Method of Controlling Several Rotary Phase Current Motors in an Electrical Railway Train from One Point of the Train.
Year: 1899

page_text: Date of Application, 5th May, 1899-Accepted, 10th June, 1899
COMPLETE DITUIFICATION.
Method of Controlling Several Rotary Phase Current Motors in an
Electrical Railway Train from One Point of the Train.
We, SIEMENS BROTHERS & CO. LIMITED, of 12, Queen Anne's Gate, Westminster,
in the County of London, Electrical Engineers, do hereby declare the nature of
this invention (as communicated to us from abroad by Siemens & Halske, Aktien
Gesellschaft, of Markgrafen Strasse 94, Berlin, S.W., Germany, Electrical
Engineers) and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:---
In working the trains of electrical railways by means of rotary phase currents,
considerable difficulty is experienced in controlling the electro motors, in particular
when several motor cars are employed in one train. The most usual method of,
regulation is that in which the turning moments necessary for starting, as also
the variations of speed while running, are produced by the variations of a
resistance introduced in the induced part of the motor armature. If this method
is to be applied to a train having several motor cars, there must be provided three
leads extending from each motor along the length of the train to the driver's.
platform, in order to enable him to control the whole of them, so that with a train
having four motors, at least twelve such leads would be required. This requires
complicated arrangements which necessarily affect the safety in working the line.
Similar disadvantages arise in the case of other known methods of regulation
such for example as by the change from "star" to "mesh" connection, and the.
converse, or the "cascade" connection, when these are to be used for regulating
several motors from one point in a train.
The present invention has for its object to obviate the above mentioned dis- .
advantages by means of an arrangement whereby the regulation of several rotary
phase motors is effected by simple means operating in a very reliable manner.
As is known, railway motors only require to develop a considerable turning
moment, when starting; as soon as the term of acceleration is completed, they run
with only a light load except when running up inclines. Rotary phase current
motors run, when lightly loaded, with a speed approaching synchronism, even when.
considerable resistances are included in the armature or induced part of the
motor.
As the loss of useful effect in the armature of such motors is in direct proportion.
to the slip, these resistances which are advantageously employed in producing a
considerable turning moment for starting, can be left in the circuit even after the
normal speed has been attained without producing much loss of useful effect.
The regulation of the turning moment on starting &c., is, according to the
present invention, effected by providing at the driver's platform a suitable
apparatus by means of which the voltage for working all the motors in the train
is varied according to requirement, while a resistance that is not subject to varia-
tion remains included in the induced part of the motor.
By varying the working pressure above or below that of the line network,
the magnetisation and, with this, the torque of the motors can be varied according

page_text: to the working requirements, in a similar manner to that occurring automatically
with continuous current series motors.."
As the turning moment of a rotary phase current motor is, within certain limits,
directly as the square of the working pressure, it follows that by this means it is
possible to obtain very considerable turning moments, such as are required for
starting and accelerating a train, by raising the working pressure above that of
the network pressure..
According as the pressure is raised more or less rapidly a greater or less accelera-
tion of the train will be obtained, provided that a certain resistance is included in
the armature of each motor.
When the normal speed has been attained on a level track, it will be of advantage
to lower the working pressure, possibly below the network pressure; by this
means the magnetising work in the motor is reduced and consequently its effective-]
ness will be increased as far as this is influenced by the magnetising work.
On going up inclines an increase of pressure will of course be effected, as also
on going down inclines for producing a greater braking action.
The most favourable amount of resistance to be introduced into the induced
part of the motor will have to be determined separately for each particular case,
it being necessary to take into consideration on the one hand the strength of the
starting current and on the other hand the loss of energy during the normal
running, if the resistances are not cut out of circuit when the normal speed is
attained. The resistances are preferably not arranged in the armatures, of the
motors themselves, on account of the development of heat caused thereby but are
arranged separately on the motor cars, with slip-ring contact connections.
When applied to a train of several motor cars the above method of regulation
affords the great advantage of a simple arrangement of conductors on the train,
as it suffices to connect the field circuits of all the motors to the common conductors
running along the train. In the simplest arrangement, there would only be
required three leads along the train, the rails constituting one of these.
The great simplicity of this arrangement and consequent reliability in working
offer such great advantages as compared with existing systems, that the disadvan-
tages of a somewhat greater consumption of electrical energy and a less
advantageous utilisation of the leads, as compared with existing systems, may
be left out of consideration.
We will proceed to describe the improved method of working with reference to
the accompanying diagrammatic drawings.
In Fig. 1 AA are the first two cars of a train in which the axles are driven
by the rotary phase current motors 13ª 13º 13³ B34.
In the induced parts of the motors are included the resistances D¹ 12 &c.
The field magnets of all the motors are connected to the leads a running along
the train, are the couplings of the leads. For simultaneously regulating the
pressure supplied to all the motors a pressure regulator C is employed, arranged
at the driver's platform.
For this purpose any known apparatus may be employed such as those used for
alternating currents for increasing or decreasing the pressure in certain circuits
of an alternating current system.
In Fig. 2 C shews by way of example such a pressure regulator. It constitutes
an auxiliary transformer with variable transforming ratio."
The working current passes through the secondary windings and through
the primary windings d¹² passes a shunt current, and these windings are,
by way of example, connected to the network by a star connection.
The regulation of the working pressure supplied to the motors can be effected
either as shewn at Fig. 2, by varying the number of secondary turns by means of a
step switch E, or by doing this in connection with the primary winding or by
varving the relative positions of the primary and. secondary windings.
If in the two first mentioned arrangements the working pressure is alší to be

page_text: decreased below the network pressure, it is only necessary to provide for the
reversal, for instance of the primary windings.
In Fig. 2 a reversing switch is indicated at F for changing the direction of
rotation of the motors.
The working current is taken from the line conductors c by means of the
contacts f f f which are only required on the first car; the course of the current
will be readily seen from the drawing.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:-
In electric railway trains having several motor cars with rotary phase current
motors the method of simultaneously controlling all the motors of the train from
one and the same point by means of a single set of conductors by providing at the
driver's platform an electrical pressure regulating apparatus of known construc-
tion which is included in the leads connecting the field magnet windings of all
the motors, in combination with a resistance included in the armature circuit of
each motor, substantially as described.
Dated this 5th day of Vav 1900