Precise Assessment of Performance of Induction Motor under Supply Imbalance Through Impedance Unbalance Factor

This paper presents precise assessment of steady-state performance of induction motor (IM) operating under voltage unbalance. The variation of two voltage unbalance factors viz. complex voltage unbalance factor (CVUF) and impedance unbalance factor (IUF) with positive sequence voltage component, reveals that degree and manner of unbalance in supply voltage is exactly reflected in CVUF and IUF, respectively. On this basis, it is shown that for the precise assessment of IM performance, knowledge of both, manner (IUF) and degree (CVUF) of unbalance is important. Further, effect of angle of unbalance, on the performance of the IM and voltage pattern is analyzed. Results depict high sensitivity of derating factor and peak copper losses to this angle. Thus, it should be included along with unbalance factors for the precise and complete performance assessment of IM.