High torque density ferrite permanent magnet vernier motor analysis and design with demagnetization consideration

This paper proposes a low speed dual stator spoke type vernier permanent magnet motor (DSSVPM) using ferrite permanent magnets (PMs). The replacement of conventional rare earth PMs reduces the cost of machine manufacturing. The design of DSSVPM uses an analytical optimization model to achieve the maximum electrical and magnetic loading whilst the ferrite PMs can still withstand the presence of fault current. The analytical model was verified using finite element analysis (FEA). The FEA results are then compared to an existing Interior Permanent Magnet (IPM) machine. The FEA results indicate the DSSVPM does not only achieve higher torque production but also higher power factor and efficiency than the existing IPM machine. After the occurrence of an electrical fault, the results show that the DSSVPM delivers higher torque production than that of the existing IPM machine, despite the minor demagnetization that appeared at the corner of each ferrite PM. The comparison concludes that the proposed ferrite DSSVPM shows considerable performance in low speed machinery applications.