Alternating flux barrier design of vernier ferrite magnet machine having high torque density

This paper proposes a new topology for a single air gap spoke type vernier permanent magnet (SVPM) machine, that uses only ferrite permanent magnets (PMs), where alternating flux barriers are placed at the bottom of pair-wise magnets on the rotor. Overall, the alternating flux barrier topology reduces the manufacturing complexity, mechanical structural challenges and thermal issues, which are predominant problems for existing high torque density spoke type vernier machine solutions having a dual stator topology. In this paper, design innovations, obtained through analytical analysis and detailed discussion, are verified using finite element analysis (FEA). These results show that the improved SVPM design not only improves the torque density compared to that of the conventional SVPM by 57% but also effectively reduce the torque ripple down to 7.6%, the torque production even surpasses that of a benchmark rare earth interior permanent magnet (IPM) machine under same size and stator current density. The comparison draws the conclusion that the new ferrite single air gap SVPM topology shows considerable promise in low and medium speed applications both as a motor or generator.