COPPER CLAD ALUMINUM CABLE CLASSIFICATION

    Copper clad aluminum cable definition:

    Copper clad aluminum cable refers to the wire and cable with aluminum core wire instead of copper as the main body and a certain proportion of copper layer coated on the outside. For the mechanical and electrical installation industry, wires and cables occupy an important position in the mechanical and electrical installation engineering. Copper, as the main raw material, accounts for 70% ~ 80% of the total cost of cable products. The price of copper cable increases rapidly with the rise of copper price, which brings great difficulties to the investors and construction parties in the control of project cost. Therefore, the research and application of copper-clad aluminum cable grow rapidly.

    The definition of copper-clad aluminum cable is introduced above. Next, we will talk about the classification and characteristics of copper-clad aluminum cable:

    Copper clad aluminum cable refers to the wire and cable with aluminum core wire instead of copper as the main body of the cable and a certain proportion of copper layer on the outside. The copper-clad aluminum cable can be divided into two categories: one is the copper-clad aluminum cable for signal or communication purposes, and the other is the copper-clad aluminum cable for power supply. In terms of its characteristics, the copper-clad aluminum cable and the pure copper cable are compared as follows.

    1、 Copper clad aluminum communication cable

    Mechanical properties: the strength and elongation of pure copper conductor are larger than that of copper-clad aluminum conductor, that is to say, pure copper is better than copper-clad aluminum in mechanical properties. From the perspective of cable design, the advantages of pure copper conductor are better than copper-clad aluminum conductor in mechanical strength, which is not necessary in the practical application process. Copper clad aluminum conductor is much lighter than pure copper, so the overall weight of copper clad aluminum cable is lighter than that of pure copper conductor cable, which will bring convenience to cable transportation and cable erection construction. In addition, copper-clad aluminum is a little softer than pure copper, and the cable produced by copper-clad aluminum conductor is better than pure copper cable in terms of softness.

    Electrical performance: because the conductivity of aluminum is worse than that of copper, the DC resistance of copper-clad aluminum conductor is larger than that of pure copper conductor. Whether this affects depends on whether the cable will be used for power supply, such as providing power to the amplifier. If it is used for power supply, the copper-clad aluminum conductor will cause extra power consumption and more voltage reduction. When the frequency is more than 5MHz, there is no obvious difference in the attenuation of AC resistance between the two different conductors. Of course, this is mainly because of the skin effect of high-frequency current. The higher the frequency is, the closer the current flow is to the conductor surface. In fact, the surface of copper-clad aluminum conductor is made of pure copper material. When the frequency is high enough, the whole current flows in the copper material. At 5MHz, the current flows in a thickness of about 0.025mm near the surface, and the copper layer thickness of the copper-clad aluminum conductor is about twice as thick as that. For coaxial cable, since the signal transmitted is more than 5MHz, the transmission effect of copper clad aluminum conductor and pure copper conductor is the same. The attenuation of the actual test cable can prove this. The copper-clad aluminum conductor is softer than the pure copper conductor, so it is easy to straighten in the production process, so to some extent, it can be said that the return loss index of the cable with copper-clad aluminum conductor is better than that with pure copper conductor.

    Economy: copper clad aluminum conductor is sold by weight, and pure copper conductor is also sold by weight. The price of copper clad aluminum conductor is more expensive than that of pure copper conductor of the same weight. But the same weight of copper-clad aluminum is much longer than the length of pure copper conductor, and the cable is calculated by length. With the same weight, the copper-clad aluminum wire is 2.5 times the length of copper wire, and the price is only several hundred yuan per ton. All in all, copper-clad aluminum has its advantages. Because the copper clad aluminum cable is relatively light, the transportation cost and installation cost of the cable will be reduced, which will bring certain convenience to the construction.

    2、 Copper clad aluminum power cable

    DC resistivity: the resistivity of copper clad aluminum wire is larger than that of pure copper wire, about 1.5 times of that of pure copper wire. When the negative value is the same, the weight of copper clad aluminum wire is about 1 / 2 of that of pure copper wire. According to the calculation of skin effect, when the frequency is above 5MHz, the resistivity is equal to that of copper conductor with the same cross section. In the use of 50Hz frequency power cable, the skin effect and proximity effect of copper conductor are gradually prominent when it is more than 150mm2. At the same time, due to the continuous development of science and technology, high-order harmonic current and energy will be injected into the power supply system, and high-order harmonic voltage of corresponding frequency will be generated on the impedance of the system, resulting in the distortion of voltage waveform and increase of power supply system In addition, the cable amplifies the harmonic wave, which produces over-voltage at the joint and damages the cable head. The use of copper-clad aluminum conductor can reduce the AC impedance (resistance) caused by high-order harmonics. In other applications, the copper clad aluminum / copper composite conductor can meet the requirements of conductor DC resistance within the upper limit of the outer diameter of the existing conductor of the same specification by improving the volume of copper in the copper clad aluminum single wire and corresponding technological measures.

    Connection mode: the copper-clad aluminum conductor can meet the habit of product selection, design, use and installation of wires and cables for many years, and it is also favorable for cable terminal compression and tin welding.

    Reduce AC resistance: AC resistance is the main basis of current carrying capacity. According to the principle of skin effect, the current flowing through the surface of a single wire per unit area is larger than the current flowing through the center of the wire per unit area. That is to say, the center of a large cross-section conductor is within the circular area formed by the same conductor, and the center of 

    It has good corrosion resistance: aluminum is easier to corrode than copper, but because the copper-clad aluminum material has been completely metallurgic, aluminum is completely covered by copper, will not be contacted by water and air, and completely achieves the same performance as copper. Copper clad aluminum / copper composite conductor is also more conducive to avoid the potential difference between copper layer falling off and copper aluminum two kinds of metals caused by poor contact between conductor and terminal due to corrosion, bumping, tight pressure and poor tin welding during long-term use of cable, accelerating electrochemical corrosion and causing the hidden danger of cable end burning. 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, which will aggravate the corrosion of aluminum conductors.

    Low cost and light weight: compared with the copper core cable with the same technical index, 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: the copper clad aluminum wire has the same weldability as the pure copper wire because it is concentric coated with a layer of pure copper, which is convenient for production. Although the copper-clad aluminum cable has been born and is gradually applied, there is still a lot of resistance, mainly for the copper-clad aluminum cable is still difficult to find the application basis of the country and industry, and difficult to get the approval of the design unit. There are still quite a lot of copper clad aluminum cable products without 3C certification, and the industry is still in the stage of product identification and enterprise standard formulation. The product specifications, characteristics and use standards of different brands are quite different, which is difficult for engineering designers to grasp when applying, and the investors are not willing to accept it for the time being. However, with the gradual improvement and approval of national standards and regulations, copper-clad aluminum cable is bound to be standardized, which will undoubtedly become the highlight of wire and cable in the next few years, driving the development of the whole industry.