Calculation of DQ-axis inductances of PM brushless ac machines accounting for skew

In this paper, the influence of skew on the d- and q-axis inductances is investigated by using a hybrid 2-dimensional finite element/analytical technique, with due account for end-effects. In addition, a dc inductance bridge technique [2] is used to measure the d- and q-axis inductances in order to validate predictions for four brushless ac motors having identical stators, which are skewed by one-slot-pitch, but different rotor topologies, viz. with surface-mounted magnets, inset magnets, and interior magnets - both radially and circumferentially magnetised.