Chris said:
Well you can't say fairer than that can you!
Cable - in case you didn't realise come in different forms. You can start with one solid core or hundreds of very thin cores bound together. The cross sectional area is the 70mm2 bit. Usually there are two other numbers something like 0.69 . 320 This means 320 strands of .69mm cable to make up the whole cable. The greater the number of strands, the more flexible it will be. Obviously one solid core would be nuts. However, I guess there are some issues to consider (if we're being anal about it) and that's to do with the fact the wire is round - a shape that doesn't tessellate (fit together) very well. The larger the wire strand, the less well it fits together and the more air there is doing to be in the cable. Guys this is thinking out loud, not fact - OK? If very high currents are being passed I guess that air heats up and bad things happen. Also the cable would be more bulky? Welding cable is usually very thin strands to make if flexible and also has a heat proof outer coating so that it doesn't melt when you shower it with sparks. I have found it to be most excellent for these applications.
I put two mega fuses in line through the installation (somewhere where you can get to them) and carry spares in the truck of course. These were from VWP.
Chris
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Hi Chris and All,,
Electricity is a strange thing, it likes to run down the outside of the copper strands first, then it gradually starts to migrate to the center of the strands when the strands are carrying more amps.
The more amps they carry, the hotter they will get with resistance.
Resistance in cables is bad.
A 50mm cable can as you quite rightly say can be made of many different constructions.
Firstly, there is the 50mm solid, very common to use solid drawn, but definatly not our cup of tea.
Then there is a multitude of stranded constructions up to say 1000 hi-flex, far more than a typical welding cable, however for our application, we treat welding cable as being very flexible, which it is compared to the normal 50mm cable we would encounter with for example "a 50mm 4 core XPLE armour"
The more strands, the more flexible, and generally the more conductive.
The insulation is again, another important criteria as to the safe current capacity of the cable, as is the trunking that the cable will be channeled through.
For example it is pointless having our new cable with current carry insulation capable of 140 deg C, if we are going to lie it alongside other cables which have a lower insulation value, of say 60 deg C.
Most PVC cable insulation run quite happy at 60 deg C. although the copper within is unhappy because of the higher resistance than at say, 30 deg C.
Gra.
