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Adapters for copper and aluminum wires

Adapters for copper and aluminum wires

1. Electrochemical corrosion of copper and aluminum conductor connections---Adapters for copper and aluminum wires

When the copper and aluminum conductors are directly connected, the contact surface of the two metals is easily formed electrolyte under the action of moisture, carbon dioxide, and other impurities in the air.

As a result, the galvanic battery with aluminum as the negative electrode and copper as the positive electrode is formed, which causes galvanic corrosion of aluminum and increases the contact resistance at the junction of copper and aluminum.

In addition, due to the significant difference between the elastic modulus and thermal expansion coefficient of copper and aluminum, after many cold and heat cycles (power-on and power-off) in operation, the

It will cause a more significant gap at the contact point to 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, resulting in a vicious cycle, which further deteriorates the connection quality and leads to excessively high temperature of the contact point and even accidents such as smoking and burning.


2. Protective measures to be taken when connecting copper and aluminum conductors

The "Code for Construction and Acceptance of Busbar Installation in Electrical Installation Engineering" clearly stipulates that when the busbar and the busbar, the busbar and the branch line, and the busbar and the electrical terminal are overlapped, the

The processing of its lap surface should meet the following requirements:

(1) Copper and copper: In the outdoor, high temperature and humid or indoor with corrosive gas to the busbar, the tin lining must be used;

Direct connection is possible in dry rooms.

(2) Aluminum and aluminum: direct connection.

(3) Copper and aluminum: Copper conductors should be tinned in a dry room. Outdoors or indoors where the relative humidity of the air is close to 100%, copper-aluminum transition plates should be used.

The copper should be tinned. Correspondingly, copper-aluminum connecting pipes can be used when connecting copper cables and aluminum cables. Likewise, copper-aluminum terminals can connect copper cables and aluminum wires. The copper should be lined with tin and so on.

The above regulations on the treatment of the lap surface according to different materials and use environments when connecting busbars and conductors prevent the galvanic corrosion of the metal at the connection.

Reduce the contact resistance at the joint to ensure good common contact and reduce combined heating.

The practice has proved that after removing the oxide layer on the metal contact surface, plating a layer of tin can stabilize the contact resistance. Why tin on the copper end? This is because: First,

Because the aluminum conductor is oxidized quickly, it cannot be tinned manually; secondly, the standard electrode potential of tin is -0.14V. After tinning the copper end,

The overlap between copper and aluminum conductors is mainly aluminum and tin contacts. The potential difference between the two is much smaller than the potential difference between copper and aluminum, which effectively prevents the galvanic corrosion of aluminum conductors at the connection.

Although tinning the copper conductor end can alleviate the process of electrochemical corrosion, a large amount of water can quickly enter the contact surface in places with high humidity and high temperature or corrosive gas.

They accelerated galvanic corrosion. Therefore, copper-aluminum transition tubes or copper-aluminum transition terminals should be used for the copper-aluminum connection in the outdoor humid and high-temperature environment.


1) The quality does not meet the requirements of national standards

The screw hole of the terminal is too large so that the contact surface of the airport is reduced, and the fixing bolt is easy to loosen; the outer diameter of the airport becomes thinner, and the tube wall becomes lighter; the depth of the tube becomes shallow,

The wire insertion part is shortened; the length of copper in the copper-aluminum transition part is shortened; the width of the contact surface is reduced so that the contact area is reduced, and the thickness of the contact surface is reduced.

2) The installation process is not precise

Whether the terminals and electrical equipment can be well connected is also one of the conditions to ensure a safe power supply during the installation process.

A poor connection can easily lead to electrochemical corrosion of copper and aluminum contact between two different metals, resulting in overheating and burnout.

3) Matching of cables and waterproof terminals

Because the electrical conductivity of aluminum is slightly worse than that of copper, the same current carrying capacity, the aluminum cable is much larger than copper cable,

Therefore, pay attention to whether the AC output of the inverter has waterproof terminals and whether it can accommodate it.
 

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