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Any motor experts here? Why are they chasing rare earth metals in the first place? In the end, the mines are going to be in China anyway, right? Why don't we de

Any motor experts here? Why are they chasing rare earth metals in the first place? In the end, the mines are going to be in China anyway, right? Why don't we design around rare earth magnets in the first place? Synchronous reluctance motors where torque density isn't a strict requirement, and brushless separately excited synchronous motors (synchro motor with electromagnets on the rotor) for high torque/energy density applications?

adrian_b 2y ago
Those kinds of motors are usable, but they have a lower energy efficiency than permanent-magnet motors, which causes a lower range for an electric vehicle. In all applications where it is possible to use motors without permanent magnets, that is usually done, because the motors without permanent magnets are normally cheaper.
Zamiel_Snawley 2y ago
Electromagnets for the rotor cause significantly more heating, exactly where it is hardest cool, and where the heat is most likely to seep into the load. For high torque density applications, heat dissipation is often the limiting factor on duty cycle. Also, the slip rings capable of passing high current to an electromagnet rotor are expensive and less robust than permanent magnets. Essentially: it’s possible but I haven’t seen an application where it’s practical.
- pwrson 2y ago
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- pbmonster 2y ago
  > Also, the slip rings capable of passing high current to an electromagnet rotor are expensive and less robust than permanent magnets. The new designs are all inductively coupled, i.e. they have a rotating transformer coil built into the shaft. No brushes, no slip rings.
  - Workaccount2 2y ago
    Coupling without using a core (or using an air core) is gonna hit efficiency pretty badly though.
    - pbmonster 2y ago
      Unfortunately, I can only find material from the marketing department on that issue. But if I understand correctly, both coils have a ferrite core (and yoke), but there is a small air gap where the rotating side is separated from the stationary side.
nyokodo 2y ago
> the mines are going to be in China anyway, right If you had read the article you’d know they have their own mine: “Hardly any firms, even in China, do what MP is attempting: produce finished magnets starting with ore that the company mines itself” Mostly China doesn’t mine materials but has concentrated the refining capacity in China for many commodities. Thankfully, we do have backup capacity so we won’t be totally screwed if China cuts us off, and the refining technology is well understood and in a conflict we or our allies can cut them off from many raw materials so their refining advantage isn’t a checkmate.
- pbmonster 2y ago
  > Mostly China doesn’t mine materials but has concentrated the refining capacity Unless I'm working on old information, this is not correct. The overwhelming majority of neodymium mining capacity is currently in China. > you’d know they have their own mine: Sure, but to make a difference from a geopolitical perspective, we need more than that. And I don't see those kind of mines being opened on a large scale anywhere in the west. Regulations are challenging and environmental resistance is significant.

adrian_b 2y ago

Those kinds of motors are usable, but they have a lower energy efficiency than permanent-magnet motors, which causes a lower range for an electric vehicle. In all applications where it is possible to use motors without permanent magnets, that is usually done, because the motors without permanent magnets are normally cheaper.

Zamiel_Snawley 2y ago

Electromagnets for the rotor cause significantly more heating, exactly where it is hardest cool, and where the heat is most likely to seep into the load. For high torque density applications, heat dissipation is often the limiting factor on duty cycle. Also, the slip rings capable of passing high current to an electromagnet rotor are expensive and less robust than permanent magnets. Essentially: it’s possible but I haven’t seen an application where it’s practical.

pwrson 2y ago
[dead]
pbmonster 2y ago
> Also, the slip rings capable of passing high current to an electromagnet rotor are expensive and less robust than permanent magnets. The new designs are all inductively coupled, i.e. they have a rotating transformer coil built into the shaft. No brushes, no slip rings.
- Workaccount2 2y ago
  Coupling without using a core (or using an air core) is gonna hit efficiency pretty badly though.
  - pbmonster 2y ago
    Unfortunately, I can only find material from the marketing department on that issue. But if I understand correctly, both coils have a ferrite core (and yoke), but there is a small air gap where the rotating side is separated from the stationary side.

nyokodo 2y ago

> the mines are going to be in China anyway, right If you had read the article you’d know they have their own mine: “Hardly any firms, even in China, do what MP is attempting: produce finished magnets starting with ore that the company mines itself” Mostly China doesn’t mine materials but has concentrated the refining capacity in China for many commodities. Thankfully, we do have backup capacity so we won’t be totally screwed if China cuts us off, and the refining technology is well understood and in a conflict we or our allies can cut them off from many raw materials so their refining advantage isn’t a checkmate.

pbmonster 2y ago
> Mostly China doesn’t mine materials but has concentrated the refining capacity Unless I'm working on old information, this is not correct. The overwhelming majority of neodymium mining capacity is currently in China. > you’d know they have their own mine: Sure, but to make a difference from a geopolitical perspective, we need more than that. And I don't see those kind of mines being opened on a large scale anywhere in the west. Regulations are challenging and environmental resistance is significant.