Improvements in Electric Transmission of Power.
Year: 1893

page_text: Date of Application, 10th Jan., 1893-Accepted, 25th Feb., 1893
'COMPLETE SPECIFICATION.
[Communicated from abroad by EDWIN WILBUR RICE, Junior, of Lynn,
County of Essex, State of Massachusetts, United States of America,
Electrician.]
'
Improvements in Electric Transmission of Power.
1, ERNEST DE PASS, of 78, Fleet Street, in the City of London, Fellow of the
Chartered Institute of Patent Agents, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and 'by the following statement, reference being had to the
accompanying drawings and to the letters and figures marked thereon, 'that is
to say :-
•
This invention relates to. a system of Electric Power Transmission employing
alternating current motors. Motors of 'this class have been devised which are
quite efficient but require an auxiliary starting means and means for maintaining
their field magnetism by a direct current.
"My invention.consists chiefly in causing a single direct current auxiliary machine
to serve for both these purposes, namely, to first act as a motor, taking current
from a direct current supply, to start the main motor, and to 'then act as
generator, driven by the main motor and feeding the field magnets thereof with a
direct current.
a
"In the system hereinafter described, but one set of mains is employed, and
switches: .are employed whereby connection is first made through such mains
between two direct current machines one of which thus starts the other, bringing
an alternating machine connected therewith up to speed, and connections are then
made through such mains between such alternating machine and an alternator at
the generating station whereby the movement of the alternating¨motor is
maintained.
"In the accompanying drawings,
Fig. 1 is a diagram of a system adapted 'for-carrying out the above described
mode. of: operation, the changing of the direct current 'machine connections and
thereby its function being effected by manually operated switches.
Fig. 2 similarly shows a system wherein this change is automatically effected.
"In Fig: 1 A is the generating station and B the receiving station, connected 'by
a.single set. of mains, L, L. At the generating station are provided the direct
current generator D and the alternator C, both of which are driven 'from suitable
sources. of. power P, being for this purpose mechanically connected' to 'the same
prime motor. At the receiving station are provided the alternating current
motor C and direct current machine D', which are mechanically connected
together and to the work 'W. Such alternating current motor may be of the
type indicated with an external stationary field magnet c and a revolving
armature c¹.
"
At each stationsare provided connections between the supply. lines L, L, and
the dalternating machine narmatures c', connections between the supply
lines L, L, and the direct current machine D or D' and connections f. between
the direct current machine and the field magnet c of the alternating machine.
Switches S1, S2, S3 are included respectively in such connections. As shown,
switching contacts S', 'S leading from 'the supply line respectively to the
alternating and the direct current machines are operated by a common handle h.
To start the system in operation, the prime motor and the generating
machines C, D, having been set in motion, the attendant at each station closes
switch contacts 'S' and opens switch contacts 'S', S. The direct current
machines are thus connected through the supply lines and machine D¹ acting as a

page_text: motor, starts the alternating motor and brings the same to speed. Then the
switches S3, S3 are closed to excite the field magnet circuits of the alternating
machines, and handles are thrown, opening switch contacts S and closing
switch contacts St. This cuts the supply line off from the direct current
machines and causes it to form the connection between the armatures of the
alternating machines, so that they then rotate in synchronism, the field magnet of
each machine being energized by a direct current machine at its own station.
Thus the energy required to maintain the excitation of the alternate motor field
magnets is transmitted by the alternating currents and but one set of supply lines
is needed.
In Fig. 2 I indicate a means for effecting the above described change in the
connections automatically when the motor has been brought up to speed. In this
case the three sets of switch contacts S1, S2, S3, at the motor station are operated
simultaneously by a common switch h¹ which is actuated by a governor or speed
responsive mechanism driven by the motor itself, so that when full speed is attained
the switch is thrown, preferably by a snap action as shown. In conjunction with
this, a similar switch may be provided at the generating station, its handle h² being
controlled by an electro-magnetic device E in the starting connection from the
direct current machine to the supply lines. This electro-magnetic device releases
its armature e when the direct current supply circuit is broken at the receiving
station, during the change of connection, and the switch 2 being thus released at
at once cuts out the electro-magnetic device and shifts the supply circuit con-
nections to the armature of the alternator.
The switch S3 is omitted in this figure, as it is not necessary to the operation of
the system, especially at the generating station, as the direct current machines
may, as shown, be permanently connected to the alternator field. An additional
switch S may, if desired, be included in the connection from the alternator
armature.
It is obvious that my invention as above described may be modified and extended
in many other ways without departing from the principle thereof. Thus it is of
course not limited to a single set of generators and receivers, nor to the common
source of power for the two generators. Any number of generating machines and
any number of receiving machines may be employed, and they may be connected
in various ways.
In fact, while I have shown a single set of mains for both the
alternating and direct current machines, my invention is not altogether limited to
this feature, as it consists broadly in the means whereby the same direct current
motor is employed as a motor to start the alternating motor, and as a dynamo to
excite the field magnet thereof.
It will also be understood that the terms field magnet and armature as herein
applied to the alternating machines, refer respectively to the part of the machine
receiving direct current and the part receiving alternating current, so that either
the field magnet or the armature may rotate according to the design of the machine.
Furthermore, one side of the set of supply mains L, L, may obviously be a ground
return. Of course transforming devices for changing the potential may be included
in the alternator connections at one or both ends of the system.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. In a system of electric power transmission, an arrangement of alternating and
direct current generators at the transmitting station, and corresponding alternating
and direct current motors at the receiving station whereby the alternating motor
may be started and its field magnet energized by the same machine, substantially
as set forth.
2. The arrangement herein described, of alternating and direct current generators
at the transmitting station, corresponding alternating and direct current motors at
the receiving station, with suitable switches and automatic devices by which the

page_text: direct current machine at the receiving station, first, starts the alternating motor,
and then acts as a generator for energizing the field magnets of said motor,
substantially as set forth.
3. In a system of electric power transmission, an arrangement of alternating and
direct current generators at the transmitting station, and corresponding alternating
and direct current motors at the receiving station, with suitable connections whereby
the alternating motor may be started by means of a direct current sent over the
intervening line, and when the said motor is at the desired speed the direct current
may be withdrawn and the alternating current supplied to the motor over the
same line, substantially as set forth.
Dated this 10th day of January 1802