What it is and what it does
The Siemens 3RK1303-6DS71-1AA3 is a reversing starter with solid-state switching contacts, rated 12 A at 400 V in AC-3 duty for motor loads. That AC-3 rating means it's built for starting and stopping squirrel-cage motors under load — the standard duty cycle for reversing starters on conveyors, pumps, or hoists where direction change is needed. It carries a full motor protection function, so it handles both overload and short-circuit protection in one package. Short-circuit protection is fuse-based, rated for 100 kA at 400 V — that SCCR tells you it can interrupt a fault up to that level without the arc flashing upstream to the panel main. The 24 V DC control supply has a tolerance window of 20.4 to 28.8 V, so it holds in during a sagging 24 V bus. Communication rides on PROFIBUS DP, not PROFINET — if your line is still on a DP backbone, this is a direct drop-in. Two digital inputs are parameterizable via the bus, and the auxiliary contacts are rated for under 1 error per 100 million cycles, which is solid-state reliability territory.
Where it goes and how it connects
IP65 rating means the housing is dust-tight and protected against low-pressure water jets — this lives on the machine, not in a clean control cabinet. It's built for washdown zones or outdoor conveyor sections where a standard contactor panel would need a separate enclosure. The main power infeed and load-side outgoing feeder both use sockets per ISO 23570, so cabling is a plug-and-play affair — no hardwiring into the starter body. The supply voltage line-side uses a hybrid plug that also carries the PROFIBUS DP communication, and the motor connection uses a hybrid socket. That hybrid connector bundles power and signal into one cable, which cuts wiring time on a multi-starter machine. It also includes brake control at 400 V AC, so if your motor has a holding brake, this starter handles the brake coil timing without a separate contactor. Dimensions are 250 mm high, 130 mm wide, and 125 mm deep — a compact footprint for a reversing starter with integrated comms and brake control. Mounts via the housing base; no DIN rail required.
Lifecycle and sourcing reality
The AC-3 motor rating is 12 A and the interface is PROFIBUS DP. If your panel uses a different fieldbus, this starter will not drop in without a gateway.