An improved single phase to three phase converter for low cost AC motor drives

A low cost four quadrant single phase to three phase converter for AC drives is described. The technique uses a single phase reversible rectifier operating at unity power factor to produce a balanced DC supply at a controlled high voltage using two IGBT power transistors. Four additional IGBT power switches operate on this high voltage to produce two pulse width modulated (PWM) waveforms using a novel space vector modulation (SVM) strategy. A three phase motor load is then connected to the centre of the DC supply, and the two PWM voltages, to give a four quadrant reversing AC drive. The unique feature of this system is the modulation strategy, which achieves higher motor voltages than any previous published method while achieving excellent harmonic suppression at high efficiency in motor sizes restricted to the rating of the single phase supply (typically 2 kW)