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.

Our skilled technician balancing a rotor with an impeller.

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.

Learn more about keeping a spare on hand in our blog post: When to have a Spare Electric Motor

We keep a large stock of spare motors for printing presses and CNC machines so that we can help out our customers in a pinch.

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 Horse Power (HP) are more economical to replace. Our experienced motor experts will help you with this determination.

HVAC Motors can typically be more economical to replace than to repair.

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

With long lead times for replacement motors, your best option may be to have our experts repair your motor back to new.

Still Unsure On What To Do? Take Our Quick Quiz:

If you’re still weighing the pros and cons, our quick quiz can help guide your decision. Just answer a few questions about your motor’s condition and application — and we’ll recommend whether repair or replacement is the better move.

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 experienced 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.

When it comes to electric motor repair, precision is everything. The smallest miscalculation in machining tolerances or assembly can lead to catastrophic failures, drastically shortening the life of a motor. We recently encountered a case that perfectly illustrates this point: a customer’s motor showed clear signs of incorrect bearing housing tolerance, leading to internal bearing preload. While this may seem like a minor oversight, the resulting damage was anything but small.

The Issue: Incorrect Bearing Housing Tolerance

In this particular case, the motor’s bearing housings were too tight, which caused an internal preload on the opposite drive-end bearing. Essentially, as the motor heated up during operation, the balls in the bearing were compressed beyond their intended load capacity. This additional friction significantly increased the heat within the bearing assembly, causing the inner race to thermally expand. Once the inner race expanded, it lost its secure grip on the shaft, becoming loose and leading to a chain reaction of failures.

A customer’s bearing that failed.

When the bearing loosened, it began spinning on the shaft, causing severe wear and damage. If left unchecked, this could have led to total failure, including rotor-to-stator contact, which would have resulted in an extremely costly repair or even complete motor replacement.

Understanding Internal Preload and Bearing Failure

Preloading in bearings is a critical factor that must be precisely calculated. It ensures that the rolling elements inside the bearing remain in constant contact with the raceways, minimizing vibration and improving stability. However, too much preload—caused in this case by an overly tight bearing housing—leads to excessive internal forces, which significantly accelerate wear and reduce bearing life.

While it is difficult to capture the exact wear patterns caused by internal preloading in a photograph, we can illustrate this phenomenon with an example from the book Rolling Bearings Handbook and Troubleshooting Guide by Raymond A. Guyer, Jr. The illustration below helps visualize what happens when excessive preload creates excessive friction and wear on the bearing components:

The Value of Experience and Proper Machining

This real-world failure highlights the importance of expert machining and careful adherence to motor repair specifications. Our team of skilled technicians has an average of 16+ years of experience in electric motor repair. Their extensive knowledge, combined with strict quality standards, ensures that each motor we repair meets or exceeds industry specifications.

At Dreisilker Electric Motors, we leverage both our experience and engineering resources to diagnose issues like improper tolerances before they lead to failure. Our machining capabilities allow us to restore worn or damaged motor components to precise OEM specifications, preventing similar failures in the future.

The Cost of Failure: What Could Have Happened

Fortunately for our customer, they caught this issue before the rotor dropped onto the stator windings. Had they continued operating the motor in this compromised state, the excessive movement could have caused the rotor to grind against the windings, leading to a short circuit and irreversible damage. A winding failure would have left them with only two options: a much more expensive rewind or complete motor replacement—both of which would have resulted in costly downtime.

Preventing Future Failures with Precision Machining

To avoid issues like these, it is crucial to work with experts who understand the intricacies of electric motor repair. Proper machining techniques, adherence to manufacturer specifications, and thorough testing all play vital roles in ensuring a long-lasting motor repair. Whether it’s bearing fits, housing tolerances, or shaft repairs, every step of the process matters.

At Dreisilker, we take machining seriously because we know how much even the smallest detail can impact the performance and longevity of your motors. If you’d like to learn more about how our machining capabilities can extend the life of your equipment, check out our Machining Capabilities here.

By prioritizing precision and expertise, you can ensure that your electric motors remain reliable, efficient, and cost-effective for years to come.