Converting buzz box do DC welder.

slowrev · Feb 23, 2005

Soundguy or anyone else out there. Is there any reason that I cannot use some BIG diodes/heatshink/fan to make an AC to DC welding converter ?
Going to use a bridge configuration. Getting ready to order the diodes and some twistlock connectors, have the rest of the stuff.

Ben

WhiteRock · Feb 23, 2005

No reason you can't do this, this is how the manufactures do it. /forums/images/graemlins/smile.gif

I have looked into this before, but never actually did it.

Get big diodes. I recommend exceeding your max current by a comfortable margin. I think you will need 3 heat sinks or to insulate 2 of the diodes for a full wave. You will probably get better thermal coupling without insulating the diodes, but will have to insulate the heat sink. But that is easier in my mind.

To get good arc characteristics I think you will need an inductor to put in series with your DC output. Seems I remember browsing some part manual for ideas. I do not know what inductance you need, so I don't know how to calculate it. You may be able to make one. I don't know if you can buy them cheap or not. I will keep an eye out.

Good luck, I'll be watching for your success.

slowrev · Feb 23, 2005

Thanks for the reply, I am getting to common anode and 2 common cathode diodes so I can get by with 2 heat sinks. and insulating the heat sinks.
On the inductor, won't the one in the AC welder cover it, if not a surplus ourfit has one for $40.

I am going to make it as a standalone unit so I can connect it to any buzz box.

Soundguy · Feb 23, 2005

I personally wouldny bother with the inductor... the secondary on the xformer is a huge one.. besides.. you'll get a minute current lag.

I'd also arange it so that you can run it DCEN.. either with quick connects on the cables, or thumbscrew contacts.. big iso switches.. etc.That will be your big advantage.. being able to reun rev-pol only rods.

Tell me how you like yours.. I have a little ac buzzbox, and access to some large iso diodes from an ultra high current power supply. Complete with large aluminum heat sinks.. etc.

Soundguy

WhiteRock · Feb 23, 2005

Good choice on the diodes. That makes it a lot easier.

Not sure what you mean by "the one in the welder". Normally a buzz box does not have an additional inductor. If you are talking about the transformer's secondary, that doesn't count from a node analysis standpoint. I am going to try to avoid getting into the details. If you want to go deeper, let me know.

I weld, but am not even close to an expert. I have been told that it is difficult to weld with a DC welder with no inductor. I do not know if this is true or not.

It definitely will not hurt anything to try. Go without it. If it doesn't seem right, you can add one later. If you have another low voltage, high current transformer laying around, we can talk about how you can experiment to see if you get any improvement in your results.

slowrev · Feb 23, 2005

WhiteRock,
My old 1958 sears 185 amp welder has another coil/inductor/saturable inductor? in the output line, not entirely sure what it is but that welder is better than any other buzz box I have used. Old but works great. My friend and I burned 5 lbs of rods straight at 110 amps one day taking turns and keeping welding. The little beast just got a little warm, but not hot.
Will let you all know how it turns out, pretty busy so it will be a few weeks.

Ben

slowrev · Feb 23, 2005

Soundguy,
Already planned on plug type connectors, will probably be the most expensive part of the convertor.
The main thing I want DC for is for vert and overhead welding. Now if I just had a 220V 50 amp varible transformer........

Ben

Taylortractornut · Feb 23, 2005

Ben I worked in a factory when I was 16 in a summer maintenance job. We had some 3 phase and some 220 GE welders that had a tig set up and stick when the factory used stckwelding in the late40's production. A friend bought a 220 model and didnt like the ac so he wentback to maintenance andboughtasurplaus ac to DC converter and put it on the input side of the welder. Later he used Diodes.