Safety relay for guarding circuits
The Siemens 3SK1122-1CB41 is a SIRIUS safety relay with solid-state enabling circuits, designed to interrupt or enable machine motion in response to safety switches and start inputs. It carries SIL 3 per IEC 61508 and IEC 62061, and PL e per ISO 13849-1 — the highest performance level for a single-channel safety function, meaning it can be used in safety circuits up to Category 4 without redundancy. The safe failure fraction (SFF) of 99 % confirms the relay detects nearly all dangerous faults internally. Rated at 24 V DC, the relay accepts a DC supply between 0.8 and 1.2 times nominal, so it holds in at 19.2 V and drops out below that — a margin that matters when the control transformer is shared with contactors. The 22.5 mm width and 100 mm height fit a standard DIN-rail footprint; depth is 121.6 mm. Screw-and-snap-on mounting lets you clip it onto the rail and secure it with a screw for vibration resistance — useful on a panel door or swing frame.
Wiring and connection
Screw-type terminals accept solid conductors: 1x (20–14 AWG) or 2x (18–16 AWG). Stranded conductors: 1x (20–16 AWG) or 2x (20–16 AWG). With core end processing (ferrules), the range is 1x (0.5–2.5 mm²) or 2x (0.5–1.0 mm²).
Environmental and EMC
Shock resistance is 10 g for 11 ms, which covers most industrial panel vibration. EMC emitted interference meets IEC 60947-5-1 Class A — suitable for industrial zones, but verify if the panel is near residential power lines.