Metals such as aluminum and copper are used in electrical wiring more often than other metals because they are very good and inexpensive conductors.
But what specific material (copper or aluminum) is better in terms of its conductive properties. In this article we will try to figure it out.
Let's start with a physical description of these materials. Copper is a soft and malleable metal with a bright golden brown tint. Aluminum is a silvery metal that is lighter and stronger than copper.
Now let's talk about the conductivity of these materials. The two metals are close in conductivity scale, with copper being the more desirable characteristic. The conductivity of copper is about 0.6 MΩ / cm, and that of aluminum is about 0.4 MΩ / cm.
As for the resistance of the conductor? A one meter long wire with a cross section of one millimeter square has a resistance of 1.7 milliohms (0.0017 ohms) if it is made of copper, and 2.5 milliohms (0.0025 ohms) if it is aluminum wire.
What is their use in wiring? Thanks to excellent electrical properties copper is widely used for electrical wiring. When distributing electricity, sometimes aluminum is used instead of copper. However, the price of aluminum is slightly higher and amounts to about one third of the cost of copper.
Aluminum in the composition of the wires has another important drawback. Aluminum was once very widely used in household wiring, but it corroded easily, which could lead to high resistance and heat build-up at the connection points. Because of this danger, the use of aluminum wire was limited in the 1970s. Therefore, copper can be seen much more often in electrical wiring today.
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Structural steels.
They are classified by characteristics and by chemical composition alloys. If high quality and ordinary. Both are carbon steels, although the carbon content in them is insignificant.
The purpose of ordinary structural alloys is the manufacture of industrial products that must be subjected to serious mechanical stress: nails, bolts, corners, channels, beams, etc. High quality structural steels are suitable for the manufacture of parts used in mechanical engineering. Of course, their withstand loads are much lower, such steel grades are much softer, they are used to manufacture parts by cold stamping. In addition, there are especially high-quality brands, they are called cryogenic. They retain their strength characteristics at extremely low temperatures. They are used to make containers for the transportation and storage of liquefied gases, and are also used in the construction of facilities in permafrost conditions.
Differs in resistance to corrosion in aggressive environments. This is its main property. The alloy is subjected to alloying, the main alloying element is chromium, and the more it is, the more resistant the steel is to corrosive effects, for example, acids. The chromium content can be from 12 to 20% (if chromium is 17 percent or more, the alloy will withstand the impact, including nitric acid 50% concentration). To enhance this wonderful property of stainless steel, give it additional physicochemical properties, it is also alloyed with nickel, titanium, niobium, molybdenum. The ratio of certain elements and their amount determines the grade of steel and its resistance to strong acids (phosphoric, sulfuric, etc.)
How can you explain this corrosion resistance? At the interface between the chromium-containing alloy and the medium, a film of oxides and other insoluble compounds forms, which protects the surface. Many different products are made from stainless steel. And not only in industry. It is not only durable, but also aesthetically pleasing material - in architecture, in the design of household items, it is used very often.
Copper.
It is the most common non-ferrous metal. Resistant to corrosion in air (only carbon dioxide contained in the air forms a greenish bloom - patina), in fresh and salt water, with alkaline solutions, but dissolves in strong acids(nitrogen, sulfuric). It is easily processed by soldering and pressure, but its casting properties are not very high. Deoxidized and oxygen-free copper is used in electronics.
Copper alloys are wear-resistant, as well as pure copper are anti-corrosion.
According to the interaction of copper with impurities, 3 groups are distinguished:
- Solid solutions: with aluminum, zinc, antimony, nickel, tin, iron (electrical conductivity and thermal conductivity decrease);
- Insoluble impurities: bismuth, lead (electrical conductivity does not change, but pressure treatment becomes difficult);
- Fragile chemical compounds: sulfur and oxygen (oxygen reduces strength, and sulfur promotes better cutting).
Copper and copper alloys have long been used to this day in the manufacture of dishes, household items, used in art and architecture.
Aluminum
It is a metal with high electrical conductivity, corrosion resistance(in air it quickly becomes covered with a thin "film" of aluminum oxide and does not oxidize further) and, perhaps, one of its main properties - it has a low density, therefore, lightness, softness and excellent workability in a cold state, i.e. bending and stamping.
Aluminum compounds are absolutely non-toxic, therefore it is actively used in Food Industry making dishes, foil, packaging, etc.
In electrical engineering, it is actively used because of its high electrical conductivity, almost the same as that of copper, but aluminum is much cheaper.
To add strength, aluminum is alloyed with copper and magnesium (in small quantities) to form a duralumin alloy.
Aluminum is widely used in various industries industry.
Brass.
Alloy of copper with zinc. The different ratio of these two components makes it possible to obtain alloys with different properties. If zinc is from 5 to 20% - brass is called red, and yellow, if the zinc content is 20-36%
These alloys are malleable and have sufficient low temperature melting. Outwardly, brass resembles gold, therefore it is often used in applied arts and decor. Furniture fittings, locks, decorative elements... Made of brass musical instruments... It is also used in the military industry.
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Yes, of course, there are many differences between copper and aluminum when applied in electrical installations, such as conductivity, weight, and, one of the most important factors- price. In the last century, aluminum was the more common metal for making electrical products such as fuses, busbars, circuit breakers, and was used for laying internal networks in residential and industrial buildings. Under the influence modern trends many designers actively replaced aluminum with copper in their products, however, in recent times trends change again, and go from copper to aluminum again. The reason for this transition is the high cost of copper.
Materials (edit)
Very often misconceptions about copper and aluminum arise from the use of different grades of metals used in electrical installations. Pure copper is used in wires, buses and other electrical equipment. Pure aluminum is poorly suited for use in electrical installations, here copper has great advantage... However, it is necessary to take into account the fact that the metallurgical industry is evolving and creates new alloys of various metals.
Respectively various properties aluminum (Al) can also change - it all depends on the processing. For example, Al 6101 is stronger than Al 1350. However, after heat treatment, Al 6101 solidifies and increases its strength. Different kinds metals such as Al 6101 and Al 1350 can have different properties compared to pure copper (Cu). Therefore, in the design process, it is very important to know the material properties for a particular use.
Conductor properties
Weight, cross-section, cost are the three main factors when choosing a conductor material. However, there are other factors to consider. For example, heating factors - how the conductivity will change when heated, how much the metal will expand, and others. As you know, when heated, metals expand; accordingly, if this factor is not taken into account, deformation of the contact points can be obtained. This property is especially important when using aluminum or its alloys, since its coefficient of thermal expansion, depending on the alloy, is approximately 42% higher than that of copper. But it is also worth noting that the heat transfer coefficient of aluminum is greater than that of copper.
The solutions were found to be quite simple - they increased the surface of the aluminum tires, which, in turn, increased heat transfer, and the tires did not deform when heated. When designing, regardless of the type of conductive material, it is necessary Special attention to give reliable connections of conductors. This is necessary to prevent deterioration of the quality of contacts over time, as well as to prevent deformation when thermal expansion and creep.
A common misconception is that aluminum is soft and must use special connectors to compress it during installation. Aluminum may need a special coating to reduce oxidation. This is due to the fact that oxidation can have significant influence on the conductivity quality of the material even in the case of an Al - Al compound. To prevent the oxidation process, conductors (this also applies to copper and aluminum) are often coated with tin or silver, since these materials have good conductivity and are not prone to oxidation under atmospheric conditions.
Corrosion, which occurs when dissimilar metals are used in one system, can also cause quite a problem. Al reacts electrochemically with copper at high humidity (moisture acts as an electrolyte). Conductors made of copper and aluminum with cable lugs are placed in connectors, which are then friction welded and encapsulated to prevent corrosive processes in the Al - Cu connection. Correct connection avoids corrosive processes as much as possible. Al and copper are compatible metals, however, do not forget that if they are incorrectly joined, corrosive processes can occur.
Weight and electrical conductivity
Perhaps not the last factor when choosing between aluminum and copper conductors is their electrical conductivity... Yes, of course, copper has the best conductivity per unit volume, but aluminum is lighter, and this is its big plus. According to Uwe Schenk, manager of Helukabel, “Raw Al is about 70% lighter than Cu. And aluminum busbars and cables are about 60% lighter than copper ones. "
However, the main indicator is still conductivity. Al grade Al6101 has almost half the conductivity of Cu (56%). The difference in the ratios of mass and electrical conductivity looks like this, for one pound of Al there is approximately 1.85 pounds of Cu. For example, a copper bus assembly weighs 550 pounds and an aluminum assembly weighs 300 pounds. This difference in weight can help save not only material costs, but also transportation and even handling costs.
The use of copper and aluminum in various electrical installations
Aluminum in electrical installations
Practically all over the world it is used in power transmission lines and switchgears. This is due to the lower weight and cost compared to Cu, which allows for fewer high voltage towers during transmission. electrical energy over considerable distances.
Brass contacts were previously used in lighting installations and various connectors. Now they are being actively replaced by aluminum contacts.
Copper in electrical installations
It is very common in communication electrical installations - here its main plus is flexibility, since it makes it easy to carry out installation in difficult areas and does not break at the same time.
Electric motors and transformers - due to the fact that these devices must have minimum dimensions and maximum performance, and since the conductivity and flexibility of copper is much better than aluminum, almost all manufacturers of electric motors and transformers use it in their products.
Mutual use of copper and aluminum
Both materials can be actively used when installing wiring in buildings. In the last century, all internal networks were made with aluminum wires. This allowed significant savings, since the length of the wiring could reach several kilometers. In modern residential buildings copper is used for wiring. Its advantages are also obvious - better conductivity (smaller section) and better elasticity.
Many people have a stereotype that aluminum cables and tires are bad. But when used correctly, you can save money and get good conductivity.
Electrical devices such as busbars, transformers, electrical cables also use both materials.
It is impossible to imagine a house or apartment without electricity in our century, light enters all apartments and houses. To determine which wiring is better than copper or aluminum, it is necessary to consider the characteristics of the two materials and conduct a comparative analysis.
Aluminum wiring
This type of wiring has become widespread in residential buildings and apartments throughout the country since the days of the USSR. You can meet aluminum even now, in any house over 15-20 years old. This was due to such alloy parameters as:
- light weight;
- cheapness.
Since aluminum weighs much less than copper, it is used more when laying power lines, which allows to reduce the load on the supports, and accordingly save on their manufacture and installation. According to the PUE, when installing a new network, aluminum cables with a cross section of less than 16 mm 2 are not used. Do not discount the cheapness, as copper is more expensive.
Minuses
However, even a high-quality aluminum wire has more disadvantages than advantages. The negative aspects include:
- lower electrical conductivity than copper (2 times difference);
- the ability to oxidize on contact with air (as a result of oxidation, a layer is formed on the surface of the wire that does not conduct electricity, which reduces the useful section and increases the resistance);
- shorter service life (20-25 years, after which the likelihood of fire increases sharply due to oxidation and subsequent heating of the contacts);
- weak mechanical strength (after several bends, the aluminum cable breaks easily);
- the complexity of installation (in this case, you will have to provide the necessary conductivity by choosing cables of a larger cross-section, with which it is extremely inconvenient to work. Such cables are produced only single-core).
Advice! You can check the quality of aluminum for a break, for this, when buying in a store, try to bend the wire 4-6 times, if its surface quickly becomes covered with cracks, then the wire is fragile and it will be difficult to work with it. It is clear that it is better to refuse such a product.
Copper wiring
When buying or building a house or apartment, it is advisable to use this type of wiring. However, keep in mind that by replacing the wiring in the apartment, you have not yet received a reliable network capable of withstanding heavy loads. Do not forget that the lead-in cable from the staircase to the apartment in old apartments is always made of aluminum. This section should be replaced, because its conductivity is now weakness new network.
Advantages of copper wiring
Comparison of the parameters presented below with the parameters of aluminum will make it possible to make right choice further. Copper, as a material for electrical wiring, has a number of advantages, which include:
- good conductivity (even after oxidation, the film on the surface does not interfere with the passage of electric current);
- service life reaches 50 years;
- high mechanical strength (the core can easily withstand bending and twisting up to 10-15 times);
- ease of installation (the industry produces several types of wires with different parameters and cores that are convenient to work with).
There is probably only one downside to a copper home network - this is its price, however, when you need to perform high-quality wiring, give preference to this material.
Copper-plated zinc alloy wires are available at hardware stores. They are cheaper than copper wires, however, the characteristics of the materials are inferior to pure copper wires.
If there is a lack of funds, it is better to perform combined wiring, power the outlet group separately with copper wires designed for high amperage, and the lighting circuits with aluminum ones. However, keep in mind that the connection between aluminum and copper is made only through special clamps or connector pads that prevent direct contact between copper and aluminum, causing strong oxidation of the latter. Due to the oxidation of the joint, resistivity contact, heating and burning occurs as a result.
Having considered the characteristics, it is easy to come to the conclusion that it is better to perform installation works use copper, however, if necessary, you can also make a network of aluminum, but you will have to monitor it more carefully. It is necessary to choose this or that type of wiring taking into account the requirements of electrical safety, because it depends on how long the network will last without the need for specialist intervention.
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The cable and wire nomenclature is traditionally divided into two categories based on the core composition criterion. We are talking about copper and aluminum cables and wires. What is the difference between them, what are the pros and cons of using both wires? We will try to find the answer to this question in this article.
Myths and truths about copper cables and wires
If you ask a specialist for advice on the choice of wires, the likelihood of getting a recommendation for the purchase of copper products is quite high. So why copper wires so popular, and are they really better than aluminum? Let's look at the veracity of the case for copper wires.
- Reason # 1: Copper cable is more durable.
Is it true? This does not correspond to reality. If you open any of the cable directories, you will read real data there: the service life of copper cables is identical to the service life of aluminum ones, namely - 15 years if the cable has single insulation, and 30 years if you use double insulation.
- Reason # 2: Copper cables are more bend resistant.
Is it true? Yes, it really is. According to GOST, a copper cable can withstand up to 80 bends, while an aluminum cable will survive only 12. But it should be borne in mind that when choosing a cable for laying into a wall, this does not play any role.
- Reason # 3: Copper is oxidized several times slower than aluminum.
Is it true? Let's take a look at aluminum. On top of its newly cleaned layer, an oxide layer that degrades the contact immediately appears. However, this process and quickly ends only on the surface. That is, in fact, aluminum does not lose its current-carrying capacity for many years, like copper. In addition, if you use terminal blocks with a special conductive paste, which strips off the oxide layer, creating a hermetic protection from air and water, then this will be a more reliable solution than high-quality copper twisting.
Advantages and disadvantages of aluminum cable
Aluminum is considered the most common metal that people use in almost all walks of life. Its weight is relatively small, there is a margin of safety, but at the same time, this metal is quite soft. If we compare copper and aluminum wires, with the same electrical conductivity parameters, the weight of an aluminum cable will be half that of a copper one. This makes it possible, for example, to make thicker aluminum wires.
As mentioned earlier, one of the significant disadvantages of aluminum is its low bendability. If you bend an aluminum wire a couple of times in the same place, it will simply break. For this reason, aluminum wires can only be used in stationary gaskets, where there is no sharp corners breakage.
Another disadvantage - instant oxidation - has already been mentioned above. The oxide film significantly impairs the chemical activity of the metal, because the oxide is a complete dielectric. Wherever this film is formed, the electric current almost does not pass. But, as you remember, conductive paste allows you to bypass this disadvantage.
It is also necessary to take into account the size of the core. The electrical conductivity increases with the size of the core. With a large current strength and a small cross-section, the resistance will increase. This will heat up the cable. Considering that aluminum has 1.5 times more resistance than copper, it is easy to guess about another drawback of aluminum. To conduct the same amount of current as with a copper conductor, you will have to use an aluminum one several times larger in size. In addition, aluminum cables heat up quite quickly, since the thermal conductivity of this metal is high.
However, the main advantage of aluminum cables and wires is their cost, which can sometimes be three times lower than the price of copper products with similar electrical conductivity.
Which cable to choose: copper or aluminum
When making a decision, you should be guided primarily by your needs and budget. As a bottom line, we can summarize when which cable is better:
- Aluminum cable. Low price, relatively low weight, breaks down upon repeated bending, conducts current better in combination with a special paste.
- Copper cable. High electrical conductivity, low resistance (the ability to use a smaller section), excellent strength, but at the same time high price.
Helpful advice
When connecting copper to aluminum cable, always use the terminal block as an intermediary to avoid metal contact. The need is due to the fact that in the places of their contact, the resistance will increase over time, heat up, which can lead to the destruction of the cable, short circuits and even fires. This knowledge should be guided when connecting any materials. different kinds with different resistance.
