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The Quest For Maintaining Efficiency in Motor Repair

In the United States, electric motors convert an estimated 50 percent of all electrical energy generated into mechanical energy.  Electric motors are the largest single category of electric technology in use today.  During this conversion, there are losses in motors that typically result in wasted heat, and over time, reduce the motor’s operating life.   Higher motor efficiencies reduce this wasted heat, which saves energy and ensures the maximum motor life. 

Managing motor populations is typically referred to as Motor Management, and organizations actively engaging in this activity are reporting 5–8 percent reductions in total electric energy consumed along with significant increases in overall reliability.  At its core, Motor Management is about managing the efficiency of your motor population, one motor at a time.  Sound Motor Management practices include: having a new motor purchase specification, a motor repair specification, regularly scheduled motor maintenance, the use of predictive tools such as current signature analysis, considering system driven approaches for certain motor driven processes and motor inventory strategies.  

Fortunately, there are many free tools to help motor users better manage the efficiency of motor populations.  The United States Department of Energy (DOE) first addressed energy use with regards to electric motors in the late 1980s when it created the Motor Challenge Program.  Today motors are addressed under the DOE’s  Best Practices Programs (  In 1991, the DOE supported the development of the HorsePower Bulletin which may be the most widely distributed document on the topic of motor management today.  It can be downloaded for free by visiting: The Motor Decisions Matter Campaign ( also provides education and useful tools from its sponsors, which include motor manufacturers, DOE, energy efficiency advocates and electric utilities.   

In more good news from the DOE, The Energy Policy and Conservation Act of (EPCA) 1992 set minimum efficiencies requirements for new motors between 1–200 horsepower (hp).  Under the Energy Independence and Security ACT (EISA) of 2007, efficiencies for motors previously covered by EPCA will rise again.  In addition, several new categories of motors will be regulated for efficiency for the first time.   This law is scheduled to go into effect December 19, 2010 for all electric motors covered.  The motor manufacturing industry helped shape these laws and has also simplified the purchasing process by standardizing efficiency for certain motors under one label,  NEMA Premium®.  Whenever possible, motor purchasers should specify NEMA Premium® when ordering new motors.  More information about this program for new motors can be found  on NEMA’s Web site (

What should motor users do when their higher efficiency motors fail?  The simple answer:  Protect your investment.   The best research we have today is from the DOE’s “United States Industrial Electric Motor Systems Market Opportunities Assessment” (1998) which states that four out of five motors that fail are repaired.   While that number may be lower today, there are plenty of reasons to believe that many motors that fail are getting repaired because, obviously,  it is good business practice to keep operations running smoothly.  What happens to motor efficiency during repair is hotly debated by many, as there is no cost-effective way to measure motor efficiency each time motors are repaired with precision.  One could certainly test the motor before and after repair, and some companies do this.  However, to ensure accuracy this should be done in a controlled environment such as a lab by experienced engineers where repeatability and accuracy are controlled.  Many motor service centers have dynamometers for load testing, which is important to the repair process.  However, these dynamometers, and the test procedures employed by most motor repair shops, are not designed for accurate efficiency measurement.  

Blind studies performed decades ago by motor efficiency test labs in Canada indicate motor efficiency can be compromised by an average of  2 percent when repaired.  The DOE’s motor decision tool, Motor Master+, defaults to 0.5 or 1.0 percent drop in efficiency for repair, depending on the size of the motor.  Other studies conducted by The Electrical Apparatus Service Association (EASA) and Advanced Energy’s motor lab found no reduction in efficiency when motors were properly repaired.  If you’d like to gain a better understanding, the “Effect of Repair/Rewinding on Motor Efficiency -  EASA/AEMT Rewind Study and Good Practice Guide” is available for purchase (  EASA is the international trade association for the motor repair industry.  Advanced Energy’s test results on motors before and after repair are the property of the motor service centers that are approved under the Proven Efficiency Verification Program (PEV), a quality assurance program for motor repair.  To see these reports contact an approved motor service center by visiting:

One half to a full point of efficiency lost may not sound like much, but it is costly in terms of operating expenses (cost of electricity), especially when considering all motors being repaired.  Using the equation in Figure 1, we can compute the loss in dollars associated with one-half percent drop and a full percent drop on an annual basis. 


There are several good examples of industry specifications that can be utilized in the development of your motor repair specification. 

The EASA Standard AR100-2006 Recommended Practice for the Repair of Rotating Electrical Apparatus is recognized by the American National Standards Institute (ANSI), and can be downloaded for free by visiting:  The Consortium for Energy Efficiency also offers a motor repair specification at:  Both  are helpful tools for developing a required repair specification  for your vendors.

Most motor repair vendors will have specifications or procedures that are relevant to their organization’s capabilities.  You should ask to see your motor repair vendor’s repair specification.  This is a good opportunity to compare the motor service centers process to your motor repair needs.  Ideally, they should match.

Another area that appears to be growing within the community of motor service centers is quality assurance programs.  Quality assurance is necessary for any business.  Some of these programs are directly targeted at maintaining efficiency during the repair process.  Efficiency is vital to both a smooth operation and the bottom line.  Therefore, we recommend that you look for motor repair vendors with these programs in place.

Some motor service centers are International Organization for Standardization (ISO) registered or certified.  ISO is a well-known quality process that emphasizes documentation.  ISO programs are general in nature and not specific to the motor repair process.  The documentation is especially helpful for new employees, but ISO programs do not necessarily assure quality as it relates to maintaining efficiency.  Some service centers employ ISO because of customer requirements and choose alternative quality assurance programs to document their ability to maintain efficiency during repair. 

EASA-Q:2000 is a quality manual for the motor repair industry.  It is available for sale from EASA, and, according to the Web site, “was created to provide EASA members a practical, cost-effective means of developing a quality management system.  The manual is a guideline for implementing the ISO 9000 series of quality system standards. EASA-Q is designed so that all electrical apparatus service organizations can use it with minimal assistance.  Inexpensive to implement and operate, EASA-Q can assist in reducing operating costs by emphasizing consistency – which often eliminates rework.  The package consists of a printed manual and CD-ROM which can be used to customize your program.” 

The SKF Certified Rebuilder Program periodically audits motor service centers.  The program focuses on training motor shop personnel on the aspects of bearing failure, replacements and root cause analysis.  The program properly identifies the main cause of motor failure and works to ensure personnel are trained to replace bearings and repair motors.  It appears to focus on reliability improvements for motors by focusing on bearing replacement.  For more information on this program visit:

The Green Motors Practices Group asks participating motor service centers to sign an annual membership agreement and subject themselves to scheduled audits from personnel not currently working in the motor repair industry.  Charter memberships in the group are available to shops at no charge.  Some of the items in this agreement include an annual commitment from executive and service center management to clearly communicate policies, support system efficiency with customers, submit calibration records and continually improve shop “champions” with eight hours of documented training per year.  A contact person is required to work on marketing aspects of the program and a second contact must be identified to work with the auditors.   A unique aspect of this program is that two utilities (Bonneville Power and BC Hydro) and some of their distributors recognize the Green Motors Practices Group under the Green Motor Initiative (GMI) Program and pay incentives to the shops and their customers for qualifying repairs.  In the first year of existence (2009), GMI claimed savings of 1,624,400 kWhs and $180,682 in paid incentives.  For more information visit:

Proven Efficiency Verification (PEV) is a motor repair quality assurance program developed by Advanced Energy.  It is specifically designed to ensure motor efficiency during the repair process.  The PEV Program began in 1999 and was originally developed with the assistance of a past EASA president.  PEV requires periodic assessments of specific equipment used in the repair process, documentation of procedures, process flow, calibrations for certain metering equipment, process controls, specific materials and repair personnel experience.  After each shop assessment, a detailed report is provided which identifies areas requiring attention.  The shop is then required to perform before and after repair testing.  Once the motor service center achieves compliance with the site assessment and the before and after testing, they are granted certification for one year and have access to all of the marketing benefits associated with being PEV certified.   Each subsequent year motor service centers are required to submit documentation through a renewal application and have motors subjected to testing before and after repair (see Report 1) at Advanced Energy’s National Institute of Standards and Technology (NIST) accredited motor efficiency test lab (see Figures 2 and 3).  There are fees associated with the program that motor service centers pay.  Currently there is no utility support and no direct involvement from the motor repair industry in the management of the program.  For more information visit:



Motor repair is a critical service that keeps our businesses and industry running smoothly.  We have federal laws in place that mandate motor efficiency, but nothing like this for the motors we repair.  When you consider that an estimated 40–60 percent of all electric energy generated in the world is delivered to motors to literally run our lives, maintaining the highest efficiency possible  is crucial. Quality motor repair saves energy, money and time (by reducing time between failures).   There is one other added benefit when motor repair is chosen over motor replacement and that is recycling.  It is estimated that on average 98.5 percent of motor materials are recycled when repaired.  When all is said and done, a quality motor repair can save money, increase efficiency and conserve natural resources. 

Kitt Butler is the Director, Motors and Drives at Advanced Energy.  He facilitates delivery of successful consulting and testing services to motor manufacturers, distributors, original equipment manufacturers (OEMs) and industrial customers.  He is known for his expertise in helping customers explore key issues that affect the reliability of their products, productivity of their processes and overall economic well-being.  Kitt participates in a variety of industry groups and helps shape motor efficiency legislation by supporting the work of the U.S. Department of Energy (DOE).  Through utility programs, Butler has helped introduce innovative new motor and drive technologies that have significantly reduced energy consumption and demand in California. Butler is intimately involved with product development, market planning and budgeting for Advanced Energy. He is currently managing all aspects of the motor and drive services group including building the organization’s new motor reliability team.  Kitt can be reached at or at 919 857-9017.

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