GB420547A - Improvements in and relating to systems of electric motor control - Google Patents

Abstract

420,547. Master control of A.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Kilbourne, C. E.; 101, Plymouth Avenue, Schenectady, New York, U.S.A.) Aug. 8, 1933, No. 22182. Convention date, Aug. 6, 1932. [Class 38 (iii)] A motor has two field windings 11, 12, and 13, 14 which are normally connected in series by a series switch 23, but which can be connected in parallel by first closing switches 24, 25, which establish parallel circuits around the series switch and the respective field windings, one of the parallel circuits including a resistance 26, then opening the series switch, and finally closing a switch 27 to short-circuit the resistance. Upon operation of a start button 35, a selfmaintaining contactor 36 closes, thereby closing a contactor 42 which connects the motor armature 10 to the supply. A contactor 46 is also energized by the closure of the contactor 36, and, after a time, causes a contactor 22 to close thereby connecting the field sections 11, 12, and 13, 14 to the supply 19 in series. Upon operation of a push button 51 or a load responsive relay 66, an operating coil 52, the coil 58 of a relay motor, and a contactor 68 are energized. The contacts 56 are thereby closed to maintain the circuit, and a contactor 71 closes so that the field sections and series switch are shunted, the shunt for the section 13, 14 containing a resistance 26. The closure of the contactor 71 opens the series switch which breaks the series connection, and causes a contactor 76 to close to short-circuit the resistance 26 so that the sections of the field are finally in parallel. After a predetermined time the relay motor 58, which is similar to that described in Specification 241,883, [Class 38 (v)], opens a switch 61 and closes a switch 64, the opening of the former de-energizing the contactor 68, and the closing of the latter energizing contactors 85, 80. The contactor 80 in closing causes the contactor 76 to drop out and reinsert the resistance 26 in the field circuit, and the opening of the contactor 76 together with the closing of the contactor 80 causes the contactor 30 to reclose and make the series connection of the field sections. The closing of the contactor 30 de-energizes the contactor 71 so that the shunts across the field sections are removed, and the sections are again in series. The contactor 85 when energized causes, after a time interval, the resetting of the timing mechanism. The cycle thus performed may be again repeated, and if overload persists is automatically repeated. The motor is stopped by operation of a button 41 to de-energize the contactor 42 which opens thereby to energize a contactor 101 which connects a braking resistance to the armature 10. Specification 419,769 also is referred to.