As a key component of power transmission, information communication and electromagnetic energy conversion, the structural design and material selection of wires and cables have a decisive impact on the performance, safety and service life of products. The following will elaborate on the structure and commonly used materials of the six main components of wire and cable – conductor, insulation, shielding, protective layer, filling structure and tensile elements.
1. Conductors
Structure: The conductor is the core part of the wire and cable and is responsible for the transmission of electric current. It is usually made of highly conductive metal materials such as copper (Cu) or aluminum (Al), and sometimes composite materials such as copper-clad steel and copper-clad aluminum are also used to reduce costs or increase strength.
Material:
- Copper: Due to its excellent electrical conductivity and corrosion resistance, it is widely used in power cables and communication cables, especially in applications where high conductivity is required.
- Aluminum: Although slightly less conductive than copper, it is less dense and less expensive, and is often used in long-distance transmission lines and certain applications.
- Composite materials, such as copper-clad steel, copper-clad aluminum, etc., combine the advantages of different materials and aim to reduce costs while maintaining certain electrical conductivity.
2. Insulation
Structure: The insulating layer is tightly wrapped around the periphery of the conductor, which plays the role of electrical insulation, prevents current leakage and short circuit, and protects the conductor from the external environment.
Material:
- Polyvinyl chloride (PVC): Low cost, good processability, it is one of the most widely used insulating materials.
- Polyethylene (PE): Good temperature resistance, suitable for medium and low voltage power cables.
- Cross-linked polyethylene (XLPE): It has excellent electrical properties, heat resistance and mechanical strength, and is the preferred insulation material for high-voltage cables.
- Rubber: such as ethylene propylene rubber (EPR) and butyl rubber (IIR), which have good weather resistance and insulation properties, and are often used in cables under special environmental conditions.
3. Shielding
Structure: The shielding layer is located outside the insulation layer, which is used to reduce electromagnetic interference (EMI) and radio frequency interference (RFI) and ensure the accuracy and stability of signal transmission.
Material:
- Bare copper wires and copper strips: Because of their high conductivity, they are often used for electric field shielding.
- Braided mesh: It is made of fine metal wire, which provides good mechanical protection and electromagnetic shielding effect.
- Aluminum foil + woven mesh: used in combination to further enhance the shielding effect.
4. Protective layer
Structure: The protective layer is the outermost layer of the wire and cable, and its main function is to protect the internal structure from external mechanical damage, chemical corrosion and environmental factors.
Material:
- Polyvinyl chloride (PVC): Low cost, good weather resistance, often used for general purpose cables.
- Polyethylene (PE): Good temperature resistance, suitable for outdoor environments.
- Low smoke and halogen-free (LSZH) material: environmentally friendly material, less smoke and toxic gas produced during combustion, widely used in occasions with high safety requirements.
5. Fill the structure
Structure: In multi-core cables, the filling structure is used to fill the gaps between the cores, so that the cable shape is rounded, which is convenient for taping and squeezing the sheath.
Material: Polypropylene (PP) rope or other non-hygroscopic materials are usually used to ensure the compactness and stability of the cable.
6. Tensile elements
Structure: In some special cables, such as overhead cables or submarine cables, tensile elements are set to enhance the mechanical strength of the cable and prevent cable breakage caused by gravity or external force.
Material:
- Steel strand: high strength, corrosion resistance, often used in the load-bearing part of overhead cables.
- Aramid fiber: light weight and high strength, with good tensile strength and fatigue resistance, suitable for occasions with strict weight requirements.
To sum up, the basic structure of wire and cable is composed of conductor, insulating layer, shielding layer, protective layer, filling structure and tensile element, each part assumes different functions, and together constitutes the overall performance of wire and cable. The choice of material is determined according to the specific use, working environment and performance requirements of the cable.