Innovative approach to mitigating vibration and noise in an external rotor permanent magnet synchronous motor

This study investigates the external rotor permanent magnet synchronous motor with fractional slot concentrated windings. A comprehensive multi-physics model is utilized to analyze electromagnetic force behaviors on permanent magnets induced by sinusoidal currents. The impact of cogging torque on motor performance and electromagnetic noise from the side cover is examined through finite element simulation. An analytical model is developed to account for slotting and pole-slot interaction effects, providing insights into the spatial distribution and frequency characteristics of electromagnetic forces on permanent magnets. An energy-centric approach is used to evaluate cogging torque and its influencing factors. The non-uniform distribution of electromagnetic forces on permanent magnets is considered, and electromagnetic nodal forces are integrated into the structural model. The radial vibration acceleration of the rotor’s external surface is computed using the Modal Superposition Method, while the Acoustic Boundary Element Method is employed to predict the acoustic radiation from the side cover and the pressure distribution in the external air domain. Simulation results show that slotting-induced electromagnetic forces significantly contribute to motor noise. Optimization of slot width reduces electromagnetic forces at modal frequencies, decreases cogging torque, and lowers overall sound pressure level, improving motor vibration and noise reduction capabilities while enhancing operational performance.