Reversing starter with integrated safety and fieldbus
The Siemens SIMATIC 3RK1308-0BC00-0CP0 is a reversing motor starter rated 3 A at 40 °C, with an SCCR of 55 kA at both 400 V and 500 V — that means it can interrupt a fault current up to 55 kA without upstream damage, sized for high-fault industrial panels. It integrates a 4 via 3DI/LC module, meaning four digital inputs plus a load circuit interface for direct motor control and diagnostics. The safe state is load circuit open, so on a trip or safety demand the power contacts drop and isolate the motor. Trip class is adjustable OFF / 5 / 10, letting you match the overload curve to the motor's thermal capacity — Class 10 for standard induction motors, Class 5 for fast-acting protection on short-time rated loads. ON-delay is 20 ms, OFF-delay 35–50 ms — fast enough for reversing service where direction change needs a dead time to prevent phase-to-phase shorting. Minimum load is 50 % of the smallest adjustable rated current, so don't undersize for a lightly loaded motor or the overload won't trip correctly.
Fieldbus and I/O mapping
Supports both PROFINET and PROFIBUS DP protocols. I/O data is 4 bytes of inputs and 2 bytes of outputs. Fastening method is pluggable in a BaseUnit. Mounting position is vertical or horizontal with derating.
Environmental and mechanical limits
Operating temperature range -25 to +60 °C with derating above 40 °C — fine for most indoor panels but watch the thermal stack if the enclosure runs hot. Storage and transport range -40 to +70 °C. Vibration resistance is 15 mm at 6 Hz, 2 g up to 500 Hz; shock resistance 6 g for 11 ms — robust for conveyor and machine-tool environments. Dimensions: 30 mm wide, 142 mm high, 150 mm deep — a single-width module that fits a standard 35 mm DIN rail enclosure. Clearance above and below is 50 mm each for ventilation and wiring access.