What it is and what it does
The Siemens 3RK1300-0FS01-0AA3 is an EM 300 DS electromechanical direct starter from the SIRIUS family, designed for the ET 200X distributed I/O system. It combines a contactor, bimetal motor protection, and a motor brake output in one IP65-rated enclosure — a self-contained motor start/stop and protection unit for a single motor load. The setting range is 0.35 to 0.5 A, and at AC-3 duty (squirrel-cage motor starting) on a 400 V supply it is rated for 0.12 kW. That 0.12 kW figure is the motor power it can switch under the standard AC-3 utilization category — the rating that governs real motor starting, not a resistive load. It communicates over PROFIBUS DP, so it integrates directly into a PROFIBUS network without a separate gateway. The main current circuit connects via tab terminals — quick-connect blades, not screw clamps — which is typical for the ET 200X form factor.
Where it goes and how it mounts
This direct starter is built for the ET 200X distributed I/O system — it mounts onto the ET 200X backplane or motor feeder module, not on a DIN rail. The IP65 rating means the entire assembly can sit directly on a machine frame or in a washdown zone without a separate enclosure. Dimensions are 134 mm deep, 140 mm wide, and 270 mm high. The 9-pole motor feeder and 9-pole power connection are part of the ET 200X interface — the starter plugs into the system bus and power rail. Operating temperature range is 0 to 55 °C, which covers most indoor industrial environments but not freezing or high-heat foundry floors.
Protection and breaking capacity
Motor protection is via a bimetal overload relay integrated into the starter — it tracks motor current and trips on sustained overload. Short-circuit protection is designed for circuit-breakers upstream, and the maximum short-circuit breaking capacity (Icu) at 400 V is 50 A. That 50 A figure is the fault current the device can safely interrupt without welding its contacts or causing a cascade failure upstream. The integrated motor brake output (product component Motor brake output = Yes) means this starter can control an externally supplied brake — typically a DC brake coil on a motor — without a separate brake contactor. The brake contact is rated for the same 400-500 V supply as the main circuit.