Cables are divided into different inner conductors. There are two main types, one is pure copper material and the other is copper clad aluminum material. The English name of copper-clad aluminum is Copper Clad Aluminum, so copper-clad aluminum conductors are also often called: CCA conductors. Copper-clad aluminum composite wire was first introduced by Germany in the 1930s, and then promoted in the United Kingdom, the United States, France and other countries, and is widely used in various fields. CATV cables in the United States began to trial copper-clad aluminum wires as early as 1968, and consumed 30,000 tons/year. Now American countries have replaced pure copper cables with copper-clad aluminum (steel) cables.
Copper-clad aluminum is formed by concentrically cladding a copper layer on the surface of aluminum or aluminum/steel alloy core material, and the thickness of the copper layer is above 0.55mm. Due to the skin effect characteristics of high-frequency signal transmission on the conductor, the cable TV signal is transmitted on the surface of the copper layer above 0.008mm. The copper-clad aluminum inner conductor can fully meet the signal transmission requirements, and its signal transmission characteristics are comparable to those of copper with the same diameter. The body is consistent.
Compare copper-clad aluminum and pure copper in the following three aspects:
1. Mechanical characteristics:
The strength and elongation of pure copper conductor cable are larger than copper-clad aluminum conductor, which means that pure copper is better than copper-clad aluminum in terms of mechanical properties. From the perspective of cable design, pure copper conductors have the advantage of better mechanical strength than copper-clad aluminum conductors, which are not necessarily required in actual applications. Copper-clad aluminum conductors are much lighter than pure copper, so the overall weight of copper-clad aluminum cables is lighter than pure copper conductor cables, which will bring convenience to cable transportation and power cable erection. In addition, copper-clad aluminum is a little softer than pure copper, and cables made of copper-clad aluminum conductors are a little bit better in flexibility than pure copper cables.
2. Electrical performance:
Because the conductivity of aluminum is worse than that of copper, the DC resistance of copper-clad all aluminum conductors is greater than that of pure copper conductors. Does this affect the main 2014 high school entrance examination sprint comprehensive review guidance Beijing area test questions Guangdong area test questions Jiangsu area test questions to see if the cable will be damaged Using power supply, such as providing power to the amplifier, if it is used for power supply, the copper-clad aluminum conductor will cause additional power consumption and voltage drop. When the frequency exceeds 5MHz, there is no obvious difference in the attenuation of AC resistance under these two different conductors. Of course, this is mainly due to the skin effect of high-frequency current. The higher the frequency, the closer the current flows to the surface of the conductor. The surface of the copper-clad aluminum conductor is actually pure copper. When the frequency is high, the entire current is plated. It flows in the copper material. In the case of 5MHz, the current flows in a thickness of about 0.025 mm near the surface, and the thickness of the copper layer of the copper-clad aluminum conductor is about twice this thickness. For coaxial cables, because the transmitted signal is above 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 point.
Copper-clad aluminum is softer than pure copper conductors and is easy to straighten during the production process. Therefore, to a certain extent, it can be said that cables with copper-clad aluminum have better return loss indicators than cables with pure copper conductors.
Copper-clad aluminum conductors are sold by weight, and pure copper conductors are also sold by weight. Copper-clad aluminum conductors are more expensive than pure copper conductors of the same weight. But the copper clad aluminum of the same weight is much longer than the pure copper conductor, and the cable is calculated according to the length. The copper clad aluminum wire of the same weight is 2.5 times the length of the copper wire, and the price is only a few hundred yuan per ton. Taken together, copper-clad aluminum is very advantageous. Since copper-clad aluminum cables are relatively light, the transportation cost and installation cost of the cable will be reduced, which will bring certain convenience to the construction.
4. Ease of maintenance:
The use of copper-clad aluminum can reduce network failures and prevent network personnel from “cutting the core in winter and cutting the skin in summer” during maintenance (aluminum strip or aluminum tube products). Due to the large difference in thermal expansion coefficient between the copper inner conductor and the aluminum outer conductor of the cable, in the hot summer, the aluminum outer conductor stretches greatly, and the copper inner conductor is relatively retracted, and cannot fully contact the elastic contact piece in the F header; in severe cold In winter, the aluminum outer conductor shrinks greatly, causing the shielding layer to fall off. When the coaxial cable uses a copper-clad aluminum inner conductor, the thermal expansion coefficient between it and the aluminum outer conductor is small. When the temperature changes, the cable core failure is greatly reduced, which improves the transmission quality of the network.
In general, the overall performance of copper-clad aluminum conductors is better than pure copper conductors, which will save users’ costs.
The industry believes that the use of copper-clad aluminum wire in the wire and cable industry is also a good way to relieve the current pressure on enterprises. The aluminum wire is coated with a layer of copper and made of bimetallic wire. Because of its small specific gravity and good transmission performance, it is especially suitable for the inner conductor of radio frequency coaxial cable. Compared with pure copper wire, its density is About 40% pure copper. The transmission characteristics are better than pure copper wire, and it is the most ideal internal conductor of radio frequency coaxial cable branch line.