The flux controllable permanent magnet brushless machines: Concepts, developments and applications

Permanent magnet brushless (PMBL) machines have become more widely used for a variety of industrial application, since they inherently offers high efficiency, high power density, and maintenance free. However, as is well known, flux control capability of PMBL machines is much more difficult to achieve than that in electric machines with DC excitation. Recently, there is an increasing tendency to study a new type of flux-controllable PMBL machines, which combine the advantage of PMBL machines with the possibility of controllable magnetic flux by auxiliary windings. The purpose of this paper is to give an overview of the flux-controllable PMBL machines on concepts, developments, and applications. Thus, the state-of the art technology of the flux-controllable PMBL machines, including their machine topologies, operation principles, characteristics, control strategies and emerging researching directions, will be reviewed and discussed.