Highlights

• A 2026 review in the International Journal of Automotive and Mechanical Engineering examines whether concentric magnetic gears—which transmit torque without physical contact—can become practical for EVs and advanced machinery, but finds most high-performance designs still rely heavily on rare-earth permanent magnets despite engineering progress.
• The study identifies “true hybrid excitation,” where electromagnetic windings share magnetic flux generation with permanent magnets, as the most promising approach to reduce rare-earth content while enabling adjustable gear ratios and improved resilience, though commercial viability remains unproven.
• For rare earth supply chains dominated by China, the findings underscore that emerging electrification technologies may become rare-earth leaner rather than rare-earth free, with the next research stage focusing on prototype validation and real-world drivetrain testing of hybrid-excited systems.

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In a 2026 review article in the International Journal of Automotive and Mechanical Engineering, Sarweash Rao Tharma Raja of Universiti Teknikal Malaysia Melaka, with collaborators Mohd Firdaus Mohd Ab Halim, Azhan Ab Rahman, and Fauzi Ahmad, examines whether concentric magnetic gears could become a practical drivetrain technology for electric vehicles and advanced machinery.

Unlike traditional mechanical gears, magnetic gears transmit torque without physical contact, reducing wear, lowering maintenance, and offering built-in overload protection. Yet the paper delivers a sober message relevant to the rare earth industry: despite meaningful engineering progress, most high-performance magnetic gear designs still rely heavily on rare-earth permanent magnets (REPMs). That dependence raises persistent concerns around cost volatility, supply-chain vulnerability, and sustainability.

The authors argue that the most promising path forward lies in “true hybrid excitation,” where electromagnetic windings share the role of generating magnetic flux rather than merely assisting permanent magnets. In principle, this approach could reduce magnet requirements while enabling new capabilities such as adjustable gear ratios and improved system resilience.

How the Review Was Conducted

This paper is not a new experimental demonstration but a structured review of prior research on concentric magnetic gear technologies. The authors analyzed advances in gear topology, magnet arrangements, passive conductors, electrified configurations, and material substitutions. A key contribution of the study is a framework distinguishing between auxiliary electromagnetic integrations—where coils merely add functionality—and true hybrid excitation, where windings act as a co-primary magnetic source capable of replacing some permanent-magnet flux.

What the Review Found

The central finding is straightforward: magnetic gears have improved significantly in torque density and design sophistication, but the field has not escaped its reliance on rare-earth magnets. Alternative strategies such as ferrite magnets, reluctance-based designs, or passive conductor structures can reduce magnet use, but they typically introduce trade-offs in performance, efficiency, size, or system complexity. As a result, hybrid-excited designs emerge as the most promising pathway because they may reduce magnet volume without sacrificing functionality.

Why This Matters for Rare Earth Supply Chains

For the rare earth sector, the findings highlight an uncomfortable reality: many emerging electrification technologies—electric vehicles, robotics, aerospace actuators, and wind power systems—continue to depend heavily on high-performance rare-earth magnets, particularly those containing neodymium, dysprosium, and terbium.

Because China dominates the global rare earth magnet supply chain, innovations that reduce magnet intensity without sacrificing performance could reshape the strategic balance of electrification technologies. At the same time, if hybrid excitation proves technically complex or expensive, the industry may remain structurally dependent on rare-earth materials for decades.

Limitations and the Real Debate

Because this is a review article rather than a prototype demonstration, it does not prove that hybrid-excited magnetic gears are commercially viable. Questions remain about manufacturing complexity, thermal management, system cost, and real-world reliability. The real engineering challenge is not simply reducing rare-earth usage—it is doing so without undermining the performance advantages that make magnetic gearing attractive in the first place.

What Comes Next

For engineers, investors, and policymakers, the study suggests the future of magnetic gearing may not be rare-earth free, but it could become rare-earth leaner. The next stage of research will likely focus on prototype development, integrated drivetrain testing, and techno-economic validation of hybrid-excited systems in real-world applications.

Citation: Raja, S.R.T., Halim, M.F.M.A., Rahman, A.A., & Ahmad, F. (2026). Concentric Magnetic Gears: A Review of Topological Advances, the Persistent Rare-Earth Magnet Dilemma, and a Hybrid Excitation Pathway. International Journal of Automotive and Mechanical Engineering, 23(1), 13161–13189. https://doi.org/10.15282/ijame.23.1.2026.2.1000 (opens in a new tab)