Pulse Width Modulation Inverter:
In presenting the arguments here attention will be focussed on a single-phase inverter. Instead of the single rectangular pulse output of Figs 11.46 and 11.48 during each half-cycle, a commutation circuitry can be devised to produce a series of short duration pulses as output in each half-cycle as shown in Fig. 11.55. The amplitude of the fundamental of this output waveform can now be easily controlled by varying the ON/OFF periods. This method of voltage control of an inverter is known as Pulse Width Modulation Inverter. It has the added advantage of low harmonic content at low output voltages. Further, the content of difficult-to-filter low harmonics in the output wave is reduced compared to the single rectangular pulse output.