Motor protection with CLASS 10E trip curve
The Siemens 3RB3026-1QB0 is a SIRIUS solid-state overload relay that protects motors against overcurrent and phase loss. Continuous thermal current rating is 25 A at both 480 V and 600 V, so this relay handles the full line current of a motor up to that frame size without derating at those voltages.
Panel fit — size S0, contactor mount
Size S0 footprint (45 mm wide, 87 mm high, 84 mm deep) mounts directly onto a contactor — no separate DIN-rail bracket needed, saving panel space. Fastening method is contactor mounting, so the relay sits on the contactor's own mounting interface. Use a Pozidriv PZ2 screwdriver with a 5–6 mm shaft diameter for the main circuit terminals.
Auxiliary contact ratings for the signaling circuit
The integrated auxiliary switch (terminals 97/98) provides a remote trip indication. This covers common PLC input and control relay voltages. Power dissipation is 0.4 W per pole — negligible thermal contribution inside the panel, so no special ventilation is needed around the relay.
Storage and transport range is -40 to +80 °C. Shock resistance is 15g / 11 ms (signaling contact 9g / 11 ms when tripped). Vibration resistance covers 1–6 Hz at 15 mm amplitude, 6–500 Hz at 20 m/s², 10 cycles — suitable for machine-mounted applications near motors or conveyors.