Electric motors can be repaired without reducing efficiency! EASA can show you how.
Consideration when deciding to repair NEMA Premium motors
A perennial question in maintenance circles is whether it’s best to repair or replace an electric motor that fails. For most plant engineers and maintenance staff, experience attests to the reliability of standard efficiency motors that have been repaired or rewound using industry best practices. Repair also can cost far less than replacement, especially if the motor has special features.
But some decision makers opt to replace failed energy efficient motors (NEMA Premium models in particular) because they’ve “heard” these motors can’t be repaired without a loss of efficiency. So, what’s the right answer? It turns out that the decision to repair, rewind or replace a failed energy efficient motor is not always so simple and straightforward as you may have heard.
The Effect of Repair/Rewinding on Motor Efficiency
Published: December 2008
The Effect of Repair/Rewinding on Motor Efficiency: EASA/AEMT Rewind Study and Good Practice Guide illustrates that when performed properly, electric motor repair/rewind does not degrade efficiency! Nor is motor efficiency reduced through multiple repairs/rewinds.
Based on a joint study by EASA and the Association of Electrical and Mechanical Trades (AEMT) of the United Kingdom, this publication concludes that using best repair/rewind practices maintains motor efficiency. Besides an Executive Summary, the report provides complete test data, extensive background information about test procedures and methodology, information about best practice repair/rewind procedures, resources for further reading, and an entire chapter on repair/replace considerations.
ANSI/EASA AR100-2010: Recommended Practice for the Repair of Rotating Electrical Apparatus
Published: September 2010
The American National Standards Institute (ANSI) has approved revisions in EASA’s Recommended Practice for the Repair of Rotating Electrical Apparatus. Designated as ANSI/EASA AR100-2010, the document is an updated version of ANSI/EASA AR100-2006. The Recommended Practice first received ANSI status (AR100-1998) in February 2000.
ANSI requires that standards be re-approved at least every five years. EASA’s Technical Services Committee proposed 36 changes to the Recommended Practice (ANSI/EASA AR100-2006); the ANSI acceptance group accepted all 36 and added 21 more proposals upon re-balloting. The ANSI acceptance group approved all 57 proposals without any objections. The Technical Services Committee proposals mainly added best practices taken from the EASA/AEMT Rewind Study. The ANSI acceptance group proposals were predominantly editorial.
The ANSI approval process that EASA must follow requires that the document be accepted by a group that presently includes representatives of industry (end users), testing laboratories, government and other standards organizations.
ANSI recognizes only one standard on a topic; therefore, the EASA Recommended Practice is the standard for repair of rotating electrical apparatus.
USDOE issues final rule regarding motor efficiency standards
The U.S. Department of Energy has issued a final rule regarding energy conservation standards for commercial and industrial electric motors.
Guidelines for Maintaining Motor Efficiency During Rebuilding
Published: November 2007
This article provides guidelines that service centers can follow to retain the operating efficiency of the electric motors they rewind and rebuild. It includes a list of DOs & DON'Ts, safe values, and correct procedures that are based on studies of variables that can impact the efficiency of rewound electric motors--e.g., core burnout temperature, winding design, bearing type, air gap and winding resistance. (Note: The article was first published in May 1992; reviewed and revised as necessary in November 2007 by EASA's Technical Services Committee.)