Proposing an External Rotor In-Hub PM Assisted Synchronous Reluctance Motor for an E-Bike

In recent years, permanent magnet (PM) motors have commercialized light electric vehicles. Due to the high cost of rare-earth PMs and environmental side effects, the structures without or with the low number of PMs that maintain the application constraints can be a good choice. The synchronous reluctance motors (SynRM) can be a proper candidate for this application. Choosing a good value for the number of flux barriers and their end position can reduce the torque ripple. To, assist the synchronous reluctance motor in improving its capabilities, especially torque density and power factor, low number of PMs can be inset in the flux barriers. This paper proposes designing and optimizing an external rotor permanent magnet in-wheel PM-assisted SynRM (PMaSynRM) for an electric bicycle application. The rotor two-barriers and three-barriers structures with different PMs, i.e., rare-earth and Ferrite and without PM (SynRM) are comprehensively investigated by finite element analysis (FEA) in both skewed and non-skewed stator in terms of average torque and torque ripple. Finally, the design concepts are validated with a prototype machine.