Calculation of wire cross-sectional area and current carrying capacity.

1. The safe current carrying capacity of the general copper wire current-carrying wire is determined according to the maximum core temperature, cooling conditions and laying conditions allowed. Generally, the safe current carrying capacity of copper wires is 5~8A/mm2, and the safe current carrying capacity of aluminum wires is 3~5A/mm2. <Key Points> The safe current carrying capacity of general copper conductors is 5~8A/mm2, and the safe current carrying capacity of aluminum conductors is 3~5A/mm2. Such as: 2.5 mm2 BVV copper wire safe current carrying capacity recommended value 2.5 × 8A / mm2 = 20A 4 mm2 BVV copper wire safe current carrying capacity recommended value 4 × 8A / mm2 = 32A 2. Calculate the copper wire cross-sectional area using copper wire safety The recommended value of the current carrying capacity is 5~8A/mm2, and the upper and lower ranges of the cross-sectional area S of the selected copper wire are calculated: S=< I /(5~8)>=0.125 I ~0.2 I(mm2) S-----copper Wire cross-sectional area (mm2) I-----load current (A) 3. Power calculation General load (can also be used as electrical appliances, such as lighting, refrigerators, etc.) is divided into two types, one type of resistive load, one This is an inductive load. For the calculation of the resistive load: P = UI For the calculation of the fluorescent lamp load: P = UIcosф, where the power factor of the fluorescent lamp load is cosф = 0.5. Different inductive loads have different power factors. When calculating household appliances, the power factor cosφ can be taken as 0.8. That is to say, if the total power of a household appliance is 6000 watts, the maximum current is I=P/Ucosф=6000/220*0.8=34(A) However, in general, it is impossible for home appliances to be used at the same time. , so add a common coefficient, the common coefficient is generally 0.5. Therefore, the above calculation should be rewritten as I = P * common coefficient / Ucos ф = 6000 * 0.5 / 220 * 0.8 = 17 (A) That is, the total current value of this family is 17A. The total brake air switch cannot use 16A, it should be greater than 17A. Kunshan copper wire

Estimated vocabulary:

Multiply by 9.5 and multiply by nine. Thirty-five by three-five, and the two groups are reduced by five. The conditions have been changed and converted, and the high temperature ninefold copper upgrade. The number of tubes to be worn is two to three, and eighty-seven percent is full of current.

Note: The current carrying capacity (safety current) of various insulated wires (rubber and plastic insulated wire) is not directly indicated in this section, but is expressed by “multiplied by a certain number of sections” and calculated by mental arithmetic. It can be seen from Table 5 3 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 multiple of the current carrying capacity and the number of sections from the wires of 4 mm' and above is lined up along the line number, and the multiples are successively decremented by 1, that is, 4 × 8, 6 × 7, 10 × 6, 16 × 5, 25 × 4. "Thirty-five times three-five-five, double-group reduction of 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). Wires from 50mm' and above The multiple relationship between 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, 70 mm' wire is three times the number of sections; the 95, 120 mm" wire carries The flow rate is 2.5 times the number of cross-sectional areas, and so on. "The conditions have been changed and converted, and the high temperature ninefold copper upgrade." The above-mentioned port is determined by the aluminum core insulated wire and the bright coating at an ambient temperature of 25 ° C. If the aluminum core insulated wire is applied in an 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 calculation method of the mouth and then 10% off; when the copper wire is insulated, the copper core is used. Its current carrying capacity is slightly larger than that of the aluminum wire of the same specification. The above-mentioned port method can be used to calculate the current carrying capacity of one line number than the aluminum wire. For example, the current carrying capacity of a 16mm' copper wire can be calculated as a 25mm2 aluminum wire.