The core of power cable is mainly composed of multiple conductors, which are divided into single core, double core and three core.

Single-core cables are mainly used in single-phase AC and DC circuits, while three-core cables are mainly used in three-phase AC

circuits. For single-core cables, the relationship between the core diameter and the cable outer diameter is relatively simple. Generally,

the wire core diameter is about 20% to 30% of the cable outer diameter. Therefore, we can estimate the core diameter by measuring

the outer diameter of the cable.

For three-core cables, since the three-phase current will generate a magnetic field in the conductors, the influence of the space

between the conductors and the insulation layer needs to be considered. Therefore, when calculating the outer diameter of the cable,

factors such as the conductor cross-sectional area, the space between the conductors and the thickness of the insulation layer need

to be considered. So how to calculate the outer diameter of the cable? Let’s take a look below.

▌01 Cable outer diameter method

The following factors need to be considered when calculating the outer diameter of a cable:

1. Conductor outer diameter: the diameter of the conductor inside the cable;

2. Insulation layer thickness: the thickness of the internal insulation layer of the cable;

3. Sheath thickness: the thickness of the outer sheath of the cable;

4. Number of cable cores: the number of cable cores inside the cable.

Taking the above factors into consideration, the following formula can be used to calculate the outer diameter of the cable:

Outer diameter = conductor outer diameter + 2 × insulation layer thickness + 2 × sheath thickness

Among them, the outer diameter of the conductor can be obtained by consulting the manual or measuring according to the

specifications of the conductor; the thickness of the insulation layer and the thickness of the sheath can be obtained by consulting

the specifications of the cable or measuring.

It should be noted that the above formula applies to single-core cables. If it is a multi-core cable, it needs to be calculated according

to the following formula:

Outer diameter = (outer diameter of conductor + 2 × insulation layer thickness + 2 × sheath thickness) × number of cable cores + 10%

When calculating the outer diameter of a multi-core cable, a 10% tolerance needs to be added to the result.

▌02 Related precautions

1. Before calculation, you should carefully confirm the cable specifications, conductor cross-sectional area and other information to

ensure the accuracy of the calculation;

2. When calculating, it is necessary to consider the usage environment of the cable, such as underground, above ground, overhead

and other environments, because different usage environments require different sheath materials to be selected;

3. When calculating, you also need to consider the installation method of the cable, such as fixed or movable, which will affect the

size and tensile strength of the cable;

4. Pay attention to the tolerance when calculating the outer diameter of the cable, and decide whether a certain tolerance needs to

be added to the calculation result based on the actual situation.

In short, the calculation of the outer diameter of the cable requires comprehensive consideration of multiple factors. If you are not

sure about the calculation method or parameters, you should consult a professional or consult relevant information.