Controlling Current of Welding Transformer

Hello,
A wire mesh welding machine has 8 welding transformer with 2 welding head per each transformer. This machine controlled by Mitsubishi FX2N-32MT PLC and Delta HMI. In the HMI screen the welding time and welding current can be increased/decreased by entering numbers. The current controlled by PLC analogue output and SCR. I tried to configure out how the SCR controlling the current but I couldn't as the drwaings not available. My question is any one know how SCR with the anlaogue output from PLC increasing and decreasing the current and how the SCR connected with the welding transformer. What confused me is only 5 SCR and 5 analogue chanel used while the machine has 8 transformers.
Thanks

The controller is called a Phase Angle Controller. Works like a lamp dimmer. Input is 0-5, 0-10, or 4-20 mA. Not sure how the transformers are connected. If you have a 3 phase transformer, only 2 phases need to be controlled. The third phase is connected directly to the contactor.

OK you said you do not have drawings. Can you send photo of transformer and other internals?

Dan Bentler

Should be a weld controller/phase angle coontroller in there somewhere. Depending on the welder manufacturer, usual suspects for the weld controller will be Harms & Wende, tecna, schaltter or clifford.