Improvements in or relating to Alternate Current Electric Distribution.
Year: 1888

page_text: COMPLETE SPECIFICATION.
Improvements in or relating to Alternate Current Electric
Distribution.
A communication from abroad by GEORGE WESTINGHOUSE, Junior, of Pittsburg,
County of Alleghany, State of Pennsylvania, United States of America, Engineer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S. M.I.M.E. of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, and 6 Bank Street, Manchester, both in
the County of Lancaster, & 323 High Holborn in the County of Middlesex, 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 :-
The invention relates to the organization of circuits and apparatus for distributing
electric currents.
The object of the invention is especially to provide convenient and economical means
for operating isolated incandescent electric lamps or other translating devices requiring
electric currents of moderate potential, and at the same time to secure the advantages
pertaining to the systems of electrical distribution and conversion known as alternate-
current or secondary systems.
In operating translating devices by these systems it is customary to transmit
currents of very high potential to points within the immediate vicinity of translating
devices, and, at or near such devices, to reduce the potential of the currents as may be
required. When, however, but a single translating device is required at any given
point, it involves a considerable expense to supply a converter or potential-reducing
device for each such translating device. But either such an organization must be
adopted or else secondary conductors must be employed for each converter of sufficient
length to-include several different and more or less distantly located translating
devices. Such conductors are necessarily of greater size than the primary conductors
or those conveying the currents of high potential and therefore a greater expense is
involved.
In general terms the invention may be said to consist in connecting a number of
Pains R} |

page_text: translating devices in series with each other and in connecting in shunt-circuit around
each device a suitably constructed inductive resistance or reactive coil, and in thus
dispensing with the converters or potential-reducing devices as usually organized.
In the accompanying drawing, figure 1 is a diagram illustrating the system as
applied to a circuit of constant current, and figure 2 is a diagram illustrating the
application to a circuit of constant electromotive force.
Referring to figure 1, A represents a suitable source of alternating, intermittent or
pulsatory electric currents, and L its circuit. In the circuit there are included in
series any convenient and required number of translating devices d, d, such for
instance as incandescent electric lamps. Around each lamp there is connected a
reactive coil r. This may consist of coils of wire p surrounding cores c of soft-iron,
the coils and core being disposed in any convenient manner. One of the devices dis
represented as having its circuit interrupted as at s.
In the circuit L there are also represented devices D, D, which may be electric
arc-lamps or other devices requiring constant currents. These, however, are not
necessary to the system but are shown as being applicable. The purpose of the
nvention, it will be understood, is to provide means for operating a number of
translating devices in series and to insure that the interruption or failure of one or
more of the devices shall not interfere with the operation of the others. It will be
evident that if several devices may be thus connected in series, currents of high
potential and consequently wires of small cross-section may be employed. It has
heretofore been proposed to connect translating devices in series and provide each with
a circuit-controller, switch, or fusible connection, which upon the failure of the
translating device will operate to automatically complete the circuit through another
conductor. The invention herein described dispenses with the necessity of all such
mechanical controlling devices, and provides a constantly closed path for the current
around each translating device, depending for its adjustment upon purely electrical
reactions.
It is evident that a simple resistance so placed would prevent the actual interruption
of the circuit, but would be impracticable, owing to the fact that if its resistance wero
high enough to prevent undue waste, when the translating device is in operation, a
large amount of energy would be consumed, when, by the failure of the translating
device, the current to supply the remaining devices would be compelled to pass through
it alone.
In this system a coil having a suitable self induction is employed instead of an
ordinary resistance and it therefore requires for its operation an alternating, pulsatory
or periodically interrupted current.
In carrying out the invention it is necessary to determine suitable proportions for a
coil which, when kept in permanent shunt circuit with the lamp, shall derive only a
small fraction of the current, by reason of its high self induction or counter electro-
motive force. The specific resistance need not be great as compared to that of the
translating device, as for example, for an incandescent lamp of 50 ohms resistance, a
suitable resistance for the coil is one ohm.
Suppose now that the circuit of the lamp or other translating device be interrupted,
while the current is being supplied in series with other translating devices. The effect
of the passage of the whole current through the coil is primarily to increase the
difference of potential at its terminals, and thereby increase the magnetic saturation
of the iron core. By suitably proportioning the amount of iron in the core the
counter electromotive force may be prevented from rising in a proportionate degree to
the applied electromotivo force and the departure is greater as the difference of
potential increases.
It would appear on first consideration that such an increase in potential between the.
terminals of one of the translating devices would necessitate an increase in the electro-
motive force applied to the entire circuit in order to maintain the current constant.
Such, however, is not necessarily the case. With a properly proportioned coil the
current is maintained at practically the normal amount without either increasing or
decreasing the electromotive force of the circuit.

page_text: In figure 2 the invention is illustrated in connection with a constant potential
circuit. The generator A has connected in its circuit L1, L2, an electric converter C
designed to be operated by currents of constant potential. Translating devices d¹, d²,
are connected in the secondary circuit of this converter. The translating devices d, d,
are connected in series as before, and they are provided with reaction coils r, r,
connected in shunt circuit as before.
Having now particularly described and ascertained the nature of the said invention,
and in what manner the same is to be performed, as communicated to me by my
foreign correspondent, I declare that what I claim is :-
The combination of two or more incandescent lamps arranged in series, each lamp
being shunted by a reactive coil, which is so proportioned as to offer a high resistance
to the passage of the current when the lamp is in operation, but whose reaction, when
the lamp is disconnected effects a resistance approximately equal to that of the lamp.
Dated this 28th day of May 1888.
WM. P. THOMPSON & Co.,
Agents for the Applicant.
WM. P. THOMPSON & Co.,
Agents for the Applicant.