Welder Ballast..?

[slamdvw]

While looking at several schematics for welder controls... would it be possible to build a primary ballast? My Hobart has a saturable core reactor, and that gave me the idea... take a MOT ( or two ) either rewind them with a heavier winding or use as it. DC bias the 'secondary' to allow more current thru the 'primary'. Would such a critter work or am I barking up the wrong tree..? Thanks
Robert

[caosesvida]

man, I don't even know what tree you are talking about!

[smithboy]

When you say "ballast", is that the same as a "transformer"? There are often many words that describe the same thing, so I just thought I'd ask. You probably need to define your other terms so you get the best response possible.

[slamdvw]

I got the idea from a local neon shop, where he uses a variable inductance choke to control the bombarder transformer. Thinking about how my welder ( and several others ) control their output currents, i wondered if the same technology couldn't be applied to the input. By ballast, i mean choke, in it's simplest form. Instead of an SCR control for the input, have an inductive control.

I had an idea that if one used a saturable core ballast ( similiar to the output control of a dialarc or a tr250 ) im sure there are others, but those two im familiar with.

[pulser]

This sounds like it could be an interesting idea, but I'm struggling to figure out what the heck you're trying to do. What would this device do for you? What would this thing control? How would it affect the arc, and what welding process are you talking about?

You mention inductance. I know of an application with an early pulsed MIG power supply, where the designer put an inductor into the final weld circuit to limit the rate and extent of very high current spikes during short circuit events. This had the effect of slowing down current fluctuations, reducing spatter, and smoothing out the arc. The prototype inductor was made in 2 minutes by simply coiling the work cable (-) around a chunk of steel.

[slamdvw]

Im trying to control a Hobart TR250 ac/dc machine, primarily used as a TIG supply. There are times on it's lowest setting (around 35 amp), it burns right thru what im trying to weld, ( sheet metal, copper tubing...). I've seen some very interesting SCR control circuits that seem to do the same thing; however, my electronics knowledge for controlling scr's is a bit lacking. ( that and the scr's i have are only 200 volt rated ) I was thinking of replacing the rectifer diodes in the welder with the SCR's and doing it that route, but back to the lack of experience I go.

After carefully studying the schematic diagram for a couple of transformer welders ( dialarc and my tr250), I came up with the idea of using the control reactor ( or magnetic amplifier as miller calls it) to control the input to the unit ( like the scr controls, but using a variable inductor instead ).