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.

Two versions of Sanifan are available, both of which can withstand high-pressure washdown. The conventional, or dry, version will satisfy most food companies' needs, Oleson believes, but if a motor is located in an area where heavy organic waste buildup is likely, a wet design is available. A hose or CIP line can be inserted into a port to flush out the area, with the waste water either exiting the endbell or returning to the CIP system via an outlet port. "It's going to take engineers time to recognize wet applications because it's a more novel approach," says Oleson, who also is the firm's CEO.

Real estate costs

The smaller a machine's footprint, the better. Whereas compactness used to fall under the soft-savings umbrella, manufacturers are beginning to affix a square footage cost to machinery. By quantifying hard-dollar savings to pricier but more compact technology, manufactures can more easily justify the expenditure. Servo motors are a beneficiary of these revised ROI calculations.

To illustrate, Michael Mikolajczak, product line manager-motion control at ABB Group, Wickliffe Ohio, cites an unnamed OEM who engineered a bun slicing machine that also collates, packages and labels the buns before discharging them to a casepacker or other downstream machines. The system measures 15 ft. in length and 5 ft. in width, with a height under 6 ft. Without the high starting torque and position-precision of a servo, such a multi-function machine would not be possible, even at three times the footprint.
Space saving is a secondary benefit in Stainless Motors' most innovative product: a 400hp water-cooled stainless motor. Elimination of cooling fins shrink the motor's dimensions to those of a 50hp air-cooled motor. But the motor's greatest distinctions are its extended service life and an efficiency rate of virtually 100 percent.

The project was commissioned by Beef Products Inc. (BPI), the Sioux City, Iowa, firm that was the center of last year's “pink slime” controversy. BPI recovers protein in beef trim to generate what it terms boneless lean beef trimmings, an additive to ground beef and hamburger patties that otherwise would contain high fat ratios.

Blocks of the lean trim are stored frozen, and Iowa's summer sun taxes BPI's ammonia compressors and the motors that drive them. Bearing failures were frequent occurrences as temperatures escalated. Stainless Motors' design pumps purified water through the motor to remove latent heat, then pipes the 120° F water to boiler feed. The motor's operating temperature was reduced significantly, and despite running at up to 42,000 RPMs, the first installation marked five years of continuous service last Thanksgiving without a day of downtime, Oleson reports.

Besides 11 water-cooled motors at BPI, only one other unit has been placed in service, driving a centrifugal pump. Piping and other infrastructure requirements extend the ROI timeline, dampening enthusiasm and making the innovation more suitable for greenfield applications. Nonetheless, advances in motor technology are occurring in many induction motors. Even supplier consolidation has not throttled back R&D work. ABB's Mikolajczak points to synergies in 2011's acquisition of Baldor, particularly in closer integration of the company's complementary drives and motors.

Terry Bell, product manager-rotary and linear servo motors at Baldor's Arkansas R&D center, seconds his point. Collaboration is evident in servos, where motor and drive integration is critical. By incorporating absolute encoders, the latest generation is significantly more precise. Instead of feeding back thousands of reference points per revolution, absolute encoders generate one million points per revolution, resulting in much higher resolution.

Servo systems derive strength from their mechatronic nature, combining mechanical motion and electronic controls in a single package. Combining an inverter with a NEMA motor and a gear box would provide similar synergies, but that is a daunting challenge in a food plant's harsh environment. SEW's NEMA motors with permanent magnets helps move development in that direction.

"There is a trend toward motor/drive packages," writes Sam Harris, business manager with Siemens Industry Inc. "not only for gains in overall efficiency, but for more precise process control" and greater reliability. A report commissioned by Siemens, Alpharetta, Ga., estimates U.S. industry could save more than $22 trillion annually if all its 40 million motors were equipped with variable frequency drives. Motors account for 70 cents of every dollar in electricity costs for industry, the U.S. Dept. of Energy estimates.

Whether the issue is energy efficiency, sanitary design or service life, suppliers see opportunities for continuous improvement in motor technology.

This article originally appeared in the March 2013 issue of Food Processing Magazine.

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