Power saving of PWM rectifier-VSI fed induction machines

The inverter fed ac drives with transistorized grid rectifier are investigated from the point of view of steady-state power saving. It is shown that the optimal power saving control of frequency controlled induction motor drive provides saving about 0.5 to 3% of rated power by flux control less then the rated flux. This valid only for motor torques less than 50% of the rated load. In case of high modulation frequency about the same energy can be saved for both the inverter and sinusoidal operations. For the rated load some power saving (0.5-1.0%) is also possible but only by the increasing of the motor flux over the rated value. Generally, the energy saving control is economical only when the technology requires the frequency control.