Power cct. breaker with two secondary trips - one trip being of electrodynamic type whose natural and breaker time cycle is smaller than that of second trip

摘要

The second secondary trip of the power circuit breaker takes over the tripping function when the first secondary trip fails. This first secondary trip is of electrodynamic type whose natural cycle, together with that of the power circuit breaker, is smaller than the natural cycle of the second secondary trip. Preferably, however, both secondary trips are triggered simultaneously. The system may contain two capacitors, charged by an operating voltage source, which may be sequentially discharged across the excitation winding of the electrodynamic trip. A thyristor and a bistable relay with two opening contacts may be series-connected to the excitation coil, the opening relay contact being each arranged between a capacitor and the excitation coil and operated in a push-pull mode.