The Siemens 3RK1300-1CS01-1AA3 is an electromechanical reversing starter from the SIRIUS EM 300 RS family, designed for direct-on-line reversing of three-phase motors up to 0.9 kW at AC-3 duty on a 400 V supply. It integrates a bimetal overload relay with an adjustable setting range of 1.8 to 2.5 A, so the same unit handles both forward/reverse contactor switching and motor protection in one enclosure. Rated for an operating voltage of 400 to 500 V, it carries a maximum short-circuit breaking capacity (Icu) of 50 A at 400 V, coordinated with circuit-breakers for short-circuit protection. Onboard PROFIBUS DP communication allows the starter to be addressed directly from a PLC without a separate gateway, and the integrated motor brake output handles DC-injected brakes for holding loads — a common requirement on conveyors and hoists where the motor must not coast when stopped.
This form factor means it occupies a defined slot in an ET 200X station rather than a standalone DIN-rail footprint; plan the backplane and gland plate accordingly. Ambient operating temperature range is 0 to 55 °C. The IP65 enclosure eliminates the need for a separate cabinet in many applications, but the tab terminals require mating connectors with the correct pitch and current rating — verify the mating half before panel build.
The 1.8 to 2.5 A setting range and 0.9 kW at AC-3 400 V rating define the motor it can handle: typically a small three-phase motor on a conveyor, pump, or actuator. The AC-3 duty category covers starting and stopping of squirrel-cage motors under load — the most common industrial motor switching condition. PROFIBUS DP onboard eliminates a separate communication module, saving a slot and reducing wiring. The integrated brake output handles DC brakes up to the supply voltage range — verify the brake coil voltage matches the 400 to 500 V supply, as some brakes require a separate DC supply.