It Just Got Easier to Specify Shaft Grounding for VFD-fed Motors

AEGIS® Shaft Grounding Rings are frequently specified as protection against bearing current damage in motors fed by inverter drives.  And now it's even easier to call for shaft grounding with this master spec for CSI Division 23 05 13, Common Motor Requirements for HVAC Motors, with AEGIS best practices added.


CSI Div 23 05 13 with shaft grounding best practices added An excerpt of Div 23 05 13 with added provisions for shaft grounding rings on VFD-fed motors.

Variable frequency drives are widely specified in HVAC applications for energy savings.  But VFDs produce capacitively coupled shaft voltages on the motors they control.  This shaft voltage can discharge through the motor bearings, leading to premature failure.  Grounding the motor shaft with an AEGIS ring bleeds off shaft voltage before it builds up enough to discharge through bearings.

For more engineering resources, including the list of major manufacturers' motors with AEGIS rings factory-installed, please see our specifications page.