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Electric motors with no rare earths

renaultgroup.com

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Re: Electric motors with no rare earths

#141

Post by monster_truck »

throwaway2037 wrote: post #99
lostlogin wrote: post #41

Earlier quoted context omitted.

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.

> BMWs have a terrible record for needing expensive repairs. EVs? That makes no sense. EVs are so much simpler to maintain compared to ICEs.

They suffer from some of the same problem your likely modern fridge does, and then kick it up two notches.

In the name of "safety", they have made design decisions such as integrating fuses directly into the very large and expensive control boards and making them non-replacable. Just in case this wasn't enough, they also tend to blow an OTP so that in the event that you have the know how to replace the fuses anyways, nothing will work. Naturally you also cannot just swap in a replacement board, as it needs to go through the same pairing process to the ECU as things like the car doors, which in most cases requires an active certificate/license on the ecu programmer that only dealerships/oem have.

Re: Electric motors with no rare earths

#142

Post by hulitu »

adrian_b wrote: post #131
snovv_crash wrote: post #96

Earlier quoted context omitted.

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 efficienc…

> The lower efficiency means a lower range for the same battery,

And some heat which must be dissipated or else they will dethrone the BMW as the leading burning car. /s

Re: Electric motors with no rare earths

#143

Post by adrian_b »

regularfry wrote: post #107
hnav wrote: post #34

Earlier quoted context omitted.

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

Other way round. He invented the induction motor (1887) which the three-phase grid was then demonstrated to drive (1891). That's how influential it was. There are other reasons a three-phase grid is handy but being able to drive these brushless contraptions must have seemed utterly wild at the time.

A three-phase grid cannot drive a two-phase induction motor, like that invented by Tesla.

In 1891, the three-phase induction motor was invented by Mikhail Dolivo-Dobrovolsky, combining the principles of the three-phase synchronous motor previously invented by Mikhail Dolivo-Dobrovolsky with the principle of the induction motors invented by Nikola Tesla and Galileo Ferraris.

Like any inventions, the induction motors of Nikola Tesla and Galileo Ferraris had not sprung out of nothing, but they were based on the experimental observation that had been known for many decades that if you rotate some magnets around a disk of copper, the disk will rotate, even if the magnets do not have any action on the disk when stationary.

Because of the symmetry, it is easier to generate electromechanically three-phase currents than two-phase currents where the phase difference must be precisely of one right angle.

Re: Electric motors with no rare earths

#144

Post by adrian_b »

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).

Brushes are used everywhere for transmitting electrical current between two parts that have an unlimited relative motion.

Brushes are typically made of graphite mixed with some binder. The graphite conducts the electrical current, but it also acts as a lubricant.

The metallic part that is in contact with the brush is called a slip ring, if it is continuous, like in synchronous motors, or a collector ring if it is segmented, like in DC motors or single-phase motors with brushes.

Re: Electric motors with no rare earths

#145

Post by ReptileMan »

whazor wrote: post #124
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…

Not sure how familiar you are with Renault, but “maintenance problems” pretty much sums up a lot of older Renaults.

As the old saying goes - better a naughty French than boring German...

Re: Electric motors with no rare earths

#146

Post by adrian_b »

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 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.

Re: Electric motors with no rare earths

#147

Post by adrian_b »

cogman10 wrote: post #15
delfugal wrote: post #6

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

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 us…

For about a half of year there have been cars with sodium-ion batteries, in China. As you say, for now they are more expensive, but it is expected that the price will drop quickly in the following years.

Because they lose neither capacity nor charging speed at low temperatures, like the lithium-ion batteries, they expect that in the future sodium-batteries will be the best choice in the countries with cold climates.

Re: Electric motors with no rare earths

#149

Post by mirsadm »

whazor wrote: post #124
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…

Not sure how familiar you are with Renault, but “maintenance problems” pretty much sums up a lot of older Renaults.

What does older mean in this context? Because some people still think the year 1996 wasn't that long ago. Modern Renault cars are fine and reliable enough. I've had 4 in my life time and had zero issues myself. I see a ton of them here in the UK and, again, they're fine.

Re: Electric motors with no rare earths

#150

Post by sofixa »

whazor wrote: post #124
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…

Not sure how familiar you are with Renault, but “maintenance problems” pretty much sums up a lot of older Renaults.

Which "older" ones? The original 5 is kind of a tank.
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