Appendix D: CABLE LOSS
The cable resistance R (ohms) for 1 conductor is calculated with following formula:
•
R (ohms) = resistivity of material (ohm m) × length (m)/cross sectional area (m
2
)
•
For copper conductors the resistivity is 1.72 10-8 (m
2
)
Example; for 1 km 2.5 mm
2
copper conductor, the resistance R is calculated as follows:
1.72 10-8 × 1000 / 2.5 10-6 m
2
= 6.88 ohms
The loss (Watt) is then R × I
2
or 6.88 ohms × 6.6
2
A
2
= 299.69 W/km or 0.299 W/m.
The loss (Watt) for a secondary cable with 2 conductors is thus 2 × 0.299 = 0.599 or 0.6 W/m.
As such we can calculate:
•
Secondary cable for a 2.5 mm
2
Cu-wire (2 conductors): 0.6 W/m
•
Secondary cable for a 4 mm
2
Cu-wire (2 conductors): 0.4 W/m
•
Primary cable for a 6 mm
2
Cu-wire (1 conductor): 0.12 W/m
The cable between the isolation transformer and the lamp adds losses that cannot be ignored when dimensioning the circuits
and selecting rating for secondary transformers and regulators.
WARNING
Cable lengths should not exceed 100 meters.
For a secondary cable of e.g., 20 m of 2.5 mm
2
CU-wire, 20 m × 0.6 W/m = 12 W equals the additional loss to be taken into
account.
For a primary cable of e.g., 100 m of 6 mm
2
CU-wire, 100 m × 0.12 W/m = 12 W equals the additional loss to be taken into
account.
UM-5056, Rev. 1.0.17, 2022/12/08
83
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Summary of Contents for AXON FAA L-852A
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