is aluminum wire as good as copper
Aluminum wire refers to its full longitudinal length and uniform cross section, which refers to the metal linear material made of pure aluminum or aluminum alloy. The products are processed along the center pressure and delivered in rolls. Cross section shapes include circle, ellipse, square, rectangle, equilateral triangle and regular polygon. It is divided into pure aluminum wire and alloy aluminum wire according to material. It can be divided into industrial aluminum wire and process aluminum wire.
In life, copper wire is used as conductor. It has good conductivity and is widely used in the manufacture of wires, cables, brushes, etc; Good thermal conductivity, commonly used to manufacture magnetic instruments and meters that need to be protected from magnetic interference, such as compass, aviation instruments, etc; Excellent plasticity, easy to hot press and cold press processing, can be made into tubes, rods, wires, strips, strips, plates, foils and other copper materials. Pure copper products include smelting products and processed products.
As an electrician, we must understand the characteristics of these two kinds of metal wires so that they can be used.
Only by making clear their advantages, disadvantages and characteristics can we make proper use of materials and make the best use of things. Otherwise, it is easy to cause improper use, ranging from line damage to fire.
Next, let's learn about the advantages and disadvantages of copper wire and aluminum wire:
Advantages and disadvantages of copper wire:
(1) Low resistivity: the resistivity of aluminum cable is about 1.68 times higher than that of copper cable.
(2) Good ductility: the ductility of copper alloy is 20 ~ 40%, that of electrical copper is more than 30%, and that of aluminum alloy is only 18%.
(3) High strength: the allowable stress of copper at room temperature is 7 ~ 28% higher than that of aluminum. Especially the stress at high temperature, the difference between them is very far.
(4) Fatigue resistance: aluminum is easy to break after repeated bending, while copper is not. In terms of elasticity index, copper is also about 1.7 ~ 1.8 times higher than aluminum.
(5) Good stability and corrosion resistance: copper wire is resistant to oxidation and corrosion, while aluminum wire is easy to be oxidized and corroded.
(6) Large current carrying capacity: due to low resistivity, the allowable current carrying capacity (maximum current that can be passed) of copper cable with the same section is about 30% - 50% higher than that of aluminum cable. Especially, there are more and more household appliances, and copper wire is basically used for home decoration.
(7) Low voltage loss: due to the low resistivity of copper cable, when the same current flows through the same section. The voltage drop of copper cable is small. Therefore, the same transmission distance can ensure high voltage quality; In other words, under the condition of allowable voltage drop, copper cable transmission can reach a long distance, that is, the power supply coverage area is large, which is conducive to network planning and reduce the number of power supply points.
(8) Low calorific value: under the same current, the calorific value of copper cable with the same section is much smaller than that of aluminum cable, making the operation safer.
(9) Low power loss: due to the low resistivity of copper, compared with aluminum cable, the power loss of copper cable is low, which is obvious. This is conducive to improving the utilization rate of power generation and protecting the environment.
(10) Oxidation resistance and corrosion resistance: the connector of copper cable has stable performance and will not cause accidents due to oxidation. The joint of aluminum cable is unstable, and accidents often occur due to the increase of contact resistance and heating due to oxidation. Therefore, the accident rate is much higher than that of copper cable. Especially in some places where copper wires and aluminum wires are connected, problems occur after a long time. Therefore, the connection of copper wire and aluminum wire must be strictly required.
(11) Convenient construction:
① The copper wire has good flexibility and small allowable bending radius, so it is convenient to turn and pass through the pipe;
② The copper wire is fatigue resistant and not easy to break after repeated bending, so the wiring is convenient;
③ The copper wire has high mechanical strength and can bear large mechanical tension, which not only brings great convenience to the construction and laying, but also creates conditions for mechanized construction.
Disadvantages of copper wire:
The price of copper wire is high and the ratio of copper wire is ficant, which determines the high cost of copper wire. As a cable, it has many performance advantages, that is, high cost! Therefore, our common overhead lines basically do not use copper wire. It is good, but it is too heavy. Therefore, overhead lines often use more aluminum wires, and copper wires are usually used for ground wires.
Advantages and disadvantages of aluminum wire:
(1) Cheap price: the price of copper pole is 3.5 times that of aluminum pole, and the proportion of copper is 3.3 times that of aluminum. Therefore, aluminum cable is much cheaper than copper cable, which is suitable for low-cost projects or temporary power consumption.
(2) The cable is very light: the weight of aluminum cable is 40% of that of copper cable, and the construction and transportation cost is low.
(3) Oxidation resistance and corrosion resistance: aluminum reacts quickly with oxygen in the air to form an oxide film, which can prevent further oxidation. Therefore, aluminum conductor is the necessary material for high-voltage, large-section and long-span overhead power transmission, but its advantages as a low-voltage line no longer exist.
Disadvantages of aluminum wire:
Aluminum wire has low conductivity, large electrical loss, poor tensile strength and low corrosion resistance. The joint is particularly easy to oxidize. If it is connected with copper wire, the joint is more prone to corrosion due to potential difference, which is easy to cause open circuit. These are relative to the use of low-voltage lines, but the advantages of aluminum wire in high-voltage lines are also quite obvious. We should make it clear that we can't assert it all at once.
Copper and aluminum wires cannot be connected together
The chemical and physical properties of copper and aluminum are very different
Therefore, copper and aluminum should not be directly connected. Of course, copper aluminum connection is inevitable. When connection is required, copper aluminum transition clamp, copper aluminum transition joint, copper wire lined with tin or aluminum wire lined with tin are generally used for direct connection.
The electrochemical properties of copper and aluminum are different
If they are directly connected, once they encounter the electrolyte formed by water, carbon dioxide and other impurities, a chemical battery will be formed. This is because aluminum is easy to lose electrons and become the negative electrode, and copper is difficult to lose electrons and become the positive electrode. Therefore, a 1.69v electromotive force is formed between the positive and negative electrodes, and a small current passes through to corrode the aluminum wire, The so-called electrochemical corrosion. This will cause poor contact between copper and aluminum and increase the contact resistance. When a current passes through, the temperature at the joint will rise, which will further accelerate the corrosion of the joint and increase the contact resistance, resulting in a vicious circle until it is burned.
Copper and aluminum are two different metals
Simply connecting them together will lead to electrochemical reaction (corrosion). For a long time, the contact resistance at the connection will increase and heat, resulting in on and off of the circuit, high and low voltage, and even fire.
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