Dual three Phase Operation of Dual Airgap Permanent Magnet Vernier Machine Having a Yokeless Rotor

In order to increase the speed range of permanent magnet machines in constant power regions, different techniques including multi-phase configurations are usually adopted. This paper presents the dual three-phase operation of a novel dual-airgap permanent magnet vernier machine having a yokeless rotor. The presented machine comprises two stators, each having a three-phase winding, and a sandwiched single yokeless rotor. The outer and inner stator windings are treated as two different sets of three-phase windings to accomplish the dual three-phase operation. To achieve this, three-phase currents are supplied to these winding sets by considering two cases: (i) out-of-phase currents having the same magnitude and (ii) in-phase currents with varying magnitudes. This dual three-phase operation provides better efficiency in the in-phase operation. The presented yokeless model has a very high mutual inductance which improves the flux linkage between two stators. Moreover, the harmonic analysis and open circuit fault analysis are presented to confirm the validity of the presented dual three-phase operation compared to the three-phase operation. 2D-FEM analysis is used to investigate the performance of the presented machine for dual three-phase operation.