[China Aluminum Industry Network] The price of copper for raw materials for cable is still high, and the profit rate of cable manufacturers has dropped sharply. Today, the price of aluminum, which is also used as raw material for cables, is much lower than copper prices. Therefore, the topic of “aluminum section copper†has been fiercely noisy. , then new aluminum alloy cable performance will meet the requirements?
Here, we compare the mature and common copper-clad aluminum power cables and wires and cables used in electrical equipment.
a) DC resistivity: The resistivity of copper clad aluminum wire is larger than that of pure copper wire, which is about 1.5 times that of pure copper wire. When the resistance value is the same (the cross-sectional area is larger than copper), the weight of copper clad aluminum wire is about pure copper. 1/2 of the line. According to the skin effect calculation, the resistivity is equal to that of a copper conductor of the same cross section at high frequencies above 50 MHz. In the use of 50Hz frequency power cables, the skin effect and proximity effect of the copper conductors gradually become more than 150mm2. At the same time, due to the start-up and operation of the equipment power of industrial and mining enterprises (such as high-frequency furnaces, high-power motors, etc.) In case of failure, energy sources that generate higher-order harmonic currents are injected into the power supply system, generating higher-order harmonic voltages at the corresponding frequencies in the impedance of the system, causing the voltage waveform to be distorted, increasing the losses in the power supply system, and increasing the conductor heating.
In addition, the cables magnify the harmonics, causing excessive voltage at the connectors and damaging the cable heads. The use of copper-clad aluminum conductors acts to reduce the AC impedance (resistance) produced by higher harmonics. In other occasions, by increasing the volume of copper in the copper clad aluminum monofilament and the corresponding technological measures, the copper clad aluminum conductor meets the DC resistance requirements of the conductor within the upper limit of the existing outer diameter of the same specification conductor.
b) The use of copper-clad aluminum conductors can meet the current practice of product selection, design, use, and installation for wire and cable that has lasted for many years, and it also has advantages for tight pressing and soldering of cable terminals.
c) Reducing AC resistance: AC resistance is the main basis for current-carrying capacity. According to the skin-effect principle, the current per unit area per surface of a single wire is larger than the current per unit area of ​​the center of the wire. In other words, the center of a large-section conductor is in the area of ​​a circle composed of the same conductor, and the center of the circle is smaller than the current passed through the circumference. Therefore, it is more reasonable and economical to use a different metal for the center conductor and the circle conductor.
In addition, the impact of AC resistance indicators in addition to DC resistance, skin effect, there is a proximity effect, compared with the same DC resistance of the copper conductor, the cross-section should be used to enlarge the copper-clad aluminum conductor, in a single conductor, aluminum in the center, Copper is in the outer circle; the enlarged copper-clad aluminum conductor increases the total cross-section of the conductor, so it also increases the surface area of ​​the conductor, improves the heat dissipation conditions of the cable, and increases the heat dissipation area, while the thermal conductivity of aluminum is similar to that of copper. Under the condition of material cost, AC resistance indicators are much more economical.
d) It has good corrosion resistance: Aluminum is more easily corrosive than copper, but due to the complete metallurgy of the copper clad aluminum material, the aluminum is completely covered with copper and will not be contacted by water and air, and it can achieve the same performance as copper. For aluminum conductors, especially in coastal areas, the chloride ions contained in the salt fog in the atmosphere will condense on the surface of aluminum, causing localized corrosion around the impurities and defects on the surface, forming holes, cracks, and micro-batteries, exacerbating the corrosion of aluminum conductors. .
e) Low cost and light weight: Copper-clad aluminum conductor cables can save more than 40% of the cost compared to copper wires with the same specifications. The proportion of copper clad aluminum wire is only 37%-40% of that of pure copper wire. When the wire diameter and weight are equal, its length is 2.5 times that of pure copper wire.
f) Good solderability: The copper clad aluminum wire has a layer of pure copper concentrically and therefore has the same solderability as a pure copper wire, facilitating production.
Through the above performance comparison, it can be seen that the “copper-aluminum-section copper†will be more effective and the trend is obvious. In the future, with the advancement of the “copper-aluminum-assembling copper†undertaking, the “copper-aluminum dispute†is expected to determine the outcome. "The major trend of the development of cable industry, while the domestic cable products will be expected to achieve the goal of low product prices and stable performance of qualified products, strengthening China's cable industry in the international competitiveness.
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