There are probably some other parts made up of glass, plastics and other materials but getting into that level of detail is probably impossible given that there isn't exactly a thorough exploration of Transformers biology, except maybe this: Transformer Biology, which only mentions that Transformers are made up of mechanical cells, but not what materials these cells consist of. read more
Other than active materials, for example, copper and grain oriented silicon steel, a large number of ferrous, non-ferrous and insulating materials are used in power transformers. Optimum utilization of these materials according to their electrical, mechanical, physical, chemical and thermal characteristics is important for using an appropriate insulating material. read more
The conducting material used for the winding depends upon the application. Small power transformers are wound with solid copper wire, insulated usually with enamel. Larger power transformers may be wound with wire, copper, or aluminum rectangular conductors. read more