| 摘要 |
PROBLEM TO BE SOLVED: To provide a ground fault interrupter with a fail-safe function improved so as to be enabled to detect leakage current in a precise sensitivity. SOLUTION: In the ground fault interrupter structured so as to convert an interphase voltage of a main circuit 1 into direct current and feed it to a leakage detecting circuit 5 and a tripping coil 3a of a switching mechanism 3, in which, a power source line 6 of the feeding circuit is to be drawn out between the phases of the main circuit astride a zero-phase current transformer, equipped with a fail-safe function so as to forcefully trip upon failure at the leakage detecting circuit, the main circuit is equipped with a dummy current circuit 11 generating reverse-phase magnetic flux so as to offset an unbalanced output generated at the zero-phase current transformer at a power source line current of the feeding circuit at normal times. The dummy current circuit is constituted by a resistor 11a and a diode 11b, and connected between the phases of the main circuit astride the zero-phase current transformer in a reverse phase with the power source line, afterwards, the resistor 11a is set so that a current flowing in the dummy current circuit at normal times be almost the same as the power source line 6 current supplied to the leakage detecting circuit. COPYRIGHT: (C)2007,JPO&INPIT
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