Motors & Drives: Tips and tools for efficient motor management, Part 3
Michael Lyda, motor and drive engineer with Advanced Energy Corp., explains tips and tools for efficient motor management in this transcript from a December 2020 webcast.
Michael Lyda, motor and drive engineer with Advanced Energy Corp., explains tips and tools for efficient motor management in this transcript from a December 2020. Part three focuses on motor management. This has been lightly edited for clarity.
Motor management advice for manufacturers
The average motor consumes at least 50 times its purchase price in electricity usage over its lifespan. The motor purchase price accounts for only 2% to 3% of the motor’s lifetime cost. A small percentage is used for maintenance and upkeep, but the overwhelming majority of a motor’s lifetime costs is it electricity usage.
Approximately four out of five motors that fail are repaired instead of being replaced. It varies widely depending on the size of the failed motor. Also, only a small percentage of end-users consider energy costs when looking at new motors or making the decision to repair or replace a failed motor. We estimate it 12%.
Every organization that uses motors should have a set of guidelines for managing their motor population.
What are the main components of a motor management system? There are three: purchasing, operations and maintenance, and lastly making the decision of repair versus replace.
What are the benefits of a good motor management system? The benefits are energy savings, cost savings, increased production, shorter downtimes. What do all those things mean to you? It means less pressure on you. In my job, happier management, less pressure on me. So how hard is it to create a sufficient motor management system?
Come up with good guidelines for your three main components. For purchasing, develop purchase specifications. Normalize what brands you use. Specify model numbers. Consider lifecycle costs instead of only looking at initial costs. Purchase backups for your most critical machines. Build up a spares inventory. Follow the practices that we discussed earlier.
Perform routine maintenance on your motors. Focus more of your time on critical motors with high usage rates. For motor repair, you want to use repair shops that you trust. Now, I would also recommend using a certified repair shop. They should hold some sort of third-party quality repair accreditation. You can feel confident in the work that’s going on at the shop.
Just like for purchasing, develop motor repair specifications. If you’re using a certified shop, they can likely help you create a repair specification. If they won’t help you do that, you might want to find a different shop.
Next, we have an example. I mentioned before that only 2% to 3% of an electric motors lifecycle cost is in its initial purchase price. And the remaining 97+% is in electricity cost. This example compares lifecycle costs between a 75-horsepower electric motor and a standard small car. Notice the purchase price, annual usage, efficiency for the motor or miles per gallon for the car, fuel cost and lifespan. We use all these variables to calculate a lifecycle cost for each product.
Notice the initial cost of the vehicle is four times that of the electric motor. Also notice the lifecycle costs for the motor is six times that of the vehicle. This adds up to some pretty hefty electricity bills for the motor, which if you have anything to do with energy at your facility, you’re already aware of.
Next, we’re going to dive a little deeper into each of the three components of the motor management system just described. Step one is to create your motor purchase policy.
Standardize your purchasing, which makes it easier to order the products you need, takes less time overall. Purchasing staff need to be professionally trained, initial cost isn’t the only factor in the equation. We saw from the example that initial cost has little impact on lifecycle cost. You may want to pre-qualify your vendors and in some cases, even perform testing. Our lab in Raleigh specializes in that.
Motor efficiency is an important factor in motor management. Many electric motors these days are efficiency regulated and have minimum efficiency requirements that must be met for legal distribution in the states. Not all, but many.
The most up-to-date efficiency requirements are called NEMA Premium levels. Each manufacturer that wants to distribute in the US is required to prove their motors meet these efficiency levels before they begin selling. The problem is the government sets regulations but does little to enforce the regulations. Once the manufacturer has met the minimum requirements, there’s little they need to do regulatory-wise to stay in compliance.
In other words, the efficiency number listed on a motor name plate isn’t necessarily what it actually operates at. It could be higher; it could be lower. From my experience, most of the time it’s going to be lower. It’s always good to perform quality checks on your motor suppliers to ensure motor build quality and running efficiency aren’t degrading over time.
Let’s discuss motor repair, which is the third and final component of the good motor management system. Step one is to ensure your vendor is providing quality repairs. Similar to developing a purchase specification, you should develop a repair specification. You’ll see many items listed in the slides that can be added to your repair specs.
As I said earlier, use accredited repair shops. There are many third-party quality repair programs out there, including EASA accreditation, SKF certified, Green Motors Initiative, AEP motor rewind, and even Advanced Energy’s own proven efficiency verification program. All these programs are good, but each has its own distinctions. The goal of any accredited repair program is to ensure your motors are being repaired to the highest quality and the process being used is standardized and followed time in and time out with every single motor.
Speaking of the quality repair motors, we have an example here showing what can happen when quality control procedures aren’t followed. This chart shows two performance curves for a 10 horsepower four-pole motor. Nameplate full load efficiency for the motor is 91%. We see the orange line, which shows efficiency when the motor was repaired, including bearing replacements with top-of-the-line motor bearings.
The bluish green line shows efficiency when the motor was repaired, including bearings that were of lower quality and not properly greased. You see quite the gap between the efficiency performance of both motors. It’s vital to make sure that your repair vendor is not making mistakes like this, or you’ll be losing money in electricity when you put these motors back into service.
Repair vendors are happy to have your business and they’ll typically keep records for motors they’ve repaired or reconditioned for you, so they can be helpful in your management system tracking. Keep an open line of communication with your vendor. Once you have a motor management system in place, keep track of your motor failures and of energy costs versus production, you can use these numbers to update and improve your policy.
When you’re purchasing motors, use lifecycle costs instead of just initial cost. Develop and use purchase and repair specs so that you get the best motors for your application and the highest quality repairs. And finally, utilize strategic preventative maintenance techniques to upkeep your motor population and extend useful life.