You have mentioned that you have to control current in 2-20 cycles. If you go by thyristor firing angle scheme it would be very diffult to achive control as you can apply correction in only 2-20 desceet step. For any feedback loop to work properly there should be large number of error sample & correction. Error sampling/correction is done at very high rate comapred to response time.(in most case like in case continous like in cas of SMPS).

Hi Anil,
What's the minimum number of samples needed to have a good PID control. 2 cycles is very rare and is used in very few application in most of the cases the number of cycles are higher In the range [ 10 to 30] In some cases as high as 100[rare]. In seam welding application the welding is continuously done unlike spot welding. Can I use PID for seam welding where welding is continously done for several seconds to a few minutes.

Regards,
Prahlad Purohit