{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RW4038-1BB04","brand":"Siemens","brandSlug":"siemens","productSlug":"3RW4038-1BB04","canonicalUrl":"https://aoctrl.com/siemens/3RW4038-1BB04","factsUrl":"https://aoctrl.com/api/mcp/products/3RW4038-1BB04","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RW4038-1BB04 soft starter, Size S2, 72 A at 40 °C, 600 V insulation voltage, screw-type terminals, integrated bypass.","salesMarkdown":"## What this SIRIUS soft starter delivers That's the headline number, but the real-world current drops to 62 A at 50 °C and 60 A at 60 °C — so if your panel runs hot, you're sizing off the 60 A figure, not the 72 A. Rated insulation voltage is 600 V, operating frequency is 50 to 60 Hz, and the control supply is 24 V at both 50 and 60 Hz. It uses thyristor stacks for the ramp and an integrated bypass contactor that closes once the motor is up to speed. That bypass means the thyristors only dissipate heat during the start — no continuous heat sink load in run state, which simplifies panel ventilation. ## Mounting and wiring reality Mounting is screw-fix or snap-on onto a DIN rail. The unit is 55 mm wide, 160 mm high, and 170 mm deep — that's a standard S2 footprint. Clearance requirements: 60 mm above, 40 mm below, 30 mm at the sides. If you're packing it into a tight enclosure, those gaps are real — you can't cheat the airflow or the bend radius on the power cables. Main circuit terminals are screw-type, accepting 2x stranded from 1.5 to 25 mm² or 2x solid from 0.5 to 2.5 mm². Auxiliary contacts take 2x conductors from 20 to 14 AWG. The maximum motor cable length is 300 m — relevant if you're feeding a motor at the far end of a plant. ## Environmental and operating limits Storage range is -40 to +80 °C. Mounting position is flexible: with an additional fan you can rotate the unit ±90° on a vertical surface or tilt ±22.5° front-to-back; without the fan, rotation is limited to ±10° and tilt to ±10°. Minimum load is 20% of the rated current — useful to know if you're starting a lightly loaded pump or fan that might not pull enough current for the soft starter to regulate properly.","metaTitle":"Siemens 3RW4038-1BB04 SIRIUS Soft Starter, 72A at 40°C","metaDescription":"Siemens SIRIUS 3RW4038-1BB04 soft starter, 72A rated at 40°C, 600V insulation, integrated bypass. Current production. Sourced to order via RFQ.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Soft Starters"],"specifications":{"Depth":"170mm","Solid":"2x (0.5 ... 2.5 mm²)","Width":"55mm","title":"3RW4038-1BB04","Height":"160mm","Upwards":"60mm","Stranded":"2x (1.5 ... 25 mm²)","Downwards":"40mm","Thyristors":"Yes","At The Side":"30mm","description":"SIRIUS soft starter S2 72 A, 37 kW/400 V, 40 °C 200-480 V AC, 24 V AC/DC Screw terminals","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":"72A","at 50 °C rated value":"62A","at 60 °C rated value":"60A","For Auxiliary Contacts":"2x (20 ... 14)","For Main Current Circuit":"screw-type terminals","Motor Overload Protection":"Yes","Using Both Clamping Points":"2x (16 ... 2)","Intrinsic Device Protection":"Yes","Adjustable Current Limitation":"Yes","Size Of Engine Control Device":"S2","Using The Back Clamping Point":"16 ... 2","Insulation Voltage Rated Value":"600V","Using The Front Clamping Point":"18 ... 2","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":"No","at standard circuit at 40 °C rated value":"37kW","at standard circuit at 50 °C rated value":"40hp","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":"200 ... 480V","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":"15W","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":"35A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$652.78 – $1,078.78","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/abef6c0dcb7773a3f16960d86680c1b5.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=178025&mlfb=3RW4038-1BB04"},"ai":{"faq":[{"question":"What are the key current ratings I need to know?","answer":"Rated current is 72 A at 40 °C, derated to 62 A at 50 °C and 60 A at 60 °C. The 60 A figure at 60 °C is the one to use if your panel ambient runs hot. Insulation voltage is 600 V, operating frequency is 50 to 60 Hz."},{"question":"Does this soft starter include a bypass contactor?","answer":"Yes. An integrated bypass contactor is built in, so the thyristors only carry current during the start ramp. That eliminates continuous heat dissipation in run state."},{"question":"What wire sizes does the main circuit accept?","answer":"Screw-type terminals accept 2x stranded from 1.5 to 25 mm² or 2x solid from 0.5 to 2.5 mm². Maximum motor cable length is 300 m."},{"question":"What clearance is needed around the unit in the panel?","answer":"60 mm above, 40 mm below, and 30 mm at the sides. The unit itself is 55 mm wide, 160 mm high, and 170 mm deep."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RW4038-1BB04","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/3RW4038-1BB04 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}}