Thermal Modelling of Small Cage Induction Motors

Doctoral thesis, 1995

The loadability of electric machines is above all determined by temperature limits. In this work, thermal network models, suitable for totally enclosed fan cooled (TEFC) induction motors, are used to predict the machine temperatures. Two specific models are suggested: one with 107 nodes, which primarily is intended as a design tool, and one with 7 nodes, for increased simplicity. The steady-state solution method is valid in a broad speed-range and for variable load. Time-dependent solutions are obtained as a function of four input variables: frequency, stator voltage, torque and ambient temperature.