They have contributed significantly to the reduction of the weight-to-power ratio of electric motors, the development of enamelled conductors, also of synthetic insulation papers or films, magnetic sheets, aluminum alloys and plastic materials. Observing the weight of a motor of the same power over time, we can see that the current engine has only 8% of the weight of its predecessor in 1891. When we confront the data of catalogs of different manufacturers, at different times, we can verify that there was a reduction in weight and, consequently, reduction of the constructive size of the motor of approximately 20% every decade, except the last two decades where the reduction was less pronounced.

This fact shows the need for periodic revision of the standards, in order 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 almost all industrial, commercial and residential facilities. Examples are the tiny motors that drive the hard drives of computers, the large number of motors that power our appliances, and the giant motors that drive pumps, compressors, fans, mills, and other myriad applications.