Derating of induction motors operating with a combination of unbalanced voltages and over- or undervoltages

This paper examines the proper application of induction machines when supplied by unbalanced voltages in the presence of over- and undervoltages. Differences in the definition of voltage unbalance are also examined. The approach adopted is to use NEMA derating for unbalanced voltages as a basis to include the effects of undervoltages and overvoltages, through motor loss calculations.