| 摘要 |
PURPOSE:To make it possible to operate an induction motor at high efficiency over the entire operating region from no-load to full-load by controlling the induction motor at an optimal power factor variable according to a predeter mined function, from a lower limit to an upper limit, depending on a supply voltage. CONSTITUTION:In order to operate an induction motor at high efficiency and to save energy, power factor of a motor 12 at the time of operation is determined by means of a power factor detector 22 while an optimal operational power factor Pfs variable according to a predetermined function from a lower limit to an upper limit depending on the supply voltage to the motor is determined by means of a multiplier 48 and a signal for bringing a detected power factor close to the optimal operational power factor is generated from an output signal generator 50. |
