Sensitivity of rotor slot harmonics due to inter-turn fault in induction motors through vibration analysis

Apart from bearing failures, induction motors are often subjected to stator winding faults as they are subjected to high mechanical, thermal, electrical stresses and also due to hostile environmental conditions etc. Current monitoring is the mostly used technique for identification of incipient level of inter-turn short faults in induction motors. Few works are also available in literature about vibration analysis of inter-turn fault motors. In vibration monitoring authors have majorly focused on the fundamental rotational and supply harmonics hardly up to four. It is not ideal to judge whether the rise in vibration amplitudes at these harmonics are due to electrical faults such as voltage unbalance, air gap eccentricity, bowed rotor, inter-turn faults or due to mechanical faults such as misalignment, looseness, weak base etc. So, there is a need for further studies in vibration analysis of motors under inter-turn fault. Experimental investigations have been performed to study the effect of inter-turn fault on rotor slot harmonic amplitudes. From the experiments, it is clear that inter-turn fault also results in increase of vibration amplitudes at rotor slot harmonics.