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.
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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 |