Accurate 3D Thermal Network Development for Direct-drive Outer-rotor Hybrid-PM Flux-switching Generator

Heat and thermal problems are major obstacles to achieving high power density in compact permanent magnet (PM) topologies. Consequently, a comprehensive, accurate, and rapid temperature rise estimation method is required for novel electric machines to ensure safe and reliable operations. A unique three-dimensional (3D) lumped parameter thermal network (LPTN) is presented for accurate thermal modeling of a newly developed outer-rotor hybrid-PM flux switching generator (OR-HPMFSG) for direct-drive applications. First, the losses of the OR-HPMFSG are calculated using 3D finite element analysis (FEA). Subsequently, all machine components considering the thermal contact resistance, anisotropic thermal conductivity of materials, and various heat flow paths are comprehensively modeled based on the thermal resistances. In the proposed 3-D LPTN, internal nodes are considered to predict the average temperature as well as the hot spots of all active and passive components. Experimental measurements are performed on a prototype OR-HPMFSG to validate the efficiency of the 3-D LPTN. A comparison of the results at various operating points between the developed 3-D LPTN, experimental test, and FEA indicates that the 3-D LPTN quickly approximates the hotspot and mean temperature of all components under both transient and steady states with high accuracy.