Basic Training Course

Basic Training Course Cables & Joints Electrical

Conductors

The size of the copper conductor forming one of the cores of a cable is

expressed in square millimeters (mm2), and the current rating of the

cable is dependent upon the cross-sectional area of each core. The very

smallest cables have conductors consisting of only one strand of copper;

larger cables however have stranded conductors consisting of many

individual strands or wires laid up together; this gives flexibility, allowing

the cable to be bent more readily during installation. To achieve a circular

conductor, the number of strands follows a particular progression: 3, 7,

19, 37, 61, 127 etc, the diameter of each strand being chosen to achieve

the desired cross-sectional area of tile whole conductor.

As seen in Figure 2, 3-core and 4-core cables in the larger sizes have

conductors with the strands laid up in a segmental formation; this

achieves a better space factor and reduces the overall diameter of the

cable. It also reduces the inductance of the cable due to decreased

spacing between phases.