DC resistivity. The resistivity of copper-clad aluminum wire is larger than that of pure copper wire, about 1.5 times that of pure copper wire. When the negative value is the same, the weight of copper-clad aluminum wire is about 1/2 of pure copper wire. According to the skin effect calculation, at high frequencies above 5MHz, its resistivity is equal to that of copper conductors of the same cross section. In the use of power cables with a frequency of 50Hz, the skin effect and proximity effect of its copper conductors gradually become prominent above 150mm2. At the same time, due to the continuous development of science and technology, high-order harmonic currents and energy will be injected into the power supply system. , the high-order harmonic voltage of the corresponding frequency is generated on the impedance of the system, which causes the waveform of the voltage to be distorted, increases the loss of the power supply system, and increases the heat generation of the conductor; in addition, the cable amplifies the harmonics and generates overvoltage at the joint. Damage to the cable head. The use of copper-clad aluminum conductors will reduce the AC impedance (resistance) generated by high-order harmonics. In other application occasions, by increasing the volume of copper in the copper-clad aluminum monofilament and corresponding technological measures, the copper-clad aluminum/copper composite conductor can meet the DC resistance requirements of the conductor within the upper limit of the outer diameter of the existing conductor of the same specification.
connection method. The use of copper-clad aluminum conductors can meet the current habits of wire and cable product selection, design, use, installation, etc. that have been going on for many years, and it is also beneficial to the tight pressing and tin welding of cable terminals.
Reduce AC resistance. AC resistance is the main basis for the current carrying capacity. According to the principle of skin effect, the surface of a single wire has a larger current per unit area than the center of the wire. That is to say, the center of a large cross-section conductor In the area of a circle formed by the same conductors, the current passing through the center of the circle is smaller than that of the circle, so it is the most reasonable and economical to use different metals for the center conductor and the circle conductor. In addition to the DC resistance and the skin effect, there is also the proximity effect that affects the AC resistance index. Compared with the copper conductor with the same DC resistance, after the copper composite conductor is used, in a single conductor, the aluminum is in the center of the circle and the copper is on the outer edge; In the composite conductor, the inner layer is copper-clad aluminum, and the outer layer is pure copper, and aluminum is not as sensitive to copper as skin effect and proximity effect. The surface area improves the heat dissipation conditions of the cable and increases the heat dissipation area, and the thermal conductivity of aluminum is similar to that of copper. Under the same material cost, the index of AC resistance is much more economical.
Good corrosion resistance: aluminum is more prone to corrosion than copper, but since the copper-clad aluminum material has been completely metallurgized, aluminum is completely covered by copper and will not be in contact with water or air, and it can fully achieve the same performance as copper. The copper-clad aluminum/copper composite conductor is also more beneficial to avoid the poor contact between the conductor and the terminal due to corrosion, bruising or tightness, poor soldering of the tin, and heat causing the copper layer to fall off and copper-aluminum during long-term use. A potential difference is formed between the metals, which accelerates galvanic corrosion and causes the hidden danger of burning the cable end. For aluminum conductors, especially in coastal areas, the chloride ions contained in the salt spray in the atmosphere will condense on the surface of aluminum, which is easy to cause local corrosion around the impurities and defects on the surface, forming holes, cracks and micro batteries, and aggravating the corrosion of aluminum conductors. corrosion.
Low cost and light weight. Compared with copper core cables with the same technical indicators, the copper-clad aluminum conductor cable can save more than 40% of the cost, and the copper-clad aluminum/copper composite conductor cable can save more than 20% of the cost. The proportion of copper-clad aluminum wire is only 37%-40% of pure copper wire. When the wire diameter and weight are equal, its length is 2.5 times that of pure copper wire.
Good weldability. Copper-clad aluminum wire has the same solderability as pure copper wire because its surface is concentrically coated with a layer of pure copper, which is convenient for production.
Although copper-clad aluminum cables have been born and are gradually being applied, there is still a lot of resistance. The main reason is that copper-clad aluminum cables are still relatively difficult to find the application basis of the country and industry, and it is difficult to obtain the approval of the design unit. There are still quite a few products of copper-clad aluminum cables without 3C certification. The industry is still in the stage of product identification and formulation of enterprise standards. The product specifications, characteristics, and use standards of different brands are quite different, and it is difficult for engineering designers to apply. Sure, investors are not willing to accept it for the time being.
However, with the gradual improvement and recognition of national standards and regulations, copper-clad aluminum cables are bound to become standardized, and will undoubtedly become the highlight of wire and cable in the next few years, driving the development of the entire industry.
