My Homemade TIG welder

[js530]

Since someone asked for it, here's my project log of building a TIG welder from the ground up (not from a stick welder). Three transformers provide 20 volts each, at probably 50 amps each. I'm going to need to install a 240 volt outlet if I really want some power, the power factor on the transformers (rewound microwave oven transformers) is pretty bad. So far I've tried the transformers and the HF/HV starter, but not together (need a cap for a low pass filter to prevent HV entering the transformers. Power control is provided by a phase angle control, two anti-parallel SCR's (while essentially a triac, triacs have problems with inductive loads, sometimes they dont turn off at zero crossing). Pictured is a triac, although im going to the surplus store tomorrow for the biggest scr's they have. Tig torch is WP17V, with valve.

Some pictures

MT1 broke off the triac

[js530]

No pictures on this update, but I did find a very large fan for the triac, and some emi suppression caps for adding HV. Also bought four 70 amp diodes, which will do until i can find some stud mounted ones on ebay. All together, less than $20.

[2muchstuff]

Do you have a wiring schematic for this. I bet I could scrounge up most of this.

[Hamadamj]

Very interesting !

[sanddrag]

I'd like to see a bead you've layed with it.

[js530]

Originally Posted by sanddrag I'd like to see a bead you've layed with it.

When I do start welding, I don't think it will be pretty. I've never welded tig or even OA, so don't expect anything great.

Schematics are in pdf and dxf

[diarmaid]

Wheres the thread on your DIY Plasma Cutter?

[js530]

Some new pictures. Sorry people on dialup (~2mb)

24-The welder on a prototype case. The "case" is pretty much non existant until I get the plasma cutter working (tin snips are painful)

25-The arc starter, only the transformer has been mounted. It's a 9kv/30ma unit, so it probably needs a seperate circuit from the welder (rated 240va)

26-The front plate, incl. circuit breaker and current adjustment pot (which is unconnected)

27-HF suppression caps, to prevent the power stage from being destroyed by the arc starter

28-A large 120 vac fan

29-The starter tank mmc, aren't those caps familiar?

30-Adjustable Spark gap, a 10-32 screw will clamp the electrodes (tungsten) in place

33-Poor man's HV wire, just some clear plastic tubing around a 600v rated wire

34-Heat sink compound

35-Triac next to triggering diac on top of a big heatsink

Does anyone have an suggestions on how to flatten aluminum sheet? It's bent out of shape from the tin snips, and I can't seem to get it flat again.

[vulcom1]

I am also very interested in your work. It would be nice if you could put some size and values of the components in your pdf file. With the rewound transformers the voltage and wire guage also would help.
Thanks, John

[js530]

The HF suppression caps are rated .047uf 1600 vdc, 900 vac with 5 parallel sets of two in series, giving a .235 uf 1800 vac bank of capacitors. Secondaries are ~22 volts, using around 20 turns of 16 ga plastic insulated (non magnet wire, much cheaper) wire. The tank cap is around 30 of the same .047uf caps in series.

I'm pretty sure I need a better power control circuit than what I have, so the details on that will come later.

[diarmaid]

Great work. Its certainly coming together.

[js530]

I finally had a chance to run both the arc starter and welder, and am slightly disappointed. There's two issues:
First, the plastic holding the spark gap pretty much caught on fire. There is a fairly easy fix, move the gap to the exact center, and if necessary, add a fan (would also provide some arc quenching=better performance)
Second, and more importantly, the arc would not sustain full power. Without a capable amp meter, I can only guess the cause. I have a feeling the transformer (I'm running only a single transformer to prevent tripping the house breaker), is saturating. The HV arc would stay on the entire time, but the high current arc would only be sporadic, despite the arc distance. I'm going to run it again tomorrow with the second transformer running off a different branch via an extension cord, and see if I can't get an arc to sustain. But it was definately a welding arc.

Edit:
After some reading, I realized saturating a transformer is impossible by excess secondary current draw (it's dependent on voltage and frequency only ) I guess my next option is the second transformer, maybe in series.