GB542569A - Improvements in operating mechanisms for electric circuit breakers - Google Patents

Abstract

542,569. Automatic circuit-breakers actuation of switches. BRITISH THOMSON-HOUSTON CO., Ltd. Jan. 8, 1941, No. 269. Convention date, Jan. 8, 1940. [Class 38 (v)] A circuit-breaker, which may be of the gasblast type, is adapted, when tripped open, to be automatically reclosed pneumatically prior to completion of the opening stroke. In the application of the invention to the trip-free mechanism of Specification 490,641, the operating rod 3 is connected to the pneumatic closing piston 5 through a chain 4, which is normally held taut by a roller 12 on a spring-controlled lever 10 pivoted at 11, a further roller .13 engaging a trippable detent 14. A prop 8 pivoted at 8' is urged by spring 8" into engagement with a roller 9 on the piston rod 5' which is urged upwardly by spring 5<SP>11</SP>. Thus, by deflecting the prop 8, the spring 6 acts directly to open the breaker and raise piston 5. By deflecting latch 14 by trip coil 15, the chain-support is removed and the breaker is, as before, opened by spring 6. In its deflecting movement, lever 10 rotates prop 8 through extension 18 thereof, spring 5" raises the piston 5, and allows spring 17 to restore lever 10 into latching engagement with 14, subsequent reclosure being as already described. The prop 8 is tripped by energization of coil 30 by closure of contacts 28 of trip relay FR. When rod 3 has moved far enough to clear the circuit, a cam 3' thereon closes contacts 21 to energize the valve solenoid 22 in series with closed switch 23, air-pressure switch 25, and limit switch 26. The initial opening movement is fairly rapid due to vents 19' in cylinder 19, and when valve 20 is opened by solenoid 22, a small quantity only of air is necessary to restore the piston 5 and reclose the breaker, which is latched.by prop 8. When energized, solenoid 22 closes at 22' the circuit of a timerelay TR which changes over and remains on contact 32 until the breaker is reclosed, thus preparing the trip circuit of coil 15 in case FR operates due to persistence of the fault. Manual tripping can be effected by changing over switch 23, 24 to energize coil 30. Reclosure is effected by switch C over closed switch 23, the device being trip free in this operation.