It has to do with the way the MOVs (surge suppressors) that protect the front-end rectifier are referenced to ground, as well as any EMI / RFI filtering capacitors or Common Mode capacitors. That's because in all areas of the world EXCEPT the US, they never use delta power systems, everything is Wye, so the internal components are referenced to ground. If we connect them to a Delta system, the MOV or Filter reference point tries to become the Wye point for your entire grid, so the first ground fault you get will take them out, then you have nothing and the drive fails on the next spike or fault. In the case of a grounded delta system though, that will not happen happen because two of the phases are already referenced to ground, the other one IS at ground potential. So you should be fine. Where you have to worry about this is on UNGROUNDED delta systems, or on 240 "High Leg" delta systems where only one winding is grounded at a center tap. In that case, you have one set of windings in the transformer that has NO reference to ground, so if a GF happens there, once again you are toast.
If it were an ungrounded or High Leg delta system, that's when you have to be careful. Drives sold by primarily US based companies will have instructions on what to do and make it easy. A few of the larger EU and more reputable Asian mfrs will likely have instructions to modify the drives, but it may be more difficult than those from US based companies. For example if you dig deep in the fine print on a Siemens drive, you will find out that you basically have to disassemble the front-end of the drive to get access to the ground reference connection for the EMC filter and MOVs, so that you can cut the wire. For Allen Bradley drives, you just remove a jumper from inside the wiring access cover. Cheap Asian drives may not address it, they don't really engineer anything, they just copy cheaply. You find out when your drive blows, then they sell you a new one.
