Magnetic Gears and Magnetically Geared Electrical Machines with Reduced Rare-Earth Materials

This thesis covers a new emerging class of electrical machines, namely, Magnetic Gears (MGs) and Magnetically Geared Machines (MGMs). This particular kind of gears/machines are able of either scaling up or down the revolution-per-minute to meet various load profiles as in the case of mechanical gearboxes. Mechanical gearboxes have historically dominated various applications due to their relatively high torque density. However, mechanical gearboxes require physical contact between the rotational components, whereas MGs and MGMs accomplish fundamentally the same function via a contactless mechanism. This physical isolation between the rotational components lead to several advantages in a 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 Permeant Magnet (PM) materials and the relatively complex mechanical structure of MGs and MGMs both of which are a consequence of the multi-airgap design. As in any engineering field, materials play a significant role and present a trad-off between the performance and cost. In addition to the previous trad-off, the concern with rare-earth PM materials is sustainability as well as price fluctuations. Current research in electrical machines demonstrate real initiatives to reduce the cost of electrical machines by reducing/eliminating the PM rare-earth content while attempting to maintain a competitive electromagnetic performance. Most advanced electrical machines use Dy-NdFeB PM with high energy product at elevated temperatures. Dysprosium (Dy) is one of heavy rare-earth elements and the key source of the price volatility. As a consequence, this thesis aims to address foregoing PM material challenges and investigate the electromagnetic performance of designs that blend different PM types in the context of MGs and MGMs. In addition, practical designs will be proposed in order to reduce the complexity related to the nature of MGs and MGMs