Improvements in the Methods of Driving Electric Railway Trains.
Year: 1892

page_text: Date of Application, 11th Mar., 1892
Complete Specification Left, 30th Nov., 1892-Accepted, 21st Jan., 1893
PROVISIONAL SPECIFICATION.
Improvements in the Methods of Driving Electric Railway Trains.
I, WILFRID L. SPENCE of, The Elms, Seymour Grove, Manchester, Engineer
do hereby declare the nature of this invention to be as follows:
My improvements relate: firstly, to a method of starting, and secondly, to a
method of stopping or braking electric railway trains or locomotives.
It has been proposed to run electric railway trains on the following system.
A single conductor carrying current at a high potential is run along the track.
A. brush on the train serves to pick up this current which is then transformed,
preferably into a multiphase alternate current, by a suitable apparatus attached to
the leading carriage.
The multiphase current so produced is then conducted along the train to a number
of separate motors fixed, it may be, one to each axle.
This system, for which Letters Patent were granted to Vandepode, No. 13042
1892, combines the advantages of the high pressure continuous current on the track
with those of multiphase alternate current asynchronous motors, (having inde-
pendent closed circuited armatures), on the train.
In my improved apparatus I combine with the aforementioned transformer an
accumulator system in the shape of one or more heavy flywheels, (which may, of
course, be integral with the armature core), mounted on the rotating shaft, with
the definite purpose of relieving the supply mains of the excessive strains involved
in starting a train from rest. I accomplish this end in the following manner :-
When the train is stopped for merely a short time I allow the transformer to
continue running and only cut off the secondary current, i.e., from the motors.
Hence the transformer will revolve at a somewhat more than normal speed and the
energy absorbed will, to a large extent, be stored in the flywheel and will be given
up to the circuit when the motors are again switched on.
It will be seen that the system is thus relieved from sudden strains, the transition
from stored to directly-supplied energy being perfectly gradual. It will also be
observed that, by suitably proportioning the parts, a plain shunt excited field may
be used in the transformer.
My improvements relate, secondly, to a method of stopping electric railway
trains whereby the use of brake blocks and mechanical friction, except, of course,
between wheel and rail, are entirely abolished.
My improvement is more readily applicable to the system described above but
with slight modifications it may be adapted to any electrically driven train.
(a.) With multiphase asynchronous independent-closed-circuit-armature motors.
To stop the train I simply cut off the alternating current and send a direct
current through the magnet coils.
This produces a stationary field which, with a rotating armature of the above-
mentioned type, generates currents of great intensity whose direction is such as to
oppose the motion of the armature. By suitably regulating the strength of the
direct current I am enabled to bring the train to rest rapidly, gradually, and
without the rebound which is universal on trains fitted with mechanical brakes.
(b.) With other motors my method consists in the use of a metallic or carbon
clip which can be made to enclose and so short circuit the armature coils,
practically converting the machine, for the time being, into a brake as described
in (a).
I employ this apparatus in the following way: The driving current is first cut
off, the clip is next applied over the commutator, short-circuiting the conductors,
and current is then sent through the magnet coils alone. A generator is thus

page_text: obtained which will exert a powerful drag on the wheel axles in a direction
opposing motion.
It would be simpler to merely short circuit the brushes but sparking would then
occur to such an extent as to rapidly destroy the commutator.
I prefer to construct the clip with a flexible spring backing to which the contact
blocks are attached, and to have the backing as a broken ring either in one or two
pieces. Normally the blocks will be out of contact with the commutator bars and
will only close over them when the parts are drawn together either mechanically or
electro-magnetically from the driver's carriage.
Dated this 11th day of March 1892.
WILFRID L. SPENCE.
COMPLETE SPECIFICATION.
Improvements in the Methods of Driving Electric Railway Trains.
1, WILFRID L. SPENCE of The Elms, Seymour Grove, Manchester, Civil
Engineer 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 :-
My improvements relate firstly to a method of starting and secondly to a means
of stopping or braking electric railway trains or locomotives.
It has been proposed to operate electric railways on the following system: a
single conductor carrying a direct current at high potential is run along the track.
A. brush on the train serves to pick up this current which is then transformed,
preferably into a multiphase alternate current, by a suitable apparatus attached to
the leading carriage. The multiphase current so obtained is then conducted along
the train to a number of separate motors fixed, it may be, one on each axle. This
system combines the advantages of the high pressure direct current on the track
with those of multiphase alternating asynchronous motors on the train.
In my improved system combine with the aforementioned rotary transformer
an accumulator in the form of one or more heavy flywheels, which may, of course,
be integral with the armature core, mounted on the rotating shaft: my purpose
being to relieve the supply mains of the abnormal strains involved in starting a
train from rest. I accomplish this end in the following manner. When the train
is stopped for a short time merely I allow the transformer to continue running with
the impressed current still on, and only cut off the secondary current, i.e., from the
motors. Hence the transformer will revolve at a somewhat more than normal
speed and the energy absorbed will be accumulated in the flywheel and will be
restored to the circuit when the motors are again switched on. It will be seen that
the system is relieved from sudden strains, the transition from stored to directly
supplied energy being perfectly gradual. It will also be observed that by suitably
proportioning the parts a plain shunt excited field may be used in the transformer..
My improvements relate, secondly, to a method of stopping electric railway
trains without the use of brake-blocks. My improvement is more particularly
applicable to the system described above but with slight modifications it may be
adapted to any electrically driven train.
(a.) To stop a train fitted with asynchronous multiphase alternating closed-
circuit-armature motors I simply cut off the alternating current and send a direct
current through the field coils. This produces a stationary field, which; with a
rotating armature of the above mentioned type, generates currents of great intensity
in such a direction as to oppose the motion of the armature. By suitably regulating
the strength of the direct current I am enabled to bring the train to rest gradually,
yet rapidly, and without the rebound which is almost universal on trains fitted with
mechanical brakes.
(.) On trains driven by commutator motors. My improved method involves the
use of a metallic or carbon faced clip which can be made to enclose the commutator

page_text: and touch all the bars so short circuiting all the armature coils. This apparatus is
employed as follows: The driving current being first cut off, the clip is applied
over the commutator short circuiting the conductors, a current is then sent through
the field coils alone thus generating currents of great strength in the armature
which therefore exercises a powerful drag on the wheels in a direction opposing
motion.
I am aware that it would be a simpler plan to merely short circuit the brushes
but this would cause sparking to such an extent as to rapidly destroy the com-
mutator, by my method sparking is entirely obviated. I prefer to construct the
clip with a flexible spring backing to which the contact blocks are attached, and to
have the backing as a split ring either in one or two pieces. Normally the blocks
will be out of contact with the commutator bars and will only close over them when
the parts of the clip are drawn together. This control may be obtained either
mechanically or electro-magnetically in any suitable manner. Amongst others the
means in use at present for actuating friction clutches are applicable for the
purpose. Although not essential in all cases I prefer that the clip with the contact
blocks should rotate with and not slide over the commutator when it is in action.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :
1. In an electric railway system, similar to that first described, the combination
with the rotary transformer of one or more heavy flywheels, which may be integral
with the armature core, mounted on the rotating shaft.
2. In an electric railway system such as that referred to in the preceding claim,
the method of manipulating the motive power which consists in letting the trans-
former revolve for some little time before switching on the motors, substantially as
described.
3. In the aforementioned electric railway system the method of stopping the
train which consists in cutting off the alternating current from the motors and in
substituting therefor a direct current whose strength may be regulated to the
requirements of the case. The internally short-circuited armatures acting as the
retarding force, substantially as described.
4. In electric railway systems employing commutator motors, the method of
stopping the train which consists in cutting off the impressed current, short-
circuiting the commutator bars by means of a circular clip, which may or may not
rotate with the commutator, and re-applying a regulated current to the field coils,
substantially as described.
Dated this 28th day of November 1892.
WILFRID L. SPENCE.