Electrically Induced Bearing Damage (EIBD)

Electrically Induced Bearing Damage (EIBD) is a widespread problem for a long time. The reason the word "avoided" has been used is due to the unknown issue regarding whether or not EIBD was a motor or VFD manufacturer warranty problem. In the end the client usually accepts the problem and costs to resolve EIBD. Therefore, another reason for writing this article is to make the end users aware of the issue so they can take the necessary steps or ask questions related to avoiding EIBD at the design or installation stage of a VFD retrofit or newer projects.

EIBD has only been found on 600 volt applications; lower voltages do not seem to be a problem.

Regardless of the make or model of the motor or variable frequency drive equipment studies have proven that EIBD can occur within one week, six months or longer from the day of repairs or new start up. The extent of motor bearing electrical damage on many motors and at numerous locations resulted in rapidly increasing noise levels and erratic high frequency acceleration vibration spectrum data. In all studies done to date the bearing defects are similar as follows: bearing balls are frosted or dull grey in appearance; raceways have deep, irregular wear all around (fluting); and grease may be discoloured and have a burned odour.

Metallurgical studies called SEM (scanning electron microscope) have also been completed on several bearings that were found with EIBD defects.