What this part is and what it does
The Siemens 3RK1300-1KS01-0AA3 is an EM 300 DS electromechanical direct starter designed for the ET 200X distributed I/O system. It's a motor-protecting combination unit that integrates a contactor, bimetal overload relay, and short-circuit protection into a single IP65 enclosure. Rated for AC-3 duty at 400 V, it handles motor loads up to 5.5 kW with a setting range of 9 to 12 A. The full-scale value is 12 A, meaning the bimetal overload is adjustable across that band to match the motor's full-load current. It includes a motor brake output for internally supplied brakes, a 9-pole motor feeder, and a 9-pole power connection — all terminated via tab terminals. The operating voltage range is 400 to 500 V AC.
Where it fits and what it connects to
This is a field-mounted unit for the ET 200X family — it bolts directly to the motor feeder module, not to a DIN rail inside a control cabinet. The IP65 rating means the enclosure withstands washdown environments, so it lives on the machine frame or near the motor, not in a sealed panel. PROFIBUS DP communication is built in, so the starter reports status and accepts start/stop commands over the fieldbus without a separate I/O slice. The 9-pole power connection carries the motor leads; the brake contact is a separate output for holding brakes common on vertical-axis drives. Dimensions are 140 mm wide, 270 mm high, and 134 mm deep — a compact footprint for a fully integrated motor starter with communication and brake control. Ambient temperature range is 0 to 55 °C during operation.
Protection and coordination
Short-circuit protection is provided by circuit-breakers integrated into the design, with a maximum short-circuit breaking capacity (Icu) of 50 A at 400 V. This means the unit can safely interrupt a fault current up to that level without upstream devices needing to clear it first — useful for selectivity in a distributed system. The motor protection is bimetal-based, so it tracks thermal load via a heating element. It's not electronic, meaning no ambient-temperature compensation or adjustable trip class — set the dial to the motor's FLA and let the bimetal do its job. Equipment marking per DIN EN 61346-2 is Q, the standard identifier for power switching equipment in industrial schematics.
Sourcing and lifecycle
For a BOM line or a line-down replacement, this order code is the correct Siemens part for an ET 200X direct starter with brake output and PROFIBUS. Sourced to order against an RFQ.