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.

You're trying to select a vendor to perform some repairs (and possibly a rebuild) on one of the critical yet problematic motors in your facility. You've received some good bids and are reviewing the vendors under consideration when you notice that one says they have a good relationship with the vendor of the motor you have. In fact, they have a service agreement with them. Their bid isn't necessarily the lowest, however.

How important is such a partnership?

HECO's Partnerships

HECO is already partnered with leading electric motor manufacturers like Siemens, Dynamatic, TECO Westinghouse, and ABB. Our manufacturer service partnerships mean that companies like these have personally evaluated our facility and repair/rebuild procedures -- and feel confident that HECO will repair the motors they've made to their already high standards or better. And not only that, but HECO can use our connections with these manufacturers to help you, too.

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.

Performing tests on an electric motor is no easy task. You have to be careful about what voltage to use, what parameters are correct for the type of motor, and what specifications the test needs to be performed according to. And there are certain electric motor test instruments that are used to gather key data to evaluate the condition of a motor. Even if you're not the one performing the tests, it's still a good idea to have an idea of what those tests are and what test instruments are involved.

These tests are referred to as "standard" however, there are many opinions out there on voltage levels, what tests can be used when, etc. Watch the video to learn more.

Electric motor inspection testing is an important part of establishing the condition of the motor and the beginning the troubleshooting process. There are several different tests involved, and a basic knowledge of what the tests are can help you understand the repair data you receive back from your electric motor repair shop.

Electric Motor Inspection Tests

The most critical motor inspection tests include the following:

• Winding phase-to-phase resistance
• Insulation resistance (IR) to ground
• DC hi-pot
• Surge comparison
• Polarization index
• AC and DC voltage drop (DC motors)

These tests should be performed by experienced technicians using the methods and voltages prescribed by  EASA (Electrical Apparatus Service Association) and IEEE (Institute of Electrical and Electronics Engineers) standards. In addition, all phase-to-phase resistance tests and IR tests must be passed prior to performing the high voltage DC hi-pot and surge comparison tests. 

Note that electric motor inspection test values are compared between the initial inspection test data and the final test data to ensure that improvements were made as a result of the repair or remanufacturing process.

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.

Being an innovator in Equipment Management with over 40 years of experience with electric motors & powertrains, it’s kind of in our blood to talk about how we do things. In conversations with perspective clients on our approach to equipment management we often hear “my motors are stored by my repair shop for free”. We have all heard the old saying “that nothing is free” and “you get what you pay for” so let’s think about “free” and what you are getting.

Having those old sayings in mind we start asking questions. Questions like, do they periodically test your motors? Do they spin the shafts? Are all of the motors in their warehouse ready for service? Have they ever sent you a motor from their warehouse that did not run or only lasted a short time? Have you ever visited their warehouse and checked on the conditions? People can spend $40,000 on a car and know exactly where their car is and its condition at all times but don’t really know where and under what conditions their $750,000 motor is stored. Oh, and another point, your $40,000 car is insured. Is your $750,000 motor insured in the “free guys” warehouse? You might want to ask.

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. 

The above video is a recording of a webinar given on 1/21/2021. Click on Uptime graphic to view webinar.

What is Uptime Elements as it relates to your asset management strategies?

Join our webinar to find out more about how Uptime Elements can benefit your enterprise. 

At its simplest level, the Uptime Elements framework is a language that aligns stakeholders across your organization for improved reliability in your company's operations.

All things that can be mastered begin with the acquisition of a specialized language that contains words, concepts and ideas.

An example would be a doctor in medical training who begins by studying the specialized words, phrases and concepts related to the practice of medicine. The same is true for reliability.

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.