Flux-Regulation Theories and Principles of Hybrid-Excited Flux-Switching Machines

A hybrid-excited flux-switching (HEFS) machine was proposed by reducing the permanent-magnet (PM) length of an original flux-switching PM machine and introducing a set of field windings into the saved space. According to the PM locations, three typical topologies of HEFS machines emerged, namely, PM-Top, PM-Bottom, and PM-Middle, respectively. The preliminary analysis indicates that different configurations of magnets and field windings have significant influences on the electromagnetic performance of HEFS machines. Hence, this paper is focused on the flux-regulation theories and principles of the three topologies of HEFS machines employing two typical magnet materials, namely, ferrite, and NdFeB, respectively. It is found that the field winding in the PM-Top machine exhibits reversal flux-regulation functions to that in the PM-Bottom one. The weakest flux-regulation capability is found in the PM-Middle one, since this can be considered as a combination of PM-Top and PM-Bottom ones. Overall, the highest magnet utilization and a strongest flux-regulation capability are exhibited in the PM-Bottom HEFS machine. The theoretical analysis is validated by both 2-D finite-element analysis-based predictions and experimental measurements on three prototype HEFS machines.