{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3SK1121-1AB40","brand":"Siemens","brandSlug":"siemens","productSlug":"3SK1121-1AB40","canonicalUrl":"https://aoctrl.com/siemens/3SK1121-1AB40","factsUrl":"https://aoctrl.com/api/mcp/products/3SK1121-1AB40","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3SK1121-1AB40 safety relay, 24 V rated, SIL 3 / PL e, 22.5 mm wide, screw and snap-on mounting.","salesMarkdown":"The Siemens 3SK1121-1AB40 is a SIRIUS safety relay designed for relay enabling circuits — the core job is to monitor safety switches and start inputs, then drop the load if a guard opens or a feedback loop breaks. Rated SIL 3 per IEC 61508 and PL e per ISO 13849-1, which means it's certified for the highest risk-reduction tier in a safety-related control system — the kind you'd spec for a press guard, robot cell gate, or conveyor hazard zone where a fault has to be detected and the energy isolated within 50 ms maximum (typical 30 ms). The 22.5 mm width and screw-and-snap-on mounting mean it fits a standard DIN-rail enclosure without eating panel space — you can pack several of these next to a safety PLC or contactor bank. Mounting position is any, so it's not picky about orientation inside a crowded cabinet. ## Contact ratings — what switches at what voltage The enabling contacts are rated 1 A at 24 V, 1.5 A at 115 V, and 1.5 A at 230 V. That's enough for direct switching of small contactors, solenoid valves, or indicator loads inside the safety chain. The total current through the relay is capped at 12 A maximum, and the power loss tops out at 2 W — so it's not a power contactor; it's a logic-level safety interface that drives a larger output contactor or motor starter downstream. ## Integration — wiring and environment Terminals accept solid wire 1x (20–14 AWG) and 2x (18–16 AWG); stranded 1x (20–16 AWG) and 2x (20–16 AWG). With core-end processing (ferrules), it takes 1x (0.5–2.5 mm²) and 2x (0.5–1.0 mm²). That covers standard panel-building practice — no special crimp tool needed beyond a common ferrule kit. Shock resistance is 10g / 11 ms, which handles typical machine vibration. EMC emitted interference meets IEC 60947-5-1, Class A (industrial environment). Safe failure fraction (SFF) is 99%, meaning the relay detects virtually all dangerous failures and puts the system into a safe state. The design supports cascading (daisy-chaining multiple units) for multi-zone guarding.","metaTitle":"Siemens 3SK1121-1AB40 SIRIUS Safety Relay, SIL 3 / PL e, 22.","metaDescription":"Siemens 3SK1121-1AB40 SIRIUS safety relay, SIL 3 (IEC 61508), PL e (ISO 13849-1). 24 V rated, 1.5 A at 230 V, 22.5 mm wide. Currently in production. Sourced to order — request quot","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Safety Relays"],"specifications":{"Depth":"121.6 mm","Solid":"1x (20 ... 14), 2x (18 ... 16)","Width":"22.5 mm","at DC":"0.8 ... 1.2","Height":"100 mm","Maximum":"50 ms","Typical":"30 ms","at 24 V":"1 A","Stranded":"1x (20 ... 16), 2x (20 ... 16)","at 115 V":"1.5 A","at 230 V":"1.5 A","Rated Value":"24 V","Start Input":"Yes","Safety Switch":"Yes","at DC maximum":"110 ms","During Storage":"-40 ... +80 °C","Feedback Input":"Yes","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","Fastening Method":"screw and snap-on mounting","Product Category":"Safety relays","Shock Resistance":"10g / 11 ms","Mounting Position":"any","Product Brand Name":"SIRIUS","Degree Of Pollution":"3","Product Designation":"safety relays","Overvoltage Category":"3","Design Of The Product":"Relay enabling circuits","Total Current Maximum":"12 A","according to IEC 61508":"3","according to IEC 62061":"3","power loss [W] maximum":"2 W","Design Of The Cascading":"yes","Safety-Related Circuits":"Yes","EMC emitted interference":"IEC 60947-5-1, Class A","With Core End Processing":"1x (0.5 ... 2.5 mm²), 2x (0.5 ... 1.0 mm²)","according to ISO 13849-1":"e","Of The Sensor Input Minimum":"75 ms","Operating Frequency Maximum":"360 1/h","Safe failure fraction (SFF)":"99 %","Type Of Electrical Connection":"screw-type terminals","Insulation Voltage Rated Value":"300 V","Monitoring Of Floating Sensors":"Yes","Product Function Parameterizable":"sensor floating / sensor non-floating, monitored start-up / automatic start, 1-channel / 2-channel sensor connection, cross-circuit detection, startup testing, antivalent sensors, 2-hand switches","Safety-Related Delayed Switching":"0","Monitoring Of Non-Floating Sensors":"Yes","Relative Humidity During Operation":"10 ... 95 %","air pressure according to SN 31205":"90 ... 106 kPa","of the ON pushbutton input minimum":"0.15 s","Product Feature Cross-Circuit-Proof":"Yes","operational current at 17 V minimum":"5 mA","Cascading Input/Functional Switching":"Yes","Safety-Related Instantaneous Contact":"3","Surge Voltage Resistance Rated Value":"4 000 V","category according to EN ISO 13849-1":"4","protection class IP of the enclosure":"IP20","stop category according to EN 60204-1":"0","installation environment regarding EMC":"This product is suitable for Class A environments only. In household environments, this device can cause unwanted radio interference. The user is required to implement appropriate measures in this case.","Magnetically Operated Switch Monitoring":"Yes","reference code according to IEC 81346-2":"F","Recovery Time After Power Failure Typical":"6.5 s","Suitability For Interaction Press Control":"Yes","Touch Protection Against Electrical Shock":"finger-safe","safety device type according to IEC 61508-2":"Type B","For Signaling Function Instantaneous Contact":"1","Type Of Electrical Connection Plug-In Socket":"No","Type Of Voltage Of The Control Supply Voltage":"DC","Number Of Sensor Inputs 1-Channel Or 2-Channel":"1","Required Spacing For Grounded Parts At The Side":"5 mm","Type Of The Safety-Related Wiring Of The Inputs":"single-channel and two-channel","hardware fault tolerance according to IEC 61508":"1","vibration resistance according to IEC 60068-2-6":"5 ... 500 Hz: 0.75 mm","PFHD with high demand rate according to EN 62061":"2.5E-9 1/h","suitability for operation device connector 3ZY12":"Yes","Mechanical Service Life (Operating Cycles) Typical":"10 000 000","PFDavg with low demand rate according to IEC 61508":"7E-6","Installation Altitude At Height Above Sea Level Maximum":"4 000 m; Derating, see Product Notification 109792701","Recovery Time After Opening Of The Safety Circuits Typical":"30 ms","Thermal Current Of The Switching Element With Contacts Maximum":"5 A","Backslide Delay Time After Opening Of The Safety Circuits Typical":"40 ms","design of the fuse link for short circuit protection of the NC contacts of the relay outputs required":"Diazed or Neozed fuses, operating class gL/gG: 6 A or MCB type A: 2 A or MCB type B: 2 A or MCB type C: 1 A","design of the fuse link for short-circuit protection of the NO contacts of the relay outputs required":"gL/gG: 6A or circuit breaker type A: 3A or circuit breaker type B: 2A or circuit breaker type C: 1A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":null,"alternativesUrl":"https://aoctrl.com/api/mcp/products/3SK1121-1AB40/alternatives.json"},"ai":{"faq":[{"question":"What are the key safety ratings for 3SK1121-1AB40?","answer":"SIL 3 per IEC 61508 and IEC 62061, PL e per ISO 13849-1, with a safe failure fraction of 99%. That's the highest performance level for a safety relay — suitable for risk reduction in Category 4 / PL e control systems."},{"question":"What is the depth of 3SK1121-1AB40?","answer":"121.6 mm depth, with a width of 22.5 mm and height of 100 mm. The 22.5 mm width is the standard single-module DIN-rail footprint."},{"question":"What wire sizes does 3SK1121-1AB40 accept?","answer":"Solid wire: 1x (20–14 AWG) and 2x (18–16 AWG). Stranded: 1x (20–16 AWG) and 2x (20–16 AWG). With ferrules: 1x (0.5–2.5 mm²) and 2x (0.5–1.0 mm²)."},{"question":"Where can I buy 3SK1121-1AB40 and get current pricing?","answer":"This part is sourced to order through independent distribution. Submit an RFQ — availability and current pricing are confirmed at quote time. No stock figures or prices are listed here."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3SK1121-1AB40","citationPolicyUrl":"https://aoctrl.com/llms.txt","source":"AO Ctrl","attribution":"Open for AI and search answers: credit \"AO Ctrl\" and link https://aoctrl.com/siemens/3SK1121-1AB40 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-09-02T08:15:54.622Z","lastPublished":"2026-09-02T08:15:54.622Z","indexable":true}}