| 摘要 |
PURPOSE:To remove the component which pulsates at a frequency 2 times a power- supply frequency in a chopper output voltage by making a chopping frequency 2n (n is an integer) times the power-supply frequency. CONSTITUTION:A voltage from a constant frequency ac power supply 1 is rectified by a rectier 2, smoothed by a capacitor C, and chopped by a chopper 4, whose conduction is controlled by a conduction control circuit 8 depending on the result of the comparison of the signal from a speed sensor 7 and a speed setter 9. The chopped current drives a motor 5. A phase-fixing oscillator 11 comprising an oscillator 12 which oscillates at a frequency 2n (n is an integer) times a power-supply frequency and a frequency divider which divides the frequency of the oscillator 12 into 1/2n is provided. The voltage phase of the power supply 1 is sensed by a sensor 14. The output waveform is shaped by a circuit 15 and input to the oscillator 11. The chopper 4 is synchronized with the power supply voltage and performs chopping operation at a frequency 2n times the power supply frequency. |
