Electromagnetic noise reduction of a high-power asynchronous motor via stator and rotor slot combination design

The bridge durability wheel load testing equipment, which employs controlled rolling loads to accelerate bridge structural damage, is driven by a 75 kW three-phase asynchronous motor. However, this motor produces significant electromagnetic noise (approximately 95 dB measured at a distance of 5 m), which causes environmental noise pollution and impairs equipment operation. To address this issue, a multi-physics coupling model integrating electromagnetic, structural-vibration and acoustic analyses is constructed using Maxwell and Ansys Workbench platforms. The two-dimensional Fourier transform (2D-FT) is adopted to extract the spatial and temporal harmonic order characteristics of radial electromagnetic force waves. Results show that the ±4 spatial-order radial electromagnetic force waves at 1680 Hz are close to the 4th-order natural frequency of the stator core, making this force component the primary excitation source. By comparing four stator and rotor slot combinations (60/54, 60/50, 54/48, 48/44), it is found that optimizing the slot combination together with a rotor skew angle can significantly suppress air-gap magnetic field harmonics, reduce the amplitude of radial electromagnetic force waves, and effectively avoid resonance caused by the coupling of electromagnetic excitations and structural modal frequencies. Among the four stator and rotor slot schemes, the 60/54 slot combination paired with a 6° rotor skew slot angle reduces the sound pressure level at 5 m from the source to 84.2 dB while maintaining motor efficiency, representing a noise reduction of 10.8 dB compared with the original prototype design. This study verifies the effectiveness of harmonic suppression and stator and rotor slot optimization in electromagnetic noise control, which offers both theoretical insights and practical engineering guidance for the low-noise design of high-power asynchronous motors.