Arc Welder Ballast

This is the latest addition to my 6" x 30", 5KVA pole transformer-powered Tesla Coil system. It is a Buzbox brand 230 Amp A/C arc welder or "stick" welder. I only paid $25 for it. The fellow I bought it from thought it had some sort of internal problem.

I removed the case and studied it carefully, but couldn't find anything wrong. I cleaned it up, painted it, and put it back together. I didn't modify it in any way, so I can still use it as a welder if I want to. Instead of messing with the welder, I built a special extension cord for my pole transformer that allows me to simply plug the welder in to form a series ballast circuit. The data plate says the welder draws a maximum of 48 Amps at 240VAC. This welder uses a simple shunted step-down transformer to convert voltage into current. The shunts are shaped like a square "U". The two laminated iron arms of the "U" slide into the core window between the primary and secondary coils.

I've tried the ballast with the welding leads open and shorted together. With the front current adjust handle pushed all the way down, the shunts are fully inserted and amperage is minimum. Even at this setting, with the welder leads shorted together the pole transformer still draws 28 Amps. That's 6720VA! A 6" coil system running at 6720 Watts is a pretty amazing sight, I can assure you. With the welding leads open circuited, the system only draws 7 to 8 Amps. Even at 7 Amps, Tesla Coil performance is excellent, with plenty of long, wild streamers. The arc welder ballast is a big improvement over the twin MOT ballast I had been using. The welder at 7 Amps gives longer sparks than the MOT ballast at 20 Amps. I suppose the main contribution of this new ballast is efficiency--I get more spark length out put for less power input than I ever have before with the 6" system. Hope you like the pictures. I always wondered what was inside an arc welder. The answer is: not much! There's only a big, fat, variable transformer, and a little blower to keep it cool...nothing to it.