A wide-speed-range hybrid variable-reluctance/permanent-magnet generator for future embedded aircraft generation systems

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 3000-36000-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.