Core loss testing is a vital yet often overlooked step in electric motor maintenance and repair. By accurately measuring power loss within the motor’s core, this test helps identify underlying issues that can compromise efficiency, increase operating temperatures, and shorten the motor’s lifespan. In this blog, we’ll explore the importance of core loss testing, the methods involved, and how it can help ensure your motors are running at peak performance, saving you time and money in the long run.

What is a motor core?

The core of an electric motor plays a fundamental role in its operation, serving as the foundation for the stator windings and providing the magnetic circuit necessary for converting electrical energy into mechanical motion.  The core is made of stacked laminations of electrical steel, must maintain its structural integrity to support the magnetic flux generated during motor operation. Any damage or distortion to the core, whether from improper stripping methods like burnout ovens or other factors, can compromise the motor’s performance. Core integrity directly impacts the motor’s efficiency, as any disruptions in the magnetic circuit can lead to increased core losses, reduced power output, and decreased overall efficiency. Therefore, preserving core integrity through Motor Safe Stripping is essential for ensuring the optimal functioning of electric motors in various industrial and commercial applications.

On the left, you see a lamination stack in a motor’s core after Dreisilker performed its MotorSafe Repair Method to strip the windings. On the right, you can see a lamination stack after burning out the windings. The Motor Safe Stripping Method (left) maintains the core’s integrity. 

What is core loss testing?

Core loss testing is a diagnostic procedure used to evaluate the efficiency and performance of the stator core in electric motors by measuring the losses incurred during operation. These losses primarily consist of hysteresis losses, which occur due to the magnetic material’s resistance to changes in magnetization, and eddy current losses, which are induced currents that flow within the core material itself, generating heat and wasting energy. During core loss testing, technicians apply a specific voltage to the motor and measure the resulting current, allowing them to calculate the core losses under various operating conditions. This testing is essential for identifying potential issues such as overheating, insulation degradation, or structural damage within the core, which can adversely affect the motor’s efficiency and reliability. By conducting core loss testing, technicians can ensure that the motor operates at optimal performance levels, thereby extending its lifespan and reducing energy consumption.

Our experienced Winder core loss testing a motor during the repair process.

How core loss testing can impact reliability:

Distortion of the core and the presence of hot spots in an electric motor can significantly impact its efficiency and overall performance. Core distortion, often caused by uneven heating or excessive temperatures during processes like burnout oven stripping, can lead to misalignment of laminations and structural irregularities within the core material. This distortion disrupts the magnetic circuit essential for motor operation, resulting in increased core losses and reduced magnetic efficiency. Hot spots, localized areas of overheating within the core, can further exacerbate efficiency issues by causing thermal stress, insulation breakdown, and potential damage to the core material. These hot spots create inefficiencies in the motor’s operation, leading to energy losses, decreased power output, and compromised reliability.

Infrared image of an electric motor’s core. It shows hot spots which would lead to inefficiencies during operation.

At Dreisilker, we utilizing our MotorSafe Stripping method to safely remove motor windings during a repair. Through proper temperature control, insulation removal techniques, and post-stripping inspections is crucial to maintaining optimal motor efficiency and performance. During the repair, if we find that the motor’s core has hot spots, we consult our customers on whether it is recommended to replace the core.

Overall, core loss testing is a critical diagnostic tool in electric motor repair. By testing and addressing core losses, we can ensure the reliability, efficiency, and longevity of electric motors, ultimately leading to cost savings and improved performance. Learn more about our full rewinding services to see all of the steps within a rewind.

Are you storing electric motors for temporary or indefinite use? Proper storage for electric motors is essential for your equipment. In the long term, properly storing your motor can help maintain its performance and reduce repair costs. Dreisilker, with over 68 years of experience in electric motor repair, provides a motor storage program so you don’t have to worry about storing your motors on your own.

When it comes to storing electric motors, there are several important components to consider. Specifically, proper environment and bearing maintenance.

The Environment of your Electric Motor Storage

It’s critical to make sure the environment where you store your electric motor is kept at optimal conditions.

Climate control

Humidity and temperature vary by type of motor, but in general it should be stored in a temperature-controlled space that is not too humid. Temperature fluctuations caused by constant naturally occurring heating and cooling cycles should also be avoided.

Threat of contamination

Electric motors should be stored in a clean environment in order to prevent contamination to the motor. Taking the extra step of covering the motor in a cardboard box or a tarp can prevent dust and other contaminants entering the electric motor.

Rodent control

Rodents such as mice or squirrels are known to cause havoc on many things, such as electric motors. Ensuring that the space where you store your electric motors is critical so that you don’t have any unexpected chewed wires or contamination from rodents nesting in your motors.

Bearing Maintenance for Electric Motor Storage

Another important factor in storing your electric motor is turning the bearings regularly. Bearing maintenance helps prevent the formation of rust, which can lead to a complete failure of the system. This can be accomplished by hand, but if you don’t want to take that approach, Dreisilker’s motor storage program can turn the bearings for you as part of our storage cycle.

When Should you Store a Spare Electric Motor?

There are many factors that go into deciding whether or not you should keep a spare electric motor on hand. Some factors include how common the motor is, how critical the motor is to your operations, and cost of a spare. Check out our guide here:

The bottom line is that properly storing electric motors is one of the most important factors in making sure that your machinery is safe and runs smoothly. Dreisilker’s motor storage program provides a service for turning bearings during storage and protection from atmospheric contaminants, so you don’t have to worry about storing electric motors on your own. With the help of Dreisilker’s motor storage program, the longevity of your motor and its performance can be maintained and repair costs can be saved.”

What does balance mean in terms of an electric motor?

Balance for an electric motor refers to ensuring that the rotating parts of the motor, such as the rotor and the shaft, are evenly distributed in weight and properly aligned. When a motor is balanced, it means that these parts spin smoothly and evenly, without causing any unnecessary vibration or wobbling.

Balancing your electric motors during a repair is important for several reasons:

1. Reducing Vibration: When an electric motor is out of balance, it can cause excessive vibration, which can damage the motor and other components in the machinery. By balancing the motor, you can reduce the vibration and prevent unnecessary wear and tear on the machine.
2. Increasing Lifespan: Over time, an unbalanced motor can cause damage to its bearings, shafts, and other components. By balancing the motor, you can prevent premature wear and extend the lifespan of the motor and the machinery.
3. Ensuring Safe Operation: An unbalanced motor can also create safety hazards by causing excessive vibration, which can lead to mechanical failure or even catastrophic failure. By balancing the motor, you can ensure safe and reliable operation.

Overall, balancing your electric motors during a repair is an important step to ensure that the motor is running smoothly, efficiently, and safely. It can help to prevent costly repairs, extend the lifespan of the motor, and improve the overall performance of the machinery.

What are the steps of balancing an electric motor?

Balancing an electric motor or any rotating apparatus requires time to make sure you get the balance correct. Here are the basic steps we take when balancing a motor:

1. Check the motor: Before balancing, ensure that the motor is clean and has no loose parts
2. Test the initial balance of the motor: We utilize a Schenk balancing machine that spins the rotor and uses computerized software to determine the balance of the rotor.
3. Attach correction weights: Our trained technician evaluates the report from the Schenk balancing machine and determines where to add correction weights onto the rotor.
4. Test the new balance of the motor: After our technician has added more (or less) weight to the motor, they then test the motor’s balance to view the report.
5. Repeat until standards are met: Our technicians repeat the process of adding or subtracting weight to the motor, testing the balance, and then reading the report. They do this until they meet our balancing guidelines.

What standards are used for balancing a motor?

Dreisilker follows ISO 1940-1 Standards. The balancing rating is determined by speed and weight, however we consistently exceed the standards by going to the next balancing grade. Overall, balancing your electric motors during a repair is an important step to ensure that the motor is running smoothly, efficiently, and safely. It can help to prevent costly repairs, extend the lifespan of the motor, and improve the overall performance of the machinery.

There are many factors to review when considering repairing or replacing your electric motor. Some elements include pricing, lead times, condition of the electric motor, past history, and more. Below you will find some general guidelines that we use when working with our customers to determine if they should repair or replace their electric motor.

How critical is your electric motor?

Does the failed electric motor result in your production being ground to a halt, or is it on a machine that you only use occasionally? If your production is down due to this motor failure, your company is losing money. The criticality of your motor to your production line impacts how you will decide to repair or replace your electric motor. This will be discussed further in regards to the cost of repair vs replace, as well as the lead time of the replacement motor.

Do you have a spare on hand? If you have a spare electric motor on hand for your failed motor, it is going to alleviate some of your decision making below because you are not pressed for time. If you do not have a spare, we’ll walk you through how to decide repair or replace when thinking about cost and lead time. We strongly recommend having a spare on hand for critical machines. However, we understand that sometimes it is not financially feasible for some companies to have a spare for their equipment.

Electric Motor Repair or Replace: Price

Whenever we have an electric motor in our repair shop, we investigate the cost of new for our customers. We always want to provide options so that our customers can make an informed decision on whether to repair or replace. Generally, when the cost of repair is 50% to 80% the cost of new, we recommend a replacement motor. We realize that this is a wide guideline, but there are many factors that go into this decision, such as lead time, energy savings, like for like replacement and etc.

Please keep in mind that one should make sure that the motor replacement option is suitable for your application. Occasionally we witness cost saving methods in the form of finding a cheap replacement from a less reliable manufacturer versus a higher cost – high quality manufacturer. If you choose to go this route, understand that the lifetime and reliability of your motor may be negatively affected and that it can result in higher maintenance costs down the line.

Another factor that can impact the price in this decision is the condition of the motor. If the failed motor requires a simple overhaul, the cost of repair might beat the guideline of 50 to 80% cost of new. However, if a motor requires a complete overhaul (think rewinding, machining work, and etc.) the cost of repair very well may exceed the cost of new.

Does size matter? Once a standard motor is below a certain size, it is more economical to replace than to repair. Generally speaking, any standard AC induction T frame motors at or below 50 to 75 are more economical to replace. Our experienced motor experts will help you with this determination.

Electric Motor Repair or Replace: Lead Time

Finding out the lead time of a replacement motor or repairing your motor is important in your decision making. If there is a replacement motor readily available and its cost is not excessively high compared to repair cost, it’s an easy decision to replace. On the other hand, if the lead time for new is longer than the lead time for a repair, you need to take a step back to evaluate. Here’s an example situation:

Cost of downtime per hour= $1,000/Hour

Standard Hours per week= 40/Week

Cost of New= $10,000, 4 weeks lead time

Cost of Repair= $20,000, 1 week lead time

Cost of new, including lost production would equal: $10,000+($1,000*(40*4))=$170,000

Cost of repair, including lost production would equal: $20,000+($1,000*(40*1))=$60,000

Electric Motor Repair or Replace: Other Factors

We have gone over two of the most important considerations in your repair vs replace decision: Price and Lead time. While these are the leading factors, some other conditions to think about include energy savings, specifications of a replacement motor, past repair history, and how often this motor has failed in the past.

Energy Savings

Motor manufacturers strive to improve energy efficiencies on their product. If your failed motor is really old, the new motor very well may have better energy efficiencies than your old one. Replacing your motor in this case may lead to energy savings.

Replacement Motor Specifications

While the replacement motor’s nameplate specifications may be the same as your old motor, the size of the actual motor itself may be different (smaller). The smaller size of the new motor may make it difficult for your team to install it in the original application. Double check the dimensions of the motor and its frame with your Dreisilker representative.

In Conclusion

There are many factors that go into deciding whether to repair or replace your electric motor. Our experience motor experts help many customers every day to make this important decision. We’ll help you figure our pricing and lead time, as well as consider any other factors that may impact your decision. Call us today if you have questions about electric motor repair or replace.