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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.

This paper studies fault-tolerant operation of multipole single-phase switched reluctance generators (SRG's), in particular, an 8/8-pole switched reluctance machine. The multipole single-phase SRG system is advantageous for reduced cost and higher efficiency compared to polyphase equivalents. However, using the classical phase-leg topology, a phase fault may prevent generating operation completely, since redundancy in the number of phases does not exist like polyphase systems. A new converter topology which connects two coil banks in parallel is proposed for higher fault tolerance with minimum additional cost. Faulty coils can be disconnected with the proposed converter and the SRG can continue generating operation after coil faults with reduced output power. Output power per coil current under faults is studied. Open- and short-circuit coils are studied through linear analysis, finite-element analysis, and static torque measurement. Generated currents under faults with the proposed converter are measured. The capability of the system to disconnect faulty coils dynamically is also shown. Index Terms - Fault tolerant, single-phase multipole machine, split-winding converter, switched reluctance generator.

This paper studies operation of the multipole single-phase switched reluctance generator (SRG) under faults, in particular an 8/8-pole switched reluctance machine. A new converter topology which connects coils two banks in parallel is proposed. The combination of multiple coils per phase and the converter circuit suggests improved operation under faults compared with conventional topologies. Output power per coil current under faults is studied by finite-element analysis and static torque measurement. Circuit equations under faults are derived and operation under faults is evaluated by simulation. An SRG controller is constructed and experiments are performed. The experimental results support the equations and simulation results. It is concluded that the SRG can continue generating operation, even when open- or short-circuited coil faults occur, with the proposed converter and proper fault detection circuits. Index Terms - Faults, single-phase multipole machine, split-winding converter, switched reluctance generator.