Electric Motor Repair Half Life

A term that has become more and more common in the motor repair industry is ‘electric motor repair half-life,’ which refers to the concept that repaired electric motors will only half as long as the original new motors. The concept brings a lot into consideration for a company concerned with equipment reliability. If the idea of a repair half-life is true, what is the impact of our repair versus replace decisions?

In the 2006 Advanced Energy study and report, “Achieving More with Less: Efficiency and Economics of Motor Decision Tools,” on page 40, a Weherhaeuser report on electric motor reliability is discussed with the following conclusions:

- 50% of new motors fail in seven years; and,
- 50% of rewinds last only 3.5 years.

This would seem to support the notion of a repair half-life. It also identifies that not all facilities enjoy the 20 to 30 year average motor life discussed in numerous articles and research papers. Usually, the failures will relate to improper application, contamination, misuse, or other outside influences placing stresses on the electrical, mechanical or both types of systems within the machine. As I have mentioned in the past, an electric motor makes an excellent, but expensive, fuse.

What makes a repaired motor, or some repaired motors, more susceptible to these issues than a new electric motor while others are not?

In the 1995 Bonneville Power Administration (US Department of Energy) report, “Industrial Electric Motor Repair in the United States,” it is outlined that: 80 percent of repair facilities change winding configuration, often without understanding the potential consequences of the changes; 41% of repair shops reported burn-out temperatures in excess of 750 degrees F; and, “proper testing, which may include tests for insulation integrity, winding resistance, vibration, rotor balance, and core loss is essential for all repairs. It appears that only insulation testing is done routinely.” Comprehensive, or even basic testing, is performed by fewer than half of the motor repair facilities.

It has been found through numerous studies, including the 1995 Canadian Electrical Association (CEA 9205 U 984), “Evaluation of Electric Motor Repair Procedures Guidebook,” that proper and improved processes will provide similar, or improved, reliability as new. A combination of the studies and results can be found in the 1997 IEEE Electrical Insulation Magazine Article, “Anatomy of and Energy Efficient Electric Motor Rewind,” (Penrose) and other papers that can be found at http://www.motordiagnostics.com/presentations.htm.

Alternative motor repair processes, such as low temperature coil removal processes, special machining processes, automated coil winding, trickle varnishing systems, and quality control systems is outlined in the 1995 IEEE Electrical Insulation Conference paper, “Time Savings and Energy Efficiency through Alternate Electric Motor Rewind Methods.” (Penrose, H. W. and Bauer, B.) This paper outlines the only process that can provide a true 24 hour turnaround for motors under 400 horsepower without having to make shortcuts. The result is energy efficiency, reliability, and a turnaround time that will allow for rapidly returning a facility to operation for critical machines.

Some of the issues that can impact the life of an insulation system, including how to calculate the expected life of an insulation system, can be found in R. L. Wall’s IEEE DEIS Web video, “Fundamentals of Motor Insulation for Repair Shops: Part 3,” http://ewh.ieee.org/soc/deis/education/video-detail/education/fundamentals-of-motor-insulation-for-repair-shops-part-3.html.

If you have questions or comments on this topic, please email me at hpenrose@dreisilker.com.

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Sincerely,

Dr. Howard W Penrose, Ph.D., CMRP
IEEE DEIS Web Editor in Chief (http://ewh.ieee.org/soc/deis)

Motor Repair Tours

Electric motors of all types cut across all industries and applications. However, most reliability and maintenance professionals have limited exposure to electric motor theory and electric motor repair. After having returned to Dreisilker Electric Motors, Inc., with our main repair shop in Glen Ellyn, Illinois (and second facility in McHenry, Illinois) along with an additional six storefront branches throughout the Midwest and Atlanta, Georgia (see http://www.dreisilker.com), we have an opportunity to educate you.

If you are a commercial or industrial/manufacturing end-user, specify electric motor repair or motor management programs, feel free to contact us for a tour of the Dreisilker Glen Ellyn, Illinois, facility. You can contact me direct at 630-469-7510 ext. 320 or email hpenrose@dreisilker.com. Trade schools, colleges and university class tours are available.

It is our goal to help you understand our industry.

Dr. Penrose Wins 2008 UAW-GM People Make Quality Happen Award

After winning the 2005, 2006, and 2007 UAW-GM People Make Quality Happen Awards for energy, environment, and reliability programs throughout General Motors as part of the Joint Task Team for Construction and Maintenance, Dr. Penrose has been awarded the 2008 UAW-GM People Make Quality Happen Award for reliability and energy programs in 2008. Programs have included reliability and maintenance task and program best practices for a reduced and changing workforce, joint US Dept of Energy/GM/UAW programs for energy and environment improvements, and the development of the GM Motor Management program.

IEEE Dielectrics and Electrical Insulation Society Web Educational Videos

We continue to convert IEEE videos for IEEE DEIS Web, of which Dr. Penrose is the Editor-in-Chief. The following videos are available under the Lifelong Learning button of the IEEE DEIS Website http://ewh.ieee.org/soc/deis/lifelong-learning/educational-videos.html:

- Rotating Machinery Workshop
- Streamers in Liquids: Basic Phenomenon
- Fundamentals of Motor Insulation for Repair Shops: Part 3
- Turn Insulation Aging of Motors Exposed to Fast Pulses of Inverter Drivers
- Utilizing Reduced Build Concepts in the Development of Insulation Systems for Large Motors
- Fundamental Demonstration of Electromagnetic Fields and Energy (Mass Inst of Tech – MIT)
- Analysis of Winding Failures in HVDC Converter Transformers
- Electric Breakdown in Solid and Liquid Insulating Materials
- Electrical Insulation of Gasses (A Tour of MIT Labs)

There are lots more to come!! Each runs from 20 minutes to 1.25 hours.

Anyone can become a member or associate member of IEEE DEIS. For information go to http://ewh.ieee.org/soc/deis and select the join button at the top of the page.

Also note: the videos have been improved. You can expand to full screen by right-clicking on the video and selecting ‘view’ and ‘full screen.’

Do Not Read if You are On an Airplane

Several weeks ago I missed Nick’s (my older son) graduation and graduation party due to maintenance issues and airline supervisors and maintenance staff attempting to convince the pilot and aircrew to take a broken plane. I provided a copy of my editorial, published several weeks ago, to the airline the day before publishing. I received a settlement from the airline and official apology.

However, my experiences are not unique. The following article was written by a journalist for Consumer Reports: http://www.consumeraffairs.com/news04/2009/08/airline_maintenance.html

We have had a number of aircraft, both domestically and abroad, either crash or have significant problems, including many that have made the news or that individuals have experienced. The issue relates to the concept of cutting corners in maintenance, including areas that may not be considered ‘critical.’ Basically, individuals or groups who have taken the basic rules for optimizing maintenance and stretching them far beyond expectations.

Review the issue and solutions by reading the 2009 Axiom Business Book Award winning “Physical Asset Management for the Executive: Caution Do Not Read This if You are on an Airplane.” Only $14.95 USD through any online bookstore or order it locally or through our direct distributor http://www.motordoc.com/detailPAM.htm