Harmonics Traceability and Suppression of Electromagnetic Noise in Fractional Slot Permanent Magnet Synchronous Motors

Fractional slot permanent magnet synchronous motors (PMSMs) have rich air-gap magnetic field harmonic components and large vibration noise. A fast traceability method is targeted for identification and suppression of the electromagnetic (EM) noise. First, the generalized traceability expression of the main air-gap flux density harmonic sources corresponding to EM noise at a certain frequency are deduced inversely. In addition, for a 10-pole, 12-slot fractional slot PMSM, a multi-physics field noise prediction model is constructed to confirm the correctness of the analytical formula. The measured noise data of the prototype presents an overall agreement with the noise prediction data. Finally, the noise frequency band of the prototype to be improved is selected, and the related magnetic field harmonics are quickly traced. After the introduction of the three-segment arc rotor and the multi-objective optimization process for output performance improvement and noise reduction, both the noise prediction model and the measured data of the newly proposed prototype exhibit a reduction in noise across each primary frequency band, and providing larger and more stable torque as well.