Importance

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Abstract

A trip device of a main circuit breaker is provided which causes only a branch circuit breaker to be set into a tripped state when an abnormal current occurs at a load of the branch circuit breaker while keeping a closed state of the main circuit breaker. The trip device of the circuit breaker has a structure including a trip latch mechanism for opening switching contacts, a stationary core, a movable core which is attracted to the stationary core to release the latch mechanism of a trip lever, an operating pin for interrupting movement of the movable core while the movable core is attracted, an operating spring charged with force when the movable core is attracted, and an inertia roller holding the operating pin, kicked when the operating spring discharges the force, and moved to a position which does not interrupt movement of the movable core. Accordingly, this structure allows a selective tripping system to be implemented simply with small size and low cost.

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First Claim