What it is and what it does
The Siemens 3RU2146-4JB1 is a SIRIUS thermal overload relay in the S3 frame size, designed to protect three-phase motors against overcurrent and phase failure by monitoring motor current and tripping a connected contactor when the thermal model exceeds the set point. Class 10 trip characteristic means it will trip in under 10 seconds at 7.2× the set current — fast enough to protect standard induction motors during a stall or jam without nuisance tripping on normal starting inrush. Rated voltage is 690 V, with motor power ratings of 30 kW at 400 V, 37 kW at 500 V, and 55 kW at 690 V, and current ratings of 52 A at 480 V and 62 A at 600 V. The relay includes a "Tripped" message indicator for quick fault diagnosis on the panel door or enclosure.
Mounting and wiring
Mounts stand-alone in any position — no DIN rail required, though it can be panel-mounted directly. Main circuit connections use screw-type terminals accepting solid conductors 2×(2.5…16 mm²) and stranded 2×(6…16 mm²), 2×(10…50 mm²), or 1×(10…70 mm²). Auxiliary control terminals accept 2×(0.5…1.5 mm²) solid or 2×(0.75…2.5 mm²) stranded. The main contact screw requires an M8 hexagon socket, 4 mm tip. Dimensions: 70 mm wide, 120 mm high, 140 mm deep — fits standard S3 panel cutouts.
Auxiliary contact ratings and ambient conditions
The built-in auxiliary contacts (typically N/O + N/C for trip and signal) carry rated currents across common control voltages: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V, and 0.75 A at 690 V. Lower-voltage DC ratings: 0.3 A at 60 V, 0.22 A at 110/125 V, 0.11 A at 220 V. Operating ambient temperature range is -40…+70 °C, with temperature compensation active from -40…+60 °C — meaning the thermal curve stays accurate across the working range without manual adjustment. Storage and transport range is -55…+80 °C. Power dissipation per pole is 5.7 W.