How to calculate the load capacity of copper wire?

The mnemonic for estimating the load capacity of copper wires in power cables is: multiply 2.5 by nine, subtract one from the top and follow the order. Thirty five times three and a half, in pairs, subtract five points. Conditions are subject to change and conversion, with high temperature copper upgraded at a 10% discount. The number of pipes passing through is 2-34, with a full load flow of 876.

Explanation: This mnemonic does not directly indicate the current carrying capacity (current) of various insulated wires (rubber and plastic insulated wires), but rather represents it as a multiple of the cross-sectional area, obtained through mental calculation. From Table 5.3, it can be seen that the multiplier decreases with the increase of the cross-section. The phrase 'Multiply 2.5 by 9 and subtract one from the top in order' refers to aluminum core insulated wires with various cross-sections of 2.5mm 'and below, whose current carrying capacity is approximately 9 times the number of cross-sections. For a 2.5mm 'wire, the current carrying capacity is 2.5 × 9=22.5 (A). The multiple relationship between the current carrying capacity and the number of cross-sections of wires with a diameter of 4mm 'and above is arranged in ascending order according to the wire number, and the multiple is gradually reduced by l, that is, 4 × 8, 6 × 7, 10 × 6, 16 × 5, and 25 × 4. The current carrying capacity of a 35mm conductor is 3.5 times the number of cross-sections, that is, 35 × 3.5=122.5 (A). The multiple relationship between the current carrying capacity and the number of cross-sections of wires with a diameter of 50mm 'and above is changed to two wire numbers grouped together, and the multiples are sequentially reduced by 0.5. The current carrying capacity of 50 and 70mm 'wires is three times the number of cross-sections; The current carrying capacity of wires 95 and 120mm is 2.5 times their cross-sectional area, and so on.

Conditions are subject to change and conversion, with high temperature copper upgraded at a 10% discount. The above mnemonic is determined for aluminum core insulated wire and exposed to an ambient temperature of 25 ℃. If the aluminum core insulated wire is laid openly in an area where the ambient temperature is higher than 25 ℃ for a long time, the current carrying capacity of the wire can be calculated according to the above formula, and then discounted by 10%; When using copper core insulated wire instead of aluminum wire, its current carrying capacity is slightly larger than that of aluminum wire of the same specification. The current carrying capacity that is one wire size larger than aluminum wire can be calculated using the above formula. The current carrying capacity of 16mm 'copper wire can be calculated based on 25mm2 aluminum wire.