A simplified thermal model for variable-speed self-cooled industrial induction motor

In this paper, a simplified thermal model for variable-speed self-cooled induction motors is proposed and experimentally verified. The thermal model is based on simple equations that are compared with more complex equations well known in the literature. The proposed thermal model allows one to predict the over temperature in the main parts of the motor, starting from the measured or the estimated losses in the machine. In the paper, the description of the thermal model setup is reported in detail. Finally, the model is used to define the correct power derating for a variable-speed pulsewidth-modulation induction motor drive.