AS-Interface bus integration and motor protection
The 3RK4320-3CQ51-0BA3: This is a direct starter (non-reversing) with electromechanical switching contacts and bimetal motor protection rated Class 10 — the standard trip class for general-purpose motor starting, protecting against overload without nuisance tripping on normal start-up inrush. It communicates over AS-Interface protocol (not PROFINET or PROFIBUS), so it drops into an AS-i network without a gateway for the motor starter itself. The control supply is 20.4–26.4 V DC, which matches the AS-Interface bus power voltage range. Rated 1 A at AC-3 400 V — this is the motor switching current, not a resistive load rating. The AC-3 duty covers starting and switching off squirrel-cage motors during running; the 1 A figure limits the connected motor size to roughly 0.37–0.55 kW at 400 V three-phase.
Panel fit and mounting flexibility
Dimensions are 205 mm deep, 245 mm wide, 215 mm high — plan for a back-panel footprint of about 245×215 mm plus clearance for cabling and heat dissipation. The enclosure rating is IP54, so it is dust-protected and splash-resistant, suitable for control cabinets or light industrial floors. Two digital inputs are available for local feedback or auxiliary signals; the unit also includes a motor brake output (400 V AC) and short-circuit protection via circuit-breakers.