Statistical analysis on a case study of load effect on PSD technique for induction motor broken rotor bar fault detection

Broken rotor bars in an induction motor create asymmetries and result in abnormal amplitude of the sidebands around the fundamental supply frequency and its harmonics. Monitoring the power spectral density (PSD) amplitudes of the motor currents at these frequencies can be used to detect the existence of broken rotor bar faults. This paper presents a study on an actual three-phase induction motor using the PSD analysis as a broken rotor bar fault detection technique. The distributions of PSD amplitudes of experimental healthy and faulty motor data sets at these specific frequencies are analyzed statistically under different load conditions. Results indicate that statistically significant conclusions on broken rotor bar detection can vary significantly under different load conditions and under different inspected frequencies. Detection performance in terms of the variation of PSD amplitudes is also investigated as a case study.