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Resource Library

Best AC Rewind Practices

  • February 2021
  • Number of views: 15324
  • Article rating: 4.0
FREE for Members of EASA
Webinar recording

This webinar recording shares some of the “best practice” rewind methods used by (and learned from) EASA service centers around the world: connection recognition, best insulating materials, wire choices and tips to save time and effort.

Controlling Stator Copper Losses in Formed Coil Rewinds

  • May 2020
  • Number of views: 10770
  • Article rating: No rating
FREE for Members of EASA
Webinar recording

This webinar recording looks at several aspects of winding design to prevent increased temperature rise and decreased efficiency.

Insulation Technology Improvements and the Repair Market

  • July 2019
  • Number of views: 5133
  • Article rating: No rating
Webinar recording

Most modern rotating electric machines operate on the same principles their predecessors have for 100+ years. However, improvements in materials technology over that time have allowed for increasingly greater power density in machine design.

Magnetic Wedges

  • February 2019
  • Number of views: 14142
  • Article rating: 5.0
Webinar recording

An increasing number of manufacturers are using magnetic wedges in their form-wound machines. When a winder fails to replace magnetic wedges in kind, the winding temperature rise can increase by 20°C, and the magnetizing current can increase by 20% or more.

Parallel circuits: More than meets the eye

  • December 2018
  • Number of views: 6900
  • Article rating: No rating

There are benefits and drawbacks to the use of multiple circuits in a 3-phase winding. Whether discussing a random winding or form coil winding, some of the considerations are shared. Topics covered include:

  • Increasing circuits, turns
  • Rotor pullover during starting
  • Increased risks
  • Factors beyond our control

Working with odd-turn (unequal-turn) windings

  • July 2018
  • Number of views: 8377
  • Article rating: 4.0

Manufacturers almost always utilize machine-inserted concentric windings for random-wound, three-phase stators when their processes can facilitate it due to lower manufacturing costs. Many service centers can produce concentric windings too, but the most common practice is to utilize the two-layer lap winding. For form-wound stators, the two-layer lap winding is almost always used by manufacturers and service centers alike. The purpose of this article is to provide some tips for working with odd-turn (unequal-turn) windings, or two-layer windings where the total number of turns per slot is an odd number (e.g., 3,5,7,9…n). In such cases, the top and bottom coil sides must have a different number of turns.

How to ensure effective motor repair and rewind

Speak the same language as your service center when it comes to setting performance expectations

  • May 2016
  • Number of views: 8431
  • Article rating: No rating
Trade press article — Plant Services

Electric motor efficiency can be maintained during repair and rewind by following defined good practices. This article builds on a previous discussion of PM and PdM for three-phase squirrel-cage motors ("PM and PdM for electric motors") by outlining some of the expectations and good practices for repairs of these types of motors.

Can you repair energy-efficient motors? Maybe.

  • April 2016
  • Number of views: 7820
  • Article rating: No rating
Trade press article — Wood Business

Most plant engineers and maintenance staff can attest to the reliability of standard-efficiency motors that have been repaired or rewound using industry best practices. They also know repair can cost far less than replacement, especially when the motor has special features. Despite this, some of them hesitate to have failed energy-efficient motors (NEMA Premium models, in particular) repaired because they’ve heard it degrades efficiency.

So, what’s the right answer? Is the decision to repair, rewind or replace a failed energy-efficient motor as simple and straightforward as you may have heard?

Improving designs in motors with multiple windings: Concentric or a conventional half-slot lap winding will help

  • July 2012
  • Number of views: 4732
  • Article rating: 4.3

One of the pleasures of helping EASA members is in discovering challenges or specific areas where we can improve on the original design of the motor manufacturer. The most recent of these, for me, has been a noticeable cluster of calls about motors with multiple windings. The call usually starts with something like this: "We wound this motor, and one speed was terribly burned." Another one I often hear is: "We rewound both speeds, and the surge test pattern for one speed indicates a winding problem." These are but a couple of examples of a design issue we are seeing with motors having more than one winding. While the use of variable-frequency drives (VFDs) is increasingly common, there are still applications using 2-speed, 2-winding motors. Cranes are a good example of one such application. When a core has more than one winding, the two windings behave as a transformer. Applying voltage to either winding induces voltage in the other winding because the two windings are inductively coupled. As long as both windings are connected 1 wye, and the leads of the second winding are left open, no magnetizing current is drawn by the second winding. When both windings are conventional and symmetrical, this arrangement works just fine. The problems start when either winding deviates from the symmetry that is so important to 3-phase motor performance.

Topics covered include:

  • Transformer effect
  • Visualizing the current flow
  • Parallel circuits

Practical service center tips to work more efficiently

  • April 2012
  • Number of views: 3223
  • Article rating: No rating

Time is a precious commodity, so making the best use of it can help you provide the best possible service to your customers. Following are just a few topics covered:

  • Tearing down of small metric motors
  • Avoiding chuck jaw marks when shaft is in the lathe
  • Avoiding over-shoot when mounting shrink fit couplings
  • Making superior brazed winding connections
  • Forming copper tubing without crimping
  • Better babbitt pouring results
  • "Hot dam"
  • Maintaining a centered hole in end of shaft when shaft is shortened
  • Removing stuck outer bearing races from end bells
  • Removing an inner race stuck on a shaft

Getting The Most From Your Electric Motors

Getting The Most From Your Electric Motors - coverThis 40-page booklet provides great advice for obtaining the longest, most efficient and cost-effective operation from general and definite purpose electric motors.

This booklet covers topics such as:

  • Installation, startup and baseline information
  • Operational monitoring and maintenance
  • Motor and baseline installation data
  • How to read a motor nameplate
  • Motor storage recommendations



EASA/AEMT Rewind Study

EASA Rewind Study cover

The Effect of Repair/Rewinding on Premium Efficiency/IE3 Motors
Tests prove Premium Efficiency/IE3 Motors can be rewound without degrading efficiency.


ANSI/EASA AR100-2020

ANSI/EASA AR100-2015 cover

Recommended Practice for the Repair of Rotating Electrical Apparatus
This is a must-have guide to the repair of rotating electrical machines. Its purpose is to establish recommended practices in each step of the rotating electrical apparatus rewinding and rebuilding processes.



EASA Technical Manual

EASA Technical Manual cover

Revised September 2022
The EASA Technical Manual is the association's definitive and most complete publication. It's available FREE to members in an online format. Members can also download PDFs of the entire manual or individual sections.