{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RW4427-3BC45","brand":"Siemens","brandSlug":"siemens","productSlug":"3RW4427-3BC45","canonicalUrl":"https://aoctrl.com/siemens/3RW4427-3BC45","factsUrl":"https://aoctrl.com/api/mcp/products/3RW4427-3BC45","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RW4427-3BC45 soft starter, 161 A at 40 °C, 690 V insulation voltage, 50/60 Hz, with integrated bypass and inside-delta wiring capability.","salesMarkdown":"## What the current ratings actually mean for the motor The 3RW4427-3BC45: The 161 A at 40 °C is the continuous full-load current it can handle in a standard 40 °C enclosure — not a starting surge, but the steady-state current after the motor is up to speed. At 50 °C ambient, that ceiling drops to 142 A, and at 60 °C it's 125 A. If your panel runs hot, the soft starter derates itself; you size the overload protection to the derated number, not the 40 °C nameplate. The minimum load threshold is 8 % of the rated current — below that the thyristor firing angle can't regulate properly, and the motor may cog or the soft starter may trip on phase loss. Keep the connected load above that floor. ## Integrated bypass — why it matters for heat and efficiency This soft starter has an integrated bypass contact system. Once the motor reaches full speed, the thyristors are shunted out, and the current flows through the bypass contacts. That means the thyristors stop conducting and the heatsink stops accumulating heat — the soft starter runs cool in steady-state, and you don't need to oversize the panel ventilation for continuous thyristor dissipation. The bypass also reduces the electrical load on the thyristors during normal running, which extends their service life — a common failure point in soft starters that lack bypass. ## Inside-delta wiring — when to use it The unit supports inside-delta circuit wiring. In that configuration, the soft starter is wired between the motor windings rather than in the line supply, so the current through each thyristor is roughly 58 % of the line current. This lets the same 161 A unit handle a larger motor — useful when retrofitting into an existing motor with a higher FLA than the soft starter's line rating would otherwise allow. The trade-off is that the motor must have all six winding leads brought out to the panel. ## Mounting and cooling clearances — don't choke the heatsink The unit is screw-fixed to a vertical mounting surface. It's rotatable ±90° and tiltable ±22.5° front/back — so you can orient it to fit the panel layout, but the vertical-surface requirement is non-negotiable for natural convection cooling. Clearance above the unit must be 100 mm, below 75 mm, and at the sides just 5 mm. Stacking units without that top clearance will bake the upper unit's thyristors. ## Terminal blocks — main power vs control wiring The main current circuit uses box terminals accepting 10 AWG to 1/0 AWG (using both clamping points) or 10 to 2/0 AWG using a single clamping point. That covers most motor feeder sizes up to 161 A. The auxiliary and control circuit uses spring-loaded terminals for 24 to 16 AWG solid or stranded — no screw tightening needed on the control wiring, which speeds up commissioning and prevents loose-terminal faults on the 24 VDC control loop. ## Protection functions built in — overload, current limit, device protection Motor overload protection is integrated, so you don't need a separate overload relay downstream. The adjustable current limitation lets you set the starting current anywhere below the full rated current — useful for limiting inrush on weak supplies or soft-coupled loads. Intrinsic device protection monitors the thyristor junction temperature and the heatsink temperature; if the thermal budget is exceeded, the soft starter inhibits a start or reduces the current to protect itself.","metaTitle":"Siemens 3RW4427-3BC45 SIRIUS Soft Starter, 161 A, 690 V","metaDescription":"Siemens 3RW4427-3BC45 SIRIUS soft starter, 161 A at 40 °C, 690 V insulation voltage, 50/60 Hz. Active production, quoted to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":null,"categoryPath":["Soft Starters"],"specifications":{"Depth":"270mm","Solid":"2x (0.25 ... 1.5 mm²)","Width":"170mm","title":"3RW4427-3BC45","Height":"192mm","Upwards":"100mm","Stranded":"2x (4 ... 50 mm²)","Downwards":"75mm","Thyristors":"Yes","At The Side":"5mm","description":"SIRIUS soft starter Values at 500 V, 40 °C standard: 93 A, 55 kW Inside-delta: 161 A, 110 kW 400-600 V AC, 230 V AC spring-type terminals!!! Phased-out product!!! Successor is SIRIUS 3RW5, Preferred successor type is >>3RW5527-3HA16<<","During Storage":"-25 ... +80°C","External Reset":"Yes","lifecycle_stage":"current","During Operation":"60°C","Fastening Method":"screw fixing","Minimum Load [%]":"8%","Mounting Position":"with vertical mounting surface +/-90° rotatable, with vertical mounting surface +/- 22.5° tiltable to the front and back","Product Brand Name":"SIRIUS","Degree Of Pollution":"3, acc. to IEC 60947-4-2","Product Designation":"Soft starter","Wire Length Maximum":"500m","Derating Temperature":"40°C","Inside-Delta Circuit":"Yes","at 50 Hz rated value":"230V","at 60 Hz rated value":"230V","at 40 °C rated value":"161A","at 50 °C rated value":"142A","at 60 °C rated value":"125A","For Auxiliary Contacts":"2x (24 ... 16)","For Main Current Circuit":"box terminal","Motor Overload Protection":"Yes","Using Both Clamping Points":"2x (10 ... 1/0)","Intrinsic Device Protection":"Yes","Adjustable Current Limitation":"Yes","Using The Back Clamping Point":"10 ... 2/0","Insulation Voltage Rated Value":"690V","Using The Front Clamping Point":"10 ... 2/0","Operating Frequency Rated Value":"50 ... 60Hz","Display Version For Fault Signal":"Display","Integrated Bypass Contact System":"Yes","For Auxiliary And Control Circuit":"spring-loaded terminals","Product Component Motor Brake Output":"Yes","during storage according to IEC 60721":"1K6 (only occasional condensation), 1C2 (no salt mist), 1S2 (sand must not get inside the devices), 1M4","reference code according to EN 61346-2":"Q","during operation according to IEC 60721":"3K6 (no formation of ice, no condensation), 3C3 (no salt mist), 3S2 (sand must not get into the devices), 3M6","during transport according to IEC 60721":"2K2, 2C1, 2S1, 2M2 (max. fall height 0.3 m)","Finely Stranded With Core End Processing":"2x (0.25 ... 1.5 mm²)","Number Of Poles For Main Current Circuit":"3","Evaluation Of Thermistor Motor Protection":"Yes","at standard circuit at 40 °C rated value":"55kW","at standard circuit at 50 °C rated value":"75hp","Finely Stranded Without Core End Processing":"2x (4 ... 35 mm²)","number of CO contacts for auxiliary contacts":"1","number of NC contacts for auxiliary contacts":"0","number of NO contacts for auxiliary contacts":"3","Type Of Voltage Of The Control Supply Voltage":"AC","at inside-delta circuit at 40 °C rated value":"110kW","at inside-delta circuit at 50 °C rated value":"125hp","Control Supply Voltage Frequency 1 Rated Value":"50Hz","Control Supply Voltage Frequency 2 Rated Value":"60Hz","Installation Altitude At Height Above Sea Level":"5 000m","continuous operating current [% of Ie] at 40 °C":"115%","Operating Voltage At Standard Circuit Rated Value":"400 ... 600V","contact rating of auxiliary contacts according to UL":"B300 / R300","Operating Voltage At Inside-Delta Circuit Rated Value":"400 ... 600V","Relative Negative Tolerance Of The Operating Frequency":"-10%","Relative Positive Tolerance Of The Operating Frequency":"10%","Relative Negative Tolerance Of The Control Supply Voltage Frequency":"-10%","Relative Positive Tolerance Of The Control Supply Voltage Frequency":"10%","Relative Negative Tolerance Of The Operating Voltage At Standard Circuit":"-15%","Relative Positive Tolerance Of The Operating Voltage At Standard Circuit":"10%","power loss [W] at operational current at 40 °C during operation typical":"55W","relative negative tolerance of the control supply voltage at AC at 50 Hz":"-15%","relative negative tolerance of the control supply voltage at AC at 60 Hz":"-15%","relative positive tolerance of the control supply voltage at AC at 50 Hz":"10%","relative positive tolerance of the control supply voltage at AC at 60 Hz":"10%","Adjustable Motor Current For Motor Overload Protection Minimum Rated Value":"18A","Relative Negative Tolerance Of The Operating Voltage At Inside-Delta Circuit":"-15%","Relative Positive Tolerance Of The Operating Voltage At Inside-Delta Circuit":"10%"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/7efecb96708f9a2c59ebce7fe05d4e49.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=231107&mlfb=3RW4427-3BC45"},"ai":{"faq":[{"question":"What compliance documentation does Siemens provide for 3RW4427-3BC45?","answer":"The unit is designed to IEC 60947-4-2 (degree of pollution 3). Siemens typically provides CE, UKCA, and EAC declarations for the SIRIUS series; specific UL and CSA listings should be confirmed against the nameplate marking on the unit ordered."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RW4427-3BC45","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/3RW4427-3BC45 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}}