Diagnosis of Open-circuit Faults in DC-Field Excited Variable Flux Reluctance Machine Utilizing Armature and Field Currents

More electric aircraft has high reliability requirements, and the DC-field excited modular variable flux reluctance machine (MVFRM) is its key component. The MVFRM has both armature and field windings, in which AC (alternating currents) and DC (direct currents) are supplied. Hence, traditional fault diagnosis is not applicable for MVFRM. In this paper, the diagnostic methodology for open-circuit faults in both windings is proposed by utilizing armature currents and field currents. Based on the internal relationship between the armature currents with αβ -axis currents and the field currents, the characteristics and diagnosis mechanisms of armature winding and field winding open-circuit faults are analyzed. The per-unit threshold setting method is adopted to improve the rapidity of the algorithm without reducing robustness. The rapidity and effectiveness of the fault diagnosis algorithm are verified by different types of open-circuit fault diagnosis experiments. Furthermore, the robustness of the fault diagnosis algorithm is verified by the variable speed and different loads of open-circuit fault diagnosis experiments.