| 摘要 |
<P>PROBLEM TO BE SOLVED: To switch a power supply, even when power failure has occurred to other power supply, without interrupting operation. Ž<P>SOLUTION: When power failure has occurred in a three-phase power supply 1, power supply abnormality detecting signal 120 is outputted by a power supply abnormality detecting circuit 30. Then, a power supply switcher 20 selects and outputs an output voltage of an uninterruptible power supply 10. A phase detection circuit switcher 43 selects and outputs phase information, outputted from an uninterruptible power supply phase detection circuit 41. Since the uninterruptible power supply phase detecting circuit 41 has been detecting phase of the uninterruptible power supply 10, when the power failure occurs, the phase detection circuit switcher 43 can output exact phase information of the uninterruptible power supply 10, immediately after the phase detection circuit switcher performs switching of outputting phase information. Accordingly, the operation is not interrupted upon switching the power supply. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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