evcome cable: low-voltage wire and cable classification and cable basic structure analysis

Author: EVCOME-EV Chargers Manufacturers

Generally speaking, cables can be divided into six categories: bare wires, magnet wires (enameled wires), power cables, electrical equipment wires and cables, communication wires and cables, and optical cables. There are a wide variety of wire and cable products, which are used in various industries. They serve two general purposes, one for carrying electrical current and the other for carrying signals. The main technical performance indicators of current transmission cables are conductor resistance and withstand voltage; the main technical performance indicators of signal transmission cables are transmission performance-characteristic impedance, attenuation and crosstalk. Of course, the transmission signal mainly relies on electric current (electromagnetic wave) as the carrier, and now with the development of science and technology, light wave can be used as the carrier for transmission. Cable basic structure. Generally speaking, the most basic structure of a cable is a conductor, an insulating layer, and an outer protective layer. According to the requirements, add shielding layer, inner protective layer or armor layer and other structures, and add some filling materials for the integrity of the cable. Conductors are the carriers that transmit current or signals, and other structures are used for protection. According to the needs of cable products, there are generally three types of protection performance, one is to protect the cables themselves from mutual or reduce influence, such as withstand voltage, heat resistance, electromagnetic field loss, communication cable signal interference, etc. Another kind of protection is to protect the current in the conductor from external influences, such as preventing current leakage, preventing electromagnetic wave leakage, etc. ;The last kind of external protection does not affect the cable, such as compressive resistance, tensile resistance, heat resistance, weather resistance, flame resistance, waterproof, anti-electromagnetic wave interference, etc. The following is a brief introduction to the structural units of power cables. Conductor (or wire core) Its function is to conduct electric current. Can be divided into solid and stranded. Materials include copper, aluminum, silver, copper-clad steel, aluminum-clad steel, etc. Copper and aluminum are mainly used. Copper conducts electricity much better than aluminum. National standards require that the resistivity of copper conductors is not less than 0.017241ω.mm2/m (20°C), and the resistivity of aluminum conductors is not less than 0.028264ω.mm2/m (20°C). The refractory layer only has this structure for refractory cables. What it does is that the cable can withstand a fire for a certain amount of time, giving us more time to use electricity when escaping. The material currently used is mainly mica tape. In a fire, the cable will burn quickly, because the mica sheet of the mica tape is resistant to high temperature and has an insulating effect, which can protect the conductor for a certain period of time in the fire. The insulating layer covers the outside of the conductor, and its function is to isolate the conductor, withstand the corresponding voltage, and prevent current leakage. There are many kinds of insulating materials, such as polyvinyl chloride (PVC), polyethylene (PE), cross-linked polyethylene (XLPE), rubber (there are many kinds of rubber, including nitrile rubber, neoprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, etc. .), fluoroplastics, nylon, insulating paper, etc. The main property of these materials is good insulating properties. Other performance requirements vary according to the use requirements of the cable. The dielectric coefficient is required to reduce loss. Some require flame retardancy or high temperature resistance. Some require that the cable will not produce smoke or harmful gases when burning. Some require oil resistance. Corrosion resistance, some require softness. The shielding layer is outside the insulating layer, and the function of the outer protective layer is to limit the electric field and electromagnetic interference. For different types of cables, shielding materials are also different, mainly including: copper wire braiding, copper wire winding, aluminum wire (aluminum alloy wire) braiding, copper tape, aluminum foil, aluminum (steel) plastic tape, steel tape, etc. The main function of the filling layer is to make the cable round and stable in structure, and part of the cable filling also plays the role of waterproof and fire resistance. The main materials are polypropylene rope, glass fiber rope, asbestos rope, rubber, etc. There are many types, but the main performance requirements are non-hygroscopic materials, and of course they cannot conduct electricity. Inner sheath The function of the inner protective layer is to protect the insulation shielding layer from damage. Inner protective layers come in several forms such as extruded wraps, winding wraps and longitudinal wraps. The ones with high requirements adopt the form of extruded package, and the ones with low requirements adopt the form of winding package or longitudinal package. Now there are many kinds of winding materials, such as the inner protective layer of steel tape armor, some use PVC tape winding, and some use polypropylene tape winding (very thin, the surface is made of particle protrusions to collect thickness). PVC tape and polypropylene tape have an impact on product quality. Silane cross-linked insulated wire cores are distinguished by color or ribbon, which has little impact on product quality, and is mainly a matter of user needs. Armor layer The function of the armor layer is to protect the cable from being damaged by external force. The most common are steel belt armor and steel wire armor, as well as aluminum belt armor, stainless steel belt armor, etc. The main function of steel belt armor is to resist compression, and the main function of steel wire armor is to resist tension. According to the size of the cable, the thickness of the armored steel belt is different, which is stipulated in the cable standard. The outer sheath protects the outermost components of the cable. There are mainly three kinds of plastic, rubber and metal. Among them, the most commonly used plastics are polyvinyl chloride plastics, polyethylene plastics, flame-retardant types, low-smoke and low-halogen types, and low-smoke and halogen-free types. .


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