There are two main categories of conductors used as cables: copper and aluminum. Aluminum is derived from aluminum alloy and copper-clad aluminum, and the original wires and cables are made of copper conductors, because its conductivity and mechanical properties are ideal, and the DC resistivity at 20°C is 1.72×10ˉ6 Ω ̇cm.
Since the 50s of the last century, our country has been embargoed by capitalist countries because copper is an important strategic material due to the start of the Korean War. Chinese people still remember the patriotic enthusiasm of responding to the call to donate their bronze vessels at home to the country. At the same time, "aluminum instead of copper" is used in all aspects of life, using aluminum wires and cables for the implementation of a technical policy. In some places where safety and reliability are not too strict, aluminum core wires and cables are used, and even in newly built homes - places that should pay attention to safety can only be compromised. Because no matter what It is that the conductive and mechanical properties of aluminum are inferior to copper. The DC resistivity at 20°C is 2.82×10ˉ6 Ω ̇cm, which is about 1.64 times that of copper. Its brittleness makes the joint prone to breakage, and also reduces the reliability of the joint due to creep characteristics. The so-called creep is at higher temperatures (such as 70°C) and higher pressures (such as bolts). Compression), the thermoplastic deformation that increases with time. It is the main cause of reduced reliability or even damage to wire and cable joints. After a long period of exploration, some countermeasures have also been found, such as strengthening inspections and regularly reinforcing the screwing bolts Wait.
Of course, there are always two sides to things, because the price of aluminum conductor wires and cables is low and light, which greatly reduces the intensity of construction labor and is welcomed.
In the period of reform and opening up, the economic development was faster, people's quality requirements were improved, and some shackles were gotten rid of, and as a result, they turned from one extreme to another, taking the lead in abandoning "aluminum instead of copper" on the southeast coast, and almost all wires and cables were made of copper conductors, with unprecedented depth and breadth. Depth - in the proportion of copper and aluminum conductors exceeds developed countries, breadth - gradually expands from the southeast coast to the interior.
The development of things went to the opposite side, due to the soaring copper price, the price of wire and cable increased exponentially, and people had to rethink. At the same time, two small whirlwinds blew, one is the emergence of copper-clad aluminum wire core cables, and the other is the introduction of aluminum alloy conductor cable technology from North America. Aluminum alloy cables came into being in China.
copper Aluminum-clad cables claim to be an alternative to copper cables. However, in fact, it is only suitable for small cross-sections and is used in high-frequency devices, and copper-clad aluminum wire can play its advantage due to the skin effect of high-frequency current. Relevant standards at home and abroad are also limited to electronic devices Item. Copper-clad aluminum wire cannot be used to make power cables, on the one hand, it is only suitable for single-strand wires, and the use of multi-strand wires loses its meaning, on the other hand, the joint technology cannot be solved, so this whirlwind quickly becomes low pressure.
Aluminum alloy conductors are electrical aluminum with trace amounts of silicon, copper, zinc, iron, boron and other elements added. The mechanical properties have been greatly improved, such as the optimization of flexibility and the great improvement of creep resistance. The conductivity of the annealing process is very close to that of electrical aluminum. The national standard GB/T3956-2008 for "conductors of cables" takes the same value for the resistance of aluminum and aluminum alloy conductors.
aluminium One of the key technologies in alloy cables is the splice. The material and process of the connector are important factors affecting the quality, and cable manufacturers who have introduced technology provide technical services in addition to selling cables. For a connector to be reliable, there must be a supplier Assign professionals to guide the construction. Therefore, its price is significantly higher than that of aluminum cables. Because of the large profit margin, the number of manufacturers has skyrocketed from the first two to more than 100, and the small whirlwind is expanding. Since all enterprises are currently self-reliant The standard production of their own enterprises seems to be the same, but the quality is very different.