1. Calculation of conductor cross-sectional area and current carrying capacity:
Generally, the safe current carrying capacity of the copper wire is determined according to the maximum allowable core temperature, cooling conditions, and laying conditions.
Generally, the safe current carrying capacity of copper wire is 5-8A/mm2, and that of aluminum wire is 3-5A/mm2.
Calculate the upper and lower ranges of the cross-sectional area S of the copper wire:
0.125 I(mm2) <S= I /(5～8)< 0.2 I(mm2)
S---Copper wire cross-sectional area (mm2) I---Load current (A)
The recommended value of the safe current carrying capacity of 2.5mm2 BVV copper wire 2.5×8A/mm2=20A 220V×20A= 4400W 4mm2
Recommended value of safe current carrying capacity of BVV copper wire 4×8A/mm2=32A 220V×32A= 7040W 6mm2
The recommended value of the safe current-carrying capacity of BVV copper wire 6×8A/mm2=48A 220V×48A=10560W
2. The relationship between wire square and current-copper wire safety calculation method
The maximum current that the national standard 1 square wire can withstand is 19 amperes, but it needs to be considered according to the use environment, temperature, and installation method. The roughest estimation method is 5A for single-phase 1000W and 2A for three-phase current. The general copper wire safety calculation method is:
If it is aluminum wire, the wire diameter should be 1.5-2 times that of copper wire.
The safe current carrying capacity of the 2.5 square millimeter copper power cord-28A.
Power 220×28=6160W The safe current carrying capacity of 4 square millimeter copper power cord-35A.
Power 220×35=7700W The safe current carrying capacity of 6 square millimeter copper power cord-48A.
Power 220×48=10560W The safe current carrying capacity of 10 square millimeter copper power cord-65A.
Power 220×65=14300W, the safe current carrying capacity of 16 square millimeter copper power cord-91A.
The safe current carrying capacity of 25 square millimeter copper power cord-120A.
The power calculation general load (can also be used as electrical appliances, such as lighting, refrigerator, etc.) is divided into two types: one type of resistive load, the other is inductive load. Calculation formula for resistive load: P=UI
The calculation formula for fluorescent lamp load: P=UIcosф, where the power factor of fluorescent lamp load cosф=0.5. Different inductive loads have different power factors. When calculating household appliances in a unified manner, the power factor cosф can be taken as 0.8.
The total power of all electrical appliances in a family is 6000 watts, and the maximum current is I=P/Ucosф=6000/(220×0.8)=34(A).
Under normal circumstances, home appliances cannot be used at the same time, so add a common coefficient, which is generally 0.5.
So the above calculation should be rewritten as I=P*common coefficient/Ucosф=6000*0.5/220*0.8=17(A), the total current value of this family is 17A.
The main brake air switch should be greater than 17A. The above is not accurate. For example, the total power is 10,000 watts (the maximum power is 6000 watts), and the 5000 watts total brake is not enough according to the public coefficient, and the maximum power plus 0.5 of the remaining power should be taken.
Sichuan Renyi Electric Co., Ltd. is registered under the name of Ren Yi, a senior technician for substation maintenance, and uses scientific research, knowledge innovation, publicity, promotion, and teaching that the temperature of electrical contacts (connectors) is lower than the temperature of its conductors (wires). The theory and technology of "thermal electrical contacts" produces and sells electrical equipment with registered trademarks that do not overheat electrical contacts (joints). Patented products are integrated.