Improvement to winding function theory for PM machine analysis

Abstract

Winding Function Theory (WFT) is one of the powerful tools in electrical machine modeling. It uses the numerical functions to model the machine windings and its air gap. In this paper, two extensions to the method are presented. Since it is not possible to model a permanent magnet by a unique winding function, this paper introduces the Magnet Function. This function states the MMF drop on the machine air gap due to the PMs. The second extension increases the accuracy of the method by considering the stator saliency. This improves the method ability in simulating the tooth related harmonics in machine torque and terminal voltages. This paper recommends a numerically-calculated permeance considering the accurate flux pass. The described procedure is applied to a PM motor. Then the model is simulated and verified by the experiments.