| 摘要 |
PURPOSE:To limit currents positively against overcurrents, and to improve the continuation of operation by providing a feedback mode between a reflux mode and an overcurrent detecting level and simultaneously turning an inverter transistor OFF in the feedback mode. CONSTITUTION:An AC power supply is fed to an induction motor 17 through a converter 14 and an inverter consisting of transistors 1-6. Currents to the induction motor 17 are detected by an AC machine 16, arithmetically operated by a computing element 18, compared with reference voltage by comparators 19-21 and given to a sine-wave PWM controller 22. The PWM controller 22 controls the transistors 1-6 through a base drive circuit 23. An overcurrent detecting level is set by a rheostat RH, a current limiting by a reflux mode is used mainly, and only a singular point where currents do not attenuate at the reflux mode is utilized for a current limiting by a feedback mode.
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