I have come across many bearings with bearing fluting (EDM) with the damage on the inner or outer bearing raceway. But this is the first bearing where I have seen it on the outer diameter of the bearing outer raceway. Has anyone else come across this?
This was on a AC soft start.
Images of the outer diameter.
This was the inner raceway.
Update: 8th August 2017.
Site Inspection: This motor drives a process blower and is isolated from the ground via rubber isolation mounts, there is no earth bonding on the motor or blower. The blower pipework is also isolated by expansion joints.
The motor supply cables are three seperate SWA with a seperate earth cable that has 28.5 Amps on it, probably due to back EMF.
After onsite shaft current discharge tests also revealing no current discharge when direct on line this looks to be Static generated Electrical discharge damage.
Update: 13th August 2017.
Responding to some comments here are some more photos:
Image of the motor and blower.
DE Rolling element.
DE Zoom into rolling element.
DE Bearing Outside diameter.