| 摘要 |
PROBLEM TO BE SOLVED: To surely detect a heavy grounding current even in the case of clamping the secondary output of a zero-phase current transformer to a certain value for prevention of electronic parts. SOLUTION: This leakage detector, which is equipped with a comparator 6 which has the output voltage of a zero-phaser current transformer 2 inputted through a low-pass filter 4 and detects the output voltage above a specified value of the zero-phaser current transformer 2, a polarity judging circuit 9 which detects the signals of a positive electrode and a negative electrode being outputted alternately from the comparator 6, and a break signal output circuit 10 which outputs a break signal, based on the AND output of the output of the polarity judging circuit 9 and the output of the comparator 6, is provided with a clamp circuit 12 which clamps the output voltage of the zero-phase current transformer 2 to a certain value, and it sets the clamp voltage to such a level that the output of the positive electrode and the negative electrode of the low-pass filter 4 is over the threshold of the comparator 6. Since waveform over the threshold of the comparator 6 remains even in case that the input of the comparator 6 is attenuated by the low-pass filter 4, the output signal of the comparator 6 is deflected to positive/negative intermittently, consquently the detection of a heavy grounding current becomes possible. COPYRIGHT: (C)2006,JPO&NCIPI
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