Lecip Corporation

Hitoshi Komori

Yoshihiro Matsui

Hideki Shimizu

Kazuhifo Kobayashi

An arrangement is made in a transformer such that voltages induced on the opposite sides of a mid-pointof a secondary windingare unbalanced by an amount on the order of 5%. When a ground terminalis not grounded while a mid-point of a load is grounded, a voltage Vis developed between the mid-pointand a non-active line terminaland is rectified to provide a rectified output which turns a transistoron, causing a light emitting elementL to emit light. The resulting light renders a light receiving elementP conductive, whereby a relayis operated to turn a switchoff. When a ground fault occurs on one side of the secondary windingwhile the ground terminalis not grounded, a ground fault detection circuitfails to detect the ground fault, but the non-grounding protection circuitdetects the ground fault and turns the switchoff.

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Motosu, Japan

Hitoshi Komori