The paper presents a perspective on the various types of motors which are currently in use or proposed for application in variable speed drives. One focus is on motors for industrial and commercial use, reflecting the large and expanding market arising from concerns about energy saving and system optimization. A second focus is on high-performance motors capable of rapid response in speed and position control systems. The machine types considered include commutator, induction, synchronous and switched permanent magnet, and synchronous and switched reluctance. Each machine type is introduced from first principles to establish a basis for comparison and also as an aid to readers who have not recently refreshed their knowledge of electric machines. >