Design and experimental verification of hybrid excitation magnetic field modulation machine for electric vehicle propulsion

As one sort of flux modulation machine based on magnetic gear effect, field-modulated machine features with low speed large torque. A novel hybrid excitation field-modulated machine (HEFMM) is proposed by introducing the concept of hybrid excitation, the flux modulation poles (FMPs) and excitation winding of which are emplaced in stator teeth and the adjacent FMPs. It can be maintained wide speed range operation through the processes of flux-enhancing and flux-weakening with no increasing machine bulk, as well as the numbers of stator and rotor slot. The working principle of proposed machine is deeply studied, as well as basic electromagnetic characteristics are calculated by finite element method, including no-load magnetic flux linkage, no-load back electromotive force, cogging torque and output torque. In addition, the processes of flux-enhancing and flux-weakening are analyzed. Finally, one prototype with one kilowatt was built and its static characteristics were tested. The results show that the proposed HEFMM has the features of high torque density, small cogging torque and wide speed range, which is promising candidate for electric vehicle direct drive field.