Sensor for a ground fault circuit interrupter

摘要

A ground fault current detection and disconnect device. A differential current sensing transformer is employed together with a second transformer having one winding in series with the neutral conductor and another winding serving as an auto-transformer with a part thereof coupled across the line and netural conductors. The auto-transformer provides an alternating current power supply to a diode bridge, the output of which provides a direct current power supply for an operational amplifier. The output of the sensing winding of the differential transformer is an input to the operational amplifier. When the output of the operational amplifier exceeds a predetermined level, an SCR is triggerred on and a circuit disconnect device, bridged across the line and neutral conductors in series with the anode and cathode of the SCR, opens the power supply to the load. Circuit elements are provided to limit the effects of surge currents and line disturbances. A test switch is provided to introduce a known line unbalance and test the circuit operation and disconnect ability.