GB195340A - Improvements in or relating to direct current circuit breakers - Google Patents

Abstract

195,340. Forges et Ateliers de Constructions Electriques de Jeumont. March 21, 1922, [Convention date]. A u t o m a t i c circuitbreakers.-A direct-current instantaneously-acting automatic circuit-breaker is arranged to be released by an electromagnet energized by two coils in two parallel blanches of the main circuit, one of said coils having a relatively large number of turns being connected in a branch of high non-inductive resistance, and the other coil, which has a relatively small number of turns in the second branch of high inductance so arranged that in the case of a sudden overload release will be effected at a lower current value than would ba the case in the event of a more slowly increasing overload. The switch arm A is released by an electromagnet having two windings in parallel branches of the main circuit, one coil a with a relatively large number of turns being of high non-inductive resistance which may be supplied by a series resistance r and the other coil b in series with an inductance c. On a sudden increase in load, due for instance to a shortcircuit, the greater part of the first influx of current passes through the coil a but in the case of a more slowly acting overload the major portion of the current passes through the coil b the two coils acting in conjunction. The coils a, b and their respective parallel circuits may ba arranged for release to be effected at a lower current value with a suddenly acting overload than would be the case in a more slowly acting normal overload. This arrangement also prevents accidental release in the case of sudden collapse in the load in which case the non-inductive branch a, r acts as a discharge path for the inductance c thus producing opposing currents in the coils a, b. An auxiliary choking coil d may be connected in the main circuit to facilitate this action. As applied to the circuit breaker shown in Fig. 2 the coils a, b are wound on a core c adapted to attract an armature b carried by the contact arm A pivoted at o. The arm A carries a second armature G adapted to be attracted by the closing electromagnet H when the control switch M is closed. The attraction of the axmature G is opposed by a spring I which may be adjusted to correspond with various valves of release by the electromagnet C. The relatively fixed contact is in the form of a horn D movable between stops K, L and above the arm A is a second pivoted sparking horn E. A blow-out coil J in series with the main current is arranged adjacent to the sparking horns E, F.