GB634892A - Improvements in or relating to electric motor control systems - Google Patents

Abstract

634,892. Control of motors ; electromagnetic switches ; protective cut-out arrangements. GENERAL ELECTRIC CO., Ltd., and TURRALL, J. C. Oct. 17, 1947, No. 27842. [Classes 38 (iii) and 38 (v)] No volt protective means for an electric motor control system having a speed controller 4, so arranged that the protective means .ensure that the controller 4 must be returned to the off or an initial starting position if the supply fails, comprises a relay 1 arranged so that the contacts 2 are closed by a voltage responsive coil 17 and are maintained by a coil 21 responsive to the motor current, the coil 21 only being energizedduring normal operation of the system. Movement of the controller into position I energizes an auxiliary relay 20 to close contacts 19, thereby energizing coil 17 to close contacts 2 and hence energize the operating coil 3 to close one of the line switches and also the interlocking contacts 26 thereon, the foregoing series of operations-only occurring when the controller is in position I. Further movement of the controller into position II energizes the coil 24 of a first starting resistor contactor, auxiliary contacts 25 thereon opening to de-energize coil 23 and hence also to de-energize the voltage responsive coil 17 the relay 1 being retained by the coil 21 carrying the motor current. Failure of the supply causes the current in coil 21 to fall, relay 1 drops out, coil 24 is de-energized, thus closing contacts 25 to prepare the circuit of the coil 17 for the resumption of the supply. If the supply for the control relays is taken from the main supply, the auxiliary contacts 25 are placed in the circuit of coil 17 and the relay 20 omitted. The coils 17, 21 are associated with a common magnetic circuit, Fig. 3, being wound one around the other and when energized cause the armature 13 to move vertically and to retain its operated position respectively, to close the contacts 2 through a link system 15.