Steady-state Performance Assessment of Induction Motor under Unbalanced Voltage Condition

This article discusses the performance assessment of a 3-Φ induction motor under supply voltage unbalance. It has been emphasized that not only degree but the knowledge of conditions of voltage unbalance is also required to obtain unique value of performance parameters, viz., efficiency, copper loss, power factor, derating factor, etc. of a 3-Φ induction motor operating under supply voltage unbalance. Further, it has been shown that different conditions of unbalances are exactly reflected in the magnitude and phase angle of the complex current unbalance factor, whereas the voltage unbalance factor gives the degree or severity of unbalance only. Hence, the inclusion of magnitude and phase angle of the complex current unbalance factor along with the voltage unbalance factor has been asserted for the precise and complete assessment of the 3-Φ induction motor. Additionally, it has been revealed that the “derating factor” and “peak copper loss” are highly sensitive to the conditions of voltage unbalance that depends on the angle of complex current unbalance factor. Hence, to find the unique values of these two performance parameters, the incorporation of complex current unbalance factor angle to define the conditions of unbalance has been emphasized. Finally, to show the accuracy of the proposed method for the precise and complete assessment of the performance of the 3-Φ induction motor, the simulation and experimental results for efficiency, total loss, and derating factor are presented.