Improvements in Supplying Electrical Energy to Railways worked by Alternating Currents.
Year: 1897

page_text: Improvements in Supplying Electrical Energy to Railways worked
by Alternating Currents.
We, SIEMENS BROTHERS & Co. LIMITED, of 12, Queen Anne's Gate, West-
minster, S.W., in the County of London, Electrical Engineers, do hereby declare
the nature of this invention (as communicated to us from abroad by Siemens &
Halske Actien-Gesellschaft, of Markgrafenstrasse, No. 94, Berlin, Germany,
Electrical Engineers,) to be as follows:-
Electromotors worked by single or polyphase alternating currents have the
disadvantage that they only work with their maximum efficiency at a certain
normal speed, and they are consequently not well suited for propelling cars on
a line on which it is required that the cars should run at different speeds or with
a different expenditure of energy on different sections.
According to the present invention this difficulty is obviated by so arranging
the line in connection with the alternating current generators, that currents
of different frequency and pressure or of different kind can be supplied to the
motors on the cars to suit the varying conditions under which the cars are
required to be propelled.
The installations employed for this purpose can be variously arranged; thus
according to one arrangement the line is divided into a number of separate
sections, namely sections on which the cars are to travel at their maximum speed
and other sections on which they are to travel at lower speeds such as on inclines
or at stations. Generally speaking, working circuits are arranged above the line,
from which the currents are supplied to the motors on the cars, there being a
single overhead wire when the return lead is constituted by the rails, and two
wires when the return lead is also to be insulated.
The current generators are so arranged that they can supply alternating
currents, for example, of two different frequencies, the pressures being generally
also different.
Each description of current is passed through a separate conductor along the
line, one of which of course can be constituted by the working circuit. Thus
there may be two dynamos, each of which supplies a feed circuit and these feed
different sections of the working circuit, or the one dynamo may supply a con-
tinuous working circuit and the other a feed circuit leading to certain separate
sections of working circuit arranged at such parts of the line where a different
speed or expenditure of energy is required.
According to another arrangement the dynamos at the main station may be
arranged to supply only one description of current to the working circuit, and
near those sections where it is required that the cars shall run at a low speed,
such as on inclines, other current generators are provided that supply separate
sections of the working circuit at those parts.

page_text: Thus on a line that has alternate uphill and downhill sections, the descending
cars may be arranged to supply the surplus energy produced to the primary circuit
of a rotary transformer so arranged that the secondary circuit supplies currents
of lower frequency to the uphill sections where the cars have to run at a lower
speed.
According to another arrangement, those sections that require a greater
expenditure of energy, such as on uphill sections or for starting, are supplied
with rotary phase currents instead of alternating currents of lower frequency.
In such cases the installation is so arranged as to supply, in addition to the
ordinary alternating currents, also rotary phase currents, the former being
supplied directly to two working circuits while a separate circuit is provided
along the line, so that the three circuits combined supply rotary phase currents.
In this case it is only necessary to provide the alternate current motor with
an arrangement whereby it is enabled to work at one time with ordinary alter-
nating current, and at another time with rotary phase currents, such arrange-
ments being already well known in connection with ordinary rotary phaso
motors.
It will of course be necessary, in cases where the pressure at the generator
station is too high for being directly supplied to the motors, to interpose trans-
formers for modifying the pressure of the currents to suit the motors.
Dated this 23rd day of December 1897
ABEL & IMRAY,
Agents for the Applicants.
Improvements in Supplying Electrical Energy to Railways worked
by Alternating Currents.
We, SIEMENS BROTHERS & Co. LIMITED, of 12, Queen Anne's Gate, West-
minster, S.W., in the County of London, Electrical Engineers, do hereby declare
the nature of this invention (as communicated to me from abroad by Siemens &
Halske Actien Gesellschaft, of Markgrafer Strasse No. 94, Berlin, Germany,
Electrical Engineers) and in what manner the same is to be performed to be
particularly described and ascertained in and by the folowing statement:-
Electromotors worked by single or polyphase alternating currents have the
disadvantage that they only work with their maximum efficiency at a certain
normal speed, and they are consequently not well suited for propelling cars on
a line on which it is required that the cars should run at different speeds or with
a different expenditure of energy on different sections.
According to the present invention this difficulty is removed by so arranging
the line in connection with the alternating current generators, that currents
of different kind can be supplied to the motors on the cars to suit the varying con-
ditions under which the cars are required to be propelled.
It is known that polyphase motors can also work with a single phase alternating
current, in which case of course they give a correspondingly smaller useful effect.
This circumstance is utilised for the above purpose in the following manner.
Assuming a line to be supplied with polyphase currents, on starting a train
or on going up inclines, the motor is required to give off the maximum amount
of energy and consequently the motor must be arranged to give that amount of
power in such manner that the combined work of all three phases is equal to the
maximum power required.

page_text: When running on a level line or down inclines, on the other hand the several
phases are loaded to so small an extent that the entire work can be transferred
to a single phase.
According to the present invention therefore, the line conductors are so arranged
that at the starting places and on inclines that is to say, wherever a considerable
expenditure of power is required, a poly-phase system of conductors is provided,
while on the level parts of the line a single phase system of conductors is pro-
vided, so that the motor then only operates with a single phase. By this means
a simplification of the system of conductors is effected, which is of particular
importance at points and crossings.
With arrangements of this kind there is either produced at the generator
station, in addition to the ordinary single phase alternate current supply, a poly-
phase current supply, or there are provided rotary transformers at the parts of the
line requiring the polyphase current. The ordinary alternate current can then
be passed directly through the two working conductors, and at the said parts of
the line a third conductor is provided at the side of the rails, so that the three
conductors combined give polyphase currents. It is to be understood that when
the voltage at the generator station is too high to be directly supplied to the
motors, transformers can be arranged for reducing the voltage for the motors.
The accompanying diagrammatic drawings shew by way of example two
arrangements for carrying out the said invention. In the arrangement at Fig. 1
there are two current generators at the supply station, namely a single phase
alternate current generator M¹, and a polyphase current generator M².
Each of the cars a and b are provided with two current collectors; those parts
of the line on which the motor is required to give off a large amount of energy
such as at stations, inclines and curves, two overhead supply conductors are
provided and also one conductor at the level of the rails while at those parts
where less consumption of energy is required there is only provided a single over-
head supply conductor together with a conductor at the level of the rails.
The overhead current supply conductors are indicated by d and f on the
drawing.
It is assumed that the car b is situated on a part of the line requiring a large
consumption of energy, so that at this point both the current collectors of the
car are put in contact with the conductors d and f. The car a on the other hand
is supposed to be on a part of the line requiring a smaller expenditure of energy,
so that the one collector is put out of action, and the motor only receives current
from a single conductor f
This conductor is connected to both generators at the supply station, but it
receives from the generator M2 only single phase alternating current. The
conductor d is only provided in separate sections which are connected to the
generator M² by a special wire c, this being connected to the third branch of the
machine.
In the arrangement at Fig. 2 there is only a single phase generator M¹ provided
at the supply station, and on the line is provided a special rotary transformer M³ M*
which converts the single phase current into a polyphase current, this being
then supplied to the motors through the line conductors d e f and the two current
collectors at those parts where a large expenditure of energy is required.
The car on the other hand being on a part of the line requiring only a small
expenditure of energy, is only supplied with single-phase current through e f.
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 railways worked by alternating electrical currents, providing those parts of
the line requiring a small expenditure of energy with conductors adapted to
supply only single phase currents to the motors on the cars, while to those parts
of the line where a large expenditure of energy is required supply conductors are

page_text: provided which are adapted to be fed with polyphase currents either from the
main supply station or from special transformers provided at the said parts of
the line which conductors supply such polyphase currents to the motors on the
cars, substantially as described.
Dated thin 95th dow of hand 1000