Hot welder.

[493mike]

Hello gentlemen,
Yesterday I had a quick repair to do and I had to move the ground clamp from the bench frame to the work. While doing this the clamp touched the sheet metal jacket on my Lincoln Idealarc 250. Big arc and current draw! Now it was turned on but, the electrode holder was empty and hanging yet. The clamp was quite warm considering the time in contact.
Any ideas?
I should add, a couple years ago I switched the polarity while the machine was on (not welding) and sparks were generated inside the jacket.
Thanks for any help guys!
Mike

 

[cvairwerks]

First thing I'd do is look for an open internal ground. Make sure you've pulled the plug or killed the breaker before opening the cover, unless you like dorking around with hot leads close to your body parts... BTDT with 40kV before and I still get twitchy around open high voltage stuff.

 

[matt_i]

I would power off, physically disconnect the cord.

Now take off the housing and look inside.

I suspect you will find char, burn, or heat marks somewhere inside, leading you to the source of the problem.

The chassis of the welder is expected to be grounded at all times. The ground wire leading to the cord/plug, is supposed to be landed on the chassis, with something like a ring terminal or other clamping screw.

You can also cycle the polarity and see if the motion of that puts anything in potential contact with the case.

Imo, the ground clamp being warm from welding isn't a symptom of anything other than possibly a poor connection at either the clamp contacts to the bench or workpiece or something related to the cord being poorly connected to the alligator clip itself. The high resistance will generate heat.

 

[493mike]

Thanks for the responses fellas. When I get some free time I'll open up the jacket for some inspection.
Mike