Citation: Pop, C.V.; Fodorean, D.; Popa, D.-C. Structural Analysis of an In-Wheel Motor with Integrated Magnetic Gear Designed for Automotive Applications. Sustainability 2022, 14, 12007. https://doi.org/10.3390/ su141912007 Received: 12 August 2022 Accepted: 20 September 2022 Published: 22 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article Structural Analysis of an In-Wheel Motor with Integrated Magnetic Gear Designed for Automotive Applications Claudia Violeta Pop , Daniel Fodorean and Dan-Cristian Popa * Department of Electrical Machines and Drives, Technical University of Cluj-Napoca, 400114 Cluj-Napoca, Romania * Correspondence: dan.cristian.popa@emd.utcluj.ro Abstract: This paper is focused on the structural analysis of a new propulsion system defined by an in-wheel motor with an integrated magnetic gear (IWM-IMG). The IWM-IMG has two levels of torque and speed. First, the state of the art of magnetic gears (MGs) is presented. Next, the proposed structure and the main designing steps are depicted. The advantages of the proposed structure are emphasized, in terms of speed increase operation, knowing that this is achieved without it being necessary to increase the fed frequency via the inverter. Moreover, the electromagnetic characteristics are briefly introduced to prove the suitability of the proposed solution for the considered application. Next, the structural analysis is detailed, where through an analytical, numerical and experimental approach, the study is validated. Keywords: in-wheel motor; integrated magnetic gear; EV application; design and structural analysis; speed operating extension 1. Introduction The concerned application in our study is the electric vehicle (EV). EVs are complex systems, and their study implies the use of different strategies and methods in an interdis- ciplinary approach [1,2]. In general, for EVs, higher speed and increased autonomy are strongly related to the weight of the propulsion unit [3–6]. To transfer the torque speed from the electric motor to the traction wheel, a gear is generally used. A high transmission ratio from the gear can be hardly obtained when using just one gear. A solution to obtain the desired transmission ratio is to use multiple linked gears [6]. Hence, the propulsion unit will be affected by the increased weight and volume, with consequences on the power density and efficiency of the overall system. To overcome this issue, a solution can be the replacement of the mechanical gear with a magnetic one. Multiple advantages to the drive chain can be achieved with this variant, emphasized later. A classical mechanical gear is a unit which transfers torque or speed from one shaft to another through mechanical teeth contact [7,8]. Thus, some important drawbacks occur. First, local friction and heat are produced at the teeth level, leading to losses. The physical contact between the teeth will also lead to the stress of the tooth flanges. Due to the long operation time, material friction and fatigue lead to the irreversible damage of the teeth. Moreover, because of the material friction, the metallic parts must be lubricated often, due to continuously varying temperatures at the teeth level. All these drawbacks are eliminated in the case of magnetic gears (MGs) because the metallic teeth are replaced with magnets. The transition from a mechanical gear to a magnetic one is shown in Figure 1. There is no physical contact between the magnetic pole pieces of an MG. Hence, there is no heating, no need for lubrication and no material damage. The losses found in the active parts are represented by the iron loss component, and the mechanical one is due to bearing friction. Moreover, the levels of noise and vibration are decreased in the case of MGs. Sustainability 2022, 14, 12007. https://doi.org/10.3390/su141912007 https://www.mdpi.com/journal/sustainability