What it is and what it does
The 3RU2146-4LB0 is a Siemens SIRIUS thermal overload relay in the S3 frame, Trip Class 10. It mounts directly onto a matching SIRIUS contactor (fastening method: contactor mounting) and protects motors by opening the control circuit when the thermal model reaches the trip point. The note 'for message "Tripped"' indicates an auxiliary contact that changes state on overload—so the PLC or indication lamp sees a clean signal, not just a bimetal curvature.
Mounting and wiring
Physical outline: 70 mm wide, 105 mm high, 125 mm deep; mounting position any. Screw terminals accept solid 2 x (2.5–16 mm²) or stranded up to 2 x (10–70 mm²) for main circuit and 2 x (0.5–1.5 mm²) for auxiliary, with a 4 mm hexagon socket driver on the M8 screws. The 'Tripped' message contact is the auxiliary signal to a PLC DI or annunciator—verify polarity if used with a DC control voltage. Per-pole dissipation is 7 W, so in a sealed enclosure consider aggregate heat from the contactor plus relay.