What this coupling relay does that a standard contactor cannot
The 3RH2131-1HB40 is a SIRIUS coupling relay — Siemens designates it specifically for switching auxiliary circuits, not main motor loads.
The arcing time runs 10 to 15 ms, so the downstream input filter on a safety PLC or fast counter must be set wider than that window to avoid false edges. Mechanical endurance is rated 30 million switching cycles typical, and the maximum switching frequency at AC is 10,000 operations per hour — the DC switching frequency is bounded by the 7 to 20 ms on-time, not a per-hour ceiling. For high-cycle applications like pick-and-place or conveyor indexing, the 30-million-cycle figure gives you a service-life budget before the contacts need replacement.
Mounting and environmental fit
The relative humidity floor is 10 %, so it handles dry climates as well as humid enclosures.