What this part is and what it does
The Siemens 3RK1300-0FS01-0AA0 is an EM 300 DS electromechanical direct starter designed for the ET 200X distributed I/O system. It's a self-contained motor starting and protection unit that combines a contactor, bimetal overload relay, and short-circuit protection in one IP65-rated enclosure, ready for direct machine mounting without a separate control panel. Rated for AC-3 duty at 400 V, it handles motor loads up to 0.12 kW with a setting range of 0.35 to 0.5 A. The bimetal overload element provides thermal motor protection, while the integrated circuit-breaker-style short-circuit protection is rated for a breaking capacity of 50 A at 400 V — meaning it can safely interrupt a fault current up to that level without upstream devices needing to clear it. PROFIBUS DP communication is built in, so the starter reports status and accepts start/stop commands directly over the fieldbus without additional I/O modules. The operating voltage range is 400 to 500 V, and it's rated for ambient temperatures from 0 to 55 °C.
Where it goes and how it connects
This starter mounts directly on the machine frame or a sub-panel — the IP65 enclosure means it's built for washdown environments and dusty factory floors. Main circuit connections use tab terminals, so you're looking at fast-on connectors rather than screw terminals. The unit includes both a 9-pole motor feeder and a 9-pole power connection, which simplifies the wiring harness in distributed architectures. Physical footprint is 140 mm wide by 270 mm tall by 134 mm deep — compact enough for tight machine-mounted enclosures but verify clearance for the PROFIBUS connector and cable bend radius. There's no integrated motor brake output on this variant, so if your application needs a holding brake, you'll need an external brake control unit.