This article presents condition monitoring of induction machine to detect the existence of broken rotor bar failurein it. Wavelet packet signature analysis is developed under no-load conditions. Signatures of fault are extracted through the combination of wavelet packet transform and FFT which is named wavelet packet signature analysis. Next step to extract the most relevant feature is the definition of mother wavelet function. To cover this aim, the standard deviation of wavelet packet coefficients is used. To alleviate the time-variant characteristics of the wavelet packet coefficients, statistical parameters in specified level and nodes are calculated as essential fault indices. The method is tested using fault-free and faulty induction motors. Applying the method presented, one, two, and three broken rotor bars are detected under no-load conditions
