Rare-earth-free reluctance motors for EVs could be world’s first

13 January 2026  

Astemo’s main drive stator and rotor (left) and the auxiliary drive rotor (right)

A Japanese joint venture between Hitachi, Honda and JIC Capital, has developed an electric motor for electric vehicles based on a rare-earth-free synchronous reluctance (SynRM) technology. The JV, called Astemo, aims to have the first practical applications of the motor by around 2030 and says that it would represent the world’s first use of SynRM motors in mass-produced vehicles.

The motor generates rotational forces by inducing magnetism in an iron-core rotor. Rare-earth-free magnets incorporated into a main drive motor are used to deliver a high output. This enables the replacement of conventional permanent magnet motors in BEV (battery EV) drive systems, which usually need large amounts of rare-earth elements.

The main motor, designed to generate a continuous driving force, achieves an output of 180kW. An auxiliary 135kW drive motor used for power assist duties, eliminates energy losses during coasting, thus developing a combined output of 315kW.

Most conventional battery EV motors rely on permanent magnets in the rotor that incorporate rare-earth elements such as neodymium to generate strong magnetic fields. But these materials entail significant geopolitical risks, and ensuring a stable supply can be a challenge.

Rare-earth-free ferrite magnets, while readily available, have a magnetic force that is only one-third or less of those using rare-earths. This means a motor needs to be three times the size to deliver the same output.

In response, induction motors and wound-field motors have been developed that avoid the need for permanent magnets. However, these require significant amounts of copper on the rotor. This represents a possible resource risk.

Astemo has developed the synchronous reluctance motor as an alternative. It generates a rotational force by using differences in magnetic resistance (reluctance) based on the shape of the rotor core. A “multi-layer flux” structure divides the magnetic force transmission path into multiple layers. The current is precisely controlled to form magnetic poles in the rotor core, and to compensate for the powerful magnetic forces generated by neodymium magnets.

Creating magnetic poles in the rotor core requires large currents to flow through the stator coils, posing the risk of the coils overheating. Astemo says it has been able to suppress heat generation by developing a structure that immerses the slots and ends containing the coils in cooling oil.

For the main drive motor, which runs continuously, a magnet-assisted synchronous reluctance design incorporating ferrite magnets achieves an output of 180kW, while limiting the size increase to 30%, compared to conventional rare-earth permanent magnet motors. For the auxiliary drive motor, Astemo has developed a synchronous reluctance motor that needs no magnets at all.

If magnets were embedded into the auxiliary drive, they could act as a braking force when the main drive rotor is coasting, resulting in energy losses. The auxiliary drive therefore operates only when needed to deliver power assistance of up to 135kW. This limits the power consumption of the entire BEV drive system.

The new rare-earth-free motor is said to deliver a similar performance to a conventional BEV motor. It reduces the procurement risks and price volatility associated with rare-earths, enabling supply of the motors to remain stable.

Furthermore, reducing energy losses across the entire BEV drive system – including both main and auxiliary drives – will curb power consumption over a wide range of driving scenarios.

Astemo, headquartered in Tokyo, employs around 80,000 people, and has operations in the Americas, Asia, China, Europe and Japan.

Astemo:  X  LinkedIn  Facebook