Bearings keep failing multiple motors

[mooreaaryan]

Good evening all.
I have a 500 hp VFD controlled motor that continues to have bearing fail. Ceramic coated bearings and insulated bearings. This week we had the ceramic coating on shaft fail and the bearings fail (according to the motor inspector and repair shop). We are using an Eaton DG1 with VFD cable. We have verified that the frame of the motor is bonded and the VFD is properly programmed and output voltage is 480v. Can anyone guide me I. The right direction on at least offering more ideas of what could be happening

 

[ActionDave]

I would stop looking for problems on the electrical side of things and start looking for mechanical problems.

 

[zbang]

From the sound of things, it probably isn't the issue, but is the motor shaft grounded? It's quick and inexpensive.

 

[ptonsparky]

I've seen enough of improper belt tension or shaft/sheave alignment that I would not discount mechanical problems.

The largest only 300, so small in comparison.

 

[Hv&Lv]

Sounds like its time to check the shaft…

 

[synchro]

Has a failure analysis been done to determine the nature of the shaft/bearing damage so that appropriate corrective actions can be taken?

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.emerson.com/documents/automation/brochure-electric-motor-problems-diagnostic-techniques-ams-en-6652274.pdf&ved=2ahUKEwiCsaiSxIb7AhV9lGoFHeA-B6YQFnoECBIQAQ&usg=AOvVaw0fSnDm6UczP-o7AI4Jfk-D

 

[Jraef]

From the sound of things, it probably isn't the issue, but is the motor shaft grounded? It's quick and inexpensive.

Failure of the ceramic coated bearings rules that out.

 

[Jraef]

Shaft alignment, vibration, mechanical harmonics (critical frequencies), false brinnelling, could be all sort of mechanical issues going on here. You have effectively eliminated the electrical causes, time to move on.