Sections & Materials

Conductors

Conductor materials

Bare annealed electrolytic copper is the material of choice for power, control and electronic instrumentation conductors. Its quality meets the requirements established in national and international standards, such as IRAM 2011, IEC 25, ASTM B-3, etcetera.
Annealed tinned electrolytic copper may be used for improved solderability and/or increased chemical resistance in conductors.
Pyrometry cables are made with special alloys for each thermocouple type and are calibrated to national and international standards, according to ASTM E 230-98 and IEC 60584-3. 



Cross sectional area

The cross-sectional area of a conductor represents the surface area of all the wires composing the conductor. It is expressed in square millimetres (mm2) and  is calculated as follows: 

                                  N x 3.14 x d2
Section (mm2) =- --------------------------
                                           4

Where:
N = number of wires in a conductor,
d = diameter of one of the wires in the strand, expressed in millimetres.



Conductor stranding

Based on the number of wires composing the strand, conductors may be classified as follows:

  • Solid (class 1)
  • Stranded (class 2)
  • Flexible (class 5)
  • Extra Flexible (class 6)

The strand selection should be based on the amount of flexibility required for a given installation and on the cable operating conditions. Concentric stranding (7 - 19 - 37 - 61 wires) is commonly symmetrical, which optimises the conductor's insulation.
The following tables illustrate the most frequent sizes and electric resistance values used in instrumentation, control and power cables. Notwithstanding, other cross-sectional and stranding values are possible.

10mm² - Class 2 - 7 wires 10mm² - Class 5 - 70 wires 10mm² - Class 6 - 100 wires 10mm² - Class 1 - 1 wire

 



Nominal stranding and electrical resistance values for copper conductors as per IRAM 2022 / IEC 60228

Cross-sectional area Class 2 Class 5
Strand construction Electrical resistance Strand construction Electrical resistance
No. of wires Maximum diameter of wire (mm)
Informative Normative ohm/km at 20°C
sq mm N° x mm ohm/km at 20°C
0.5 7 x 0.305 36 13 0.21 39
0.75 7 x 0.365 34.5 20 0.21 26
1 7 x 0.425 18.1 26 0.21 19.5
1.5 7 x 0.52 12.1 25 0.26 13.3
2.5 7 x 0.67 7.41 42 0.26 7.98
4 7 x 0.85 4.61 48 0.31 4.195
6 7 x 1.03 3.08 71 0.31 3.3
10 7 x 1.34 1.83 70 0.41 1.91
16 7 x 1.69 1.15 111 0.41 1.21
25 14 x 1.50 0.727 172 0.41 0.78
35 19 x 1.52 0.524 243 0.41 0.554
50 19 x 1.74 0.387 348 0.41 0.386
70 37 x 1.52 0.268 320 0.51 0.272
95 36 x 1.83 0.193 422 0.51 0.206
120 45 x 1.83 0.153 540 0.51 0.161
150 55 x 1.83 0.124 674 0.51 0.129
185 61 x 1.93 0.0991 820 0.51 0.106
240 61 x 2.21 0.0754 1085 0.51 0.0801
300 61 x 2.48 0.0601 1356 0.51 0.0641
400 71 x 2.58 0.047 1789 0.51 0.0486
500 91 x 2.58 0.0366 1582 0.61 0.0384
630 118 x 2.58 0.0283 2117 0.61 0.0287


Nominal stranding and electrical resistance values for copper conductors as per ASTM B 8 (expressed in AWG)

Gauge Equivalent section Strand construction Class of strand Electrical resistance
AWG/MCM mm2 N° x mm ohm/km at 20°C (*)
24 0.205 7 x 0.20 B 87.6
22 0.324 7 x 0.24 B 55.4
20 0.517 7 x 0.31 B 34.4
18 0.821 7 x 0.39 B 21.9
16 1.31 7 x 0.49 B 13.7
14 2.08 7 x 0.62 B 8.63
12 3.31 7 x 0.78 B 5.46
10 5.26 7 x 0.98 B 3.42
9 6.62 7 x 1.10 B 2.7
8 8.37 7 x 1.23 B 2.14
7 10.53 7 x 1.38 B 1.7
6 13.28 7 x 1.55 B 1.35
5 16.8 7 x 1.75 B 1.07
4 21.1 7 x 1.96 B 0.847
3 26.67 7 x 2.20 B 0.672
2 33.6 7 x 2.47 B 0.532
1 42.4 19 x 1.69 B 0.425
1/0 53.5 19 x 1.89 B 0.335
2/0 67.4 19 x 2.13 B 0.266
3/0 85 19 x 2.39 B 0.211
4/0 107 37 x 1.92 C 0.167
250 127 37 x 2.09 B 0.142
300 152 37 x 2.29 B 0.118
350 177 37 x 2.47 B 0.101
400 203 61 x 2.06 C 0.0883
450 228 61 x 2.18 C 0.0786
500 253 61 x 2.30 C 0.0709
550 279 61 x 2.41 B 0.0643
600 304 61 x 2.52 B 0.0593
650 329 91 x 2.15 C 0.0546
700 355 91 x 2.23 C 0.0505
750 380 91 x 2.31 C 0.0471
800 405 91 x 2.38 C 0.0442
900 456 91 x 2.53 C 0.0395
1000 506 127 x 2.25 D 0.0355


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