| 摘要 |
PROBLEM TO BE SOLVED: To reduce potential fluctuation, by adjusting a common-mode potential which is decided as the average of the sum of output voltages of different phases to zero by means of a three-level inverter constituted by connecting self-arc-extinguishing elements in series, by utilizing the fact that the output voltage of each phase changes to three levels. SOLUTION: An induction motor 6 is driven by rectifying electric power from an AC power sourcethrough a rectifier 2 and filtering the rectified electric power by means of capacitors 3 and 4, and then, constituting a multistage DC voltage PWM converter (three-level converter) 5. A control circuit 7 of the converter 5 is constituted of a voltage command selection section 701, a gate pulse generating section 702, a gate pulse processing section 703, and a pulse distributing section 704 and generates gate pulse signals (gu1-gw4) to the converter 5 based on three-phase command values Vu-Vw. The converter 5 generates output voltages Fu-Fw of U-W phases in accordance with the gate pulse signals to self-arc-extingushing elements 501-504 of the phases. The capacitors 3 and 4 prevent potential fluctuation by changing the output of the rectifier 2 at three levels by dividing the output into voltages of Vdc/2 each. |
