GB493262A - Improvements in and relating to liquid-blast electric circuit breakers - Google Patents

Abstract

493,262. Liquid-blast switches. BRITISH THOMSON-HOUSTON CO., Ltd. March 11, 1938, No. 7642. Convention date, March 11, 1937. [Class 38 (v)] A liquid-blast switch comprises a single pressure-confining chamber immersed in liquid, relatively movable contacts biassed to open position in the chamber and arranged to form simultaneously at least one pair of breaks in series, one of the pair being a pressure-producing break and an exhaust port disposed in the casing adjacent the other of the pair, so that the arc pressure is effective to drive liquid through the port to quench the arc thereat and a movable switch member operable in the liquid outside the chamber for controlling the contacts therein and being in series therewith. Opening movement of the switch member causes initially separation of the contacts in the chamber for breaking the circuit and subsequently separation of the switch member from the contacts to form an isolating gap in the liquid. The Figure shows one pole of an oil circuit-breaker provided with a bridging- member 2 co-operating with a pair of main fixed contacts as 15. The cylindrical fibre pressure-chamber 4 carries a sleeve 26 in which is slidable a piston 25 carrying a vented cuplike member 24 in which, in turn, is slidable a thimble 23 on an insulating rod 8. Contact bridges 5, 6, 7 are mounted on the rod 8, and biassed upwardly by means of springs 29 and, in the case of contacts 5, 6, towards an upper stop 27. Contacts 5, 6 bridge fixed contacts 9, 10 and 11, 12, respectively, whereas 7 engages a contact 13 and is connected at 14 to the contact 15, the circuit being completed by conductors 17, 18, 19, of which 18, 19 are covered by insulation 18<1>, 19<1>. A pair of diverging ports is located adjacent each movable contact as shown at 34, 35, 36, and faced with arc-resisting insulating-material, as 34<1>. Contact 15 is biassed by springs 32 so as to have a limited " wipe " at 33 with respect to the rod 8, and is provided with a stop 37. When the member 2 is lowered to open circuit, spring 20 acting on the piston 25 the rod 8 to follow it, so producing the initial breaks between the contacts in chamber 4, and setting up immediately an oil-blast across the contacts adjacent the ports 34, &c. The piston 25 assists the blast when the arc pressure due to moderate currents, is inadequate, but with heavy are-pressures, the sliding connection at 23, 24 and the springs 32 respectively permit the piston 25 to be forced upwards and the rod 8 and contacts 5, 6, 7 to be accelerated downwards and the interruption. Arrest of the stop 37 by the end-closure 30 enables the necessary isolating gap at 2, 15 to be established.