Fail-safe reversing starter with PROFINET — 3RK1308-0DA00-0CP0
The Siemens 3RK1308-0DA00-0CP0 is a SIMATIC fail-safe reversing starter built for motor control in safety-related circuits. It integrates a 4 via 3DI/LC module, meaning four inputs are configurable as standard digital inputs or as a light-curtain/safety-mat interface, giving you flexible safety I/O without an extra slice. The part carries a 55 kA short-circuit current rating at 400 V and 500 V, so it can ride out a bolted fault upstream without the cabinet going dark — that's the SCCR the panel label needs. Communication is dual-protocol: PROFINET and PROFIBUS DP are both on board. That means it drops into either a modern PN line or a legacy DP segment without a gateway. The device is pluggable into a BaseUnit, so swapping a failed unit means pulling the module off the base — wiring stays put. That's a five-minute swap versus a re-termination job.
Trip Class and thermal protection — adjustable, not fixed
Trip Class is adjustable: CLASS OFF, 5, or 10. CLASS OFF means the overload function can be disabled for short-cycle applications where the motor is already protected downstream. CLASS 5 is for submersible pumps or compressors that need a fast trip to avoid winding damage; CLASS 10 is the standard motor start. The minimum load is 50 % of the smallest adjustable rated current, so you cannot run this below half its set point — that prevents nuisance tripping on lightly loaded motors. ON-delay is fixed at 35 ms; OFF-delay spans 35–50 ms. That window is tight enough for most reversing applications where you need a dead-time between forward and reverse to avoid a phase-to-phase short. The safe state is load circuit open — when the safety function triggers, the output contacts drop and the motor coasts.
Mounting and environment — DIN-rail panel integration
The module is 30 mm wide, 142 mm tall, 150 mm deep — a single-width slice on the DIN rail. Mounting position can be vertical or horizontal, but horizontal requires derating per the manual. Clearance above and below is 50 mm each for airflow and wiring access. Operating temperature is -25 to +60 °C with derating above 40 °C; storage and transport range is -40 to +70 °C. Shock rated at 6g / 11 ms; vibration at 15 mm up to 6 Hz, then 2g to 500 Hz. That covers most industrial cabinet environments — conveyor lines, pump skids, machine tools.
Lifecycle and sourcing — active, quoted to order
Lifecycle stage is current — Siemens still builds this order code. No end-of-life notice or successor part is documented.