Evaluating Grid Harmonics Effect on Induction Motor Using Reduced Thermal Model

Electric motors have become one of the most important staples of industry. Electric motors' lifespan is highly affected by hotspot temperature of the motor during operation. Therefore, calculating and monitoring hotspot temperature can significantly increase motor's lifespan. However, obtaining motor's hotspot temperature through complete lumped parameter thermal model (LPTM) requires high computational effort. On the other hand, the deployment of power electronic devices has considerably increased voltage harmonics in the network. These voltage harmonics and unbalances can increase the hotspot temperature of electric motors above permissible levels and decrease motor's lifespan, if not controlled. In this paper, a reduction method for lumped parameter thermal model is proposed based on sensitivity analysis, in order to simplify the thermal model as well as maintaining desired precision. The efficiency of the model is evaluated in highly harmonic-polluted and voltage-unbalanced networks. The results indicate negligible error in reduced thermal model approximation compared to complete model.