They're also used by Nissan [1], BMW [2], and Indian EVs [3].

European firms like ZF, Valeo, MAHLE, and Schaffler along with British firms like AEM have been working with their Indian JVs as well as Indian players like Sona Comstar and Sterling for a couple years now to integrate supply chains for mass-producing EESMs.

EESMs as well as the larger OEM story played a role in helping land the EU-India and the UK-India FTAs because the supply chains for French+Italian (Renault, Stellantis), Japanese (Toyota, Honda, Suzuki), Korean (Hyundai-Kia), and Indian automotive manufacturers merged.

On the other hand, EESM EVs aren't a thing here in North America nor China yet as both primarily use PMSMs (edited typo).

[0] - https://news.ycombinator.com/item?id=48510402

[1] - https://leandesign.com/nissan-ariya-magnet-free-motor-teardo...

[2] - https://www.bmwblog.com/2025/02/20/bmw-gen6-electric-motors-...

[3] - https://www.reuters.com/world/china/india-revs-up-alternate-...

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Edit: can't reply

> does Nissan still use these motors, the car in the linked article has been discontinued

Yes. The Ariya was discontinued in North America but is still manufactured and sold in Asia.

> European and Indian manufacturers/engineering are definitely not in the same category though

It's the same manufacturers and supply chain now.

Renault and their OEMs are the biggest driver for EESM, and Renault's largest markets and manufacturing hubs are France, India, and Romania. Heck, Renault is now going to start exporting it's Made in India cars and parts back to the EU [0] becuase of the EU-India FTA.

And the European OEMs have transferred the IP for EESMs to Indian JVs as I mentioned. It's the same style of tech transfer as Samsung did for BYD and TDK for CATL for battery chemistry in the 2000s. Heck, Valeo [1], MAHLE [2], and ZF [3] are opening factories and R&D hubs dedicated to EV transmission manufacturing in India for domestic and export usecases.

Also, if you've ever driven a Japanese (Toyota, Honda, Suzuki) or Korean (Hyundai, Kia) make care in the EU, Middle East, or Asia outside of their home countries their parts sourcing and even the entire manufactured car would have come from India, such as the Toyota Urban Cruiser EV [4].

[0] - https://m.economictimes.com/industry/auto/auto-news/india-eu...

[1] - https://www.valeo.com/en/valeo-inaugurates-new-electric-powe...

[2] - https://auto.economictimes.indiatimes.com/news/auto-technolo...

[3] - https://press.zf.com/press/en/releases/release_66050.html

[4] - https://newsroom.toyota.eu/the-all-new-toyota-urban-cruiser/

This is a helpful explanation of what this technology is and looks like. (Munro)

Technically the brushes can wear out, although there are claims they are good for 150,000-250,000 miles it seems.

Advantages:

- Not subject to the price and supply chain volatility of rare earth permanent magnets.

- For highway dominant drive cycles, the cycle efficiency of EESMs can be higher than state of the art IPMSMs. EESMs tend to have their best efficiency at moderate torques and high speeds because of their excellent field weakening characteristics. I tend to think that they would be a good fit for application in class 8 trucks or as auxiliary motors in automobiles with two powered axles.

- The output torque doesn't necessarily decrease with rotor temperature. In IPMSMs the permanent magnet flux linkage decreases with rotor temperature.

- At least theoretically, with proper control, it is possible to operate EESMs with unity power factor and decrease the kVA rating of the stator inverter.

- If there is a stator inverter fault, there are schemes to denergize the rotor which have some safety implications.

Disadvantages:

- DC current needs to be transferred to the rotating field winding. For automotive applications this tends to be done either with brushes and slip rings or brushlessly using a high frequency transformer with a rotating rectifier. In either case additional power electronics and other components are needed for the field power transfer and control which reduces some of the potential cost savings of the elimination of the permanent magnets. If brushes and slip rings are used with oil spray/oil jet cooling of the rotor they need to be sealed in a separate compartment. I am a little surprised that Renault has stuck with brushes and slip rings versus an inductive high frequency transformer solution. I think this has limited their power density.

- For very torque dense machines, cooling the rotor field winding is challenging, and in my opinion is best accomplished by oil spray/oil jet cooling.

- It is difficult to reach the same maximum speeds as IPMSMs in an automotive package size. The rotor field winding retention system to keep the field turns from moving into the airgap at high speeds needs considerable attention during the design.

- The overall axial length of the non-active region of EESMs is typically longer than IPMSMs because of the field winding end turns and field excitation system. - EESM efficiency is dominated by the manufacturable slot fill of the field winding. - High performance current/torque regulation is considerably more difficult.

High performance EESMs have been used in aerospace generator applications for decades, albeit with a different rotor excitation system than what is used in automotive applications. Renault (and their supplier Continental) really led the commercialization of EESMs into automotive mass production. Now BMW has followed suit and multiple suppliers have EESM designs (Mahle, ZF, etc.) GM had a really nice EESM design and high frequency transformer excitation which they published back in 2014. My colleagues and I built several generations of EESMs as part of U.S. Dept. of Energy projects (https://www.osti.gov/servlets/purl/1837809) and I think they have their place as EV traction motors for certain applications.