GB222942A - Improvements in electric circuit breakers and the like - Google Patents

Abstract

222,942. British Electrical & Allied Industries Research Association, Whitney, W B., and Wedmore, E. B. July 9, 1923. Sparking, preventing.-In order to minimize the injurious effect of sparking at the contacts of A.C. circuitbreakers, two or more pairs of break contacts in series are employed so adjusted as to separate in succession during, substantially, one cycle of the alternating current, when the circuit-breaker opens. The time-interval between the succession of breaks is adjusted to correspond, in the case of a single-pole circuit-breaker with a double break, to a half cycle of the alternating current. In the case of a three-phase circuit the circuit-breakers in the phases are timed in relation to one another also. As shown in Fig. 1, applied to a single-pole oil circuit-breaker with the usual main bridging contact 10 and auxiliary sparking contacts 12, the setting is such that the main contact 10 first leaves the fixed contacts 11 followed by the left-hand sparking contact succeeded by the right-hand sparking contact. In the arrangement shown in Fig. 4, a number of pairs of auxiliary contacts 12, 13 in series are adapted to separate in succession.