| 摘要 |
PROBLEM TO BE SOLVED: To provide a circuit breaker with single-phase, three-wire neutral line absent phase protection, capable of preventing non-connection of an absent phase detecting lead wire even when using a single-phase, three-wire neutral line absent phase detecting point added unit. SOLUTION: This circuit breaker includes a NOT circuit 5 that detects a voltage between a connecting point with a neutral line N of the absent phase detecting lead wire 3 and one voltage pole L2 to be reversed and output to an abnormal voltage detecting circuit 4, wherein the non-connection of the absent phase detecting lead wire 3 is prevented by outputting no voltage to the abnormal voltage detecting circuit 4 so as to prevent the operation of the abnormal voltage detecting circuit 4 when the absent phase detecting lead wire 3 is connected to the neutral line N and the NOT circuit 5 detects the voltage and by outputting a voltage exceeding a trip voltage to the abnormal voltage detecting circuit 4 so as to operate the abnormal voltage detecting circuit 4, outputting a breaking signal from the abnormal voltage detecting circuit 4 to turn on a switching element 6, and exciting a trip coil 7 to operate a tripping mechanism 8 so as to interrupt an electric circuit when the absent phase detecting lead wire 3 is not connected to the neutral line N and the NOT circuit 5 detects no voltage. COPYRIGHT: (C)2008,JPO&INPIT
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