What it is and what it does
The Siemens 3RK1300-0KS01-0AA4 is an EM 300 DS electromechanical direct starter designed for the ET 200X distributed I/O system. It combines a motor starter, bimetal overload protection, and a PROFIBUS DP interface in a single IP65-rated enclosure, so it can be mounted directly on the machine or in a field junction box rather than inside a central panel. The setting range of 0.9...1.25 A covers small motors up to 0.37 kW at 400 V AC-3 duty — the rating that governs switching of squirrel-cage motors during starting and running.
Key ratings and what they mean for fit
The 0.37 kW rating at AC-3, 400 V is the motor power this starter can handle under the heaviest standard duty — starting and stopping a motor at full load. The operating voltage range of 400... 500 V means it works on 400 V or 480 V line supplies common in European and North American industrial plants. The short-circuit breaking capacity (Icu) at 400 V is 50 A, so the integrated circuit-breaker can safely interrupt a fault up to that level without upstream damage — sized for the motor branch, not the main feeder. IP65 protection means the housing is dust-tight and protected against water jets from any direction — suitable for washdown areas, outdoor installation, or food-and-beverage lines where hose-down cleaning is routine. The ambient temperature range of 0... 55 °C covers most factory-floor conditions but note the lower bound: it is not rated for freezer or cold-store environments.
Integration and connectivity
This starter communicates via PROFIBUS DP, so it plugs directly into a PROFIBUS network without an extra gateway — the bus cable connects to the integrated bus interface. The main current circuit connects via tab terminals, typical for the ET 200X system's 9-pole motor feeder and power connection. A built-in motor brake output (DC 500 V / 1 A) handles internally supplied brakes, saving an external brake rectifier or contactor. The enclosure dimensions — 140 mm wide, 270 mm high, 134 mm deep — fit the ET 200X modular footprint; plan the gland plate and cable entry accordingly.