Improvements in Regulating Phase Relation of Alternating Currents.
Year: 1896

page_text: Date of Application, 11th Feb., 1896-Accepted, 14th Mar., 1896
COMPLETE SPECIFICATION.
Improvements in Regulating Phase Relation of Alternating
Currents.
:..
I, JAMES DEVONSHIRE, Secretary of the British Thomson-Houston, Limited,
of No. 38 Parliament Street, Westminster, London, (a communication to me from
abroad by Ernst J. Berg, Electrical Engineer, of Schenectady, State of New
York, United States of America,) 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 the control of alternating current apparatus, and has
particular reference to so regulating the phase relation of alternating currents (by
which I mean the relation between current and electro-motive force in such
circuits), as to increase the efficiency of a system of distribution.
It is well known that the most efficient operation under ordinary circumstances
is obtained for alternating current systems of distribution when the current and
electro-motive force in the circuit are in phase. I have devised an arrangement
of apparatus which will respond to a difference of phase between the current and
electro-motive force, and by such response will tend to correct the distortion or
displacement of phase between the two power elements in the circuit.
To attain the objects of my invention, I prefer to employ a synchronous motor
connected between the lines of the system of distribution. To control the
excitation of this motor I employ an ordinary resistance, though any other means
of so controlling the field may be used to accomplish my purpose. To control the
amount of resistance in circuit with the field I connect to the rheostat a current-
actuated device influenced by the amount of current passing to the synchronous
motor, and opposing this current device a watt-mechanism, so that when the
current is in phase with the electro-motive force, the power exerted by the watt-
mechanism is balanced by that of the current-actuated device, and the resistance
will not be changed. When, however, the current lags, it becomes larger and
therefore the current actuated mechanism acts with more force than the watt-
mechanism, which depends upon the relation between the current and electro-
motive force for its energy. The amount of resistance is then changed, the
excitation of the synchronous motor is altered, and its effect upon the lines
between which it is coupled is so varied as to restore the phase relation of the
current.
The acccompanying drawing shows diagrammatically a convenient embodiment
of my invention.
A is a generator of alternating currents, represented as of the three-phase type,
although this is immaterial, it being well understood in the art that the number of
phases generated does not affect the invention. a, b, c, are the lines leading from
this generator; a, b, c are leads from the lines to the armature k of the
synchronous motor K. In the lead a' is a coil B actuating a core C, which forms
In the lead c' is connected the series.
the current actuated device of my invention.
coil E of the watt-meter device D; the shunt coil F of the same device is arranged
at a right angle to the series coil, and is connected between the lines b', c'. "A
rotating shuttle or magnetic body G is mounted in the field of the coils which are
of course provided with a suitable magnetic supporting structure. An arm g is
fixed to the shaft carrying the shuttle G, and is actuated by its rotation. A system
of levers H, H', H, actuates the controlling arm of the resistance 1 coupled in the

page_text: circuit of the field magnets k¹. The motor is represented as self-excited, but may
be separately excited, without affecting the invention.
Other forms of apparatus may be readily devised embodying the essence of my
invention, which is briefly, the use of opposing electro-magnetic devices the
opposition of which is balanced when the current and electro-motive force of
the alternating current circuit are in phase, but of which one will overpower the
other whenever these two power components are out of phase, and the actuation by
these electro-magnetic devices of any suitable means for restoring the phase
relation. The particular arrangement which I have devised is simple and
convenient and is to be preferred, but it is manifest that those skilled in the
art could readily change the devices without departing from the principles set out
herein.
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 from abroad, I declare that what I claim is :-
1. An alternating generator, lines extending therefrom between which electro-
motive forces are to be maintained, electro-magnetic devices responsive to a change
in phase relation of current and electro-motive force in said lines and acting in
opposition to each other, such opposition being balanced when the current and
electro-motive force are in phase, and means actuated by the electro-magnetic
devices for restoring the phase relation.
2. A generator of alternating electro-motive forces, lines leading therefrom
between which such forces are to be maintained, an electro-magnetic device
actuated by the current in such lines and a watt-mechanism connected to the
lines, the two devices acting in opposition and being balanced when the current
and electro-motive force are in phase, and means actuated by a disturbance of the
balance for restoring the phase relation when displaced.
.
3. A generator of alternating electro-motive forces, lines leading therefrom
between which such forces are to be maintained, a synchronous motor connected
to the lines, a solenoid in one of the lines, a watt-mechanism comprising a series
coil and a coil in shunt; the solenoid and the watt-mechanism being in opposition
to each other when the current and electro-motive force of the circuit are in phase,
means for controlling the excitation of the synchronous motor, and a connection
between such means, the solenoid and the watt-mechanism.
4. A generator of alternating electro-motive forces, lines leading therefrom
between which such forces are to be maintained, a synchronous motor connected
to the lines, a solenoid in one of the lines, a watt-mechanism comprising a series
and a shunt coil, the solenoid and the watt-mechanism being in opposition to each
other when the current and electro-motive force of the circuit are in phase, a
resistance in the field circuit of the motor, and a connection between the solenoid,
watt-mechanism and resistance.
5. The means for preserving the phase relation of current and electro-motive
force in alternating circuits herein set out, consisting of a current actuated device
and a watt-mechanism opposed in their action, and means actuated thereby for
restoring the phase relation when disturbed.
Dated this Eleventh day of February 1896.
For the Applicant,
J. C. CHAPMAN,
70, Chancery Lane, London, W.C., Chartered Patent Agent.