In order to save on cabling, our company uses 3 wire EMC cables to connect electric machines to their VFD's. Some folks in our company think we should really use a dedicated ground wire, many are of the opinion that using the shield as ground (at least for wire diamaters < 6 mm²) is just fine. Recently we had some problems with bearings of machines that were running for 1-2 years: fluting, and a washboard like appearance of the raceways, as described in SKF documentation.
Can this problem be related to the omission of the ground wire? Are there any other compelling reasons to use a ground wire?
We often also don't use load reactors after EMC cabling. We use Danfoss drives (type FC102), which are said to have built in filters that are able to drive about 75 meters of cable without the need for additional filtering.