How to connect aluminum wire and copper wire together?
Copper wires and aluminum wires cannot be directly connected. Copper wires and aluminum wires can be connected by a certain method. Copper wires and aluminum wires are made of different materials and therefore have different characteristics. To connect them together, special treatment is required.
1. To connect single-strand small-section copper and aluminum wires, the copper wire should be tinned before connecting with the aluminum wire.
2. When connecting multiple strands of large cross-section copper and aluminum wires, copper-aluminum transition connecting pipes or copper-aluminum transition clamps should be used.
3. If the aluminum wire is connected to the copper terminal of the switch, a copper-aluminum transition nose should be used.
The reason why copper and aluminum can not be directly connected
The potentials of copper and aluminum are different, and the part in contact with copper and aluminum will accelerate the oxidation of the aluminum wire due to the galvanic reaction, and the copper and aluminum joints will have poor contact over time.
This is a chemical problem. The chemical properties of metals are relatively active and inactive. For example, gold never rusts. This shows that gold is chemically inactive. Iron is prone to rust, and iron is more active than gold.
If the two metals are put together, it will accelerate the oxidation of the active metal. Compared with copper, aluminum is much more active than copper. Therefore, aluminum acts as the negative electrode of the battery and is rapidly oxidized and corroded. The higher the temperature (the higher the current Large) The faster the oxidation rate, the more oxide film is formed, which affects the electrical conductivity of the wire.
When copper and aluminum conductors are directly connected, the contact surfaces of these two metals are easily formed into electrolyte under the action of air, moisture, carbon dioxide and other impurities, thus forming a primary battery with aluminum as the negative electrode and copper as the positive electrode. It causes galvanic corrosion of aluminum and increases the contact resistance at the junction of copper and aluminum.
Because the elastic modulus and thermal expansion coefficient of copper and aluminum are quite different, after multiple cooling and heating cycles (power on and off) in operation, a large gap will be generated at the contact point, which will affect the contact and increase Contact resistance.
The increase in contact resistance will cause the temperature to rise during operation. Corrosion and oxidation will intensify at high temperatures, creating a vicious circle, further deteriorating the quality of the connection, and finally resulting in excessively high contact point temperature and even accidents such as smoking and burning.
