Improvements in Systems of Controlling Electric Motors.
Year: 1899

page_text: Date of Application, 30th Oct., 1899-Accepted, 20th Oct.,
1900
COMPLETE SPECIFICATION.
Improvements in Systems of Controlling Electric Motors.
We, THE BRITISH THOMSON-HOUSTON COMPANY LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of our
said invention (which has been communicated to us from abroad by Alexander
S. Garfield, residing at Paris, France, Electrical Engineer) and in what manner
the same is to be performed to be particularly described and ascertained in and by
the following statement:-
The present invention relates to systems of motor control; it is particularly
adapted to those cases in which large and heavy trains are to be moved by a
plurality of motor cars which may be interspersed throughout a train with cars
provided with no motors or controlling apparatus. In addition to the motors and
controllers upon each of these cars, and in lieu of the master controller which
is sometimes employed in train systems, signalling devices are used and motormen
are stationed at the different controllers to operate them synchronously, or as
nearly so as may be desirable, so that substantially the same current and propelling
power may be utilized and exerted by each of the sets of motors. It is manifest
that it is immaterial how many of the cars there may be, and, further, that any
The character of the
desired number of motors may be employed upon each car.
signalling device is also immaterial, but preferably an automatic arrangement is
used which would indicate not only that a difference in current was present, but
the extent of the difference, so that each motorman may intelligently manipulate
his controller to bring the currents to equality and thus prevent the shocks and
jerks which would occur with motors using different currents. For this purpose
it is preferable to use a differential ammeter for each motor, with leads extending
through the train; the ammeters are so connected that when the same current is
flowing, all of these except the one connected to the first or leading car will be at
zero. Ammeters of the shunt type are used as they are manifestly best adapted
to the exercise of the invention, but other indicating devices might be used with
good results, and their use we aim to cover by the claims appended.
The accompanying drawing is a diagram showing the invention as applied to a
train of three cars. It is unnecessary to illustrate in full the different combina-
tions of circuits which would be employed between the controllers and the motors,
as these are so well understood in the art. We have therefore indicated all of the
parts diagrammatically.
In the drawing A indicates the supply conductor extending along the track, and
T, T, the travelling contacts furnishing current to the train wire T W. The well-
known third rail system is thus indicated, although of course any system involving
making travelling connection could be substituted for it, or in fact any system
whatever, so far as the present invention is concerned, which would supply current
at constant potential to a number of sets of motors.
Nothing in the invention limits it to a train control system, as for some
purposes it may be very desirable to run motors located in different places with
approximately the same current, and in this case the invention could be applied
to stationary motors; but it is manifest that its greatest utility will be in the
movement of railway trains.

page_text: In the main trolley lead for each car, is a suitable controlling device K; this is
indicated in the drawing as a rheostat, and is designed to vary the speed and
torque of the motors from zero to maximum by any approved system of regula-
tion. At R is the resistance of the ammeter. There are two coils to each
ammeter; on the first car the first coil AM is connected in shunt to the
resistance R which is in series with the motors M1, M2, between the trolley T
and ground at G. Leads L', L2 connect one of the coils in each ammeter upon
the different cars in multiple, with the resistance R. On the other cars the second
or opposing coils AM³ of. the 'ammeters are connected to coil AM of the first
indicator, a double-pole double-throw switch S being provided upon each car
by which the proper coil for the direction of motion of the train may be connected
in. Of course the coil AM¹ in each case indicates the current supplied to its
own set of motors.
The operation of the device is as follows: when the train is started, the coil AM¹
of the first differential ammeter connected in series with the first set of motors
on the left of the train indicates the current flow in them and the leads L¹, L²
connect in multiple with this ammeter coil the coils AM2 of all the others. This
will displace the needles of the ammeters on the other cars; but when current is
admitted to their motors by the manipulation of the controllers K, the needles will
gradually return to their central position until when the current in the two
coils AM, AM of each ammeter is the same, the needle will be at zero, thus
indicating that the current flow in each of the succeeding sets of motors equals
that in the leading set. Of course in the first ammeter the needle will be always
displaced sufficiently to indicate current flow.
Owing to the fact that a number of the coils of the ammeters may be connected
in multiple with the first of the resistance R, it is theoretically necessary to adjust
that resistance in order to keep the calibration of the different instruments
substantially similar, and we have therefore shown a switch KS for adjusting the
shunt resistance of the first car. In practice however this will with all ordinary
numbers of cars be unnecessary, the drop across the resistance terminals being
small and the resistance of the ammeter coils being so high that the current will
divide between them in the ordinary way, the change in the ampere turns of each
coil being inconsiderable.
Having now particularly described and ascertained the nature of our said
invention (which has been communicated to us from abroad) and in what manner
the same is to be performed, we declare that what we claim is :-
1-The combination with a number of different independently regulated motors,
of an indicating device adjacent to one motor for showing the current flow in
another.
2-The combination with a number of independently regulated motors, of an
indicator adjacent to one of the motors, and means controlled by the current in
another motor for operating the indicator.
3-In a system of motor control, the combination with a number of motors or
sets of motors and indicators near each motor or set, of regulating switches, and
means controlled by one of the regulating switches for operating all the indicators.
4 In an electric railway system, the combination of a number of cars equipped
with its own controller and motors regulated thereby, of a differential ammeter
upon each car, with some of its coils connected to indicate the current flow in the
motors upon that car, and the other coils connected to record the current flow in
other motors upon another car.
5 In an electric railway system, the combination of motors and controllers
therefor upon a number of cars, an ammeter for registering the current flow in the
leading car, and indicating devices upon the other cars in circuit with the ammeter
and responsive to its indications.
¤—The combination with a number of motor-cars, each provided with its own

page_text: controller and motors regulated thereby, of a shunt ammeter upon the leading car
of the train indicating the current flow in the motors thereof, and differential
ammeters upon the other cars of the train, each of which has some of its coils
connected in multiple to the calibrating shunt of the first named ammeter and
its other coils serving to indicate the current flow in the motors of the car upon
which they are situated.
7-In an electric railway system, the combination with a plurality of motor-
cars in a single train, of motor controllers upon said cars, an indicator upon one
of the motor cars, and means governed by the motor controller upon another car
for operating said indicator, substantially as described.
8 In an electric railway system, the combination with a plurality of motor-
cars in a single train, of motor controllers, one upon each of said motor-cars; an
indicator located near one motor controller to be within the presence of the
motorman operating the latter controller, and means governed by another of said
motor controllers for operating said indicator, substantially as described.
Dated this 25th day of October 1899.
THE BRITISH THOMSON-HOUSTON CO., LTD.
J. J. MANHEIM,
A. R. MONKS,
}
Directors.
ALFRED CLEMENTS,
Assistant Secretary.