On Tesla's induction motor

The article incorrectly implies that the only way to make a synchronous machine is with a permanent magnet, and thus all synchronous machines have temperature issues. On the contrary, it is entirely possible to build synchronous machines with driven rotors (e.g., through slip rings) that have none of the temperature issues associated with using permanent magnets (it's the magnets themselves that are temperatures sensitive, not some intrinsic property of the synchronous machine design). They are more expensive to manufacture than the good old squirrel cage induction motor, but synchronous machines in general are more efficient over a wider range of output rotational rates than induction machines, have somewhat better failure modes, and are much easier to start up.

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

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.

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

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.

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.

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.

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.

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.

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!

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.

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.

"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...