GB450295A - Improvements in and relating to control systems for multiple electric motor drives - Google Patents

Abstract

450,295. Control of several A.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. Dec. 18, 1935, No. 35135. Convention date, Dec. 19, 1934. [Class 38 (iii)] An electric drive suitable for carding- machines comprises asynchronous motors m interconnected on their stator and rotor sides, and includes a main relay a for connecting the motors to the supply, a relay l1 operated simultaneously with the relay a to reduce the rotor resistance w, and a braking relay b arranged to connect the stator windings to a single phase of the supply when the relay a is opened to stop the motors. Upon operation of a starting switch the relays a, l1, are closed and maintained over auxiliary contacts of the relay a, a time delay relay also being energized which effects closure of a relay l2 to short-circuit the resistance w when the motors have come up to speed. Upon operation of a stop switch the relays a, l1, l2, are de-energized and back contacts on the relay a energize the relay b which connects the motor stators across a single phase of the supply, each stator having two phase windings connected in parallel. The time delay relay is also de-energized when the stop switch is operated, and, after a time interval, effects the de-energization of the relay b. Resistances d are permanently connected in the rotor circuits to reduce mechanical shocks on starting. The relay b may be so interlocked with the relay a that the drive cannot be restarted until it has first come to rest, and the relay b has dropped out.