A study of voltage sag effects on induction motors

Abstract

Voltage sags are a common power quality problem occurring in power systems. They are usually characterized by remaining voltage, duration, and phase jump. Several industrial equipment, especially induction motors, are highly sensitive to voltage sags. This thesis studies the effects of unsymmetrical and symmetrical voltages sags on behavior of an induction motor. Both experiment and computer simulation using EMTP-ATP are conducted to observe variations of current, speed and torque of the induction motor during voltage sags of its supply. Voltage sags affect not only motor supply but also contactors that control the operation of motors. Thus, the sensitivity of an ac coil contactor to voltage sags is investigated by a test. Computer simulation is also carried out to study the response of contactor to voltage sags.