The Siemens 3RB3143-4UD0 is a SIRIUS solid-state overload relay in Size S3, designed to protect motors against overload and phase imbalance by monitoring motor current and tripping when it exceeds the set threshold. Its adjustable trip classes — CLASS 5E, 10E, 20E, and 30E — let you match the relay's thermal response to the motor's starting characteristics: Class 10E for standard start times, Class 20E for higher-inertia loads, and Class 30E for long-start applications like crushers or centrifuges.
Mounts directly onto a contactor via the Fastening Method: Contactor mounting — no separate DIN-rail bracket needed, which saves panel space and simplifies wiring. The relay accepts screw-type terminals for the main current circuit (M6 bolts) and solid/stranded control wiring from 0.25 to 1.5 mm² (2x conductors). Dimensions are 70 mm wide, 106 mm high, and 124 mm deep — fits standard S3 contactor footprints.
Withstands shock up to 8g / 11 ms during operation and 15g / 11 ms per IEC 60068-2-27 for the signaling contact in tripped position; vibration resistance is 1–6 Hz at 15 mm amplitude and 6–500 Hz at 20 m/s² for 10 cycles. Storage and transport range is -40 to +80 °C.