Improved Means for Preventing Installations for Electrical Trans- mission of Energy, in particular Electrical Railways, from Causing Disturbances in Telephonic Circuits.
Year: 1897

page_text: Date of Application, 24th Mar., 1897
Complete Specification Left, 21st Dec., 1897-Accepted, 12th Feb., 1898
PROVIDIONAL SPECIFICATION.
Improved Means for Preventing Installations for Electrical Trans-
mission of Energy, in particular Electrical Railways, from
Causing Disturbances in Telephonic Circuits.
We, SIEMENS BROTHERS AND CO. LIMITED, of 12, Queen Anne's Gate, West-
minster, in the County of London, Electrical Engineers, do hereby declare the
nature of this invention (which has been communicated to us from abroad by
Siemens & Halske, of 94, Markgrafenstrasse, Berlin, in the German Empire,
Electrical Engineers) to be as follows:-
In installations for electrical transmission of energy that are worked by con-
tinuous currents with parallel connected motors and overhead conductors, in parti-
cular in the case of electrical railways, considerable disturbances occur in adjacent
telephone installations, owing to there being produced, from various causes, certain
alternating currents, which either penetrate directly into telephonic circuits that
are arranged parallel with the earth circuit of the motor current, or which produce,
by electrostatic or electrodynamic action, currents of varying direction in the
telephonic circuit.
According to the present invention, such disturbances in telephonic circuits are
greatly diminished by the employment of means whereby the occurrences of the
said disturbing alternating currents in the circuits of the power-transmission in-
stallations are more or less prevented.
Heretofore it was endeavoured to effect this by introducing choking coils into
the one circuit at the central station, which, however, only had a slight effect.
Our correspondents have found that the pulsating alternating currents not only
circulate between the motors and the current-generating machine, but also appear
as equalising currents between the several motors connected in parallel.
The equalizing currents are mostly purely local, that is to say, they will only pass
through the space between the separate motors, and only a small portion thereof
will pass back into the central station, they can consequently not be stopped by
choking coils at such station; this fact explains why the said arrangement has
not proved effective, in particular on long lines with a considerable number of
motor vehicles.
The present invention consists mainly in providing choking coils in all parallel
branches of the circuit, that is to say, immediately in front of each motor, or it
may be on every motor vehicle. These choking coils are windings with high
elf induction and low Ohmic resistance, and they have the property that, with a
given potential-difference between their ends, they only allow the passage of
lternating currents of small strength, while they allow of a continuous current of
onsiderable strength, or, otherwise, a passing alternating current is subject to
onsiderable loss of potential, while a continuous current is hardly subject to any
oss of potential in passing through them.
At the same time, in both cases the loss of energy is comparatively small.
It has been shewn by experiments that if with this arrangement the size of the

page_text: choking coils and the number of windings, as also the iron cores or iron casings
be suitably proportioned, the disturbances almost entirely disappear.
If there are several motors in a vehicle, it is of course sufficient to employ a
single choking coil for all the motors, as no disturbing alternating currents can
then pass into the working circuit.
W
By means of the choking coils provided at 'all the places of consumption the
current impulses of varying direction produced by the current generators are also
choked off.
་་་
If however all the current transmissions do not pass through choking coils, and
if the circuit has considerable capacity, such choking coils must also be provided
in the circuits directly at the current generators.
The above described arrangement can also be employed with advantage for
electrical railways working according to the so-called mixed system with accumu-
lators, in which the accumulators are charged from overhead conductors in districts
where these exist, while in districts where they do not exist the accumulators supply
current to the motors.
In this mode of working the pulsations caused by the motors are mostly unim-
portant with reference to telephone disturbance as compared with the pulsations
of the charging current, produced by variations in the contact resistances.
If all the current pulsations caused by the motor and the accumulators are to be
choked, off, the choking coils are placed in the common circuit of the motor and
accumulator battery. If on the other hand it is sufficient, for reducing the tele-
phone noises, to prevent the current pulsations produced by the charging currents
of the accumulators, the choking coils are only placed in the circuits of the
latter.
In this case the choking coils can be made smaller, as they need only be cal-
culated for the mean charging current.
If the prevention of the telephone noises is to be very complete, the choking
action can be increased by providing, in addition to the choking coils in the motor.
vehicles, also induction coils in each feeder to the working circuit. It is in this
case immaterial whether such choking coils are placed at the central station itself
or at the junctions of the feeders with the working circuit, which may be divided
into separate sections.
By means of these choking coils all the pulsations passing from or to the central
stations are weakened.
The weight of these choking coils, as also the dimensions of their copper and iron
parts, can be of any desired amount according to the required reduction of the
telephone noises.
The choking coils on the separate vehicles can be made smaller than in the
case where the coils on the feeders are not provided.
It will be seen that by this choking both at the central station and on the
separate vehicles a considerable reduction of the pulsations and consequently a
great diminution of the motor noises caused by the working of the line can be
effected, without excessively loading the motor vehicles by the weight of the coils
or occupying too much space thereby.
Approximately the same action will be obtained if the choking coils are intro-
duced at certain distances apart in the working circuit.
:
In this arrangement the choking coils will also be in the neighbourhood of the
places of consumption if the distances between the several coils are sufficiently
small. In this case, stronger pulsations can only occur, if two vehicles on the
same working circuit take simultaneously current from the overhead conductor
between two choking coils.
If the distances between the contiguous choking coils are sufficiently small, the
current pulsations can only occur on a small section of the line. The telephonic
disturbances will therefore also in this case be small.
With this arrangement the working circuit may either be continuous with the
choking coils arranged in series thereon, or the working circuit may be divided

page_text: into sections supplied by feeders in which are arranged the choking coils. If the
telephone circuits only extend along short sections of the line, it will suffice to
employ the above described arrangement of choking coils at such sections.
In this case the main circuit may, at such part, be arranged underground, and
feeders containing the choking coils extend up from it to the divided sections of
the part overhead working circuit near which the telephone circuit runs.
.When accumulators are carried on the motor vehicles which are supplied with
current from the over head working circuit, it is often only a question of neutra-
lising the current pulsations occurring between the accumulator batteries of the
several vehicles, which more particularly give rise to telephonic disturbances.
For effecting this, the self induction of the field magnet windings of the motor
or motors can be utilised. With series wound motors the field magnet windings
can be directly utilised for this purpose, by connecting the accumulators, either
parallel to the armature alone or parallel both to the armature and to a portion of
the field magnet windings. By the self induction of the windings thus included
in the charging circuit of the accumulators, the current pulsations will be
weakened. With shunt-wound motors the same result can be obtained by pro-
viding an auxiliary winding (compound winding) on the field magnets.
With the above arrangements the charging current of the accumulators can be
utilised for assisting in magnetising the field magnets.
Dated this 24th day of March 1897.
ABEL & IMRAY,
Agents for the Applicants.
Improved Means for Preventing Installations for Electrical Trans-
mission of Energy, in particular Electrical Railways, from
Causing Disturbances in Telephonic Circuits.
We, SIEMENS BROTHERS AND CO. LIMITED, of 12, Queen Anne's Gate, West-
minster, in the County of London, Electrical Engineers, do hereby declare the
nature of this invention (which has been communicated to us from abroad by
Siemens & Halske, of 94, Markgrafenstrasse, Berlin, in the German Empire,
Electrical Engineers) and in what manner the same is to be performed to be parti-
cularly described and ascertained in and by the following statement:-
In installations for electrical transmission of energy that are worked by con-
tinuous currents with parallel connected motors and overhead conductors, in parti-
cular in the case of electrical railways, considerable disturbances occur in adjacent
telephone installations, owing to there being produced, from various causes, certain
alternating currents, which either penetrate directly into telephonic circuits that
are arranged parallel with the earth circuit of the motor current, or which produce,
by electrostatic or electrodynamic action, currents of varying direction in the
telephonic circuit.
According to the present invention, such disturbances in telephonic circuits are
greatly diminished by the employment of means whereby the occurrences of the
said disturbing alternating currents in the circuits of the power transmission in-
stallations are more or less prevented.
Heretofore it was endeavoured to effect this by introducing choking coils into
the one circuit at the central station, which, however, only had a slight effect.
Our correspondents have found that the pulsating alternating currents not only
circulate between the motors and the current generating machine, but also appear
as equalising currents between the several motors connected in parallel:

page_text: The equalising currents are mostly purely local, that is to say, they will only pass
through the space between the separate motors, and only a small portion thereof
will pass back into the central station, they can consequently not be stopped by
choking coils at such station; this fact explains why the said arrangement has
not proved effective, in particular on long lines with a considerable number of
motor vehicles.
The present invention consists mainly in providing choking coils in all parallel
branches of the circuit, that is to say, immediately in front of each motor, or it
may be on every motor vehicle. These choking coils are windings with high
self induction and low Ohmic resistance, and they have the property that, with a
given potential difference between their ends, they only allow the passage of
alternating currents of small strength, while they allow of a continuous current of
considerable strength, or, otherwise, a passing alternating current is subject to
considerable loss of potential, while a continuous current is hardly subject to any
loss of potential in passing through them.
At the same time, in both cases the loss of energy is comparatively small.
It has been shewn by experiments that if with this arrangement the size of the
choking coils and the number of windings, as also the iron cores or iron casings
be suitably proportioned, the said disturbances almost entirely disappear.
If there are several motors in a vehicle, it is of course sufficient to employ a
single choking coil for all the motors, as no disturbing alternating currents can
then pass into the working circuit.
By means of the choking coils provided at all the places of consumption the
current impulses of varying direction produced by the current generators are also
choked off.
If, however, all the current transmissions do not pass through choking coils, and
if the circuit has considerable capacity, such choking coils must also be provided
in the circuits directly at the current generators.
The above described arrangement can also be employed with advantage for
electrical railways working according to the so-called mixed system with accumu-
lators, in which the accumulators are charged from overhead conductors in districts
where these exist, while in districts where they do not exist the accumulators supply
current to the motors.
In this mode of working the pulsations caused by the motors are mostly unin-
portant with reference to telephone disturbance as compared with the pulsations
of the charging current, produced by variations in the contact resistances.
If all the current pulsations caused by the motor and the accumulators are to be
choked off, the choking coils are placed in the common circuit of the motor and
accumulator battery. If on the other hand it is sufficient, for reducing the tele-
phone noises, to prevent the current pulsations produced by the charging currents
of the accumulators, the choking coils are only placed in the circuits of the
latter.
In this case the choking coils can be made smaller, as they need only be cal-
.culated for the mean charging current.
If the prevention of the telephone noises is to be very complete, the choking
action can be increased by providing, in addition to the choking coils in the motor
vehicles, also induction coils in each feeder to the working circuit, as shewn
at J1 J2 J3 in Figure 1 of the accompanying diagrammatic drawings. It is in
this case immaterial whether such choking coils are placed at the central station
itself (as on the drawings) or at the junctions of the feeders with the working
circuit, which may be divided into separate sections.
In Figure 1 the working circuit is, for example, divided into the sections T 1
T2 T3 which are each fed by a separate feeding line in which are inserted the
choking coils J1 J2 J3. In addition, there is in each motor car a choking
cail 1 2 3 4.
By the coils J1 J2 J3 all the pulsations entering or passing from the central
stations are weakened

page_text: The weight of these choking coils, as also the dimensions of the iron and copper
parts are optional, according to the degree to which it is desired to reduce the
telephone noises. The choking coils 12
on the cars can be of
smaller dimensions than would be required if the coils J1 J2 J3 were absent.
It will be seen that by this choking both at the central station and on the
separate vehicles a considerable reduction of the pulsations and consequently a
great diminution of the motor noises caused by the working of the line can be
effected, without excessively loading the motor vehicles by the weight of the coils
or occupying too much space thereby.
By this arrangement all current pulsations occurring in the working of the line
that have a disturbing action upon the telephones are reduced, whether the
disturbances arise from the pulsations of the electro-motive force, or from the
motors on the cars, or from imperfect contacts in the several circuits (such as at
the rails or at the over-head conductors). In this it is immaterial whether the
disturbances caused by the current pulsations are due to dynamic induction
(transformer action) static induction (capacity action), or to direct penetration of
a portion of the working currents into the telephones.
Approximately the same action will be obtained if the choking coils are intro-
duced at certain distances apart in the working circuit as shewn at Figures 2 and 3.
In this arrangement the choking coils will also be in the neighbourhood of the
places of consumption if the distances between the several coils are sufficiently
small. In this case, stronger pulsations can only occur, if two vehicles on the
same working circuit take simultaneously current from the overhead conductor
between two choking coils.
If the distances between the contiguous choking coils (say i2 and 3) are
sufficiently small, the current pulsations can only occur on a small section of the
line. The telephonic disturbances will therefore also in this case be small.
Figures 2 and 3 shew examples of such arrangements. In Figure 2 the choking
coils 1 2 3 4 are introduced at suitable distances apart directly into the
working circuit. All current pulsations produced say in car III Figure 2 are
weakened by the choking coils 1 and 2.
The current pulsations produced by the cars I and II are partly choked off by
the choking coil il, and partly pass into the closed circuit between the cars I
and II.
If the distance between 1 and 2 is small, and consequently the distance
between the cars I and II, between which current pulsations can occur, is also
small, considerable telephone disturbances cannot occur. In Figure 3 the working
circuit is divided into separate sections T1 T2 T3 which, for example are fed by
a common feeding circuit. The choking coils i 1 i2i3 are placed in the connecting
lead between feeding circuit and working circuit.
At the end of the circuit the choking coils i4 15 16 are introduced in series in
the working circuit. The action is the same as with the arrangement at Figure 2.
For increasing the choking action in the arrangements at Figures 2 and 3
choking coils can also be included at the central station either in the main circuit,
or in the several feeding circuits. Also the choking action can be farther increased
by providing a somewhat smaller choking coil on the several motor cars.
If the telephone circuits only extend along short sections of the line near the
electric working circuit, it will be sufficient to apply the arrangements shewn at
Figures 2 and 3 only in these sections.
Figure 4 shews a diagram of such an arrangement. For the sake of simplicity
only a single feeding circuit is shewn, from which at certain intervals the working
circuits are fed. In the section in which the telephone circuits ✗ are near the
working circuits the feed circuit is continued as a subterranean cable. In the
branch leads to the divided working circuit choking coils i are introduced. At
the end section where no telephonic disturbances are anticipated, the feeding
circuit again appears as an overhead circuit, and no choking coils are introduced.

page_text: When accumulators are carried on the motor vehicles which are supplied with
current from the overhead working circuit, it is often only a question of neutra-
lising the current pulsations occurring between the accumulator batteries of the
several vehicles, which more particularly give rise to telephonic disturbances.
:
For effecting this, the self induction of the field magnet windings of the motor
or motors can be utilised. In this case choking coils are provided on the field
magnet limbs as at Figure 5 in place of separate choking coils. With series
wound motors the field magnet windings can be directly utilised for this purpose,
by connecting the accumulators either parallel to the armature alone as at car I
Figure 5, or parallel both to the armature and to a portion of the field magnet
windings, as at car II Figure 5. With this arrangement therefore, the field
magnet winding of the motor or a portion thereof is included in the charging
circuit of the accumulators. By the self induction of the windings thus included
in the charging circuit of the accumulators, the current pulsations will be weakened.
With shunt-wound motors the same result can be obtained by providing an
auxiliary winding (compound winding) on the field magnets as shewn at car III
Figure 5. The auxiliary winding here represents the shunt winding.
With the above arrangements the charging current of the accumulators can be
utilised for assisting in magnetising the field magnets.
By this arrangement the charging current of the accumulators will also be better
regulated, so that the disadvantage of greater loss of energy in the field magnets
will be counterbalanced. In those sections in which the motor or motors is or
are fed from the accumulators the latter can be connected parallel to the motors.
According to another arrangement we employ the said choking coils in con-
nection with the condensers such as are arranged parallel to the motors, which
condensers (such as liquid condensers or accumulators acting as condensers) serve
to take the sudden variations of potential difference at the terminals of the motors,
as the potential difference at these points in that case only changes slowly, corres-
ponding to the extent to which the accumulators or condensers are charged. This
maintenance of the potential difference at the terminals necessitates the production
of equalising currents between condenser and motor.
If there is only one motor or one motor car with one or more motors, with the
terminals of which a condenser is connected in parallel, these equalising currents
pass directly between condenser and motor that is to say within the car and do
not penetrate into the external circuit, and consequently do not cause telephone
disturbances.
The conditions are however different if there are several motors or groups of
motors connected to the working circuit at varying distances apart, as is the case
for example with electric tramways, where the current is taken from overhead
conductors. If in this case a condenser is only connected in parallel to a single
motor the condenser will only protect the telephone line from the current pulsa-
tions of the said motor, but will strengthen current pulsations arising from the
other motors connected to the circuit in consequence of the equalising currents
between the condenser and the other motors. It is therefore necessary to connect
condensers in parallel to all the motors or motor groups, in order to prevent
stronger pulsations that arise from the motors.
In this case there also occur equalising currents between the several condensers
in consequence of their different degree of charging. These do not cause dis-
turbances in the telephones so long as the resistances in the circuits between the
several motors remain constant, that is, with stationary installations.
In working electric railways however there occur in consequence of imperfect
contacts at the rails or overhead conductors, caused by the springing off of the
contact rollers or bars &c. considerable variations of resistance between the motors.
In consequence whereof considerable equalising currents are produced between the
condensers which cause great disturbances in the telephone lines, and it is for
preventing these disturbances that the choking coils are employed. It has been
found by experiment that these disturbances, although much stronger than those

page_text: caused directly by the motors, can be sufficiently weakened by considerably smaller
choking coils than is possible with the disturbances caused directly by the motors.
By the arrangement of condensers in parallel with the motors and choking coils
in the working circuit, the total weight of the protecting devices (condensers and
choking coils) and in particular the consumption of energy by such devices, is
considerably decreased.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, we declare that what
we claim is :-
1. For reducing disturbances in telephone lines caused by installations for the
transmission of electrical energy, in particular electric railways, providing at
each place of consumption viz. on each motor car a choking coil so arranged as to
prevent alternating currents of such strength as to have a disturbing influence,
from occurring in the line wires, substantially as described.
2. The application of choking coils such as are referred to in the first claim, to
installations in which the motor cars are partly worked by accumulators, such
choking coils being introduced either in the common supply circuit for both motors
and accumulators, or only in the charging circuit for the accumulators, sub-
stantially as described.
3. The application of choking coils such as are referred to in the preceding
claims, both on the motor cars, and in the separate feeding circuits, for the
purpose of producing a strong choking action when the cars have only a light
load, substantially as described.
4. In the application of choking coils such as are referred to in the first claim,
providing the said choking coils at short distances apart either in the entire
length of the working circuit, or only in certain sections thereof, substantially as
described.
5. In electrical railways partly worked by accumulators on the cars, that are
charged during the running, the inclusion of part or the whole of the field magnet
windings of a series wound motor in the charging circuit of the accumulators,
substantially as and for the purpose described.
6. In electrical railways partly worked by accumulators on the cars, that are
charged during the running, the inclusion of a compound winding of the field
magnets of a shunt wound motor in the charging circuit of the accumulators,
substantially as and for the purpose described.
7. In electric railway installations provided with choking coils such as are
referred to in the preceding claims, and in which a condenser is connected in
parallel to each motor or group of motors, providing choking coil in the common
supply circuit of the motor and condenser, substantially as and for the purpose
described.
Dated thin 01st day of Decembar 100%