Investigation of an Integrated Magnetic-Field-Modulated Brushless Double-Rotor Machine With an Improved PM Rotor

The integrated magnetic-field-modulated brushless double-rotor machine (IMFM-BDRM) can be a promising candidate for the electrical-continuously variable transmission (e-CVT) in hybrid electric vehicles (HEVs) due to its brushless and compact structure. However, the large permanent-magnet (PM) eddy current loss and the conflict between torque density and mechanical strength limit its application. In this article, an IMFM-BDRM with an improved PM rotor is proposed to solve those problems. First, the structure of the proposed machine is introduced, and the magnetic field modulation mechanism is analyzed by the magnetic circuit method. The research shows that the modulated magnetic fields in the proposed IMFM-BDRM are produced mainly because of the variation in the flux paths, which is quite different from that in the traditional IMFM-BDRMs. Second, the electromagnetic performances are analyzed by the finite-element method. The effects of the structure parameters of the two rotors on torque performance are further investigated. Finally, to evaluate the overall performance of the proposed IMFM-BDRM, a traditional IMFM-BDRM with the same stator is designed to compare their performances. The comparison results show that the proposed machine has more advantages of output torque, PM loss, and efficiency than the traditional IMFM-BDRM.