Influence of stator lamination on motor noise

27 Dec 2023
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Motor noise can be divided into three categories: aerodynamic, mechanical and electromagnetic noise sources, and in recent years, people are increasingly concerned about the impact of electromagnetic noise sources, which is mainly for two reasons: small and medium-sized motors, especially the motor rated below 1.5kW, electromagnetic source noise dominant sound field; This type of noise is mainly due to the difficulty of changing the magnetic properties of the motor once it is manufactured.
In previous studies, the influence of various factors on motor noise has been widely explored, such as the influence of pulse width modulation current on the acoustic noise behavior of internal permanent magnet synchronous motor drivers; The influence of winding, frame and impregnation on the stator resonance frequency; The influence of iron core clamping pressure, winding, wedge, tooth shape and temperature on stator vibration behavior of different types of motor.
However, in terms of stator iron core laminates, the effect on motor vibration behavior has not been fully studied, although clamping of laminates is known to increase the stiffness of the iron core, and in some cases they may even act as shock absorbers. Most studies model the stator core as a thick and uniform cylindrical iron core to reduce modeling complexity and computational burden.
McGill University researcher Issah Ibrahim and his team studied the effect of laminated and unlaminated stator cores on motor noise by analyzing a large sample of motors. They built a CAD model based on the measured geometry and material properties of the actual motor, and the reference model was a 4-pole 12-slot built-in permanent magnet synchronous motor (IPMSM). The modeling of the laminated stator iron core is done using the laminated model toolbox in Simcenter 3D, which is set according to the manufacturer's specifications, including damping coefficient, lamination mode, interlayer permissions, and shear and normal stress of the cement. To accurately assess the acoustic noise emitted by the motor, they developed an efficient acoustic model that allows coupling between the stator-fluid to model the acoustic fluid around the existing stator structure to analyze the acoustic field around the IPM motor.
The researchers observed that the vibration mode of the laminated stator iron core has a lower resonance frequency than that of the unlaminated stator iron core with the same motor geometry; Despite frequent resonances during operation, the sound pressure level of the laminate stator iron core motor design is lower than expected; A phase relation value of more than 0.9 indicates that by relying on the proxy model to accurately estimate the sound pressure level of the equivalent solid-state stator iron core, the computational cost of modeling the laminated stators for acoustic research can be reduced.
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