Boosting the induction motor with the Technique of discrete frequency control

Abstract

This paper presents a new control strategy for induction motor starting based on discrete frequency control (DFC). Considering the inversely proportional relation between the motor electromagnetic torque and the power supply frequency, the DFC technique is based on generating voltage waveforms of the sub frequencies of the power supply frequency. The generated voltages with low frequencies are analyzed by the symmetrical components method. The waveform voltage with the best positive sequence is selected. The proposed control strategy performances are simulated using the software PSIM, and experimentally verified on a laboratory machine. With respect to the classical Booster technique, the proposed new strategy leads to a significantly reduced starting current and an improved starting electromagnetic torque