We've written more than one story about the Energy Independence and Security Act, which mandated higher-efficiency motors as of last December, and about the general subject of energy efficient motors. That's all still true. But it's time for us, and maybe you, to move on, to look beyond your motors to other components of the drive train for energy savings.[pullquote]
"Why only focus on motors with efficiencies above 96 percent when they are connected to other components in the system that may be as low as 50 percent?" asks John Malinowski, senior product manager for AC motors at Baldor Electric Co., Fort Smith, Ark. "We're nearing the maximum achievable efficiency with conventional AC induction motors. If you have an old motor, you may get up to 8 percent more efficiency with a NEMA Premium motor or you can look at the entire system and replace transformers, gearing, drive and even the pump or compressor to get more than 50 percent energy savings."
(By the way, after being one of the world's leading motor companies for years, Baldor was acquired at the end of last year by global automation company ABB, itself a worldwide supplier of motors.)
"The truth is, premium-efficient motors are only one part of the drivetrain," a spokesman for SEW Eurodrive agrees. "While you can certainly save energy by replacing a motor with a premium-efficient model, you can save even more by looking at your entire drive train."
Being Baldor's senior principal engineer for Dodge gearing, Chuck Russell likes to point out the effect the gearbox has on overall system efficiency. Comparing his own company's worm gearboxes to helical gear systems, he says:
"At a 5:1 ratio [reduction], a good worm gearbox could have an efficiency rating as high as 95 percent, and that's great. But start changing that ratio. At 60:1, its efficiency could drop to 66 percent. That's typical of most manufacturers' worm gear boxes.
"Change the worm gearbox to a [more expensive] helical gear box. At 5:1,.you'll get the same efficiency, 95 percent. So helical gears are just as good but not better. But at 60:1, a helical gearbox is still 95 percent efficient, instead of 66 percent. That's where you get the savings.
"As you go up in ratio, a worm gearbox's efficiency goes down," he says, "but a helical gearbox stays at the same efficiency."
Where does the efficiency go? It takes a certain amount of power to spin those bearings, rub up against seals, get those gears to mesh, even to churn the oil or lubricant.
Russell offered what he called a realistic example of payback. Take a 2 hp motor running 16 hours a day at an electrical cost of 12 cents per kilowatt hour. Cranking that up from a 5:1 ratio to a 60:1 reduction, the helical gear box would pay for itself in two years, Russell says.
SEW-Eurodrive also offers helical gear reducers and helical bevel gear reducers. "These units use less energy, run cooler and last longer than typical single-worm gear units," marketing material states. It addition, "The [stainless steel] material, design and smooth finish mean high resistance to bacteria, chemicals and processes common to the food processing industry."
New Baldor parent ABB further notes that installing variable-speed drives can reduce the power consumption of motors dramatically, typically by around 30 percent, leading to significant cost savings and reductions in greenhouse gas emissions.
"The vast majority of electric motors in [industrial] plants control pump and fan operations, operating at full speed even when they don't need to," reads an ABB report on the subject. "Most are controlled by throttling – which is like braking a car while the accelerator is still flat on the floor. It damages equipment and wastes huge amounts of energy. Resistors and split-ring motors can also be used to control process speeds, but this approach also wastes energy.
"Variable-speed drives offer an alternative, energy-efficient means of motor control. Drives allow motors to draw only the power they need to perform their tasks, cutting waste and reducing wear and tear on equipment. They also save on raw materials by improving the quality of processes they control."
When you restrict the subject of motors to food plants, you need to think in terms of stainless steel. "Even parts of the system where there is no food contact, that never required stainless before, the food safety liability is driving more and more food processors to demand stainless steel," says Mike Kargl, vice president of Italvibras USA Inc.
As the name implies, it's an Italian company specializing in electric vibrating motors, moving food products along on conveyors and through cookers, dryers and refrigeration units, with U.S. headquarters in Princeton, Ill.
Stainless steel may be more expensive, "but food manufacturers are not willing to compromise food safety because of price," he says.