Comparative Study of Flux-Switching PM and EE Machines with Dual Armature Winding Configuration

Flux-switching electrically excited (FSEE) machines offer appealing advantages, including low cost, no risk of demagnetization, and good flux regulation capability. Nonetheless, they typically exhibit much lower torque density compared with flux-switching permanent magnet (FSPM) machines. To overcome this limitation, FSEE machines with dual armature (DA) windings wounded on both stator and rotor teeth are proposed by full utilization of rotor space. It is found that increasing field current is not effective to enhance torque output for both the FSEE and DA-FSEE machines, because it deteriorates flux leakage for the stator armature winding. In contrast, the rotor side of the DA-FSEE machine generates relatively large torque per unit loss. As unique for DA-FSEE machines, the strong interaction between the two sets of armature windings entails an optimal combination of stator and rotor armature current phase angles for high torque output, whereas the Id=O control is optimal for FSEE and DA-FSPM machines. The final results show that the DA-FSEE machine can generate up to 75% more torque than the FSEE machine.