The Siemens 3RQ4050-2SM50 is a SIRIUS 3RQ4 output optocoupler relay in the narrow 6.2 mm housing. It switches one normally-open contact at a thermal current of 3 A, controlled by a 24 V DC input. This is a galvanically isolated coupling relay, meaning the 24 V DC control side and the switched load side are optically separated. Use it to pass a PLC digital output to a higher-current load (up to 3 A) or to a different voltage domain without a common ground. The 6.2 mm width packs tight on a DIN rail — typical for dense control panels where every millimeter of rail space is accounted for.
RoHS compliance is confirmed effective September 2024. This is typical for electronic components with soldered joints or certain contact alloys — it does not affect normal handling or installation, but it must be declared in the supply chain documentation for EU end users.
Integration notes
At 6.2 mm wide, it occupies one module position — adjacent relays or terminals can be ganged without spacing issues. No end brackets required for a single unit, but in a multi-module row, standard DIN-rail end clamps keep the assembly from shifting during wiring. The 24 V DC input draws from a standard control supply. No coil suppression is built into the optocoupler input — if the driving PLC output is an inductive load (e.g., a relay coil), fit a free-wheeling diode across that coil to protect the PLC output transistor. The 3 A thermal current rating is the continuous carry current at ambient up to 40 °C; derate for higher enclosure temperatures per the Siemens SIRIUS application manual.