Analytical Evaluation of Core Losses, Thermal Modelling and Insulation Lifespan Prediction for Induction Motor in Presence of Harmonic and Voltage Unbalance

Electrical motors are the ubiquitous workhorses of the industry, working over wide range of conditions and applications. Modern motors, designed to exact ratings using new materials and improved manufacturing techniques, are now much smaller but have higher loadings. They are being operated much close to the overload point than ever before. To ensure a satisfactory life span for the motor, temperature rise must be limited to the safe values. This paper proposes an analytical approach to estimate core losses of induction motor supplied by either harmonic content or voltage unbalance source. A thermal model based on the thermal lumped parameters is introduced and used to predict the insulation lifespan of the motors. Lumped parameters network of the motor is developed based on dimensions of the motor, thermal resistances, thermal capacitances, and loss sources. Then, the model is used to estimate the temperatures in different parts of the machine and the insulation lifespan of the motor. Finally, the predicted results using the model are verified by experiments.