What lands on the BOM
The ABB ACS550-U1-031A-4+B055+K466 is an AC drive with the part string as listed. Every suffix has to match what the panel was designed around, because option codes change I/O, filter content, or coating and a partial string is a different SKU. The unit weighs 15.42 kgs per the listed spec, which puts it in the one-person lift zone and drives how it sits in the cabinet — it needs the cabinet bottom rail or a backplate span that won't flex under that mass once the motor cable glanding is tightened up.
Where this class of drive gets specified
Two option codes travel with this build — +B055 and +K466 — and these are content-changing suffixes, not cosmetic ones. Any panel cut-sheet, schematic, or I/O map written against this part number has to be checked against the option data, not just the base drive, because the options shift what shows up on the terminals and what the drive was coated or filtered for.
Sourcing reality
ABB as the brand anchors the ACS550 family for buyers running other ABB VFD BOM lines — same parameter structure, same keypad, same assistant software — so this slot usually drops into a panel already configured for ACS550 drives without a commissioning reset.