The Siemens 3RB3046-2UD0 is a SIRIUS solid-state overload relay, Size S3, designed to protect motors against overload and phase failure. It mounts directly onto a contactor, saving panel space and simplifying wiring. Rated for a CLASS 20E trip curve, it allows motors with longer starting times — like conveyors or crushers — to start without nuisance tripping, while still providing protection during running overloads.
The CLASS 20E trip class means the relay will allow the motor to draw up to 600% of its full-load current for 20 seconds before tripping. Its auxiliary switch is integrated and rated for switching at various control voltages: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V, and 0.55 A at 60 V. These ratings cover the common control supply voltages found in most panels, so you can wire the trip signal directly into a PLC input or a holding circuit without an interposing relay. That means the trip curve stays accurate even if the relay is mounted near a warm motor starter or inside a non-air-conditioned enclosure. It withstands shock of 8g for 11 ms and vibration of 1-6 Hz at 15 mm amplitude, 6-500 Hz at 20 m/s², for 10 cycles. This is enough for most industrial environments, including conveyor lines and machine tools.
This relay is designed for direct contactor mounting — it snaps onto the contactor's own terminals, eliminating separate DIN-rail space and the wiring between the contactor and the overload. The fastening method is listed as "contactor mounting" and it accepts any mounting position. The control circuit terminals accept 2x (0.25 to 1.5 mm²) solid or stranded. Use a Pozidriv PZ2 screwdriver with a 5-6 mm diameter shaft. Physical dimensions are 70 mm wide, 106 mm high, and 124 mm deep. The S3 size is the largest frame in the SIRIUS 3RB3 family, sized for the 50 A thermal current rating.
The substance prohibitance date is listed as 03/01/2017, which aligns with RoHS compliance requirements. No additional compliance documentation (UL, CSA, CE) is listed in the spec record, but as a Siemens SIRIUS component it typically carries CE marking for the European market.