Patent GB-541321-A (GB)
Title: Improvements in control systems for fluid-pressure operated circuit breakers
IPC: H01H33/32
Filed: 1940-12-23
Abstract: 541,321. Valves. BRITISH THOMSONHOUSTON CO., Ltd. Dec. 23, 1940, No. 18047. Convention date, Dec. 22, 1939. [Class 135] [Also in Group XXXVII] A control system for a fluid-pressure actuated switch comprises a valve controlling the supply of switch opening and closing fluid and operated by a solenoid-armature, means normally tending to hold the valve and armature in a neutral position, control means, including "trip" and "close" switches for selectively energizing the solenoid to move the valve to either side of the neutral position, and a relay mechanically operated by closure of the switch for preventing repeated closure thereof when the operator does not release the "close" switch in the event that the switch fails to remain closed, due for example to a fault. In the application of the invention to the gasblast switch of Specification 544,017, [Group XXXVII], the movable contact 12 of which is slid by means of an arm 23 on a shaft 22 rotatable by means of the rod 20 of the piston 19, opposite faces of the latter are connected by pipes 44, 45 to annular chambers 38, 40 in a valve block 37, the movable valve member 41 having an annular space 42 adapted to connect either chamber 38, 40 with a central chamber 39 connected to the tank 32, the other being opened to atmosphere. Normally the valve 41 is held centrally by springs 51 but is movable to either side by energization of a tripping winding 47 or closing winding 48 of a solenoid 46, or by a manual handle 62. Winding 47 can be energized by the press-button 64 or trip contacts 67, and winding 48 by the closing button 68. After a certain travel, contacts 56 engage seal-in contacts 58 or 59 controlled by springs 60, 61 to ensure completion of the switching operation. During the opening operation a lever 27 operates the blast-valve as described in Specification 541,165, [Group XXXVII], and a lever 28 opens the switch 65 in the circuit of winding 47 and also changes over a switch 69 from contacts 69b to contacts 69a by rotating a lever 70 anticlockwise about pivot 73. To reclose 68 is depressed to energize 48 over the now-closed contacts 69a, and contacts 65 are closed relatively early to prepare the control circuit for a possible tripping. Also during the closing movement, the levers 70, 72 change the relay 69 from contacts 69a to 69b and the latter contacts if the button 68 is held depressed by the operator, make the circuit of winding 691 of relay 69, which holds contacts 69b closed and so prevents winding 48 from being re-energized if the breaker has tripped out immediately after closure. The circuits of both windings 47, 48 include normally-closed contact 66 of a switch 34 responsive to the tank-pressure. If the latter falls unduly, contacts 66 open and insert in circuit a resistance 661 of such value as to prevent operation of the valve 41 by either winding, while allowing sufficient current to flow through either winding to hold the valve displaced and enable an operation, once started to be finished. Each pole 52 of the solenoid 46 has a tapered part 53 co-operating with correspondinglytapered ends 54 of the armature 49. Lamps 77, 78 indicate the condition of the switch 34 and lamps 75, 76 that of the switch proper.