Variable Frequency Drives (VFDs) have become very common in many different applications. VFDs allow the operator to precisely set the speed of a motor. There are other advantages of VFDs, but the most commonly cited advantage is substantial energy savings. As energy prices have risen, VFDs have become more common.

 

There are disadvantages to VFDs as well. A most frequently occurring problem is motor bearing damage caused by high-frequency currents or “noise” that are a byproduct of VFDs. The high-frequency currents are also referred to as common mode currents or Sigma currents. 

These high-frequency currents will seek the path of least resistance which usually means they pass through the motor bearings as they seek ground. The passage of the high-frequency currents often causes Electrical Discharge Machining (EDM) in the bearings. EDM causes pitting to the bearing raceways. Other terms for EDM are bearing frosting or fluting.

Until recently, the most common way to mitigate the damage to bearings has been the use of grounding rings which divert the damaging high-frequency currents away from the bearings. On 100-hp motors and larger, it is also recommended that insulated or ceramic bearings be used to reduce bearing damage. Grounding rings and insulated bearings are an expensive solution to the problem.

 

A different, better, and less expensive approach has emerged as an alternative to grounding rings and insulated bearings. CoolBLUE® inductive absorbers / common mode chokes and NaLa® differential mode line absorbers absorb the high-frequency currents to a level where they are no longer damaging to motor bearings. In addition to protection of the motor bearings, this approach also protects the motor windings.

 

We were a little skeptical when we first heard about the CoolBLUE® products. After doing our own testing in our shop and in the field, we saw dramatic and positive results. High-frequency currents dropped substantially. See the results of one of our in-shop tests. Shortly after our in-shop tests, we did a test at a local high school. Take a look at our test results. We have done extensive testing of CoolBLUE products. Take a look at the videos of our testing we have on YouTube.

 

CoolBLUE® has more complete information on its website. Check out the CoolBLUE® website for more details. CoolBLUE® has a design / application guide which sets forth what products to use depending on the horsepower of the motor. CoolBLUE® also has a presentation that goes in to more detail about CoolBLUE® products and the advantages of the products.

Topeka Electric Motor is an exclusive distributor of CoolBLUE® products in North Dakota, South Dakota, Nebraska, Iowa, Kansas, Missouri, Oklahoma, and Arkansas. Call us to learn more about CoolBLUE®.