Analytical Modeling and Analysis of a YASA Axial Flux Permanent Magnet Machine Based on an Improved Exact Subdomain Method

To tackle the prolonged modeling and optimization times of traditional Finite Element Method (FEM) for yokeless and segmented armature (YASA) axial flux permanent magnet (AFPM) machine, this paper introduces an efficient analytical modeling approach utilizing an improved exact subdomain (ESD) Method. The ESD method partitions the machine’s domain into subdomains, deriving analytical general field solutions via separation of variables, and then obtaining analytical expressions for particular solutions through boundary conditions to form a linear system for undetermined coefficients. This method solves for the magnetic vector potential A, simplifying the coefficient matrix by incorporating symmetric boundary conditions and periodic coefficients. To enable automatic phase distribution and current application for any fractional slot concentrated winding (FSCW) configuration, a three-phase winding matrix is constructed, allowing for parameterization of slot and pole numbers, which enhances its applicability to optimization algorithms. Validation through finite element simulations confirmed that the proposed ESD significantly reduces computation time while maintaining accuracy (static magnetic field calculation time decreased by approximately 95%, transient electromagnetic field calculation time by approximately 93%). This research provides an effective tool for rapid electromagnetic performance calculation and initial design and optimization of YASA-type axial flux machine.