A study on the shaft stability and prediction of electromagnetic and NVH characteristics of permanent magnet synchronous machine according to the different pole/slot combination

In this study, electromagnetic noise sources of permanent magnet synchronous motors with 8-pole 9-slot and 12-slot fractional slot concentrated windings were analyzed through finite element analysis, and the radiated noise/vibration levels were compared through structural-acoustic analysis. In addition, the stability of the rotational shaft generated vibration was analyzed. Electromagnetic noise sources are classified into cogging torque, torque ripple, and unbalanced magnetic force. The effect of electromagnetic noise sources on vibration/noise was analyzed in the frequency domain through the electromagnetic-mechanical coupling analysis. The noise level was compared to the electromagnetic noise source characteristics for each frequency using the waterfall diagram, and additional vibration due to mechanical resonance was analyzed using critical speed analysis while taking the rotor's bearing stiffness into account.