Improvements in Regulating Alternating Current Electric Motors: of the Induction Type.
Year: 1896

page_text: Date of Application, 14th Apr., 1896-Accepted, 23rd May, 1896
COMPLETE SPECIFICATION.
Improvements in Regulating Alternating Current Electric Motors:
of the Induction Type.
I, JAMES DEVONSHIRE, Secretary of the British Thomson-Houston Limited,.
of 38 Parliament Street, Westminster, London (a communication from abroad by
William B. Potter, Electrical Engineer, of Schenectady, in the 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 regulation of induction electric motors, particularly
as applied to tramway work.
The ordinary, and in many cases preferred method of regulation of such motors.
is by the now well-known "tandem parallel" system; but in some cases, on
account of the complication of connections required in that system, I have found
it desirable to use resistance control; this is particularly true where the
great torque of motors in multiple is desired in starting, and where stops are
infrequent, as in long distance electric railways; in which case long runs being
made with the motors in multiple with all the resistance cut out, they are working
at their maximum efficiency, and the slight loss of efficiency over the
tandem-multiple system in starting and at moderate speeds is immaterial.
For the purposes of my invention therefore, I connect the motors permanently
in multiple between the trolley lines and ground, or between the supply lines, if
three metallic conductors be used, in the three-phase system which I have taken.
as a convenient illustration. The circuit of each armature I close through
resistances, and these resistances I so connect that they may be operated simul-
taneously. Nothing in my invention limits it to the use of trolley lines, or to
railway work alone.
The accompanying drawing shows a diagram of my invention.
Therein A, A are armatures, B, B' the fields, the latter indicated merely by
straight lines as a convenient illustration. The two fields are permanently
connected in multiple between the trolleys T, T', and the ground at G.
I have indicated that a third trolley may be used, as shown by the trolley T' in
dotted lines, and in this case a metallic connection may be substituted, as shown by
the dotted line connections in the circuit of the armatures. Resistances R, R' &c.,
are shown closing the circuits of the armatures, and means, such as a slider S, for
cutting out these resistances in variable amounts or for bringing the armatures
upon dead short-circuit, are also used. These are connected by bars C, C, so that
operation of one simultaneously operates the other.
It is preferred that the resistances shall be arranged in the armature of each
motor, and that a number of contacts may be arranged upon the shaft so that they
may be short circuited in varying amounts, as this arrangement dispenses with
sliding contacts; but this forms no part of my invention, having heretofore been
proposed by others.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to me
from abroad, I declare that what I claim is :
1. The method of regulating alternating electric current motors of the induction

page_text: type, which consists in connecting the fields permanently in multiple between the
supply lines, closing the circuits of the armatures through separate simultaneously
variable resistances, and varying the resistances to regulate the speed of the
motors.
2. In combination, alternating electric current supply lines, induction motors
having their fields permanently connected in multiple between such lines and the
circuits of their armatures closed through resistances, and means for simultaneously
varying the resistance in the armature of each of the motors.
Dated this 14th day of April 1890.
For the Applicant,
J. C. CHAPMAN,
70 Chancery Lane, London, W.C., Chartered Patent Agent.