Here You Go.

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.

When you need a motor to stop and you can’t just let it naturally come to rest, then you probably need an electric motor brake. And it’s very important that you get the right motor brake for the job.

What All Motor Brakes Have in Common

While there are several different types of motor brakes, there are certain things they all have in common. First is their purpose: motor brakes are responsible for stopping an electric motor or holding its driven load. Motor brakes accomplish this by using friction between mating surfaces to generate the necessary stopping torque. They are used when stopping needs to occur in a limited amount of time, as opposed to a gradual stop achieved by simply powering down an electric motor.

Types of Electric Motor Brakes

Most motor brakes fall under the category of electromechanical brakes and there are two basic categories: spring set and electrically set.

In a spring set brake, springs actuate the brake so that it applies torque when the power is disconnected. The brake is disengaged through either electromagnetic, hydraulic, or pneumatic actuators. Spring set brakes are well adapted to rapid stop and hold applications and are often used as fail-safe holding brakes. They don’t offer much control over the stopping time, however, unless the actuator is hydraulic or pneumatic.

In an electrically set brake, on the other hand, the brake applies torque along as power is present to provide the actuating force via a magnetic coil. You’ll see these brakes used with high-cycling or soft-release applications.

There are also permanent magnet brakes which use the force of permanent magnets as opposed to springs to apply the necessary pressure to generate stopping torque. To disengage these brakes, a magnetic flux is created by applying enough current to the coil of the break to cancel out the ever present magnetic field created by the permanent magnet. These brakes work well when a highly controlled stop is necessary (e.g., escalator).

We've all heard of ultrasound being used at the doctor's office, but can you use it to monitor and troublshoot your plant floor equipment?

The answer is a resounding Yes. In fact, no predictive maintenance program should be without ultrasonic capabilities.

How Does Ultrasound Testing Work?

The term ultrasound describes sound waves that are high frequency and beyond the range of human hearing. Ultrasound equipment detects sounds within these ranges and allows you to tune out other sounds that you aren't interested in. Because sound is directional, ultrasound also allows you to pinpoint where the sound is coming from.

As you get closer to the source of a particular sound, the intensity (measured in dB) increases. The output can be a plot showing how the intensity of sound varies over different frequencies. Ultrasound testing equipment can also modify the sound so that it is something you can learn to recognize through a pair of headphones. For example, an open valve has a rushing sound.

In part 1 of How to Test an Electric Motor, we talked about the importance of testing and different types of tests that you can perform. In part 2, we are going to talk about more of these tests and how you can put test data to good use.

Shaft Current Test

When you suspect that the motor bearings have suffered electrical damage, then you likely need to perform a shaft current test.

So how can bearings experience electrical damage? When capacitive coupling exists between the motors and the windings, it can create a voltage on the shaft that can be discharged through the motor bearings. When that happens, it leaves behind surface damage like pitting, fluting, and craters. This type of damage shortens the useful life of the motor bearings and can lead to premature motor failure.

You can detect and measure shaft voltage (and bearing currents that result from it) by either using an oscilloscope with special voltage probes or a shaft voltage tester such as the one made by Aegis . If you're wondering why you can't use a multimeter, it's because the voltages occur too quickly for it to capture. The oscilloscope, on the other hand, allows you to observe those changes over time despite this.

There are so many different tests that you can perform on an electric motor -- and that's why it's key that you know what the purpose is of these tests, how they work, and what the data means. This blog post is the first in a two-part series on the subject of electric motor testing.

We'll start with a quick review of why testing is important followed by a discussion of rotor bar, hipot, surge, and motor winding resistance as well as a discussion of vibration analysis.

Importance of Testing

Bearing problems may be the number one cause of electric motor failure, but electrical faults are a close second. And electrical failures require your maintenance group to go about testing the motors in your care.

The most obvious benefit of testing is troubleshooting. When a motor isn't working right or fails, you can use testing to track down the most probable cause of the problem. You can also use test results as a measure of a motor's performance. That data, in turn, can inform decisions about repairs, maintenance, rebuilds, and replacements.

Regular testing is key to your maintenance program and contributes to the performance and reliability of the motors in your care. For example, you can detect minor problems before they become expensive failures. And remember, well maintained motors have much higher reliability, and both the M&O costs and energy costs for them are lower.

Local "turn and burn" repair shops specialize in getting your motor in for repairs and getting them back to you ASAP. While that might be good for emergencies, is it a good way to handle all your motor repairs?. Let's discuss the difference between reactive maintenance costs vs. planned costs for electric motors

"Turn and Burn" Repair Shops

You have to strike a balance between keeping your production lines running and staying within your M&O budget. When a motor fails, you need things running ASAP and you don't have a ton of money to invest in your motors. That local "turn and burn" repair shop can get your motor back to you in 48 hours, doing a bearing swap and rewind in their own shop. It's fast and convenient and seems to do a good job of minimizing downtime while staying in budget.

The problem with such shops is that they don't have the time to perform extensive analysis on your motor. And this kind of analysis is necessary to find the root cause of the problem. If you don't find that root cause, then you keep paying over and over for the same repair.

If you continue using a "turn and burn" shop, you'll realize that you are sending the very same motors in for the same issues. Hasty repairs caused by their time constraints starts an expensive cycle for your facility. This cycle eats up money and increases downtime over the long haul.

Why do facilities keep using "turn and burn" electric motor repair services?

Most of the time, it has to do with the maintenance mindset or paradigm in use.

Perhaps you've just installed a drop-in replacement motor,  or maybe you're installing a new power train. You turn the electric motor on and ... its's rotating in the wrong direction! What the heck is going on? Is there something you can do to reverse my electric motor?

The answer is yes -- most of the time there is. The first step to figuring out how to fix your rotation problems is to establish whether it is a AC or DC motor. From there, the solution depends on exactly what type of motor you are working with.

Did you know that the vast majority of electric motor failures are preventable?

There are some failures you can't prevent because everything has a limited lifespan. But many of the motors we have come into our shop for repair have suffered a failure that was not necessary. And when we talk about parts that wear out, all too often they wear out way too soon.

Winding Failures

Motor windings account for about 32% of all AC electric motor repairs. These winding failures fall into four major categories related to what causes them: thermal stress, mechanical stress, electrical stress, and environmental stress.

How many times can you repair an electric motor? It's a question that comes up from time to time and the answer is actually pretty straight forward, but it might be worth going through the processes to understand it more clearly. 

Is there a limit to how many times you can have a motor repaired before you can't do it anymore? The short answer is that an electric motor can be repaired indefinitely. There is a caveat, however: there is a limit to how many times you can simply recondition a motor as repeated varnish dips eventually will require a burnout and rewind. Let's take a look at the process to better understand the limitations. 

What you may think is just a "mom & pop", local electric motor repair shop may have more capabilities and a farther reach than you think.

Finding the Right Shop

People often assume that a local shop is only going to have a local reach with little capabilities. For example, let's say your facility is in Chicago and you need a repair shop to keep your motors and drive-trains running. But, you've heard some good things about a shop in Kalamazoo and have found the information on their site helpful. But you figure the Kalamazoo shop doesn't have the reach to meet your motor repair needs, so you settle for a local shop. After all, it is more convenient and they seem to do fine with repairing your motors ... or do they?

Does Distance Matter?

The truth is that distance does matter, but not always in the way you think. When looking at motor repair and maintenance, it is easy to assume that a shorter distance means a better option. Keep in mind that there is the possibility that sending your motors to a shop further away could mean access to better quality repairs.

A little math often shows that the extra costs associated with distance might pay for themselves if the repair quality with more expertise, experience & equipment. Some research and a few phone calls might reveal that the Kalamazoo motor repair shop charges are still extremely competitive with your local shop. Also, you might be surprised to learn that the Kalamazoo shop partners with certified local shops in other states, including yours.