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An Improved Equivalent Magnetic Network Model of Modular IPM Machines

This article develops an improved equivalent magnetic network (EMN) model for analysis of a modular interior permanent magnet (IPM) machine. First, focusing on the local magnetic saturation, the stator tooth crown is divided into three parts based on its structure and flux density distribution. To model the specific flux path, the tooth tips on both sides are approximated to right-angled trapezoids and the middle part is divided into isosceles trapezoid. Second, an improved air-gap model is proposed, which divides the air-gap magnetic network into three layers. The middle network uses cross-shaped mesh (CS-M) elements to represent the path of tangential and radial fluxes. The top and bottom layers are composed of parametrized nonlinear permeances between stator, rotor edge nodes, and middle network nodes, whose values are the function of angle respect to CS-M elements. In this way, as the machine rotates, the structure of the EMN model can be kept invariant, and only permeances of bottom layers should be modified. Then, the EMN model is extended to the analysis of the machine with skewed stator. The accuracy and effectiveness of the proposed EMN model are verified through comparisons with finite element analysis and experimental tests.