What wire is better: aluminum or copper?
In living conditions aluminum, copper and алюмомедь are most often used. With first two all it is clear, but here that it алюмомедь? It is not alloy as it is possible to think at first as heavy and light metals connect extremely badly, and the composite material consisting of the aluminum core and covered from above with the copper layer. Why to connect these two materials, will become clear after consideration of their properties.
Aluminum - the fine material, light, cheap, possesses quite
decent conductivity, well gives heat, it is chemically resistant.
However is a little "but", significantly worsening reputation of this metal.
- Aluminum wire soft, but not flexible. Remember how the wire from this material well breaks if to bend it several times. The conclusion simple - such wires use only in stationary installations and where there are no acute angles of turn of the cable when laying.
- Aluminum quickly is oxidized on air. Aluminum oxide - the high-melting film of dark color which is formed on the surface of metal and is dielectric. In places of contact can seriously interfere with the current of electric current. From here both excessive overheating, and risk to lose contact in junctions.
- Aluminum - the great conductor, but only if does not contain impurity what to achieve very difficult. In comparison with copper, this metal has conductivity, smaller by one and a half times.
Copper, along with numerous pluses, has not smaller quantity of minuses.
Advantages: the conductivity is higher, than at aluminum, flexibility, does not form the oxidic film. Vein thickness depends on flexibility. For example, aluminum conductors cannot be thinner than 2,5 mm2, and it is possible to make veins 0,3 mm2 thick of copper.
Shortcomings: high cost, high density, and consequently, and weight, impossibility of direct connection with aluminum veins. At contact these two metals form galvanic couple, and the arising currents destroy contact. For this reason in need of contact use special plugs of connection.
Alyumomed — the mechanical composite consisting of the aluminum core and the copper shirt which occupies 10% of vein volume. Combines merits of aluminum and copper.
Minuses: on all indicators concedes to conductors from separate metals. Plus - low cost.
Wires and cables are issued with the section of the vein from 0,3 to 800 mm2. In life such extreme values are not used. Extreme indicators for the house are conductors with the section of veins from 0,35 to 16 mm2, is rare - 25 mm2. First of all thickness of the vein depends on tension and current intensity. Dependence here simple: the more section, the is higher the carried-out loading.
Calculation of necessary section, depending on loading, is made on difficult formulas therefore all data on this question are shown in tab. 1. More detailed data on dependence of loading on the section of copper conductors are provided to tab. 2.