The Siemens SIRIUS 3RK1325-6LS71-2AA3 is a direct motor starter in a fully enclosed IP65 housing — built for standalone mounting right at the motor, not buried in a central panel. It handles 5.5 kW at 400 V (7.5 hp at 460/480 V) and communicates over AS-Interface, so it's a fit for distributed field-mount architectures where you want to pull the control cabinet out of the process area.
Trip class and motor protection
Trip class is selectable among CLASS 5, 10, 15, or 20 — that's the maximum time in seconds the overload relay allows before tripping under a locked-rotor condition. For a pump or fan with a normal start, CLASS 10 is typical; for a high-inertia load like a centrifuge, CLASS 20 gives the extra time to get up to speed without nuisance trips.
Power supply and control voltage
The control supply is 24 V DC nominal, with a tolerance range of 20.4 to 28.8 V. That's a standard 24 V industrial bus — no exotic voltage rail needed. The maximum permissible voltage is 31.6 V, so keep the bus regulated; a floating 24 V supply that drifts high under light load can push past that ceiling.
Digital inputs and fieldbus
Four digital inputs are onboard, addressed via M12 plug. The only fieldbus protocol supported is AS-Interface — no PROFIBUS or PROFINET on this variant. That means it slots into an AS-i network, not a standard PROFINET IO controller. If your line is built around PROFINET, this isn't the drop-in; you'd need the AS-i gateway to bridge.
Physical dimensions and mounting
The enclosure measures 294 mm wide, 215 mm high, and 159 mm deep — that's a substantial footprint, not a slim line module. It's screw-fix mounting, not DIN rail, so plan for four mounting points on the backplate. Mounting position is flexible: vertical, horizontal, or flat, though horizontal is recommended for optimal heat dissipation. IP65 means it's sealed against dust and low-pressure water jets — fine for washdown zones or outdoor installation under a canopy.
Environmental limits
Shock resistance is 12g for 11 ms, vibration resistance 7 mm / 2g — typical for industrial machinery but not extreme off-road or marine duty.