 The properties needed for motor windings are similar to those needed for transformers, but with the additional requirement to withstand mechanical vibration and centrifugal forces at operating temperatures.Transformer windings are normally made from copper but aluminium is a suitable competitor where weight and first cost are decisive factors.In North America, aluminium is the predominant choice of winding material for low-voltage, dry-type transformers larger than 15 kilovolt-amperes (kVA).