Abstract: In an uninterruptible power supply, a signal generator generates a semiconductor switch drive signal for driving a semiconductor switch and continuously generates the semiconductor switch drive signal while AC power is being supplied via a bypass circuit.

Abstract: An uninterrupted power supply apparatus includes input lines configured to receive AC power from an AC power supply having a grounded neutral point, a converter configured to convert the AC power of the input lines to DC power for output to intermediate lines, a power storage unit connected to the intermediate lines, an inverter configured to convert DC power of the intermediate lines into AC power for output to output lines, grounding capacitors connected between the input lines and a ground, a phase voltage detecting unit configured to detect phase voltages between the input lines and the ground, and a control unit configured to monitor fluctuations of the phase voltages detected by the phase voltage detecting unit to detect a failure that causes abnormal voltage to the input lines.

Abstract: In an uninterruptible power supply, a signal generator generates a semiconductor switch drive signal for driving a semiconductor switch and continuously generates the semiconductor switch drive signal while AC power is being supplied via a bypass circuit.