To reduce the sizes and the cost of a sine-wave converter by advancing the phase of a line current flowing to a three-phase AC power source from that of a regenerated current outputted from a power rectifier means when regenerated energy is generated.

When regenerative operation is made, the output voltage of a motor 4 is converted into a direct current by means of a reverse-converting circuit 3 and the current is used for charging a smoothing capacitor C0. As a result, the output voltage of the capacitor C0 is converted into a three-phase AC voltage by means of a power rectifier circuit 2. Then the circuit 2 outputs an output voltage *VCRS and, because of the voltage *VCRS, a regenerated current *IRC which flows to a three-phase AC power source 1 from the circuit 2 flows through a connecting line SR. The current *IRC is divided into a capacitor current *IC and an R-line current *IR and the current *IC flows to a capacitor CR and the current *IR flows to the R-phase of the power source 1. When the regenerated current *IRC flows, in addition, a voltage drop *VLR occurs across a coil LR and the phase of the current *IR advances.