A Novel Stator Wound Field Flux Switching Machine with the Combination of Overlapping Armature Winding and Asymmetric Stator Poles

A novel 24/17-pole 3-phase stator wound field flux switching (SWFFS) machine with the combination of overlapping armature winding (OAW) and asymmetric stator poles (ASP) is proposed for higher torque density in this paper. Firstly, the air-gap modulation principle of the 24/17-pole OAW-SWFFS machine is analyzed to better understand its torque production mechanism. Secondly, since the torque capacity will be greatly restricted due to the serious magnetic saturation introduced by the OAW configuration, two effective measures are proposed from two perspectives in this paper to solve this problem. The first measure is to reduce the magnetic saturation directly by optimizing the area ratio of armature slot and excitation slot and thus the torque density can be improved effectively. The second measure is to further enhance the open circuit flux linkages, back electromotive force (EMF) and thus the torque density by adopting the proposed ASP structure. Furthermore, the accurate ASP distances which are corresponding to the largest back EMF can be obtained effectively based on the air-gap field modulation theory. Finally, the proposed design is validated experimentally by a prototype machine. The simulated and experimental results show that about 25.7% higher torque density can be obtained when compared with 24/14-pole SWFFS machine.