| 摘要 |
PROBLEM TO BE SOLVED: To prevent rush current from flowing in a normally opened contact and thereby eliminate a rush current preventive circuit by closing the normally opened contact after detecting a phase and a voltage of an AC input power and operating a converter as an inverter by means of a controller and generating the voltage of the same phase as the AC input power on a cable way. SOLUTION: In an uninterruptible power supply, power from an AC power supply 1 is received and the AC voltage is converted to DC voltage by a converter 6 and then the DC voltage is smoothed by capacitors 8a, 8b and them the smoothed DC voltage is input into an inverter 7 and the DC voltage is converted by the inverter into AC voltage synchronous with the input AC power and then higher harmonic wave components of the AC voltage are removed by a filter 10 and finally the AC voltage with no higher harmonic wave components is output. In such an uninterruptive power supply, an AC voltage driving relay 2 is installed which is driven by a normally closed contact 14 which is operated by an auxiliary power supply 16 and whose normally opened contact 2a is installed at the input power 1 side and operating coil 2b is installed closer to the converter 6 than the normally opened contact 2a and which turns AC input on and off. Since the driving coil 2b of the AC voltage driving relay 2 is installed closer to the converter 6 than the normally opened contact 2a, the driving coil 2b of the AC voltage driving relay 2 does not operate when the normally opened contact 2a is in an open state. |
