Should I Repair or Replace My Transformer?

Transformer problems rarely happen at a good time. 

Maybe your oil test came back showing gassing. Maybe the unit is leaking. Maybe a bushing failed, or the tank is badly corroded. Now you have a critical question to answer:

Should you have the transformer repaired? Or should you replace the unit entirely? 

There isn’t one right answer for every job. The best choice depends on your transformer’s condition and age. How quickly you need power restored, whether your existing footprint is difficult to match, and what your facility will need in the future.

In the past, the easiest solution was just to order a brand new unit. Lead times were reasonable, so you could get an identical transformer (or something really close) relatively quickly. 

But today, industry lead times can stretch anywhere from weeks to several months. And that’s for the “regular” transformers. Never mind custom units. (If you need a transformer fast, reach out about Maddox’s stock and remanufactured options.) Time is now one of the biggest factors in deciding whether to repair or replace. Cost is another major hurdle. Since 2019, the price of new units has skyrocketed. Increasing by an estimated 77% for power transformers and between 78% and 95% for distribution transformers.

In this article, we’ll walk through the questions to ask when deciding if you should repair or replace your transformer. We’ll cover what causes transformer damage, when rewinding your transformer makes sense, and how Maddox ensures your repaired unit runs like new. 

What causes transformer damage?

Let’s start with the basics. What actually causes a transformer to fail? While there are many minor issues that can pop up, major transformer damage typically comes down to three big contributors: aging, overloading, and catastrophic events.

Aging

Just like any other piece of equipment, transformers naturally break down over time. The biggest issue with aging isn't the steel core or the tank—it's the cellulose paper insulation wrapped around the windings. Over time, this paper slowly loses its mechanical and dielectric strength. And once the insulation becomes brittle and weak, the transformer is highly susceptible to internal faults and short circuits. In fact, a published IMIA study shows that insulation failure is the leading cause of transformer failures.

Overloading

While old age is inevitable, overloading speeds up the clock. Pushing a transformer past its nameplate capacity generates excess heat inside the unit. Heat is one of the biggest enemies of a transformer because it rapidly accelerates the breakdown of the cellulose insulation. If your facility is constantly demanding more power than the unit was designed to handle, the insulation will deteriorate quickly. That will leave the windings with little protection against mechanical stress and overcurrents. 

Catastrophic Events

Unlike the gradual deterioration that comes from aging and overloading, catastrophic events can suddenly cause significant damage. These events include natural disasters like lightning strikes, floods, and hurricanes, as well as severe system faults. These events attack the fundamental integrity of the transformer, resulting in severe winding or core damage. When a catastrophic event occurs, your options are usually limited to a complete rewind or a full unit replacement.

If I find a problem with my transformer, what should I do?

A transformer can show symptoms (like an oil leak, an unusual noise, a hot spot, or a bad test result) without making the root cause obvious. 

If you get a concerning test result, you should:

1. Run the same test again to confirm the issue. Take photos of any visible damage. Also, investigate whether the unit was frequently overloaded. 
2. Review the results with an expert (like the engineers at Maddox) to determine if the unit is worth repairing. 
3. Get the transformer into the shop for a more thorough evaluation in a controlled environment.

At Maddox, we run a full battery of tests to diagnose possible problems and assess the overall condition of your transformer. We’ll send you a detailed evaluation of what we found and our recommendations for repairs or if necessarily full replacement. You can then choose which repairs you would like to move forward with.

When does a transformer repair make sense? 

Repairing your transformer is often the best option when the problem is isolated. The transformer is otherwise in good condition, and keeping the existing unit saves time, money, or installation headaches.

Walk through the below questions to determine if a transformer replacement is your best option.

Are the problems limited to replaceable parts?

Many transformer issues are repairable because they involve easy to replace or repair components.

Examples include:

• Leaking gaskets
• Damaged bushings
• Minor tank leaks
• Corroded or damaged hardware
• Failing gauges
• Loose connections

If the core and coil assembly is still in good condition, repairing or replacing the damaged components is usually the best bet. It extends the life of the transformer without the cost or hassle of replacing the entire unit.

Is the transformer’s footprint hard to match? 

The transformer’s footprint is one of the biggest reasons to repair instead of replace.

Your original transformer may have unique features like specific dimensions, bushing locations, or throat connections. Replacing the transformer may require a lot of extra work to match your existing system set up.

If the old transformer fits the site perfectly, repairing or rewinding it can avoid a long retrofit project.

Can you wait for a newly built transformer? 

Brand-new custom transformers can involve long lead times, especially for more unique units. If your existing transformer can be repaired or rewound, you may be able to restore service sooner than waiting for a new one. 

Transformer Rewinding

This is especially true for minor repairs or component replacements. If the windings are damaged but the tank, core, and other major components can be reused, rewinding may be the best option. Transformer rewinding replaces the damaged coils while keeping the existing core and tank. This can preserve the original footprint, reduce the need for installation changes, and avoid paying for a completely new transformer.

When does replacing a transformer make sense?

Repairing your transformer isn’t always the right solution. Sometimes, the smarter choice is to replace the unit entirely. Here are three specific scenarios where replacing your transformer is the better path forward:

Does your transformer have severe internal damage?

If the core and coil assembly is badly damaged, the financial argument for a repair can change quickly. A minor component fix is one thing, but a major rebuild is another. If testing reveals extensive insulation failure, severe winding damage, or a history of repeated failures, a replacement might be your best bet. While rewinding can be a great solution, it doesn't always make sense. For instance, if the enclosure or tank is completely unusable, a rewind is essentially just building a brand-new unit from scratch. This is especially true for older units. If the transformer is more than 30 years old, you should strongly consider replacing it. At a certain point, a "repair" can turn into basically building a brand-new transformer.

Is the transformer no longer right for your load?

A transformer can be perfectly repairable and still be the wrong unit for the job. If your facility has changed since the unit was installed, your electrical needs may have changed with it. Maybe your load has increased, your voltage requirements have shifted, or you are adding new equipment. In those cases, replacing the transformer with a properly sized unit may be the better long-term decision. Repairing an undersized or poorly matched transformer may solve the immediate issue, but it could leave you facing the same problem in the future.

A perfect replacement is sitting in stock.

Sometimes, speed wins. Maddox actually keeps thousands of new and remanufactured transformers in stock and ready to ship. If a matching unit is already sitting in our inventory, swapping it out might be faster than waiting for a shop repair. This is especially true if the in-stock unit perfectly matches your physical layout and voltage needs. In an emergency, your fastest path to restoring power might be to rent a temporary transformer, buy the in-stock replacement, and deal with the failed unit later.

For example, when a winter storm destroyed the transformers powering a Philadelphia school and medical facility. The property developer faced lead times of several months from other suppliers. However, because Maddox had the right remanufactured units in stock, and delivered two 500 kVA padmounts the very next day, getting the facilities back online within just 48 hours.

Why should I trust Maddox with repairing my transformer?

Once you know your transformer has a problem, the next question is who you should trust to evaluate it.

At Maddox, transformers are what we do every day. We have locations across the country and a team with deep experience evaluating, repairing, rewinding, and remanufacturing transformers. That means we can help you figure out what’s actually wrong with your unit and whether it makes more sense to repair it, rewind it, or replace it.

Every repaired transformer goes through rigorous testing to help verify it is ready for service. And because remanufacturing is such a big part of our business, our team knows how to restore transformers the right way.

We also stand behind our repair work with the same 3-year warranty as our new units. If you need your transformer evaluated for repair, fill out the form at the bottom of this page and our team will help you take the next step.

Conclusion: Choosing Between Repairs or Replacements

When a transformer has a serious problem, the choice between repairing versus replacement isn’t always obvious. Sometimes a minor repair is the fastest and most cost-effective path. Other times, a rewind, rental, or new transformer is the better long-term solution.

The key is to start with a proper evaluation. Once you know what failed, how severe the damage is, and what your site actually needs, you can compare your options more clearly.

Also, the right answer may combine more than one of these options. You might rent a transformer now, rewind the failed unit, and reinstall it later. Or you might install a new replacement transformer now and sell or scrap the failed unit.

If your transformer is having issues and you need to review your options, fill out the form below. Our team will evaluate your unit and help you decide the best path forward.

We’re ready to help get your project back online quickly.