{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RA2125-4AH26-0FB4","brand":"Siemens","brandSlug":"siemens","productSlug":"3RA2125-4AH26-0FB4","canonicalUrl":"https://aoctrl.com/siemens/3RA2125-4AH26-0FB4","factsUrl":"https://aoctrl.com/api/mcp/products/3RA2125-4AH26-0FB4","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RA2125-4AH26-0FB4 direct-on-line motor starter, size S0, 7.5 kW at 400 V AC-3, Class 10 thermal overload, snap-on 60 mm busbar system, spring-loaded terminals.","salesMarkdown":"## What this SIRIUS direct starter delivers The 3RA2125-4AH26-0FB4 is a Siemens SIRIUS direct-on-line starter — a pre-assembled combination of a contactor, thermal overload relay, and circuit-breaker in one S0 frame, designed to snap onto 60 mm busbar systems. The thermal overload is bimetallic, Trip Class 10 — it protects motors with normal acceleration times (up to 10 seconds at locked-rotor current) without nuisance tripping on startup. ## Mounting and wiring — busbar snap-on with spring terminals Mounts by snapping onto 60 mm busbar systems in a vertical orientation — no DIN rail required, which saves panel width and simplifies busbar tap-offs in distribution-style builds. Main power and auxiliary/control circuits both use spring-loaded terminals — no screw torque checking, faster wiring, and vibration-resistant terminations. Dimensions are 165 mm deep, 45 mm wide, 260 mm tall — the 45 mm width (roughly 2.5 standard modular units) fits tightly spaced busbar layouts. Clearance requirements: 50 mm upwards, 20 mm forwards, 10 mm downwards, 20 mm at the side — plan these into the enclosure layout for airflow and access. ## Supplied sub-assemblies — what comes in the package The starter ships as a complete unit with the contactor (3RT2026-2FB40), link module (3RA2921-2AA00), circuit-breaker (3RV2021-4AA25), and busbar adapter (8US1251-5NT11) already assembled and tested. The circuit-breaker provides magnetic short-circuit protection coordinated with the contactor and overload — no separate fuse or MCCB needed upstream for the motor branch. An auxiliary switch can be added via the product extension slot — the frame accepts one without additional wiring modifications. ## Environmental limits and operating conditions Storage and transport range is -50 °C to +80 °C — wide enough for unheated warehouses or container shipping in most climates. Rated for 50/60 Hz supply and relative humidity 10 to 95 % during operation — suitable for indoor industrial environments without condensation control.","metaTitle":"Siemens 3RA2125-4AH26-0FB4 SIRIUS Direct Starter","metaDescription":"Siemens 3RA2125-4AH26-0FB4 SIRIUS direct-on-line starter, 7.5 kW at 400 V AC-3, Class 10, snap-on 60 mm busbar. Current production — quoted to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Motor Starters"],"specifications":{"Depth":"165 mm","Width":"45 mm","title":"3RA2125-4AH26-0FB4","Height":"260 mm","Upwards":"50 mm","Forwards":"20 mm","Backwards":"0 mm","Downwards":"10 mm","Trip Class":"CLASS 10","At The Side":"20 mm","Rated Value":"24 ... 24 V","description":"Load feeder fuseless, Direct-on-line starting 400 V AC, Size S0 10.0...16.0 A 24 V DC Spring-type terminal for 60 mm busbar systems (also fulfills type of coordination 1) Type of coordination 2, Iq = 150 kA 1 NO+1 NC (contactor) with diode combination plugged in at the front","During Storage":"-50 ... +80 °C","lifecycle_stage":"current","During Operation":"-20 ... +60 °C","During Transport":"-50 ... +80 °C","Fastening Method":"for snapping onto 60 mm busbar systems","Mounting Position":"vertical","PROFIsafe protocol":"No","Product Brand Name":"SIRIUS","Type Of Assignment":"2","Product Designation":"Direct (on-line) starter","Size Of Load Feeder":"S0","PROFINET IO protocol":"No","at 400 V rated value":"7 500 W","Design Of The Product":"for 60 mm busbars","For Main Current Circuit":"spring-loaded terminals","Temperature Compensation":"-20 ... +60 °C","Of The Supplied Contactor":"3RT2026-2FB40","Of The Supplied Link Module":"3RA2921-2AA00","Size Of The Circuit-Breaker":"S0","at AC-3 rated value maximum":"690 V","Design Of The Overload Release":"thermal (bimetallic)","Of The Supplied Busbar Adapter":"8US1251-5NT11","Design Of The Switching Contact":"electromechanical","Operating Frequency Rated Value":"50 ... 60 Hz","Design Of The Short-Circuit Trip":"magnetic","Of The Supplied Circuit-Breakers":"3RV2021-4AA25","degree of protection NEMA rating":"other","For Auxiliary And Control Circuit":"spring-loaded terminals","Product Extension Auxiliary Switch":"Yes","Relative Humidity During Operation":"10 ... 95 %","Surge Voltage Resistance Rated Value":"6 kV","Number Of Poles For Main Current Circuit":"3","Product Function Short Circuit Protection":"Yes","protocol is supported AS-Interface protocol":"No","number of NC contacts for auxiliary contacts":"1","number of NO contacts for auxiliary contacts":"1","shock resistance according to IEC 60068-2-27":"6g / 11 ms","Type Of Voltage Of The Control Supply Voltage":"DC","at 400 V according to IEC 60947-4-1 rated value":"150 000 A","operational current at AC-3 at 400 V rated value":"15.5 A","Mechanical Service Life (Switching Cycles) Of Contactor Typical":"10 000 000","insulation voltage with degree of pollution 3 at AC rated value":"690 V","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"10 ... 16 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/0167b7bdf93b63178b89acaa7b76046b.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=553840&mlfb=3RA2125-4AH26-0FB4"},"ai":{"faq":[{"question":"Does the 3RA2125-4AH26-0FB4 mount on a DIN rail or a busbar?","answer":"It snaps onto 60 mm busbar systems, not a standard DIN rail — the fastening method is specifically for busbar mounting in a vertical position."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RA2125-4AH26-0FB4","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/3RA2125-4AH26-0FB4 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-08-11T15:51:03.652Z","lastPublished":"2026-08-11T15:51:03.652Z","indexable":true}}