Online fault detection of stator winding faults in IM driven by DTC using the off-diagonal term of the symmetrical component impedance matrix

In this paper an in-service non-intrusive stator winding inter-turn fault detector (FD) for an inverter-fed induction machine (IM) is proposed. The FD is based on the computation of the off-diagonal term of the sequence components (SCs) impedance matrix. This technique was proven efficaciously for direct on-line (DOL) IM, as it deciphers its abnormal impedance behavior with neither additional hardware nor IM parameter's knowledge. Additionally, the FD technique is immune to sensor errors. The hypothesis of this article is that the offdiagonal sequence impedance is not affected by the Direct Torque Control (DTC) and therefore, the contribution of this article is the adaptation of the FD to an inverter-fed IM under DTC. Simulation reinforced by experimental results demonstrated the correctness of the hypothesis, as well as the robustness of the FD method for closed-loop controlled IM, against other detectors used in DOL IM, where their signatures are hidden by the controller.