DZ519 breaker(GV3Motorcircuitbreaker)is applied to comtrol theoverload, phade-broken,short-circuir protection and non-frequent start of three-pha squirrel-cage asynchronous electromotor in the circui withmax AV 690 and 1A- 80Acurrent,and is used as distribrtion line protrction and nonfre quent overload conversion, and is also usedas the isolator.