Analytical prediction of electromagnetic performances and unbalanced magnetic forces in fractional-slot spoke-type permanent-magnet machines

This paper presents an analytical method for the computation of electromagnetic performances and non-intrinsic unbalanced magnetic forces (UMF) in fractional-slot spoke-type permanent-magnet (STPM) machines. It is based on the two-dimensional (2-D) subdomain method in polar coordinates considering the drive current: i) sinusoidal, and ii) six-step rectangular. It involves solution of Laplace's and Poisson's equations in the stator slots, the air-gap, the buried tangential PMs into rotor slots, and the non-magnetic region under PMs. The results obtained with 2-D analytical model (viz., the electromagnetic performances and the non-intrinsic UMF) are verified with those issued from finite-element method (Fem).