Improvements in Electric Tramway and Electric Transmission of Power Systems.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Electric Tramway and Electric Transmission of
Power Systems.
CHARLES WILLIAM GODSON LITTLE, Heckington, Lincolnshire, Engineer, do
hereby declare the nature of this invention to be as follows:-
My invention relates to that part of an electric tramway or power system in
which the current is conducted back from the translating devices to the generator
or to what is technically known as the return circuit. The object of my invention
is to provide means whereby the difference of potential between any two points in
the return circuit can be automatically controlled.
With reference to electric tramway systems it is necessary in order to comply
with the requirements of the Board of Trade that the difference of potential between
the two ends of an uninsulated return conductor should not exceed a specified
amount (at present seven volts) and in order to meet this in the case of a long line
it is frequently necessary to employ what is technically termed a booster dynamo by
means of which current is withdrawn from the uninsulated return by means of an
insulated conductor or conductors attached to the uninsulated return at one or more
points and returning through the booster to the proper pole of the generator. By
this means if the difference of potential between the two specified points in the
uninsulated return be too high it may be lowered by increasing the electromotive
force of the booster causing it to withdraw more current. My invention consists in
combining with the booster an electro magnetic device which is in circuit with
or is electrically connected to an insulated conductor running between the points
between which the potential has to be regulated, this conductor may, by the
sanction of the Board of Trade, be the same conductor which is used for measuring
the difference of potential as required by the Board of Trade. The electro magnetic
device is such that when the difference of potential between the two points of the
uninsulated return exceeds a certain amount the current passing through the wind-
ings of the electro magnetic device varies thereby causing a plunger or coil to
operate a relay or mechanical arrangement controlling the electro motive force of
the booster so as to reduce the excessive potential between the two points of the
uninsulated return. By this means the power necessary to drive the booster will
always be a minimum thereby effecting a great saving in power and at the same
time enabling the requirement of the Board of Trade to be more reliably complied
with. My invention will apply equally as well to an insulated return if it be
necessary to regulate the drop of potential by means of a booster.
1002

page_text: Improvements in Electric Tramway and Electric Transmission of
Power Systems.
I, CHARLES WILLIAM GODSON LITTLE, of Heckington, in the County of Lincoln,
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 invention relates to that part of an electric tramway system or other system
for the electric transmission of power in which the current is conducted back from
the translating devices to the generator, or to what is technically known as the
return circuit. The object of my invention is to provide means to automatically
control the difference of potential between any two points in the return circuit.
"
In electric tramway systems it is necessary in order to comply with the require-
ments of the Board of Trade that the difference of potential between the two ends
of an uninsulated return conductor should not exceed a specified amount (at present
seven volts) and in order to meet this in the case of a long line it is frequently
necessary to employ what is technically termed a booster" dynamo by means of
which current is withdrawn from the uninsulated return by means of insulated
conductor, or conductors, attached to the uninsulated return at a point or points and
returning through the "booster" to the proper pole of the generator.
By this
means if the difference of potential between the two ends of the uninsulated return
conductor be too high it can be lowered by increasing the electromotive force of the
booster so as to cause it to withdraw more current. My invention consists in
combining with the "booster an electro-magnetic device which is in circuit with,
or is electrically connected to, an insulated conductor rurning between the points
between which the potential has to be regulated, this conductor may, be the same
conductor which is used as aforesaid for measuring the difference of potential as
required by the Board of Trade. The electro-magnetic device is such that when the
difference of potential between the two points of the uninsulated return exceeds a
certain amount the current passing through the windings of the electro-magnetic
device varies thereby causing a plunger, or coil, to operate a relay, or mechanical
arrangement, controlling the electro-motive force of the "booster so as to reduce
the excessive potential between the two points of the uninsulated return. By this
means the power necessary to drive the "booster" will always be a minimum thereby
effecting a great saving in power and at the same time enabling the requirement
of the Board of Trade to be reliably complied with.
}
My invention is equally applicable to an insulated return in all cases where the
drop of potential is regulated by means of a booster."
The accompanying diagram illustrates an arrangement according to my inven-
tion as applied to an electric tramway system from which its general application will
also be understood.
A and B are the terminals of the excitation circuit of the "booster" dynamo A³,
and C is a variable resistance in the said excitation circuit. D is the contact arm
moving over the contacts of the said resistance and operated by the worm F engag-
ing with a worm wheel E on the axis of the said arm D. The said worm F is on the
spindle of the armature G of a motor the field of which is indicated at H and the
commutator of which is marked I. P shows the source of electro-motive-force for
the armature G as consisting of accumulators but any other convenient source may
be used. Q is a solenoid coil whose terminals are connected to the return circuit
at P2 and P3. R is the solenoid core in the said coil and attached to an insulating
piece carrying the contacts N, O, for making contact with the contacts J, M, and

page_text: K, L, as hereinafter described. S is the main generator feeding the trolley wires P
with current.
When the difference of potential between the points P³ and P³ is too high the
core R is drawn into the coil Q so as to make electrical contact between J and N
and between K and O which as the contacts J, M and K, L, are connected as
indicated in dotted lines allows an electric current to pass from the source P through
the said contacts and the flexible leads T T to the armature G causing it to revolve
in a direction to cause the worm gear E, F, to operate the arm D to lower the
resistance C and therefore cause the "booster" A to withdraw more current from
the return circuit at the point P³. The potential between the points P2 and P³
being thus reduced the core R will descend and when the potential falls below a
predetermined point the contacts between J and N and between K and O will be
broken and contact will be made between L and N and between M and O, which will
supply current from the source P so as to cause the armature G to revolve in the
reverse direction so that the worm gear E F will operate the arm D to increase the
resistance in C and so lower the electro-motive-force of the "booster" A8 and there-
fore cause less current to be withdrawn from the return circuit at P³ and raise the
potential between the points P2 and P3.
It will be evident that in place of the coil Q and core R, an electro-magnet may
be used having a fixed core acting upon a moveable armature with which the
contacts N, O, are connected.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to performed I declare that what I
claim is:-
"
1. In combination with electric tramway systems or other systems for the electric
transmission of power having an insulated or uninsulated return wherein the drop
of potential is regulated by a booster" an electro-magnetic device in a conductor
between the points between which the potential is to be regulated the said electro-
magnetic device operating an arrangement whereby the electro-motive force of the
booster" is controlled substantially as and for the purpose hereinbefore
described.
"
2. An arrangement for automatically controlling the difference of potential
between two points of the return circuit of an electric tramway system or other
system for the electric transmission of power substantially as hereinbefore described.
Dated this 5th day of January 1898.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.