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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).

  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.