A description of the application
Transformers and electric motors use either copper or aluminium windings.
Windings consist of wires coiled typically around a core, forming magnetic fields, which interact with current.
In this context, the efforts and consequent environmental aspects related to losses in conductors and losses in magnetic fields depend on the selection of material (type and weight) and the geometry and compactness achieved.
The challenges that appear regarding this application
In the case of transformers, it is frequent to use aluminium windings, although these may have bigger dimensions (for example, transformers for grid and net distribution stations, which can have up to several tons of weight). The aluminium could be regarded as the cheaper option when compared to copper. But aluminium wires must have higher diameters than copper wires to achieve the same resistance. As a consequence, a larger magnet core has to be used when using this type of wiring, increasing the need of ferrous materials to manufacture this type of product. Thus, there is additional material demand.
Whilst transformers are static, electric motors are dynamic (rotation). In this case, the selection of materials becomes even more relevant, as besides the direct influence it has in the manufacturing phase (amount and type of materials used), there are also effects in the use phase, if the losses are taken identical due to larger (aluminium) or lower (copper) cross section. The weight increases energy demand for rotation, but geometry and compactness influence the energy demanded for the rotation due to the moment of inertia, which reduces energy demand by a factor to the square of the radius of a rotating shape.
When selecting the environmental preferred solution, it is important to consider all these different, partly contrarily influencing aspects in terms of amount of material used (kg), energy demanded (kWh) and energy losses avoided (kWh).
How copper serves as a key factor to overcome this hurdle
The use of copper in windings for transformers might increase the demand of conductor material compared to aluminium (kg) due to the higher density of copper, although it needs wires with lower cross section than aluminium to ensure comparable resistivity. But copper saves electrical steel for the magnetic core. The electrical steel is typically a silicon alloyed grain oriented steel and can have up to twice as much environmental impact than mechanical steel per same weight due to its intensive treatment during rolling to orientate the silicon grains. Therefore both material demands and their environmental impacts need to be considered copper and grain oriented steel compared to aluminium and grain oriented steel.
In the case of electric motors, the use of copper enables also a more compact product. This reduces now also losses in the use phase caused from moment of inertia, since the effect of compactness typically supersedes the effect of the higher material weight of copper by its higher density compared to aluminium. This is the reason why, the use of aluminium in electric motors is rather seldom.
In this case, the use of copper is a key factor, allowing increasing the compactness, lowering the moment of inertia and consequentially decreasing the energy demand during use of a motor, which compensates the additional environmental impact of manufacture.
The key message as a conclusion
The use of copper windings in the transformers and electric motor applications is beneficial, allowing saving materials in the manufacturing phase and, in the case of electric motors, saving energy in the use phase.