200 A solid-state overload relay for motor protection
The Siemens 3RB2153-4FX2 is a SIRIUS S6-size solid-state overload relay rated for 200 A operational current at up to 1000 V AC-3e. It protects three-phase motors by monitoring current through straight-through transformers and tripping on overload. Trip class is field-adjustable among CLASS 5E, 10E, 20E, and 30E. This lets you match the relay's thermal memory to the motor's starting profile — a high-inertia load like a centrifuge needs 20E or 30E to avoid nuisance trips during acceleration, while a pump or compressor can run on 10E.
Electronic design and auxiliary contact ratings
The overload release is electronic rather than bimetallic. This means no ambient-temperature tracking error — the relay compensates for -25 to +60 °C operating ambient and holds its trip curve across the range, unlike a thermal bimetal that drifts with panel heat. These cover the common PLC input and relay coil voltages found in most panels. The relay trips when motor current exceeds the upper setting by a factor of 3.5. This threshold is high enough to ride through brief inrush but catches sustained overloads before the motor insulation degrades.
Panel fit and mounting options
The 3RB2153-4FX2 measures 120 mm wide, 119 mm high, and 155 mm deep. It mounts directly onto a contactor or as a stand-alone unit on the DIN rail. The S6 frame size is the largest in the SIRIUS overload relay range, sized for the 200 A current path. The main current path uses straight-through transformers — no looping the motor leads through the relay body, which saves panel wiring time. Rated for 15g / 11 ms shock and 1-500 Hz vibration per IEC 60068-2-27.
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