What it is and what it does
The Siemens 3RK1303-5CS44-3AA3 is a reversing starter in the SIRIUS 3RK3 family, designed for direct-on-line reversing of three-phase motors up to 9 A in AC-3 duty at 400 V. This is the current-carrying capacity for switching motor loads under full load — the 9 A AC-3 rating governs the motor FLA it can handle, not the thermal continuous current. The unit integrates a solid-state motor protection function, so it provides overload and phase-loss protection without a separate thermal relay. It operates on a 24 V DC control supply (20.4 to 28.8 V range) and communicates via PROFIBUS DP. The IP65 enclosure means the entire assembly — electronics, power connections, and bus interface — is sealed against dust ingress and low-pressure water jets. This makes it suitable for washdown areas or outdoor cabinets where a standard IP20 panel-mount starter would require a separate enclosure.
Key ratings and what they mean for fit
The 100 kA rated short-circuit current at 400 V (SCCR) means this starter can be installed on a supply capable of delivering up to 100 kA fault current without needing upstream current-limiting fuses to protect it. That simplifies panel coordination — you can feed it from a transformer or busway with a high available fault current and still meet code. The short-circuit protection is fuse-based, so the incoming line-side fuses must be selected to coordinate with the solid-state overload. Brake control with 400 V AC is built in — the starter can directly switch a 400 V AC brake coil for holding brakes on vertical-axis motors, eliminating a separate contactor. The load-side outgoing feeder uses an ISO23570 socket, so the motor cable plugs in with a standardized connector rather than hard-wired terminals. This reduces wiring time and makes swap-out faster. Four digital inputs (M12 sockets) are onboard and parameterizable, giving two dedicated inputs for feedback or limit switches. There are no digital outputs on this variant — the reversing contactor status is communicated via PROFIBUS DP rather than hard-wired auxiliary contacts. The mechanical switching contacts are rated for fewer than 1 error per 100 million operating cycles, which is the expected mechanical endurance for the contactor block.
Where it goes in a panel or machine
This is a self-contained reversing starter in an IP65 enclosure — it mounts directly on the machine frame or a wall bracket, not inside a control cabinet. The hybrid plug for line-side supply and the hybrid socket for communication transmission mean you run one hybrid cable for both power and PROFIBUS DP to the unit. The supply voltage line-side connection uses a hybrid plug as well, so the entire wiring interface is a single multi-conductor cable per unit. The form factor is 250 mm high, 130 mm wide, 107 mm deep — compact enough for distributed installation on a conveyor line or packaging machine where individual motor starters are mounted near the motor rather than in a central MCC. The minimum operating frequency of 1 switching cycle per hour is the lower bound for the mechanical contactor; for applications requiring frequent reversing (e.g., shuttle tables), verify the duty cycle against the application.
Lifecycle and sourcing reality
The substance prohibition date of 05/01/2012 reflects RoHS compliance (the EU RoHS exemption sunset for certain substances). The unit is RoHS-compliant per that date. No UL or CSA listing is explicitly stated in the evidence; verify local code acceptance for the specific installation jurisdiction.