Impact of steady-state voltage supply anomalies on three-phase squirrel-cage induction motors

In this paper, the consequences of steady-state voltage supply anomalies on the behavior, losses and operating limits of low-power, low-voltage, three-phase, squirrel-cage induction motors is presented. The study is mainly based on simulations and previously published works, but experimental results are also presented. The well-known motor derating curves proposed by NEMA are questioned. It is demonstrated that they are too general, and do not consider combined effects of voltage unbalance, magnitude deviation, and distortion. Additionally, the effects of ambient temperature and motor characteristics (e.g. rated power, frame type, rotor type and efficiency class) should also be considered. Another important issue discussed in this paper is the fact that voltage unbalance and voltage distortion definitions should be properly revised in order to eliminate ambiguities. A clear methodology to evaluate the impact of the referred power anomalies on motors is proposed. An artificial neural network-based approach for mathematical description of motor derating curves as a function of multiple variables is also proposed and validated. Several relevant considerations on motor simulation within power quality scope are presented.