{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RT1945-5AH21","brand":"Siemens","brandSlug":"siemens","productSlug":"3RT1945-5AH21","canonicalUrl":"https://aoctrl.com/siemens/3RT1945-5AH21","factsUrl":"https://aoctrl.com/api/mcp/products/3RT1945-5AH21","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RT1945-5AH21 magnet coil, Size S3, screw terminal, 48 V AC, 50/60 Hz, phased-out product with successor SIRIUS 3RT2.","salesMarkdown":"The Siemens SIRIUS 3RT1945-5AH21 is a magnet coil for Size S3 contactors in the SIRIUS family. It provides the electromagnetic actuation for the contactor's main and auxiliary contacts, converting electrical control signals into mechanical switching action. The coil is rated for 48 V AC at both 50 Hz and 60 Hz, drawing 0.8 to 1.1 A at 50 Hz. It terminates via screw terminals, matching the standard wiring practice for panel-mounted contactor assemblies. This part is a phased-out product. The manufacturer lists its lifecycle stage as current, but the description explicitly marks it as phased-out with the successor being the SIRIUS 3RT2 series. The official successor is the SIRIUS 3RT2 family, but a direct drop-in replacement for the 3RT1945-5AH21's specific mounting and coil voltage should be verified against the 3RT2 catalog. ## Integration into a SIRIUS contactor panel This coil mounts onto a Size S3 SIRIUS contactor frame. The screw terminals accept the control wiring from the PLC or control relay. When replacing a failed coil on an existing S3 contactor, the 3RT1945-5AH21 is the direct service part. For new builds or panel retrofits, the 3RT2 successor series should be evaluated for form, fit, and function compatibility.","metaTitle":"Siemens 3RT1945-5AH21 SIRIUS Magnet Coil, 48 V AC, 50/60 Hz","metaDescription":"Siemens SIRIUS 3RT1945-5AH21 magnet coil for Size S3 contactors. 48 V AC, 50/60 Hz, screw terminal. Phased-out; successor is SIRIUS 3RT2. Sourced to order against RFQ.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Contactors"],"specifications":{"at 50 Hz":"0.8 ... 1.1","lifecycle_stage":"current","Product Brand Name":"SIRIUS","Product Designation":"Magnet coil","at 50 Hz rated value":"48 V","at 60 Hz rated value":"48 V","Type Of Voltage Of The Control Supply Voltage":"AC"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$61.72","priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=166495&mlfb=3RT1945-5AH21","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RT1945-5AH21/alternatives.json"},"ai":{"faq":[{"question":"What is the 3RT1945-5AH21's rated voltage and current?","answer":"The coil is rated for 48 V AC at both 50 Hz and 60 Hz. At 50 Hz, it draws between 0.8 and 1.1 A. The control supply voltage type is AC."},{"question":"What replaces the 3RT1945-5AH21?","answer":"The manufacturer lists the SIRIUS 3RT2 series as the successor. Verify the specific 3RT2 order code for Size S3 with a 48 V AC coil before ordering for a retrofit."},{"question":"Where can I buy the 3RT1945-5AH21?","answer":"This part is sourced and quoted to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RT1945-5AH21","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/3RT1945-5AH21 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}}