Basic Information about Wire and Cable (Part 2)

Basic Information about Wire and Cable (Part 2)

The structure of cable


Its role is to conduct current. There are solid conductor and stranded conductor. The conductor material including copper, aluminum, aluminum alloy, silver, copper clad steel, aluminum clad steel, etc. Commonly used are copper and aluminum. and copper has much better electrical conductivity than aluminum.

2. Refractory layer

Only fire-resistant cables have this structure. Its function is to support cable withstand a certain time in the fire, giving people more time to use electricity when they escape. Currently, the main material used is mica tape. Because the mica sheet of the mica tape is resistant to high temperature and has an insulating effect,when the cable is on fire, it can protect the conductor and make it keep working for a certain period of time.

3. Insulation Layer

The insulation layer is wrapped around the conductor, its role is to isolate the conductor, withstand the corresponding voltage, and prevent electric leakage. There are various insulating materials, such as polyvinyl chloride (PVC), polyethylene (PE), cross-linked polyethylene (XLPE), rubber (there are many types of rubber, including nitrile rubber, neoprene, styrene butadiene rubber, Ethylene propylene rubber, etc.), silicone rubber, nitrile polyvinyl chloride, fluoroplastics, etc. The main performance of these materials is better insulation performance, other performance requirements vary according to the cable use requirements, some require a small dielectric coefficient to reduce losses, some require flame retardant properties or high temperature resistance, some requires the cable will not produce dense smoke or harmful gas when burning, some require oil resistance and corrosion resistance, and some require softness.

4. Shield layer

The shield layer is between insulation layer and outer sheath, the function is to limit electric fields and electromagnetic interference

For different types of cables, the shielding materials are also different, mainly including: copper wire braid, copper wire winding, aluminum wire (aluminum alloy wire) braid, copper tape, aluminum foil, aluminum (steel) plastic tape, steel tape etc..

5. Filler

The function of filling is mainly to make the cable round and stable in structure, and the filling of some cables also plays a role of water resistance and fire resistance. The main materials are polypropylene rope, glass fiber rope, asbestos rope, rubber, etc. One of the main performance requirements for filler is non-hygroscopic material, and non-conducting.

6. Inner sheath

The function of the inner sheath is to protect the insulated wire core from being damaged by the armor layer or the shield layer.

The inner sheath has two forms: squeeze and wrap. For the demanding ones, the squeeze bag is used, and for the lower ones, the wrapping is used. Now the materials used for wrapping are various, such as the inner sheath of steel tape armor, some are wrapped with PVC tape, and some are polypropylene tape (very thin, the surface is made of particle protrusions to make up the thickness). Can it be used? it depends on the market positioning of cable product quality. This is kind of the same as whether the silane cross-linked insulation core is color-coded or color-banded. but not all the same. The use of PVC tape and polypropylene tape around the wrapping tape has an impact on product quality. Whether the silane cross-linked insulation core is distinguished by color or by color ribbon has little effect on product quality, mainly due to user needs.

7. Armor layer

The role of the armor layer is to protect the cable from external forces. The most common are steel belt armor and steel wire armor. The main function of steel belt armor is to resist compression, and the steel wire armor is mainly to resist tension. According to the size of the cable, the thickness of the steel tape used for armoring is different, which is specified in each cable standard.

8. Outer sheath

It it a protection layer at the outermost layer of a cable. There are three main types: plastic, rubber and metal. Among them, the most commonly used plastics are polyvinyl chloride plastics and polyethylene plastics, as well as flame retardant, low-smoke and low-halogen types, and low-smoke and halogen-free types according to cable characteristics.

Magnesium hydroxide could be used in sheathing layer, insulation layer and filling layer, and KMT manufactures MDH in different particle sizes, purities, which can meet different customer requirement. For more information, please feel free to contact me.

Thank you for your time!

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