welding cable sizing

[dai]

does larger than necesery cable draw current from the set??
i know if the cable is too small it will warm up


reason i ask is my new 200 amp set turned up with a 16mm earth lead and it was warming when welding,so rang supplier and he sent down 50mm lead
the mma lead is 25mm so i asked for a 25mm earth

isnt 50mm suitible for like 400-500 amps

 

[brightspark]

does larger than necesery cable draw current from the set??
i know if the cable is too small it will warm up


reason i ask is my new 200 amp set turned up with a 16mm earth lead and it was warming when welding,so rang supplier and he sent down 50mm lead
the mma lead is 25mm so i asked for a 25mm earth

isnt 50mm suitible for like 400-500 amps

no it doesnt draw current it carries a lot more without voltage drop its just a pig to use and pull round and costs more 25 would have been adequate no point in having one larger than the other as its only as good as the smallest cable

 

[rtbcomp]

Don't worry - the cable size doesn't cause more current to be drawn. (To be pedantic it may slightly but only because there will be less losses in a thicker cable).

Thicker cable = less voltage drop and more efficient welding.

 

[dai]

aye,cheers guys, it doesnt seem any different when welding,just heavier,and was wondering

 

[mike os]

50mm.... sell it for scrap

bigger CSA = less loss, so theoretically better , but only if all the relevant cables are oversized.

 

[dai]

50mm.... sell it for scrap

bigger CSA = less loss, so theoretically better , but only if all the relevant cables are oversized.

the set is a tec arc multi process inverter
she's a cracking set and welds really well
most of the welding is mig altho use mma quite a lot when outside
the mma torch lead is 25mm
now the earth lead is 50mm
and theres a mb25 mig torch

 

[brightspark]

this will take the guesswork out of it and answer your question theres nothing to benefit by putting larger cables on than needed .u wont get any extra power or any extra loss if u do

 

[dai]

this will take the guesswork out of it and answer your question theres nothing to benefit by putting larger cables on than needed .u wont get any extra power or any extra loss if u do

cheers

 

[Welderpaul]

50mm cable is horrible. Weighs a tonne, and retricts movement of the rod holder.
We rarley weld on site at such high amperages that warrent cable of that size, but when we do, inevitably we need miles of it to get where we need to be.

 

[dai]

50mm cable is horrible. Weighs a tonne, and retricts movement of the rod holder.
We rarley weld on site at such high amperages that warrent cable of that size, but when we do, inevitably we need miles of it to get where we need to be.

good job its only the earth then

 

[Steph]

If the earth cable was heating up, then I'd be concerned with the cable used inside the machine as well. If you look inside, I'd be really surprised if you didn't find they had used the same light-duty cable linking the DC-supply to the dinse socket on the front panel. I replaced mine with 35mm on my 250A machine. Remember, electrons flow from negative to positive, so the earth lead is crucial in the welding process. If you consider the welding liner and wire diameter, it stands to reason that it wouldn't be able to transfer anywhere near as much power as the heavy earth cable, and it doesn't have to, as most of the energy is transferred into (left behind in) the arc. Well that's my theory anyway, and I'd be interested to hear from others on this, as I could be completely wrong! But again, looking at the liner and filler wire, it could never conduct anywhere near as much power as the earth lead. Don't flame me, as I'm really only thinking out loud here.

Steph

 

[dai]

If the earth cable was heating up, then I'd be concerned with the cable used inside the machine as well. If you look inside, I'd be really surprised if you didn't find they had used the same light-duty cable linking the DC-supply to the dinse socket on the front panel. I replaced mine with 35mm on my 250A machine. Remember, electrons flow from negative to positive, so the earth lead is crucial in the welding process. If you consider the welding liner and wire diameter, it stands to reason that it wouldn't be able to transfer anywhere near as much power as the heavy earth cable, and it doesn't have to, as most of the energy is transferred into (left behind in) the arc. Well that's my theory anyway, and I'd be interested to hear from others on this, as I could be completely wrong! But again, looking at the liner and filler wire, it could never conduct anywhere near as much power as the earth lead. Don't flame me, as I'm really only thinking out loud here.

Steph

i hope i would be right in thinking that the set is constructed properly and some friday afternoon guy cut any piece of earth cable he got his hands on and sent it in the box

 

[Steph]

i hope i would be right in thinking that the set is constructed properly and some friday afternoon guy cut any piece of earth cable he got his hands on and sent it in the box

I wouldn't assume that at all, as the set I have had the identical cable used internally to that which the earth cable was made from. The use of the lighter duty cable would have been purely cost driven, or rather profit driven. Of course the only way you'll know is if you have a peek inside to check.

 

[eddie49]

Whilst it's true that electrickery is a flow of electrons, and, since they carry a negative charge, they do actually go from negative to positive ( rather than "conventional flow", which thinks of current moving from positive to negative ), all these electrons do have to end up where they came from eventually. Otherwise, all the copper atoms in the welding transformer would collapse into an untidy heap of protons and neutrons.... So the current in both the earth lead and the torch cable has to be the same. I haven't taken a MIG torch cable apart, so I don't know how the total surface area of the conductors would compare with an earth lead.

 

[Steph]

I haven't taken a MIG torch cable apart, so I don't know how the total surface area of the conductors would compare with an earth lead.

I have, and the only conductive material I can see is the torch lead liner (a spiral of steel), and the filler wire, neither of which is as conductive as copper, and combined have far less cross-sectional area available to carry the energy supplied by the power supply. My argument is that the bulk of the energy/power (joules/watts) carried by the earth lead is expended in the arc and weld itself, as this is where the load is that the power supply 'sees'. Being that we are dealing with DC, that 'energy' flows down the earth lead. I've also noticed that gasless wire MIG welding requires that more voltage (about +5V) be applied, and I can't help wonder that this is to compensate for the voltage drop across the negative (reversed polarity) torch lead liner due to its increasing resistance as it heats up?

Steph

 

[SirDick Diodenob esquire]

A good quality mig torch has a large cross sectional area of copper using thin braided copper woven around the wire feed tube so the csa could be difficult to check . I have a good quality Murex torch which I think has at least the equivalent of 40 mm sq inside and a Nu Tool Mig with a really poor quality torch that looks like its got about 10 sq mm or less of copper , wouldnt be good for more than about 100 amps if that . I would like to know whats the difference between a good quality torch and a cheap chinese made one apart from the price , there must be more to it than just the csa of the internal conductor but having read various manufacturers websites they dont exactly say why we should be willing to pay more for a good make ?

 

[Steph]

I wondered about whether there was an outer core. I noticed the different size torches claim different current handling figures. I have a cheap Chinese Binzel MB15 copy on my Chinese made Mig Star 250 MIG, and I have to say, as a welding package, it's far exceeded what my expectations where of it. That's with the exception of the 25mm dinse connector and socket, and 25mm cables, plus the tiny work-clamp. I installed a genuine Binzel connector and socket for the 35mm earth lead, and bought a good quality 400A work-clamp.

I've had a CigWeld TransMIG 275 and a WIA 220S MIG in the past, and this one is on par with both of those in my opinion. That's not to say that there isn't a plethora of junk Chinese welders out there, just that this one seems to be the exception to the rule... so far

 

[shenion]

I have, and the only conductive material I can see is the torch lead liner (a spiral of steel), and the filler wire, neither of which is as conductive as copper, and combined have far less cross-sectional area available to carry the energy supplied by the power supply. My argument is that the bulk of the energy/power (joules/watts) carried by the earth lead is expended in the arc and weld itself, as this is where the load is that the power supply 'sees'. Being that we are dealing with DC, that 'energy' flows down the earth lead. I've also noticed that gasless wire MIG welding requires that more voltage (about +5V) be applied, and I can't help wonder that this is to compensate for the voltage drop across the negative (reversed polarity) torch lead liner due to its increasing resistance as it heats up?

Steph

The same current flows in both leads. It has to be. Electrons are not "consumed in the arc". Their energy levels may change, but the same amount flows through both wires.

The differences in arc/mig voltages have to do with the process and wire size. Stick 1.6mm wire in a MIG and you don't need much voltage to get large currents. Arc is also a spray process while smaller MIG is short-arc.

 

[Steph]

The same current flows in both leads. It has to be. Electrons are not "consumed in the arc". Their energy levels may change, but the same amount flows through both wires.

The differences in arc/mig voltages have to do with the process and wire size. Stick 1.6mm wire in a MIG and you don't need much voltage to get large currents. Arc is also a spray process while smaller MIG is short-arc.

Yes, I quite specifically didn't state 'current' as I know it is constant throughout the circuit. Very basic electronics that is, but the power is consumed in the arc, and the high energy carrying electrodes, as you put it, run through the earth lead, and that energy is expended creating the arc, and in the heat which is generated. As there is only a single load in the circuit, the arc, all the power is used across that load, and only a tiny amount across the resistance of the earth and return path, that being the torch lead. If we were talking AC it would be another matter, as the energy pushes and pulls, etc.

 

[shenion]

No difference if AC or DC. Resistance of the work lead and torch is the same. The heat in the leads will be the same regardless of the polarity.