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This study investigates the accurate modelling and the modal natural frequencies of the stator system of a permanent magnet synchronous motor with concentrated winding used in the in-wheel motor system of the electric vehicle. The equivalent material physical properties of each component in the stator system are determined by the correction formula and the empirical coefficient. Meanwhile, the contact conditions between each component are also analysed. According to the structural analysis of stator system, different equivalent finite-element models of winding and frame, together with their effects on the accuracy of simulation results, have been built and investigated, respectively. In addition, the prototype of the motor is fabricated; then the experimental modal analysis of the stator system and its subassemblies are carried out during the manufacturing process. Through comparisons of the results between experiments and finite element anaysis (FEA), the final model of the stator system is determined and verified to be of high accuracy to predict the vibration behaviours of the investigated motor with concentrated winding. Finally, several factors influencing the modal frequencies of stator system are analysed, which could provide certain reference value to the structural design of stator system.

This paper studies the non-uniform air-gap caused by stator and rotor deformations, together with its effects on the spatial and temporal spectrum of the radial magnetic force density in an interior permanent magnet synchronous motor (IPMSM). According to the mathematical model of the deformed air-gap length, the superposition method is adopted to derive the air-gap permeance. Then, the formulas of the magnetic flux field and radial force density of the IPMSM considering air-gap deformation are obtained. Considering the stator oval deformation and the rotor centrifugal distortion in the electromagnetic finite element models (FEMs), the finite element analysis (FEA) and experiments of the investigated IPMSM are carried out to verify the results obtained by the theoretical analysis at different operations. Finally, the mathematical correlation between air-gap deformation and electromagnetic vibration is obtained. The result is helpful in solving problems of mutual influence between electromagnetic and mechanical characteristics during the optimization design of IPMSM.

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