AC-Welder converted to DC?

Factual Questions
1

I have been talking with a professional Welder and he made a remark that his Welder was DC and because of that he could produce cleaner, better welds without
spluttering. Now my question, can i easely convert my 220V 200Amp AC Welder to DC? what parts would i need?

Thanks

2

You’d need a big-assed rectifier, like those used in '70s vintage diesel locomotives. It’ll be cheaper to buy a DC rig.

3

I agree. You’d need a rectifier to handle the full current of your AC unit. And that wouldn’t be cheap at all. Best to set that unit aside and buy an AC/DC unit.

Here’s a Lincoln AC/DC Unit for under $540.

4

I’ve done it. As others have said, you need 4 big assed rectifiers. Not at all economical unless you can get them surplus for cheap. I think mine came from either hosfelt, jameco, or all-electronics. Commercial rigs usually used a center-tapped transformer to save two rectifiers. This is not practical on a home-made converter, as the transformer cores are typically welded, precluding rewinding.

These will need large heatsinks, which need to be isolated, as the mounting stud on the large rectifiers is hot. I got 2 each rectifiers with anodes to the studs, and two with cathodes to the studs, this allowed me to use only two heat sinks. If all the rectifiers are the same polarity, you need three heat sinks. (If you can’t work out why, you shouldn’t be attempting this)

You can get by without it, but a large inductor after the rectifiers makes for a much smoother arc. something on the order of .25 - 2H (Yes Henrys, not mH) would be about right. Note that this must be a gapped core, and must be wound with heavy enough wire to carry the arc current. It will be about as big as the transformer in your AC buzz box.

DC can have a little less spatter, and gives you more electrode options, and can be easier to maintain the arc, but it isn’t a cure all. In some cases AC is much better. For example, welding in tight corners the arc blow makes DC a real pain. Also you need to keep any fixturing magnets well away from the arc. The magnets cause wicked blow, and the current in the workpiece can cause them to let go unexpectidly.

5

Hi “Kevbo” you make it sound like not an idea to follow up upon but you seem to know your trade, my main problem is that i am welding 1.2mm Stainless steel and i can not adjust my welder lower than 60amps, so i am using 2mm rods, i could get thinner rods but they get to much current and flare, could i some how halve my amps with a resistor?
Thanks