Inter-turn short circuit fault diagnosis methods for eVTOL propulsion motor based on back EMF harmonic analysis

The faulty degree assessment and faulty phase detection method of eVTOL propulsion motors Inter-Turn Short-Circuit (ITSC) are proposed in this paper based on the back electromotive force (back EMF) characteristics. A sliding mode observer (SMO) is utilized to dynamically monitor dq -axis back-EMF variations caused by ITSC faults. Faulty severity quantification is performed through second harmonic component analysis, while faulty phase identification is achieved by characterizing residual signals in the abc -axis back-EMF framework. The mathematical relationship between the rotational speed and the faulty degree evaluation indicator is established to overcome the limitation of the traditional method under variable rotational speed conditions, thereby enhancing the engineering applicability of the method is improved. Simulation and experimental results show that the proposed method remains effective under steady-state and variable-speed operating regimes.