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Aluminium as a conductor - the benefits increase as copper prices soar

With the price of copper widely predicted to break through the $10,000(US) per tonne mark, Legrand has underlined the benefits of its aluminium Zucchini busbars and cast resin transformers.

Legrand offers a wide selection of aluminium busbars and cast resin transformers. Its Zucchini MR aluminium busbar range is available in all sizes from 160 to 1,000A, while its SCP busbar range is offered in all sizes up to 5,000A. Both systems feature a large selection of tap-off boxes that allow the supply and protection of a wide range of loads using different devices such as fuses, MCBs and MCCBs. The company also manufactures both products with copper conductors should the project and conditions define that copper must be the material of choice.

Steve Marr, marketing manager for the company’s power distribution division, said: “Traditionally, aluminium had been regarded as the poor relation to copper as an electrical conductor, but recent advances have meant that it is now an exceptionally high performance product that compares very favourably with copper in terms of mechanical strength, heat stability and thermal conductivity characteristics.

“Add to the mix the soaring price of copper, which is fast making it prohibitively expensive, and we feel certain aluminium will soon be the electrical conductor of choice here in the UK.”

In contrast, Legrand’s range of cast resin transformers is manufactured solely with aluminium conductors due to the fact the benefits of aluminium far outweigh copper in these systems. The Zucchini EdM range answers every high power, medium voltage market need, providing as it does rated power to 17,000kVA, primary voltage to 36kV and secondary voltage if required,

Key benefits of aluminium for use in busbar systems:
• Cost: On the world’s commodity market, aluminium tends to have a more stable value and, unlike copper, is not so sensitive to the ‘ebb and flow’ of consumer demand, political uncertainties and other economic factors. As a result, aluminium has consistently provided huge cost savings for specifiers and contractors.
• Weight: Aluminium is up to 70 per cent lighter than copper. This not only saves money on transportation, but also on the time, effort, and therefore cost, of installation.
• Conductivity: In general the conductivity of copper is significantly better than aluminium (aluminium’s conductivity is 62 per cent that of copper). However, the weight of copper is three times that of aluminium, which - as previously stated - has a significant impact on the cost of installation and transportation. When you compare an aluminium system against a copper-based system of equal size and weight, aluminium scores twice as conductive as copper.
• Jointing: In the past, specifiers have been critical of the fact that aluminium is susceptible to oxidisation, which affects the contact conductivity at the joint. Manufacturers of busbar systems have overcome this factor by completely electro-tin plating the conductor bars, which eliminates any problems associated with jointing dissimilar metals.
• Safety: Unlike ferrous metals, aluminium does not generate sparks when used in combination with other metals, making it the ideal choice for use in potentially inflammable or explosive environments.
• Non-magnetic: As aluminium is nonmagnetic it is ideal for use in applications that need minimum magnetic interference. These include high-voltage applications as well as electronics.
• Mechanical strength: Aluminium alloys have a mechanical resistance of 60 to 530 Newton/mm². This is more than sufficient.

Key benefits of using aluminium instead of copper windings for cast resin transformers:
• The coefficient of thermal expansion of aluminium is more similar to the coefficient of the resin than coppers. When the transformer is loaded the ideal compatibility between the expansion coefficient of aluminium and of the resin used for casting prevents the creation of cracks in the cast resin coils.
• Since aluminium windings work at a lower current density than copper windings this characteristic enables them to have a better short term overload capacity.
• Aluminium wound cast resin transformers are lighter in weight than the copper wound ones due to the difference in the specific weight of the two materials.
• Aluminium wound transformers compared with equivalent copper wound ones guarantee the same efficiency.

(Nguồn: Legrand Electric, published 02/04/2011)