What this relay does
The Siemens 3RU2126-4AB0-ZW96 is a SIRIUS thermal overload relay — size S0, Class 10 trip curve — that protects motor circuits by monitoring current and opening the contactor on overload. The "for message "Tripped"" variant means the integrated auxiliary switch signals a trip condition directly to a PLC or indicator lamp, which saves a panel builder from wiring an extra block. Rated value is 690 V, with power ratings of 7.5 kW at 400 V and 500 V, and 11 kW at 690 V. The auxiliary contact carries 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V — enough to drive a small relay or input card directly.
Mounts directly to the contactor — no DIN rail needed for the relay itself, though the contactor typically clips onto one. Size S0 footprint (45 mm wide, 85 mm deep, 85 mm tall) is the standard for this frame class. Screw terminals accept 2x (0.5…1.5 mm²) or 2x (0.75…2.5 mm²) solid or stranded wire; use a PZ2 Pozidriv bit with a 5–6 mm shaft diameter. Temperature compensation is active from -40 to +60 °C, and the relay operates from -40 to +70 °C.