Loss of life in induction machines operating with unbalanced supplies

This paper estimates motor life when a motor is supplied with a combination of over- or undervoltages with unbalanced voltages. The motor life is predicted by estimating the stator winding insulation life of squirrel cage motors using Arrhenius' equations. Electrical and thermal models are used to calculate motor losses and temperatures, respectively. The thermal model parameters are obtained from simple motor testing techniques rather than from complex methods requiring motor design data.