Iron loss in a modular rotor switched reluctance machine for the ´more-electric´ aero-engine

The only means of satisfying the electrical power requirements of ´more-electric´ aircraft is to integrate electrical machines within the engines. Given the harsh environment in terms of the ambient temperature and rotational speed, a switched reluctance machine is likely to be favoured for the high-pressure spool. Given the space envelope constraints, a high pole number machine is required. However, the diameter of a conventional SR rotor is limited by the hoop stress in the laminations. This paper presents the proposed modular motor that enables the diameter to be increased by ∼20% for the same mechanical stress. Unlike the conventional SR machine, the stator and rotor poles have the same pitch, the difference in pole number, which is necessary for continuous torque production, being achieved by appropriate spacing of the rotor modules. Further, since the rotor back-iron is not continuous, two phases on adjacent stator teeth must be excited at any instant, which results in short flux paths.