Thermal Modeling of an Air-Cooled Electrical Machine for Propeller-Driven Aircraft

This paper compares different modeling approaches for the thermal behavior of electrical machines. The focus is on the stator slots, where high loss densities in the electrical conductors encounter low thermal conductivity of the insulation materials. Three slot models for the thermal behavior in the stator slot (concentrated conductor, homogenized slot, and sectional homogenized slot) are presented and compared. The models are embedded in lumped parameter thermal networks to represent the interaction between slot, stator and housing. Thermal measurements on the test bench are used to validate their predictive power for the thermal behavior of the stator slot. The results show that contact resistances have significant influence on the thermal behavior of the stator and lead to higher hotspot temperatures than initial calculations suggest. The measurements are used to derive thermal conductivities that are used to trim the modeling approaches with respect to hotspot temperature prediction.