| 摘要 |
PURPOSE:To control an output-voltage variation, when all loads are switched to a feed from an inverter circuit, by feeding a load corresponding to a part of all load capacity from an ordinary by-pass circuit and other loads from an ordinary inverter circuit. CONSTITUTION:Usually, switching circuits 31 are controlled by a switching controlling circuit 39 so that loads corresponding to about 1/2 of the capacity of all loads are fed from an inverter circuit 29 and loads corresponding to the other about 1/2 of said capacity are fed from a by-pass circuit 22. When an instantaneous power failure or power failure is generated in an AC power 20, switching circuits provided at loads having been fed from the ordinary by-pass circuit 22 are controlled by said switching controlling circuit 39 on the basis of an output signal from a voltage detector 35 so as to be switched to a feed from the inverter circuit 29. Also, the switching controlling circuit 39 having inputted a detection signal from a load detector 37 and a failure detector 38 switches all loads to a feed from the by-pass circuit 22.
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