Computationally efficient approaches for evaluation of rotor eddy current loss in permanent magnet brushless machines

The paper describes a number of computationally efficient techniques for predicting rotor eddy current loss in permanent-magnet brushless machines. In particular, a correction factor which takes into account the finite length effect of magnets is employed to adjust analytically predicted losses for each harmonic. The results are compared with 3-dimensional (3D) finite element (FE) calculations. A simplified 3D FE model, in which the stator magneto-motive force (MMF) is distributed as current sheets in the slots of a highly permeable, thin-walled cylinder, is employed to quantify the 3D eddy current distribution in magnets and their associated losses. Appropriate boundary conditions are set to reduce model complexity and size, and hence computation time. The utility and accuracy of these approaches are discussed and compared, and their relative merits are assessed.