mshields
Senior Member
- Location
- Boston, MA
I have a couple of Chilled water pumps whose bearings after only 6 months of operation are shot.
These motors are VFD driven and it has been suggested that Shaft Current induced by the VFD are the culprit. I've never heard of this. The suggested solution by the HVAC contractor is to install an AEGIS SGR ring on the motors. This provides a path from the shaft to the frame of the motor hence creating a lower resistance path than the path via the bearings.
Makes sense! But I'm wondering why the motor isn't designed to do this without this extra part. I'm also dubious because the only empirical data I have on this SGR device is a white paper by the manufacturer.
I could say, sure, go ahead and install these things on the two motors whose bearings failed but then the questions becomes what about all of the other VFD driven motors on the job; should we install these devices on all of them?
Your input would be greatly appreciated.
Thanks,
Mike
These motors are VFD driven and it has been suggested that Shaft Current induced by the VFD are the culprit. I've never heard of this. The suggested solution by the HVAC contractor is to install an AEGIS SGR ring on the motors. This provides a path from the shaft to the frame of the motor hence creating a lower resistance path than the path via the bearings.
Makes sense! But I'm wondering why the motor isn't designed to do this without this extra part. I'm also dubious because the only empirical data I have on this SGR device is a white paper by the manufacturer.
I could say, sure, go ahead and install these things on the two motors whose bearings failed but then the questions becomes what about all of the other VFD driven motors on the job; should we install these devices on all of them?
Your input would be greatly appreciated.
Thanks,
Mike