{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RT1045-1BG40","brand":"Siemens","brandSlug":"siemens","productSlug":"3RT1045-1BG40","canonicalUrl":"https://aoctrl.com/siemens/3RT1045-1BG40","factsUrl":"https://aoctrl.com/api/mcp/products/3RT1045-1BG40","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS power contactor, order code 3RT1045-1BG40, S3 size, screw-type terminals, AC-4 rated 66 A at 400 V, AC-2 rated 37 kW at 400 V, DIN-rail and screw mounting.","salesMarkdown":"## What This Contactor Does and Where It Fits It mounts on standard 35 mm or 75 mm DIN rail using the screw-and-snap-on fastening method, or can be screw-mounted directly to a backplate. The main current circuit uses screw-type terminals, which is the standard termination for panel builders who prefer secure, serviceable connections over spring-clamp. Solid wire capacity goes up to 2x (0.75... 4 mm²) maximum, and stranded accepts 2x (10... 50 mm²), so it handles the heavier power feeds typical of an S3 contactor. That 66 A figure tells you the contactor can handle the electrical wear of frequent plugging or jogging without welding contacts. For standard motor starting (AC-3), this contactor switches up to 45 kW at 500 V and 21.1 kW at 690 V, covering the bulk of three-phase induction motors in the 30-60 hp range depending on line voltage. The AC-2 rating of 37 kW at 400 V covers slip-ring motor duty where the rotor circuit is switched. Mechanical life is typical at 10 million operations, and the AC-3 switching rate maxes at 1,000 cycles per hour — fast enough for most conveyor or pump cycling, but not for high-speed pick-and-place. The AC-4 rate drops to 300 cycles per hour, reflecting the heavier arc wear in that duty. ## Environmental Fit and Protection RoHS compliance is documented with a substance prohibition date of May 1, 2012, so it meets the EU directive for lead and other restricted substances. No special compliance documentation beyond the standard declaration is needed for most industrial installations. Dimensions are 70 mm wide, 146 mm high, and 152 mm deep — a compact S3 footprint that fits alongside other SIRIUS components on the same DIN rail. The auxiliary contact block options (not included with this base unit) share the same coil suppression as the main contactor. If you're adding aux contacts downstream, verify free-wheel diode polarity before energizing inductive loads — standard practice for any DC-suppressed coil circuit.","metaTitle":"Siemens 3RT1045-1BG40 SIRIUS Power Contactor, S3 Size, 66 A","metaDescription":"Siemens 3RT1045-1BG40 SIRIUS power contactor, S3 size. AC-4 rated 66 A at 400 V, AC-2 rated 37 kW. Screw terminals, DIN-rail mount. Active production.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Contactors"],"specifications":{"Depth":"152 mm","Solid":"2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²), max. 2x (0.75 ... 4 mm²)","Width":"70 mm","at DC":"14 ... 20 ms","Height":"146 mm","Stranded":"2x (10 ... 50 mm²)","Arcing Time":"10 ... 15 ms","Rated Value":"125 V","On The Front":"IP20; IP20 on the front with cover / box terminal","Initial Value":"0.8","During Storage":"-55 ... +80 °C","Of The Terminal":"IP00","at AC-1 maximum":"900 1/h","at AC-2 maximum":"400 1/h","at AC-3 maximum":"1 000 1/h","at AC-4 maximum":"300 1/h","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","Fastening Method":"screw and snap-on mounting onto 35 mm and 75 mm standard mounting rail","Full-Scale Value":"1.1","Size Of Contactor":"S3","Solid Or Stranded":"2x (2.5 ... 16 mm²)","Product Brand Name":"SIRIUS","Degree Of Pollution":"3","Product Designation":"power contactor","at 24 V rated value":"10 A","at 60 V rated value":"2 A","Of Contactor Typical":"10 000 000","at 110 V rated value":"1 A","at 220 V rated value":"0.3 A","at 230 V rated value":"6 A","at 400 V rated value":"3 A","at 500 V rated value":"45 kW","at 690 V rated value":"21.1 kW","Side-By-Side Mounting":"Yes","at 1000 V rated value":"37 W","For Main Current Circuit":"screw-type terminals","at AC-2 at 400 V rated value":"37 kW","at AC-4 at 400 V rated value":"66 A","Substance Prohibitance (Date)":"05/01/2012","at 40 °C minimum permissible":"50 mm²","at 60 °C minimum permissible":"35 mm²","Insulation Voltage Rated Value":"1 000 V","at 230 V at 60 °C rated value":"38 kW","at 690 V at 60 °C rated value":"114 kW","at 1000 V at 60 °C rated value":"82 W","at AWG cables for main contacts":"2x (10 ... 1/0)","For Auxiliary And Control Circuit":"screw-type terminals","With Type Of Assignment 2 Required":"fuse gL/gG: 160 A","closing power of magnet coil at DC":"15 W","holding power of magnet coil at DC":"15 W","Surge Voltage Resistance Rated Value":"6 kV","With Type Of Coordination 1 Required":"fuse gL/gG: 250 A","at AWG cables for auxiliary contacts":"2x (20 ... 16), 2x (18 ... 14), 1x 12","operational current at AC-12 maximum":"10 A","number of NC contacts for main contacts":"0","number of NO contacts for main contacts":"3","reference code according to IEC 81346-2":"Q","Finely Stranded With Core End Processing":"2x (0.5 ... 1.5 mm²), 2x (0.75 ... 2.5 mm²)","Number Of Poles For Main Current Circuit":"3","Contact Reliability Of Auxiliary Contacts":"1 faulty switching per 100 million (17 V, 1 mA)","Thermal Short-Time Current Limited To 10 S":"760 A","Finely Stranded Without Core End Processing":"2x (10 ... 35 mm²)","Type Of Voltage Of The Control Supply Voltage":"DC","Required Spacing For Grounded Parts At The Side":"6 mm","contact rating of auxiliary contacts according to UL":"A600 / Q600","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","Of The Contactor With Added Auxiliary Switch Block Typical":"10 000 000","For Short-Circuit Protection Of The Auxiliary Switch Required":"fuse gL/gG: 10 A","number of NC contacts for auxiliary contacts instantaneous contact":"0","number of NO contacts for auxiliary contacts instantaneous contact":"0","Of The Contactor With Added Electronically Optimized Auxiliary Switch Block Typical":"5 000 000"}},"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=444373&mlfb=3RT1045-1BG40","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RT1045-1BG40/alternatives.json"},"ai":{"faq":[{"question":"What are the key power ratings for this contactor?","answer":"AC-4 rated at 66 A at 400 V for reversing/inching duty. AC-3 rated at 45 kW at 500 V and 21.1 kW at 690 V for standard motor starting. AC-2 rated at 37 kW at 400 V for slip-ring motor duty."},{"question":"What wire sizes does the screw terminal accept?","answer":"Solid wire: 2x (0.5... 1.5 mm²), 2x (0.75... 2.5 mm²), max. 2x (0.75... 4 mm²). Stranded: 2x (10... 50 mm²). The main circuit uses screw-type terminals."},{"question":"Does this contactor mount on standard DIN rail?","answer":"Yes, it mounts on both 35 mm and 75 mm standard mounting rail using the screw-and-snap-on method. It can also be screw-mounted directly to a panel backplate."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RT1045-1BG40","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/3RT1045-1BG40 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}}