Transformers in power distribution networks

In electrical engineering terminology, transformers are regarded as electrical machines, although they only convert one form of electricity into another form of electricity. Due to this relatively simple function, among other reasons, their losses are lower than those of any equipment converting electricity into some other form of energy. They are probably the most efficient machines ever devised by man. Transformer efficiencies are around 80% for very small units used in domestic appliances and nearly 99% at the level of distribution networks. The efficiency further increases with increasing unit power rating. The largest units achieve efficiencies of up to 99.75% at rated load and even 99.8% at half load. At first glance, it looks rather unlikely that there is any savings potential left that would be commercially significant, but in fact there is. It is true that the payback periods are fairly long, but a transformer has a lifetime expectancy of well over 40 years and the majority of all transformers are operated continuously at a high degree of loading. As a result, an improved transformer design, primarily through the use of more active material, will usually pay off several times over the lifespan of the transformer.