| 摘要 |
PROBLEM TO BE SOLVED: To provide a protection breaker that operate on an overvoltage caused by the open-phase of a neutral conductor and that will not activate by high-frequency noise. SOLUTION: A ferrite core bead 10 is inserted in a voltage detecting circuit, that transmits voltage information between voltage lines L1, L2 and a neutral conductor N to an abnormal voltage monitor circuit 6 that detects overvoltage by the open-phase of the neutral conductor and outputs operating signals of a tripping coil 3, that opens a contact point 4 of a main circuit 2.
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