{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3RW4038-2BB05","brand":"Siemens","brandSlug":"siemens","productSlug":"3RW4038-2BB05","canonicalUrl":"https://aoctrl.com/siemens/3RW4038-2BB05","factsUrl":"https://aoctrl.com/api/mcp/products/3RW4038-2BB05","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3RW4038-2BB05 soft starter, Size S2, 72 A at 40 °C, 50/60 Hz, 600 V insulation, integrated bypass, screw and snap-on mounting.","salesMarkdown":"The 3RW4038-2BB05 is rated 72 A at 40 °C, derating to 62 A at 50 °C and 60 A at 60 °C. For a 40 °C panel ambient, this soft starter handles a 37 kW (50 hp) motor at 400 V — the derating curve matters if your enclosure runs hot. The integrated bypass contactor eliminates the continuous I²R loss through the thyristors after start, so the 72 A rating applies to the bypass path, not the SCRs. This keeps the enclosure heat rise lower than a non-bypassed design at full load. ## Mounting and clearance — what fits in the panel Size S2 envelope: 160 mm height, 55 mm width, 170 mm depth. Screw and snap-on mounting to DIN rail — the snap-on foot saves rail space vs through-bolt mounting. Clearance requirements: 60 mm above, 40 mm below, 30 mm at the sides. These are the minimum air gaps for natural convection cooling — stacking devices tighter forces derating. Mounting position restrictions: with the optional fan, the unit can be rotated ±90° and tilted ±22.5° front/back; without the fan, rotation is limited to ±10°. For vertical panels without the fan, keep the unit within 10° of plumb. ## Termination and wiring — main and control For a 72 A motor circuit, 16 mm² stranded is typical — the dual clamping point accepts two conductors per pole for daisy-chaining. Auxiliary contact terminals accept 2x (24... 14) AWG. The control supply is 24 V AC/DC at 50/60 Hz — confirm your control transformer matches; 24 VDC is also acceptable since the rectifier is internal. Maximum motor cable length is 300 m — beyond that, capacitive charging current from the cable can cause nuisance overcurrent trips during start. For long cable runs, add an output reactor. ## Protection and control features Built-in motor overload protection and intrinsic device protection — the soft starter monitors both motor current and its own thyristor temperature. Adjustable current limitation lets you set the start current between 20% and 100% of the rated motor FLA. Minimum load is 20% of the rated current — below that, the motor current may be too low for the overload detection to function accurately. External reset input allows remote fault reset from a PLC or pushbutton. Fault indication via a red LED — the display version shows the fault code for diagnostics. Thyristors are used for the power switching; the inside-delta circuit is not supported, so the unit must be wired in-line with the motor. Sourced through authorized distribution channels. For current pricing and availability against your BOM quantity, submit an RFQ — the unit is quoted to order with confirmed lead time at quote issuance.","metaTitle":"Siemens 3RW4038-2BB05 SIRIUS Soft Starter, 72 A, Size S2","metaDescription":"Siemens 3RW4038-2BB05 SIRIUS soft starter, 72 A at 40 °C, Size S2, integrated bypass. Active production, quoted to order. Request RFQ.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Soft Starters"],"specifications":{"Depth":"170mm","Solid":"2x (0.25 ... 2.5 mm²)","Width":"55mm","title":"3RW4038-2BB05","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, 45 kW/500 V, 40 °C 400-600 V AC, 24 V AC/DC spring-type 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 (24 ... 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","during storage acc. to IEC 60721":"1K6 (only occasional condensation), 1C2 (no salt mist), 1S2 (sand must not get inside the devices), 1M4","For Auxiliary And Control Circuit":"spring-loaded terminals","during operation acc. 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 acc. to IEC 60721":"2K2, 2C1, 2S1, 2M2 (max. fall height 0.3 m)","Product Component Motor Brake Output":"No","reference code acc. to DIN EN 61346-2":"Q","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":"No","at standard circuit at 40 °C rated value":"45kW","at standard circuit at 50 °C rated value":"60hp","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","touch protection on the front acc. to IEC 60529":"finger-safe, for vertical contact from the front","continuous operating current [% of Ie] at 40 °C":"115%","Operating Voltage At Standard Circuit Rated Value":"400 ... 600V","protection class IP on the front acc. to IEC 60529":"IP20","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%","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":"-20%","relative negative tolerance of the control supply voltage at AC at 60 Hz":"-20%","relative positive tolerance of the control supply voltage at AC at 50 Hz":"20%","relative positive tolerance of the control supply voltage at AC at 60 Hz":"20%","Adjustable Motor Current For Motor Overload Protection Minimum Rated Value":"35A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$745.49","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/6d89b1ba443b4481ac64a85e71b9d21b.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=33690&mlfb=3RW4038-2BB05"},"ai":{"faq":[{"question":"What is the maximum motor cable length for 3RW4038-2BB05?","answer":"The maximum motor cable length is 300 m. For longer cable runs, capacitive charging current may cause nuisance trips during start-up; an output reactor is recommended beyond this distance."},{"question":"Does 3RW4038-2BB05 support inside-delta wiring?","answer":"No, the inside-delta circuit is not supported. The unit must be wired in-line with the motor phases."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3RW4038-2BB05","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/3RW4038-2BB05 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}}