Quasi-steady state characterization of induction machine behavior under voltage sag and momentary interruption conditions

Induction motors are susceptible to stalling under voltage sag or momentary interruption conditions. This situation may result in havoc in industries such as steel milling. The present paper presents a methodology for characterizing the performance of induction motors under voltage sag and momentary interruption conditions. The method neglects the dynamics of the electrical circuit of the induction motor. It utilizes the steady state model for the analysis. The concept of the critical duration, or the critical time, of the power quality condition-whether a voltage sag or a momentary interruption-beyond which the machine stalls, is introduced is established. This critical time is a direct function of many parameters, e.g., the machine loading, the voltage sag depth, etc. This critical time is the maximum fault duration allowed if induction motor stalling is to be avoided.