| 摘要 |
PURPOSE:To control overcurrent rapidly by reducing the slip frequency supplied to an induction motor when the overcurrent is generated in the induction motor in a frequency region higher than the rated frequency of the induction motor. CONSTITUTION:The command of an overcurrent detecting circuit 10 is inputted to a slip-frequency control circuit 8. When overcurrent is generated in an induction motor 3 in the frequency region higher than the rated frequency of the induction motor 3, the overcurrent is detected by means of the overcurrent detecting circuit 10, the slip frequency is reduced by means of the frequency control circuit 8, and brought close to zero, and the overcurrent is controlled. Reliability can further be improved by jointly using the lowering of output voltage and the reduction of the slip frequency at the same time as the overcurrent is detected in a high-frequency pulse-width modulation region. |
