What it is and what it does
The Siemens 3RK1300-1FS01-0AA3 is an EM 300 DS electromechanical direct starter from the SIRIUS family, designed for the ET 200X distributed I/O system. It integrates a motor-protective function via a bimetal overload relay, a contactor, and a PROFIBUS DP communication interface into one IP65-rated enclosure — a self-contained motor feeder for decentralized automation architectures. Rated for AC-3 duty at 400 V, it delivers 1.9 kW switching capacity for standard three-phase squirrel-cage motors. The setting range spans 3.5 A to 5.0 A, matching the full-scale current of the bimetal element. That 1.9 kW / 3.5–5.0 A band covers common small conveyor, pump, and fan motors in the 2–3 hp range at 400 V.
Where it fits — panel and field deployment
The enclosure measures 270 mm high, 140 mm wide, and 134 mm deep, with IP65 ingress protection. That means the entire starter assembly — contactor, overload, PROFIBUS electronics, and brake contact — lives in a field-mounted enclosure that handles washdown environments. No separate control cabinet needed for this motor branch; it mounts directly on the machine frame or a mounting plate near the motor. Main current circuit connections use tab terminals, typical for the ET 200X system's plug-in motor feeder cables. The 9-pole motor feeder and 9-pole power connection are built into the housing, so field wiring reduces to the PROFIBUS drop and the motor cable. Operating ambient temperature range is 0 to 55 °C.
Motor brake output and short-circuit protection
A key differentiator on this variant is the integrated motor brake output — it includes a brake contact for internally supplied brakes, AC 400 V. That saves an external brake rectifier or contactor for motors with spring-applied brakes, common on vertical-axis loads or conveyors that need a holding brake. The short-circuit protection is designed to work with circuit-breakers (not fuses), and the maximum short-circuit breaking capacity (Icu) at 400 V is 50 A.