Taking apart a large transformer

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Meh, I picked it up pretty well on my own (though under the slag I am still finding beads attached to only one piece of work :P ). I learn pretty quickly though.

For stick and TIG, you need an AC or DC output with current limiting. For MIG, you need an adjustable constant voltage output.
The first is done by either a series inductor or resistor, or more commonly, a transformer specifically designed to be lossy. The losses (mainly inductive) are adjustable by what's called a magnetic shunt, which effectively splits the transformer in two, magnetic field-wise.
The second, MIG, is done by taking a standard transformer (which has good regulation, meaning the voltage does not drop much when a load is applied - aka, constant voltage) and adding taps to it. So you might have 240V primary down to 15, 20, 25, 30, 35V taps on the secondary.
Looking at your transformer, it appears to have two windings, a small one on the bottom and a large one on top, seperated by laminated iron (the same construction as the main iron core) magnetic shunts. (Or are those wood blocks??) I'm guessing this is a ferroresonant transformer, and the oil can caps were the resonant part.
Meaning: primary is loosely coupled to the secondary, which has a certain value of inductance. Combined with the capacitance, it resonates at 60Hz. By constructing the transformer properly, it can be ran on the edge of saturation in the secondary (top) side - if primary voltage increases, it saturates more and stops working as well. (Saturation is where the iron core simply stops accepting a larger magnetic field, it maxes out.) If primary voltage drops (brownout), it comes out of saturation, efficiency goes up and secondary voltage remains constant.
That's my guess. Depending on the windings, your transformer may be welder ready right now!
Tim
-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @ http://webpages.charter.net/dawill/tmoranwms
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At the very least, I will need to read a good book.

I see.

A resistor would lead to a lot of wasted energy, no?

Oh, I see.

I am going by memory, but you are right and the separator looks more like iron to me.

Interesting.
Wow, that would be interesting. I told my wife that I might make a welder out of that transformer, she displayed relatively little reaction.
In other words: the hypothesis is that the transformer is designed to saturate so that the output on the secondary winding is limited by that. If this hypothesis is true, then, I can weld using current from the small secondary winding.
i
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Ignoramus584 wrote:

Some possible ideas:
http://home8.inet.tele.dk/jan_p/welder/mig1.htm http://www.dansworkshop.com/Homebuilt%20arc%20welder.shtml
Two car batteries can do this. You would make a...power supply...going full circle... http://www.rockmodified.com/2003/april/welder/welder.html
Some reading to expand on what the previous poster has said concerning transformers. http://www.ee-one.com/new-5788474-4313.html
This cute..and cheap. I like the variable output set up. A speed controller for a fan motor may be better. It's an inductive load. Sadly, there is NO transformer. Some big automotive alternators put out between one and two HUNDRED amps. Around the house, you're lucky to need seventy or eighty. With a gas engine, you could use this for a portable battery charger.
http://www.turbomustangs.com/forums/attachment.php?sy5fceab2048370a44fa6cf38a11559e&postid 078
http://snipurl.com/bsv4
which was found here:
http://www.turbomustangs.com/forums/showthread.php?sHd1c48bf754c2b7147477bae8b58221&threadid 99
http://snipurl.com/bsv2
You'd have to add a high frequency superimposed wave to the output for welding aluminium, though. A flow guage is nice to have for the gas..
I hope this guy never gets seduced by the dark side of the force..long download but worth it.
http://www.zalp.com/photolog.htm
mike
--
A few GymyBobisms..the saga continues:
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Thanks Mike, super interesting stuff.
igor

http://www.turbomustangs.com/forums/attachment.php?sy5fceab2048370a44fa6cf38a11559e&postid 078
http://www.turbomustangs.com/forums/showthread.php?sHd1c48bf754c2b7147477bae8b58221&threadid 99
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Ignoramus7928 wrote:

...blush...
mike
--
The trouble with people is not that they don't know but that they know so
much that ain't so.
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Friend of mine used to harvest the coils off the back of picture tubes from TV's. He'd smash the black iron out with a hammer, and compact t he copper parts.
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Christopher A. Young
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