Magnetic Flux Path and Inductance Analysis of Flux-Switching Machines with Different Field and Armature Winding Configurations

Wound-field flux-switching machines (WFFSMs) have both field and armature windings in the stator eliminating permanent magnets in the rotor for a simple and robust machine design. These two windings need to be optimally placed within the limited stator to maximize the power density and thermal performance. However, the field winding introduces additional magnetic flux paths through stator bridges leading to an inefficient and longer flux path and reduced torque density. Therefore, WFFSMs require in-depth magnetic flux analysis depending on the different winding configurations and rotor design. This paper investigates the magnetic flux path of WFFSMs with different winding configurations in comparison with a conventional flux-switching permanent magnet machine having an identical geometry. The energy conversion loop analysis is conducted to visualize and quantify the impact of the longer magnetic flux paths. Using the finite element method (FEM), incremental (dynamic) inductances are calculated considering saturation and cross-coupling effects. The behavior of dq-inductances of both FSPM and WFFS machines are comprehensively studied and compared. To reduce the adverse impact of the longer magnetic flux, a rotor tooth width optimization is conducted.