{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RA2120-4CE27-0BB4","brand":"Siemens","brandSlug":"siemens","productSlug":"3RA2120-4CE27-0BB4","canonicalUrl":"https://aoctrl.com/siemens/3RA2120-4CE27-0BB4","factsUrl":"https://aoctrl.com/api/mcp/products/3RA2120-4CE27-0BB4","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RA2120-4CE27-0BB4 direct-on-line motor starter, S0 size, 22 A AC-3 at 400 V, 690 V max, Class 10, spring-loaded terminals, screw and snap-on 35 mm DIN rail mounting.","salesMarkdown":"## 22 A AC-3 at 400 V — the motor-starting rating that decides fit The 3RA2120-4CE27-0BB4: That 22 A figure is the motor full-load current it can switch under IEC AC-3 duty — the standard for squirrel-cage motors during starting and plugging. For a 400 V three-phase motor, this covers loads up to roughly 11 kW (15 hp), though the exact horsepower depends on the service factor and local code. The S0 frame size keeps the footprint compact: 45 mm wide, 243 mm tall, 107 mm deep. ## Spring terminals and pre-assembled contactor — fewer line items on the BOM The main circuit uses spring-loaded terminals — no screw torque to verify, no loose strands. The supplied contactor is a 3RT2027-2BB40, and the link module is 3RA2921-2AA00, so this is a factory-assembled starter that ships as one order code. That collapses three BOM line items into one, which simplifies procurement and reduces the cost per PO for tail-spend categories. The clearance requirements are: 50 mm above, 20 mm in front, 10 mm below, 20 mm at the sides. That 0 mm rear clearance means it can sit flush against the back panel — useful when gland-plate depth is tight.","metaTitle":"Siemens 3RA2120-4CE27-0BB4 SIRIUS Motor Starter, 22 A AC-3","metaDescription":"Siemens 3RA2120-4CE27-0BB4 SIRIUS direct-on-line motor starter, 22 A at AC-3 400 V, 690 V max, Class 10, S0 size, spring terminals, DIN rail.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Motor Starters"],"specifications":{"Depth":"107 mm","Width":"45 mm","Height":"243 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","During Storage":"-50 ... +80 °C","lifecycle_stage":"current","During Operation":"-20 ... +60 °C","During Transport":"-50 ... +80 °C","Fastening Method":"screw and snap-on mounting onto 35 mm DIN rail","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 230 V rated value":"3 hp","at 400 V rated value":"11 000 kW","at 480 V rated value":"22 A","at 600 V rated value":"22 A","Design Of The Product":"for standard rail or screw mounting","For Main Current Circuit":"spring-loaded terminals","Temperature Compensation":"-20 ... +60 °C","at 110/120 V rated value":"1.5 hp","at 200/208 V rated value":"7.5 hp","at 220/230 V rated value":"7.5 hp","at 460/480 V rated value":"15 hp","Of The Supplied Contactor":"3RT2027-2BB40","Of The Supplied Link Module":"3RA2921-2AA00","Size Of The Circuit-Breaker":"S0","at AC-3 rated value maximum":"690 V","at AC-3 at 400 V rated value":"22 A","at AC-3e rated value maximum":"690 V","Substance Prohibitance (Date)":"10/01/2009","at AC-3e at 400 V rated value":"22 A","Design Of The Overload Release":"thermal (bimetallic)","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":"3RV2021-4CA20","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 %","Without Load Current Share Typical":"5.9 W","holding power of magnet coil at DC":"5.9 W","Surge Voltage Resistance Rated Value":"6 kV","at AC in hot operating state per pole":"5.8 W","Number Of Poles For Main Current Circuit":"3","Product Function Short Circuit Protection":"Yes","protocol is supported AS-Interface protocol":"No","with high demand rate according to SN 31920":"73 %","reference code according to IEC 81346-2:2019":"Q","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","Mechanical Service Life (Operating Cycles) Of Contactor Typical":"10 000 000","Response Value Current Of Instantaneous Short-Circuit Trip Unit":"286 A","insulation voltage with degree of pollution 3 at AC rated value":"690 V","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"16 ... 22 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/7c64d9631b4c1692f56ff0944f45be29.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=171094&mlfb=3RA2120-4CE27-0BB4","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RA2120-4CE27-0BB4/alternatives.json"},"ai":{"faq":[{"question":"What is the AC-3 current rating of 3RA2120-4CE27-0BB4?","answer":"The AC-3 rated current at 400 V is 22 A, with a maximum AC-3 voltage of 690 V. This is the motor full-load current it can switch under IEC AC-3 duty — the spec that determines motor starter fit for standard induction motors."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RA2120-4CE27-0BB4","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/3RA2120-4CE27-0BB4 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}}