What landed on the BOM
The ACS550-U1-078A-4+B055+K462: It sits in the Motor Drives class — Drives under Motors & Motor Controls — which is where the ACS550 family has always been specified for general-purpose fan, pump and conveyor applications.
Same-series alternate the planner actually weighs
The ACS550-U1-096A-4 is a same-series, same-U1-frame alternate at 19.96 kgs, with the caveat that the +B055 and +K462 suffix is not automatically carried and the configuration has to be reconciled against the as-built drawing.
Sourcing posture for a configured suffix string
The base order code ACS550-U1-078A-4 is a long-running ABB drive, and the configured string with +B055 and +K462 is what was specified into the BOM; the configuration is the part, not an accessory. The supply posture for that configured string is to quote it to order against an RFQ so the configuration is locked against the factory build sheet and the unit ships as -B055 -K462 from the configurator, not as a base drive with options retrofitted in the field.