Dear Kai,

Thanks a lot for your reply,

All these calculations and tables assume, that mains voltage is stable. But it is not, neither in amplitude nor in shape!

Considering this factor is there a way to predict the firing angles in advance in order to get the target current set by user in control panel. It will be a great help if you let me know what exactly can be done to overcome this problem.

I have seen several Resistance welding controllers such as Miyachi, they are very good at predicting firing angles to get target current even with single cycle weld they fire the thyristor so well that the attained current is within 2% limit of target current. With two cycle weld the feedback from first cycle can be used to judge the firing angle for second cycle. But with single or half cycle welders there is no referece how do these contrllers manage to do the task so well. To me its a big mystry, I could never figure out?

Thanks & Regards,
Prahlad Purohit