PROBLEM TO BE SOLVED: To make it possible to operate an inverter always with the highest modulation factor and design a transformer with a high primary voltage by separating a converter input from a commercial power supply and connecting it to a battery during commercial power interruption and operating the converter as a booster chopper using a battery voltage as a power source.
SOLUTION: First switching means 7 which opens the circuit in response to a detection signal from power interruption detection means 12 is provided at the input side of a commercial power supply 1 and a converter 2. And second switching means 8 is provided constituting a booster chopper circuit, which is closed in response to a detection signal of power interruption detection means 12 and connects a positive terminal of a battery 6 to at least one input terminal of the converter 2 and also connects a negative terminal of the battery 6 to a negative terminal of the converter 2. In this way, a control voltage range of the inverter 3 can take a higher primary voltage of a transformer accordingly, thereby permitting a decrease in a current applied to a semiconductor during normal operation.
【課題】 蓄電池からの給電期間に、蓄電池の電圧低下 の影響を除去し、インバータ入力直流電圧を一定に保持 する。
【解決手段】 商用電源１の停電時にコンバータ２と商 用電源１の間を第１の開閉手段７で解放し、蓄電池６を コンバータ２の出力側からコンバータ２の入力側に第２ の開閉手段８を介して接続変更して、コンバータ２を昇 圧チヨッパとして動作させ、蓄電池６の電圧が低下して もインバータ３の入力直流電圧を一定に保持する。