On Tesla's induction motor(economist.com)
economist.com
On Tesla's induction motor
http://www.economist.com/blogs/babbage/2011/04/induction_motors
81 comments
That's a pretty cool inductive motor hack. Personally, my favorite esoteric motor has to be the wobble motor built using electropermanent magnets (essentially, programmable permanent magnets):
http://www.hizook.com/blog/2010/12/07/electropermanent-magne...
Do you know of any other "cool" motor hacks?
http://www.hizook.com/blog/2010/12/07/electropermanent-magne...
Do you know of any other "cool" motor hacks?
Brusa has an induction motor with magnets embedded in the rotor. At high torque, the induction overrides the permanent magnets. At lighter loads, the permanent field dominates and turns it into a synchronous motor.
http://www.diyelectriccar.com/forums/showthread.php/evdl-syn...
http://www.diyelectriccar.com/forums/showthread.php/evdl-syn...
Another friend of mine from grad school did his thesis on something like this.
http://dspace.mit.edu/handle/1721.1/18013
"We propose a novel variation of a doubly-fed induction generator which aims to improve power density and simplify construction. Our design is a doubly-fed, dual-rotor, axial-flux, permanent-magnet machine."
The magnets for that thing were truly scary. Every once in a while I gave him a hand with the assembly and it took three or more of us to safely install each magnet in the rotor.
http://dspace.mit.edu/handle/1721.1/18013
"We propose a novel variation of a doubly-fed induction generator which aims to improve power density and simplify construction. Our design is a doubly-fed, dual-rotor, axial-flux, permanent-magnet machine."
The magnets for that thing were truly scary. Every once in a while I gave him a hand with the assembly and it took three or more of us to safely install each magnet in the rotor.
Ah yes, AC motors, the bane of most of the EE's in my graduating class since computing electromagnetic fields in a rotating context was such old technology. At the time the only 'use' for them was machine tools and blower fans, both of which took advantage of the fact that you could plug them directly into a 3-phase power line and they would run at 60 RPM all day and all night.
Variable frequency 3-phase inverters which can support the current capacity to generate 100HP+ (75KW) was really only invented with iGBTs in the last couple of decades. The article doesn't mention that the inverters have to be cooled, as they are a significant source of heat as well.
Variable frequency 3-phase inverters which can support the current capacity to generate 100HP+ (75KW) was really only invented with iGBTs in the last couple of decades. The article doesn't mention that the inverters have to be cooled, as they are a significant source of heat as well.
I had no idea about IGBTs. Thanks!
http://en.wikipedia.org/wiki/Insulated-gate_bipolar_transist...
http://en.wikipedia.org/wiki/Insulated-gate_bipolar_transist...
Another permanent-magnet-less motor design is the switched-reluctance motor. Its primary advantage over the induction motor is its dirt-simple rotor construction - it's essentially just a properly shaped chunk of iron, where an induction motor would require a copper squirrel-cage.
Its disadvantage relative to the induction motor is that it requires some cleverness in its controller and/or sensors in order to run at all. I actually wrote some control software for one as a side project - it was a somewhat frustrating experience (though a good portion of the frustration was due to malfunctioning hardware).
http://en.wikipedia.org/wiki/Switched_reluctance_motor
Its disadvantage relative to the induction motor is that it requires some cleverness in its controller and/or sensors in order to run at all. I actually wrote some control software for one as a side project - it was a somewhat frustrating experience (though a good portion of the frustration was due to malfunctioning hardware).
http://en.wikipedia.org/wiki/Switched_reluctance_motor
Also interesting is their capability to produce their full Torque output at 0 RPM. For applications requiring high torque for "station keeping", this is crucial, and is pretty unique to SRM (Switched Reluctance Machine) motors.
I've been quite interested in repurposing the little Dyson "digital motor", but I suspect that a complete drive system redesign would be necessary to enable full variable RPM control (ie. 0-max, in both directions).
Question for turbofail: did your project happen to use the SRM motor from the Neptune front-load washers, or some other motor?
I've been quite interested in repurposing the little Dyson "digital motor", but I suspect that a complete drive system redesign would be necessary to enable full variable RPM control (ie. 0-max, in both directions).
Question for turbofail: did your project happen to use the SRM motor from the Neptune front-load washers, or some other motor?
It was a custom-made SRM made by someone else. They were intending to use it in an electric vehicle.
Very interesting! WP also says, "Stepper motors are similar to switched reluctance motors (which are very large stepping motors with a reduced pole count, and generally are closed-loop commutated.)" I didn't know!
Interesting point to note here (since this article seems to float from point to point) is the fact that tesla's battery to wheels efficiency ratio is 88%, which the article states is 4x the average. Seems to me like Toyota's investment in tesla was a better deal than we initially assumed.
Nothing to write home about. Electric engines are efficient.
If you look at the efficiency from, say, coal burned in the power station to electricity in the batteries to driving, electric cars fare similar to internal combustion engines. (Burning your fuel in the big power station is more efficient than a car's internal combustion engine, but going through the extra steps of transmitting the energy to your home and then into the batteries eats some of that.)
If you look at the efficiency from, say, coal burned in the power station to electricity in the batteries to driving, electric cars fare similar to internal combustion engines. (Burning your fuel in the big power station is more efficient than a car's internal combustion engine, but going through the extra steps of transmitting the energy to your home and then into the batteries eats some of that.)
This is rarely mentioned explicitly, but seems to be behind many of the "green car" claims: uranium "burned" in the power station is CO2-neutral, cheap and plentiful (even in politically stable regions.)
That's the ultimate advantage of electric cars: independence from any single energy source. Have sunshine? Use solar. Have water? Use hydro. Have uranium? Use fission.
And advances to generation technology increase the efficiency of everything downstream accordingly.
And advances to generation technology increase the efficiency of everything downstream accordingly.
The disadvantage at this point is that our current capacitance technology is less energy dense and slower to replenish than a fossil fuel tank. What happens when your daily commute doesn't fit comfortably within the vehicle's range?
Energy technology should ultimately improve our versatility. Putting batteries in a car doesn't achieve that goal just yet.
Energy technology should ultimately improve our versatility. Putting batteries in a car doesn't achieve that goal just yet.
For most Americans, todays batteries are more than sufficient to handle the daily commute. For outliers, they can choose to keep their ICEs or opt for hybrids like the Volt. To discount current tech for not being equivalent is just making excuses for the status quo. It's tantamount to simple FUD.
It most certainly is NOT fud. There are real consequences to your suggestion in the form of higher prices for both fuel and hardware. Right now we commute because it makes economic sense to commute, but if the fossil fuel cars and their fuel suddenly make that commute too costly it will negatively impact those who commite, their employers, and probably the communities in which these companies operate.
This all happens because there are a few folks who naively believe that batteries are a clean way to store energy.
This all happens because there are a few folks who naively believe that batteries are a clean way to store energy.
How is pointing out that today's batteries are perfectly sufficient for the vast majority of commuters going to cause fossil fuels and the cars that drive them to become too costly?
You've gone from suggesting the batteries are insufficient to suggesting that correcting your misinformation and fear-mongering will itself raise the price of ICEs and their fuel.
You're burning down strawmen of your own imagining.
You've gone from suggesting the batteries are insufficient to suggesting that correcting your misinformation and fear-mongering will itself raise the price of ICEs and their fuel.
You're burning down strawmen of your own imagining.
See Better Place's business model: buy the car, but rent the batteries, and have charging stations where they can be swapped in about as much time as filling your tank.
http://www.betterplace.com/
http://www.betterplace.com/
[deleted]
Definitely. Particularly given that new tech will initially be costly and not necessarily fit in a car.
And by abstracting out of the car, you get to skip re-running acceleration/skid/crash tests, redesigning for the particular size/weight/balance signature of the new tech, retooling the lines to manipulate the thing, rewriting/testing the controller code to drive the damn thing, etc.
And perhaps most importantly: you avoid compromising a technology's best efficiency curve in the quest to meet the demands of the driving model.
e.g. even if you're burning fossil fuel to generate power, for whatever reason, there are vastly more-efficient ways to do it than the way we do in in-car ICEs. Those ways just happen to be ill-suited to the power-demands of personal vehicles.
And perhaps most importantly: you avoid compromising a technology's best efficiency curve in the quest to meet the demands of the driving model.
e.g. even if you're burning fossil fuel to generate power, for whatever reason, there are vastly more-efficient ways to do it than the way we do in in-car ICEs. Those ways just happen to be ill-suited to the power-demands of personal vehicles.
Consider, too, that the diesel engines in large locomotives are basically rolling power plants. The diesel fuel doesn't directly power the drive train; it's used to generate electricity to power its electric motors.
Indeed. Those giant dump trucks often employed in open-pit mines operate the same way. Like this one: http://en.wikipedia.org/wiki/Liebherr_T_282B
Note the transmission type is listed as "AC electric"
Note the transmission type is listed as "AC electric"
One of the major reasons for these trucks and the locomotives having electric motors, is that maximum torque is available from 0 rpm in an electric motor. A diesel or petrol engine will max torque further up it's power band. This means these large machines are much easier to get moving.
Likewise for tugboats. Reversing the direction of a propeller is quicker and causes much less wear than with a transmission.
Consider transportation of oil and gas (petrol / auto gasoline) along with gas refining versus electricity generation and transmission.
In any case full electric cars allow centralized power generation, in turn allowing more opportunities for clean power.
In any case full electric cars allow centralized power generation, in turn allowing more opportunities for clean power.
Liquid fuel does have one serious upside that electric doesn't: storage.
And portability. And being reliable/known. Which is why militaries require large amounts of fossil fuels for now.
I remember when I was in the Army that our 5-ton dump trucks had lots of onboard stuff running off pressurized air, presumably making the vehicle more durable to electrical failures
Combine with local stored fossil fuels, and basic mobility/counter-mobility, and you have a harder-to-cripple ground force.
I remember when I was in the Army that our 5-ton dump trucks had lots of onboard stuff running off pressurized air, presumably making the vehicle more durable to electrical failures
Combine with local stored fossil fuels, and basic mobility/counter-mobility, and you have a harder-to-cripple ground force.
And recharge time: I calculated once that refilling your gas car occurs at a rate of approximately 5 Megawatts!
But, for 95% of trips, an overnight charge at 120V is sufficient.s
But, for 95% of trips, an overnight charge at 120V is sufficient.s
What we really need for electric cars is battery swapout. Just pull into the nearest station, trade out the drained battery for a fresh one, and you're off! Meanwhile, the station sets the drained battery on the charging array, and in a few hours, it's ready for the next customer!
In theory. I can see at least a couple of challenges in making such a system feasible. It's not like you can just shove the batteries into a massive underground tank, for example.
In theory. I can see at least a couple of challenges in making such a system feasible. It's not like you can just shove the batteries into a massive underground tank, for example.
That's actually being done by Better Place.
http://en.wikipedia.org/wiki/Better_Place
http://en.wikipedia.org/wiki/Better_Place
Not really. For those rare trips you drive more than 100 miles, rent a liquid-fueled vehicle. They're much better suited for such trips.
An electric vehicle is more specialized as a every-day commuter vehicle. It is cheaper in that duty.
Like a gas car, your cell phone can do anything your desktop can do, but your desktop is better suited for some tasks (i.e. faster for writing letters) even if its mobility is less.
An electric vehicle is more specialized as a every-day commuter vehicle. It is cheaper in that duty.
Like a gas car, your cell phone can do anything your desktop can do, but your desktop is better suited for some tasks (i.e. faster for writing letters) even if its mobility is less.
swapout is DOA. 30kw/h = 1000A x 120V x 15min. With coffee and wi-fi 15 min is nothing for most of the people. Replacing pumps with electricity chargers, the gas stations will easily morph into Starbucks and Starbucks/Safeways/etc... will morph into charging stations.
15 minutes? Are you kidding? It takes that long to get your oil changed and most people can't even be bothered to do that every 3 months / 3000 miles.
you are mixing things that can be delayed till next Monday and things that can't
What would the capital cost of such a scheme be and how fast could adoption happen? I am very skeptical of a large roll-out since all the current infrastructure is obsolete.
Yeah, we have a country built for a liquid fuel economy and electric just doesn't fit. I have some serious fears of technology not as versatile as previous and not as cheap.
Not to mention that in an accident, the available energy with liquid fuel is a fraction of the total. Only the gaseous portion will expode. With a battery, the entire stored energy is available should it arc.
it'll be interesting to see if with this renewed nuclear scare if we'll see centralized power generation as such a benefit. as small scale energy production gets more cost effective I could see many homes generating their own power (solar, thermal) - though I'm not saying any time soon.
[deleted]
well were they comparing the 88% to regular combustion engines or existing electric/hybrid cars?
Read the article. They say `conventional cars'.
Some electric motors are 95% efficient.
85-90%: typical brushless DC motors: http://en.wikipedia.org/wiki/Electric_motor#Brushless_DC_mot...
92.4%: minimum standard for 125hp NEMA B motors: http://www.engineeringtoolbox.com/electrical-motor-efficienc...
96%: new record efficiency achieved in 2009: http://newenergyandfuel.com/http:/newenergyandfuel/com/2009/...
85-90%: typical brushless DC motors: http://en.wikipedia.org/wiki/Electric_motor#Brushless_DC_mot...
92.4%: minimum standard for 125hp NEMA B motors: http://www.engineeringtoolbox.com/electrical-motor-efficienc...
96%: new record efficiency achieved in 2009: http://newenergyandfuel.com/http:/newenergyandfuel/com/2009/...
One of the biggest benefits -- which thankfully gets a line or so halfway down -- is that induction motors require far less cooling accessories. This is big for cost and weight savings.
A good point. With low weight and maximum torque from 0 to 6000 rpm, it will be interesting to see what performance cars will look like in 20 years.
[deleted]
[deleted]
The batteries weigh a lot and require cooling. A Lotus Elise, which the Tesla Roadster is based on, weighs and costs less.
The Nissan Leaf does not have battery cooling. Only the volatile type of Lithium batteries and NiMH batteries require cooling the first for life expectancy and safety and the latter because they are tremendously inefficient and give off large amounts of heat.
I think that a 350 mile range and 10 minute charge is ultimately the holy grail for electric cars. Most cars built try to shoot for 400 on highway gas mileage.
10 minute charge is not possible with the current grid. You would need 1,500A service - just for the car (most homes have 200).
The cables would be as thick as your arm.
You can do battery swaps instead, but it requires an infrastructure build out first.
The cables would be as thick as your arm.
You can do battery swaps instead, but it requires an infrastructure build out first.
I never said the home would be the primary charge point, you wouldn't charge like this at home, but at a charge station.
I'm implying that these are the specs necessary for an electric car to truly be taken seriously as a replacement for a gas vehicle.
Furthermore, charging at a higher voltage, say even 720 volts (about twice the current roadster's voltage) gets you down to 500 amps to charge a Tesla in 10 minutes, which is manageable for cables. Charge stations could have a reserve/buffered system they can charge from that way they wouldn't be hitting the grid all at once if 5-6 cars show up. You could do a similar thing at your house (basically a large UPS)
The battery swap thing is a pipe dream, IMO.
I'm implying that these are the specs necessary for an electric car to truly be taken seriously as a replacement for a gas vehicle.
Furthermore, charging at a higher voltage, say even 720 volts (about twice the current roadster's voltage) gets you down to 500 amps to charge a Tesla in 10 minutes, which is manageable for cables. Charge stations could have a reserve/buffered system they can charge from that way they wouldn't be hitting the grid all at once if 5-6 cars show up. You could do a similar thing at your house (basically a large UPS)
The battery swap thing is a pipe dream, IMO.
Even a 1 hour recharge is not bad. After driving for 350 miles, I wouldn't mind stopping for a nice lunch. While you're having lunch, the car's batteries get recharged, for much less than the price of the lunch.
EVs are better at everyday driving. You could make a house using a sawzall, but it will be better and faster to use a miter saw for most of the work and a sawzall for the odd chop while up on the roof.
I'd be more interested in having a 100-mile range and an onboard gas-powered generator to give me effectively-unlimited range when I'm road-tripping and damn-near-free trips when I'm commuting.
The article incorrectly states that the Nissan Leaf needs a gearbox. In fact, it has a single reduction gear and an AC induction motor, just like the Tesla Roadster. (Well, ok, not as powerful...) As a Leaf owner, I can tell you it makes for a very interesting torque curve. From 0-30 it is VERY fast, from 30-60 it is pretty average, and from 60-90 it is dog slow acceleration.
Which units are you using?
Leagues per hour, of course. Just like how I measure fuel consumption in rods per hogshead.
Handy conversion factors: one league per hour is 4.82 kph, 1.34m/s, or if you're stuck in a backward country that uses obsolete units like hogsheads, 3mph.
One rod per hogshead is 4.7 million liters per 100km, 0.021 m/ℓ, or 49μmiles per gallon.
One rod per hogshead is 4.7 million liters per 100km, 0.021 m/ℓ, or 49μmiles per gallon.
Shouldn't that at least be furlongs per fortnight?
It's interesting how inventions from the early part of the 1900s are becoming more useful today. I remember reading an article which stated that engineers were re-discovering mathematical models from the early 1900s for use today.
The big concern I have is that we'll end up with more expensive hybrid cars and China will have the cost-effective stuff.
The big concern I have is that we'll end up with more expensive hybrid cars and China will have the cost-effective stuff.
Yes, re-using old inventions is important.
As another example: In the last 20 years there has been an explosion in the power of mathematical optimization, because numerics got fast and stable enough that algorithmic techniques that had been put into the bottom drawer decades ago have been resurrected. Those techniques were initially numerically unstable (or needed too much computation to keep them stable).
As another example: In the last 20 years there has been an explosion in the power of mathematical optimization, because numerics got fast and stable enough that algorithmic techniques that had been put into the bottom drawer decades ago have been resurrected. Those techniques were initially numerically unstable (or needed too much computation to keep them stable).
I drive a 2001 Ford F350. I get dirty looks from Prius drivers every day. Little do they know (and the econ article mentions this) that their little buzzbombs contain 2.2 pounds of neodymium which is both radioactive and massively damages the environment in its production and disposal.
I bought my truck used. I bought it with 150k miles on it and I plan to put on another 400k miles before it goes to the big diesel garage in the sky. These f'ing Prius yuppies buy a car every 2 years thinking that saving a few gallons of gas is going to save the planet. Try saving the environmental cost of producing that horrible pile of radioactive and chemical garbage by buying a 10 year old used car and driving it for the next decade.
Edit: And buy American darnit!
I bought my truck used. I bought it with 150k miles on it and I plan to put on another 400k miles before it goes to the big diesel garage in the sky. These f'ing Prius yuppies buy a car every 2 years thinking that saving a few gallons of gas is going to save the planet. Try saving the environmental cost of producing that horrible pile of radioactive and chemical garbage by buying a 10 year old used car and driving it for the next decade.
Edit: And buy American darnit!
You sure beat up that strawman pretty well. Good thing no chemicals are used in making fuel or in the production of your F350. And nobody is driving older Prii, you'll have to tell some of my customers they don't actually exist.
How radioactive is neodymium? It looks like most of its isotopes are stable and the rest have half-lives significantly exceeding the current age of the universe, just like ²³⁸U.
PBS video on rare earth mining in China, specifically mentioning the Prius engine and battery e.g. the battery contains 22 pounds (10 kg's) of lanthanum.
http://www.youtube.com/watch?v=JL4fluj004o
http://www.youtube.com/watch?v=JL4fluj004o
I think you responded to the wrong comment? I wasn't talking about lanthanum, although it's slightly radioactive too.
The metal harvested for your frame is also harmful to the environment in its manufacture and production.
This ultimately gets back to the allegation that the dust-to-dust cost of a Prius is less eco-friendly than that of a HumVee, which is a meme that was running around few years ago, and which was ultimately debunked based on a number of faulty assumptions, some of which you make in your argument.
- There is no resale market for Prii
- A Prius won't last as long as a more standardly built vehicle
- The Prius uses an extraordinarily large amount of nickel, which is toxic and/or unrecoverable.
As I said, these were ultimately proven false enough that no informed person can seriously believe that a gas guzzling Hummer is better for the environment. I'd wager the same argument holds true for an F150 as well.
As for the presence of radiation in neodymium, you probably have the same amount of radiation in your alternator, only your alternator isn't shielded, as it is in Prius batteries. Pepto Bismol is also radioactive, and has a half-life longer than the age of the universe -- it doesn't necessarily imply that it's unsafe.
Also, please, let's try to keep the drama down, pretty please? There is a great deal of rhetoric and emotion in your post that needn't be there.
This ultimately gets back to the allegation that the dust-to-dust cost of a Prius is less eco-friendly than that of a HumVee, which is a meme that was running around few years ago, and which was ultimately debunked based on a number of faulty assumptions, some of which you make in your argument.
- There is no resale market for Prii
- A Prius won't last as long as a more standardly built vehicle
- The Prius uses an extraordinarily large amount of nickel, which is toxic and/or unrecoverable.
As I said, these were ultimately proven false enough that no informed person can seriously believe that a gas guzzling Hummer is better for the environment. I'd wager the same argument holds true for an F150 as well.
As for the presence of radiation in neodymium, you probably have the same amount of radiation in your alternator, only your alternator isn't shielded, as it is in Prius batteries. Pepto Bismol is also radioactive, and has a half-life longer than the age of the universe -- it doesn't necessarily imply that it's unsafe.
Also, please, let's try to keep the drama down, pretty please? There is a great deal of rhetoric and emotion in your post that needn't be there.
I never made any of the allegation's in your bullets. The simple fact is that producing a Prius is bad for the environment and buying a new one every few years is a hell of a lot worse for the environment than buying a 10 year old vehicle and driving it another decade.
That, along with an ignorance for the environmental impact of the materials used in a Prius was my point.
Also, please, let's try to keep the drama down, pretty please? There is a great deal of rhetoric and emotion in your post that needn't be there.
That, along with an ignorance for the environmental impact of the materials used in a Prius was my point.
Also, please, let's try to keep the drama down, pretty please? There is a great deal of rhetoric and emotion in your post that needn't be there.
There isn't any malice in my post. But I inferred rhetoric and emotion in yours by the number of expletives / euphemisms. I can't possibly construe your post (or this reply) in any fashion that isn't snarky, at the very least. I urge you to read the guidelines: http://ycombinator.com/newsguidelines.html
You definitely imply (both in your original post, and in this one) that every Prius owner is buying a new Prius every few years. That is a logical fallacy, in a variety of ways -- both that it is fact, and that it is necessarily bad. Even if that is the case, then that means there is bound to be a very good supply of cheap Prius cars available for the secondary market. Hooray.
The true fact of the matter is that producing cars (or trucks) is bad for the environment. A Prius may be bad in different ways than a Ford, but tearing up the Earth to produce an easier means of transport isn't eco-friendly.
You definitely imply (both in your original post, and in this one) that every Prius owner is buying a new Prius every few years. That is a logical fallacy, in a variety of ways -- both that it is fact, and that it is necessarily bad. Even if that is the case, then that means there is bound to be a very good supply of cheap Prius cars available for the secondary market. Hooray.
The true fact of the matter is that producing cars (or trucks) is bad for the environment. A Prius may be bad in different ways than a Ford, but tearing up the Earth to produce an easier means of transport isn't eco-friendly.
This happened yesterday:
American mining company Molycorp has bought up a 90.023 share in Estonia's rare earth metals producer AS Silmet, taking control of one of very few sources of the much-sought materials outside China.
http://news.err.ee/economy/c12a9355-2b41-46d3-b00e-875806144...
Relevant, I hope.
American mining company Molycorp has bought up a 90.023 share in Estonia's rare earth metals producer AS Silmet, taking control of one of very few sources of the much-sought materials outside China.
http://news.err.ee/economy/c12a9355-2b41-46d3-b00e-875806144...
Relevant, I hope.
Rare-earth elements are not actually that rare.
A few Canadian companies hold the rights to many of the resources in the USA.
For example there are some nice lithium sources in the USA but the Canadian companies will not mine them until there is a certain profitability level.
A few Canadian companies hold the rights to many of the resources in the USA.
For example there are some nice lithium sources in the USA but the Canadian companies will not mine them until there is a certain profitability level.
I suspect that even if the resources were owned by US companies, they still wouldn't mine them, for exactly the same reason.
Yes but it's an actual "homeland security" issue that we don't own the resources in our own country that are critical for our future infrastructure/transportation needs (vs. the theater issues at the airport).
Being owned by canadians, an economy that is intimately tied and dependent to the fate of the US economy, speak the same language and are fairly friendly neighbours overall isn't that bad. And if the US really wanted to, they could pass some BS law to retake those land claims.
If the resources are here and shit hits the fan (I don't see that ever being the case with Canada, but hypothetically), we can just take them. It's not a homeland security issue.
If you don't own them personally, why do you care about the passport of the guy who does own them?
There are a lot of Canadian resources owned by American companies. Should we swap?
Lithium is an alkali metal, not a rare-earth element, so it's not such a good example.
"it is puzzling to see why anyone should worry about potential shortages of neodymium and other rare-earths for alternative power and transport."
Well, I'm sure the military doesn't want to redesign everything that already uses them - we're broke enough as it is...
Well, I'm sure the military doesn't want to redesign everything that already uses them - we're broke enough as it is...
In many cases, it's cheaper to (try to) solve these problems with smart drive electronics, i.e., add additional complication to the cheap part of the system rather than to the expensive part. But for the highest output machines---multi-megawatt generators, for example---synchronous machines remain king.
There are some other fun things you can do with motor drive electronics. A lab mate of mine in grad school wrote a cool thesis on using the iron in an induction machine as an electric transformer in such a way that the motor drive and power converter could be controlled independently. In essence, in a Y-connected three-phase system, the motor is insensitive to 3rd harmonic content in the drive signal, so you can pass energy through the air gap in the 3rd harmonic and rectify it on the other side to turn your induction machine into the magnetics for a power converter.
http://dspace.mit.edu/handle/1721.1/28691