The Siemens 3RK4320-3JQ51-1BA3 is a SIRIUS reversing motor starter designed for AS-Interface bus communication, combining a contactor, motor protection via bimetal overload relay, and short-circuit protection into one unit. Operating voltage is 340 to 440 V AC at 50/60 Hz, and the control supply is 20.4 to 26.4 V DC — a 24 VDC nominal rail powers the AS-Interface bus and the coil logic.
Where it goes in a panel
At 245 mm wide, 215 mm high, and 205 mm deep, it occupies a compact footprint for a reversing starter with integrated brake control (400 V AC brake output is built in). IP54 protection means it handles dust and splashing water — suitable for installation inside a cabinet with a moderate ingress rating, not for open washdown zones. Two digital inputs are available on the unit for local control signals, and the AS-Interface protocol handles the bus communication (no PROFIBUS or PROFINET onboard).