(07-31-2020, 11:39 PM)Vinny Wrote: When I got the new motor for my mill the manufacturer listed which ones could be used with a VFD - fortunately this one was on that list.
Usually if a motor manufacturer says an item is suitable for a VFD it’s because the insulation is up to the fast rise times of the wave form, and the fan is good for a wider range of speeds and still give adequate cooling. I very much doubt this intriguing bearing issue is even thought about.
Back in the day big disk drives, I’m talking 20” platters, often had an earthing bush pressing on the end of the shaft, but the maintenance books referred to it as a static discharge device not an induced current device.
Andrew Mawson, proud to be a member of MetalworkingFun Forum since Oct 2013.