On-line monitoring and diagnosis of broken rotor bars in induction motor

The monitoring and the diagnosis of the defects in induction motors starting from the stator current are very interesting, since it is an accessible and measurable quantity. The spectral analysis of the stator current makes it possible to highlight the characteristic frequencies of the defects but in a wide frequency range depending on half the sampling frequency, making it very difficult to monitor on-line the defects. In order to facilitate the use of the relevant frequencies of the breaking-bar defect we proposed the extraction of the frequency components using two methods, namely, the amplitude and the instantaneous frequency. The theoretical bases of these methods were presented and the results were validated on a test bench with an induction motor of 5.5 kW.