Improved thermal model for predicting end-windings heat transfer

The thermal analysis of the end space region of an electrical machine is mainly linked to the characterization of the convective heat transfer between the solid surfaces and the cooling fluid, normally air. Different relations have been proposed in literature by several authors but the calculation of the heat transfer coefficients (HTC) is still mainly related to empirical correlation factors, based on the experience. The aim of this work is to investigate the convection inside the end space region with the double objective of studying how the geometry influences the HTCs and of developing a new improved correlation for the computation of the HTCs. The study is conducted with the support of an advance CFD software. The investigation leads, as main result, to a dimensionless equation that links the Nusselt number to the rotational Reynolds number in the end-space region.