Detailed explanation of the relationship between wire cross-sectional area and current
Updated on 2012-01-05 13:07:31 Article source: Internet
Wire diameter withstands current Cross-sectional area
The relationship between conductor cross-sectional area and current
The general safe calculation method for copper wires is:
The safe current carrying capacity of a 2.5 square millimeter copper power cord - 28A.
The safe current carrying capacity of 4 square millimeter copper power cord - 35A.
The safe current carrying capacity of 6 square millimeter copper power cord - 48A.
The safe current carrying capacity of 10 square millimeter copper power cord - 65A.
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.
If it is aluminum wire, the wire diameter should be 1.5-2 times that of copper wire.
If the copper wire current is less than 28A, it is definitely safe to take 10A per square millimeter.
If the copper wire current is greater than 120A, take it as 5A per square millimeter.
The current that can normally pass through the cross-sectional area of ??the wire can be selected according to the total number of currents it needs to conduct. Generally, it can be determined according to the following jingle:
Ten under five, a hundred The upper two, the three realms of two, five, three, five and four, seven, ten, nine and a half times and a half, the copper wire upgrade counts.
Let me explain to you, for an aluminum wire less than 10 square meters, just multiply the square millimeters by 5. If it is a copper wire, go up one level. For example, for a 2.5 square meter copper wire, press 4. Square calculation. The cross-sectional area is multiplied by 2 for anything above 100 square meters, multiplied by 4 for anything below 25 square meters, multiplied by 3 for anything above 35 square meters, and multiplied by 2.5 for 70 square meters and 95 square meters. These few formulas should be easy to remember. Well,
Note: This can only be used as an estimate, not very accurate.
In addition, if you remember that copper wires with a diameter of less than 6 square millimeters are safe indoors, and the current per square does not exceed 10A, from this perspective, you can choose 1.5 square meters of copper wire or 2.5 square meters of aluminum Wire.
Within 10 meters, the wire current density is 6A/mm2, which is more suitable. 10-50 meters, 3A/mm2, 50-200 meters, 2A/mm2, and above 500 meters, it should be less than 1A/mm2. From this perspective, if it is not very far away, you can choose 4 square meters of copper wire or 6 square meters of aluminum wire.
If the power supply is really 150 meters away (regardless of whether it is a high-rise building), 4 square meters of copper wire must be used.
The impedance of a wire is directly proportional to its length and inversely proportional to its diameter. When using the power supply, pay special attention to the wire material and wire diameter of the input and output wires. To prevent excessive current from overheating the wires and causing accidents.
The following is a table of wire diameters and the maximum current that copper wires can withstand at different temperatures.
The impedance of a wire is directly proportional to its length and inversely proportional to the wire diameter. When using the power supply, please pay special attention to the wire diameter of the input and output wires to prevent overheating and accidents caused by excessive current. , the following table is the wire diameter and current specifications of the wire at different temperatures. (Please note: Please follow the following table for wire specifications for normal use)
The wire diameter is generally calculated according to the following formula:
Copper wire: S= IL / 54.4*U`
Aluminum wire: S= IL / 34*U`
Where: I——The maximum current passing through the wire (A)
L—— Length of wire (M)
U`——Allowable power drop (V)
S——Cross-sectional area of ??wire (MM2)
Explanation :
1. The U` voltage drop can be selected based on the range of equipment (such as detectors) used in the entire system and the power supply voltage ratings used to power the system.
2. The calculated cross-sectional area moves upward