Investigation of a Magnetic-Field Modulated Brushless Double-Rotor Machine with the Same Polarity of PM Rotor

Aiming at the problem of large permanent magnet (PM) loss in traditional magnetic-field modulated brushless double-rotor machines (MFM-BDRMs), an MFM-BDRM with the same polarity of PM rotor is proposed, which can reduce PM loss, save PM material, improve the mechanical strength of PM rotor, and still keep good electromagnetic performance. First, the magnetic field distribution in the air gap, the back electromotive force, the inductance parameters, and torque performance of the proposed MFM-BDRM are investigated. To obtain the optimum design scheme, the design rule of main parameters, such as the pole-arc coefficient and thickness of PMs, the span ratio, and thickness of magnetic blocks, are investigated. On this basis, a detailed design procedure of the proposed MFM-BDRM is further provided. Finally, to evaluate the overall performance of this new MFM-BDRM, a traditional MFM-BDRM with the same size is designed to compare their performances.