What it is and what it does
The Siemens 3RK1300-1JS01-0AA0 is an EM 300 DS electromechanical direct starter designed for the ET 200X distributed I/O family. It integrates a contactor, bimetal motor protection relay, and PROFIBUS DP communication into a single IP65-rated enclosure — a self-contained motor feeder for a remote or decentralized panel. Rated at 4 kW in AC-3 duty at 400 V, with an adjustable setting range of 7.0 to 10 A (full-scale 10 A), it's sized for small three-phase induction motors — pumps, fans, conveyors — on a 400 to 500 V supply. The bimetal overload relay provides Class 10 or Class 20 motor protection, depending on the trip curve selected. The IP65 rating means the entire assembly — contacts, bimetal, electronics — is sealed against washdown and dust ingress, so it can be mounted directly on a machine frame or in a field enclosure without a separate cabinet. The main circuit connects via tab terminals (fast-on), typical for this form factor.
Communication and integration
Built-in PROFIBUS DP lets the starter communicate directly with a PLC over the fieldbus — no separate gateway or I/O block needed for motor control. The ET 200X backplane carries both power and bus data to the module; addressing is set via the rotary switches on the base unit. No AS-Interface on this variant, so if the site uses AS-i for sensor-level networking, this module won't participate on that bus. The PROFIBUS DP interface handles the start/stop commands, overload trip feedback, and diagnostic data. Dimensions are 140 mm wide, 270 mm high, and 134 mm deep — it occupies a single slot on the ET 200X mounting rail. The 9-pole motor feeder and 9-pole power connection are pre-wired through the backplane; field wiring lands on the tab terminals for the motor leads.
Protection and fault handling
Short-circuit protection is provided by circuit-breakers, coordinated to limit let-through energy below the starter's withstand. The maximum short-circuit breaking capacity (Icu) at 400 V is 50 A — this is the fault level the device can safely interrupt without external fuses, assuming proper Type 1 or Type 2 coordination with the upstream breaker. Ambient temperature range during operation is 0 to 55 °C. Above 55 °C the bimetal overload relay must be derated per the thermal curve; the enclosure's IP65 seal also traps heat, so check the mounting orientation for natural convection. No integrated motor brake output — if the application needs a DC injection brake or mechanical brake control, that function must be added externally via a separate contactor or brake rectifier.