Effects of Large Induction Motors on Voltage Sag

Voltage sags is a problem affecting the electrical qualities. In this paper, effects of large induction motors on voltage sag characteristic are discussed. Moreover, the influences of different mechanical loads of the motors on voltage recovery are investigated. The study results show that reactive power contribution owing to the motor's trapped flux linkage prevents fast collapse of the voltage, resulting in non-rectangular shape of sag. The motor's negative torque induced during fault interval causes speed loss. The constant torque of mechanical load gives rise to the most speed loss, leading to a longer reacceleration and a great delay in voltage recovery.