| Summary: | This thesis compares the performance of 5- and 3-phase PM generators connected to a diode bridge rectifier under normal and open-circuit failure conditions. Also it describes the design of 5- and 3-phase prototype PM generators with the same volume and rated speed. The permanent magnet generator has advantages such as: simple construction, no excitation field winding, low maintenance cost. The advantages of using diode bridge rectifiers are simplicity and cost. A simulation model is developed for 5- and 3-phase systems that includes the generator self- and mutual-inductance and phase resistance. The developed model demonstrates the effect that both self- and mutual-inductance have on the 5-phase system including an important reduction in the shaft torque ripple. The 5-phase system displays considerably lower peak-to-peak shaft torque ripple compared to three-phase system. Also it is shown that the five-phase system can use a lower value of capacitance for the same output voltage ripple. In addition, the 5-phase system requires diodes with lower current ratings compared to the 3-phase system. The operation and performance of the 5- and 3-phase systems under open-circuit phase failure is assessed and discussed. It is shown that in terms of shaft torque ripple the 5-phase system has a performance superior to the 3-phase system. With two open-circuit phase failures, the 5-phase system has adjacent and non-adjacent open-circuit failure modes. Non-adjacent failures are shown to produce a less extreme operating condition compared to adjacent phase failures in terms of torque ripple and dc output voltage ripple. The rms current in the dc link capacitor is discussed for the 5-phase and 3-phase systems under normal and failure conditions. If, under normal conditions, the capacitor is specified to give the same output voltage ripple in the 5- and 3-phase system, then during open-circuit failure, the 5-phase system displays a larger per-unit increase in rms current in the dc link capacitor compared to the 3-phase system. For systems making use of the fault tolerance of the 5-phase generator, the specification of the dc link capacitor becomes driven by the rms current during the fault. Simulation and FEA results are verified by experiments on practical 5- and 3-phase prototype generators. Good agreement is observed.
|
|---|
