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# How can I build a 220V welder using 220V microwave oven transformers? Answered

I read TimAnderson's Instructable on building a homemade welder from microwave oven transformers, but that instructable is for a 110V setup, what should I change to make it work using 220V transformers on 220V.
(I already gathered all the materials...)

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If your microwaves came from a 240v oven, you should do it exactly the same as in the Instructable. connect the primary's in parallel. If they came from 110v ovens, you should connect them in series.

sorry ment "transformers came from a 240v oven...

Thanks a lot, I guess I will have to investigate some more, because I've received both answers, in terms of connecting the primaries in series or parallel. I think that if I connect them in parallel, the outcome voltage might be too high (therefore having a lower current), and if I connect them in series I'm not sure what the result might be, but I'm guessing lower than in Tim's Instructable.

Here, when tim says that you should wire in parallell, is olny if the transformers are made for 120v. if you run two 120v transformer in series on 240v, they will get 120v each. but your transformer came from 240v ovens and wants to run on 240 each. so you should parallell wire them. an arc stick needs nat least 35v+ to get started, so you cant wire two 240v transformers in series...

Thank's a lot, I totally agree with your solution, once i build it I will tell you how it goes.

Is that 220V single phase? If so, looking at step 5 in Tim's ible, and subbing a 220VAC single phase source for the dual 110VAC sources the primary would be wired like the pic below BE VERY CAREFUL. The circuit Tim shows in step 5 of his ible has no safety features included.

Thanks for your help. Yes it's 220V (from the wall, residential not industrial) single phase. By the way, what does subbing means?... (English it's not my first language), so according to your diagram that's the setup for the welder using 220V and two 220V microwave transformers?

Now that I've had some time to think about it seandouge has the primary wiring right but if you're running yours off 220, the secondary wiring might be wrong now. It might put out double the volts that it should.

If the transformers are 2- 220v on 220v. wouldn't the wiring be the same as 2 - 110v transformers on 110 v. And I agree about no safety devices anywhere.

Yes, I think if it were 2-phase, you'd connect it as originally shown Or possibly like this (too tired to confirm...I'm sure if I'm wrong someone will come and remind me of my folly...)

About the safety devices I was thinking of making a enclosure with the microwave metalic case and grounding it. Maybe a shorter (it's that the word?, I mean it as in installing a fuse) Any suggestion is appreciated. Thnks again