In this section, the current carrying capacity (safety current) of various insulated wires (rubber and plastic insulated wire) is not directly indicated, but "the cross-section multiplied by a certain multiple" to indicate that it is obtained by mental arithmetic. It can be seen that the multiple decreases as the cross section increases.

 

       "Twenty-five times down to nine, go up one minus one" is said to be 2.5mm' and below various cross-section aluminum core insulated wires, the current carrying capacity is about 9 times the number of sections. For example, a 2.5 mm' wire has a current carrying capacity of 2.5 x 9 = 22.5 (A). The relationship between the current carrying capacity of the wires of 4 mm' and above and the multiple of the number of sections is the upper row along the line number, and the multiple is successively decreased by 1, that is, 4 × 8, 6 × 7, 10 × 6, 16 × 5, 25 × 4.

 

       "Thirty-five times by three-five, two pairs of points minus five", said that the 35mm" wire current carrying capacity is 3.5 times the number of sections, that is, 35 × 3.5 = 122.5 (A). For wires of 50mm' and above, the multiple of the current carrying capacity and the number of sections becomes a set of two two line numbers, and the multiples are successively reduced by 0.5. That is, the current carrying capacity of the 50, 70mm' wire is the number of sections 3 Double; 95, 120mm" wire current carrying capacity is 2.5 times the number of its cross-sectional area, and so on.

 

       "The conditions have been changed and converted, and the high temperature is 90% copper." The above-mentioned port is determined by an aluminum core insulated wire and a plain coating at an ambient temperature of 25 ° C. If the aluminum core insulated wire is applied to the area where the ambient temperature is higher than 25 °C for a long time, the current carrying capacity of the wire can be calculated according to the above-mentioned port and mouth calculation method, and then 10% of the wire can be used; when the aluminum wire is used, the copper core insulated wire is used. The current carrying capacity is slightly larger than that of the standard aluminum wire. The above-mentioned port method can be used to calculate the current carrying capacity of one wire number than the aluminum wire. For example, the current carrying capacity of a 16mm' copper wire can be calculated by 25mm2 aluminum wire.