Practical answer
Common-mode voltage, grounding paths or shaft voltage in variable-frequency drive systems may discharge through a bearing and produce fine fluting, pits or local melting. Contamination and mechanical damage can look similar, so retain the failed components for surface examination.
Corrective work may include better grounding, cable and shielding changes, a shaft-grounding ring, insulated bearings or hybrid ceramic bearings. Motor, drive and bearing specialists should select the measure together; repeatedly fitting a standard bearing may not remove the cause.
On-site checks
- Use of a variable-frequency or high-frequency drive
- Motor grounding, shielding and shaft-grounding condition
- Regular fluting, pitting or melting on the raceway
- Grease color and contamination condition
Record for enquiry or analysis
- Motor and drive models and switching frequency
- Shaft-voltage or grounding measurements
- Close photographs of rings and rolling elements
- Historical failure interval at the same position
Suffix rules and allowable values vary by manufacturer. Confirm the final selection against current manufacturer documentation and actual machine conditions. Reference entry points:NSK · Schaeffler medias