Improvements in Electro-motors and in Apparatus for the Electric Propulsion of Tramcars, Railway Locomotives or Trains, and other Vehicles.
Year: 1897

page_text: Date of Application, 18th Feb., 1897
Complete Specification Left, 18th Nov., 1897-Accepted, 15th Jan., 1898
PROVISIONAL DIECIFICATION
Improvements in Electro-motors and in Apparatus for the Electric
Propulsion of Tramcars, Railway Locomotives or Trains, and
other Vehicles.
We, WILLIAM EDWARD AYRTON, Fellow of the Royal Society, Professor at the
City and Guilds of London Central Technical College, Exhibition Road, London,
and ARTHUR HINTON ALLEN, Electrical Engineer, of 78A Santos Road, West
Hill, Wandsworth, London, S.W., do hereby declare the nature of this invention
to be as follows:-
The object of this invention is to provide means for stopping and starting
vehicles that are propelled electrically, without necessitating the large waste of
power that usually occurs with the methods at present in use.
Our method may be used whether the current initially supplied for propelling
the vehicle be a direct or an alternating one.
In order to start a vehicle quickly the electro-motor must exert a large torque,
and, in the case of vehicles electrically propelled in parallel, this large torque is
usually produced by a large current sent along the trolley wire, or underground
conductor, as well as through resistance coils on the vehicle itself. But, as the
speed at starting is really small, the actual power required is no greater than that
necessary to drive the vehicle at full speed. Hence the arrangement at present
usually adopted for quick starting is a wasteful one.
In order to avoid this waste of energy at starting it is necessary that, while the
current supplied to the motor on the car is large, the current flowing through the
trolley wire, or underground conductor, and supplied to the vehicle, is not larger
when the vehicle is started than when it is running at considerable speed.
This result we attain by using one, or other, of the following ways to supply
alternating currents to one or more motors of the induction type which are coupled
direct, or by means of suitable gearing, to the axle, or axles, of the vehicle.
When an alternating current is sent from the generating station through the
trolley wire, or undergrond conductor, we cause this alternating current to flow
through the primary coil of an alternate current transformer on the vehicle, while
the induction motor, or motors, is attached to the secondary coil of such a trans-
former, one or other of the ordinary well-known devices being employed for split-
ting the single alternating current into two or more such currents differing in
phase, and we arrange the secondary coils of this transformer so that they can
be joined mainly in parallel for starting the vehicle, and mainly in series when
the vehicle is running.
or
Hence, while a relatively small current is received by the vehicle at the ordinary
working pressure, a much larger current is supplied to the induction motor,
motors, at a much lower pressure at starting. It is well-known that the starting
torque of an induction motor may be made much larger than the torque at full

page_text: speed for the same ecurrent by suitable design, or by inserting resistance in the
secondary circuit of the induction motor. Hence the torque at starting will be
greater than the torque at full speed, both on account of this property and because
of the large current employed, while the current supplied to the vehicle remains
at, or below, its normal value.
In the case of a direct current.being sent out from the generating station, and
received by the vehicle from the trolley wire, or underground conductor, we use
this direct current to rotate a "rotary converter" on the vehicle, which converter,
by means of two or more slip rings on the shaft, connected with fixed points on
the rotating armature, supplies one, or more, alternating currents to the induction
motor, or motors, coupled to the axle, or axles, of the vehicle. These alternating
currents being out of phase with the impressed electromotive force may have a
greater root mean square value than the direct current which is supplied to
the rotary converter, and, therefore, will give a large torque in the induction motor
while starting, without requiring an excessive current to be supplied through the
trolley wire, or underground conductor.
"6
In the case of a constant, or nearly constant, pressure supply of electrical energy
as in the usual case of vehicles propelled electrically in parallel, this rotary con-
verter may with advantage be a direct current shunt motor which will then run
at a practically constant speed whether the vehicle be at rest or in motion, and
will take power from the trolley wire, or underground conductor, in proportion to
that required to drive the vehicle. In the case of long stoppages such a rotary
converter may be stopped as well as the induction motor or motors.
Instead of employing a rotary converter we may use a direct current motor
mechanically geared to an alternator generating one, or more, alternating currents.
We vary the speed and torque of the induction motor, or motors, and, therefore,
the speed of the vehicle, either by inserting resistance into the circuit, connecting
an induction motor with the rotary converter, or into the part of the motor in which
a current is induced by the rotation of the magnetic field, or by varying the
number of pairs of poles in the induction motor, or by varying the excitation of
the field magnet of the rotary converter or the field magnet of the alternator where
a separate alternator geared to a direct current motor is used to generate the alter-
nating current, or currents.
Or instead of electrically connecting this alternator, or the alternating portion
of the rotary converter, direct with the induction motor, or motors, we sometimes
insert an alternate current transformer, and then we vary the speed and torque
of an induction motor by inserting resistance in either the primary or the secondary
circuit, or circuits, or in both of such a transformer or of the induction motor, or
we arrange the secondary circuit of the transformer in sections and employ an
arrangement for coupling different numbers of the sections in parallel and in
series as previously described.
In stopping the vehicle or in controlling its speed when descending gradients
we take advantage of the fact that when the rotating part of an induction motor
which is electrically driven by alternating currents is caused to rotate at a greater
angular speed than that of the rotating magnetic field the motor becomes a gene-
rator and causes alternating currents to flow into the generator, or rotary con-
verter, from which it previously received such currents. We, therefore, provide
means for reducing the angular speed of rotation of the magnetic field below that
of the rotating part of the induction motor, either by varying the number of pairs
of poles of the induction motor, or by causing the armature of the rotary con-
verter, or alternator, to rotate at a lower speed, so that the induction motor being
mechanically driven by the motion of the vehicle generates alternating currents
which flow into the trolley wire, or underground conductor, where an alternate
current system of supply is used; or, which are converted into continuous currents
by the rotary converter, and delivered to the trolley wire, or underground con-
ductor, in that form in the case of a direct current supply.
By this means part of the energy usually wasted in heating the brakes and

page_text: wheels of the vehicle, is returned to, the mains, thus reducing the consumption of
energy, and the wear and tear of the brakes.and wheels.
Improvements in Electro-motors and in Apparatus for the Electric
Propulsion of Tramcars, Railway Locomotives or Trains, and
other Vehicles.
1
1
We, WILLIAM EDWARD AYRTON, Professor of Applied Physics at the City and
Guilds of London Central Technical College, Exhibition Road, London, Fellow of
the Royal Society, and ARTHUR HINTON ALLEN, of 78A Santos Road, West Hill,
Wandsworth, London, S. W., Electrician, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:
The object of this invention is to provide means for stopping and starting
vehicles that are propelled electrically, without necessitating the large waste of
energy that usually occurs with the methods at present in use.
Our method may be used whether the current initially supplied for propelling
the vehicle be a direct or an alternating one.
In order to start a vehicle quickly the electro-motor must exert a large torque,
and, in the case of vehicles electrically propelled in parallel, with a constant or
nearly constant pressure of supply, this, large torque is usually produced by a
large current sent along the trolley wire, or underground conductor, from the gene-
rating station, as well as through resistance coils on the vehicle. itself. But, as
the speed at starting is really small, the actual power required is no greater than
that necessary to drive the vehicle at full speed. Hence the. arrangement .at
present usually adopted for quick starting is a wasteful one...
In order to avoid this waste of energy at starting it is necessary that while the
current supplied to the motor on the car is large, the current flowing through the
trolley wire, or underground conductor, and supplied to the vehicle, is not larger
when the vehicle is beginning to move, than when it is running at considerable
speed, other conditions remaining the same.
This result we attain by using one or other of the following ways to supply
alternating currents to one or more motors of the induction type, which are coupled
direct, or by means of suitable gearing, to the axle, or axles, of the vehicle. By
an induction motor we mean a motor which is operated by one or more alternating
currents, but which, unlike a synchronous motor, will start from rest.
(1). When an alternating current is sent from the generating station through
the trolley wire or underground conductor, we cause this alternating current, to
flow through the primary coil of an alternate current transformer on the vehicle,
while the induction motor, or motors, is attached to the secondary coil of such a
transformer, one or other of the ordinary. well-known devices being employed for
splitting this single alternating current into two or more such ourrents differing
in phase, and we arrange the secondary coils of this transformer in separate
sections so that they can be joined mainly in parallel for starting the vehicle,, and
mainly in series when the vehicle is running. Hence, while a relatively, small
current is received by the vehicle at the ordinary working pressure, a much larger
current is supplied to the induction motor, or motors, at a much lower pressure at
starting
....

page_text: It is well-known that the starting torque of an induction motor may be made
much larger than the torque at full speed for the same current by suitable design,
or by inserting resistance in that portion of it in which currents are induced.
Hence the torque at starting will be greater than the torque at full speed both on
account of this property and because of the large current or currents furnished to
the motor by the transformer, while the current supplied to the vehicle remains at
or below its normal or average value.
(2). In the case of a direct current being sent out from the generating station
and received by the vehicle from the trolley wire, or underground conductor, we
use this direct current-to-rotate-a-rotary-converter on the vehicle, which converter,
by means of two or more slip rings on the shaft, connected with fixed points on
the rotating armature, supplies one, or more, alternating currents to an induction
motor, or motors, coupled to the axle or axles of the vehicle.
In the case of a constant or nearly constant pressure supply of electrical energy,
as in the usual case of vehicles propelled electrically in parallel, this rotary con-
verter may with advantage be a direct current shunt wound motor with slip rings
as previously described, which will then run at a practically constant speed
whether the vehicle be at rest or in motion, and will take power from the trolley
wire or underground conductor in proportion to that required to drive the vehicle.
as well as the
In the case of long stoppages such a rotary converter may be stopped
induction motor or motors.
(3). Instead of employing a rotary converter we may use a direct current motor
mechanically geared to an alternator generating one or more alternating currents,
which are supplied to the induction motor or motors.
(4). Instead of electrically connecting this alternator or the alternating current
portion of the rotary converter direct with the induction motor or motors we may
insert an alternate current transformer or transformers, the primary coils of which
receive current from the alternator or rotary converter while the secondary coils
supply currents to the induction motor or motors, and then we sometimes vary
the speed and torque of an induction motor by inserting resistance either in the
primary or in the secondary circuit, or circuits, or in both, of such a transformer,
or of the induction motor; or we sometimes arrange the secondary coils of the
transformer in sections and employ a device for coupling different numbers of the
sections in parallel or in series or in parallel-series as previously described.
(5). We sometimes vary the speed and torque of the induction motor or motors,
& therefore the speed of the vehicle, either by inserting resistance in the circuit
connecting an induction motor with the rotary converter, where such is used, or
into the part of the motor winding in which a current is induced by the rotation
of the magnetic field, or by varying the number of pairs of poles in the induction
motor or by varying the excitation of the field magnet of the rotary converter or
the field magnet of the alternator where a separate alternator geared to a direct
current motor is used to generate the alternate current or currents.
(6). In stopping, the vehicle, or in controlling its speed when descending
gradients, we take advantage of the fact that when the rotating part of an induc-
tion motor which is electrically driven by alternating currents is caused to rotate
at a greater angular speed than that of the rotating magnetic field the motor
becomes a generator and causes alternating currents to flow into the generator or
rotary converter from which it previously received such currents.
We therefore provide means for reducing the angular speed of rotation of the
magnetic field below that of the rotating part of the induction motor, either by
varying the number of pairs of poles of the induction motor, or by causing the
armature of the rotary converter or alternator to rotate at a lower speed, so that the
induction motor being mechanically driven by the motion of the vehicle generates
alternating currents which flow into the trolley wire or underground conduct
where an alternate current system of supply is used; or which are converted int
continuous currents by the rotary converter and delivered to the trolley wire or
underground conductor in that form in the case of a direct current supply. By

page_text: Is means part of the energy usually wasted in heating the brakes and wheels of
the vehicle is returned to the mains, thus reducing the consumption of energy and
the wear and tear of the brakes and wheels.
(7) Some of the arrangements described in paragraphs (1), (2) & (4) for driving
an electrically propelled vehicle are illustrated in the accompanying sheet of draw-
ings, which shew the electrical connections for certain special cases.
The.
reference letters stand for similar parts in each figure.
In Fig. 1, for example, is seen an alternating current transformer ST receiving
current from the overhead trolley wire or underground conductor by the
mains MM; this transformer having subdivided secondary coils SC and supply-
ing currents to a two-phase induction motor IM which is geared to the axle of
the vehicle. The several sections of the secondary coil are here shewn joined in
parallel by the regulating switch RS, so as to give a large current at low pressure
to the winding of the stationary part SP of the induction motor; this current is
split into two components differing in phase by means of the phase-splitting devices
indicated in the figure, of which C is a condenser or condensers and IC is an
inductance coil, or by other equivalent means, so as to be suitable for starting the
induction motor with a large torque, while the primary coil of the transformer
receives only a small current from the mains.
Fig. 2. shews the same arrangement as Fig. 1., the switches however being altered
as they would be when the vehicle was running at full speed. The regulating
switch RS now connects up the sections of the secondary coil SC in series so as to
give a smaller current than before, at a higher pressure, to the induction motor.
It will be seen that the phase-splitting devices, which are not necessary when the
motor is running at a good speed, are here shortcircuited by the cut-out switches S S,
which are in practice operated by the same handle as that which actuates the regu-
lating switch RS.
In Fig. 3. is shewn the method of using a rotary converter in combination with
an induction motor for driving an electrically propelled velicle. The rotary
converter RC is drawn with a ring armature A and two pole pieces PP; but any
of the usual forms of closed coil armature may be used, with any number of pairs
of poles.
Resistance may be inserted in the circuit or circuits between the rotary converter
and the induction motor as at R, R, ог in the secondary circuit of
the induction motor, which in that case is not short-circuited as shewn in the
drawings, but wound with one or more circuits joined to collecting rings carried
on the shaft of the rotating part R P of the induction motor, or otherwise arranged
so as to permit of the insertion of resistance in the circuit or circuits.
Fig. 4. illustrates the mode of driving the vehicle with a transformer or trans-
formers TT in combination with a rotary converter RC and an induction
motor IM. The same remarks apply to the drawing of the rotary converter as
to that shewn in Fig. 3.
The drawing shews the regulating switch RS set so as to join the sections of
the secondary coil SC in parallel, as when starting the vehicle.
In each of these drawings the induction motor is shewn of the two-phase type;
but any number of phases may be used, with corresponding modifications in the
design of the rotary converter, transformers and induction motor. Further, instead
of the secondary portion of the induction motor being that which rotates, while
the primary portion is stationary, the secondary portion may be stationary and the
primary portion be that which rotates.. The direction of rotation of the revolving
part of the induction motor is controlled by means of an ordinary reversing switch,
which may be used to interchange the connections of the primary portion of the
induction motor; this is omitted from the drawings for the sake of clearness.
We would have it understood that the drawings are intended only to illustrate
particular cases of the application of our methods of electrically propelling vehicles,.
and are not to be regarded as illustrating all the methods of carrying out our device
for driving vehicles by means of an induction motor, or motors, in such a way

page_text: that when the vehicle is started the current for that vehicle passing along the over-
head trolley wire, or underground conductor, is not thereby caused to greatly
exceed the average value of the current.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed; we declare that what
we claim is: -
(1) In the case where an alternating ourrent is supplied to the vehicle, the device
for driving the vehicle by the combination of an alternate current transformer
having a secondary coil divided into separate sections with one, or more, alternate
current motors of the induction type. receiving alternating currents from the said
transformer, either directly, or after the currents have passed through a 'device,
or devices, for altering their phase-relationship, substantially as described.
r
(2) In the case. where a direct current is supplied to the vehicle, the device for
driving the vehicle by the combination of a rotary converter receiving direct
current from the external source of energy with one, or more, induction motors
receiving alternating currents from the said rotary converter, substantially as
described.
*1.300°
(3) In the case where a direct current is supplied to, the, vehicle, the device for
driving the vehicle by the combination of a direct current motor receiving direct
current from the external source of energy with an alternate current generator to
which it is mechanically geared, and with one or more induction, motors receiving
alternating currents from the said alternate current generator, substantially, as
described.
'd
(4) In the case where a direct current is supplied to the vehicle, the, device for
driving the vehicle by the combination with either of the two combinations
described in claims numbered (2) and (3) of one or more alternate current trans-
formers having their secondary coils divided into separate sections, the primary
coils of which transformers receive alternate currents from the rotary converter,
or from the alternate current generator, as the case may be, while the induction
motor or motors receive alternate currents from the secondary coils of the trans-
formers, substantially as described.
(5) In the case where direct current is supplied to the vehicle and either a
rotary converter, or a motor generator, is used together. with one or more induction
motors, the method of regulating the speed, of the induction motor by varying the
excitation of the field magnets of the rotary converter or of the alternate, current
generator as the case may be, or by varying the number of sections in series or in
parallel of the secondary coil of the transformer where such is used, substantially
as described. .
7
(6) The combination of any two or more of the combinations claimed, herein
with one another..
100M