Optimization of a Multipolar Permanent-Magnet Rotor Comprising Two Arc Segments per Pole

This paper investigates the optimal design of a brushless machine with an internal rotor comprising a permanent magnet (PM) array that is made up from discrete anisotropic arc segments. The particular case where the magnet array is constructed from two arc segments per pole is considered, where the magnets are alternately magnetized normally and tangentially to the rotor surface. The influence of the relative magnetic airgap and magnet thickness on the optimal PM array arrangement is analyzed, and it is shown that the optimal arrangement is largely independent of the airgap width. Both analytical and numerical approaches to the optimization problem are presented, the latter using a 2-D parametric finite-element model.