Reversing starter with AS-Interface — what fits in the panel
The Siemens 3RK4320-3KQ54-1BA2 is a SIRIUS reversing motor starter with integral AS-Interface bus communication — a single unit that handles forward/reverse motor control and overload protection over a two-wire network. The enclosure measures 245 mm wide by 205 mm deep by 215 mm high with IP54 protection — splash-proof and dust-limited, suited for panel-mount in industrial environments where occasional washdown or airborne dust is present.
Control supply and bus integration
Control supply is 20.4–26.4 V DC — standard 24 V nominal, drawn from the AS-Interface bus or a separate DC rail. The unit communicates over AS-Interface protocol, not PROFIBUS or PROFINET, so the network master must support AS-I. Two digital inputs are available on the unit for local control signals or feedback, reducing the need for separate I/O blocks at the motor centre.
Mounting flexibility and motor brake output
The unit mounts on a vertical surface with ±180° rotation possible and can be tilted forward/backward by ±22.5° — useful for cable entry positioning in tight enclosures or when aligning with existing conduit. A motor brake output is included as a product component — the starter can control an external brake coil directly, eliminating a separate brake contactor for reversing applications that need holding brakes. Maximum operating frequency is 80 operations per hour — this is a duty-cycle limit for the bimetal overload and contactor wear, not a continuous switching rate.