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Stator slot skewing and rotor step-skewing methods are the most commonly used methods to reduce the torque ripple and electromagnetic vibration in the electric vehicle (EV) drive motor industry. However, these two methods have limitations on the suppression of the 0th-order vibration component and multiples of rotor magnetic pole number order vibration components. This article presents a novel rotor-segmented motor with different pole widths to reduce electromagnetic vibration for EVs. The principle of the presented new rotor segmented motor to mitigate the 0th-order and the multiples of rotor magnetic pole number orders vibration components are analytically analyzed and illustrated. Three multiphysics field models, i.e., conventional motor, rotor step-skewing motor, and the presented motor, were established. The electromagnetic vibration properties related performances, including air-gap flux density, radial force, torsional force, and vibration response, are extensively compared. Finally, the rotor step-skewing motor and the presented motor were prototyped, and extensive tests were conducted. The results show that the presented motor has a specific mitigating effect on electromagnetic vibration, with a significant decrease in the 0th-order vibration amplitude and the overall vibration level is the same as that of the rotor step-skewing motor.

Interior permanent magnet machines (IPMSMs) have attractive features, including high power density, high efficiency, and excellent control performance. However, the unsuppressed torque ripple of IPMSM will cause declined torque quality, increased vibration, and reduced reliability. This article presents a novel composed T-shaped notching rotor to suppress torque ripple for IPMSM. The mathematical models of cogging torque and winding factors considering T- shaped notches are established, respectively. Although the principle of the novel rotor design is clearly explained by mathematical models, the accurate dimensions of the composed T-shaped notch are difficult to calculate. Therefore, two-dimensional finite element analysis and multiobjective design optimization are employed to calculate the T-shaped notch dimensions. The electromagnetic performance of the proposed rotor machine is compared with that of the commonly notching rotor machine. In addition, the mechanical strength of the novel rotor is verified by calculations of stress and deformation. Finally, the proposed prototype with a novel rotor is fabricated, and extensive experiments are conducted. The results show that the torque ripple of IPMSM can be significantly reduced by the novel composed T-shaped notching rotor.

Irreversible demagnetization (ID) is one of the essential indicators that must be considered in the motor design stage. To address the problem that the existing magnetic circuit method can only determine the average operating point of the permanent magnet (PM), based on the PM subdivision model and the subdomain method, a novel calculation method for local ID (LID) of the motor is established in this article, which realizes the fast and accurate positioning and calculation of LID of the PM. The accuracy of the proposed method is verified by finite-element simulation and prototype test. To accurately simulate the multiphysical field coupling of electric–magnetic–machine–thermal–control in inverter-PM motor system, a dynamic model integrated with the drive control scheme is proposed, in which the ID cumulative effect and magnetic saturation effect are considered. The ID process of each PM unit and the motion behavior during dynamic process can be precisely simulated, and the LID state can be retained to evaluate its effects on motor performance. Finally, a fast temperature calculation method based on multiple regression analysis is presented, and the interaction between temperature rise, load, and ID, as well as the LID performance under sudden load and flux-weakening control are investigated.

In view of the shortcomings of the existing calculation methods of electromagnetic forces, this article proposes an analytical method (AM) combining the magnetomotive force permeance method and the improved subdomain method. The amplitude of each force density component considering stator teeth saturation and current harmonics is calculated, and the specific order and frequency components in the radial and tangential electromagnetic force densities are analyzed and sorted out. In modal analysis, the stator core and the casing are regarded as cylindrical shells with axial ribs, the natural frequencies of the stator are obtained based on the energy method, and the accuracy is well verified by the modal test. Finally, the frequency response functions of low-order modes of the stator only related to the stator structure parameters are determined, and the vibration accelerations under different working conditions are obtained based on the linear superposition principle by only updating the electromagnetic forces. Compared with the multiphysical coupling finite element analysis, the total calculation time of the proposed AM is reduced by more than 92%, which facilitates the fast prediction and effective reduction of electromagnetic vibrations in the motor design stage.