The Siemens 3RK1323-2AS51-1AA3 is an ECOFAST reversing starter — a compact, IP65-rated motor starter designed for decentralized installation in AS-Interface networks. It handles reversing motor loads up to 4 kW at AC-3 / 400 V, meaning it directly controls the forward/reverse direction of a three-phase induction motor without needing a separate contactor pair. The IP65 enclosure lets it mount directly on the machine frame or conveyor section, not just inside a control cabinet, so it suits washdown zones or outdoor conveyor lines.
A 4 kW, 400 V three-phase motor draws roughly 8-9 A full-load current; the starter's rated operational current of 9 A (full-scale value) matches that closely. Motor protection uses a thermistor input (PTC) rather than a standard bimetallic overload. That means the motor winding must have a PTC thermistor embedded; if the motor has only a standard thermal model, this starter won't provide overload protection without an external relay. The brake output (400 V AC for internally supplied brakes) is built in — one less component to wire when the motor has a holding brake. Communication is via AS-Interface (AS-i), not PROFIBUS DP — confirmed by the protocol flags. That means it connects to an AS-i master/gateway, not a PROFIBUS DP network. The bus communication function is present, so status and control commands travel over the yellow AS-i flat cable.
Deployment context
This starter is built for distributed motor control — mount it on the machine frame, not in a central cabinet. The IP65 rating means the enclosure withstands hose-directed water and dust ingress, so it goes on a conveyor line in a food plant or a packaging line where washdown is routine. The 130 mm width and 250 mm height fit a typical machine-mounted junction box footprint; the 91 mm depth is shallow enough to clear guarding panels.