| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive uninterruptible power supply system that operates normally even when power returns after outage continues for a long time.SOLUTION: An uninterruptible power supply system includes uninterruptible power supply apparatuses U1 to U3. Each uninterruptible power supply apparatus, in the case of outage: turns off a switch S3 and makes a bypass power supply switching instruction signal &phgr;BPA be at an "H" level and latched, when a corresponding switch of an output board 7 is turned on and output voltage Vo lowers below the lower limit voltage VL; and, in the case of power return, turns on switches S4, 4 when the signal &phgr;BPA is at the "H" level. Thereby, each of the uninterruptible power supply apparatuses U1 to U3 individually performs bypass power supply switching operation and operates normally even when power returns after the outage continues for a long time. |
