The Siemens SIRIUS 3RK4340-3GR51-0BA0 is an I/O-controlled motor starter MCU (Motor Control Unit) configured as a direct starter with electromechanical switching contacts. It is designed for three-phase motor loads up to 2.5 A in AC-3 duty at 400 V, making it suitable for standard induction motors on pumps, fans, and conveyors in a control panel. Rated operating voltage is 340 to 440 V AC at 50/60 Hz, and the control supply is 20.4 to 26.4 V DC.
The AC-3 rating of 2.5 A at 400 V is the load-bearing number for motor switching — it covers starting inrush and breaking under load. Class 10 trip protection (bimetal) means the overload relay will trip within 10 seconds at 7.2× rated current, matching standard motor start profiles for pumps and light conveyors. Operating frequency is rated at 80 cycles per hour, which governs the thermal cycling of the bimetal and contacts — fine for normal start/stop duty, but not for high-reversing or jogging applications. Ambient temperature range is -25 to +35 °C; above 35 °C you need to derate or provide additional cooling. The mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt, giving flexibility in tight enclosures.
RoHS compliance is confirmed with a substance prohibitance date of May 1, 2012, covering the EU RoHS directive. The part carries a reference code per IEC 81346-2 (Q for switching device), which helps with documentation traceability in larger projects.