Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
A bridge circuit is used. Two IGBTs in the bridge are simultaneously turned on at 50/60Hz and then the other two. Then, the output becomes an AC waveform at 50/60Hz. This is for square/quasi sine waveforms. For sinusoidal it's slightly different, in the sense that the IGBTs are turned on at different duty cycles at a specific time period (of the modulation frequency).