Design of Axial Flux Permanent Magnet Machine for Miniaturized Integrated Starter–Generator System Applications

This article proposes the design of a miniaturized integrated starter–generator (ISG) system applied to a portable mobile power plant. The system utilizes a single-stator and single-rotor axial flux permanent magnet (PM) machine to meet the demands of light weighting and compaction. The stator adopts fractional slot concentrated winding to save space. The rotor is constructed in segmented PMs, resulting in an 83% reduction in eddy current loss. A quasi-3D magnetic equivalent circuit model is proposed for fast and accurate electromagnetic analysis. By optimizing the initial design using a multi-objective genetic algorithm, the power density of the optimized design reaches 1.23 kW/kg. To handle the axial attraction force, a fixing solution with stepped-shape PMs and aluminum alloy rings is introduced. In addition, the external heat of the engine and the anisotropic heat transfer coefficient of silicon steel are fully considered in computational fluid dynamics. The results show the efficient performance of the designed air-cooled structure. Finally, a prototype is manufactured and tested in the modes of starter and generator. The experimental results validate the prediction of the analytical method and the high performance of the ISG machine.