Convection Heat Transfer and Flow CalculationsSuitable for Electric Machines Thermal ModelsDavid A. Staton and Andrea Cavagnino, Member, IEEEAbstract—This paper deals with the formulations used to predictconvection cooling and flow in electric machines. Empiricaldimensionless analysis formulations are used to calculate convectionheat transfer. The particular formulation used is selected tomatch the geometry of the surface under consideration and thecooling type used. Flow network analysis, which is used to studythe ventilation inside the machine, is also presented. In orderto focus the discussion using examples, a commercial softwarepackage dedicated to motor cooling optimization (Motor-CAD) isconsidered. This paper provides guidelines for choosing suitablethermal and flow network formulations and setting any calibrationparameters used. It may also be considered a reference paper thatbrings together useful heat transfer and flow formulations that canbe successfully applied to thermal analysis of electrical machines.Index Terms—Dimensionless correlations, electrical machines,flow analysis, thermal model.