GB505609A - Improvements in and relating to electric motor control - Google Patents

Abstract

505,609. Induction motors. BRITISH THOMSON-HOUSTON CO., Ltd., and ADKINS, B. Nov. 15, 1937, No. 31363. [Class 35] In a speed control system for induction motors of the type in which a polyphase commutator machine is connected in the rotor circuit and excited from the secondary side of a transformer or autotransformer, the primary side of which is connected across the terminals of the polyphase machine, control being obtained in steps by means of taps on the transformer, fine control between the taps is obtained by means of an induction regulator. The Figure shows an arrangement for giving regulation below synchronous speed only in which the primary winding 9 of the polyphase machine is connected to the slip rings 4 of the induction motor 1 through a switch 6 and an autotransformer 15 is connected across the leads. Tappings on the autotransformer are connected through a rheostat 14 to the exciting winding 10 of the polyphase machine and the secondary winding 11, 12 of an induction regulator, the primary windings 18, 19 of which are connected across the primary leads of the polyphase motor. The induction regulator is preferably of the type which consists of two units the secondary voltage rotors of which rotate in opposite directions as the vectors are rotated. In a modification for giving speeds above synchronous speed as well as below by means of a frequency changing exciter control near synchronous speed is obtained by means of a rheostat in series with the exciter. The exciter may also be controlled by a second conduction regulator and the power-factor adjusted by a rheostat in the exciting circuit.