Bar breakage mechanism and prognosis in an induction motor

In recent years several methods have been proposed in order to detect broken bars in the cage of induction motors, yielding the necessity of testing their performance in different conditions and their thresholds in assessing incipient cage damage. This paper presents the first results of a fatigue test designed to produce in the most natural way the breakage of a bar in order to determine the effectiveness of different motor current signature analysis. The high accuracy of the transient methods based on the study of the startup current, allows proposing some physical models of the breakage with the aim of establishing the remaining life of the induction motor, once the incipient defect has been detected.