Cable Sizing
To size a cable, you need to consider several factors that affect the current carrying capacity and voltage drop of the wire.
These factors include:- The type of current (AC or DC) and the frequency of the supply.
AC current has more resistance and voltage drop than DC current, and higher frequency also increases the resistance.- The installation method and the ambient temperature.
Different installation methods, such as buried in the ground, clipped to a surface, or enclosed in a conduit, have different thermal resistances and heat dissipation rates.
Higher ambient temperature reduces the current carrying capacity of the wire.- The conductor material and the cross-sectional area.
Copper and aluminum are the most common conductor materials, but they have different resistivities and ampacities.
The cross-sectional area of the wire determines how much current it can carry without overheating or melting.- The length of the wire and the voltage drop. Longer wires have more resistance and voltage drop than shorter wires.
Voltage drop is the difference between the supply voltage and the load voltage, and it depends on the current, resistance, and power factor of the circuit. Excessive voltage drop can reduce the efficiency and performance of the electrical equipment.
To size a cable, you need to calculate the required current carrying capacity and voltage drop for your circuit or installation, and then select a wire size that meets or exceeds these requirements. You can use one of the cable sizing calculators I mentioned in my previous message to help you with this process.
Alternatively, you can use some formulas and tables to manually calculate the wire size, but this can be more complicated and time-consuming.I hope this explains how we size a cable.