Copper wire table

Discussion in 'General Electronics Chat' started by someonesdad, Nov 29, 2010.

  1. someonesdad

    Thread Starter Senior Member

    Jul 7, 2009
    I've attached a 20 °C copper wire table that I made from a python script I wrote. I've occasionally found errors or inconsistencies in published tables. Plus, they're often only in our screwball US units and I usually want to work in SI. The table is based on two properties of commercial copper: a specific gravity of 8.9 and a conductivity of 58 MS/m. Diameters are given to 4 significant figures and the other stuff is to 3 significant figures; the last three columns are to 2 significant figures. Note there are also SI prefixes cuddled in as suffixes because I like engineering notation.

    The Amps columns represent an approximate maximum current for 3 or less conductors and <= 30 °C. The temperatures are the rated temperatures of the plastic insulation. These numbers come from a regression I made from US NEC data relating current density to wire size; you can find the details in a spreadsheet in the file here. The numbers are rounded to two significant figures and are approximate. It's your responsibility to decide whether they represent good practice or not (I just use them as guidelines for estimating purposes). IIRC, the values for wires larger than around 12 gauge are reasonably consistent with the NEC; for smaller wires the numbers might be a bit conservative. I've attached the python function used for this current density should you wish to know its numbers.

    The first part of the table is short and covers the wire sizes I use most of the time. I have a script that dumps these numbers to the console when I type "wire".

    If you're interested in a formula for the diameter of AWG wire sizes, take a look at the units.dat file of the GNU units program (which you should be using, as it's a fantastic tool).
  2. bertus


    Apr 5, 2008