Rare Earth and Power: Advanced Magnets May Improve Future Motors

Rare earth permanent magnets are being incorporated in NEMA induction motors — plus other recent developments in motor efficiency and performance.

By Kevin T. Higgins, Managing Editor

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Who can forget the sweet, soul stylings of Rare Earth and Power, the magnetic force that revolutionized American manufacturing in the 21st century?

Doesn't sound familiar? Probably because RE&P never played a single note. Instead, the reference is to the rare earth magnets already used in many servo motors that will be incorporated in NEMA induction motors in the not-too-distant future.

The 17 elements in rare earth aren't really rare, but China achieved a virtual monopoly of mining and extraction operations five years ago. Rather than export elements such as neodymium, the Chinese leveraged their position to produce finished goods such as permanent magnets, which are composed of neodymium, iron and boron. Shortages ensued and prices skyrocketed, resulting in 600 percent increases in some servo motors. Prices are easing, but sticker shock has retarded many manufacturers' enthusiasm for new applications of servo technology.

The upside is that rare earth mining has become a more attractive proposition. The Molycorp mine in Mountain Pass, Calif., is expected to begin producing 40,000 tons a year of the 17 elements later this year. Increased availability should bring stable pricing and domestic production of finished goods that depend on neodymium, including permanent magnets. That's good news for buyers of both servo and next-generation NEMA motors.

Higher efficiency requirements under the Energy Independence and Security Act of 2007 became effective December 19, 2010. In IE-3 applications, a 5 hp, four-pole, 1800 rpm premium NEMA motor must deliver 89.5 percent nominal full load efficiency; in IE-2 applications, that motor's efficiency rating is 87.5 percent. Even higher efficiencies are expected when IE-4 standards are in place in three years, and OEMs are considering technical options in achieving them. At the list are rare earth magnets.

"The time may be right for the kind of major jump in savings that can be achieved with permanent magnet technology," suggests Chris Wood, industry account manager-food and beverage for SEW Eurodrive, Lyman, S.C. Use of permanent magnets in NEMA motors will produce double-digit efficiency gains.

SEW expects to introduce a permanent magnet induction motor to the U.S. market later this year. The motors already are in service elsewhere. Four slots in the rotor hold two north and two south magnets, resulting in four poles at synchronous speed. The units boost efficiency 19 percent, are more powerful, and allow manufacturers to drop down two frame sizes.

While advanced magnets may improve tomorrow's motors, hygienic design is impacting today's. Expanding use of stainless-steel induction motors, particularly in high-pressure washdown environments, has been accompanied by re-engineering to extend those motors' service life.

An upgraded version of Baldor's SSE Super-E stainless motor debuted in January at the International Production & Processing Expo, which drew processors of meat and poultry products. A fully welded, flat base replaced the spot-welded base on the original version, eliminating potential microbial harborage points. A breather drain was dropped in favor of four condensate drain holes at both ends.

"Condensation got in during washdown, and there was no way for the water to get out," explains Kay Cabaniss, food and beverage manager for Baldor Electric Co., Fort Smith, Ark. The changes should extend service life and eliminate oxidation of bearings.

Airborne contaminants are receiving new scrutiny as food companies prepare for more stringent food safety requirements. Electric motors are potential contributors: biofilms can form under the endbell and on the fan and shroud, out of sight from visual inspection. As the fan blows air across the motor's surface, microbes become airborne, posing an invisible contamination threat that can settle on food-contact surfaces. To address the danger, chief engineer John Oleson of Stainless Motors Inc., Rio Rancho, N.M., redesigned his motors to include Sanifan, a cleanable fan assembly. A polished stainless fan, secured with a blind-tapped stainless nut, replaces a plastic fan, and elastomeric seal eliminates metal-to-metal contact points where microbes could gain a toehold.

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