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12. Appendix
12-1
In the case of Hitachi twisted shielded cable (CO-DS-IREVV-SX,(10 pairs to 52)), the
maximum conductor resistance in the cross section of 0.18mm
2
under the temperature 20 °C is
121.5 ohm/km (according to Hitachi’s Guide Book).
12. Appendix
12.1 Calculation of External Wiring Resistance
Assuming that the cross section and length of tinned annealed copper wire are S(mm
2
), and L(m),
the resistance R(Ω) of the wire is
R 0.01854 L / S
For example, for a cable whose cross section is 0.18 mm
2
and length is 200 m, the resistance is
R 0.01854 200 / 0.18 = 20.6 Ω
Because the current terminal of EH-PT4 doubles in both ways, the resistance also doubles
20.6 Ω 2 = 41.2 Ω.
Because this resistance is the value when the ambient temperature around the wire is 20 °C, if the
ambient temperature is over 20 °C, the resistance rises. The rise per 1 °C is about 0.4%.
In case the ambient temperature is 40 °C, the resistance is
R = 41.2 (1 + 0.004 (40 - 20))
44.5 Ω
Concerning the details of resistance, investigate individually for each wire. It may be slightly
different from the calculated value.
Reference