{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RT1944-5AC21","brand":"Siemens","brandSlug":"siemens","productSlug":"3RT1944-5AC21","canonicalUrl":"https://aoctrl.com/siemens/3RT1944-5AC21","factsUrl":"https://aoctrl.com/api/mcp/products/3RT1944-5AC21","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS magnet coil, 3RT1944-5AC21, 24 V AC 50/60 Hz, screw terminal, Size S3.","salesMarkdown":"The Siemens 3RT1944-5AC21 is a SIRIUS magnet coil designed for Size S3 contactors. The coil draws an inrush current of 0.8 to 1.1 A at 50 Hz, which is the peak current the control transformer or PLC output must handle during pickup. The 0.8 to 1.1 A at 50 Hz is the inrush (closing) current, not the holding current. The holding draw is significantly lower — the coil's apparent holding power is around 12.5 VA on the S2-size sibling (3RT1036-1AB00), and the S3 coil here will be similar. This matters when sizing the control transformer: the inrush pulse is brief but must not drop the supply voltage below the coil dropout threshold (typically 18 V AC for a 24 V nominal coil). The coil mounts on a Size S3 contactor via screw terminals. When replacing a failed coil in an existing panel, confirm the contactor frame size — the 3RT1944-5AC21 fits only S3 frames, not S0 or S2. The screw terminal accepts 2x (0.5 to 1.5 mm²) solid or stranded, or 2x (0.75 to 2.5 mm²) with ferrule.","metaTitle":"Siemens 3RT1944-5AC21 SIRIUS Magnet Coil, 24 V AC, 50/60 Hz","metaDescription":"Siemens 3RT1944-5AC21 SIRIUS magnet coil for Size S3 contactors. 24 V AC, 50/60 Hz, screw terminal. Phased-out product; successor is SIRIUS 3RT2 series. Sourced to order.","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":"24 V","at 60 Hz rated value":"24 V","Type Of Voltage Of The Control Supply Voltage":"AC"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=333648&mlfb=3RT1944-5AC21","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RT1944-5AC21/alternatives.json"},"ai":{"faq":[{"question":"What replaces the 3RT1944-5AC21?","answer":"The SIRIUS 3RT2 series is the direct successor. The specific replacement order code depends on the contactor frame size and control voltage. For a 24 V AC coil on an S3 frame, the 3RT2 equivalent is the form-fit-function swap."},{"question":"Will the 3RT1944-5AC21 drop into a panel wired for the 3RT7037-1AC20?","answer":"No — the 3RT7037-1AC20 is a Size S2 coil. The 3RT1944-5AC21 is Size S3. The mounting hole pattern and terminal spacing differ. The S3 coil is physically larger (115 mm depth vs 91 mm) and will not fit an S2 contactor frame."},{"question":"What is the inrush current of this coil?","answer":"At 50 Hz the inrush current is 0.8 to 1.1 A. This is the peak draw during pickup; the holding current is substantially lower."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RT1944-5AC21","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/3RT1944-5AC21 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}}