The Siemens 3RB1025-2NB0 is an electronic overload relay in the SIRIUS 3RB10 series, sized for motor protection in the 0.4 to 1.6 A range. Class 20 trip curve means it allows a 20-second thermal overload before tripping — matched to standard induction motor startup profiles on pumps, fans, or light conveyors. Mounts directly to a contactor in the S0 frame, saving DIN-rail space inside the panel.
The 0.4 to 1.6 A setting range covers small motors — think fractional-horsepower drives or small conveyor sections. Class 20 is the standard thermal memory for general-purpose induction motors; it rides through a normal start without nuisance tripping but still protects against a stalled rotor or sustained overload. Screw connection keeps wiring straightforward for panel builders who prefer a terminal screw over spring-cage. Manual reset only — no auto-reset option, so the relay stays tripped until someone pushes the button. That is deliberate for applications where an unexpected restart could be a safety concern.