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Electric motors with no rare earths

renaultgroup.com

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Re: Electric motors with no rare earths

#41

Post by lostlogin »

PedroBatista wrote: post #11
bgarbiak wrote: post #4

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.

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?

The bit the gets me more than the sale price is servicing.

BMWs have a terrible record for needing expensive repairs.

I know you shouldn’t rely on anecdote, but it seems I do.

Re: Electric motors with no rare earths

#44

Post by userbinator »

somat wrote: post #39
dmitrygr wrote: post #2

Seems to be: replace permanent Nd magnet with an electromagnet.

There is something... weird about this. this tech has existed.... a long time. And I am not familiar with what is common in electric cars so may be missing something obvious but thought this was already how it was done. let me explain my limited understanding. With ac motors electromagnets can be used in the rotor. there is even a super clever way to do it where the electromagnet in the rotor is driven wirelessly via…

Permanent magnet motors are simpler and cheaper to make, at least in the small (yes, small --- there are electric motors in the MW range in industrial applications, which are themselves larger than an average car) sizes found in EVs.

Re: Electric motors with no rare earths

#45

Post by genter »

hnav wrote: post #36
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 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).

I've probably taken apart 10 automotive alternators. Every single one had brushes.

Re: Electric motors with no rare earths

#46

Post by themafia »

hnav wrote: post #31
hijinks wrote: post #29

let me guess.. but its 2x the price?

no, but requires introduces brushes (slip-rings really) which is a wear item

Cars already have lots of wear items and a mature service industry for them. If I can reliably get at least 50k miles out of it, then I wouldn't be all that bothered, as this is not likely to be an expensive part or service.

Re: Electric motors with no rare earths

#47

Post by raverbashing »

dheera wrote: post #37
hnav wrote: post #36

Earlier quoted context omitted.

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).

Slip rings have brushes.

Yes but they wear less than DC brushed motors exactly because it's a slip ring and not a commutator

Re: Electric motors with no rare earths

#48

Post by ahartmetz »

raverbashing wrote: post #47
dheera wrote: post #37

Earlier quoted context omitted.

Slip rings have brushes.

Yes but they wear less than DC brushed motors exactly because it's a slip ring and not a commutator

Because it's the discontinuities in the commutator where the sparks fly (with much help from self-induction of the motor's coils) and erode the ring and brushes.

Re: Electric motors with no rare earths

#49

Post by ahartmetz »

isopede wrote: post #43

Does regenerative braking work with a motor like this?

After watching a Munro video about it, I see your point. In the motor shown, the rotor gets its magnetic field simply by inducing a current and a field in it in reaction to the stator's field. There are no electromagnets in the rotor like I expected. In that case, I'm not sure either... I'd say more likely than not but it's complicated since the stator basically needs to induce a field and at the same time recover energy from the field that comes back from the rotor. I would further guess that the phase shift between the two components makes it possible to treat them separately.

Previous comment: Don't see why not - the "field" coils (the ones that replace the permanent magnets) need to be energized, which can initially come from the batteries if necessary.

Re: Electric motors with no rare earths

#50

Post by hnav »

genter wrote: post #45
hnav wrote: post #36

Earlier quoted context omitted.

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).

I've probably taken apart 10 automotive alternators. Every single one had brushes.

yeah I misspoke, I meant to say that it's a brush riding on a slip-ring (continuous contact, no arcing, lasts long) rather than a bunch of contacts in a cylinder (commutator, arcing, wears out).
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