NEMA, the Rosslyn, Va.-based National Electrical Manufacturers Association, established its Premium-motors program
(www.nema.org/gov/energy/efficiency/premium) to save end-users money and to improve system reliability and efficiency.The program establishes motors’ efficiencies. Those appear in Tables 12-12 and 12-13 of “NEMA Standards Publication MG 1- 2003, Motors and Generators.” The tables contain nominal efficiencies that low-voltage and medium-voltage motors, from one horsepower (HP) to 500 HP, must have to be labeled Premium. The program’s scope includes continuous-rated, NEMA Design A or B, squirrel-cage induction motors that are single-speed, polyphase, one to 500 HP and have two, four or six poles.
Pay now or later?
When considering the purchase of these Premium motors, it’s a “pay me now or pay me later” proposition, suggests John Malinowski, product manager for AC/DC motors with industrial-motor manufacturer Baldor Electric Co.
(www.baldor.com), in Ft. Smith, Ark. What does that mean? Mainly, to offset higher future costs, view purchases in terms of lifecycle costs, he suggests. For example, the efficiency of the average installed base of 200-HP motors is approximately 93.5 percent, he contends. If electricity costs 7.5 cents per kilowatt, annual cost of operation at that efficiency becomes $104,839, he estimates. But with NEMA Premiums, which are 96.2 percent or more efficient, the annual cost to operate is $101,869, Malinowski calculates, an annual savings of $2,970. Over 20 years, that’s not chump change. But will that motivate end-users? That depends. But there are other savings possible through NEMA Premiums. For example, they’re built to tighter tolerances, Malinowski explains. With regard to insulation, that means that for every 10 degrees Celsius cooler that the motor operates, “that doubles the insulation life of the motor.”Another advantage of the cooler-running capability is reduced heat production, which can translate to less demand on plant air-conditioning systems. Besides energy savings, lower heat losses also mean smaller fans, and that means reduced ambient-noise levels, Malinowski suggests.The tighter tolerances also produce better balanced motors, Malinowski says. That improved balance, plus the cooler-running ability, increases bearing life, he asserts. In addition, the fact that Premium motors are built on cast-iron frames makes it easier to align a motor’s shaft with the load—and that further extends bearing life.Another reason to consider Premium motors, especially now, would be to avoid the steadily rising cost of materials-of-construction. “We’ve seen a cycle of cost increases in the motor industry that is higher than in the last few years. We’re seeing double-digit increases on materials just this year,” Malinowski relates. “[But] what you pay for today will be a better investment, because the motor’s [expected] life is 20 years.”Providing assistance for end-users is the Boston-based Motor Decisions Matter
(www.motorsmatter.org) public-awareness campaign. At MDM’s Web site, end-users can access various tools. These include the Motor Planning Kit and MotorSlide Calculator. The latter calculates annual energy costs and savings, based on parameters such as electricity costs, motor size and efficiency, and operating hours.Another MDM tool of interest to end-users is the Simple Savings Chart. It allows side-by-side comparisons of annual energy costs and annual energy savings for pre-EPAct 1992 (U.S. Energy Policy Act of 1992), EPAct 1992 and NEMA Premium motors. Malinowski notes that EPAct 1992 motors “would be 95 percent efficient,” compared to the minimum 96.2 percent efficiency of a NEMA Premium Motor. C. Kenna Amos,
[email protected], is an
Automation World Contributing Editor.
