Abstract: The tripping velocity of miniature circuit breaker has a great effect on the short circuit breaking capacity;the quicker velocity,the better current limiting ability,also the better short circuit breaking performance.How to improve the tripping velocity based on the small changes of existing mechanism,is always a difficult point.The tripping plunger to trip is used,then go on pushing the moving contact,by which it improves the tirpping velocity of miniature circuit breaker.This method is verified by motion simulation,high-speed photography and short circuit breaking tests.

Key words: miniature circuit breaker(MCB), short circuit breaking, tripping velocity, motion simulation