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Hi all,

We have two compressors in the plant, one running on VFD and has an AEGIS ring at motor DE. Two motors and a spare are used interchangeably. Can we also use the VFD motor with AEGIS ring on the direct drive if needed? Plant electrical people saying we should not use the motor with AEGIS ring on the direct drive, it might cause grounding issue in case of an electrical failure.

Any insights on this is much appreciated.

Tags: motor, VFD, electrical, insulation

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@Registered Member posted:


I can't see where the grounding ring would pose a problem with the direct drive motor. If you don't really need it in that application can you remove it? If nothing else make it last longer, for what they cost.

The ring is fitted internally due to the limited space between the motor and the pulley so removing it isn't seem like an option.

I couldn't find an issue but curious to know if there is at all any problem with that as they are saying!


In theory....the stator of the motor is grounded via a wire in motor junction box going to an earth ground. This is designed to handle short circuit current to ground. There should be fuses/overloads that also protect the stator

The AGEIS shaft grounding ring is not connected to the stator, just the motor shaft. This is designed to dissipate any voltage/current induced into the motor rotor while in operation. It is my opinion....that this style of grounding ring is not designed for dirty environments, have seen rust/grease/dirt cause the carbon fingers not to make contact.

The likely hood of any electrical issues due to a grounding ring will improve bearing life, not create an electrical issue.

Other option for grounding rings design



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