13
2018-08-01
Supply cable sizing
The wire size of the supply cable can be determined by calculating the resistance pr meter R.
The calculation presupposes that a voltage drop of e.g. 2V is accepted in the supply cable:
R(per m) = Udrop / (I * L) [Ω/m]
where:
Udrop
is the accepted voltage drop (2V) in the cable [V]
I
is the current [A]
L
is the longest distance of supply cables from transformer to a component [m]
Example:
Udrop
= 2V, I = 4A, L = 20m
R (per m) = 2V / (4A * 20m) =
0,025 Ω/m
In the diagram a Wire cross section Area of 0,7 mm2 can be read.
0,7
0,6
0,8
0,9
1
1,1
1,2
1,3
1,4
1,5
0
0,1
0,2
0,3
0,4
0,5
0,20
0,10
0,15
0,05
0
Wire cross section area as a function of resistance per m for copper wire
Copper resistance [Ω/m]
W
ire c
ro
ss s
ec
tio
n a
re
a [
m
m
2 ]
