Model of air cooled windings for traction machine

This article presents a concept of direct cooled windings for electrical machines, pumping air through hollow rectangular copper windings. The thermal constraints pose a serious limitation in the performance of many applications of electrical machines, not least in electrical vehicles. The difference between temporary maximum output and continuous output is often substantial. This difference can be decreased with effective cooling methods, such as direct cooling of the windings. The concept of direct cooled windings are modeled in a empirical-lumped parameter model. The model is described in the article and experimentally validated through experiments. Finally the results of the model regarding optimized dimensions for electrical machines are presented and discussed. The results show that a current density of 16 A/mm²(insulation and cooling channels accounted for) can be achieved. 18 A/mm²is achievable with other dimensions, but with lower efficiency. The pump power for the coolant air is similar in magnitude to the amount of resistive losses.