Why are cables armored?
First, let's understand what armored cable is: it refers to a cable with a protective metal armor layer.
The purpose of adding armor to cables is not only to enhance mechanical protection such as tensile and compressive strength, prevent chemical corrosion, and extend service life, but also to improve the cable's anti-interference performance through shielding.
Common armoring materials include steel strips, steel wires, aluminum strips, and aluminum tubes. Steel strips and steel wire armor layers have high magnetic permeability and provide excellent magnetic shielding, which can be used to resist low-frequency interference. They also allow armored cables to be laid directly underground without conduit, are cost-effective, and are widely used in practice.
Why are cables twisted?
Cables are typically composed of several conductors or groups of conductors (each group having at least two conductors) twisted together to form a rope-like structure.
Wires of varying specifications and numbers, twisted together in a specific sequence and lay length, create a larger diameter conductor. This twisted, large-diameter conductor is more flexible than a single wire of the same diameter, resulting in better bending properties and less likely to break during swing tests. This makes it easier to meet the requirements for certain types of wire that require flexibility, such as medical-grade wire.
Finally, from an electrical perspective, when current is applied to a conductor, it generates heat due to resistance, which reduces the lifespan of the insulation and protective layer. To ensure efficient cable operation, the conductor cross-section should be increased. However, a single wire with a large cross-section is difficult to bend and lacks flexibility, making it difficult to manufacture, transport, and install. Mechanically, flexibility and reliability are crucial, and twisting multiple individual wires together can resolve this conflict.
