This valuable publication explains the findings of a major study that analyzed the impact of repair/rewinding on the energy efficiency of Premium Efficiency/IE3 electric motors. This study was a follow up to a 2003 study.

A special discounted collection of 7 webinar recordings focusing on various aspects of electromechanical repair.

Just $35 for EASA members!

On many occasions, a different motor type is desired or needed. In these cases it is essential that the replacement motor provides the required performance, and do so reliably.

Selection of replacement motors is usually straightforward if the ratings are equivalent. Sometimes, however, a different type of motor is necessary or desirable. For success in these cases, it is essential that the replacement motor provide the required performance — and do so reliably.

When faced with an ailing or failed motor, plant operators typically consider whether to repair or replace it. According to a 2014 study conducted by Plant Engineering magazine for the Electrical Apparatus and Service Association (EASA), just more than one-half of plants have a policy of automatically replacing failed electric motors below a certain horsepower rating. While that horsepower rating varied depending upon the plant’s installed motor population, the average rating was 30 hp.

While such policies address a portion of the motors used at most plants, they do not cover what occurs with those motors. That question was addressed in a more recent research project commissioned by EASA that focused on the disposition of electric motors considered for repair.

An easy-to-use, 4-page service order worksheet providing places to record the most important motor repair data.

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.

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?

The paper "Repair/Replace: What to Do When the Decision Is to Replace" by Tom Bishop, presented at the EASA Convention 2007, addresses the considerations and steps involved when the decision is made to replace an electric motor rather than repair it. This comprehensive guide covers selecting the right motor for the application, dealing with usual and unusual electrical and mechanical conditions, preventing problems by recognizing the causes of the original motor failure, and adding value by providing additional features and services to increase the reliability of the replacement motor.

You may have experienced this situation before: Your best customer just called to say he has a plant down and is in desperate need of a 100 hp, 6-pole, 460-volt motor. And he needs it now! You check your stock and find one that's pretty close. The frame is right, but it's a 125 hp unit at 575 volts. What can you do? You know that the motor will run at 460 volts, but how much horsepower will it produce?