Induction motor thermal aging caused by voltage distortion and imbalance: loss of useful life and its estimated cost

This paper reports the effect of voltage distortion and imbalance (VDI) on the thermal aging of the insulation of low-voltage induction motors. The study is based on a detailed thermal modeling of actual motors in the 2-200-hp range. The dollar value of the useful life lost was estimated for different VDI conditions. Two important conclusions were reached. First, voltage subharmonics have a dramatic effect on motor thermal aging. Second, the overall cost of motor loss of life due to harmonic pollution and voltage imbalance, in the US today, is estimated to be in the range of 1-2 billion dollars per year.