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Comment by promiseofbeans | Hacker News Reader

I saw a video recently of Tesla bragging that they had a new motor with only 3(?) powerful magnets in it. This makes me think that less magnets is a good thing - can anyone explain to me the reason to use less magnets in motors? (To me it just seems that less magnets would make it harder to spin with a magnetic field, but I'm no engineer).

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If having fewer magnets means less rare earth consumption for the same performance, then that's a benefit in itself - the same one as is being claimed for this motor.

https://news.ycombinator.com/item?id=37454238

I think it just dictates the number of poles the motor has? The fewer the poles the less torque it has, but higher RPM. Either way you have to gear it down for EV use, so I suppose it doesn't really matter much in the end, except if it makes the rotor less likely to explode.

I would've expected very high pole counts to be more practical though, since a lower RPM is more manageable in terms of bearings wearing out. On the other hand, steppers have a high pole count and their efficiency is crap so maybe they can get more power out with fewer poles.

Steppers are super optimized for being super precise and easy to controle while being (relatively) cheap to build.

They have weird "trick" geometry that means you can move the rotor to many different angles (tens, hundreds) with far fewer stator windings.

The cost of this is really low power and efficincy if you just want to spin them.

Unless you want to chase Tesla with marketing numbers trading off torque for something else is almost always a good tradeoff.

Modern electric motors are much stronger than most users need.

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