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A novel radial flux sensing technique for stator turn fault detection in induction motors in online mode using observer coil

This paper presents a novel radial flux sensing technique to detect and locate stator inter-turn faults in induction motors in online mode. The proposed simplified, inexpensive technique has yet not been reported in literature. The methodology is based on the use of observer coils placed in stator slots along with the stator winding. A sinusoidal voltage is induced in the observer coil (OC) due to the interaction with the stationary stator and the dynamic rotor. The RMS, fundamental, third and total harmonic distortion (THD) analysis of the voltage spectra of the OCs is found to exhibit variations in relation to the severity of inter-turn faults as compared to the healthy condition. The mathematical theory of the technique is provided and supported by an experimental validation. Experiment for confirming the performance of the proposed method was done on 0.746 KW three phase 4 poles 440V squirrel cage induction motor, increasing the fault level in steps from 1% to 15% combined with variations in load from no load to full load.