What this compact starter does in the panel
The Siemens 3RA6120-2BB34 is a SIRIUS compact starter — a direct starter that integrates a contactor and overload relay into a single 45 mm-wide housing. It is designed for continuous operation per IEC 60947-6-2, meaning it handles sustained motor starting duty without derating for repetitive cycling. The adjustable trip class (CLASS 10 and 20) (cite:) lets you match the thermal curve to the motor start profile: Class 10 for fast-starting loads like pumps, Class 20 for high-inertia loads like fans or conveyors. The 24 V DC/AC control voltage (cite:,) matches standard PLC-driven panel voltages.
That depth is worth noting — it extends 165 mm from the mounting surface, so verify clearance to the gland plate or enclosure door. Shock resistance is rated at 6g for 10 ms (cite:), and vibration resistance follows a 4 to 5.8 Hz / 15 mm displacement curve, then 5.8 to 500 Hz at 20 m/s² (cite:). This is robust enough for most industrial machinery but not for extreme mobile or off-road equipment without additional isolation.