{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RB3123-4VB0","brand":"Siemens","brandSlug":"siemens","productSlug":"3RB3123-4VB0","canonicalUrl":"https://aoctrl.com/siemens/3RB3123-4VB0","factsUrl":"https://aoctrl.com/api/mcp/products/3RB3123-4VB0","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RB3123-4VB0 solid-state overload relay, Size S0, 40 A rated thermal current, 690 V rated insulation voltage, adjustable trip classes CLASS 5E/10E/20E/30E, screw-type terminals, contactor mounting.","salesMarkdown":"## What this solid-state overload relay does The Siemens 3RB3123-4VB0 is a SIRIUS solid-state overload relay — it protects motors by monitoring current and tripping on overload, with a configurable trip class that lets you match the relay to the motor's starting profile. The trip class is adjustable across CLASS 5E, 10E, 20E and 30E, so the same relay can handle fast-starting pumps (Class 10E) or high-inertia loads like centrifuges (Class 30E) without swapping hardware. The relay sits in the S0 frame size — the standard footprint for contactor mounting across the SIRIUS contactor range, so it mates directly with S0-size contactors without an adapter plate. ## Trip class adjustability and what it means for the motor The 3RB3123-4VB0 lets you set the trip class to 5E, 10E, 20E, or 30E — that's the maximum time in seconds the relay allows at 7.2× the current setting before tripping. A Class 10E setting trips in 10 seconds, which suits standard squirrel-cage motors starting direct-on-line; Class 20E gives 20 seconds for harder-starting loads like conveyors; Class 30E allows 30 seconds for high-inertia fans or crushers. The adjustment is on the relay face, no module swap needed. The trip threshold logic is straightforward: the motor current must stay above the lower current setting value and below the upper current setting value multiplied by 3.5. This means the relay trips when current exceeds the upper setting by a factor of 3.5 — a hard stall or phase-loss condition clears the motor off the line fast, while the adjustable class governs the thermal curve for normal overloads. ## Panel fit and wiring details Mounts directly onto the contactor — no DIN rail bracket needed. The S0 size means it occupies the same 45 mm width as the matching S0 contactor, keeping the motor starter assembly compact. The screw terminals use Pozidriv PZ2 screwdriver tip with a shaft diameter of 5 to 6 mm. Power dissipation is 1 W per pole — three poles total 3 W at rated current. That's low enough that no special ventilation is needed in a standard IP20 enclosure, but the heat does add to the panel's thermal budget if you're packing several starters in a small cabinet. Shock resistance is 15 g for 11 ms on the main contacts (9 g for the signaling contact in tripped position), and vibration resistance per IEC 60068-2-27 covers 1-6 Hz at 15 mm amplitude and 6-500 Hz at 20 m/s² for 10 cycles. The relay carries a 'Note for message tripped' designation — meaning the auxiliary contact 97/98 changes state when the relay trips, giving a positive signal to the control system. This is the standard N/C alarm contact that opens on trip, used for remote fault indication. The kit is complete: the relay ships with the screw terminals ready for the main circuit wiring, the auxiliary contact block is integrated, and the trip class selector is on the face. No separate accessory pack is needed for basic installation — just the matching S0 contactor and the control wiring.","metaTitle":"Siemens 3RB3123-4VB0 SIRIUS Solid-State Overload Relay, 40 A","metaDescription":"Siemens 3RB3123-4VB0 SIRIUS solid-state overload relay, 40 A thermal current, S0 size, adjustable trip classes 5E-30E. Active production, quoted to order.","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":"3RB3123-4VB0","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":"1 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 10...40 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":"40 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":"40 A","at 600 V rated value":"40 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":"40 A","for AC motors at 500 V at 50 Hz":"7.5 ... 22 kW","for AC motors at 690 V at 50 Hz":"11 ... 37 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: 80 A, J: 100 A","Display Version For Switching Status":"Slide switch","Surge Voltage Resistance Rated Value":"6 kV","With Type Of Coordination 1 Required":"gG: 125 A, J: 150 A","at AWG cables for auxiliary contacts":"1x (20 ... 14), 2x (20 ... 14)","for 3-phase motors at 400 V at 50 Hz":"5.5 ... 18.5 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":"40 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":"3 W","Adjustable Current Response Value Current Of The Current-Dependent Overload Release":"10 ... 40 A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$125.73","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/0a6210f0cb44fc5d4951d78b23543e27.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=394612&mlfb=3RB3123-4VB0"},"ai":{"faq":[{"question":"How can I order the 3RB3123-4VB0 or check availability?","answer":"The 3RB3123-4VB0 is sourced to order against the BOM quantity through independent distribution."},{"question":"What trip classes does the 3RB3123-4VB0 support?","answer":"The relay supports four adjustable trip classes: CLASS 5E, 10E, 20E, and 30E. This covers fast-starting motors (5E/10E) through high-inertia loads (20E/30E) without changing the relay hardware."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RB3123-4VB0","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/3RB3123-4VB0 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}}