A study on voltage sag in industry system with adjustable speed drive

The awareness of electric power quality has increased over the past decade as electronic equipment has become more susceptible to power disturbances. The most distruptive power disturbances is voltage sags. Voltage sags produce an important effect on the behavior of adjustable speed drives (ASD's). Tripping of ASD is one of the greatest voltage sag problem, causing motor to stop with the resulting loss of time and production, or damaged equipment may cause significant economical loses. This paper is focused on the effect of voltage sags on adjustable speed drive (ASD) which commonly used in industry system. Voltage sags are normally used described by magnitude variation and unbalanced (asymmetry). These factors are important to determine the behavior of ac motor drive during sags. A VSI (Voltage Source Inverter) driving a three-phase induction motor is analyzed through digital simulation. Simulation on sag depth and three types of voltage sags which are based on voltage sag classification, with an emphasis on the changes dc bridge voltage, rms inverter voltage and motor speed were done. Thus, voltages and speed measurement are obtained. Simulation result clearly show that the different types of sags and sag depth would cause dc-link voltage variation and finally result in motor speed changes.