Improvements in and relating to fluid actuated operating mechanisms for electric circuit breakers

摘要

619,944. Fluid-pressure servomotor-control systems valves. BRITISH THOMSONHOUSTON CO., Ltd. Nov. 29, 1944, No. 23857. Convention date, Nov. 29, 1943. [Class 135] [Also in Group XXXVII] The invention, which is an improvement on the mechanism disclosed in Specification 548,520, comprises an operating mechanism for a circuitbreaker 10, wherein there is interposed between a source 42 of operating fluid and a fluid motor 38, a valve 81 for substantially instantanously relieving the pressure acting in one direction on the motor to enable high-speed reversal thereof, the valve being operable in response to the back pressure resulting upon the reversal of the motor, and having a non-return valve 88 for increasing its opening speed. Upon overload, a latch 26 is moved anti-clockwise by coil. 31 to allow levers 16 and 17 also to move anti-clockwise to open the circuit-breaker 10. To reclose the circuit-breaker, a switch 60 is closed to energize a time-delay relay 67 and a, valve operating coil 59, which moves a pilot valve 45 upwards, where it is held open by a permanent magnet 57 after the relay 67 opens. Opening of this valve exhausts the space 52 above main valve 46 which opens, at the same time closing an exhaust valve 47. The flow of operating fluid moves the valve 81 to the left (as seen in the Figures) to close exhaust ports 87, at which point valve 88 opens against spring pressure to supply fluid to the cylinder 39 to cause piston 40 to return the levers 16, 17 to the position shown in Fig. 1. At the end of its upward stroke, the piston closes a limit switch 72 to energize a coil 71 which neutralises the holding flux of the magnet 57, thus allowing valves 45 and 46 to close and valve 47 to open, thereby exhausting the space 48 behind the valve 81. The valve 88 now closes and valve 81 moves to the right to open ports 87 so that the piston 40 is free to move downwards again. If the breaker is reclosed on to a fault, a winding 76 energized simultaneously with trip coil 31, closes the valves 45, 46 in the same way as coil 71. A switch 61 opens when the pressure of the source 42 falls below a predetermined value. In a modification (Fig. 3, not shown), the valve 81 faces the opposite direction to that shown in Fig. 2, so as to reduce the volume of the space 48, thereby to increase the speed of response of dump valve 44. Specification 619,943, [Group XXXVII], also is referred to.