Analysis of Contra-Rotating Brushless Integrated Flux-Modulation Machine With Open-Slot Structure for Wind Power Generation

This paper presents a contra-rotating (CR) brushless integrated flux-modulation (BIFM) machine with open-slot structure for wind power generation, termed CR-BIFM machine. The presented machine employs two contra-rotating rotors coupled with two sets of wind turbine blades, thus being able to capture more wind energy than conventional single-rotor wind turbines. Due to the dual flux-modulation effect and flux-bridge effect, the presented machine exhibits high torque/power density, making it suitable for direct-drive wind power generation without issues related to mechanical gearboxes. As two sets of windings share the same stator slots in the presented machine, the decoupling design of windings is systematically investigated from the perspective of air-gap modulated magnetic field, considering the influence of both stator and rotors. The advantages of the presented machine are comprehensively evaluated compared to the baseline machine, showing that the presented machine exhibits higher torque/power density, higher efficiency, higher power factor, higher PM utilization, and better vibration performance. Finally, a prototype is fabricated and tested to validate the analysis.