welder repair

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Old 01-10-04, 04:33 PM
perkins236
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welder repair

I have a 250 amp welder it is worked by 220 volts, I have a problem with it, the thermostat did not work and I think what you call the secondary winding has melted, it is a piece of wire (it looks like soldering wire it is silver in color) one end of this wire was connect to the ground clamp connector and the other end to the electrode holder connector I have unwound all of it off the transformer (about 20 foot of it) it is about 3/16 " in diameter. it came off in pieces ,the welder still hummed when I turn it on before I unwound the wire and it would weld a little but didn't have proper power.
is there anything I can do to fix my welder
 
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Old 01-11-04, 06:05 PM
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perkins236:

No, the welder will have to be rewound by a shop that regularly does this type of work.

Even if you only see damage on the secondary winding the primary may have also taken a hit due to overloading of the secondary.
You would need a meg-ohmeter to check this.

If your machine is an inexpensive ac machine you may find it would be less costly to replace it.
 
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Old 01-11-04, 10:42 PM
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Is it reasonable to fix this welder yourself? I would say 'it depends.' If I were a pro that used the welder to make a living I wouldn't mess with it. On the otherhand, if I were a hobbyest that could afford to spend some time I'd give it a try. The biggest risk to the transformer you described is an over heated primary winding. Heat can cause the enamal insulation on wire to degrade and you could get a shorted turn on the primary. Such a failure won't be detected with a megger. The megger is usually used on electrical equipment that may have been exposed to moisture. If your welder hums and doesn't blow any fuses or throw out any breakers, the transformer is probably OK.

I used to rewind transformers when I was a kid and didn't know any better. Today, I still don't know much better, but don't have the time to mess with such stuff. I still use some of the transformers I rewound more than 30 years ago. The biggest problems you have are obtaining suitable secondary wire and getting that wire back on the transformer without putting a nick the insulation. If the transformer primary IS damaged it might not last too long, but that's the risk you'll have to take if you decide to give it a try.

If you can get it, 25 feet of wire won't cost you much. Someone once said "Better to have tried and screwed up, than to not have tried at all." Over the years I've had my share of screwups but then again, I've had my share of success too!! It just could be that you have a very favorable risk reward ratio going for you.
 
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