Variable frequency drives, or VFDs, have become an increasingly popular feature of many industries – and for good reason. VFDs can enhance the accuracy of your motor’s performance, improve your energy savings, and reduce your operating costs. But while VFDs can remove many common operation problems, they also present a new issue: motor bearing damage.
VFDs create high frequency currents that cannot be used by the motor, which can travel along the motor cable, affecting the efficiency and longevity of the motor. In most cases, motor bearings can last over a 100,000 hours in many applications, however, damage through undesired high frequency currents can lead to motor bearing failure within one to several months. This has prompted the search for an effective solution.
Inductive Absorbers and Shaft Grounding Products
Up until recently, various shaft grounding products have been used to try to combat these destructive currents coming from a VFD. These devices use a fiber or brush that connects with the motor shaft. This connection ensures that damaging currents don’t move through the motor bearing, but are instead re-directed to the ground through the motor casing and the brush. Grounding the shaft does not remove the destructive currents from the system, but instead provide them with a different path to the ground.
CoolBLUE inductive absorbers, on the other hand, are a more recent solution that absorb the high frequency currents generated by the VFD before it can connect with the motor. This offers a simple, quick, and effective solution for reducing motor malfunctions.
The Issues with Shaft Grounding Technology
Although shaft grounding can sometimes be effective in minimizing the destructive effects of high frequency currents from a VFD, they’re brimming with problems that make it difficult to rely on this solution for long-term motor protection:
- Installing shaft grounding can be a difficult process. The performance of these solutions depends on accurate installation, with full mechanical alignment and the fibers of the brush touching all sides.
- You must install new shaft grounding whenever making changes to the motor, such as when you install new bearings or replacing the motor. Shaft grounding products are a consumable commodity.
- The shaft must be consistently cleaned to rid it of any debris, and sometimes it may be necessary to apply protective coatings to the shaft itself. Oil and grease could instantly damage the efficiency of the grounding rings.
- Not all motor applications running from a VFD can accept shaft grounding, think submersible pumps and explosion proof motors.
- There are hundreds of different products out there, which can mean choosing the right option for you becomes increasingly complicated.
- Application analysis is necessary for every single motor, which can take a great deal of time and lead to a lot of maintenance cost.
The Benefits of CoolBLUE
The issues with shaft grounding for VFD applications have left many industry professionals searching for a more reliable solution, and CoolBLUE inductive absorbers are a proven answer.
As a solution that absorbs the high frequency currents generated by a VFD before it can hit the motor, CoolBLUE cores behave as a definite purpose common mode choke system. They do not wear out, and last for the life of the application, outlasting replacement motors and VFDs, with no need for any maintenance or cleaning. What’s more, CoolBLUE systems:
- Require no use of any extra parts or a complicated installation processes that might require business downtime.
- Aren’t susceptible to shaft contaminants and do not need any coatings to keep them working perfectly.
- Need only offer a few options to cover motors of all shapes and sizes, which makes purchasing the right CoolBLUE cores simple.
- Involve one application per system, so you don’t have to invest in extra cores per motor.
CoolBLUE or Shaft Grounding? The Answer is Clear
Shaft grounding can’t remove destructive currents from a VFD. Instead, they provide a path to the motor casing. However, if that casing isn’t properly grounded, the stray currents will simply re-enter the system and damage the VFD. Over time, contamination of the shaft grounding surface makes the shaft grounding product ineffective which makes maintaining your systems a nightmare.
CoolBLUE inductive absorbers are a simpler and more effective solution because they absorb the VFD spectrum of common mode currents instantly, before they can reach the motor. The currents simply dissipate into thermal energy, with no need for shaft preparation or motor modifications. When it comes to protecting your motor longevity, CoolBLUE is the obvious choice.
Contact Sloan Electric today to speak to our expert team about how you can start benefitting from the possibilities of CoolBLUE inductive absorbers now.