I've heard the same thing, but havn't seen it evidenced in the field. I do notice some replacement motors have lots of decals and marketing literature that say "VFD Ready". I do know that Danfoss, for instance, wants to see certain megger values for old motors that are being fitted with a VFD beforehand to keep the warranty good on the drive.charlie b said:I have heard of problems with using a VFD on a motor not designed for a VFD. The problems were caused by current leakage through the bearings, and resulted in very early failure of the bearings. I have also heard that the only ways to prevent this problem are to use ceramic bearings or to use some sort of ground strap/brush on the shaft. Is this no longer a consideration? :-?
don_resqcapt19 said:I haven't see the issue in the field either. It is very common for us to put a VFD on a older motor that is not rated for "inverter duty". We have not seen the bearing or winding failure problems