Method for detecting broken rotor bars in an asynchronous electric motor based on measured phase currents

Abstract

   Violation of the integrity of the rotor bars in the squirrel-cage winding of an asynchronous electric motor is currently the most common rotor defect occurring during motor operation. Running an asynchronous electric motor with such damage can lead to complete failure, as operation with damaged rotor bars may cause them to contact the stator windings. It is noted that during operation, such faults can be identified using spectral analysis methods. However, applying these methods faces challenges in processing the results and detecting broken rotor bars, since any changes in the electrical and mechanical parameters of an asynchronous electric motor introduce modulations in the stator current spectrum. A criterion for detecting broken bars in the squirrel-cage rotor winding of an asynchronous electric motor is proposed, based on the measured instantaneous values of the stator phase currents represented in vector form. The proposed fault detection criterion not only identifies breaks in a group of bars, but also detects damage to a single bar, making the method sensitive enough to diagnose rotor faults without decommissioning the motor. The effectiveness of the proposed criterion for determining broken bars in the squirrel-cage rotor winding is confirmed through mathematical modeling.