SIRIUS coupling relay — auxiliary circuit switching in a Size S00 frame
The 3RH2131-2SB40 is a SIRIUS coupling relay — essentially an auxiliary contactor for switching control and signal circuits, not main motor power.
The DC coil is rated 24 V with a pick-up voltage range of 0.85 to 1.85 times rated value — so it reliably pulls in at 20.4 V and stays sealed up to 44.4 V. Closing power is 1.6 W, which keeps heat dissipation low in a crowded panel. This covers most signal-level loads — PLC inputs,指示灯, small solenoid valves — but not motor starting. The built-in suppressor diode across the DC coil protects nearby electronics from the inductive kick when the relay de-energises — a common failure point in control panels if omitted.
Clearance and environment — where it fits without surprises
This keeps arcing from tracking to neighbouring components and meets pollution degree 3 requirements for industrial environments.