What it is
The ABB ACS800-U1-0004-2+P901 is a wall-mount low-voltage drive from the ACS800-U1 series, sitting in the industrial motor-drives line at 5.44 kgs on the nameplate data. The +P901 suffix is a factory build option applied to the base 0004-2 frame, so the part is identified as a single configured order code rather than a bare frame catalog number. Plan for it the way you plan any ACS800-U1 — same cabinet footprint class, same control board family, same firmware generation as the rest of that series.
How it compares
ABB's current-generation cross-shop candidate in the same wall-mount frame is the ACS880-01-07A6-5 — listed at 6.35 kgs on the same motor-drives line. The ACS880-01 family is the documented successor architecture to the ACS800-U1, but the two are not pin-for-pin drop-in: control terminal mapping, firmware toolchain (DriveStudio / Drive Composer) and parameter set structure all moved between generations. If a panel was specified around the ACS880-01-07A6-5, plan on a re-parameter and a wiring review before treating an ACS800-U1-0004-2+P901 as a like-for-like replacement; do not assume the existing commissioning file ports across without checking.