GB784556A - Improvements in or relating to automatic electric circuit breakers - Google Patents

Abstract

784,556. Automatic circuit - - breakers. ALLIS - CHALMERS MANUFACTURING CO. Sept. 15, 1955 [Sept. 22, 1954], No. 26484/55. Class 38 (5). An A.C. circuit-breaker has a tripping device comprising a core 42, a coil 21, a tripping armature 46, a latch 54, 56 to hold the armature against movement, a heater 62 energized in proportion to the current in the coil 21, a bimetallic element 61 which is heated by the heater to release the latch and tripping means (not shown) actuated by the armature. In Fig. 9 an armature-like member 47 is pivoted on a shaft 49 but is adjustably fixed by a bolt 64. The member 47 carries a coil 52 inductively coupled to the coil 21 and connected to the heater 62. Under prolonged overload conditions, the flux produced by the coil 21 in the core 42 is sufficient to attract the armature 46 but it is latched by the latch. The current induced in the coil 52 energizes the heater 62 and the bimetallic element is heated. One end of the coiled bimetal is fixed to the latch cam 54, Fig. 5, and the other end is fixed to a shaft 60 which may be turned through worm and wheel gearing 71, 68 to set the initial position of the latch cam 54. Thus, when the bimetal is sufficiently heated, it turns the latch cam 54 clear of a roller 58 carried by the armature 46 which is now attracted and through a striker 72 causes the tripping of the circuitbreaker. Should a high excess current condition occur, a further armature 48 is immediately attracted to produce tripping of the circuitbreaker without delay. The general arrangement of the circuit-breaker contact assembly, tripping mechanism and closing mechanism is that described in Specification 775,940.