An efficient PWM technique for split phase induction motor operation using dual voltage source inverters

A PWM (pulse width modulation) strategy is proposed for a split phase induction motor drive, where at low speeds each of the inverters is operated with conventional three-phase space phasor modulation, thereby avoiding fifth and seventh harmonics in the motor voltage. At the higher end of the speed range a voltage space phasor modulation based on the twelve-sided polygonal vertices is used, so that the benefit of a higher speed in the modulation range is retained. A technique for achieving the transition to that range without current transients is proposed. The scheme is verified through computer simulation, using a space-phasor-based model of the split phase motor. Details of a practical control circuit for voltage space-phasor-based PWM pulse generation are presented, and the results from an experimental drive are highlighted