Patent ID: 7936543

Claim:
A ground fault circuit breaker for use with a circuit having at least one line conductor and a neutral conductor, the circuit breaker comprising: a differential transformer having a first magnetic core, the differential transformer being coupled to detection circuitry, the hot conductor and neutral conductor both running through the first magnetic core; a ground-neutral transformer having a second magnetic core, at least the neutral conductor running through the second magnetic core; an oscillator coupled to the ground-neutral transformer, the oscillator providing current to the ground-neutral transformer at an oscillation frequency; and a test circuit that simulates a ground-to-neutral connection, comprising: a test conductor, a portion of which runs through the first magnetic core, the test conductor being electrically connected to the neutral conductor; and a switch coupled to the test conductor, wherein closing the switch closes the test circuit and creates a test path loop along the test conductor for coupling current induced in the ground-neutral transformer to the differential transformer, the coupled current causing the detection circuitry to indicate a successful test.