Finite element analysis and experimental validation of eddy current losses in permanent magnet machines with fractional-slot concentrated windings

Permanent-magnet machines with fractional-slot concentrated windings are easy to manufacture. Their popularity therefore is steadily increasing. Without a proper design, however, the induced eddy-current losses in the solid rotor get rather high. The modeling and the prediction of eddy-current losses for these machines are thus very important during the design process. This paper focuses on the finite-element analysis and the experimental validation of eddy-current losses for this kind of machine with a small axial length. Two-dimensional and three-dimensional transient finite-element models are developed for computing the eddy-current losses. The rotor motion is taken into account using an Arbitrary Lagrangian-Eulerian formulation. The total iron losses are measured experimentally and a method to separate the rotor iron losses from the total iron losses is presented. The validation results show that the two-dimensional finite-element model overestimates the losses due to the end-effects being neglected. The three-dimensional model agrees much better with the measurements in both no-load and on-load operations.