Earth electrode and power electrode wire area?

I have googled unsuccessfully. I have data about voltage drops etc. But what is acceptable?

Is there anywhere that I can find what are of wire I need, given my expected current and length of wire?

I ask because (Hi. I'm troy McClure...You may recognise me from...) I am setting up a welding traveller based on a Cobramatic push-pull welder. I need to extend the wired from the power source to the feeder, and also the erath electrode wire. I also may need to install a solid wire from the feeder to the gun, rather than the water-fed one that's there at present. While the water fed is superior, they cost a small fortune, unless I can cobble one up, which may or may not be worth the trouble.

I have asked a couple of welding shops, and had vastly (in?)different replies, both between thenselves and from the wire that is already on the welder.

Data

Welding current 220A max MIG Distance from welder to feeder 5 metres 916 feet) Distance from feeder to gun = 8 metres (25 feet)

Existing wire intended to go from welder to feeder length = 2 metres (6.5 feet) area = 70mm^2 !!!!!!

I am sure the welding shops were talking a lot less than this. I do knwo that the same feeder is designed to provide power to a 400 Amp gun, if required. So it's all swings and roundabouts.

Any help appreciated.

Reply to
Old Nick
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On Fri, 14 Jan 2005 14:12:07 +0800, Old Nick vaguely proposed a theory ......and in reply I say!:

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hmm....unusually slow response.

HOWEVER. I realised (and meant to post) that it may well have nothing to do with voltage drop, but simply the cable's ability to carry the current without burning up the shop. Hence although the original cable is short, to carry the 400A it has to be large.

I am going with 50mm^2. It is not that much more expensive and cannot hurt.

Reply to
Old Nick

Voltage drop is an issue with MIG, but you should be OK with 50 mm^2 and it certainly won't burn down the shop at 220 amps.

Reply to
Don Foreman

On Sat, 15 Jan 2005 01:13:30 -0600, Don Foreman vaguely proposed a theory ......and in reply I say!:

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Yes. Well this was why I lpt fiorst to that conclusion.

I actually have alittle proggy that looks at this sort of stuff. I see a 1.4 V drop over the 25metres total distance that I will use, at 220 A and 50mm^2.

OK. I feel safe . But if VD (sorry!) is an issue, then why have the makers of this thing used 70mm^2 for a 2metre length? It seems way overkill even at 400A, if I can get away with 50mm^2 over 13 metres (X2 I might add allowing for the earth lead).

Reply to
Old Nick

I came up with about the same voltage drop. MIG voltage is typically around 24 volts, so I figured 5% of that should not be a problem.

However, I note that the (factory) 10-foot ground lead on my Milller

210 is 3AWG, which is 5.827 mm dia. or 26.6 mm^2. Scaling that by 75/10 would suggest 200 mm^2!

One reason for using a spoolgun is to operate at significant distance from the power supply. It may just be that welders using heavy cables for minimum VD over long runs don't calculate cumulative VD in the circuit but wouldn't appreciate seeing 2 meters of "wimpy wire" at the feeder end.

>
Reply to
Don Foreman

On Sat, 15 Jan 2005 11:34:01 -0600, Don Foreman vaguely proposed a theory ......and in reply I say!:

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Hehe. It is when you NEED that 220A!

Not quite, because you have to factor in the electrode lead length as well. It may not be as long (?) but....anyway it still leaves me with

100mm^2.

Now there's a question. These cables a _multi_ strand. Dioes that gauge of the cable allow for that? So are your strands equivalent to

3AWG solid wire? I am assuming so. Iwill mic my present earth lead........no...maybe I shouldn't. 200mm^2 cable is simply beyond me

All image! I do see a point actually. The company can say "Well _we_ weren't the reason that you were getting low voltage!" This machine seems to operate in overkill mode all through.

I figure that if I do get troubles, I can either add a paralell run of cable, or shorten the whole thing. Advice is that 50mm^2 will do.

Reply to
Old Nick

A 5% drop in voltage won't affect max current much. In short-circuit transfer (which is the case at 220 amps) current is set more by wire speed.

Yes.

Reply to
Don Foreman

On Fri, 14 Jan 2005 14:12:07 +0800, Old Nick vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

rrrghh!

So I go to the shop, and buy my 50mm^2 cable, as it's cut and on the bench, and as I write out the cheque, the guy says "You know rhis is way overkill for your job?" _He_ was nearly overkilled.

I calmly (Calm...Calm) advised him that (a) his own staff had advised me (b) it was better to spend the extra $50 and make sure....

Reply to
Old Nick

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