Motor Notes : Evolution and Kinds of Motors

Nikola Tesla is said to have invented the alternating current (AC) motor in 1888. Since that time, motors have evolved tremendously, owing to various innovations in elemental technologies–constituent materials (magnets, steel plates, and so on), materials for semiconductor devices, component technologies, and control techniques, among others. For example, an induction motor with a five horsepower output developed early in 1900 had advanced to the point where, in early 2000, it was reduced to about 1/5 of the size and weight.^{(note 1)}

The global annual volume of motor production is currently about 10 billion units, and the power consumed by these motors accounts for roughly 50% of the world’s electric power use. General and basic demands made of motors are “compactness and light weight”, “high efficiency”, “low noise”, and “minimal vibrations”. In addition to these requirements, work is continuing to develop motors with characteristics that are optimal for uses in various markets (information, home appliances, house equipment, industrial applications, automobiles, etc.). Hereafter applications will further expand through improvements in the characteristics of motors themselves and combined advances in driving and control circuits, and motor demand will continue to trend upward. In particular, propelled by energy conservation regulations for home appliances and industrial equipment as well as by environmental regulations for the automotive markets primarily in North America and Europe, in the automobile industry there will be development of HVs, EVs, PHVs, FCVs, 48-volt mild hybrid vehicles, etc., with more entries into the market and further increases in the number of motors used.

Thus demand for motors will continue. Motor types are traditionally categorized according to the driving power supply (AC or DC). However, recently there has been a trend toward mechatronic integration of the driving circuit and the motor in the same case, and so a simple division of motors into AC and DC according to the power supply is no longer appropriate for these circumstances. When considering diversification of motors, it is thought classifications such as the following may be used, which take into consideration selection of a motor according to the purpose, with motor types based on ① the type of power supply, ② the principle of torque generation, ③ the motor construction, and ④ applications and characteristics.

Note 1: From the December 2010 edition of Hitachi Review