Observer-based fault detection in induction machines

In this paper, we present a methodology for the design of the rotor flux observer for induction motors and its applications to fault detection. We start with the well-known α-β model of induction motors. We employ a change of coordinates to transform the fifth order α-β model to a third order model expressed in terms of complex differential equations. After that, an inverse transformation is used to revert back to the original coordinates. Moreover, we use the designed observer in order to detect some faults arising in the induction motor. By doing so, a proper fault monitoring system is realised. We consider mainly the effects of voltage sag, stator inter-turn short-circuit and broken rotor bar faults that usually arise in induction motors. The validity of the proposed approach is verified with results from simulation of the model of the induction motor.