Design and Analysis of a New Hybrid Excitation Vernier Motor with Reduced Permanent Magnet

This article presents the investigation of a new permanent magnet (PM) reduced hybrid excitation wound field vernier motor with Halbach PM array. The flux interaction between tangentially magnetized PMs and the field winding is analyzed. It is found that the flux contribution from the field winding is enhanced due to the reduced magnetic saturation in the rotor poles. Meanwhile, the air gap flux density from the PMs is improved because of the existence of magnetomotive force (MMF) from the field winding. Under load condition, the interaction between PMs and q axis armature current further enhances the PM flux in the air gap. As a result, the torque performance is significantly upgraded. Then, a small amount of radially magnetized PM is added in the rotor pole to form the Halbach PM array and additionally increases the flux concentration effect. The proposed design is compared with a conventional surface Halbach PM array vernier motor in torque density, torque ripple, PM utilization and no load back EMF. The result shows that the proposed topology exhibits 4% higher torque density, lower torque ripple, 75% higher PM utilization and 35% reduced no load back EMF. Finally, a prototype is manufactured to confirm the validity of the proposed idea.