The Effect of Broken Rotor Bar on the Low Frequency Components in the Axial Stray Flux of Induction Motors

The flux radiates out of the frame can be detected in the vicinity of operating motors. Spectrums of the external flux for induction machines are rich in harmonics and they are not quite the same as current spectrum. This paper gives new explanations and analysis for the slip frequency component in the axial stray flux spectrum. Experimental validation is performed. The whole broken bar is removed from the sample rotor to avoid inter-bar current. The axial stray flux spectrum for a dynamic eccentricity sample is compared with the broken bar sample and a healthy sample. The experiment results confirmed the analysis that broken rotor bar is the main cause of the slip frequency component in the axial stray flux rather than dynamic eccentricity regardless the presence of inter-bar current.