Misalignment and rotor fault severity indicators based on the transient DWT analysis of stray flux signals

Recent investigations have assessed the validity of stray flux analysis under starting as a way to diagnose several types of faults in induction motors. In these recent works, it was proven that the time-frequency analyses of the electromotive force (EMF) signals induced in external coil sensors attached to the motor frame enables to track the transient evolutions of characteristic components introduced by the different faults. These evolutions can be used as reliable evidences of the presence of these faults. This work goes beyond the current works regarding transient analysis of the stray-flux by proposing different fault severity indicators based on the Discrete Wavelet Transform (DWT) analysis of transient EMF signals. Several DWT indicators are proposed and properly evaluated considering different types of faults as well as different positions of the considered flux sensor. The results show how the proposed starting-based indicators can be useful in order to set future threshold values based on the starting flux analysis that enables to determine the severity of the corresponding fault in the motor.