Synthesis of Consequent Pole Vernier Permanent Magnet Machine Based on Oscillating Magnetic Potential Difference Model

In recent years, consequent pole vernier permanent magnet machine (CPVPMM) has been found higher torque capability and less magnet usage compared to the surface-mounted counterpart, i.e., surface-mounted VPMM (SVPMM), thus attracting extensive interests. Meanwhile, the theoretical basis of CPVPMM is not well-established because of its unconventional PM arrangement. Due to the simplified dual-salient permeance model widely adopted in CPVPMM, the misinterpretation in the time–space distribution of magnetizing magnetomotive force (MMF) and air-gap permeance leads to deviated sizing equations, which hinders the development of CPVPMM. This article proposes a new analytical model, i.e., the magnetic potential difference between the stator core and rotor surface, based on the modified dual-salient permeance and the resultant improved MMF. Via the proposed model, a new analytical derivation featuring precise calculation of air-gap flux density is obtained to clarify the working mechanism of CPVPMM and give helpful design hints to fulfill high torque density. For the first time, it is identified the phenomenon of potential difference oscillation and additional harmonic exists in both CPVPMM and SVPMM. The influence of potential difference oscillation on working flux density is quantitatively analyzed, which reveals the operating principle of CPVPMM and also unveils the underlying torque improvement mechanism over SVPMM, which gives new insight into enhancing torque of vernier machines. Finally, the analytical and FEA results are validated by experiments.