By Tuan Nguyen
Posting in Design
Japanese researchers have created a revolutionary electric motor that doesn't require rare earth elements, a development that may drastically reduc...
Japanese researchers have created a revolutionary electric motor that doesn't require rare earth elements, a development that may drastically reduce the cost of electric vehicles.
The motor relies on switched reluctance technology, a form of magnetic resistance, to switch electricity on and off inside an electromagnetic wire coil that houses a steel rotor. The effect is rotary motion that turns at different speeds and with enough force to produce high levels of torque. Although the latest prototype produces a relatively low output of 50kW, researchers at the Tokyo University of Science are working to further refine and scale up the technology where it can offer the same kind of performance as motors currently on the market.
A commercial-ready rare earth-free motor would translate to more affordable EVs and hybrids since as much as 20 to 25 pounds of expensive rare earths goes into the manufacturing of the vehicle's motor and lithium-ion battery. Currently, China supplies 97 percent of the world's rare earth metals, a virtual monopoly that has enabled them to drive up costs simply by means of curbing exports.
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However, one of the major challenges to getting the technology on the market is that switched reluctance motors are difficult to control. The researchers are hoping real-time computing that does a better job of handling the necessary complex algorithms can lead to a device that's more reliable and less prone to vibration and noise.
"There is a concern that noise and vibration might be problems when the motor is loaded into a vehicle," says Professor Nobukazu Hoshi in a Diginfo video interview. "So, I will experiment with control methods and new structures to reduce noise and vibration by conducting trial tests, as well as design and develop a motor drive circuit."
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Jul 28, 2011
That is great for positional control, but not so great for power and smoothness, two of the most important features for a vehicle motor. This will probably be a dead end, until -- again -- we run out of permanent magnets to use. But developing it to at least basic utility, would have the positive advantage of letting the Chinese know that we have alternatives. That might help the bargaining, when the next "shortage" comes along.
I stripped an old 30's technologies console radio and found it had a large speaker, much larger in fact than most consoles of this era. I was curious, how could this device drive it? On dissection, I found it had no permanent magnet, instead it had an electromagnet in place of one. The coil for this was fed from the power supply. The problem was, even though filtered, that 'reference field' carried 'hum'. This Japanese device does not seek to establish a stable magnetic reference field to buck against, it modulates the reference field just like one would modulate the signal field. This allows all kinds of field templates to be impressed. So, instead of Class A (full wave signal with a stable reference amp), it uses Class B ideology (half wave one direction, half wave other direction). With computer control, shifting the pole phases like a stepper motor, one can use pure Class D ideology (square waves with the drive inductors as integrators). And with regenerative braking and some kind of inertia coupling, one may be able to use Class C (single sided pulse switched for 1/2 or so phase)? Thing is the Japanese just found massive amounts of rare earths floating in the slurry at the bottom of many locations in the open ocean... very deep! They have the tech to extract and filter that slurry cost effectively, so no longer depending on the Chinese for rare earths... I guess THIS project was started before that discovery?
The technology for these motors dates back to some of the first electric motors every made. The question is, can their design change really get them the same performance as motors made with rare earth materials? Right now the answer is a big NO.
When speaking or thinking about electrical cars in general, people often think how tedious it will be to constantly have this car charging and its not like just changing a car or truck part...