What this reversing starter does
The Siemens 3RA6250-2CB33 is a SIRIUS reversing compact starter — a single device that combines a reversing contactor pair and an overload relay for controlling the direction of a three-phase motor. It's designed for continuous operation per IEC 60947-6-2, meaning it's rated to run a motor load indefinitely within its thermal limits, not just for occasional reversals. The 24 V AC/DC control voltage is the standard low-voltage safety signal used across most PLC and safety-relay outputs. The coil draws 2.8 W at AC maximum and 2.9 W at DC maximum, so a typical 24 VDC power supply with 0.5 A per device has headroom for multiple starters on the same rail. That's a high-rupturing-capacity device suited for installations with large transformer feeds or high available fault current — common in industrial distribution.
Trip class and motor protection
The overload relay is adjustable between Trip Class 10 and Class 20. Class 20 allows up to 20 seconds — needed for high-inertia loads like fans or centrifuges. The same device covers both without swapping a thermal element. Rated operational current at 480 V is 4 A, and at 600 V also 4 A. The rated power at 400 V is 1 500 W — roughly a 2 hp motor at 400 V three-phase.
Any mounting position is acceptable, but vertical orientation on the rail is recommended for heat dissipation. Shock resistance is 60 m/s² (6g) for 10 ms across three shocks per axis, and vibration resistance covers 4 to 5.8 Hz at 15 mm amplitude, then 5.8 to 500 Hz at 20 m/s² for 10 cycles. That's robust enough for machine-mounted applications near presses or conveyors. The main circuit connection uses plug-in terminals without screw terminals, so verify the mating plug is ordered separately if not already in the BOM.