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Electric Ship Propulsion 



COMMANDER SAly'ROBINSON, U. S. N. 



Published attd Printed in. U. S. A. 

by 

SIMMONS-BOARDMAN PUBLISHING COMPANY 

WOOLWORTH BUILDING. NEW YORK, N. Y. 
Tkahspobthtioh Bldc Houe LirB Bldc. The Arcidi 

Chicago. III. Washihgtok, D. C Clbvelahd, Ohio 

14 Victoria St., Wist- 444 Haison Blanche Fikst Natiohu. Bane 

kiHSTU, S. W. I, Armex Blpo. 

Ldmdoh. Eho, New Qxlbahs, Lt, Cihcihhati, Ohiq 



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Copyright 
1922 

SlMMONS-BoABDMAN PUBLISHING COUPANY 



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"^^ 



FOREWORD 



IT is assumed that the readers of this volume will have an 
elementary knowledge of the theory of steam turbines, 
electric generators, induction motors, etc.; it would not be 
possible to treat all these subjects adequately in a book of this 
kind. An attempt has been made to cover as thoroughly as pos- 
sible the special points that arise in connection with the propul- 
sion of ships by electricity and to compare this method with 
others that are already in use or projected. Where use is made 
of apparatus that has not previously been thoroughly described 
in existing text-books, a full description of it is given. 

The author wishes to thank Messrs. Maxwell Day, E. F. W, 
Alexanderson, A. H. Mittag, W. C. Watson and Eskil Berg 
of the General Electric Company, Messrs. W. Sykes, W. E. 
Thau and M. Cornelius of the Westinghouse Company and 
Commander J. S. Evans, U. S. N., of the Navy Department for 
their assistance in the preparation of this book; also Marine 
Engineering and Shipping Age for the use of an article by 
Renwick Z. Dickie in the March, 1920, issue on "Diesel Electric 
Propulsion"; also the American Institute of Electrical Engineers 
for the use of an article by George B. Pulham in the January, 
1920, issue of the Journal on the Wutsty Castle; also the 
American Society of Naval Engineers for the use of an article 
by Lieutenant W. R. Carter in the Atigust, 1916, issue of the 
Journal on "The Ljungstrom Turbine." 



ly Google 



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Table of Contents 



CHAPTER I 
History of Electric Propulsion and Types of Ships for 

Which it is Best Adapted i 

CHAPTER II 
Systems of Propulsion ii 

CHAPTER III 
Propeller Characteristics i8 

CHAPTER IV 
Characteristics of Alternating Current Motors and Gen- 
erators for Ship Propulsion 27 

CHAPTER V 
Special Cftaracteristics of Turbines and Governors for Elec- 
tric Propulsion 64 

CHAPTER VI 
Ventilation, Heaters, Fire Extinguishers 67 

CHAPTER VII 
Switchboards, Interlocks and Controls 73 

CHAPTER VIII 
Wire, Cable, Insulators and Insulation 79 

CHAPTER IX 
Exciters and Other Auxiliaries 89 

CHAPTER X 
The Jupiter 92 



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CONTENTS 

CHAPTER XI „a 

The U. S. S. l^ew Mexico 115 

CHAPTER XH 
The Calif omia, Maryland and West Virginia . . . . 156 

CHAPTER Xni 
The Tennessee, Colorado and Washington 193 

CHAPTER XIV 
United States Battle Cruisers and Battleships Nos. 49 — 54 239 

CHAPTER XV 
The Wulsty Castle 243 

CHAPTER XVI 
Diesel' Electric Drive 264 

CHAPTER XVII 
Care and Upkeep 270 



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Electric Ship Propulsion 



CHAPTER I 

History of Electric Propul&ion and Tj^s of Ships for Which 
It Is Best Adapted 

THE propulsion of ships by electricity had been proposed for 
many years and in many forms, but until the use, of 
turbines became general there was no real reason for its 
adoption and consequently no serious efforts were made in that 
direction. But the rapid development of the turbine brought this 
question up again, and in an entirely new light. The unsatisfac- 
tory performance of backing turbines, the poor efficiency of high 
speed propellers and the great disparity between the weight and 
economy of high speed turbines for driving alternators and low 
speed turbines for driving propellers made it highly desirable that 
some method be found of reconciling the inherently opposite 
characteristics of the turbine and propeller. At that time the 
mechanical reduction gear had not been brought up to its present 
state of perfection, so that any method which offered an immedi- 
ate solution of the problem was very attractive to marine engineers. 

More recently a new type of prime mover, the Diesel engine, 
has come into the marine field. This engine is also unsuitable for 
direct connection to the propeller on account of the difficulty of 
starting it under load and reversing it, and also because its best 
speed is somewhat greater than the best propeller speed. Here, 
again, electric propulsion offers a solution of all these difficulties. 

Mr. W. L. R. Emmet, of the General Electric Company, was 
the first engineer to make a successful attempt to introduce electric 
propulsion for ships. His efforts were at first directed toward its 
application to battleships, which seemed to be the class of vessel 
most suited for the purpose. But it was decided by the United 
States Navy Department that the suitability of electric propulsion 



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2 ELECTRIC SHIP PROPULSION 

for marine purposes should first be tried in an experimental 
installation, and the collier Jupiter was selected for this purpose. 
This vessel was commissioned in April, 1913, Her trials, and 
also her performance in service, were so satisfactory that, in 1915, 
it was decided to install electric machinery in the battleship New 
Mexico; since that time, all capital ships of the United States 
Navy have been designed for electric propulsion. 

Outside of the United States, the development of electric 
propulsion has been very limited. This is doubtless due to the 
situation caused by the World War. The Swedish Ljungstrom 
Steam Turbine Company, of Sweden, has equipped two small 
cargo vessels, the Mjolner and the Wulsty Castle, with electric 
machinery. This equipment has shown a remarkable improve- 
ment in economy, amounting to about 40 percent, over a recipro- 
cating engine installation in a sister vessel. 

Practically coincident with the development of electric propul- 
sion has come the remarkably rapid improvement in the mephani- 
cal reduction gear. At the present time both systems have been 
developed to a point where they can be used on practically any 
type of ship. But as each class of ship is a complete problem, it 
will be necessary to consider each one separately in arriving at a 
conclusion as to what is the most satisfactory propelling 
machinery. 

It must be understood that the following subdivision of ships 
into classes can only be considered as a rough guide and not as an 
absolute one; also, the developments in the art are very rapid, and 
in a short time we may see a very large extension of the Diesel 
engine in the marine field over that laid down in the following 
subdivision of classes of ships. 

In any comparison of various types of propulsion it is neces- 
sary that all efficiencies involved should be considered in order to 
make the comparison complete. The propeller efficiency plays a 
large part in determining the overall efficiency of propulsion, and 
it may be assumed that for vessels using a single screw, or twin 
screws, the most efficient propeller speed will be very low because, 
in these cases, it will be possible to use a propeller of large diam- 
eter; the exception to this rule is in the case of destroyers, and 
other light, high-speed vessels, and these are treated as a separate 
class. Where it is necessary to use four screws, the propeller 



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HISTORY OP ELECTRIC PROPULSION 3 

speed will be fairly high. In the case of the turbine, the condi- 
tions are just the reverse of that of the propeller — that is, the 
smaller the horsepower of the turbine the higher the speed at 
which it must be run in order to preserve maximum efficiency. 
Therefore, it will be seen that all the parts of the machinery 
installation, from the turbine to the propeller and including the 
shafting, must be taken into consideration when making compari- 
sons of efficiency. 

In drawing conclusions as to the suitability of various types of 
prime movers, the following assumptions will be made: 

(i) The loss in backing turbines will be about \yi per- 
cent. 

(b) The loss in a turbine due to the use of two casings 
and inter -connecting pipes, instead of a single casing, will be 
about lyi percent. 

(c) The shafting losses with gear drive will be about 1 
percent greater than for electric drive, except for vessels of 
Class 3. 

(d) The loss in a double reduction gear will be about 5 
percent. 

(e) The loss in a single reduction gear will be about 2j4 
percent, 

(f) Alternating current generator loss (including excita- 
tion and ventilation) will be about 3 percent. 

(g) The alternating current motor loss (including venti- 
lation, and also excitation for synchronous motors) will be 
about 5j/2 percent for induction motors and 4j^ percent for 
synchronous motors. 

(A) Transmission loss, including excitation, when using 
direct current will be about 13 percent. 

The first class of ship to be considered will be the low powered 
cargo vessel requiring not more than about 3,000 shaft horsepower. 
For this class of vessel, the Diesel engine in its present state of 
development is quite suitable. That there are not more ships of 
this type equipped with Diesel engines is probably due to the 
difficulty of starting this engine under load and reversing it; 
neither of these difficulties are met with where electric drive is 
used in connection with it. 



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4 ELECTRIC SHIP PROPULSION 

The use of electricity with Diesel engines involves a trans- 
mission loss of about 13 percent (direct current will be used) but 
there is no loss at all in over -all efficiency and in some cases there 
is an appreciable gain due to its use, as will be seen. 

Direct connected, Diesel-engined ships use twin screws operat- 
ing at a speed considerably higher than is suitable for the best 
propeller efficiency. By the substitution of Diesel-electric pro- 
pulsion a low speed, single screw can be used. The use of the 
twin screws will increase the effective horsepower necessary to 
propel the ship on account of the appendage resistance of the 
propeller struts ; the thrust deduction will be greater when using 
twin screws than when using a single screw ; and the low speed, 
single screw will be more efficient than the high speed twin screws. 

The net result of these various differences in efficiency is that 
the electric transmission losses are made up by the gain in propul- 
sive efficiency; in some cases the electric driven ship will actually 
show a higher over-all efficiency than the direct connected ship. 

In addition to the above advantages, the electric driven ship 
will also be more reliable ; this is partly on account of the greatly 
reduced liability of derangement due to the fact that it is not 
necessary to start the engine under load, nor reverse it; it is partly 
due to the fact that with electric drive a greater subdivision of 
power can be made, thus using smaller engines; and it is also 
partly due to the fact that the engine can be designed especially 
for reliability and economy since it is entirely free of the pro- 
peller. The cost of upkeep will also be reduced since there will 
be fewer derangements of machinery. 

This type of propelling machinery should be very attractive 
for this type of ship since it should give about double the effi- 
ciency of any other form of propulsion. It will be heavier than 
either a turbo electric or turbine with mechanical reduction gear 
installation, but this disadvantage is far outweighed by the great 
increase in efficiency. 

The second class of ship to be considered will be cargo vessels 
and passenger vessels requiring more than 3,000 shaft horsepower, 
but less than enough to require the use of four screws ; the maxi- 
mum speed will vary considerably, depending on the character of 
the ship, but it will probably not be greater than about 20 knots 
and for most ships of this class it will be less than this. The 



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HISTORY OP ELECTRIC PROPULSION S 

slower speed ships of this class will use a single screw, and the 
higher speed ships twin screws; in either case the most efficient 
propeller speed will be very low, so that in order to use the most 
efficient possible turbine, as well as propeller, it will be necessary 
to use a double rediiction. 

That this is true is shown by the fact that European ship- 
builders, who originally were using single reduction gears, are now 
changing over to the double reduction gear. The increased loss 
due to the use of the double reduction gear is more than made up 
by the increased turbine and propeller efficiencies, especially the 
turbine efficiency, which is the one most affected. Using the table 
of losses previously given, and taking losses (a), (6), (c) and 
(d) for the double reduction gear, and losses {/) and (g) for the 
electric drive, it will be seen that turbo electric propulsion is more 
efficient than the mechanical double reduction gear by yi percent 
or IJ^ percent, depending on whether induction motors or syn- 
chronous motors are used ; in other words, there is practically no 
difference in efficiency. 

However, it is believed that electric machinery is more suitable 
since it has other advantages. The cost of upkeep should be very 
much less with the electric than with the mechanical installation. 
This point has been thoroughly demonstrated by the Jupiter, which 
has had practically no expense for the electrical part of her ma- 
chinery during the six years she has been in commission. When 
her upkeep expense is compared with that of a similar ship 
equipped', with gears, the difference is very apparent. Also, the 
efficiency of the electric machinery will remain constant, while 
that of the mechanical gear will depreciate unless renewals are 
made. The electric machinery can be arranged to give a better 
disposition of cargo space than is possible with machinery which is 
connected to the propeller shaft; it will be possible to do away 
entirely with shaft tunnels of single screw vessels by placing the 
nropelhng motor well aft in the stern of the boat; this latter is 
quite an important point, not only from the standpoint of addi- 
tional cargo space, but on account of the better arrangement of the 
space. In certain cargo vessels which discharge their own cargo, 
it will be possible to utilize the main machinery for running deck 
winches, thus giving more efficient and more reliable deck ma- 
chinery. 



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6 ELECTRIC SHIP PROPULSION 

The statement is sometimes made that electrical machinery is 
more complicated and requires greater care and attention than 
geared turbines. This may be true with some electric installa- 
tions, but it certainly is not true for this type of ship. Nothii^ 
could be simpler than the operation of the electric machinery for a 
ship of this class, if it is properly designed. The difference ia 
weight between the two types of machinery will be very small and 
will be negligible. 

The third class of ship to be considered will be the high speed 
passenger vessel with sufficient horsepower to make the use of 
four screws necessary. In this case the most suitable turbine 
and propeller speeds will be such that a single reduction can be 
used between turbine and propeller. However, with the mechani- 
cal reduction gear it will be necessary to use an independent 
turbine for each of the four shafts and each of these turbines 
will be contained in two casings, while the electrically propelled 
ship will use only two turbines, each contained in a single casing, 
so that the turbine losses previously assumed, given in {b) of the 
table of losses, will be doutjled. In this case the losses of the 
reduction gear will consist of (a), 2(b) and (e), and the losses 
of the electric drive will consist of (/) and (fir). This shows the 
reduction gear to be Ij^ percent more efficient, assuming that 
induction motors would be used with the electric drive. 

As in the case of Class 2 ships, there is practically no difference 
in efficiency. But the advantages enumerated under Class 2 ships 
for electric machinery hold equally well here, so that electric pro- 
pulsion is also the most suitable for this class of ship. In fact, it 
can be broadly stated that, unless there is a considerable advantage 
in efficiency due to the use of mechanical gears, electric propulsion 
should be used owing to its other advantages. 

The difference in the weight of the two types of machinery for 
this class of vessel will be very small and is negligible. 

The fourth class of ship to be considered will be the light 
draft, high speed, high powered naval vessel, such as the destroyer, 
scout cruiser or light cruiser. These vessels may be fitted with 
twin screws, three screws or four screws. The screws are always 
high speed, so that only a small reduction between turbine speed 
and propeller speed is required; in no case will it be more than 



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HISTORY OF ELECTRIC PROPULSION 7 

8 to 1 and k may be as low as 4 to 1, so that a single reduction can 
always be used. 

With this type of ship, the mechanical gear has a very decided 
advantage over the electric machinery. A small change in the 
displacement of these vessels means a very large increase in horse- 
power required to make the speed. Consequently the saving of 
weight becomes of the greatest importance. Owing to the small 
reduction used, there will be a saving in weight per horsepower by 
the use of the mechanical gear. This will mean a reduction of 
the displacement and, therefore, also of the total turbine horse- 
power required as compared with the electric machinery, and, 
consequently, a further reduction in weight. 

In regard to comparative efficiencies, the losses of the gear 
will consist of (a), (b) and (e), from the table, and the losses of 
the electric drive will consist of (/) and (g). The mechanical 
gear, therefore, will be about 3 percent more efficient at full 
power than the electric machinery. This will mean a reduction 
in the turbine horsepower required and a corresponding reduction 
in weight- 
It will be seen that, if we use the weight and horsepower re- 
quired by the electric machinery as a basis of comparison, all 
saving in weight by the use of mechanical gears becomes accumu- 
lative, so that the hnal saving in weight and total reduction in 
horsepower are very large. 

There is another important point in connection with the use 
of gears for this class of vessel. These ships seldom steam at 
their maximum power, so that the actual tooth pressure of the 
gears is very low. This gives the gears a very much longer life 
than in the case of ships steaming at full speed all the time, as is 
the case with a merchant vessel. 

The fifth class of ship to be considered will be the capital ships 
of the Navy — that is, the battleship and battle cruiser. These 
vessels will always be fitted with four shafts. Here the reduction 
is considerably more than in the case of light naval vessels, being 
as much as 12 to I in some instances, but still within the range of 
a single reduction, although at the expense of a slight loss in 
propeller efficiency in some cases. 

At full power the difference in over-all efficiency of trans- 
mission, assuming equal propeller efficiency in the two cases. 



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8 ELECTRIC SHIP PROPULSION 

would be about the same as for Class 4 ships. At the cruising 
speeds of the ship, the electric machinery would have an advantage 
ni from 15 to 25 percent. This advantage comes trom the fol- 
lowing causes : first, the electric machinery can use two reduction 
ratios, thus keeping up the turbine speed at the lower speeds of 
the ship; second, with the electric machinery, only one turbine is 
used at the lower speeds, thus doubling or quadrupling the load 
on the turbine and generator according to whether the ship has 
two or four turbo generators ; and, third, the number of auxil- 
iries for serving the turbines in use in the electric engine room 
will be only one-half or one-fourth of what will be necessary for 
the geared engine room. Cruising speed economy is of great 
importance in these ships ; of course the most important economy 
is that at full power, but in such a case as this, where the differ- 
ence at full-power is small, the great improvement at cruising 
speeds is of the greatest importance. 

As regards the weights of the two installations, there will be 
■o very great difference. For battleships, the geared installation 
will probably be somewhat lighter ; for battle cruisers, the condi- 
tion will be reversed. In neither case, however, will the difference 
be great enough to be of any consequence. 

From the above it will be seen that from a comparison of 
economies the electric machinery has considerable advantage for 
this type of ship. However, there are other considerations that 
give it a more decided advantage. 

The most important of these is the flexibility of the electric 
machinery as regards installation. The steam part of this equip- 
ment, being entirely independent of the propeller shafts, can be 
arranged so as to get the maximum protection against torpedoes 
and gunfire. This is an advantage that can hardly be overesti- 
mated for this type of ship, as it makes it possible to protect the 
ship itself, as well as the machinery, in a way that is entirely 
impossible with any type of machinery where the prime mover 
must be connected to the propeller shafting. With the electric 
machinery, the motors are attached to the shafting but they can 
be placed in much smaller compartments than can steam turbines, 
thus reducing the danger to the ship in case the compartment is 
flooded, and, at the same time, allowing greater protection to the 
.compartment. The motors can be placed so as greatly to reduce 



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HISTORY OF ELECTRIC PROPULSION 9 

the length of shafting required for the turbine drive, thus cutting 
down the number of bulkheads pierced by the shafting and adding 
to the reliability of the shafting, as well as adding to the protec- 
tion of the ship. 

The installation arrangement also adds considerably to the 
reliability of the steam machinery ; all of the main auxiliaries can 
be grouped in the engine rooms, allowing greater duplication, 
both of the units themselves and also of the piping systems, and 
at the same time giving them better protection. The leads of 
steam, exhaust and other piping are simplified, the length short- 
ened and the pipes are given better protection. The maximum 
pipe diameter required will also be less — a point which is very 
important in the case of the main steam pipe of a battle cruiser. 

There are other minor advantages of electric machinery which 
are of more importance to a military ship than to a merchant ship. 
With a gear drive, damage to a turbine means that one propeller 
must be dragged; with electric machinery, turbine damage only 
operates to reduce the speed of the ship and not the method of 
propulsion, as all screws will still be used. A dragging screw 
may add as much as 20 percent to the horsepower required to 
drive the ship at some speeds; it will reduce the maneuvering 
qualities of the ship; and in most instances it will be necessary 
to prevent the shaft of the damaged turbine from revolving, in 
which case, the horsepower will be still further increased and the 
speed of the ship limited to that at which it is possible to keep 
the shaft locked (usually with the "jacking gear") — generally a 
very low speed. The ability to run all screws from one generator, 
virtually gives duplicate or quadruplicate main engines, conden- 
sers and auxiliaries so far as maneuvering at slow speeds or in 
harbors is concerned. As an example of this advantage, the New 
Mexico has found it useful to keep both main turbo generators 
running when entering certain ports. When one condenser be- 
comes plugged with mud, a shift is made to the other, an opera- 
tion which requires only a few seconds of time. With a turbine 
drive, this would usually mean a burned-out condenser. When 
cruising at low speeds, only one generator will be used and con- 
sequently only one set of engine room auxiliaries, thus reducing 
the necessary attendance and supervision. 

In the above discussion of the relative merits of gears and 



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10 ELECTRIC SHIP PROPULSION 

electric propulsion for the various classes of ships the question of 
superheat has been entirely neglected. The present tendency is 
toward the use of more superheat for marine purposes. With 
backing turbines, very high temperatures are produced during the 
short interval of time in which steam is flowing through the back- 
ing turbine and the ahead turbine is still turning over in the ahead 
direction. Considerable experimental work has been carried out 
in regard to this point with the result that most engineers recom- 
mend that the superheat be limited to 80 or 100 degrees F. with 
geared turbines. This excessive temperature lasts for only a very 
short time, but it may cause local distortions which will even- 
tually cause the turbine to strip. From experiments made, some 
engineers have placed this temperature as high as 1,100 degrees F. 
With electric machinery, the turbine always revolves in the same 
direction and it does not start up under load, so that the limitations 
caused by a reversing turbine do not exist, and we may shortly be 
using superheat of 250 to 300 degrees F., which will mean a very 
great increase in the economy. 

To recapitulate, the following table shows the type of ma- 
chinery best adapted to each class of ship : 

(1) Low speed cargo vessels of less than 3,000 shaft 
horsepower — Diesel electric propulsion. 

(2) Cargo and passenger vessels requiring more than 
3,000 shaft horsepower, but not enough to require the use of 
four screws — turbo electric propulsion. 

(3) Passenger vessels of high speed and sufficient horse- 
power to require four screws — turbo electric propulsion. 

(4) Destroyers,' scout cruisers and light cruisers — geared 
turbines. 

(5) Battleships and battle cruisers— turbo electric pro- 
pulsion. 



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CHAPTER II ! ■■ 

Systems of Propulsion 

THE first question to be decided in regard to electric propul- 
sion is what system shall be used. Some of the points to 
be considered in decidii^ this question are reliability, effi- 
ciency, simplicity, flexibility and weight. 

It will be necessary first to decide whether alternating or direct 
current shall be used. In nearly all land applications of elec- 
tricity it has been found most satisfactory and economical to 
transmit power in the form of alternating current to the point of 
application, where it is in many cases converted into direct current 
before it is used. In order to transmit power over long distances 
without great loss it is necessary to use high voltage, while it is 
usually desirable to use low voltage at the point of application. 
Akernating current has a great advantage over direct current in 
respect to the method of transforming high voltage to low, or 
vice versa. In a transformation of voltage with direct current, 
■ power is supplied to a motor which drives a generator which 
delivers current at the desired voltage. The apparatus is ex- 
oehsive, requires constant attention and its efficiency is never 
greater than 90 percent. The transformation of voltage with 
alternating current is accomplished by means of a transformer, 
which is cheap, has an efficiency of over 97 percent and requires 
no attention. For ship propulsion, however, none of these ad- 
vantages holds, as the distance of transmission is short and no 
voltage transformation is required. 

But there are other advantages that make it proper to use 
alternating current. for turbo electric propulsion. The direct cur- 
rent generator is essentially a slow speed machine, mainly on 
account of the difliculties of commutation at high speeds. This 
makes it necessary to use a gear reduction between turbine and 
generator in order to get the best steam economy and this adds 



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12 ELECTRIC SHIP PROPULSION 

one more link in the chain between the turbine and propeller and, 
at the same time, reduces the efficiency of the turbine by the 
amount of the gear loss. 

The weight of the direct current turbo generator will also be 
much greater than that of the alternator, it being assumed that 
voltages as high as 5,000 may be used with alternating current. 

The efficiency of transmission of the alternating current system 
will be greater than that of the direct current system; the maxi- 
mum efficiency for the first being about 92 percent and for t|ie 
second about 87 -percent. 

The alternating current system, having no commutator and no 
sliding contacts with high voltage, is much more reliable than the 
direct. This difference between the two systems is greater on 
board ship than ashore, owing to the fact that the air for ventila- 
tion is always charged with salt moisture. 

The direct current system would be somewhat simpler and 
more flexible than its rival, but the latter is quite satisfactory in 
this respect, so that the advantage is of little importance. 

Having decided on alternating current as being the most suit- 
able for turbo electric ship propulsion, the next point to decide is 
which is the best of the various alternating current systems that 
have been proposed. Many patents have been taken out covering 
special arrangements of motors and generators to get several 
speeds, but none of them has been put to any practical use by an 
actual installation in a ship. Most of these are schemes for get- 
ting a great number of speeds by changing electrical connections 
while keeping the speed of the generator constant. While these 
schemes might work in a merchant vessel, none of them would be 
suitable for a war vessel because it is necessary for these ships to 
have any desired speed within the limit of the full power of the 
vessel — in other words, an infinite number of speeds. Also, in 
most of these arrangements it has been proposed to use a multi- 
plicity of generators and motors, some of which would not be in 
use at full speed ; this is not economical of either space, weight or 
money. Before describing the arrangements that have actually 
been used, and indicating probable future developments, a brief 
description will be given of some of the proposed schemes. 

Mr. Henry Mavor has patented, in England, a system of ship 
propubion which consists of several squirrel cage induction motors 



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SYSTEMS OF PROPULSION 13 

on a shaft and an equal number of generators, the latter having 
different frequencies. By various combinations of generators 
and motors a number of propeller speeds can be obtained. For 
example, suppose we have the following arrangement : 

Generator Speed Number of Poles 

A 1800 revolutions per minute 2 

B 1800 revolutions per minute 4 

C 1800 revolutions per minute 8 
Motor 

E • 16 

F 32 

G 64 

Then, at full power, if generator A drives motor E and generator 
B drives motor F and generator C drives motor G, each motor will 

be running at —5- =: 225 revolutions per minute. If it is desired 

to run at a lower speed, we may use generator A to drive motor F 
and generator B to drive motor G, the propeller shaft will then 

1800 
run at -rr^ = 112.5 revolutions per minute, or we may use gen- 
erator A to drive motor G, when we shall get a propeller speed of 
—~y- ^ 56.25 revolutions per minute. The disadvantages of 

such a system are very apparent. It is not desirable to subdivide 
the power of the ship to any such extent; if the ship had two 
shafts, there would be required six generators and six motors, 
and only three speeds would be available even then. Also, no 
scheme is feasible that involves running several generators to 
drive motors on one shaft, as the difficulty of maintaining syn- 
chronism is too great. 

Mr. Mavor has also patented a "spinner" motor which has 
two rotating elements and one stationary one. The stationary 
element is similar to the stator of other induction motors and the 
inner rotating member is similar to other rotors. The inter- 
mediate rotating member is supplied with a squirrel c^e winding 
on its outer periphery and with a primary winding on its inner 
periphery. The object of this arrangement is to provide variable 
speed with one supply of frequency, and also to provide a means 
of starting the low resistance squirrel cage motor which has very, 



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14 ELECTRIC SHIP PROPULSION 

little torque for starting. This is accomplished by first startii^ 
up the intermediate rotating member, which will require prac- 
tically no torque for starting. When this member has reached 
its speed, a brake is applied and, while it is gradually brought to a 
stop, the other rotating member will gradually be brought up to 
speed without taking an excessive current owing to the low fre- 
quency that is imposed on it. This motor has three speeds when 
supplied with only one frequency. This is accomplished as 
follows : 

(a) Slow speed by running the intermediate member in 
the opposite direction to that of the rotor on the propeller 
shaft. 

(b) Intermediate speed by holding the intermediate mem- 
ber stopped. 

(c) Full speed by running the intermediate member in 
the same direction as the rotor on the propeller shaft. 

This motor could not, of course, be built in large sizes on 
account of the arrai^ement necessary to give the intermediate 
member proper bearings, nor could a laige brake be provided. 
The power factor of such a motor will also be very poor. 

Mr. Hobart has described a system which he calls the alter- 
phase system of ship propulsion. It is based on the fact that a 
motor stator winding which has been arranged to correspond to, 
say, P poles for a three-phase system, will be suitable for a 
quarter-phase system when arranged with ^ P poles. This 
change in polar arrangement may be made by taking the terminals 
to a switch which will be double-throw, giving the quarter-phase 
connection in one throw and the three-phase in the other. A 
motor arranged in this manner must be supplied by two different 
phase systems, which may be obtained from two generators, one 
wound for quarter-phase, and the other for three-phase, or from 
a single generator wound to supply both phases. The objections 
to such a system are that it involves the use of generators which 
are dissimilar and not interchangeable, or else the use of a com- 
plicated generator ; it is not necessary to do either of these, as the 
same result can be obtained by arranging the motors for pole- 
changing; this can be very readily and simply effected on motors 
without in any way changing the generator. This method will be 
described in Chapter IV, 



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SYSTEMS OF PROPULSION IS 

Many other schemes have been proposed for electric propul- 
sion, but space forbids their enumeration ; the foregoing examples, 
however, illustrate how difficult it is for one entirely to chai^ his 
methods of thinking when confronted with a problem involving 
entirely new conditions. The electrical engineer is used to dealing 
with problems where the frequency and voltage are constant and 
it is difficult for him to think in any other terms but these. 

The method of ship propulsion in use in this country is that of 
variable frequency — that is, speed changes are made in the prime 
mover itself, Just as with any other steam engine, and the gen- 
erator and motor are considered simply as a reduction gear. This 
arrangement is very flexible and gives an infinite number of 
speeds ; it is also very simple, as it keeps the number of necessary 
switches down to a minimum ; it is efficient for all loads since the 
reduced frequency and voltage that go with reduced load maintain 
a very high efficiency for both the motors and generators; all 
motors are alike and all generators are alike, so that all spare parts 
are the same. For ships which have a high speed, but which 
generally cruise at a low speed, the system may be used in con- 
junction with an induction motor which has its stator and rotor 
wound for two different pole arrangements, thus giving two speed 
reductions; or, if the power to be transmitted is great enough to 
require two motors on each shaft, the two speed reductions may 
be obtained by running the two motors on one shaft in cascade, or 
in parallel. By properly dividing up the power plant and using 
only part of it at the lower speeds, a very efficient arrangement 
can be obtained at all speeds up to the maximum. 

Having settled on the plan of using variable frequency, we 
can now proceed to a more detailed consideration of the require- 
ments of the classes of vessels discussed in Chapter I. For the 
second class of vessel it will be possible to use turbo generators 
driving either synchronous motors or induction motors. A syn- 
chronous motor has some advantages over an induction motor; it 
is slightly more efficient ; it would have a much larger air gap ; it 
would have unity power factor, so that the generator would be 
lighter and more efficient; it would have no high voltage in its 
rotor, there being only the low voltage exciting current in the 
rotor fields ; and, being more efficient, it would require less venti- 
lation. To oppose these advantages, there is the disadvantage of 



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16 ELECTRIC SHIP PROPULSION 

this motor being less flexible than the induction motor. It Is 
necessary to use a high resistance squirrel cage winding on the 
rotor field to produce the necessary torque for reversal and the 
operation oi starting or reversing this motor is more complicated 
than in the case of an induction motor. It is not believed that 
this motor would be satisfactory for the high speed vessels of 
Class 2 on account of the difficulty of getting the necessary torque 
for reversal. When everything is taken into consideration, it is 
beHeved that the induction motor will really be the most satisfac- 
tory for all vessels of this class on account of the simplicity of 
the installation, and the ease of operation. 

For vessels in Class 3, it would be necessary to use induction 
motors, as synchronous motors would not be satisfactory for the 
reasons given above. For these ships it would seem to be unneces- 
sary to provide two-speed motors, as these ships do not use a 
greatly reduced speed often enough to make the additional compli- 
cation worth while. 

For vessels in Class 5, turbo alternators and induction motors 
would seem to be the most satisfactory, for the same reasons as 
have already been given. The motors would be arranged for poie- 
changii^ to give economy at cruising speed. 

The exact arrangement of motors and generators will have to 
be decided in each individual case by the conditions governing. 
However, it should always be borne in mind that, for a marine 
installation, the simplest possible plant is the one to be most de- 
sired and unnecessary complications should not be introduced 
unless they add very considerably to the reliability or efficiency of 
the plant. Running alternating current generators in parallel 
should be avoided, if possible, and should not be attempted at all, 
if the speed of the generators in parallel must be changed. The 
power plant should not be divided more than is necessary for relia- 
bility and for giving the best economy under the desired operating 
conditions, as it should be remembered that the fewer the number 
of units the more efficient they will be and the less the total 
weight will be. For example, a single generator is quite satis- 
factory for a freighter and two are enough for a battleship ; for a 
battle cruiser, it will be necessary to use four, as the size would be 
prohibitive if a less number were used. 

In the case of a ship which only uses reduced speed for 



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SYSTEMS OF PROPULSION 17 

maneuvering, it is possible to use a constant frequency and an 
induction motor with a definite-wound rotor which is connected 
to external resistances through slip rings, Mr. Ljungstrom, in 
his latest electrically propelled ship, uses this method. Speed 
variations are accomplished by inserting a varying amount of re- 
sistance into the rotor circuit. The arrangement he has used is 
very simple in the way~it is worked out and that is a great point in 
its favor. This scheme would, of course, be unsatisfactory for a 
war vessel, as the motor is very inefficient at all speeds except lijll 
speed; it is even questionable whether an arrangement that pro- 
vides only one efficient speed is satisfactory even for a freight 
steamer, particularly since the lower speeds are so very inefficient; 
Also, this method could not be used for large power, as the 
rheostats would be too large. 

The reasons given in the first part of this chapter for using 
alternating current apply only to the case of turbo electric [iro- 
pulsion. For Diesel electric propulsion direct current will be 
more suitable, as will be seen when that subject is discussed. 



ly Google 



CHAPTER III 
Propeller Characteristics 

WHEN electric propulsion was first proposed, it was be- 
lieved that a propeller load was an ideal one for electric 
machinery. This is true when a ship is steaming steadily 
but when a ship is maneuvering the propeller characteristics are 
such as to be very exacting on an induction motor. 

When the design of the New Mexico's propelling machinery 
was begun it was found that, while the data on propellers were very 
complete for the normal condition of "ahead steaming," there was 
practically no information available regarding the characteristics 
of a propeller under maneuvering conditions. As these conditions 
are the most important in their bearing on induction motor design, 
it was decided to investigate propeller action thoroughly before 
designing the motors. It was fortunate that this decision was 
made, as the motors would not have been able to reverse the pro- 
pellers, if the commonly accepted ideas regarding propeller torque 
had been used as a basis of design. 

The first experiments were made in the model tank. Fig. I 
shows a complete set of contour curves of propeller torque ob- 
tained by running a model of the Delaware's propeller. These 
curves cover all conditions of speed of the ship ahead and astern, 
and revolutions per minute of the propeller ahead and astern. 

The curves shown are curves of equal torque. If a vertical 
line is drawn through any speed, the revolutions per minute cor- 
responding to each torque curve can be found; if these revolutions 
per minute are plotted against torque, the result will be as shown 
in Fig. 2. 

In this figure the revolutions per minute and torque have been 
plotted as a percentage of the revolutions per minute and torque 
required to drive the ship at the given speed. This curve has been 
drawn for the full speed condition but it will have the same gen- 
eral shape for any speed ; at the lower speeds the maximum torque 
i8 



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D,„t,..= b:, Google 



20 ELECTRIC SHIP PROPULSION 

point during reversal is a greater percentage of the driving torque, 
being about 120 percent at 10 knots as compared with 95 percent 
at 21 knots. 

Fig. 3 shows a curve that was obtained from the Jupiter. It 
is similar in all respects to that obtained from the model tank but 
the maximum point is lower, being only about 77 percent of the 
"full-load driving torque." Two points are shown at the "stop" 
poitit, one being the point at which the propeller will start re- 
volving ahead and the other the point at which it will start 
revolving astern ; the difference between the two is twice the shaft 
friction. 

The above experiments with the model of the Delaware's 
propeller and with the Jupiter established the following important 
facts : 

First — On reversal, the propeller speed drops suddenly to 
about 70 percent of its original speed, which is the speed 
corresponding to zero torque. 

Second^ — From zero the torque increases to a maximum, 

this maximum being substantially the same as the ahead torque. 

Third — Maximum torque occurs when the propeller speed 

has dropped to about 40 percent of the original speed. 

For reasons that will be seen later on, these three facts have 

an important bearing on the design of the electric ship propulsion 

machinery. 

On the New Mexico the maximum torque required during 
reversal was found to be about 106 percent at 18 knots; this 
agrees very closely with the model tank experiments on the 
Delaware and would indicate that, with high speed ships, the 
■- torque required for reversal is a greater percentage of the driving 
torque than is the case of low speed ships, although for each indi- 
vidual ship the lower speeds require a greater percentage of torque 
for reversal than the high speeds. 

The other condition of maneuvering that most affects the 
design of machinery is "turning," Very few marine engines are 
fitted with speed governors, the control of speed being entirely 
dependent on the throttle. With constant throttle opening, a re- 
ciprocating engine will develop practically a constant torque, 
regardless of whether the ship is turning or going straight ahead, 
and the steam flow and the power will vary directly as the revo- 



Digmze. by Google 



PROPELLER CHARACTERISTICS 























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il Full Uod B.P.M.(I!2.!B.P,M.) 

Fic. 2.— Propeller Torque Curves for U. S. S. Delaware. Ship Going 
Ahead at a Constant Speed of 2i Knots, Derived from Model Propeller 
Tests in Undisturbed Water 



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Fic. 3.— Propeller Torque Curves for U. S. S. Jupiter, Ship Going Ahead 
at Constant Speed of 10 Knots 



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22 



ELECTRIC SHIP PROPULSION 



lutions per minute of the engine. With the same conditions for 
a turbine the amount of steam How will remain practically con- 
stant and the revolutions per minute of the turbine will decrease 
as the torque imposed on it increases; also, the power will vary 
approximately as the revolutions per minute of the turbine. With 
an engine or turbine fitted with a speed governor the revolutions 
per minute will be kept constant and the power will vary as the 
torque. 

Figs. 4, 5 and 6 show horsepower curves taken on the Dela- 
ware, Jupiter and New Mexico, respectively, while these ships 













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were turning. In Fig. 4 the curves marked "throttle untouched" 
show the changes in horsepower that take place when the ship 
turns with the throttle opening the same as before the turn was 
started ; it will be noted that the change is comparatively small and 
is exactly the reverse of the changes shown in the curves marked 
"throttle open." The curves marked "throttle open" show the 



Digmze. by Google 



PROPELLER CHARACTERISTICS 



il 



D,„t,..= b:, Google 



24 ELECTRIC SHIP PROPULSION 

changes on the same ship when the throttle is changed to maintain 
"constant revolutions per minute." It will be noted that the 
power on the screw on the outboard side of the turning circle 
drops and that on the screw on the inboard side of the turning 



Fic. 6.— Power Curves taken on U. S. S. New Mexico while Ship was 
Turning with 35 Degrees Right Rudder 

circle rises. After a short time the power on the outboard screw 
also rises. 

Figs. 5 and 6 show the same phenomenon. Here the engine is 
governed and the condition is the same as that on the Delaware 



Digmze. by Google 



PROPELLER CHARACTERISTICS 25 

wHen the turn was made with "throttle open." These curves are 
smoother than those of the Delaware, as power readings could be 
taken more frequently ; they also show the changes in power more 
clearly. 

In Fig. S (the Jupiter) the power first drops onthe outboard 
screw, reaching a minimum when the ship has turned through 
about 20 degrees ; it then begins to rise, reaching its original value 
when the ship has turned through about 40 degrees, and reaching 
a constant value when the ship has turned through about 140 
degrees. The power rises on the inboard screw from the begin- 
ning to the end of the turn. 

In Fig. 6 (the New Mexico) the power was measured on the 
generators instead of the motors and, therefore, one curve shows 
total power when only one generator is being used. This curve 
is marked "14.5 knots." The other two curves each represent 
power on only one side of the ship. When turning with one 
generator at 14.5 knots, the power rose steadily until the ship had 
turned for 2 minutes and 20 seconds, when it became constant. 
When turning with two generators at 19.5 knots, the power on 
the outboard screws reached a minimum at 40 seconds of turn, . 
reached its original value at 1 minute and 10 seconds of turn and 
became constant at 1 minute and 30 seconds of turn. The power 
on the inboard screws rose steadily until it became a maximum 
at 50 seconds of turn; this latter was due to the fact that the 
input of the turbine at this speed was limited to 15,000 kilowatts. 

From the three figures we see that on the Delaware, turning 
at 12 knots with the rudder at only 16 degrees, the increase of 
power on the inboard screw was 58.75 percent. On the Jupiter, 
turning at 14 knots with the rudder at 25 degrees, the increase of 
power on the outboard screw was 4.6 percent, on the inboard 
screw 53 percent and the total increase of power was 29 percent. 
On the New Mexico, turning at 14,5 knots with the rudder at 35 
degrees, the total increase of power was 50 percent; turning at 
19.5 knots with the rudder at 35 degrees, the increase of power 
on the outboard screws was 14 percent and the increase on the 
inboard screws was 42 percent, this latter being limited by the 
maximum allowed steam flow. 

It will be seen from the above figures that when turning at 



Digmze. by Google 



26 ELECTRIC SHIP PROPULSION 

high speeds with large rudder angles, the increase of power be- 
comes greater than the maximum output of the generators and 
means must be provided for limiting the steam flow to the turbine 
so that it will slow down when a certain predetermined load has 
been reached. 



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CHAPTER IV 

Characteristics of Alternating Current Motors and Generators 
for Sliip Propulsion 

IN Chapter III we have seen what the characteristics of a prop- 
peller are ; in this chapter it will he shown how to meet these 
conditions in the design of alternating current generators 
and synchronous and induction motors. The characteristics of 
direct current machinery for ship propulsion will he given in the 
chapter on Diesel electric propulsion. The methods used for the- 
induction motor will be described first since the induction motor 
must be used in connection with the reversal ot the synchronous 
motor. 

The design problem is different from any encountered in land 
practice, due to the fact that ordinarily any one motor is only a 
part of the load on the system from which it is being fed; any 
overload that one motor can pull will, therefore, have practically 
no effect on the voltage of the system, so that the motor is always 
operated with a constant voltage. With a ship installation, the 
conditions are entirely different ; the motor constitutes the entire 
load of the generator, so that the voltage will be very materially 
affected by large changes of load and this entirely chains the 
characteristic curve of the motor. Fig. 7 shows the torque 
characteristics of a double squirrel cage induction motor when 
fed from constant voltage, and also when fed from a ship's alter- 
nator. At 200 percent slip (when reversal begins), when the 
motor is fed with constant voltage, the torque is nearly six times , 
as great as it is when the motor is fed from a ship's alternator. 

Since the maximum power that can be drawn from any gen- 
erator is limited by its drop in voltage with increase of current, it 
follows that the maximum power that can be exerted, even 
momentarily, by the motor will always be limited by the genera- 
tor, regardless of how large we may make the motor. The only 
way the maximum power of the generator can be increased is by 



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28 



ELECTRIC SHIP PROPULSION 



increasing its voltage by giving it more exciting current. The 
maximum allowed exciting current will be limited by the heating 
of the generator field, so that the maximum torque of the motor 
will really be limited by the heating of the generator field. 

It is desirable from the standpoint of weight and economy 
that the generator should be made as small as possible ; the best 
economy will be obtained, if the generator works at about its 









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Fig. 7. — Comparison of Characteristics of a Double Squirrel Cage In- 
duction Motor when Operated on a Power Circuit of Constant Potential 
and the Same Motor used for Ship Propulsion 

normal capacity at the full power of the ship. But it is also 
necessary to provide the large torque for reversal that is shown to 
be necessary in Chapter III. Since this torque is required for 
only a short interval of time, it is possible to use a very large 
exciting current for this period without overheating the field ; as 
soon as reversal has been accomplished, the current can be restored 
to its normal value. Thus we can use a generator which is of the 
proper size for full speed driving and which will also furnish the 
necessary torque for reversal. 

This method takes care of the loss of voltage of the generator 
due to overload but there still remains the problem of getting 



Digmze. by Google 



MOTORS AND GENERATORS 29 

large torque with an induction motor when it is out of syn- 
chronism with its generator. A reference to Fig. 2 of Chapter III 
shows that this torque must be about 100 percent of the torque 
required to drive the ship. This is indeed an exacting condition^ 
for an induction motor that must have the highest economy when 
driving. This large torque may be provided, (1) by using a 
motor having a wound rotor with slip rings and inserting resist- 
ance in the rotor circuit; (2) by the use of a double squirrel cage 
motor; or (3) by the use of a combination of a high resistance 
squirrel cage with a wound rotor, the latter being open circuited 
when it is desired to reverse. In the case of (1) — resistance 
inserted in the rotor circuit — this resistance may be (a) in one 
solid block, or (&) in the form of a variable resistance which can 
be cut out gradually. Each of these methods will be illustrated 
by describing a typical installation. The Jupiter will illustrate 
(1) (a), the Tennessee (I) (fc), the Ne^v Mexico (2), and the 
California (3). 

The single block of resistance is the simplest of these methods 
and will be described first. 

Fig. 8 shows torque curves of the Jupiter's motors under 
various conditions of excitation and with and without external 
resistance ; the propeller torque curve is also shown, A compari- 
son of curves A, B and C shows very clearly the effect of in- 
creasing the generator excitation and a comparison of curves B 
and D shows the effect of inserting external resistance in the 
rotor circuit. The curves are all made using constant frequency, 
the generator runnii^ at 1,990 revolutions per minute. 

It is evident from curve E that the propeller could not be 
reversed by using curve D, as the motor torque is less than the 
propeller torque. By inserting external resistance, however, the 
motor torque is at once brought above the propeller torque, so that 
the propeller will be reversed and brought up to speed in the 
reverse direction. It will be brought up to 37.5 revolutions per 
minute (intersection of B and E), if curve B is used, and to 46.5 
revolutions per minute, if curve C is used. 

In order to develop sufficient power when backing it would be 
desirable to carry the maximum allowable excitation when re- 
versing. With this arrangement it is simpler not to provide for 



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D,„t,..= b:, Google 



MOTORS AND GENERATORS 



31 



cutting out the external resistance when reversing ; the resistance 
should, therefore, be capable of giving continuous operation. 

The operation of inserting resistance takes care of the re- 
versing condition satisfactorily and also the condition of starting 
up from rest. This operation can be carried out with the gen- 
erator running at full speed, if desired. However, when it is 
desired to reverse this operation and cut out the resistance it will 
be necessary to change the frequency (speed of the generator). 

Referring to Fig. 9, suppose that the ship is going ahead and 
the propeller has been brought up to 86 revolutions per minute 





























































































































































































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Fig. 9.— Motor Torque Curves of U. S. S. Jupiter 

{about 11 knots) with resistance inserted and excitation at 300 
amperes (curve C) ; this is the maximum speed that can be ob- 
tained using curve C and is represented by the point x. If the 
resistance were now cut out, the motor would pass from curve C 
to curve D and the motor would fall "out of step," as the motor 
torque would be less than that required to drive the propeller at 
that speed. If, however, the turbine is slowed down before the 
resistance is cut out, curve D will move to another position, say 
tliat of curve F. This corresponds to a frequency of 29,1 cycles 
(1,746 revolutions per minute of the generator). Curve F inter- 



Digmze. by Google 



32 



ELECTRIC SHIP PROPVLSIOM 



sects curve C at the point x and has an excess of torque above that 
required to drive the propeller at that speed, so it will accelerate 
the propeller till the point y has been reached. This corresponds 
to 96 revolutions per minute or about 12.3 knots. If the turbo 



610CI/ZI?5Hp -Z4/WI 




AiVern fi. P. M. 

—Approximate Torque Curves 



100 lis IBO ns 
of U. S. S. Tennessee 



generator is now speeded up, curve F will move to the right and 
the propeller revolutions per minute will be increased till the 
point 3 has been reached on curve D. This point corresponds to 
14 knots or the designed speed of the ship. 



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MOTORS AND GENERATORS 



33 



When arranged as described above, the single block of resist- 
ance installation is the simplest possible method of operation, since 
reversal is accomplished merely by opening one switch and closing 
another — it being unnecessary to change either the speed of the 
turbine or the field of the generator. But when it is desired to 
utilize the full power of the installation during backing, the vari- 
able resistance method is more suitable; it is necessary to cut out 
the resistance to obtain full power and this can be accomplished 











































































































































































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more readily with a variable resistance than with a single re- 
sistance. 

Fig. 10 shows the torque curves of the Tennessee motor, 
which is provided with a variable resistance. The operation of 
reversal '\i started with all resistance in the rotor circuit. In this 
condition the motor has the torque characteristic shown by curve 
A. As the resistance is gradually reduced, the characteristic 
changes from curve A to curve D, passing through an infinite 



Digmze. by Google 



34 ELECTRIC SHIP PROPULSION 

number of curves, such as B and C. Curve E gives the propeller 
characteristic and it will be seen that this curve lies above curve 
D ; in other words, the propeller torque is greater than that given 
by the "out of synchronism" part of curve D. In order to bring 
the motor into synchronism with the generator, it will be necessary 
to reduce the frequency (turbine speed) at the same time that 
resistance is cut out. This will have the effect of moving curve D 
over to the right and it must move at least as far as the position 
shown by curve F. Curve £ intersects curve F on the stable side 
of curve F and this condition will therefore give stable running. 
As the ship loses headway due to the backing of the propellers, 
the propeller torque curve will fall lower and lower, passit^ 
through successive curves, such as G ; as this occurs the speed of 
the generator can be increased to keep the point of intersection of 
the two curves near the maximum point of the motor torque curve, 
thus keeping the power delivered to the propeller up to the 
n^iximum. 

The General Electric Company has perfected a type of motor 
which furnishes the necessary torque for reversal without the use 
of external resistance. It is called a double squirrel cage motor, 
since the rotor has two independent squirrel cage windings. Fig. 
11 shows the torque characteristics of this type of motor as com- 
pared with an ordinary motor of the same rating. It will be seen 
that for a slip of 200 percent the double squirrel cage motor has 
seventeen times as much torque as the ordinary motor. 

Fig. 12 shows the arrangement of the bars in the slots of a 
double squirrel cage motor. The rotor slots are double, with a 
narrow air gap connecting them ; the outer slot contains a German 
silver bar of high resistance and the inner slot a copper bar of low 
resistance. At low frequencies of the rotor the reactance due to 
leakage of flux across the narrow air gap will be of little im- 
portance; this is the condition that obtains when the motor is 
running at practically the synchronous speed of the generator. 
When the motor stator connections are reversed while the pro- 
peller is revolving, the rotor frequency will be double that of the 
generator at the instant of reversal. Under this condition the 
reactance due to the leakage across the narrow air gap becomes the 
predominating factor, so that there will be very little current flow- 
ing in the inner squirrel cage and the motor will become prac- 



Digmze. by Google 



MOTORS AND GENERATORS 



35 



tically a high resistance squirrel cage motor with large torque for 
reversal. Thus, in one motor, we have combined a high resistance 
squirrel cage for reversal and a low resistance squirrel cage for 
ordinary running conditions ; the transition from one condition to 
the other is entirely automatic 



■ 


1 1 


.MS' 

.m' 


1 1 




1 1 


s. 


«--.42'--> 


1 1 






1 1 


1 1 


i 









+ 



— Copptr s^virrtl eag*. 



The torque characteristic curve is really the resultant obtained 
by combining the torque curves of the two squirrel cages and that 
accounts for the dip in the torque curve which occurs at a slip of 
0.3 in Fig. 11; this point is the intersection of the two torque 



Digmze. by Google 



36 ELECTRIC SHIP PROPULSION 

curves. While the two circuits are not connected electrically in 
any way, the result is the same as if the two squirrel cages were 
in parallel. 

By the use of such a motor, all external resistance can be omit- 
ted and the operation of reversal will also be simplified. This 
motor will, however, have a lower power factor than a motor with 
external resistance and it will, therefore, require a larger gen- 
erator. 

In order to make the action of this motor entirely clear, there 
is shown in Fig. 13 an equivalent xrircuit of the New Mexico's 
motors. This circuit differs from the ordinary equivalent circuit 
of an induction motor in having the additional circuit, x^ r^ in its 
rotor circuit. In this circuit : 

Xf represents the reactance of the primary or stator. 

Tf represents the resistance of the primary or stator. 

Xc represents the common reactance of the two squirrel cages. 

Tb represents the resistance of the outer squirrel cage. 

r, represents the resistance of the inner squirrel cage. 

Xt represents the reactance of the inner squirrel cage, which 
is not aiso common to the outer squirrel cage. 

&m represents the magnetizing susceptance. 
The values of the different parts of the circuit given in F^. 13 
are for the New Mexico's motors. The following table of calcu- 




lations shows the method of solving the problem of obtaining the 
torque for any condition of slip; the two conditions taken are 
for a slip of 0.01 (normal running) and for a slip of 1.00 
(standstill) : 



Digmze. by Google 



MOTORS AND GENERATORS 



THEORY AND CALCULATION OF CHARACTERISTICS OF 
THE DOUBLE SQUIRREL CAGE INDUCTION MOTOR 



s 


O.OI 


1.00 


Slip of thii Motor 




0.0503 


0.0503 


Resistance of squirrel 
cage winding in bot- 
tom of rotor slot*. 
This winding will here- 
after be called the 
lower squirrel cage; 
the squirrel cage in the 
top of the rotor slots 
will be called the up- 
per squirrel cage. 


"^ap^r 


S.03 


0,0503 


Equivalent resistance of 
lower squirrel cage at 
slip s. 


". 


0.713 


0.713 


The reactance of the 
lower squirrel cage 
which is not mutual 
with the upper squirrel 
cage. 


^l-%^< 


25.8 


0.51 


Equivalent impedance 
squared of lower 
squirrel cage at slip s. 


''-'? 


0.19s 


0.0986 


Conductance of lower 
squirrel cage at slip s. 


^•-I - 


0.0276 


MO 


Snsceptance of lower 
squirrel cage. 


'"b 


0.66s 


0.665 


Resistance of upper 
squirrel cage. 


^P-? 


66.5 


0.665 


Equivalent resistance of 
upper squirrel cage at 


'''k. 


0.01502 


1.502 


Conductance of upper 
squirrel cage at slip s. 


ffab-«a+^b 


0.21 


1.602 


Resultant conductance of 
both squirrel cages in 
parallel. 



D,„t,..= b:, Google 



ELECTRIC SHIP PROPULSION 



=^ab+ba 



<=r^+x^ 



o.ro54 

ai427 



0.1054 

MOS 



Slip of the Motor 



Admittance squared of 
both squirrel cages in 
parallel but not includ- 
ing mutual reactance. 

Resultant rotor equiva- 
lent reactance at slip j, 
both squirrel cages in 
parallel 



Resultant reactance of 
both squirrel cages in 
parallel, but not includ- 
ing the mutuai react- 
ance. 

Mutual reactance of both 
squirrel cages. 

Total resultant rotor re- 
actance of both squir- 
rel cages in parallel. 

Impedance squared of 



Conductance of rotor. 



Susceptance of rotor. 



Magnetizing susceptance. 

Resultant susceptance of 
rotor and magnetizing 
susceptances. 

Admittance squared of 
rotor and magnetizing 
circuits combined. 



Resultant resistance of 
rotor and magnetizing 



Digmze. by Google 



MOTORS AND GENERATORS 



s 


oot 


1.00 


Slip of the Motor 


. ""> 


2.24 


0.518 


Resultant reactance of 


""yL 






rotor and raagnetizi:^ 
circuits. 


'p 


0^3 


0.063 


Resistance of primary 
winding. 


'p 


0.42 


0^ 


Reactance of primary 

winding. 


"'»n+'p 


3-33 


0.382 


Total equivalent resist- 
ance of motor at slip s. 


-«„+»„ 


2.66 


0.938 


Total equivalent react- 
ance of motor at slip s. 


z-V.^^.' 


4.26 


1.01. 


Total equivalent impe- 
dence of motor at slip 


P.F.-t 


0.781 


0.378 


Motor power factor. 


-1 


98s 


4,150 


Motor current at 4200 
volts (normal voltage) 
and at slip s. 


S.K.W.= ^^ 


3.170 


S.490 


Torque per phase in syn- 
chronous kilowatts. 


T=79.3XSJK.W 


251,000 


43S,«» 


Total torque in pound- 
feet at slip s. 


^■^-S^ 


6460 


13,150 


Kilowatt input into mo- 
tor not including core 
loss. 



By using the above method the torque, current, power factor, 
etc., can be found for any given slip and the complete charac- 
teristics of the motor can be obtained. These have been plotted 
in Fig. 14 for a voltage of 4,200 and a frequency of 35,5 cycles. 
The same method can be used to determine the characteristics at 
any other desired frequency and voltage. 

The action of this motor during reversal is similar to that 
described for a motor with externa! resistance, but there is one 
point of difference. With external resistance the amount of 



Digmze. by Google 



40 ELECTRIC SHIP PROPULSION 

resistance can be made so great that the motor will be on the stable 
part of its curve from the very beginning of the reversal ; this is 
evident from a reference to curve A in Fig. 10. This is not true 
in the case of the double squirrel cage motor, which is on the 
unstable part of its curve till the propeller has been reversed and 
brought up to the synchronous speed. 

This action will be better understood by a reference to Fig. 15, 
which shows the entire operation of reversal of this motor. The 
explanation is complicated somewhat by the fact that, at full speed, 
the motors are arranged for 24 poles and when reversal takes 
place they are changed to 36 poles. This is done, however, only 
because the torque is somewhat greater with the 36-pole arrange- 

y JO 000 

leooo 
; IS 000 



:; 8000 

4000 



I 

■jOjOO 



Fio. 14.— Giaracteri sties of U. S. S. New Mexico's Double Squirrel 
Cage Induction Motor for Constant Potential of 4,200 Volts and a Fre- 
quency of 35-5 Cycles 

ment than with the 24-pole and does not in any v^ay affect the 
principle of the reversal. 

In Fig. 15 the motor is running on curve A at 21 knots, the 
torque required being indicated by the point x, which is the inter- 
section of the propeller torque curve B and the motor torque 
curve A. When it is desired to reverse, the motors are changed 
to 36 poles, the turbine speed is reduced, the motor connections 
are reversed and the excitation of the generator is increased to 
150 percent normal excitation. 

The reversed torque curve is shown as curve C. It will be 
seen that the torque of this curve exceeds the torque of curve B 
at all points, so that the propeller will be reversed and brought 
up to the speed indicated by the point y (intersection of B and C). 



Digmze. by Google 




D,„t,..= b:, Google 



42 ELECTRIC SHIP PROPULSION 

There are two points where curve B comes very close to curve C; 
the first occurs at about 55 revolutions per minute ahead and the 
second at about 35 revolutions per minute astern. If the speed 
of the turbine were not sufficiently reduced, it might very well 
happen that the propeller would he reversed ; hut, owing to curve 
C being too far over to the left (turbine speed being too high), 
the propeller would not come up to speed but would simply hang 
at the intersection of curves B and C in the unstable portion of 

'/I'Moff/t wtjgt 

'gr- tapping on the fop 

Taptbars ihrit Hmts with .OOS'mica fopt t,=ir lap and 
four a/ppiagj and baliingi in i/arni'sh. 



Separa/ar .ISO'm. 



Fig. i6.— Rotor Winding Insulation of Motors on U. S. S. California 

curve C. It is therefore best, in this operation, to have a certain 
definite speed to which the turbine is always brought during 
reversal; after the motor and generator come into synchronism, 
the turbine can be speeded up till the point y is near the top of 
curve C. 

The desirability of knowing the exact time that the motors 
and generators come into "step" has brought out the necessity for 
an instrument that will indicate this condition ; this instrument 
will also be useful in deciding on the amount of excitation that is 



Digmze. by Google 



MOTORS AND GENERATORS 43 

necessary when the ship is making a turn, as will be seen when' 
that point is discussed later on. Such an instrument has been 
devised by Mr. Alexanderson, of the General Electric Company, 
and installed on the New Mexico; it will be described under 
instruments and switchboards. With such an instrument there 
can never be any doubt as to whether or not the motor has "pulled 
into step"; as the motor approaches synchronism, the pointer of 
the instrument travels over from the unstable or unsafe part of 
its dial to the safe or stable part. 



Fig. I?.— U. S. S. California: Motor and Propeller Torque Curves 
The method of combining a high resistance squirrel cage with 
a definite winding to obtain large reversing torque without the use 
of external resistances has been used for the motors of the 
California. The rotor of the motor has a high resistance squirrel 
cage winding and also a definite winding, both being located in 
one slot. The arrangement of the windings is shown in Fig. 16. 
The squirrel cage bar is placed at the bottom of the slot and the 
definite winding is placed on top of it. 

Fig- 17 shows the torque curves of such a motor, both when 



Digmze. by Google 



44 ELECTRIC SHIP PROPULSION 

the definite winding is open circuited (or entirely inactive) and 
also when the definite winding is short circuited. Curve A is the 
open circuited condition and curve B the short circuited condition. 
Curve A is simply the torque curve of the high resistance squirrel 
cage and curve B is the resultant torque curve of the squirrel cage 
and the definite winding, although the squirrel cage has very little 
effect on this curve in its stable portion. 

When it is desired to reverse the motor, the definite winding 
is opened by a' switch and the motor will then operate on curve A; 
after the motor has been reversed, the definite ' winding is short 
circuited by closing the switch and the motor then shifts to curve 
B; before this change is made, however, it will be necessary to 
slow the turbine speed so that curve B will be in a position where 
its torque will be greater than the propeller torque. 

In fact, this must always be done with any arrangement for 
reversal where it is desired to cut out the resistance after reversal 
has taken place. The two operations of reducing the frequency 
and increasing the excitation may be said to be a necessary part 
of any method of reversal, except for the single case of reversal 
with a single block of resistance, which is left permanently in 
the circuit during reversal. 

In Fig. 17, for curves A and B, it has been asstuned that the 
generator has been slowed to a frequency of U.67 cycles. At 
this speed the intersection of curve A and curve C (propeller 
torque) is at the point x. The torque on curve B at these revo- 
lutions per minute is much greater than that on curve A, so that 
when the short circuiting switch is closed and the motor shifts 
to curve B there will be an excess of motor torque over propeller 
torque and the propeller will be accelerated until it reaches the 
point y (intersection of B and C); the turbine can then be 
speeded up. 

Various other methods have been proposed for utilizing the 
effect of a high resistance squirrel cage in combination with a 
wound rotor to give the desired torque for reversal. 

According to one of these, the primary is arranged so that 
a portion of it can be interrupted. The general scheme is shown 
diagrammatically in Fig, 18. The arrangement of the circuits is 
shown in the upper part of the figure; the dotted half of the 
primary winding is taken to a switch so that it can be opened 



Digmze. by Google 



MOTORS AND GENERATORS 



45 



independently of the other half of the winding. The effect of 
opening this switch can best be understood by remembering that 
the induction motor is a transformer. The lower half of the 
figure shows an equivalent transformer circuit for the circuit 
shown in the upper half of the figure. The stator winding is 
equivalent to two primary transformer windings in parallel; the 
wound portion of the rotor winding (being all in series) may be 
considered as two secondary transformer windings in series ; the 




I t I ■ t t If 1 1^>s;i; 



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00000000000000 yTRRR)"00000000000' 



TnjiJCOToooooooiri po^woooooooooo* 



two parts of the squirrel cage winding located under the definite 
winding may be considered as two independent secondary trans- 
former windings. When the dotted primary winding is opened, 
the other primary will still induce current in its secondary and, 
since the two secondaries are in series, current will flow in both 
of them. The secondary under the dotted primary will now act 
as a primary and induce current in the squirrel cage underneath 
it. This portion of the squirrel cage winding will become highly 
active for producing torque. This method has the objection that 
only half the coils are effective for producing torque. 



Digmze. by Google 



46 



ELECTRIC SHIP PROPULSION 



Another method of utilizing the high resistance squirrel cage 
for obtaining large torque for reversal is to arrange the primary 
winding so that it can be changed by switching in such a way as 
to neutralize the wound portion of the secondary, thus making 
only the squirrel c^e effective. The scheme is illustrated dia- 
grammatically in Fig, 19. Each phase of the primary is divided 




Fio. 19.— Diagram Showing Method for Obtaining large Torque for 
Reversal by Neutralizing Definite Wound Rotor by Changing Connections 
of Primary 

into three circuits in parallel. With the switch in the "up" posi- 
tion, both the wound secondary and the squirrel c^e will be 
active, if the rotor windings are arranged in series as shown in 
the lower part of the figure. Consider the portion of the secon- 
dary which is under the primary windings marked "a" ; this por- 
tion of the secondary circuit is shown at the bottom of the figure 
marked "a-a-a," The three induced voltages wjll be in proper 



Digmze. by Google 



MOTORS AND GENERATORS 47 

phase and will, therefore, cause load current to flow. When the 
switch is thrown to the "down" position, the wound secondary is 
made ineffective. Consider the same portion of the wound secon- 
dary as before; one of each of the three legs will be acted on 
simultaneously by the three phases, so that the total induced 
voltage around the circuit will be zero (as the three induced 
voltages are equal) and 120 degrees apart in phase. 

Both this method and the one previously described would be 
unsuitable for use with a motor wound for pole changing. They 
might, however, be useful in the case of a motor located a long 
distance from the point o£ control, as it would make it unneces- 
sary to return the leads from the secondary to the control point. 

We have just seen the various methods by which induction 
motors can be arranged to give the necessary torque for backing; 
it will now be shown how the same thing can be done with 
synchronous motors. 

The synchronous motor will be provided with a squirrel cage 
winding on its rotor to assist in the operation of reversal. In 
reversing, the turbo generator will be set to run at a constant 
low speed (about one-fourth speed) and its field will be opened;, 
at the same time the connections to the synchronous motor will. 
be reversed and double excitation will be applied to its field. Th& 
synchronous motor will now become a generator driven by the 
propeller and will supply power to the main turbo generator, 
which will now be acting as a high resistance squirrel cage induc- 
tion motor, the solid field of the generator acting as a high resist- 
ance squirrel cage. The power supplied to the turbo alternator 
from the synchronous motor will tend to reverse its direction of 
rotation; but, since it is driven by a governed turbine, it will 
continue to run in the original direction at a constant speed and 
the power supplied to it from the synchronous motor will be ab- 
sorbed in heating the rotor. If the combined torque necessary to 
drive the turbo alternator and the synchronous motor is greater 
than the torque of the propeller, which is now driving the syn- 
chronous motor, then the speed of the latter will be reduced until 
the two torques are equal. 

Before proceeding with the remainder of the operation of 
reversal, a further explanation will be made of the above sequence 
of events. Fig. 20 shows the combined torque curve of the 



Digmze. by Google 



48 



ELECTRIC SHIP PROPULSION 



synchronous motor and the turbo alternator when the latter is 
acting as a squirrel cage induction motor and the former as a 
generator. Curve B is the torque curve of the propeller and 
curve A shows the combined torque curve of the synchronous 
motor and turbo alternator. It will be noted that the shape of 
this curve is very similar to that of an induction motor when 
supplied with current of constant frequency. This is due to the 
fact that the torque curve is the resultant of the PR losses in the 
rotor of the alternator, the stator of the alternator and the stator 
of the synchronous motor. At the point a, when power is first 
applied to reverse, the losses in the alternator rotor predominate, 
but as the synchronous motor slows down, decreasing the fre- 
quency of the current, the skin efifect of the alternator rotor will 



\ 


::: 




























1 T~'^ 








-?-^v 


. 2 Z 




;t""^ 


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f 


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~>+4 ' ' 




I ~~- "- 




" s z 








1.J 


oLLU-i-L 




L^ 


-It __. 



Motor and 

decrease and the effective resistance of the rotor will decrease, 
while the resistance of the stator windings of both alternator and 
motor will remain constant. Therefore, the rotor losses will 
become a smaller percentage of the total losses as the propeller 
slows down. As the synchronous motor approaches standstill, 
the alternator rotor resistance is reduced so much that the syn- 
chronous motor approaches the condition of being short circuited 
through an external resistance equal to the resistance of the 
generator stator winding. 

If it were not for the preponderating influence of the stator 
losses at the low speeds, curve A would fall very rapidly with 



Digmze. by Google 



MOTORS AND GENERATORS 49 

reduction of speed, instead of having a peak like an induction 
motor torque curve. The effect of this peak in the curve has a 
very important bearing on the operation of reversal, as will be 
explained after the description of the entire process has been 
completed. It will not be possible to brii^ the propeller to abso- 
lute standstill by this action, as the torque of curve A is zero at 
standstill. 

As soon as the propeller speed has been reduced to the point 6 
(intersection of curves A and B), the excitation of the synchro- 
nous motor is reduced ; this will have the effect of shifting curve A 
to curve D, 

The next step is to apply excitation to the alternator and, as 
soon as this field has built up, remove excitation entirely from 
the synchronous motor. The squirrel cage winding of the latter 
now becomes effective, making it an induction motor, and the 
torque shifts from curve D to curve C. The propeller will now 
be reversed and brought up to speed in the opposite direction ■ 
till the point c is reached. Curve C is the torque curve of the 
squirrel cage on the rotor of the synchronous motor. During the 
interval in which there is excitation on both motor and generator 
the torque will be -slightly less than the sum of the torques due 
to the induction motor and the synchronous motor as there is a 
certain amount of interference between the two. As soon as the 
excitation has been entirely removed from the synchronous motor 
the torque on the propeller will be that represented by curve C. 

The point c is the highest speed that can be attained by the 
squirrel cage, but this is less than synchronous speed, so the next 
step in the operation will be to bring the motor up to full syn- 
chronous speed, as represented by the point e in Fig. 21. To do 
this, normal excitation will be applied to the synchronous motor 
and double-excitation to the alternator. The propeller will then 
be accelerated, as explained below, until it reaches point g on curve 
B, which is full synchronous speed as represented by e. The 
turbo generator and motor can then be speeded up together to the 
desired speed. 

Since the action of a synchronous motor in pulling into syn- 
chronous speed from a lower speed is not as generally understood 
as other electrical problems, it may be well to review this point 
here. During the process of pulling into synchronism, the torque 



Digmze. by Google 



50 



ELECTRIC SHIP PROPULSION 



of the synchronous motor will pass through cycles of positive and 
■negative torque and the effect of this alternating torque will be 
to set up oscillations in the speed of the rotor, so that it will 
-oscillate above and below the point c. If these oscillations are 
great enough, the point g will be reached in swinging past point c; 
at that instant' the motor will be at synchronous speed and there 
will be a very large positive torque to hold it at that speed. 
Tendencies to oscillate out of synchronism will be checked, since 
increase of speed will result in a decrease of torque, and vke versa; 



















- ,-:->- Z 


^ ^ 






i*f-- " f "' 


-- : : " s z 


^y 


_ __ _ __ __v__ 



Percent R.P.M.Astern 



snt R.P.M. Ahead 

s Motor in Pulling 



also, all other torques, such as those due to induction motor action 
and hysteresis, will tend to check any fluctuations. 

Whether or not a synchronous motor can oscillate into syn- 

■ chronism from any given speed will depend on the amount of 
load on the motor. For example, in Fig, 21, at the speed i, there 

■ must be no load on the motor, if it is to be brought up to 
synchronism ; at the speed represented by the point k, the load, or 
"resisting torque," can be that indicated by the point k (that of 
the propeller at that point) ; as higher speeds are chosen, greater 
loads can be thrown on the motor until, at the point h, the maxi- 
mum torque of the motor and synchronous speed of the motor are 

- reached simultaneously. The point k is the intersection of curves ^ 

- hi and B and it represents the lowest speed of the propeller from 

■ which the motor can be brought up to synchronism. It is essential 



Digmze. by Google 



MOTORS AND GENERATORS 51 

that the point c must never be to the right of the point k, if the 
motor is to be brought into synchronism. 

Having seen the complete cycle of reversal of a synchronous 
motor, we can return to an examination of the effect of the peak 
in curve A, Fig. 20. First, it makes it possible to reduce the 
synchronous motor excitation before applyii^ generator excita- 
tion and this reduces the rush of current when this change is made. 
Second, it reduces very much the propeller speed at which curves 
A and B intersect from what it would be if it were not for the 
effect of the stator winding losses; in other words, the point h 
would be very much to the right of its present position, if it were 
not for the effect of the stator resistance. Point m, Fig. 20, 
shows the maximum propeller speed at which it would be possible 
for the induction motor to reverse the propeller. If the effect of 
the stator windings were removed from curve A, the point b would 
be to the right of point m. This would necessitate the use of a 
higher resistance in the induction motor to bring the point m 
farther to the right and this would incline curve C more to the 
right, bringing point c over to the right and making it more 
. difficult to bring the motor into synchronism. There is a third 
possible advantage that results from the shape of curve A; by 
inserting resistance in the line between the motor and alternator, 
the position of the peak can be moved to the right as much as 
desired, so that it could be brought directly over the maximum 
point in curve B, if necessary. 

The efficiency of the synchronous motor is slightly better than 
that of the induction motor; it has a power factor of about 100 
percent and it also has a large air gap and no high voltages in 
its rotor. As a result of the high power factor and superior 
efficiency, a considerable savii^ of weight is effected by its use. 
On the other hand, the operation of reversal is more complicated 
and it is doubtful if the advantages outweigh this. In any cage, 
it should not be used for high speed ships on account of the 
difficulty of obtaining sufficient reversing torque; the large air gap 
of the synchronous motor does not allow the construction of a very 
efficient squirrel cage, which must be used in the process of 
reversal. Another objection to the synchronous motor is that it 
gives only one speed reduction. 

The next point to be explained in connection with the design 



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52 



ELECTRIC SHIP PROPULSION 



of generators and motors for propulsion will be the method of 
obtaining combined motor and generator characteristic curves. As 
an example of this it will be shown how the characteristics of 
motor and generator can be combined to give the curve shown 
in Fig. 7. 

In Fig. 22 are shown the characteristic curves of the New 




Fig. 22. — U. S, S. New Mexico: Turbo Generator Voltage and Kilowatt 
Curves with High Voltage Connection and at 35.5 Cycles. Amperes and 
Kilowatts are One-Half of Actual Generator Value, that is, they are 
Values per Motor 

Mexico's generators under various conditions of power factor and 
excitation but at a constant frequency of 35.5 cycles. The motor 
characteristic curves shown in Fig. 14 were calculated for the 
same frequency, so the characteristics of motor and generator can 
be combined to give the lower curve shown in Fig. 7 by trans- 
ferring the readings of the motor characteristic to the generator 
characteristic in the manner illustrated in the following; 



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MOTORS AND GENERATORS 5 

Point A shows the volts and amperes of the motors when 
drawing 3,000 kilowatts per phase at 100 percent generator 
excitation and 80 percent power factor. ■ This point is 
obtained by finding the point on the curve marked "kilo- 
watts at 80 percent power factor and 100 percent excita- 
tion," which gives 3,000 kilowatts; then a vertical line 
through this point to the point A will give the data desired. 
■ This method presupposes a knowledge that the power factor 
of the motor, under these conditions, will be 80 percent; 
if this were not known, it could shortly be determined by 
"trial and error" and an error of a few percent in the power 
factor would not appreciably displace the point A. 

Point B shows the volts and amperes of the motors when 
drawing 3,000 kilowatts per phase at 150 percent generator 
excitation and 70 percent power factor. This point is ob- 
tained in a similar manner to point A for 100 percent 
excitation. 

Point C gives the current drawn by the motor when 
operated at 4,200 volts and at the same slip as that of point 
B. The point C lies on a straight line connecting point B 
with the origin ; therefore the ratio of volts to amperes 
will be a constant for all points on this line; also, if the 
load is increased with the voltage in such a way as to main- 
tain the slip constant, the power factor and efficiency will 
remain constant. We can, therefore, pick off from Fig. 14, 
at the amperes corresponding to point C, the power factor 
and efficiency of the point B. 

Point D shows the maximum kilowatts (6,500 per phase) 
at 150 percent excitation and 80 percent power factor. This 
is the load at which the motors will "fall out of step." 

Point E shows the volts and amperes corresponding to 
point D. 

Point F shows the amperes drawn by the motor at 20 
percent slip and 4,200 volts, the amperes for this point 
being taken from F^. 14 at 20 percent slip. 

Point G shows the volts and amperes of the motors at 
same slip as point F and when fed from the generator with 
100 percent excitation and at 40 percent power factor. 



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_ 54 ELECTRIC SHIP PROPULSION 

Point H shows the maximum kilowatts at 100 percent 
excitation and 80 percent power factor. 

Two very important points of these curves are the points D 
and H; these have a very important bearing on the turning of the 
ship, since it is the maximum output of the generator that is the 
limiting feature and not the motors or turbine. If the generator 
capacity were greater than that of the turbine, the turbine would 
slow down, if its capacity were exceeded, but in actual practice 
the turbine is alway.s designed with a margin over the generator. 

We will now consider the condition that arises when a ship 
makes a turn. In Figs. 4, 5 and 6, Chapter III, we saw that when 
a ship turns a large overload is imposed on the propellers and a 
particularly heavy overload on the propellers on the inboard side 
of the turning circle. It is obvious from Figs, 4, 5 and 6 that 
on a high speed ship, which is turning, the screws on the inside 
of the turning circle must slow down during the turn ; otherwise 
it would be necessary to have machinery of much greater capacity 
than would he necessary for the full speed desired. In other 
words, if the generator is to work normally somewhere near the 
point H, Fig. 22, and hence at its best efficiency, some means 
must be found to limit the load in turning. 

The problem has been solved by limiting the power of the 
turbine for any given speed. This is accomplished simply by 
fixing a limit to the maximum amount of steam that the turbine 
can take; the method of doing this will be described in detail in 
another chapter. The result of this is that when the turbine reaches 
its capacity any further demand for power by the generator will 
simply cause the turbine to slow down until the demand is reduced 
to what the turbine can give. The steam limit can be set to give 
any desired margin over the amount of steam required for the 
speed, but the greater the margin allowed, the more excitation it 
will be necessary to carry on the generator field. 

The excitation should always be kept to a minimum, as excess 
field current means excess heating in the field and will also reduce 
the efficiency of transmission, if the excess is too great. There 
is quite a wide range of excitation, however, for which the effi- 
ciency of transmission will be practically constant. It would not 
be desirable to carry just enough excitation to keep the motors 



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MOTORS AND GENERATORS 



55 



in step under normal conditions when turning, since a slight 
variation from the normal would throw the motors out of step. 
Therefore, a certain margin of excitation should be allowed as a 
factor of safety. Just how much jnargin should be allowed should 
be determined by experiment for each ship. 

On the New Mexico, experiments were made to determine the 
minimum allowable excitation when steaming straight ahead ; then 
the steam limit was set and the minimum excitation determined 





Fio. 23.— U. S. S. New Mexico: Excitation Curves 

for the ship when turning under this condition. It was found that 
the excitation required for turning (with steam limit set) was 
about 10 percent greater than that required for straight steaming. 
The excitation is actually carried about 10 percent higher than this, 
or 21 percent higher than that required for straight steaming, 
This is doubtless on the safe side, and further experience tnay 
show that a reduction can safely be made. For ships that are 
not cruising in formation, the amount could certainly be reduced. 
Fig. 23 shows the excitation used on the New Mexico. One 
set of curves shows the excitation at which the motors drop out 
of step when steaming on a straight course. The next set of 
curves shows the excitation at which the motors drop out of step 



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56 ELECTRIC SHIP PROPULSION 

when turning with the rudder at 35 degrees and with the steam 
limit set. The third set of curves shows the excitation that is 
actually carried. 

In addition to the special rjequirements for providing torque 
for backing and turning, it is frequently desirable to arrange 



Fig. 24.— U. S. S. New Mexico: Statbr Coil Diagram 

motors to give two different speed reductions. This will usually 
not be necessary for merchant ship work where the speed variation 
is small except when maneuvering, but, for a man-of-war, it will 
always be desirable to have the two speeds in order to obtain the 
best turbine efficiency at the cruising speed of the ship. For a 
battleship of 21 knots speed, the motors will usually be arranged 
to allow the turbine to run at full speed at about 15 knots as well 
as at the full speed of the ship. 



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MOTORS AND GENERATORS 



57 



This is accomplished by winding the stator of the motor with 
two polar arrangements and bringing the end connections to a 
double throw switch; in one throw this switch will give, say, 24 
poles, and in the other 36 poles. If the generator has 2 poles, 
then there will be a speed reduction of 12 to 1 in the first case 
and 18 to 1 in the second case. This double polar arrangement 
of stator winding may be accomplished either by providing two 
independent stator windings — one for each polar arrangement — 
or by arranging one winding to give the two sets of poles. Previ- 




Fig. 25. — Winding used for Motor 



U. S. S. Hew Mexico 



ously this latter method of pole changing had been limited to the 
single case of a 2 to 1 change in the speed reduction ; for example, 
a motor might be wound to give 24 poles and also 48 poles, but not 
an intermediate number of poles. This change does not fit the 
case of a battleship, so a new type of winding was developed which 
will give any desired change in the Speed reduction. This type of 
winding is somewhat better adapted to a quarter-phase system 
than to a three-phase and, for that reason, the quarter-phase 
system was adopted for the New Mexico. The motors of the 
Tennessee have independent stator windings for the two polar 
arrangements and a three-phase system is used. 



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58 ELECTRIC SHIP PROPULSION 

The New Mexico's motor stator winding is shown in Figs. 24 
and 25. The method used in working out this winding is shown 
in Fig. 26, In this figure the arrows represent complete coils 
and also indicate the direction of current flow in the coil. The 
first group shows the arrangement for 24 poles. Actually there 
are shown only 4 poles for each phase ; this is one-sixth of the 
complete diagram, which is made up of six parts in parallel, as 
may be seen by a reference to Figs. 24 and 25. The second 
group shows the 36-poIe arrangement ; six poles are actually shown, 
the remainder being made up of six parallel circuits as before. 
It will be noted that in the 36-poIe arrangement the two phases 
are not entirely symmetrical for each polar area. For example, the 
first polar area has five coils in phase a and six coils in phase b, 
but the total number of coils in each phase is, of course, the same. 
The third group of arrows shows how the coils are divided into 
sixteen groups for winding, eight of these groups consisting of ' 
5 coils each and eight of 3 coils each. The fourth group of 
arrows shows how the groups are connected to form a complete 
section of the winding. Figs. 24 and 25 show six of these com- 
plete groups connected in parallel to form the complete motor 
winding. At the bottom of Fig. 26 the complete winding with 
its connections to the switch is shown diagrammatically. With 
this system of winding practically any desired ratio of speed reduc- 
tions can be worked out. 

When a motor has its stator arranged for two different num- 
bers of poles the motor rotor will operate satisfactorily under 
both conditions, if the rotor has a squirrel cage winding, since 
this type of winding does not have definite fixed polar areas but 
will automatically accommodate itself to any number of poles on 
the stator. But if the rotor has a definite winding, then it must 
be specially arranged to meet the condition of pole-changing. 

Fig. 27 shows how this has been accomplished in the case of 
the Tennessee. Here the rotor winding acts as a definite winding, 
when the 24-pole arrangement of the stator is in use, and as a 
squirrel cage winding when the 36-pole arrangement of the stator 
is in use. The definite winding is used with the 24-poIe arrange- 
ment because the Tennessee's motors are arranged to reverse on 
the 24-pole combination and it is necessary to have the rotor 
winding connections come out to slip rings for this purpose so 



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tit i 


ft 


a 


.t 








ill? ^ 


Z Z * 

f W ' 1 

1 i i 
t ~z I 

Ill f 

il II «^««~ 
1 1 



D,„t,..= b:, Google 



60 



ELECTRIC SHIP PROPULSION 



that external resistance can be inserted. If the motors had been 
arranged for reversal on the 36-pole combination, the arrangement 
of the rotor winding would have been reversed. The change that 
takes place in the rotor winding is automatic and is within the 
winding itself. 

Fig. 27 represents one-sixth of one jAase of the rotor winding. 




The upper group of conductors shows the direction of the E. M. F. 
in the coils when the stator is arranged for 24 poles and the lower 
group shows the direction when the stator is arranged for 36 
poles. 

The coils are arranged in groups and, by means of group 
connectors ^A), are connected for 24 poles in two parallel cir- 
cuits for each phase as shown by the diagram at the top of the 
figure ; the phases are then connected in star as shown in the small 
diagram to the right of tW conductors. Under this condition the 



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MOTORS AND GENERATORS 



61 



machine will operate in the usual manner for induction motors 
with a definite winding. 

Since each phase consists of two parallel circuits, it follows 
that corresponding points in the two circuits will have the same 
potential. In the arrangement shown, these points are located at 
a and a}, b and b', c and c', etc. These points of equal potential 
are joined together by special connectors {B). When the motor 
is operated on 24 poles, these connectors will carry no current 
since they have equal potential. ' But when the motor is operated 
on 36 poles, the conditions change, as shown by the diagram at 



Ay™ 



^TmW 



^MiHLQJlil,^ 







Fig. 28.— The Square Circuit High VoUj^e and the Diametrical Circuit 
Low Voltage Connections on Each Turbo Generator on the U. S. S. New 
Mexico which is Obtained by Switching 

the bottom of the figure, so that in the space occupied by 4 poles 
in the upper diagram we now have six poles in the lower diagram. 
By tracing out the direction of the E. M. F. in the coils as indi- 
cated by the arrows, it will be seen that the special conductors 
(5) now serve as short circuits connecting pairs of coils in series. 
Such a pair of coils is indicated by heavy lines in the lower 
diagram and separately in the small diagram to the right at the 
bottom of the figure. The entire rotor winding now consists of 
'a, number of coils short circuited in pairs and will therefore have 
characteristics similar to those of an ordinary squirrel cage motor. 
Due to the distance between the two coils in a pair, a slight 
magnetic balancing action is obtained similar to that on a squirrel 
cage motor. 



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62 ELECTRIC SHIP PROPULSION 

There is another special condition that arises in connection 
with electric propulsion. At the low speeds of the ship one 
generator will be used to drive four motors and at the high speeds 
each generator will drive only two motors. Therefore, the resist- 
ance and impedance of the motor circuit will be twice as great 
at high speed as at low speed. It is possible to arrange the 
generator windings to take advantage of the greater current path 
offered by the four-motor condition and this has been done on 
the New Mexico. When driving with four motors, the generator 
windii^ is arranged to give two parallel circuits for each phase ; 
when driving with two motors, the generator windings are ar- 
ranged in the form of a square. 




Fig. 29. — Method of Arranging the Generator Field Winding to Provide 
for Two Different Polar Arrangements 

The arrangement of the generator windings is shown in Fig. 
28, It will be noted that the impedance of the generator winding 
is changed in the ratio of two to one when changing from the 
high voltage to the low voltage condition, so that it is changed 
in the same proportion as the motor circuit when it changes from 
two motors to four motors. Each end connection of the parts 
of the generator winding, numbered 1, 2, 3, etc., is taken to an 
8-pole, double-throw switch ; one throw of the switch gives the 
parallel connection on the generator and the other throw gives the 
square connection. This switch is also tised as a disconnecting 
switch by placing it in the neutral position with both "throws" 
open. If the turbine speed and flux density are the same for 
both arrangements of the generator winding, the voltages will be 
in the proportion of 1 to V2 for the parallel and square connec- 
tions, so that if the low voltage is 3,000 the high voltage will be 
4,242. 

It is possible to arrange the generator for pole chai^ng 
instead of the motor and thus get two speed reductions between 



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MOTORS AND GENERATORS 63 

generator and motor. The method of arranging a generator field 
winding so that it will be capable of giving two different polar 
arrangements is shown in F^. 29. The winding is normally a 
4-pole one; by means of switching, the direction of current flow 
is changed in the right half of the coil and the field becomes 
2-pole as shown. This arrangement will not generally be used 
because the rotor end windings are complicated and increase the 
length of the rotor to such an extent that, in the case of a large 
turbo alternator, the critical speed will be below the maximum 
speed desired. 



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CHAPTER V 

Special Characteristics of Turbines and Governors for Eleciric 
Propulsion 

TURBINES and their governors for electric drive differ 
slightly both from land turbines and from high speed 
marine geared turbines. Land turbines run at a constant 
speed and are at all times under the control of a governor set for 
a constant speed; marine turbines are controlled entirely by a 
throttle, except that the maximum speed is usually limited either 
by a maximum speed governor or by an emergency governor. 

A turbine for electric propulsion should at all times be under 
the control of a governor since the load is thrown off and on 
suddenly and it would not be possible to get satisfactory operation 
using a throttle; but, since an infinite number of speeds of the 
turbine are required, it is necessary that the governor should be 
capable of very rapid adjustment from one speed to another. 
Also, since the control gear will usually not be in the same com- 
partment as the turbine, it will be necessary for the governor 
adjustments to be made by distant control. 

Two methods of accomplishing this have been used on naval 
vessels. One method is entirely mechanical and direct. By means 
of rods and bell-cranks, the motion of a hand operated lever in 
the control room is transmitted to the fulcrum of the governor. 
Moving the governor fulcrum will change the speed at which the 
fly-ball weights balance the springs and thus change the speed of 
the turbine. The other method balances the centrifugal force of 
the weights by an oil pressure ; the control of the oil pressure is in 
the control room and any variation will change the speed at which 
the balance is maintained. Both methods will be described in 
detail in succeeding chapters. Mr. Ljungstrom uses a constant 
speed governor in his installations, and varies the speed of the 
motors by an external resistance, but this is unsuitable for a war 
vessel and it is very doubtful if it is really satisfactory for a 
64 



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TURBINES AND GOVERNORS 65 

merchant vessel, as a great deal of fuel will be wasted if it becomes 
necessary to do much steaming at reduced speeds. 

It is necessary that the governor should function properly at 
all speeds of the turbine from about one-fourth speed to full speed. 
This is a very stringent requirement and necessitates great care in 
details of design. The ordinary constant speed governor would 
not be at all satisfactory for low speeds as its directive force 
would be so small as to cause serious hunting of the turbine. 
The governing at one-quarter speed must be practically as good 
as at full speed since the ship may use that speed for considerable 
periods of time when maneuvering, and also because it is essential 
to tiave good control at that speed to get good results in backing. 
If the governor hunts badly, the probabilities are that the turbine 
will be stalled during backing, or else it will be difficult to get the 
motor "into step" with the generator. In order to get good 
governing at the low speeds, the change in the angle of successive 
cams must be very gradual, if the control is by cam-operated 
valves ; if a throttling governor is used, the valve and seat must be 
designed to restrict the steam flow greatly without actually seating 
the valve. Too much emphasis cannot be laid on the design of 
the governor, as the operation of the plant will never be satis- 
factory without a good governor. 

The governor does not appear to be affected in its action by 
the rolling and pitching of the ship, as perfectly satisfactory 
governing is obtained in the roughest weather. However, parts 
of the governor, such as weights, may be displaced by this motion 
unless they are positively secured. The ordinary method of 
holding the weights on their knife edges by spring tension alone 
is not satisfactory, as has been demonstrated by experience. 

It has been found by experience that the periodic swing of a 
governor in a seaway tends to start up rapid vibrations in the 
hydraulic relay, operated by the governor, and it has been neces- 
sary to fit a dash pot on the transmission arm ; this entirely does 
away with, the trouble. The dash pot should be fitted with a 
needle valve so that it can readily be adjusted. 

In addition to having perfect governor control it must also 
be possible to limit the maximum amount of steam flow. The 
reason for this is the effect on the generator produced by turning 
the ship, which has been described in the previous chapter. This 



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66 ELECTRIC SHIP PR0PVLSt6>i 

practically amounts to a combination of governor and throttle 
control. Since the required position of this steam limit will vary 
for each speed of the ship, it must be adjustable, either auto- 
matically or by hand. In practice, it should be set to give the 
minimum flow consistent with good governing at the speed desired. 
If hand adjustment is used, it will have to be distant control, as 
the lever for controlling the limiting mechanism will be in the main 
control room. 

The means for transmitting motion from the control room to 
the governor may be mechanical, electric, hydraulic, steam, etc., 
but the mechanism for actually limiting the motion of the governor 
or hydraulic relay must take the form of a positive stop. Means 
must also be provided, by springs or otherwise, for allowing the 
actual governor movements to continue, although without doing 
any work, after the stop has been reached. 

Actual details of governors and steam limits will be discussed 
in later chapters. 

On marine turbines it is customary to utilize the surplus 
auxiliary exhaust steam in the main turbines. For purposes of 
economy this is also desirable in the case of turbines for electric 
propulsion. If this is done, the auxiliary exhaust must auto- 
matically be shut off the turbine and directed into the main con- 
denser when the load is thrown off the turbine. It thus becomes 
necessary to have a valve in the auxiliary exhaust line which is 
operated by the governor and which is really the first admission 
valve of the turbine. 

In addition to the main governor it is necessary for safety to 
fit an emergency governor which will shut steam off the turbine 
in case it over-speeds. As it is necessary that all sources of steam 
supply be closed, this governor must operate an automatic valve 
in the auxiliary exhaust line to the turbine as well as the main 
throttle. 

Details of steam and exhaust connections to turbines will be 
discussed in later chapters. 



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CHAPTER VI 
Ventilation, Heaters, Fire Extingui^ers 

VENTILATION is very important and must be carefully 
worked out for any electrically propelled ship, if the 
maximum length of life is to be obtained for motor and 
generator insulation. For merchant ships this offers no difficulty 
whatever, as a simple arrangement of ventilating ducts to and 
from the compartment or machine to be ventilated can very 
readily be worked out. For a war vessel it is desirable that the 
size of the opening in the decks be reduced to a minimum. Large 
volumes of air are required for cooling electrical apparatus, and 
it is not feasible to supply this air at high velocity ; therefore, it 
will require unusually large deck openings unless the air is utilized. 
for other purposes after it has been used for cooling, so that the 
total air used is no greater than would be required if the electrical 
apparatus were not used. 

The simplest method is to take the exhaust air from the 
generators and motors (or at least as much as possible of it) and 
use this for supplying the forced draft blowers in the firerooms. 
In this way the deck openings are not made any larger than they 
would have to be to supply the firerooms. 

Another method of ventilating is to coo! the air by means of 
circulating water and use the same air continuously. No instal- 
lations of this type are in use on board ship at present, but this 
system will be used in the future in capital ships of the Navy, 

Fig. 30 shows the plan of a type of cooler that has been 
proposed for the generators of battleships 49-34. This is called 
the radiator type of cooler since the arrangement is somewhat 
similar to the radiators of automobiles. It consists of sixteen 
sections of tubes arranged as shown. Each tube has a spiral fin 
soldered to its outer periphery to increase the transfer of heat. 
Circulating water passes through the tubes ; the air passes across 
the tubes. The various sections of the cooler are practically 



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D,„t„.= b, Cowrie 



VENTILATION, HEATERS, FIRE EXTINGUISHERS 69 







rizr 



" i. 



^ 



Fio. 31.— Type of Cooler Used for Main Motors 



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70 . ELECTRIC SHIP PROPULSION 

integral with the generator and are supported by the generator 
foundations. The whole is enclosed in a sheet iron lagging, so 
that the only change produced in the external appearance of the 
generator by the addition of the cooler is to give it a greater 
diameter. An eliminator, consisting of a set of baffle plates and 
drain, is provided so that the failure of a tube will not send salt 
water into the generator. 

The same type of cooler sections is used for the main motors 
but the cooler is external to the motor. The general arrangement 
is shown in Fig, 31. 

In arranging air ducts to or from a machine there should 
always be an offset in the duct, fitted with a coaming. So that spray 
or water coming down the duct will be trapped and can be drained 
off without getting into the machinery. 

The various units of the propelling machinery should be as 
nearly self-contained as possible and, therefore, the generators 
should be provided with their own ventilating tans. This arrange- 
ment also makes for economy of weight and space. The motors 
will have to be provided with exhaust fans but the main motors 
themselves should be designed to give as much fan action as 
possible, as it is desirable not to have the motors dependent on 
auxiliaries, if it can be avoided. 

When a generator or motor is not in use it should be closed 
up to keep dirt and moisture from entering it. As it is not 
possible to close the openings up absolutely airtight, there will 
always be a certain amount of moisture present and this will be 
condensed and deposited on the coils due to the fact that the 
temperature of the air inside the machine will usually be dif- 
ferent from that of the compartment. The temperature of the 
compartment will undergo periodic changes, as will also the 
temperature of the air inside the motor or generator, but the two 
cycles will never coincide, since there will always be a certain 
amount of time lag between the two cycles. To prevent this, 
all generators and motors should be provided with heaters which 
should be kept turned on when the machine is not in operation. 

Steam heating coils can be satisfactorily fitted in a generator. 
They should be located in the base of the generator. All joints 
should be external to the generator to prevent the possibility of 
leaks getting into the generator. 



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VENTILATION, HEATERS, FIRE EXTINGUISHERS 71 

Electric heaters can be fitted into the base of a motor ; it will 
usually not be feasible to fit steam coils, owing to the design of the 
motor and also to its distance from a "supply of steam. The 
heaters should be located as' far as possible from the motor wind- 
ings to avoid damage to them in case of a short circuit in the 
heater. 

Motor compartments should be provided with radiators for 
heating them, if they are separated from the reniainder of the 
machinery. 

Provision must be made for by-passing part of the air from 
the exhaust of both generators and motors back to the compart- 
ment from which they draw air unless the ventilating air is 
supplied by totally enclosed ducts. This will prevent these com- 
partments from becoming unduly cold in cold weather. It will 
also prevent the motor or generator from becoming cooler than 
the compartment in which it is located; if this should happen, a 
rapid condensation of moisture would take place in the tnachine 
as soon as it was shut down. 

As the most serious damage that can occur in a generator is 
from a fire caused by a short-circuit, each generator should be 
fitted with a steam fire extinguisher. To make this effective the 
supply of air to and the discharge of air from the generator must 
be arranged so that they can be shut off at the same time that 
steam is turned on. A fire extinguisher of this type will probably 
prevent serious damage to the insulation and ought surely to 
prevent any damage to the laminations. 

The main factor in putting out the fire is the element of time ; 
if the fire has been burning for any appreciable time, considerable 
damage will be done. As soon as the fire is discovered, excitation 
should be removed from the machine and steam shut off the tur- 
bine ; next, the inlet and outlet dampers to the air ducts should be 
closed ; then steam should be turned on the generator extinguisher. 

In order that the steam supply may not damage the generator 
insulation by leakage, it should always be fitted with a valve and 
also a cock ; the latter should be so arranged that any leakage past 
it, when it is shut ofl, will be directed into the engine room and not 
into the generator. 

The volume of steam which will be required may be deter- 
mined from the cubic feet of air space in the generator, allowing 



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72 ELECTRIC SHIP PROPULSION 

one pound of steam per minute for each 2,5 cubic feet of enclosed 
space, if the leakage past the air dampers does not exceed 10 
percent. If the leakage is greater, the amount of steam should 
be approximately one pound of steam per minute for each 20 
cubic feet of leakage air. The leakage air should in no case 
exceed 20 percent. 

A fire should be extinguished practically instantaneously after 
the application of steam, but it will be found necessary to leave 
the steam on for about half a minute to prevent re-ignition. 

The best location of steam inlets is on the inner shield, so that 
the jets will impinge directly on the end windii^s and be carried 
through the generator by the action of the fan. 



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I 



CHAPTER VII 

Switchboards, Interlocks and Controls 

N any control arrangement the following considerations 
should govern: 

(1) No switches should he provided that are not really 
useful. The possibilities of providing different combiniitions 
with electrical apparatus are so great that there is always a 
temptation to overdo it. 

(2) All instruments, levers, etc., used in the operation 
and control of the machinery should be grouped- together 
where they can be handled (or at least supervised) by one 
man. 

(3) Sufficient interlocks should be provided to prevent 
the possibility of damage due to a mistake in operation. 

Switchboards and all parts mounted on them should be of rigid 
construction. This is particularly necessary for war vessels which 
are subject to severe shocks. There is always a tendency in this 
sort of construction to determine the size of a part by the stress it 
has to undergo in normal operation. This is not a safe rule ; no 
part on a switchboard should be of flimsy construction but should 
be rugged enough to stand severe and repeated shocks and 
vibrations. 

Switchboard structures should always be covered over on top 
with inclined sheet metal covers to deflect water from exposed 
connections inside the structure. 

Unless switches are so large as to make it impracticable, they 
should always be arranged for hand operation as a normal condi- 
tion. In cases where this is not practicable, electro pneumatic 
operation will probably be the most satisfactory. In any case, 
switches should always be so arranged that they can be operated 
by hand in an emergency. Where switches are held closed by 
73 



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74 ELECTRIC SHIP PROPULSION 

power, they should always be so designed that they will not open 
automatically in case of failure of the supply of power. 

In general, where either air or electricity is used in the normal 
process of operation, the source of supply should be duplicated at 
least once. 

All switches should be so designed that they will not open 
under shock. Plain knife blade switches should be secured, when 
closed, by latches. 

No porcelain or other fragile material should be used as insu- 
lators on switches. Some of the various forms of bakelite have 
been found to be best for this purpose. 




Rg. 32 

All resistances or grids used in the circuits or on the switch- 
board should be shock proof. In general, these will be of very 
light sections ; in that case, 'cast iron will not be a satisfactory 
material for this purpose. 

The switches should be so arranged that normally they will 
not be operated when the circuit is alive — ^that is, the field of the 
generator should always be opened first. This will greatly reduce 
the strain on the insulation of both generators and motors and 
increase the life of it. The operating switches should, however, 
be of sufficient capacity to open full load current in an emergency. 
One reason for this is that the armature circuits of motors and 
generators are highly inductive and there is very considerable 
"electrical momentum" in these circuits ; this can best be explained 
by a reference to Fig. 32. It was found by experiment that, after 
opening the switch marked "3 phase switch," a very high voltage 
persisted in the motor circuit for several seconds and in order to 



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SWITCHBOARDS. INTERLOCKS AND CONTROLS 75 

"kill" the circuit it was necessary to open one of the motor 
switches. It is, therefore, necessary that all switches be able to 
handle large current, even if the field is removed from the main 
generator before moving any switches. 

The field switch should be of the air break type, designed to 
open double the normal full exciting current without excessive 
arcii^ or burning of contacts. The field switch and the rheostat 
for controlling the voltage of the exciting circuit should be oper- 
ated by the same lever and the connections should be arranged so 
that the field switch will be opened when the exciting voltage is at 
its minimum value. Auxiliary contacts must be provided on the 
field switch so that it will short circuit the main field through a 
resistance before the switch is openedi It is very important that 
this resistance should be absolutely shock proof, as damage to the 
field would be sure to result, if this resistance should become open 
circuited by breakage ; for this reason, cast iron grids should not 
be used for this purpose. 

Where the size of the installation permits, the main operating 
switches, such as reversing and pole changing switches, should be 
of the oil break type in preference to the air break type, as the 
operation is much quieter. 

No fuse or automatic circuit breakers should be provided in the 
power circuit on account of the unreliability of this class of 
apparatus and also because, in the short leads of circuits on board 
ship, these protective devices do not really give much protection. 
For example, a short circuit in the generator is more probable 
than at any other point in the circuit and against this a circuit 
breaker would give no protection. 

A protective device, called a balanced relay, has been developed 
which really gives protection without having the objectionable 
features of circuit breakers. It consists of coils energized by 
current from the different phases of the circuit. As long as the 
conditions are normal these coils will be in balance but anything 
that disturbs the equality of current in the phases (such as a short 
circuit in generator, motors or transmission circuit) will upset the 
balance of the coils. The coils are so arranged that when un- 
balance takes place they automatically trip out the main field 
switch, thus taking power off the circuit. This protective device 
has given satisfactory operation. 



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76 ELECTRIC SHIP PROPULSION 

As to the number of switches to be provided, these should be 
kept to the minimum consistent with the necessary operations to 
be performed. Simplicity should be the guide in this matter. 
There are certain switches that should be provided in all installa- 
tions; for example, it should always be possible to cut out an 
individual motor without affecting the operation of the others; 
also, it should always be possible to propel the ship, using all 
shafts, with one generator and, therefore, the two sides of the 
ship should be provided with a switch tying them together and, 
also, with switches for cutting out any generator. 

The number of interlocks should also be kept down as much as 
possible but enough should be provided to make it impossible to do 
harm to the machinery through errors of operation. Interlocks 
should be mechanical when this is feasible. In the case of power 
operated switches which have no positive mechanical connection 
to the control levers, the latter should be equipped with locks so 
that they can not be moved to full position until the switch has 
responded to the partial movement. All interlocks should be 
operated by the final movement of the lever — that is to say, the 
interlock should not be released till the full travel of the lever has 
been completed. 

Switchboards should be equipped with signal lights which will 
show whether or not any important operation has been carried 
out in response to the movement of the proper lever. The most 
important of these lights should be fitted two in parallel so that, if 
one burns out, no mistake will be made in reading the signal. 
Signal lights should be fitted only for important things, as too 
many of them would tend to confuse the operator. 

Instruments for use on board ship should be carefully balanced 
so as to be unaffected by the roll and pitch of the ship. They 
should also be rugged enough to be shock proof. As most elec- 
trical instruments are designed for operation on circuits having 
constant frequency and constant voltage, they will usually not be 
suitable for an electric propulsion circuit. For example, watt- 
hour meters of commercial design are correct for only one condi- 
tion on board ship; so far it has been impossible to supply a 
satisfactory instrument of this type for ship propulsion work and 
it has been necessary to calibrate theSe instruments for one condi- 
tion of voltage and frequency and provide curves giving the error 



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SWITCHBOARDS, INTERLOCKS AND CONTROLS 77 

at other frequencies and voltages. The following list of instru- 
ments will give a general idea as to the number required for an 
electric propulsion switchboard : 

One alternating current voltmeter for each generator (ar- 
ranged to read all phases). 

One alternatii^ current ammeter for each generator (arranged 
to read all phases). 

One indicating wattmeter for each generator, 
. One watt-hour meter for each motor. 

One power factor meter for each generator. 

One frequency meter for each generator (this should he 
graduated in revolutions per minute and should have one scale for 
the generator revolutions and scales for motor revolutions — both 
high speed and low speed connections, if two are used). 

One instrument for each generator for indicating when gen- 
erator and motors are "in step." (Stability meter.) 

One speed meter for each generator (this must be independent 
of the main propulsion circuit so that it will always give an "indi- 
cation" when the generator is running). 

One ammeter for each motor. 

One direct current voltmeter for each generator field. 

One direct current ammeter for each generator field. 

Temperature indicators for motors and generators. 

Necessary gages, clocks, counters, etc. 

The ammeters provided for the generators should have scales 
with a very large range, so that they will not "go off the scale" 
when the motors are reversed ; this will make the scales much 
greater than would be necessary for normal use but it is necessary 
for proper operating that the operator should know the instant 
that the current begins to fall in the circuit. 

An instrument which will show when an induction motor b in 
step with its generator is a new one, as there has been no necessity 
for such an instrument in the past. Mr. Alexanderson, of the 
General Electric Company, has designed such an instrument. One 
of them is installed on the New Mexico and is giving good satis- 
faction. It is called a "stability meter" because it not only indi- 
cates when the motor and generator are in step but also indicates 
the factor of safety, or amount by which the voltage can be low- 
ered before the motor will "fall out of step." It consists of an 



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78 ELECTRIC SHIP PROPULSION 

ammeter element and a voltmeter element working together on the 
same pointer and so arranged that their torques are opposed ; the 
voltmeter element is equipped with a reactor instead of the usual 
resistor so that its indications will be inversely proportional to the 
frequency and directly proportional to the voltage. Therefore the 
reading of the meter will be volts divided by amperes and fre- 
quency or impedance per cycle. The characteristics of the gen- 
erators and motors are such that the load impedance per cycle at 
which the generator gives its maximum output is always the same 
regardless of the speed or field excitation; the maximum output 
of the generator, which is the breakdown load of the electrical 
equipment, thus corresponds to an indication of the instrument 
which is always at the same point on the scale. The scale is 
divided into ten parts, one-half indicating when the motor and 
generator are "in step" and the other half indicating when they 
are "out of step." A glance at this instrument during reversal 
will show just when the motors have come "into step." During a 
turn, the instrument will show whether or not the motors are 
approaching too close to the "out of step" part of the scale and 
will enable the operator to increase the field excitation of the 
generator in time to prevent the motors from "falling out of 
step." 



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CHAPTER VIII 
Wire, Cable, Insulators and Insulation 

THE cable used and the method of installing it are of the 
greatest importance in connection with any electric drive 
installation. The cable installation should be practically 
permanent, like the main steam pipe of the ship. 

If all the electric machinery is contained in the same compart- 
ment, then the cable "runs" become very simple and most of the 
problems in connection with it disappear entirely. In this case, a 
good rubber covered cable, mounted on non-fragile insulators 
(such as bakelite), will probably be entirely satisfactory and will 
certainly be the cheapest. The cable should always be given 
mechanical protection and also covered over to keep water from 
drippii^ on it. 

It is seldom that such a simple case as that described above is 
met with in practice. Even in merchant ship installations it will 
usually be desirable to place the motors some distance from the 
generator's and it will be necessary to pierce bulkheads and run 
through wiring passages. This condition will always obtain on 
naval vessels. This immediately brings up two conditions that 
must be met ; the first condition is that the cable insulation, which 
normally is in a warm compartment (perhaps for several years), 
must remain absolutely watertight, if the compartment becomes 
flooded; the second condition which must be overcome is the 
inductive effect of alternating current cables when surrounded by 
closed magnetic circuits, such as a bulkhead through which cables 
must pass. 

Many cable arrangements have been proposed to meet these 
conditions but it is believed that the recommendation submitted 
to the United States Navy Department by the "Standards Com- 
mittee (subcommittee on wires and cables) of the American Insti- 
tute of Electrical Engineers" is the most suitable in every way for 



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80 ELECTRIC SHIP PROPULSION 

an installation on board ship. The specifications for this cable 
and the method of installing it are as follows : 

(fl) Alternating current cable may be either single or 
multi-conductor. 

(b) Large alternating current cables should be provided 
with rope core to reduce skin effect. 
■ (c) The shape of cables should be round, 

(d) The wires of cables should be tinned, (Tinning is 
required mainly because it facilitates making good brazed 
joints at cable terminals.) 

(e) Impregnated jute should be used as a filler for multi- 
conductor cables. 

(/) A separator of treated paper or cloth tape should be 
used between the cable and the insulation. 

(g) The insulation should be black varnished cambric of 
the highest standard ; this should be covered by a jacket of re- 
inforced rubber. Between the layers of varnished cambric 
there should be a suitable mineral base compound which will 
not dry out, oxidize or combine with the film of varnish on the 
varnished cambric or the reinforced rubber. 

(A) The insulation should be protected by a sheath of 
pure lead in the case of multi-conductor cables and by a non- 
magnetic armor in the case of single-conductor cables. The 
armor should consist of two bronze tapes laid up so that the 
outer layer overlaps the space between turns of the inner 
layer. The space between turns should be 10 percent of the 
width of the tape." The tapes should be protected against 
unfurling at the cable ends. There should be a covering over 
the armor of cotton tape impregnated with a flame proof 
compound. 

(i) Sii^le conductor cables should be mounted on insu- 
lators which will not break under the severest shock. The 
bronze armor should be solidly grounded at the middle point 
only and the remainder of the armor should be kept clear of 
grounds. Multi-conductor cables should be mounted on ap- 
proved support!! and the lead sheath should be grounded at 
several points. 



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WIRE, CABLE, INSULATORS AND INSULATION 81 

(/) All varnished cambric cable tenninals should be 
sealed against the admission of moisture, 

(ft) All alternating current cables should be given a test 
between conductors and ground of 20,000 volts applied for 
one minute. 

(/) In all cases, cable supports must be arranged to pre- 
vent chafing the cables at the point of support. 

(»») The supports of alternating current cables should be 
not more than 2 feet apart. These supports should be de- 
signed to give sufficient strength to take care of all short 
circuit conditions. 

(n) When single-conductor cable is used for alternating 
current, the following precautions must be observed in instal- 
ling it : 

(1) Closed magnetic circuits around individual cables 
must be avoided. 

(2) No magnetic material must be allowed between 
cables of a group. 

(3) In passing through bulkheads, the cables must be 
so grouped that the inductive effects of a group are prac- 
tically eliminated. 

(4) Cables must be spaced as closely as is consistent 
with proper supports and good ventilation. 

(5) The distance of the centers of cables from bulk- 
head stiffeners should generally be not less than 3 inches 
and from parallel bulkheads the distance should be not less 
than 4*4 inches. 

In selecting the insulation for the cable proposed, the fine 
insulating qualities and great length of life of varnished cambric 
have been recognized. In order entirely to preserve these quali- 
ties, however, it is necessary to protect this insulation from ex- 
posure to air or moisture and for this purpose the reinforced 
rubber jacket is put on. The specific insulating and dielectric 
constants of this jacket are not very high, so it is necessary to 
combine it with the varnished cambric to get the desired amount 
of insulation. By placing the reinforced rubber outside of a 
thickness of the varnished cambric, the potential gradient is re- 
duced so that the lower dielectric strength of the reinforced rub- 



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82 ELECTRIC SHIP PROFVLSION 

ber does not materially lower the total dielectric strength of the 
cable. The rubber jacket is impervious to moisture (even after 



\\\t—f.iii^- 



FiG. 33. — Cross Sections o£ Two Sizes of Singrle Conductor Cable used on 

U. S. S. California 

long exposure to hot dry air) and has great mechanical strength, 
so that the combination of the two is ideal. 



>r rubber fac*d fuM 

with abaut iilap. 

Fic. 34.— Cross Section of 3-Conductor Cable used on U. S. S, Tennessee 

Reinforced rubber is made by calendering a rubber compound 
into one or both sides of a cotton fabric previously dried and 
waterproofed. Under this process the fabric obtains a thorough 
filling of rubber which, during calendering, becomes partially 



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WIRE, CABLE, INSULATORS AND INSULATION 83 

vulcanized. The prepared fabric is then cut into tapes and ap- 
plied over the varnished cambric insulation in the usual manner, 
except that all contact surfaces and interstices are filled with 
rubber cement. The insulated cable is then dried under moderate 
heat and the rubber is further vulcanized. This last process 
reduces the rubber coverii^ to a homogeneous structure, the 
various layers of rubber tape being united into a solid jacket by 
the vulcanizing process. 

This gives a very elastic and tough covering for the cable — one 
that is also permanently waterproof and will stand continuous 
high temperatures and vibrations. The outer surface of this 
jacket may crack after exposure to heat but the crack will extend 
only through the first thin layer of rubber; as soon as the cotton 
reinforcing is reached, the crack stops and the rest of the jacket 
will be solid. 

In Fig. 33 there are shown cross sections of the two sizes of 
single-conductor cable used on the California. The small cable is 
used for the connections to the motors and the large cable for the 
connections to the generators. In Fig. 34 is shown a cross 
section of the three-conductor cable used on the Tennessee. 

The ends of the cables must be sealed by pot heads both to 
prevent moisture from entering at that point and also to prevent 
gradual "eating away" of the insulation at the point where it is 
cut away to make the terminal connection. This phenomenon ", 
always accompanies any abrupt change in thickness of insulation . 
which produces sharp corners. In Fig. 35 is shown a pot head 
for a three-conductor cable of the Tennessee; in Fig. 36 is shown 
the same thing for a single-conductor cable of the California. An 
examination of these figures will show the extreme care that has 
been taken in the design of the details of these pot heads to guard 
against the possibility of having moisture get in. 

In regard to the relative advantages of the use of single- 
conductor or multi-conductor cable, there are advantages for both. 
The single-conductor cable is much simpler to connect to the 
generator or switchboard. A comparison of Figs. 35 and 36 will 
show the three-conductor pot head to be much more complicated. 
The use of the three-conductor cable makes it imperative to use 
bus bars at both generator and switchboard for the terminals, as 
it will be necessary to have several multi-conductor cables in 



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84 



ELECTRIC SHIP PROPULSION 



parallel for each phase. Again, the insulation between phases is 
not quite so good when three conductors are combined in one 
cable as when the cables are independent of each other. On the 
other hand, the multi-conductor cable is absolutely neutral and 
can be run through steel bulkheads, stifFeners, etc., without re- 
quiring any special arrangements; it can also use a continuous 
lead sheath, as there is no danger from circulating currents in the 
sheath. This gives better protection to the cable than does the 

WAtit hsMling. tht cab/t !l/ett rtHirad fy fht od^iihn of 
rornish camhriz fapr e^ki/ wtfh tvrmih, si/pphpiwrheimih 
?k^rsarnibbtrh^stparahd^*^ni'Shc^pbnc9ndHi*n 




wi%cmilM» H p'illniint<WfaTnfi»iwiMtnWi 1 — .^a-: — u_i — T ii, =___. 

Fig. 3S-— Pot Head for 3-Conductor Cable used on U. S. S. Tennessee 

bronze armor. Since there is no danger from circulating cur- 
rents, the lead sheath may be grounded at numerous points and, 
therefore, the supports for this cable need have only mechanical 
strength and no insulating properties ; since the single-conductor 
cable is grounded only at its middle point, there is greater danger 
of this one connection being broken, thus allowing static charges 
to accumulate on the cable. 

In connection with the use of single-conductor cable, one of the 
specifications is a requirement that there must be no closed mag- 
netic circuits around the individual cables. This necessitates cut- 



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IVIRE, CABLE. INSULATORS AND INSULATION 



85 



ting holes in bulkheads suflRciently large to allow the whole group 
of cables to pass through. The hole is dosed by a bronze plate 
secured to the bulkhead and the individual cables passing through 
the plate are made watertight by means of stuffing boxes. Since 
the armor of the cable must not be grounded at this point, the 
stuffing box must be provided with packing which has some insu- 
lating properties. The insulation required is not very great, as 
its only purpose is to prevent the possibility of circulating cur- 
rents in the armor. The same requirement applies to other insu- 
lators used £or supporting this cable. In Fig. 37 are shown the 
bulkhead plate and the stuffing box used on the CaHfarnia. 

The greatest care must be exercised in running cable and 






^'Bb TirmtdCoppvWiH 

fUltilwHhhtfSoliif 
fCvrtlamI Tut Cot^ tf Vamith 
^Va'Paihtr Tapt 




mkawHhtnJhirmdboek. Vm wiakt m€eliaiiieti fH of eahU 

mItminaltfiA-tringlnilitrfjxtcatf 
' ~ ' •at ttrmliKdand 



Fig, 36.— Pot Head for Single Conductor Cable used on U. S. S. California 

making connections at the switchboard to see that the principle of 
"no magnetic circuits around single wires or cables" is carried 
out. In the switchboard, in particular, these circuits may be 
established and they will give trouble, due to overheating the 
metal forming the circuit, until the trouble has been remedied. 

Exposed bare copper used for making connections to genera- 
tor, motor or switchboard should always be protected from water 
dripping on it. If these connections are made in a compartment 
which is normally filled with air containing a great deal of steam 
or moisture, these connections should be covered over and then 
supplied with dry warm air under pressure so as to make sure 
that the connections will always be free from moisture. This 
can best be. accomplished by running a small pipe to supply air 



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86 ELECTRIC SHIP PROPULSION 

from the generator exhaust duct ; this air will always be warm and 
dry and will be under sufficient pressure to insure a flow of air. 
In addition, all such connections should be made waterproof by 
successive applications df tape, each application being covered by 



several, coats of varnish, each of which is dried before the .next is 

applied., ■"'..• 

After the cable installation is .complete inthe ship,, -it should be 
tested, for,one,.tminute by 15,000 -vplts, puring -this -test, .^1 .. 
switch connections, etc., should be made in suiji a inannei;<^at all,.; 
insulation. between the- circuits :and growidwtU be tested.' In,,- 



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WIRE, CABLE, INSULATORS AND INSULATION 87 

selecting this test voltage, and also that for the cable itself, it is 
assumed that the maximum voltage used at any time will not 
exceed 5,000 volts. 

Cable used for direct current wrhich'is used in connection with 
propulsion should conform, to the same specifications in regard to 
insulation as alternating current cable. With this cable the lead 
sheath may be omitted and some form of fireproof braid substi- 
tuted to give mechanical protection. 

Insulators which are to be used on board ship should be made 
of non-fragile material; in the case of war vessels, it must be 
proof against the severest shock and also against continuous and 
severe vibrations. These conditions eliminate the use of any form 
of porcelain ; even on merchant vessels, it will he found that this 
material is not satisfactory, as insulators made of it will crack or 
break off in the course of time. The material that has proved 
most satisfactory to date is bakelite ; this is a compound which is 
made up in various proportions, depending on the degree of insu- 
lation required. It is very tough and elastic and can be relied on 
to withstand any shocks or vibrations. 

The insulation used for the coils of the main generators and 
motors should consist mainly of mica, as it should he able to 
withstand continuously a temperature of 300 degrees F, If the 
machines are designed so that a temperature rise of 150 degrees F, 
will not be exceeded under the most severe conditions of service, 
then the life of the insulation should be as great as that of the 
remainder of the machinery. Thermo-couples should be provided 
for measuring the temperature of the coils in at least three places 
in the windings ; the instruments for indicating the temperature 
should be located on the main switchboard. 

The end windings of the stator coils of the generators are 
subject to a continuous blast of very moist salt air when the 
machine is running; this makes it imperative that special care 
should be taken to make these end windings moisture proof. This 
can best be accomplished by successive dippings and bakings of 
the ends of the coils until they are covered with a thick coating of 
varnish ; this coat should be renewed by spraying varnish on about 
once a year after the vessel has been in commission about three 
years. 

Owing to the presence of so much moisture in the air, no 



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88 ELECTRIC SHIP PROPULSION 

hygroscopic material should be used as insulation where this can 
be avoided. It is necessary to use a certain amount of asbestos on 
the generator rotor coils on account of the high temperatures 
encountered but wherever used it should always be treated so as to 
be as nearly moisture proof as possible. 



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CHAPTER IX 
Exciters and Other Auxiliaries 

IT will practically always be necessary to use an independent 
generator for furnishing excitation to the main generator 
field. Exciters which are direct connected to the main gen- 
erators are not suitable on account of the wide variations that 
take place in the speed of the generators. 

The source of exciting current should always be duplicated to 
insure reliability ; this is usually best accomohshed by making the 
exciter a duplicate of the generators which furnish light and 
power to the ship. These generators are usually larger than 
would be necessary for excitation alone but the excess power can 
be utilized to drive some of the main engine auxiliaries. In this 
case, it will be necessary to supply a booster in the main generator 
field circuit so the voltage supplied to the main field can be varied 
without affecting the voltage of the exciter which also supplies the 
auxiliaries. When a booster is used it should be arranged so that 
it can be cut out in case of emergency and excitation taken direct 
from the exciter, which must be designed to have the necessary 
wide range of voltage required for excitation. When exciting 
direct from the exciter, the auxiliaries will, of course, have to be 
supplied from the ship's power circuit. 

No fuses or circuit breakers should be allowed in the circuit 
which supplies excitation to the generator field ; any interruption 
of this circuit would probably damage the field itself and would 
certainly burn up the circuit breaker on account of the high voltage 
induced in the field by a quick break of its circuit. 

All motor driven main engine auxiliaries, whether supplied by 
exciters or ship's generators, should always have at least two 
sources of supply in order to give sufficient reliability. 

Auxiliaries which are necessary for proper functioning of the 
boilers are not suitable for motor drive ; for example, boiler feed 
pumps and fuel oil service pumps should be driven directly by 
89 



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90 ELECTRIC SHIP PROPULSION 

turbines or engines. If motor driven pumps are used for forced 
lubrication, some emergency arrangement should also be pro- 
vided. One method of doing this is to provide a small gear pump 
driven from the main generator shaft ; another method is to have 
half of the lubrication pumps motor driven and the other half 
steam driven and then use the motor driven pump to get the best 
economy but have the steam driven pump arranged to come in 
automatically in case of temporary failure of the motor driven 
pump. Still another method is to have the oil discharge line 
connected to the oil supply tanks through a check valve, so thfit in 
case of failure of pressure the tanks will supply oil ; if the lubri- 
cation pumps are arranged to supply oil to overhead tanks which 
feed the bearings by gravity, then no emergency arrangement need 
be provided, as the oil in the gravity tank will be sufficient to save 
the turbine bearings in case of failure of the pump. This latter 
method is the favorite one in use in the merchant service for 
geared turbines and would also be ideal for the same ships fitted 
with electric propulsion. For naval vessels it is not feasible to 
get sufficient head for gravity tanks, as they must be located be- 
neath the protective deck. 

For naval vessels, which will be subject to the shock of gun 
fire, the same care should be taken to avoid the use of fragile 
material in the starting panels of auxiliaries as in the case of the 
main switchboard. All starting panels for auxiliaries should be 
rugged and all the switches, resistance grids, circuit breakers, etc., 
should be shock proof. 

Starting panels should be arranged to start the motors auto- 
matically, as soon as power is supplied, after a temporary inter- 
ruption of the service. 

Generally it will be best to supply current to auxiliaries 
through switches, instead of circuit breakers. Each starting 
panel should be provided with a circuit breaker for its own motor ; 
this will give a more reliable arrangement than providing the 
generator with a circuit breaker. 

It is difficult to lay down a general principle as to when electric 
driven auxiliaries should be used ; each ship is a separate problem 
in this respect; the character of service the ship has to perform, 
the size of the installation, etc., will be deciding factors. As a 
general rule, electric driven auxiliaries will be more economical 



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EXCITERS AND OTHER AUXILIARIES 91 

than steam driven ones. This is so because the power can be 
generated in large turbo generators which have more efficient 
turbines than the small ones. This arrangement also makes it 
possible to keep the, load factor on the turbines high, as a turbo 
generator can be cut out, if the auxiliaries are running at low 
capacity. A second reason for the high efficiency of electric 
driven auxiliaries is the fact that the speed of the electric motor 
can always be made to suit the auxiliary which it is to drive with- 
out sacrificing any motor efficiency. A third reason is the fact 
that the efficiency of electric motors does not fall off as rapidly 
with reduction of load as that of a small turbine. The final 
result is that the over-all efficiency is better where electric driven 
auxiliaries are used than where turbine driven auxiliaries are used. 



ly Google — 



CHAPTER X 
The Jupit e r ' 

THE Jupiter is a twin screw, single deck, cargo vessel de- 
signed for a speed of 14 knots when developing 5,500 
shaft horsepower with a load displacement of 19,230 tons 
and a draft of 27 feet 6 inches. On her trials she developed 7,150 
shaft horsepower and made a speed of 14.99 knots. 

Completed in 1913, the Jupiter has been in continuous com- 
mission since that date and has a greater number of "miles 
steamed" to her credit than any other collier during the same 
period of time. There has been only one "Navy Yard repair 
job" to the machinery and that was to the main turbine a few 
months after commissioning. Her performance has demonstrated 
the highly reliable character of this type of machinery. 

The propelling machinery consists of one 5,500 kilowatt turbo 
generator, two induction motors, two water cooled rheostats, one 
main switchboard and one auxiliary propelling turbo generator of 
450 kilowatts. Excitation is furnished by one of the ship's 35 
kilowatt generators of which there are three. 

The weight of the propelling machinery is as follows : 

Bedplate 16.3 tons 

Main turbine 28.7 " 

Main generator 35.7 " 

Main motors (a) 76.8 " 

Rheostats (2) 5.8 " 

Switchboard and cable 3-7 " 

Atixiliary generator 8J> " 

Total 175.0 tons 

General Arrangement of Machinery 

The machinery is all contained in one engine room. The main 
turbo generator is mounted on its bedplate on the centerline of 
the ship; the auxiliary generator is mounted on a platform above 
92 



ze. by Google 



THE JUPITER 93 

the main generator and on the port side of the engine room. Both 
the main and the auxiliary turbines exhaust into the same con- 
denser. The two motors are connected directly to two propeller 
shafts. The main switchboard is located at the forward end of 
the engine room on the centerline and on each side of it is one of 
the water cooled rheostats. The ship's three 35-kilowatt gen- 
erators, any one of which may be used for excitation, are located 
on a platform in the after end of the engine room on the starboard' 
side. 

General Description 

At 15 knots, the turbine runs at about 2,130 revolutions per 
minute and the motors at 117 revolutions per minute, the reduction 
being approximately 18 to 1. All charges in speed are made by 
varying the speed of the turbine. Reversal is accomplished by 
reversing the connections of two of the three phases and insertit^ 
resistance in the rotors of the motors. All control of speed, 
direction of rotation of motors, etc., is from the main switchboard. 
In case of breakdown of the main turbo generator, the ship can be 
propelled at a speed of about 6 knots by the auxiliary generator^ 

Main Turbine i 

The main turbine, shown in Fig. 38, is a nine stage Curtis 
turbine. The turbine wheels are made of forged steel and are 
pressed onto the shaft, the diameter of which decreases slightly, 
in steps, from the low pressure end to the high pressure end ; the 
turbine shaft is a solid steel forging. . ■ 

The first stage has two rows of moving buckets and the other 
stages have only one row each. The blades of the first stage are 
made of monel metal which resists the erosive effect of the high 
velocity steam in the first stage. The fixed blades of the first 
stage are also made of monel metal and are secured in an inter- 
mediate segment which is bolted to the turbine casing. The 
blading of the second to sixth stages inclusive is made of brOnze. 
The blading of the seventh and eighth stages is made of monel 
metal to resist the erosive and corrosive effects of water in the 
steam. The ninth stage blading is made of nickel steel ;*originalIy 



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THE JUPITER 93 

this blading was also made of monel metal but it was found that 
this long blading did not stand up well in service and blades would 
occasionally break oH so it was changed to steel. All blades arc 
secured to the wheels by being inserted into dovetail grooves. 

The turbine casing is an iron casting, divided along its hori- 
zontal axis and arranged for upward exhaust. The head end oi 
the turbine which contains the steam chest is a steel casting; the 
admission valves are contained in the steam -chest. 

The expanding nozzles for the first stage are of bronze and 
are bolted to the steam chest. The nozzles for the remaining 
stages are cast into the intermediate diaphragms which are of cast 
iron. 

The packing rings for the intermediate diaphragms are made 
of soft brass and divided in halves to facilitate renewal ; originally 
these rings were made of aluminum but it was found that this 
metal deteriorated rapidly due to the action of boiler compound. 
These rings are turned with a number of very fine ridges on their 
inner circumference and are adjusted so that they have practically 
no clearance from the shaft; if any ring rubs when the turbine 
becomes hot, the ridges wear away to give sufficient clearance. 

The shaft packing at each end of the turbine consists of carbon 
rings in sections which are held together by garter springs resting 
in grooves in the outer circumference of the rings. The rings 
are prevented from turning with the shaft by a stop secured to the 
garter springs. The rings are supported by fiat springs which 
keep them centered with the shaft. There are four of these rings 
on the low pressure end and two on the high pressure end of the 
turbine. Both high pressure and low pressure stuffing boxes are 
also sealed with steam. 

The governor is mounted on a vertical shaft driven by a worm 
gear from the turbine shaft. It consists of weights resting on 
knife edges and acting by centrifugal force against a coiled spring. 
The motion of the weights operates a small pilot valve which 
adpiits oil pressure to the cylinder of a hydraulic relay. The 
piston of this relay operates a rack which, in turn, moves the cam 
shaft mounted on the steam chest ; the position of this cam shaft 
determines the number of admission valves that are open and thus 
controls the speed of the turbine. At the end of the governor 
arm Which operates the pilot valve is connected a diamond shaped 



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96 ELECTRIC SHIP PROPULSION 

frame or parallel motion transmitter which is connected, by a 
system of rods and bell crank levers, to the operating stand in 
front of the main switchboard. 

The operating stand contains a small hand wheel which oper- 
ates a worm which, in turn, is geared to a segment mounted on 
one of the bell cranks of the transmission system. Motion of the 
hand wheel is thus transmitted to the parallel motion transmitter 
at the turbine and gives the governor a different fulcrum for each 
position of the hand wheel. 

The governor, hydraulic relay and parallel motion transmitter 
are shown in Fig. 39. The hand wheel drives a very fine pitch 
worm so that it requires considerable motion to change the speed 
of the turbine one revolution; it is possible to adjust the speed 
accurately to a tenth of a revolution. 

There are eight admission valves, controlled by the hydraulic 
relay. These are globe valves and are kept on their seats by 
4ieavy coiled springs ; they are opened by motion of the cam shaft. 
The stems of these valves must be kept free and the springs 
properly adjusted or the valves will stick open after they have 
been in that position for a long time. This difficulty has been 
overcome in later des^ns by making the cam shaft positively close 
as well as open the admission valves. Each valve is raised by a 
lever which has a roller on the end which rides on a cam on the 
cam shaft. 

The bearings are of the spherical, self-alining type and both 
the upper and lower halves are water cooled, the water passing 
through copper coils imbedded in the "babbitt." Water is sup- 
plied from the main circulating pump or sanitary pump and passes 
through a twin strainer before going to the bearings; these 
strainers are of very fine mesh and must be cleaned frequently. 
Oil for the bearings, and also for the governor, is supplied by a 
gear pump driven from the lower end of the governor shaft. The 
oil reservoir is in the bedplate of the turbine and is fitted with 
vents, level indicator and strainer at the filling connection. Oil 
also passes through a strainer after leaving the pump and before it 
goes to the oil cooler ; from the cooler the oil goes to the bearings 
and returns to the reservoir by gravity, A steam pump mounted 
on the bedplate is used to supply oil in starting up and shutting 



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98. ELECTRIC SHIP PROPULSION 

down. Oil is supplied to the bearings at a pressure of about 25 
pounds per square inch. 

The thrust bearing is of the Kingsbury type. The outer 
surface oi the block is threaded and works in a nut which is 
secured to the turbine end bearing ; this nut is fitted with a worm 
wheel which engages a worm mounted on a shaft projecting 
through the bearing and fitted with a hand wheel. By moving 
this hand wheel the whole thrust bearing will be moved forward 
or aft and carry the turbine rotor with it, thus giving it the desired 
position in the turbine casing. A sight hole is fitted in the turbine 
casing for measuring the blade clearances so that the rotor can be 
property set. The float in the thrust is set at about 0.017 but is 
capable of being altered by changing the thickness of the shims 
used in adjusting the thrust bearing. 

The turbine is solidly coupled to the generator as it is a three 
bearing set, there being two turbine bearings and one generator 
bearing. 

The throttle valve is a Schutte-Koerting automatic valve fitted 
with quick closing attachment which can be tripped by hand or by 
the emergency governor. 

The emergency governor consists of a weight, mounted in a 
recess in the shaft near the turbine end, which is restrained by a 
coiled spring from motion due to the centrifugal force of the 
revolving shaft until the turbine speed rises to about 2,300 revolu- 
tions per minute, at which point the weight flies out and trips a 
trigger and allows the throttle valve to close. 

Main Generator 

The main generator, shown in Fig, 40, is a two pole, three 
phase alternator rated at 4,350 kilowatts but which develops 5,500 
kilowatts with ease. The normal voltage at the rated speed is 
2,300 volts. 

In most respects the generator is of ordinary commercial 
design, but an attempt was made in this installation to produce a 
flame proof winding for the stator. The stator winding insula- 
tion is shown in Fig. 41. It will be seen that both the slot portion 
of ;the coil and the end connections are covered with asbestos; this 
was done to protect the coil against damage by flame in case of a 



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ELECTRIC SHIP PROPULSION 



VS'asbtsfos tapt buHad tnfirt ltngth.gi¥» 

VS'osbtsfes fapt '/7 lap tntire langHi. &vt 

Wtrf h> sMporHon lopp*(l unt/tr wtJgt. 
plicoHon. 

yarsofmica tope i'llap oiti twa lanrs eF 
vlaysr of asbestos tap* fobi bvtfttl and 



'-I'longhllorranct mode For camprassio 



[Effd bands only 
Ttn> kiytrs mieo lap* 
.010" thick ptr Iqytr 



•msios 

•MOIoihd 
/osbadi€/fd- 



r Ho\oT End Winding Locing 



Fio. 41.— U. S. S, Jupiter: Generator Sutor Winding Inaulation 



Digmze. by Google 



THE JUPITER 101 

short circuit in the generator. It has not been a success and will 
not be used in future installations. The asbestos on the end con- 
nections is subject to continuous bombardment by a stream of air 
saturated with salt moisture when the turbine is running and, 
being very hygroscopic, it absorbs this moisture with consequent 
lowering of the value of the insulation. When the machine is 
idle, the inside of the generator becomes a condenser, due to 
changes in engine room temperature, and moisture is deposited on 
these coils. This difficulty was overcome by thoroughly varnish- 
ing the end connections to make them impervious to moisture and 
by fitting steam coils for heating the generator when it is idle so 
as to prevent moisture from depositing. The air intake for the 



Fig. 42.— Generator Rotor for U. S. S. Jupiter 

generator was also blanked off from the bilge and ducts were run 
up into the upper part of the engine room so as to secure dry air 
for ventilation. 

The generator rotor, shown in Fig. 42, is a solid steel forging 
having radial slots machined in it to receive the rotor windings. 
The insulation of the rotor coils consists of mica and asbestos. It 
is necessary to use a protective covering of asbestos in this case on 
account of the high temperature in the rotor; the insulation is, 
however, entirely covered and protected. Fans for ventilating 
the generator are attached to each end of the rotor. 

Air for ventilation is drawn from the engine room through the 
end bells at each end of the generator and then discharged by the 
fans into the air gap between the rotor and stator ; it then passes 
through radial ducts in the stator and is collected in a casing 
around the stator and finally discharged from the top of the stator 
into a duct leading to the forced draft blowers in the fireroom. 



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THE JUPITER 103 

The generator bearing is similar to the turbine bearings except 
that the pedestal for supporting it is entirely independent of the 
stator instead of being mounted on it. 

Main Motors 

The two main motors are mounted in watertight pits recessed 
into the inner skin of the ship. They are induction motors of the 
definite wound type ; Figs. 43 and 44 show the stator and rotor, 
respectively. 

The rotor windings connect to three shp rings which are con- 
nected to the water cooled rheostats. These slip rings can be 
short circuited by a slider working on the shaft and operated by a 



^ One SmitcoHwi fap^ 
lintn finis/t, haifiap, 
Smrmshts bahmd6 
hears btttvttntaeh 
vantish, tmoffitr hpt, 
holfhp and € mart 
varnishts. bakmd 



Moior Rotor Winding InsuloHon Motor Stator Winding Intulotion 

Fio. 45-— U. S. S, Jupiter: Motor Winding Insulation 

lever in front of the switchboard. The short circuiting device 
consists of a brass segment under each ring and a corresponding 
segment on the slider. The segments on the slider are made up 
of thin brass strips which are interleaved to form a spring which 
will have to be compressed as it slides under the solid segment of 
the ring; this insures good contact for the short circuit. To 
prevent burning these contacts there are provided auxiliary con- 
tacts which consist of carbon blocks on the solid segments and 
brass contact fingers on the slider ; these fingers are renewable 
and are arranged to make and also break the circuit before the 
main contacts. 

The motor winding insulation is shown in Fig. 45. It will 
be seen that it consists entirely of fibrous insulation, which is well 
varrushed. While this insulation has been entirely satisfactory it 
is not believed that it is really suitable as the motor temperature 



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104 



ELECTRIC SHIP PROPULSION 



is higher than it should be for this type of insulation ; also this 
insulation is hygroscopic unless it is thoroughly protected by 
varnish. 

The motor frame is surrounded by a sheet metal housing con- 
necting to a duct on top of the stator which leads to the blower 
room of the forced draft blowers. It was intended that the 
blowers should draw air through the motors and thus ventilate 
them but this arrangement is not satisfactory as the blowers are 




--^7V|* e'-jw »| 

Fig. 46.— Water Cooled Rheostat on U. S. S. Jupiter 
seldom used and the lagging on the motors really only serves to 
hold the heat in. 

The motor bearings are of the spherical, self-alining type and 
are adjustable in the supports at each end of the motor frame. 
They are self-oiling, being fitted with oil rings which dip in reser- 
voirs in the lower part of the bearing. 

Rheostats 
The water cooled rheostat is shown in Fig. 46. 
two of these, one being located on each side of the n 
board. 



There are 
ain switch- 



Digmze. by Google 



THE JUPITER 105 

The rheostat consists of a top header, bottom header, three 
large porcelain cylinders, three small porcelain cylinders and 
three non-inductive resistances. The resistances are made of 
calorite and consist of spiral coils laid up on a wooden spindle and 
having the connections of alternate coils reversed so as to make 
the resistance non-inductive. The large porcelain cylinders rest 



Fig. 4?.— a-Stage Turbine used ti 

on rubber gaskets on the bottom header ; the resistances are placed 
inside these cylinders. A rubber gasket and a brass ring are 
placed on the top of each large cylinder and a small cylinder rests 
on each of these. The top header rests on rubber gaskets on top 
of the small cylinders. Water from the circulating pumps-enters 
the bottom header, passes through the cylinders and out through 
the top header. The circulating water forms a part of the 



Digmze. by Google 



ELECTRIC SHIP PROPULSION 



Bill of Material for Turbine Shown in Fig. 47 



Vuo* af PMt 



. 3, ■ Gear Cbiiiik 
3, Oil Pump Caain 

• 4; Governor Shaft 
5. Bashing 

?6. Gear 



ins for Governor 



Split ColUr 
Governor Do 
Bracket for ( 



Floating Lever 

Glud 

Hrdraalic Crlindet 



Crlinder 
Valve S. 



'alve'ta. 



"S.. 



3|. Collar Fin and Sleeve 

36. Spring Support 

3?; AfGu&ng Screw 

4a! Traveling Nut 



Hune ot Put 



Shaft 
Shaft 



Tri"l^nge 



PackLDg Sleeve 
Crou Kev 
Packing Sleeve 



e Head (Upper Half) 
e Head (LoWer Half) 
e Shell (Lower Half) 
e Shell (Upper Half) 



Second Stage Noizle 
Intermediate Segment 
Diaphragni, md Stage 
Noiile Diaphragm, 3rd Stage 

Pint Stage Wheel 
Second Stage Wheel 
Third Stage Wheel 



t Blade, 2Dd Stage 



Turbine Shaft 
Connection to Reduction ( 
Oil Pressure Gage 

Bushing for Gage Board 



1 of Material for Auxiliary Turbo- Generator Shown in Fig. ^ 



Vami of Fart 



g (Lower) 
g ^Middle) 
g Cover 



5. Oil Deflector 

.6. Holder for Ojl Deflector 

7- Bearing 4' / 8" 

8. Oil Guard 

9. Oil Supplj Pipe 

■ 0. Bolt for Ccupfing Flanges 
ii. Adjusting Screw 

II. Shims 

\3- Thrust Plate 

,4. Cover 

U. Bearing s" 1 » 

1«. Stud for flexible Gears 

17. Gears (Flexible) 

■ 8. Huh 

19. K^ for Shaft and Gear* 



Shaft for Gears 



Bolt 

Collar 

Shaft 


or Coupl 


ng F 


and Pin 


on 


Cover 


for Oil 


Tank 


NmiI 


for Oili 


g Ge 




g Coil 




§?n 


for Oil Tank 



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108 ELECTRIC SHIP PROPULSION 

electric circuit when the resistances are in use. These can be 
used continuously, if desired. 

Auxiliary Turbo Generator 
The auxiliary generator, shown in Figs. 47, 48 and 49, is a 
2-poIe, 3-phase, geared set. The gear ratio is approximately 6 to 



Fig. 4g.— Auxiliary Generator on U. S. S. Jupiter 

1 ; the speed reduction between the generator and motors is 18 
to 1 ; the turbine runs at a speed of 5,000 revolutions per minute, 
the generator at 828 revolutions per minute and the motors at 45 



Digmze. by Google 



THE JUPITER 109 

revolutions per minute. The turbine is rated at 450 kilowatts 
and the normal voltage is 450 volts. 

Bill of Blateria] for Auxiliary Generator Shown in Fig. 49 

Put Put 

Ko. Nam* of Put Mo. Nuia oT Ptrt 

!(l) M- Screw, FUt Head No. u. Twenljr- 

four for Connection Strip 

60, Clamp 

61. H" Bolt Sixteen H" Lons for 
CUmp 

Lator 6a. Lockwashpr 

63. Lockwasher 

for 64. Balancing Wright Bolt 

65. ^- Nut. Thirteen W" Thick for 
for BaUncing Wright Bolt 

66. Balancing Veight 



a" Screw Filliater Head. Thirteen 

iM' Long for Binding Bands 
Binding Band 

Staior Coil Winding 

Wi« Screen 

Lng 

S/16" Cap Screw. Eighteen yi- 

Long for Wire ScneS 
Terminal 
Cable. 640.000 CM., Eitra Flexible 





)r Fran 






Shield 










Slat. 


ir Fram 


e Bins 


57 


ai' Lo 
Bolt. 


'"^hirteer 


«?' 


X,.." 


"^-en 4^ 


_ Shields 






Bolt. 


Eight 3^ 



a 1ST.. 

JO.' Space Bl« 



39. Fan Blade 

40. yr Bolt. Thii 

Fan 

41. Lockwasher 

43. Centering Ring 

U'. Connection Str 
i' Ri™,"'"' "'"' 
i'Xck 



Brush Holder Y 


or B. H. Rigging 




H' Bolt. Siiti 


:en H' Long for 


Support 




Suppbn 




Thumb Screw 




Wing Screw 




Spring Fulcrum 




Spring 




Barrier 




Bulbing 




Buihing 




Buabing 
Brush Holder 






Guard 




But Ring 




H" Nut. Elev, 


:n M* Thick for 


Stud 




Collector Ring 




Shell Inaulation 




Collector Shell 




Plug 




a- Screw. Flat 


Head. Ten ■«- 



KG,,. 



Eye Boll 

slotted Lug 

Hinge 

Cable Conneclor 

Rivet 

Collector Lead 



%" „ . .. _,_. .... ...... 

End Plate 114. Beading 

Lead Wedge .. 115. Coil Wedge 

Terminal 116. Coil Wedge 



58. Lead Wedge 



; Support 1 
s"'^'oV Siileen foi 
binding Support 



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no 



ELECTRIC SHIP PROPULSION 



This set is installed as a "stand-by" in case of failure of the 
main set and ordinarily is not used as it can not be run in parallel 
with the main set. It has a governor for speed control but there 
is no adjustable feature to it so that speed changes must be made 








BB 



Descnpiion of Instruments d Switches 

on Switch Board. 

1 - Ammeter 7 - Voltmeter 

2 ■ Voltmeter 8 - Field Ammeter 

J- Voltmeter 9 - Field SK/itnh ZSOV-ZOOA 

■f - Wattmeter 10 - Lever Switch 250 V. - 800 A 

5 - Ammeter II -■ Lever Switch 600V.'ZOOOA 

6 - Ammeter 12 - Freld Rheostat 

Fig. SO-— Main Switchboard on U. S. S. lupiUr 

by the throttle. Excitation is furnished by the same sets as for 
the main turbo generator. 

Main Switchboard and Wiring 

The main switchboard is shown in Fig, 50 and a diagram of 
the wiring in Fig. 51. The switchboard contains all the instru- 
ments, levers, etc., necessary for the control of the engines except 
the levers for short circuiting the rheostats which are located in 
front of the switchboard, on? on eagh side, and the speed control 



Digmze. by Google 



THE JUPITER HI 

stand which is directly in front of the center of the board. All 

control levers are within easy reach of one man. There are the 
following switches, levers, instruments, etc. : 




,.-. ...juHBrtaker 
C.T- Current Tmnsf. 

P.Tr PotTransf. 
RMr Rheostat 
" " Resisfanct 



Fig. 51.^— Wiring Diagram for Main Switchboard on U. S. S. JuptU 






"ahead" oil switch for each main motor, 
"astern" oil switch for each main motor, 
exciter field switch, 
double-throw field switch for supplyi:^ i 



r emergency gen. 



I double-throw generator cut-out switch for connecting either main 
or emergency generator to the main buses. (Located on the back 
of the switchboard.) 

I field ammeter for main or emergency generator, 

I field voltmeter for main or emergency generator. 

1 voltmeter for main generator. 



Digmze. by Google 



ELECTRIC SHIP PROPULSION 



r for main generator. 
(j) I voltmeter for emergency generator. 
(k) I ammeter for emergentg- generator. 
(0 I indicating wattmeter for main generator, 
(w) 1 ammeter for each main motor. 
(n) I integrating wattmeter for each main motor. 
(o) I rheostat for exciter field. 

Ip) I turbine speed control stand. (Located in front of switchboard.) 
Iq) I short circuiting lever for each main motor. (Located alongside 
the motors.) 
The following interlocks are provided : 

Mechanical 

(1) "Ahead" and "astern" oil switches are interlocked so 
that both can not be closed at the same time. 

(2) Both the "ahead" and "astern" oil switches are inter- 
locked with the rheostat short circuiting levers so that the oil 
switches can not be closed until after the rheostats have been cut 
in. After an oil switch has been closed, it is then possible to cut 
out the rheostats. 

Electrical 

(1) The short circuiting levers are locked by under current 
relays which will not permit short circuiting the rheostats until 
the current in the main circuit has fallen to a predetermined value. 
This lock does not prevent moving the levers to cut in the 
"rheostats," 

From the wiring diagram (Fig. 51) it will be seen that the 
leads are as simple as possible. The main buses can be supplied 
by either the main or emergency generator. The generator dis- 
connecting switch is double-throw, so that it is impossible to con- 
nect both generators at the same time ; the same arrangement is 
applied to the field supply switch for the generators. Of the 
three leads to the main motors, one is taken direct and the other 
two pass through the "ahead" and "astern" switches to give 
proper direction of rotation to the motors. 

Operation of the Machinery 

(1) Getting Under Way, Coming to Anchor or Maneuver- 
ing Alongside Ships or Docks. — For this condition, the rheostats 
would be kept cut in ; this ararngement gives the simplest possible 
operating conditions. 



Digmze. by Google 



THE JUPITER 



113 



(a) To go "ahead," close the "ahead" switch or switches. 

(b) To go "astern," open the "ahead" switches and close 
the "astern" switches. 

Either motor can be stopped, started, or backed inde- 
pendently of the other and the results obtained in ship handling 
are much better than can possibly be obtained with other types 
of machinery. 

(c) Speed changes are made by changing the setting of 
the speed control wheel as desired. 

(2) Cruising.— ^or this condition the rheostats must be 
short circuited; the change would be made to this condition with 
the ship going ahead with rheostats in. 

(a) To go "ahead standard speed," open the exciter field 
switch and set the turbine for slow speed. As soon as the 
under-current relays unlock, move the levers to short circuit 
the rheostats. Close the exciter field switch. As soon as the 
generator field has built up, bring the turbine up to the desired 
speed. This operation requires a total of about 25 seconds. 

(&) To go "astern," open the "ahead" switches, move 
the levers to cut in the rheostats and close the "astern" 
switches. The total time required is about 4 seconds. 
From this it will be seen that even when the machinery is in 
the cruising condition the ship can be almost instantaneously re- 
versed. There are colliers in the United States Navy practically 
identical with the Jupiter and which are fitted with reciprocating 
engines and also geared turbines. None of these ships compares 
at all favorably with the Jupiter in handling alongside ships or 
dodcs. 

Trials 

The following table gives the results of the official trials of the 
ship, conducted shortly after commissioning : 



Duration of Trial 


48 Hours 


34 Hours 




Feb. 14-14 

ig.452 


Feb, 18-14 






2/ 7'/i' 
19,350 


Displacement, in tons 



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ELECTRIC SHIP PROPULSION 



Pressures (gage) : 

MaJn steam boilers, pounds 

Engine room, pounds 

Turbine, pounds 

First stage, pounds 

Forced lubrication, pounds 

Oil to governor relay, pounds 

Steam seals, pounds 

Auxiliary exhaust pressure (absolute) 
Air pressure to boilers, in inches of wa 

Vacuum, inches 

Revolutions, or double strokes per minute: 

Starboard motor 

Port motor 

Main turbine 

Condensate pumps 

Dry-air pumps 

Circulating pumps 

Feed pumps 

Blowers 

Temperature, in degrees Fahrenheit: 

Main injection 

Overboard discharge 

Hottest bearing (middle) 

Oil from cooler 



Field amperes, main generator 

Field volts, main generator 

Volts, main generator 

Amperes, starboard motor 

Amperes, port motor 

Amperes, main generator 

Kilowatts, starboard motor 

Kilowatts, port motor 

Kilowatts, total 

Shaft horsepower, starboard shaft 

Shaft horsepower, port shaft 

Shaft horsepower, total (torsion meter) . 
Water consumption data: 

Total pounds per hour 

Pounds per hour, auKJliaries 

Pounds per hour, turbine 

Pounds per hour per shaft horsepowei 

(turbine) 

Fuel consumption data: 

Pounds of coal per hour 

Pounds of coal per hour per shaft 
horsepower 

Pounds of coal per hour per sq. ft. H. S. 

Tons per day 

Kind of coal 

puality of coal 

Slip of pri^eller. percent 

Shaft horsepower per sq. ft. grate surface 
Knots per ton of coal 



a8.2 


a&S 


iifi.72 




116.72 


77.077 


2.130 
3,600 


1,410 
3,600 


193 


iJ^ 




17 


^29 





5.525-8 
3,603 

3.549 
7,152 

105,764 

83,552 



1.662 



■■^ 



40,066 
15.246 
24^20 



2.5056 



S4Xfi2 



.613 
12739 

New River and Geo. Creek 
Run of mine j Run of mine 
8-74 



15-9 



4-43 



Digmze. by Google 



CHAPTER XI 
The U. S. S. New Mexico 

THE New Mexico is a battleship having a displacement of 
32,000 tons at a 30-foot draft. She is 624 feet long over- 
all and has a beam of 97 feet A-]^ inches. She was de- 
signed for a speed of 21 knots but made a speed of 21.31 knots on 
standardization and developed 31,300 shaft horsepower at 170 
revolutions per minute of the propellers and 2,070 revolutions per 
minute of the main generators. 

The main propelling machinery consists of two alternating 
current turbo generators, four induction motors, two 300-kilowatt 
direct current generators for excitation and motor driven auxil- 
iaries, two motor generator boosters, a main switchboard, an ex- 
citer switchboard, ventilating blowers for the main motors and the 
necessary wire and cable for connecting up the generators and 
motors to the switchboards. 

The weight of the machinery is as follows : 

4 main motors 479,046 pounds 

2 turbo generators 5^^958 " 

2 boosters 4^800 " 

I main switchboard 39I840 " 

Cable 20^56 " 

Total 1,110,900 " = 500 tons 

General Arrangement of Machinery 

The general arrangement of the machinery in the three engine 
rooms and the motor rooms is shown in Fig, 52, which gives a 
single line wiring diagram of the main alternating current and 
direct current wiring and also gives the location of the main 
operating switches and levers. All of the main engine auxil- 
iaries, two of the main motors and the alternating and direct 
current switchboards are located in the central compartment. The 
two generators are located in compartments outboard of the center 
115 



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116 



ELECTRIC SHIP PROPULSION 



engine room and the outboard motors are located in compartments 
abaft the generator rooms. Communication between motor rooms 
and generator rooms is provided for through a watertight door. 
Each main motor is connected directly to a propeller shaft. 



Firt and dilg* Ptfpps-^ fted Ptstr^t Pvmp^ 



_, — -r^ir* and B'Igt Pumpi 



d - --" - b 



n n n a.™ 

\U/P'""P 0!IC«j€r ^"■^ \P 




Fig. 52. — U. S. S. New Mexico: Arrangement of Machinery 

General Description 

The main motors are provided with pole chaining switches 
which can be thrown to give them 24 poles or 36 poles ; since the 
generators are 2-pole, this .will give speed reductions of 12 to 1 
and 18 to 1, respectively. The alternating current switchboard is 
provided with a tie switch so that one generator can be used to 
drive all four motors. 



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THE U. S. S. NEW MEXICO 117 

For speeds up to 15 knots, one generator is used to drive four 
motors, the latter being on the 36-pole arrangement; the limit of 
speed with this arrangement is the maximum speed of the gen- 
erator. 

From 15 knots to 17 knots, one generator is used to drive four 
motors, the latter being on the 24-pGle arrangement ; the limit of 
speed with this arrangement is the load on the generator. The 
generators are required to stand 25 percent overload but this 
requirement can not be met when one generator is driving since 
full load will be reached at -a reduced speed of the generator and, 
consequently, the full ventilation of the generator will not be 
obtained. 

From 17 knots to full speed, two generators are used, each 
driving two motors. In this case the two sides of the ship are 
entirely independent of each other in every way. 

When one generator is used to drive, the speeds of the four 
motors must always be the same although the motors on either 
side of the ship can be kept at standstill or backing while the 
motors on the other side are going ahead; also, when one gen- 
erator is being used, it is always necessary temporarily to remove 
power from all motors to make changes in the direction of rota- 
tion of either pair of motors since the generator circuit is always 
killed by taking power off the generator field before opening or 
closing any of the main switches. 

The motors are always backed on the 36-pole arrangement 
since that gives a higher torque for reversal than the 24-pole 
arrangement. 

The two motors on one side of the ship are always handled as 
a unit but either one of them can be disconnected when desired. 
"" — Motor generator boosters are located in the main generator 
field circuit for giving the desired changes in field current. The 
field current comes from the 300-kilowatt exciters and passes, in 
series, through the generator of the booster ; by varying the field 
of this generator and by reversing its field so as to "buck" or 
"boost" the exciter voltage, any desired voltage can be impressed 
on the slip rings of the main generator field. 

This arrangement makes it possible to use exciters of the same 
size as the ship's light and power generators, thus making spare 



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118 ELECTRIC SHIP PROPULSION 

parts interchangeable and also making it possible to use the ship's 
generators for excitation without complication. 

The exciters, being constant voltage machines with this ar- 
rangement, can be used to furnish power for purposes other than 
excitation since this load amounts to only about 55 kilowatts on 
each exciter at the full power of the ship. The remainder of the 
available power is used to run the main circulating pumps, main 
condensate pumps, main air pumps, forced lubrication pumps, and 
ventilating blowers for the main motors. 

The exciters are made non-condensing and exhaust against a 
back pressure of ten pounds per square inch gage. The exhaust 
steam is used in the low pressure stages of the main turbines, thus 
giving a very fine efficiency. 

The speed of the propellers is varied by changing the speed of 
the main turbines; the latter are under the control of a governor 
at all times and the speed changes are accomplished by varying 
the setting of the governor. 

Main Turbine 

A section of the main turbine is shown in Fig, 53. It is a 
10-stage, General Electric-Curtis turbine. The first stage is 
velocity compounded, having two rows of moving buckets, and 
the other stages are pressure compounded, having a single row of 
moving buckets on the wheel. 

The wheels are pressed on the shaft and keyed. The tenth 
stage wheel is secured against a shoulder on the shaft and the 
first stage wheel is secured by a cross key in the wheel and shaft, 
thus preventing fore and aft motion of the wheels. The wheels 
are separated approximately 0.01 inch by crushing pieces inserted 
between the wheels. The blades are secured to the wheels by 
dovetails, as shown in Fig, 53, 

The intermediate segment, carrying stationary blading, in the 
first stage of the turbine is secured to the casing by conical-headed 
through bolts, thus preventing any damage due to their coming 
loose and getting into the moving parts of the machinery. 

All stages except the first have complete peripheral admission. 
The first stage expanding nozzles are secured to the steam chest 
by countersunk, cheese headed screws; sufficient metal is peened 



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120 ELECTRIC SHIP PROPULSION 

over the heads of these to prevent them frcm getting into the 
machinery in case of breakage. The admission nozzles for the 
remaining nine stages are cast into diaphragms which separate the 
successive stages. These diaphragms are split through the hori- 
zontal plane and are secured in the casing against shoulders. The 
lower half of each diaphragm may be rolled out without lifting 
the rotors. When the casing is lifted, the top half of the dia- 
phragm may be lowered by backing off a screw on each side which 
takes the weight of the diaphragm when it is lifted from the 
lower half. Leakage past diaphragms, along the shaft, is pre- 
vented by packing rings of the labyrinth type, made of soft brass. 

The turbine casing is split in a horizontal plane and also in a 
vertical plane at both high pressure and low pressure ends. This 
makes it possible to lift off the portion of the turbine casing cover- 
ing the blading without disturbing the exhaust trunk of the turbine 
and also without removing the steam chest at the high pressure 
end of the turbine. 

The shaft openings in the casing at each end are sealed by 
labyrinth packing rings which are supplied with sealing steam 
from the turbine itself when the turbine is not loaded sufficiently 
to give steam pressure high enough for this purpose; when the 
pressure falls too low, sealing steam is supplied from the main 
steam line through a reducing valve. There is an unloading valve 
on the steam sealing line between the high pressure end and low 
pressure end which maintains the proper pressure on the sealing 
line by spilling the excess steam into the eighth stage of the main 
turbine. 

The turbine casing is drained, through valves, by a Arain pump 
located in the center engine room. 

A flexible jaw coupling, which is totally enclosed by a housing 
contained in the middle bearings, couples the turbine to its 
generators. 

The turbine is provided with a bearing at each end mounted 
on brackets which are integral with the turbine casing. The 
bearings, which are of the self-alining type, are supplied with 
forced lubrication from pumps located in the center engine room. 
These pumps also supply oil pressure for operating the main 
governor hydraulic relay. The bearings are also water cooled and 
are supplied with water by the main circulating pump or oil cooler 



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THE U. S. S. NEW MEXICO 121 

circulating pumps. The cooling coils consist of copper coils 
imbedded in the babbitt of the bearings. The bearing at the high 
pressure end carries the turbine thrust bearing, which is of the 
plain, collar type. The outside shell of the thrust bearing is 
provided with worm and worm wheel attachment for moving the 
turbine in the fore and aft direction, to give proper clearance 
between the buckets and nozzles. There is a clearance indicator 
at the end of the turbine shaft. 

The turbine casing has two openings, one into the fifth and 
one into the eighth stage, for the admission of exhaust steam, 
cither from the exciting units or from the exhaust line of the ship. 
These openings are provided with stop check valves and also 
automatic trip valves. The stop valves are provided so that steam 
can be admitted to either stage as desired ; the "check" feature is 
added to prevent steam by-passing from the fifth stage to the 
eighth stage in case both valves should be open and the steam in 
the fifth stage of a higher pressure than that corresponding to the 
auxiliary exhaust pressure. The trip valves are operated by the 
emergency governor. The exhaust line is also provided with a 
valve for by-passing exhaust steam direct to the main condenser. 
This valve can be locked open by hand so that the exhaust steam 
passes direct to the main condenser continuously ; it is also spring 
loaded and set at ten pounds pressure so that pressure in excess 
of this will relieve itself into the main condenser. This valve is 
also directly operated by the main turbine governor so that, when 
the main turbine governor closes all valves on the steam chest, 
further motion of it will open this by-pass valve, thus admitting 
the exhaust steam direct to the condenser and by-passing the main 
turbine. This valve is shown in diagram in Fig. 54. 

The emergency governor consists of a ring mounted on the 
main shaft and held in place by a spring. This ring is slightly 
unbalanced so that overspeeding the turbine will force the heavy 
side out against the pressure of the spring and trip the trip valves 
of the fifth and eighth stages of the turbine and the main throttle 
valve, thus shutting off all sources of supply of steam to the turbine. 
At the same time it throws a control valve on the hydraulic relay 
which doses all the admission valves on the steam chest so that 
steam will be shut off the turbine even if the main throttle should 



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122 



ELECTRIC SHIP PROPULSION 

n also be tripped by a 



stick when it is tripped. The steam valves ca 
hand pull located in the center engine room. 

The main governor is driven by a worm gear from the high 
pressure end of the turbine shaft. It is of the flyball type, the 
weights being mounted on knife edges and working against a 
spring. This governor is adjustable and can be set to give any 
desired speed from 700 revolutions to 2,200 revolutions ; when 
once set it will maintain that speed regardless of changes in load. 




A diagrammatic sketch of the governor and its control gear is 
shown in Fig. 54. The governor weights operate the pilot valve 
of a hydraulic relay, which in turn admits oil pressure to a piston 
driving a rack ; this, in turn, drives a pinion which is mounted on 
a camshaft. Motion of these cams opens successive valves in the 
steam chest of the turbine, thus admitting the desired amount of 
steam. The control mechanism for the governor is moved from 
the center engine room by means of rods and bell cranks, as indi- 
cated in Fig. 54. The effect of the motion of this transmission 
system is to shift the fulcrum about which the governor weights 



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124 ELECTRIC SHIP PROPULSION 

act and thus to give a different speed for each setting of the 
fulcrum. 

In addition to the system of bell cranks for setting the ful- 
crum, there is another system of bell cranks and rods coming from 
the center engine room which operates a stop shown diagram- 
matically in Fig. 54. The effect of this stop is to limit the motion 
of the governor for any given setting, thus limiting the amount of 
steam that the turbine can take for that setting. This steam limit 
is necessary in connection with the turning of the ship as was 
explained in Chapter III, 

Main Generator 

A cross section of the main generator Is shown in Fig. 55 and 
the assembled rotor is shown in Fig. 56. The generator is 



Fig. 56. — Rotor of Main Generator for U. S. S. New Mexico 

normally rated at 11,500 kilowatts at 80 percent power factor and 
has an overload rating of 25 percent. It is quarter-phase, two- 
pole and designed to run at about 2,100 revolutions per minute. 

The stator windings of the two phases are arranged as shown 
in Fig. 28 and described in Chapter IV, Both ends of each inde- 
pendent winding are brought to the terminals of a double throw 
switch, which, when in one throw, puts the winding in the dia- 
metral or parallel connection and, with the generator operating at 
designed speed and field strength, gives 3,000 volts; with the 
switch in the other throw, the windings are thrown into the square 
or series connection and this arrangement at designed field and 
speed of the generator gives 4,242 volts. 

The windings are arranged in this way so as to give the maxi- 
mum efficiency of the generator when one generator is driving four 
motors and also when it is driving only two motors, as explained 



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THE U. S. S. NEW MEXICO 



125 



in Chapter IV. In the first case the low voltage connection is 
used and this utilizes the increased current path when using four 
motors. When using the high voltage connection, only two 
motors are driven from one generator, thus cutting the current 
path down to one-half its value in the other case. The switches 



'^orm sh/ msulafhn wifhUaytr 
.020%om filire,r-by<r.0?OYlB. 
i^fibn.l-hjtrM'bsieshs. all 

kgtthst wiHt shtlloc. Oo/sic/i i 
, ^^ insi<J«ofinsijlffliofigivtnlcoaf 
■ ;-S of ofr drying Japan. 
'"^ ITn Qbo\fe insvl&fhn h ejiftnti 

2"btyii'i<i CQrt. 




«s3 

1^1 



■ ■ Each him loped with .OOi'mica lap* 
H/Cg, with sf icier, pressed k ,fflf 
whin osiemhiing. 



■' fnsiA and oufslde coils wound 
wiih 2/oytrs .BBS 'mica hptH lap, 
ollofhtrcolls I lay .OOS'micavxt 
hlaa 
On kip of Coils and under miea lap* 
l-slrip- OSO'fleiiiblemica.On hp of ma 
fapel-stria. OSTt^ilt fibrtfln mslship 
MQ'fkxAle mka.onmaO-dnftd 
fHect.BIO'flenibhmka. ThtoUv* 
is inendmlh.Oli'lidiidaH)pililt{p. 
Co'lSybeg'hningQlarw andttlrnd<ng 
i''i ' artgiYtn an addilicrtol kiyer pf 
jtcrion OTioii .OlShsbeshsfapt lilop,tivr sM 
OuUide fffCor* 'msulafian. 
Apply 2 coah Hack varnish. 
Jifler bhoks are In pkKe leoai compciindrOnihkl ccaf 

iif*ISObkK,li varnish. 
Affer cork and rings art asambkd, rofcr isbalndSddja. 



for making this change in "set up" are mounted on the outboard 
bulkheads of the center engine room and are operated in the 
center engine room; they are called the "generator disconnecting 
switches." 

The generator rotors are designed with a large factor of safety 
in regard to heating in order to take care of the condition that 



Digmze. by Google — 



126 ELECTRIC SHIP PROPULSION 

exists in backing when over-excitation is applied to the main 
field. The slip rings for admitting exciting current to the field 
and the ventilating fans are not shown in the drawing of the rotor 
given in Fig. 56 but are shown in Fig. 55. The slip rings are at 
the end of the generator away from the turbine and are external 
to the bearings, thus reducing the length .of the rotor ; the cable 
connections to the sHp rings are led through slots in the shaft 
The ventilating fans are attached to each end of the rotor as 

llaram-.0O4' 

' ampoanckd im- 

'prtswrt wiHi 

'eahpeiihpa>- 
wi'^ifkitr.inka 
.OOS'micocemnf- 
rstf.a)l'jbpanta 
i/asaiwe. 



^'Ywgtajt layer 
i1vornish,?ceah 
rchtvo/ofyor- 
imiXdry. Cofhn 
'addif&i^ laytr 
^tirh^aihprv 

'.OlS'lhrnfibrsmoiilikdh^l ptirHon,lappti 

I on fop. &ye alb I coal of an air- drying Japan. 

'•'F!lkrl.04"s.m'wh:h fibrt and .OIQ''raf/ hide 

f'ire. AlinnTPaM^'nade^crvryrtssiofUffcoris. 

End clipi 

Sire dips4lByeri of mica fapel^lap andAlaytrs of 
biackdoiii andlktyerofaiHimlapeharriishfilled) 



shown in Fig. 55. Air is taken in around the shaft at each end of 
the generator and, after being discharged by the fans, is directed 
by guide vanes to the air gap between rotor and stator; it then 
passes through radial ducts in the stator, is collected in an annular 
chamber around the stator and is finally discharged through an 
exhaust duct to the main deck of the ship. The rotor is a solid 
steel forging having radial slots machined in it to secure the rotor 
windings. The rotor windings are insulated by mica and asbes- 
tos. A section of the rotor winding is shown in Fig, 57. 



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THE U. S. S. NEW MEXICO 



127 



The insulation of the main generator stator winding consists 
mainly of mica with fibrous material on the end windings. The 
entire insulation of the coils is treated to make it moisture proof. 
The generator stator windings are provided with thermo-couples 
for measuring the rise in temperature; the leads from these 
thermo-couples are taken to the main switchboard in the center 



"oshv i IVashtr 

Fig. sq.— U. S. S. Neva Mexico: 
Method of Insulating Bolts Secur-' 
ing Generator in place 

engine room. A section of the stator winding is shown in Fig. 58. 
The generator bearings are of similar design to the turbine 
bearings. They are supported on pedestals which are mounted on 
foundations built in the ship and are not attached to the generator 
casing. The pedestal at the end of the generator rests on insula- 
tion and is secured by insulated bolts, one of which is shown in 



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128 



ELECTRIC SHIP PROPULSION 



Fig. 59; by insulating one end of the generator, the possibility of 
havir^ circulating current through the rotor and bearings is pre- 
vented. These currents do not usually occur in turbo generators 
but when they do they are very troublesome and cause rapid 
deterioration of the "babbitt" in the bearings ; it is therefore best 
to make sure they can not occur. 

Main Motors 
The overall dimensions and the details of the main motors are 
shown in Figs. 60, 61, 62, 63 and 64. The motors are of the 



m 



h li'-i'— -M k- 

FiG. 6o. — U. S. S. New Mexico: Main Induction Motor 

double squirrel cage type which has already been described in 
Chapter IV. These are the first large motors of this type that 
have been built. They are rated at 7,250 horsepower each, at 167 
revolutions per minute, which corresponds to a speed of 21 knots 
of the ship. 

The motor stator windings are arranged to provide for pole 
changing; the pole changing switches are located in the center 
engine room. One throw of these switches will give 24 poles on 
the stator of the motor and the other throw will give 36 poles. 
The arrangement of the stator winding to provide for pole 
changing is shown in Figs. 24, 25 and 26 and has already been 
described in Chapter IV. 

The stator is shown in Fig. 61 and the method of securing the 
stator end winding is shown in Fig. 63. The insulation is similar 




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THE U. S. S. NEW MEXICO 



Fig. 6i. — Main Motor Stator for U. S, S. New Mexico 



Fig. 62.— Main Motor Rotor for U. S. S. New Mexico 



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ELECTRIC SHIP PROPULSION 



D,„t,..= b:, Google 



THE V. S. S. NEW MEXICO 



131 



to that of the generator stator, consisting mainly of mica, except 
for the end windings which are provided with fibrous insulation, 
tiie whole being treated to make it moisture proof. A section of 
the stator winding is shown in Fig. 65. 

The motor rotor is shown in Figs. 62 and 64. The rotor 
winding is a double squirrel cage winding. This type of motor 
has been described in Chapter IV and the details of the rotor slot 
are shown in Fig. 12. Kach slot in the rotor consists of one slot 



.4S'-l\.- Coils madt up of SIvrns of. ??$••. 
copptr. CeHon vtrtr . XTon i 







.OOS'mica faptH/ap. Eitttnd tad' iuv^essirt taptslighiff farthtr 
thafl fhe previoijs ofte so ai fo aroid an abnjpf changt from ma foptd h 
fht ontaptd seciiut of fht ceil. Top* sonshfing nf.gOi'mKO ctmmf 
btiwttn hnlqytrs ef .OQI'Japontst paptr eentpound as obort. 

"X-Tapt Hft ceils all onr wit* .OOS'lintn fmish, 
pari and i^lap on tht tnd. 6ive five 
niah. This trtatmtnt of tape and rarnish 
felol thiclmtsi of .OSI' on one sida. 



'fllltr J>B' oil press boar 
Supple 



idfo/Aece'landetrerkipplnffon/fie/ap. 



Eiplaitalion of Irtsulolion. 

(sUThtilotpartoflhecoilisfapedwiih mica hipi Hlapfftm Hmts, 
the first faping tjfending approfimaft^ I'arovnd the bend. Tht 
iecond taping Ei^'and the third toping !• 

(bj Thnt trealmenis of tape and varnish ore then applied, each Inafinent 
cmsating of .OOS'lintn finished tapm,halijoinfonlht slot part and 
^Iflap on the ends, and flirti dif^ings =f varnish, and two dippings 
and bakings of mrnish are thin applied. 

(cJ Afttr the coils art assembled and connected, Ihe windings art 
sprayed nvilh vgrnish and baked; the sialor frame irith the utindingi 
in place being put into an oven. It is the/t ^nlren out and this treaf- 



•r .09" oil press board. 

Fig. 6$. — U. S. S. New Mexico: Motor Stator Winding Insulation 

near the periphery of the rotor and one deeper in the iron of the 
rotor, the two being connected by a long, narrow air gap. Each 
of these slots is provided with an independent squirrel cage. The 
squirrel cage in the outer slot is composed of high resistance bars 
and thabof the inner slot is composed of low resistance bars. The 
high resistance bars are made of German silver and the low 
resistance bars of copper. The bars are wedged tightly into the 
slots in both cases without insulation. Each squirrel cage has 
the end of its bars connected by short circuiting rings ; in the case 
of the high resistance bars this short circuiting ring is divided 



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132 ELECTRIC SHIP PROPULSION 

into segments connected by flexible copper connections to provide 
for expansion caused by the rush of current that takes place 
when the motor is reversed. This method of construction is 
shown in Fig. 64, 

Reversal of the motors is accomplished simply by reversing 
the connections of the two leads of one phase of the motor. This 
is accomplished by reversing switches located on the alternating 
current switchboard in the center engine room. 



The main motors are ventilated by suction blowers located one 
on each side of each motor on top of its casing; these draw air 
through the motor and discharge it into ducts which lead up to 
the atmosphere on the main deck. 

Exciter Switchboard and Excitation 
The exciter switchboard is shown in Figs. 66 and 67. A dia- 
gram of the exciter switchboard and direct current wiring is given 



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THE U. S. S. NEW MEXICO 



133 



in Fig. 68. From this wiring plan it will be seen that there are 
two buses for supplying the auxiliaries. One of these buses can 
be supplied by either of the exciters and the other is supplied by 
the after distribution board. This makes it possible always to 
have two live buses in the engine room for the engine room 
auxiliaries. The switch supplying each of these units is made 
double throw, so that if anything goes wroi^ with one circuit the 




auxiliaries may be quickly transferred to the other bus without 
stopping the operations. 

The booster is a motor generator set, the motor end of which 
is a constant speed motor and the generator end of which has a 
separately excited, reversible field. The leads to both motor and 
generator are shown in Fig. 68. The field current for excitation 
of the main generator passes in series through the booster genera- 
tor and regulation of the strength of the main field current is 
obtained by varying the voltage of the booster generator. This 
either bucks or boosts the voltage of the 300-kiIowatt generator, 
according to the throw of the field lever. The range of the 



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134 ELECTRIC SHIP PROPULSION 

booster generator is about 60 volts in either the buck or boost 
direction. 

The booster motor starting switch is interlocked with the 
main field switch so that the former must be closed before the 



latter and, conversely, the latter must be opened before the former ; 
this prevents possible damage to the booster generator commutator 
by passing current through it while the machine is standing still 



Digmze. by Google 



THE U. S. S. NEW MEXICO 135 

and also prevents the possibility of causing the booster generator 
to run away by opening the motor starting switch. 

Exciting current can be taken through either booster from 
either exciter. The arrangement of the switches does not make it 
possible to take exciting current from the after distribution room 
but temporary jumpers are provided so that in a few seconds this 
connection can be made. In this case provision is made to lock 
closed the circuit breakers of the generators supplying the after 
distribution room. 

The board is also arranged so that it is possible to use the 
300-kilowatt units in the engine room for exciting the main gen- 
erator field direct by short circuiting the booster in case of trouble 
with it. In this case the power for driving the engine room 
auxiliaries on the side of the ship where the booster is disabled 
would have to be taken from the after distribution room. 

Provision is also made for supplying the ship's circuit from 
either of the exciters ; when cruising at slow speeds there will not 
be much direct current used, and it is possible to cut out the ship's 
generators and run only on the two exciting units. This gives 
very economical operation, as it not only provides for very effi- 
cient generation of the power by using the exciter exhaust in the 
main turbine but it allows all the dynamo condenser auxiliaries to 
be shut down. 

The exciter switchboard, in addition to the other direct cur- 
rent switches mounted on it, has also the main field switches which 
are solenoid operated and are controlled from the main switch- 
board. These switches are located at the top of the center panel 
shown in Fig. 66, They are provided with magnetic blow-out to 
reduce the arcing on opening the main field and are also provided 
with auxiliary switches which short circuit the main field through 
a discharge resistance previous to the opening of the main field 
switch. These switches are arranged for hand operation in case 
of failure of the solenoid operated feature. They are also ar- 
ranged so that they can be tripped out by balanced relays located 
on the main switchboard. 

All other switches on the exciter switchboard are of the knife 
blade type. 

Indicating lamps are placed to show which bus is alive, thus 



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136 ELECTRIC SHIP PROPULSION 

facilitating the operation of the switching and lessening chances of 
mistake. 

The main exciter supply switches and buses are arranged so 
that the exciters can not be thrown in parallel on the same bus or 
in parallel with the ship's circuit. It is preferable to keep the 
auxiliary supply on each side of the ship entirely independent of 
each other and therefore no equalizers are provided. 

No circuit breakers are provided in the supply lines from the 
exciters because the main fields are on these lines and the quick 
opening of a circuit breaker would cause such a great rise of 
potential in the field circuit that it would burn up the circuit 
breaker and might puncture the field insulation. 

The following table gives the name and use of all switches, 
instruments, etc., on the exciter switchboard (the "part numbers" 
refer to Fig. 67) : 

Part No. Description of Apparatus Name Plate Inscription 

I, DH-3 ammeter, 150-0-150 amp, scale with 

shunt ,. . Booster Motor 

Z. DH-3 ajmneter, 200 amp. scale with shunt Air Pump 

3. D-27 lever switch, d-p., d-t., 250 volt, 135 

amp Air Pump Bus No. i 

4. D-27 lever switch, d-p., d-t., 250 volt, 135 

amp Air Pump Bus No. 2 

5. DH-3 ammeter, 1,500 amp. scale with shunt Main Circulating Pump 

6. D-27 lever switch, t-p., d-t., 250 volt, 1,200 

amp. Main Circulating Pump 

—Bus No. 2 

7. D-27 lever switch, t-p., d-t., 250 volt, 1,200 

amp Main Circulating Pump 

—Bus Nol I 

8. DH-3 ammeter, 100 amp. scale with shunt Hotwell Pump 

9. D-27 lever switch, d-p., d-t, 250 voltj 65 

amp. Hotwell Pump — Bus 

No. I 

10. D-27 lever switch, d-p., d-t., 250 volt, 65 

amp Hotwell Pump — Bus 

No. 2 

11. D-37 lever switch, d-p., d-t., 250 volt, 65 

amp Lubricating Oil Pumps 

—Bus No. I 
13. D-27 lever switch, d-p., d-t., 250 volt, 65 

amp Lubricating 0:1 Pumps 

—Bus No. 2 

13. D-27 lever switch, s-p., d-t., 250 volt, 350 

amp Booster 

14. D-27 lever switch, s-p., d-t, 250 volt, 350 

amp Generator Field 

15. D-27 lever switdi, s-p., d-t., 250 volt, 350 

amp Bus 



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THE U. S. S. NEW MEXICO 137 

Part No. Description of Apparatus Name Plate Inscription 

16. D-2? lever switch, d-p„ d-t., 250 volt, 135 

amp. Ventilating Blower No. 

I (or 4) Bus No. I 

17. D-27 lever switch, d-p., d-t., 250 volt, 135 

amp. Ventilatirw Blower No. 

1 (or 4) Bus No. a 

18. D-27 lever switch, d-p., d-t., 250 volt, 135 

amp Ventilating Blower No. 

2 (or 3) Bus No. I 

19. D-27 'ever switch, d-p., d-t, 250 volt, 13s 

amp Ventilating Blower No, 

2 (or 3) Bus No. 2 

20. Switch stop for 65 amp., d-t lever switch 

21. Switch stop for 350 amp., d-t. lever switch 

22. Switch stop for 135 amp., d-t. lever switch 

23. Name Plate '. Starboard 

34. Name Plate Port 

25. Clear hull's eye indicating lamp Blower. No. 41 

20. Qear bull's eye indicating lamp Blower No. 43 

27. Clear bull's eye indicating lamp ,■ Blower No. 42 

^ Clear bull's eye indicating lamp Blower No. 44 

39. Clear bull's eye indicating lamp Blower No. 47 

30. Clear bull's eye indicating lamp Blower No. 51 

31. Clear bull's eye indicating lamp Blower No. 49 

32. Clear bull's eye indicating lamp Blower No. 53 

33. Clear bull's eye indicating lamp Blower No. 54 

34. Qear bull's eye indicating lamp Blower No. 50 

35- Clear bull's eye indicating lamp Blower No. 52 

36. Clear bull's eye indicating lamp Blower No. 48 

37. D-27 control bus transfer switch, t-p., d-t, 

350 volt, 65 amp,, with resistance After Distribution 

Board 

38. D-27 control bus transfer switch, t-p., d-t., 

2SO volt, 65 amp., with resistance Three- Wire, D.C. Con- 
trol 

39. D-27 control bus transfer switch, t-p., d-t., 

ago volt, 65 amp., with resistance To Control Bus Selec- 
tor Switch 

40. D-27 lever switch, t-p., d-t., 250 volt, 65 

amp Exciter No. 2 

41. D-27 lever switch, t-p., d-t., 250 volt, 65 

amp Exciters 

42. D-27 lever switch, t-p., d-t, 250 volt, 65 

amp Exciter No. I 

43. Solenoid operated field switch, d-p., s-t., 

250 volt, 350 amp Generator Field— Star- 

44. Solenoid operated field switch, d-p., s-t., 250 

volt, 350 am^ Generator Field— Port 

43. D-27 lever svntch, s-p., d-t., 250 volt, 350 

amp Generator Field, 240 

Volt 

46. D-27 lever switch, s-p., d-t, 250 volt, 350 

amp. Generator Field, 120 

Volt 

47. DH-3 ammeter, 2,000 amp. scale with shunt Positive Ammeter 

48. DH-3 ammeter, 2,000 amp. scale with shunt NegaeJve Ammeter 



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138 ELECTRIC SHIP PROPULSION 

Part No. Description of Apparatus Name Plate Inscription 

49. DH-3 voltmeter, 300 volt scale Starboard (or Port) 

Voltmeter 
VOLTAGE 

fBus Grounds 
c ;; — ^;::^ t, — >c ^ . '• , r—' 
Pos. Neg. — Pos. Neu. Pos. Grd. — Neu. Grd. 
— Neu. Neg. — Grd. Neg. 

51. Field rheostat mechanism 

52. D-27 lever switch, s-p., s-t^ 250 voh, 350 

amp Booster Generator, 

Neg. 

53. D-27 lever switch, s-p., s-t., 250 volt, 35° 

amp Booster Motor, Neg. 

54. H-16 starting switch, s-p., 4-t., 250 volt, 150 

amp Booster Motor Starter 

55. Mechanical interlock between booster motor 

starting switch and generator field switch 

56. D-27 lever switch, t-p., 6-t., 250 vott, 1,800 

amp Port Exciter 

57. D-27 lever switch, t-p., 6-t, 250 volt, I.800 

amp Bus No. i Starboard 

58. D-27 lever switch, t-p., 6-t., 250 volt, 1,800 

amp Starboard Exciter 

SQ. D-27 lever switch, t-p., 6-t., 250 volt, 1,800 

amp A f t e r Distribution 

60. D-27 lever switch, t-p., 6-t, 250 volt, 1,800 

amp Bus No. i Port 

61. Bureau name ptate 

62. Name plate New Mexico 

63. Lamp bracket 

64. Solenoid control relay, s-p., 125 volt 

€5. Generator field discharge resistance 

66. Fuse base 

67. Lamp bracket 

Main Switchboard 

The main switchboard, the main alternating current wiring 
and the direct current wiring for electric locks are shoWn in Figs. 
69 to 77, inclusive. Figs. 69 to 75, inclusive, show various views 
of the structure of the main switchboard and of the arrangement 
of disconnecting switches and of the interior of the board itself, 
tc^ether with the mechanical interlocks between switches. 

From these views it will be seen that the main switchboard is a 
cell structure, built up on angles and carrying panels for mounting 
instruments on its forward face. The remaining part of the 
switchboard is enclosed with grille work; there is a door at each 
end which gives access to the passageway down the middle of the 
cell. This passageway gives access to the mechanical interlodcs 



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140 ELECTRIC SHIP PROPULSION 

located inside the structure, to all the oil switches and to the bus 
tie switch. The latter is the only switch that is actually operated 
from the inside of the cell structure. 

Fig. 74 shows the various operating levers on the front of the 
switchboard. Fig. 69 shows the front of the main switchboard 
with all instruments and levers. All the levers used in the opera- 
tion of the engines are shown in these views. By referring to 
Fig. 77, the purpose of all the electric switches used in the various 
operations can be seen. The switchboard is located in the after 



Fig. 70. — U.S. S. New Mexico: Propulsion Control Equipment, Front 
View with Panels Removed 

end of the center engine room and the operator faces aft when 
handling the switches. 

There is a disconnecting switch for each main generator. 
These are operated in the center engine room and are mounted 
iOn the outboard bulkheads on each side as shown in Fig. 69. 
These switches are of the knife blade type mounted on large 
brass plates which are bolted to the bulkhead and form a part of 
it. These plates are necessary since single conductor cable is used 
to connect the generator to the main switchboard ; it is necessary 
tp replace the part of the bulkhead surrounding the cable will? 



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THE U. S. S. NEW MEXICO 141 

non-magnetic material to prevent its overheating and causing 
losses in the circuits. The insulators for this switch are heavy 
molded blocks of bakelite, which is very tough and is not suscep- 
tible to breakage by shock or vibration. The switches are double 
throw, one position being for low voltage and the other for high 
voltage. The reason for using double throw switches has already 



been discussed in Chapter IV. These switches are interlocked as 
described below. 

The bus tie switch, also of the knife blade type, is mounted 
inside the cell structure and is operated at that point. It connects 
the starboard and port buses so that either generator can run all 
four motors when desired. The bus tie switch and the two 
generator disconnecting switches are mechanically interlocked in 
such a manner that only two of them can be thrown in at any 
One time. This makes it impossible to connect the two generators 



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142 ELECTRIC SHIP PROPULSION 

to the same bus and thus put them in parallel. They are also 
mechanically interlocked so that the generator disconnecting 
switches can be thrown into the low voltage position only when 
the bus tie switch is closed, and into the high voltage position 
only when the bus tie switch is open; this interlocking makes it 
certain that the generators will always be operated in the most 



efficient way, as has already been described in Chapter IV and 
illustrated by Fig. 28. 

The motor disconnecting switches are mounted at the top of 
the cell structure on each side and at the back. These switches 
and the levers for operating them are shown in Fig, 72. These 
switches are also of the knife blade type. 

None of the knife blade switches can be operated when alive. 



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THE U. S. S. NEW MEXICO 143 

How this is prevented will be explained later on in this chapter 
when the subject of electric locks is discussed. 

The reversing switches are of the laminated brush type and 
are oil break. They have auxiliary contacts and are intended to 
be large enough to break full load current, but in the actual 
operation this is never done, as the field is always opened before 
moving them. The ahead and astern switches are mounted in 



Fio. 73.- 

the same oil tank. This switch is shown in Fig. 75. It will 
be seen that there is a brush on each side, the two arms being 
pivoted at the center. The arrangement of the levers is such that 
one of these arms is moved up and the other down at the same 
time, one closing for the ahead direction and when, moved in the 
opposite way the other closes for the astern direction. The func- 
tion of this switch is merely to reverse the connections of two 
leads (one phase) to the motor. A third lead is, however, inter- 



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144 ELECTRIC SHIP PROPULSION 

nipted by this switch, as, otherwise, opening this switch would 
still leave one phase connected to the motor, which would then 
run as a single phase motor, if it were already running. The 
fourth lead to the motor passes direct from the bus to the motor 
and is not interrupted by the reversing switch. The reversing 
switches for the two motors on one side of the ship are operated 
by the same lever on the front of tlie switchboard. 



The pole changing switches are in every respect similar to 
the reversing switches. Contact of the laminated brushes on one 
side connects the motor for 24 poles and contact on the other side 
for 36 poles. The switches for the two motors on one side of 
the ship are operated by one lever on the front of the switchboard. 

The pole changing and reversing switches are mechanically 
interlocked with the field lever so that they cannot be moved 
unless the field lever is in the open position. They are also inter- 



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THE U. S. S. NEW MEXICO 145 

locked with each other so that the reversing lever cannot be 
throv™ in the astern position except when the pole changer is in 
the 36-pole position, thus always insuring maximum torque for 
backing. 

The main field switches have already been described under the 
subject of the "exciter switchboard" ; they are operated by the out- 
board small levers shown in the center panel of the main switch- 
board. 



The speed levers are the two small inboard levers at the center 
of the main switchboard. They are connected by bell cranks and 
rods to the governor control gear, as shown in Fig. 54 and previ- 
ously described under the subject of the "main turbines." These 
levers are moved by worms working over quadrants but they can 
also be moved by lifting the worms out of engagement when 
large changes of speed are desired. The speed levers and field 
levers are mechanically interlocked so that the speed lever must 
be moved to the slow speed position before the field switch can be 
opened ; also, the speed canhot be increased very greatly without 
carrying the field lever with it and increasing the excitation on the 
main field of the generator. This interlock insures that the gen- 



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146 ELECTRIC SHIP PROPULSION 

erator will always be at low speed before reversal of the motors 
is attempted. 

The steam limit levers are mounted directly underneath the 
field and speed levers; they consist of short arms moving on 
notched quadrants. The motion of the steam limit levers is trans- 



^Srarbfara Induction Motvrt port Induerion rtarorM 

Fig. 76.— U.S. S. New Mexico: Control and Interlock Wiring 

mitted by rods and bell cranks to a stop on the operating gear of 
the main governor. This lever can be set to allow any desired 
number of valves to open on the main turbine, and when once set 
the amount of power that can be developed by the turbine is 
limited by the amount of steam that the given number of valves 
will pass. The necessity for these fevers has been explained in 
Chapters IV and V. The relative position of the steam limit stop 
and governor operating mechanism is always shown at the main 



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THE U. S. S. NEW MEXICO 147 

switchboard, as will be explained later on in this chapter under 
the subject of electric locks. 

The electric locks, indicating lamps, booster field control and 
main field switch control wiring are shown in Fig, 76. The buses 



Fig. 77. — U. S. S. New Mexico: Main Alternating Current Wiring 

for these are supplied by a double throw, transfer switch and a 
double throw, ordinary knife blade switch. The transfer switch 
supplies current either from the exciter bus or from the after 
distribution room. In transferring from one to the other the 
circuit is not interrupted but resistances are inserted directly in 



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148 ELECTRIC SHIP PROPULSION 

the two circuits so as to make it safe to transfer from one to the 
other. This is necessary since there will always be a slight differ- 
ence in potential between the ship's circuit and the exciter circuit. 
The supply bus from the exciter is fed through a double throw 
switch which can be thrown on either exciter. 

The booster field rheostat and main field switch control are 
shown in Fig. 76. The first motion of the field lever closes the 
contact for the closing coil and this closes the main field switch; 
further motion of the lever reduces the strength of the booster 
generator field until the middle point of the rheostat is reached 
at which point the booster generator field takes no current 
During this part of the field lever movement the booster voltage 
"bucks" the exciter voltage. The next motion of the field lever 
reverses the connections of the booster field and the booster voltage 
will now "boost" the exciter voltage; further movement of the 
lever increases the strength of the booster field. Reverse motion . 
of the lever reverses this procedure, the last motion of the lever 
being to dose the contact for the tripping coil which opens the 
field switch. 

The main field switch, when closed, electrically locks the main 
generator disconnecting switch, motor disconnecting switches and 
the door to the cell structure of the main switchboard, which are 
on the same side of the ship as the field switch. This insures 
that none of these switches will be moved while the circuits are 
alive. There is a red lamp for indicating when it is closed and 
a green lamp for indicating when it is open. When only one 
generator, and consequently one field switch, is in use, the bus tie 
switch will always be closed. The bus tie switch is provided with 
an auxiliary switch which connects the two interlocking systems 
on the two sides of the ship so that either field switch will then 
operate all locks. 

There is a balance relay in each main generator circuit as 
shown in Fig, 77 ; the connections from this relay to the trip coil 
of the main field switch are shown in Fig. 76. This relay is 
normally in the open position and is held rigidly so by the solenoids 
in each circuit. In case of short circuit on either of the phases 
of the generator itself, the motors or the cables, the pull on the 
solenoids of this relay will become unbalanced, and the contacts 
in the direct current circuit will be closed, tripping out the main 
field switch, thus taking all power off the damaged circuit. 



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THE U. S. S. NEW MEXICO 149 

Under-Ioad relays are also provided for each generator circuit. 
These are shown in Fig. 77 and their connections to the electric 
locks are shown in Fig. 76. The solenoids of these relays are 
adjustable and can be made to open at any desired value. Until 
this relay opens, the reversing and pole changing levers are locked 
so they cannot be moved. A blue lamp indicates when this circuit 
is closed. 

White and red lamps are provided on each side of the board 
to show the relative position of the steam limit stop and the main 
governor control gear. The white light indicates an opening of 
about yi inch' (this is adjustable) between the stop and governor 
gear. When both lamps are %hted this indicates contact between 
the stop and governor gear ; when the white light goes out, leaving 
only the red lamp on| it indicates that the governor gear is hard 
up against the stop. This enables the operator to keep his steam 
limit properly adjusted for each speed of the ship. 

The following table gives the name and use of all switches, 
instruments, gages, levers, etc., on the main switchboard (the "part 
numbers" refer to Fig. 69) : 

TURBINE EQUIPMENT 
Part No. Description of Apparatus Name Plate Inscription 

13. Steam limit control lever Steam Limit Control 

14. Red bull's eye lamp for steam limit indicat- 

ing switch 

15. Clear bull's eye lamp for steam limit in- 

dicating switch 

16. Speed control mechanism Speed Control Mecha- 

45. Steam gage Main Steam 

46. Steam gage Main Turbine, Steam 

Chest 

47. Steam gage Main Turbine, First 

Stage 

48. Steam gage Exciter Exhaust 

49. Steam gage Auxilianr Exhaust 

50. Pressure gage Oil to TurtMnes 

51. Pressure gage Feed Water 

53. Pressure gage Oil to Governor 

54. Vacuum gage Main Condenser 

GENERATOR EQUIPMENT 
Put No. Description of Apparatus Name Plate Inscription 

I. Generator disconnecting switch, 8-p., d-t. Generator Disconnect- 

• (A) Auxiliary switch, d-p., c.o ing Switch 

•(B) Magnetic locking device 

3. Balance relay Balance Relay 



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150 ELECTRIC SHIP PROPULSION 

Part No. Description of Apparatus Name Plate Inscription 

6, Reversii^ lever mechanism Ahead — Astern 

* (A) K-31 oil circuit breaker, 3-p., d-t., 

5,000 volt, 3,000 amp 

* (B) Magnetic locking device 

7. Interlock between reversing and pole- 

changing levers 

la Field control mechanism Field Control Mechan- 

* (A) Booster rheostat 

* (B) Pipe mechanism for (A) 

11. Interlock between field control lever and 

reversing and pole-changing 

12. Interlocflc between bus section and field 

switches . 

* (A) Bus section switch, 4-p., s-t., 

2,400 amp., 5,000 volt, operating 

mechanism and auxiliary switch 

17. Across>ship mterlocking shaft for 12 

23. Red bull's eye lamp for field switch Generator Field, closed 

24. Green bull's eye lamp for field switch Generator Field, open 

25. H-2 ammeter, 15 amp. with 10,000 amp. 

scale Generator Ammeter 

26. H-2 voltmeter. 150 volt with 6,000 volt 

scale Generator Voltmeter 

27. DH-3 temperature indicator (70-250 deg. 

F.) scale ' Generator Temperatuie 

Indicator 

27. DH-3 temperature indicator (20-izo deg. 

C.) scale Generator Temperature 

Indicator 

28. DH-3 field ammeter, 600 amp. with shunt.. Generator Field Am- 

29. DH-3 field voltmeter, 300 volt Generator Field Volt> 

31, H-2 indicating wattmeter, no volt, 4 amp.. Generator Wattmeter 

* (A) E-18 current transformer, 3,000/5 

* (B) AQ-i potential transformer, 

4,400/110 volt, 200 w 

* (C) Fuse support with fuse holder 

and fuse, 4,400 volt 

32, H-4 speed indicator, 110 volt, 1,000-2,600 

r.p.m. scale Generator Speed Indi- 

39. Ammeter transfer switch Generator Ammeter 

Transfer Switch 

40. Voltmeter transfer switch Generator Voltmeter 

Transfer Switch 

41. Balance relay cut-out switch Balance Relay Cut-Out 

42. Temperature indicator transfer switch . . . Temperature Coils 

43. Temperature indicator test switch Test 

44. Temperature indicator supply switch ...... Indicator Supply 

58. Interlock between generator disconnecting 

switches and bus section switch 

59. Booster generator field switch Booster Gener ator 

Field 



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THE U. S. S. NEW MEXICO 151 

MOTOR EQUIPMENT 
Part No. Description of Apparatus Name Plate Inscription 

2. Motor disconnecting switch, 8-p., s-t., 600 
amp., 5,000 volt 

* (A) Magnetic locking device , r, t 

S. Pole-changing lever mechanism 24 Poles— 36 Po'es 

* (A) K-31 oil circuit breakers, 6-p., 

d-t., 5,000 volt, 1,500 amp 

* (B) Magnetic locking device „ , 

8. Under current relay Under Current Relay 

9. Blue bull's eye indicating lamp for S ..... . 

18. Revolution counter 

Stop clock — average starboard shafts 

Stop clock — average all shafts 

Stop clock — average port shafts 

IS-4 vsatthour meter, no volt, 5 amp 

IS-4 watthour meter, no volt, 5 amp 

• (A) W-2 current transformer, 800/5 

• (B) AQ-i potential transformer, 4400/ 

no volt, 200 w 

• (C) Fuse support with fuse holder 

and fuse, 4,400 volt 

34. H-2 ammeter, 5 amp. with 1,600 amp. scale Motor No. 2 (or 3) 

A.C. Ammeter 

35. H-2 ammeter, 5 amp. with 1,600 amp. scale Motor No. I (or 4) 

A.C. Ammeter 

36. Direction indicator motor No. 2 (or 3) 

37. Direction indicator motor No. i (or 4) . . 
53. Electrical speed indicator motor No. 2 (or 

3) 

55. Electrical speed indicator motor No. I (or 

4) 

* Located inside celt. 

MISCELLANEOUS EQUIPMENT 
Part No. Description of Apparatus Name Plate Inscription 

4. Speed indicator for engine room telegraph 

22. Qock 

38A, Name plate 

38B. Name plate 

56. Lamp bracket 

57. Rudder position indicator 

60, Sheet iron protecting shield 

List of Mechanical and Electrical Locks on the Alternating 
Current and Direct Current Switchboards 

Alternating Current Switchboard 
Mechanical 
(1) The bus tie switch and the two generator disconnectii^ 
switcties are interlocked so that only two of them can be dosed 
at any one time. 



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152 ELECTRIC SHIP PROPULSION 

(2) The bus tie switch and the two generator disconnecting 
switches are interlocked so that when the bus tie switch is closed, 
the generator disconnecting switches can be closed only in the low 
voltage position and when the bus tie switch is open the generator 
disconnecting switches can be closed only in the high voltage 
position. 

(3) The generator field switch lever is interlocked .with the 
reversing and pole changing switches so that the latter two can not 
be moved from either the open or closed position unless the field 
switch is open ; when the bus tie switch is closed, one field lever 
will lock the switches on both sides of the ship ; when the bus tie 
switch is open, each field lever locks only the switches on its own 
side of the ship, 

(4) The field levers and speed levers are interlocked so that 
the speed lever must be brought to a low speed position before the . 
field can be opened and, conversely, the field must be increased, 
if a large increase of speed is made. 

(5) The reversing switches and pole changing switches are 
interlocked so that the reversing switches can not be thrown to 
the "astern" position unless the pole changing switches are in the 
36-pole position. 

(6) Motor disconnecting switches are locked when closed so 
they can not be opened by shock. 

Electrical 
(1) When the main field switch is closed, the switchboard cell 
doors, generator disconnecting switches and motor disconnecting 
switches are locked so that they can not be moved whether they 
are in the "open" or "closed" position ; when the bus tie switch is 
closed, one field lever locks both sides of the ship; when the bus 
tie switch is open, each field lever locks only the door and switches 
on its own side of the ship. 

Direct Current Switchboard 

Mechanical 

(1) The field switches are interlocked with the booster motor 

starting switches so that the starting switch must be closed before 

its corresponding field switch can be closed; conversely the field 

switch myst be open befprp the starting switch can be opened. 



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THE V. S". S. NEW MEXICO 153 

Eleclrical 
(1) There are no electrical locks on the direct current switch- 
board, but all switches that open the main field circuit are marked 
with red handles as a warning not to open them without first 
making sure that the main field switch is open. 

Operation of the Machinery 
Three conditions of normal steaming were described in the 
beginning of this chapter and the operation of the machinery for 
both ahead and astern motion of the ship will be described for 
each of these conditions. The first condition is with one generator 
and four motors, the latter being arranged for 36 poles ; the second 
condition is with one generator and four motors, the latter being 
arranged for 24 poles ; the third condition is with two generators 
and four motors, the latter being arranged for 24 poles. The 
operation is as follows ; 

(1) Getting Under Way with One Generator, the Motors 
Being on the 36-Pole Connection. — Before reporting ready to get 
under way, the generator that it is desired to use would be tested 
out and then set to run at low speed ; the bus tie switch would be 
closed and the generator disconnecting switch would be closed in 
the low voltage position. The field switch of the generator and 
the pole changing and reversing levers would be open. On receiv- 
ing a signal "Ahead," 

(a) The pole changing switch would be thrown in the "36- 
pole" position. 

(fc) The reversing lever would be thrown in the "Ahead" 
position, 

(c) The field switch would be closed and brought up to the 
desired field strength. 

(rf) The turbine would then be brought up to the desired 
speed. 

(2) Reversing. — With the ship going ahead under conditions 
described above, under (1), on receiving a signal "Astern," - 

(a) The field switch would be opened and the speed lever 
brought to low speed at the same time. 

(fc) As soon as the under-current relay operates, the revers- 
ing leviers would bp thrown to the "Astern" positi.pn. 



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154 ELECTRIC SHIP PROPULSION 

(c) The field switch would then be closed and over-excita- 
tion applied to the generator until the motors have reversed and 
come up to synchronous speed, when the field would be reduced 
to its norma] value. 

(rf) The speed of the turbine would then be brought up to 
whatever is desired. 

(3) Getting Under Way with One Generator, the Motors 
Being on the 24-Pole Connection. — In this case, getting under way- 
is exactly as described under (I), except that the pole changing 
switches would be thrown into the 24-pole position. 

(4) Reversing, — Assuming the ship to have gotten under way 
with conditions as described above under (3), on receiving a signal 
"Astern," 

(o) Open the field switch and throw the speed lever to low 
speed at the same time. ' 

(fr) Throw pole changers to 36-poIe position. 

(c) Throw reversing switches to "Astern" position. 

(d) Apply over-excitation to the field of the main generator 
until motors have come into synchronism, and then reduce field 

, to normal value. 

{e) Bring turbine up to desired speed. 

(5) Getting Under Way with Two Generators. — In this case 
the bus tie switch would be open and the two generator disconnect- 
ing switches would be closed in the high voltage position. Field 
switches would be open; generators would be running at slow 
speed and pole changing and reversing switches would be open. 
If signal "Ahead" is received, the operatbns carried out would be 
exactly as described under (3), except that it would be performed 
on two generators instead of one. 

(6) Reversing. — After having gotten under way with condi- 
tions as above described under (5), if a signal "Astern" were 
received, the operations would be exactly as described under (4), 
except that they would be carried out for two generators instead 
of one. 

Trials 
The New Mexico held two sets of official trials. On the first 
trials, the ship had been out of dock for about seven weeks and 
required an excessive horsepower to make her speed, so she was 



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THE U. S. S. NEW MEXICO 



155 



docked and a second set of trials run. The water rates were not 
so good at two points on the second trials as on the first due to 
the fact that at these speeds the ship was "bucking" a heavy head 
sea. The ship did not quite come up to her guaranteed water 
rates at any speed except ten knots. 

The following tables give the water rates obtained on the two 
trials and also data obtained on the second trials. Water rates 
include the steam for excitation, main air pumps, main condensate 
pumps, main circulating pumps, forced lubrication pumps and 
main motor ventilating blowers, as well as for the main turbines. 



Speed. 

Full speed 
19 knots . . . 
IS knots . . 
10 knots . . 



12.01 
12.33 
12.475 
13,96 





4-hour 

fuU 
power 

triaL 


4-hour 
I9-knot 
trial 


4-hour 
15-knot 
triaL 


1-hour. 

lO-knot 

trial. 


Steam at boilers, pounds gage 


278.6 
272.1 

139-7 
^•„ 
30.83 

41 


274^ 

2?4-2 

1044 

29-S 
30-77 

3-4 


273-8 
274-6 
86.4 

29.5 

30.92 
2.3 




Turbines first stage, pounds gage . . 


42.5 




30-79 
1-7 


Fireroom air pressure, inches of 





Feed water temperature, degrees F. 
Main generators, volts 

amperes 

field, volts . . . 

field, amperes 

revolutions i 

Main motors, amperes 

revolutions per t 

ote 

Slip of propellers, percent 

Speed, in knots 

Shaft horsepower (from curve) 



t9-knot 
trial. 



182.8 

4,257- 
1^3-5 
171-7 
318,25 



trial- 



3.740. ■ 
1,56s. 
152-15 



14-97 
19.37 
23,233- 



10-knot 
trial. 



1483 
ia36 
3,690. 



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CHAPTER XII 
The California, Maryland and West Virginia 

THE machinery of the California, Maryland and IVest VW- 
gima is similar to that of the I^ew Mexico, but there are 
some differences. Owing to the arrangement of the ma- 
chinery compartments, the wiring layout in particular is entirely 
different. These ships were originally designed to use electric 





Ingint 
Doom 






AfUr 




"™ /'H" 


\ 


r.z 




Maffr 
ffcem 





Fig. 78. — U. S. S. California, 
Maryland, and West Virgima: Ar- 
rangement of Machinery 

propulsion so that all its advantages are utilized, instead of merely 
adapting the machinery to a ship already designed as was the case 
with the New Mexico. This chapter will, therefore, cover only 
those points in which the machinery differs from that of the 
New Mexico. 

156 



ze. by Google 



CALIFORNIA, MARYLAND AND WEST VIRGINIA 157 

The arrangement of machinery compartments is shown in Fig. 
78, The turbo generators and all auxiliaries, except forced draft 
blowers for the boilers, are located in two adjoining engine rooms, 
one forward of the other, on the centerHne of the ship. In these 
compartments are also located the ship's generators, the exciters 
and the direct current switchboards; the main switchboard is 
located in the main control room which is just abaft the after 
engine room. Two of the main motors are located in a compart- 
ment abaft the main control room and the other two are located 
in compartments alongside the main control room. 

The propelling machinery is of the same horsepower as that of 



Fig. 79.— U.S. S, California: Propulsion Unit No. 2 Assembled for 
Test; lo-Stage Curtis Steam Turbine, 2,065 R. P. M., Direct Connected to 
10,600 Kilowatt Alternating Current Generator 

the New Mexico and the "general description" of the machinery 
of the New Mexico given in Chapter XI applies equally well to 
these ships. 

Main Turbine 
The turbine and its details are shown in Figs. 79, 80, 81 and 82 ; 
it is similar to that of the New Mexico, the most important differ- 
ence being that it is arranged for downward exhaust. The main 
condenser is located beneath the turbine and this makes all arrange- 
ments for disassembly and repair very simple; it also makes the 



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158 ELECTRIC SHIP PROPULSION 

turbine middle bearing, coupling and turbine gland much more 
accessible than where the condenser is overhead. 

Fig. 82 shows the auxiliary oil pump which is fitted to the end 
of the shaft driving the governor. This pump will supply suffi- 
cient oil to lubricate the main turbo generator and to operate the 
hydraulic relay for the governor very slowly. In case of failure 
of the forced lubrication pumps, the supply of oil to the main 
motors is automatically shut off and all the oil supplied by the 
auxiliary pump is used for the main generator. This is an 
improvement over the New Mexico where the only provision for 



V of Assembled Tur- 
1 Unit No. I 

an emergency supply of oil to the generator is a gravity feed 
from the supply tanks in the engine room. The turbine bearings 
are not water cooled as on the New Mexico but are provided with 
a more liberal oil supply. 

The auxiliary exhaust and exciter exhaust connection to the 
main turbine is shown in Fig. 83. The non -condensing turbo 
generator exhausts into the auxiliary exhaust line through a 
constant back pressure valve set at 10 pounds gage pressure. 
The auxiliary exhaust passes through a constant back pressure 
valve set at 10 pounds gage pressure, then through a strainer, then 
through a butterfly valve controlled by the main governor, then 
through a quick closing valve actuated by the emergency governor, 
then through one of two stop check valves and into the fifth or 
eighth stage of the main turbine. 



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CALIFORNIA, MARYLAND AND tVEST VIRGINIA 159 



Fig. 8i.— U.S.S. California: Hydraulic Ope- 
rating Mechanism and Operating Governor for 
Propulsion Unit No. i 



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160 



ELECTRIC SHIP PROPULSION 



The auxiliary exhaust also has a by-pass to the condensers 
and this is fitted with a constant back pressure valve set at 15 
pounds gage pressure. The valve set at 10 pounds keeps this 
pressure on the auxiliary exhaust line unless the supply to the 
main turbine is shut off, in which case the pressure will rise to 
15 pounds and the exhaust will pass into the condenser. 

The back pressure valve from the non-condensing exciter is 
provided so that in case this machine is being used in port and 
the exhaust is being used in the evaporators a constant pressure 
will be maintained on the exciter exhaust. 

The butterfly valve is really the first admission valve of the 




turbine and it is opened by the main governor before any of the 
admission valves on the turbine are opened, and is closed after 
they are all closed. 

The quick closing valve is provided so that the emergency 
governor can shut off all steam supply to the turbine in case of 
over-speeding. 

Two openings are provided in the turbine casing so as to 
utilize the auxiliary exhaust at the most economical point; the 
openings are closed by stop valves which are provided with 
"checks" to prevent steam by-passing in case they should both 
be open at the same time or in case the pressure in the turbine 
casing should be higher than that in the exhaust line. 



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CALIFORNIA, MARYLAND AND WEST VIRGINIA 161 

The method of controlling the speed, the steam limits, etc., are 
similar to those used on the New Mexico. 

Main Generator 
The main generator is shown in Figs. 84 and 85. It is prac- 
tically identical with that of the New Mexico except as to venti- 



lating arrangements. The air intake and outlet are provided with 
quick closing valves which are operated by levers on the generator 
casing as shown in Fig. 85. The valve for closing the air outlet 
is shown in Fig. 84; it consists of a series of shutters connected 



Digmze. by Google 



162 ELECTRIC SHIP PROPULSION 

together like a Venetian blind and operated by a single lever. 
These valves are provided so that in case of fire in the generator, 
all air can be shut off and steam can be admitted to the interior 
of the air casing to smother the fire. 

Main Motors 
The main motor is shown in Fig. 86. The stator and its 
windings are practically identical with that of the New Mexico. 
The contactors used for short circuitiAg the rotor winding can 



Fig. 86.— U.S. S, California: Main Motor 

be seen mounted on the frame of the motor. Direct current 
heaters are placed in the base of the stator. 

The rotor of this motor has already been described in Chapter 
IV ancl a section of the rotor winding is shown in Fig. 16. It 
is entirely different from that of the New Mexico. 

The definite wound part of the rotor winding connects to 
slip rings carrying brushes which connect to solenoid operated 
contactors mounted on the frame of the motor. These contactors 
are operated by direct current and are controlled by motion of 



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CALIFORNIA, MARYLAND AND WEST VIRGINIA 163 

the field lever on the main switchboard. As explained in Chap- 
ter IV, the definite winding is not short circuited until the motors 
have been brought "into step" with the generator ; also the act of 
short circuiting takes place with 150 percent over-excitation on 
the generator so as to insure sufficient torque for bringing the . . 
motors "into step" with the generator under the new conditioft,.-. 
After the motors come "into step," the excitation is reduced t»""' 
normal. \ ■ 

In the reverse movement of the field lever, the field switch and ' 
contactors open simultaneously so that it is not possible to open, 
the field switch and leave the contactors closed. 

The definite winding on the rotor is arranged to work with a - " 
stator arranged for pole changing in a similar manner to that^' 
described in Chapter IV and illustrated by Fig. 27, except that 
in this case the definite winding is arranged to give equivalent 
squirrel cage action with the stator arranged for 24 poles instead 
of 36 poles ; this is done because these ships are arranged to back 
on 36 poles as is the case with the New Mexico, and the equivalent 
squirrel cage winding is not suitable for backing. 

The motors are always started in either the ahead or astern 
direction with the stator winding arranged for 36 poles and with 
the definite winding on the rotor "open circuited" so that only the 
high resistance squirrel cage winding is effective; after the motor 
is "in step" with the generator the definite winding can be short 
circuited. If the motors are backing the 36-pole connection can 
not be changed; but, if they are going ahead, a shift can be made 
from 36 poles to 24 poles, if desired. In this case it will be im- 
material whether the contactors are dosed or not since the definite 
winding of the rotor becomes an equivalent squirrel cage when 
the stator winding is arranged for 24 poles. 

It will be noted that the motors can neither be started nor 
reversed when the stator winding is arranged for the number of 
poles which converts the definite winding of the rotor into an 
equivalent squirrel cage; the squirrel cage will be of very low 
resistance and would therefore not give sufficient torque to reverse 
the motor. 

Thermo-couples for measuring the temperature rise of the 
stator coils are fitted on the motors as well as on the generators. 

The motor bearings are arranged for ring lubrication as well 



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164 ELECTRIC SHIP PROPULSION 



tL' Otel Lamp 
fh.-BlHatM 



KHJl-mmaur. 



Fic. 87.— U. S. S. California: Direct Current 
as forced lubrication so that they can run independently of the 
lubricating system in case of failure of the latter. 
Switchboards 

There is a direct current switchboard in each engine room for 
the 300 kilowatt generators and also for the motor driven auxili- 
aries and for excitation. There is a direct current switchboard 
in the control room for controlling the ventilating blowers for 
the main motors and also for supplying direct curiiient to the 
"control circuit." There are two terminal and testing boards in 
the control room for controlling the control circuits, instruments, 
etc. There is a main switchboard in the main control room for 
controlling the main turbo generators and motors. Each of these 
boards and the wiring will be described below. 
Direct Current Wiring 

The direct current wiring is shown in Fig, 87. From the 
diagram it will be seen that any one of the generators in an 
engine room can be used for furnishing excitation and power 
for the motor driven auxiliaries or for supplying current to the 
ship's distribution boards. When a generator is being used to 



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CALIFORNIA, MARYLAND AND WEST VIRGINIA 165 



Switchboard Wiring, Back View 

supply the auxiliary bus, it is connected in by a knife blade switch 
and there is no circuit breaker in the circuit ; when used to supply 
the ship's, power and light bus, the current passes through a circuit 
breaker. Generators can be run in parallel on the power and light 
bus but not on the auxiliary bus ; this is prevented by interlocking 
the three ^generator switches so that only one can be closed at a 
time. This interlock can be released by hand, if desired, so that 
in an emergency a generator could be paralleled before cutting it 
out so as not to interrupt the supply of excitation. 

The connections from the ship's power and light bus to the 
distribution boards are in duplicate and each set is provided with 
switches so that, in case of trouble on one lead, it can be cut out 
and the distribution board can still be supplied although at reduced 
capacity. 

The switches for supplying the auxiliaries are double throw ; 
one throw is to the auxiliary bus of the room in which the 
auxiliary is located and the other throw is to a stand-by bus. 
This stand-by bus is supplied through a double throw switch, one 



Digmze. by Google 



166 ELECTRIC SHIP PROPULSION 

throw of which connects to the light and power bus in the same 
room as the auxiliary and the other throw to the auxiliary bus 
in the other engine room. This really provides three sources of 
supply for excitation and auxiliaries. 

If only one engine room is in operation, the double throw 
switch for the staild-by bus will be on the light and power bus. 
If both engine rooms are in operation, the double throw switch 
for the stand-by bus will be on the other engine room's auxiliary 
bus. This latter arrangement is the better of the two and will 
always be used when the ship is ready for full power but can not , 
be used when cruising since only one engine room will be in use^ 

The current for the stand-by bus will come through a circuit- 
breaker in both cases, but the ship's power and light bus breaker 
will be set for only a normal overload, whereas the breaker on 
the lead from the auxiliary bus will be set at such a high value 
that nothing less than a dead short circuit will open it. It was 
thought to be necessary to have this breaker since the floodii^ 
of one engine room would put a short circuit on the auxiliary bus 
of the other engine room. 

The switch for supplying the blower control panel in the main 
control room is fused since these auxiliaries are not located in the 
same compartment as the switchboard and it was thought best to 
give some protection against damage to the long leads to the 
ventilating blowers. However, these fuses will not blow under 
anything less than a short circuit and spare fuses are kept in 
place on the switchboard. There are indicating lamps to show 
whether or not these fuses have blown. 

All the switches on the blower control panel are double throw 
so that any ventilating blower can be supplied from the auxiliary 
bus in either engine room, The switch for supplying the control 
circuit is also located on this panel. This is a transfer switch so 
that it makes contact with one bus before leaving the other ; this 
momentarily parallels the supply buses from the two engine rooms, 
so resistances are inserted in series between the two contacts to 
take care of any small difference in voltage on the two buses. 
A transfer switch is used on this circuit since the control circuit 
should never be opened, as will be seen later. The two buses 
supplying this panel have indicating lamps so that the operator 
will always know which is alive. Indicating lamps are also provided 



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CALIFORNIA, MARYLAND AND WEST VIRGINIA 167 

both on the control panel and in the motor rooms to show when 
the blowers are running. 

All auxiliaries are provided with circuit breakers at their start- 
ing panels; these are really the only protection that is given a 
generator, when it is supplying the auxiliary bus, but it is believed 
to be quite adequate. 

Two of the generator switches in the after er^ne room are 
made double throw so as to provide for a shore connection; one 
of these switches energizes the power and light bus and the other 
energizes the auxiliary bus. This will provide for power in both 
engine rooms since the auxiliaries in an engine room can run off 
either auxiliary bus and the ship's service can be supplied since 
the two distribution rooms can be connected together. 

To improve the economy and to increase the range of speed, 
the main circulating pumps, forced lubricating pumps and excita- 
tion for the main field are arranged so that, at low powers, they 
can be run off the 120-volt circuit. In order not to unbalance 
the 300 kilowatt generators too much, some of these are arranged 
to be between positive and neutral and others to be between 
neutral and negative. Furthermore, the arrangement is reversed 
in the two engine rooms so that if the auxiliaries in both engine 
rooms are run from one engine room the load will be exactly 
balanced. 

Field and Booster Wiring 

The field and booster wiring is indicated in Fig. 87, but, owing 
to the importance of this circuit, it is thought best to show it 
separately in Figs. 88a and 88b. 

The supply switch for the booster and the field is electrically 
locked so that it can not be opened unless the field switch is open. 

The field circuit passes through a single pole, double throw 
switch for changing the field from the 120-volt circuit to the 240- 
volt circuit and vice versa; this switch is mechanically interlocked 
with the field lever so that it can not be opened unless the field 
switch is open. Both this switch and the field lever are located 
on the main switchboard. 

In case of failure of the booster set, it can be short circuited 
and the excitation taken direct from the 300-kilowatt generator 
which will have its voltage varied to suit. This will necessitate 
transferring the auxiliaries to the stand-by bus, or emergency bus. 



Digmze. by Google 











a>n> 


■ard 




AfftrDCBtard 


1 ., 


ACCtll 


1 




rm, 

mch. 












th-r. 












A/h 




































C/at 












4Sa-Aa.S. 

6.L.-6-W. 
I.C.-lnhrk 
tkL-Ortrh 


Motor Btiasfer 




A.C.gen. 







Fig. 88 a.— U. S. S. California: Field and Booster Wiring, Port Side 



Digmze. by Google 





ForwantD.C.B«^ 


k 

•Si 


ACSk 


Bcositr M<,t0f 





Fia 88 b.— U.S. S. California; Field and Booster Wiring, Surboard Side 
169 



D,„t,..= b:, Google 



170 ELECTRIC SHIP PROPULSION 

as it is designated in Fig. 87. The short circuiting of the booster 
is accomplished by the transfer switch shown in Fig. 88. The 
first motion of this switch opens the field of the booster ; further 
motion closes the short circuit (this momentarily short circuits the 
booster generator on itself but this will do no harm since its field 
is open) ; further rrtbtion opens the connection to the booster 
generator and entirely disconnects it from the line. 

In case trouble develops in the booster, the proper procedure 
for cutting it out would be first to get all the auxiliaries oflf the 
generator to be used for excitation, then gradually reduce the 
voltage of this generator and, at the same time, move the main 
field lever to maintain proper field strength. When the generator 
voltage has been reduced until it is the same as that on the main 
field, the booster can be cut out by the transfer switch without 
causing any jump in the main field current. Of course, in a 
sudden emergency, where it would be necessary to get the booster 
off the line without delay, it could be short circuited without wait- 
ing for anything else since the main field will safely carry tJie 
current due to 240 volts. 

While not absolutely necessary, it is desirable that the booster 
set should always be started up before the main field switch is 
dosed. This will prevent any possibility of burning spots on 
the commutator of the booster generator by having current pass 
through it at standstill. '-■ 

The booster, motor, is provided with circuit breaker protection. 
This circuit breaker-has an auxiliary switch which opens the field 
circuit of the booster generator and prevents any possibility of 
the latter running away when the circuit breaker opens. In case 
of opening of this circuit breaker, there would be a sudden rise 
in the voltagfe'on the main field circuit as in the case where the 
booster was shott circuited. 

The lever^for-opening and closing the field switch also operates 
the booster generator field rheostat and the short circuiting con- 
tactors for the main motors. 

As shown in Fig. 88, when going in one direction the first 
15 degrees of motion of the field lever closes the field switch, 
during the next 30 degrees of motion the field of the booster is 
reduced and this increases the main field. Further motion 
reverses the direction of the booster generator field and causes it 



Digmze". by Google 



CALIFORNIA, MARYLAND AND WEST VIRGINIA 171 

to boost the supply voltage and this continues for the next 30 
degrees of motion when maximum boost is reached. At the same 
time, the field lever comes up against a stop which must be lifted 
before further motion can take place; after the stop is removed, 
further motion will close the contactors on the main motors. This 
stop is placed in the field lever travel to insure that the operator 
will not inadvertently close the contactors before the motors have 
pulled into step as indicated by the instruments. 

After the contactors are closed the excitation must be reduced 
to prevent overheating of the main field. This is insured by a 
sprii^ on the field lever which will pull it back, if the operator 
should leave it in the over-excited position. 

Reverse motion of the field lever reduces the excitation and 
its final motion is to open the contactors and the main field simul- 
taneously. Just before the field switch is opened, an auxiliary 
swritch is closed which short circuits the field through a discharge 
resistance. 

Green indicating lights to show when the field is open and 
red indicating lights to show when it is closed are placed on the 
main switchboard and also on the generator switchboards in each 
engine room. 

Generator and Auxiliary Switchboards 

The switchboard for the after engine room, shown in Fig. 89, 
is identical with the one in the forward engine room except that 
the generator supply switches at the bottom of two of the panels 
are made double throw to provide for the shore connection. 

There is a panel for each generator and two for the auxiliaries. 

All circuit breakers on this board are shock proof and have 
time limit attachments. In addition, the generator circuit breakers 
have reverse current trips and shunt trips. 

The connections to these switchboards are shown in Fig. 87. 

Switchboard for Motor Ventilation Control 
This switchboard is shown in Fig. 90. It is located in the 
main control room. The connections to it are shown in Fig. 87. 

Alternating Current Wiring 
The main alternating current wiring and switches are shown 
in Fig. 91. 



Digmze. by Google 













„ Google 



CALIFORNIA. MARYLAND AND WEST VIRGINIA 173 
Bill of Material for Switchboard Shown in Fig. 89 
Part 



Ham! of Put 

:• IH- . . .- 
. «- . .• .- 



Ampere Shunt 
joo Voll Vollmclet 

350 Volt Vollmett 
per; ^unt 



asp" Veil "niU. S. P, S. T. Slart- 

asrVoires A. D. P. D. T. Le' 

Switch 
aso Volt 37S A. D. P. D. T. Lc' 

Switcfa (broken Bat:k) 
aso Volt 1000 A. T. P. D. T. 

aso Voll lODo/jQOQ A. T. P. S. T. 

Lever Switch 
AuxiUarj- Switch for 406 S. 

C. O. 
aso Volt I3S A. D. P. D, T. Le. 

Switch 
aso Volt J7S A. T. P. D. T. Lei 

Switch 
aso Volt srs A. T. P. D. T. Lei 

Switch 
iSo Voll loDo/iooo A. T. P. D. T. 

JSo Volt 13s A. T. P. D. T. Lc' 



> A. T. P. S. T. 

Ii 

L. S. P. S. T. Lever 



. D. P. T. IR. 



;. T. L. OL. and U. V. 
i» 1350/500 A. S. P. ~ 
and SHlINT TRIP 
lit laso/soo A. T. P. 



Point D. P. Voltmeter Switch 

Point S. P. Ground Switch 
(itch Slop for 405 



MO a: N^-fe. C. S^Er 




















Ships Service— Light ; 




































Spare (No Marking) 













n Pump No. i— 



—Aft 

— For'd 
—Aft 



Ventilatinju Blower No. , 

Dynamo Hotwell Pump— Aft 

Djnamo Hotwell Pump— For'd 

Dynamo CirculatinK Pump— Aft 

Dynamo 

ToUl Amperea For'd 

■VM,\ Amn^r-. For'd 

Field I 



A. C. Gem 
Shore Con 



r Uotor 



d Out 
r Diaconnected 



D,„t,..= b:, Google 



174 



ELECTRIC SHIP PROPULSION 

Put 



Aft Distribut 
Aft Diatribuii 



B of Put 

Itor In 

in Switchboard 
in Switchboard 
in Switchboard 



) Motor Ventilating I 



Voltnge Gcnsrator No. 4— G«ier«- 

tor No. s— Generator No. 6 
Booster— For'd bus— Blank 
MadT for Bureau of Steam Eng;i- 




Fia 90. — U. S. S.' California: 
Switchboard for Motor Ventila- 
tion Control 

Bill of Material for Switchboard Shown in Fig. go 
Put Put 

Vo. Kama of Part Ho. Ham* of Part 

Koo. Panel 3' B" 1: a' 8" x iW. ao4- Besislanei 

Bevel 5C '"■ ^™'^ '"' n a' S" « iM", Be«l 

aoi. Sw— Da? D. P. D. T. ajo Volts fij M." 

Amperer — ---"-■ ^-" ■>- 

' ' ," ikotor No. I— OuA'd 



Amper, 



d Bh. 



Digmze. by Google 



CALIFORNIA, MARYLAND AND WEST VIRGINIA 175 



Nam* of Put 

0. ., Motor "- ■ 
—Aft Bua 



Port— Aft Bu: 

Fan No, 3, M 

Port^Foi^d 1 



Port— For^d Bu 

Fan No. i. Moti 

Port— Aft Bn* 



No. 1— Ouib' 
No. I— Outb' 

■ No. I— 1 



■r No. 4— Out 
r No. 4— Outb 



Nun* of Put 

Aft Bus 

1. Motor No. 


4— OotbM 


4— Ot-tb'd 


1— Oulb-d 


1, Motor No. 


.— Outb'd 


1. Motor No. 


a-Inb'd 


. 1. Motor No 


I— Inb'd 


I. Motor No 


a-Inb'd 


. 2. Motor No 


S— Inb'd 


1. Motor No. 


4— Outb'd 


2, Motor No. 


4— Outb'd 



There is an 8-poIe, double throw disconnecting switch for 
each generator; these switches are similar to those used on the 
New Mexico and serve identical purposes. 

The same may be said of the 8-pole, single throw, discon- 
necting switch for each main motor, the 3-pole, double throw, 
reversing switches for each pair of motors, the 6-pole, double 
throw, pole changing switches for each pair of motors, and the 
4-pole, single throw, bus tie switch for connecting one generator 
to four motors. 

Balance relays and under-current relays similar to those on 
the New Mexico are also fitted. 

The main difference between the alternating current wiring of 
the New Mexico and that of the California is the additional leads 
of the California's motors to the contactors. Temperature coils 
are also furnished for the main motors as well as for the 
generators. 

Control Wiring 

The direct current wiring for controlling the electric locks, 
indicating lamps and electrically operated switches is shown in 
Fig. 92. This wiring is mainly in the main control room. 

The supply of current comes from either the forward or after 
engine as already explained under "Direct Current Wiring." 



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176 ELECTRIC SHIP PROPULSION 



Fig. 91.— U.S. S. California; Main 



D,„t,..= b:, Google 



CALIFORNIA, MARVLAUD AND WEST VIRGINIA 177 



Alternating Current Wiring and Switclies 



D,„t,..= b:, Google — 



i;8 ELECTRIC SHIP PROVULSION 

After passing through the double throw supply switch, the circuit 
■ divides and passes through heavy fuses to the two boards. 

In addition to the indicating lamps, which have already been 
mentioned, there are lamps for indicating whether the motor con- 









Fig. 92.— U.S. S. California: Direct Current Control Wiring 

tactors are open or closed, to show the position of the steam 
limit lever and to show when the undercurrent relays release. 

When the main motor disconnecting switches are opened they 
open auxiliary switches which interrupt the circuits to the con- 
tactors and also to the indicating lamps. 



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CALIFORNIA, MARYLAND AND WEST VIRGINIA \79 

The reversing switches and pole changing switches are elec- 
trically locked until released by the opening of the under-current 
relays which are set to open at a predetermined value of the line 
current. 

The balanced relay is arranged to trip the field switch in case 
of unbalance in either of the phases. " 

When the bus tie switch is closed it cross connects the control 
wiring of the two terminal boards so that one field kver will 
control the contactors on all four motors. ; 

Terminal and Testing Boards 

These boards contain the connections for the control wiring 
shown in Fig, 92, There are two of them and they are located 
in the main control room. They are shown in Figs. 93, 94, 95 
and 96. These figures show the switching which makes it pos- 
sible to isolate any individual circuit that is grounded or otherwise 
gives trouble. Provision is also made for testing for grounds 
and for checking any of the instruments on the main switchboard 
by temporarily inserting a test meter into the circuits. 

Experience gained on the New Mexico indicates that these 
boards will greatly facilitate checking up trouble with the small 
wirii^ on the switchboards and also make it very simple to install 
meters for the trials. 

Main Switchboard 

The complete main switchboard is shown in Fig. 97. A view 
with the front panels removed is shown in Fig. 98 and a view of 
the operating levers is shown in Fig. 99, 

The table with Fig. 97 gives the names of all the operating 
levers, etc. Fig. 99 shows the operating levers as they are 
actually mounted on the board. It will be noted that the arrange- 
ment is better than that on the New Mexico as all levers are 
easily accessible. The steam limit lever has been brought up on 
a level with the field and speed levers; also the field selective 
switch has been placed on the main switchboard. 

The bus tie switch, generator disconnecting switches and 
motor disconnecting switches are all operated by levers which 



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f 


200 








4:^' , 

Main Port Tcjting and Terminal Board 



^ ' Tlfl 




Main Mc 


4:S^ * 

rboard Tesiine and Terminal Board 



Fig, 93.— Testing and Terminal Boards 





® 


Section of 
Cul-oot Switch !IS 


"•..j^iy^ 




Section of Receptacle t 







Section of Receptacle £10 witt<ou 

Fic. 94.— Details of Cut-out Switch and Receptacles 



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CALIFORNIA, MARYLAND AND WEST VIRGINIA 181 



NOTES 

Receptacles 210 and accompanying plugs provide for insertion of port- 
able meters in secondary circuit of each current transformer for checking 
present meters or obtaining new readings. This is accon^lished as fol- 
lows; With plug out, secondary current from transformers enters ter- 
minal K, passes through M, T, L, R, S, and N, and leaves terminal J. 
Spring T assures positive contact between L and R. With plug in, sec- 
ondary current from transformers enters terminal K, passes through 
M, T, L, P. W, to one meter stud and then from other meter stud 
through V, O, U. R. S and N, and leaves terminal J going. through cir- 
cuit instruments back to transformers. Leads V and W must be at- 
tached to portable meter before inserting plug in receptacle. This pre- 
vents opening secondary of current transformer when L leaves R. 

Receptacles 211 and accompanying plugs are used for testing potential 
and grounds or attaching a portable meter. 

Receptacle 212 is used as a grounding terminal or fuse receptacle, 
and tests for grounds or potential are made with this receptacle in con- 
nection with plug assembled with receptacle 211. 

When 212 is used as a grounding terminal F is a solid metal plug, 
whidi may be i^moved from plug E if ground is not desired for testing, 
or any other purpose, but there is no danger of opening secondaries of 
current transformer since their common connection comes to and leaves 
same terminal G, otherwise F is a fuse in which case line comes to G, 
goes through F, leaves through H. 

Cutout switches 215 are used for distributing control circuits to various 
pieces of apparatus in cell and for isolating any control circuit in case 
of grounds. Test for grounds should be made at the main control switch 
on front of ventilating control switchboard by touching one side of 
megger or magneto to switch stud and connecting other stud of megger 
or magneto to ground. !f ground is indicated, open and close cutout 
switches on terminal boards until the proper switch is ojiened which re- 
moves indication of ground and isolates the grounded section. 

Each cutout switch is provided with a name plate, of which the small 
letters apply to connections to upper studs and larger letters to connections 
to lower studs. Blade B is locked closed by means of screw and 
washer A. 

Name plates for auxiliary terminal boards are made of engraved baka- 
lite, letters lilted in with white enamel. For main testing and terminal 
boards name plates are made of engraved white metal, with white line 
border and letters, dull black background. 



can be handled from the floor ; those for the generators are on 
the front of the switchboard and those for the motors on the 
sides of the board. All these switches are mechanically inter- 
locked with the reversing switches so they can not be moved 
unless the latter are open ; this insures an absolutely dead circuit. 
On the New Mexico these switches are interlocked with the main 
field switches and it is possible to operate so rapidly that current 
will be flowing when the disconnecting switches are opened. 



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182 



ELECTRIC SHIP PROPULSION 



All of these switches are positively held in either the open or 
closed position so they can not be opened or closed by shock or 
short circuit. 

The bus tie switch is interlocked with the reversing switches 
so that they can not be operated unless the bus tie switch is fully 
closed or fully open. The bus tie and generator disconnecting 
switches are interlocked so that only two can be closed at one 




Fia 95. — Auxiliary Terminal Boards 



iU of. Material for Auxiliary Terminal Boards Shown in Fig. 95 

PMt 
Hun* of rut Ho. 

"'SlU^' - -' '"' ' '**'' v,v. 

Panel iiii' i 4' CM' « 'H'. »n. 



«IJ4" 



Hune of Part 
tot Testing RecepUcle 
Testing Receptacle 
Tening and CioundiiiE Recep- 



yel 



Pot. Cut Out Switch 

Relay Cat Out Switch 

I Volts 10 A. S. P. S. T. LEVER 



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CALIFORNIA, MARYLAND AND WEST VIRGINIA 185 



Bill of Material for I 

Hkmii ot Part 



1 Switchboard Shown in Fig. 97 

Put 

No. Nuns of Part 






Masnetic Locking Device for 40J 
Boosler Field Rheostat Starb'd 
Field Control Lever SUrb'd 
Field Control Lever Port 
Steam (Speed) Control Leuet 



resting Terminal Boa 
;ell Door Starb'd 
Bus Tie Switch 5000 
Amperes 4 P. S. T. 



Volts, a40i 
5wild. Por 



Motor Disconnecting Switches 

Field Switch 240 Volts, 400 Am- 
peres A. D. P. S. T. 

Field SelectiTc Switch 240 Volts. 
375 Amperes S. P. D. T. 

Field Selective Openting Lever 
SUrb'd 

Field Selective Operating Lever 

Pipe Mechanism tor loba Port 



Grill 


Work 


Fro 






Fram 


e Work 


(F 


ont Extension) 


Steel 


Panels 








Fram 




Pro 






Field 


'Contro 


Pi 




Pipe 


Mecha 


ism 


for 


Steam an 


Speed Con 




Sffd 


"& 






for 


Sleam an 


■ed Con 


rol 






Oper 


Lever 


fo 


°Mo 


tor Discon 




'■LS 


tch 


End 


Port 


(^ 




Mo 


tor Diseon 




ting S» 


.tch 




Sfb'd 


O^r 


Lever 


fo 


M< 


or Discon 




ting Switch 


Front Fort 


Ope' 


I^iver 




Mo 






ling S^ 




Fron 


I Sfb'd 


Inte 


ock Si 




Field an 


Fi 






Lev 


r. Sfb'd 






Fie 


d an 


d Field S 





""DisconnKtinj-Switche.StVd 
Frame Work Port End of Cell 






Frame Work Sfh'd. End of Ce 




Pot Trans. Base and Supports 


4og: 


Pot. Trans. Base and Supports 








lir?S;I?"Kl ^Fm« 






Sos! 


Inwttor V^^ w"rk 


606. 


""J?Sf.T.£rs-"S. f«™" 




toy. 


Disconnecting Switch Port 






Anang. of Bus Bars and Supporl 




Cable Terminals— Motor 








Tank Li'fte" 




Tank Lifter 




Tank Lifter 


8do. 


Set of Connections for Pot Trans 


80 J. 


Interlock between Starb'd Moto 




Disconnecting Switch and Pol 
Changing OiT Circuit Breaker 
Field Switch a4<. Volt^ 400 Am 
peres D. P. S. T. Port 




804. 




2J0O 


FiSd Switch MO Volts, 400 Am 
_pcres D. P. 1. T. St'b'd 
Hknds OS Signal 



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186 ELECTRIC SHIP PROPULSION 



Fig. 99, — U. S. S. California: View Showing Operating Levers 



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CALIFORNIA, MARYLAND AND WEST VIRGINIA 187 

time and also so that a disconnecting switch can be closed only in 
the low voltage position when the bus tie switch is closed and in 
the high voltage position when the bus tie switch is open. 

The speed and field lever interlock is similar to that on the 
New Mexico; this is also true of the interlocks between the field 
lever and the reversing and pole changing levers. 

The pole changing and reversing levers are mechanically 
interlocked so that the reversing levers can be thrown to the 
"astern" position only when the pole changers are in the 36-pole 
position. They are also interlocked so that in going ahead the 
ship must be started by first throwing the "ahead" and 36-pole 
switches and then changing to the 24-pole switch, if desired. 
These interlocks make it necessary always to back with the 36-pole 
combination and also to start ahead with it. In case it is desired 
to use the 24-pole combination in going ahead, the shift can be 
made after starting ahead. This insures that all backing and 
starting will be done with the high resistance squirrel cage motof . 

The field switch is mechanically operated instead of by sole- 
noids as in the case on the New Mexico. This switch is mounted 
on the bulkhead of the control room just forward of the switch- 
board ; it has a tripping coil so that it can be opened electrically 
by the balance relay. 

Locks and Interlocks 

All of the locks that have been described in connection with 
the various switchboards are listed in Fig. 100, which also con- 
tains a single line wiring diagram to show the relation of the 
various switches. 

Operation of the Machinery 

The three conditions of normal steaming are identical with 
those described for the New Mexico. The operation of the 
machinery in the ahead and astern directions is also the same but, 
owing to the dissimilarity of the main motors, there is a slight 
difference in the actual operations performed by the field lever, 
so a description will be given of reversing under each condition. 

(1) Getting Under Way With One Generator, the Motors 
Being Arranged for $6-Poles. — Close the generator discon- 
necting switch on one generator and also the bus tie switch. 



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CALIFORNIA. MARYLAND AND WEST VIRGINIA 189 
Pig. 100— Notes 
(i) Field circuit breaker A is electrically tripped by balance relay H 
when there is an unbalance in line or generator. 

(2) Speed lever S is provided with an adjustable stop which prevents 
its operation in advance of the field lever A. A similar stop on the field 
lever prevents it from being thrown to the "Field Off" position tinless 
the speed lever is thrown to the low steam position. 

(3) Lever for field selective switch B is mechanically interiodked with 
lever for field circuit breaker A so that selective switch cannot be operated 
unless circuit breaker is open. 

(4) Booster field rheostat U and field circuit breaker A are mechani- 
cally interlocked in elTect since their mechanisms are operated simultane- 
oush' by the same lever. 

(5) Lever switch L is electrically interlocked with field circuit breaker 
A so that it cannot be opened until circuit breaker is open, but can be 
closed independent of circuit breaker. 

(6) Contactor control switch is operated by same lever as field cir- 
cuit breaker. It opens simultaneously with field breaker and is closed at 
end of over excitation stroke after motors have pulled into step and a 
Stop has been relieved. 

(7) Motor disconnecting switches F are mechanically interlocked 
with their respective pole changing oil circuit breaker D, so that motor 
disconnecting switches cannot he opened or closed unless their respective 
pole changitig oil circuit breaker is in open position. This interlodc pre- 
vents opening or closing motor disconnecting switches under load, but 
does not prevent running of one motor while the disconnecting switches 
of the other motor are open. 

(8) Bus tie switch M and generator disconnecting switches C are 
mechanically interlocked so that any two only can be closed at same time. 

(9) Bus tie switch M and generator disconnecting switches C are 
medianically interlocked so that when bus tie switch is open the genera- 
tor disconnecting; switches can be thrown into high voltage position only. 

(10) Bus tie switch M and generator disconnecting switches C are 
mechanically interlocked so that when bus tie switch is dosed either of 
the generator disconnecting switches can be thrown into low voltage 
position only ; bus tie switch cannot be opened unless both generator 
switches are opened. 

(ii) Bus tie and generator disconnecting switches are mechanically 
interlocked with levers of reversing oil circuit breakers so that they cannot 
be operated unless reversing breakers are open (see interlock No. 13). 

(12) Levers for pole changing and reversing oil circuit breakers 
E and D are electrically locked so that they cannot be operated until 
current has fallen to a predetermined value as controlled by an under 
current relay N. 

(13) Levers for pole changing and reversing oil circuit breakers 
E and D are mechanically interlocked with lever of field circuit breaker A 
so that they cannot be operated unless field lever is in off position. 

(14) Levers for pole changing and reversing oil circuit breakers 
E and D are mechanically interlocked with levers for field circuit breakers 
A so that when either field is used alone the oil circuit breakers on the 
opposite side are also locked against operation. In other words, when 
using one generator, both fields must be open to unlock and therefore the 
one not in use should be secured in the open position by a stop. 

(is) Levers for oil circuit breakers are mechanically interlocked 
with levers for bus tie switch so that they cannot be operated unless bus 
tie switch is in either extreme positicm. 

(16) Lever for iwle changing and reversing oil circuit breakers 
E and D are mechanically interlocked so that D cannot be thrown in 
ahead position unless E is m 36 pole or off positioiL This tnterlod^ biyir- 



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190 ELECTRIC SHIP PROPULSION 

ever, may be voluntarily relieved but should not until ship is actually 
movinK ahead. 

(17) Levers for pole changing and reversing oil circuit breakers 
E and D are mechanically interlocked so that reversing lever cannot be 
thrown into astern position unless the pole changing lever is in 36 pole 
or off position, also the pole changing lever cannot be thrown into the 24 
pole position when the reversing oil circuit breaker is in the astern posi- 
tion; this makes it impossible to back in the 24 pole position. 

(18) Lever switches G on aft or forward boards are mechanically 
interlocked so that only one switch on either board can be in at any one 
time, but in case of emergency this mechanical lock can be relieved, by 
hand, so that any other switch may be thrown in. 

The field switch would be open and the turbine running at slow 
speed. On receiving a signal "ahead" ; 

(a) Throw pole changers to 36-pole position. 

(b) Throw reversing levers to "ahead" position. 

(c) Close field switch and put on over-excitation 
until motors are in step. Lift the stop and continue the 
motion of the field lever until the contactors are closed, 
then reduce the field to normal strength. 

■ (d) Bring the turbine up to the desired speed. 

(2) Reversing, — With the ship going ahead under condi- 
tions described above under ( 1 ) , on receiving a signal "astern," 

Xtt) Move the speed lever to low speed position and 
open the field at the same time; the contactors will also 
open. 

(b) As soon as the under-current relays release the 
locks, throw the reversing levers to the astern position. 

(c) Close the field switch and put on over-excitation. 
As soon as the motors come into step, lift the stop and 
move the field lever until the contactors close, then reduce 
the field to its normal strength. 

(rf) Bring the turbine up to the desired speed. 

(3) Getting Under Way zvith One Generator, the Motors 
to Be on the 24-Pale Connection. — Arrangements would be 
made as described above under (1). On receiving a signal 

I "ahead," 

(a) Throw the pole changers to the 36-pole position. 

(b) Throw the reversing levers to the "ahead" posi- 
tion. 

(c) Close the field switch and put on over-excitation 
until the motors are in step, then lift the stop and continue 



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CALIFORNIA, MARYLAND AND IVEST VIRGINJA 191 

the motion of the field lever until the contactors are closed, 
then reduce the field strength to normal. 

(rf) Bring the turbine up to the desired speed. After 
the ship has gathered speed ahead, the chaise can be made 
to the 24-pole condition. 

(e) Move the speed lever to the low speed position 
and open the field at the same time; the contactors will 
also open. 

{/) As soon as the under-current relays release the 
locks, throw the pole changers to the 24-pole position. 

{g) Close the field switch and put on over-excitation 
until the motors come in step, then lift the stop and move 
the field lever till the contactors close and then reduce the 
field to normal strength, (It is not necessary to close the 
contactors since they are not effective on the 24-pole com- 
bination but they should always be closed so as to make 
the operation the same in all cases. ) 

(A) Bring the turbine up to the desired speed. 

(4) Reversing. — Assuming the ship to have gotten under 
way as described above under (3), on receiving a signal 
"astern," 

(a) Move the speed lever to the low speed position 
and open the field at the same time; the contactors will 
also open. 

(6) As soon as the under-current relays release the 
locks, throw the pole changers to the 36-pole position and 
the reversing levers to the "astern" position. 

(c) Close the field switch and put on over-excitation. 
As soon as the motors come into step, lift the stop and 
move the field lever until the contactors close, then reduce 
the field to its normal strength. 

^d) Bring the turbine up to the desired speed. 

(5) Getting Under Way with Two Generators and the 
Motors to Be on the 24-Pole Combination. — In this case, the 
bus tie switch would be left open and the generator discon- 
necting switches would be closed in Jhe high voltage position. 
If a signal "ahead" is received, the operations would be per- 
formed exactly as described above under (3), except that they 
would be performed on two generators instead of on one. 



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)2 • ELECTRIC SHIP PROPULSION 

(6) Reversing. — After having gotten under way with 
conditions as described above under (5), if a signal "astern" 
is received, the operations would be performed exactly as de- 
scribed above under (4), except that they would be performed 
on two generators instead of on one. 



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CHAPTER XIIl 
The Tennessee, Colorado and Washington 

rIESE ships are all sister ships of the California and their 
machinery compartments are identical with those of thie 
California. The propelling machinery is being furnished 
by the Westinghouse Company and differs very considerably from 
that of the California in its details, although the general arrange- 
ment is the same. The number of units used, the grouping of 
the units, the propeller speed and the generator speed are the 
same in both cases. 

Main Turbine 

A cross section of the main turbine is shown in Fig. 101 and a 
photograph of the turbine coupled to a water brake is shown in 
Fig. 102. It is of the semi-double-flow type and has both impulse 
and reaction elements. The steam first flows through the impulse 
wheel, then through the single flow, reaction element and then . 
divides and flows through the two double flow elements. 

A dummy piston is located between the impulse wheej and the 
adjacent low pressure, reaction stage. '■ ' 

The turbine cylinder is of cast iron and is divided in the hori- 
zontal plane. It is arranged for downward exhaust. There Is 
an external pipe for cross connecting the two double flow elements. 

The arrangement of auxiliary exhaust connections to the 
main turbine is shown diagrammatical ly in Fig. 103. This ar- 
rangement is very similar to that of the California. The excit^ 
exhausts to the auxiliary exhaust line through a constant back 
pressure valve. The auxiliary exhaust connects, through a con- 
stant back pressure valve, to the cross connection between the 
two low pressure reaction stages of the turbine; there is a stop 
check valve at the connection and the line is provided with ja 
butterfly valve, actuated by the emergency governor. The auxil- 
193 



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TMNESSEE. COLORADO AND WASHINGTON 195 

iary exhaust line is also provided with connections, through con- 
stant back pressure valves, to the main and dynamo condensers. 
There is also a by-pass valve controlled by the main and emer- 
gency governors which by-passes the auxiliary exhaust from the 
main turbine to the main condenser when the governor shuts all 
steam off the turbine, when the emergency governor trips or when 
the oil supply fails. With this arrangement of valves the auxil- 
iary exhaust can be used in the feed heaters, the evaporators, and 
the main turbine, or sent direct to the condensers. The constant 



Fig. 102.— U. S. S. Tennessee: Main Turbine Coupled to a Water Brake 

back pressure valve between the exciter and the auxiliary exhaust 
line is fitted so that there will be a constant pressure on the 
exciter exhaust when the auxiliary exhaust is not being used in 
the main turbines. 

The steam chest is provided with hand operated valves for 
admitting steam to the expanding nozzles. The number of valves 
to be open at any time will depend on the maximum speed to be 
maintained. If these valves are properly operated, the proper 
inlet pressure to the nozzles will be maintained and the n 
efficiency of the turbine will be obtained. 



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1^ MLECTRIC ship PROPVLStOM 

The glands are of the labyrinth type and are sealed by both 
water and steam. 

The bearings are of the spherical, self-alining type and are 
divided horizontally. The thrust bearing is of the Kingsbury 
type and is arranged for adjusting the rotor endwise. The lubri- 
cation is forced feed, being supplied by forced lubrication pumps 
in the engine rooms. There is no emergency pump on the tur- 
bine, so one of the forced lubrication pumps is driven by a steam 
turbine and controlled by a pressure regulator which will auto- 

-■- JOOKw. fhn-Qondtnsmg St* 



f bodf prtssurt 
v/ spring rrfief 



•sort caniralbdby 
■antrel vairt aid 
B iTttchofiitm^ 



Fig. 103. — U. S. S. Tennessee: Diagram Showing Arrangement of Auxil- 
iary Exhaust Connections to Main Turbine . 

matically start up this pump in case of failure of the electric 
driven pump. 

The turbine is coupled to the generator by a flexible coupling 
which is arranged to take any unbalanced thrust of the generator ; 
this is different from the California, where a thrust collar is pro- 
vided on the generator shaft. 

The speed control system, the main and emergency governors, 
the steam limit device and the gland control system are shown in 
Fig. 104. 

The details of the operation of the speed control are as 
follows : 



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V|J.| 


lil.. 



^TWv^t.^ 



D,„t,..= b:, Google — 



m ELECTRIC SHIP PROPULSION 

Oil from the forced lubrication system at not less than 60 
pounds per square inch gage pressure is admitted to the upper 
port indicated on the "governor control" (see Fig, 103) which is 
located in the main control room. The floating lever of the 
"control" is set to the desired position by a worm wheel and oil 
will be admitted through a piston valve to the under side of the 
main piston, causing this to lift until the oil pressure is balanced 
by spring pressure. The lifting of this piston causes the piston 
valve to lift at the same time, shutting off the oil supply to the 
under side of the piston, so that a balance will be obtained. There- 
fore, for any position of the lever handle there will be a corre- 
sponding position of the piston and a corresponding pressure 
under the piston. A motor driven vibrator constantly moves the 
valve up and down a small amount, causing a fluctuation of pres- 
sure under the piston, with a resultant small movement, thus 
eliminating any tendency towards sticking. 

The oil pressure from the piston is communicated through a 
pipe to a piston on the governor. The governor is revolved 
through gearing by the main turbine shaft and, being of the fly- 
ball type, the weights will exert a pull, which will balance the 
pressure on the piston. For every oil pressure there will be a 
definite corresponding speed at which the weights will just balance 
the pressure of oil on the piston. The angles of the governor 
arms and links are so arranged that a slight change in speed will 
cause the governor to move from one extreme position to the 
other for any given oil pressure. 

The governor is connected through linkage to the floating lever 
of a hydraulic relay which operates the main governor controlled 
inlet valve. A part of the linkage consists of a bell crank made 
in two parts but held together by means of a spring ; this permits 
the motion of the governor to continue after it comes up against 
the steam limit stop as will be explained later. 

This bell crank is connected to one end of the floating lever, the 
middle of which is connected to the oil relay plunger and the 
other end of which is connected to the operating gear on the gov- 
ernor controlled inlet valve. Oil is admitted at the center of the 
oil relay and if the governor weights move outward, due to an 
increase in turbine speed, the floating lever will be raised, allow- 
ing oil to pass into the top of the operating cylinder of the inlet 



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TENNESSEE, COLORADO AND WASHINGTON 199 

valve and to pass out from the bottom of it at the same time, 
causing the piston in this cylinder to move downward and, by 
means of the lever indicated, to shut the governor controlled inlet 
valve, thus shutting off steam from the turbine. The return con- 
nection to the end of the floating lever at the same time moves 
the relay piston back to a position where oil is cut off, so that for 
every governor position there will he a corresponding position of 
the operating cylinder and of the inlet valve as well. 

As has already been stated, a part of the connecting linkage 
between the governor and floating lever consists of a divided bell 
crank held together by a spring. A link from the floating lever 
connection engages at its lower end with a "steam limit stop" in 
such a manner as to be free always to move downward but only 
upward as far as the limit will permit. Thus the governor can 
always move its end of the floating lever to shut off steam but can 
only move it in the direction of admitting steam as determined by 
the steam limit. After reaching this limit, further motion of the 
governor will separate the two parts of the bell crank but will not 
have any effect on the turbine speed. The position of the steam 
limit stop is controlled by a small motor which is operated from 
the control room where the position of the stop is shown by an 
indicator and a red signal lamp. 

Connected to the end of the turbine spindle is the automatic 
stop governor. This stop consists of an eccentric weight held in 
place by a spring. When the turbine speed reaches a predeter- 
mined point this weight flies out, causing the disengagement of 
the catch on the lever indicated, allowing a steam valve to open 
and releasing the pressure from under the piston of the automatic 
stop cylinders, one of which is shown connected to the main 
throttle valve and the other of which is shown connected to the 
automatic stop valve. These two stop cylinders are supplied 
with steam from a small pipe connection from the main steam 
line, so that, when the automatic stop governor trips, the pressure 
underneath the piston is reduced, causing the pistons to move 
downward their full amount. The automatic stop cylinder and 
automatic stop valve cause the oil pressure to build up in the top 
of the operating cylinder of the inlet valve and to exhaust from the 
bottom, thus causing the inlet valve to close. At the same time 
the cylinder on the main throttle valve releases the catch con- 



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200 ELECTRIC SHIP PROPULSION 

nected to the handwheel operated lever, allowing the spring on 
the main throttle valve to force this valve shut. The throttle 
valve cannot be opened again until the turbine has slowed down 
sufficiently for the automatic stop valve lever to be again caught on 
the trigger and the handwheel has been revolved to the closed 
position, re-engaging the catch on the main throttle valve. 

The main turbine shaft glands, as stated above, are supplied 
with both steam and water, the steam being taken from the main 
steam line through a reducing valve and used at a pressure of 
about 5 pounds gage. The water is taken from the feed line 
between the feed pump and the feed water heater. This water 
connection is provided with a plug which has a J^ inch orifice, thus 
limiting the amount of water which can be used by the gland 
system. This water supply to the glands is kept at the proper 
pressure by means of a relief valve set at 7}^ pounds, the excess 
water passing through the relief valve back to the feed tank. 

The valve for shifting from "steam" to "water" on the glands 
is operated by a small governor driven through gearing from the 
main turbine spindle. This govfimor is adjusted to operate at 
between ys ■ and j4 full speed. Below this speed the weights 
are in the "in" position and the steam relay plunger or piston 
valve is in its top position. This allows steam to exhaust from 
under the piston shown on the gland control valve; since the 
upper part of this cylinder in which this piston operates is sup- 
plied with high pressure steam, the piston will drop, allowing the 
steam to pass, as indicated, through the reducing valve to the 
glands. When the governor speed reaches the predetermined 
amount, the governor moves toward the outer position and the 
steam relay piston to the lower position. This cuts off the escape 
of steam from under the gland control valve piston; the valve 
then rises its full amount, shutting off the opening into the gland 
steam line and, at the same time, admitting water from the high 
pressure line, referred to above, to the glands. An indicator on 
this gland control valve shows whether it is in the water or steam 
position. This gland control valve is fitted with a by-pass around 
it on both the steam and the water lines, so that it is possible to 
supply steam or water to the glands by hand in case it is desired to 
disconnect this valve for cleaning or inspection. 

A spring is fitted on the top of the governor controlled inlet 



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TENNESSEE. COLORADO AND WASHINGTON 201 
valve, connected through the lever to the operating cylinder. This 
spring tends to close the valve so that in order to hold it off its 
seat, the pressure in the bottom of the operating cylinder will 
have to be a few pounds higher than that in the top. A pipe con- 
nects the oil pipe of the operating cylinder to a similar cylinder 
on the auxiliary exhaust by-pass valve, so that, when the ttiain 
governor controlled inlet valve is open, the pressure underneath 
the piston of the operating cylinder, being connected to the top of 
the operating piston of the auxiliary exhaust by-pass valve, will 
hold this valve shut since the closing pressure will be greater than 
the opening pressure. When, due to a speeding up of the main 
turbine, the governor causes the governor controlled inlet valve to 
shut, the pressure in the top of its operating cylinder will become 
greater than that in the bottom, which, in turn, will cause the 
pressure in the bottom of the auxiliary exhaust by-pass valve 
cylinder to be greater than that on top, thus opening the by-pass 
valve as desired. This by-pass valve may also be opened at any 
time by hand but it cannot be held shut, if the piston tends to 
open it- 

Main Generator 

A cross section of the main generator is shown in Fig. 105. 
The generator rotor is shown in Fig. 106. The method of wind- 
ing the generator stator is shown in Fig. 107 and the complete 
stator is shown in Fig. 108. 

The main generator is two pole, three phase. The speed, 
rating, etc., are the same as for the sister ships, California and 
class. 

The maximum designed voltage is 3,400. 

Rotor: The turbo generator is generally in accordance with 
standard construction. The generator rotor is of the radial slot 
type. The rotor is a solid forging of low chrome nickel steel. 
The body of the rotor and shaft are forged in one piece. The 
rotor coils are held in the slots by brass wedges. The end con- 
nections are supported against centrifugal force by forged steel 
rings. 

Stator: The stator core is built of laminations of electric 
sheet steel annealed and varnished. Paper is placed at intervals 
in the core to further break up eddy currents. The stampings 



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TENNESSEE, COLORADO AND WASHINGTON 203 
Bill of Material for Main Generator Shown in Fig. 105 

t Fut 

HunB of Put Ko. Nam* Of F*Tt 

ring Around Frame 
enno Couple Conn 



Fingfr Plate 
EaS Plate 
Brush Holder 



ouple C 

„.- . .-mbly and Shaft 

''ield Coil Betaining Ring 

{otating End Plate 

:o11ector 

^ield Co ill 

lotatini Part Assembly 

tough turned Shaft 



have rectangular punchings through which the air is circulated for 
cooling. The laminations are assembled in a cast iron frame of 
sufficient section to insure ample rigidity and also of ample 
strength to care for short circuits. The laminations are clamped 
between cast iron end plates properly cored to allow of proper air 
circulation. 

Insulation: The insulation of the rotor body is a mica trough, 
made of plate mica. The insulation between turns consists of 



flexible mica between thin paper and treated asbestos. The upper 
turns of the coil are wrapped with half-lapped mica tape to insure 
against grounding by creepage. The upper insulation in the slot 
consists of flat pieces of mica. The insulation on the ends of the 
coil is the same between turns as in the rotor body ; the coils are 
individually wrapped with half-lapped, asbestos tape, treated with 
varnish and baked. 



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204 ELECTRIC SHIP PROPULSION 



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TENNESSEE, COLORADO AND WASHINGTON 205 

The stator coils are placed in open slots and are secured in 
position by means of fibre wedges. The insulation on the indi- 
vidual parts of the stator coil consists of half-lapped mica tape 
around each strand of the conductor, this tape being for the pur- 
pose of breaking up eddy currents. The coil has but one turn, 
so that insulation between turns, other than that needed to prevent 
grounding, is unnecessary. After the strands were taped, the 
straight part was dipped in bakelite and then put into a form and 
hot pressed. The entire coil was then impregnated in a special 



Fig. 109. — U. S. S. Tennessee: Rotor of Main Motor 

gum for the purpose of excluding air pockets and adding to the 
strength of the coil. The straight part was then insulated with 
mica folium, which, after being wrapped around the coil, was 
ironed in a machine made especially for the purpose. This 
should give a coil which is extremely solid in the slot part and 
one that will withstand high temperatures, since most of the 
insulation is mica. The ends of the coil are wrapped with a 
sufficient number of layers of treated tape to insure against 
breakdown. Varnish was used to fill the pores of the tape after 
each layer was wrapped. The final coil ends were wrapped with 



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206 ELECTRIC SHIP PROPULSION 

tape and treated with varnish. The coil ends are rigidly sup- 
ported in the manner shown in Fig. 107. 

Venlilation: The ventilating fans are secured to each end of 
the rotor for creating a pressure of air in the end beils, this 
pressure being sufficient to drive the required amount of air 
through the axial ventilating slots to the center opening through 
which the air escapes. It will be noted that this differs from the 
California where the ventilating slots were radial. 



Fig. ho. — U. S. S. Tennessee: Method of Winding Main Motor Stator 

Bearings: The bearings are similar to those used on the 
turbine and are lubricated from the forced lubricating oil system. 



Main Motors 

The revolutions per minute and rating of the main motors are 
the same as those of the California. They are three phase and 
the stators are wound for both 24 poles and 36 poles, the two 
windings being entirely independent of each other. The rotors 



,y Cookie 



TEl^NESSEE, COLORADO AND WASHINGTON 207 
are of the definite wound type and the rotor windings are arranged 
as shown in Fig. 27 and described in Chapter IV. 

The motor rotor is shown in Fig. 109. The method of wind- 
ing the stator is shown in Fig. 110 and the complete motor, with 
ventilating ducts and fans, is shown in Fig. 111. 

Frame: The stator frame is cast steel with circular and 



Fic. III. — U. S. S. Tennessee: Main Motor Complete 

cross ribs to obtain proper stiffness. The cross ribs of the frame 
are dovetailed for supporting the laminations. The outer part 
of the frame is covered with sheet metal for the purpose of 
directing the flow of the air recjuired for ventilation. The frame 
has brackets at either end for supporting the bearings ; the open- 
ings in the brackets are covered with mesh doors. 



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208 ELECTRIC SHIP PROPULSION 

For the purpose of maintaining the motor at the proper tem- 
perature, when not in operation, so as to prevent sweating, heating 
elements for connection to the 240 voh direct current circuits are 
located between the laminations and the outer sheet metal lagging. 

Brackets: The brackets for supporting the rotor bearings are 
of cast steel, machined to fit the frame without depending upon 
dowel bolts for maintaining the proper position of the bracket. 
Jack screws are provided to facilitate the removal of the bracket 
from the frame. The brackets are fastened to the frame by 
means of tap bolts. The center of the bracket is open and drilled 
for bolts for supporting the bearing housing. ' Provision is made, 
by means of eight jack screws, for adjusting the position of the 
bearing housing after the motor has been assembled. When the 
housing is in the correct position the ring of bolts will be tightened 
and the jack screws can then be backed off, if desired. Cross 
arms are provided on the brackets at the collector end of the 
motor for carrying the rotor and stator connections. 

Bearings: The bearing housing is of cast steel, split and 
arranged so that the parts may be moved axially for the removal of 
the bearing shells. The bearing shells are of cast iron with 
spherical seats and split horizontally. The shells are lined with 
babbit. Eye bolts are provided so that the weight of the bear- 
ii^ and housing may be taken off the shaft when it is desired to 
remove the bearing. The bearings are lubricated by oil brought 
in through the bottom of the spherical seat, then passing through 
a copper tube to the top of the shaft. Oil slingers are provided 
on the shaft to prevent creepage of oil and proper drain passages 
are provided to carry the oil to the overflow. Oil rings are also 
provided so as to make the motor independent of the forced 
lubrication system in an emergency. 

Rotor: The rotor spider is of cast steel pressed and keyed on 
the shaft. The cross arms of the spider are dovetailed to carry 
the secondary laminations. The spider carries the coil supports 
which are bolted to it by tap bolts. Two fans are provided at 
cither end to assist the ventilation of the motor. 

Collector: The collector is mounted on the shaft. The rings 
are of bronze bolted separately to the supporting ring.. The 
collector rings are insulated from the rest of the machine with 
micarta bushings, giving ample creepage space, and after assembly 



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TENNESSEE, COLORADO AND WASHINGTON 209 

were impregnated with varnish to fill up crevices where dirt or 
moisture might collect. The rotor connections are bolted to the 
inner periphery of the rings. 

Brush Gear: The brush arms are supported by a ring bolted 
to the brackets. The arms are insulated from the ring by micarta. 
Provision is made for placing of barriers between the collector 
rings, if this should be found desirable. 

Stator Punckings: The stator punchings are of the s^- 
mental type, dovetailed into the frame. They are arranged for 
axial ventilation, the air entering at both ends of the motor. The 
punchings are held between finger and end plates, the latter being 
fastened with tap bolts and through bolts. 

Rotor Punckings: The rotor has segmental punchings dove- 
tailed into the spider and arranged for axial ventilation with a 
central opening for the exit of air. The end plates are bolted to 
the spider. 

Windings: There are two independent windings in the stator, 
one for each set of poles. One set of slots accommodates both 
of these windings, there being two coil sides of each set of coils 
placed in the slot, one directly above the other. 

The rotor has a three phase, two parallel, star conn ected 
winding with balancer connections suitable for operation on the 
24-pole winding. This winding has already been described in 
detail in Chapter IV. 

Insulation: Bpth sets of the stator coils are of the diamond 
formed type and are completely insulated before being placed in 
the slots. A single 36-pole formed coil is composed of a sii^le 
strap, taped overall with one layer of cotton tape, overlapped on 
the coil ends but not overlapped on the straight portions which he 
in the slot. The 24-pole formed coil differs from the 36-pole 
coil in that it is composed of four single conductors wound in 
parallel with the individual conductors insulated with mica tape 
to reduce the eddy currents in the copper. The four conductors 
are taped together with cotton tape from end to end, the tape 
overlapping only on the coil ends, similar to the 36-pole coil 
described above. 

The rotor coils are of the diamond type and consist of two 
straps connected in parallel after being placed in the slots. Each 
strap is completely formed and insulated before assembly in the 



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210 ELECTRIC SHIP PROPULSION 

machine. The rcECson for insulating these straps separately is to 
permit the use of partially closed slots in the rotor and at the 
same time retain all of the advantages of being able to insulate 
■ the formed coils outside of the machine. 

The remainder of the description pertaining to the insulation 
of the coils of these motors is general and applies to the coils of 
both rotor and stator unless otherwise stated. 

The straight parts of the coils imbedded in the core are sub- 
jected to the highest temperature of the motor and require the 
best kind of insulation from the heat resisting standpoint. Con- 
sequently, the imbedded portions of the coil are wrapped with 
several thicknesses of mica folium, reinforced with extra heavy 
mica plate, which extends all around the coil. This covering is 
first applied loosely by hand and the coil is then placed in a special 
machine equipped with electrically heated bars, which revolve 
under spring pressure, around the wrapper. This softens the 
bond and permits the wrapper under the pressure of the bars to 
slide on itself, resulting in an extremely solid and compact insu- 
lation. The coil is then placed in a cold press and pressed to the 
required dimensions. The covering tapers down to the strap a 
good safe distance away from where the end plates will come, in 
order to insure a good connection between the insulation of the 
straight parts of the coils and the insulation of the coil ends. 

The coil ends are surrounded by air and do not require as high 
a heat resisting insulation as the straight part of the coils. They 
are covered by a number of layers of bias treated tape; this has 
great flexibility which permits it to adjust itself to a snug fit at 
all bends and corners of the strap. The fabric is of close texture, 
giving considerable mechanical strength to withstand the stresses 
set up in the coil ends due to abrupt changes of load on the motor. 
It is thoroughly impregnated with insulating varnish before being 
applied to the coils. An additional coating of insulating varnish 
is applied after each wrapping in order to seal the joints between 
the half overlapping tape. This tape is joined to the insulation of 
the straight parts of the coils with a specially prepared cement. 

The last covering for the coil ends consists of one layer of 
overlapped cotton tape. Micarta strips are placed on the sides o£ 
the coil ends under the cotton tape to serve as spacers between 
adjacent coils after assembly. This outside covering is thoroughly 



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TENNESSEE, COLORADO AND WASHINGTON 211 

filled by means of several successive treatments of insulating 
varnish, each-coating being baked on for a long period with the 
final result that the coil ends possess a coating impervious to 
moisture and capable of withstanding salt deposits and foreign 
particles of dirt which may eventually find their way into the 
motor through the ventilating system. 

All of the insulation, except where the cross connections join, 
having been put on the coils, is again placed in molds and pressed. 

The part of the coil which spans the ventilating duct in the 
center of the core is armored with a copper sheet as an extra 
protection against erosion. 

The slots are lined with a very tough paraffined fish paper cell 
to protect the insulation of the formed coil from injury in the 
assembling operations. This cell laps over the top of the last coil 
under the micarta wedges which are driven in from the ends of 
the slots. The individual formed coils are separated from each 
other by micarta spacers, any additional space in the slot being 
filled in with mica plate leaving no room for coil movement. 

The figure of eight connectors joining the coil ends are insu- 
lated with several alternate layers of drilling and bias treated tape. 
The last covering is overlapped cotton tape treated in the same 
manner as the last layer of cotton tape on the coil ends. 

The cross connections and balancer connections are insulated 
with the same material as the coil ends. In addition they are 
spaced from each other and protected from the cleats by micarta 
spacers. 

The stator coil supports are insulated in the same manner as 
the coil ends. The rotor coil supports are covered with several 
layers of drilling, each layer being held in place by one layer of 
cotton tape, not overlapped. Each layer of drilling and tape is 
dipped in insulating varnish and baked before the succeeding 
layer is applied. Micarta strips are held in place over the top 
layer of drilling with cotton tape. The entire support then 
receives a number of dippings and bakings. 

Each bottom stator coil is fastened by means of a heavy copper 
wire to the bottom coil support. This coil support consists of an 
insulated steel ring held in place by brttckets bolted to the frame. 
Another insulated steel ring support is placed between the. inde- 
pendent stator windings and is held in place by copper wires 



D,gmze..byCOOglC 



212 ELECTRIC SHIP PROPULSION 

which extend around the ring and the individual coil ends of both 
stator windings. Thus, it is seen that all coil extensions are 
grouped into a single mass which is rigidly supported from the 
motor frame. 

The rotor coil extensions rest upon a wide support, the insu- 
lation of which has been given previously, and are drawn down by 
extra heavy bands. This banding is separated from the coils by 
layers of treated fuller board. 

Liquid Rheostats 

The motors are reversed by insertit^ resistance in the rotor 
windings and reversing the connections of two of the phases. 
The motors are reversed on 24 poles since the rotor has an equiva- 
lent squirrel cage winding when the stator is connected for 36 
poles. The method of reversii^ these motors has been described 
in Chapter IV and the torque characteristic curves are shown in 
Fig. 10. 

The resistances consist of liquid rheostats which are located 
in the main control room and which connect to the glip rings of 
the motors. An outline of one of these rheostats is shown in 
Fig. 112. 

The rheostat consists of two tanks, one mounted above the 
other and connected together. The liquid, which consists of a 
solution of sodium carbonate, is contained in the lower tank and 
is circulated through the upper tank by the motor driven centri- 
fugal pump. The upper tank has two overflows one of which 
may be closed by the operating valve. The lower internal over- 
flow fixes the minimum level of the electrolyte in the upper tank, 
at which point all of the three long electrodes are partially im- 
mersed. This gives the point of maximum resistance in the rotor 
circuit. Each lead of the rotor is connected to the three inter- 
leaved groups of electrodes. Insulating barriers are placed 
between the three long electrodes, the tops of the barriers beit^ 
above the level of the electrolyte when the maximum resistance is 
in circuit. At this point the rheostat may have double the normal 
rotor vohage on it during reversal of the main motors; the use 
of barriers is an additional protection against flashing. In addi- 
tion the distance between the electrodes is such that the n 



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TENNESSEE, COLORADO AND WASHINGTON 213 

possible potential per unit distance is well within what has been 
found permissible by experience in similar rheostats. The fact 
that the longer electrodes are always immersed insures that the 
rotor circuit can never be opened with the consequent insulation 



Tank 



1 of Material for Liquid RheostatB Shown L 

Furt 
Hun* of Put Ho. Hu 



imblr 



Insulator Assembly 

Valve Details 

Valve Details 

Valve Operating Detail* 

Barrier 

Cooling Coils 

Emergencv Valve Detail 

Pump Vjtve 

Cover Plates 

Fittings 

Trap Do. 

Collar (it 



B. Tap Bolt 
B. Tap Bolt 





X. Nul' 




" M. B 


Motor 




f-"-i 


. Flang 


a- H 


«. I. S 


•"ii 


1." 


^el^n' 


" M. B. 


1- Bro 


g,;p^? 


k Wash 
Detiila 


Water 


«--?^. 



E ■ 



'■i.XMS'd 



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214 ELECTRIC SHIP PROPULSION 

stresses that might be thrown on the rotor, if this were done. It 
also prevents insulation stresses on the stator during switching as 
the energy stored in the stator may be dissipated in the rotor 
resistance. 

The pump runs continuously and there is always a vigorous 
circulation of the electrolyte. This effectively prevents the for- 
mation of gas bubbles on the electrodes which might cause a 
variation of the resistance by reducing the effective Area. The 
pumps for each pair of rheostats can be cross connected so that 
one pump can supply both rheostats in an ernergency. 

When the lower overflow is closed by the operation of the 
valve, the level of the electrolyte in the upper chamber rises until 
the upper fixed overflow is reached. At this point the minimum 
resistance is in circuit and the short circuiting switch for the rotor 
leads may be closed. The electrolyte continues to circulate and, 
if the short circuiting switch is not closed, there is very little 
additional loss. 

The three groups of electrodes are mounted on substantial 
insulated conductors, the leads for the three phases being brought 
up through the top of the tank for connecting to the cables. The 
top of the tank is closed and provided with a vent pipe to allow 
of the escape of any vapors from the electrolyte. The design is 
such that roHing or pitching of the ship will not materially affect 
the resistance in the rotor circuit and splashing is also prevented 
by the closed top. 

A cooling coil is fitted in each rheostat, the cooling water 
being supplied from the water service. 



Switchboards 

There is a direct current switchboard in each engine room for 
the 300-kilowatt generators and also for the motor driven auxil- 
iaries and for excitation. There is a main switchboard in the 
control room for controlling the main motors and turbo genera- 
tors. There are two direct current switchboards alongside the 
main switchboard ; these are for controlling the motor ventilating 
blowers, rheostat circulating pumps, etc. Each of these switch- 
boards and the wiring is described below. 



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TENNESSEE, COLORADO AND WASHINGTON 215 

Direct Current Wiring 

The direct current wiring is shown in Fig. 113. This arrange- 
ment is practically the same as that of the Caiifornia but there are 
some minor differences. All the auxiliaries are run ofif the 240- 
volt circuit at all times. The arrangement of the short circuiting 
switch for the booster is also slightly different but accomplishes 
the same purpose. The main field switch does not close any con- 



FiG. 114. — U, S. S. Tennessee: Generator and Auxiliary Switchboard 

tactors for the main motors since they are not provided with 
them. 

Generator and Auxiliary Switchboard 

This switchboard is shown in Fig. 114. There is one of 
these in each engine room. The connections to it are given in 
Fig. 113. The arrangement of interlocks is identical with that of 
the California. 



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i<> 



fc E9 » 



D,„t„.= b,Coo'^le 



ELECTRIC SHIP PROPULSION 



Control Room Wiring 

The control room wiring, shown in Fig. 115, includes the 
main alternating current wiring and also the direct current wiring 
for the blower motors, etc. The arrangement of the latter is 
practically identical with that of the California except that there 
are additional switches for the rheostat circulating pumps and the 
small vibrator motor used for keeping the pressure of the oil to 
the governor pulsating. 

The alternating current wiring is arranged with a separate bus 
for each main motor. All switches used in this circuit are oil 
switches. The following switches are provided : 

4 36-pofe pole changers. 

4 24-pole pole changers. 

4 ahead switches. 

4 astern switches. 

4 short circuiting switches for the rheostats. 

4 generator switches. 

2 tie switches. 

Some of these switches are provided with disconnects so that 
the entire switch can be removed from the circuit and repaired. 
Since there is a separate bus for each motor this can be done at 
any time without affecting more than one motor. The type of 
switch used is shown in Fig. 116. All the switches are similar to 
this one. 

The arrangement of levers for operating the switches is en- 
tirely different from that of the California class since a separate 
lever is provided for each set of switches instead of combining 
them; for example, the "ahead" and "astern" switches on the 
California are operated by two different throws of the same lever, 
while on the Tennessee a separate lever is provided for each. 
The following list gives the levers used in operation : 

2 36-pole pole changer levers. 
2 24-pole pole changer kvers. 
2 ahead levers. 

2 short circuiting levers. 
2 generator levers. 

2 field levers. 

2 speed control wheels. 

z rheostat valve operating levers. 



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TENNESSEE, COLORADO AND WASHINGTON\ 219 . 



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ELECTRIC SHIP PROPULSION 
1 of Material for Oil Circuit Breaker Shown in Fig. ii6 



Ho. Sua.* of Put 

I, Supporting Frame for Breili 
J. Supporlmg Frame for Due 



Vf and Moving Contact Ask 
connecting Contact Assembly 



iW' M. B. Tap Bolt 
'■■" M. B. T»p Bolt 




The following description gives the use and method of oper- 
ating each of the oil switches : 

Pole Changers. — These switches are operated in pairs — that is, 
one lever operates the pole changers for a pair of motors. There 
is one lever for each pair of 24-pole changers and another lever 
for each pair of 36-pole changers. They are made 2-pole to 
make them easy to operate. It is not necessary to make them 
3-pole as they are between the motors and the reversing switches 
and the latter have 3-poIe disconnects. 

Reversing. — These switches are operated in pairs — that is, one 
lever operates the reversing switches for a pair of motors. There 
is one lever for each pair of ahead switches and another lever for 
each pair of astern switches. They are made 2-pole to make them 
easy to operate but they are provided with 3-pole disconnects. 

The switches can be disconnected simply by lowering them by 
a lever as shown in Fig. 116. They must be open before they 
can be lowered; after they are lowered the oil tanks can be re- 
moved for overhaul. Moreover, after a switch has been lowered, 
it can be disconnected from the operating lever and the other 
switch on that lever can then be worked by itself. In order 
completely to disconnect any motor, it will be necessary to dis- 
connect (lower) both the ahead and astern switches as each has 
one phase running straight through to the motor. However, any 
motor can be disconnected by means of the generator switches, if 
both generators are running so that the tie switches are open. As 
this would always be the case in action, this is the most important 
condition. 

Generator. — These switches are operated in pairs — that is, one 
lever operates both switches for one generator and another lever 



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TENNESSEE, COLORADO AND WASHINGTON 221 

operates both switches for the other generator. They are made 
2-pole to make them easy to operate but they are provided with 
3-pole disconnects. They can be disconnected simply by lowering 
them by a lever. They must be open before they can be lowered ; 
after they are lowered, the oil tank can be removed for overhaul. 
Also, after a switch has been lowered, it can be disconnected 
from the operating lever and the other switch on that lever can 
then be worked by itself. If the tie switches are open (botii 
generators running), disconnecting one generator switch would be 
the quickest way to disconnect any particular motor; this method 
could not be used if only one generator is in use because each 
generator switch then supplies one motor direct and also another 
motor (on the other side of the ship) through a tie switch. If 
only one generator is in, the switches of the other generator 
should invariably be kept disconnected (lowered) as otherwise 
one phase of that generator will be alive due to the fact that the 
generator switches are 2-pole. 

Tie. — Both tie switches are operated by one lever. These 
switches are 3-pole; they can be disconnected simply by lowering 
them by a lever. They must be open before they can be lowered ; 
after they are lowered, the oil tanks can be removed for overhaul. 
After a switch has been lowered it can be disconnected from the 
operating lever and the other switch on that lever can then be 
worked by itself. 

Short Circuiting. — These switches are operated in pairs — that 
is, one lever operates the short circuiting switches for a pair of 
motors. They are made 2-pole to make them easy to operate and 
there is no necessity for making them 3-pole. 

All these switches arc operated in oil and are capable of 
breaking full load currents. 

In order to prevent improper operation of the switches, inter- 
locks are provided as shown in Fig. 117. The interlocks for 
each lever are as follows : 

36-POLE POLE CHANGER 

(1) Cannot be dosed unless field lever is open. (Both field 
levers when tie switch is closed.) 

This interlock prevents closing the main circuit with load on 
by dosing the pole changer. 



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ELECTRIC SHIP PROPULSION 



Fig. 117— Lever Interlocking in Control Room 
Table 1 — Sequence of Hanipulations 

TO OPERATE WITH ONLY ONE GENERATOR 



df [die 



*IVI ^.anXg- b," f " 



Set Siwed Control "Slow." 
CloK both "34 pole." 
QoM both "Alead." 
Oose "Field." 
Cloie both "Rbeo. Valves." 
"■- .liquid in both Rheoi. 



Close 



height. 



Open 
Adjui 



"Moto 



n both "Rheo 



Sec't 



To 0«t Vndar Way from BtaudMUI lod 



Adjust speed control to get the ship going 
thru the water at lEe desired tfctd 

Set Speed Control "slow." 
Open ^' Field." 
Open both "Motor Sec'd." 
Open both "34 Pole." 
Oose both "36 Pole." 
Clome ■•Fi»ld7' 



Btop from SI Pol* Bmmlug 



Open "Fit 
Open both 



I 24 Pole Bnimiii^ 



;iose "Back." • 

:!ose "Field." 

lose both "Rheo. Vilves." 

.How liquid in both Rheoa. lo reach n 

lose both "Motor Sec'd." 
ipen both "Rheo. Valtes." 

Btop fiom 38 PoU Bumlni 

Set Steam Control "slow." 

Open "Field." 

Open both ".6 Pole." 

Open "Ahead."' 

Close both "14 Pole." 

B0T«r» from 38 Polo Bunnliis 



TO OPERATE WITH BOTH GENERATORS ("Tie" open.; 






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TENNESSEE, COLORADO AND WASHINGTON 225 



Fig. 117— Lever Interlocking in Control Room 
Table II— Intecloclring Table— Tie Breaker Open 



■Ltrm 


OondltloDi Bsqalisll 

irs,.ir' °" 


Lacking AccompUahod 

fllDBMl 


Condition* KaqDlioIl 
Bvtore I.em Ota 
B> Opowd 


Motor Tiei. 


Either "Gen'r," open, 
loth "Fields" open. 
Both "Rheo. Valve." 

BoT"'Motor Sec'd." 
open. 


See other uble.) 






After Gen'r. 


Po''tr""Motor Sec'd." 
open. 


open. 


Po",?'j'Motor See'd." 


For'd. Gen't. 


'For'd. Field" open. 
Starh'd "Rheo. ValveV 

Stob'd' "Motor Sec'd." 
open. 


'For'd. Field" open. 
Starh'd. "Rheo. Valve." 

S<a?b'd" "Motor Sec'd." 
open. 


14 Pole. 


"Field" open. ^_ 


'36 Pole" open. 


"Field" open. 

"Rheo. Valves" open. 

"Motor Sec'd." open. 


36 Pole. 


"Field" open. 

"»4 Pole" open. 
"Back" open. 


itially open or if sub 
sequent ly opened. 


Same as for "14 Pole." 


Ahead. 


"Sfif ?^lSU" open 
"Moto'r Seo'd." open. 


"Back" open. 


Same as for "a4 Pole " 


Back. 


"Field" open. 

"Rheo. Valverf' open. 

"Motor Sec'd." open. 

"f6''?^i'e"''^o'p"e-n. 


"Ahead" open. 
"36 Pole" open. 


Same aa for "34 Pole." 


Field. 


"Rheo. Valves" open. 
"Motor Sec'd." open. 


... M.. .„„ ., 
-,. ™.- .... ., 

"Back" open or closed 
"Ahead" open or closed 
"Gen'r." open or closed 
"Motor Ties" open o 
closed. 


Low oil pressure .in 
Governor aystem, in- 
dicating a slow speed 
setting of turbine. 


Rheo. Valve.. 


"Field" elosed. 


1 Samea. for 'IField 


No Realrictiona. 


Motor Seo'd. 


"Field" eloKd. 
"Rheo. Valves" closed. 


No- Restrictions. 


Turbine Speed 
Control. 


No Reatrictioni. 


"Field" closed. 


No Restriction*. 



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ELECTRIC SHIP PROPULSION 

Fig. 117 — Lever Interlocking in Control Room 
Table III— Interlocldns Table— Tie Breaker Clewed 



iMa 


B> Otond 


Olotad 


OondtUoni Baqnii^d 
Bofora L«tw Can 
B* Opanad 


Motor Tiei. 


(See other table.) 


Port and Starboard In 


bsj£^j:is;^!"vX"^. 

BoX""Motor Sec'd." 
open. 


--a,-*"" 


BoX°"Motor Sec'd." 




Same u for "Motor 


Port • 34 Pole. 


isis ■■iire'^,'"vx.".^' 

Bo^r-Motor Sec-d." 
Port ■ '"36 Pole" open. 


Port * "36 Pole" open 


Same as for "Motor 


Port • 36 Poles. 


Both "Fields" open. 
Both "Kheo. Valves" 

BoT°"Molor Sec'd." 

open. 
Port* "24 Pole" open. 
Port ■ "Back" open. 


Port * "Ahead open i: 
initially open or if 
subsequently opened 


Same as for "Motor 
Ties." 


Port * Ahead. 


Both "Fields" open. 
Both "Rbeo. Vafves" 

BoX""Motor Sec'd." 

Port*"' "Back" open. 


Port - "Back- open. 


Same !»s for "Motor 


Port" Back. 


Both "Fields" open. 
Both "Rheo. Valves" 

Bo°E'" 'Motor Sec'd." 

?£r^";^''Kt;''o"^s: 


Port" "Ahead" open. 
'on • "36 Pole" open 


'T,U-'' '" """" 


'"f4r "'•' 


BoT"'Motor Sec'd." 


Both "36 Pole" open 

or closed. 
Both "34 Pole" open 

Bo'th '"Back" open or 

closed. 
Both "Ahead" open or 

^closed. "'1^ 
Ort°eV""Field"''o^: 


Low oil pressure , In 

ITcating'a ^ow speed 
setting of turbine. 


'•"a;,,".'-- 


Either "Field" closed. 


1 Sao,, as for -Field" 


No Restrictions. 


■■'■^.d.'"'" 


Either "Field" closed. 
Pott' "Rheo. Valves- 
closed. 


■ irerdi'^'W""'" 




For-d or After 


Xo Restriclioni. 


Cort-esponding "Field' 
leve? close! 


No Reslriciioni, 



■ Locking for the Staib< 



il with that for the Port Levei 



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TENNESSEE, COLORADO AND WASHINGTON 227 

(2) Cannot be closed unless astern switch is open. 

This prevents dosing the astern switch on the 36-pole condi- 
tion which would give a big rush of current since the 36-pole 
condition does not provide for rheostat connection. 

(3) Cannot be closed unless 24-pole pole changer is open. 
This prevents dosing the 24-pole and 36-pole switches at the 

same time. 

(4) Cannot be opened unless field lever is open. (Both field 
levers when tie switch is dosed.) . , 

This prevents interrupting main circuit with load on by ojieij- 
ing the pole changer, 

24-FOLE POLE CHANGER 

(1) Cannot be dosed unless field lever is open. (Both field 
levers when tie switch is dosed.) 

Same reason as for (1) of 36-pole pole changer. 

(2) Cannot be closed unless 36-pole pole changer is open. 
This prevents both pole changers being closed at the same time. 

(3) Cannot be closed unless valve lever is open. 

This insures that the motors will always be started up with 
the maximum rheostat resistance in the secondary circuit. 

(4) Cannot be dosed unless short circuiting switch is open. 
This interlock prevents having the short drcuiting switch in 

when operating. This switch would nullify the effect of the 
resistance, if it were closed. 

(5) Cannot be opened unless fidd lever is open. (Both fidd 
levers when tie switch is closed.) 

Same reason as for (4) of 36-pole pole changer. 

(6) Cannot be opened unless valve lever is open. (Both 
"valve levers when the tie switch is closed.) 

This insures that the valve lever will always have been opened 
an appreciable time before any other levers on the board are 
opened or -dosed, thus making sure that all the water in the rheo- 
stat tank will have run out, thus giving the maximum resistance 
for operating the motor. 

. (7) Cannot be opened unless short circuiting switch is open. 
(Both short circuiting switches when tie switch is closed.) 
. This interlock follows on account of the methods used for 



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228 ELECTRIC SHIP PROPULSION - 

securing the other interlocks. It does have a certain value in that 
it insures that the short circuiting switch will always be opened 
before transferring from the 24-pole condition to the 36-pole 
condition, thus getting all the levers ready to answer a signal to 
back. 

VALVE LEVER 

(1) Cannot be closed unless field lever is closed. (Either 
field lever when tie switch is closed.) 

This insures that the valve lever will not be closed until after 
field has been established, since, if the valve lever were closed first 
and field established afterward, it would amount to doing away 
with the resistance entirely as the rheostat tank would probably 
be nearly up to the maximum level by the time field would be 
established. 

SHORT CIRCUITING SWITCHES 

( 1 ) Cannot be closed unless valve lever is closed. 
(Operator should wait till rheostat tank is at its maximum 

level position before closing short circuiting switch ; gage glass on 
tank will show height of liquid.) 

This insures that the short circuiting switch will not be closed 
until the liquid is at its maximum level and consequently the 
minimum resistance, thus insuring against large rushes of current 
due to putting motor out of step with generator by suddenly 
changing the resistance of a secondary. 

(2) Cannot be closed unless field lever is closed. (Either 
field lever when tie switch is dosed.) 

ASTERN SWITCH 

(1) Cannot be dosed unless field lever is open. (Both fidd 
levers when tie switch is dosed.) 

Same reason as for (1) of 36-pole pole changer. 

(2) Cannot be closed unless ahead switch is open. 

This prevents closing ahead and astern switches at the same 
time. 

(3) Cannot be closed unless 36-pole pole changer is open. 
This prevents backing on the 36-pole connection which con- 
nection does not provide for resistance in the motor secondaries. 



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TENNESSEE. COLORADO AND WASHINGTON 229 

(4) Cannot be dosed unless valve lever is open. (Both 
valve levers when tie switch is dosed.) 

This prevents badting except when fflll resistance is in the 
motor secondaries. 

(5) Cannot be closed unless short drcuiting switch is open. 
(Both short drcuiting switches when tie switch is closed.) 

This prevents an attempt being made to back with the rheostat 
short circuited. 

(6) Cannot be opened unless field lever is open. (Both fidd 
levers when tie switch is closed.) 

Same reason as for (4) of 36-pole pole changer. 

(7) Cannot be opened unless valve lever is open. (Both 
valve levers when tie switch is closed.) 

Same reason as for (6) of 24-pole pole charter. 

(8) Cannot be opened unless short circuiting switch is open. 
(Both short circuiting switches when tie switch is dosed.) 

Same reason as for (7) of 24-pole pole changer, 

(9) Cannot be disconnected unless switch is open. (Any 
one of the four motors can be disconnected independently of the 
others.) 

This prevents the disconnection being made on a live switch. 

(10) Cannot be closed until it has again been raised. 

This prevents connection being made when the switch is alive. 

(11) Oil tank cannot be removed until switch has been 
lowered. 

AHEAD SWITCH 

(1) Cannot be dosed unless field lever is open. (Both field 
levers when tie switch is closed.) 

Same reason as for ( 1 ) of 36-pole pole changer. 

(2) Cannot be closed unless astern switch is open. 

This prevents closing ahead and astern switches at the same 
time. 

(3) Cannot be closed unless 24-pole pole changer is closed. 
This insures that in going ahead the motor will always be 

started up on the 24-pole connection; change can be made to 
36-pole connection when desired but should not be done until ship 
has picked up her speed ahead through the water. 



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'230 ELECTRIC SHIP PROPULSION 

(4) Cannot be dosed unless valve lever is open, (Both 
valve levers when tie switch is dosed.) ■ 

This insures starting up the motors with maximum resistance 
in the secondaries. 

(5) Cannot be closed unless short circuiting switch is open. 
(Both short drcuiting switches when tie switch is dosed.) 

This will prevent the short circuiting switch from being dosed 
on startif^ up and thus short circuiting the rheostat resistance. 

(6) Cannot be opened unless field lever is open. (Both fidd 
levers when tie switch is closed.) 

Same reason as for (4) of 36-pole pole changer. 

(7) Cannot be opened unless valve lever is open, (Both 
valve levers when tie switch is closed.) 

Same reason as for (6) of 24-pole pole changer. 

(8) Cannot be opened unless short circuitit^ switch is open. 
(Both short circuiting switches when tie switch is dosed.) 

Same reason as for (7) of 24-poIe pole changer. 

(9) Cannot be disconnected unless switch is open. (Any 
one of the four motors can be disconnected independently of the 
others.) 

This prevents the disconnection being made on a live switch. 

( 10) Cannot be closed until it has again been raised. 

This prevents connection being made when the switch is alive. 

(11) Oi! tank cannot be removed until switch has been 
lowered. 

CONTROL VALVE 

Turbine speed can be raised or lowered without restriction. 

FIELD LEVER AND BOOSTER RHEOSTAT 

(The same lever opens and closes the main field and raises and 
lowers the rheostat resistance of the booster field.) 

. ( 1 ) The field switch is closed with maximum voltage "across 
generator field. In closing, the lever travel reduces the buckit^ 
voltage of the booster to zero and then boosts the voltage above 
the exciting bus voltage of 240. The field switch is dosed at the 
extreme forward position of the lever travd and is brought back 
to give the desired exciting voltage. The field switch is ntit 



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TENNESSEE, COLORADO AND WASHINGTON 231 

tripfied until the lever has been brought back the whole way to 
the jopen position so that practically the entire lever travel is 
utilized for getting voltage variation, 

(2) The field lever cannot be opened (can be closed) unless 
steain is partially cut off corresponding to a predetermined oil 
pressure in the governor control system and consequently to a 
predetermined low speed of the turbine. 

(3) At the point where the field is opened the booster has! 
bucked the excitation voltage down to approximately 50 volts. 

: (4) The field jlever cannot be closed unless the valve lever' 
and the short circuiting lever are open. (Both valve levers and 
both short circuiting levers if tieswitch is closed.) 

(5) With the tie switch closed, one field lever cannot be 
dosed unless the other field lever is open. 

. I 

TIE swrrcH 

.' <1) Cannot be closed unless both field levers are open. 
;■■ This prevents closing the tie switch on a live circuit. 
' (2) Cannot be closed when both generator switches are closed. 
This prevents paralleling the two generators. , 

■ (3) Cannot be opened unless both field levers are open. ; 

This prevents opening the tie switch on a live circuit. ! 

(4) Cannot be lowered (disconnected) unless it is open. 
This prevents disconnection being made when switch is alive. I 

(5) Cannot be closed until it has again been raised. 
iThis prevents connection being made when switch is alive. 

. (6) Oil tank cannot be removed until switch has beenj 
lowered. 

GENEBATOB SWITCHES ! 

i(l) Cannot be closed when other generator switch and tiel 
switch are closed. I 

This prevents paralleling the two generators. i 

{2) Cannot be closed unless field lever is open. (Both field; 
levers when tie switch is closed.) i 

This prevents the switch from being closed when alive. 

(3)' Cannot be Opened unless field lever is open. (Both field 
levers when tie switch is closed.) I 



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TENNESSEE. COLORADO AND WASHINGTON 233 



It of Material Eor Main Switchboard Shown in Fig. ii8 



h Hun* of Put 

Panel 3' 0" High x i' 9- Wide 
Jt i«". W Bevel— Ebony Asbes- 
tos Wood^ 
Pinel 1' 0" High z a' i" Wide 
I iVi*, «" Bevel— Ebony A^e«- 

Pml 3'"o" High X a" 8H' Wide 
" '^',J*' Ebony Asbes- 



Wooi 
Panel r High x a' H" 






Long 



{ Pressure 



bony , . 
P»nel 8- High 

. 4M' F«d"w»t! 

j8o lbs. Worki 

4«- Oil Prcssu 

80 lbs. Working ^r,:»urc 

a>i* Sleun Gage a-300 lbs. aso lb! 

Working Presiure 
. 8>4" Steam Gage a-;6a Ibi. aSo Ibi 

Working Pressure 
8M- Combined Vadiinm and Pre! 

'"? lb>*^o?kin° 



8^- 






a Volts Coils. < 



kTS 



TiDO Kilowatt Gear Train 
Frequency Meter — Type SD — lao 

Volts. Marked in R. P. M. with J 

Scales. 1000-1400 for Turbine, So- 

aoo for Motor (w Poles), 60-130 

far Motor (36 Poles). 
Shaft and Turbine Speed Indicator 

and Cutout Sw. 
Time aock 
Stop Clacks 

Four Shaft Revolution Counter 
Name Plates 

Filister Head Brass Machine Screw 
Knife Switch, 73 Amperes, 350 Volt*. 

a P. D. T. 
Cap Nut 

Chamfered Washer 
Soft Rubber Washer 
Bevel Washer 
ii~ I aW' Machine Bolt 

U" 1 ■>•• lit R T.n Hnit 



Bfi" Combined Vacuum and Pres- 
sure Gage '30 Inches to 4a lbs. 
10 lbs. Working Pressure 

Ammeter — Type SM— 8 1/3 Am- 
peres. Coil c-aooo Amperes Scale 

Ammeter— Type SM — 13M 1 
Coil 0-40D0 Amperes Scale 

Voltmeter— TV pe SM— 133 
0-4000 Volt Scale 

Ammeter— Type SX— 0-400 . 
Scale 

Voltmeter— Type SX— 0-40. 



Rubbei 
Fuse 



46: 



Qeats 

t 10a R. I. F. P. Wire with 

■.T Compound 



4/. Rudder Indicator 

48. Power Factor Meier— 3 Phase— Type 

SI— 10 Amperes, 100 Volts Coils 

49. Candelabra Base Lamp Receplacle* 

CO. Candelabra Base Lamp Receptacle* 
Red Lenses 

51. Set of Candelabra Base Lamp Recep- 
tacles Red and Green Lenses 

SI. Candelabra Lamps, 8 Candlepowcr, 
140 Volta 



Name Plate Designations 



Tint Una 
For'd A. C. Gen. 
After A. C. Gen. 



Starboard 
Aux. Bus 

Bl^er No, i 
Blower No. a 
Rbeo. Pumps 
Blower No. i 
Blower No. a 



After Eng. Room 



Outb'd Motor 
Inb'd Motor 



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234 ELECTRIC SHIP PROPULSION 

Gage & Electrical Inatniment— "Dial MarkdngB" — Starb'd Side 



10. FonoriJ Feed Syalcm i7- Motor a Inb'd Slarb'd 
It. Forward Oil Supplr to GoTemor iS. For'd A. C. Generator 

11. Forward Forced Lubrication Oil Sup- 19, For'd A. C. Generator 

p[7 10. For'd A. C. Gen. Field 

la. Forward Mam Turbine Ste«ni CheM »i. For'd A. C. Gen. Field 



_ __ u C. Gen 

I*. Forward Main Turbine. Firrt Stage aj. Motor t Outb'd Starb'd 

Inlet I]. Motor 1 Inb'd Starb'd 

ij. Forward Main Condenier 14- For'd Turbine Motor, i6 Pole, 14 

16. Forward Main Turbine Aux. Ex- Pole 

hauai 4S. For'd A. C. Gen. 

i>. Motor 1 Outb'd Slarb'd 

Gage ft Electrical Inatniment— "Dial Markings" — Port Side 

lUml Rami 

ID. After Feed STStem 17. Motor 3 Inb'd Port 

It. After Oil Supply to Governor iB- Aft A. C. Generator 

11. After Forced Lubrication Oil Sup- 19. Aft A. C. Generator 

ply =0. Aft A. C. Gen. Field 

■ 1. After Main Turbine Steam Cheat 31. Aft A. C. Gen. Field 

13. Port Main Steam m. Aft A. C. Gen. 

14. After Main Turbine, Firat Stage In- aj. Motor 4 Outb'd Port 

let aj. Motor j Inb'd Port 

15. After Main Condenser 34. Afl Turbine Motor. jS Pale, 34 Pole 

16. After Main Turbine 48. Aft A. C. Gen. 

17. Motor 4 Outb'd Pact 

This prevents the switch from being opened when alive. 

(4) Cannot be lowered (disconnected) unless it is open. 

. This prevents the disconnection being made when the switch is 
alive. 

(5) Cannot be closed until it has again been raised. 

This prevents connection being made when the switch is alive. 

(6) Oil tank cannot be removed until switch has been 
lowered. 

' Main Switchboard and Control Room IJirect Cubbent 
Switchboards 
The direct current switchboards for the control room and the 
instrument panels for the main switchboard are shown in Fig, 
118. The connections to these boards are given in Fig. 115, The 
assembled main switchboard and operating levers are shown in 
Fig. 1 19. A cross section of the control room is shown in Fig. 
120. This shows the relative position of the main switchboard, 
operating levers and water cooled rheostats. 

Operation of the Machinery 
The following tabular list of operations gives all possible con- 
ditions of perfonnance : 



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TENNESSEE, COLORADO AND WASHINGTON 23S 




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236 ELECTRIC SHIP PROPULSION 

Condition i. — Starting up — Either one or two turbo gen- 
erators, 

(If starting up with one turbo generator, the tie switch will be 
closed ; if starting up with two turbo generators, the tie switches 
^ill be open. Either one or both sets of generator switches will 
be closed depending on whether one or two turbo generators are 
io be used; if only one generator is used, the switches of the other 
generator should be opened and lowered so as entirely to discon- 
ilect that generator.) 

(a) See that all levers, including main field, are open. 

(b) Move speed wheel to slow speed. 

' (c) Start turbine from engine room by throttle and as soon 
as governor has taken control of the turbine open throttle wide, 
' (d) Put on field. 

(e) Bring turbine up to full speed and then to over-speed, 
trying out the emergency trip. 

(/) As soon as turbine speed has dropped, set speed wheel to 
slow speed. 

(g) Open throttle. 

(A) Take off field. 

(i) Close 24-poIe levers. 

The turbine is now ready for operation. 

Cotidition s. — To go ahead. 

(Assume all operations under Condition i to have been per- 
formed.) 

(a) Close ahead lever. 

(b) Close field lever. 

(c) Close valve lever. 

(rf) Close short circuiting lever when the water in the rheo- 
stat has risen to the maximum level in the tank, 
(e) Bring up to desired speed. 
(/) Open valve lever. 

Condition 3. — To change from 24 to 36 poles. 
(This will be done only after the ship has picked up speed by 
going ahead on the 24-pole connection.) 
(a) Set speed wheel for slow speed. 
(&) Open field lever, 
(c) Open short circuiting lever. 



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TENNESSEE, COLORADO AND WASHINGTON 237 

(d) Open 24-poie lever. 

(e) Close 36-po1e lever, 
(/) Close field lever, 
(gf) Adjust speed. 

Condition 4. — To back (when going ahead on 36-pole con- 
nection) . 

(The same conditions will apply when going ahead on the 
24-pole condition, except that it will then be unnecessary to change 
the pole levers.) 



(«) 


Set speed wheel for slow speed. 






(6) 


Open field lever. 






(0 


Open 36-pole lever. 






w 


Open ahead lever. 






(.') 


Close 24-pole lever. 






(/) 


Close astern lever. 






(») 


Close field lever. 






(*) 


Close valve lever. 






(••) 


Close short circuiting lever when 


liquid in 


rheostat has 


risen to 


maximum level. 






(;■) 


Bring up to desired speed.- 






(*) 


Open valve lever. 






Condition 5. — To go ahead after having 


been backing. 


(») 


Set speed wheel for slow speed. 






(6) 


Open field. 






(0 


Open short circuiting lever. 






(d) 


Open astern lever. 






(«) 


Oose ahead lever. 






(ft 


Close field. 






(9) 


Close valve lever. 






(*) 


Close short circuiting lever when 


liquid in 


rheostat has 



risen to maximum level. 

(») Bring up to desired speed, 
(y) Open valve lever. 
Condition 6. — To stop. 

WHEN OPERATING ON 24 POLES 

(a) Set speed wheel for slow speed. 
(6) Open field lever. 



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238 ELECTRIC SHIP PROPULSION 

(c) Open short circuiting lever, 

(d) Open ahead iever. (This leaves ship in position to go 
either ahead or astern with minimum number of levers to be 
operated.) 

WHEN OPERATING ON 36 POLES 

(o) Set speed wheel for slow speed. 
(6) Open field lever. 

(c) Open 36-pole lever, 

(d) Open ahead lever. 

(e) Close 24-pole lever. (This leaves the ship ready to go 
ahead or astern by closing the minimum number of levers.) 

Note: The 36-pole condition on the motors should never be 
established until after the ship is going ahead tkrough the water 
at the desired speed ; otherwise, a large rush of current might fol- 
low an attempt to change from the 24-pole condition to the 36-pole 
condition. For example, if the ship had been backing until she 
had acquired a speed astern of, say, 10 or 12 knots, and she was 
then started ahead on the 24-pole condition and an attempt was 
then made to shift to the 36-pole condition without waiting for 
the ship to pick up speed ahead, a large rush of current would 
follow, due to the fact that the motors would drop out of step 
during the act of changing from the 24-pole condition to the 
36-pole condition. 

The ahead lever can not be closed until after the 24-pole lever 
has been closed. The ahead connection on 36 poles can not, 
therefore, be established until the 24-pole lever has been closed 
and then opened. This insures that the ship will always be 
started on the 24-pole connection — that is, on the rheostats. 



Digmze. by Google 



CHAPTER XIV 
United States Battle Cruisers and Battle^ps Nos. 49-54 

THE horsepower for these vessels is so much greater than 
that for previous battleships, being 180,000 shaft horse- 
power for the battle cruisers and nearly 60,000 shaft horse- 
power for battleships Nos. 49-54, that it is necessary to modify 
somewhat the methods used for control. 

: In the case of battleships Nos. 49-54, the number of main 
generators, the number of main motors and the general arrange- 
ment of machinery are the same as for previous battleships. 
There are, however, no motor driven auxiliaries in the engine 
rooms. 

The most important change from previous methods which has 
been made in these battleships is the substitution of power operated 
for hand operated switches in the main control room. This was 
done because the switches will be so large that it will be impossible 
to operate them by hand with the desired rapidity. Hand opera- 
tion will, of course, be provided for emergency use ; but the system 
of power operation provided will make these ships easier to handle 
under normal conditions than the older battleships, as all control 
levers will be very small and easy to move. The actual movement 
of a switch will also be faster than when moved by hand. 

The system used will be an electro pneumatic one; control 
valves will be moved by electric solenoids and the valves will 
control the admission of air to a cylinder which will operate the 
desired switch or switches. This system makes it very necessary 
that the supply of both electricity and air for control purposes be 
made very reliable. There will be three sources of supply of 
electricity, one from each engine room and one from a storage 
battery located in the main control room. There will also be three 
sources of supply of air, one from the steam driven compressors 
in the engine rpoms, one from the main supplied by the ship's 



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240 ELECTRIC SHIP PROPULSION 

service compressors located in the compressor rooms, and one from 
motor driven compressors located in the main control room. 

In the case of the battle cruisers, the number of units is twice 
what it is in the battleships. There are four main generators, 
two in each engine room, and eight main motors, two on each 
shaft. 

Since there are two motors on each shaft, it is possible to 
concatenate them instead of providing them with pole changing 
to obtain the two speed reductions desired, and this method has 
been used by the Westinghouse Company in the ships which it is 
supplying; the General Electric Company uses pole changing. 

In order to be able to use one, two or four generators, or three 
generators in an emergency, the "set up" switching is more com- 
plicated than in the case of the battleships where two generator 
disconnecting switches and a bus tie switch are sufficient for this 
purpose. 

Fig. 121 shows the arrangement of "set up" switching neces- 
sary on the battle cruisers and also gives a list of the various 
combinations that can be made. Normally the ship will be run 
by one, two or four generators. If one generator is used, it will 
run all four shafts. If two generators are used, one will run 
the starboard shafts and the other the port shafts. If four gen- 
erators are used, each will run one shaft. In this way the load 
will always be the same on all generators. Three generators 
make an awkward combination as it would be necessary to have 
one of them run a shaft on each side of the ship, in order to keep 
the power on both sides the same, and this generator would have 
to run at a different speed from the others and would be differ- 
ently loaded. This combination would only be used in case of 
emergency where it was desirable to make as much speed as 
possible with one generator broken down. 

By referring to Fig. 121, it will be seen that there are eleven 
combinations of generators that can be made besides those possible 
with three generators. In addition to the generator combinations 
it will be possible to use either of the two motors on each shaft 
up to a speed of 25 knots except where concatenation is used and 
in that case the choice of motors will be between 19 and 25 knots. 

Ip will readily be seen that it is necessary to provide some 
means of showing visually to the operator just what the effect of 



Digmze. by Google 



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D,„t,..= b:, Google 



242 ELECTRIC SHIP PROPULSION 

any combination of switches will be, and this will be done by 
providing a small diagram with indicating lights which will be 
controlled by the position of the switches. In addition, interlocks 
will be provided so that it will be impossible to make improper 
combinations, such as paralleling generators. This combination 
of switches has nothing to do with the operation of the machinery 
after the proper "set up" has been made. The control of the 
machinery will be practically as simple as in the case of the 
battleships. 

The control system of the battle cruisers for operating switches 
is practically the same as that for battleships 4p-54 — that is, 
electro pneumatic. 



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CHAPTER XV 
The Wulsty Castle 

THE IVuhty Castle is a 10-knot cargo vessel of the Chamber's 
Castle Line. She has a cargo capacity of about 6,000 tons. 
Her length between perpendiculars is 356 feet 3 inches, 
beam 48 feet 9 inches, and load draft 24 feet. 

The machinery of the Wulsty Castle may be taken as typical 
of the Ljungstrom system of electric propulsion as applied to low 
powered cargo vessels. The machinery consists of : 

2 625-kilowatt turbo generators, 
a 785 -horsepower induction motors. 

1 main switchboard. 

2 liquid rheostats. 

2 auxiliary switchboards. 
Motor dnven auxiliaries. 

General Description 

With this system of propulsion, the turbo generators are run 
at constant speed and variations in speed are accomplished by 
means of liquid rheostats in the secondaries of the main motors. 
This method of speed control is suitable only for a ship that does 
not require changes of speed, and in reality provides only for 
maneuvering around docks, etc., since it is uneconomical to reduce 
the speed of an induction motor by inserting resistance in its 
secondary. However, this method of control is satisfactory for 
this type of ship and it is not in any way a necessary part of the 
Ljungstrom system which could be adapted to variable frequency, 
ij desired. 

The ship has only a single screw with both main motors geared 
to the propeller shaft. The two generators are run in parallel to 
supply the motors ; this can readily be done since the generators 
are always run at constant speed. If variable frequency were 
used, it would be necessary to have each generator supply its own 
motor on a separate propeller shaft. 



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244 ELECTRIC SHIP PROPULSION 

Main Turbines 

The main turbine is of the radial flow type, consisting of two 
disks carrying concentric intermeshing rings of reaction blading. 
The two disks revolve in opposite directions and each one carries 
an alternator on its shaft ; each turbine is in reality two turbines. 
It will be seen that this type of turbine is really only suitable for 
driving electric generators, since it is only in that way that the 
energy developed by the two wheels can be combined; the two 
generators are permanently paralleled and act as if they were 
only one machine. An arrangement of mechanical gears can be 
worked out for this turbine, but it is very complicated. The use 
of the electric generator is the ideal way of extracting energy from 
this machine and electric propulsion really makes it possible to use 
it for marine purposes. 

Since the two disks of this turbine revolve in opposite direc- 
tions the virtual blade speed is twice the- actual blade speed. 
Moreover, since the turbine, is of the radial flow type, with the 
steam expanding from the center of the turbine outward to its 
periphery, the condition is ideal for taking care of the rapidly 
increasing voltmie of steam as it expands. These two points make 
this turbine very interesting and, while it is at the present time 
only in its infancy, it offers great possibilities in the way of 
improvement in economy and reduction in weight and space. The 
construction of this turbine, however, offers many difficulties and 
brings up problems not met with in other turbines. The manu- 
facturers claim to have overcome all these and the o^ration of 
the M joiner and the tVulsty Castle has demonstrated "that this is 
true for small turbines at least. Owing to the comparative new- 
ness of this turbine a description of its details will be given. 

Blading. — The turbine consists of two turbine disks with a 
number of concentrically arranged blade rings fixed on each disk. 
The blade rings of one disk run between the blade rings of the 
other disk at the same speed of revolution but in the opposite 
direction. The live steam enters at the center of the turbine and 
passes through the blade rings radially outward. Although there 
are no fixed blades, the blades of one disk act as guide blades for 
the steam going to the blades of the other. It is seen that the 
relative velocity between blades and guide blades is twice as high 



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THE WULSTV CASTLE 



245 



as would be the case if one set were stationary and therefore 
the work done in each blade ring is four times as' great. Conse- 
quently, due to the moving guide blades, only one-fourth the 
number of blade rings will be required to develop the work ordi- 
narily obtained from the steam. This accounts for some of the 
saving in weight and space claimed. 

The steam enters at the center of each turbine disk (disks are 




practically identical) inside of the innermost blade ring through 
a number of holes in the body of the disk as shown in Fig. 122. 
As the steam increases in volume by expansion the length of 
the turbine blades must be proportioned to meet this increase in 
volume. The cross section of a pair of turbine disks with blade 
rings' showing this blade proportioning would appear as shown 
in Fig. 123. 



ly Google — 



246 



ELECTRIC SHIP PROPULSION 



In turbines of large powers requiring very large quantities of 
steam, single blades in the wide rings would not have sufficient 
tensile strength to withstand the stresses set up by the centiifugal 
force at high speeds of rotation. In order to get around this 
difficulty the widest blade rings are divided into ^sections as shown 
in Fig. 124. Something like Fig, 125 would result in large tur- 
bines if full length blades were used. In Fig. 124 the sections 
are connected to strengthening rings which are attached to the 
outer edges of the blade rings. 

The manufacturers feature their design and workmanship of 
blade rings and blades. Fig. 126 shows the complete blade ring 




Fic I33.—Wulsty 
Castle: Turbine 
Blade Ring Show- 
ing Proportioning 
to Meet Increase 
in Steam Volume 



Fig. 124.— IVulsty Castle: 
Method of Dividing Blade 
Rings to Provide Sufficient 
Blade Strength for Tur- 
bines of Large Power 



Fia i2S.—Wulsty Castle: 
Type of Blade which would 
be Required in High Power 
Turbines where Full Length 
Blades are Used 



system for a 1,000-kilowatt turbine. It will be observed that this 
has the continuous full length blades. 

The method of assembling blades and rings is shown by 
Fig. 127. The nomenclature is as follows: 

Turbine disk i 

Seating rin^ 2 

Calking stni; 3 

Expansion ring 4 

Rolling ridges S and 6 

' ■ Tightening strips 7 

Calking strips 8 

Strengthening rings 9 

Dovetail profile 10 ' 

. Turbine blades 11 

The ends of the blades are given the proper shape to fit into 
punched slots and are then welded to the disk by spot welding. 



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THE WVLSTY CASTLE 




Fig. 126. — WuUiy Castle: Complete Blade 
Ring System with Disks and Journals for a 
i.ooo Kilowatt Turbine 



S and 6. P^l/ing Rldgtt 



Tightining Sfr/pi 
Sfrthgfiitning S, 



Fio. 127.— tf(*/jiy Castle: Section showing Blade 
lUi^s and Strengthening; Rings 



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248 ELECTRIC SHIP PROPULSION 

During the welding the disks are held on a mandrel and the 
blades are kept in their proper positions by means of thin sheet 
iron strips in which are punched hdles of the same cross section 
as the blades and at a distance corresponding to the pitch and 
spacing of the blades. These strips are put in place at the time 
of assembling the blades and rings, the angles of the blades are 
thus adjusted and the blades prevented from being thrown out 
of place during welding. When the welding is completed the 
sheet iron strips are cut away and the welding disks turned down 
to a finish of the profile shown by 10 in Fig. 127. Outside these 
welding rings strengthening rings are fastened. The strengthen- 
ing rings are first given a cross section shape as shown by 12 of 
Fig. 128, then the projecting edges (6) are rolled down to fit over 



Fig. 128.— H'ufi/jp Cas- 
tle: Method of Assem- 
bling Blade Rings 

the dovetailed rim of the welding ring. The expansion ring is 
also secured by rolling down the edges (5) on the outer side 
of the strengthening ring. The seating ring (2) edges are like- 
wise rolled down over the outer bulbed circular ridge of the 
expansion ring. Finally the tightening strips (7) are placed in 
the grooves and calked in by the calking strips and the blade 
ring is completely assembled as shown by Fig. 127. The surfaces 
(9) and the outer edges (7) of the tightening strips are finished 
off and the blade rings inserted into their proper grooves in the 
turbine disk and secured there by the calking strips (3), 

Turbine Disks. — Fig. 122 shows a turbine disk made in several 
sections. It is made in the latter way to avoid the stresses and 
alterations in shape due to the influence of the varying and ir- 
regularly distributed steam temperatures and pressures. This 
occurs most frequently when startir^ up. It is when steam is 
first admitted to the turbine that variations in pressure, tempera- 



Digmze. by Google 



THE WULSTY CASTLE 249 

ture and load are most likdy to occur. Even under uniform 
running there would be high pressure, high temperature steam 
in contact with the center of the disk, while at the circumference 
or outer blades the steam would be at low pressure and lower 
temperature. Under such conditions a plane disk would take a 
dished shape. A very thick disk which would not dish would be 
subjected to internal stresses which would be liable to crack the 
material. The sections shown in the disk of Fig. 122 are joined 
by means of expansion rings (see 1, Fig, 122), which allow for 



any expansion or contraction and prevent stresses from taking 
place in the material. 

In each hub of each turbine disk are a number of holes for 
admitting steam to the blades (see 2, Fig. 122) ; some holes are 
also arranged farther out on the disk to allow full pressure steam 
to be admitted to the blades which ordinarily use expanded steam 
(see 3, Fig, 122). This is for full power or overload work and 
corresponds to the usual practice of by-passing the high pressure 
turbine. 

The center hole of the turbine disk is tapering and the hub 
is secured to the shaft by means of a number of ro'und keys, 
which are held in place by a locking device screwing into the end 
of the shaft. 



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250 ELECTRIC SHIP PROPULSION 

■ In order to avoid play between the hub and the shaft due to 
unequal heating, the shaft is made hollow inside the casing; this 
serves to make the changes in temperature in shaft and hub follow 
one another rapidly. 

Axial Thrust. — The counteracting of the axial pressure on the 
inner side of the turbine wheel is accomplished by the aid of two 
dummy disks provided with concentric labyrinth packings. One 
disk is placed at the back of the turbine wheel and the other 
attached to the stationary steam chests as shown by A and B in 



Fig. 130.— Wulsty Castle: Eji- 
larged Details at Labyrinth 
Packing of a Dummy Disk 

Fig. 129. Steam is admitted between the dummy disks from the 
center of the turbine arid the inner labyrinth packings have the 
full steam pressure. In the remainder of the packings the pres- 
sure gradually drops as the distance of the packings from the 
center increases until finally, outside the outermost, it drops to 
condenser pressure. 

The packings are divided into two sections as shown in F^. 
129. Any axial motion of the rotating wheel affects the clearances 
in these sections, so that a motion increasing the passages in the 
outer section will not be increasing them in the inner section, and 
vice versa. ' This causes the labyrinth disk on the turbine wheel 
to take the position (axially) required for making the steam 
pressure ou the ^tire dummy disk to equal the steam pressure 



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THE WVLSTY CASTLE 



251 



on the side of the turbine disk to which the blade rii^s are 
tastened- Therefore no thrust bearings are used. 

In Fig. 130 the labyrinth disks (3 and 4) are fastened to 
the turbine wheel and the steam chests by means of expansion 
rings shown in Fig, 129. The tightening strips (7) are calked 
into the annular projections (8) which fit into grooves (9). 
Due to the proportions of the metal in the two labyrinth disks. 




Fig. 131.— Wvlsty Castle: Cross Sec- 
tion of Two Labyrinth Rings of Shaft 

the expansion is expected to remain constant and consequently 
cause no chaise in the clearances. 

Shaft Packings. — Another design of labyrinth packing is used 
to prevent air from getting into the turbine around the shaft. 
Fig, 131 shows the cross section of two labyrinth rings. Every 
other ring is fixed to the shaft. Those not fixed to the shaft are 
secured to the stationary stuffing box around the shaft. The 



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252 ELECTRIC SHIP PROPULSION 

rit^s are held by feathers which prevent them from turning. The 
packing edges of the rings are very thin and are set at an angle 
of 45 degrees; if by accident these edges come in contact with the 
ribs of the next ring, there will be no damage done, the edge 
merely wearing off until contact ceases. 

The thickness of all the rings is the same ; therefore the clear- 



FiG. i32.-^Wulsly Cattle: Cross Section of Main Bearii^s 

ances between ribs is expected to be constant, either hot or cold, 
as the expansion and contraction will remain constant in each. 
The clearances are therefore made very small and consequently 
the leakage is expected to be very small. There are special pipes 
fitted to the packing boxes so that leaking steam may be sent to 
the feed water heater and some of its heat utilized. 

Mtnn Bearings. — ^A cross-section of the bearing with its adjust- 



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THE WULSTY CASTLE 



253 



ing screws is shown by Fig. 132. The bearing consists of two 
halves (6) and (7) with bearing boxes. The halves rest against 
adjusting screws through intermediary washers (8). The adjust- 
ing screws are locked by means of set screws (9) and locking 
washers (10). There are twelve holes in the washer and only 




Fig. 133. — WuUty Castle: Longitudinal Section of 1,000 Kilowatt Turbine 

eleven in the bearing surface on which it rests. This allows for 
very accurate adjustment of bearing without too fine a threading 
of adjusting screws. 

The bolts (4) which hold the upper and lower halves of the 
bearing boxes together are tapered and fit accurately in reamed 
holes, thus at the same time serving as securing dowels for the 



Digmze. by Google 



254 ELECTRIC SHIP PROPULSION 

cap. After the bearing boxes are adjusted, which is usually done 
during erection of the turbine in the shop, they will keep that 
position accurately and never need to be changed. 

To prevent the bearing from slipping axially and from being 
turned by friction, another adjusting screw (21) is used. It has 
a spherical end which fits into a corresponding recess in the upper 
half of the bearing. The spherical end is made eccentrically to 
the axis of the adjusting screw and therefore the bearing can be 
shifted axially by turning the screw, which is afterward locked by 
a washer and set screw in the same way the main adjustit^ screws 
are locked. 

The two halves of the bearing are fastened together by the 
screws (13), which have their relative position fixed permanently 
by the dowel pins (14) and (15). The anti-friction metal is put 
into the bearing halves in the usual manner. 

Steam Intel and Discharge. — The high pressure steam enters 
through the steam inlet passage of the turbine casii^, this passage 
being located within the steam discharge passage. The inlet 
passage branches off here into two pipes B^ and Bj (Fig. 133), 
which join steel pipes h, and b^ and communicate with the cham- 
bers of the steam chests in the turbine casing. From here the 
steam is admitted through the hubs to the center of the turbine 
wheels. 

By means of overload valves, the stems of which are accessible 
outside of the turbine casing, steam can be admitted when desired 
into the overload channels. The overload valves are constructed 
to act automatically when conditions necessitate. The exhaust 
steam passes from the outermost blade ring throi^h the annular 
space between it and the turbine casing and through the discharge 
passage into the condenser below. 

Lubricalion. — The lubrication is by means of the usual rotary 
gear oil pump driven off the vertical governor shaft by worm 
gearing. The pump is mounted in the oil tank together with an 
oil cooler and a hand oil pump. 

Governor. — ^The governor is a centrifugal one mounted on the 
same vertical shaft as the oil pump. As mentioned above, this 
shaft is worm driven from the turbine shaft. The motion of the 
governor sleeve is transmitted to a throttling governor valve by 
means of an oil relay. 



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THE WULSTY CASTLE 255 

An emergency governor is fitted to each of the main shafts 
of the turbine outside the bearing boxes. It acts by means of 
a releasing device or trigger on a slide valve, which cuts off the 
oil pressure from the oil cylinder of the governor valve, should 
the speed become excessive. 

WuLSTV Castle's Turbines 
Steam is supplied to these turbines at a pressure of about 220 
pounds per square inch (gage) and a temperature of about 
550 degrees F., which represents about 150 degrees F. of super- 



heat. The turbines run at a speed of 3,600 revolutions per minute 
and are each rated at 625 kilowatts. Each turbine has 39 blade 
rings of which 20 are mounted on one disk and 19 on the other. 
The external diameter is 28 inches, the overall length 17>^ inches, 
and the weight 448 pounds. 

Generators 
Each turbine has two generators which are commonly referred 
to as one generator since they are permanently connected in paral- 
lel and have their fields in series; they will be referred to from 
now on as one unit. 



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256 ELECTRIC SHIP PROPULSION 

The generators are 2-pole, 60-cycle, 3-phase, 650-voIt, delta- 
connected machines rated at 625 kilowatts each. One of the 
generators is shown in Fig. 134. 

Ventilating fans are attached to the generator rotor for supply- 
ing the necessary air for cooling the generator windings; the 
exhaust from the generators is led to the fireroom where it sup- 
plies a Howden's forced draft system under the boilers at a 
pressure of about -^ inch of water. 

Excitation for the fields is furnished by direct current genera- 
tors mounted on the turbine shafts; provision is also made for 



Fig. 135. — Wulsly Castle: Rolors of Main Induction Motors' 

exciting either or both generators from the ship's 20-kilowatt 
generating set. 

Main Motors 

There are two main motors geared to the same propeller shaft. 
They are of the definite wound rotor type of induction motor, 
each rated at 785 horsepower, and have a speed of about 714 
revolutions per minute at full power. They are 10-pole and have 
an efficiency of about 95 percent and a power factor of about 
87.5 percent at full power. 

The bearings are of the spherical type and are arranged for 
forced lubrication. 

Ventilation is provided by fans mounted on the rotor spider. 



Digmze. by Google 



THE WULSTY CASTLE 257 

The motors are shown in Figs, 135 and 136. The collector 
rings for connecting the secondary winding to the liquid rheostats 
and also the lever for short circuiting the secondary winding are 
shown in Fig. 135. 

The gears for connecting the motors to the propeller shaft are 
shown hi Fig. 137. The reduction ratio is 9.4 to 1, giving about 
76 revolutions per minute of the propeller at full power. 

The thrust block is of the Michel (pivoted, segmental) type 
and is incorporated in the gear case. 

Two gear driven oil pumps are mounted on the ends of the 



Fia i3lS.—Wulsty Cattle: Main Motors in Course of Erection 

pinion shafts and they supply forced lubrication for the motor 
bearings, gear bearings and thrust bearii^. 

Switchboard and Wiring 

The switchboard is equipped with an oil switch for each 
generator and for each motor so that either generator or either 
motor can be cut out, if desired. There is also an oil switch for 
reversing the motors. There is also a maneuvering wheel for 
controlling the reversing switch, the liquid rheostats and the 
exciter fields. 

Interlocks prevent closing the main motor switches, unless the 
maneuvering wheel is in the stop position, and also prevent closing 



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258 ELECTRIC SHIP PROPULSION 

the motor short circuiting switches, unless the maneuvering wheel 
is in either the full ahead or full astern position. 

An ammeter is provided for each generator, a voltmeter is pro- 
vided for the common bus and a voltmeter is provided for each 
exciter. 

The wiring, switches, etc., are shown in Fig. 138. The' reverse 
current relay between the generators shown in this figure was 
originally installed on the ship but has since been removed. 



Fig 137. — Wulsty Castle: Reduction Gearing with Cover Removed 
Liquid Rheostats 

There are two of these rheostats, one for each main motor. 
One of them is shown in Fig. 139. As will be seen, it consists 
of electrodes of cone shaped nickel castings dipping into an electro- 
lyte of K O H. Two 1J4 horsepower motors circulate this liquid 
through coolers. 

When the maneuvering wheel is in the stop position, the tips 
of the cones are raised clear of the liquid, thus breaking the 
secondary circuits of the motors. 

Operation 

The two turbo generators are run in parallel. They are first 
brought up to speed and synchronized and then connected to the 
bus. 



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THE WULSTY CASTLE 



259 



The turbines are never throttled for the purpose of reducing 
the speed of the ship; this is always done by manipulating the 
liquid rheostats in the secondaries of the motors. 

Reversal is effected by reversing two piiases of the main motor 
circuits and at the same time inserting the resistance into the 
secondaries of the motors. 



.:..S^ 




II ^ 



ML 



^.&.AIitrnaferOffSwiteh TC OilSwitdi.TripUil E.V. EiahrW/mtUr 

M.S, MamMcterSmtel, D.T. 7rt»jfi™wftr«f«™fi.or k.k. AINrnafor Ammtfir 

^SLOixrai,yC«lfyrSw:tch B.L.£ampi(P/Ml<fM,li»,Jas i.i.a.e,al,rfkkilkgiJah«- 



n..^ Liquid Ptfer Starf, 



ii.t^ VperaftngCvl for 5w 

^a.ecamy&ikhiK^mirhdt^m^ Bisistanit m liiririt " 

r,.T.ii<moT/5»ij<™*- art^,^ iN. Bus Bar Velimthr X.'^'li^rBfiag Walt'^tftr 

Fig. 138.— Ifu/jJy Castle: Diagrammatic Sketch of Electrical Connections 



Digmze. by Google 



260 ELECTRIC SHIP PROPULSION 

Referring to Fig. 138, it will be observed that the first motion 
of the maneuvering wheel from the stop position in either direc- 
tion closes the reversing switch for ahead or astern running as 
the case may be. The necessary direct current for operating 
the automatic reversing switch, it will be seen, is supplied, through 



Fig. 139. — IVulsty Caslle: Variable Liquid Resistance for Controller 

a change-over switch, from either exciter. Further motion of 
the wheel (o) cuts out the operating coil of the reversing switch 
and closes the economy coil circuit, (d) lowers the tips of the 
cones into the electrolyte and starts up the main motors, (e) ad- 
justs the shunt regulators of the exciters to meet the changing 
load conditions, (d) locks the main motor switches to prevent them 
being reclosed should they open with an overload, and finally (e) 



Digmze. by Google 



THE WULSTY CASTLE 261 

in the full speed position unlocks the main motor short circuiting 
hand lever. The speed, then, varies as the angle through which 
the wheel has been turned from the stop position, 120 degrees 
representing full speed. From about IS revolutions per minute 
any speed can be obtained up to 76 ; a special locking arrangement 
enables the wheel to be clamped in any desired position. A suit- 
ably adjusted counterbalance weight allows the wheel to be turned 
freely. The time required to reverse the propeller from full speed 
ahead to full speed astern, or vice versa, is merely the time required 
to .turn the wheel from one extreme position to the other and is 
approximately 10 seconds. 

Considerable difficulty was at first experienced in bringing the 
motors up near enough to synchronous speed to enable them to be 
safely short circuited. To surmount this difficulty, a hand op- 
erated, non-inductive, grid type buffer resistance can be placed 
in parallel and operated in conjunction with the liquid controller 
when short circuiting the rotor windings. 

Auxiliaries 
Practically all of the auxiliary machinery in this plant is motor 
driven, three-phase squirrel cage motors of substantial construc- 
tion being .used. Two small switchboards, for the control of these 
motors, are mounted on the after engine room bulkhead. Most 
of these motors are not equipped with starting devices and are 
therefore usually run up with the generators, in preference to 
switching them directly across full line voltage. Two 17-horse- 
power motors drive the main circulating pumps for the condensers 
at 1,730 revolutions per minute, while two 14-horsepower motors 
operate the combined kinetic air and condensate- pumps at the 
same speed. The 20-horsepower boiler feed pump motor runs 
at 3,515 revolutions per minute and is equipped with a star-delta 
starting device. Two small motors, of 1>4 horsepower each, cir- 
culate the electrolyte of the main motor controllers and run at 
1,100 revolutions per minute. A 33-horsepower motor, speed 
1,720 revolutions per minute and fitted with an auto-starter, drives 
the ship's lighting dynamo while at sea, and a 700 revolutions per 
minute 12-horsepower motor, fitted with a star-delta starter, 
operates the ship's steering gear. This last motor normally runs 
light and is loaded only when the steering wheel on the bridge is 



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262 ELECTRIC SHIP PROPULSION 

moved, this movement being transmitted to the steering compart- 
ment by means of telemotor gear. 

GENERAL PARTICULARS OF SIX HOUR, FULL POWER 

TRIAL WITH SHIP MOORED AT QUAY, SUNDERLAND, 

ENGLAND 







Wednesday, 


July 3. 1918. 








Revi. per min. 




Port turbine 








flk 


Time 






p-tn. 


Turbine 


Pro- 
peUer 










Amperei 




STi. 


||S g 












PrMsure 


iSfi 


1.30 


Synchronized both turbines 


2.0 


3,600 




660 








28.9 


3.0 


3,600 


?5 




700 


190 


S82 


28.S 


4.0 


3,600 




650 


700 




578 


28.g 


S 


3,550 


75 


630 






%1 


As 


3,550 


74 






200 










650 


650 




S89 


28.9 




3.525 


75 


630 


630 


195 


588 


28.9 


9-30 


Shut down 


Aver- 














ages 


3,568 


74-5 


644 


670 


195 579 


289 





Starboard turbine 




KUowatti 






Am- 
peres 


Before valve 


Vacuum 

Kenoto- 
mcter 




Time 


of 
sea 
4» 


Port 


Star- 
board 






Pres- 


Temp, 


Total 



1.30 












2.0 


600 


190 


560 


28.7 


■■^ 


6g6 






3-0 




190 


590 






^ 






4-0 




210 


590 


28.7 


58 


S 


1776 


S-o 






S80 


28.7 


S8 


645 






700 




574 












7.0 






^ 


2fi.7 


■^8 


646 


665 








195 


5«5 


28.7 


^ 




652 


1,253 


9-30 


Shut down 


Averages 


648 1 199 1 580 I aa? 


58 


653 


628 


■•- 



D„;t,..= b:, Google 



THE WULSTY CASTLE 



Power used by auxiliaries as measured on trial: 

Two circulating pumps 274 kilowatts 

Two air or kinetic pumps 27-0 

One boiler feed pump 15.2 " 

Electrical steering gear 6.2 " 

lighting circuits 4.2 " 

Total for auxiliaries 80.0 kilowatts 



Less energy absorbed in motors of 95 per- 
cent efficiency 60.0 kilowatts 

Less energy absorbed in gearing of 98 per- 
cent efficiency 24.0 " 



Balance or net power on propeller shaft 1,117 kilowatts 

1,117 kilowatti = 1,117 -T- 0.746 = 1,496 shaft horsepower. 



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CHAPTER Xyi , , . "[ 

Diesel Electric Drive 

THIS method of propulsion has been very littlfe'used tlfi'to 
the present, having been confined to yachts and other small 
vessels. It is now being proposed for larger vessels and 
it is quite probable that there will shortly be some installations 
made in cargo vessels. , ^. 

The point at which the dividing line occurs between the Diesel 
electric drive and turbo electric drive was fixed at 3,000 shaft 
horsepower in Chapter I, but this point will really depend on the 
size in which reliable Diesel engines can be buJlt. There is no 
doubt but what the adoption of electric drive in connection with 
Diesel engines will give a great impetus to the development of 
the marine Diesel engine, since it will no longer be subject to the 
handicaps which are imposed on it when it is connected directly to 
the propeller. The most important of these handicaps are the 
limitations on the revolutions, the necessity for reversal and the 
necessity for starting under load, all of which are done away with 
by the use of electricity. 

With the Diesel electric drive, as with the turbo electric drive, 
the first point to be decided will be whether to use alternating or 
direct current. In Chapter II it was decided that alternating 
current was more suitable for the turbo electric drive, but it will 
now be shown that the reverse is true for the Diesel electric drive. 

From the point of view of maneuvering, direct current has 
the advantage; speed regulation can be accomplished simply by 
varying the generator field, and reversal is also simpler. The 
switching operations would be simpler with direct current, since 
it would not be necessary to open the main circuit for reversal. 
Alternating current machinery would be about 5 percent more 
economical than direct current machinery and would be somewhat 
more reliable, since there would be no commutators on the main 
264 



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DIESEL ELECTRIC DRIVE 265 

units. However, it will usually be necessary to run several units, 
either in series or parallel, to get the required power, owing to 
the limitations as to size of the Diesel engine; this reason alone 
makes alternating current unsuitable. Alternating current gen- 
erators can not be run in series and parallel operation is not 
satisfactory for marine propulsion on account of the difficulty 
of changing speed; in this case it is complicated by the fact that 
Diesel engines themselves are really not suitable for parallel 
operation. 

The above limitations make the use of direct current and series 
operation the most suitable for Diesel electric propulsion. This 
is a very flexible arrangement and has several advantages. By 
running two or more generators in series, the difficulty of accurate 
governing with Diesel ei^nes is done away with because accurate 
governing is not necessary. Another advantage of the series 
arrangement is that, if it is desired to run at reduced speed and 
power, one generator can be cut out and the remainder run at 
normal voltage, speed and load, thus giving a very fine economy 
at reduced speeds. There are limits, of course, to the number 
of generators that can be run in series on account of the excessive 
voltage generated, but there will be no difficulty in this respect for 
vessels in Class 1 of Chapter I. 

Excitation for the generators and motors would be furnished 
by independent direct current units which would be interchange- 
able with the ship's power and lighting units. The method of 
separate excitation gives perfect control of the speed and is also 
ideal for reversal. It would not be necessary to open the main 
circuit at all during reversal ; it would only be necessary to reverse 
the generator field. In large installations it would also be neces- 
sary to insert resistance in the main circuit, but this would be short 
circuited immediately after reversal. By controlling the field 
strength of the generators, reversal could be accomplished without 
carrying excessive current in the system. Speed control of the 
propeller would be accomplished by varying the field strength of 
the motors or generators, or both. 

The normal arrangement would consist of two or more Diesel 
engine generators in series and one or two motors on the propeller 
fhaft, depending on the horsepower of the installation. The 



Digmze. by Google — 



266 ELECTRIC SHIP PROPULSION 

motors would also be arranged for series operation and one would 
be cut out, if the load were sufficiently reduced. 

For example, suppose a plant to consist of three generators 
and two motors. All would be in operation in series at full 
power. If it is desired to operate with two generators, they 
would be run at the same speed as before and each would carry 
the same volts, amperes and load as before, so that the efficiency 
of the generators and engines would be unchanged. If we assume 
the propeller load to vary as the cube of the revolutions (or speed 
of the ship), then the propeller would run at about 87 percent 
of full speed. The two motors would be run in series as before 
and would take the same current as before, but the field strength 
would be only about 77 percent of what it was before and there 
would be only a slight falling off in motor efficiency. 

If it is desired to reduce the speed still further, two generators 
would be cut out ; the third would be run as before and give the 
same efficiency as before. The propeller would run at about 70 
percent of full speed and only one motor would be used. This 
would carry full load current and approximately full field, and 
it would carry two-thirds of its normal full load, since only one 
motor is in operation. Its efficiency would be somewhat reduced, 
but, owing to the fact that the losses would be confined to one 
motor, the overall efficiency would not drop off very much. 

The speed of the ship in the three cases would be 10 knots 
{assumed), 8.7 knots and 7 knots. Here then we have a 10-knot 
ship which is capable of slowing to 7 knots with very little falling 
off in efficiency. This shows, also, how very reliable such a ship 
would be on account of the duplication of generators and motors. 

For obtaining speeds intermediate between 10 and 8.7 and 
between 8.7 and 7 and below 7 knots the field of the motors or 
generators would be changed according to the conditions of opera- 
tion, the arrangement always being such as not to require more 
than normal full field. If using three generators and two motors, 
speed would be reduced by reducing the field of the generators 
without changing that of the motors. If using two generators and 
two motors, speed could be reduced by increasing the field of the 
motors, since in this case the motors are using only 77 percent 
normal excitation. If using one generator and one motor, it 
would be necessary tp reduce the generator field to reduce the 



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DIESEL ELECTRIC DRIVE 



267 



speed, since the motor would have practically full field. These 
are the conditions that would obtain in steady running. For speed 
reduction for maneuvering purposes only, it might be simpler to 
use generator field control entirely. 

During reversal, full field would be kept on the motors and 
the field of the generators would be regulated to provide full load 
current at all times, thus giving full load torque for reversal. 
For emergency reversal it would be desirable to use more than 
full load current and this could be done for a short time, the 
current being reduced to normal as the ship loses headway. 

The Diesel electric drive has a peculiar advantage when used 
for cargo vessels on account of the flexibility of the machinery 
arrangement. It is possible to locate the generators on the upper 
deck and the motors can be placed well aft so that the cargo space 





DiCMl 

Electric 
Drive 


Triple 




1,400 

230 

-45 

403 
$0^9 

Ti 

95 


1,400 
300 

1.25 

7 
270 

95 
fi50 

■i;.oo 

3.000 




Fuel used per hour per horsepower 




Fuel used per day at sea, barrels 

Fuel used per day in port, barrels 

Lubricating oil per day at sea, gallons . . , 
Lubricating oil per day in port, gallons . , 
Lubricating oil per year, barrels 


















6.74 
1.00 

3,400 
155.832 

3,900 
13.504 








Cargo carried in deadweight tons, tons . . 


Cargo spaee (40 cubic feet per twi), tons 


2,900 

37,462 

1.125 

$62,004.12 

$150,000.00 
$150,000.00 


Water used in year for power plant, tons 
Total cost of fuel, water and lubricating 


$28^21.40 

$170,000.00 

$203,682.72 


Net profits of ship based on steam plant 

economy at $50 per deadweight ton , , , 

Total net profits, including fuel saved .... 



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D,„t,..= b:, Google 



DIESEL ELECTRIC DRIVE 269 

is almost entirely undisturbed. Fig. 140 shows an arrangement 
that has been proposed for a cargo vessel. It consists of three 
500-horsepower Diesel generators driving two motors on one 
propeller shaft. The table on page 267 is an estimate that has 
been made comparing the Diesel electric drive proposed for these 
vessels with a reciprocating engine installation. 

Over a period of a year in the operation of the vessel, taking 
the present cost of fuel and water, she would have an increased 
carrying capacity of 400 tons, and would net her. owners about 
$53,682 additional, through the saving in coal, water and weight, 
or a net gain in the commercial etiliciency of the ship of about 
35.7 percent. 



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CHAPTER XVII 
Care and Upkeep 

THE care-and upkeep of a steam electric plant on board ship 
offers certain difficulties that are not encountered in a simi- 
lar plant ashore, and for that reason the experience gained 
from the operation of the Jupiter and the New Mexico may be use- 
ful to prospective operators of similar plants. The principal 
enemies of this type of plant are salt water and heavy shocks, and 
to these may be added coal dust on ships carrying coal as a cargo. 
Salt moisture will find its way into the ventilating systems 
and salt is likely to be deposited on the end windings of generators 
and motors. These windings should be examined frequently and 
any salt found should be removed by gasoline. About once a year 
these end windings should be sprayed with varnish. The varnish 
used should be air drying ; the simplest way to apply this is to use 
a compressed air sprayer at a pressure of from 25 to 30 pounds. 
All connections on the generators, motors and switchboards 
should be examined at the end of a run and before getting under 
way to see that they are all tight. 

The interior of both generators and motors should be examined 
to see that they are not acting as condensers when idle, thus 
accumulating moisture on the windings. If heaters are provided 
and used, this should not occur. The following table gives the 
routine that has been laid out for the New Mexico and covers 
all necessary inspections and tests: 
(_A) Daily: 
(1.) Jack over main generators, main motors and auxiliary 
machinery (operating forced lubrication system while 
this is being done). 
(2.) Operate governor mechanism under oil pressure by 

movement of pilot valve, 
(3.) Examine, oil and clean governor control transmission 
mechanism. 

2^» 



Digmze. by Google 



CARE AND UPKEEP 271 

(4.) Dry out turbine by running turbine drain pumps fif- 
teen minutes. 

(5.) Inspect generators and motors for moisture (including 
ventilation ducts, air pockets under generators and fan 
housings over motors). 

(6.) Examine high toision leads and terminals for dirt and 
moisture. 

(7.) Move all generator and motor disconnecting switches. 

(8.) Move pole changing and reversing oil switches. 

(9.) Move swritches on exciter switchboard. 
(10.) Operate field control switches. 

(B) Weekly; 

(1.) Move all auxiliaries by power, • 

(2.) Operate exciters and test overspeed trips and back 
pressure relief valves. 

(3.) Operate main throttle and stage valve trips by hand 
gear. 

(4.) Make insulation test by bridge me^er of all electrical 
circuits and machines. 

(5.) Make insulation test of main generator bearing stand- 
ards to ground. 

(C) Quarterly; 

(1.) Examine stater coils of main generators and motors 
for dryness and preservation of insulating material, 
particularly for condition as regards presence of oil 
or salt or cracking of varnish. 

(2.) Take bridge gage readings of main generators and air 
gap measurements of main motors. 

(3.) Clean generators and motors by vacuum cleaner. 

(4.) Take air gap measurements of auxiliary motors and 
examine for condition of armature and field windings. 

(5.) Overhaul collector rings, brush rigging, brushes and 
commutators. 

(6.) Examine by test all bus bar securing bolts and con- 



(7.) Examine all leads and connections of instruments and 
instrument transformers. 



Digmze. by Google 



2 ELECTRIC SHIP PROPULSION 

(8.) Examine all high potential cables and their supports 

and go over all terminal connections. 
(9.) Inspect carefully high potential insulators, 
(10.) Go over contact adjustment of all main switches with 

feelers. 
(11.) Open oil switches and compensators for examination 
as to quantity and condition of oil. 

Note: 

(a) Whether carbonization has taken place. 

(i) Whether burning of contact fingers or bar has 

occurred, 
(c) Whether moisture is present. 
See: 

(a) That contacts are fitted and adjusted to make 

and break at same time. 
(fc) That contacts have even make and break over 

entire surface, 

(c) That auxiliary contacts are adjusted to take 
the arc. 

(d) That links and springs are in smooth working 
order. 

(e) That oil switch supports are secure and 
switches in alinement. 

(12.) Determine insulation resistance of high potential wind- 
ings and leads by calculation, using high resistant volt- 
meter method. 

(13.) Go over holding down bolts on generators and motors 
and staybolts in motor rotors. 

(14.) Inspect bearings and note effectiveness of oil guards 
in preventing oil entering windings. 

(15.) Check turbine shell expansion (longitudinal). 

(16.) Take turbine wheel clearance in first stage and check 
against clearance indicator. 

(17.) Remove governor casing and inspect mechanism for 
condition and adjustment. 

(ZJ) Semi-annually: 

(1.) Calibrate all electrical instruments. 
(2.) Inspect resistance grids. 



Digmze. by Google 



CARE AND UPKEEP 273 

(3.) Inspect flexible jaw coupling between turbines and 

generators. 
(4.) Overhaul self-closing throttle valves, 

(E) Annually: 

(1.) Spray with high grade insulating varnish all stator end 

connections. 
(2.) Spray auxiliary motor brush connections and field and 

armature windings, 
(3.) Remove transil oil from oil switches and compensators 

— renew or filter same. 
(4.) Lift turbine casings for wheel and diaphragm inspec- 

dpns. 
(5.) Examine shaft packing and steam seals. 

(F) After Overhaul: 

(1,) Run drying out heat run on generators and motors 
until all insulation resistances show above 5 megohms. 

(2,) Operate hand tripping gear with turbine turning over, 

(3.) Operate overspecd safety devices on main turbines, 
taking tachometer readings of speeds at which emer- 
gency trips function. 

(4.) Calibrate steam lever at no load. 

(5.) Test by hand gear spring loaded exciter exhaust valves. 

(6.) Turn over main motors by power ahead and astern. 

(G) Before Getting Underway: 

(1.) Make insulation resistance test. 

(2.) Examine switchboards and leads for cleanliness and 
for tightness of connections. 

(3.) Operate all switches, field control circuits and inter- 
lock circuits. 

(4.) Examine oil switch mechanism. 

(5.) Trip out turbine by hand gear. 

(6.) Trip out turbines by overspeed trips, operating gover- 
nor pilot valve by hand in doing so. 

(7.) Trip exciters by overspeed trips. 

(8.) Try out boosters. 

(9.) Try main motors ahead and astern. 



ly Google 



'4 ELECTRIC SHIP PROPULSION 

(H) In Operation: 

(1.) Take oU temperature readings frequently until settled 
down — then hourly. 

(2.) Take field resistance by voltmeter ammeter reading 
until constant temperature is reached, 

(3.) Take ground tests hourly on exciter switchboard cir- 
cuits. 

(4.) Read thermometers half hourly on ventilation exhaust 
outlets and r^ulate blowers for air supply accordingly. 

(5.) Adjust setting of steam limit levers at each change of 
speed. 

(6.) Inspect hourly for oil or moisture on windings- 
noting oil guards. 

(7.) Inspect ventilation ducts for moisture — in bad weather 
continuous rounds — in fair weather once each watch. 

(8.) Inspect collector rings and brushes, main generators, 
hourly. 

(9.) Read turbine clearances half hourly. 
(10.) Daily — test for stray current generator standards. 

(/) Upon Securing: 

(1.) Take insulation tests while windings are warm. 

(2.) Examine windings for dirt; oil or salt. 

(3.) Clean rotors and end windings of motors by vacuum 

cleaner. 
(4.) Examine switchboards for dirt and loose connections. 
(5.) Go over oil switch mechanism. 

(6.) If to be secured for a considerable' period, seal up 
motors after cleaning. 



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