Effects of voltage unbalance on normalized performance parameters

This paper evaluates the influence of unbalance supply voltage in calculating the various normalized performance parameters of three phase induction motor (3-φ IM). Firstly, the ratio of the various performance parameters of 3-φ IM, viz., stator copper loss, rotor copper loss, efficiency, output power, and output torques, under the condition of unbalance and balance supply voltage are calculated. This ratio is considered as the normalized values of the performance parameters. Secondly, the current unbalance factor, i.e., ratio of negative-to positive sequence current, is considered to evaluate the negative effects of unbalance supply on various performance parameters. The accuracy of the results of the proposed assessment method is validated through Matlab simulation. It is reveal that the unique estimation of the various performance parameters is possible only when the normalized performance parameters are considered with current unbalance factor. Further, linear relationship between voltage and current based index is derived. It is shown that, it is easy to estimate voltage based index from current based if rating of the motor is available. Finally, the need of inclusion of current based index in place of voltage based index is highlighted.