GB285605A - Improvements in or relating to electric switches - Google Patents

Abstract

285,605. General Electric Co., Ltd., and Angold, A. E. Dec. 13, 1926. Automatic circuit-breakers. - High - speed circuit-breakers of the type described in Specification 254,455 are retained in the closed position by a permanent magnet, a load winding being associated with the hold-on magnet in a manner similar to that described in Specification 252,514, the release of the circuit-breaker occurring in dependence of on a magnetizing force which tends to increase the flux density in the permanent magnet, so preventing any weakening of this magnet. As shown in Fig. 1 the movable contact-carrying arm 4 is held in the closed position by an armature 13 engaging polar projections 26, 27 of a permanent, magnet 16, the armature being carried at the end of a lever 22 pivoted at 24 which is itself connected by a link 23 to the arm 4, the members 22, 23 forming a toggle. The permanent magnet 16 is associated, as shown in Fig. 2, with a winding 30, 31 carrying the load current, this winding being placed upon outer extensions 28, 29 of the pole peices 26, 27. As the current in the winding 30, 31 increases, owing to the fact that its M.M.F. opposes that due to the permanent magnet in the pole-pieces 26, 27 and the armature 13, the flux of the permanent magnet is directed from this path into a path including the polar extensions 28, 29 and the air path between them and at the same time an additional flux in this path is set up by the load winding. Thus a point is reached when the attraction of the armature 13 is no longer sufficient to overcome the action of the spring 11, the flux through the permanent magnet being however increased during the circuit breaker release. As the magnetic circuit of the load winding 30, 31 possesses great reluctance by including a large air gap, this winding may be of large ampere-turns and suitable portions of the magnetic circuits may be laminated in order to obtain quick response with suddenly changing currents. The polar extension 28, 29 may carry a separate opening winding which may be controlled by a reverse-current relay. The degree of overload caused by operation of the circuitbreaker may be varied by adjust ably mounting the armature 13 with respect to the link 22 or by varying the position of the hold-on magnet 16 and its associated parts about the centre 24.