| 摘要 |
PURPOSE:To widen a driving range according to the fluctuation of a load, by making the duty ratio of a PWM variable so that the characteristic of V/F may be variable according to the load fluctuation of an AC motor. CONSTITUTION:An excess current detection circuit 7 detects excess current at the DC power section of a power converter, namely, the output current of a smoothing circuit 3 and supplies its output to a count data output circuit 14. By this method, by a micro-computer 10, the output of a constant A count value T for PWM variation command is delivered from the count data output circuit 14 in a microcomputer 10 to a counter 11 of a PWM control circuit 6. The PWM control circuit 6 is composed of a counter 11, a rectangular wave output circuit 12, and a waveform synthesizing circuit 13 having its output connected to an inverter driving waveform shaping circuit 15. |
