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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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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