| 摘要 |
PROBLEM TO BE SOLVED: To provide an uninterruptible power supply whose AC switch composed of thyristors can be cut off as quickly as possible by the use of a power converter. SOLUTION: Power is supplied to a load device 9 from a commercial power source 3 through the AC switch 1 composed of anti-parallel connected thyristors. If a power failure is detected under this condition by a power failure detection means 12, a reference sinusoidal voltage generating circuit 11 generates a high- voltage synchronous sinusoidal voltage Vref2 higher by a voltage difference command value ΔV than a synchronous sinusoidal voltage Vref1 of the same phase as the commercial power source, when a current detection means 11a detects a current of positive polarity. The reference circuit 11 generates a low- voltage synchronous sinusoidal voltage Vref3 lower of the command value ΔV than the sinusoidal voltage Vref1, when the detection means 11a detects a current of negative polarity. Consequently, a power converter 5 outputs a voltage by which the line 17b side voltage of the AC switch 1 with respect to the other line 17a side comes to apply reverse bias voltages to thyristors in an on-state, and the thyristors in an on-state are quickly turned off. |
