--- title: It Just Got Easier to Specify Shaft Grounding for VFD-fed Motors description: CSI Division 23 05 13 with Shaft Grounding Rings image: https://blog.est-aegis.com/hubfs/Imported_Blog_Media/230513-300x176.png --- [![Electro Static Technology](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/electro-static-technology.svg "Electro Static Technology")](https://www.est-aegis.com/) [![Aegis](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/Aegis.svg "Aegis")](https://www.est-aegis.com/) - [+1 866-738-1857](tel:+1%20866-738-1857) - [Products](https://www.est-aegis.com/products/) - [AEGIS® SGR – for motors under 500 HP/375 kW](https://www.est-aegis.com/product/sgr/) - [AEGIS® uKIT – for common NEMA/IEC frame size](https://www.est-aegis.com/product/sgr-ukit/) - [AEGIS® RPPR – for reactor recirculating pumps](https://www.est-aegis.com/rppr-resources/) - [AEGIS® EV and EVO Rings - for electric vehicles](https://www.est-aegis.com/product/ev-evo-rings/) - [AEGIS® PRO Series – for motors over 300 HP/225 kW](https://www.est-aegis.com/product/pro-series/) - 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Variable frequency drives are widely specified in HVAC applications for energy savings.  But VFDs produce [capacitively coupled shaft voltages](https://www.youtube.com/watch?v=e7JXCTCjhOc) 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](https://www.youtube.com/watch?v=sX1gQosdW5Q) 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](https://www.est-aegis.com/specs.php?__hstc=45788219.d38e1bdd6dd558caf8870293bd9d7528.1741204794773.1741204794773.1741204794773.1&__hssc=45788219.1.1741204794773&__hsfp=867848667). 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