{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RB3123-4SB0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RB3123-4SB0","canonicalUrl":"https://aoctrl.com/siemens/3RB3123-4SB0","factsUrl":"https://aoctrl.com/api/mcp/products/3RB3123-4SB0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RB3123-4SB0 solid-state overload relay, size S0, 12 A thermal current, 690 V rated, adjustable trip class 5E/10E/20E/30E, screw terminals, contactor mounting.","salesMarkdown":"## S0 form factor, contactor-mount, adjustable trip class The Siemens 3RB3123-4SB0 is a SIRIUS solid-state overload relay in the S0 size class, measuring 45 mm wide, 87 mm high, and 84 mm deep — a footprint that fits standard S0 contactor mounting rails without extra DIN-rail hardware. Its key differentiator is the adjustable trip class: selectable between CLASS 5E, 10E, 20E, and 30E, which lets the same relay cover both fast-acting protection for short-time rated motors and slower curves for high-inertia loads that need longer acceleration without nuisance tripping. ## Thermal rating and motor current setting window Rated thermal current is 12 A at 690 V, with the same 12 A rating at 480 V and 600 V — no derating across common industrial voltage levels up to 690 V. The overload detection logic triggers when motor current exceeds the upper current setting value multiplied by 3.5, and resets when current drops below the lower setting value — this 3.5× threshold means the relay tolerates startup inrush without false trips as long as the motor stays within the setting range. Power dissipation is 0.2 W per pole, which keeps the heat load low inside a crowded panel — at 12 A continuous, three poles dissipate 0.6 W total, negligible for enclosure thermal budgeting. ## Auxiliary contact ratings across control voltages The signaling contact (97/98) is rated 2 A at 24 V, 4 A at 120 V, and 3 A at 230 V — these are the current-carrying limits for the tripped-indication circuit feeding a PLC input or alarm lamp. At 60 V the contact handles 0.55 A, at 110 V and 125 V it handles 0.3 A, and at 220 V it handles 0.11 A — the contact rating follows a clear inverse voltage-current curve, so for 24 VDC control circuits the full 2 A is available, while higher-voltage DC circuits must be derated accordingly. ## Environmental endurance and vibration resistance Shock resistance is 15g for 11 ms on the main body, with the signaling contact derated to 9g for 11 ms in the tripped position — this matters for mounting on a contactor that sees repetitive shock from switching large loads. Vibration resistance spans 1-6 Hz at 15 mm amplitude and 6-500 Hz at 20 m/s² for 10 cycles, which covers the typical spectrum found on motor control center panels near large rotating equipment. ## Termination and wiring capacity The control circuit accepts up to 2x 10 mm² stranded wire for the larger auxiliary connections, with a Pozidriv PZ 2 screwdriver tip specified — the 5 to 6 mm shaft diameter means a standard electrician's screwdriver fits without adapters.","metaTitle":"Siemens 3RB3123-4SB0 SIRIUS solid-state overload relay, S0","metaDescription":"Siemens 3RB3123-4SB0 SIRIUS solid-state overload relay, size S0, 12 A thermal current, 690 V rated, adjustable trip classes 5E/10E/20E/30E. Active production.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Overload Relays"],"specifications":{"Note":"for message \"tripped\"","Depth":"84 mm","Solid":"1x (0.5 ... 4 mm²), 2x (0.5 ... 2.5 mm²)","Width":"45 mm","title":"3RB3123-4SB0","Height":"87 mm","Maximum":"IMotor < upper current setting value x 3.5","Minimum":"IMotor > lower current setting value","at 24 V":"2 A","at 60 V":"0.55 A","Per Pole":"0.2 W","Stranded":"2x 10 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","Trip Class":"CLASS 5E, 10E, 20E and 30E adjustable","Rated Value":"690 V","description":"Overload relay 3...12 A Electronic For motor protection Size S0, Class 5...30 Contactor mounting Main circuit: Screw Auxiliary circuit: Screw Manual-Automatic-Reset Internal ground fault detection","During Storage":"-40 ... +80 °C","Thermal Current":"12 A","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","During Transport":"-40 ... +80 °C","Fastening Method":"Contactor mounting","Shock Resistance":"15g / 11 ms","For Main Contacts":"M4","Mounting Position":"any","Solid Or Stranded":"1x (0,5 ... 4 mm²), 2x (0,5 ... 2,5 mm²)","Product Brand Name":"SIRIUS","Product Designation":"solid-state overload relay","Vibration Resistance":"1-6 Hz, 15 mm; 6-500 Hz, 20 m/s²; 10 cycles","at 480 V rated value":"12 A","at 600 V rated value":"12 A","Size Of Overload Relay":"S0","For Main Current Circuit":"screw-type terminals","Temperature Compensation":"-25 ... +60 °C","Design Of Screwdriver Shaft":"Diameter 5 to 6 mm","Size Of The Screwdriver Tip":"Pozidriv PZ 2","according to IEC 60068-2-27":"15g / 11 ms; Signaling contact 97 / 98 in position \"Tripped\": 9g / 11 ms","at AC-3e rated value maximum":"690 V","Substance Prohibitance (Date)":"10/01/2009","Design Of The Auxiliary Switch":"integrated","Design Of The Overload Release":"electronic","Operating Frequency Rated Value":"50 ... 60 Hz","Operational Current Rated Value":"12 A","for AC motors at 500 V at 50 Hz":"1.5 ... 5.5 kW","for AC motors at 690 V at 50 Hz":"2.2 ... 7.5 kW","for remote-reset function at DC":"24 V","For Auxiliary And Control Circuit":"screw-type terminals","Between Main And Auxiliary Circuit":"690 V","Relative Humidity During Operation":"10 ... 95 %","With Type Of Assignment 2 Required":"gG: 50 A, J: 45 A","Display Version For Switching Status":"Slide switch","Surge Voltage Resistance Rated Value":"6 kV","With Type Of Coordination 1 Required":"gG: 63 A, RK5: 45 A","at AWG cables for auxiliary contacts":"1x (20 ... 14), 2x (20 ... 14)","for 3-phase motors at 400 V at 50 Hz":"1.5 ... 5.5 kW","Of The Auxiliary And Control Contacts":"M3","Between Auxiliary And Auxiliary Circuit":"300 V","due to burst according to IEC 61000-4-4":"2 kV (power ports), 1 kV (signal ports) corresponds to degree of severity 3","reference code according to IEC 81346-2":"F","Finely Stranded With Core End Processing":"1x (0.5 ... 2.5 mm²), 2x (0.5 ... 1.5 mm²)","Number Of Poles For Main Current Circuit":"3","For Main Contacts With Screw-Type Terminals":"2 ... 2.5 N·m","number of CO contacts for auxiliary contacts":"0","number of NC contacts for auxiliary contacts":"1","number of NO contacts for auxiliary contacts":"1","For Auxiliary Contacts With Screw-Type Terminals":"0.8 ... 1.2 N·m","operational current at AC-3e at 400 V rated value":"12 A","Size Of Contactor Can Be Combined Company-Specific":"S0","electrostatic discharge according to IEC 61000-4-2":"6 kV contact discharge / 8 kV air discharge","Type Of Voltage Supply Via Input/Output Link Master":"No","contact rating of auxiliary contacts according to UL":"B600 / R300","Installation Altitude At Height Above Sea Level Maximum":"2 000 m","Response Time Of The Grounding Protection In Settled State":"1 000 ms","Response Value Current Of The Grounding Protection Minimum":"0.75 x IMotor","Arrangement Of Electrical Connectors For Main Current Circuit":"Top and bottom","For Short-Circuit Protection Of The Auxiliary Switch Required":"fuse gG: 6 A","insulation voltage with degree of pollution 3 at AC rated value":"690 V","Product Component Removable Terminal For Auxiliary And Control Circuit":"Yes","power loss [W] for rated value of the current at AC in hot operating state":"0.6 W","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"3 ... 12 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$402.54","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/653a168a3972ac8f7e1cd9648031e24f.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=376813&mlfb=3RB3123-4SB0"},"ai":{"faq":[{"question":"What does the note 'for message tripped' mean on this overload relay?","answer":"The note indicates that the signaling contact (terminals 97/98) changes state when the relay trips from an overload condition — it is a dry-contact output that can drive a PLC input, alarm, or status lamp to indicate the motor has been disconnected by the overload protection."},{"question":"What trip classes are available on the 3RB3123-4SB0?","answer":"The trip class is adjustable to CLASS 5E, 10E, 20E, or 30E — selectable via a dial on the relay face, letting you match the protection curve to the motor's acceleration time without stocking multiple fixed-class relays."},{"question":"Will the 3RB3123-4SB0 fit a panel designed for a 3RV2021-1GA15?","answer":"No — the 3RB3123-4SB0 is a solid-state overload relay in size S0 (45 mm wide) designed to mount directly on a contactor, while the 3RV2021-1GA15 is a motor circuit breaker with a different footprint and mounting method. They are not mechanically interchangeable without rewiring the panel layout."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RB3123-4SB0","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/3RB3123-4SB0 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}}