Automatic ground fault circuit interrupter

Claim 1

An alternating current power distribution system including at least two load current carrying conDuctors receiving power from a supply circuit at the feed end and delivering power at the delivery end, one of said conductors, termed the neutral, being grounded at said feed end and the other conductor, termed the live conductor, being above ground potential; means for protecting said live conductor from current leakage to ground due to a fault creating a conductive path which bypasses said neutral conductor comprising: a. first and second current coils connected in series between the infeed and the delivery end of said neutral conductor; b. a plurality of windings inductively coupled to said coils whereby upon current flow a voltage is induced in said windings; c. a current coil in series with said live conductor and inductively coupled to one of said current coils in current cancelling phase relation; d. resistance means establishing a reference current flow in said series connected current coils, thereby establishing an induced voltage in said windings; e. means additively combining the reference voltage of one winding of said first current coil and the reference voltage of one winding of said second current coil for actuation of circuit closing means; f. a power supply energized at the infeed end of said line; g. gated semiconductors in series between said lines and the load supplied therefrom; h. an oscillator energized from said power supply for controlling the gating of said semiconductors at a predetermined frequency, said circuit closing means being connected between said power supply and said oscillator, whereby, upon current flow in said live conductor bypassing said neutral conductor, said reference voltage is cancelled in the secondary winding of said second current coil, releasing the actuation of said circuit closing means, thereby disconnecting the power supply from said oscillators and resulting in nonconductivity of said semiconductors.