The Siemens 3RU2126-1JB0-ZX95 is a SIRIUS thermal overload relay — S0 frame size, Class 10 trip curve, rated 690 V. It's the part that sits between a contactor and the motor, watching current and tripping on overload before the winding insulation gives up. The thermal bimetallic release means it tracks the motor's heating curve naturally, no electronics to fail in a vibration-heavy panel. The auxiliary switch is integrated — no add-on block needed — and carries the 'Tripped' signal back to the PLC or indicator lamp.
The S0 frame is the mid-size in the SIRIUS family; it handles motor power up to 7.5 kW at 690 V. The auxiliary contact ratings cover most control voltages you'll find in a panel: 2 A at 24 V and 230 V, 3 A at 120 V, 1 A at 400 V. Temperature compensation is active from -40 to +60 °C, so the trip point doesn't drift when the panel heats up in summer or the line runs near a furnace.
Mounts directly to the contactor — no DIN rail bracket needed, no extra hardware. Accepts 2× (0.5 to 1.5 mm²) or 2× (0.75 to 2.5 mm²) solid or stranded wire per terminal. Screw terminals take a Pozidriv PZ2 bit, shaft diameter 5 to 6 mm. Main circuit connections use M4 screws. Mounting position is any, so you can lay it sideways in a shallow enclosure if needed.
This is a current-production part in the SIRIUS portfolio. No end-of-life notice, no last-time-buy deadline — it's the standard thermal overload relay for S0 contactors and will be for the foreseeable future.