What this part does and where it fits
The Siemens 3RH1131-2KB40-2AA0 is a SIRIUS auxiliary contactor — a control-circuit relay that switches signal or low-power loads in a motor starter or PLC output bank. It carries three instantaneous normally-open contacts, each rated for 10 A at 24 V, 6 A at 230 V, and 1 A at 690 V, so it handles everything from a PLC input to a small contactor coil. The 24 V DC coil draws 11 W to close and 4 W to hold, with a built-in varistor surge suppressor across the coil. It mounts on a DIN rail or with screws, and the size S00 footprint (45 mm wide, 60 mm tall, 73 mm deep) fits the standard SIRIUS contactor grid — same panel cutout as a 3RT10 contactor.
Key ratings and what they mean for your panel
The 24 V DC coil is the standard control voltage for most industrial PLCs and safety relays — no extra power supply needed if your cabinet already runs 24 VDC. The 3 NO contacts are instantaneous (no make-before-break or delayed action), so they switch at the same moment the coil picks up, which matters when you need simultaneous signal feedback or interlocks. The contact reliability spec — one incorrect switching operation per 100 million at 17 V, 1 mA — means these contacts are reliable even at dry-circuit levels, so they can switch PLC inputs without gold-plating. The IP20 front protection means the contactor is finger-safe from the front but not sealed against dust or water — it belongs inside a panel. Pollution degree 3 is typical for industrial control panels. The surge voltage resistance of 6 kV gives margin against switching transients. Wire it with solid or stranded conductors from 0.25 to 2.5 mm² — standard for control wiring. The mounting position is flexible: you can rotate it ±180° on a vertical surface, or tilt it ±22.5° forward/backward, so it fits in tight layouts. Operating temperature range is -25 to +60 °C, storage and transport from -55 to +80 °C.