A Study of End-effect on Demagnetization in Surface Permanent Magnet Motor without Overhang

In order to compensate the low performance of ferrite magnet, surface permanent magnet mounted (SPM) motor has considerably thicker magnet than air-gap length, thus end effect, which is determined by the ratio between magnetic air-gap and stack length, is negligible. As a result, 2-D finite element analysis (FEA), which is not possible to consider end effect, is generally used to ensure analysis accuracy in SPM motor without overhang structure. However, unlike other analysis such as back-EMF, demagnetization analysis of SPM cannot be ensured by 2-D FEA, because end effect is no longer ignored. In the demagnetization, magnetic air gap, which determines the level of end effect, is increased by the fact that the permeability of magnetized magnet is almost similar to vacuum, thus only 3-D FEA is used to ensure analysis accuracy. We has found this phenomenon by comparison between the results of 2-D and 3-D FEA, and finally we are plan to validate the simulation result by experiment test.