A Threshold-Based Stator Inter-Turn Fault Diagnosis for Induction Motors Using the Negative Sequence Current’s Magnitude and Phase Angle

This article introduces a novel threshold-based stator inter-turn fault (SITF) detection and faulty phase identification method for induction motors (IMs) through the negative sequence stator current analysis, where the negative sequence current magnitude level (NCL) is used for SITF detection, and the negative sequence current’s phase angle ( $\measuredangle {I}_{2}$ ) is used for the faulty phase identification. Through the systematic experimental investigation of NCL’s behavior under various unbalanced voltage conditions (0.1%–1.7%), a detection threshold (ThSITF) of NCL equal to 10% is established. Three angular zones for $\measuredangle {I}_{2}$ are defined for the faulty phase identification: ±60° for Phase A, 60°–180° for Phase B, and 180°–300° for Phase C. Experimental validations on a 2.2-kW IM demonstrate accurate SITFs detection across different fault severities and motor loading levels using the proposed method. Extensive testing results for six SITFs with 2, 3, 5, 10, 13, and 15 shorted turns at Phase B reveal a linear correlation between the fault severity and NCL. The proposed method remains effective for variable frequency drive (VFD)-fed IMs, showing enhanced sensitivities at a higher frequency.