The issue with tantalum is not that any one source has a stranglehold on the supply, but that no one has real control over the best sources. These are in the jungles of the eastern Congo, where there is no real rule of law, and consequently the mines are fought over with deadly results. It makes the mining in the American "wild west" of the 19th century look very tame indeed. Many people think these mines are a key source of conflict in the Congolese civil war that has been raging for over a decade and has killed literally millions of people.
When I watched James Cameron's movie Avatar about the fight over mining "unobtainium" in the jungles of another planet, I immediately thought of the tantalum mining in the Congo. (I wonder if it was inspired by that.) Of course, the irony of the movie to me is that a lot of tantalum was required in the computers that created the images for the movie.
It wouldn't be the first time people got fooled by hype. All types have their place and REE's is when they are cheap, lower hp. Once the price rises, temps/amps go up REE's just don't look that good.
I stated my case and I guess we'lll have to see what the next generation of hybrids and EV's brings. I'd bet almost all future over 2k lb EV's will not use REE's and far less in hybrids. Mostly REE;s under 50hp or so and not above that mostly.
I'm pricing out now for a production 1300lb EV and looking at what is available SepEx DC motors put out more power/$ and 3x's the reserve power/torque for the same amps as any REE's motor can starting and in the lower speed ranges and match them at high speed. To get the same power from a REE motor costs 4'6x's as much.
2 of these series motors in the Killicycle drag bike did 172mph, 7.8sec in the 1/4 mile show how they can be pushed. A 12hp rated they get 150hp from shows how much reserve they have. Try that with with a REE motor and you'll have some recycling to do.
And those EV'ers build DC controllers that put everyone else to shame for over a decade, over 700kw the size of a shoebox big business is just getting able to do.
@JimT: tantalum, while not a rare-earth metal, is indeed a rare metal. If I recall correctly something like 500-1,000 tpa is produced globally, from just a handful of sources.
I agree, Ann. What snared us in this case was China's low price over a decade or two. We have plenty of rare earth materials in both California and Colorado. But we shut down the plants when China's low prices made our mining unprofitable. Likewise with Australia. That changed last year.
Your experience with rare-earth and induction motors does not match mine at all. If what you say about the rare-earth motors were true, nobody would bother paying the premium for them for any application.
Rare-earth motors have smaller and lighter rotors than induction motors of equivalent power ratings. Because their magnetic fields are always there, they provide quicker response at higher efficiencies, including starting from stop.
You pay a significant premium for these capabilities, particularly in larger motors. Because of the permanent magnet field, you cannot field weaken them to nearly the extent that you can with induction motors. Demagnetization of the permanent magnets is at least a theoretical issue, but does not stop them from being used in applications that have the most stringent reliabilitly requirements. Proper current monitoring and control generally prevents this from being a real problem in most applications. Demagnetization does not come from steady use within design limits; it comes from a sudden overcurrent condition well outside of design limits.
Of course, the tradeoff between rare-earth and induction motors depends in part on the relative pricing betwen the materials for the two. If the required rare-earth materials get a lot more expensive, it will skew the decision toward induction motors.
(Sorry for the late comments – this topic has soared to 25+ comments in < 48 hours I've been pre-occupied)Reviewing the entire thread, I was specifically wondering if anyone had identified other rare-earth materials facing a similar jeopardy; specifically, Tantalum comes to mind.
I know that tantalum (as in tantalum chip capacitor), recently faced a similar peril.One former Engineering VP (around 2004) encouraged the R&D engineers to find a suitable replacement for tantalum caps, due to the single excavation location (somewhere n Australia) and the rising costs of that unique material. I'm wondering if Tantalum is considered "Rare-Earth", and if have any insights to the global outlook for it's use in electronics-? Maybe your future article segments will cover this-?
No doubt in smaller motors REE's are better but in EV's not so much.
Variable field AC motors give far better power/size/weight especially starting torque. Induction still does very well at a little lower eff.
Old style Sep-Ex motors in bigger dia are about as eff and put out 3x's the starting torque. And the controllers for it are 25% of the price as likely the motor is too.
I put a 9hp REE motor in my EV subcar and soon afterward I found oput how little torque it had burning up trying to start up a slight hill. Yet my 3.5hp series motor easily did the job and with field weakenng pulls up to 5500rpm.
My point is that REE's are not needed for EV's, hybrids, is an obvious fact.
Don't get me wrong I like REE's, just in my wind generators where it works well I'll start building next month.
Since you work designing them could you comment on how well they are standing up to high emps, magnetism in high power REE units? I know the Prius had some problems with magnets weakening enough they had to be replaced.
Thanks, Rob, for that info. That doesn't surprise me. China is certainly not the only country or political entity to ever behave like that. But what's different in their case is the fact that they control such huge volumes of so many different resources, materials, and products.
This is a great article on RE market and what it means for engineers. RE elements are coproduced-the demand for and the increased supply of one makes the others abundant. Currently, neodymium dominates demand and supply since it is used to make NdFeB magnets for PM motors primarily used in hybrid cars. Yttrium used in high-temperature superconductors, lanthanum used as a catalyst and the others, used in semiconductor, lasers, and batteries, get a free ride from neodymium.
It must be remembered that the recent success of the high torque PM motor owes its success to high power semiconductor switching and processor control as much as to high energy product neodymium permanent magnets. Many researchers are investigating high starting torque RE-less induction motors using semi power switching and processors. Toyota has announced that it will have a RE-less motor in their 2014 hybrid. Chorus Motors already has an RE-less induction motor in the field able to taxi passenger jets without using jet power.
Some see a sinister motive in China to use cheap labor and an abundance of RE deposits to monopolize the RE magnet market. China has launched an ambitious wind generation campaign with the goal of producing 100-gigawats by 2020 which will require more RE than they can supply with current technology. Chinese wages are climbing and the Chinese are investigating practical ways of making wind generators without RE magnets.
If you have any more information on this subject, I would like to know. fred@etcheverrys.com
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