PURPOSE:To improve the reliability and to reduce the size, by controlling a chopper circuit when electric energy accumulated on the power inverter side is higher than a predetermined amount and recovering the accumulated electric energy to power rectifier side. CONSTITUTION:A PAM inverter comprises a power rectifier 1, a surge current control resistor R1, a chopper circuit 2, a power inverter 3 and the like. A recovery discharge circuit 7 comprising a resistor R3 and a transistor TR3 is connected between a common joint 4 of the resistor R1 and a transistor R1, and a current detector (Hole CT)HCT2 is inserted into a path connecting between the common joint 6 and the power inverter 3. Consequently, a discharging resistor for discharging/consuming energy accumulated in a smoothing capacitor at the power inverter side or a magnet switch to be employed as a condition for stopping operation of the inverter can be eliminated.
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