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Knowledge: The Structure And Material Of Cable Products
Nov 16, 2017

The structural components of wire and cable products can be divided into four main structural components: conductor, insulation layer, shielding and protective layer, as well as filling elements and bearing elements.According to the requirements and applications of the product, some products have a very simple structure, only one structural member of the conductor, such as an aerial bare wire, a contact wire, a copper aluminum confluence, etc.The external electrical insulation of these products is ensured by the use of insulator and space distance (ie, air insulation) when the installation is installed.

The structure of cable products is made up

The vast majority of wire and cable products section (cross-sectional) shape is exactly the same (ignore due to manufacturing error), a long strip of the product, this is because in the system or equipment is used as a line or coil and characteristics.Therefore, the research and analysis of the structure of cable products can only be observed from its cross section.

The structural components of wire and cable products can be divided into four main structural components: conductor, insulation layer, shielding and protective layer, as well as filling elements and bearing elements.According to the requirements and applications of the product, some products have a very simple structure, only one structural member of the conductor, such as an aerial bare wire, a contact wire, a copper aluminum confluence, etc.The external electrical insulation of these products is ensured by the use of insulator and space distance (ie, air insulation) when the installation is installed.

1. Conductor

Wire is the most basic essential component for the transmission of electrical current or electromagnetic information.The conductor is short for conductive wire core and is made of nonferrous metals such as copper and aluminum.Optical fiber optic cables, which have developed rapidly over the past 30 years, are used as conductors of optical fibers.

2. Insulation

It is a component of the electrical insulation around the periphery of the wire.That can ensure the transmission of electric current or electromagnetic waves, light waves travel along the wires and not flow to outside and only on the conductor has the potential of the potential difference (i.e., on the surrounding objects formed, namely voltage) can be isolated, which is to ensure the normal transfer function of the wire, and to ensure the safety of the external object and personal.

The conductor and insulation layer are the two basic components that constitute the cable product (except the bare wire type).

3. Sheath

When the wire and cable product installation runs in various different environments, it must have the components that protect the whole product, especially the insulation layer. This is the protective layer.

Because the insulation materials are required to have excellent electrical insulation performance, the materials must be extremely high purity and impurity content.Often cannot balance the protection of the outside world, so for the outside world (i.e., installation, use and use of) all kinds of mechanical force or under resistance, resistance to atmospheric environment, resistant to chemicals or oils, to prevent violation of biological, and reduce the fire hazard must be borne by the various security layer structure,.

Many dedicated to good external environment, such as clean, dry, no indoor mechan-ical damage) of cable products, or insulation material itself has certain mechanical strength, weather resistance of products, can not covering the artifacts.

4, shielding

A component that isolates electromagnetic fields in cable products from the external electromagnetic fields;The cable products also need to be isolated from each other within their internal lines (or line groups).It can be said that the shielding layer is an "electromagnetic isolation screen".

Over the years, the industry has used the shielding layer as part of the sheath structure, and the author believes it should be a component alone.The reason is that the function of the shielding layer is electromagnetic isolation -- that is, the information transmitted in the cable products can not be interfered with outside instruments or other lines.Electromagnetic coupling of all kinds of electromagnetic waves does not enter into cable products through electromagnetic coupling. These functions require different functions than traditional protective layers.Also, because the shielding layer is not only set on the outside of the product, it is also placed between each line pair or a multi-log cable.In recent years, with the rapid development of the information transmission system with wire and cable, electromagnetic wave interference source, and the atmosphere is more and more, to get screened varieties have multiplied, to shield as a basic component in the cable products, have converged.

5. Fill structure

Many core wire and cable products are more, such as low voltage power cables are mostly four core, five core cable (applicable to three-phase systems), telephone cable in the city is about 800, 1200, 2400 to 3600.These or insulated wire core line to cabling (or grouping many cabling), one is the shape is not round, the second is a large gaps between the insulation wire core (see chart 1), so you must add filling structure when cabling, filling structure is relatively rounded in order to make the cable diameter for package, sheath, also in order to make the stability of cable structure, internal calculus, in use, manufacture and installation of tensile, compression and bending) to receive strength evenly without damage to the internal structure of the cable.

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Figure 1. Clearance schematic diagram of a 2-4 low-voltage power cable in cable

Therefore, the filling structure is an auxiliary structure, but it is also necessary, and its material selection and shape design are also detailed.

6. Tensile elements

Conventional wire and cable products use the armor layer of the armor layer to withstand the pull of the outside force or gravity.The typical structure is steel tape armoring and steel wire armoring (for example, the undersea cable should be used to use the thick steel wire of the 8mm, twisted and synthetic armor layer).But fiber optic cable in order to protect the fiber from the tension of the tiny, so as to avoid fiber has slight deformation and affect the transmission performance, was set up in the cable structure of primary and secondary coating and special tensile force components.In addition, the structure of the insulating layer is made of thin copper wire or thin copper strip on the phone's headphone line, which is the tensile element.In short, in recent years, the development of the special fine, soft, at the same time requires many curved, twisted and used products, the tensile elements play a major role.

Overview of wire and cable materials

In a sense, the wire and cable manufacturing industry is a material processing and assembly industry.One is that the amount of materials is huge, and the materials in cable products account for 60-90% of the total cost of manufacturing.Secondly, there are many types and varieties of materials used. The performance requirements are particularly high, such as copper for conductors, and the purity of copper should be more than 99.95%, and some products should be pure copper without oxygen.Third, the selection of materials will have a decisive influence on the manufacturing process, the performance of the product and the service life.

At the same time, the benefits of cable manufacturing enterprises are closely related to whether the material selection, processing and production management can be scientifically saved.

Therefore, it is necessary to make the design of wire and cable products simultaneously with the selection of materials. In general, several materials are selected to be selected through process and performance screening tests.

2. The materials of cable products shall be divided into conductive materials, insulating materials, protective materials, shielding materials and filler materials according to their use parts and functions.But some of these materials are common to several structural parts, such as shielding copper wire and copper strip.In particular thermoplastic materials, such as polyvinyl chloride, polyethylene, etc. can be used in insulation or sheath as long as the ingredient is changed.

3. The materials used in the manufacturing of cable products are very broad, and the variety specification (brand number) is very large. Table 1 shows the summary table of the main material categories.

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Common material summary table of wire and cable

4, due to the use function of cable products, application environment and conditions of use, so while the one kind of material has its basic performance requirements (common), but each series, variety of products will have some special performance requirements (features).For example, the common requirement of electric wire and cable for electric power system for insulation layer is high insulation performance.As used in high voltage power cables, must stress that can withstand the high electric field strength, high insulation resistance, dielectric loss is small, and require almost no impurities (including air gap) in the insulating layer.While the medium voltage power cable (6-35kv) has these requirements, it can be reduced in degree.As for low voltage wire and cable only request has the certain and insulation resistance, crushing strength, light, and in order to economy requires insulation layer has good mechanical and climate resistance, make its in many cases, can need not protect layer (such as PVC plastic insulated wire).

5, because the material plays a key role on the performance of the product, but also because of many kinds of materials involves a wide range of knowledge, the material of the same name as the molecular structure, molecular weight distribution is different, the mixture with chelating agent, the ratio of different, so there are a lot of brands and formula.The result is that the materials of various brands have different technological conditions, and the finished product performance is very different.So cable manufacturing enterprises must request production workers are familiar with the process characteristics of commonly used materials, strictly implement process operation procedures and requirements into the factory inspection department to strictly quality control of materials and their preparation of the material.