What the order code calls for
ACS550-U1-077A-4 is an AC drive in the ACS550 series, listed by ASEA BROWN BOVERI as an AC DRIVE at 29.03 kg unit weight.
Why the 29.03 kg figure actually matters here
On a small DIN-mounted drive weight is trivia; on an ACS550 frame it is not. At 29.03 kg the unit needs a real cabinet backplate or swing-frame mount, and any field-service swap is a two-person lift with a hoist or panel-extraction tray. Watch that figure against the door swing and the gland-plate cable bend radius — a heavier drive in a tighter cabinet is the recipe for a strained cable gland the first time the door opens after commissioning.
Sourcing posture for this code
No lifecycle status entry sits on this seed code, so production state is not asserted one way or the other. The two option-suffixed siblings on file (ACS550-U1-072A-4+B055+L512 at 34.02 kg, ACS550-U1-059A-4+B055 at 36.29 kg) carry factory-fit option codes and are configured variants, not drop-in alternates for a base U1-077A-4.