The selection of the cross-sectional area of the conductor for automobile control cables based on the current load requires a combination of factors including the load current, voltage drop, heat generated by the conductor, mechanical strength and the environment in which the conductor is laid.
Calculate the load current
Calculate the load current based on the power and rated voltage of the electrical equipment.
2. Determine the allowable current-carrying capacity of the conductor
The allowable current-carrying capacity of the wire is determined based on the material of the wire (such as copper or aluminum) and the laying conditions (such as temperature, cooling conditions, laying methods, etc.). Generally, the safe current-carrying capacity of copper wires is 5 to 8A/mm², and that of aluminum wires is 3 to 5A/mm².
3. Select the cross-sectional area of the wire
Select the appropriate cross-sectional area of the conductor based on the allowable current-carrying capacity and the calculated load current.
If the load current is 20A and the allowable current-carrying capacity of the copper wire is 8A/mm², then the required cross-sectional area of the wire is:
4. Consider the voltage drop
The voltage drop of the conductor should be controlled within the allowable range to ensure the normal operation of the electrical equipment.
5. Consider mechanical strength
To ensure the mechanical strength of wires in automotive circuits, the cross-sectional area of low-voltage wires should generally not be less than 0.5mm², while for important lines such as power lines, it is recommended that the cross-sectional area be no less than 1.0mm².
6. Consider working hours
For electrical equipment that operates for a long time (such as lighting, air conditioning, etc.) : Conductors with 60% of the actual current-carrying capacity can be selected.
For electrical equipment that operates for a short period of time (such as starting motors, relays, etc.) : Wires with a current-carrying capacity of 60% to 100% of the actual current can be selected.
7. Reference standards and forms
Based on the cross-sectional area of the wire and the allowable current, the appropriate wire can be selected by referring to relevant standards or tables. For example:
Copper wire: The allowable current carrying capacity of a 2.5mm² wire is 20A (2.5×8A/mm²).
Aluminum wire: The allowable current carrying capacity of the 2.5mm² wire is 12A (2.5×5A/mm²).
8. Special applications
- Starting cable: The main terminal that connects the battery to the magnetic switch of the starter motor. Its cross-sectional area is usually not determined by the magnitude of the working current but is limited by the voltage during operation.
High-voltage circuits: According to the insulation requirements for withstanding high voltage, wires with small cross-sectional areas of the core but thick insulation cladding are adopted.
9. Summarize the steps
Calculate the load current.
2. Determine the allowable current-carrying capacity: It should be determined based on the conductor material and environmental conditions.
3. Select the cross-sectional area of the wire.
4. Check the voltage drop: Ensure that the voltage drop is within the allowable range.
5. Consider mechanical strength: Select low-voltage conductors with a cross-sectional area of no less than 0.5mm².
6. Consider the working time: For long-term operation, use 60% of the current-carrying capacity; for short-term operation, use 60% to 100% of the current-carrying capacity.
7. Reference standards and tables: Select the wire specifications that comply with the standards.
By the above steps, the cross-sectional area of the conductor of automobile control cables can be selected scientifically and reasonably according to the current load to ensure the safety and reliability of the circuit.
