The Siemens 3RB3143-4UX1 is a SIRIUS solid-state overload relay, Size S3, with a thermal current of 50 A. Trip class is adjustable across CLASS 5E, 10E, 20E, and 30E, giving you flexibility to match motor start characteristics — fast trip for short starts, slower for high-inertia loads. The relay trips when motor current exceeds the upper current setting value by a factor of 3.5, and resets when current drops below the lower setting. The auxiliary switch is integrated, with switching capacity rated at 2 A at 24 V, 4 A at 120 V, and 3 A at 230 V — enough for a PLC input or contactor coil in most panels. Power dissipation per pole is 0.07 W, so heat buildup in a dense enclosure is minimal.
Mounts in any position via stand-alone installation — no DIN rail required, though it can be panel-mounted. Dimensions are 70 mm wide, 106 mm high, 124 mm deep, fitting a standard Size S3 footprint. Vibration resistance is 1-6 Hz at 15 mm amplitude, 6-500 Hz at 20 m/s² for 10 cycles. Shock resistance is 8g for 11 ms on the signaling contact in tripped position, 15g for 11 ms per IEC 60068-2-27 on the main body. That holds up in most industrial machinery environments.
Substance prohibitance date is 03/01/2017, confirming RoHS compliance from that date forward.