The ABB ACS355-03E-01A9-4 is an IP20 inverter drive in the ACS355 series, sized for 3-phase 400 V supply at 0.37 kW (0.5 hp) continuous output with a 1.9 A nominal current rating — the smallest 400 V frame in the family, intended for sub-half-horsepower induction or permanent-magnet motors in OEM machines, conveyor sections, fan and pump skids, and small positioning axes. It sits on the RO frame, so the panel cut-out and DIN footprint are the compact end of the ACS355 line — worth flagging when the cabinet was originally laid out for an R1 frame, because R0 is narrower and the wiring gutter geometry differs.
Reading the ratings for the real load
The 1.9 A continuous figure is the normal-duty rating at 0.37 kW, with 22 W typical losses at nominal operating point. Variable-torque fans and pumps let the drive ride below 1.9 A most of the cycle; constant-torque conveyors and mixers stay inside that 1.9 A limit. The DC bus window is 250–840 V on this model, with 840 V as the maximum and 250 V as the minimum. That window matters when the drive is fed from a common DC bus rather than the AC line.