A New Permanent Magnet Brushless Double-Rotor Induction Machine

The magnetic-field modulated brushless double-rotor permanent-magnet machine offers a promising electrification solution, potentially replacing traditional mechanical transmissions like the planetary gear set in hybrid power systems. However, it suffers from drawbacks, including uneven air-gap-length distribution, significant leakage, and limited magnetic field conversion capacity, which limits power factor improvement. To address these issues and enhance the power factor and efficiency, this paper proposes a new permanent magnet brushless double-rotor induction machine. The key innovation lies in the introduction of the nested-loop inductor into the permanent magnet double-rotor machine, leveraging the principle of electromagnetic induction rather than magnetic field modulation for the transformation of pole pairs between the permanent magnet and armature magnetic fields. The induced current in the nested-loop inductor generates additional magnetomotive force, substantially improving the magnetic field conversion capacity and consequently achieving a higher power factor compared to the modulating ring. The simulation results by finite element analysis verify the superiority of the proposed machine.