How does three phase full converter work?

My question is for firing angle(alpha)=0,why is T1 triggered at 30?

• Because you should draw a rectified voltage from six diode bridge. Then you will notice that diodes doesn't start conduct at $\omega t=0$, but they switch when one phase becomes more positive than other. – Marko Buršič Mar 4 '17 at 13:08
• @MarkoBuršič can u please elaborate? – nrb Mar 4 '17 at 17:32

The sinusoidal wave is positive for 180 degrees.

The switched half-cycle is stepped on at 30 derees, and stepped down at 150 degrees to align withe she sinusoidal wave.

The positive half cycle is from 0 to 180 in the diagram below.

Here is some ascii art depicting the stepped approximation of a sine wave:

    ____________
___|            |______               ___
|_____________|
0  30          150    210           330 360

• But for alpha=0 it should conduct from wt=0 right? – nrb Mar 4 '17 at 5:15
• Yes, it will conduct in the interval $[ 0 ; {4 \pi / 6} ]$ leading 30 degrees. – skvery Mar 4 '17 at 5:19
• Try this first. Draw the stepped three-phase inverter currents. See how they commutate every 60 degrees. Then add the sinusoidal wave one of these approximates. See you in chat. – skvery Mar 4 '17 at 5:27