Here You Go.

One of the extra steps we can perform at HECO when performing repairs, maintenance, or rebuilds on your electric motors is magnetic degaussing. While some may feel this step is unnecessary, experience has taught us that it can help prolong the life of your bearings and your motor!

Why Magnetic Degaussing of Motor Components is Important

You may be wondering why magnetism is an issue -- are motors all about electromagnetism and currents? It's true that AC electric motors experience magnetic induction via an electromagnetic field in the motor windings. However, we're talking about a different type of magnetism: one that can damage your motor instead of make it turn.

The type of magnetism that is a source of concern would be, for example, placing a metal screwdriver against the end of the motor shaft and having it remain in place when you remove your hand. That is the kind of magnetism that causes problems. More specifically, magnetized components parts can result in bearings that appear to have been subjected to shaft circulating currents and static discharge -- and these can cause serious damage to motor bearings.

When you repair an electric motor, it is critical to organize, observe, and interpret findings properly to make the right decisions about the motor in question. One way to do this is to prepare a set of Observations and Findings based on what was found during the inspection process. Let’s talk about what to expect when reading through this information.

What Are Motor Repair Observations and Findings?

For every motor that comes into our shop, we summarize the repair and test results into observations and findings. This information gives an overview of what we discovered during the testing and inspection process, explains how it relates to issues that the motor had, and also provides potential reasons for the failure so that the client can prevent it from happening again. The test data it’s based on informs the troubleshooting and repair process, and this summary helps the customer make a decision about needed repairs.

Why Not Call it “Cause of Motor Failure”?

In the old days, this used to be called “Cause of Failure” but, when we think about it, is that really what it is? “Observation and Findings” seems to be better terminology for the information contained because we may not know the entire story of what happened to the motor, despite all the data we can gather from inspection and testing. If we want to have a true RCA or (Root Cause Analysis) an investigation is needed - generally more than just looking at the motor itself, which may just be a result of the failure.

Whether you send a motor in a for a repair it is going to eventually go into a baking oven. For purposes of this article, we are not referring to the higher temperature "burn-off" ovens used in the rewind process - we are referring to just baking ovens. And how your repair vendor bakes that electric motor is key to high quality, reliable repairs. So why is baking necessary?

Why Baking a Motor is Necessary

There are two different processes that involve baking: cleaning and curing.

HECO repairs always involve careful cleaning of the motor in order to remove every trace of contaminant such as dust, grease, and oil. When you pressure wash or steam clean a motor, the windings are going to be wet and that moisture must be baked out at high heat. If not, the remaining moisture could lead to failure or you might end up varnishing over that trapped moisture if the motor needs to be rewound. And as you probably already know, moisture and electric motors just don't get along well.

And that leads us to the second time that baking and electric motor is required: curing resin. Whether the motor is a full rewind or a recondition it may require either a varnish dip or a VPI (Vacuum Pressure Impregnation) process, Either way, the resin must be heat cured. The curing process usually takes significantly longer to complete than baking the moisture out (partial days instead versus hours). It is vital that the resin insulation is fully cured and that it has not been applied over trapped moisture, or there is a risk of failure that we at HECO just aren't willing to accept.

An electric motor repair shop is more than just tools, test instruments, and equipment. It’s made up of employees...team members...that have experience, a commitment to the shop’s core values, are active participants in apprenticeships, and serve as effective team leaders and managers. And it’s just as important that their work and expertise be respected. 

When it comes to inspecting electric motors, it’s not just the electrical components that are important. The mechanical aspects of a motor are extremely important to its performance, which is why mechanical inspection of electric motors is so important.

Critical Fits for Electric Motors

Electric motor inspection, when done correctly, always includes a mechanical inspection. As the motor is carefully dismantled, critical fits are measured. These critical fits include …

• Bearings fits
• Journal fits
• Housings
• Seal fits
• Keyway
• Shaft extension size
• Etc.

For an electric motor to run efficiently and productively, attention must be paid to the often mundane aspects of mechanical fits and tolerances.

You hear the world "quality" all the time. Many times its one of those words that you ignore. I always think of it as a word that is used so frequently that it doesn't mean much anymore.

However, when it comes to having your electric motor's repaired, the word quality really does have a meaning and there are many ways to verify and ensure quality repairs are done properly. Here are a few of the bullet points to consider:

1. Documented data & images during inspection
2. Inspection/incoming report
3. Formal quotation/estimate
4. Calibration program and calibrated equipment
5. Modern technology (where appropriate)
6. Documented procedures/processes
7. Final report

One of the first steps we take in our repair process here at HECO is steam cleaning your electric motor. Electric motor parts can get extremely dirty and the interior of the motor is often covered in dirt and dust (on DC motors: carbon dust). Sometimes technicians can’t visually check for signs of wear or damage -- or accurately troubleshoot the motor, for that matter --  when the motor is still dirty.  

Dirty Motors

We all know electric motors get dirty -- and don’t worry: we won’t judge you if your motors look filthy. Depending on the environment and motor enclosure, we usually expect to open one up and see a significant buildup of dust and other debris. Sand, fly ash, cement, paper pulp, carbon black, etc. buildup alone can impact motor performance and efficiency, causing areas to overheat, contaminate lubricants, accelerate wear, and damage the windings. Carbon dust is conductive, which means it can cause shorts if they get in the wrong area. However, accumulations like this are natural, but that doesn’t mean your motor has to stay that way.

Are your electric motor bearings wearing out long before they should? The problem might be bearing fluting … and the good news is that there are ways to prevent it.

What is Fluting?

Fluting is a form of electrical damage suffered by electric motor bearings when alternating (AC) or direct (DC) current actually passes through the metal bearing. As the currents pass through the bearings, they can leave behind surface damage that results in premature bearing failure.

The winding insulation on your electric motor has a major impact on its life expectancy and reliability, which means that using the wrong insulation class could be very costly. The best way to avoid this mistake is to be familiar with the basics of NEMA insulation classes.

You've got a electric motor that needs to be repaired yesterday, but you're also working with a pretty constrained budget. You've got a electric motor repair vendor in mind, but you've heard that they outsource work. Is that a smart choice?

Vendors that Outsource Electric Motor Repair 

The capabilities of electric motor repair shops can vary significantly. One shop might be able to manufacture an expertly engineered motor from a shell of a stator while another is just a two man crew that does bearing swaps. When you use a shop that doesn't have extensive capabilities, you run the risk that they will outsource critical aspects of your motor's repair to someone else.

Due to limitations -- which could involve tools, equipment, money, or technicians -- a shop may find it best to outsource some of the electric motor repairs they are responsible for. Some repair shops are able to do all repairs in house, while others may use a hybrid approach where only certain repair jobs are outsourced. However, there are some motor repair shops that outsource almost everything.

Why Electric Motor Repair Shops Outsource

There are quite a few reasons behind repair shops choosing to outsource. In some instances, it may be more economical for them (but not necessarily for you!) to send certain repair jobs out to other shops. For example, good technicians can be hard to come by, especially if a repair shop isn't willing to pay for talent and experience.

The equipment and tools needed to support repairs may be more expensive that the shop can afford. This is often true with tasks such as motor rewinding as well as VPI. And it may be an issue of having the space for the right equipment to perform certain repairs. This can especially be true when it comes to repair large motors and A-NEMA motors.