What is this part and where does it fit?
The Siemens 3RK4320-5DQ64-1BA3 is a SIRIUS reversing motor starter designed for AS-Interface networks. It integrates a solid-state motor protection relay (Class 10 trip class) and reversing contactor into one unit, rated for AC-3 motor duty at 1.25 A on a 400 V line. The IP54 enclosure means it's suited for panel-mount in industrial environments where dust and splash are present, but not for direct washdown.
The AC-3 rating of 1.25 A at 400 V defines the maximum motor load this starter can switch under typical starting conditions (inrush up to 7–8x FLA). Class 10 trip means the overload relay will open the circuit within 10 seconds at 7.2x the set current — standard for standard-duty induction motors like pumps and small conveyors. The 340–460 V operating range covers 400 V nominal systems with tolerance. AS-Interface communication is built in, so this unit connects directly to an AS-i network without an external gateway module. Two digital inputs are available on the starter for local sensors or pushbuttons. The reversing design allows forward/reverse control of a single motor through the same AS-i node. The control supply voltage is 20.4–26.4 V DC, standard for AS-Interface power. The main circuit uses three poles. Brake control for 400 V AC motors is integrated — no separate brake contactor needed for applications like hoists or conveyors with holding brakes.