The Siemens SIRIUS 3RA6120-1DB32 is a compact starter — a direct-on-line motor starter that packs the contactor and overload relay into a single 45 mm wide unit. It's sized for continuous operation per IEC 60947-6-2, meaning it's built for sustained motor duty, not just occasional jogging. The screw-type terminals on the main circuit accept solid conductors from 0.5 to 4 mm², or two conductors up to 2.5 mm² each, which covers the common motor feed sizes for fractional through moderate-horsepower motors.
The headline number is the breaking capacity: 53 kA at 400 V. At 480 V it's rated 12 A continuous, and at 600 V also 12 A, so it's sized for motors in the 5.5 kW range on a 400 V line. The overload relay is adjustable between Trip Class 10 and 20. Class 20 gives you 20 seconds, which handles high-inertia loads like centrifuges or crushers that take longer to spin up. You dial it in on the front without swapping heaters. Coil voltage is 24 V DC, drawing about 2.8 W AC or 2.9 W DC. That's a standard PLC-level control voltage — no need for a separate 110 V control transformer in the panel. Two LEDs on the front give you local status: one for the coil energized, one for the overload tripped. No IO-Link or AS-Interface onboard — this is a plain-vanilla hardwired starter.
Environmental toughness for the plant floor
It'll survive a hot motor control center in summer and a cold warehouse in winter. Shock-rated to 60 m/s² (6 g) for 10 ms, three shocks per axis, and vibration tested to 20 m/s² from 5.8 to 500 Hz. That's enough for most industrial environments — conveyors, pumps, compressors — without nuisance trips from mechanical vibration. Pollution degree 3, so it's rated for conductive dust and occasional condensation — typical for an unsealed panel in a factory or warehouse. Not for washdown zones; that's what the IP65-enclosed SIRIUS variants are for.