Dear Dan,
Thanks for your reply,



I am very sorry but I haven't come across any good internet site that gives information on Resistance welding. I learnt first about this in a subject Welding Technology that I had during my Graduation. I learnt more when I came in contact with S.M. Engg. for whom I am working with and designing the controller.



The Resistance welding controller goes beyond just maintaining the current.
1. Its job is to control all resistance welding parameters that include current, Pressure, heat, Water circulation for cooiling, 2. Provide various cycle timings such as Squeez, Precompress, Forge, Weld cycles, Hold, Index, Index delay, etc.
3. Control Outputs such as Solenoid valves of various cylinders, Index Output, Motor Output for seam welding machines.
4. Take inputs from Foot Switch, Thermal switch, pressure switch, seam cut off etc.
5. Provide a good user interface for programming, executing weld schedules, Provide diagnostic routines for trouble shooting.



Is it? Whats soft start...



You are right Dan, these resistance welders are very noisy, But with good techniques its very much possible to make precise measurements of current. [ Thanks to Kai for great noise reduction trick I learnt from him and the links that he gave ].

Measuring primary current can give an approximate idea of whats going on secondary but it may be very inaccurate too. Its always better to measure the secondary current directly.

Thanks & Regards,
Prahlad Purohit