Difference Between Concentric Lay (Normal Lay) and Bundle Lay of Wires and Cables

The so-called twisting means that several single wires with the same diameter or different diameters are twisted together according to a certain direction and certain rules to form a whole twisted wire core. When the twisted wire is directly used as an electric wire, it is called bare stranded wire, such as steel-reinforced aluminum stranded wire, aluminum-clad aluminum stranded wire, etc. Stranded wire, as the conductor of insulated wire and cable, is called stranded wire core, which is the main component of insulated wire and cable.

Strands are divided into regular and irregular ones.

Normal stranding can be divided into normal concentric single strand stranding and normal concentric single strand stranding:

Common stranded wire: Single wire with the same diameter is twisted regularly layer by layer in concentric circles, and the twisting direction of each layer is opposite.

Combined stranded wire: It is made of single stranded wires with the same diameter, different materials or different diameters and materials.

Normal concentric strand stranding: it is a stranded wire that is concentrically twisted by a plurality of common strands or bundles.

Irregular twist (bundle): a twisted wire made up of a plurality of single wires twisted together in the same twist direction but not according to the twist rule. The positions of the single wires are not fixed with each other, and it is difficult to keep the shape of the bundle round.

The biggest difference between bundle and common stranded wire is that each monofilament of common stranded wire has a fixed position and is regularly twisted layer by layer; There is no fixed position between the individual filaments of the bundle, and they are twisted together according to the twisting rule. Because each single wire in the bundle is twisted in one direction, there is a large sliding margin between each single wire during bending, and the bending resistance is small, so the bending performance of the bundle is particularly good. For the wire and cable products that need to be flexible and used for frequent movement, the bundle is used as the conductive core. Characteristics of twisted wire core ⑴ Good flexibility: The wire core formed by twisting a plurality of smaller diameter monofilaments can improve the bending ability of the cable, and facilitate the processing, manufacturing, installation and laying of wires and cables. Good stability: The wire core formed by twisting a plurality of monofilaments according to a certain direction and twisting rules, because the position of each monofilament in the twisted wire is alternately located in the elongation area at the upper part of the twisted wire and the compression area at the lower part of the twisted wire, will not deform when the twisted wire is bent. Good reliability: When a single wire is used as the conductor of a wire and cable, it is easy to be affected by the unevenness of materials or the defects generated in the twisting process, and the defects such as the wire core formed by twisting a plurality of single wires will be dispersed and not concentrated on a certain point of the conductor, so the reliability of the conductive wire core will be much stronger.

High strength: Compared with a plurality of twisted cores, the strength of a single wire with the same cross section is higher than that of a single wire.

Explanation of terms: (1) Pitch: the distance that a monofilament advances one week in the axial direction. (2) Pitch-diameter ratio: the ratio of the pitch length of stranded wire to the diameter of stranded wire. (3) Relationship between pitch and strand softness: The smaller the pitch, the better the strand softness, whereas the larger the pitch, the worse the strand softness. (4) Twisted-in coefficient: in a pitch of twisted wire, the ratio of the actual length of the monofilament to the pitch length. (5) Stranding direction: right direction (Z direction) left direction (S direction).

(6) Compression conductor: Common compression conductors include compression circle, sector and compression tile (five-core cable) semicircle (two-core cable).

Pressing purpose: (1) Pressing the sector conductor: reducing the outer diameter of the cable, saving the product cost and reducing the weight of the cable.

(2) Compacting round conductor: improving the surface quality of twisted conductor, reducing the conductor diameter and increasing the conductor filling coefficient. The compacted conductor surface is smooth and round without burrs, and the electric field on the conductor surface is uniform.

According to GB/T 3956 "Conductor of Cable" standard, there are four kinds of conductors, namely, the first, the second, the fifth and the sixth. The first type is a solid conductor, and the second type is a twisted conductor, both of which are suitable for the conductor of fixed cable laying; Types 5 and 6 are stranded conductors, which are used for flexible cables and cords, and the sixth is softer than the fifth.