Motor vibration and noise is an important index to measure motor performance. How to reduce vibration and noise is one of the important topics in the field of motor design. Analysis, calculation, and reduction of motor vibration and noise have attracted more and more attention from motor designers. Based on the three main types of noise sources of motors, this paper firstly analyzes their causes and mechanisms and secondly introduces their main research methods. Although there are many summary articles on the research of motor vibration and noise, most of the theories and research methods on the causes of various kinds of noise are not comprehensive enough, lacking theoretical calculation and analysis, especially for mechanical noise and aerodynamic noise. This paper summarizes the research in the recent ten years, especially in the recent five years, with a view to providing a reference for the future development of this field.

Thanks to the magnetic field modulation effect, the magnetic field modulation motor (MFMM) significantly improves torque density and magnetic field harmonic utilization by breaking the constraints of traditional motor excitation and armature pole number matching. This advantage enhances its development potential in fields such as new energy vehicles, aerospace, power generation, and the military. This article first starts with the basic principle of magnetic field modulation, and adopts the excitation unit position classification method to systematically summarize the evolution laws of major MFMM topology structures such as the permanent magnet synchronous motor, switch magnetic flux motor, and flux reversal motor in recent years. It also analyzes the research progress of key performance such as the torque characteristics and power factor of these motors. Research has pointed out that the MFMM still faces core challenges such as high torque ripple, complex structure, low power factor, and multiple losses. Based on a review of the main achievements in the field, the future development direction of MFMMs is proposed to promote its development in the fields of precision drive and efficient energy conversion.

This paper presents a 10 kW outer-rotor field-modulated permanent magnet vernier generator tailored for low-speed direct-drive applications. It employs an outer-rotor Spoke-array configuration, which effectively mitigates the leakage flux between adjacent pole pairs. First, the topology and operating principle of the proposed generator are elaborated. Analytical calculations of key design parameters are then performed to accelerate the modeling process. A systematic parametric sweep is conducted to optimize the motor parameters, based on which a 2D finite element analysis model is established. Comprehensive FEA simulations are carried out to investigate its flux regulation capability, static and dynamic characteristics, and permanent magnet demagnetization risk. The results demonstrate that the Spoke-array permanent magnet array effectively suppresses leakage flux, achieving a volumetric power density of 387.5 kW/m³, and the no-load back electromotive force achieves a peak amplitude of 270 V with a total harmonic distortion as low as 3.7%, which is significantly higher than that of conventional permanent magnet vernier generators. Finally, a 30-slot/23-pole prototype is fabricated and tested. The experimental results show excellent agreement with the simulation predictions, validating the effectiveness of the proposed design.