Axial-Flux Hybrid-Excitation Synchronous Machine: Analysis, Design, and Experimental Evaluation

This paper presents an axial-flux machine with hybrid excitation (HE), in which the flux linkage can be regulated in an extremely wide range by using a rotating excitation winding. This machine shows a theoretically infinite constant power speed range and also exhibits a high degree of fault tolerance against uncontrolled generator operation. The machine has a single-stator double-rotor topology, with one rotor mounting permanent magnets and the other supporting the excitation winding. After a review of the state of the art of HE machines, this paper examines the principle of operation of this machine. Subsequently, a prototype is designed, analyzed with finite-element analysis, and built. Finally, experimental results are reported to confirm the theoretical predictions and the benefits and drawbacks of this novel topology.