Analysis of the end winding heat transfer variation with altitude in electric motors

This paper considers the determination of heat transfer coefficients on the end windings of an electric machine. The correct determination of these coefficients is of importance since they are regularly used in the thermal analysis electric machines. The heat transfer equations for the end windings given in the literature are generally not expressed as correlations of non-dimensional parameters and so do not allow for changes in operating conditions such as the variation in pressure with altitude that is found in electric machines operating in aircraft. A simple correction is proposed to allow for changes in end winding heat transfer with altitude. This may be implemented in software packages such as MotorCAD — for calculating the thermal performance of electric machines.