Line-connected permanent magnet generator with adjustable excitation for variable-frequency AC aircraft power systems

Although permanent magnet synchronous machines are often a favored option for aerospace applications due to their high-power density and high efficiency, they almost always need to operate in conjunction with power electronics inverters in order to realize the desired power quality over a wide range of speeds and loads. The presence of these inverters leads to concerns of system complexity, reliability and overall system-level power density. This paper proposes a directly line-connected permanent magnet generator with adjustable field excitation for variable-frequency AC aircraft power systems. The voltage regulation at various load and speed conditions is achieved by controlling the space off between a pair of flux shorting endplates and the rotor core. The proposed topology is shown to be capable of meeting the speed regulation, load regulation and power quality requirements set in MIL-STD-704 for a representative power rating, by a combination of aspect ratio adjustment, winding short pitching, asymmetric rotor pole shaping, stator tooth shaping, and geometry parameter global optimization. Compared to the conventional permanent magnet generator in tandem with inverters, the proposed line-connected permanent magnet generator with adjustable excitation has the potential to eliminate the complexity and reliability concerns over power electronics inverters.