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In the electromagnetic design stage of PM motors, the consideration of reducing torque ripple is as important as the improvement of motor efficiency. In this article, the electromagnetic performance of the magnet-shifted surface-mounted PM motor is analyzed and calculated in detail. The Maxwell tensor method is used to explain the mechanism of mitigating cogging torque, and it will obtain the optimal magnet-shifted angle more quickly than Finite element parameterization. According to the change rule of winding flux linkage, the winding factor of the proposed motor is calculated, which describes the principle of harmonic generation fundamentally. The magnetic field is affected by many factors and the demagnetization curve of motor materials is nonlinear, so a multiobjective optimization strategy based on the genetic algorithm and the finite element calculation is selected to acquire the best parameters.

The sideband current harmonic components are inevitable in a permanent magnet synchronous motor (PMSM) drive system driven by a voltage-source inverter with space vector pulsewidth modulation (SVPWM). The research on the characteristics of sideband harmonic currents would provide guidance to the cause of electromagnetic force waves, vibration, and acoustic noise of the motor. In this article, the main components of sideband harmonic currents in PMSM drive by the SVPWM method are analytically derived. The frequency and spatial order of the sideband harmonics and radial electromagnetic force are calculated based on finite element analysis (FEA). Then, an experimental test of an eight-pole/48-slot interior PMSM with a voltage-source inverter controlled by the classical vector control strategy is carried out, and the phase stator currents, vibration response, and acoustic noise signals are collected. The results finally verify the accuracy of the derivation analysis of sideband currents and indicate the relation between sideband harmonic currents and electromagnetic vibration, which provides a reference for further studies of vibration suppression.

This work proposes an analytical method for calculating magnetic fields considering the parallel magnetization and magnetic bridge saturation effects. The calculation method can be applied to any irregular regions with high precision and fast calculation speed, enabling accurate magnetic field calculations inside the permanent magnet (PM). First, to address the challenge posed by complex PM shapes in U-shaped interior PM synchronous machine, a novel subdivision equivalence method is conducted. Additionally, using the equivalent PM domain with variable remanence, the saturation effects of the inner magnetic bridge inside the rotor can be calculated. Furthermore, an exact solution for arbitrary partial parallel magnetization in the sector-shaped subdomain and a new method to solve the boundary value problems are introduced. Finally, the calculation results are compared with the finite element method and experiment to verify the effectiveness of this method.

High frequency (HF) voltage injection is the main method to realize zero-low speed sensorless control of interior permanent magnet synchronous motor (IPMSM). However, additional signal injection interacts with the fundamental frequency to generate new voltage components, and new sideband harmonic components will be introduced under space vector pulse width modulation (SVPWM), resulting in extra electromagnetic vibrations and acoustic noises, which has a serious impact on vibration performance of the motor. The sideband harmonic components and the main frequency distribution of electromagnetic force waves generated by control of pulse voltage injection under the space vector pulse width modulation are comprehensively analyzed in this paper, which provides a basis for the selection of the frequency and amplitude of the injection voltage. The experiment platform is built to verify the correctness of the theoretical analysis. The electromagnetic vibrations and acoustic noises can be significantly reduced by appropriately matching the injection signal frequency with the operating speed and motor modal frequency.

A novel multiobjective optimization model is presented for the interior permanent magnet synchronous motors (IPMSMs). First of all, in the model initialization stage, appropriate design variables are determined for the actual topology. Also, with reference to the engineering needs, the key electromagnetic characteristics relating to the no-load and on-load magnetic fields are selected as the main optimization objectives in order to achieve global performance improvement. Next, in the model prediction stage, two performance prediction models are proposed, studied, and implemented in parallel. One is an analytical model (AM) based on the improved subdomain approach and the magnetic equivalent circuit. It is utilized to predict the no-load electromagnetic characteristics of IPMSM. The complex structure and core nonlinearity of IPMSM are also reasonably accounted for. The other is a surrogate model (SM) based on the intelligent machine learning language (support vector regression). It is utilized to predict the on-load electromagnetic characteristics of IPMSM. The reliance on finite-element analysis is further also minimized. The proposed AM and SM have commendable behavior in terms of analysis speed, prediction accuracy, and storage consumption. Meanwhile, AM screens credible samples as well as provides robust support for the construction of SM. All of these signs build a solid foundation for a substantial boost in optimization efficiency. Afterward, in the model optimization stage, the advanced nondominated sorting genetic algorithm III is investigated to complete the final multiobjective optimization. Ultimately, a large number of calculations, simulations, and experiments have highlighted the effectiveness, rationality, and engineering practicality of this research.

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.