- Thread starter Shedendman
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madkayaker
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that's it all the welding kit i have come across and PAT has been class one e.g. has an earth and that includes stuff in plastic cases with no exposed metal bits the transformers are earthed and the outputs isolated from earth
Thanks guys,
So maybe I was using the wrong technical term, double-insulated, if it only applies to the plug, and not the outside casing, as I maybe thought.
All the double-insulated kit I have seen has plastic casings of some kind or another, so there's no way it could be shorted by any outside electrical current through the casing.
Like my mate's Kempi inverter mig, for example. You can stand that plastic case on any welding job, and weld the job without any problems, except you might begin to melt it if it was too close...
So I can rephrase my question: Obviously the casing cannot be earthed if it is both insulated from the insides of the welder, and incapable of carrying a current?
And answer it myself: No. Therefore in this case (pardon the pun) however steely your building, the earth clamp and welder casing cannot possibly be electrically connected.... So the example given does not hold up if the case of the welder is insulated.
Following from this, would it be correct to say that at least most pro quality welders would have a case that is insulated from earth, that is, the surface on which it is standing, whether the case is made of plastic, steel, or other materials?
And what happened here below, electrically? Was it likely there was a reoccurring fault inside the welder to allow this to happen?
1. "On a couple of occasions recently while working on my very rusty 1978 vw bay window I have had the welder inside the van to keep it dry or out of the sun. As one of its little plastic feet is missing it has grounded the machine and caused a short on the pcb,which without any problem I have repaired and had running again within ten minutes (and a cup of tea )."
Turning into a interesting discussion. I don't think they made us insulate those welders from the job on which they were standing, for nothing.
So maybe I was using the wrong technical term, double-insulated, if it only applies to the plug, and not the outside casing, as I maybe thought.
All the double-insulated kit I have seen has plastic casings of some kind or another, so there's no way it could be shorted by any outside electrical current through the casing.
Like my mate's Kempi inverter mig, for example. You can stand that plastic case on any welding job, and weld the job without any problems, except you might begin to melt it if it was too close...
So I can rephrase my question: Obviously the casing cannot be earthed if it is both insulated from the insides of the welder, and incapable of carrying a current?
And answer it myself: No. Therefore in this case (pardon the pun) however steely your building, the earth clamp and welder casing cannot possibly be electrically connected.... So the example given does not hold up if the case of the welder is insulated.
Following from this, would it be correct to say that at least most pro quality welders would have a case that is insulated from earth, that is, the surface on which it is standing, whether the case is made of plastic, steel, or other materials?
And what happened here below, electrically? Was it likely there was a reoccurring fault inside the welder to allow this to happen?
1. "On a couple of occasions recently while working on my very rusty 1978 vw bay window I have had the welder inside the van to keep it dry or out of the sun. As one of its little plastic feet is missing it has grounded the machine and caused a short on the pcb,which without any problem I have repaired and had running again within ten minutes (and a cup of tea )."
Turning into a interesting discussion. I don't think they made us insulate those welders from the job on which they were standing, for nothing.
madkayaker
Pro sparkey Pro Welder
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i can only presume that there was a fault on the machine or the earth clamp placement and the current found a alternative path through the welder
madkayaker
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the MMA/ TIG unit does PAT a couple of them
brightspark
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the case on the input side of the welder is earthed the output leads are through the isolation transformer. so as was said in an earlier post the output earth lead isnt conected to the welder frame it just makes the circuit up when welding .so even if the welder was sat on a piece of plate that was being welded it wouldnt damage the welder. if it did u wouldnt be able to weld structures as they are naturaly earthed to ground giving the output earth clamp a path back to the welders incomer earth . the only problem u could have is if the trigger was pulled on torch and the feed wire touched the welder case whilst the ouput eath was conected to the structure it would use the thin earth supply mains lead as a return and burn out the lead
brightspark
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sorrey i should have said if welder was insulated and the output eath clamp was conected to frame of building if the live torch touched the welder case it would have the return path through the mains earth lead but its hardly likely someones going to do that
Thanks, MK.
So in conclusion perhaps we should advise those with steel-cased hobby welders to check the case of their machine is insulated from the welding surface, especially inside a vehicle. Either by plastic feet or wheels, or by sitting it on an insulating surface like a plywood board or, if it's not close to the job, a rubber mat. Although any current from the job is unlikely to find a path into the welder, and any short inside the welder is unlikely to find its way out onto the job, it's better to be safe than sorry.
So in conclusion perhaps we should advise those with steel-cased hobby welders to check the case of their machine is insulated from the welding surface, especially inside a vehicle. Either by plastic feet or wheels, or by sitting it on an insulating surface like a plywood board or, if it's not close to the job, a rubber mat. Although any current from the job is unlikely to find a path into the welder, and any short inside the welder is unlikely to find its way out onto the job, it's better to be safe than sorry.
madkayaker
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all of my hobby welders (2 clarke migs and 1 sip stick) have plastic feet they came with them on
Yeah, so have mine. But some folks lose them...
"As one of its little plastic feet is missing it has grounded the machine and caused a short on the pcb,which without any problem I have repaired and had running again within ten minutes (and a cup of tea )."
What pcb burn-out would that be, a fuse?
"As one of its little plastic feet is missing it has grounded the machine and caused a short on the pcb,which without any problem I have repaired and had running again within ten minutes (and a cup of tea )."
What pcb burn-out would that be, a fuse?
