Investigation on Magnetic Force of a Flux-Modulated Double-Rotor Permanent Magnet Synchronous Machine for Hybrid Electric Vehicle

Flux-modulated double-rotor (FMDR) machine topology has recently attracted much attention, particularly for the hybrid electric vehicle (HEV) propulsion. To maintain the driving stability and safety of the vehicle, the analysis of the magnetic force and the evaluation of the vibration performance for such kind of machine are indispensable. However, for the FMDR machine with the magnetic-gearing (MG) effect, there are at least two rotating magnetic fields with different speeds and frequencies. This leads to the complicated time harmonics of the radial force density. Actually, the publications on the FMDR machine hardly take into account the magnetic force or vibration characteristics. In this article, the sources, variations, and different kinds of magnetic forces are thoroughly investigated for a proposed FMDR machine. First, the machine topology and operation principle are introduced. Second, the theoretical analysis of the flux density and radial force density is implemented from the harmonic point of view, which is followed by the finite-element simulation, comparison, and validation. Also, an effective solution is proposed and discussed for the problem of different mixed electrical frequencies in the machine. Finally, the distributions of different kinds of magnetic forces appearing in the FMDR machine are concluded.