What it is and what it does
The Siemens 3RK1303-5CS41-1AA3 is a reversing starter designed for motor control in industrial automation. It's a fully enclosed unit rated IP65, so it handles washdown environments—think food processing lines or outdoor conveyor sections where dust and moisture are daily facts. The 9 A AC-3 rating at 400 V means it switches standard three-phase induction motors up to roughly 4 kW in reversing duty, handling the full locked-rotor current on each start. The 100 kA SCCR at 400 V tells you this thing can sit downstream of a high-capacity distribution board without needing extra fusing for fault current coordination.
Field-fit and integration
This starter communicates over PROFIBUS DP, not PROFINET, so it slots into existing DP networks without a gateway. The 24 V DC control supply is fed through a hybrid plug for the line side and a hybrid socket for transmission to the next device—daisy-chain the supply and bus in one connector. Two M12 sockets handle the digital inputs, both parameterizable. The load-side outgoing feeder uses an ISO 23570 socket, and the main energy infeed is the same standard. Physical dimensions are 250 mm high by 130 mm wide by 107 mm deep—that's a compact footprint for a reversing starter with integrated bus and brake control. The brake control runs at 400 V AC, so no separate contactor for the brake coil on hoist or vertical-axis applications.