Effect of optimal torque control on rotor loss of fault tolerant permanent magnet brushless machines

Summary form only given. Fault tolerant permanent magnet brushless machine designs differ significantly from conventional brushless machines, of the type which are generally used for applications such as machine tool spindle drives, for example, in that only alternate stator teeth carry a concentrated wound coil. This results in the fundamental stator MMF having fewer poles than the permanent magnet rotor, and the torque being developed by the interaction of a higher-order stator MMF harmonic with the field of the permanent magnets. The fundamental and lower order MMF space harmonics can then give rise to significant rotor eddy currents.