Influence of skew and cross-coupling on d- and q-axis inductances and flux-weakening performance of PM brushless AC machines

A method is proposed for predicting the d- and q-axis inductances and flux-weakening performance of PM brushless AC machines accounting for skew and d-q axis cross-coupling. The method is based on a d-q-axis flux-linkage model, a hybrid 2-D FE-analytical method being used to predict the d- and q-axis inductances. However, it only requires 2-D FE analysis of the magnetic field distribution over a cross-section of the machine. The developed method is used to predict the torque-speed characteristic of an interior PM brushless AC machine with one stator slot-pitch skew, which is compared with predictions from a direct FE analysis and validated by measurements.