This paper covers a new emerging class of electrical machines, namely, Magnetic Gears (MGs) and Magnetically Geared Machines (MGMs). This particular kind of gears/machines is capable of either scaling up or down the revolutions-per-minute to meet various load profiles as in the case of mechanical gearboxes, but with physical isolation between the rotating components. This physical isolation between the rotational components leads to several advantages in favor of MGs and MGMs over mechanical gearboxes. Although MGs and MGMs can potentially provide a solution for some of the practical issues of mechanical gears, MGs and MGMs have two major challenges that researchers have been trying to address. Those challenges are the high usage of rare-earth Permanent Magnet (PM) materials and the relatively complex mechanical structure of MGs and MGMs, both of which are a consequence of the multi-airgap design. This paper presents designs that reduce the PM rare-earth content for Electric Vehicles (EVs). Additionally, the paper will ensure having practical designs that do not run the risk of permanent demagnetization. The paper will also discuss some new designs to simplify the mechanical structure.
Comparison between rare-earth and ferrite permanent magnet flux-switching generators for gearless wind turbines
