Induction motors loss of life due to voltage imbalance and harmonics: a preliminary study

This paper reports preliminary results of a study that deals with the effect of voltage imbalance and distortion upon the thermal aging of induction motor insulation. The study is based on a detailed three-dimensional modeling of heat transfer flow and the monitoring of the temperatures of hot spots. It has been learned that subharmonics have a remarkable effect on thermal aging and that it is possible to correlate voltage harmonics with lost useful life and with lost capital. Finally, it is proven that harmonic and imbalance derating curves are not universal at all, but vary with motor size and design.