Motor protection for 480/600 V branch circuits
The Siemens 3RB3133-4UW1 is a SIRIUS solid-state overload relay in Size S2, designed to protect motors in 480 V and 600 V systems where the continuous thermal current is 50 A at both voltage levels. Rated voltage is 690 V with a maximum AC-3e switching voltage of 690 V, so it covers 400 V, 480 V, and 600 V motor branch circuits without derating. The trip class is field-adjustable among CLASS 5E, 10E, 20E, and 30E, letting the commissioning engineer match the relay's thermal curve to the motor's starting profile — a 5E setting for fast-cycling loads, 30E for high-inertia starts.
Trip response and diagnostic output
The relay trips when the motor current exceeds the upper current setting value by a factor of 3.5 or more, and resets when current drops below the lower setting value — this hysteresis prevents nuisance re-closure on a stalled motor. A dedicated signaling contact (97/98) changes state on trip, with a note for message 'tripped' — this can drive a PLC input or alarm lamp directly. The auxiliary switch is integrated into the relay housing, saving a separate add-on module and reducing wiring in the panel.
Environmental and mechanical fit
Dimensions are 55 mm wide, 81 mm high, and 109 mm deep — it mounts on DIN rail in any position, with stand-alone installation fastening. Operating temperature range is -25 to +60 °C, storage and transport from -40 to +80 °C, with temperature compensation active across the full operating band. Shock resistance is 15 g for 11 ms per IEC 60068-2-27, and vibration resistance covers 1–6 Hz at 15 mm amplitude and 6–500 Hz at 20 m/s² for 10 cycles — suitable for machine-mounted panels on conveyors or presses.
Wiring and termination
Terminals accept solid or stranded wire: 1x 0.5–4 mm² or 2x 0.5–2.5 mm², with a Pozidriv PZ2 screwdriver tip and 5–6 mm shaft diameter for the clamping screws. The main current circuit uses straight-through transformers — the motor leads pass directly through the relay body, eliminating external current transformers and reducing panel wiring labor. Power dissipation per pole is 0.03 W, so thermal buildup in a crowded enclosure is negligible even at full rated current.
Sourcing and lifecycle status
Substance prohibitance date of 10/15/2014 confirms RoHS compliance for the European market. Sourced and quoted to order against the BOM quantity through independent distribution; availability and current pricing confirmed at RFQ time.