GB581640A - Improvements in and relating to safety systems for tap changing devices - Google Patents

Abstract

581,640. Locking switches. BRITISH THOMSON-HOUSTON CO., Ltd. June 10, 1943, No. 9328. Convention date, June 13, 1942. [Class 38 (v)] A tap-changing switch 11 can only be operated when a circuit-breaker 16 is in the open position. The switch 11 is operated by turning a shaft 13 either by hand at 26 or by a motor 22 and one revolution of the shaft 13 corresponds to movement from one tap to the next. The shaft 13 carries a disc 27 with a notch 28 normally engaged by a plunger 29 to prevent operation of the tap changer and the plunger 29 can be raised only by operation of a lock 34 or by energization of a solenoid 32. The key of the lock is normally held fast in a lock 33 and can only be removed by turning the key so that the bolt 36 moves to the right and this is prevented by a block 37 when the switch 16 is closed. To energize the solenoid 32 a push 25 is depressed but this has no effect unless contacts 21 are also closed which only occurs when the switch 16 is open. When the shaft 13 is unlocked by raising of the plunger 29 contacts 42 are opened thereby preventing closing of the switch 16 by means of a push button switch 41.