The Siemens SIRIUS 3RB3036-2UD0 is a solid-state overload relay in Size S2, designed for contactor mounting — mates directly to the 3RT2 contactor frame. CLASS 20E trip class means it allows a 20-second cold start for motor loads before tripping, matching the acceleration curve of standard three-phase induction motors driving fans, pumps, or conveyors. Rated thermal current of 50 A at 690 V (AC-3e) covers a broad motor range up to that current draw in 400 V and 690 V line supplies.
Trip Class and Motor Protection
CLASS 20E is the standard trip class for general-purpose motor starting — it holds through a 20-second locked-rotor condition without nuisance tripping, then clears on sustained overload. The integrated auxiliary switch provides a separate signal contact (97/98) that changes state on trip, letting a PLC or annunciator capture the fault immediately. The note for message "tripped" on the relay face confirms the switch position for commissioning checks.
The 3RB3036-2UD0 mounts directly onto the contactor via the fastening method specified — no separate DIN-rail footprint needed, saving panel width. Dimensions: 55 mm wide, 99 mm high, 104 mm deep. Main circuit wiring accepts screw-type terminals: solid or stranded 2x (0.25–1.5 mm²) for control wiring, and 2x (10–35 mm²) or 1x 50 mm² for the power circuit. Screwdriver shaft diameter 5–6 mm, Pozidriv PZ 2 tip. Contact rating of the auxiliary switch: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V — sufficient for direct PLC input or relay coil drive without an interposing relay. Shock resistance rated at 15g / 11 ms; vibration resistance per 1–6 Hz, 15 mm and 6–500 Hz, 20 m/s² for 10 cycles.