GB584915A - Improvements in controlling apparatus for electric motors - Google Patents

Abstract

584,915. Controllers. GENERAL ELECTRIC CO., Ltd., and GARRARD, C. J. O. June 11, 1943, No. 9419. [Class 38 (iii)] With auxiliary switches.-A control system for a direct current shunt motor comprises a starting switch for the armature circuit, a speed-regulating rheostat in the shunt field circuit, and a second switch for inserting an armature resistance at starting, all operated by a single movable member. As shown, the rheostat indicated by the studs 4 is varied by the arm 5. When the arm is moved anti-clockwise to a position of low rheostatic resistance, a roller 23 thereon engages a forked end 21 of a pivoted member and opens a switch 12 to place resistance in the armature circuit. The pivoted member is biassed to a position wherein the switch 12 is closed by a spring 24. A contact 25 on the movable arm touches a fixed contact 7<1> to close a circuit which energizes a relay closing a main switch in the armature circuit to start the motor. The arm is held in this position whilst the motor starts and is then released so that the spring 24 moves the arm 5 clockwise into a position corresponding to low motor speed and closes the switch 12 to short circuit the armature resistance. Thereafter normal speed control is provided by further movement of the arm 5. The starting switch may operate a relay which closes both a main armature switch and a hold-in contact for the relay ; a push-button to release the relay may be provided at a position remote from the motor. The control system illustrated in the Figure accompanying the Provisional Specification shows the motor having additionally a series field winding. The system further comprises a reversing switch and pilot lamps to indicate closure of the main armature switch. The usual overload relay, discharge resistance for the shunt field winding, and fuses are shown.