Flat magnets in surface-mounted permanent magnet machines: Influence and design

The presented work analyzes the influence of using Flat Magnets (FM) instead of a Single Curved Magnet (SCM) in surface-mounted Permanent Magnet Machines (PMM). FMs distort the air gap flux density due to non- constant air gap height above magnets and air spaces between magnets. Consequently, the air gap flux density fundamental harmonic component is smaller than that produced by a SCM. The larger the number of FMs, the better the approach to a SCM configuration; but this trend is not lineal and, therefore, there is an optimal number of FMs which makes maximum the efficiency/cost ratio. This work makes also possible to implement reduction factors in analytical calculation algorithms of PMM in order to consider FMs with their respective air gap flux density reduction. The proposed method uses finite element method software and obtains accurate results with very low computation time.