Electric motor design keeps running into the same wall: the rare-earth permanent magnets that made EV motors efficient and compact also tie the whole industry to a volatile, geographically concentrated supply chain with a heavy extraction footprint. That dependence is treated as an acceptable cost of performance, but it doesn’t have to be. This piece works through how motors actually generate torque, where magnetless alternatives have historically fallen short, and how a systems-level approach, rather than a simple material swap, closes that gap.
Types of Electric Motors and Their Mechanics
Every traction motor uses a stator to create a rotating magnetic field and a rotor that converts that field into torque. The principal distinction is how the rotor obtains its field, or, in reluctance machines, how it aligns with the lowest-reluctance magnetic path.
In a permanent-magnet synchronous motor, magnets in the rotor couple directly to the stator field, so the rotor turns in synchronism. Induction motors instead induce current in rotor conductors, creating an electromagnetic rotor field without rare-earth material. Synchronous-reluctance motors use shaped steel flux paths rather than rotor magnets or windings; wound-field synchronous motors create rotor flux electrically. These alternatives avoid magnets, but reluctance and wound-field designs generally require higher current for comparable torque, raising I²R losses and thermal demands [1]. The engineering task for any rare-earth-free EV motor is therefore to balance torque, efficiency, noise and behaviour across the full drive cycle against that higher current draw [1].
Innovations in Rotor Excitation Design
Permanent-magnet motors establish rotor flux with fixed rare-earth magnets. Electrically excited synchronous machines instead create that flux by supplying power to a rotor field winding, making excitation controllable rather than fixed by the rotor material. That distinction matters: field strength can be adjusted to the operating point, and the motor avoids embedding rare-earth magnets in its torque-producing rotor.
Several developers are pursuing this route. AEM secured £16 million to accelerate rare-earth-free motor development [2]. ZF’s in-rotor inductive-excitation design, for example, transfers energy for the magnetic field within the rotor shaft itself [3]. The open question across these approaches is how that excitation power is delivered and controlled without adding rotor-side power electronics. Cooled Motors’ exciter and control design answers this by running on standard three-phase power electronics, allowing it to replace a PM motor without a costly platform change. [Cooled Motors Internal]
Limitations of Current Solutions: Performance Compromises
Permanent-magnet motors deliver the efficiency and power density that made them the EV default, but that performance is tied to a material input whose cost, availability and footprint sit outside the motor designer’s control. Rare-earth magnets have held more than 75% of the EV motor market since 2015, despite concerns over price volatility, environmental impact and concentration in processed-material supply [4].
The result is a system-level compromise: electrification scales only as reliably as its magnet supply. Expanding domestic heavy-rare-earth capacity addresses that exposure but preserves dependence on the same constrained input [5]. Magnetless architectures must therefore match EV torque and efficiency requirements without simply trading material risk for higher current, greater copper losses and tighter thermal limits. Rare-earth-free induction, reluctance and wound-rotor machines offer viable routes, but each still needs deliberate design work to close that performance gap, rather than treating magnet removal as a drop-in fix [1].
Advantages of Magnetless Motor Designs
Removing permanent magnets eliminates exposure to their price volatility, concentrated supply chains and extraction footprint, along with the magnets’ direct material cost. The engineering test is whether that resilience can be won without surrendering efficiency or output. Rare-earth-free designs can meet demanding requirements when rotor, windings and control are built around the different torque-production mechanism, rather than treated as a simple material substitution. AEM, for instance, says its magnet-free motors are being productionised for higher-power and higher-torque applications while targeting competitive performance, efficiency and cost [2].
Cooled Motors’ prototype and simulation work goes further, indicating 35% higher performance than best-in-market permanent-magnet motor designs no older than five years, at 98% efficiency. [Cooled Motors Internal] That figure suggests the trade-off between magnet removal and performance is not fixed, but a function of how deliberately the rest of the motor is engineered around the new excitation method.
Cooled Motors’ UESM Solution and Its Unique Advantages
The UESM is built to remove magnets without accepting the thermal and integration penalty that usually comes with higher rotor current. Its electrically excited rotor, winding architecture, control strategy and cooling are engineered as one traction system, so field strength can be controlled while heat is managed at both rotor and stator, rather than tolerated as a limit on continuous output.
Cooled Motors’ CoolShaft™ liquid-cools through the rotor shaft and CoolDisc™ provides stator-side thermal control; together, the company states, they enable higher continuous power density and improved efficiency. [Cooled Motors Internal] This is what makes the higher current inherent to magnetless excitation manageable rather than a hard ceiling on output. And because the exciter and control design runs on standard three-phase power electronics, it replaces a PM motor without requiring a costly platform change. [Cooled Motors Internal]
Integrated Design: A System-Level Approach
A viable magnetless drive is a system design problem, not a component substitution. Rotor excitation, electromagnetic control, winding layout, thermal paths and manufacturing sequence determine one another: raising current to produce torque raises losses, so cooling and control must preserve continuous output without creating an impractical assembly or vehicle interface.
Cooled Motors integrates rotor and stator thermal management with an exciter and control design compatible with standard three-phase power electronics, enabling replacement of PM motors without a costly platform change. [Cooled Motors Internal] That integration still requires an added cooling circuit and careful vehicle-level packaging, but treating those as design constraints from the outset, rather than penalties discovered after the magnets are removed, is what separates a workable magnetless motor from a compromised one. Rare-earth capacity expansions may reinforce incumbent supply, but they do nothing to remove the strategic exposure that comes with depending on those materials in the first place [5].
Sources
- Electric Vehicle Motors Free of Rare-Earth Elements—An Overview — mdpi.com
- AEM secures £16M to accelerate rare earth-free electric motor innovation – Tech.eu — news.google.com
- press.zf.com
- IDTechEx — idtechex.com
- $104M Utah heavy rare earth expansion targets materials for six million EVs yearly – Interesting Engineering — news.google.com