Induction Machine Broken Bars Fault Detection Using Stray Flux after Supply Disconnection

The aim of this paper is to present a new approach to detect broken bars fault in squirrel-cage induction machine. This approach is based on the study of stray flux signal after the supply disconnection. This type of test is useful especially for the maintenance purpose when it is possible to remove the load and supply effects. In this case, the current in rotor side decrease by its time constant and the spectrum induced in a search coil around the induction machine is analyzed with a time-frequency method allowing the rotor faults detection. The broken rotor bar effect is analyzed in the induced stator voltage spectrum too, but the experimental results show that its sensitivity is weak with respect to the given by the search coil induced voltage spectrum