| 摘要 |
A current leakage breaker is provided to improve reliability of a test operation by preventing a malfunction of a leakage detection circuit caused by a noise and an offset voltage. A switching contact device switches an AC circuit. A zero-phase converter(3) detects a leakage current of the AC circuit, and has a test winding to which a test leakage current is supplied. A leakage detection sensitive setting unit(11) is connected to a secondary side of the zero-phase converter(3) to set the leakage detection sensitivity. A leakage detection circuit(4) determines the leakage current of the AC circuit from an output of the secondary side of the zero-phase converter(3), and outputs a signal when the leakage current occurs. A tripping unit(5) opens the switching contact device by receiving an output signal of the leakage current detection circuit(4). A test circuit(6) has an oscillation circuit and a test switch, generates a test leakage current having a predetermined frequency which is different from a power frequency, and provides the test leakage current to the test winding of the zero-phase converter(3) when the test switch is switched on. An amplifying unit(10) is installed between the secondary side of the zero-phase converter(3) and the leakage current detection unit(4). The amplifying unit(10) has an operational amplifier and an active filter circuit which integrates a passive filter circuit with the operational amplifier. The amplifying unit(10) amplifies an output current provided from the secondary side of the zero-phase converter(3) to the leakage current detection circuit(4), and provides the amplified current corresponding to the predetermined leakage current detection sensitivity. The active filter circuit has a filter circuit switching unit which is switched between a low pass filter in a normal mode and a band pass filter in a test mode.
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