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  • Hacker News
  • Really sounds promising. The question is will the French have the will to build it in bulk on shore in France or Europe? There’s no point if they want to sub it out to the world to build cheaper somewhere else?

    This technology does show that you should never give up on industry, research, development and building on shore.

    by Danox
  • One of the most interesting thing about commodity bottlenecks is that they often accelerate substitution ; scarcity can end up by making a material being less important
    by latentframe
  • Why not just use an induction motor with VFD?
    by RobotToaster
  • As said in the parent Web page, lower energy efficiency, thus shorter range with the same battery.

    Another poster has mentioned that BMW also uses EESMs instead of permanent-motor magnets.

    BMW uses EESMs as the main motors, on the rear axle, while they use induction motors as auxiliary motors on the front axle.

    Besides being cheaper, the induction motors have the advantage that if they are used only as auxiliary motors, you can cut the power supply to them at any time, in which case they will consume nothing.

    So their lower efficiency does not matter, because most of the time they are turned off.

    by adrian_b
  • Electrically excited synchronous machines (EESMs), also known as wound field synchronous machines (WFSMs) have a number of potential advantages and disadvantages compared to interior permanent magnet synchronous machines (IPMSMs). IPMSMs are the dominant motor topology currently in use for North American electric vehicles.

    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.

    by ipbrown
  • It’s interesting that EESMs can be more efficient at high/highway speeds, and it’s something I had read before. This seems to me to be a key advantage of EESMs, because when people worry about EV range, they worry mainly about range on long-distance, high-speed journeys.

    (I have a Renault EV and it’s excellent. Aside from the motor technology, it’s relatively light, has a heat pump as standard, and a good-sized battery).

    by gmac
  • I see another advantage..

    You can switch a motor without permanent magnets to "idle mode".

    I understand in Tesla dual motor configurations, the front motor is without magnets. The excitation field will be turned on when you need extra power, but at crusing speed it does not cause extra "drag". From one teardown I've seen, they even went so far to use cheaper and less efficient IGBTs for the front drive, and more efficient SiC Mosfets for the rear motor (in the same vehicle!). If you need extra acceleration briefly, lower efficiency can be accepted.

    by schobi
  • How soon to see rare-earth-free paired with CATL Sodium batteries? Seems a price war, range war is imminent.
    by delfugal
  • Unlikely.

    EESMs are primarily manufactured by European OEMs (ZF, MAHLE, Schaffler, AEM) and their Indian JV partners (Sona Comstar, Sterling, and the India branches of the OEMs listed). Both have been blocked via export controls from accessing battery tech from China over the past few years, and a major reason for the push for EESMs was for an ex-China supply chain, especially after China began export controlling rare earths to the EU [6].

    Additonally, Chinese and American EVs tend to use PMSMs unlike European and now Indian EVs. Also, the EU is cracking down on automotive exports (cars and OEMs) from non-FTA states as part of the EU Industrial Accelerator Act (which btw has made China go ballistic [2][3][4][5]).

    On the other hand, they will most likely use Japanese or Korean solid-state batteries as Idemetsu Kosan is in the process of mass producing them [0][1] as is LG [7], and both Japan+SK are FTA partners with the EU.

    [0] - https://www.chiyodacorp.com/en/projects/solidelectrolytefaci...

    [1] - https://battery-tech.net/battery-markets-news/idemitsu-kosan...

    [2] - https://www.globaltimes.cn/page/202605/1361926.shtml

    [3] - https://www.globaltimes.cn/page/202605/1362200.shtml

    [4] - https://www.globaltimes.cn/page/202605/1362161.shtml

    [5] - https://www.ft.com/content/5903318c-319b-426e-b05d-062f7620f...

    [6] - https://www.reuters.com/world/china/eu-lawmakers-rebuke-chin...

    [7] - https://blog.lgchem.com/en/2026/03/25_solid_state_battery/

    by alephnerd
  • Could be wrong, but AFAIK the CATL Sodium batteries haven't yet hit LFP pricing.

    You are unlikely to see a vehicle with sodium batteries until after that happens, and it needs to be significantly less than LFPs as you Na batteries have more weight per Wh. I believe they also have a shorter lifespan (but not NMC short). Edit correction, looks like CATL is promising 15000 cycles, which is much longer than LFPs which usually come in at 7000 to 10000.

    It seems far more likely to me that if the Na prices tank, you'll probably first see them deployed as grid and home battery solutions.

    by cogman10
  • "At the same time, China is also the world's leading producer of electric cars..."

    Kind of interesting for a professionally branded company to use "..." like that

    by E-Reverance
  • Clearly making a motor with induced magnetic fields both for the stator and rotor isn't the innovation here, since a large fraction of industrial motors do not have permanent magnets.

    I would assume the innovation here would need to be making it small and efficient for any meaningful torque output? Usually when you see claims of a 93% efficient electrical motor its the result of taking an absolute beast of a 2kW machine and operating it at 400W. Does anyone have insights into what Renault are doing here?

    by dcanelhas
  • The real innovation is in making them brushless and essentially maintenance free while still being efficient enough.
    by rbanffy
  • It's interesting that this is a brushed design. In the RC car community, brushless motors are generally regarded as superior, but those of course have the rare earth magnet problem.

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

    by giobox
  • It's brushless: https://www.evspecifications.com/images/news/6ec9484/additio...
    by Devorlon
  • It's technically not a brush but a slip-ring. The design of these motors is very similar to automotive alternators, just scaled up 100x (in terms of power).
    by hnav
  • "Brushless DC motors" are good because brushed DC motors are constantly switching polarity, which causes arcing of the brushes, which causes wear. The brushes are not there to energize the rotor; the rotor is just magnets after all. The brushes are there to tell the stator to change polarity.

    Brushless DC motors don't arc -- because they switch stator polarity with electronics that sense the position of the rotor without rubbing parts. (They can also fine-tune the stator current spikes to make the motor very efficient over a wide speed range, which brushed DC motors cannot do.) The lack of arcing is more important than the fact that they don't have rotating contact points.

    Brushed AC motors have rotating contact points (slip rings) but they don't arc (ideally), so the contact points don't degrade as fast as brushed DC motors do. But they do carry a lot of current because their purpose is to energize the rotor. Brushed AC motors are not ideal, but making an AC motor "brushless" is not nearly as big a win as making a DC motor brushless.

    Wait. You're saying DC motors require current that's constantly switching polarity? So they're sort of really AC internally?

    Yep. All motors require constantly changing current. The distinction between AC and DC motors is whether you feed the motor externally with current that is already alternating sinusoidally, or whether the motor itself turns external DC into some kind of AC.

    by dreamcompiler
  • Broader point is this: Middle East created oil crisis back in 70s. Since then US economy has grown enormously while it's still using pretty much same amount of oil, imported or otherwise. They shot themselves in their foot. Iran is doing this now, telling the world to avoid Hormuz. They will learn to do that.

    China is doing that by blackmailing countries with rare earth.

    Answers will be found. Especially as some of finest brains across 2 continents + Japan are very interested in doing it. In the past, China could flood market at right time to make alternatives unviable. But that trick has worn off.

    In this context, 92% or even 80% efficiency of permanent magnets is no big deal. It'll not be the answer to every use case but will satisfy many and limit demand.

    by kopirgan
  • In the long term solutions will be found, but in the short term they can gain an enormous bargaining chip. If food prices double because we've burnt the last drop from the Strategic Petroleum Reserve, the administration will give them just about anything they want to avoid utter political destruction.

    The game theoretic definition of a threat is something that harms you, but harms them so much that they will avoid forcing you to trigger the threat. It's a different matrix from the Prisoner's Dilemma, but still leaves you guessing about the personality of your opponent. The personality of Iran seems reasonably consistent. The US, less so.

    by jfengel
  • I don't know. Europe had the opportunity to make themselves energy independent multiple times; instead they doubled down on Russian oil, and in response to the latest invasion, they instead doubled down on Qatar natural gas...

    Germany spent enough on solar to have nuclear power for winter heating and instead they get nearly nothing from it when energy (note I said Energy not Electricity) demand is the highest: winter heating.

    Now, if they had put that solar in North Africa and ran cables, sure, but they didn't. Or if they did Drake's landing solar storage, that would also work. But they spent a fortune only to still be completely dependent on fossil fuels and are destroying the economic base because of the cost.

    by coryrc
  • BMW also makes rare-earths-free motors for their EVs and - at this very moment - theirs are far more advanced. They offer almost twice the power (up to 300kW vs 160kW) and are on a 800v architecture.
    by bgarbiak
  • Which is quite the contrast to Mercedes new axial flux electric motor, which goes all in on rare earths- the design relies on the highest end high-grade permanent magnets.

    Still, presumably Mercedes ambitions are for few motors than BMW or Renault.

    by Quarrel
  • The cheapest EV model Renault sells is around €20K, the cheapest BMW EV is around €65K.

    It's safe to say the companies are not in the market bracket, no?

    by PedroBatista
  • A historical pioneer in the complex technology of electric motors without magnets

    Those who know the history of electric machines will find the title and verbiage very amusing. Motors with no permanent magnets were the first practical ones, and at this point wound-rotor motors are over a century old.

    It's worth noting that some of the biggest motors have always been designed this way, because the size of magnets required would make them both too expensive and dangerous, and still not powerful enough for their size; a field coil can generate a field that's only limited by the current and resistive heating of the winding, but rare earth magnets have fixed limits on field strength.

    by userbinator
  • Verbiage? What about the _nounage_?
    by hackrmn
  • What advantage do permanent magnets provide that it isn't the case that all motors are made without them?
    by xeonmc
  • Not quite true: you're also limited by the mechanical strength of your windings and core (this is the upper limit on superconducting magnets like at CERN and in fusion plants).
    by XorNot
  • You're right about the verbiage being amusing.

    All big generators have an exciter coil that is used to generate the magnetic field. It has the advantage of allowing voltage regulation through adjustment of the field, rather than after the fact, which would be far less efficient.

    In both motors and generators, there is an efficiency hit related to the need to supply power in order to generate the field, but when you scale up the system, it actually becomes more efficient to use the electromagnet. With the rare-earth mineral shortage, it makes even more sense.

    by anonymousiam
  • Long ago, when I was in Cub Scouts, one of the projects was to build an electric motor. The parts list was:

    1. a plank to form the base

    2. several 6 inch nails

    3. wire

    4. a tin can (as a source of sheet metal)

    5. tape

    No magnets. But it worked perfectly fine when connected to a dry cell. Adventurous science lad that I was, I decided it would work better when connected to AC. So I attached a power cord and plugged it in.

    A loud vibration ensued, and then it burst into flames. My mom wasn't happy.

    by WalterBright
  • Unfortunately, their Web page does not say a single word about the important problems of their motors.

    The electrically excited synchronous motors have been known forever, but they had not been used in EVs because of 2 disadvantages.

    The first is that traditional EESMs require brushes, i.e. sliding electrical contacts, which are worn out by friction, so such motors require frequent maintenance for changing the brushes.

    It is possible to make brushless EESMs, but they require a rotating transformer and a semiconductor rectifier inside the rotor.

    The second disadvantage is a lower efficiency than with permanent magnets, which cannot be improved so much as to match PM motors, because the electrical currents that circulate through the rotor windings must generate heat. The lower efficiency also makes cooling more difficult.

    Renault says that their EESMs have an efficiency of 92%. This is a good efficiency, even if not as good as attainable with permanent magnets. Losing a few percents in efficiency is an acceptable compromise for avoiding the use of expensive and supply-constrained chemical elements.

    What I wonder is whether Renault reaches this 92% efficiency with EESMs having brushes, or with brushless EESMs, and this is what I would have liked to read on the parent Web page.

    Brushless EESMs usually had a lower efficiency, so 92% would be impressive for them, while it would look normal for EESMs with brushes.

    If Renault has succeeded to make a brushless EESM (i.e. maintenance-free) with an efficiency of 92%, that is something worth to brag about. Otherwise, making a traditional EESM would not be great news, because everybody has avoided those because of the maintenance problem.

    by adrian_b