3
\$\begingroup\$

enter image description here

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

\$\endgroup\$
  • \$\begingroup\$ 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. \$\endgroup\$ – Marko Buršič Mar 4 '17 at 13:08
  • \$\begingroup\$ @MarkoBuršič can u please elaborate? \$\endgroup\$ – nrb Mar 4 '17 at 17:32
0
\$\begingroup\$

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.

enter image description here

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

    ____________
___|            |______               ___
                       |_____________|
0  30          150    210           330 360
\$\endgroup\$
  • 1
    \$\begingroup\$ But for alpha=0 it should conduct from wt=0 right? \$\endgroup\$ – nrb Mar 4 '17 at 5:15
  • \$\begingroup\$ Yes, it will conduct in the interval \$ [ 0 ; {4 \pi / 6} ] \$ leading 30 degrees. \$\endgroup\$ – skvery Mar 4 '17 at 5:19
  • \$\begingroup\$ 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. \$\endgroup\$ – skvery Mar 4 '17 at 5:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.