Trip actuator including a thermoplastic bushing, and trip unit and electrical switching apparatus including the same

摘要

A circuit breaker includes separable contacts, an operating mechanism structured to open and close the contacts, and a trip unit cooperating with the operating mechanism to trip open the contacts. The trip unit (80) includes a sensor (87) structured to sense current flowing through the contacts, a processor (88) structured to output a trip signal responsive to the sensed current, and a trip actuator. The trip actuator includes a housing (4,17) including a recess (6), a coil (8) within the recess, the coil having an opening therethrough, a magnet (12) within the recess, a thermoplastic bushing (14) including a conduit therethrough, the thermoplastic bushing being coupled to the housing, and an armature disposable within the opening of the coil and slidably disposed within the conduit of the thermoplastic bushing. The magnet attracts the armature toward the housing. A spring (22) biases the armature away from the housing, in order to cause the operating mechanism to trip open the contacts.