What this SIRIUS reversing starter is
The 3RK4320-3BQ51-1BA2 is a Siemens SIRIUS motor starter MCU designed as a reversing starter for AS-Interface networks. It integrates electromechanical switching contacts, bimetal motor protection (Class 10 trip), and bus communication into one unit — no separate contactor-plus-overload assembly needed. The operating voltage range is 340–440 V, 50/60 Hz. Control supply is 20.4–26.4 V DC, and the unit communicates via the AS-Interface protocol (supported natively, no PROFIBUS or PROFINET onboard). Two digital inputs are available for local control signals.
Ratings that matter for fit
The 0.8 A AC-3 rating at 400 V defines the maximum motor current this starter can switch under full-load starting conditions. Ambient temperature range of -25 to +50 °C covers most indoor panel environments; the IP54 enclosure rating means it's dust-protected and splash-resistant, suitable for installation in cabinets on the plant floor without additional sealing. Mounting flexibility is generous: ±180° rotation possible on a vertical mounting surface, and the unit can be tilted forward/backward by ±22.5° on that same surface — useful when panel layout forces an angled orientation. Dimensions are 205 mm deep, 245 mm wide, 215 mm tall — confirm the DIN rail or backplate footprint before panel cut-out. The reversing starter design means it occupies more space than a non-reversing unit.