Diagnosis of Interturn Short-Circuits in SRMs by High-Frequency Switching of Phases Amid Low-Torque Unaligned Rotor Positions

Abstract

The inherent problems of torque ripple, noise and vibrations associated with switched reluctance motors (SRMs) are escalated when the machine is subjected to inter-turn short-circuits (ITSCs). Also, leaving it unchecked can ultimately lead to a complete winding short-circuit due to the insulation failure owing to the heat produced by locally generated hotspots. To avoid such ruinous damage, the diagnosis of ITSCs is very critical. This article proposes a method of diagnosing ITSCs by injecting high-frequency signals in the phases in their low torque regions around unaligned rotor positions. The proposed method utilizes the drive power converter to inject and diagnose the ITSCs and thus requires no additional hardware. It has a higher sensitivity even toward minor fault conditions, i.e., as low as ITSC of 4 turns ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \approx$</tex-math></inline-formula> 4% ITSC over a phase). The devised fault indicator is immune to load or speed variation and, hence, better detection reliability. Also, the method can diagnose the fault under load and speed transients proving it to be more robust. Experiments are performed on a test rig of customized 8/6 SRM emulating the ITSCs to verify the potency of the proposed scheme.