What this reversing starter handles
The 3RK4320-3AQ54-1BA3 is a SIRIUS motor starter MCU designed for AS-Interface networks — it's a reversing starter, meaning forward and reverse direction switching is built into one unit without needing external contactors for the reversal. Rated 0.63 A at AC-3 duty at 400 V (same figure for AC at 400 V general), this covers small motors — think fractional-horsepower pumps, small conveyors, or valve actuators where the load current stays under that threshold.
AS-Interface integration and control supply
Communication runs over AS-Interface protocol (supports AS-i), not PROFIBUS or PROFINET — so this starter belongs on an AS-i flat-cable segment, not a higher-bandwidth fieldbus. The control supply is 20.4–26.4 V DC, matching the standard 24 V DC AS-i power rail. Two digital inputs are available on the unit — enough for a local start/stop or limit switch feedback, but limited if you need multiple sensor inputs at the node. It includes a motor brake output controlled at 400 V AC — useful for holding brakes on vertical-axis drives or rapid-stop applications where the brake engages when the motor de-energises.
Mounting and environmental limits
IP54 rating means dust-protected and splash-resistant — fine for a control cabinet interior, but not for direct washdown or outdoor exposure without an enclosure.