# Less Rare-Earth Electromagnetic Design for a High-Performance Permanent Magnet Motor
## 1 Introduction  
The reduction of CO\({}_{2}\) emissions policies has created a significant investment in transitioning fossil fuel vehicles to electric or minimizing fuel consumption with hybrid technologies. Although alternatives such as reluctance and induction machines could be possible, the electromobility (e-mobility) industry still relies on permanent magnet (PM) motors due to their higher efficiency and power density. Therefore, the implementation of rare earth elements (REEs) is typical for high-performance machines. Moreover, since 2011, western countries have declared REEs critical raw materials because of the risk in supply from China. In addition, the expected growth in sales of electric vehicles (EVs) [1] and the implementation of REEs in other applications will create a significant demand for REEs [2], in particular for Neodymium. For this reason, there is a need to look for electric motor design alternatives that can eliminate or reduce REEs. This paper's interest is on the latter. The design feature in this paper is the topological advantage the so-called banana-shaped (also known as crescent-shaped or arc-shaped) magnet geometry provides to the magnetic structure of the motor. [PERSON] et al. [3] findings show that although they have the same magnet weight, the electromotive force of the motors with arced magnets is higher than the block types analyzed. [PERSON] et al. [4] compare the three-layer V-shaped structure with the three-layer arc-shaped structure, resulting in higher torque for the latter because of a better ratio of magnet and reluctance torque. Similarly, [PERSON] et al. [5] state that the double-layer arced structure required the least magnet material compared to the conventional block type structures to achieve the targeted performance. Their work [3; 4; 5] demonstrates that the arc-shaped structure provides the advantage of efficient use of the magnet material compared to the block type. Therefore, opening the possibility of less rare-earth designs. From the literature, it is noticeable that few scientific publications have addressed this issue and those that have, made the study with either neobonded or ferrite magnets. However, the interest of this research is on Neodymium-Iron-Boron (NdFeB), the typical structure for high-energy PM. Compared with other technologies (Alnico, Ferrite, Samarium-Cobalt), NdFeB magnets provide advantages such as higher coercivity and higher magnetic flux density remanence. In addition, the addition of Dysprosium and Terbium (heavy RE) enhances the thermal stability properties of these magnets. Moreover, NdFeB magnets with these complex shapes have manufacturing difficulties for mass production. One reason is that taking the conventional production route for sintered magnets requires cutting, leading to significant scrap. This material waste could be a reason for the lack of studies on NdFeB sintered magnets with arc shapes. However, new manufacturing technologies, such as additive manufacturing or Powder Injection Molding (PIM), can potentially implement these geometries on sintered magnets for mass production shortly. For instance, nowadays, there are commercial ring-shaped examples of sintered NdFeB [6]. Therefore, studying this type of topologies in electric motor design is attractive. Although magnet manufacturing-specific details are out of the scope of this paper, it should be mentioned that this work is part of the European Low-Ree Motors project [7] founded by EIT raw materials, where new magnet manufacturing processes are studied (PIM and Cerium substitution) for rare-earth reduction. So, for this reason, the banana-shaped topology is selected as a complex shape magnet that could be developed through PIM. The study presented in this paper intends to check before implementing a specific manufacturing process if rare-earth reduction could be achieved for this topology through electromagnetic design only, taking a baseline motor as the starting point.