A Novel Control-Independent Online Fault Diagnosis of Inter-turn Short Circuits in SRMs using Signal Injection Technique

Abstract

Most of the existing diagnosis techniques for inter-turn short circuits (ITSC) in switched reluctance motors (SRMs) suffers from three major issues. Firstly, the problem of lower sensitivity where the system cannot detect ITSC if a lower number of turns are short-circuited. Secondly, interference of load variation on the detection reliability in which the fault index might initiate false alarm without any fault. And lastly, the dependency of the diagnosis system on the control strategy on which the motor is operating. This paper proposes a novel method to diagnose ITSC in SRMs independent of control schemes with better sensitivity and reliability using signal injection technique. In SRM, not all the phases take part in the torque production at any instant. The idle or inactive phase is injected with a high-frequency (HF) voltage signal for a pre-selected injection ratio within an electrical cycle. Any change in the winding parameters owing to ITSC fault is deciphered by monitoring the high-frequency currents generated in the phase windings. The results are validated experimentally for a four-phase 8/6 SRM employing two control strategies: chopped current control (CCC) and angle position control (APC).