The Siemens 3RB3143-4XW1 is a SIRIUS solid-state overload relay in the S3 frame size, rated for 115 A thermal current through straight-through transformers. It protects motor circuits by monitoring current and tripping on overload, with adjustable trip classes covering 5E, 10E, 20E, and 30E — so you can match the relay's response to the motor's starting profile and driven load inertia.
Trip characteristics and setting range
The trip mechanism responds when motor current exceeds the upper current setting value times 3.5, and resets when current drops below the lower setting value. With four selectable trip classes, this relay handles everything from quick-protection 5E for short-acceleration motors up to 30E for high-inertia loads that need a longer start window without nuisance tripping.
Mounts in any position, standalone installation. Shock-rated at 8 g / 11 ms in normal operation, and the signaling contact (97/98) holds 15 g / 11 ms when tripped — built for industrial vibration environments like conveyor drives or mill tables.
The integrated auxiliary switch provides the "tripped" message contact. Its switching capacity spans 2 A at 24 V, 4 A at 120 V, 3 A at 230 V, and 0.11 A at 220 V — covers PLC input cards and control relays across common control voltages. Per-pole power dissipation is 0.2 W, negligible for panel thermal budgeting.