The Siemens 3RK1300-1AS01-0AA4 is an EM 300 DS electromechanical direct starter designed for the ET 200X distributed I/O system. It is a self-contained motor starting and protection unit that combines a contactor, overload relay, and short-circuit protection in one IP65-rated enclosure, ready for on-machine mounting without a separate control panel. Rated for AC-3 duty at 0.55 kW on a 400...500 V supply, it covers small three-phase motor loads — pumps, fans, conveyors — in a decentralized architecture. The setting range of 1.1...1.6 A (full-scale value 1.6 A) matches the motor full-load current, with bimetal thermal protection for overload sensing. PROFIBUS DP communication is built in, so the starter exchanges start/stop commands, fault status, and current data directly with the controller over the fieldbus without hardwired I/O. An integrated motor brake output (DC 500 V / 1 A) handles internally supplied holding brakes — common on vertical-axis or quick-stop applications.
The AC-3 rating of 0.55 kW at 400 V is the motor-switching capability under typical starting conditions (6× inrush, breaking under load). That is a hard ceiling: a 0.75 kW motor exceeds this starter's rating. The setting range 1.1...1.6 A must bracket the motor's nameplate FLA — if the motor draws 1.7 A, this starter cannot be adjusted to protect it. Short-circuit breaking capacity is 50 A at 400 V (Icu). That limits the available fault current on the feeder. If the panel's prospective short-circuit current exceeds 50 A, an upstream fuse or circuit breaker must coordinate to keep the let-through within this starter's rating. This starter mounts directly on the machine frame or a mounting plate in washdown zones — no separate enclosure needed. The operating temperature range is 0...55 °C; above that, derate or relocate.
Dimensions are 134 mm deep × 140 mm wide × 270 mm high. The main current circuit connects via tab terminals — a fast, tooled connection method common on decentralized starters. The 9-pole motor feeder and 9-pole power connection are part of the ET 200X system cabling, so this starter plugs into the backplane bus and the motor cable in one assembly step. Electromechanical switching contacts mean no semiconductor voltage drop or leakage current — full galvanic isolation when open. The bimetal overload relay provides inverse-time thermal protection; it resets automatically after the bimetal cools, or manually via the test/reset button on the front face.