| 摘要 |
PROBLEM TO BE SOLVED: To provide an earth-leakage circuit breaker wherein malfunction due to high-frequency leak is prevented. SOLUTION: The earth-leakage circuit breaker A is provided with a zero- phase current transformer 5 that detects unbalanced current passed through the main electric circuit 2 between a grounded commercial power supply 1 and a load 3, a resistor 6 for detection that is connected between the terminals of the zero-phase current transformer 5 and converts currents passed through the zero-phase current transformer 5 into voltage signals, and a leak detection circuit 8 as a leak control portion that opens contacts 4, 4 placed in the main electric circuit 2 according to a voltage signal converted by the resistor 6 for detection. The circuit breaker is also provided with a filter 7 that is placed between the resistor 6 for detection and the leak detection circuit 8, and eliminates the high-frequency components in detected signals by the resistor 6 for detection. The filter 7 comprises a CR filter provided with an input-side resistor 9 and a capacitor 10, and the input-side resistor 9 also acts as a limiting resistor that limits input current to the leak detection circuit 8.
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