What it is, in the buyer's terms
The ABB ACS355-03U-12A5-4+J400 is a 5.5 kW ACS355-class drive carrying the +J400 option suffix, ordered against a BOM line that expects the full option code to land on the nameplate and in the shipping carton markings. It sits in the Motors & Motor Controls › Drives › Motor Drives class — a general-purpose wall-mount VFD frame rather than a module that drops onto a shared backplane, so panel layout and door swing are driven by its 4.17 kg mass and the standard ACS355 footprint the buyer is already familiar with.
Ratings and what they govern for fit
On a 5.5 kW rating the drive pairs to a 400 V class induction motor in the typical ABB sizing envelope, so the procurement check is that the motor nameplate kW and the drive's kW class match before the panel is wired — not just that the order codes line up. The +J400 suffix is the option string that has to survive the PO as written; option codes are where ACS355 builds most often get returned because a digit or letter was dropped in transcription, so the order-line text should read ACS355-03U-12A5-4+J400 character-for-character. At 4.17 kg the drive is a one-person lift onto DIN-rail or into a wall-mount cubicle, so handling during the FAT/SAT and any field swap does not need a second technician — but the cabinet still needs to be sized for the ACS355 thermal envelope with the clearance ABB calls out, which is the real panel-side constraint rather than the weight itself.
Sourcing and the RFQ posture
ABB is the manufacturer of record on this order code and the drive is part of the active ACS355 product family the channel still quotes against. For a procurement line on ACS355-03U-12A5-4+J400 the right move is to specify the full MPN including the +J400 suffix into the RFQ so the quote comes back matched to the option set the integrator actually needs, rather than a base unit that would have to be re-ordered once the gap shows up on the nameplate check.