Reversing starter for motor direction control
The Siemens 3RA6250-2CB34 is a SIRIUS compact reversing starter — a single device that handles forward/reverse motor control without separate contactors and interlocks. It integrates the reversing contactor pair, overload relay, and short-circuit protection coordination into one 191 x 90 x 165 mm package that snaps onto standard DIN rail. Rated for continuous operation per IEC 60947-6-2, it delivers a 53 kA short-circuit current rating at 400 V — enough to coordinate with most upstream MCCBs or fuses in a distribution panel without cascading failure.
The overload relay is adjustable between CLASS 10 and CLASS 20 trip curves. CLASS 10 trips in under 10 seconds at 7.2× FLC — suited for motors that accelerate quickly (pumps, fans). CLASS 20 allows up to 20 seconds, covering high-inertia loads like conveyors or centrifuges where start time exceeds 10 seconds. The same device covers both, so you set the class during commissioning without swapping the relay. The control circuit is AC/DC 24 V, 50/60 Hz, drawing 2.8 W AC or 2.9 W DC maximum, which keeps the thermal load on the enclosure low. Three onboard LEDs indicate status — run, fault, and network communication — so a technician can read the starter's state without opening the panel door or connecting a laptop.
Panel environment and mounting
The enclosure is pollution degree 3 rated — suitable for industrial environments where conductive dust or condensation is present. Operating temperature range is -20 to +60 °C; storage and transport range is -55 to +80 °C. Vibration resistance is tested to 4–5.8 Hz at 15 mm amplitude, then 5.8–500 Hz at 20 m/s² for 10 cycles. Shock resistance is 60 m/s² (6g) for 10 ms, three shocks per axis. These ratings confirm the starter holds its settings and connections in a panel mounted on a machine frame or near rotating equipment.