Analysis of Open Phase and Phase-to-Phase Short Circuit Fault of PMSM for Electrical Propulsion in an eVTOL

This paper analyzes permanent magnet synchronous machines (PMSM) under open phase and phase-to-phase fault conditions within an electric vertical take-off and landing (eVTOL) aircraft. The development of a detailed mathematical model for a PMSM under the open phase fault (OPF) and phaseto-phase short circuit fault (P2PSCF) conditions are presented and implemented in MATLAB/Simulink along with its results within a ring bus electrical distribution system (REDS) for an eVTOL is presented. The behavior of both faults is investigated. Fault-tolerant control (FTC) is applied during the post-fault operation, and the copper losses and torque ripple are analyzed. Two fault mitigation techniques, 1) disabling the inverter (FTC1) and 2) creating a virtual neutral point (FTC2) with the inverter, are introduced for the P2PSCF. FTC1 had a peak-to-peak torque ripple of 309Nm with 1.55kW reduction of copper losses. FTC2 was found to respond faster than FTC1 and generated 157Nm peak-to-peak torque ripple. The OPF FTC was analyzed where only current references are changed for the same PI controller structure to enable a fail-operational state for the eVTOL. The OPF FTC achieved 348Nm peak to peak torque ripple compared to 371Nm to pre-fault conditions.