Broken bar detection in induction motors - using non intrusive torque estimation techniques

One of the most important issues when implementing control and fault diagnosis systems for induction motor drives is obtaining accurate information about the state of certain motor electromagnetic signals such as stator flux and electromagnetic torque. This paper examines the detection of rotor imperfections through spectral analysis of the electromagnetic torque, computed by three stator flux estimators, and using only non-invasive sensors such as current and voltage sensors. The variable structure observer, the extended Luenberger observer (ELO) and extended Kalman filter (EKF) are used to estimate flux components without resorting to the use of intrusive speed sensors. The aim of this paper is to make a comparison and a classification between these approaches. Experimental results demonstrate the significant potential of these methods in detecting these types of faults.