Vertical hollow shaft motors can fail due to electrical bearing damage. You can prevent this by following shaft grounding best practices.
BREATHING NEW LIFE INTO LARGE MOTORS- SGS Shaft Grounding Systems Ensures Electric Customers the Most Reliable Power Possible
AEGIS® Shaft Grounding Installation Guide
Save pump motors from VFD-induced damage
SKF TKGR Shaft Grounding Ring Kit: Installation Instructions, PDF, Manufactured Goods
Shaft Grounding Devices - Emerson Bearing
FHN Series Parallel Shaft Helical Gear Reducer with Power Lock-Box Size 97-80:1 Ratio-213/5TC - WorldWide Electric Corporation
What is Shaft Grounding?
Vertical HOLLOSHAFT Motors with AEGIS
Processes, Free Full-Text
Shaft Grounding, Shaft Grounding, Variable Speed, AC Motors - NEMA, Electric Motors
Vertical Hollow Shaft Motors