GROUND FAULT CURRENT INTERRUPTER CIRCUIT WITH OPEN NEUTRAL AND GROUND LEAD PROTECTION

摘要

A ground fault current interrupter circuit is provided in which open neutral and open ground conditions create actuation of the interrupter circuit, as well as a ground fault. This is achieved by utilizing a supplemental secondary winding on the differential transformer of a common type of ground fault interrupter circuit. An open neutral lead or an open ground lead produces a current flow through the supplemental secondary winding that induces a trip signal in the secondary winding to initiate opening of the power line. In a second embodiment the supplemental secondary winding induces a trip signal in the transformer only for an open ground lead, while tripping for an open neutral is achieved by directly gating an SCR switch. The circuit arrangements also protect against other conditions, such as a potential in excess of a predetermined voltage between the neutral and ground leads or a reversal of the input connections.