World Grain - December 2011 - 52

FEEDOPERATIONS

Replacing a standard efficiency motor with Epact motor
Standard Efficiency Motor Efficiency @ 75% Loading 84.0 % Annual Energy Cost $1,998 Purchase Price $233 Replace with Epact Motor Efficiency @ 75% Loading 88.2 % Annual Energy Cost $1,903 Annual Savings $95 Payback Period 2.44 years

Replacing a standard efficiency motor with NEMA Premium motor
Standard Efficiency Motor Efficiency @ 75% Loading 84.0% Annual Energy Cost $1,998 Efficiency @ 75% Loading 90.5% Replace with NEMA Premium Motor Annual Energy Cost $1,855 Annual Savings $144 Payback Period 2.10 years

ing at these costs, the purchase of the motor is about 1% of the total cost. Add in 4% of the cost for rebuilding and an additional 5% for downtime due to various reasons. These three items add up to only 10% of the 20-year lifecycle cost. Thus, 90% of the cycle cost is the cost of power to operate the motor. With this in mind, selecting and using motors with the highest efﬁciencies is important and cost saving. MOTOR EFFICIENCY RATINGS The National Electric Manufacturers Association (NEMA) publishes more than 500 standards, application guides, white papers, and technical papers. Many of these address construction and performance standards for electric motors. They establish the efﬁciency standards for motors of different construction and types. Beginning with the energy crisis in the early 1970s, motor manufacturers began building and selling motors they called “high-efﬁciency” and “energy-efﬁcient” motors, but these terms were not clearly deﬁned. These motors, however, were more efﬁcient than what were considered the “standard-efﬁciency” motors of that time, but also cost more to purchase. The U. S. Congress enacted the Energy Policy Act of 1992 that gave the Department of Energy (DOE) the authority to set minimum efﬁciency standards for certain classes of motors, including
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many of the ones commonly used in the grain handling processing industries in the U.S. Any motors built after Oct. 27, 1997 had to meet these minimum standards. These motors became known as Epact motors. They range from 1% to 4% more efﬁcient than earlier “standard-efﬁciency” motors. Motor manufacturers continued to improve motor construction, performance and operation efﬁciencies that surpassed even the Epact efﬁciencies. In June 2001, NEMA established standards for these motors and designated them as “NEMA Premium” motors. Let’s pick one motor size to do a comparison of original costs and annual savings installing Epact or NEMA Premium motors in place of a standard-efﬁciency motor (see chart above). We will use a 5-hp, 1,800-rpm motor at 75% loading and the electrical power to operate the motor costs $0.075 per kilowatt hour. Any motor purchased, of the types covered by the Energy Policy Act of 1992, will be at least an Epact motor. It may be wise to look at existing “standard-efﬁciency” motors and determine if replacing them with an Epact motor may result in signiﬁcant cost savings over the lifecycle of the motor. In motor selection and/or replacement for new and existing equipment, consider the additional cost savings for purchasing a NEMA Premium motor. NEMA Premium motors should be considered:

1. For new installations. 2. When purchasing new equipment packages. 3. When making major modiﬁcations to processes and facilities. 4. To replace oversized or underloaded motors. 5. As part of an Energy Conservation Program. Choosing the proper motor for the application can result in signiﬁcant electrical energy savings over the lifecycle of the motor. REFERENCES
1. U.S. Department of Energy (US DOE). Fact Sheet: Determining Motor Load and Efficiency. 2. Energy Efficiency Guide for Industry in Asia – www.energyefficiencyasia.org. 3. Introduction to Premium Efficiency Motors - www.copper.org. 4. Presentation to Grain Elevator and Processing Society (GEAPS), Siouxland GEAPS Chapter, John O’Brian, Toshiba International, Inc. Fred Fairchild is a professor in the Deparment of Grain Science and Industry at Kansas State University. Prior to coming to Kansas State in 1994, he worked in the industry designing, construction and commissioning of numerous mill facilities. He is a licensed professional engineer. He can be reached by e-mail at fjf@k-state.edu.
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December 2011 / World Grain / www.World-Grain.com

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World Grain - December 2011

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