Engineers know that to design a device you need to build beyond the anticipated peak load so the device doesn’t just break the first time it gets used at peak load. For the rest of us that means we’re always buying a safety margin that assures that our investment is worthwhile and long lasting. With the Detroit Auto Show filled with so many vehicles that incorporate electric motors another peak problem is visible and being addressed.

Electricity when moving down the wire encounters resistance that becomes heat. Inside of an electric motor that runs at a steady state an engineer can specify the build so that heat is minimal and lost so the wiring and the magnets stay within the working parameters for the performance needed. But in a vehicle installation a motor would be expected to operate from 0 revolutions per minute up to the rated top speed. Most motors benefit from a capacitor surge at 0 rpm to start and at high speed would be nearing the capacity of the wiring to carry current. At both ends of the performance zone the motor would be shedding heat.

The current art in magnets, which surround the shaft and windings and are attached to the shell, are usually alloys of metals that are strong magnets for the winding magnets on the shaft to push on. One problem has been that the alloy magnets lose their effectiveness as the temperature climbs. In the variable speed world of electric drives, this matter is a significant problem. These two engineering problems, overbuilding for reliability and building to avoid excess heat buildup make for quite large and heavy solutions.

Enter Iver Anderson, Bill McCallum and Matthew Kramer at the Ames Laboratory operated by Iowa State University for the U.S. Department of Energy. The Ames Lab is a low-key but historically significant contributor to U.S. economic growth in materials, energy resources, high-speed computer design and environmental cleanup and restoration. What the researchers have done is explore the alloys of magnets usually used in these types of motors and design an alloy that offers much higher operating temperatures which can be produced at low cost and manufactured quickly and efficiently.

It’s interesting to note that the U.S. automobile companies have already set out parameters of vehicle electric motor specifications. The leading qualification for a good motor would be to operate well at up to 200 degrees Centigrade or 392 degrees Fahrenheit. In comparison, many woods and paper ignite in the 450 F range, which makes the 200 degree C a high standard. The new alloy proposal adds yttrium and dysprosium to neodymium solve the heat gain – magnetic decline problem. With most neodymium-iron-boron magnets at half strength at 125 degrees C, the new alloy at near full strength at 200 degrees C offers a solution to production of electric motor magnets for vehicles.

Magnetic Powders

Fine, spherical 2-14-1 permanent magnet alloy powders produced by argon gas atomization.




The Ames team then went to the next stage, devising a manufacturing process that could produce the magnets in volume that can meet the anticipated demand. Using blasts of first helium and later argon to make droplets from a stream of melted alloy the manufacturer has a powder to use for injection molding large volumes of magnets.

The significant measure that gives pride and a sense of success is called “crossover in temperature” at which the properties of their magnet powders become better than other powders for high temperature use. The crossover temperature point is when one product becomes more advantageous than another, meaning the lower the temperature the earlier the advantage becomes useful. The Ames team is quite pleased to drive the crossover temperature down to 75 C from 175 C.

Now motors can be built lighter and more powerful within the specifications of a vehicular application. These kinds of background developments are significant to the move to electric drives. We often think about the energy and fuel issue without a full awareness of the need to engineer solutions that function effectively in the new machines we’ll be buying. More power, built at lower costs, with better reliability and higher efficiency is coming up in electric drive power units soon.


4 Comments so far

  1. Lara Ordones on May 21, 2011 7:39 PM

    Awesome post. I so good to see someone taking the time to share this information

  2. Carmon Gata on September 1, 2011 11:08 AM

    I’ve been checking your blog for a while now, seems like everyday I learn something new 🙂 Thanks

  3. Adelle Duggin on September 22, 2011 11:34 AM

    Thanks for posting. Good to see that not everyone is using RSS feeds to build their blogs 😉

  4. Rachael Garkow on September 28, 2011 6:00 PM

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