UNINTERRUPTIBLE POWER SOURCE AND METHOD FOR OPERATING THE SAME

PROBLEM TO BE SOLVED: To provide an uninterruptible power source for minimizing decrease in reliability by suppressing the time for operating a rectifier and an inverter in parallel with a necessary minimum limit. SOLUTION: The rectifier 2 converts the output from an AC power source 1 to a DC. An inverter 3 converts the DC into an AC. A rectify-inverter 4 rectifies and inverts a current. The output from the rectifier 2 and the AC output from the rectify-inverter 4 are supplied to a load 6 via a switch unit 5. Opening and closing of first and second switches S1, S2 are controlled, in response to the detected signal of a first current detector 10 for detecting the charging current of a storage battery 7. A controller 8 operates the inverter 2 and the rectify-inverter 4 in parallel, when the remaining capacity of the battery 7 is high, while the battery 7 is charged by one of the inverter 2 and the rectify-inverter 4, when the remaining capacity of the battery 7 is low.