Food Engineering

Tech Update: Motors & Drives

May 1, 2011

Power transmission technology is in flux, and that adds up to a wealth of options for food and beverage manufacturers.



Servo power systems have followed their induction-motor counterparts in offering washdown-ready motor options. Stainless steel housings make servo drives compatible with conditions found in processing areas, not simply packaging departments.


Technician Scott DeVizio of Stainless Motors prepares a 400hp, water-cooled electric motor for testing. Besides shrinking the motor’s overall size, water cooling can boost efficiency to close to 100 percent and reduce bearing wear in high-stress conditions.

 

Mass production is gradually giving way to the Age of Customization. The shift is evident in motor and drive technology.

The days when manufacturers’ processes were dictated by narrow power options are gone. Food and beverage companies have committed themselves to meeting the highest global standards in food safety and hygienic production while also pursuing world-class machine performance. They are pushing suppliers to modify off-the-shelf equipment to meet the particular needs of food production, including optimized OEE and machine reliability. Whether they need electronic variable speed drives or mechanical power, food engineers can pick from a wide assortment of production-ready options.

The availability of stainless steel motors is one example. A rarity 10 years ago, stainless steel induction motors have become de facto standards in poultry production. Automation firms are following their mechanical brethren by introducing stainless steel versions of drives that can stand up to moisture and are air tight. Lean principles compel suppliers to engineer platforms that support multiple variations, depending on the end-user’s needs. Andy Hansbrough, vertical marketing manager-packaging at Radford, VA-based Kollmorgen, estimates more than one million variations of the firm’s drive systems can be delivered. “Design engineers are savvy fellows and know exactly what they want,” he says. “To be innovative and meet their needs, we’ve pursued the lean philosophy and pride ourselves in providing custom-like solutions off the shelf.”

For evidence of mechanical innovation, look no further than Albuquerque, home of Stainless Motors Inc. Company Founder and Chief Engineer John C. Oleson never expected his firm to be more than a niche supplier, building the occasional stainless AC motor to meet specialty applications for pharmaceutical manufacturers. Instead, the motor builder rode a demand wave that has made it the preeminent US supplier of those power systems.

If crude oil reaches the $140 a barrel prices it commanded three years ago, interest should spike for one of Oleson’s most interesting engineering achievements: a water-cooled stainless motor (see “Water cooled and stainless,” Food Engineering, February 2009). The first of these  motors was 400hp and powered ammonia compressors at Beef Products Inc. in South Sioux City, NE. Bearing failure with conventional motors was a frequent event in summertime, when demand pushed RPMs as high as 4,000. In autumn, Oleson’s first water-cooled motor marked its third anniversary of continuous performance.

The purified water that cools the engine is piped to boilers and for other waste-heat applications, pushing motor efficiency to a theoretical 100 percent. The incoming water lowers the operating temperature approximately 50°F, accounting for the bearing’s longevity. But the upfront design work and piping requirements add cost, and the recent economic collapse and temporary easing of oil prices cooled commercial interest. “If you go by the MBA rulebook and say you need an ROI in three years, it’s a pretty tall bill,” acknowledges Oleson. “But at five years, it absolutely does pay back.” Interest in the motors is picking up, and Oleson anticipates an order to build a 700hp water-cooled motor.



The evolution of drive systems for conveyors can be seen in this display from SEW-Eurodrive. Above, Chris Wood of SEW-Eurodrive eyes a motor and converter assembly with a belt to deliver power to the conveyor. Premium and super-premium motors (next photo) combined the power train in a single unit, resulting in sanitary enhancement. The newest generation (two photos down) has on-board electronics and starting torque three times higher than the continuous torque, resulting in much lower power requirements to drive the system.

Motors R Us

The motor world’s biggest change this year occurred in the boardroom, not the R&D lab, when Baldor Electric Co., North America’s largest NEMA motor supplier, was acquired by the Swiss automation conglomerate ABB Ltd. (see related story below). Other than basing the combined motors and drives operations in Fort Smith, AR, little is clear of what the merged operations will mean in terms of technical change. “The low-voltage drives business is a great enhancement,” says David Steen, an AC motors product manager at Baldor, quickly adding, “We don’t see AC and DC motors going away or being replaced.”

While Baldor includes electronic drives and controls in its lineup, the company’s bread and butter long has been NEMA motors, particularly energy-efficient units. Demand for premium efficiency motors has grown about 25 percent in recent years, Steen reports, and new requirements from the Department of Energy should spur additional growth. US standards for energy efficiency are the highest in the world, he points out, and Baldor continues to push the innovation envelope. The firm hopes to introduce line start permanent magnet induction motors later this year, Steen says.

The efficiency improvement over general-purpose motors can be negligible, however, particularly as the motor’s size increases. The payback comes when a systems approach to gearing and motors is taken. Calculating the return on mechanical drive-system efficiency requires number-crunching skills, however. “That’s a significant issue we continue to deal with, day in and day out,” says Steen. The company sponsors webinars and educational forums to help plant personnel explain to upper management why investing in premium power systems is a smart business move.



 

Factoring in energy consumption plays to the total cost of ownership calculations being made by many industrial firms. Those calculations are necessary if companies are to upgrade to mechatronic drive systems. “There’s a lot more than just installing more energy-efficient motors when it comes to optimizing your system,” observes Chris Wood, industry account manager at SEW-Eurodrive Inc., Richmond, VA. Upgrading a motor might yield a 10 percent efficiency gain; upgrading the entire system can mean a 30 to 40 percent improvement, he points out.

To illustrate, Wood cites the performance gains created with SEW’s Movigear, the company’s mechatronic option that incorporates controls with the motor and drive in a single unit. “Movigear is just catching on in North America,” he says, though European manufacturers have been transitioning to it for several years. A fully automated bus system is a prerequisite.

The motor is only a few points more efficient than the prior generation, but double-digit reductions in energy costs can be realized, and overall efficiency gains are even higher. The decentralized drive technology also facilitates more compact construction, requiring about a quarter less space. The components come at a higher cost, but SEW estimates the premium is recouped within two years on the basis of electric costs alone. The system most often is used to power conveyors, and Movigear’s high starting torque is a big advantage in the start-up phase compared to conventional systems.




Hydrophilic servos

Flexibility and speed are critical needs in packaging, and “that’s where servos thrive,” observes Adam Shively, a servomotors product manager at Milwaukee-based Rockwell Automation. “Upstream, it’s more of a continuous process, and continuous duty doesn’t lend itself to servos.” Nonetheless, the automation supplier has developed a line of stainless servomotors to meet the hygienic requirements of in-process machinery. The MP-Series motor is available in three International Protection Ratings, including the rigorous IP69K, which certifies resistance to 1,200psi washdown.

Considerable cost is added with stainless, and dissipation of waste heat can be an issue. Beckhoff Automation LLC, Burnsville, MN, complements its stainless options with food-grade AM3000 synchronous servomotors. An FDA-compliant white coating that meets IP67 standards adds to the motors’ cost, allows Joe Martin, packaging and converting sales manager, but the markup is a fraction of what stainless housings command. “We were able to alter the molecular composition of the paint so that it adheres to the metal and doesn’t peel or flake,” adds Martin.

As servos have shrunk in size and become faster and more affordable, their applications have expanded beyond pure packaging, he continues. “We’re seeing a blending of processing and packaging,” with machines combining multiple steps, such as slicing, filling and sealing. Because it is a sealed unit, a servo sucks in moisture when it cools, and that presents a problem for the onboard electronics. Beckhoff is upgrading controls technology in its drives through a partnership with Fertig Motors GmbH, a start-up firm headed by the founder of Elau AG, which was acquired by Schneider Electric in 2004.



If any gaps in Baldor’s paint-free and washdown-ready motors, gears, drives, inverters and other power-transmission solutions existed, they were filled when the manufacturer was acquired by ABB Inc. Source: Baldor Electric Co.

 

Pumps and fans account for a major share of industrial power consumption, but those machines seldom are outfitted with energy-conserving components such as variable speed drives, acknowledges Ivan Spronk, product marketing manager at Schneider Electric United States, Raleigh, NC. Instead, sophisticated drives like Schneider’s Altivar 32 are applied to applications such as packaging machines. “Because it is electronic solid state, it is easy to turn on and off” when not engaged in value-added production, says Spronk. More importantly, “with AC variable speed drives, you can slow equipment down when you don’t have to run at full speed,” saving significant amounts of energy over the machinery’s useful life.

Many of the new drive’s improvements relate to reduced wiring and minimizing panel space. A more compelling advancement is the kind of simplified programmability that threatens the long-term need for controls engineers. For example, an option card that is easily attached to the drive delivers Ethernet connectivity without any code writing. Users can use Boolean to customize the drive to a specific machine application while saving on installation components. Spronk likens it to the network capability of smart phones.

Kollmorgen’s Hansbrough credits the consumer electronics industry for pushing automation suppliers to deliver more compact and economical drives and easier-to-program controls. “With innovation, you have some failures,” he concedes, “but innovations developed for that market are migrating to industry and delivering technology that is more flexible, more reliable, and comes at a lower cost.”

Package proliferation forces manufacturers to change over packaging machines more frequently as they try to “run as close to demand as possible,” adds Hansbrough. That in turn has opened the door to more automated power sources that can be changed over with the push of a button. At the same time, suppliers like Kollmorgen have developed motor-drive combinations with software in the drives’ electronics, eliminating the need for a controller and thereby lowering costs.

The end-user always is right, and if stainless motors and drives are specified, power transmission specialists are ready to oblige. But if anodized aluminum or two-part stainless steel epoxy paint is acceptable, manufacturers can have an hygienic design that doesn’t break the bank, suggests Dan Throne, business manager-food & beverage at Bosch Rexroth Corp., Hoffman Estates, IL. If the motor is positioned outside the operating environment, stainless is a redundancy that only adds cost. Standard aluminum motors are used in an aseptic filler using Rexroth drives, Throne notes.

Last fall, Rexroth introduced a “near motor” servo drive that mounts directly onto a machine, near the motor and away from the control cabinet. The configuration reduces cabinet size and lowers cooling and wiring costs. The integrated drive ranks as a niche product, with applications skewing to light-duty work in the fractional-horsepower range. Another specialty offering is explosion-proof motors that are required in starch molding for candy. Motor sparks must be isolated from airborne starch particles to control a potentially explosive process.

Stainless Motors also is catering to the need for explosion-proof motors designed specifically for food. Bolts that hold the units together typically are on the exterior for added strength, “but that is exactly what our customers do not want,” says Oleson. After a 62-week approval process, Stainless Motors secured UL approval for an explosion-proof motor that “looks just like a NEMA frame motor,” he says. “How we pulled it off is the subject of our patent.”

An Oleson innovation that was too arcane to secure a defensible patent involves a positive pressure lubrication system for gearbox roller bearings. When a worm gearbox is mounted vertically, as is the case with many mixers, the upper bearings and gears can become starved of lubrication, particularly at low RPMs. Oleson’s invention relies on a cam-driven pump off the output shaft to fling lubrication upward. “With every revolution, a squirt of oil goes to the top,” he explains. “I think it’s very important in preventing premature failure.”

Strictly speaking, gear lubrication is neither motor nor drive technology, but the invention exemplifies the many ways power transmission systems continue to improve and evolve. Just as the equipment itself is associated with motion, the technology itself is kinetic.

For more information:
David Steen, Joe Martin, Dan Throne, Andy Hansbrough, Adam Shively, Ivan Spronk, Chris Wood, John C. Oleson,



Power transmission's 800-lb. gorilla

The familiar and the new always share an uneasy coexistence, and transition occurs in fits and starts that obscures change. This is evident in the trend away from mechanical to electronic power.

Variable speed drives ultimately will replace electric motors and mechanical power transmission, though no one living today will be around when the transition is complete. Induction motors remain the power source of choice in industry and likely will remain so for the foreseeable future. But automation companies are placing their bets on servos, which explains Rockwell Automation’s decision in June 2006 to divest itself of the power systems group composed of Dodge bearings and gears and Reliance electric motors. Among the potential suitors rebuffed by Rockwell before the eventual sale to Baldor Electric Co. five months later was ABB Ltd., reliable sources say. Milwaukee-based Rockwell simply didn’t want an automation competitor to acquire its old-school power group.

All of which added extra punch to January’s acquisition of Baldor by ABB. More immediately, the deal filled a gaping hole in the electric-motor lineup of ABB, which did not have any NEMA-rated motors. For Fort Smith, AR-based Baldor, it armed its sales force with perhaps the most comprehensive line of power options available, regardless of whether end-users prefer electronic or mechanical solutions.