What determines a wires current carrying capacity rating?

Question

Easy question? I'm interested in what comes back as I have found it's not as simple as it seems. Suggest away friends

WarrenW · Accepted Answer

Here is a link to a free cable calculator based upon New Zealand wiring regs. http://www.generalcable.co.nz/newzealand/NZDownloads/Gencalc.aspx#download enjoy. Cheers Warren.

WarrenW · Answer

Ok, this has lots of factors.

1. Cross sectional area

2. Frequency of the signal (the higher the frequency the less effective cross sectional area)

3. Proximity of other cables or materials that may be inductive

4. Is it buried in the ground?

5. Environmental issues like temperature

6. Allowable voltage drop

and the list goes on.

There are some calculators available to allow a lot of these to be taken into account for typical mains power applications.

http://www.cablecalc.com/cable.htm is one

Cheers

Warren

Former Member · Answer

I have found it is usually because the higher rated cable the manufacturer thinks it is OK to let it get hotter.