Analysis And Optimization Design Of Flux Switching Permanent Magnet Machine For Electric Vehicles

The flux switching permanent magnet (FSPM) machine is a new type of doublysalient permanent magnet machine. It has switched reluctance machine (SRM) advantagesincluding simple structure and high mechanical strength. It also has the characteristics ofhigh power density like permanent magnet machine. As the waveform of backelectromotive force (EMF) is sine wave, FSPM machine is suitable for a variety ofalternating current field. It can overcome the vibration and large noise which are caused byswitching current frequently in SRM. Both windings and permanent magnets are installedon the stator, to avoid the influence of centrifugal force to permanent magnets and theproblem of PMs demagnetization which caused by heat dissipation difficulties. Because ofthe good performance of FSPM machine, it is a good selection for driving EVs which isvery suitable to be in-wheel machine. Therefore, FSPM machine is a popular researchdirection in recent years. To improve the acceleration and comfort performance of electricvehicles (EVs), the FSPM machine for electric vehicles is designed and analyzed in thispaper and the torque performance of FSPM machine is optimized.First of all, the theory of FSPM machine is introduced. The running mechanism isanalyzed. The mathematical mode of FSPM machine is built through magnetic circuitequation, electric circuit equation, mechanical equation, electromagnetic torque equation.The model of FSPM machine is also set up by d-q coordinate transformation. Both modelsare used to provide theoretical basis for machine design.Secondly, due to the special structure of FSPM machine, the unique design featuresare introduced in this paper. The choices of machine materials, magnetic circuit structure,size ratio have been made and the main parameters and winding structure are calculated indetails to get the preliminary design schemes of12-solt/10-pole and12-solt/11-poleFSPM machine. To establish the12-solt/10-pole and12-solt/11-pole machine models byusing Ansoft finite element analysis (FEA) software. To verify these two design schemescan achieve the index requirements, the performance of FSPM machines are simulated andanalyzed separately.Once more, by using the software of FEA, the influences of machine structural sizeson torque characteristics are investigated. In order to get the optimal ranges of machinestructural sizes, the investigations are focused on air-gap length, width of rotor teeth, width of stator teeth, width of stator yoke and height of rotor teeth. The analysis results providereferences to get the reasonable design scheme of12-solt/10-pole and12-solt/11-poleFSPM machine.Finally, on the premise of unchanging the stator and winding structure, five novelrotor teeth shapes, including notched teeth, stepped teeth, eccentric teeth, the combinationof notched and stepped teeth, the combination of notched and eccentric teeth, are appliedon the rotors of12-solt/10-pole and12-solt/11-pole FSPM machine to reduce coggingtorque and torque ripple, respectively. The optimization design process of five novel rotorteeth shapes are provided, and then, the performance of FSPM machines with differentrotor teeth shapes are compared and evaluated comprehensively from aspects of coggingtorque, torque ripple, electromagnetic torque, flux linkage, back EMF, and so on. Theresults show that five novel rotor teeth shapes can improve the performance of FSPMmachines.