An increase in power of the electric motors is due to the development of enamelled conductors, papers or synthetic insulation films, magnetic plates, aluminum alloys and plastic materials have notably contributed to the reduction of the weight ratio by the power of these machines. https://www.mrosupply.com/sprockets/finished-bore/262280_41bs36-58_martin-sprocket/ Observing the weight of an electric motor of the same power over time, we can see that the current engine is only 8% of its predecessor’s weight in 1891.
Examples are the tiny motors that drive computer hard drives, the wide variety of motors that power appliances, and the giant motors that drive pumps, compressors, fans, mills, extruders and many other applications. Comparing the data of catalogs of different manufacturers from different times, we can verify that there was a reduction of weight and, consequently, reduction of the constructive size of the engine for the same power, of approximately 20% every 10 years, except the last two, in which the reduction was less pronounced.
It is clear that there is a need for periodic revision of the standards to adapt the relationship between powers and carcasses to the sizes achieved through technological development. This technological evolution is mainly differentiated by the development of new insulation materials that support higher temperatures. Today electric motors are present in virtually every industrial, commercial and residential facility.