What the line is asking for
The ABB ACS550-01-180A-4 is the cataloged order code on the ACS550 drive line, a general-purpose industrial drive in the wall-mount form factor. The -01 suffix is the panel/cabinet-mount execution; -U1 within the family is the enclosed variant, so the suffix shift changes the mechanical package. At 69.00 kgs the unit is a two-person lift, which matters for the rack layout and the hoist point a maintenance team has to plan around.
What the frame and suffix actually decide
The other family-coded alternative on the desk, ACS550-U1-157A-4, is the same series at 157 A and a heavier 89.81 kgs in the U1 enclosed form factor. It is a smaller current frame inside the same product line; if the panel was originally specified for the U1 enclosed execution the wiring harness and gland plate do not move across to a -01 frame. Weight difference there is the chassis mass change, not a selection parameter.