A PWM inverter in which the maximum three-phase RMS pole-to-pole output voltage is increased, to more efficiently utilize a fixed DC power supply, by generating substantially sinusoidal changing pole voltages having no values within predetermined zones adjacent to each power supply limit, and by switching each pole voltage to a power supply limit for a predetermined number of electrical degrees during each half cycle, resulting in step changes in the pole voltage waveforms from the substantially sinusoidal changing waveform to a fixed power supply limit.