Novel stator electrically field excited synchronous machines without rare-earth magnet

This paper systematically presents the development of novel stator electrically field excited synchronous machines having salient pole rotors without any coils or magnets. This kind of new machines does not use slip-rings/brushes required in the conventional rotor wound field machines and combines the synergies of wound field machines, permanent magnet machines, switched reluctance and synchronous reluctance machines. The paper describes the machine topologies, winding configurations, electromagnetic performance, torque/power density, and efficiency, as well as acoustic noise and vibration, together with a comparison with Toyota Prius interior permanent magnet machines in terms of torque/power speed characteristics and efficiency.