The Siemens 3RA2328-8XB30-1BB4 is a SIRIUS reversing contactor assembly — a pre-wired pair of contactors with mechanical interlock, ready to reverse a three-phase motor without you having to source and wire two separate contactors plus a mechanical interlock block. It ships with two 3RT2028-1BB40 contactors inside, so the reversing pair is matched from the factory. Rated for 18.5 kW at 400 V and 34 A at 480 V in AC-3 duty, it handles the common motor sizes you see on conveyors, pumps, and fans in a 400 V plant. The 24 VDC coil keeps control voltage low and safe — standard for PLC-driven panels.
The S0 frame size is compact: 90 mm wide, 101 mm tall, 107 mm deep — fits a standard 8-inch deep enclosure with room for fusing or a soft start downstream. That means you can fit it into tight corners or angled subpanels without derating. Clearance around the assembly: 6 mm upward, forward, downward, and to the sides; zero clearance needed behind. That 6 mm gap is enough for airflow and tool access when landing wires.
Main power circuit terminals are screw-type, accepting 2x (1 … 2.5 mm²) solid or 2x (2.5 … 10 mm²) stranded — covers the range from control wiring up to the 10 mm² tails you'd run for the 34 A motor feed. Coil terminals are also screw-type, same gauge range. Two instantaneous auxiliary contacts are built in (one N/O, one N/C typically) for status feedback to the PLC or to seal in the reversing logic. That saves adding a separate auxiliary contact block for basic reversing control.
Shock rated at 13.5 g / 5 ms on AC and 15 g / 5 ms on DC, so it holds up in applications near vibrating machinery. The AC-3 switching frequency maxes out at 750 operations per hour, so it can keep pace with a rapid line.
Because it's an active SIRIUS catalog number, lead time is quoted to order. If you need to keep a spare on the shelf for a critical line, this is a straightforward min/max item — no last-time-buy pressure.