Design And Optimization Of High-Torque-Density Vernier Permanent-Magnet Machine

With the increasing concern of energy saving,emission reduction,space usage reduction and the reliability improvement of transmission structure,the direct-drive motor of low speed and high-torque density has become a focus of research.Among them,the Vernier permanent-magnet(VPM)machine can achieve a large output torque using the magnetic-gearing effect.With its low-speed high-torque characteristics,the VPM machine is a good candidate for ship propulsion,wind power generation,electric vehicles and other applications.In this thesis,the following research is carried out on VPM machines:1.The state of the art of VPM machines is presented.The torque density,advantages and disadvantages of different VPM machines are analyzed.2.A VPM machine with spoke-array permanent-magnet is proposed.The working principle,torque and power factor are analyzed.3.The finite-element electromagnetic model,analytical thermal model and finite-element thermal model of the motor are established and verified.The coupled thermal-electromagnetic optimization model is carried out with the objective to maximize the output torque in a given volume.The dimensional parameters,slot-pole combinations and maximum output torque of the motor are obtained for a given outer diameter.Then the optimized structure results are analyzed and sizing rules are derived.With the limitations of a given outer radius of 70 mm,maximum winding temperature of 120 ? and maximum permanent-magnet temperature of 100 ?,the torque density of VPM machine can reach 60 Nm/L,which is higher than the conventional permanent-magnet synchronous machines with the same outer radius.4.According to the optimization results,the end effect and thermal model of the motor are analyzed jointly,and the electromagnetic structure is adjusted.The mechanical structure design and the design of the motor are completed.