What the order code resolves to
The ABB ACS550-U1-059A-4+K451+L502 is an ACS550-series general-purpose drive built around the 380-480 VAC three-phase output stage rated 59 A at 30 kW, which is the rating that decides motor fit for any VFD sizing pass on this build. The +K451 suffix adds the RDNA-01 DeviceNet adapter as the fieldbus slice, and +L502 layers in the pulse encoder interface option for closed-loop speed feedback — both are factory-installed suffixes, not field-retrofittable modules, so they have to be on the PO.
US panel and NEMA framing
The -U1- construction code on this build is the US installation and NEMA-compliance variant, which is the right pick when the drive is being specified into a NEMA-style US panel rather than the IEC-default frame, and it is what makes the +K451/+L502 option suffix set legitimate for a North American build.
Handling and cabinet fit
The drive ships at 21.32 kg, which puts it in the bracket where the unit needs a two-person lift or a panel-side mounting aid rather than a benchtop swap, and it should be planned around that mass in the cabinet layout and any rigging step.
Where it sits against the next-frame sibling
The ACS550-U1-059A-4+B055 sibling holds the 059A current code but reworks the enclosure to the +B055 option, which is a different mechanical build rather than a true cross-reference — the electrical rating carries, but the cabinet cut-out and conduit entry change, so it does not drop in for the +K451+L502 build without a mechanical re-spec.