i wanna design dis in multism,

1.DONNO HOW TO ADJUST FIRING ANGLE OF SCR TO 45 DEGREE...PLZ

 

I don't know Multisim, but, if you think about it, the method is not too hard.

Your line voltage runs at a constant frequency. That means that each positive AC excursion takes a fixed amount of time. You can detect when the line voltage crosses zero for a timing reference. So, having the zero crossing detected, use a timer function to wait for a 45 deg interval and fire the SCR.