Are VFD motors more likely to cause electrical arcing in bearings?

[agpearson]

I was reading up on failure modes for bearings and saw pictures of the fluting that results from arcing across balls & races. I have heard that VFD motors are more likely to have this problem than single speed motors? Is this true? If so, why?

 

[Skogsgurra]

It is very true. See the "neighbour" thread on ultrasonic in bearings. The electrical phenomenon is being discussed at some length there. I have put together a short paper that can be found at

http://www.gke.org/beppe/files/Bearing currents on one page 1.pdf

The goal was to put everything on one page. So it is rather condensed.

There is a pdf presentation available at

http://www.gke.org/presentationer/files/EDM Physics and Reality 1.pdf

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[unclesyd]

Adding a tidbit of information from our experience.

We found out almost from the beginning using VFD's you didn't want to put more than two on single transformer. We had a serious problem when we converted fan motors on a 7 cell cooling tower to VFD. We wiped out four motors until the problem was diagnosed and resolved. All our VFD's in this service are now on separate feeds. There is also some type of filtering system at substation feeding the cooling towers, Separating the drives was a very expensive problem to correct.. I can only assume that it payed off as there are still VFD drives on the cooling towers.