As more industrial companies turn to variable frequency drives (VFDs) to enhance efficiency and productivity, it’s important to remember that these systems come with their own distinct drawbacks – notably, their shaft voltages that can lead to motor bearing damage.
Since a significant number of motor failures can be linked back to bearing failure, engineers should pay close attention to the bearings, shafts, and bearing housings when conducting maintenance checks on their motors. Here, we’ll look at the steps to diagnosing and fixing motor bearing problems, as well as what you can do to prevent issues in the future.
Step 1: Examine the Motor
The first step in troubleshooting motor bearing failure involves carefully inspecting housings and bearings for any kind of contamination, dirt, scratches, or dents that might indicate damage. Look out for:
- Excessive grease around the bearing
- Blackened edges or discoloration
- Signs of heat (such as scorching)
- Contamination or corrosion
Step 2: Find the Root Cause
Once you have confirmed that bearing damage is the problem, you’ll need to think about what specifically is causing your issue. There are various factors that can cause their own distinct types of damage to a bearing. For instance:
- Contamination or inadequate lubrication: If the lubrication between the bearings is too thin because of contamination or viscosity, metal-to-metal contact could cause scraping and scratches on bearings.
- Damage via vibration: Motors that do not have the rotor shaft properly held in place can be subject to vibration. Similarly, a motor exposed to external vibration can also experience damage in the long term.
- Insufficient bearing load: Most bearings in motors require a minimum load to function properly. If the load is insufficient, you may notice smearing in the raceways.
- Improper installation: If a bearing is poorly installed, this can lead to misalignment and imbalance that eventually damages the motor.
Step 3: Call a Professional
Now that you have a general idea of what may be behind your motor bearing problem, you’ll be ready to call a professional for help with repair.
Bearings that are severely wiped or pitted will need replacing. If this is the case, you will also need to examine surrounding components, such as the shaft, to reduce the risk of further damage. Sometimes it’s possible to apply new metal to a shaft without the need for replacement. Consider the entire support system to ensure that replacing one bearing problem doesn’t simply transfer the problem onto a new bearing.
After your motor repairs are complete, make sure that your service firm checks the components thoroughly for fit and performance. For example, after re-assembling the motor, it’s a good idea to check the bearings for freedom of rotation. You’ll also need to conduct comprehensive tests when the motor is back in operation. This might include insulation resistance tests, current and voltage tests, and vibration analysis.
Step 4: Take Preventative Measures
In most motors using VFDs, electrical damage to your motor bearings will begin at the initial installation and gradually grow worse over time. As a result, almost all motor bearings will eventually fail. The best way to prevent such expensive and time-consuming damage in the first place is to divert induced shaft currents away from the bearings using choke modes.
Although there are numerous options available for bearing safety, the most effective method currently on the market is CoolBLUE inductive absorbers. CoolBLUE absorbers can protect the motor bearing pathways from additional damage by muting the high-frequency signals within a motor with a VFD. CoolBLUE absorbers are incredibly durable, and aren’t impacted by the motor installation environment. What’s more, they are easy to install, meaning that downtime is minimized, and industries can avoid bearing problems in the future.
To learn more about this revolutionary technology, contact Sloan Electric today and speak to one of our experts about the possibilities of CoolBLUE.