The noise of electric motors can be divided into three categories: aerodynamic, mechanical and electromagnetic noise sources. In recent years, people have paid more and more attention to the impact of electromagnetic noise sources. This is mainly due to two reasons: (a) in small and medium-sized motors, especially motors rated below 1.5kW, electromagnetic source noise dominates the sound field; (b) this type of noise is mainly due to the fact that its magnetic properties are difficult to change once the motor is manufactured. In previous studies, the influence of various factors on motor noise has been widely explored, such as the effect of pulse width modulated current on the acoustic noise behavior of internal permanent magnet synchronous motor drives; the influence of windings, frames and impregnation on the stator resonant frequency; the influence of core clamping pressure, windings, wedges, tooth shape, temperature, etc. on the vibration behavior of stators of different types of motors. However, in terms of the stator core laminations, the impact on the vibration behavior of the motor has not been fully studied, although it is known that the clamping of the laminations can increase the stiffness of the core and even in some cases they may act as shock absorbers. Most studies model the stator core as a thick uniform cylindrical core to reduce modeling complexity and computational burden. McGill University researcher Issah Ibrahim and his team studied the impact of laminated and non-laminated stator cores on motor noise by analyzing a large number of motor samples. They built CAD models based on the measured geometric dimensions and material properties of the actual motor, with the reference model being a 4-pole, 12-slot interior permanent magnet synchronous motor (IPMSM). The modeling of the laminated stator core was completed using the Laminated Model Toolbox in Simcenter 3D, which was set according to the manufacturer's specifications, including parameters such as damping coefficient, lamination method, interlayer allowance, and shear and normal stress of the adhesive. In order to accurately evaluate the acoustic noise emitted by the motor, they developed an efficient acoustic model that allows coupling between the stator and the fluid, modeling the acoustic fluid around the existing stator structure to analyze the acoustic field around the IPM motor. Figure 1. (a) 2D electromagnetic model. (b) Variation range of design variables in the entire design space. The researchers observed that the vibration modes of the laminated stator core have lower resonant frequencies relative to the non-laminated stator core of the same motor geometry; despite frequent resonances during operation, the sound pressure level of the laminated stator core motor design was lower than expected; the correlation coefficient value exceeding 0.9 indicates that the computational cost of modeling laminated stators for acoustic studies can be reduced by relying on a surrogate model to accurately estimate the sound pressure level of the equivalent solid stator core. Figure 2 Sound pressure levels of laminated and non-laminated stator core samples of a 4-pole 12-slot IPM motor
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