The measured effects of under-voltage, over-voltage and unbalanced voltage on the efficiency and power factor of induction motors over wide ranges of load

This paper investigates the effects of over-voltage, under-voltage and unbalanced voltage on the performance of induction machines in terms of line currents, power factor and efficiency. A set of three motors of 50 hp, 100 hp and 300 hp respectively, has been tested thoroughly at five different voltage conditions: rated voltage, 10% over-voltage, 10% under-voltage, 1.25% unbalance, and 2.5% unbalance. At each one of these voltage conditions, a load run series was performed for every motor. The data obtained shows how the different motors behave similarly, in terms of line current and power factor and differently in terms of efficiency, when subject to the particular voltage conditions.