| 摘要 |
PURPOSE: To improve reliability in uninterruptible power-supply system, in which power feeding to a load is changed alternately between an inverter unit and a commercial power supply. CONSTITUTION: The maximum current value at a load is calculated in a maximum value calculating circuit 11, while an effective value is calculated in an effective value calculating circuit 12. A crest factor is calculated from the maximum value and the effective value in a factor calculation circuit 13. When the effective value or the maximum value is over a given level and at the same time the crest value is over a given level during the power feeding from an inverter unit 2, the power is switched to the commercial power supply 1 from the inverter unit 2 through an uninterruptible switch 3. |
