Effects of load conditions on rotor eddy current loss in modular permanent magnet machines

The paper describes an investigation into rotor magnet eddy current losses in modular machines within the context of a 250kW, 5-phase fault-tolerant permanent magnet generator for a “more-electric” aero engine. It is shown that the interaction of the rotor permanent magnets and stator slotting results in dominant space harmonics having the same pole-pairs and frequencies as those generated by the stator mmf, with their interactions resulting in on-load rotor eddy current being lower than no-load eddy current loss.