8 ms·
No rare earth metals in the Model S
- diydsp 13y agoFascinating! but I would add that not only DC motors use permanent magnets, but also many synchronous motors, including stepper motors.
- kvprashant 13y agoStepper motors are small in scale, are they not? And, synchronous motors are also AC motors in steady state.
- invaliddata 13y agoStepper motors simply provide accurate and fast occasional rotational positioning. This requires high torque at a wide rpm range, including 0 rpm, for obvious reasons. stepper motors are a very bad application for induction motors, since everything other than steady state operation requires advanced control systems and switching power supply circuitry. For the basic induction motor without an advanced control system, the starting torque must be provided by inefficient means, and is still very limited. Synchronous motors are motors where the rotation of the magnetic field is synchronous with the rotation of the motor. For all induction motors, the induced field is a result of a varying magnetic field across the element in question. This implies that the speed of the rotor must be different than the speed of the magnetic field. Thus, no induction motor is a synchronous motor, almost by definition.
- baddox 13y agoI actually wasn't aware that induction motors don't use permanent magnets. RC model aircraft is a hobby of mine, and all I knew is that the commonly-used brushless AC motors certainly use permanent magnets.
- invaliddata 13y agoAs a first order simplification, motors are all about pairs of magnetic fields attracting / repelling each other. Often, one side of the pair is a permanent magnet. If instead the magnetism is induced (implying no magnet involved, as the other side must be switchable / controllable / varying, thus not a permanent magnet), you have an induction motor. At low power levels, permanent magnet motors (specifically brushless motors) tend to have higher efficiency than induction motors, additionally, they don't require complicated control systems to operate efficiently at varying speeds. Thus you are unlikely to see an induction motor in an RC model anytime soon.
- dskhatri 13y agoYep, Permanent Magnet AC (PMAC) motors are common types of synchronous motors. They are generally more compact than induction motors for the same power output. Induction motors are generally less expensive. An official (not forum post) article comparing the two: http://www.teslamotors.com/blog/induction-versus-dc-brushless-motors http://www.teslamotors.com/blog/induction-versus-dc-brushles... DC Brushless and PMAC are interchangeable. Oh, and nowadays, you don't need sensors (hall, encoder etc). 'Sensorless' motor control is possible by sensing the back emf of the motor or reconstructing the motor current via (super inexpensive) shunt resistors on the legs of the inverter.
- mchannon 13y agoWhile the motors may be REE-free, I wouldn't be so sure about the rest of the vehicle. Many models of LED's, lasers, displays, headlights, and power circuits use trace but nonetheless essential amounts of rare earths. The motors and actuators (power windows and locks, charge port and frunk poppers) and seat heater relay might also contain them.
- deleted 13y ago[deleted]
- dnautics 13y agoindium's not a rare earth metal.
- sologoub 13y agoDefinitely doubt it's possible to have a completely REE-free modern electric car. The post name is definitely click-bait and should be clarified.
- arthulia 13y agoI think it would be difficult to have a modern car that is REE-free.
- 001sky 13y agoTesla does not use rare earth metals in our battery or motor. The HN Title [1] should be changed, as it is in effect editorializing beyond the information provided, IMHO. As others have noted, there is no information to suggest the statement is generally true, beyond these two sub-system components. [1] Currently: "No rare earth metals in the Model S"
- dnautics 13y agothere are almost certainly rare earth metals in the speakers, for example, although the mass would be relatively cheap compared to what you would need for a motor. Does the tesla have regenerative braking system, and I wonder if there are rare earth metals there?
- skriticos2 13y agoThey have a 17" display in the dashboard. That certainly has some rare earths in it combined with all the latest electronics. Here is an article: http://www.pbs.org/wgbh/nova/next/physics/rare-earth-elements-in-cell-phones/ http://www.pbs.org/wgbh/nova/next/physics/rare-earth-element...
- joezydeco 13y agoGood point. Almost every capacitive touchscreen uses a vapor-deposited coating of indium tin oxide (ITO) as a transparent conductor. Granted, it's a microscopic amount of indium, but still.
- avmich 13y agoIndium isn't a rare earth element, is it?
- jonnathanson 13y agoTechnically it's not in the set of rare earth metals, though it is rare (at least in naturally occurring and isolated form).
- fersho311 13y agoI wasn't sure what the implications of rare earth metals were, so I looked it up. In sort, Rare metal extraction involves substantial pollution in the mining, onsite processing, and refining phase. Mines create environmental degradation through topsoil loss, poorly controlled tailings ponds that leach into groundwater as well as lakes and rivers, roads slicing through habitat, and the use of large amounts of energy to extract and process the materials they uncover. Some rare earth metals require substantial processing, and that provides a number of opportunities for pollution at every step of the way. More here: http://www.theguardian.com/commentisfree/2011/sep/26/rare-earth-metals-technology-boom http://www.theguardian.com/commentisfree/2011/sep/26/rare-ea...
- steven2012 13y agoI think it's more to do with the fact that China has a monopoly on most rare earth metals, and the supply can get constrained, like they did last year against Japan.
- zafka 13y agoActually, there are a number of places with large Lanthanoid deposits, but since China was supplying them so cheap, the mines were not economical. Now that China is tightening supplies, they have reopened the California mine in Mountain Pass that used to be a major supplier.
- dragonshed 13y agoNitpick: China doesn't have a monopoly on rare earth metals, they just have the least restrictive policies on mining them, and they won't export the raw materials which forces companies to bring their processing operations into china. The US has plenty of rare earths, they just always come up with thorium, which regulators regard as a nuclear waste that must be disposed of at exorbitant cost to the mine operators.
- pedalpete 13y agoAs others have stated, China does not have a monopoly, but they do supply 95% of rare-earth metals, and have been buying mines in other countries, which is leading to a monopoly type situation. http://www.mining.com/china-growing-uneasy-over-greenlands-rare-earth-ambitions-98403/ http://www.mining.com/china-growing-uneasy-over-greenlands-r...
- chao- 13y agoThe linked page describes this as something that "absolutely belongs up on the Model S Facts page". Is there anything particularly negative about rare earth metals aside from their potential scarcity? Edit: fersho311 answers my question in the same minute I ask it. Thanks :)
- jlgreco 13y agoWhy is this notable, beyond possibly price associated with them? The only issue with rare earth metals is that at various times the supply of them has been politically shaky, though I think that is currently not the case? I'm not really sure...
- dnautics 13y agocurrently not the case, as the US has spun up rare earth metal mines (molycorp, e.g.) also the environmental concerns are less (not to say they are nonexistent) when the US does it because we tend to care about the environment more than china does, especially in california. Also don't be decieved by the term, rare earth metals aren't really all that rare. If anything their expense comes from the difficulty in extracting them selectively from their ores - because rare earths are chemically similar (has to do with the f electron shell being physically "buried" under the d and s shells) they tend to ore together, and then become tricky to separate.
- zafka 13y agoIt would be possible to build a more compact motor using NFeB magnets, but the cost outweighs the slight weight/performance gain. It is also my understanding that induction motor that Tesla uses is more efficient at regenerative braking.
- codex 13y agoNo other electric car manufacturer can make this claim, as the rest use permanent magnets in their motors despite the higher cost. Why, I don't know.
- pkulak 13y agoWhy do you say that? I'm pretty sure every other car uses synchronous AC motors, just like Tesla. Do _any_ AC motors use permanent magnets?
- codex 13y agoI believe they all do; the LEAF's is described here: http://www.johnwmorehead.com/new-nissan-leaf-rare-earth-electric-motor-innovation/ http://www.johnwmorehead.com/new-nissan-leaf-rare-earth-elec...
- hristov 13y agoBecause they want to have DC motors, while Tesla uses an AC motor. There are various advantages disadvantages to both. DC motors require permanent magnets. The AC motor on the other hand has the problem that the power coming out of the battery is DC. So it has to be converted back to AC in order to be used in an AC motor. The Tesla has a large inverter that converts the DC to AC. Most other makers choose to have a DC motor in order to remove the need for an inverter. Some people joke that Tesla chose an AC motor, because that was the motor invented by Nicola Tesla. But the AC motor has other advantages such as its excellent torque curve. The latter ensures that the model s has no gearbox while it features amazing acceleration at all speeds.
- pkulak 13y agoWell, I know for a fact that the Leaf also uses an AC motor with an inverter. It's documented all over the place. But, they have permanent magnets in theirs, while Tesla apparently does not.
- amalag 13y agoLithium?
- archangel_one 13y agoNot a rare earth element.
- fancyketchup 13y agoLi more abundant in the Earth's crust than Cu, Zn, or Ni. I don't think we're going to run out any time soon.
- achy 13y agoDoes anyone know the relative merits of induction vs brushless with regards to regenerative braking?
- kineticfocus 13y agoThere's a good answer in the comments section... http://www.teslamotors.com/blog/induction-versus-dc-brushless-motors http://www.teslamotors.com/blog/induction-versus-dc-brushles... ... search for 'regenerative'
- hristov 13y agoI think the point the poster is trying to get across is that there are no more rare earth metals in a Tesla model S than any other car of its class. Of course there may be some small amount of rare earth metals in the speakers or the electronics, but this is not an increase from any other car. The issue of rare earth metals was used by some nay-sayers to incorrectly argue that the Tesla model S is more environmentally damaging than equivalent gasoline powered cars.
- smackfu 13y agoThis is just a forum post by Joe Random, not sure why it was posted here.
- kvprashant 13y agoFor the purpose of discussion.
- phy6 13y agoThe typical hipster that would complain about "rare earth" metals in a car they'll never afford doesn't care about the rare earth in their iPhone or iPad (which is one of the reasons they are made in China).