Parallel-path power flows in magnetic-geared permanent magnet machines with sandwiched armature stator

Due to the large torque density of magnetic gears(MGs), magnetic-geared permanent magnet machines(MGPMs) have become promising competitors in the family of direct-drive machines. According to the deployment of armature stators, MGPMs can be generally classified into three types, viz., MGPM with inner armature stator(MGPM-IAS), MGPM with outer armature stator(MGPM-OAS), and MGPM with sandwiched armature stator(MGPM-SAS). Our investigation finds out that the MGPM-SAS can achieve parallel-path power flows better than the MGPM-OAS, while the MGPM-IAS is with serial power flow paths. Therefore, the torque capability of MGPM-IAS is limited by the torque transmission capability of its integrated MG. However, the MGPM-SAS has the possibility to offer even higher output torque than its integrated MG. This paper focuses on the MGPM-SAS. And three typical MGPMs and their power flow paths are introduced; the interaction of electromagnetic fields in MGPM-SAS is analyzed; simulation calculation and experimental verification are conducted to demonstrate the validity of the theoretical analysis.