| 摘要 |
<P>PROBLEM TO BE SOLVED: To sense an AC ground failure condition to cut off a power to a prescribed load such as a motor while linked to it. <P>SOLUTION: A switching mechanism connecting to first and second power conductors together so operates as to alternately connect the phase of a load to the first and the second power conductors according to a prescribed switching ratio. During a normal operation, the voltages of the first and the second power conductors are constant to a reference potential. If an accidental electric path occurs for at least one phase of a load having a reference voltage, the voltage at the first and the second power conductors changes on time base in relation with the switching ratio. A detector is connected to the first power conductor at an input port, to receive a voltage or current signal of the first power conductor. When an electric path accidentally occurs between a load and a reference potential, the voltage or current signal of the first power conductor changes by a sufficient magnitude relative to a threshold value detected with a detector, and an output signal of the detector represents a detected failure. <P>COPYRIGHT: (C)2004,JPO |
