Modelling and Analysis of PM Demagnetization and its Effect on Vibration in SPM Machines

This paper presents a modelling technique to estimate the changes in vibration spectrum due to non-uniform demagnetization. A modulation function is defined that accounts for the nature of demagnetization in the magnets. Using this function and the conformal mapping based approach, the field distribution in the air-gap is obtained. As this approach is semi-analytical, the electromagnetic step of performing vibration spectrum analysis of a machine become faster. The modulation function introduces the effects of magnet demagnetization into the air-gap flux density. The mechanical stress distribution obtained from the field distributions is fed to mechanical harmonic response solver to estimate the level of acceleration corresponding to the particular frequencies of vibration. The results and discussion related to the extent of demagnetization and the corresponding changes in vibration spectrum are presented.