GB668276A - Improvements in gas-blast electric circuit-breakers - Google Patents

Abstract

668,276. Gas-blast switches. WHITNEY, W. B., BRISCOE, E. M., HUDSON, A. A., and BRITISH ELECTRICAL & ALLIED INDUSTRIES RESEARCH ASSOCIATION. April 11, 1949. [April 20, 1948] No. 10930/48. Class 38 (v). In a gas-blast switch, the blast pressure is obtained from the gases discharged from an explosive or other gas emitting cartridge into the switch container, the arrangement being such that the relatively cool air or gas in the container is initially driven against the arc for a period of at least one cycle from the commencement of the arc. The container has three parts ; a tank 12 into which the cartridge 40 discharges when a firing pin 48 is struck by a hammer 47 ; an intermediate chamber 13 housing the switch operating mechanism ; and a switch chamber 14 in which a moving contact 17 co-operates with a fixed nozzle contact 15. The three parts of the container are separated by filters 44, 45 of expanded metal or perforated metal plates, and the resin bonded paper wall 19 of the switch chamber 14 may have a quartz lining 20. When the cartridge is fired, the gases are directed by a nozzle 43 on to the end wall of the tank 12 so as to reduce the kinetic energy of solid particles in the gases. The gases then pass through the filter 44 into the chamber 13 and then through the filter 45 into the chamber 14. The pressure in the chamber 13 forces down a piston 26 against the pressure of a spring 28, to retract the contact 17. A blast of air, which is followed by the blast of the cooled and filtered gases, flows from the chamber 14 through the nozzle contact 15 to extinguish the arc drawn between the contacts. The downward movement of the contact 17 is limited by the engagement of a collar 30 on the piston rod 29 with the spring loaded piston 31 of a dash pot 32. As soon as the pressure in the chamber 13 falls, the spring 28 returns the piston 26 to reclose the contacts 15, 17, but in the meantime an isolating switch 138 will have been opened. The contact 17 has a lip 18, and the contact 15 an insert 56, of highly refractory metal such as a sintered tungstencopper mixture. A single cartridge and tank may be used for all three phases of a three phase switch. The insertion of a fresh cartridge may be effected manually or by an automatic cartridge feed. The tank 12 may be of large thermal capacity, or have cooling fins or be cooled by water. Specifications 26694/01, [Class 38], and 278,764, [Class 38 (v)], are referred to.