Design and Analysis of a Dual-Rotor Field Modulation Machine with Triple PM Excitation

This paper proposes a new dual-rotor field modulation machine with triple permanent magnet (PM) excitation (DRTE-FMM) that offers a simple structure and high torque/power density required for large telescope drives. The machine is composed of a conventional magnetic gear (MG) portion and dual PM excitation field modulation machine (FMM) portion so that each shares two-thirds of its key components with the other. This sharing provides significant benefits for reducing the machine volume and the number of air-gap layers. PM excitation is present at each side of both the inner and outer air-gaps to increase the flux density. The modulated harmonics of the DRTE-FMM are rich so that it is able to provide high torque production for high power density. The process of evolving this DRTE-FMM topology from the conventional FMM and conventional MG structures are examined. The modulation relationships between the harmonics of the proposed design are investigated by drawing on analytical techniques for the flux density and torque production in conventional FMMs and MGs. The proposed topologies and operating principles are presented, followed by discussions of the machine's air-gap flux density and torque production characteristics, including design optimization. The results show that the proposed machine can achieve high power density with low torque ripple compared to other advanced dual rotor machines in the literature.