A permanent-
magnet ground fault circuit
interrupter plug with self-diagnosing function having an
enclosure and a permanent-
magnet mechanism encased in the
enclosure. In one embodiment, the permanent-
magnet mechanism includes a frame
assembly having a crossbeam, a frame pressure post and a core connecting post positioned at each side of the crossbeam, a core attached to the core connecting post and positioned inside a coil
assembly, a spring sleeved on the core connecting post and positioned therebetween an inner
cam of the coil
assembly and the crossbeam of the frame assembly; a circuit-breaking coil and a circuit-connecting coil wound on the coil assembly, respectively, a permanently magnet positioned proximately to the core, a pair of movable contact arms with each having one movable contact positioned at each lateral side of the frame pressure post for communicating with the frame assembly, a pair of fixed contacts positioned above the corresponding movable contacts, and a
metal oxide varistor with one end electrically connected to a first terminal of a power source directly and the other end electrically connected to a second terminal of the power source from a load side across a
circuit breaker.