per Minute.
a
ftm-
ft
1.500
2.000
2.500
3.000
3.500
4.000
4.500
5.000
6.000
7.000
8.400
^3
i
1.45
1.9
2.3
2.7
3.
3.2
3.4
3.4
3.1
2.2
.0
.20
1
2.3
3.2
3.6
4.2
4.6
5.0
5.3
5.3
4.9
3.4
.0
.25
1
3.3
4.3
5.2
5.8
6.7
7.2
7.7
7.7
7.1
4.9
.0
.30
1
4.5
5.9
7.0
8.2
9.1
9.8
10.8
10.7
9.3
6.9
.0
.36
1
5.8
7.7
9.2
10.7
11.9
12.8
13.6
13.7
12.5
8.8
.0
.42
u
9.2
12.1
14.3
16.8
18.6
20.0
21.2
21.4
19.5
13.8
.0
.54
li
13.1
17.4
20.7
23.1
26.8
28.8
30.6
30.8
28.2
19.8
.0
.60
n
18.
23.7
28.2
32.8
36.4
39.2
41.5
41.8
37.4
27.6
.0
.72
2
23.2
30.8
36.8
42.8
47.6
51.2
54.4
54.8
50.
35.2
.0
.84
For a temporary installation when the rope is not to be long in use, it
might be advisable to increase the work to double that given in the tables.
Slip of Ropes and Relts.
(W. W. Christie.)
Some French trials, with constant resistance, the power expended and
slip in several modes of transmission was as follows :
Ropes, 158.54 gross h.p., Slip, 0.33 per cent.
Cotton belt, 159.67 " " 0.78 "
Leather " 158.84 " " 0.96 "
" " 160.23 " " 0.78 "
Stated in percentage value, the results were :
Ropes, 100.00 gross power, Slip, 0.100.
Cotton belt, 100.87 " " 0.237.
Leather " 100.37 " " 0.292.
" 101.07 " " 0.237.
958
SHAFTING, PULLEYS, BELTING, ETC.
Manila Cordage.
Tarred
Hemp.
Size, Cir-
Size,
Weight of
Feet in
Breaking Strain
Weight of
cumfer'ce.
Diameter.
100
one
of New Ropes.
100
Inches.
Inches.
Fathoms.
Pound.
Pounds.
Fathoms.
For Hopes in use
11
s
31
20
deduct J from
40
n
44
14
these figures, for
55
if
rs
60
10
chafing, etc.
75
2
|
79
7i
3000
100
1
fa
99
6"
4000
125
122
5
5000
155
2|
¥
146
4
6000
190
3
176
3|
7000
225
3i
Its
207
3
8500
265
3i
240
2*
9500
300
3|
li
275
2^
11000
355
4
)f
305
2
12500
405
a
355
1X3
14000
455
395
n
16000
500
5'
If
490
n
20000
630
5*.
If
595
1
24000
750
6"
2
705
10 in.
27000
910
6|
2J
825
8*
31500
1050
7
2*
960
7*
37000
1235
7*
2*
1100
6|
42500
1400
8"
2|
1255
5*
4850o
1600
8*
2!
1415
5
54500
1820
9
3
1585
4*
61500
2050
Hawser laid will weigh J less.
Hotes on the Uses of Wire Rope.
(Roebling.)
Two kinds of wire rope are manufactured. The most pliable variety con-
tains 19 wires in the strand, and is generally used for hoisting and running
rope.
For safe working load allow | or \ of the ultimate strength, according to
speed, so as to get good wear from the rope. Wire rope is as pliable as new
hemp rope of the same strength ; but the greater the diameter of the
sheaves the longer wire rope will last.
Experience has proved that the wear increases with the speed. It is,
therefore, better to increase the load than the speed. Wire rope must not
be coiled or uncoiled like hemp or manila — all untwisting or kinking must
be avoided.
In no case should galvanized rope be used for running. One day's use
scrapes off the zinc coating.
Tal»le of Strains Produced Uy
lioads on Inclined Planes.
Elevation in 100 Ft.
Strain in Lbs. on
Rope from a Load
Elevation in
100 Ft.
Strain in Lbs. on
Rope from a Load
of 1 Ton.
of 1 Ton.
Ft. Deg.
Ft. Deg.
10= 5%
212
90 = 42
1347
20= 1H
30 = 16f
404
100 = 45
1419
586
110 = 47|
1487
40 = 21|
754
120 = 50J
1544
50 = 26}
905
130 = 52*
1592
60 = 31
1040
140 = 54*
1633
70 = 35
1156
150 = 56J
1671
80 = 38|
1260
160 = 58
1703
ROPE DRIVING.
959
Table of Transmission of Power l»y Wire Hopes.
Showing necessary size and speed of wheels and rope to obtain any de-
sired amount of power.
(Roebling.)
Diam.
Diam
Diam.
Diam.
of
No. of Rev-
Horse-
of
No. of Rev-
of
Horse-
Wheel
in Ft.
olutions.
Rope.
Power.
Wheel
in Ft.
olutions.
Rope.
Power.
4
80
a
3.3
10
80
ii
58.4
100
f
4.1
100
it
73.
120
5.
120
87.6
140
1
5.8
140
16
102.2
5
80
T75
6.9
11
80
11
75.5
100
8.6
100
ii
94.4
120
10.3
120
113.3
140
17S
12.1
140
is
132.1
6
80
*
10.7
12
80
I
99.3
100
i
13.4
100
I
124.1
120
h
16.1
120
148.9
140
18.7
140
1
173.7
7
80
16.9
13
80
|
122.6
100
21.1
100
153.2
120
1%
25.3
120
1
183.9
8
80
f
22.
14
80
|
148.
100
s
27.5
100
i
185.
120
I
33.
120
8
222.
9
80
f
41.5
15
80
f
217.
100
5.
51.9
100
T
259.
120
1
62.2
120
i
300.
Hoisting- Ropes (lO Wires to the Strand).
(Trenton Iron Company's List.)
Iron.
Crucible Steel.
g
_5
S3
£ a
■SMS
II
i*s
0>
® a,
° fl
§Oo2
3 ao
02 O
^ o o
§*g>§.3
Circumfei
of Hemp
of Equal
Strength
Circumfei
of Hemp
of Equal
Strength
1
-5
7
8.
74
15
151
8
164.69
32.9
9
2
2
«i
6.3
65
13
14*
7
132.37
26 5
8
3
It
5+
5.25
54
11
13
6h
108.13
21.63
n
4
1*
5
4.1
44
9
12
5
97.17
19.44
6
5
H
4*
3.65
39
8
iii
4f
86.38
17.3
16i
5*
b*
IS
4f
3.
33
6.5
1
4*
61.00
12.2
15
5
6
U
4
2.5
27
5.5
4
50.17
10.
12i
5
7
U
31
2.
20
4
8
3*
38.00
7.7
11
U
8
1
»*
1.58
16
3
7
3
29.2
5.8
9
4
9
f
2§
1.2
11.5
2.5
6
2^
21.55
4.
8
3|
3*
10
2f
.88
8.64
1.75
5
2+
14.99
3.
6k
m
&
2
.7
5.13
1.25
4*
2
12.53
2.5
5|
3
\%
IB
1*
.44
4.27
.75
4
1*
8.81
1.75
5i
4|
m
10f |
1*
.35 3.48
.5
3J
7.52
1.5
2
960
SHAFTING. PULLEYS, BELTING, ETC.
The drums and sheaves should be made as large as possible. The mini-
mum size of drum is given in a column in table.
It is better to increase the load than the speed.
Wire rope is manufactured either with a wire or a hemp center. The
latter is more pliable than the former, and will wear better where there is
short bending. The weight of rope with wire center is about 10 per cent
more than with hemp center.
Power Transmission and Stranding* Ropes (9 Wires to the
Strand).
(Trenton Iron Company's List.)
Iron.
Crucible Steel.
a m
=4H
A 00
<H
&
"!&
,. o
O^h'B
,M^2
luiO
^^A
u
a
c3
a
B OD
"® ESS
bO'-w
.5
bOoo
3 °
o _ j;
fto2
cd o"So
.fit
.5 3
0=2+3
cu o rt
lit
H
0
o
M
Ph
O
m
Ah
b
11
1*
4f
3.37
36
9
lOf
88.38
22
33
12
l|
4i
2.77
30
3
10
67.2
16.8
13
]J
4
2.28
25
9i
60.67
15.2
15
14
ii
3|
1.82
20
5
8
39.84
10.
11
15
3i
1.5
16
4
7
31.82
8.
1
16
'|
2f
1.12
12.3
3
6*
24.7
6.2
17
1
.88
8.8
2i
3
18.48
4.6
7|
18
T5
.7
7.6
2
5
16.32
4.
71
19
f
2
.57
5.8
1*
4f
12.44
3.1
6
20
~lF.
If
.41
4.1
1
4
9.33
2.3
8
21
!■'
1?
.31
2.83
1
3*
6.89
1.7
22
IB
If
,23
2.13
»
2f
5.23
1.3
3|
23
H
.19
1.65
2*
3.93
1.
3|
24
A
.16
1.38
2i
3.25
.81
3
25
A
f
.125
1.03
2
2.96
.75
2|
Wire Rope.
Tons breaking weight =z (diameter in quarter inches)2.
MISCELLANEOUS TABLES.
WEIX^EiTJ* ASD J1EASIHES.
Measure of Capacity.
Gallon. — The standard gallon measures 231 cubic inches, and contains
8.3388822 pounds avoirdupois = 58372.1757 grains Troy, of distilled water, at
its maximum density 39.83° Fahrenheit, and 30 inches barometer height.
Bushel. —The standard bushel measures 2150.42 cubic inches =77.627413
pounds avoirdupois of distilled water at 39.83° Fahrenheit, barometer 30
inches. Its dimensions are 18£ inches inside diameter, 19^ inches outside,
and 8 inches deep ; and when heaped, the cone must not be less than 6
inches high, equal 2747.70 cubic inches for a true cone.
Pound. — The standard pound avoirdupois is the weight of 27.7015 cubic
inches of distilled water, at 39.83° Fahrenheit, barometer 30 inches, and
weighed in the air.
Measure of I<eng-th.
Miles.
Furlongs.
Chains.
Rods.
Yards.
Feet.
Inches.
1
8
80
320
1760
5280
63360
0.125
X
10
40
220
660
7920
0.0125
0.1
1
4
22
66
792
0.003125
0.025
0.25
X
5.5
16.5
198
0.00056818
0.0045454
0.045454
0.181818
1
3
36
0.00018939
0.00151515
0.01515151
0.0606060
0.33333
1
12
0.000015783
0.000126262
0.001262626
0.00505050
0.0277777
0.083333
1
Measure of Surface.
Sq. Miles.
Acres.
S. Chains
Sq. Rods.
Sq. Yards
Sq. Feet.
Sq. Inches
1
640
6400
102400
3097600
27878400
4014489600
0-001562
X
10
160
4840
43560
6272640
0.0001562
0.1
1
16
484
4356
627264
0.000009764
0.00625
0.0625
1
30.25
272.25
39204
0.000000323
0.0002066
0.002066
0.0330
X
9
1296
0.0000000358
0.00002296
0.0002296
0.00367
0.1111111
I
144
0.00000000025
0.000000159
0.00000159
0.00002552
0.0007716
0.006944
X
Measure
of Capacity.
Cub. Yard.
Bushel.
Cub. Feet.
Pecks.
Gallons.
Cub. Inch.
1
0.03961
0.037037
0.009259
21.6962
1
0.803564
0.25
0.107421
27
1.24445
X
0.31114
0.133681
0.0u0o47
100.987
4
3.21425
X
0.429684
0.001860
201.974
9.30918
7.4805
2.32729
X
0.004329
46656
2150.42
1728
537.605
231
X
961
962
MISCELLANEOUS TABLES.
measure of liquids.
Quarts.
1
0.25
0.125
0.03125
0.004329
1
0.5
0.125
0.17315
2
1
0.25
0.03463
4
1
0.13858
231
57.75
28.875
7.21875
1
Measures of Weights.
AVOIRDUPOIS.
1
0.05
0.00044642
0.00002790
0.00000174
20
1
0.000558
0.0000348
2240
112
0.0625
0.0016
1
0.0625
573440
28672
256
16
1
1
0.083333
0.004166
0.0001736
1.215275
12
1
0.05000
0.002083333
14.58333
240
20
1
0.0416666
291.6666
24
1
7000
Pound Avoir.
0.822861
0.068571
0.0034285
0.00014285
1
APOTHECARIES.
Pounds.
Ounces.
Drams.
Scruples.
Grains.
1
0.08333
0.01041666
0.0034722
0.00017361
12
1
0.125
0.0416666
0.0020833
96
8
1
0.3333
0.016666
288
24
3
1
0.05
5760
480
60
20
X
Equivalents of Xiineal
Measures — Metrical and English.
Meters.
English Measures.
Inches.
Feet.
Yards.
Miles.
Microne . .
Millimeter .
Centimeter
Decimeter .
Meter . . .
Decameter
Hectometer
Kilometer .
Miriameter
mm
cm
.0001
.001
.01
.1
1.
10.
100.
1,000.
10,000.
.003937
.039371
.393708
3.937079
39.370790
.000328
.003281
.032809
.328089
3.280899
32.80899
328.0899
3280.899
.000109
.001094
.010936
.109363
1.093633
10.93633
109.3633
1093.633
'.000621'
.006214
.0b2138
.62i382
6.213824
MISCELLANEOUS TABLES.
Equivalent!!) of Einca 1 measures — Met. and Bug-
963
. — Continued.
English Measures.
Meters.
Reciprocals.
.02539954
.3047945
.9143S35
5.029109
20.11644
1609.3149
39.37079
3.280899
3 feet = 1 yard
5J yards=16g- feet=l rod or pole
4 poles = 66 feet = 22 yards = 1 chain (Gunter's)
80 chains = 320 poles = 52S0 f t.= 1760 yds. = lmile
1.093633
.1988424
.0497106
.0006213S
A Gunter's chain has 100 links. Each link = 7.92 inches = 0.2017 meter.
Equivalents of Superficial Measures — Metrical and JBng*.
(METRICAL AND ENGLISH MEASURES.)
Milliare . . .
Cen tiare=sq. met
Declare . . .
Are
Decare (not used)
Hectare . . .
Square kilometer
Square
meters.
.1
1.
10.
100.
1000.
10000.
1000000.
English Measures.
Square
inches.
155.01
1550.06
15500.59
1550059.
Square
feet.
1.076
10.764
107.64
1076.4
10764.3
107643.
Square
yards.
.119
1.196
11.960
119.6033
1196.033
2.4711431
247.11431
English Measures.
Metrical Measures.
Reciprocals.
1 square inch
144 square inches = 1 square foot .
9 square feet = 1 square yard . .
30i sq. yds. ) _ 1 perch = 1 square rod
272^ sq. ft. j ~ or pole
160 perches = ) _ , acre
10 sq. chains j — l acre
640 acres = 1 square mile ....
6.451367 sq. cent
.09289968 sq.mt
.8360972 " "
4046.711
2589894.5
.1550059
10.7642996
1.196033
.00024711
.00000038612
Equivalents of "Weigvhts —Metrical and Eng-lisli.
Grammes
English Weights.
Oz.
avoir.
Lbs.
avoir.
Tons
2000 lbs.
Tons
22401bs.
Troy
Aveight.
Milligramme .
Centigramme .
Decigramme .
Gramme . . .
Decagramme .
-Hectogramme .
Kilogramme .
Myriagramme .
Quintal . . .
Millier or Tonne
.001
.01
.1
1.
10.
100.
1000.
10000.
100000.
1000000
" *0353
.3527
3.5274
35.2739
352.7394
3527.3943
' '.0022
.02205
.22046
2.2046
22.0462
220.4261
2204.6215
.001102
.011023
.110231
1.102311
.000984
.009842
.098421
.984206
.015 Grs.
.15 "
1.543 "
15.43235"
.... oz.
32.150727"
321.507266"
3215.07266 "
32150.72655"
English Weights — " Avoirdupois
." | Grammes.
Reciprocals.
.06479895
1.771836
28.349375
453.592652
45359.265
50802.376
907.18524
1016.04753
15.43234875
24.34375 grains =z 1 dram
16 drams = 1 ounce = 437.5
16 ounces = 1 pound = 7000
100 lbs. = 1 cwt. (American
112 lbs. = 1 CAvt. (English) .
20 CAvt. = 1 ton (Am.) in kil
20 cwt. — 1 ton (Eng.) in ki
.564383
grains
grains
) . . . .
.0352739
.00220462
.000022046
.00001968
.001102311
OS . . .
.000984206
English Weights — " Troy."
.06479895
1.555175
31.103*96
373-241954
15.43234875
24 grains = 1 dAV
20 dAVt — 1 oz.
fc
.6430146
.3215073
12 oz. — 1 lb.
()Ci9.K7Q9.Z
964
MISCELLANEOUS TABLES.
CD
'fcJO
S3
CO COCN
! ! ! . .i-l COO 00
"r-5 cod
.0027
.0275
.27512
2.7512
27.5121
275.1209
ji
.00022
.0022
.022
.2201
2.201
22.00967
220.0967
CO
.00026
.00264
.02642
.26418
2.64179
26.4179
264.179
E3 oj
.0353
.3532
3.5317
35.317
353.1658
q|
.061
.61
6.10
61.027
610.271
6102.706
6^
. . . " ' 'nod
HO
p
.001
■ .01
.1
1.
10.
100.
1000.
10000.
Cub. Cent.
Cub. Decim
Ciib. Met.
Millistere . .
Decistere . .
Decastere
Hectostere .
'3
3
Millilitre . .
Centilitre . .
Decilitre . .
Litre ....
Decalitre . .
Hectolitre .
Kilolitre . .
Myriolitre .
i- — X l- X SNt-iOM
■inOl-KOHlOO'*
OCOCOOOO-tL-ClCO
»HHtooiaHO-f
Hnioooo-n:!. co :o
'— x -f i- i- :: i- i- o i-i
CC Cl ffl to CO -t x -t- " X
cqq^iqrjioNMO^
d ' ' "r-i-* cod "d
. .'g . J
t> d
ig^gf
0,-, °'g'2C'
1 «m § -3
« 5 p 4» +S g § j2 -=j
MISCELLANEOUS TABLES. 965
Metrical Measures Equivalent to English Measures.
Meters.
Inches.
Feet.
lm/m
0.039
0.0033
2
0.079
0.0066
3
0.118
0.0098
4
0.157
0.0131
5
0.197
0.0164
6
0.236
0.0197
7
0.276
0.0230
8
0.315
0.0262
9
0.354
0.0295
10»/m = le/m
0.394
0.033
2
0.787
0.066
3
1.181
0.098
4
1.575
0.131
5
1.969
0.164
6
2.362
0.197
7
2.756
0.230
8
3.150
0.262
9
3.543
0.295
10c/ m = .lm
3.937
0.328
.2
7.874
0.656
•3
11.811
0.984
.4
15.748
1.312
.5
19.685
1.640
.6
23.622
1.969
.7
27.560
2.297
.8
31.497
2.625
.9
35.434
2.953
lm0
39.371
3.281
Table for the Conversion of Mils. (l-lOOO Inches) into
Centimeters.
Centi-
Centi-
C
enti-
Centi-
Mils.
meters.
Mils.
meters.
Mils. m
eters.
Mils.
meters.
1
.00254
18
.04571
35
08888
52
.1321
2
.00508
19
.•04825
36
09142
53
.1346
3
.00762
20
.05079
37
09396
54
.1372
4
.01016
21
.05333
38
09650
55
.1397
5
.01270
22
.05587
39
09904
56
.1422
6
.01524
23
.05841
40
1016
57
.1448
7
.01778
24
.06095
41
1041
58
.1473
8
.02032
25
.06348
42
1067
59
.1499
9
.02286
26
.06602
43
1092
60
.1524
10
.02540
27
.06856
44
1118
61
.1549
11
.02793
28
.07110
45
1143
62
.1575
12
.03047
29
.07364
46
1168
63
.16f0
13
.03301
30
.07618
47
1194
64
.1626
14
.03555
31
.07872
48
1219
65
.1651
15
.03809
32
.•08126
49
1245
66
.1676
16
.04063
33
.08380
50
1270
67
.1702
17
.04317
34
.08634
51
1295
68
.1727
966 MISCELLANEOUS TABLES.
Table for the Conversion of Mils. — Continued.
Centi-
Centi-
Centi-
Centi-
Mils.
meters.
Mils.
meters.
Mils.
meters.
Mils.
meters.
69
.1752
77
.1956
85
.2159
93
.-2362
70
.1778
78
.1981
86
.2184
94
.2387
71
.1803
79
.2006
87
.2209
95
.2413
72
.1829
80
.2032
8S
.2235
96
.2438
73
.1854
81
.2057
89
.2260
97
.2465
74
.1879
82
.2083
90
.2286
98
.2489
75
.1905
83
.2108
91
.2311
99
.2514
76
.1930
84
.2133
92
.2336
100
.2540
English Measures Equivalent to Metrical Measures.
CO
w
.
.2
«
3
■g
£
<p
5
1
5
I
§
1
C
g
^
^
3*2
0.794
l
0.0254
0.01
.003
10
3.048
l\
1.588
2
.0508
0.02
.006
20
6.096
2.381
3
.0762
0.03
.009
30
9.144
X
3.175
4
.1016
0.04
.012
40
12.192
6
3.969
5
.1270
0.05
.015
50
15.240
-3g
4.762
6
.1524
0.06
.018
60
18.288
f
5.556
7
.1778
0.07
.021
70
21.336
6.350
8
.2032
0.08
.024
80
24.384
_9
7.144'
9
.2286
0.09
.027
90
27.431
6
7.937
10
.2540
.1
.030
100
30.479
t
8.731
11
.2794
.2
.061
200
60.959
9.525
12
.3048
.3
.091
300
91.438
M
10.319
.4
.122
400
121.918
IS
f
¥
re
f
n
§i
ii
¥
11.112
.5
.152
500
152.397
11.906
.6
.183
600
182.877
12.700
13.494
14.287
15.081
15.875
16.668
17.462
18.256
19.050
19.843
20.637
21.430
22.224
.7
.213
700
213.356
.8
.244
800
243.836
.9
1.0
3
4
5
6
7
8
9
10
.274
.305
.610
.914
1.219
1.524
1.829
2.134
2.438
2.743
3.048
900
1000
274.315
304.794
II
23.018
il
23.812
§1
l
24.606
25.400
MISCELLANEOUS TABLES.
967
Conversion of Inches and Eig-Iith* into Decimals of a
foot.
Fractions of an Inch.
Inches.
0
§
1
I
|
f
1
i
0
.0000
.01041
.02083
.03125
.04166
.05208
.0625
.07291
1
.08333
.09375
.10416
.11458
.125
.13&41
.14588
.15639
2
.16666
.17707
.1875
.19792
.20832
.21873
.22914
.23965
3
.25
.26041
.270
.28125
.29166
.30208
.3125
.32291
4
.33333
.34375
.35416
.364
.375
.38541
.39588
.40639
5
.41666
.42707
.437
.44792
.45832
.46873
.47914
.48965
6
.5
.51041
.520
.53125
.54166
.55208
.5625
.57291
7
.58333
.59375
.60416
.614
.625
.63541
.64588
.65639
8
.66666
.67707
.685
.69792
.70832
.71773
.72914
.73965
9
.75
.76041
.770
.78125
.79169
.80208
.8425
.82291
10
.83333
.84375
.85416
.864
.875
.88541
.89588
.90639
11
.91666
.92707
.937
.94792
.95832
.96873
.97914
.98965
12
1 foot.
foot.
foot.
foot.
foot.
foot.
foot.
foot.
Jg in. = 0.005208 ft ; ^ in. = 0.00265 ft. ; £ in. = 0.001375 ft.
GREEK EETTEltS.
Alpha.
Beta.
Gamma.
Delta.
Epsllon.
Zeta.
Eta.
Theta.
Iota.
Kappa.
Lambda.
Mu.
(KATRIFlftAl FORCE.
F=z centrifugal force in pounds.
W= weight in pounds.
v = velocity in feet per second.
r — radius of circle in feet.
n = revolutions per minute.
Nu.
Xi.
Omicron.
Pi.
Rho.
Sigma.
Tau.
Upsilon.
Phi.
Chi.
Psi.
Omgga.
F =
Wrn2
AICITIAR VELOCITY.
The number of degrees per second through which a body revolves about a
center.
w = 2n n
where
to = angular velocity.
n rr revolutions per second.
FRICTION.
The following laws of friction are only approximate, the first not being
true where pressures are very great, and the third beyond a velocity of 150
feet per minute.
968
MISCELLANEOUS TABLES.
1. Friction varies directly as the pressure on the surfaces in contact.
2. Friction is independent of the extent of the surface in contact.
3. Friction is indi pendent of the velocity, ichen the surfaces are in motion.
4. Rolling friction varies directly as thep>ressure, and inversely as the diam-
eter of the rolling bodies, where the cylinders or balls are of the same
substances, and are pulled or pushed, as in a car or wagon.
Where the load is propelled, by a crank fixed on the axle, the law it
reversed.
TE9IPEIIATVRE, or UTTSKSIKir OF HEAT.
Standard Points — Fahrenheit. Centigrade. Reaumur,
Boiling point of water under ) _ oioo inno Qno
one atmosphere . . . .) ~ AVl 1UU m
Melting point of ice . . . . 32° 0° 0°
<A^solute..?er°5 known M =ahout-461°.2 -274°
theory only
■
- 2199.2)
9° Fahrenheit = 5° Centigrade r= 4° Reaumur.
Temp. Cent. =: - (Temp. Fah. — 32°) :
■ Temp. R6au.
Table of Comparison of Different Thermometers.
Fah.
Beau.
Cent.
Fah.
R^au.
Cent.
Fah.
Reau.
Cent.
212
80.0
100.0
180
65.7
82.2
148
51.5
64.4
211
79.5
99.4
179
65.3
81.6
147
51.1
63.8
210
79.1
98.8
178
64.8
81.1
146
50.6
63.3
209
78.6
98.3
177
64.4
80.5
145
50.2
62.7
208
78.2
97.7
176
64.0
80.0
144
49.7
62.2
207
77.7
97.2
175
63.5
79.4
143
49.3
61.6
206
77.3
96.6
174
63.1
78.8
142
48.8
61.1
205
76.8
96.1
173
62.6
78.3
141
48.4
60.5
204
76.4
95.5
172
62.2
77.7
140
48.0
60.0
203
76.0
95.0
171
61.7
77.2
139
47.5
59.4
202
75.5
94.4
170
61.3
76.6
138
47.1
58.8
201
75.1
93.8
169
60.8
76.1
137
46.6
58.3
200
74.6
93.3
168
60.4
75.5
136
46.2
57-7
199
74.2
92.7
167
60.0
75.0
135
45.7
57.2
198
73.7
92.2
166
59.5
74.4
134
45.3
56.6
197
73.3
91.6
165
59.1
73.8
133
44.8
56.1
196
72.8
91.1
164
58.6
73.3
132
44.4
55.5
195
72.4
90.5
163
58.2
72.7
131
44.0
55.0
194
72.0
90.0
162
57.7
72.2
130
43.5
54.4
193
71.5
89.4
161
57.3
71.6
129
43.1
53.8
192
71.1
88.8
160
56.8
71.1
128
42.6
53.3
191
70.6
88.3
159
56.4
70.5
127
42.2
52.7
190
70.2
87.7
158
56.0
70.0
126
41.7
52.2
189
69.7
87.2
157
55.5
69.4
125
41.3
51.6
188
69.3
86.6
156
55.1
68.8
124
40.8
51.1
187
68.8
86.1
155
54.6
68.3
123
40.4
50.5
186
68.4
85.5
154
54.3
67.7
122
40.0
50.0
185
68.0
85.0
153
53.7
67.2
121
39.5
49.4
184
67.5
84.4
152
53.3
66.6
120
39.1
48.8
183
67.1
83.8
151
52.8
66.1
119
38.6
48.3
182
66.6
83.3
150
52.4
65.5
118
38.2
47.7
181
66.2
82.7
149
52.0
65.0
117
37.7
47.2
MISCELLANEOUS TABLES. 969
Table of Comparison of Different Thermometers — Continued.
Fah.
R^au.
Cent.
Fah.
R£au.
Cent.
Fall.
R6au.
Cent.
116
37.3
46.6
70
16.8
21.1
24
—3.5
—4.4
115
36.8
46.1
69
16.4
20.5
23
—4.0
—5.0
114
36.4
45.5
68
16.0
20.0
' 22
—4.4
—5.5
113
36.0
45.0
67
15.5
19.4
21
—4.8
—6.1
112
35.5
44.4
66
15.1
18.8
20
—5.3
—6.6
111
35.1
43.8
65
14.6
18.3
19
—5.7
—7.2
110
34.6
43.3
64
14.2
17.7
18
—6.2
—7.7
109
34.2
42.7
63
13.7
17.2
17
—6.6
—8.3
108
33.7
42.2
62
13.3
16.6
16
—7.1
—8.8
107
33.3
41.6
61
12.8
16.1
15
—7.5
—9.5
106
32.8
41.1
60
12.4
15.5
14
—8.0
—10.0
105
32.4
40.5
59
12.0
15.0
13
—8.4
—10.5
104
32.0
40.0
58
11.5
14.4
12
—8.8
—11.1
103
31.5
39.4
57
11.1
13.3
11
—9.3
—11.6
102
31.1
38.8
56
10.6
13.3
10
—9.7
—12.2
101
30.6
38.3
55
10.2
12.7
9
—10.2
—12.7
100
30.2
37.7
54
9.7
12.2
8
—10.6
—13.3
99
29.7
37.2
53
9.3
11.6
7
—11.1
—13.8
98
29.3
36.6
52
8.8
11.1
6
—11.5
—14.4
97
28.8
36.1
51
8.4
10.5
5
—12.0
—15.0
96
28.4
35.5
50
8.0
10.0
4
—12.4
—15.5
95
28.0
35.0
49
7.5
9.4
3
—12.8
—16.1
94
27.5
34.4
48
7.1
8.8
2
—13.3
—16.6
93
27.1
33.8
47
6.6
8.3
1
—13.7
—17.2
92
26.6
33.3
46
6.2
7.7
0
—14.2
—17.7
91
26.2
32.7
45
5.7
7.2
—1
—14.6
—18.3
90
25.7
32.2
44
5.3
6.6
— 2
—15.1
—18.8
89
25.3
31.6
43
4.8
6.1
—3
—15.5
—19.4
88
24.8
31.1
42
4.4
5.5
—4
—16.0
—20.0
87
24.4
30.5
41
4.0
5.0
—5
—16.4
—20.5
86
24.0
30.0
40
3.5
4.4
—6
—16.8
—21.1
85
23.5
29.4
39
3.1
3.8
—7
—17.3
—21.6
84
23.1
28.8
38
2.6
3.3
—8
—17.7
—22.2
83
22.6
28.3
37
2.2
2.7
—9
—18.2
—22.7
82
22.2
27.7
36
1.7
2.2
—10
—18.6
—23.3
81
21.7
27.2
35
1.3
1.6
—11
—19.1
—23.8
80
21.3
26.6
34
0.8
1.1
—12
—19.5
—24.4
79
20.8
26.1
33
0.4
0.5
—13
—20.0
—25.0
78
20.4
25.5
32
0.0
0.0
—14
—20.4
-25.5
77
20.0
25.0
31
—0.4
—0.5
—15
—20.8
—26.1
76
19.5
24.4
30
—0.8
—1.1
—16
—21.3
—26.6
75
19.1
23.8
29
—1.3
—1.6
—17
—21.7
—27.2
74
18.6
23.3
28
—1.7
—2.2
—18
—22.2
—27.7 .
73
18.2
22.7
27
—2.2
—2.7
—19
—22.6
—28.3
72
17.7
22.2
26
—2.6
—3.3
—20
—23.1
—28.8
71
17.3
21.6
25
—3.1
—3.8
Number of Degrees Cent. =
= Unmber
of Degrees Fah.
Tenths of a Degree — Centigrade Scale.
Degrees
Cent.
.0
.1
.3
.3
.4
.5
.6
.7
.8
.9
Fah.
Fah.
Fah.
Fah.
Fah.
Fah.
Fah.
Fah.
Fah.
Fah.
0
0.00
0.18
0.36
0.54
0.72
0.90
1.08
1.26
1.44
1.62
1
1.80
1.98
2.16
2.34
2.55
2.70
2.88
3.06
3.24
3.42
2
3.60
3.78
3.96
4.14
4.32
4.50
4.68
4.86
5.04
5.22
3
5.40
5.58
5.76
5.94
6.12
6.30
6.48
6.66
6.84
7.02
970
MISCELLANEOUS TABLES.
HTuml>er of Degrees Cent. = Jf umber of Degrees
fall. — (Continued.)
Tenths of a Degree
— Centigrade Scale
Degrees
Cent.
.0
.1
.2
3
.4
.5
6
.7
.8
.9
Fab.
Fab.
Fah.
Fah.
Fah.
Fah.
Fah.
Fah.
Fah.
Fah.
4
7.20
7.38
7.56
.7.74
7.92
8.10
8.28
8.46
8.64
8.82
5
9.00
9.18
9.36
9.54
9.72
9.90
10.08
10.26
10.44
10.62
6
10 80
10.98
11.16
11.34
11.52
11.70
11.88
12.06
12.24
12.42
7
12.G0
12.78
12.96
13.14
13.32
13.50
13.68
13.86
14.04
14.22
8
14.40
14.58
14.76
14.94
15.12
15.30
15.48
15.66
15.84
16.02
9
16.20
16.38
16.56
16.74
16.92
17.10
17.28
17.46
17.64
17.82
lYumber of Degrees Fall. _: ^imil^r of Degrees Cent.
Tenths of a Degree -
- Fahrenheit Scale
Degrees
Fah.
.0
.1
.2
.3
.4
.5
.6
.7
.8
.9
Cent.
Cent.
Cent.
Cent.
Cent.
Cent.
Cent.
Cent.
Cent.
Cent.
0
0.00
0.06
0.11
0.17
0.22
0.28
0.33
0.39
0.44
0.50
1
0.56
0.61
0.67
0.72
0.78
0.83
0.89
0.94
1.00
1.06
2
1.11
1.17
1.22
1.28
1.33
1.39
1.44
1.50
1.56
1.61
3
1.67
1.72
1.78
1.83
1.89
1.94
2.00
2.06
2.11
2.17
4
2.22
2.28
2.33
2.39
2.44
2.50
2.56
2.61
2.67
2.72
5
2.78
2.83
2.89
2.94
3.00
3.06
3.11
3.17
3.22
3.28
6
3.33
3.39
3.44
3.50
3.56
3.61
3.67
3.72
3.78
3.83
7
3.89
3.94
4.00
4.06
4.11
4.17
4.22
4.28
4.33
4.39
8
4.44
4.50
4.56
4.61
4.67
4.72
4.78
4.83
4.89
4.94
9
5.00
5.06
5.11
5.17
5.22
5.28
5.33
5.39
5.44
5.50
Coefficients of Expansion at Ordinary Temperatures.
(Solids.)
Material.
Coefficient of Expansion.
•
°F.
°C.
.0000114
.0000104
.00000306
.0000100
.0000055
.0000078
.00000961
.00000399
.00000521
.00000841
.0000046
.00000587
.00000677
.0000206
.0000187
Brick
Cement and )
from
.000010
Concrete j
• " to
.000014
.0000173
.00000719
.00000938
.0000151
.0000083
.0000106
.0000122
Glass ....
Gold
from
' * to
Tron, cast
Iron, wrought
MISCELLANEOUS TABLES.
971
Coefficients of ^Expansion —
{Continued.)
Material.
Coefficient of Expansion.
°F.
°c.
.0000158
.000004
.0000026
.0000049
.00000494
.0000020
.0000040
.0000067
.0000108
.0000056
.00000611
.00000689
.0000116
.00000276
.0000163
.00002S4
Marble (average)
Masonry . . .
Platinum . . .
Porcelain . . .
Sandstone . . .
Silver ....
from
' * to
from
• * to
.0030017
.00300S8
.00000890
.0000036
.0000070
.000012
.0000194
.0000102
Steel, untempered
Steel, tempered
.0000110
.0000124
.0000209
.00000496
.0000293
HEAT.
Specific Heat of Substances.
The specific heat of a body at any temperature is the ratio of the quantity
of heat required to raise the temperature of the body one degree to the
quantity of heat required to raise an equal mass of water at or near to its
temperature of maximum density (4°C. or 39.1°F.) through one degree.
Specific Heats of Metals.
(Tomlinson.)
Metal.
Specific Heat at
0°C. or 32°F.
50°C.orl22°F.
100°Cor212°F
0.2070
0.0901
0.0941
0.1060
0.0300
0.0320
0.0473
0.0547
0.0523
0.0901
0.2185
0.0923
0.0947
0.1130
0.0315
0.0326
0.0487
0.0569
0.0568
0.0938
0.2300
Copper
German Silver
Iron
Lead
0.0966
0.0952
0.1200
0.0331
0.0333
Platinum Silver
Silver
0.0501
0.0591
0.0595
Zinc
0.0976
Mean Specific Heat of Platinum.
(Pouillet.)
Between 0°C. (32°F.) and 100°C.
" 300°C,
(212°F.)
(572°F.) ,
500°C. (932°F.)
700°C. (12920F.) .
1000°C. (1832°F.) .
1200°C. (2192°F.) .
0.0335
0.0343
0.0352
0.0360
0.0373
0.0382
972 MISCELLANEOUS TABLES.
Mean Specific Heat of Water.
(Regnault.)
Between 0°C. (32°F.) and 40°C. (104°F.) . . . . . 1.0013
" " " " 80°C. (176°r.) 1.0035
" " " " 120°C. (248°F.) 1.0067
" " " " 160°C. (320°F.) 1.0109
" " " " 200°C. (392°F.) . . . . 1.0100
" " " " 230°C. (446°F.) 1.0204
Mean Specific Heat of Glass (Kohlrausch) 0.19
Specific Heat of Gases and Vapors at Constant Pressure.
Air
Carbon monoxide
Carbon dioxide .
Hydrogen . . .
Nitrogen . . . .
Oxygen . . . .
Steam . . . . „
Specific Heat for
Equal.
Volumes. "Weights,
0.2375
0.2370
0.2405
0.2989
0.2375
0.2450
0.1952
3.4090
0.2438
0.2175
0.4805
Regnault
Regnault
Wiedermann
Regnault
Regnault
Regnault
Total Heat of Steam.
British Thermal "Unit : (B. T. U.) is the quantity of heat which
will raise the temperature of one pound of water one degree Fah. at or near
its temperature of maximum density 39.1°.
French Calorie : is the quantity of heat that will raise the tempera-
ture of one kilogramme of pure water 1°C. at or near4°C.
Pound Calorie: is the quantity of heat that will raise the tempera-
ture of one pound of water 1°C.
1 B. T. IT. = .252 Calories.
1 Calorie = 3.968 B. T. IT.
1 lb. Calorie = 2.2046 B. T. IT.
1 pound Calorie = § Calorie.
The mechanical Equivalent of Heat.
Joule gives
Professor Rowland,
1 B. T. IT. =
1 B. T. U. :
772 ft.
778 ft.
1H.P, = 42.416 B. T. IT.
(See Table of Energy Equivalents on p. 684.)
MISCELLANEOUS TABLES.
973
Off)On«OHHHnWMMO
uoq.iBO
8nl^A
•3-0
sauojBQ
•spunoj
•*0 I J°
-, -fiionoowN-fOL't-'fcionHHrii-
i :. ; i ". o 'O m « l: -t o o o t ro -t i - :: c i ■;
uo -*< x:i co co i- co m-c-triKc i_- o >: cc :
~ -rl-l-l- X i— i 0 HriCCH-jiMhKL-'XC
CC C O O CO i- M rt 01 CO CO- 01 0 O -^ O © C ^>
•Slip3.T£)
•no I jo
•SlUK.tf)
vdvn I jo
>0 CC X X CO X -f — 01 C-. HNCCC C-. CO CC — CO -
l- = i- -f = c i- r. r. (M oc t x t- cc .oc?i-
- i- = cc — CC -f L- — c-. CC I- r- co -t- -. \-
'-i.t'-i-.-n-c x x x :i r. r. ~ c - ic v. _
Ol rH 01 CO X ICO L- •* (O C K CC ICO t- 01 01 -t C
OdrirtHriricq'rlrilOriridddwrirlr
•I = JJV
AcJIA'B.I*)
ogxoadg
•g r= U9.§
-oap^H
A^IAIU-E)
0ff'l09dg
•noi^snq
■xaoQ jo
sjotipojj
•cjqSpAi
-noopjj,\[
loqraAg
-noaioj\[
+ '-' re £f 2J. jp £ S
-i r-i T-i ©' OO'rid
. O i-i X' CC X CC CO CO
CC t- CO X CC CC L- I-
. ~ - C I- X X 00 CO
• HOrtdddrtri
t - :• 1 1- h r. o Ji » « -f r. i- ci
^ :* £ g§ -? Lr2 .3 « £ - ± £ y 7 •: :
CO 01 ^ 1-1 0"l r^ ,- rt O © CO CO -f CO i*.0
d -f -r 10 rv 0 t~ ^h
r • : "-' f: c r ""• -
~00C0t~COCli-HC5
o c: « r; c 1- c 10 ci 01 t~ 00 c c ■ o tc~ O t-
- l.o 1: 1: x o t- l: j> v; •+ c: ^ c: uo 10 — x
lOOioocjin-fcc^a
ci o 1 oi -t t- ci x r. -
t-XNOn-frt-|
- r •_- co 10 cc x c
qxocto.c:-
ddddOr-Hi-Hi-Hr-^C-
^-1^
NNNNiH-fiHOOli-'HOlOlO^HON
. . n * -t •* ci ft cm ci cc c: c cc rt -f : 1 ci r.
cc cc. C5 cc cc cc cc, x c. x l- cc. cc. lo. co © ■* O © co
" id t^ id t>^ cc! — id cc! t- t- co' id id 1— t-^ ■* 06 h co
1-1 01 01 01 01 -f- 10 CO L-ClCU^riHHHMCO'*
W" w'wVkWWWWod0 £ £
czcz :::
Er 2? ~f 3! 5 ~ r- 2? ?' 90 co ^j ^3 rt _ oi 01 cc. -1
i id t- id 1- cc! — 10 cc! t- t^ cd 10 -^ •-
1— 01 01 01 0 1 -f LO CO t^ C<l CO t- "! n
EH .(MOO^CM
i s o K W WW WW W W ^ffi m" • «
nU w m w ^ -f c: c 1 O r-t • lv —
0 OOOOOOO SW [z .^
-•rd 5
, — ^ -
w-
ID S
2 3, — -r -
5a 1°
lag
i^4
: 2 SW^
WSo^<J^aHfq^M^a:o^o^^^O
5QQ
o^I^h
o o
&g
EH
W^W
974
MISCELLANEOUS TABLES.
Specific Gravity.
Names of Sub-
stances.
15
2 . .g
Names of Substances.
In
« <v a
02 be
£ 8
--
02 be
^ a"-1
Woods.
Cedar, Indian
1.315
.0476
Oil, Linseed ......
.940
.0340
" American
.561
.0203
" Olive . . .
.915
.0331
Citron ....
.726
.0263
" Turpentine
.870
.0314
Cocoa-wood . .
1.040
.0376
" Whale . .
.932
.0337
Cherry-tree . .
.715
.0259
Proof Spirit . .
.925
.0334
Cork .....
.240
.0087
Vinegar . . .
1.080
.0390
Cypress, Spanish
.644
.0233
Water, distilled
1.000
.0361
Ebony, American
1.331
.0481
" sea . .
1.030
.0371
" Indian .
1.209
.0437
'• Dead Sea
1.240
.0448
Elder-tree . . .
.695
.0252
Wine. ....
.992
.0359
Elm, trunk of .
.671
.0243
Port . .
.937
.0361
Filbert-tree . .
.600
.0217
Fir, male . . .
.550
.0199
Miscellaneous.
" female . .
.498
.0180
Ebonito .......
1.8
Hazel ....
.600
.0217
Pitch .......
1.6
Jasmine, Spanish
.770
.0279
Asphaltum
.905
.0327
Juniper-tree . .
.556
.0201
1.650
.0597
Lemon-tree . .
.703
.0254
Beeswax
.965
.0349
Lignum-vitte . .
1.333
.0482
Butter
.942
.0341
Linden-tree . .
.604
.0219
Camphor ....
.988
.0367
Logwood . . .
.913
.0331
India rubber . .
.933
.0338
Mastic-tree . .
.849
.0307
Fat of Beef . . .
.923
.0234
Mahogany . . .
1.063
.0385
" Hogs . . .
.936
.0338
Maple ....
.750
.0271
" Mutton . .
.923
.0334
Medlar . . > . .
.944
.0342
Gamboge ....
1.222
.0442
Mulberry . . .
.897
.0324
Gunpowder, loose .
.900
.0325
Oak, heart of, 60 old
1.170
.0423
" shaken
1.000
.0361
Orange-tree . .
.705
.0255
" solid .
'(
1.550
.0561
Pear-tree . . .
.661
.0239
• i
1800
.0650
Pomegranate-tree
1.354
.0490
Gum Arabic . . .
1.452
.0525
Poplar ....
.383
.0138
Indigo
Lard ......
1.009
.0365
"' white Spanish
.529
.0191
.947
.0343
Plum-tree . . .
.785
.0284
Mastic .....
1.074
.0388
Quince-tree . .
.705
.0255
Spermaceti . . .
.943
.0341
Sassafras . . .
.482
.0174
Sugar .....
1.605
.0580
Spruce ....
.500
.0181
Tallow, sheep . .
.924
.0334
old . . .
.460
.0166
" calf . . .
.934
.0338
Pine, yellow . .
.660
.0239
" ox . . .
.923
.0334
" white . .
.554
.0200
Atmospheric air .
.0012
000043
Vine .....
1.327
.0480
W'g't
Walnut ....
.671
.0243
Gases. Vapors.
cu.ft.
Yew, Dutch . .
.788
.0285
gr'ns.
" Spanish
.807
.0292
Atmospheric air . ....
1.000
527.0
Iiiquids.
Ammoniacal gas ....
.500
263.7
Acid, Acetic . .
1.062
.0384
Carbonic acid .....
1.527
805.3
" Nitric . .
1.217
.0440
Carbonic oxid .....
.972
512.7
" Sulphuric .
1.841
.0666
Carbureted hydrogen . .
.972
512.7
" Muriatic .
1.200
.0434
Chlorine
2.500
1316
" Fluoric . .
1.500
.0542
Chlorocarbonous acid . .
3.472
1828
" Phosphoric
1.558
.0563
Chloroprussic acid . . .
2.152
1134
Alcohol, comraer,
.833
.0301
Fluoboric acid
2 371
1250
" pure
.792
.0287
Hydriodic acid .....
4.346
2290
Ammoniac, liquid
.897
.0324
Hydrogen .
.069
36.33
Beer, lager . . .
1.034
.0374
Oxygen
1.104
581.8
Champagne . .
.997
.0360
Sulphuretted hydrogen
1.777
9370
Cider .....
1.018
.0361
Nitrogen
.972
512.0
Ether, sulphuric
.739
.0267
Vapor of alcohol ....
1.613
851.0
Naptha ....
.848
" turpentine spirits
5.013
2642
Egg
1.090
.0394
" water ....
.623
328.0
Honey ....
1-450
.0524
Smoke of bituminous coal
.102
53.80
Human blood
1.054
.0381
" wood
.90
474.0
Milk .....
1.032
.0373
Steam at 212° .....
.488
257.3
MISCELLANEOUS TABLES.
975
TABLE Or SMJCIJFIC CJHAVITCY AXn UHflT
weicwiiiw.
Water at 39.1° Fahrenheit = 4° Centigrade ; 62.425 pounds to the cubic foot
(authority, Kent, Haswell, and D. K. Clark).
Specific
Gravity.
Authority
Lbs. per
Cubic
Foot.
Lbs. per
Cubic
Inch.
Aluminum, pure cast
" " rolled
" " anne'ld
" nickel alloy, cast
" " " rolled
" " " ann'ld
Aluminum Bronze, 10%
5%
Brass, cu. 67, zn. 33 cast
" cu. 60, zn. 40 "
Cobalt . . .
Brass, plates .
high yellow
Bronze composition
cu. 90, tin 10
Bronze composition
cu. 84, tin 16
Lithium . •
Potassium .
Sodium o .
Rubidium
Calcium . .
Magnesium .
Caesium . .
Boron .
Glucinum
Strontium .
Barium . .
Zirconium .
Selenium „ „
Titanium . .
Vanadium ,
Arsenic . .
Columbium .
Lanthanum .
Niobium . .
Didymium .
Cerium . .
Antimony »
Chromium „
Zinc, cast . .
" pure .
" rolled .
"Wolfram . .
Tin, pure . .
Indium . .
Iron, cast
" wrought
" wire . .
Steel, Bessemer
" soft
Iron, pure
2.85
2.76
2.74
7.70
8.405
8.50
8.832
0.57
0.87
0.97
1.52
1.57
1.74
1.88
2.00
2.07
2.54
3.75
4.15
4.50
5.30
5.50
5.67
6.00
6.20
6.27
6.80
6.861
7.15
7.191
7.119
7.29
7.42
7.218
7.70
7.774
7.852
7.854
7.86
Haswell.
Thurston.
R.-A.
P. R. C.
Thurston.
Haswell.
R.-A.
Haswell.
R.-A.
Haswell.
R.-A.
Haswell.
R.-A.
Haswell.
R.-A.
Haswell.
R.-A.
Kent.
Haswell.
Kent.
R.-A.
159.63
167.11
165.86
178.10
172.10
170.85
480.13
515.63
519.36
524.88
530.61
535.38
541.17
551.34
36.83
54.31
60.55
94.89
98.01
108.62
117.36
124.85
129.22
158.56
234.09
259.06
280.91
330.85
343.34
353.95
374.55
387.03
391.40
408.26
417.00
418.86
429.49
428.30
446.43
448.90
444.40
455.08
463.19
450.08
480.13
485.29
479.00
489.74
490.66
.0924
.0967
.1031
.0996
.3006
.3036
.3132
.'3191 '
.0213
.0314
.0350
.0549
.0567
.0629
.0679
.0723
.0748
.0918
.1355
.1499
.1626
.1915
.1987
.2048
.2168
.2240
.2265
.2363
.2413
.2424
.2457
.2479
.2583
.2598
.2572
.2634
.2681
.2605
.2779
.2808
.2837
.2834
.2840
976
MISCELLANEOUS TABLES.
IA.BIE OF
SPECIFIC «RA¥IT1
. — Continued.
Specific
Gravity.
Authority.
Lbs. per
Cubic
Foot.
Lbs. per
Cubic
Inch.
Kilos per
Cubic
Deem.
Manganese ....
8.00
R.-A.
499.40
.2890
8.00
Cinnabar
8.809
Haswell.
505.52
.2925
8.098
Cadmium
8.60
R.-A.
536.85
.3107
8.60
Molybdenum . . .
8.60
"
536.85
.3107
8.60
Gun Bronze ....
8.750
Haswell.
546.22
.3161
8.750
Tobin Bronze . . .
8.379
A. C. Co.
523.06
.3021
8.379
Nickel
8.80
R.-A.
549.34
.3179
8.80
Copper, pure . . .
Copperplates and sheet
8.82
"
550.59
.3186
8.82
8.93
A. of C. M.
556.83
.3222
8.93
Bismuth
9.80
R.-A.
611.76
.3540
9.80
Silver
10.53
657.33
.3805
10.53
Tantalum ....
10.80
674.19
.3902
10.80
Thorium
11.10
692.93
.4010
11.10
Lead
11.37
709.77
.4108
11.37
Palladium ....
11.50
717.88
.4154
11.50
Thalium
11.85
739.73
.4281
11.85
Rhodium
12.10
755.34
.4371
12.10
Ruthenium ....
12.26
765.33
.4429
12.26
Mercury
13.59
848.35
.4909
13.59
Uranium
18.70
1167.45
.6755
18.70
Tungsten
Gold
19.10
1192.31
.6900
19.10
19.32
1206.05
.6979
19.32
Platinum
21.50
1342.13
.7767
21.50
Iridium
22.42
1399.57
.8099
22.42
Osmium .....
22.48
1403.31
.8121
22.48
- R.-A. — Professor Roberts-Austen.
Haswell — Haswell's Engineer's Pocket Book.
P. R. C. — Pittsburg Reduction Co.'s tests.
Kent — Kent's Mechanical Engineer's Pocket Book.
Thurston — Report of Committee on Metallic Alloys of U. S.
Board appointed to test iron, steel, and other metals.
Thurston's Materials of Engineering.
Riche — Quoted by Thurston.
A. C. Co. — Ansonia Brass and Copper Co.
A. of C. M. — Association of Copper Manufacturers.
SPECIFIC GRAVITY AT ©2° FAHBEIHMT
ahimh^im: auti* AirmwiM alloys.
Aluminum Commercially Pure, Cast ........•••• '
Nickel Aluminum Alloy Ingots for rolling
'• " Casting Alloy
Special Casting Alloy, Cast c
Aluminum Commercially Pure, as rolled, sheets and wire
" " " Annealed . .
Nickel Aluminum Alloy, as rolled, sheets and wire ........
" " " Sheets Annealed
OF
2.56
2.72
2.85
3.00
2.68
2.66
2,76
2.74
Weig-Ht.
Using these specific gravities, assuming water at 62 degrees Fahrenheit,
and at Standard Barometric Height, as 62.355 lbs. per cubic foot (authority,
Kent and D. K. Clark). . „„„„,,.
Sheet of cast aluminum, 12 inches square and 1 inch thick, weighs 13.3024 lbs,
Sheet of rolled aluminum, 12 inches square and 1 inch thick,weighs 13.9259 lbs,
Bar of cast aluminum, 1 inch square and 12 inches long, weighs 1.1085 lbs,
Bar of rolled aluminum, 1 inch square and 12 inches long, weighs 1.1605 lbs.
Bar of aluminum, cast, 1 inch round and 12 inches long, weighs .870b lbs.
Bar of rolled aluminum, 1 inch round and 12 inches long, weighs .9114 lbs.
1 1ST D EX.
Aboard ship, condensation of steam,
904
Acceleration, horse-power of, 447
Accumulators, electric, 552
Aerial cable, specifications for, 171
lines, resistance of, 43
Air-pumps, 923
Air space in grates, 831
Aging of iron, 344
Alloys, relative resistance of, 181
Alternating current arc lamps, 394
current armature windings, 259
current circuits, measuring power
in, 51
current conductors, 103
current dynamos, 230
current electro-magnets, 87
current motors, 273
current switchboards, 590
current wiring chart and table, 131
current wiring formula, 127
E.M.F. and current in terms of
d. c, 288
wiring, 121
Alternators in parallel, 269
Aluminum conductors, 174-179
data on, 174
production of, 680
weight and specific gravity, 976
American woods, weight, coal value,
849, 850
Ammeters, 25
Ammunition hoists, electrically op-
erated, 740
Amperes per car, 431
Angular velocity, 967
Annealing of armor plate, 693
Annunciator wiring, 138
Anthracite coal, properties of, 851
Anti-induction cables, 142
Arc circuits, insulation resistance
of, 59
Arc lamps, continuous current, 393
lamps, alternating current, 394
lamps, candle-power of, 398
lamps, inclosed, 394
lamps, installation of, N.E.C., 770
lamps, regulation of, 395
switchboards, 582
Ardois's system of signaling, 735
Armatures, alternating current, 259
cores, 250
Armature cores, energy dissipation
in, 80
reaction, 264
windings, 251
windings for converters, 291
Armatures, faults in, 329
Army, electricity in the, 711
Arresters, lightning and current,
653
Automatic telephone switches, 650
Axle speed, per car, 455
Balancing coils for arc lamps, 400
Balancing of three-phase lines, 118
Ballistic galvanometer, 24
galvanometer tests, 66
B. & S. gauge, law of, 203
Baths for plating, 678
Batteries, E.M.F. of, 53
internal resistance of, measure-
ment of, 62
resistance of, 42
secondary, 552
Battery cells, arrangement of, 18
Battle order indicators, 750
Beams of uniform strength, 814
safe load on Southern pine, 822
special forms, coefficient of
strength, 813
white pine, formula for, 821
Bell wiring, 137
Belt, length of, 953
length of, in a roll, 953
weight of, 953
Belting, horse-power of, 951
Bends, loss of head due to, 870
Bituminous coal, properties of, 851
Block signals, 432
Boiler flues, collapsing pressure,
915
settings, 836
settings, dimensions, 838
test report, 885, 886
tests, A. S. M. E. rules, 879
tubes, dimensions lap-welded, 914
Board of fire underwriters' rules,
762
of trade tramway regulations, 504-
508
Boat cranes, electrically operated,
742
Bonding, test of rail, 519-522
977
978 INDEX.
Bonds, rail, 502
Centrifugal force, 967
Booster system, railway, 514
Characteristics of dynamos, 245
Boosters, continuous current, 285
Charging current per mile of cir-
for storage batteries, 568
Boulenge chronograph, 715
Brackets for trolley poles, 441
cuit, 134
storage batteries, 582
Chemical action in storage batteries,
Brake controllers, 484
553
Brakes, emergency, 465
Chimney construction, 841
Brass, composition of rolled, 825
height of, 844
table, 840, 841
Aveight of sheet and bar, 825
Bridging system, telephone, 664
thin shell brick, 842, 843
Brill cars, dimensions of, 466
Chimneys, draught power, 840
Brick chimneys, dimensions and
dimensions and cost of iron
cost, 845
(guyed), 846
Chloride of silver cell, 15
foundations, 794
work, 823
Choke coils, 605
Bricks, sizes, 823
Chronograph, 715
weight and bulk of, 824
Circuit breakers, 596
British thermal unit, 972
Circuits, tests of railway, 516-520
Brown's rail bond tester, 522
metallic telephone, 651
Bunsen photometer, 389
overhead, on poles, 651
Burglar-alarm wiring, 139
underground, telephone, 652
Burton electric forge, 693
Circulating pumps, 924
Bus excited dynamos, 588
Coals, heating value of, 850
Bushel, 961
proximate analyses, 852
space required to stow a ton, 853
Cable joints, 201
Coast-defense guns, manipulation
testing, 220
Cables, data on, 158
of, 721
Codes, telegraphic, 642
underground, 652
Coefficient of inductance, measure-
Calcium carbide, production of, 677
ment of, 48
Calorie, French, 972
of self-induction, definition of, 47
pound, 972
Coke, analysis of, 853
Calorimeter, Carpenter's, quality
weight and bulk, S53
curves, 894
Collapsing pressure, boiler flues, 915
Carpenter's throttling, 890
Columns, Baker's formula, 803
diagram for throttling, 892
Gordon's formula, 802
separating, 893
Hodgkinson's formula, 802
thiottling, 889
hollow cast iron, strength, 807
Candle-power of arc lamps, 398
hollow cvlindrical, strength, 80S
of incandescent lamps, 404
N. Y. City building laws, 803
Capacity effects on circuits, 105
pillars or struts, 802
measurement of, 46
solid cast iron, strength, 807
of conductors, 110
wrought iron, strength, 809
of cables, tests of, 223
Combustibles, table of, 848
Carbons, arc light, 396
Common-battery system, 658
Carrying capacity of copper wire,
Commutating machines, A. I. E. E.
153
report, 295
capacity of wires, National Elec-
Comparison of columns of water in
trical Code, 768, 788
feet, 929
Car heating, electric, 499, 689
Compound cables, 229
heating, cost of, 690
engines, cylinder ratios, 919
lighting, electric, 547
wiring diagrams, 476-480
wiring, rules for, N. E. C, 775
Concrete foundations, 794
Condensation in steam pipes, 904
in steam pipes aboard ship, 904
Cars, dimensions of, 466-469
in heating pipes, 904
weight of, 470
Condenser, ejector, 923
Cary-Foster Bridge, 40
jet, 921
Cast iron, test, 796
surface, 922
Caustic soda, production of, 676
Condensers and pumps, 921
Cement, adhesion to bricks or rub-
arrangement of electrical, 46, 223 i
ble, 796
standard electrical, 28
and sand, 796
Condensing engines, number of ex-
average strength of neat, 796
pansions for, 919
mortar, 795
Conducting system, calculation of,
Centigrade in Fahr. equivalents, 969
510-514
Central stations, storage batteries in,
Conductivity of cables, 228
560-576
of copper, 140
979
Conductivity, with millivoltmeter,
measurement of, 62
Conductors for electrical distribu-
tion, 97
for incandescent circuits, 101
properties of, 140
Conduit railway systems, 531-536
work, National Electric Code, 772
780
Contact plate system of General
Electric Co., 543-546
Continuous current dynamos, 230
current motors, 270
Controllers, installation of, 475
dimensions of, 487
electric brake, 484
rheostatic, 483-485-
series parallel, 481-486
Converter armature windings, 291
Converters, rotary, 286
Cooking, electric," 685
electric, cost of, 685
Copper bar data, 587
data, 140
electrolytic refining of, 680
Copper-plating, 67S
Copper, temperature coefficient of
pure, 185
weight of round bolt, 825
wire, bard-drawn, 142
wire table, 143
Avire table, National Electric Code,
769
Core losses, 72
loss, test for, 312
Cost of arc and incandescent lamps,
414
of operating mining plants, 696-700
Cowles' aluminum process, 680
Cross arms, dimensions of, 219
Crosses in cables, 225
Cubic measures, metrical equiva-
lent, 964
Current consumption per car, 454
densities for various metals, 269
density in street railway conduc-
tors, 445
measuring with voltmeter, 56
wave form of, 705
Curves, effort exerted on, 453
railway, 423
Cutouts, installation of, National
Electric Code, 781
Cylinder ratios, compound engines,
919
Deck winches, electrically operated,
744
Deflection table, for wire spans,
209-218
Densities, average current, for vari-
ous metals, 269
Depreciation on street railways, 498
Diagrams for car wiring, 476-480
Dielectrics, resistance of, 193
disruptive value of, 194-197
strength, A. I. E. E. report, 300
values of various (table), 197
Dimensions of railway cars, 466-469
Dip in span wire, 439
Direct current switchboards, 589
deflection method, 220
Discharge of water through an ori-
fice, 935
Disruptive value of dielectrics, 194
Distribution and diffusion of light,
409
of electric energy, 92
of light by incandescent lamps,
412
Ditches, data for flumes and, 933
Double truck cars, power required
by, 453
Draft power for combustion of
fuels, 844
Draw-bar pull test, 522
Drop at end of railway line, test of,
519
in street railway conductors, 446
Dry batteries, 17
Ductility of boiler plate, 835
Duplex telegraphy, 639
telephony, 661
Dynamo and motor regulation, A. I.
E. E. report, 301
Dynamos, alternating current, 230
continuous current, 230
efficiency test of, 319
rooms, N. E. C, 762
Dynamos and motors, efficiency of,
294
and motors, rating of, 303
and motor standards and testing,
293
and motors temperature rise in,
307
and motors, tests of, 306
E.M.F. of, 53
for U. S. Navy, 727
insulation of, measurement of, 60
method of exciting, 588
resistance of, 43
Dynamotors, 284
Economical distributing conditions,
93
Economizers, tests of, 874, 875
Economizers, 873
Eddy current factors, 79
current, loss in dynamo and mo-
tor, 313
current loss curves, 78
currents in iron cores, 72
Edison-Lai ande cell, 16
Efficiency curves of dynamos, 247
of arc lamps, 399
of incandescent lamps, 402
test of dynamos, A.I.E.E. report,
319
test of motors, 325
test of railway motors, 523
Ejector condenser, 923
Elastic limit, 804
Electric brake controllers, 484
cooking, 685
lighting, 386
080
Electric power transmission, 99, 549
welding, 691
Electrical code, national, 762
measurements, 38
standardization, A. I. E. E. report,
293
units, 4
Electricity meters, 615
Elevated railway data, 471^74
Elevation of outer rail, 428
Electro-chemistry, application of,
676
dynamometer, 32
magnetic railway system, 536
Electrolysis, 675
of pipes, 524-529
Electrolytic refining of copper, 680
Electromagnetic units, 5
Electro-magnets, alternating-cur-
rent, 87
depth of Avinding for, 87
heating of, 87
lifting power of, 83
M.M.F. of, 81
permament amp. for (table), 88
properties of, 81
relation between constants of, 86
Avinding of, 84
Electrometallurgy, 677
Electrometer method for measure-
ment of E.M.F., 45
Electrometers, 30
Electromotive force of dynamos, 230
Electroplating, 677
Electrostatic units, 4
voltmeter, 31
Electrotyping, 677
Elements of the usual sections, 805,
806
Emergency brakes, 465
E.M.F., Avave form of, 705
measurement of, 45
of batteries, measurement of, 53
Energy and work, units of, 12
Engine telegraphs, U.S. navy, 750
Equation of steam pipes, 907
of steam pipes, table, 909
Equipment list for one car, 480
Exhaust injectors, 868
steam, pump, 872
Expansion, coefficients of, 970
of metals, 184
of Avater, 858
Factor of safety, 804
Factors of evaporation, 895
of evaporation, table, 896
Fahrenheit in centigrade equiva-
lent, 970
Faults in incandescent lamps, 408
in Avires or cables, 226
of car motors and remedies, 523
Feeder points, location of, 512
Feeders, arrangement of railwav,
508-510
Feed-Avater heaters, 871
pipes, sizes of, 869
purification by boiling, 861
Feed-water, saAing by heating, 871
Field magnets, 265
telegraph and telephone, 726
Fire alarms, for U. S. navy, 753
Fire, temperature of, 849
Flanges, standard pipe, 915
Flat plates, safe pressure on, 834
rolled iron, Aveight of, 797
Flexure of beams, fundamental
formulae, 810
FIoav of steam through pipes, 905
of Avater in pipes of various sizes,
869
of Avater over weirs, 937
Flumes and ditches, data for, 933
Flux densities, G6
Fly-Avheels and pulleys, centrifugal
tension in, 925
Foot valve, 924
Forging electrically, 691
Foundations, 792
Friction, 967
loss in dynamos and motors, 312
of Avater in pipes, 870
Fuel, 846
economizers, 873
kinds and ingredients of, 846
Fuels, heat of combustion, 847
Fuller cell, 15
Furnaces for oil fuels, 855
Fuse data, 694
table, 204
Fuses, electric, for gun-firing, 722
for railway circuits, 465
installation of, N.E.C., 782
Fusion of metals, temperature de-
termined by, 849
Gallon, 961
Galvanized iron Avire data, 154
Galvanometers, 20
resistance of, 42
Garton lightning arrester, 614
Gas lighting, electric, N.E.C., 786
light wiring, 139
passages and flue-area, 831
Gaseous fuels, 855
Gases, composition of, 855
and vapors, specific heat of, 972
General Electric single- phase alter-
nators, 241
Electric surface contact raihvay,
543-547
Generator sets, tests of U. S. Navy,
728
German silver Avire, data on, 180
Gold-plating, 679
Grades and curves, 423, 428
horizontal effort on, 454
Grate surface, 831
surface per horse-poAver, 831
Gravity cell, 14
Greek 'letters, 967
Ground connections for lightning
arresters, 607
connections, National Electric
Code, 767
return drop, test of, 578
981
Guard wires, 445
Guns, manipulation of, 721
Gutta-percha, data on, 198
Guys for trolley wire, 444
Gyrostatic action on dynamos, 266
Hall's aluminum process, 680
Haulage in mines, cost of, 696
Headway of cars, 457
Heat conducting power of metals,
185
intensity of, 968
mechanical equivalent of, 972
of the electric arc, 400
transmitted through cast-iron
plates, 911
units, 3, 683, 973
Heaters, feed-water, 871
electric, installation of, N.E.C.,
771
Heating apparatus, efficiency of, 688
apparatus, portable, 779
apparatus, principles of, 683
cars by electricity, 499
cars electrically, 689
of armatures, 263
of bare conductors, 153
of electro-magnets, 87
pipes, condensation in, 904
surface of steam boilers, 830
surface per horse-power, 831
Helm angle indicators, 750
Hemp, tarred, weight of, 958
High potential circuit breakers, 597
potential oil switches, 595
potential systems, N. E. C, 775
volta°e transmission, 550
Hollow"shafts, 848
Hopkinson's efficiency test of dyna-
mos, 321
Hopkinson's permeability test, 66
Horizontal effort of cars, 452
return tubular boiler, 829
tubular boiler height above grate,
831
Horse-power, brake, 918
boiler, to supply heating pipes,
904
indicated, 918
mill power, 928
nominal, 918
of a running stream, 928
of a waterfall, 927
of acceleration, 447
of steam boilers, 829
of traction, 449
of water, cubic feet table, 939
of water, miner's inch table, 939
per car, 450
water flowing in a pipe, 928
House circuits, resistance of, 43
Human body, resistance of, 61
Hydro-electro thermic system, 693
Hydrometers, 555
Hysteresis loss in transformers, 332
factors, 73
loss in dynamos and motors, 313
meter, 75
Hysteretic constants, 72
I-beam foundations, 795
I-beams, spacing and size, 817
Impedance coil, use of, 671
diagrams, 114
effect of, 104
table, 136
Impulse water-wheels, 944
Illuminating power, 393
Incandescent lamps, 402
lamps, candle-power of, 404
lamps, faults in, 408
lamps, life of, 411
lamps, proper use of, 403
Inches and eighths in decimal of a
foot, 967
Inclined planes, strains in rope on,
958
Inclosed arc lamps, 394
Incrustation, causes and prevention
of, 858
tabular view, 859
Inductance and impedance table,
136
Inductance factors, 107
of aerial lines, 50
Induction coils, connections of, 757
motors, 274
motors, current taken by, 125
motors, tests of, 324
motors, transformers for, 124
Inductive resistance of lines, 106
Injector vs. pump for feeding boil-
ers, 868
Injectors, exhaust, 868
live steam, 866
live steam, deliveries for, 867
performance of, 868
Installation of street car motors,
474
of telephones, 653
Insulating joints, N.E.C., 784
Insulation of dynamos, measure-
ment of, 60
of light and power circuits, meas-
urement of, 58
of motors, measurement of, 61
regulations, National Electrical
Code, 777
resistance, A.I.E.E. report, 300
resistance, N.E.C. 764
resistance of arc circuits, 59
resistance of cables, 220
resistance of circuits, 44
Insulators, specific resistance of, 193
Intensities of sources of light, 386
Intercommunicating telephone sys-
tems, 668
Interior lighting, 393
telephone systems, 663
Internal resistance of batteries,
measurement of, 62
International electrical units, 9
Iron, aging of, 344
and steel, 796
magnetic properties of, 64
plating, 679
982 INDEX.
Iron, weight of, 796
Manila ropes, centrif ugal-tension,955
wire data, 154-157
ropes horse-power diagram, 956
Irons, electric, 691
ropes horse-power of, 955
Isolated plants, storage batteries
ropes weight and strength, 958
for, 566
Marine boiler, 829
Avork rules, N.E.C., 787
Jet condenser, 921
Masonry, 823
Jointing gutta-percha covered wire,
average ultimate crushing load, 824
199
Material for one mile of overhead
Joints of cables, testing of, 222
line, 436
per mile of track, 429
Mean effective pressure, table of,
920
spherical candle-poAver, 399
Kapp efficiency test of dynamos, 315
Kelvin electric balance, 33
Measurement of E.M.F. of batteries,
electric balance tables, 36
55
Krupp's resistance wires, 191
of capacity, 46
of E.M.F. , 45
Lamp specification for United States
of flow of water, 936
navy, 732
of high resistances, 58
Leaded wires and cables, 166
of insulation of dynamos and mo-
Leclanche cell, 15
tors, 60
Leonard's system of motor control,
of internal resistance of batteries,
62
of low resistances, 57
Life of incandescent lamps, 411
Light, measurement of, 389
of mutual inductance. 49
proper use of, 411
of power in alternating current
units of, 387
circuits, 51
velocity and intensity of, 386
of resistance of human body, 61
Lighting, electric, 386
of self-inductance, 48
of cars, 547
Measurements, electrical, 38
schedules, 414-422
Mechanical equivalent of heat, 972
-svstem specifications for U. S,
stoking, 856
Navy, 731
Metallic circuits, requirements of,
Lightning and current arresters, 653
651
arresters, function of, 601
Metals, resistance of, 141
arresters, location of, 764
specific heat of, 184
arresters, non-arcing, 602
weights and specific gravity, 975
conductors, 701
Meters, electricity, 615
rods, installation of, 702
alternating current, 620
rods, tests of, 704
Wright discount, 035
Lime mortar, 795
Metric measures in English meas-
Lineal measure, metrical equiva-
ures, 965
lent, 962
Metropolitan Street Railway system,
Liquid fuels, 854
532-536
Load factor of railway system, 510
Miles per hour, feet per minute,
Loading and training gear for guns,
(Table), 457
739
Milliken repeater. 637
Long-distance lines, 660
Mill power, 928
transmission, 550
Miner's inch measurements. 937
Loop test of cables, 226
Mines, electrical land, 723
Lord Rayleigh's method for meas-
Mining plants, operation of, 696
urement, E.M.F., 45
Miscellaneous materials, 825
Loss of charge method, 221
tables, 961
of head due to bends, 870
Modulus of elasticity, 804
of elasticity and elastic resis-
Machine shops, horse-power in, 758
tance, 814
shops, men employed in, 758
Moisture in steam, determination
tools, power used by, 758
of, 889
Magnet telephone, theory of, 645
in steam, tables, 891
Magnetic circuit, principle of, 82
Moment of inertia, 804
circuit of dynamos, 236
of inertia of compound shapes, 805
flux, formula for, 82
Monocyclic circuit connections, 126
properties of iron, 64
system wiring formula, 128
units, 4
Moonlight schedules, 414-422
Magnetization curves, 65
Mortars, cement and lime, 795
curves of dynamos, 245
Motor equipments, 425
Magneto generator, 650
-generators, 284
Manganine wire, 188
trucks, weight of, 464
983
Motors, alternating current, 273
continuous current, 270
installation of, N.E.C., 764
insulation resistance of, 61
railway, 424
rating of railway, 457
series-wound, 271
shunt-wound, 272
testing of railway, 522
tests of A. I. E. E. report, 322
types of railway, 460
weight of railway, 470
Multiphase induction motors, 274
Multiple-unit system, Spr ague, 489-
498
Multiplex telephony, 661
Mutual Inductance, meas. of, 49
inductance of aerial lines, 50
induction of circuits, 117
National Electrical Code, 762
Navy, electricity in United States,
727
standard wires, 159
Ness automatic telephone switch,
672
Niagara-Buffalo transmission line,
117
Niagara line construction, 117
Nickeline wire, 187-191
Nickel plating, 679
Non-arcing lightning arresters, 602
Northrup's galvanometer, 25
Ohm, standard, 27
values of, 141
Ohm's law, 38
Oil brake switch, 594
Output of dynamos and motors,
266
Overhead line construction data,
117, 436
railway system, 508-510
Overload capacity of dynamos and
motors, A. I. E. E. Report, 303
Paper insulated wires and cables,
166
Party lines, 659
Paving, cost of, 430
Peckham trucks, 471
Permeability curves, 248
values, 66
Permeameter, 68
Permissible loads on foundation
beds, 794
Petroleum,chemical composition of,
854
oils, chemical composition, 855
Photometers, 389
Piles, arrangement of, 794
safe load on, 793
Pipe flanges, standard, 915
riveted hydraulic, 934
standard dimensions, steam, gas
and water, 912
wooden-stare, 933
wrought iron extra-strong, 913
Pipes, equation of steam, 907
sizes of feed-water, 869
Plate iron, weight of, 800
Plates, heat transmitted through,
911
Platinum, specific heat of, 971
Plotting of electrical waves, 708
Poles for trolley systems, 438
Polyphase induction motors, 275
Portland cement — recommenda-
tions, 796
Position indicators, 749
Post-office bridge, 39
Power and induction factor table,
106
curves, 448
factor chart, 137
factor, determination of, 122
factor, formula for, A. I. E. E.
Report, 305
measurement of, in alternating
current circuits, 51
station, 424
station, capacity of, 459
station construction-chart, 791
stations, batteries in, 575
systems for U. S. Navy, 735
transmission, 548
Pressure loss in water pipes, 870
of water, table, 931
Primary cells, 14
Projectors, 395
for U. S. Navy, 733
Prony brake, 758
brake test of motors, 322
Properties of saturated steam-tables,
899
of timber, 818
Protected rail bonds, 501
Protection of steam heated sur-
faces, 910
Pulleys, 951
centrifugal tension in fly-wheels
and, 925
to find size of, 951
Pump, duplex-cylinder, direct-act-
ing, 866
Pumping hot water, 863
Pumps, circulating, 924
condensers and, 921
efficiency of small direct-acting,
864
exhaust, 872
feed, 863
single-cylinder direct-acting, 865
Pure copper wire table, 151
Purification of feed water by boil-
ing, 861
Quadruplex telegraphy, 640
Quality of steam by color of issuing
jet, 895
Radiators, electric, 689
Radius of gyration, 805
Range indicators, 753
Rate of combustion due to chimney
height, 844
984
Rates for incandescent lighting, 414
Hating dynamos and motors, A. I.
E. E. report, 303
street railway motors, 457
Kail bonding, test of, 519-522
bonds, 502
bonds, protected) 501
Rail welding, 694
conductivity of, 504
Rails, sectional areas of, 504
weights of, 426
Railway circuits, tests of, 516-520
motor testing, 324, 522
motors, 424
motors, rating of, 457
motors, types of, 460
Railways, battery plants for, 575
conduit, 531-537
depreciation on, 498
surface contact, 536-546
switchboard connections, 591
third rail, 529-531
turnouts, 431
Reactance coils, 361
diagrams, 114
Reaction of armatures, 264
Receiver, Bell, 646
capacity, 921
telephone, 645
Rectifying mychines, A. I. E. E.
report, 297
Regulation of dynamos and motors,
A. I. E. E. report, 310
Regulations of board of trade,
504-508
Regulators, a. c. feeder, 362
Renewal of lamps, 407
Repeaters, 637
Repeating coil, 660
Report of A.I. E. E. committee on
standardization, 293
on water-power property, 926
Resistance boxes, 27
boxes, location of, N. E. C, 763
increase in, 307
insulation, A. I. E. E. report, 300
internal of batteries, 62
measuring with voltmeter, 57
measurement of, 38
metals, 186
of dielectrics, 193
of human body, measurement of,
61
of metals, 141
of wires, 42
ribbon, 187
test of armature, 328
Return circuit, 499
drop, test of ,518
feeder booster, 515
Reverse current circuit breakers,
598
Revolution indicators, 750
Revolutions of car wheels, 451
Rheostatic controllers, 483-485
Riveted hydraulic pipe, 934
Riveted steel pipes, 932
Rope driving, 954
Rope, H. P. of transmission, 957
strains in, on inclined planes,
958
Ropes and belts, slip of, 957
Rotary converters, 286
Round and square wrought iron,
weight of, 799
Rules for conducting boiler tests, 879
Safe carrying capacity of wires, 153
load on piles, 793
load on wooden beams, 820
Safety valves, calculations for lever,
877
valves, rules, 877
Sag of wires and cables, 205
Sand and cement, 796
recommendations, 796
Saturation test, A. I. E. E. report,
327
Scale-making materials, solubility
of, 859
Schmidt chronograph, 718
Schultz chronograph, 717
Scotch boiler, 829
Searchlight data (table), 714
projectors, 395
Searchlights, 711
for TJ. S. Navy, 732
Sectional rail construction, 542
Self-induction, effect of, 104
Semaphores, 433
Separating calorimeter, 893
Separation of metals, 680
Separators, 875
tests of, 876
Series-parallel controller, 481-486
Series-wound motors, 271
Sewing-machines, power required
by, 757
Shafting, centers of bearings, 947
cold rolled, horse-power of, 947
deflection of, 946
hollow, 949
horse-poAver of, 947, 949
power and size, 945
table for laying out, 949, 950
Shunt boxes, 26
Shunt-wound motors, 272
Signaling systems, National Elec-
trical Code, 785
Signal lights for IT. S. navy, 734
Silicon bronze wire, 219
Silver, electrolytic refining of, 681
Simultaneous telegraphy and tele-
phony, 662
Single-phase alternators, 241
Single-truck cars, power required
by, 453
Size of conductors, calculation of,
99
Skin effect factors, 103
Slide-Avire bridge, 40
Slip of ropes and belts, 957
Smashing point of incandescent
lamps, 403
Sockets, specifications for, N, E. C,
774, 782
985
Soldering fluid formula, 787
Solid rail bonds, 500
Spacing and size of I beams, 817
Span wire data, 440
wire dip, 439
Spans of wire and cable, table of,
205
Specific energy dissipation, 80
gravity and unit weights, 975
gravity, various substances, 974,
975.
heat of gases and vapors, 972
heat of metals, 184, 971
heat of substances, defined, 971
heat of water, mean, 972
resistance table, 192
Speed and torque of motors, 271
of cars, 455
of water through pump-passages
and valves, 864
recorder, 754
Spikes, 429
Sprague multiple unit system, 489-
498
Square and round bars of wrought
iron, weight of, 799
Squier-Crehore Photo-Chronograph,
720
Standard cells, 11, 18
Standardization, report of A. I. E.
E., 293
Static transformer, 331
Station equipment, 424
Stays, boiler head, 835
Steam, 829
and exhaust pipes, for cylinder
sizes, 908
and gas pipes, standard sizes, 908
boiler braces, 836
boiler efficiency, 831
boilers, working pressure, 832, 833
boilers, types, 829
determination of the moisture in,
889
engines, classification, 916
engines, horse-power of, 918
engines, tests of various types, 917
flow of, through pipes, 906
moisture in, tables, 891
outflow of, to atmosphere, 905
pipes, 906
pipes, condensation in, 904
pipes, loss of heat from, 910
total heat of, 972
ports and passages, 921
properties of, 899
Stearns duplex, 641
Steel beams, formulae for greatest
safe load, 812
Steel plate chimneys, 845
plate chimneys, brick lining, 845
plate chimneys, foundation dimen-
sions, 845
weight of, 796
wire data, 154-157
Steering gear, electrically operated,
745
Stone foundations, 794
Storage batteries, 552
batteries, advantages of, 560
batteries, capacity of, 554
batteries, charging, 558
batteries, E. M. F., of, 554
batteries for surface contact rail-
way, 546
batteries, in power stations, 575
batteries, installation of, 556-561
batteries, installation of, N. E. C,
765 •
batteries, manufacturers of, 563
batteries, solutions for, 555
batteries, testing, 579
Strain and deflection table for wire
spans, 215-218
Stranded Avire cables, 157
Stray field in dynamos, 237
Street car motors, installation of,
474
car wiring, 160
lighting by arc lamps, 401
railway batteries, 575
railway depreciation, 498
Strength of materials, 803
of riveted shell, 832
Struts, safe load for white pine, 827
Submarine cables, testing of, 228
cables, data on, 173
Substation system, 516
Suggestions, general, National Elec-
trical Code, 790
Sulphate of copper, resistance of, 67C
of zinc, resistance of, 676
Sulphuric acid, resistance of dilute
675
" Superior " wire, 188
Supplies for installing lamps, 760
Surface condenser, 922
contact railway system, 536-546
Suspension of trolley wire, 443
Switches, automatic telephone, 650
specifications for, N. E. C, 781
Switchboards, telephone, 655
specifications for the U. S. Navy,
729
layout of, 585
construction of, 585
for arc circuits, 592
location of, 763
Symbols, electrical engineering, 1
synopsis of (table), 6
Synchronizers, 267
Synchronous machines, A. I. E. E.
lieport, 295,
motors, 281
motors, tests of, 326
Tables of weights and measures,
961, 962
Tangent galvanometer, 21
Telegraph, anti-induction cables, 142
cables, specifications for, 170
codes, 642
for U. S. Army use, 724
wire data, 154
Telegraphy, American, 636
European, 636
98G
Telephone, anti-induction cables,
142
cables, specifications for, 163
circuits, 651
switchboards, 655
systems, interior, 663
systems intercommunicating, 668
wire data, 154
wires, aluminum, 176
Telephones installation and main-
tenance of, 653
for U. S Army use, 724
for IT. S. Navy, 753
Telephony, 645
duplex and multiplex, 661
Temperature coefficients of conduc-
tors, 182
effect in wire spans, 207
or intensity of heat, 968
rise in dynamos and motors, 307
rise of, A. I. E. E. report, 298
Tensile strength of copper wire,
(table), 208
Testing of cables, 220
of dynamos and motors, 293, 306
rail bonds, 519-522
railway motors, 5:22
Tests of American woods, 819
of street railway circuits, 516-520
Thermo-electric scale, 757
Thermometers, comparison of F. R.,
and C, 968
Third-rail systems, 529-531
Thompson-Ryan dynamo, 265
Thomson galvanometer, 22
double bridge, 41
method for measuring capacity, 46
Three-phase circuits, balancing of,
118
circuity energy in, 233
wiring formula, 130
Three-wire system, railway, 514
Throttling calorimeter, 889
calorimeter, calculation curves
for, 892
Thunderstorms, safety during, 703
Ties, railway, 429
Time element for circuit breakers,
600
Tools for installing dynamos, 759
Torque and horse-power, 465
of motors, 271
Track bonding, test of, 519-522
laying, 430
return circuit, 499
Tractive coefficient, 458
effort, 458
force, 450
Transformer, air-blast, 338
cores, 331
design of, 335
heating tests (tables), 339
duties of, 332
efficiencies of, 340
equations, 334
expense of operating, 346
losses in (table), 332
regulation of, 344
Transformer, static, 331
Transformers, commercial (tables),
347
connections of, 366
constant current, 357
high potential, 356
in connection with converters, 292
testing of, 372
Transmission of electric power, 99
of power, 548
Transmitter, Edison carbon, 645
Blake, 647
solid-back, 648
Transverse strength of bars, 810
strength of beams, formulae for,
811
Trenton beams and channels,
strength, 815
Trimming arc lamps, 402
Trolley poles, 437
systems, 508-520
wire, size of, 512
wire suspension, 443
Avires, specification, N. E. C, 766
Trucks, weight of, 464, 470
Tubes, sizes lap-welded boiler, 914
Tubular iron and steel poles, 438
Turbines, data, McCormick tvpe,
942
data, Pelton impulse, 943
dimensions, etc., 941-943
dimensions of Victor, 941
impulse, 941
installing, 941
parallel, outward and inward flow,
940
Turnouts on railways, 431
Turret-turning system, 737
Two-phase four- wire circuits, 120
Ultimate crushing load for masonry
materials, 824
Underground cables, 652
electrical construction, 203
Units, electrical and mechanical,
table of, 684
electrical engineering, 2
of light, 387
U. S. standard gauge for sheet and
plate iron and steel, 801
Velocity _, angular, 967
Ventilating fans for U. S. Navy, 744
Vertical fire-tube boiler, 829
Voltage regulation for incandescent
lamps, 405
Volt, determination of, 10
Voltmeter, tests with, 53
high resistance of, 54
Voltmeters, 25
Vulcanized india-rubber, 198
Walmsley's rail tester, 521
Ward Leonard turret-turning sys-
tem, 737
Water analyses, table of, 862
calculations of horse-power, 939
Water column equivalents, 929
Water, cubic feet discharged, per
minute, 935
expansion of, 858
flow of, over weirs, 937
flow of, through an orifice, 936
for boiler feed, 858
gas, 973
heat units per pound, 904
mean specific heat of, 972
table of pressure of, 931
theoretical velocity and discharge,
tube boiler, 829
weight above 212° F., 857
weight of, per cubic foot, 904
weight per cubic foot, 856
wheels, 940
Water-power, 926
expense, yearly, 930
property, report, synopsis, 926
Water-tight door gear, United
States navy, 747
Wattmeter price chart, 634
Wattmeters, 615
testing and calibrating of, 620
Westinghouse integrating, 625
reading of, 632
connections of, 617
Wave form of current and E. M. F.,
705
meter, 706
Weatherproof insulation, N. E. C,
778
Weaver speed recorder, 754
Weber photometer, 391
Weights and measures, 961
metrical equivalent, 963
of cars, motors and trucks, 470
of copper and brass wire and
plates, 826
of flat rolled iron, 797
of iron, 796
of motor trucks, 464
of plate iron, 800
of round bolt copper, 825
of sheet and bar brass, 825
987
Weights and measures of square and
round bars, wrought iron, 799
Weight of steel, 796
and specific gravity of metals, 975
of rails, 426
Weir dam measurement, 937
table, 938
Weirs, Francis' formula?, 938
Welding by electricity, 691
Westinghouse electro-magnetic rail-
way sytem, 537
Wheatstone bridge, 28, 38
White core wires and cables, 160-166
Winding of armatures, 251
of electro-magnets, 84
Wire rope, galvanized iron, 827
rope, notes on uses of, 958
rope, pliable hoisting, 828
rope, transmission by means of,
827
ropes, horse-power, etc., of, 959
table of A. I. E. E., 143-150
Wires, capacity of, N. E. C, 788
general rules for, National Elec-
trical Code, 771
resistance of, 42
spaces occupied by (table), 91
Wiring formulae, 127
of cars, 475-480
interior, National Electrical Code,
768
specifications for U. S. navy, 730
specifications, N.E.C., 765
Wood as a fuel, 854
bulk, 853
properties of, 818
weight per cord, 854
Wooden beams, safe load, 820
stave pipe, 933
Woods, comparative resistance of,
219
test of American, 819
weights of various, 439
Wright discount meter, 635
Yachts, battery plants for, 571
ADVERTISEMENTS.
WAGNER ELECTRIC MFG. CO.,
^T- LOUIS, XX. <S- J±a
BUILDERS OF
Static Uranfornters
Switcbboarba
(a) For long distance transmission.
(b) For rotaries.
(c) For lighting service.
(d) For power motor service.
(e) For any voltage.
(f) For any unit capacity.
For isolated plants.
For street lailway power stations.
For Central Lighting stations.
For transmission sub-stations.
For high or low frequency single
H.ltC£UatinC$ phase alternating current sys-
Current Motors *e™8: 208 nan M
Jbor 104, 208 or 500 volts.
Direct
Current /iDotors
For 500, 250 and 110 volts direct
current.
Generators for Direct Current in sizes up to 50 K. Wa
Switches of every description for all kinds of service.
Switcbbcarfc
Instruments
Indicating voltmeters.
Indicating ammeters.
Indicating wattmeters.
For alternating and direct current
Butomatic
IRCCiUlatOrS for series alternating current arc lighting.
Wagner Electric Mfg. Go's General Offices and Factory s
ST. LOUIS, SVSO,, U. S. A.
BRANCH OFFICES:
New Orleans : 510 Gravier St.
Foreign Dept.. Havemeyer Bldg., New York.
Mexico City : Chas. L. Seeger, Aparlado, 2100.
London : C. R. Heap. 47 Victoria Street.
Yokohoma, Japan : Bagnall & Hilles.
New York: 203 Havemeyer Bldg.
Boston : 620 Atlantic Avenue.
Philadelphia: 1000 Betz Building.
Chicago: 1624 Marquette Building,
San Francisco: 1 20 Sutter Street.
Paris, France: E. H. Cadiot & Cie, 12 Pue St., Gecges.
General electric! Company
Manufactures, in its own shops,
DIRECT AND ALTERNATING
CURRENT GENERATORS
for Railway, Lighting and Power Work.
RAILWAY MOTORS
and Complete Electrical Car Equipments.
INDUCTION, SYNCHRONOUS and
DIRECT CURRENT MOTORS
for Machine Shops and General Power Purposes.
ARC AND INCANDESCENT LAMPS.
BARE AND INSULATED
WIRE and CABLES,
THOMSON RECORDING WATTMETERS
and every variety of
Switchboard and Portable Instruments.
General Office, Schenectady, N. Y.
Sales Offices in all Large Cities.
WESTON
STANDARD
PORTABLE, DIRECT-READING
Voltmeters and
Ammeters
FOR
Alternating
and Direct
Current
Circuits.
The only Stan-
dard Portable In-
struments of the
type deserving this
Weston Standard Portable, Direct Beaming Voltmeter.
Millivoltmeters, Voltammeters, Ammeters,
Milliammeters, Ground Detectors and
Circuit Testers, Okmmeters,
Portable Galvanometers,
Our Portable Instruments are recognized as the STANDARD the
world over. The Semi-Portable Laboratory Standards are still better.
Our Station Voltmeters and Ammeters are unsurpassed in point of ex-
treme accuracy and lowest consumption of energy.
Weston Electrical Instrument Co,
WAVERLY PARK, ESSEX CO., N. J.
As good as they can be,
A.R.E THE
Zimflars ail Hit lifl Grafle Sjeciallies.
Switch Boards,
Panel Boards,
Feeder and Main
Boards,
Knife Switches,
Automatic
Switches,
Etc., Etc., Etc.
Catalogues, Bulletins and Prices furnished upon request.
ZIMDARS & HUNT,
MANUFACTURERS OF
ELECTRIC LIGHT AND POWER SPECIALTIES,
127 Fifth Ave., New York.
J
;,»«,»
thekftokt, 3xr. a-.
MANUFACTURERS
OF
BARE COPPER WIRE,
RUBBER INSULATED WIRE,
MAGNET WIRE,
TROLLEY WIRE.
ROUND AND FIGURE EICHT SECTION
AERIAL CABLES,
AND OVERHEAD GABLES
FOR UNDERCROUND WORK.
GALVANIZED STEEL STRAND
FOR SUSPENSION AND SPAN WORK.
COLUMBIA and JOHNSTON RAIL BONDS.
BRANCHES:
117 Liberty St., New York. 171 Lake St., Chicago.
"?8 Superior St., Cleveland. 27 Tremont Sts, San Francl9C<k
W. T. C. MACALLEN CO,
338 Congress St., Boston, Mass., U.S.A.
MANUFACTURERS OP
Electric Railway Material
Solid Mica Insulating Joints
Canopy Insulators
Special Joints for Air Brakes
Photographic Developing Trays
MOULDED SPECIALTIES, ETC
The Macallen Solid Mica Insulating Joint
is the recognized Standard Insulating Joint, and ia
approved by all Boards of Underwriters. We test
all Joints with 25 lbs. of Air Pre-sure.
. . WE DESIGN . .
and make Special Insulators for high voltage and.
other special purposes, and pay particular attention
to engineers designs.
CATALOGUE AND PRICE LIST FURNISHED UPON APPLICATION.
Automatic time Switches
ARETO-DAYA VALUABLE AD-
JUNCT .IN ELECTRIC LIGHT-
ING IN GIVING OPPORTUN
ITY TO USE THE CURRENT
AT POINTS NEEDED FOR A
CERTAIN LENGTH OF TIME,
AND THROWING IT OFF AT
A GIVEN HOUR AUTOMATIC-
ALLY.
Tn Shew mindow Display
IT ESPECIALLY COMMENDS
ITSELF. ONE WILL HAVE
LIGHTS BURNING DURING
THE EARLY PART OF THE
NIGHT IF IT CAN B£ TURN-
ED OFF WITHOUT AID AT A
SET HOUR. AGAIN, THOSE WHO HAVE BEEN IN
THE HABIT OF BURNING LAMPS ALL NIGHT CAN
SAVE THE CURRENT AFTER THE HOUR WHEN A
DISPLAY IS NOT USEFUL, THUS SAVING THE
COST OF CUTOUT MANY TIMES BY THE SAVING
OF CURRENT.
the time Clock
SHOWN IN CUT IS A CUTOUT WHICH WE LIST
AT $i5.oo 2 POLE, AND $17.50 3 POLE.
GOOI> DISCOUNT TO TRADE.
WE MAKE IN ADDITION TO IT A TIME CLOCK
WHICH AUTOMATICALLY THROWS CURRENT,
AND ALSO TURNS IT OFF, AND A SIGN SWITCH
WHICH OPERATES TO ALTERNATELY THROW
ON. AND OFF THE CURRENT AT SHORT INTER-
VALS OF TIME, SAY HALF MINUTE PERIODS
64 Cortlandt Street,
C*3
SOKT,
NEW YORK.
The BallS Wood Co.,
BUILDERS OF
p$^ram£pEED.EHI|IE£
FROM 50 TO 1000 H. P,
FOR ELECTRICAL AND POWER PURPOSES.
Office, 120 Liberty Street, Neiv York,
Works, Elizabeth, New Jersey.
It is justly considered a triumph of engineer-
ing skill to build an engine for an Atlantic
Liner which will operate for six days continu-
ously under a practically uniform load at a pis-
ton speed of eight miles per hour.
A Ball and Wood Compound Condensing
Engine, (cylinders 21 in. and 46^ in, x 24 in.),
completed a continuous duty run at 3 P, M.,
August 3d, 1900, of 59 days, 22 hours, with
an overload of 13 per cent, and at a piston
speed of 600 feet per minute, equivalent to a
distance of 9804 miles. This without a hot
bearing or a moment's interruption.
John D. Biggeet, Pres. and Treas.
R S. Robb, Vice President.
John P. Robinson, Sec.
Pittsburgh Trolley Pole Co.,
KEYSTONE
TROLLEY POLES
Manufactured by Patent Process
from Tubular Steel, continu-
ously tapered to any size.
Durable, Shapely and
Strong, Sufficiently
Elastic to Bend and
Recover Perfect
Shape and Strength.
"KEYSTONE."
TRADE MARK
MANUFACTURERS OF
KEYSTONE TROLLEY POLES
PATENT TAPERED.
Mechanical Engineers.
Iron and Steel Workers.
RIVER and INLAND,
BLACKSMITH WORK,
WATERS TUYERES,
BLOW PIPES,
WAGON SKEINS,
WHIFFLETREES.
Works : 1 15- 117 Water Street, \
Offices : Tradesmens Building, )
JL. D. Telephone 177.
Pittsburgh, Pa,
American Vitrified
Conduit Company.
Vitrified Salt Glazed Underground and Interior
Conduits. Multiple Duct. Self Cen-
tering. Single Duct.
CONTRACTORS FOR
Complete Installation
of Conduit Systems. .
General Office : 39-41 Cortlandt Street, New York.
SHOW WINDOW LIGHTING.
Frink's Special Patent Window Reflector.
Lights by reflecting downward and inward, from lamps concealed
in the top of the window, near the glass. The lamps are concealed
from view.
FRINK'S Jk SHADES,
The Best Shades -JSRL AU sizes ancl styles of
made. They reflect ^flRS^ Shades and Clusters.
all the light there is. A Hg !5S^ Every Kind of Elec-
Not the cheapest, but jffiwf ..trie Fixture,
the most econom- ^mj, W Send for Catalogue.
I. P. FRl^R, 551 Pearl St., Mew York.
NOV 5
WXRr e i
NOV 1 1901
H. C. ROBERTS ELECTRO
SUPPLY CO.
831 Arch Street, Philadelphia, Pa.
LINE MATERIAL AND
CONSTRUCTION TOOLS.
Electrical Appliances of Approved Manufacture
always in Stock.
CATALOGUE
OF
ELECTRICAL BOOKS,
Eighty Pages, Alphabetically Arranged,
Classified by Subjects and Authors,
SENT GRATIS ON APPLICATION.
D. Van Nostrand Co.,
PUBLISHERS,
23 Murray and 27 Warren Sts., NEW YORK.
Live Music Archive
Librivox Free Audio
Metropolitan Museum
Cleveland Museum of Art
Internet Arcade
Console Living Room
Books to Borrow
Open Library
TV News
Understanding 9/11