The Siemens 3RB3026-2SE0 is a SIRIUS solid-state overload relay in the S0 size, designed to protect motors against overload and phase imbalance. It mounts directly onto a contactor, saving DIN-rail space in the panel. Rated for CLASS 20E trip class, it allows a motor to draw starting current for up to 20 seconds before tripping — the standard choice for normal-starting loads like pumps and fans.
The 12 A thermal current (Ith) is the continuous current the relay can carry without tripping — match this to the motor full-load current (FLA) on the nameplate. The auxiliary signaling contact is integrated and rated for switching: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V — enough to drive a PLC input or a small indicator lamp directly. The relay is marked for message "tripped" on the signaling contact (97/98), so the panel wiring can distinguish a trip condition from a healthy state. Shock resistance is 15g / 11 ms per IEC 60068-2-27, with the signaling contact derated to 9g / 11 ms in the tripped position — robust enough for most industrial environments.
The S0 size measures 45 mm wide, 109 mm high, 85 mm deep — fits the standard contactor footprint. The screwdriver tip needed is Pozidriv PZ2 with a shaft diameter of 5 to 6 mm. Vibration resistance is 1-6 Hz at 15 mm amplitude, 6-500 Hz at 20 m/s² for 10 cycles — stable on a machine frame.