Application of aluminum and its alloys in the electrical industry

Aluminum conducts current and is one of the best conductors in existence. It is used to make conductive busbars, cable lugs and sleeves, cable for overhead power lines, self-supporting insulated wire (self-supporting insulated wire) and wires of smaller cross-section (for domestic or industrial needs), coaxial television cable.

Types of aluminum electrical cable Source ru.prom.st

Other properties

Today, aluminum is produced almost twice as much as copper. And in comparison with all mined metals, it is second only to steel. This confirms that every year the electrical industry is increasing its use. This is explained by a number of reasons, which we will consider further.

Electrical performance of aluminum

According to the International Annealed Copper Standard (IACS), the latter is rated as 100% conductive. According to the above information, aluminum conducts electricity at only 61% equivalent to the generally accepted standard.

Thus, an equal percentage will only be achieved with larger cross sections. Since copper is significantly heavier than aluminum, such an “increased” conductor in mass will still be lighter than copper.

Comparative density of aluminum and copper Source aluminum-guide.com

This fact has been proven through complex mathematical calculations, the result of which shows that 1 kg. aluminum provides equal conduction speed to that of 2 kg. copper Therefore, if certain technical conditions for the size of conductors do not require this, copper is replaced with aluminum.

Healthy! If for use in home wiring the weight of an electric wire does not have a special role, then when used on overhead power lines (overhead power lines), the weight of the current-carrying conductors has a significant effect. Therefore, take the one that is lighter, that is, aluminum.

Strength index

Provided the cross-section is the same, copper conductors are stronger than aluminum conductors. Although, this figure can be easily increased by alloying or thermomechanical treatment, or by increasing the cross-section.

The table shows that aluminum is 2 times weaker in tensile strength Source aluminum-guide.com

The values ​​​​given in the table show that aluminum conducts current, but is inferior to copper in terms of “break strength”. However, it is able to withstand its own weight and does not overload the overhead power line supports as much as copper.

In addition, extruding aluminum involves obtaining cross-sections of complex shapes, which cannot be obtained from steel. Based on such objective reasons, new elements can be designed in such a way that they will be the most effective in comparison with acceptable analogues from other materials.

Resistivity of pure metals at low temperatures

Vibrational processes in the molecular lattice prevent the free movement of electrons. This explains the increase in resistance as temperature increases. A linear dependence is observed from a slight positive temperature, up to the melting point. The corresponding phase transition is accompanied by a sharp increase in electrical resistance. Of course, such a regime after destruction is not working.

Theoretical indicators “a” are confirmed by the results of experiment “b”. If the structure of a pure metal is distorted by impurities (impurities, alloy components), a random distribution of electric charge carriers will occur. This, in turn, will increase the circuit losses (resistance).

Advantages and disadvantages of aluminum wiring

The widespread use of aluminum wiring was practiced in old buildings. The main criterion in those days was easy availability and low cost of metal. The possibility of a lack of cable cross-section was not considered in those days due to the lack of electrical household appliances in the apartments of average citizens.

Types of SIP cable for connecting a cottage Source yandex.net

Positive factors

The low weight of aluminum wire makes it popular when installing high-voltage power lines. This condition has already been stated earlier, so let’s consider a number of other aspects:

• Relatively low price of metal and products made from it. This factor plays a role when laying long lines. For example, to fully electrify a country house, more than 1,000 m of wire may be needed.
• Resistance to chemical oxidation. This condition is relevant given that the cores are hidden by plastic insulation.
• Durability of areas without insulation. As mentioned earlier, a protective film is formed on the surface of aluminum, which prevents the occurrence of oxidative processes.

High-voltage line with a voltage of 35 kV Source cdn.pixabay.com

Conductor resistivity table

In some situations, expenses are not considered. Military and space technology is created using conductors made of precious metals. Such solutions help reduce cross-section and weight, increase resistance to radiation and other special effects.

For the manufacture of serial products for household and industrial purposes, more affordable materials are used.

Data for calculating the electrical parameters of conductors taking into account temperature changes

The use of stainless steel wire helps to increase strength while optimizing cost. To improve anti-corrosion properties, special additives are used. They increase the resistance of a steel conductor by almost 10 times compared to its copper counterpart.

In any case, the specific conditions during use, as well as the purpose of the products, are of particular importance. Nickel, for example, exhibits ferromagnetic properties at extremely low temperatures below the threshold “Curie point” (-358 0°C). Silicon, which is used to make microcircuits and transistors, has special semiconductor parameters.

Copper and aluminum

The need to replace a section of electrical wiring may arise under various circumstances (damage, installation of an additional branch, other reasons). In this situation, “copper to copper” or “copper to aluminum” is connected. Contacts made of different metals require special attention, and the reason lies in the following:

• They differ in different resistivities. Even a tightly screwed contact will weaken over time due to aluminum's tendency to thermal expansion.
• Copper also has an oxide protective film. However, it differs from aluminum in different resistances, as a result of which this is reflected in an increase in the contact temperature.

Safe contact of copper and aluminum Source mosoblzhilservis.rf

Important! Connections under load can become a source of sparks, which negatively affects the conductor capacity and can cause a fire.

Methods for connecting aluminum and copper wires Source uk-parkovaya.ru
Connecting copper and aluminum wires is acceptable. However, to do this you must adhere to the following methods:

• Pre-tin the copper with a soldering iron and solder.
• Treat the contact with a special anti-oxidation lubricant.
• Use special metal devices (adapters): “Nut”; Made of 3 parallel plates, in which a current-carrying core is laid between the outer ones; Self-clamping or screw terminal blocks; Crimping; Bolted connection; Spring terminals.

Connection of SIP and aluminum cable Source www.volt-m.ru

Metal resistance table

To be convinced of the benefits of copper, it is necessary to make an appropriate comparative analysis. Below are the metal resistance values ​​in the summary table.

Basic electrical parameters of conductors made from different materials

Important! The low resistance of an iron conductor is not enough for the widespread use of corresponding products in practice. Active oxidation provokes rapid destruction.

Resistance calculation

To correct temperature changes, the last column of the second table shows separate multipliers for each position. The calculation is performed using the formula RT = Rn * (1+PC*T), where the given symbols mean:

• RT – electrical resistance in Ohms at a certain temperature;
• Rn – conductor resistance at zero temperature;
• PC – correction factor;
• T – operating temperature in degrees Celsius.

Application

Aluminum is used in metallurgy as a base for alloys (duralumin, silumin) and an alloying element (alloys based on copper, iron, magnesium, nickel). Aluminum alloys are used in everyday life, in architecture and construction, in shipbuilding and automotive industry, as well as in space and aviation technology. Aluminum is used in the production of explosives. Anodized aluminum (coated with colored films of aluminum oxide) is used to make jewelry. Metal is also used in electrical engineering.

Concept of electrical resistance

This term refers to the property of creating obstacles to the passage of electric current in a circuit. The relationship between physical quantities is described by the classical formula R=U/I (symbols for resistance, voltage and current, respectively). The movement of electrons occurs under the influence of an electromagnetic field, a potential difference. Any distortion of the crystalline structure of the molecular lattice increases the resistance of metals. This reason explains the strong dependence of the parameter on the purity of the material and temperature. Thus, standards for pipe products allow the use of various alloys. Electrical copper (grade M006) is created with a controlled amount of foreign impurities of no more than 0.1%.

The qualified use of this material is preceded by an assessment of all significant factors. In addition to the cost, they clarify:

• features of mechanical and other types of processing;
• stability of electrical parameters under certain operating conditions;
• resistance to external influences, durability.

In some situations, the significant initial investment is justified by extended service life and reliability.

Comments:

Stanislav

Unfortunately, even now developers do not hesitate to use aluminum cables. I saw in one new building an incoming aluminum cable from the meter to the consumer. At the same time, the construction company showed documents that, according to the rules, this is allowed...

Yurievich

Stanislav, the fact of the matter is that, according to pre-revolutionary rules, in some cases this is actually allowed, but people who invest money in these apartments even before construction expect that at least in this they will not be deceived, but aluminum is input is a very common practice.

Michael

And for me, one master connected aluminum with copper in a junction box with twists. The apartment almost burned down. And most importantly, at first everything works as it should, and only six months later it begins to spark, hiss and melt...

Oleg

In low-voltage and low-current networks, wiring made of copper, oxygen-free copper, silver or gold makes sense. And your networks have 220 V. Don’t fool around and don’t litter our people’s heads with garbage. They are already very weak. 16 sq. section - you have to be a complete fool to invent this nonsense. In power shields, the risers are laid thinner. Factories have produced and will continue to produce aluminum wires, regardless of your stupid articles.

Anton

Regarding the fragility of aluminum wire: I hung a chandelier in an old house built by captured Germans in the first years after the war - the soft aluminum wires bent so easily that it seemed as if under their own weight. This is the aluminum wire of the post-war years. And now in wires and cables it’s not aluminum, but duralumin; if you bend it, it even cracks, sometimes cracking at the bend.

irakli

moemu domu 46 let i aluminumevaia provodka rabotaet dosixpor bez problem 2.5mm a ne 16

Sergey

And my apartment burned down from overheated oxidized aluminum contacts. House 74 years old, Moscow. Luckily no one was hurt. Now only copper and arc-flash circuit breakers.

Sergey

Poor boy! Did he read this nonsense or memorize it?

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