How to Test the Continuity of the Ground Clamp Wires on a Welder
Richard.
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- #2
I'm no leccy guru here but you shouldn't be getting ocv till the trigger is applied. Now as it's not feeding wire continuously it's not a short on the switch wires but my guess would be a short somewhere on that giving you permanent ocv.
- #3
If you're getting a "nasty belt" off it I'd say it's putting out significantly more than normal OCV, it sounds like something is pretty wrong inside.
First thing is to stop using it and take the cover off to have a damned good look to see if anything obvious stands out.
Put a voltmeter between the tip and the earth clamp, turn the welder on and see what reading you get.
- #4
With it unpluged use a multimeter to make sure you have continuity between the earth pin on the plug and the metal case.
Then repeat the same test but to the earth clamp.
- #5
When you take the cover off, look inside for a bank of capacitors (or one big one) There should be a bleed resistor fitted to these (it) It could be that that has failed and needs replacing. It is usually a ceramic type. Post a pic of the in side to allow us to indicate where to check/look.
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- #6
There should be no continuity between the case and the earth clamp.
If you're getting a shock when touching the earth clamp or workpiece then this is live with respect to ground.
If it was the capacitor (which wouldn't be charged to more than OCV anyway) you would only get a shock (if at all) if you touched the earth clamp and the nozzle.
Plug the unit into an RCD and connect the welding earth to a proper ground (water pipe perhaps) switch on and if it trips the RCD you have a short inside between the earth clamp and mains.
As Woz says stop using it and have a good look are get a qualified person to look for you. The first thing I would be looking for is a bit of stray welding wire touching the mains live somewhere,
- #10
Is that a contactor sitting/ hanging close to the base?
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- #11
I can't see a capacitor in there, could be hidden by the wires.
Once you've seen these sparks, does repeating the exercise, without pulling the trigger, still produce them? Do they only appear with the unit plugged into the mains?
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- #14
Just double check that the welding earth is
NOTconnected to the case. Use a multimeter. If they have become connected the earth conductor in the mains lead can carry some of the welding current under certain circumstances, which will melt the insulation.
Also if you stand the welder on your workpiece (e.g. the floor of your car) make sure the rubber feet are in place so the welder and workpiece are isolated from each other.
skotl
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- #15
I think ive found the problem just started to unbolt all the components to check condition of the wires and found the mains power in where it runs along side the earth lead had got hot off the earth leas and the back edge where you cant see till you disasseble has melted to earth lead.
Thanks for all the tips
Are you saying that the live lead is contacting the earth lead? If so then you have two problems as that should trip the RCD (I'm assuming the circuit is RCD protected and, if it's not, it needs to be for this exact scenario!).
So if the live is leaking to earth / the body and nothing is blowing or tripping then you need to find out why.
Richard.
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- #16
I quite agree. Otherwise there is no point in even having the earth there.
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- #17
I'd check the plug too for incorrect wiring. Check continuity between the case and the earth pin on the plug. It's possible the earth conductor in the mains lead may have burnt out.
Turbo
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- Fermanagh, Northern Ireland
- #19
What I would advise is to fit a new 240v mains cable & a new cable between the earth clamp & welder, routing each one so that they are apart from each other & other cables.
What worries me is the fact that the cables have melted, the 240v cable shouldn't have melted unless some has replaced the fuse with a bolt or used very light cable. It should have 2.5mm2 240v flex fitted, preferably rubber covered.
The cable to the earth clamp should be 25mm2, anything lighter will get warm if you're welding at higher settings.
BTW congrats on keeping your welder going, I too have an antique sealey supermig 180 which refuses to die despite its age. I think yours has had an upgrade, the relay on the circuit board probably died (a common problem) & someone has fitted a proper contactor instead.
Source: https://www.mig-welding.co.uk/forum/threads/electric-shock-off-earth-clamp.76638/
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