Analysis and Fault Tolerant Control of a Five-Phase Axial Flux Permanent Magnet Synchronous Machine

2021-9-06
Bayazıt, Göksenin Hande
This study investigates the fault-tolerance capability of an air-cored, axial flux, five-phase permanent magnet synchronous machine. The air-cored stator is designed by adopting a novel winding topology that is called flat winding. The coils of flat winding are made by bending and grouping one within another of the flat wires made of a laser-cut thin aluminum sheet. This topology provides superior current ratings, better cooling performance, and a robust structure for the stator. As the coils are covered with epoxy resin afterward, inter-turn short circuit risk, which is the most common stator fault in electrical machines, is completely eliminated. Therefore, in this study, the main focus is the analysis and mitigation of winding open-circuit fault. Another advantage of the proposed topology is its multiphase structure. The phase number, which is five, is chosen as an optimum point between minimum over-rating of phase currents in fault mitigation operation and the overall system complexity. In the scope of this study, the design of a five-phase winding structure, analysis of the sizing of the 1.4 kW, 26 Nm, 525 RPM machine are made. Analytical models for both healthy five-phase and open-circuit faulted four-phase machines are derived, and the simulation models for these drive operations are developed. Open-circuit fault mitigation strategies are investigated, and reduced-order Clarke transformation matrix method without third-order harmonic injection is adopted. On top of that, these analytical models and simulations are verified experimentally on the manufactured prototype. Closed-loop speed control is performed for normal and faulted operation modes with standard field-oriented control, using conventional PI controllers. Finally, it is concluded that the machine is advantageous for its robust structure, low electrical time constant. Still, niche measurement, acquisition devices and driver are necessary due to the air-cored machine’s low phase inductance.

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Citation Formats
G. H. Bayazıt, “Analysis and Fault Tolerant Control of a Five-Phase Axial Flux Permanent Magnet Synchronous Machine,” M.S. - Master of Science, Middle East Technical University, 2021.