{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RW4028-1TB05","brand":"Siemens","brandSlug":"siemens","productSlug":"3RW4028-1TB05","canonicalUrl":"https://aoctrl.com/siemens/3RW4028-1TB05","factsUrl":"https://aoctrl.com/api/mcp/products/3RW4028-1TB05","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RW4028-1TB05 soft starter, size S0, 38 A at 40 °C, 24 V AC/DC control, screw terminals, integrated bypass, active production.","salesMarkdown":"## Rated current and thermal derating — the real-world limit The 3RW4028-1TB05 is rated 38 A at 40 °C ambient. The minimum load is 20 % of the rated motor current — below that the soft starter may not trigger the bypass contactor reliably. Size the motor so its FLA sits between 20 % and 100 % of the 38 A ceiling at your panel ambient. ## Integrated bypass and thyristor stack — what that means for heat This unit has an integrated bypass contact system and uses thyristors for the ramp-up. Once the motor is at speed, the bypass closes and the thyristors are out of circuit — so the heat load in the panel drops to the bypass contactor's dissipation, not the full SCR conduction loss. That matters for the vertical mounting surface limits: without an additional fan, the unit allows +/-10° rotation; with a fan, +/-90° rotation and +/-22.5° tilt front-to-back. The bypass also means the soft starter doesn't need to dissipate SCR heat continuously during run — the enclosure stays cooler than a non-bypassed design at the same current. ## Mounting, clearance, and panel fit Required clearances: 60 mm above, 40 mm below, 15 mm at the sides. The 155 mm depth is the body only — allow extra for the screw terminals on the main circuit and the control circuit. Pollution degree 3 per IEC 60947-4-2 — suitable for industrial enclosures where conductive dust or occasional condensation is present. ## Control voltage and wiring Control supply is 24 V AC/DC at 50/60 Hz — the same 24 V rail that powers the PLC cabinet. Main circuit terminals are also screw-type. Maximum motor cable length is 300 m — beyond that, capacitive charging current from the cable can interfere with the thyristor gating. An external reset input is provided for remote restart after a fault trip.","metaTitle":"Siemens 3RW4028-1TB05 SIRIUS Soft Starter, 38 A, 24 V AC/DC","metaDescription":"Siemens 3RW4028-1TB05 SIRIUS soft starter, 38 A at 40 °C, 24 V AC/DC control, size S0, integrated bypass. Active production, quoted to order.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Soft Starters"],"specifications":{"Depth":"155mm","Solid":"2x (0.5 ... 2.5 mm²)","Width":"45mm","title":"3RW4028-1TB05","Height":"125mm","Upwards":"60mm","Downwards":"40mm","Thyristors":"Yes","At The Side":"15mm","description":"SIRIUS soft starter S0 38 A, 22 kW/500 V, 40 °C 400-600 V AC, 24 V AC/DC Screw terminals Thermistor motor protection","During Storage":"-40 ... +80°C","External Reset":"Yes","lifecycle_stage":"current","During Operation":"-25 ... +60°C","Fastening Method":"screw and snap-on mounting","Minimum Load [%]":"20%","Mounting Position":"With additional fan: With vertical mounting surface +/-90° rotatable, with vertical mounting surface +/- 22.5° tiltable to the front and back Without additional fan: With vertical mounting surface +/-10° rotatable, with vertical mounting surface +/- 10° t","Product Brand Name":"SIRIUS","Degree Of Pollution":"3, acc. to IEC 60947-4-2","Product Designation":"Soft starter","Wire Length Maximum":"300m","Derating Temperature":"40°C","Inside-Delta Circuit":"No","at 50 Hz rated value":"24V","at 60 Hz rated value":"24V","at 40 °C rated value":"38A","at 50 °C rated value":"34A","at 60 °C rated value":"31A","For Auxiliary Contacts":"2x (20 ... 14)","For Main Current Circuit":"screw-type terminals","Motor Overload Protection":"Yes","Intrinsic Device Protection":"Yes","Adjustable Current Limitation":"Yes","Size Of Engine Control Device":"S0","Insulation Voltage Rated Value":"600V","Using The Front Clamping Point":"1x 8, 2x (16 ... 10)","Operating Frequency Rated Value":"50 ... 60Hz","Display Version For Fault Signal":"red","Integrated Bypass Contact System":"Yes","For Auxiliary And Control Circuit":"screw-type terminals","Product Component Motor Brake Output":"No","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 (0.5 ... 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":"22kW","at standard circuit at 50 °C rated value":"30hp","control supply voltage 1 at DC rated value":"24V","number of CO contacts for auxiliary contacts":"1","number of NC contacts for auxiliary contacts":"0","number of NO contacts for auxiliary contacts":"2","Type Of Voltage Of The Control Supply Voltage":"AC/DC","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","Relative Negative Tolerance Of The Operating Frequency":"-10%","Relative Positive Tolerance Of The Operating Frequency":"10%","For Auxiliary Contacts Finely Stranded With Core End Processing":"2x (20 ... 16)","relative negative tolerance of the control supply voltage at DC":"-20%","relative positive tolerance of the control supply voltage at DC":"20%","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":"19W","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":"23A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$537.21","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/1ef287929a347c37847aacae05113073.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=161375&mlfb=3RW4028-1TB05"},"ai":{"faq":[{"question":"What is the maximum motor cable length for the 3RW4028-1TB05?","answer":"The maximum motor cable length is 300 m. Beyond this, capacitive charging current from the cable can interfere with thyristor gating."},{"question":"Does the 3RW4028-1TB05 have an integrated bypass contactor?","answer":"Yes, it has an integrated bypass contact system. Once the motor reaches speed, the bypass closes and the thyristors are out of circuit, reducing continuous heat dissipation."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RW4028-1TB05","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/3RW4028-1TB05 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}}