What this part is and what drives the fit
The Siemens SIMATIC 3RK1308-0DB00-0CP0 is a fail-safe reversing starter — a single device that combines a reversing contactor pair with a safety monitoring function, so it both controls motor direction and drops the load circuit open when a safety demand is asserted. It is a current-production part (lifecycle stage: current). The headline number for sourcing fit is the 55 kA short-circuit current rating at 400 V and 500 V. That means this starter can be installed on a line-side fault current up to 55 kA without needing an upstream current-limiting device — a real panel-space and coordination saver in high-fault installations. The adjustable trip class (OFF / 5 / 10) lets you tune the overload curve to the motor's thermal capacity: Class 10 for standard induction motors, Class 5 for submersible or high-inertia loads that need a faster trip, or OFF for use with an external overload relay. It is a 4 via 3DI/LC module, meaning it integrates four safety-related digital inputs and a load circuit interface into one 30 mm wide DIN-rail housing. The 30 mm width is tight for a reversing starter with integrated safety — a conventional contactor pair plus separate safety relay would take 45–60 mm of DIN rail.
Deployment context and integration
Mounts vertically or horizontally on a DIN rail via a pluggable BaseUnit. Horizontal mounting requires derating per the manual — so for a panel build, plan for vertical orientation to keep the full 55 kA SCCR and rated current. The 150 mm depth means it clears a 200 mm deep enclosure with room for wiring ducts. PROFINET and PROFIBUS DP onboard — no separate gateway module needed. The safety communication runs over PROFIsafe via the same bus cable, which keeps the safety CPU separation clean: the fail-safe logic lives in the starter, not in a separate safety relay on the DIN rail. Operating temperature range is -25 to +60 °C with derating above 40 °C. For a molding cell with barrel-zone heat radiating into the cabinet, that 60 °C ceiling is tight — plan for forced ventilation or a filtered fan if the enclosure ambient exceeds 50 °C.
Safety ratings and what they mean for guarding
B10d value of 10,100,000 cycles — that is the number of operations before 10% of the population has a dangerous failure. For a reversing starter cycling a conveyor or mixer every 30 seconds, that works out to roughly 9.6 years of continuous 24/7 operation before the B10d is reached. The safe state is load circuit open, so a fault or safety demand drops the motor contactor open. ON-delay time is 35 ms, OFF-delay is 35 to 50 ms. That 35 ms off-delay means the safety response is fast enough for most guarding applications (light curtains, interlock switches) without nuisance trips from brief power dips. Shock resistance rated at 6g / 11 ms and vibration resistance to 15 mm at 6 Hz, 2g to 500 Hz — this is a machine-mount part, not a control-room module. It can live on a vibrating press or conveyor frame.
Sourcing and lifecycle posture
This is a current-production part — no end-of-life notice on record. It is sourced and quoted to order against an RFQ through independent distribution; availability and current pricing are confirmed at quote time. The 24 V DC control supply accepts 20.4 to 28.8 V — a standard 24 V industrial bus, no special power supply needed. Overvoltage category III and pollution degree 2 mean it is rated for fixed industrial installation with transient overvoltages up to 4 kV.