A Comparative Study of the Effect of Voltage Unbalance and Sinlge Phasing on Three Phase Induction Motor Characteristics

Balanced supply voltage enables three phase induction motors (IMs) to operate with high effectiveness and avert a reduction in their lifespan. However, when there is a presence of unbalanced voltage, utmost problems in these motors' performance will exist. Voltage unbalance occurs when there is an inequality in voltage magnitude and phase shift, while single phasing exists when one of the phases becomes open during motor operation. In this paper, we study the problem of voltage unbalance and single phasing and introduce its effect on the performance of three phase IMs using Matlab/Simulink. We consider three scenarios of voltage unbalance, namely unbalance in magnitude, unbalance in phase shift, and unbalance in magnitude and phase shift in addition to single phasing. A comparison between these scenarios is discussed. In this work, we apply the method of symmetrical components to derive the motor equivalent circuit and characteristics when operating under the above-mentioned scenarios. Simulation results show that the higher adverse impact on three phase IM characteristics is caused by the unbalance in magnitude and phase shift, followed by single phasing, the unbalance in phase shift only and the unbalance in magnitude only.