Motor Efficiency Impacts Bottom Line

A recent Chicago seminar laid out the details on ways to save big on energy costs through smarter motor management.

Motors eat up 63 percent of electricity consumed in today’s factories and plants. And while industrial motor users can’t control the price of electricity, they can take steps to reduce their electrical power consumption through the use of higher efficiency motors and variable frequency drives. What’s more, the savings can be substantial over the 20-year life of a motor. 

That’s the message that industrial motor manufacturer Baldor Electric Co., Fort Smith, Ark., and Motion Industries Inc., a Birmingham, Ala.-based distributor, were looking to get across this week during a Chicago seminar for motor end-users. About 80 customers turned out for the Nov. 2 event, titled “Proper Selection of Electric Motors for Increased Reliability and Energy Savings,” according to John Malinowski, Baldor’s product manager for AC & DC motors. 

By the numbers 

Malinowski detailed the numbers during a presentation before the group, comparing life cycle cost between a conventional motor and one designated NEMA Premium—a motor efficiency specification set out by the National Electrical Manufacturers Association.  

Only about 2 percent of the life cycle cost of a motor is in its purchase price, Malinowski said. So even though a NEMA Premium motor will cost more up front than a non-premium motor, that cost is quickly offset by its lower electrical consumption.  

According to U.S. Department of Energy surveys, the average 200 horsepower motor in use today—a typical size for a compressor application, said Malinowski—is about 93.5 percent efficient. That compares to 96.2 percent for a NEMA Premium motor. For a motor that runs continuously at a cost of 7.5 cents per kilowatt hour, a NEMA Premium motor will cost about $3,000 less per year to operate—at $101,869 vs. $104,839 for the average non-premium motor, Malinowski told the audience. That’s an annual savings of around $3,000, which translates to $60,000 over 20 years of operation, he said.  

Not all motors run continuously, of course, and the savings would be less for motors smaller than 200 horsepower. But given the tens or hundreds of motors of all sizes running in many plants, its not hard to see how the combined savings of using all NEMA Premium motors could add up to big numbers. 

The key to successfully implementing a motor purchasing policy based on life cycle cost—instead of lowest initial cost—is to get management buy-in, Malinowski said. “This is what we’re trying to get you to do, to go to management in your companies. You really need the commitment from the top to make the better investment.” He recommended setting motor energy savings goals and developing an action plan for achieving those goals. 

Survey your plant 

A starting point is to survey the target plant. Malinowski identified three levels of surveys.  

A “level 1” survey involves simply taking inventory of all motors in a plant and tagging each motor with the intended action when the motor fails. “You don’t want some third-shift guy just picking any motor up and putting it in there, because once that machine is running again, the chances are you’re not going to shut it down to put the right motor on it.” This is important, because if motors are grossly oversized for the load, for example, they can be extremely inefficient, Malinowski said.  

A “level 2” survey is more advanced. In this case, users take current measurements of each motor, while the motor is running, to make sure that it is “right-sized,” said Malinowski. “This is going to uncover some of these motors that somebody stuck on there just to get it running, and it’s way oversized.” When a motor runs at very light load, “at 50 percent, the efficiency starts dropping off significantly,” he said. Malinowski puts the “sweet spot” for peak motor efficiency at about 80 percent of full load. 

A “level 3” survey gets into system considerations, in which plant users analyze their processes and consider changes that could improve energy efficiency. It is at this level that use of variable speed drives on fans and pumps can be considered as a way to control flow and save energy, said Malinowski. Use of increased efficiency gear reducers can also make a difference. And AC servo motors should also be considered. “The efficiency on a servo motor is probably a couple of points higher than a NEMA Premium motor,” Malinowski noted, while also offering higher throughput.

Baldor Electric Co.
www.baldor.com

Motion Industries Inc.
www.motionindustries.com

More in Software