Effects of unbalanced voltage on induction motor operating points under different load torque profiles

Unbalanced voltages seriously affect steady-state performances of induction motors. In this paper, analytical formulation for finding the steady-state operating points of induction motors with different load torque profiles is presented when the motors are operating under unbalanced condition. The effect of single-phase voltage unbalance on motor performance is demonstrated as the load torque of induction motor is related to constant, linear, speed-squared torque characteristics. The result shows that the constant torque type is one of the most severe loads that cause significant increases in motor's active and reactive powers during presence of under-voltage unbalance.