The Siemens 3RU2146-4KD0 is a SIRIUS thermal overload relay — the part that sits between the contactor and the motor, watching winding current and tripping on a sustained overload before the insulation cooks. CLASS 10 means it opens within 10 seconds at 7.2× the thermal setting, fast enough to protect a standard squirrel-cage motor start but not so fast it nuisance-trips on the inrush. Size S3 frame, rated 690 V, with the auxiliary switch built into the housing — no separate add-on block needed for the trip-indication signal.
Mounts directly to the contactor via the fastening method — no DIN rail required, though the 70 mm width and 125 mm depth fit comfortably on a standard DIN-rail panel if the contactor is rail-mounted. Screw-type terminals on the main circuit accept solid 2x (2.5…16 mm²) or stranded up to 1x (10…70 mm²). The auxiliary circuit uses smaller terminals, 2x (0.5…2.5 mm²) solid or stranded. Temperature-compensated from -40 to +60 °C, so it tracks the motor heating curve even in a warm cabinet.
Substance prohibitance date of 03/01/2017 aligns with EU RoHS and REACH compliance scoping — the relay is manufactured to meet those material restrictions. Operating range -40 to +70 °C, storage and transport -55 to +80 °C. Mount in any position; no derating curve to chase for orientation.