| 摘要 |
PURPOSE:To enable the smooth torque control of an induction motor by reducing the variation in the fundamental wave voltage and the displacement in the phase at the switching time when a PWM inverter is switched between 3-pulse and 1-pulse modes. CONSTITUTION:A source oscillation frequency f0 is counted by a counter 10, is stored in ROMs 11-13, is compared with a DC voltage VC by D/A converters 14-16, and modulation pulse is formed under the exclusive OR conditions 20-22 with the respective phase fundamental wave pulses. The resetting circuit 23 of the counter 10 is switched at the time of switching between 3-pulse and 1-pulse modes, thereby reducing the variation in the effective value of the fundamental wave voltage, and the displacement of the phase can be reduced by the signal from a lead 1-pulse clock generator. Accordingly, the current jump at the switching time can be reduced, thereby reducing the conversion capacity of the inverter and controlling the smooth torque of a motor. |
