Discriminating broken rotor bar from oscillating load effects using the instantaneous active and reactive powers

A new strategy for detection and diagnosis of broken bars and load oscillations is proposed. The proposed technique is based on the analysis of the instantaneous active and reactive powers spectra, and allows the correct distinction between broken rotor bars and low-frequency load oscillations. A suitable fault severity factor is also proposed, which allows the broken rotor bar fault quantification, while being practically independent of the motor load. By using the proposed technique, a broken bar fault can be detected and diagnosed, even in the presence of load oscillations at frequencies next to twice the slip frequency. Extensive experimental results, both from laboratory and industrial cases, validate the proposal.