Topology comparison of ferrite magnet synchronous machines with consideration of low inertia

In order to replace rare-earth magnets five different machine topologies are considered, designed and studied in detail. With a synchronous reluctance machine (SRM) a machine without magnets is included in this comparison. The improvement by the insertion of cheap ferrite magnets in a SRM is studied by designing two different types of a permanent magnet assisted synchronous reluctance machine (PMASRM). With this approach torque density and power factor can be significantly increased. As an alternative a spoke-type PMSM with ferrite magnets and a Vernier machine containing a Halbach ferrite cylinder are designed and studied. Despite all optimizations and improvements in design, electrical machines without rare earth magnets lead to greater weight and ultimately to a greater moment of inertia. Therefore the reduction of the moment of inertia is also considered in this comparison.