Analysis of the Endwinding Cooling Effects in TEFC Induction Motors

The paper deals with the endwinding cooling problems of Total Enclosed Fan Cooled (TEFC) induction motors. In order to obtain information about the phenomena involved in the motor end space, three "ad hoc" prototypes have been build. The complete test bench set up together the followed test procedures are reported in detail. The measurement results have shown that all the motor part overtemperatures (winding, endwindings, stator lamination and external motor frame) decreasing with the inner air speed increasing. The measured motor overtemperatures and losses allow the thermal resistance identification of a simplified thermal model suitable to describe the thermal behaviors of the prototypes. By the thermal resistance between the endwinding and the motor frame, the related heat exchange coefficients have been evaluated as a function of the rotor speed. The proposed procedure allows separating the forced convection contribution by the other thermal exchange phenomena that occur in the end space regions. The obtained heat transfer coefficients are in agreement with the results reported in the past literature.