What it is and what it does
The Siemens 3RK1325-6LS41-3AA3 is a SIRIUS reversing starter — a motor starter that can change rotation direction without an external contactor interlock. It's designed for reversing loads like conveyors, hoists, and pumps where forward/reverse cycling is part of normal operation. Rated at 5.5 kW at 400 V (7.5 hp at 460/480 V, 10 hp at 575/600 V), it handles common three-phase motor sizes in a compact IP65 enclosure — meaning it's sealed against dust and low-pressure water jets, so it can sit directly on the machine frame or near the motor, not just inside a panel.
Key ratings and what they mean for fit
Trip class is selectable between CLASS 5, 10, 15, and 20. That's the maximum time in seconds the overload relay allows before tripping at 7.2× full-load current. Class 10 is the default for standard motor starting; drop to Class 5 for fast-cycling or high-inertia loads that need tighter thermal protection, or go to Class 15/20 for hard-starting applications like crushers or compressors. Supply voltage is 24 V DC nominal (20.4 to 28.8 V operating range), with a maximum permissible of 31.6 V. That's the control voltage for the internal logic and AS-Interface communication — not the motor power circuit. The motor power comes through the HAN Q4/2 connector on the main circuit side. Four digital inputs are available for local control signals — enough for start, stop, forward, and reverse commands without an external I/O block. Addressing is via an M12 plug, which is standard for fieldbus nodes in distributed installations. On-delay is 85 ms, off-delay 65 ms — fast enough for most sequencing but not for safety-rated stop categories; if you need SIL/PL-rated off-delays, the internal timer isn't the path. Shock resistance is 12g at 11 ms, vibration resistance 7 mm / 2g, so it holds up on machine-mounted applications near rotating equipment.
Where and how to mount it
Mounting position is flexible — vertical, horizontal, or flat — but horizontal is recommended for best heat dissipation from the overload relay. Fastening is by screw fixing; no DIN-rail clip on this unit, so plan for four screws into a backplate or machine frame. IP65 means the enclosure is dust-tight and protected against water jets from any direction — suitable for washdown areas in food processing, outdoor installations under a canopy, or dusty environments like sawmills. The degree of pollution rating is 3, so it's designed for conductive or dry non-conductive pollution typical of industrial floors.
Lifecycle and sourcing reality
The operating temperature range is -25 to +55 °C, storage and transport -40 to +70 °C. That covers most plant-floor environments without derating; if your ambient regularly exceeds 55 °C, you'll need to consider a different enclosure or forced cooling.