What is the way of thinking to chose the proper wire gauge for the following system?:
There are calculators in web but I don't know the reasoning behind clearly. One example here: http://www.powerstream.com/Wire_Size.htm
As far as I know, the current is the only parameter which causes the heating and voltage drop. But voltage also taken into account when sizing the wires. I think they want to size the wire that it would cause %3 voltage drop.
Here is my example. Is my way of calculation correct?:
Lets say the intrinsic resistance of copper is rho. So for my system for the voltage drop ΔV to be 3%:
ΔV = 48 * 0.03
The total resistance is: [2*L*rho/(wire area)] so
ΔV = 48 * 0.03 = [2*L*rho/(wire area)] * I
(wire area) = [2*L*rho/(48 * 0.03)] * I
So in my case:
I = 3A
rho = 1.68 * 10^-8 (copper)
lets say L = 10 meters
wire area = [2*10*(1.68 * 10^-8)/(48 * 0.03)] * (3)
wire area = 7 * 10^-9 meter^2
Is that correct?
EDIT
The following two calculators calculate totally different results: