| 摘要 |
PURPOSE:To reduce harmonics of output voltage and improve responsiveness, by providing a ratio adjusting circuit, performing pulse width modulation in correspondence with voltage command, and varying ratio of modulating wave and carrier wave. CONSTITUTION:A converter 2 and an inverter 5 are provided. A thyristor of the converter 2 is controlled by signals of a voltage/frequency command circuit 7 and a DC voltage detector 8. A signal from the command circuit 7 along with one from an output voltage detector 13 is given to a control circuit 14 via an oscillator 11 and a multiplier 12. Its output and that produced at a sawtooth wave generator 16, which outputs carrier wave, are compared at a comparator 17. A thyristor of the inverter 5 is controlled. This reduces harmonics and betters responsiveness because DC voltage is controlled and at the same time ratio of modulating wave and carrier wave for pulse width modulation control is controlled. |
