Analytical Model of a Six-Phase PMSM for the Simulation of Stator Winding Faults on Turn Level

The major limitation of the lifetime and reliability of electrical machines are stator winding faults. Inter-turn faults are for that matter often the origin of more severe faults, which can lead to complete system failures. Particularly, three-phase permanent magnet synchronous machines (PMSMs) have significant drawbacks in terms of fault tolerant operation. In comparison, six-phase PMSMs are more complex to analyze and to operate, but for this reason, also offer greater possibilities for the control scheme during fault. This paper presents the first analytical machine model to investigate the behavior of six-phase PMSMs with stator winding faults on turn level. In order to keep the model compact, the levels of abstraction vary within the stator winding circuit. The machine model is acausally implemented, which allows the simulation with current sources and current controlled voltage sources. The simulation results of the presented model are compared with the simulation results of an equivalent finite element analysis model. The average torque differs between the two models in case of an inter-turn fault at nominal load operation by 0.3 %, the amplitude of the fault current differs by 3.3 % and the frequency spectra of the voltages show equal characteristics, while the computation time is 200 times faster with the analytical model. We use the developed model for the analysis of the machine behavior under stator winding faults relevant in practice. With the machine analysis's outcome, we are able to develop a more sophisticated fault management system, which enhances fault tolerant operation in comparison with three-phase PMSMs.