Why do cables need to be armored and twisted?

Armored cable refers to a cable with a metal material armored protective layer. The purpose of the cable plus the armored layer is to enhance the tensile strength, compressive strength and other mechanical protection to extend the service life, but also to improve the anti-interference performance of the cable through shielding protection.
Commonly used armor materials include steel tape, steel wire, aluminum tape, aluminum tube, etc., among which the steel tape and steel wire armor layer has high magnetic permeability, has a good magnetic shielding effect, can be used for anti-low frequency interference, and can make the armor The cable is directly buried and laid without the need to pass through the pipe, and it is cheap and good-quality in practical applications.

Copper wires of different specifications and different numbers are twisted together according to a certain arrangement sequence and twisting pitch, and then they become conductors with larger diameters. The conductors of this kind of twisted large-diameter stranded conductors are better than single-stranded conductors of the same diameter. The copper wire is more flexible, the wire made has good bending performance, and it is not easy to break during the swing test. It is easier to meet the requirements for some wires that require softness (for example, medical-grade wires).
From the perspective of electrical performance: After the conductor is energized, it generates heat due to the electrical energy consumed by the resistance. As the temperature increases, the performance life of the insulating layer and protective layer materials will be affected. In order to make the cable run efficiently, the cross section of the conductor should be increased, but a single wire with a large cross section is not easy to bend and has poor flexibility, which is not conducive to production, transportation, installation and laying. In terms of mechanical properties, flexibility and reliability are also required. If multiple single wires are twisted and twisted together, the contradiction can be solved.