The VW3A28301 is an RS485-Modbus connection kit from the Altivar accessory line, designed specifically for the ATV28 variable speed drive. The kit composition is a connection cable — it's the physical link to get Modbus serial comms onto that drive.
Fit note for the ATV28
This kit is a spare part / connection accessory destined for the ATV28 drive. If you're retrofitting Modbus onto an ATV28 that shipped without the serial option, this is the factory cable kit that mates to the drive's comms port. No field wiring guesswork — it's a plug-and-play cable assembly, not a loose connector.