A New Staggered Dual Stator Field Modulation Machine with O-Shape Permanent Magnet Excitation

The paper proposes a new staggered dual stator field modulation machine with O-shape permanent magnet (PM) excitation (OPM-SDSFMM), which can provide high quality torque production. The O-shape PM excitation in rotor is composed of two radially magnetized PMs and two tangentially magnetized PMs, which offers high sinusoidal air-gap magnetic field with high flux density. The inner stator is rotated along shaft to a position that the angle between central lines of teeth of the inner and outer stators is 15 degrees to form staggered dual stator structure, which can reduce the flux leakage and increase output torque production effectively. To verify the advantages of the proposed OPM-SDSFMM, two designed machines with bilateral PM excitation and with aligned dual stator structure, respectively, are presented and analyzed. The topology, operating principle and key design parameters of proposed OPM-SDSFMM are clarified. The electromagnetic performances, such as back electromotive force (back-EMF) and torque characteristics, are calculated using finite-element analysis (FEA). The FEA-predicted results show that the proposed OPM-SDSFMM is a desirable choice for direct-drive applications because of high back-EMF amplitude and high torque production with low torque ripple.