The Siemens SIMATIC 3RK1308-0AB00-0CP0 is a direct-on-line motor starter in the 3RK1 family, designed for switching and protecting single-speed induction motors up to 1 A at 40 °C ambient. It integrates a contactor, overload relay, and PROFINET/PROFIBUS DP communication into one 30 mm-wide module that plugs into a common BaseUnit — no point-to-point wiring for the power bus. The safe state is load circuit open, and the trip class is adjustable OFF / 5 / 10, so you can match the thermal curve to the motor start profile. It draws 4 bytes of input data and 2 bytes of output data over the fieldbus, which is enough for status, control, and diagnostic feedback without eating into your PLC I/O budget.
Rated 1 A at both 40 °C and 50 °C — that is the continuous current the starter can carry in a 40 °C panel without derating. If your motor FLA is 0.9 A, this is a clean fit; above 1 A you step up in the family. The minimum load is 50 % of the smallest adjustable rated current, so it will not nuisance-trip on a lightly loaded motor.
Communication and control
This starter supports PROFINET and PROFIBUS DP protocols. ON-delay is 20 ms, OFF-delay 35 to 50 ms. On-site operation is supported. Supply voltage is 20.4 to 28.8 V.
Mounting can be vertical or horizontal, but horizontal requires derating per the manual. Ambient operating range is -25 to +60 °C with derating above 40 °C; storage and transport go from -40 to +70 °C. Shock resistance is 6 g for 11 ms, vibration 15 mm at 6 Hz and 2 g up to 500 Hz — typical for machine-mount near conveyors and small pumps, but not for high-vibration crushers or presses.
Lifecycle stage is current. MTBF is 48 years.