Improved Analytical Modeling of Permanent Magnet Leakage Flux in Design of the Coreless Axial Flux Permanent Magnet Generator

This paper presents an improved magnetic circuit model of a coreless axial flux permanent magnet (AFPM) machine for the evaluation of its air-gap leakage flux. In the coreless AFPM machine, the stator axial length is one of the effective parameters in the calculation of the air-gap leakage flux factor. It is important to correctly update the leakage flux factor value corresponding to the variation of machine dimensions during the optimal design procedure. In this regard, first, an improved magnetic equivalent model of AFPM is achieved by using a nonlinear iterative algorithm to consider the magnetic saturation of rotor back iron cores. Then, the distribution of the flux in all parts of the machine is obtained. In other words, a quasi-3-D model of the coreless AFPM machine is considered based on the sizing equations to analytically obtain the air-gap leakage flux factor in terms of machine dimensions. Finally, the 3-D finite-element model of the machine is prepared to confirm the validity of analytical results. Very little difference between parameter values illustrates the accuracy of the proposed model.