ELECTRICAL CABLING CHARACTERISTICS
|
Nominal Size: |
Full load current ( Amps) |
Resistance per metre at 20° C (°Ω) |
|
.63 |
5 |
0.024 |
|
.80 |
6 |
0.021 |
|
1.00 |
8.75 |
0.016 |
|
1.25 |
10 |
0.013 |
|
1.60 |
13 |
0.009 |
|
2.00 |
17.5 |
0.008 |
|
2.50 |
22.75 |
0.007 |
|
3.00 |
27.5 |
0.005 |
|
4.00 |
32 |
0.004 |
|
6.30 |
43 |
0.003 |
|
8.00 |
55 |
0.002 |
VOLTS DROP
To determine the volts drop in a single core the following information is required:
1. Size of conductor
2. Volt drop/metre/amp
3. Length of wire
4. Amps (loading of cable)
5. Operating temperature
Volts drop = Volt drop/metre/amp x length x Amps x temperature conversion factor
EXAMPLE
Consider a cable 2.0 mm2, 10 metres long with a loading of 15 Amps operating at 30DC
Volt drop = Vd/m/A x 1 x I x Temp factor
From graph, volts drop/m/A for 2.0 mm2 = 0.0085
Temperature conversion factor
Volts drop = 0.0085 x 10 x 15 x 1,039 = 1.325 Volts
In D.C.systems, the conductor resistance at its operating temperature should be used in the calculation of the volt drop withinthe cable. Note that a multiplier of 2 is needed since both the load and return contribute to the drop in voltage provided theyare of the same nominal size.
(Resistance temperature conversion factor. Table G SABS 150-1970 page 41)