Comparative Analysis of Wound-Field Flux-Switching Machines with Different Field and Armature Winding Configurations

Wound-field flux-switching (WFFS) machines have both field and armature windings in the stator, eliminating the need for permanent magnets in the rotor. This leads to a simple and robust electric machine design with variable flux operation capability. However, it is important to note that these two sets of windings (i.e., field and armature) need to be optimally placed within the limited stator geometry to maximize the power density and cooling capability. Since there are two amenable winding configurations (i.e., circumferential and toroidal) for the two winding sets, it will naturally generate a two-by-two matrix with four winding configurations for the WFFS machines. This paper will explore all four possible combinations of the field and armature windings to find the optimal WFFS machine design compared to a conventional permanent magnet flux-switching machine with an identical stack length and outer diameter. The electromagnetic performances, including flux linkage, back-emf, rated torque, and cogging torque, are analyzed and compared by 2D finite element analysis. The advantages and disadvantages of all the WFFS machine types are summarized considering cooling capability, power density, and manufacturing complexity.