3 Phase Cable

[dcocks]

Hi
I need to extend the cable or shall i say put a longer one on my 300 amp
3 phase mig.
anyone know of a good online suppler its 4 core 3 lives and a earth must be quite old i would think.
Thanks in advance David

 

[Archie]

City Electrical Factors will be able to get it but I suspect they won't keep it in stock at the local distributors. I've also previously been recommended Wilts Wholesale though I've not used them. I'm sure you already know that 4 core flex is anything but cheap....

EDIT: Just spotted you were after an online dealer. CEF don't deal online so sorry about that.

 

[Robotstar5]

Try this www.qvsdirect.com/

 

[theoss]

I see it is a fairly old topic, but;

The cable I would use to extend the length of a three phase welding machine supply cable would be SY cable.

It's often specified for automation equipment, but it is tougher than normal flex and much more flexible than steel wire armoured cable. It has a a layer of clear PVC, a metal braid, then another PVC sheath and finally the insulated individual conductors.

Most wholesalers can get this easily, if they don't stock it.

I don't recommend CEF for price though. I find edmundon electrical or Newey and Eyre much more competitive. Probably about £1/ metre for what you need.

 

[madkayaker]

don't forget the earth the Brade

 

[theoss]

don't forget the earth the Brade

using those fiddly awkward glands...

I would earth but I find it very common to see a plastic stuffing gland used and no attempt made to earth the braid at all. Since screening is primarily provided to prevent interference in sensitive control circuits it seems disregarded by some

Maybe there is a better choice of cable, I just seem to have seen used/ used a lot of this stuff for portable three phase machines.

 

[madkayaker]

use stuffing glands if you want and then just twist brade together and use crimp

 

[theoss]

use stuffing glands if you want and then just twist brade together and use crimp

Thats's what I did last time making some generator supply leads for some portakabiins.

 

[Pete.]

We use 3-phase cables of this type at work and we never ever earth the braid. We have dozens of them, and they are hard-worked too in a demolition environment.

 

[madkayaker]

the Brade should be earthed to give e.m.f shielding (not a great concern) and a earth protection if the cable is pierced with out hitting the cpc.

 

[theoss]

the Brade should be earthed to give e.m.f shielding (not a great concern) and a earth protection if the cable is pierced with out hitting the cpc.

Here is what Wiki has to say about SY

http://en.wikipedia.org/wiki/SY_Control_Cable

I always thought the steel braid was for RFI protection on sensitive circuits, but here they say it is for mechanical protection.

 

[madkayaker]

Ive never relied on the Brade as an earth but always treated as a protection that needs earthing

 

[theoss]

Ive never relied on the Brade as an earth but always treated as a protection that needs earthing

That's one thing I have never seen, braid used as a current carrying earth!!!

If you read electrics forums you might have seen the many debates regarding using steel armour as an earth on an SWA cable...

 

[madkayaker]

steel amour as you know can be used as CPC but depends on size. I don't go on sparky forum to much like work!

 

[Robotstar5]

I always thought the steel braid was for RFI protection on sensitive circuits, but here they say it is for mechanical protection.

Will have to check but I think CY cable gives RFI protection as it has a screen layer.

 

[madkayaker]

i think you right on that. YY is the Grey flex, CY has the tinfoil in it and SY is the armor braid

 

[eil]

Im like theoss here I havent seen as yet the braid earthed on SY cables, Which should be.... is that right?

 

[madkayaker]

it should

 

[theoss]

Im like theoss here I havent seen as yet the braid earthed on SY cables, Which should be.... is that right?

I have seen the braid earthed, but it is sometimes neglected when using the cable as a supply flex to a machine, rather than a control or instrument circuit. On control circuits where RFI is seen to be a potential problem, you use a brass gland that is secured onto the SY braid (similar to an SWA gland, but not the same item).

What I meant is that actual earthing of the equipment supplied is always done by an earth conductor inside the cable, and earthing of the screen is sometimes neglected with none RFI sensitive equipment, even though it should be earthed for safety reasons should the cable become damaged.

Now, the other common workshop cable is steel wire armoured, which isn't normally used to supply mobile equipment, but is sometimes seen in use.

With this type of cable, it is acceptable to use the galavanised armouring wire inside the cable as the earth (therefore for a single phase supply you only need a two core cable), until you start dealing with heavy cables (I think 95mm is the largest cable size you can use armouring as earth without an earth core). Although it is a subject of varying opinion.

 

[madkayaker]

for SWA you have to work out the earth size needed through Adiabatic Equations or there is charts out there.