Electric motors with no rare earths • Hacker News Board

Re: Electric motors with no rare earths

#171

Post by CarVac » Sat, Jun 13, 2026, 1:14 PM UTC

adrian_b wrote: post #146

RobotToaster wrote: post #128

Why not just use an induction motor with VFD?

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 moto…

> 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.

EESMs have this advantage too, you can simply cut power to the field winding.

Re: Electric motors with no rare earths

#172

Post by kopirgan » Sat, Jun 13, 2026, 1:15 PM UTC

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.

Re: Electric motors with no rare earths

#173

Post by Daub » Sat, Jun 13, 2026, 1:18 PM UTC

WalterBright wrote: post #97

Daub wrote: post #87

Earlier quoted context omitted.

Been there. Im gonna guess that 90% of HN folk have similar stories to tell.

The Cub Scouts in the 1960s were a lot of fun. Each den meeting involved a project. The other one I remember was we each built a kite from scratch. Mine was a bit fragile, and the first gust of wind shredded the sticks and plastic film. But it was still fun! As a teen I built a flame thrower. No, I'm not going to explain how to build one. My dad told me that God looks out for little boys, because otherwise they'd nev…

> if you're fascinated by things that burn and explode, this book is not for you.

Translation… ‘read me now!’

Re: Electric motors with no rare earths

#174

Post by amelius » Sat, Jun 13, 2026, 1:23 PM UTC

Devorlon wrote: post #154

giobox wrote: post #32

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.

It's brushless: https://www.evspecifications.com/images/news/6ec9484/additio...

Makes me wonder why they made that choice, if what your parent commenter said is true.

Re: Electric motors with no rare earths

#175

Post by ece » Sat, Jun 13, 2026, 1:42 PM UTC

Karliss wrote: post #156

bornfreddy wrote: post #132

Earlier quoted context omitted.

Interesting question, it looks like they are / will be brushelss: > Group will gradually embed new technological improvements from 2024 on its EESM: stator hairpin, glued motor stack, *brushless* and hollow rotor shafts. [0] https://www.evspecifications.com/en/news/6ec9484 That said, what sibling says about the maintenance problems is very true. :-/

All sources point that their 2025 models are still using brushed rotors. Here is a teardown video it's from Nisan car but it's using a Renault electric motor https://www.youtube.com/watch?v=BFmp9ODkCA8 . In the picture at Renault website (section describing their next gen 2027 motors) you can clearly see the 2 slip rings on right side. That might be just a placeholder using their last gen motor, but I would expect th…

Compared to an ICE, maintenance of brushes is still quite an improvement.

Re: Electric motors with no rare earths

#176

Post by torginus » Sat, Jun 13, 2026, 1:49 PM UTC

adrian_b wrote: post #120

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 brushe…

Munro took apart a Nissan Ariya which has this exact kind of motor. The maintenance is basically removing a tiny cover and replacing the tiny and cheap carbon brushes every 100k km or more. It's basically cabin filter level maintenance.

And they said that PMSM motors are more efficient at low RPM, but their coils get saturated at higher RPMs meaning they lose efficiency at highway speeds (which actually affect the range number people car about).

So overall not such a bad tradeoff, if it makes cars less expensive.

Re: Electric motors with no rare earths

#177

Post by redeeman » Sat, Jun 13, 2026, 2:08 PM UTC

wongarsu wrote: post #135

hdrz wrote: post #117

Earlier quoted context omitted.

It rusts just like iron, but the rust (AlOx, or alumina) stays bonded to the metal and actually protects it.

In other words: it rusts, but it doesn't rust like iron. It rusts in a much less destructive way because the aluminum oxide protects the rest of the aluminum from oxygen

it does not rust, it corrodes :)

Re: Electric motors with no rare earths

#178

Post by jfengel » Sat, Jun 13, 2026, 2:35 PM UTC

kopirgan wrote: post #172

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 f…

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.

Re: Electric motors with no rare earths

#179

Post by RicoElectrico » Sat, Jun 13, 2026, 2:41 PM UTC

adrian_b wrote: post #120

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 brushe…

> 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.

Wouldn't the back EMF help here? In brushed DC motor it surely does, reducing losses way below what full voltage over winding resistance would incur.

Re: Electric motors with no rare earths

#180

Post by rdtsc » Sat, Jun 13, 2026, 3:20 PM UTC

anonymousiam wrote: post #93

userbinator wrote: post #38

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 requ…

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 s…

> 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

That and not having huge strong magnets is nice when doing maintenance.