| 摘要 |
PURPOSE:To improve control stability by determining the polarity of a power converter in phase with the alternating current flowing from the power converter to a load. CONSTITUTION:The controller of a power converter is provided with a detector 16 for detecting the alternating current of each phase flowing to the three-phase induction motor 6 of a load from the output end of a transistor inverter 5, and this output is fed to a control circuit 9. The control circuit 9 is composed of a frequency command section 17, a PWM signal producing section 18, a voltage polarity discriminating circuit 19, a current polarity discriminating circuit 20, a phase synchronizing circuit 21, a short-circuit-proof period producing circuit 22, and a logical circuit section 23. Then, as command voltage polarity signal, voltage polarity signal is phase-synchronized with alternating current polarity phase. As a result, sine wave current excellent in quality can be fed to the induction motor 6 of the load.
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