Survey of rare earth permanent magnet applications

Trends in permanent magnet usage are reviewed with emphasis on the emerging role of high energy density rare earth cobalt magnets. Permanent magnet excited devices and machines are compared to electomagnetic devices in terms of volumetric efficiency, relative cost and important functional features. Examples of using high energy permanent magnets in transportation systems and motion control systems are described. An important conclusion of this paper is that rare earth cobalt magnets are more than a replacement for electomagnetism. The properties allow electrical machines and devices not possible or feasible with electomagnetism.