Last year, the plant upgraded a large, critical motor system by adding a variable frequency drive (VFD). The main impetus for this decision was to stop the damage from across the line starts, an outcome that has since been verified.
Unfortunately, the motor spun its thrust bearing a few months after installing the VFD. In the post-mortem, the motor shop found severe pitting in what was left of the bearings. Grounding the motor housing didn’t prevent a recurrence. What shou