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35 WEST 33RD STREET ^.y 1017 

CHICAGO, IL 60616 may, lyi/ 

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Fig. No. 

D.C.Brj^ak Itagnet ] 
Conicai P]ungere 2-3-4 
A.C.Brealr Magnet 5 
Compound Over] oad 6 
Series Overload with I.T.E. 7 
CDapper Switches v-ith norrnaDDy opened con- 
tacts 8 
C3apper svcitches vuth norma] 3 y closed con- 
tacts 9 
Clapper switches with open and closed con- 
tacts 30 
D.C, Magnetic lockout switch ID 
A. C. Clapper switch 12 
Three-phase relay 13 
Vihrg.ting relay 14-1 5-1 6 
Clapper switch and D.r. series relay 17 
Diagram sewage control panel l8 
photograph B fi » ]^ 
A. C, Thermostat Panel 20 
Photograph of A.C. thenriOPtat panel 21 
A. C. Potential starter 22 
Diagrams - starting ststions 23 
A. C, Secondary resistance starter 24 
D.C. Pump controller 25 
A, C. Shovel heist 26 
A.C. •• swing 27 
Photograph Shovel Hoist and Swing Panel 28 
Semi-Automatic Printing Press Diagram 29 
Photograph of " " Controller 3© 
Full Automatic « « « ^] 
A.C, Semi-Automatic Elevator 32 
D.C. « « « 32A 
Photograph Semi-Automatic Elevator 32B 
D.C, Full Automatic Elevator 320 
A.C. « « ■ 33 
Submarine Ammunition Conveyor 33A 


jq CofJ-noo »s = 

Submarine Subicerglng Contro]3er 34 

* Prope] ] ing •« 34A 
" Signal V'orlr 35 

" BaDJast Centrifuga] Pump ControDDer 36 

* CircuDating Water Pump " 37 
A.C. Coa3 Tower 38 
A. C. Skip hoist 39 
Kramer System Ki3 3 ControDler 40 
Transfer Pane3 4] 
Machine TooD Control 3 er Non-Rerersihle 42 

•• " " Reversil:)3e 43 

A.C, Washing Machine Pane] 44 

D.C. « H « 4^ 

A.C. Extractor " 46 

D.C. « » 47 

Photograph - Laundry Pane3 48 

A.C. Coke Handling Equipment 48a 

D.C. " « •• 49 

D.C. Ore Un3oader 50 

A.C, Mine Hoist 53 

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Pump Starters 

Electric Shove] Control 

Printing Press Control 

ED evator Control 

Su'bmarine Controlling Equipment 

Coal Hand] ing Control Equipment 

Blast Furnace Control 

Mi] 3 Control 


Laundry Machine Control 

Special Coke Handling Apparatus 

Ore Unloader 

Heavy Duty Hoist Controller 










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TViis thesis is intended to cover tV>e 
operation of e] ectro-magnets as applied to motor 
controD , No attempt has "been made to enter into the 
theoretical explanation of the principles involved; 
this in itself would constitute a thesis of unusual 

The first chapter, a classification of electro* 
magnets, consists of a "brief outline of electromag- 
netic switches, v'ith such explanation of construction 
and operation as will familiarize the reader with the 
various types of switches considered in the following 

The succeeding chapters constitute a discussiofi 
of standard and special types of controlling equip- 

The rapid development of el ectro- magnetic 
switches during the past century has been unusually 
surprising. The effect which an electric current, 
flowing in a wire, can exercise upon a compass 


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need]e, was discovered hy Oersted in 3820, Research 
work by Arago , Ampere and Davy quickDy fo3 3owed. In 
the Matter part of 3 820 Arago announced that a copper 
wire carrying a current y/ou3 d attract iron f i3 ings. 
But it was not unti3 3 825 that the e3 ectro -magnet 
was discovered. At that time WiDiiam Sturgen construc- 
ted severa3 e3 ectromagnets, showing in his experiments 
that the po3 es of the magnet cou3d he reversed by 
winding the wire about the iron in the opposite di- 
rection. His first pub3ic3y exhibited e3ectromag- 
net weighed about seven ounces and was ab3 e to 3 if t 
a 3oad of nine pounds. 

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In ordinary practice it has been found 
convenient to classify solenoid switches in three 
general groups. (l) Plunger type electro magnet 
without fixed core and a movahle armature. (2) 
Plunger type electro magnet with a fixed core and 
a movable armature. (3) Clapper type magnetic 

The essential parts of electro magnetic 
switches are the contacts, blowouts, magnet coil 
and the frame. 

The type of contact depends on the duty 
which the switch must perform. Cqcybon as a general 
rule is used only on auxiliary contacts which are 
not subject to severe and constant duty. Solid 
copper is now used on contacts which carry and 
rupture normal values of current up to about one 
thousand amperes. This type of contact should 

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.hn:\0 J i% i 


close with a rolling motion to prevent the first 
rush of current from welding them, or pitting the 
final carrying surfaces. For higher current val- 
ues it is common practice to use laminated copper 
brushes in addition to the solid ones, making and 
breaking the current on the solid contacts, other- 
wise the laminations would soon be welded togetheo 
The blow-out coil is a very essential part of 
the larger switches since it is necessary that the 
arc be broken as soon as possible to prevent burn- 
ing of the contacts. The coil is connected in 
series with the circuit through the contacts, the 
current passing in such a direction that the mag- 
netic field set up due to the sudden decrease in 
current tends to blow the arc away from the switch 

The magnet coil must be so designed 
that when energized, ittwill positively and in- 
stantly close the contacts on a range of voltage 
from twenty percent below to fifteen percent above 
normal. The insulation of the coil must stand the 
required high voltage test as well as any traces 
of moisture and acids, or a considerable rise in 


The frame of the switch must in the first 
place be designed with mechanical strength such 
that it will stand up under very severe use. It 
must be of such design that the iron will not be 
over-saturated when the coil is energized and in 
the case of alternating current switches) it should 
be of a laminated structure. When the coil is de- 
energized, the magnetism must break down instantly 
to permit the switch to open at once. 

Plunger Type Electro Magnet Without 
Fixed Core and a Movable 

This form of electro magnet is not used 
to a very great extent. One of the most interest- 
ing applications is its use in the manufacture of 
circular loom for cleaning the inside of the final 
product. The coil of the magnet is placed around 
the loom with the plunger inside and is of such 
strength as will hold the plunger within its mag- 
netic field when the loom is drawn through it; the 
plunger acting as the cleaning tool. 

?ig. 1. 


Plunger Type Electro-Magnet With Fixed Core 
and a Movable Armature. 

Brake Magnets. 

The D.C, brake magnet, one of the simplest 
forms of the plunger type electro magnet, is shown 
in detail in figure (l). -From this sketch is can 
readily be seen that the coil is well surrounded 
by a solid soft iron frame which affords a very 
efficient return path for the flux and a protection 
from external injury. The design of the frame and 
coil depend upon the load, length of travel, du- 
ration of excitation, and the interval between ex- 

The cross section of the plug and plunger 

^'"9 3 

^n V 

^/j a. 

depends upon the magnetic flux required to produce 
the pre-determined pull. In case a short stroke is 

#3 3 

required, a plug and plunger with flat sealing sur- 
faces is preferable. However, if the stroke is of 
considerable length, it has been found necessary 
to make the sealing ends of the core and plunger 
conical. The reason for this may be explained by 
reference to figures 2,3 and 4. 

At the beginning of the stroke the forces 
tending to close the switch are represented by F 
and Fi , figure 3, th8 resultant being R. As the 
plunger nears the plug the forces F and F^^, pull 
in a direction nearing 90° to the resultant R, as 
shown in figure 4. The resultant force R therefore 
keeps getting smaller. The result is that we have 
a strong pull at the commencement and a weaker pull 
at the sealing point. This prevents the switch from 
jvimping in with a hammer blow as would be the case 
with the flat surface plunger. 

The alternating current brake magnet, 
figure 5, is essentially the same as the D.C, brake, 
except that the plunger and frame are made up of 
laminations, to cut down hysteresis and eddy current 



Fig. 55 



A simple modification of the brake mag- 
net is found in the overload. This magnet is de- 
signed for continuous duty, its coil or coils carry- 
ing full load current at all times. The ampere 
turns are calculated to produce a flux of such 
strength as will permit the plunger to remain in 
the unsealed position on normal load current of the 
motor, "but in case of an overload, the plunger will 
come into sealed position at the same time opening 
an auxiliary contact which in turn opens the main 
line switch. 

Overloads may be grouped into four class- 
88;(l) Overloads with series coils. (2) Compound 
overloads. (3) Overloads with an inverse time ele- 
ment. (4) Overloads with an inverse time element 
with instantaneous trip on excessive overload. 

The series coil overload consists of a 
single coil connected in series with the armature 
and s-cts instantaneously on an overload. When the 
equipment trips thus opening the main line switch, 
the coil of the overload is de-energized and the 






1 1 

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Pig. 6. 
Conipoui.d Cverloed. 

Inverse Tiue Element Overload. 


#3 6 

plunger drops into the unsealed position. 

The compound overload, figure 6, is made 
up of two coils, one in series with the armature 
circuits, and the other across the line ahead of 
the main switch. In case of an overload both coils 
act to draw the plunger into sealed position, thus 
opening the main line switch. In this case however, 
the plunger does not drop into normal position be- 
cause the shunt coil remains energized until the 
shunt circuit is opened by the operator, usually at 
some remcte point by means of a snap switch. 

An overload with an inverse time element 
shown in figure 7 is a series overload, the instan- 
taneous operation of which, is checked by means of a 
dash pot. This relay will not operate on momentary 
overloads or line surges. The heavier the overload 
the quicket the operation. The action of the relay 
can be made instantaneous on excessive overloads 
by addition of a calibrated valved in the piston of 
the dash pot. 

Clapper Type Magnetic Switch. 

The clapper type magnetic switch is essen- 
tially a horse shoe magnet with a coil on one leg, 
the armature being hinged in such a position that 



Pig. 8. 




.i- ■5^^^^^.^3iP^ 

Pig. 9. 


it completes the magnetic circuit when the switch 
is closed. There are many modifications of this 
type of switch, several of the more important forma 
are shown in figures 8 to 11 inclusive. 

Figures 8 and 17 show clapper switches with 
one normally opened contact. This type of switch 
is also made with two or more contacts, each style 
as a usual thing being held open iDy gravity and 
magnetically closed. 

A switch with normally closed contacts is 
shown in figure 9. This switch is held closed by 
springs or gravity. The spring is used in case a 
quick and positive operation is required. 

A combination of the open and closed types 
is shown in figure 10 and is used to control and 
operate many combinations tf control circuits. 

Figure 11 shows a very interesting modification 
of the clapper switch and is known as the D.C. mag- 
netic lock-out switch. This switch consists of 
two coils in series, one coil acting to close the 
switch and the other tending to open or lock it 
out. The closing coil '•C has more turns than 

Fig. IC. 


■ ./\ ' 

-d .; 

?ir. 11. 


the lock out coil "L". The closing coil has a 
complete iron circuit for the flux whereas the 
lock-out has not. The' cross section of the iron 
circuit of the closing coil is of such size that 
it will be over- saturated by the inrush starting 

The lock-out coil is of such design that its 
pull will be stronger than that of the closing coil 
on the inrush current and the switch is held open. 
As the current drops to normal the pull exerted 
by the closing coil remains about constant whereas 
the lock-out coil's pull weakens and at some pre- 
determined value the switch will close. 

The A,C, clapper siwtch, figure 12, is almost 
invariably required to be double pole. In case of 
a three-wire three-phase circuit, the two-pole 
switch is sufficient to open the entire circuit. 
As to a four-wire two-phase, one line of each 
phase is opened or else two switches are used. 

Three- Phase Relays. 

The three-phase relay, figure 13, is 
used with a slip ring motor in order to cut out 










Pig. 12. 
^ C. Clapper- arltoh. 

/=>S. ^3 



the several steps of starting resistance. These 
relays are shorted out after a few seconds of 
operation and are therefore designed for very 
intermittent duty and are correspondingly light and 
sensitive. Three-phase relays are manufactured 
with three separate coils and are so connected that 
they form the star point of the resistance in the 
secondary circuit of the motor. These relays are 
short circuited when corresponding resistance steps 
are cut out of the circuit by the succeeding clapper 
switches. Due to the fact that the relay forms the 
star point of the resistance, the potential differ- 
ence "between any two points of the relay is very 
small, therefore, the insulation "between coils is 
very slight. 

To prevent this relay from pumping on low fre- 
quencies, the three equal coils are connected in 
the three phases of the secondary circuit with one 
end of each connected together. With this connec- 
tion the total pull exerted will be constant re- 
gardless of the frequency if the Current is balanc- 
ed and constant. It is very important that the relay 


does not pump up and down with a change in frequency 
because the frequency in the secondary changes from 
that of the primary frequency at stand-still to as 
low as one or two cycles at normal speed, depending 
on the percent slip. 

Some relays do not have the three coils connect 
ed to form the star point of the starting resist- 
ance in vilnidh case the coils are heavily insulated. 
Relays of this type when connected "between the re- 
sistance and the slip rings of the motor are known 
as jam relays. The jam relay is used to re- insert 
resistance in the rotor circuit of the motor when a 
certain maximum torque is reached, so that if the 
motor is stalled by encountering an excessive load, 
the torque will be automatically increased up to the 
maximum which the machine can operate. This avoids 
stalling the motor with the resistance short cir- 
cuited, which would result in opening the circuit 

Vibrating Relay, 

The vibrating relay, figure 14, is a 
spring opened single-pole clapper switch of very 

Pig. 14. 
Vi^bratinf^ Relay. 


light and sensitive construction, used to auto- 
matically accelerate the motor by varying the shunt 
field current. The operation of this relay may be 
explained by reference to figure 15. 




The shunt field of the motor is connected 
through the clapper switch contacts wdiich are shunt- 
ed by a variable resistance. The relay coil is 
wound in two separate series sections, each in the 
same direction and carry the armature current. 
When the main line switch closes (not shown in the 
diagram) the inrush current closes the relay .cutting 
out the resistance R, thereby increasing the shunt 
field current which reduces the inrush current. As 
the motor speeds up and the inrush current drops to 


a pre-detennined setting, the relay will open, re- 
inserting the resistance in the shunt circuit. 
This causes an increase in speed with the second in- 
rush of current of somewhat lower value than the 
first. The relay will repeat , through this sequence 
of operations until the motor has attained full 


^/y. /e 
It can readily be seen that the vibrating re- 
lay when used in connection with one or more arma- 
ture accelerating switches, affords a very effect- 
ive means of producing a smooth acceleration. When 
the last accelerating switch closes, it shorts out 
one section of the coil. Now in case the motor is 
overloaded to about 150 percent, the current through 


the coil L will be sufficient to close the relay 
and slow up the motor. 

By winding the two coils of this relay differ- 
entially and connecting one in series with the arma- 
ture and the other across the line, as shown in fi- 
gure 16, the relay can be used as a protection from 
overhauling loads. Under normal operation of the 
motor, this switch is held closed by the current 
through the series coil. In case of an overhauling 
load the motor will act as a generator, the rever- 
sal of current will drop the relay, reinserting re- 
sistance in the field circuit, thus lowering the 
generated voltage preventing the motor from pumping 
back into the line. 

D.C, Series Relay, 

A D.C. series relay shown in the lower 
part of figure 17, is a small clapper type, normally 
closed switch, held in position by an adjustable 
spring. The stationary contact of the switch is 
also adjustable to permit the changing of the mag- 
netic gap. 

In operation, this switch will be opaied by 
an inrush of current, thus breetking the control 

Pi(^. 17. 

iSfl I^UfCB 


circuit of the next accelerating switch. As the 
current decreases in value, the relay will close. 
The opening and closing point of this relay being 
determined by the length of the air gap and spring 

In the manufacture of motor controlling equip- 
ment, combination of the foregoing electro magnets 
are assembled on panels, forming a self starting 

Plunger Type with Self Starters. 

Plunger type self starters are of two 
gneral classes, the gravity or dash-down type and 
the dash-up type. These starters are always made 
with conical ceiling ends to the plunger and core. 
The otherwise rapid operation of this equipment is 
checked by means of a dash pot which may either be 
an air or oil dash. The oil dash is used where the 
apparatus is subject to great changes in external 
temperatures. The oil is one the viscosity of which 
doew not vary with ordinary changes of temperatures. 

Potential Type Self Starters. 

The potential self starter is an A.C, 



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equipment in which the motor is started from the 
lovr taps of a transformer, being thrown directly 
across the line after the motor has attained about 
fifty percent full speed. This operation is accom- 
plished by menas of a timed relay and several clap- 
per switches depending upon the size of the motor 
and number of transformer taps. 

Primary and Secondary Resistance Self 

The primary resistance self starter is 

used to cut out one or more steps of resistance in 

the primary circuit of a squirrel cage induction 

motor. This action is produced by means of a timed 

relay and two or more clapper switches. 

The secondary resistance self starter is si- 
milar to the primary stqrter. The circuits in 
this case being controlled by a timed dash pot and 
two or more clapper switches, or three-phase re- 

D,C. Clapper Type Self Starter. 

A D, C. Clapper type self starter is one 
in whicli the acceleration is controlld by a combina- 
tion of D. C. Clapper switch and series relays; 


clapper and lock-out switches; and clapper and timed 
limit relays. 


The constantly increasing dernand for - 
pumping machinery has led to the development of 
various types of equipment. 

For installations where the requirements 
are limited to starting the apparatus at a pre- 
determined time the hand starter is usually entirely 
satisfactory. But for most installations the re- 
quirements on the demand of the pump are such that 
the starting and stopping time are not known in ad- 
vance, such as in the case of a fire pump connected 
to a sprinkler system. 

The advantages of the solenoid operated 
starters are that a float siwtch in connection with 
a gravity system afford a means of maintaining 
fixed limits in water level in reservoir; or by 
means of a pressure gauge, the pressure of a com- 
pressor or vacuum system can "be held "between fixed 
limits; the saving in operating cost, because the 
motor is operated only when needed. 

LO 89q[\i 


In some instG^llations such as mine pumps, it 
is essential that the controller automatically re- 
start the motor after a voltage failure and subse- 
quent restoration of the supply. 

In order to start some motors which have a 
very large starting load it is necessary to use an 
unloader solenoid in connection with the starter, 
which removes the load during starting. 

Sewage Elevation Controller. 
A very interesting pannel for controlling 
pumps in connection with a sewage system, is shown 
in diagram 18. This panel is designed to operate 
four pumps in connection with a sewage disposal 
plant. A photograph of the panel is being shown in 
figure 19, The number of pumps required for service 
depend upon the head of sewage in a large reservoir, 
the object of the panel is to automatcially start 
and stop one or more of the pumps as the case may 

The essential parts of this equipment are, 
four identical motor control panels, 1-3-4-5, a 

Fig. 18, 

Pis. 19. 
Swnrage Pumping Station Panel 


general control and meter panel 2, and a five point 
float switch. The motor control panels are poten- 
tial self starters. Each pannel is equipped with 
a dash-pot relay and two clapper switches. The gener- 
al control has two wattmeters, a knife switch, clap- 
per switch and Flug board. The plug "board is 
used for connecting the motors in such a manner 
that they can be operated in any desired sequence. 
For convenience consider that the flow of se- 
wage has been light and the tanks almost empty and 
pumps not operating. As the sewage rises in the 
tanks the first contacts 1 and L of the float switch 
close completing the circuits for the clapper switch 
T. T then closes connecting the low voltage tap of 
the transformer to the buss bar. As the sewage con- 
tinues to rise the second contacts 2 and L of the 
float switch close, energizing the clapper switch S, 
and the dash -pot relay. The clapper switch closes 
starting the motor on low voltage. As the timed 
relay closes, it opens the circuit of switch S, 
dropping it out and instantly closing the circuit of 
S2, placing the motor direct across the line, If 


MS 3 


the pump started has not sufficient capacity to 
handle the incoming sewage, the othea* motors will 
te started as their control circuits are closed 
through the contacts of the float switch. 

Ae the sewage recedes the pumpswill be cut 
out, by operation of the float switch, in the re- 
verse order to which they were started, 

CompresBfir Pump Starter. 

A thermostat control panel for a small auto- 
matic refrigerator plant is shown in diagram 20, 
The essential pK" ts of the equipment are two A»C«,SW., 
timed relay, two overloads, high pressure cut-out, 
thermostat, and the usual knife switches, fuses and 

The apparatus is for operating a two- phase 
four-wire induction motor, connected to an ammonia 
compressor. When the temperature of the refrigera- 
tor becomes warm, the thermostat closes the con- 
tacts H and 0, energizing relay R, which closes 
energizing relay D, The relay D in closing places 
a short across the two overload coils then closes 
the circuit of the main line switch M. This opera- 

Pig. 2C. 
A. 0. Tiiermostat Control Psnel. 


tion throws the motor across the line and also 
opens the circuit of the timed relay D, which starts 
to decend to its original position. As D, decends 
it closes the contact for the switch 1 R, which 
shorts out the resistance in the rotor circuit; 
it next removes the short from the two overload 
coils. The motor then operates at full speed. As 
the refrigerator cools off, the thermostat closes 
the contacts and C, short-circuiting the coil of 
relay R which open the contact circuit and shuts 
down the motor. 

A photograph of a three-phase thermostat con- 
trol panel is shown in figure 21. 

Potential Pump Starter. 
A potential starter for pumping equipment as 
may be used for small installations, is shown in 
diagram 22. The motor here shown is two- phase, four 
wire, but by making changes as noted on the diagram, 
a two-phase, three-wire, or a three-phase induc- 
tion motor may be used. The control equipment is 
made up of three magnetic switches, one timed re- 
lay; two inverse time element relays and one po- 



Thermostat Panel 
Pig. 21. 

Fig. 2'^.. 
A. C. Potential aterter. 


tential 8ta;rter. 

This paiel ia controlled by connecting the con- 
trol lines C, K, and LX to the corresponding lines 
of any of the three wire starting stations shown in 
diagram 23. )l?hen the starting connection is made, 
the switches Si and S2, and the timed relay D are 
energized. The switches close and the motor is 
connected to the low voltage taps of the trans- 
former. As the timed relay nears the end of its 
stroke the circuit of the switch S2 is opened and 
the circuit of S3 closes. On closing the switch, 
S3 opens the circuit of 83 and connects the motor 
across the line. This leaves the motor operating 
at normsj;! speed with the timed limit over-load 
protection and may be stopped in the usual manner. 
The switches S2 and S3 are mechanically interlocked 
so that they cannot be closed, at the same time 
short-circuiting a part of the transformer. 

Secondary Resistance Starter. 

A Secondary resistance type self start- 
er as may be used in connection with small pumps, is 
shown in diagram 24, This equipment is for a three- 
phase wound rotor induction motor and consists of 


Fig. ^3. 
Starting Stations. 

?iS. PA. 
A. 0. aacondary Resistanoe barter. 


one main clapper switch, one gravity type timed 
accelerator, tv^o inverse time element overloads. 
When the power is thrown onto this apparatus, by 
closing the knife switch the timed accelerator is 
brought to its upper-most position opening its own 
control circuit. This operation de-energizes the 
acclerator but it is held in position mechanically. 
It also closes the pick-up circuit for the main 
switch, thus preventing the motor from being thrown 
across the line with its secondary resistance short- 
circuited. To start the equipment, the start button 
is depressed, closing the main switch. The main 
switch on closing, starts the motor and also trips 
the latch of the accelerator. The accelerator de- 
scends cutting out the resistance. In case the motor 
is shut down either by pushing thestop button or by 
an overload, the main switch will open and the ac- 
celerator will again come to its uppermost position. 

In case this equipment is being used on a va- 

cuum system of / demand and where it is not neces- 
sary to run the motor at full speed, an attachment 
may be added to the accelerator by means of which 


its descent may "be stopped at any position. This 
€tttachment may "be made so tViat the fina3 position is 
set eitVier mechanica] Dy at tVie starter or e3ectric- 
a3]y from a remote point. 

r..C. Pump Starter. 
Figure 25 shows a wiring diagram for a ] ockout 
se]f starter, v/ith either tvro or three wire control 
as used for driving pumping machinery. This equip- 
ment consists of: one main switch, and four mag- 
netic 3oc]!rout switches. The contrcD wires L-C-K 
m.ay "be connected to any of the controDDing devices 
shown in figure 23. The apparatus is started by 
cDosing the contact of the start sv.'itch. This ener- 
gizes the main svdtch coi] closing it, which starts 
the motor with a]] the resistance in the circuit, 
and a] sc cuts in a protecting resistance. The motor 
is "brought up to speed "by the action cf the four 
magnetic loclrout switches. The Dast 3ocV-out switch 
is equipped with a shunt coi3 which ho3ds the switch 
c3osed through a]3 variations of 3oad, 

Fig. ?.5. 
B. C. Pump Controll«T. 




The first electrically operated shovel 
used direct current motors but on account of the 
necessity of transmitting the power, to the shovels, 
usually over long distances, most of the shovels 
are now equipped with alternating current motors. 

The ordinary electric shovel is equipped with 
three motors, one each for hoisting, thrust and 
swing. On the large type of shovel it has teen 
found that the automatic control, although consum- 
ing more power, will handle more ground in a given 
time than will a non-automatic. However on the smal- 
ler type of machine the drum type control is used 
on the swing and thrust, the hoist usually being 

The hoist control equipment is shown dia- 
grammatically in figure 26. The hoist motor is 
usually a wound rotor induction motor. The control 

Pig. 26. 
A. 0. 3iovel Hoist Controller. 


panel ia not equipped for reversing the motor be- 
cause there is always sufficient load to overhaul 
the motor when brakes are released. The essential 
parts of the hoist panel are: circuit breaker equip- 
ed with series overloads; main line switch, five 
accelerating switches, four accelerating three- 
phase relays; four jam relays and one drum master 

In hoisting, the motor can be brought up to 
full speed automatically by placing the master in 
the high speed position, 6. With the master in this 
position, the main and first accelerating switches 
close. The inrush of current energizes the first 
accelerating relay R2 which opens and remains open 
until the current drops to a pre-determined value, 
permitting the relay to close and energize the se- 
cond accelerating switch 3R. The operation con- 
tinues through the remaining relays until the motor 
is at full speed. If the operator wishes to run 
the motor at any intermediate speed he can do so 
by placing the master on one of the intermediate 
points. There are six different speeds to select 

lin- i, " i; 


For convenience, suppose the dipper is hoist- 
ing through soft ground and suddenly encounters an 
excessive heavy otstruction, tending to stall the 
motor. For just such emergencies this controller 
is equipped with four jaming relays: j^ » J2» ^Z* 

J4. Each relay is set to open and close at differ- 
ent current values. If the otstruction is light, 
the ja.m relay j]^ with low calibrations will open, 
cutting out the last accelerating switch 6R, thereby 
reinserting resistance in the rotor circuit, and 
automatically increasing the torque up to the maxi- 
mum which the machine can stand. This prevents stall- 
ing the motor with the resistance short circuited, 
which would result in opening the circuit breaker 
and loss of power. Had the obstruction been very 
heavy, more of the jam relays would have operated. 
If it would be possible for the motor to hoist 
through the obstruction at a low speed depending 
on the number of jam relays that operated, the hoist 
motor would continue at low speed until past the 
obstruction. It would then be automatically accel- 
erated to full speed. In case the dipper strikes 

, J 3 lift 111' 


a load sufficient to stall the motion instantly, 
the hoist motor which is operating at a high speed 
could not be stopped at once without some injury 
to the moving parts. The momentum of the motor 
in this case is absorbed in a friction clutch. 

The swing motion is controlled by a full 
reverse automatic selfstarting equipment shown dia- 
grammatically in figure 27. The panel is equipped 
with: circuit breaker with series overloads, two 
reversing main switches, four accelerating switches, 
four accelerating relays and one master controller. 
The operation of this panel is the same as that of 
the hoist except that the motor has reversing swit- 
ches and there are no jam relays. The accelerating 
relays on this panel are very essential because the 
inertia of the boom is very high and if the acceler- 
ation was too fast the shovel would be lifted off 
the track. In the case of a drag line where the 
boom is very long, the adjustment of the accelerat- 
ing relays is of still greater importance. 

The thrust motion of the shovel is controlled 
essentially the same as the swing except that suf- 
ficient permanent resistance is left in the secon- 

Pig. 27. 
j^^ C. 3iuvel a^ing C^ntrullpf. 


dary circuit so that the speed torque curve is near- 
ly a straight line when the controller is in the 
maximum to have the bucket follow the curvature 
of the "bottom of the pit without danger of wrecking 
the machine by exerting undue stresses on the thrust 
and hoist motor. 

A photograph of the hoist and swing panels 
are shown in figure 28. 


ijl&a«q gax 



Pig. 28. 




Many experiments on tVie drive and con*ro] of 
Darge printing presses made "by tVie leading printers 
of this country, during the past year, has resulted 
in the unaminous selection of an automatic two-mo- 
tor control system. 

Such a system must meet the following require- 
ments: (1) Slow and uniform threading in speed, (2) 
Smooth acceleration and decel leration. (3) Must 
quickly slow down and again accelerate. (4) Be ahle 
to operate continuously at various speeds to accommo- 
date different grades of paper, (5) Shut down the 
press from various points ahout the equipment, (6) 
Control should he simple and substantial. (7) Must he 
possible to quickly stop the press without imposing 
too great a stress on the paper. 

When the press is started it is run at a very 
slow speed to enable the operator to feed the paper 
over the various rolls and avoid tearing the paper. 

CmMaiiiJ dl> 


After tVie paper has "been adjusted through the entire 
press, it is permissihDe to run the apparatus at a 
very high rate of speed. Due to tearing of the pa- 
per, uneven suppjy of inV, etc, the press usual 3y 
operates on s] ow speed about ten or twenty percent 
of the time. It is much more efficient to use a 
ema]] s] ow speed motor for this purpose than to 
operate a 3arge high speed motor at a slow rate of 
speed. Therefore, tVf-c motors are used on most of 
the large presses, 

Semi-Automatic Control. 

A wiring diagram for a semi-automatic A.C, 
control system is shown in figure 29. The essen- 
tial parts of this equipment are two main magnetic 
switches, one controlling the large and the other 
the small motor; hand operated secondary resistance 
regulator; tvtro series overloads in the large motor 
circuit; three protecting fuses in the slow speed 
motor circuit; one small clapper switch controlling 
the "brake solenoid and a two-pole Vnife sv.itch. 

The two-pole knife switch has tv^o functions to 
perform; when thrown down it releases the hrakes 

f='S' 2^ 


of the press and a3 so opens the controD circuit, per- 
mitting the operator to turn the press by hand and 
at the same time making it impossihDe to start the 
motor. When thrown in the up position, the control 
circuits are Cjosed. 

T^-e start switch on the pane] is a norma] ]y 
opened push hutton and may -be connected in para] 3 e] 
with any number of starting switches about the print- 
ing press. The stop button is a norma] ]y closed 
push button switch and is cornected in series with 
the run ajnd safety buttons which wi]] remain in 
either the closed or open position. These two 
buttons may be connected in series with any number 
of siffiiDar sets of buttons. 

At several points on the press, switches in- 
stalled are in series with the large motor control 
switch and are held in the closed position by the 
paper. In case the paper breaJrs.the switch opens, 
shutting down the press. 

To start the press the handle of the secondary 
resistance starter must be in its extreme starting 
position in order that the control circuit of the 


sma] ] motor wiJ] "be cDosed tVirougb its auxiDiary 
contacts. If a] 3 tVie run and safety stop switches 
are c3osed and in tbe running position, the sma]] 
motor can "be started "by closing one of the start 
"buttons. This sma] ] motor is a three-phase squirre] 
cage induction motor. 

The press can te run at a high rate of speed 
by revolving the regulator by hand to the next 
auxiliary confact, closing the circuit for the large 
motor switch, which on closing, opens the svdtch 
for the small motor. From this point the speed is 
controlled by the hand regulator. The large motor is 
a vound rotor three-phase, induction motor, the 
regulator varying the resistance in the rotor or 
secondary circuit. 

„ The apparatus may be stopped by an overload, 

tripping the overload relay; a brake in the paper 
opening the paper brake switch, or by pushing the 
safety or stop buttons, A photograph of a duplex 
semi-automatic printing press controller is shown in 
figure 30. 



Pig. 30. 

it.c. s«ii - MJfOi'Afic nm. mrtm miKTtm f^ss mmm:u:m 


TtiZZ Automatic. 
An A.C. foj] autoaiatic prirtiz^ press control]- 

isg equipaent is srctm in dia^ras 3^' In addition t* 
t're sejcl automatic apparatus, t^^is ^saiel consists of: 
noxB&lJy open •on* and toff* switc'res, rcrma3 3y 
closed stop and safety s'witches, rctor operated speed 
reguj ator. 

YTie operating fe^tares are the same as t'rose cf 
the seEi-auto3Eatic except that the secondary circuit 
of t*-e large actcr is meter operated. The eq-ipm^t 
is started "by pressing the "on^ 'button, energizing 
the "on* switch, the sBia3 3 meter s-»itch and the 
■bralre re]ay, a: =o the pi3ot or rheostat ictor. The 
pijOt motor will coirtlnue to operate as Z zns as the 
•on* siwtcr is energized. Its operation will "be 
stopped if the •on* "button is released before the 
press is at fuj 3 speed, and the press motor »iJ3 con- 
tinue to operate at that speed. As this Motor oper- 
ates, it »il ] shut dOTRi the ssaZ j xotcr and start 
the large one, as ir: the case of a sesni-autosatic. 
The pilot Eotor is autoaiatica: ly stepped at "both 
ends of its tra-el . 

PIG. £1 


If the press is running at high speed, it can 
"be sDowed down by hoDdirg in the off "button untiD 
the speed has been reduced to that desired. 

If at any time the safety button is pushed it 
wiDD be impossible to speed up the motor but it can be 
slowed down or stopped. In case the motor is stopped 
it cannot be started until the safety switch is open. 


TVie development of electric motors on 
control equipment particularly suited to the work 
of operating passenger and freight elevators, has 
resulted in a most satisfactory system of operation 
The controlling equipment of passenger elevators 
is subject to very severe operation, due to the great 
number of times which the motor must be stopped and 
started and often times suddenly reversed to permit 
the car to make an even landing. Due to the quick- 
ness of operation required to give good service, the 
full magnetic equipment provides the best control 
system. On the other hand, for freight, service, 
where the speed is slow and operation infrequent, it 
seldom pays to install an expensive electric con- 
trol , the mechanical or semi automatic equipment be- 
ing most satisfactory. 

In designing any system of elevator control 
the primary consideration is safety and is often 


times overlooked in an attempt to give service, the 
rea3 prolaBem of the passenger e] evator. For the 
greater part the control equipment is ca]]ed upon to 
perform the following functions: First: to accelerate 
the motor automatically under all conditions of load 
"by cutting out starting resistance hy means of ser- 
ies relay or dash pot control. Second: to control the 
speed by cutting resistance in or out of the shunt 
field circuit in D.C. equipment. Third: to hring the 
elevator to a quick smooth and accurate stop at all 
landings, regardless of load. With a mechanical 
brsk-e it is not possible to obtain a smooth accurate 
stop, due to the fact that the elevator will coast 
farther with a heavy than a light load. The energy 
stored in a moving mass is proportional to the square 
of the velocity. The mechanical brake is capable of 
absorbing this energy in direct proportion to the velo- 
city, while the dynamic brake will dissipate energy 
proportional to the square of the velocity. A combi- 
nation of these two brakes gives the best results. 
Fourth: to disconnect the equipment from the line 
in A.C. system, when operator has lever at the off 


position. In D.C. apparatus, the shunt fie]d of the 
motor is partia]3y excited when the motor is at rest 
This arremgement gives a quicker start than is the 
case when the fie3d circuit is open, and results in 
a saving of both time and energy. 
Semi Automatic Contro] , 

Referring to figure 32, a wiring diagram of 
an A.C, semi-automatic freight elevator control. 
This equipment controls a squirrel cage motor and 
consists of two essentia] parts, a reversing drum 
and the main switch. The drum is located at the 
motor and is operated "by cables from the elevator. 
In the rotation of the drum the contacts for the 
main line current are closed before the control cir- 
cuit of the main line switch. This prevents the 
making or breaking of the current on the contacts of 
the drum. The contacts of the main STfitch are 
equipped with blow-out coils. The control circuit 
for the switch passes through the limit and slack 
cable sv/itches. 

The limit switches, usually consist of a final 
up and down switch, which stop the car at the top 

Fig. 32. 
A. 0. 9=»mi-jintoTGetic T^levetor Cor^rolle?. 


and bottom if t>ie operator faiDs to bring the equip- 
ment to a stop. When the car opens, the up Dimit, 
it is impossib] e to move the car in the up direction 
tut it can operate in the downward direction. In 
addition to the tv/o 3 svdtches it is customary 
to add tv'o over-trave] limits so that in case of 
failure of the stop Dimit switch, the car wi]] "be 
stopped "before any damage can "be done to the ma- 
chinery. If the car does over-travel , it is im- 
possible to move the elevator in either direction. 
After the trouble has b'^'en located the car can be 
moved by either short circuiting the limit switch 
or by closing the line switch by hand." The floor 
limit switches may be hatch switches or they may be 
traveling cam limit switches geared directly to the 
hoisting drum. 

The slacV cable switch is a safety switch 
which is bal anced- between spring and the cable ten- 
sions, in such a manner that if one or more of the 
cables become sUacy the switch will be opened, making 
it impossible to operate the car. 

In most elevator installations door switches 


are used to prevent operation of t>ie car vitVi doors 

PuDD Automatic. 

Figure 33 is a wiring diagram of a fu]3 auto- 
matic elevator controDDer as may be used for light 
passenger service or dumb waiters. 

This equipnent is for a two phase, four wire 
squirre] cage induction motor. The essentia] parts 
of the equipment are: three magnetic switches ;f 3 oor 
stop device; push "buttons in the car and at landings; 
s3aclr cable switch; door switch, over travel switches 
and a solenoid operated brake. 

For convenience, consider the car to be at the 
third floor as indicated by the floor stop device. 
This floor stop device is geared directly to the 
hoisting drum. The four relays are spaced'^ to corres- 
pond to the distance between floors. To start the 
elevator from the car or any landing the button cor- 
responding to the floor, to which we wish the car 
to stop, is pushed; for instance number one. In 
this case the relay number one of the floor stop 
device would drop making contact for the down and 

Fig. 32A. 
D. C. a^r.i-A^itomstio Elevator Controlled. 



main switch . The motor in then thrown across the 
Dine and the e] evator starts doirin. When at the firwt 
landing the reD ay numher one wi]] "be opened "by the 
insuDated contact between the up and down ribhons 
of the fDoor stop device. The switch wi3] then open 
and the car stop. 

Now consider that we are on the first floor 
and push button number four, starting the car up. 
If we wish to stop the car at some intermediate 
point, we can do so by pressing the emergency stop 
button which energizes the emergency stop coil of 
the floor stop device. This operation will trip 
out the relay and stop the car. The car could then 
be started for the desired floor. 

If the car is in operation and any button, 
other than the emergency button, is pushed, the re- 
lay will not operate because the control circuit 
for the first relay operated is made through the 
normally closed auxiliary contacts cf the up and 
down switch. The control circuit of the relay is 
made through a resistance H.K, , the object being 
to prevent the closing of two relays at one time. 


TVie resistance H.K. is of such va]ue that the volt- 
age wi]] be too ] ow to operate tv?o coiDs at once. 
This resistance K.K. is also 3 arge enough to pre- 
vent operation of any relay when the Dine voltage 
is "below seventy-three percent normal. 

Figure 32-A represents a D.C, semi-autoraatic 
elevator controller. A photograph of an installa- 
tion is shown in fugure 32-B. The control equip- 
ment consists of: one clapper sv/itch, one solen- 
oid operated accelrator, and a reversing drum. 
This drum is operated from the car by cable ,as 
shown in the photograph. The main line circuits 
are closed first, then the clapper switch circuit, 
eliminating arcing on the drum contacts. The mo- 
tor then starts as a compound motor and is acce- 
lerated by the accelrator which, on reaching its' 
last step, cuts out the series field. 

A.D.C. full automatic elevator controlling 
equipment is shown in figure 32-C. This appara- 
tus consists of: one main clarper switch, tvo 
clapper reversing switches, one locV-out switch, 
service switch, two field switches, one timed 



Elevator controller installation 
?ig. S2B. 





acceDerator, five accelerating switches, two vi- 
brating relays, one double coil overload maciiine 
limit switcVi, car svitcb, and tbe ordinary slack 
ca"bl e.hatcViway and safety switches. 

This apparatus is designed for operating a 
high speed freight elevator. To start the equip- 
ment the service switch located in the car is 
closed. This sv/itch is nothing more than an addi- 
tional safety device. On closing the service 
switch, the shunt field circuit is completed 
through the external resistance V-V] , By replac- 
ing the car switch in the first running position 
the main and direction switches close, the dynamic 
braVe is also released. These switches on closing, 
energize the timed accelerator which closes the 
contacts of the five accelerating switches. These 
accelerating switches on closing cut out the arma- 
ture resistance. This equipment is designed for 
accelerating the car at two different rates of 
speed depending upon the load to be carried. For 
this particular ini=;ta]l ation the car was required 
to lift a heavy load for about one half the operat- 


ing time; during t^e remaining period ] ighter 
loads were carried. It was therefore necessary 
to bave two accelerating rates in order to oijerate 
at a higVi efficiency. T^ese two acce] crating rates 
are ottained by dividing fHe starting resistance 
into two separate parts, acceD crating at a >iigV» 
rate of speed on about one ha] f the tota] resist- 
ance. The ynife switch K is used to interconnect 
the resistance on p]acing the car switch in the 
second position, the fina] speed is obtained by 
-opera,ticn of the two vibrnting re] ays. 

In high speed e]evator operation it has been 
found nccesp.ary to have a smooth dece] 3 eration. 
In this equipment the timed acce] eration is de- 
signed to have its operation retarded in both di- 
rections by a doub] e dash pot. On stopping the 
car the dynamic brake is set direct] y across the 
armature but as the tiired re] ay opens, it re-in- 
serts the armature resistance, which now acts as 
a dece] ] crating resistance, giving a very smooth 



TTie control pane] for the chain munition con- 
veyor is shown in diagram 33A. The equipment consists 
of two main switches, one magnetic single coil over- 
load, one hand operated starting hox and speed regu- 
lator,' one hand operated reversing switch and a re- 
mote push button for stopping the apparatus. 

The object of the panel is to carry the muni- 
tion from the magazine to the place of discharge by 
means of a specially designed chain conveyor. The 
direction of rotation is controlled from the panel 
by the hand reversing switch. In order to start the 
motor the starting lever must be in the neutral 
position. The lever must be in this position in or- 
der that the interlocking resistance A.B, will not 
be connected in series with the main switch coils, 
permitting them to be connected across the ] ine on 
full voltage. A.B. has enough resistance to prevent 
tHe switch from closing when in series with it, but 
if the switch is closed, the insertion of the re- 

Pig. gSA. 
aitmsrine loiiiitioii conveyor. 


sistance wi]3 not trip tVie switch. By turning the 
starting hand] e to the start position, the two main 
switches close, operating the motor with a]] the re- 
sistance in the armature and fieDd circuits. The 
resistance of the armature circuit is cut out as 
"With the ordinary starting "box and the speed may "be 
regulated in a similar way. 

The motor may he stopped by the hand operated 
lever or by the remote stop "button. The remote con- 
trol buttons may be equipped with a catch for locking. 
them in the open position in case something goes 
wrong with the apparatus. 

There are various methods of submerging and 
raising the submarine, the controlling panels of one 
of the American Submarines is shown in figure ^A, 
The panel consists of two magnetic reversing switches 
equipped with sinlge normally open and closed con- 
tacts, one double coil overload and one remote 
switch. This remote control switch is a three-point 
switch, the other two positions depending on whether 
the boat is to be submerged or not. 

Pig. 34. 
aibmaririe 9aTDiiierging Contrullor. 


To start fhe mo4ior tV>e snap switoVi is closed, 
energising fhe corresi^onding coil of t'ne main switch, 
cDosing it, a] D owing tVie Dine current to pass 
through the motor and the norma] Uy cDosed contact 
of the other main switch bacV to the line, ^hen 
the main switch closed it opened the auxiliary con- 
tact, which is connected in series with the other 
switch coil, thus insuring against closing both 
switches at the same time. In case of an overload, 
the current through the series coil of the overload 
will cause its plunger to raise, tripping its auxi- 
liary contact, shutting down the motor. After the 
plunger has operated in this manner, the shunt coil 
of the overload is sufficient to hold it open. If 
it were not for this shunt coil, the main switch would 

To shut down the motor, the snap switch is 
opened, the main line switch trips and a short is 
placed across the armature of the motor through the 
nojmially closed contact of the second main switch. 
The short across the motor causes it to stop quickly 


due to its dynamic breaking effect. TVie usual dy- 
namic braVe is eMminated in t><is case because of 
]aclc of space on a submarine, a compact equipment 
being essentia]. Tbis same equipment is used to 
raise and Dower f^e periscope. 

Tbe main propeD ] ing equipment consists of two 
separate motor driven propel 3 ers. The control 
apparatus for tbis equipment is one of tbe most 
interesting electrical features of submarine con- 
trol ,^8 sbown in figure 34-A. 

In general, tbe panel may be controlled from 
tbree different places, at tbe pane] by band opera- 
tion, in tbe engine room and at tbe central cruising 
station. Tbese tbree starting stations are mecbani- 
cally interlocked by a lever wbicb must be inserted 
in its proper position at tbe starting station to be 
operated. Tbis lever is so designed tbat it cannot 
be removed unless tbe starting station masters are 
all in tbe off-position. Tbe band operation is used 
at tbe panel in case of emergency, sucb as burning 
out of coils or tbe failure of tbe auxiliary power, 
Tbe motors are driven from tbe main batteries. 



■111 i — T • lining 

/9^. J^>? 


TV>e equipment consists of four main switches, 
two for forward and two for reverse, four accelera- 
ting relays, one field switch having two norma] ]y 
open contacts and one normally closed, one double 
coil overload and one relay. The switcbes of this 
panel are of very heavy construction, balanced with 
heavy weights to as i^ure quick and positive action. 
These weights are installed to hold the switches 
open, if not in use, when the bo9t is rocVing on a 
heavy sea. 

The operation of the propelling starting equip- 
ment is similar to other panels except that the 
acceleration depends upon the operator. The direc- 
tion of rotation and the acceleration are controlled 
from an ordinary master, Wnen the master is in the 
off position and all switches open, the field switch 
on opening, closes its down contacts which shorts the 
field through the discharge resistance. This is ne- 
cessary to prevent the high voltage kiclr of the 
field current, caused by the sudden breaking of the 
field, from breaking down the insulation of tve cir- 


Tl^e diagram for tVie magnetic ] ockout ..starter 
for submarine signa] worV is shown in diagram 35. 

TVie olDject of this equipment is to obtain A.C, 
current for v/ireDess, a]] other voDtages are D.C, 

The equipment consists of one main switch, . 
two DocV-out switches, one douh]e coi] overDoad, 
one fie]d relay, and two fieDd rheostat^, one in 
the fie]d for speed variation and the other in 
the fie]d of the generator for To3tage regulation. 

This apparatus is controlled from an ordinary 
single pole Vnife switch, which when closed, ener- 
gizes the irain switch. When the main switch closes, 
the line tc the motor is comipleted, and the fields 
of the generator and motor are closed. The inrush 
of current through the motor energizes the two coils 
of locVout switch 2 R, which will close when the 
current drops to given value causing the cur"^ent 
to flow through the tvo coils of the lockout 3 R. 
3 R closes as soon as the current decreases to its 
setting value. The motor is then directly across the 
1 ine. 

The equipment for controlling the "bal 1 ast ,cen- 

Pig. 35. 
aibmsrine Ojntroller. 


trifuga] pump apparatus is shown in figure 36, The 
essentia] parts of the equipment are: hand operated 
drum, hand operated field regulator, one overload, 
one magnetic switch and one hand operated locking 
lever. Thio equipment is encjosed in a water-tight 
compartment . 

To start the pump, the locking lever is- placed 
in the running position. This will energize the 
main sv<'itch coil and close it. Now "by moving the 
drum to the first position, the motor v/ill start 
with all the resistance in the circuit. By moving 
through the next three steps the resistance will 
he cut out of the armature circuit. The speed of 
the motor is then regulated hy adjusting the field 
rheostat. In ca^e of an overload or voltage failure 
thf motor wil 1 he shut dowr^ by the opening of the 
main svitch. In an ordinary shut-down, the drum is 
moved to the off position and the main switch will 
remain closed. The pump can be operated in the re- 
verse direction by reversing the drum. 

Figure 37 is a diagram for controlling the 
operation of the circulating water pump used for 

Pig. 36. 
ai>5F.£ririe BsHssi Oor.troller. 

?ig. 37. 
Oiroulating "Vater Puir.p Controller. 


coo3ing tV>e engine. This equipment consists of: one 
master drum, series overload, and one main svdtcV.. 

To stat't fhe equipment the master is placed 
in the first position, this closes the main sv/itch 
and starts the motor vith a]! the resistance in the 
circuit. The movement of the master to the second 
position cuts out the first step of resistance and 
also opens the pick-up circuit, for the main switch 
coil and cuts in a protecting resistance in series 
with the coil of the main switch. TVie motor may then 
te speeded up to f u] 1 speed "by rotation of the mas- 
ter. T>>e motor is shut down "by "bringing the master 
to the neutraj position. If shut down by action of 
the overload, it is necessary to hring the master 
■bac>- to the first position before the mctor car "be 
started again. 


A Coa] tower operating equipment is shown in 
diagram 38. The object of this apparatus is to 
contro] the hoist, and rac? of a 3 arge coa3 "bridge 
as used for unloading coa] "boats. 

The equipment consists of three separate 
paneDs. Pirst the hoist, control 3 ing the hoist, 
closing and opening of the bucVet. Second, the 
racy controlling the movement of the carriage up 
and down its track. Third an accessory panel con- 
trolling a small motor generator set for operating 
the "braVes and clutch. 

The hoist controller consists of: one main 
switch, two reversing switches, five accelerating 
switches, four three-phase relays, one circuit 
breaVer equipped v/ith overloads and a no-voltage 
release, hand operated master and a normally closed 
push button. 

To lower the bucket the master is placed in the 

^i'9- 38 


first position energizing tVie main and lov/ering 
switches. The next four steps of the master, wi3] 
bring the motor to f u] ] speed by operation of the 
four series relays. The bucy-et may be opened any- 
where during its descent by cDosing the hand lever 
which energizes the brake and clutch coils which 
control the opening and closing of the bucVet. To 
hoist the bucVet the master is placed in the first 
position with the hand lever closed starting the 
bucVet up with both the braVe and clutch energized, 
the motor can be brought up to speed in the usual 
manner. After the master has passed the first hoist- 
ing position, the control circuit for the clutch is 
opened and cannot be closed in order that the bucicet 
will remain in the locked position. In case something 
happens to the equipment during operation, the push 
button near the master may be opened, which will 
open the no-voltage release, and shut down the appa- 

The rack controlling equipment consists of: 
one main switch, two reversing switches, three 
accelerating s-witches, theee accelerating relays. 


one master, a circuit breaker equipped witVi a no- 
vo] tage re] ease, and a norma] ]y c]osed pus>» 'button, 
Tbe operation of this equipment is contro]]ed by 
tbe operation cf tbe master and the series re] ays, 
In case of an emergency, tbe circuit breaVer can 
be tripped by bushing the emergency push button. 


A. C. Skip Hoist. 

Figure 39 is a wiring diagram of an A.C, fu3] 
automatic skip hoist as used on a charging machine 
of a b3ast furnace. The charging machine consists 
of two tram cars which op!?!rate "by cahDe and so con- 
nected that one car discharges into the -^urnace 
while the other is Doading. The ohject of the con- 
tro] pane] is to operate these cars automatical Dy. 

This pane] consists of two main magnetic 
switches U and D; two accelerating relays 2R and 
3R; two three-phase relays and a timed relay. The 
main switches are used to control the direction of 
rotation and are mechanically and electrically in- 
terlocked, making it impossihle to close "both at once. 

TV\e equipment is started "by pushing eit>ier 
fhe up or dov/n "button which in turn closes the up 
or down main switch. In case the car is at the 
"bottom and the down "button pushed the apparatus 

?lg. 39. 
A. C. 3{ip ?.oist Cur.troller. 


wiD] not start due to the fact that the car is 
ho3 ding open the fina3 down limit switch. The main 
switch "being cDosed, the first accelerating re3ay 
is energized and he3d in the open position, thus 
cutting in the maximum starting resistance. As the 
motor speeds up, th^ current drops and at a pre- 
determined value the relay closes, energizing the 
first accelerating switch 2R which shorts out the 
first portion of starting resistance and energized 
the second relay. The relay now opens and remains 
open until the current drops to the setting of the 
re3ay, at which time the second accelerating switch 
c3oses, cutting out the last step of resistance and 
throws a short across the slip rings of the motor. 
The motor then operates at full speed. 

For convenience, suppose that the car was at 
the bottom and started up with a load. As the car 
nears the top it opens the slow down switch, thus 
opening the two accelerating switches on the pane3 
and the motor slows down. The car finally hits the 
up limit and the down start. This stops the motor 
and energizes the timed relay R. This oil dash re- 
lay is adjusted so that the car has time to unload 


before it closes tVie contact of the down switch. 
The unloading is accomplished by passing the car 
over the t:p of the inclined track. The car at the 
bottom opens a hopper and continues to load until the 
car starts up and closes the hopper, VIThen the con- 
tact of the down switch closes, the motor reverses 
and the equipment starts in the opposite direction. 

This pane] is a] so equipped with several safety 
switches which may be opened at any time. An emer- 
gency start button is installed for testing out the 
control circuits from the panel . 


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A. C. Stee] Mi3 3. 

An A.C, fu]3 reverse Kraemer system speed 
controller for operating a large sheet steel mill 
is sV»ov?n in diagram 40, This installation is for 
a 6600 volt, 3 phase, 20C0 horse pover wcund rotor 
induction motor. The noain object of the equipment 
is to yeep the motor at a constant speed regardless 
of load. A constant speed is essentia] to prevent 
the shef^ts from varying in thiclmess. In addition 
to the usual switch control equipment this appara- 
tus has a Kraemer motor mounted on the shaft of 
the induction motor. This Kraemer motor is a shunt 
D,C. motor, A rotary converter is also used with 
this equipment. The D.C.side of the converter is 
connected across the armature of the Kraemer motor 
and the A.C. side is connected through the controlling 
equipment tc the s] ip rings of the induction motor. 

The controlling equipment of this installation 

^/^. yo 


consists of three separate pane3s, one consisting 
of two so] enoid operated oil sYritches used for 
reversing the direction of rotation of the induc- 
tion motor, Pane3 A is equipped with accelerating 
switches and relays for cutting out the resistance, 
two field switches, one for the Kraemer motor and 
the other for the rotary converter, four small 
cDapper relays for cutting in the accelerating swit- 
ches; and one A.C, switch. The oTDject of this A.C.. 
switch is to form an electric interlocV "between 
the A.C, and D. C, voltages, thus making sure that 
all switches will open in case either source of 
supply fails. Panel H consists of: three clapper 
relays, three D.C, clapper switches, and one drum 
type master controller. 

In starting the equipment the master is placed 
in the fir'^t position which closes the relay for 
the forward main svfitch, also the three switches 
C] , C2. C3; E] and E2 are also closed. All these 
switches on closing, connect the slip ring of the 
induction motor to th# total resistance. The motor 
then starts with all the resistance in the circuit, 


the Kraemer motor running id] e. The induction motor 
may now "be run up to f u] ] speed "by "bringing the 
master to the fourth position. The Dast three 
acce3erating steps are then brought in by their 
accelerating re] ays which are independent of the 
master. By moving the master tc the fifth position, 
re] ays 8P3 and 8R2 c]ose. The tvvo svatches on clos- 
ing, place a short across the slip rings of the in- 
duction motor and at the same tirre opens the cir- 
cuit of the accelerating switches, allowing them 
to open. At this point, the induction motor is 
operating at full speed and the Kraemer motor is 
running idle and the rotary converter is standing 
still. By moving the master tc the sixth positon 
the short is removed from the induction motor by 
opening 8R and 8R2, C] , C2 and C3, E3 and E2; the 
slip rings are immediately connected to the A.C. 
side of rotary converter by the closing of s-vvitches 
A], A2. A3, D] , D2. D3,and the two field switches 
F] and F2. This energizes the field of the rotary 
converter and Kraemer motor. The rotary will then 

#3 08 

he brought up to speed by the two sources of power. 
Now by adjusting tbe fie]d current of tbe Kraemer 
motor and tbe rotary converter tbe ejquipment may be 
operated at tbe desired speed, and it v;i3] continue 
to run at a constant speed. 

In case of an ordinary shut down.tbe master 
may be brought to the off position, or by pressing 
the stop button. In case of an emergency when it 
is desired to stop immediate3y, the stop button and 
the pDug in switch may be c]osed. The action of the 
entire equipment wi] 3 then bring the motor a3most 
instant3y to a stand-sti3D. 

This apparatus may be run in the reverse di- 
rection on s3 ow speed on3y, it being impossib3e to 
cut out more than the first step of resistance. 



Transfer Pane] , 

Diagram 4] shows a scheme of connections for 
transferring an A. C, motor from the A.C. power Dine, 
in case of failure, to a motor generator set opera- 
ted from storage batteries. 

The essentia] parts of the equipment are: 
two cDapper switches with A.C.coiDs, two c]ap"per 
switches with D.C,coi3s, one D.C, se]f starter, 
one phase faiDure re] ay. 

To start the equipment with the A.C.Dine, the 
] ef t hand single pole switch and phase failure 
relay are closed, the two switches with A.C, coil s 
close throwing the motor direct across the line. 
At this time the right hand single pole switch is 

In case of outage of the A.C. power line, one 
or more lines failing or a phase reversal, the 
phase failure relay will open, tripping the A.C, 

Fig. 41. 

TrSuiSfor OOV.tTOlleT. 


switches, TVi^ 3 eft hand switch, on opening, wi]] 
c3ose the coi] of the D.C, seDf starter through its 
auxiliary contact. This wi] ] start the motor, genera- 
tor set and as soon as the se]f starter reaches the 
end of its trave] the contacts for the two switches 
with D. Cecils wi] I c]ose, connecting the motor 
across the generator. 

Machine Too] Contro] , 

Diagram 42 shows the connections for a non- 
reversahle machine too] contro]] er. This equipment 
consists of: one main switch and one lockout switch. 
The apparatus is controlled from a two-hutton station, 
the stop button "being normally closed and the start 
normally opened. By pushing the start button, the 
main switch closes connecting the motor to the line 
through the starting resistance. The maintenance 
contact also closes, so that the starting button 
can be released. The motor is then accelerated 
through the three lockout switches in the usual 
manner. The last lockout is equipped with a shunt 
ceil in order that it will stay closed on a very 

Pig. 42 
Nonreversable Machine Tool Controller. 


]igVit 3oad as may occur on making a DigVit cut. W>ien 
fhe apparatus is shut down tVie main switch on open- 
ing puts a short across the armature through the 
dynamic break resistance. 

Diagram 43 shows similar connections for a 
fu3] reverse too] control 3 er. The only characteri- 
stic difference "being that the apparatus is equipped 
with a field discharge resistance. The control is, 
however, handled with a two-direction master. 

Pig. 4£ 
Beversg.lole L£cTiii:e Tuol Coi.:troller. 



An A. C. control D ing equipment for an electric 
driven washing machine is shown in figure 44. This 
apparatus is used for automaticaD 3y reversing the 
direction of rotation of washing machine. The 
equipment clDnsists of: one magnetic switch, one 
motor driven drum controller and one remote control 

The machine is started by pressing the start 
Tautton which closes the circuit for the motor driv- 
ing the drum. This motor will then revolve the 
drum, closing the circuit of the main motor. As 
the drum turns through about 170 degrees the main 
motor will continue to revolve in the direction 
started. For the next 10 degrees the motor will 
be shut off and through the following 170 degrees 
the main motor will operate in the reverse direction 
and will be stopped during the next 10 degrees. 
This operation of r.^versing the main motor forty 
times a minute will continue until shut down. 

Fig. 44. 
A. C. 'yasher Controller. 


A similar equipment for D.C, control is sV»own 
in figure 45. The operation is tVie same as fhat 
of the A.C.controD] er. 

The controller for operating the extractor 
or drying machine is shown in figure 46. This is 
an A. C, three-phase, equipment consisting of: main 
clapper switch, one special overload, and one re- 
mote control button with indicating lamp. The ob- 
ject of this apparatus is to revolve a large per- 
forated tanV containing very wet clothes at a 
high rate of speed. Due to the heavy weight of 
clothes at the start, the inrush current to the 
high speed motor is five to seven times normal . 
Therefore, on starting this motor, by pushing the 
start button, it is necessary that the button be 
held in the closed positi'on until the inrush cur- 
rent has dropped below the tripping point of the 
overload. The operator is notified when the cur- 
rent has reached normal value by the lighting of 
the indicating lamp. l?/hen the button is pushed 
on starting, the overload opens the maintaining 
circuit of the main switch, also the lamp cir- 

D. G. '.Yasher Controller. 

Fig. 46. 
A. C. Extractor Oontro-ller. 

#3 20 

As the current nears norma] vaDue, t'ne overDoad 
closes, comp] eting t>ie 3 amp and maintaining circuits. 
The 3ajnp wiD 3 remain 3ightedi unti3 fhe motor is 
shut down. 

The wiring diagram for a D.C. extractor pane] 
is shown in figure 47. 

Figure 43 shows a photograph of a 3arge wash- 
ing machine pane3 consisting of severa] washers and 

Pig. 47. 
E. c. Extractor controller. 

rig. 48, 


#3 23 

Specia] Colre HandDing Apparatus, 

A wiring diagram of one section of tv^e coVe 
handling equipment of fhe New York gas pDant is 
shown in figure 48^. This is an A.C,pane3 designed 
to operate seventeen motors of the coye conveying 
equipment including the crusher and screening appa- 

In this insta]]ation the crusher is made up 
of two ] arge cylinders , geared together, with sur- 
faces provided with projecting Knives. .These knives 
are so constructed that they always remain at the 
sane distance from each other when revolving. The 
action is similar to gears of the same size re- 
volving out of mesh. 

The motors of this conveying equipment are all 
squirrel cage induction motors of various sizes. 
The smaller motors are started hy means of one 
clapper switch which throws them directly across 
the line. The larger motors are started with three 
OP ftiore clapper switches which connect them across 
the low voltage taps of the transformer on starting 
■^11 motors are protected hy two time limited over- 

^> "^SA 

#3 25 

Doads and fuses. They are a]] started and stopped 
"by means of push "buttons. 

The crusher may be started and stopped inde- 
pendent of the rest of the equipment. Of the 
tweDve conveyors, conveyor 6, 6/^, 6g, 8 and 9 a^^i 
operated independent of other apparatus. Conveyor 
5 and 7A can on] y "be started aft'er either or "both 
the screens have "been started. Conveyor 4 may he s 
started when 5 and 7A are operating. 

Conveyor Bj and ]] are reversible . If B3 is 
started west it is possible to start conveyor 12 
and at no other time can 3 2 be operated. After 3 2 
is in operation, number 3 3 may be started west but 
cannot be started east. These three conveyors are 
shut down in the reverse order from which they were 
started. If these three conveyors are not in motion, 
]] may be started east but not west. 

After 3 3 has been started east, number 3 3 can 
be put in operation, and on3 y at this time. With 
33 in motion B] can be started east. This set of 
conveyors is shut down in the reverse order to which 
they were started. 

#3 26 

It might "be interesting to know tViat tViis 
p]ant has a much larger equipment than the one 
Just described, 

A similar equipment for D.C, control is shown 
in figure 49, 

Pie. 45 

#3 28 

Ore UnDoader. 

A wiring diagram for a series re] ay operated 
"beam ore hoist is shown in fiisiure 50. This appara- 
tus consists of: one main switch, six accelerating 
ST^/itches, one dynamic brake switch, three auxiliary 
sv/itches, four clapper relays, five r.C. series relays, 
four limit switches and one transfer switch. 

This equipment is started "by placing the mas- 
ter in the hoising position, which closes the main 
switch and releases the dynamic "brake. The motor 
then comes to full speed through the action of the 
five series relays and their corresponding clapper 
switches. In this installation there is no field 
speed control. In lowering, the master is placed in 
the lowering position and due to the heavy weight of 
the beam and bucket the motor acts as a dynamic brake. 

Since the apparatus is not provided with field 
resistance, it has an external field discharge re- 
sistance which is inserted, when the main knife 
switch is open by means of its auxiliary contactB. 

3t IVO'. 

:i ; J^ & r 

PlA'. 50. 

Heavy Duty Hoist Contro]]er. 
A Vieavy duty Vioist controller as may "be used 
in mines, is shown diagrammatica] Dy in figure 5^ . 
T'l^e pane] is made up of two reversing switcVies, two 
cJapper type re] ays, two auxiliary cDapper re] ays, 
used as ] imit switches, over-speed governor and one 
traveling nut ] imit switcVi, This nvrt switch consists 
of two parts, one part is geared directly to the 
tight cable drum, the other is geared to the loose 
cable drum. There are also two over-travel limit 
switches, one plug switch and a master controller. 
This master is directly connected to the liquid rheo- 
stat controller. The liquid rheostat is used to 

give/very smooth and long range of acceleration. 

The apparatus is started by placing the con- 
troller in the running position and is accelerated 
by moving the master. As the master is moved for- 
ward, the water raises in the rheostat, cutting out 
the rotor resistance=k 

The equipment is automa+ical ly stopped by the 
limit switches. The plug switch has a long chain 


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connected tc it which hangs down the shaft which 
can be pulled at any time, removing the plug from 
its receptacle and shutting down the equipment.