A question about workshop electrics for my welder (newb)

[Dave Moore]

I agree with crazydave, don’t put an extension in the mains if you can help it, much better to use an extension on the welding cables and don’t coil the cables either. We had a 240/110v welding plant for stick, tig (on carbon, stainless steel and aluminium) never a problem even on big pipes although no good on 110v.

 

[dickm]

I agree with crazydave, don’t put an extension in the mains if you can help it, much better to use an extension on the welding cables and don’t coil the cables either. We had a 240/110v welding plant for stick, tig (on carbon, stainless steel and aluminium) never a problem even on big pipes although no good on 110v.

One caveat to that. When we moved up here, my 100amp Oxford buzz box would occasionally trip the circuit when it was switched on. A knowledgeable electronics Prof ex-colleague explained to me that the big inductance of the transformer meant that on start up, it could look to the circuit breaker as though it was presenting negative resistance (I think that's what he said) hence a momentary very high draw. Running it off a thick extension lead seems to provide enough resistance on start-up to avoid the problem, so that's what I always do.
One other tip; if you do metalwork in the same shed as your woodwork, be *****y careful about sparks, and ALWAYS do a good check when you've finished to make sure nothing is smouldering. Of course, if you have a squeaky clean, sawdust/chip free shop, you should be OK!

 

[ChaiLatte]

Running it off a thick extension lead seems to provide enough resistance on start-up to avoid the problem

You might have to discuss that with your friendly professor. A thick extension lead will have less resistance per unit length than a thin one. Conductance is proportonal to cross-sectional area. Resistance is the inverse of conductance.

Also, since his welder is an inverter, how much relevance do the electrical characteristics of a transformer machine (buzz box) have to his situation?

 

[guineafowl21]

Nothing like an electrical installation thread for a spirited discussion.

 

[Dave Moore]

One caveat to that. When we moved up here, my 100amp Oxford buzz box would occasionally trip the circuit when it was switched on. A knowledgeable electronics Prof ex-colleague explained to me that the big inductance of the transformer meant that on start up, it could look to the circuit breaker as though it was presenting negative resistance (I think that's what he said) hence a momentary very high draw. Running it off a thick extension lead seems to provide enough resistance on start-up to avoid the problem, so that's what I always do.
One other tip; if you do metalwork in the same shed as your woodwork, be *****y careful about sparks, and ALWAYS do a good check when you've finished to make sure nothing is smouldering. Of course, if you have a squeaky clean, sawdust/chip free shop, you should be OK!

I had a Myford ML8 lathe that used to trip the breaker on start up due to surge so went to electrical suppliers who sold me a MCB of same rating but one that didn’t trip on the surge. Don’t know how that works but it sorted the problem.

 

[sawtooth-9]

Nothing like an electrical installation thread for a spirited discussion.

Yep !
Certainly seems to get the "sparks" flying.

 

[guineafowl21]

I had a Myford ML8 lathe that used to trip the breaker on start up due to surge so went to electrical suppliers who sold me a MCB of same rating but one that didn’t trip on the surge. Don’t know how that works but it sorted the problem.

You swapped a B type breaker for a C type, which allows a larger momentary surge. You’re meant to check the circuit is suitable for the change.

Here come 100 posts about loop impedance...

Run.

 

[nickds1]

Not going to enter into the general discussion, but will issue a warning...

If using a long extension cable on a reel, unravel it all before use, especially if using a high frequency load...

This is not about driving the load, it's more about fault conditions and the inductance of the protective ground (earth) cable if it's coiled.

I've received very nasty deep burns as a result of a spark jump from supposedly earthed equipment that was powered from an extension that was still largely coiled on its reel.

Uncoil the extension and the protective ground has far lower inductance so gives better protection, especially to high frequency energy if around inverters, stuff generating arcs etc.

Just saying...

Edit: there is at least one other good reason to uncoil extension leads: heat

Coiled leads don't allow normal heat loss from cables, so the cable current capacity can be seriously derated and cause the insulation to become damaged and even melt at well below the fused level...

 

[dickm]

You might have to discuss that with your friendly professor. A thick extension lead will have less resistance per unit length than a thin one. Conductance is proportonal to cross-sectional area. Resistance is the inverse of conductance.

Also, since his welder is an inverter, how much relevance do the electrical characteristics of a transformer machine (buzz box) have to his situation?

Cable thickness is a compromise. Too thin and it might overheat, too thick and it might not have enough resistance to do the trick. Agree about uncoiling; important point. Tried it with my extension lead and it worked, which is enough for me. Sadly, old colleague is no longer with us, so further discussion would need a ?clairvoyant?.
Yes, I agree old Oxford buzzboxes are very different from modern things with inverters etc. (which are well beyond my near-80 year old brain) but thought it was worth a mention for other stick in the muds. (And no, I don't weld in mud!).
Unlike the blacksmith we used when I was a boy. He was standing in a puddle outside the forge and somehow took the full force of his arc welder, which threw him across the yard. When he went home, his wife insisted he go and see the Doctor immediately. Which in those days was possible. Dr Beach looked at him, said "Maldwyn, any normal guy would be dead after that. You're not, so go home and forget about it." Sadly, he wasn't tough enough to resist pancreatic cancer.

 

[Spectric]

Here come 100 posts about loop impedance

There are no problems doing this if you like living on the edge, but having seen the results when a fault does occur I know the risk are to high but for many non electrical folk they take the view that if it works then all must be ok which upto the point of the fire is true.

 

[guineafowl21]

There are no problems doing this if you like living on the edge, but having seen the results when a fault does occur I know the risk are to high but for many non electrical folk they take the view that if it works then all must be ok which upto the point of the fire is true.

You’re right, of course. It was more a joke about electrical threads, where everyone likes to contribute what they know (me included), then descend into arguments about domestic installers and ring circuits. Meanwhile, back at the ranch, the answer for the OP is - blue plug? Blue socket. Refer to electrician.

 

[graduate_owner]

Not going to enter into the general discussion, but will issue a warning...

If using a long extension cable on a reel, unravel it all before use, especially if using a high frequency load...

This is not about driving the load, it's more about fault conditions and the inductance of the protective ground (earth) cable if it's coiled.

I've received very nasty deep burns as a result of a spark jump from supposedly earthed equipment that was powered from an extension that was still largely coiled on its reel.

Uncoil the extension and the protective ground has far lower inductance so gives better protection, especially to high frequency energy if around inverters, stuff generating arcs etc.

Just saying...

Edit: there is at least one other good reason to uncoil extension leads: heat

Coiled leads don't allow normal heat loss from cables, so the cable current capacity can be seriously derated and cause the insulation to become damaged and even melt at well below the fused level...

Regarding the heat generated, I can remember as a teenager plugging a 3kW fan heater into a partly unwound extension cable. The whole thing melted into a sticky, smelly mess. The cable couldn't be unwound when cool, it was a solid mass of plastic - not that I would have wanted to use it again, even as a teenager.

K

 

[Phil Pascoe]

We threw dozens of them out when women wouldn't listen and used vacuum cleaners on nearly fully wound 5a reels.

 

[Spectric]

Because we are dealing with Ac a fully wound extension lead is not a pure resistance but a reactance comprising of Inductance and capacitance which can introduce a phase shift in voltage and current which may make maters even worse, never thought about measuring it though as it is easier to just unwind the extension lead.