A loss minimised sinusoidal PWM inverter

Traditional PWM AC motor drives perform well over a wide speed range and have many positive features associated with their simplicity. However, the waveforms used are significantly less than ideal at high modulation depths and low switching rates, particularly with regard to harmonically induced motor losses. An improved strategy for digitally producing PWM based on conventional triangulation methods is presented. A novel technique for reducing the harmonic losses resulting from sinusoidal PWM waveforms is analysed in depth and realised on a 40 kVA inverter. Tests with this inverter on 7.5 kW and 15 kW motors confirm that the inverter´s performance is significantly enhanced for certain operating conditions, without any significant sacrifice.