A Novel Diagnosis Method for Interturn Short-Circuits in SRMs by Tracking Post Turn-Off Phase Currents Under Current Chopping Control
Mahetab Alam, Nikhil Gugulothu, Saifullah Payami
Abstract
Current chopping control (CCC) is widely preferred for low- and medium-speed applications in switched reluctance motor drives. With precise current regulation, the consequence of interturn short-circuits (ITSCs) is not reflected much in the faulty phase current. Also, the fault features are difficult to extract in the online mode for minor short-circuits (SCs). Moreover, ITSCs are responsible for hotspots in the defective winding, ultimately leading to a complete winding short-circuit due to persisting heating effect. Even the associated complications of switched reluctance motor (SRMs) such as torque ripple, noise, and vibrations are amplified to a greater extent under ITSCs. Therefore, diagnosing ITSCs is critical to shun such unwanted characteristics and failures. This article proposes a simple and novel method to diagnose ITSCs even with minor SCs in SRMs operating under CCC. With the reduction in the inductance due to ITSCs, the decay time of the faulty phase current post turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> also reduces. This variation is monitored for all the phase currents within their respective aligned rotor positions to diagnose ITSC. The proposed method has better detection reliability regarding diagnosis under varying load conditions. The scheme is validated experimentally on a test setup of a customized four-phase SRM having winding taps for emulating ITSCs.