An Experimental Investigation on Broken Rotor Bar in Three Phase Induction Motor by Vibration Signature Analysis using MEMS Accelerometer

Three phase Squirrel Cage Induction Motors (SCIM) are continuously subjected to electrical, thermal, mechanical and environmental stresses in any industrial application. Such stresses can result in rotor bar damage. Due to such faults an unsymmetrical magnetic field will be setup and can lead to reduction in developed torque, increase in speed fluctuations, noise and vibrations. The present work utilizes the motor vibrations as a medium to detect and diagnose the broken rotor bars under no load and on load condition by using state-of-the-art, MMA6270QT MEMS accelerometer. Spectral analysis of motor vibration signals by using FFT analysis yields twice slip frequency components (1±2ks).fs around fundamental frequency and 2sfs frequency component in low frequency range which indicates rotor bar damage fault. A simple method has been proposed to compute severity of fault by comparing the magnitude average of side band harmonic frequency with fundamental frequency component. Experimental results have demonstrated the effectiveness of the proposed technique.