The Siemens 3RB3026-2RB0 is a SIRIUS solid-state overload relay, size S0, designed for contactor mounting. Its primary job is to protect motor circuits against overload conditions, and it reports its status via a signaling contact with a dedicated 'tripped' message output. The relay is rated for CLASS 20E trip class, meaning it allows a motor to draw starting current for up to 20 seconds at cold start before tripping — a standard choice for general-purpose induction motors driving pumps, fans, or conveyors where starting loads are moderate. The thermal current rating is 0.4 A (at 480 V and 600 V rated value), and the rated insulation voltage is 690 V. This sets the upper bound for the motor full-load current it can protect — for a 0.4 A motor, the relay will track the thermal model and trip on sustained overcurrent.
The relay mounts directly onto a contactor — the fastening method is contactor mounting, so it clips onto the matching SIRIUS contactor frame without additional DIN-rail space. This keeps the panel layout compact: the relay adds 45 mm width and 84 mm depth to the contactor stack. Wiring is via screw-type terminals on the main current circuit, accepting 1x (0.5 to 4 mm²) solid or 2x (0.5 to 2.5 mm²) stranded per pole. The auxiliary switch is integrated, with contact ratings: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V — sufficient for signaling to a PLC input or a control relay.
Storage and transport range is -40 to +80 °C. The relay withstands 15g shock for 11 ms (signaling contact in tripped position: 9g / 11 ms) and vibration per IEC 60068-2-27. RoHS compliance date is noted as October 1, 2009, indicating the part meets EU RoHS restrictions from that date forward.