{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RB2123-4QD0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RB2123-4QD0","canonicalUrl":"https://aoctrl.com/siemens/3RB2123-4QD0","factsUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4QD0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS solid-state overload relay, 3RB2123-4QD0, contactor mounting, adjustable trip classes 5E/10E/20E/30E, ATEX Ex II (2) GD, IP20 front, 690 V AC-3 max.","salesMarkdown":"The Siemens SIRIUS 3RB2123-4QD0 is a solid-state overload relay designed for contactor mounting, protecting motor circuits against overload and phase failure. It offers adjustable trip classes 5E, 10E, 20E, and 30E, letting you match the thermal curve to the motor's starting profile — a 5E setting for fast-starting pumps, 30E for high-inertia loads like centrifuges. The solid-state design means no heating elements to drift — the trip current stays consistent over the -25 to +60 °C operating range, and the relay draws negligible power (0.05 W per pole at rated current). Mounts directly onto a contactor (contactor mounting), saving DIN-rail space in a crowded panel. The front face is IP20 — finger-safe for the enclosure interior — and the housing is 45 mm wide, 73 mm tall, 75 mm deep, which fits standard 45 mm modular spacing. Main circuit terminals accept screw-type connections for 2x (0.25... 1.5 mm²) solid or 2x (14... 10 AWG) stranded — sized for control wiring, not power tails. The auxiliary contact block is not included (0 auxiliary contacts), so plan for a separate contactor auxiliary if you need a status signal back to the PLC. This class of solid-state overload relay is used in motor control centers and individual starter enclosures to protect three-phase induction motors from sustained overcurrent. The ATEX certification (PTB 06 ATEX 3001 Ex II (2) GD) means it can be installed in the safe area feeding motors in Zone 1 or 2 gas or dust hazardous locations — a common requirement in chemical, oil & gas, and grain-handling lines.","metaTitle":"Siemens SIRIUS 3RB2123-4QD0 solid-state overload relay, adju","metaDescription":"Siemens SIRIUS 3RB2123-4QD0 solid-state overload relay, contactor mounting, adjustable trip classes 5E/10E/20E/30E, ATEX Ex II (2) GD, IP20 front, 690 V AC-3 max. Active production","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Overload Relays"],"specifications":{"Depth":"75 mm","Solid":"2x (0.25 ... 1.5 mm²)","Width":"45 mm","Height":"73 mm","Maximum":"2 000 m","Upwards":"0 mm","at 24 V":"2 A","at 60 V":"0.55 A","Forwards":"0 mm","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 5E, 10E, 20E and 30E adjustable","At The Side":"6 mm","On The Front":"IP20","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":"690 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 (14 ... 10)","Surge voltage resistance rated value":"6 kV","Reference code acc. to DIN EN 81346-2":"F","at AC in hot operating state per pole":"0.02 W","Finely Stranded With Core End Processing":"2x (0.25 ... 1.5 mm²)","Number of poles for main current circuit":"3","at AWG conductors for auxiliary contacts":"2x (24 ... 16)","For Auxiliary And Control Current Circuit":"spring-loaded terminals","Number of NC contacts for auxiliary contacts":"1","Number of NO contacts for auxiliary contacts":"1","with degree of pollution 3 at AC rated value":"690 V","Electrostatic discharge acc. to IEC 61000-4-2":"6 kV contact discharge / 8 kV air discharge","Size of contactor can be combined company-specific":"S0","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":"6 ... 25 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=316243&mlfb=3RB2123-4QD0","alternativesUrl":"https://aoctrl.com/api/mcp/products/3RB2123-4QD0/alternatives.json"},"ai":{"faq":[{"question":"What compliance documentation does this relay carry?","answer":"It carries ATEX certification PTB 06 ATEX 3001 Ex II (2) GD for gas and dust hazardous-area motor protection. EMC burst immunity is rated at 2 kV on power ports and 1 kV on signal ports per IEC 61000-4-4, severity level 3. The surge voltage resistance is 6 kV."},{"question":"Will 3RB2123-4QD0 drop into a panel specified around a 3RT1015-1BB42 contactor?","answer":"The 3RB2123-4QD0 is designed for contactor mounting, and the 3RT1015 series is a common SIRIUS contactor family. The 45 mm width matches the standard 45 mm contactor footprint, so it will mount directly without rewiring the main circuit — but verify the auxiliary contact count (0 on this relay) against your control scheme."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RB2123-4QD0","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/3RB2123-4QD0 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}}