This is a discussion between many engineers on the subject of bearing currents from VFD control valve. The obvious answer to this problem is to not use the VFD when there are better ways of controlling the flow. The CSV is the answer to this problem. Everything mentioned below is just a Band-Aid. If a hammer is the only tool you have, then every problem looks like a nail. Of course to a VFD technician, a VFD is the only tool they have to work with. These problems cannot be solved unless you have the forsight and ability to look beyond a VFD to the CSV for a real solution. (Electrical) 27 Feb 09 11:26 I have searched on this and found some discussion, but I am curious as to what anyone has found to be a good solution to the problem. In my case, I had a new 200HP motor/pump setup(pumping chilled water) that the bearings failed after about 6 months. The motor is fed by a new IGBT VFD. A single ground wire initiating at the source is run straight through to the motor and grounded at the termination box. There are currently no chassis grounds. I have found much discussion online, particularly a white paper by Reliance Motor, but I was looking for some real solutions that have worked. Right now we are looking at a ring assembly sold by a company called Shaft Grounding Systems. I am also considering adding some chassis grounds, and/or refeeding the motor from the VFD with continuously corrugated cable.

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