The cascade weld control AC outputs (H1, H2) are wired to the appropriate terminals on the primary side of each transformer. The transformer secondary’s are wired to the weld gun and copper buss bar. The transformer outputs are isolated by the design of and properties of the welding transformer and thus you can connect one leg of each transformer secondary together on a common bus. This connection can also connect to the machine frame or ground. The control, transformer and machine should all be connected to the plant distribution ground.
24 Gun Cascade Welder
There is much more involved here, than can be covered in this forum. A machine builder should be contacted to address critical topics such as:
Exceeding SCR Voltage Rating
Single or Simultaneous Firing
These are important questions for qualified machine builders.
Yes, the negative of multiple transformers can be connected together.
Reference: RWMA- Resistance Welding Manual, 4th Edition