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We have posted this exchange at MaintenanceForums.com to encourage additional discussion and to expand the learning from this information.

Please feel free to add your voice and experience to this discussion.

Read replies or post your own here

Original Tip: “Motor rewind shops will agree that seldom - if ever - is it feasible to rewind a motor more than once. This is due to the cumulative damage to the windings during failure.”

Feedback: The windings are replaced so no cumulative damage

Original Motor Tip: “One fact related to electric motor operations is that rewound motors operate less efficiently than new motors….”

Feedback: Efficiency should be almost the same as windings are replaced with the same as before - you may have a little more heat loss through the iron because the windings on smaller motors (1000 hp and less)are burnt out in ovens @ a high temperature.

Feedback provided by Lucy Malone
Catalyst Paper
Campbell River,B.C. 

Original Tip: One fact related to electric motor operations is that rewound motors operate less efficiently than new motors.

Feedback: Only sometimes, if not done correctly, blanket statements are seldom all encompassing.

Original Tip: Worn motors can be “reconditioned”, that is reinsulated before any damage to the windings occurs

Feedback: Motors can be baked out, cleaned, revarnished, new lead wire installed.

Reinsulated implies much more.

Neil Gillespie
Electrical Engineer

A recent article from the Reliabilityweb Maintenance Tips I received on July 17th, has gotten my blood boiling!

The author of the article made many statements in regards to motor maintenance, repair, rewinding and replacement that must be challenged, due to their blatant inaccuracy and falsehood!

In the article he states, quote (One fact related to electric motor operations is that rewound motors operate less efficiently than new motors.)Unquote. That statement is absolutely false! I direct your attention to the following publication from the Electrical Apparatus Service Association, Inc., EASA,
http://www.easa.com/indus/index.html
titled, “The Effect of Repair/Rewinding on Motor Efficiency”. I quote, (The 22 new motors studied were divided into four groups to accommodate the different test variables. The test results summarized below show no significant change in the efficiency of motors rewound using good practice repair procedures (within the range of accuracy of the IEEE 112B test method), and in several cases efficiency actually increased.) Unquote.

Later in the article the author states, quote (What they may be reluctant to admit is that rewound motors will operate less efficiently than new motors. Depending on who you talk to, estimates range from 50% to 90% efficiency for rewound motors versus new. Hence, it can be demonstrated that repaired motors will increase energy consumption.) Unquote. Once again, he is in error. I quote (The average efficiency change for each group also falls within the range of accuracy for the test method, (plus or minus 0.2%), showing that motors repaired/rewound following good practices maintained their original efficiency, and that in several instances efficiency actually improved.) unquote.
http://www.easa.com/indus/index.html

The author might want to do his homework before he submits another sales pitch disguised as an article. I would suggest the following, “A Guide to AC Motor Repair and Replacement”. He can find it here, http://www.easa.com/indus/index.html

Tip response provided by Stephen Powell
Service Manager
Turnupseed Electric Service, Inc.
Tulare CA

We published a tip in the July 17 issue that created a great deal of feedback. All of the feedback offered a 180 degree response to the original Motor Tip and attempt to correct what they state are mis-statements by the original tip author.

We accept responsibility for publishing the original tip from a new source who happened to be a supplier to this industry and we apologize for not vetting the information more carefully.

We appreciate all of those who emailed and we are sending Maintenance Tips hats and Stainless Steel. Diamond Plate Coffee Mugs as a small thank you. We hope the replies below go some distance to provide new information.

Respectful discussion is always encouraged throughout the Reliabilityweb.com network and we hope you can learn from our missteps. Additional comments are welcome.

Thank you for your patience and understanding.

Terry O