Impact of different end region cooling arrangements on endwinding heat transfer coefficients in electric motors

In this paper the impact of different end region cooling arrangements on the endwinding heat transfer is analyzed. An experimental approach to the problem solving has been adopted: two ¿ad hoc¿ prototypes have been built, and a test bench has been assembled. Open drip proof ¿ODP¿ and total enclosed fan cooled ¿TEFC¿ frames have been taken into account. In addition the cooling effect of the fins always present in the induction motor cage end-rings have been analyzed too. The paper reports in detail the set up of the test procedures and the obtained results. Particular care has been devoted to the determination of the heat transfer coefficients concerning the thermal transfer between endwinding and external frame. The obtained results are of basic importance for the determination of the thermal resistances between endwindings and end caps to be utilized in thermal networks usually adopted in thermal model analysis.