What this SIRIUS compact starter is
The Siemens 3RA6400-2DB42 is a SIRIUS compact starter for IO-Link, a direct starter design that combines a contactor and overload relay in a single 45 mm wide package. Rated 12 A at 400 V AC, it handles motor loads up to 5.5 kW at 400 V, with an adjustable trip class of 10 or 20 to match the motor's thermal characteristic.
At 45 mm wide, 191 mm tall, and 165 mm deep, it takes up a single 45 mm slot in the cabinet — tight enough for a crowded panel but leaves room for the spring-loaded main circuit terminals. The spring-loaded terminals on the main circuit accept 2x (0.25 to 1.5 mm²) solid or stranded wire — no ferrules needed, but strip length matters if you want a clean cage grip.
IO-Link and control logic
This starter communicates via IO-Link at COM2 speed (38.4 kBaud), so it feeds back motor current, trip status, and operational data to the controller without extra analog wiring. Three onboard LEDs give a quick visual on status — run, fault, and communication — handy when you're walking the line and don't want to break out a laptop. The coil is 24 V DC, drawing up to 2.9 W at rated voltage, so it's a light load on the 24 V supply but watch the inrush if you're ganging several on one bus.
Environmental toughness
Vibration resistance is tested to 20 m/s² at 5.8 to 500 Hz, and shock resistance to 6g for 10 ms on all axes — tough enough for a conveyor line or a pump skid.