Actually, I have no plans to build it. I'm just curious what one would have to do to build one.
Obviously, I need a lot of amps. But how many do I really need? What voltage would I need as a minimum?
Obviously, I need some form of current limiting so the system does not self-destruct or self-damage with that level of current (e.g. the work being a solid short). Inductive, rather than resistive, might be the way to go. But can this impedance be made a part of the transformer itself (as opposed to a separate winding) by designing the transformer to handle its own fault current availability without damage (e.g. wires thick enough to not overheat at the design current maximum while that maximum is achieved via the secondary impedance).
Will I need to have the ability to select the current?
What safety features must it have, both electrically, and mechanically? I'm not trying to make something to be UL listed, just to make it be actually as safe as something like this can be expected to be.
I'm sure I'll get a suggestion to go buy a welder and tear it apart and see what is inside. But that's really not what I want. I want to know the numbers (like amps and volts and impedance) and other theoretical stuff, but based on today's real world needs, too.