GB421183A - Improvements in and relating to electric motor control systems - Google Patents

Abstract

421,183. Control of motors. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London, and JEFFERSON, H. F., Hillside, Bilton Road, Rugby. June 15, 1933, No. 17109. [Class 38 (iii)] Travelling to predetermined limits.-An A.C. motor operating, for example, the feed motion of a machine tool through definite predetermined amounts, is brought to rest in the desired position by magnetic locking between the poles of the motor and stator. Upon closure of a switch X, contactor ST is closed to connect the motor stator to the supply, and an interlock switch of the contactor ST completes the circuit of contactor SC, which connects through resistance R, the rotor winding of the motor. The motor runs and operates, either directly or through gearing, a drum switch MNOP which, when it reaches positions intermediate positions 2 and 3, 4 and 5, or 8 and 1, depending on the setting of a master switch to positions “, ¢, or 1, interrupts the circuit of contactor SC and completes that of a self-maintaining contactor LK and his contactor connects the rotor winding to the supply and the stator and rotor poles are pulled into and maintained in line, the switch MNOP resting in positions 3, 5, or 1. Upon opening of the switch X all contactors drop out, and upon reclosing a similar cycle of operation takes place. In a simplified arrangement the resistances R are permanently connected to the rotor windings. In order that variations of load shall not cause the motor to pass a desired stopping position, a drag brake may be provided, and the motor arranged to give an excessive torque. Further, two contactors may be provided performing the function of the single contactor SC, operating alternatively, and mechanically interlocked with the contactor LK.