2. Electromechanical conversion concepts and techniques

2.1 Classification elements

Since the invention of the first electric motors in the nineteenth century, virtually every possible combination of the three essential components (copper, air, iron) of an electric motor or actuator has been considered for electromechanical conversion. What's more, unlike medium- or high-power motors, which have relatively stabilized and identified designs, the field of small electric motors has given rise to a great deal of proliferation and conceptual diversity; only economic or feasibility constraints limit the imagination of designers. In electromagnetic systems, the generation of force is generally the result of a coupling between two fields attached, respectively, to two bodies in motion relative to each other.

However, an...