Calculation of conductor 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 temperature of the core, cooling conditions and laying conditions. 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 cross-sectional area of the copper wire. Use the recommended value of the safe current carrying capacity of the copper wire to 5~8A/mm2, and calculate the upper and lower ranges of the cross-sectional area S of the selected copper wire: S=< I /(5~8)>=0.125 I ~ 0.2 I(mm2) S-----Cu wire cross-sectional area (mm2) I-----load current (A)
3. The 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 is an inductive load. For the calculation of the resistive load: P = UI For the calculation of the fluorescent lamp load: P = UIcos ф, where the power factor of the fluorescent lamp load is cos ф = 0.5. The power factor of different inductive loads is different. When the household electrical appliance is uniformly calculated, 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.