GB236068A - Improvements in and relating to electric motor control systems - Google Patents

Abstract

236,068. English Electric Co., Ltd., and Bremner, F. D. H. Aug. 26, 1924. Master control systems; controlling travel for a fixed number of revolutions.-In a system comprising a master switch 4 which produces circuit conditions cancelled by the movement of a secondary switch 18 driven by an electric or pneumatic auxiliary motor, a relay 3 is adapted upon failure of voltage to short-circuit its coil by way of segments 8 cn the switch 4, so that it cannot be reenergized until the switch 4 is moved to its off position. Normally the relay 3 is energized from conductor 6 through resistance 12 to earth, thereby moving its armature 1 on to contact 13 and completing a circuit, when the switch 4 is moved to its first position, through reversing switch 10, auxiliary contacts on a reverser 11, line-breaker coils 5, and segment 17 of switch 18, to earth. Closing of the line-breaker causes auxiliary contacts 16 to complete an alternative earth connection for coils 5 so that switch 18 can then be moved from its initial position. Failure of voltage allows the armature 1 to drop on to contact 14 completing the short circuit for the coil 3, and also breaking the circuit for the coils 5, with consequent opening of the line-breaker. Where the control circuit and the main motor circuit are not derived from the same supply, an interconnection between the no-volt relay of the motor circuit and the relay 3 is provided, so that the latter is de-energized whenever the main supply fails.