Electric motors with no rare earths • Hacker News Board

Re: Electric motors with no rare earths

#131

Post by adrian_b » Sat, Jun 13, 2026, 9:21 AM UTC

snovv_crash wrote: post #96

sitharus wrote: post #64

Earlier quoted context omitted.

A lack of wear components. A permanent magnet motor uses permanent magnets on the rotor, but an electrically excited synchronous motor has an electromagnet on the rotor. This requires a rotating electrical contact which has normally been made with slip rings and carbon brushes. These wear over time and need replacement. Most large electric generators are externally excited synchronous generators using carbon slip rin…

You can also make squirrel-cage rotors that are auto-inductive in the sense that they resist slip from the rotating field of the stator. This is also extremely simple to manufacture and doesn't require driving separate fields or anything similar.

This is mentioned in the parent page, where it is also mentioned that their disadvantage is a lower energy efficiency than either electrically-excited synchronous motors or permanent-magnet motors.

The lower efficiency means a lower range for the same battery, which is why the companies that have used them in the past, like Tesla, have abandoned them.

Permanent-magnet motors have the highest possible energy efficiency, followed by electrically-excited synchronous motors, than by the induction motors mentioned by you.

Both permanent-magnet motors and induction motors do not contain parts that need frequent maintenance, while this property is more difficult to achieve for electrically-excited synchronous motors.

Re: Electric motors with no rare earths

#132

Post by bornfreddy » Sat, Jun 13, 2026, 9:23 AM 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…

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. :-/

Re: Electric motors with no rare earths

#133

Post by [deleted] » Sat, Jun 13, 2026, 9:23 AM 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…

[deleted]

Re: Electric motors with no rare earths

#134

Post by lloeki » Sat, Jun 13, 2026, 9:36 AM UTC

hdrz wrote: post #117

echoangle wrote: post #90

Earlier quoted context omitted.

It also helps that they are made from aluminum which doesn’t rust like iron does.

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

Rust being literal Fe2O3 makes a convincing argument that aluminium sure oxidises but doesn't rust pretty much by definition ;)

Re: Electric motors with no rare earths

#135

Post by wongarsu » Sat, Jun 13, 2026, 9:40 AM UTC

hdrz wrote: post #117

echoangle wrote: post #90

Earlier quoted context omitted.

It also helps that they are made from aluminum which doesn’t rust like iron does.

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

Re: Electric motors with no rare earths

#136

Post by dmurray » Sat, Jun 13, 2026, 9:43 AM UTC

regularfry wrote: post #106

sroussey wrote: post #92

Earlier quoted context omitted.

After 22 years, my z4 has needed batteries and a starter. Recently, there was a problem with the engine misfiring but it was $200. LA, California

If you had bought a 7 or 5 Series at that time, you would not have had that experience. The 2001 7 Series had something like a 25% roadside breakdown rate.

25% every journey, or 25% over the lifetime of the car? Neither seems really believable but I don't understand how else you would measure this.

Re: Electric motors with no rare earths

#137

Post by rbanffy » Sat, Jun 13, 2026, 10:02 AM UTC

WalterBright wrote: post #83

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…

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…

That 60Hz sound is a sure sign we did something very wrong. By the time you hear it it’s usually too late to say “Uh oh”

Re: Electric motors with no rare earths

#138

Post by rbanffy » Sat, Jun 13, 2026, 10:08 AM UTC

dcanelhas wrote: post #111

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 mach…

The real innovation is in making them brushless and essentially maintenance free while still being efficient enough.

Re: Electric motors with no rare earths

#139

Post by adrian_b » Sat, Jun 13, 2026, 10:12 AM UTC

hnav wrote: post #34

Jblx2 wrote: post #18

Earlier quoted context omitted.

Synchronous motors: running on software since the 1880s. Nikola really was ahead of his time!

He invented the induction motor which runs right off the grid.

Tesla had invented a kind of two-phase induction motor, but the three-phase induction motor that is the ancestor of the modern induction motors was invented in 1891 by Mikhail Dolivo-Dobrovolsky (working in Germany at AEG), who had also invented in 1888 the three-phase grid, the three-phase generator and the three-phase synchronous motor.

The Dolivo-Dobrovolsky motor is the ancestor of all high-power induction motors, while the Tesla motor can be considered the ancestor of the single-phase induction motors that have been used (more frequently in the past than today) for several household appliances, like washing machines (or reel-to-reel magnetic tape recorders, a half of century ago).

Re: Electric motors with no rare earths

#140

Post by rbanffy » Sat, Jun 13, 2026, 10:14 AM UTC

dreamcompiler wrote: post #77

pfannl wrote: post #16

Earlier quoted context omitted.

Also known as: “we removed the rare earths and added software.”

Rare earth magnet motors require software too if you want them to be maximally efficient. You could embody that software in e.g. an FPGA of course, but it's still software.

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