GB500731A - Improvements in electric circuit breakers of the impulse type - Google Patents

Abstract

500,731. Fluid - blast switches. WHITEHEAD, C. D. Aug. 12, 1937, Nos. 22235 and 28636. [Class 38 (v)] Circuit-breakers of the impulse type, wherein a blast or impulse of liquid or gas is supplied under pressure to the separating contacts from a pump or through a valve from a pressuresource, comprise a main fixed contact mounted in or on a rigid support, a co-operating moving contact secured to the vertically-movable bridge or cross-bar of the breaker, a pump cylinder or valve chamber at the side of and rigidly secured to or integral with the said rigid support, and a spring-loaded piston or valve disposed in the cylinder or chamber and adapted to be operated directly by said bridge or a member secured thereon, the arcing taking place within a relatively small explosion pot or chamber which is in direct communication with the cylinder or valve chamber. The arrangement is adapted to be applied to an existing circuit-breaker. In Fig. 1, the bridge-member 8 of a conventional double-break circuit-breaker carries a main contact 7 co-operating with. a sleeve contact 12 as described in Specification 409,085, which contact 12 is mounted in a metal support 5 in which is an insulating member 13 defining an explosion space 4 containing the fixed arcing contact 1. The movable arcing contact 6 is slidable under the action of spring 11 in a bore in contact 7. The space 4 is preferably lined with refractory insulation, and communicates at 15 with a cylinder 14 secured to, or integral with, the member 5 and containing a disc-valved piston 16' mounted with lost motion on a spring-controlled rod 17, the base of which is engageable by a part 24 on the bridge 8 so as to stress the spring 20. When the bridge is lowered, fluid is forced through 15 into space 4 and out of the contact 12 or, alternatively, out of a port or ports in the chamber 5, but the chamber and inlet ports are so dimensioned and disposed that the are is extinguished in the chamber by the pressure of the fluid and that due to the arc. The piston and cylinder may function as a valve chamber and valve, the piston uncovering a port in the cylinder leading to a fluid reservoir, or other forms of valve chamber and valve may be employed. In Fig. 2, main fixed and moving contacts 12, 7 are shown ui a housing 25 with a relief port 26, and the impulse takes place at the arcing contacts 1, 6. The contact 1 is urged downwards by spring 11 and is surrounded by the piston 16 which is urged by spring 20 against the flange 28. In opening, contact 1 follows contact 6 until arrested by stop 34 just above the insulating closure 32, but the piston 16 lags behind, due to viscosity of the fluid in space 4, until again arrested by the flange 28. In Fig. 3, a pump 14, 16 leads at 50 to the space 44 between two plates 43, which space communicates over ports 45 with the space 4 in a refractory insulating tube 35 on the metal member 25. Main and auxiliary fixed sleeve contacts 12, 39 co-operate, respectively, with the movable contact 7 and with the tubular stem 38 of contact 1. In opening circuit, 7 separates from 12, but the spring 11 still urges contact 1 into engagement with 7 until arrested by a flange 40, in which position it lies beyond 12 without, however, fouling the latter. There may be one pump or valve per phase or per break or for all three phases of an A.C. breaker. The Specification refers also to arcing tips of refractory metal for arcing contacts, which tips may be connected by current-reducing low resistances to the associated contacts.