Induction motor cracked rotor bars fault analysis using an improved Root-MUSIC method

The progressive cracking in the squirrel cage rotor bars of induction motors can lead to irreversible damage. For this reason, an early analysis of this type of faults is very necessary. Amongst the existing analysis methods, the Power Spectral Density (PSD) estimation by Periodogram, is considered as a very popular technique and is widely used in industry. However, this technique presents some drawbacks such as, a frequency resolution conditioned by the acquisition time and an identification for low harmonics quasi impossible. To overcome these drawbacks, a proposed method is presented in this paper, known as the Root-MUSIC method. This method used initially in the domain of RADAR for localizing mobile targets, is being applied to the domain of induction motors diagnosis. This method presents a high robustness to measuring noise and a frequency resolution largely superior to classical methods. In addition and in order to reduce the important computation time which is the main drawback of this method, Root-Music will be applied to only a specified frequency band; one that carries information about the sought fault. The obtained experimental results show the effectiveness and the merits of Root-Music and display the proposed improvements for cracked rotor bars fault detection in squirrel cage induction motor.