The Siemens 3RK1325-6KS41-2AA3 is a SIRIUS direct motor starter in a fully enclosed IP65 housing, designed for distributed motor control on AS-Interface networks. It integrates the contactor, overload protection, and AS-i communication into one field-mounted unit — no separate control cabinet needed for the motor branch. The 24 VDC supply (20.4 to 28.8 V) powers both the logic and the coil, and the unit accepts four digital inputs for local sensors or pushbuttons.
Trip class flexibility and motor protection
The overload relay is selectable among trip classes 5, 10, 15, and 20, which means you can match the thermal memory to the start profile of the load — fast starts (class 5) for low-inertia fans, slower starts (class 20) for high-inertia conveyors or crushers. This is the same trip-class range found on Siemens stand-alone overloads, so coordination with upstream breakers follows familiar curves.
The housing measures 159 mm deep by 294 mm wide by 215 mm high, with screw fixing for panel or machine-frame mounting. It can be installed vertically, horizontally, or flat, though horizontal orientation is recommended for thermal performance. Vibration resistance is 7 mm / 2g, shock resistance 12g / 11 ms — suitable for machine-mounted applications on pumps, conveyors, and small compressors.
Network and I/O architecture
Communication is via AS-Interface only — no PROFIBUS or PROFINET on this variant. Device addressing uses an M12 plug. The main circuit connection is a HAN Q4/2 plug per ISO 23570. Four digital inputs are available for local sensing; the starter supports direct-on-line starting (no reversing). On-delay is 85 ms, off-delay 65 ms.