An original analytical expression of the maximum magnet thickness in surface mounted permanent magnet motors

An exact two-dimensional (2-D) analytical model (AM) of slotless permanent magnet (PM) machines in polar coordinates is used to determine the analytical equations of the air-gap flux density at no-load operation. The authors show that, for a radial magnetization, there is an optimal magnet thickness which permits to maximize the no-load flux density. In order to use easily and directly this optimal value during the design of surface mounted PM motors (SMPMM), the authors propose an original analytical expression of this maximum magnet thickness that have been obtained by interpolation of the values given by several analytical computations. This interpolation function could be applied to SMPMM having a parallel or radial magnetization direction.