Combined Analytic-Linear-FE Approach for Fast Stress Analysis of High-Speed Interior PM Rotors

Because of the complex rotor assemblies, the design of high-speed interior permanent-magnet (IPM) machines has to deal with highly conflicting requirements arising from the electromagnetic and mechanical optimization. Suitable Finite Element (FE) models for stress analysis of IPM rotors have to incorporate non-penetration contact constraints at the PM-lamination interface then causing geometric nonlinearity which increases the computation time considerably. This paper presents a systematic mixed analytic-FE approach to derive realistic equivalent pressure distributions representing the contact interaction PM-lamination and to be applied to the lamination boundaries in a linear and homogeneous FE model. This allows fast FE analyses to be easily run using open-source general-purpose FE solvers and avoiding non-linear contact formulations. The analytical pressure distributions are implemented in the open source FE solver Freefem++ and validated by (geometric) non-linear static FE analyses with a commercial package implementing “real” non-penetration contact constraints.