The Siemens 3RU7126-4EB0 is a SIRIUS thermal overload relay in the S0 frame size, rated for 32 A operational current and Trip Class 10. It mounts directly onto a matching S0 contactor, protecting motor circuits against overcurrent by thermally sensing the load current and tripping the contactor's control circuit. Trip Class 10 means the relay will trip within 10 seconds at 7.2× the current setting — the standard for standard-duty motor starting where acceleration time is under a few seconds.
Rated operational current of 32 A at 690 V AC/DC covers a wide range of three-phase motor loads up to roughly 15 kW at 400 V. The auxiliary contacts handle 3 A at 24 V and 2 A at 230 V, sufficient for signalling to a PLC or contactor coil. The relay is designed for contactor mounting — it clips directly onto the front of a SIRIUS S0 contactor, saving DIN-rail space and reducing wiring.