Hi Anil,
Thank you very much for your feedback.

Thyrisor firing angle control is widely used for speed control of DC motor. There output is speed. You can go through litera of DC motor control.

Thank you very much Anil for reference to usefull motor control documents in your previous posts I will be very greatfull if you can please give me some more links on this issue.

WHat is output current range. ? Instead of Thyristor you can go for MOSFET or IGBT. They can give you better control as there switching freq can be in range of 10 khz and you can apply correction in vert short duration of 100-500 usec whereas in case of thysitor it will be only after interval of 10 msec.

In my application at present I am using a bi-phase [ Two Phase ] line feeding my thyristor. The thyristor gate is controlled by a 8051 based controller card. The thyristor chops the voltage in order to meet the set current and the thyristor is feeding the primary of welding transformer. The primary current is usually 100-2000 Amperes. The welding transformers have a turns ratio of 20 to 50. The secondary current is thus of the order of 2000Amperes to 100000 amperes. This secondary current is applied to the job to be welded which acts as a load across the secondary. Kindly suggest me what else can be used in place of thyristor.
Below is the simplified schematic of my welding machines for understanding what excatly I am doing.




http://mumbai.mtnl.net.in/~prahlad/weld.gif
Thanks & Regards,
Prahlad Purohit