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This paper considers the operation and control of a brushless ac prototype embedded aircraft generator that has been designed for use as an alternative to the emergency run air turbine. To meet the wide operating speed requirements, the generator utilizes a hybrid rotor construction comprising permanent magnet and variable reluctance sections. The constant current source characteristics of the design are exploited to derive the phase information required by the ac vector controller, thus avoiding the use of a shaft-mounted rotor position sensor. The methodology behind the controller operation is presented together with test results taken from a prototype generator system, and this is contrast with the results taken from the conventionally controlled machine with resolver position feedback. Index Terms--Embedded aircraft generation, hybrid permanent-magnet (PM)/variable reluctance machines, power factor control, sensorless control.

This paper presents recent research into the use of an embedded generation system as an alternative to the emergency ram air turbine on aircraft, the proposal being to utilize the windmill effect of the low-pressure turbine of the main aircraft engine for emergency power generation. A novel topology of a high specific output ac permanent-magnet generator is described that has been designed to be driven directly from the low-pressure turbine via an integral fixed-ratio gearbox, the requirement being to generate a regulated 270-V dc 0-20-kW emergency supply over a 12 : 1 3000-36 000-r/min generator shaft speed range. The methodologies behind the machine design and operation are described together with test results taken from a prototype generator system. Index Terms--Embedded aircraft generation, high-speed permanent-magnet (PM) generators, hybrid PM/variable-reluctance (VR) machines.