GB219723A - Improvements in or relating to electric circuit breakers and the like - Google Patents

Abstract

219,723. Reyrolle & Co., Ltd., A., Clothier, H. W., and Leeson, B. H. April 3, 1923. Automatic circuit-breakers; electromagnetic switches; sparking, preventing; cut-out arrangements. - A high-speed overload switch, or current diverter (which introduces a resistance into a circuit without actually breaking it) comprises two separate magnetic circuits, one having two air gaps and energized by a series winding and tending to move on the armature connected to the contact member in a direction to break the circuit, and the other energized by a shunt winding and tending to hold the armature in the position in which the circuit is closed. An additional winding on the shunt core may be used to enable the switch to be closed electromagnetically. In the construction shown for use in a traction system, the core A carrying the series winding D is formed with a gap in which the contacts are located and are subjected to the blow-out action of the flux therein, as described in Specification 167,846. The armature C is pivoted at C<1> and serves as a keeper for the second gap in the series core or for the shunt core B energized by the windings E, E'. It is shaped so as to bed closely upon the respective pole faces and is connected by rods H controlled by springs H<2> to the pivoted movable contact-member F. The switch is shown in the closed position in Fig. 2, the contact member F engaging the fixed contact F'. When on fault, the series current increases (usually accompanied by a drop in the shunt current) the pull of the series magnet on the armature overcomes that of the retaining shunt magnet and the pull increases as the armature moves, while, at the same time, the retaining force falls off thereby affording a high-speed action. Moreover, at the commencement of the heavy overload, the reduced flux through the armature due to the shunt winding admits, in the same direction, an increased flux from the series core and, consequently, the reactance of the series winding is increased and the rise of the overload current is retarded. A variable resistance J is provided to adjust the shunt current, and, in the form shown in Fig. 2. the switch in opening, instead of breaking the circuit, increases a resistance K in shunt with it. As used in connection with a traction system in which bus-bars L, L<1>, Fig. 3, supply overhead and track conductors N, N', ordinary circuitbreakers 0, P are employed and in the event of fault, the high-speed switch F, F<1> introduces resistance into the circuit which is broken finally by the circuit-breakers 0, P. The circuit-breaker P, in opening, completes the circuit of the auxiliary closing coil E<1> on the core 13 and the high-speed switch is automatically reclosed.