GB766891A - Improvements relating to selsyn systems - Google Patents

Abstract

766,891. Control of A.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd. Feb. 25, 1955 [March 12, 1954], No. 7328/54. Class 38(3) In a system for operating two or more dynamo-electric machines in mutual synchronism, a polyphase-wound receiver machine B, b, is started from standstill and accelerated into synchronism with a polyphase-wound transmitter A, a. Two terminals of the primary winding A of the transmitter are short-circuited, and the primary windings A, B, are connected to a single-phase supply. With the transmitter machine in operation, the machine B, b is started by closing switch S1 to interconnect the secondary windings, and switch S2 is engaged with contact 1, thus connecting impedence Z in series with one phase of the winding B. The controlled machine will thus accelerate and automatically synchronize with the controlling machine, whereupon, the switch S2 is changed over to the contact 2 to short-circuit two of the terminals of the winding B and to provide symmetrical connections for the machines. The impedance Z may consist of a resistor, capacitor, or choke, or any combination thereof. In another arrangement, the connection of the primary windings of the machines to the single-phase supply is provided by a contactor having its operating winding controlled by a push-button switch. A contact of the control switch alternatively completes a circuit for the operating winding of the contactor of forms a short-circuit across two phase windings of the controlled machine, Fig. 2 (not shown). In the latter embodiment, the switch S1 is omitted. The windings of the machines may be delta-connected. Impedance may be connected in each phase of the controlling machine to cause the ratio of the synchronised torque to the motoring torque of the controlled machine to be maintained at a high value during the accelerating period.