ac welder to dc

[gopher]

looking for ideas to make a ac welder to dc welder

[Swarf&Sparks]

big bridge rectifier

[Evan]

And in a box, like this.

[Swarf&Sparks]

No water cooling Evan?

[Evan]

Nah, just air. It has a couple of other tricks though. It contains a booster transformer that supplies about 140 vac to the outlet (normal here is 120 on a branch circuit). This is to compensate for voltage drop on long extension cords when running power tools.

There is also a big capacitor on the DC out side to aid arc striking. It charges to the full open circuit voltage and gives an extra zap at the strike as well as providing some filtering.

[Swarf&Sparks]

Add a gas BBQ piezo striker to initiate arc, and you could damn near TIG weld with that.

[QSIMDO]

I saved instructions on how to do that but it's at home.
Unless someone else is more forthcoming before then I'll post what I have later.

IF I can get home!
We're flooded everywhere around.

[Swarf&Sparks]

Consult the oracle (google)
Frinstance
http://forum.doityourself.com/showthread.php?t=224297

[Ian B]

Evan,

You mention a 'big capacitor'; how big, what voltage rating and is it an electrolytic?


There's often mention of an in-line inductor (something like this: http://www.surpluscenter.com/item.as...tname=electric ); have you found the need for one of these?

tia,

Ian

[Evan]

You mention a 'big capacitor'; how big, what voltage rating and is it an electrolytic?

Umm, it's about this big (holds hands apart about six inches).

I would have to look inside to see. I built that about 15 years ago. Still works fine. It's electrolytic, rated at around 150 volts and 20,000 mfd. I have several more of those kicking around. I put a fat bleeder on it to discharge it in a few seconds after turning the welder off. You have to be a bit more aware of not making a circuit through yourself as it raises the open circuit voltage from around 80 ac to about 115 vdc. Strikes nice.

[added]

I haven't used an inductor. That's mainly to prevent damage on motor-generator welders. The capacitor I used serves to absorb spikes too and the diodes I used are great big ceramic packaged jobs rated at a couple of thousand amps surge and several hundred continuous. I put them on copper heat sinks too. The capacitor is pulse rated. A non pulse rated capacitor won't last more than a few hundred arc strikes.