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Microwave Transformer Arc Welder.

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ahron11

Sat Jul 12 2008, 05:43AM

Registered Member #1572 Joined: Fri Jul 04 2008, 11:14PM
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Posts: 19

Well, the time has come to make something that is really cool besides my 5 stage coilgun. I have decided to make an arc welder and/or spot welder out of microwave transformers with the secondaries rewound either with 6AWG or 10AWG wire. I have already made two but they are just practice. I have a few more MOT's but I would like more, much more. muahahaha. well, maybe like 6 or 7. Does anyone know an easy place to pick some up?

Dr. SSTC

Sat Jul 12 2008, 05:46AM

Registered Member #1407 Joined: Fri Mar 21 2008, 07:09AM
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try your local electronics recycling plant

quicksilver

Sat Jul 12 2008, 02:26PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Send me a private message and I'll share my sources. I have gotten a shed full by finding some good opportunities but I don't want to clutter the thread with that.

On the idea of making a spot-welder; I think that may be your easier route and that the electrodes could be Tungsten rods (used for spark gaps) you may get one to be quite a prize. Overall less money & time.

And arc-welder would be more of a challenge to me. You would need SERIOUS current and it would need to be finely controllable. What I'm thinking is that from each MOT you're getting less than one amp. You know you're going to need about 100+ to do anything fun. I don't see the current boost as the challenge so much as the circuit-strength to manipulate that. It may be there that the costs in commercial ones actually are.

The old, big "buzz-boxes" had a monster transformer, designed just for such a task. BUT they also had the rest of the components on scale with that current level and that's where I see a challenge.

ahron11

Sat Jul 12 2008, 04:31PM

Registered Member #1572 Joined: Fri Jul 04 2008, 11:14PM
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And arc-welder would be more of a challenge to me. You would need SERIOUS current and it would need to be finely controllable. What I'm thinking is that from each MOT you're getting less than one amp. You know you're going to need about 100+ to do anything fun. I don't see the current boost as the challenge so much as the circuit-strength to manipulate that. It may be there that the costs in commercial ones actually are. -Quicksilver

Well, if you rewire the secondary with thicker wire, you can get less voltage and pull more amps. For example if you have a 1kw MOT, and the input is 120V, then you are drawing about 8.3 Amps. So if you rewire the secondary with about 10 turns of 6 AWG wire, and it produces 8 volts, then it would be putting out around 125amps. Just use the power formula ( Power=voltage*current).

Nik

Sat Jul 12 2008, 05:06PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

As far as i remember straight out of a transformer AC isn't so good for arc welding and if you are going to do DC welding you are going to need some serious rectifiers and an inductor or capacitor to keep your DC current from dropping to 0 every 1/120th of a second.

Shaun

Sat Jul 12 2008, 08:29PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Yes ahron you can rewind MOTs for low voltage and very high amperage. But something like that you would use for a spot welder. Quicksilver was talking about making an arc welder, where you must strike a high-current arc to the object to be welded. This requires a high voltage since it must arc.

Lakeowner

Sat Jul 12 2008, 09:32PM

Registered Member #1370 Joined: Mon Mar 03 2008, 09:01AM
Location: Finland
Posts: 56

Try local flea markets and companys dealing with junk electronics. I suggest you to hook many MOTs in series for higher voltage (>10V).

is quite cheap full-wave rectifier. Try to use it like some TIGs: scratch the surface and weld.

jason_gze

Sat Jul 12 2008, 10:49PM

Registered Member #1176 Joined: Sat Dec 15 2007, 12:29AM
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I dont know about you guys, but none of my stick welders are 'high voltage' you must physically strike the electrode to start the arc.

You can pull a 10cm arc with 10v easily if you have enough current to maintain it.

ahron11

Sat Jul 12 2008, 11:35PM

Registered Member #1572 Joined: Fri Jul 04 2008, 11:14PM
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Posts: 19

Well what I am planning on doing is rewinding the secondaries with 6AWG insulated wire and then maybe like use ten turns or however many I can fit on there. Plus with each transformer having around 8 to 10 volts, I will wire them in series and get more voltage too.

ahron11

Sun Jul 13 2008, 05:25PM

Registered Member #1572 Joined: Fri Jul 04 2008, 11:14PM
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Posts: 19

Also after I acquire the transformers I will need a cheap or free source to either salvage or buy 6AWG or 10AWG wire.

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