[lt paul]

would it be possible to rewind a microwave transformer for use in a power supply? if so are there any special considerations to take into account
thanks

[ynneb]

If You are going to rewind the transformer, you may as well just get a brand new one wound for you. That way you can have exactly the amperage and voltage you want.

If however the transformer you already have matches up to your specs and is working, then use that.

[lt paul]

the issue is that i have a nice big transformer from of a 650 watt microwave that i could rewind to put out any voltage i want when i had it wound as a spot welder puting out 4.3 volts it got the secondary-my-windings hot enough to fuse together. i can simply wind it until it seems about right then check with a muti meter and adjust as needed.

thanks for any insights

[teilhardo]

How did you take off the outer coil? Isn't it epoxied together?

[lt paul]

YEs the windings are epoxied but that's nothing a (insert coughing fit from epoxy dust here) dremel and a pack of reinforced discs cant handle. here is a pic of the xfrmer in its previous life as a spot welder

[teilhardo]

Thanks

now i know the details involved. To bad I don't have a grinder

[Swede]

Originally posted by lt paul
the issue is that i have a nice big transformer from of a 650 watt microwave that i could rewind to put out any voltage i want when i had it wound as a spot welder puting out 4.3 volts it got the secondary-my-windings hot enough to fuse together.
thanks for any insights

What was the guage of your secondary for the spot welder application? From the picture, it's tough to tell. It looks a bit light. Have you tried heavy automobile jumper cable?

[teilhardo]

Hey Swede,
How did you make the transformer for the spot welder?
What fancy tools did you cut open the primary with?
-Tei

[doug6949]

A friend of mine rewound a microwave xfmr and it seems to be working fine. Not purdy but functional. His home page is http://ns1.dicomm.net/~axtein/dro/ . I don't recall if he mentions the project specifically but I'm sure he will answer an email.

Doug

[teilhardo]

Thanks, I'll check it out

[gmfoster]

I rewound one and found that as usual it 1 volt per turn. However mine was a very inefficient transformer due to the fact they welded the laminations together to decrease hum. In an hour or so it would be very hot just from it own losses. I just cut off the secondary with a hammer and chisel and it was a pain but nothing that anyone with tiime and determination couldn't accomplish. However as I didn't need near that much current I found an old transformer for a HP quiet jet with blowen fuses and cut the plastic case off to replace the fuses. Its about perfict at 22 volts center tapped and rated around 3 amps.

I used 20 turns of number 12 wire for the secondary on the microwave transformer I rewound..

Garry

[Swede]

Originally posted by teilhardo
Hey Swede,
How did you make the transformer for the spot welder?
What fancy tools did you cut open the primary with?
-Tei

Fancy tools?! How about a hacksaw to cut through the secondary (down to the primary level) on both sides - then, a pair of pliers. It was a pain, no doubt, not something you'll do every day for fun. I think it boils down to the transformer. Some of them are lightly shellac'ed, others can be darned near potted in some bizarre hi-test epoxy.

[lt paul]

for spot welding i was using 8 gauge car audio cable. swede your site is the one that has inspired me to build my cnc machine. i found it in a search for hoimebrew spot welders.

[Bubba]

To respond to Doug6949, yes I rewound a Microwave transformer to power my cnc system (4 gecko 320's). First off, I cut the secondary winding (2000 V) off using a "portaband" powered hacksaw to cut the winding off the side of the laminations. Then, I used a piece of rod and a big hammer to punch the remainder of the coil out. Next, I took a piece of wire and made a 1 turn coil to see what kind of voltage would be produced. It turned out to be .9V+ so I could figure out the number of turns needed for the final AC voltage. When winding the coils, make sure you protect the wire insulation by taping or covering the corners of the E laminations to minimize the problem of scraping the insulation off the magnet wire. Take your time and "try" to pack the wire so it looks neat (lotsa luck).

Yes, I will answer E-mails, but housecalls are restricted to my local area

The reason I have not put any of this on my web site YET, is I am trying to get my mill/drill cnc(d) and still have some things I want to get done before I put it up there.

Art,
AKA Country Bubba
[email protected]