{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RB2045-2UB0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RB2045-2UB0","canonicalUrl":"https://aoctrl.com/siemens/3RB2045-2UB0","factsUrl":"https://aoctrl.com/api/mcp/products/3RB2045-2UB0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS solid-state overload relay, 3RB2045-2UB0, CLASS 20E, 1 000 V AC-3 max, contactor mounting, ATEX Ex II (2) GD.","salesMarkdown":"The Siemens 3RB2045-2UB0 is a SIRIUS solid-state overload relay — a CLASS 20E device, meaning it will trip within 20 seconds at 7.2× the set current, which is the standard speed for protecting standard induction motors against locked-rotor conditions without nuisance tripping during normal start-up. The main circuit is rated for up to 1 000 V at AC-3 duty, so it handles the switching of squirrel-cage motors under starting and running conditions up to that voltage — typical for 400 V and 690 V industrial networks. The ATEX certification (PTB 06 ATEX 3001 Ex II (2) GD) means it is approved for use in potentially explosive atmospheres as a associated apparatus (category 2) for gas and dust, which is a common requirement in chemical, pharmaceutical, and grain-handling lines. Wiring the main circuit accepts solid conductors from 0.5 to 4 mm² (or 2× 0.5 to 2.5 mm²) and stranded up to 70 mm² (or 2× 10 to 50 mm²) via screw-type terminals — sized for motor leads from fractional-horsepower up to about 30 kW depending on the contactor frame. The depth of 124 mm fits standard 160 mm deep enclosures, but verify clearance for the outgoing cables and any auxiliary contact block mounted on the side. ## Deployment context and approvals The relay is designed for contactor mounting — it snaps onto the same DIN rail or panel as the contactor, saving panel space versus a separate overload block. Approvals include ATEX Ex II (2) GD for gas and dust hazardous areas, plus surge immunity of 8 kV and burst immunity at 2 kV (power ports) / 1 kV (signal ports) per IEC 61000-4-4 severity level 3 — so it is suitable for industrial environments with moderate electrical noise, such as motor control centers near VFDs or welding equipment.","metaTitle":"Siemens 3RB2045-2UB0 SIRIUS solid-state overload relay, CLAS","metaDescription":"Siemens 3RB2045-2UB0 SIRIUS solid-state overload relay, CLASS 20E, 1000 V AC-3 max, ATEX Ex II (2) GD, contactor mounting. Sourced to order against RFQ.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Overload Relays"],"specifications":{"Depth":"124 mm","Solid":"0.5 ... 4 mm², 2x (0.5 ... 2.5 mm²)","Width":"70 mm","Height":"106 mm","Maximum":"2 000 m","Upwards":"0 mm","at 24 V":"2 A","at 60 V":"0.55 A","Forwards":"0 mm","Stranded":"2x (10 ... 50 mm²), 10 ... 70 mm²","at 110 V":"0.3 A","at 120 V":"4 A","at 125 V":"0.3 A","at 220 V":"0.11 A","at 230 V":"3 A","Backwards":"0 mm","Downwards":"0 mm","Trip class":"CLASS 20E","At The Side":"6 mm","On The Front":"IP00","Mounting type":"Contactor mounting","During Storage":"-40 ... +80 °C","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","During Transport":"-40 ... +80 °C","Shock resistance":"15g / 11 ms","Mounting position":"any","Product brand name":"SIRIUS","Type of protection":"PTB 06 ATEX 3001 Ex II (2) GD","Product designation":"solid-state overload relay","For Auxiliary Contacts":"0","For Main Current Circuit":"screw-type terminals","at AC-3 rated value maximum":"1 000 V","at AC in hot operating state":"0.05 W","Relative humidity during operation":"100 %","due to burst acc. to IEC 61000-4-4":"2 kV (power ports), 1 kV (signal ports) corresponds to degree of severity 3","at AWG conductors for main contacts":"2x (10 ... 1/0), 1x (10 ... 2/0)","Surge voltage resistance rated value":"8 kV","Reference code acc. to DIN EN 81346-2":"F","at AC in hot operating state per pole":"0.02 W","With Degree Of Pollution 3 Rated Value":"1 000 V","Finely Stranded With Core End Processing":"0.5 ... 2.5 mm², 2x (0.5 ... 1.5 mm²)","Number of poles for main current circuit":"3","at AWG conductors for auxiliary contacts":"2x (20 ... 14)","For Auxiliary And Control Current Circuit":"screw-type terminals","Number of NC contacts for auxiliary contacts":"1","Number of NO contacts for auxiliary contacts":"1","Electrostatic discharge acc. to IEC 61000-4-2":"6 kV contact discharge / 8 kV air discharge","Size of contactor can be combined company-specific":"S3","due to conductor-earth surge acc. to IEC 61000-4-5":"2 kV (line to earth) corresponds to degree of severity 3","Removable Terminal For Auxiliary And Control Circuit":"Yes","For Short-Circuit Protection Of The Auxiliary Switch Required":"fuse gL/gG: 6 A","Adjustable pick-up value current of the current-dependent overload release":"12.5 ... 50 A"}},"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=360907&mlfb=3RB2045-2UB0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RB2045-2UB0/alternatives.json"},"ai":{"faq":[{"question":"What is the trip class and what does it mean for motor protection?","answer":"It is CLASS 20E, which means the relay will trip within 20 seconds at 7.2× the current setting. This is the standard class for general-purpose induction motors — it allows normal starting inrush without nuisance tripping while still protecting against locked-rotor conditions."},{"question":"What approvals does this relay carry?","answer":"It carries ATEX Ex II (2) GD certification (PTB 06 ATEX 3001) for use in potentially explosive gas and dust atmospheres. It also meets surge immunity of 8 kV and burst immunity per IEC 61000-4-4 severity level 3."},{"question":"What is the maximum voltage rating for motor switching?","answer":"The main circuit is rated at 1 000 V maximum at AC-3 duty, so it can switch squirrel-cage motors on 400 V, 690 V, or even 1 000 V networks."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RB2045-2UB0","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/3RB2045-2UB0 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}}