Open-circuit fault analysis of diode rectified multiphase synchronous generators for DC aircraft power systems

The more-electric concept is becoming prevalent in all modes of transport, particularly civil aerospace where significant savings on fuel and improved efficiency can be achieved through the use of electrical power systems. Increased electrical loading for in-flight cabin air conditioning, galley services and entertainment systems has led to a re-evaluation of aircraft architecture. DC electrical networks offer the opportunity to decouple the frequency of generated supply from the speed of the gas turbine engine, enabling the independent optimisation of both systems. Using generator-rectifier systems with a higher phase number upholds the safety critical nature of air transport whilst also allowing for a reduction in DC voltage ripple and reducing or eliminating the need for filter capacitance. A multiphase generator has built-in redundancy, offering the potential for continued operation with an open-circuit winding or diode fault, but with implications on the rating and DC power quality. This paper provides analysis, simulation and experimental validation of a reconfigurable, wound-field multiphase synchronous generator connected to a diode rectifier under open-circuit fault conditions for two winding configurations, star and delta.