Improvements relating to electrical control systems for devices such as circuit breakers or contactors

摘要

932,754. Protective cut-out arrangements. WHIPP & BOURNE Ltd., and C. L. WHIPP. Oct. 30, 1959, No. 36839/59. Class 38 (5). A control system for a circuit-breaker or contactor comprises a release and operating coil C, a low-voltage relay A for providing a shortcircuit path through the coil C and overloadresponsive relays having contacts E11, E21 for providing a second short-circuit path through the coil C, the D.C. resistance of the second path being greater than that of the first, so that the flux produced by the coil C decays more rapidly in the event of an overload than it does in the event of low voltage conditions and the release of the circuit-breaker or contactor is quicker in response to overload than it is in response to low voltage. When normal voltage exists at the leads L3, L4, the relay A changes over its contacts A1 The circuit-breaker or contactor may then be closed by operation of a switch S2 to energize the coil B of a closing contactor which closes contacts B1 to energize the coil C. The circuit-breaker or contactor closes auxiliary contacts C5, C6 to prepare the short-circuit paths, closes auxiliary contacts C7 to complete a retaining circuit and opens contacts C8 to deenergize the coil B of the closing contactor. When the relay A releases under low voltage conditions, contacts A1 complete the first shortcircuit path through normally closed contacts E12, E22 of the overload relays and the contacts C6. Under overload conditions either or both of the contacts E11, E21 are closed to complete the second short-circuit path through the contacts C5 and a resistor R2, and either or both contacts E12, E22 of the overload relays are opened to prevent completion of the first short-circuit path. The circuit-breaker or contactor may be opened by manually closing a switch S1 to complete a third short-circuit path through resistors R2, R3. The relay A may be supplied through a rectifier. To prevent hunting of the circuit-breaker or contactor, the system may be provided with anti-hunting relay circuit of Specification 917,631.