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OM-263 706 Page 21

SECTION 7 − ELECTRICAL DIAGRAMS

956172128_A

Figure 7-1. Circuit Diagram For STi 270

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Summary of Contents for STi 270

Page 1: ...Processes Description TIG GTAW Welding Stick SMAW Welding OM 263 706A 2013 11 Arc Welding Power Source STi 270 And STi 270C CE ...

Page 2: ...ducts Please take time to read the Safety precautions They will help you protect yourself against potential hazards on the worksite We ve made installation and operation quick and easy With Miller you can count on years of reliable service with proper maintenance And if for some reason the unit needs repair there s a Troubleshooting section that will help you figure out what the problem is The par...

Page 3: ...Guide 11 4 7 Connecting 3 Phase Input Power 12 4 8 Connecting To 3 Phase Engine Generator w 400 Volt Output 13 SECTION 5 OPERATION 14 5 1 Controls STi 270 Model Shown 14 5 2 Preparing Unit For Stick SMAW Welding STi 270 Model Shown 15 5 3 Preparing Unit For TIG GTAW Welding STi 270 Model Shown 16 5 4 Process Control 17 5 5 Lift Arc Start Procedure 17 5 6 Stick Start Procedure Scratch Start Techniq...

Page 4: ...triction of the use of certain hazardous substances in electrical and electronic equipment Standards IEC 60974 1 Arc Welding Equipment Welding Power Sources edition 3 2005 07 IEC 60974 10 Arc Welding Equipment Electromagnetic Compatibility Requirements edition 2 0 2007 08 EN 50445 2008 Product family standard to demonstrate compliance of equipment for resistance welding arc welding and allied proc...

Page 5: ...kneeling or lying or when there is a high risk of unavoid able or accidental contact with the workpiece or ground For these conditions use the following equipment in order presented 1 a semiautomaticDC constant voltage wire welder 2 a DC manual stick welder or 3 an AC welder with reduced open circuit volt age In most situations use of a DC constant voltage wire welder is recommended And do not wor...

Page 6: ...pared according to AWS F4 1 and AWS A6 0 see Safety Standards D Do not weld where the atmosphere may contain flammable dust gas or liquid vapors such as gasoline D Connect work cable to the work as close to the welding area as practical to prevent welding current from traveling long possibly unknown paths and causing electric shock sparks and fire hazards D Do not use welder to thaw frozen pipes D...

Page 7: ...ING PARTS can injure D Keep away from moving parts such as fans D Keep all doors panels covers and guards closed and securely in place D Have only qualified persons remove doors panels covers or guards for maintenance and troubleshooting as necessary D Reinstall doors panels covers or guards when maintenance is finished and before reconnecting input power READ INSTRUCTIONS D Read and follow all la...

Page 8: ... NFPA Standard 51B from National Fire Protection Association Quincy MA 02269 phone 1 800 344 3555 website www nfpa org OSHA Occupational Safety and Health Standards for General Indus try Title 29 Code of Federal Regulations CFR Part 1910 Subpart Q and Part 1926 Subpart J from U S Government Printing Office Super intendentof Documents P O Box 371954 Pittsburgh PA 15250 7954 phone 1 866 512 1800 the...

Page 9: ...mation Safe37 2012 05 Wear dry insulating gloves Do not touch electrode with bare hand Do not wear wet or damaged gloves Safe2 2012 05 Protect yourself from electric shock by insulating yourself from work and ground Safe3 2012 05 Disconnect input plug or power before working on machine Safe5 2012 05 Keep your head out of the fumes Safe6 2012 05 Use forced ventilation or local exhaust to remove the...

Page 10: ...Symbols And Definitions A Amperes I Output On Gas Tungsten Arc Welding GTAW Shielded Metal Arc Welding SMAW V Volts Voltage Input 3 Phase Static Frequency Converter Transformer Rectifier Voltage Output Off Remote Lift Arc Start GTAW Protective Earth Ground Process High Temperature Hot Start On Percent Positive Negative Alternating Current Hz Hertz Arc Force DIG I2 Rated Welding Current X Duty Cycl...

Page 11: ... con ducted as well as radiated disturbances This equipment does not comply with IEC 61000 3 12 If it is connected to a public low voltage system it is the responsibility of the installer or user of the equipment to ensure by consultation with the distribution network operator if necessary that the equip ment can be connected ce emc 2 2011 09 3 2 IP Rating IP Rating 23S This equipment is designed ...

Page 12: ...0180 190200 210 220230240250 260270280 110 3 5 Duty Cycle And Overheating Duty Cycle is percentage of 10 min utes that unit can weld at rated load without overheating If unit overheats output stops and cooling fan runs Wait fifteen min utes for unit to cool Reduce amper age or voltage or duty cycle before welding NOTICE Exceeding duty cycle can damage unit and void warranty Overheating 0 15 A or V...

Page 13: ...e input power requirementsand or rated output For future reference write serial number in space provided on back cover of this manual 4 2 Selecting A Location Special installation may be required where gasoline or volatile liquids are present see NEC Article 511 or CEC Section 20 1 Line Disconnect Device Locate unit near correct input power supply Location And Airflow 1 460 mm 18 in 460 mm 18 in 2...

Page 14: ... 3 35 2 50 1 60 1 0 70 2 0 95 3 0 120 4 0 120 4 0 This chart is a general guideline and may not suit all applications If cable overheats use next size larger cable Weld cable size is based on either a 4 volts or less drop or a current density of at least 300 circular mils per ampere For distances longer than those shown in this guide call a factory applications representative Milan Ref S 0007 K 20...

Page 15: ...ly compatible See NEC articles 210 21 630 11 and 630 12 Input Voltage V Three Phase 40 Duty Cycle 380 440 10 Input Amperes A At Rated Output 16 Max Recommended Standard Fuse Rating In Amperes 1 Time Delay Fuses 2 20 Normal Operating Fuses 3 25 Min Input Conductor Size In mm2 AWG 4 2 5 14 Max Recommended Input Conductor Length In Meters Feet 45 149 Min Grounding Conductor Size In mm2 AWG 4 2 5 14 R...

Page 16: ...OM 263 706 Page 12 4 7 Connecting 3 Phase Input Power input2 2012 05 956172127_1 A GND PE Earth Ground L1 2 1 L2 L3 3 3 4 5 6 7 Tools Needed ...

Page 17: ... ter minal first Connect input conductors L1 L2 and L3 to disconnect device line terminals 7 Over Current Protection Select type and size of over current protec tion using Section 4 6 fused disconnect switch shown Close and secure door on disconnect device Follow established lockout tagout procedures to put unit in service 4 7 Connecting 3 Phase Input Power Continued 4 8 Connecting To 3 Phase Engi...

Page 18: ...nuous beep signal indicates an input line phase loss A flashing LED and intermittent beep signal indicates a loss of one or more command sig nals 7 Process Control See Section 5 4 8 VRD Switch STi 270 Models Press and release switch to select or disable VRD voltage reduction device 9a CELL VRD Switch STi 270C Models Press and release switch to select I or O to disable Cell function When Cell funct...

Page 19: ... function CELL pro ceed as follows press and release the CELL VRD switch to enable CELL function and light corresponding LED Cellulosic electrode provides outstanding arc stability and penetration It s ideal for welding in all positions Hot Start Use Hot Start to increase output amperage at the start of a weld to help prevent elec trode sticking To change Hot Start setting proceed as follows press...

Page 20: ...rol 4 Ammeter Voltage Display Meter 5 Process Selector Switch Prepare unit for TIG welding as follows connect electrode holder and work clamp see Section4 4 Turn power on Allow time for unit to complete its start up cycle Press and release Process control to se lect TIG welding and light corresponding LED 1 2 3 5 4 Current A Time Main Amps Remote 2T Trigger Operation All Models P R ...

Page 21: ...G Electrode 2 Workpiece Turn gas on Touch tungsten elec trode to workpiece at weld start point Hold electrode to work piece for 1 2 seconds and slowly lift electrode Arc is formed when electrode is lifted Normal open circuit voltage is not present before tungsten electrode touches workpiece only a low sensing voltage is present between electrode and workpiece The solid state output contactor does ...

Page 22: ... to workpiece use a quick twist to free it When VRD is off normal open circuit voltage 50 volts is present before electrode touches workpiece When VRD is on normal open circuit volt age is not present before electrode touches workpiece only a low sensing voltage is present between electrode and workpiece 1 2 3 5 7 Amperage Control All Models 1 Amperage Control Rotate control clockwise to in crease...

Page 23: ...Δ Repair l Replace To be done by Factory Authorized Service Agent Every 3 Months nl Labels n l Gas Hoses Every 3 Months nΔ lCables And Cords Every 6 Months Durning heavy service clean monthly Do not remove case when blowing out inside of unit see Section 6 2 6 2 Blowing Out Inside Of Unit Do not remove case when blowing out inside of unit To blow out unit direct airflow through front and back louv...

Page 24: ...rratic or improper weld output Use proper size and type of weld cable see Section 4 3 Clean and tighten all weld connections see Section 4 3 Fan not operating Check for and remove anything blocking fan movement Have Factory Authorized Service Agent check fan motor Wandering arc Use proper size tungsten see Section 8 Use properly prepared tungsten see Section 8 Reduce gas flow rate see Section 4 4 ...

Page 25: ...OM 263 706 Page 21 SECTION 7 ELECTRICAL DIAGRAMS 956172128_A Figure 7 1 Circuit Diagram For STi 270 ...

Page 26: ...OM 263 706 Page 22 Figure 7 2 Circuit Diagram For STi 270C 956172129_A ...

Page 27: ... 11 to 35 CFH cubic feet per hour Figures listed are a guide and are a composite of recommendations from American Welding Society AWS and electrode manufacturers 8 2 Preparing Tungsten Electrode For DC Electrode Negative DCEN Welding Or AC Welding With Inverter Machines Grinding the tungsten electrode produces dust and flying sparks which can cause injury and start fires Use local exhaust forced v...

Page 28: ...nmentally safe way Wear proper face hand and body protection Keep flam mables away 1 Workpiece Make sure workpiece is clean before welding 2 Work Clamp Place as close to the weld as possible 3 Torch 4 Filler Rod If Applicable 5 Gas Cup 6 Tungsten Electrode Select and prepare tungsten according to Section 8 Guidelines The inside diameter of the gas cup should be at least three times the tungsten di...

Page 29: ...rch to front of pool Repeat process 75 75 Welding direction Form pool Tilt torch Add filler metal Move torch to front of pool Repeat process Remove rod Welding direction 15 9 3 Positioning Torch Tungsten For Various Weld Joints ST 162 003 S 0792 75 70 90 20 20 10 15 75 20 40 30 15 75 90 15 Butt Weld And Stringer Bead T Joint Lap Joint Corner Joint ...

Page 30: ...less current than a large one Fol low recommendations of the elec trode manufacturer when setting weld amperage see Section 10 2 4 Insulated Electrode Holder 5 Electrode Holder Position 6 Arc Length Arc length is the distance from the electrode to the workpiece A short arc with correct amperage will give a sharp crackling sound Correct arc length is related to electrode di ameter Examine the weld ...

Page 31: ...LET ALL ALL EP EP EP EN EP EN EP EP EN EP EP 6010 6011 6013 7014 7018 7024 NI CL 308L EP ELECTRODE POSITIVE REVERSE POLARITY EN ELECTRODE NEGATIVE STRAIGHT POLARITY ELECTRODE AMPERAGE RANGE DIAMETER MED 10 3 Striking an Arc S 0049 S 0050 Weld current starts when elec trode touches workpiece 1 Electrode 2 Workpiece 3 Arc Scratch Technique Drag electrode across workpiece like striking a match lift e...

Page 32: ...To produce the best results hold a short arc travel at a uniform speed and feed the electrode downward at a constant rate as it melts 1 1 2 2 Groove Welds Fillet Welds 10 5 Poor Weld Bead Characteristics S 0053 A 1 Large Spatter Deposits 2 Rough Uneven Bead 3 Slight Crater During Welding 4 Bad Overlap 5 Poor Penetration 5 4 2 3 1 10 6 Good Weld Bead Characteristics S 0052 B 1 Fine Spatter 2 Unifor...

Page 33: ...r wide groove weld joints or bridging across gaps a weave bead or multiple stringer beads work better 1 Stringer Bead Steady Movement Along Seam 2 Weave Bead Side to Side Movement Along Seam 3 Weave Patterns Use weave patterns to cover a wide area in one pass of the elec trode Do not let weave width ex ceed 2 1 2 times diameter of electrode 1 2 3 10 9 Welding Lap Joints S 0063 S 0064 1 Electrode 2...

Page 34: ...re good welds The single or double V groove weld is good for materials 3 16 3 4 in 5 19 mm thick Generally the single V groove is used on ma terials up to 3 4 in 19 mm thick and when regardless of thickness you can weld from one side only Create a 30 degree bevel with oxy acetylene or plasma cutting equip ment Remove scale from material after cutting A grinder can also be used to prepare bevels 30...

Page 35: ...ive Actions Arc length too long Reduce arc length Damp electrode Use dry electrode Workpiece dirty Remove all grease oil moisture rust paint coatings slag and dirt from work surface before welding Excessive Spatter scattering of molten metal particles that cool to solid form near weld bead Possible Causes Corrective Actions Amperage too high for electrode Decrease amperage or select larger electro...

Page 36: ...ase and or maintain steady travel speed Burn Through weld metal melting completely through base metal resulting in holes where no metal remains Possible Causes Corrective Actions Excessive heat input Select lower amperage Use smaller electrode Increase and or maintain steady travel speed Waviness Of Bead weld metal that is not parallel and does not cover joint formed by base metal Possible Causes ...

Page 37: ...bly For STi 270 Quantity Dia Mkgs 1 057116003 Strap Shoulder Assy 1 2 156122096 Wrapper 1 3 179310 Label Gen Precautionary 2 4 956172112 Label Side STi 270 2 5 PC5 057084194 Circuit Card Capacitor And Relay Board 1 6 PC1 057084199 Circuit Card Inverter Control Board 1 7 193919 Knob Pointer 1 8 356029259 Nameplate Front STi 270 1 9 156118094 Panel Front 1 10 PC3 057084196 Circuit Card Display Board...

Page 38: ...ink Secondary Output 1 28 D1 D2 028069158 Kit Diode Power Module 2 29 L1 057098025 Choke 1 30 T1 058021164 Transformer 1 31 T2 058021163 Transformer Toroidal 400 VAC 1 32 HD1 056167009 Probe 400A 1 33 056076260 Dinse Socket Female 50 MMQ 2 34 246623 Bezel Front 1 35 956172116 Label Negative 1 36 956172115 Label Positive 1 37 216031080 Bus Bar 3x15 L 110 1 38 316031024 Bus Bar 4x20 L 110 2 39 15600...

Page 39: ...y 1 2 156122096 Wrapper 1 3 179310 Label Gen Precautionary 2 4 956172113 Label Side STi 270 2 5 PC5 057084194 Circuit Card Capacitor And Relay Board 1 6 PC1 057084195 Circuit Card Inverter Control Board 1 7 193919 Knob Pointer 1 8 356029260 Nameplate Front STi 270 1 9 156118094 Panel Front 1 10 PC3 057084196 Circuit Card Display Board 1 11 PC6 057084197 Circuit Card Cad CITO MMA 1 12 156122097 Bul...

Page 40: ...2105 Heat Sink Secondary Output 1 31 L1 057098025 Choke 1 32 L2 057098026 Choke 30 A Citoflex 1 33 T1 058021162 Transformer 1 34 T2 058021163 Transformer Toroidal 400 VAC 1 35 HD1 056167009 Probe 400 A 1 36 056076260 Dinse Socket Female 50 MMQ 2 37 246623 Bezel Front 1 38 956172116 Label Negative 1 39 956172115 Label Positive 1 40 216031080 Bus Bar 3x15 L 110 1 41 316031024 Bus Bar 4x20 L 110 2 42...

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Page 43: ...ning Gear and Trailers Subarc Wire Drive Assemblies Water Coolant Systems USA Models Non Integrated Work Stations Weld Tables No Labor 5 6 Months Parts Batteries 6 90 Days Parts Accessory Kits Canvas Covers Induction Heating Coils and Blankets MIG Guns Remote Controls Replacement Parts No Labor Spoolmate Spoolguns Cables and Non Electronic Controls Miller s True Blue Limited Warranty shall not app...

Page 44: ...ry Zip Postal Code Please complete and retain with your personal records Owner s Record Always provide Model Name and Serial Style Number Contact a DISTRIBUTOR or SERVICE AGENCY near you Welding Supplies and Consumables Options and Accessories Service and Repair Replacement Parts Owner s Manuals Contact the Delivering Carrier to For Service File a claim for loss or damage during shipment For assis...

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