Design Methods for Surface-Mounted Permanent Magnet Synchronous Machines

Permanent magnet synchronous machines (PMSMs) provide several advantages compared with induction machine, such as higher power and torque density, and better dynamic response. Among PMSMs, Surface-mounted permanent magnet (SPM) machine has simple rotor configuration and easy control strategy due to its isotropic characteristics. Plenty of publications have illustrated the fundamentals and the design methods of SPM machines. Based on these, this dissertation presents new design methods for SPM machines. Both design methods are comprehensively illustrated. The presented design methods are embedded into a machine design platform available online. One of the new methods is an automatic design procedure using multi objective optimization method, whose principle is to combine multi objective differential evolution (MODE) optimization with finite element analysis (FEA) to obtain the machine with the best trade-off among the targeted objectives, like maximum torque, minimum torque ripple, good flux weakening capability, etc. Two cases are reported by using such automatic design method, one for a SPM machine with concentrated winding (CW-SPM) and the other with distributed windings (DW-SPM), respectively. The CW-SPM machine is designed for traction application. In this case, design equations, magnetic FEA, multi objective optimization, simplified structural and thermal co-design are presented. Torque and power profiles of the designed machine are reported. The losses and efficiency map are also presented. The DW-SPM machine is capable of low cogging torque thanks to the automatic design procedure. Dependent on demagnetization limit and optimal magnet span calculation, the magnet bounds in optimization process are obtained. The cogging torque and maximum torque waveforms of three different machines on Pareto front are shown, which are obtained by MODE optimization and FEA simulations. One optimum machine is selected as the best trade-off machine among PM volume, torque and cogging torque behaviors. Besides the automatic design process, the other design method called parametric design for SPM machines is reported. The parametric design provides a very effective and concise solution for SPM machine design without losing precision on the machine performance calculation. Three steps of parametric design development are reported. For each step, design flowcharts and examples are presented. Firstly, a parametric design plane was established based on rotor split ratio x and per unit magnetic loading b. All the sizing equations, torque and power factor calculation are functions of x and b. An example for designing a CW-SPM for traction application is reported. Later the parametric design plane was modified into the x and l_m⁄g plane, the latter parameter being the magnet-airgap length ratio. The design process of DW-SPM machines using the parametric plane is described. A prototype 一s built and verified the validity of the design process. Then, a general design approach based on accurate steel loading for both DW and CW SPM machines is proposed. By using subdomain model during the design process, the stator sizing equations are improved by considering the only one most loaded slot pitch rather than the entire pole pitch. Five different cases of SPM machines are analyzed to get the precise flux quantities passing through the most loaded teeth in one slot. A comprehensive parametric design flowchart for SPM machines is addressed. By using the parametric method, machine models are built according to each sizing situation. The steel loadings on both each tooth and yoke are measured by FEA and compared with target steel loading B_fe at open load condition, which shows good agreements with analytical cases. Finally, the designs are also tested at the respective rated currents. The presented methods give insightful and effective means in SPM machine design