What it is and what it does
The Siemens 3RK1300-1JS01-1AA0 is an EM 300 RS electromechanical reversing starter designed for the ET 200X distributed I/O system. It integrates a reversing contactor pair, bimetal overload relay, and PROFIBUS DP communication into a single IP65-rated enclosure. Rated for AC-3 duty at 4.0 kW on a 400 V supply, with a setting range of 7.0 to 10 A. The bimetal overload protection tracks motor heating directly — no electronic curve to configure, just a thermal replica of the winding. For a 4 kW motor at 400 V, that setting range covers the full-load current typical of a 7.5 to 10 A motor nameplate. The 50 A short-circuit breaking capacity (Icu) at 400 V means this starter coordinates with a upstream circuit breaker sized to that fault level — the contactor and overload can survive a bolted fault up to that current without welding or bursting.
Where it fits and how it connects
This is a direct-on-line reversing starter for a three-phase motor — forward, reverse, and overload protection in one package. It mounts on the ET 200X backplane or directly in the field via its IP65 housing. Tab terminals on the main circuit accept fork or ring lugs; the 9-pole motor feeder and 9-pole power connection mate to the ET 200X system cabling. PROFIBUS DP is the onboard fieldbus. No AS-interface on this variant. The bus connection carries start/stop, direction, and feedback signals — the reversing logic is handled inside the starter, not in the PLC, so a single PROFIBUS node controls the entire motor direction. Operating voltage is 400 to 500 V AC, three-phase. Ambient temperature range of 0 to 55 °C covers most industrial enclosures and field-mounted installations.