Prediction of internal temperature in three-phase induction motors with electronic speed control

Internal temperatures of induction motors with electronic control are not only affected by the harmonic components of the electronic source but also by the reduction of the cooling capacity as the motor speed drops. This paper develops a model able to determine the internal temperatures in a squirrel-cage three-phase induction motor fed by an inverter. The temperatures are calculated in a 20-node-thermal network whose parameters depend on the voltage wave supplied by the source and the motor speed. Through this model, it is possible to determine the temperatures in the tested motor and to analyze the influence of the fundamental frequency voltage on steady slate temperatures and motor performance limitation, specifically the maximum acceptable load, so that the motor does not exceed its normal steady state temperature when is supplied by an inverter. (C) 1998 Elsevier Science S.A. All rights reserved.