How to select line type - line diameter selection datum
In automobile wiring harness, different conductor diameters (cross section area) are used in different places.
Criteria for confirming the line diameter of car harness
When confirming the conductor cross section area, we need to consider the voltage drop and the heating of the conductor, which can be determined from the following aspects.
The current intensity of 1. electric equipment
I=P/UN (P - load power; UN - rated voltage).
2. traverse section area
A=I P L/UVL
L (I - current, Ampere; P - power, power, tile; A - traverse area, square millimeter; P - copper wire resistivity, general value 0.0185 Omega.Mm /m; L - wire length, meter; UVL – conductors allowed voltage drop, volt)
3., in order to avoid heating wire transition, we should check the current density.
According to the formula, the cross section area S is mainly chosen according to the working current of the electric equipment. However, for the small power equipment, the wire will be easily broken because of the small cutting area and low mechanical strength, so in the car harness, the minimum section area of the wire should not be less than 0.5 square millimeters. In addition, the traverse section area also has to consider the voltage drop. The maximum allowable value of the voltage drop of the general vehicle circuit is 0.8V. When the generator operates at rated load, the maximum allowable value of the voltage drop of the power line is 0.3V. The maximum allowable value of voltage drop is 0.5V when starting motor starts. This is because the conductor resistance will increase and the temperature will rise as the conductor cross section area is small. The increase of resistance will cause voltage drop to increase, which may lead to insufficient supply voltage of power supply equipment and unable to work normally. Higher temperature will accelerate the aging of wires and shorten their service life. Too high temperature may even cause fire and cause huge losses.