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Considering efficiencies: to rewind or replace an electric motor

Published: 3 April 2018 - Sarah Mead

When motor failure occurs, it can have a huge impact on your business in terms of productivity and monetary losses. You want to get your processes up and running as quickly as possible, so you may not have time to thoroughly weigh up electric motor rewinds against full motor replacement.

However, this isn’t a decision you should take lightly. With new high-efficiency motors available, should you invest in a new motor that promises higher efficiency levels but with significantly greater costs? Or, do you commit to a motor repair or rewind? While the cost is often lower, many are concerned about the potential inefficiencies that an electric motor rewind can bring — yet are these worries grounded in fiction?

A selection of studies around smaller motors is responsible for this belief. It is claimed that carrying out a rewind can drop efficiency by between 1% and 5% each time it is rewound. Considering the associated expense and sheer volume of energy these motors use, this is naturally concerning. More recent research has countered these findings though.

EASA and AEMT, in association with Nottingham University, carried out tests on 22 new motors that range from 50 to 300 hp. Overall, the results found that when electric motors were rewound using good practice, there was no significant change in the efficiency of the motors. However, in some instances, efficiency actually increased. This clearly dispels the belief that a rewind is actually detrimental to a motor’s performance.

Your key considerations

The above findings suggest that electric motor replacement may not be your only option — except, of course, in cases of catastrophic failure. It’s very important to fully evaluate your options to make sure you make the right choice in terms of operation, cost and efficiency. This can be done by asking a number of key questions, as explained by Houghton International:

How suitable is your electric motor for your requirements?

An electric motor that was once suitable may now be unsuitable as your operational needs have shifted. Review the scale of the damage alongside the requirements for the motor’s processes and duty cycles. If the motor is no longer suitable or too damaged, your option is to replace the motor.

Check the condition of the stator core and rotor

If you’re confident your electric motor is still suitable for your operations, you then need to check the stator core and rotor. If significant damage is present, it may be more beneficial to purchase a new motor, as depending on the extent of the damage, repairs can be costly.

Always fully consider your options when buying a new motor. For example, if the lead times for the motor you need are long, you may decide to repair rather than replace to minimise downtime.

Have other mechanical parts been damaged?

When motor failure occurs, it’s possible that damage may occur to the shaft, frame, bearing housing and other mechanical parts. Examine the extent of the damage; you may be able to replace the affected parts at a lower cost than replacing the entire motor.

Is it an EPAct or Nema Premium motor?

If your motor has failed, you may use it as an opportunity to invest in a more efficient model. If you are considering making the investment, make sure you fully understand the return you’ll receive from doing so. Consider the energy savings you’ll make alongside the expected life of the motor and its hours of operation. Always consider your overall budget too, to make sure the replacement aligns with your current financial position.

It’s important to remember that electric motor repair that’s carried out by a qualified service centre will not dramatically reduce efficiency. What’s important is that you consider all of your options to ensure you make the right choice for your needs and operations.

Houghton International -

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