A general approach for the analysis and comparison of hybrid synchronous machines with single-axis or bi-axial excitation

.Hybrid Excitation Synchronous Machines allow broad flux regulation, and therefore a very wide Constant Power Speed Range. Literature shows that it is possible to build them both with a Single-Axis and with a Bi-Axial excitation. This paper presents a unified approach for the analysis, comparison and performance prediction of the two structures. Finite element simulation and experimental tests are carried out on a Torus-type Axial-Flux prototype, which - having two rotors, one equipped with PM and one with WE - allows for an easy structure reconfiguration on the same machine.