Manuals / Lincoln Electric / Power Tools / Welding System

Lincoln Electric SVM170-A Thermal And Overload Protection, Wire Feed Overload Protection

Models: SVM170-A

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THERMAL AND OVERLOAD PROTECTION

E-6	THEORY OF OPERATION	E-6

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THERMAL AND OVERLOAD PROTECTION

The POWER MIG 255C has built-in protective ther- mostats that respond to excessive temperatures. One is located on the output choke. The other thermostat is located on the SCR heat sink assembly. They open the wire feed and welder output circuits if the machine exceeds the maximum safe operating temperature. This can be caused by a frequent overload, or high ambient temperature.

The thermostats are self-resetting once the machine cools sufficiently. If the thermostat shutdown is caused by excessive output or duty cycle and the fan is oper- ating normally, the power switch may be left on and the reset should occur within a 15 minute period. If the fan is not turning or the air intake louvers are obstructed, then the input power must be removed and the fan problem or air obstruction be corrected.

OVERCURRENT PROTECTION

The machine will automatically reduce the output if the load on the machine exceeds 300 to 320 amperes. This protects the welding power SCR’s from excessive short circuit currents and from exceeding their temper- ature rating before the thermostats can react.

WIRE FEED OVERLOAD PROTECTION

The POWER MIG has solid state overload protection of the wire drive motor. If the motor becomes over- loaded, the protection circuitry turns off the wire feed speed and gas solenoid. Check for proper size tip liner, and drive rolls, for any obstructions or bends in the gun cable, and any other factors that would impede the wire feeding. To resume welding, simply pull the trigger. There is no circuit breaker to reset, as the protection is done with reliable solid state electronics.

POWER MIG 255C

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Lincoln Electric SVM170-A Thermal And Overload Protection, Wire Feed Overload Protection, Theory Of Operation

Contents

Safety Depends on You POWER MIG 255CSERVICE MANUAL View Safety Info View Safety Info View Safety Info View Safety InfoELECTRIC AND MAGNETIC FIELDS may be dangerous SAFETYFOR ENGINE powered equipment CALIFORNIA PROPOSITION 65 WARNINGSFUMES AND GASES can be dangerous ELECTRIC SHOCK can killARC RAYS can burn SAFETYCYLINDER may explode if damaged FOR ELECTRICALLY powered equipmentWELDING SPARKS can cause fire or explosion SAFETYReturn to Master TOC Return to Master TOC Return to Master TOC PRÉCAUTIONS DE SÛRETÉSAFETY Return to Master TOCMASTER TABLE OF CONTENTS FOR ALL SECTIONS RETURN TO MAIN MENUINSTALLATION SECTION INSTALLATIONTABLE OF CONTENTS SECTION APHYSICAL DIMENSIONS TECHNICAL SPECIFICATIONS - POWER MIG 255CINPUT - SINGLE PHASE ONLY INSTALLATIONINPUT POWER, GROUNDING AND CONNECTION DIAGRAMS SAFETY PRECAUTIONSUNCRATING THE POWER MIG 255C LOCATIONReturn to Master TOC INSTALLATIONReturn to Section TOC FIGURE A.1 - DUAL VOLTAGE MACHINE INPUT CONNECTIONSReturn to Master TOC INSTALLATIONReturn to Section TOC FIGURE A.2 - TRIPLE VOLTAGE MACHINE INPUT CONNECTIONSSHIELDING GAS GUN AND CABLE INSTALLATIONAUXILIARY POWER RECEPTACLES INSTALLATIONOPERATION SECTION TABLE OF CONTENTSOPERATION SECTION BOPERATIONB-2 Read entire Operation section before operating the POWER MIG 255CObserve all safety information throughout this manual ELECTRIC SHOCK can killWELDING CAPABILITY PRODUCT DESCRIPTIONRECOMMENDED PROCESSES AND EQUIPMENT LIMITATIONSDESCRIPTION OF CONTROLS WIRE SIZE CONVERSION PARTSWIRE DRIVE ROLL OPERATIONDRIVE AND IDLE ROLL SETS PROCEDURE FOR CHANGINGWIRE REEL LOADING - READI REELS, SPOOLS OR COILS OPERATIONWIRE DRIVE CONFIGURATION FEEDING WIRE ELECTRODEIDLE ROLL PRESSURE SETTING TO START THE WELDERReturn to Section TOC Return to Section TOC Return to Section TOC OPERATIONReturn to Master TOC Return to Section TOCINSTRUCTIONS TO ENTER SLOW RUN-IN SETTING RUN-IN SPEED ON STAN- DARD POWER MIG FEEDERFAST OR SLOW RUN-IN MODE SELECTION INSTRUCTIONS TO ENTER FAST RUN-INFAN CONTROL AVOIDING WIRE FEEDING PROBLEMSWIRE FEED OVERLOAD PROTECTION INPUT LINE VOLTAGE PROTECTIONOVERCURRENT PROTECTION B-10WELDING THERMAL OVERLOAD PROTECTION OPERATIONSECTION C ACCESSORIESACCESSORIES SECTION TABLE OF CONTENTSALTERNATIVE MAGNUM GMAW GUN AND CABLE ASSEMBLIES TIMER KIT INSTALLATION Optional K1701-1DRIVE ROLL KITS MAGNUM GUN CONNECTION KITSPOOL GUN OPERATING INSTRUCTIONS FOR TIMER KITCONNECTING THE SPOOL GUN TO THE POWER MIG 255C ACCESSORIESFIGURE C.1 MAKING A WELD WITH THE PRINCE XL SPOOL GUNMAKING A WELD WITH THE MAGNUM SG SPOOL GUN ACCESSORIESReturn to Section TOC Return to Section TOC Return to Section TOC ACCESSORIESSG Spool Gun Wire Feed Speed Return to Section TOCReturn to Section TOC Return to Section TOCReturn to Section TOC Return to Section TOCSECTION D MAINTENANCEMAINTENANCE SECTION TABLE OF CONTENTSCONTACT TIP AND GAS NOZZLE INSTALLATION GENERAL MAINTENANCEGUN CABLE CLEANING LINER REMOVAL AND REPLACEMENTMAINTENANCE LINER REMOVAL, INSTALLATION AND TRIMMING INSTRUCTIONS FOR MAGNUM 250LGUN HANDLE DISASSEMBLY Return to Master TOCReturn to Section TOC Return to Section TOC Return to Section TOC MAINTENANCED-4TABLE D.2 ACCESSORIES AND EXPENDABLE REPLACE Return to Section TOCSECTION E THEORY OF OPERATIONTHEORY OF OPERATION SECTION TABLE OF CONTENTSDiagram are the subject of discussion INPUT LINE VOLTAGEAND MAIN TRANSFORMER POWER MIG 255CDiagram are the subject of discussion OUTPUT RECTIFICATION ANDFEEDBACK CONTROL POWER MIG 255CPOWER MIG 255C CONSTANT VOLTAGE OUTPUTDiagram are the subject of discussion THEORY OF OPERATIONDiagram are the subject of discussion WIRE DRIVE MOTORAND FEEDBACK POWER MIG 255CTHEORY OF OPERATION WIRE FEED OVERLOAD PROTECTIONTHERMAL AND OVERLOAD PROTECTION OVERCURRENT PROTECTIONReturn to Section SCR OPERATIONTHEORY OF OPERATION Return to MasterReturn to Section TOC Return to Section TOCReturn to Section TOC Return to Section TOCTABLE OF CONTENTS TROUBLESHOOTING AND REPAIRTROUBLESHOOTING AND REPAIR SECTION Return to Master TOC Return to Master TOC Return to Master TOCReturn to Section TOC F-2TROUBLESHOOTING AND REPAIRF-2HOW TO USE TROUBLESHOOTING GUIDE Return to Master TOCReturn to Section Return to Section TOC TOC TROUBLESHOOTING & REPAIRPC BOARD TROUBLESHOOTING PROCEDURES Return to Master Return to Master TOC TOCSYMPTOMS TROUBLESHOOTING GUIDEPROBLEMS MISADJUSTMENTSSYMPTOMS TROUBLESHOOTING AND REPAIRPROBLEMS MISADJUSTMENTSSYMPTOMS TROUBLESHOOTING AND REPAIRPROBLEMS MISADJUSTMENTSPROBLEMS FUNCTION PROBLEMSTROUBLESHOOTING AND REPAIR SYMPTOMSPROBLEMS WIRE FEEDING PROBLEMSTROUBLESHOOTING AND REPAIR SYMPTOMSPROBLEMS WELDING PROBLEMSTROUBLESHOOTING AND REPAIR SYMPTOMSPROBLEMS F-10TROUBLESHOOTING AND REPAIR SYMPTOMSMAIN TRANSFORMER TEST TEST PROCEDURESF-11 TEST DESCRIPTIONMAIN TRANSFORMER TEST continued TEST PROCEDUREF-12 TROUBLESHOOTING AND REPAIRF-13 F-13TROUBLESHOOTING AND REPAIR MAIN TRANSFORMER TEST continuedF-14 F-14TROUBLESHOOTING AND REPAIR MAIN TRANSFORMER TEST continuedTROUBLESHOOTING AND REPAIR F-15RECTIFIER DIODE BRIDGE TEST F-15TEST PROCEDURE F-16TROUBLESHOOTING AND REPAIRF-16RECTIFIER DIODE BRIDGE TESTING continued Return to Section TOC Return to Section TOCRECTIFIER DIODE BRIDGE TESTING continued F-17TROUBLESHOOTING AND REPAIR F-17Return to Section TOC F-18F-18 Return to Section TOCTROUBLESHOOTING AND REPAIR STATIC SCR RECTIFIER ASSEMBLY TESTF-19 F-19TROUBLESHOOTING AND REPAIR STATIC SCR RECTIFIER ASSEMBLY TEST continuedF-20 TEST PROCEDURESTATIC SCR RECTIFIER ASSEMBLY TEST continued F-21TROUBLESHOOTING AND REPAIR F-21Return to Section TOC F-22F-22 Return to Section TOCTROUBLESHOOTING AND REPAIR ACTIVE SCR RECTIFIER ASSEMBLY TESTF-23 F-23TROUBLESHOOTING AND REPAIR ACTIVE SCR RECTIFIER ASSEMBLY TEST continuedF-24 TEST PROCEDUREACTIVE SCR RECTIFIER ASSEMBLY TEST continued F-25TROUBLESHOOTING AND REPAIR F-25ACTIVE SCR RECTIFIER ASSEMBLY TEST continued F-26TROUBLESHOOTING AND REPAIR F-26TROUBLESHOOTING AND REPAIR WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TESTF-27 F-27TROUBLESHOOTING AND REPAIR WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST continuedF-28 TEST PROCEDURETROUBLESHOOTING AND REPAIR F-29TEST FOR SUPPLY VOLTAGE TO TACHOMETER WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST continuedTROUBLESHOOTING AND REPAIR F-30TEST FOR FEEDBACK VOLTAGE TO CONTROL BOARD WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST continuedTROUBLESHOOTING AND REPAIR NORMAL OPEN CIRCUIT VOLTAGE WAVEFORMF-31 F-31TROUBLESHOOTING AND REPAIR TYPICAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADEDF-32 F-32F-33 F-33TROUBLESHOOTING AND REPAIR Return to Section TOC Return to Section TOC Return to Section TOCTROUBLESHOOTING AND REPAIR ABNORMAL OPEN CIRCUIT VOLTAGE OUTPUT CAPACITOR BANK NOT FUNCTIONINGF-34 F-34TROUBLESHOOTING AND REPAIR TYPICAL SCR GATE VOLTAGE WAVEFORMF-35 F-35Return to Section TOC F-36F-36 Return to Section TOCF-37 COMPONENT REPLACEMENT PROCEDURESCONTROL PC BOARD REMOVAL AND REPLACEMENT DESCRIPTIONPROCEDURE CONTROL PC BOARD REMOVAL AND REPLACEMENT continuedREMOVAL AND REPLACEMENT F-38TROUBLESHOOTING AND REPAIR CONTROL PC BOARD REMOVAL AND REPLACEMENT continuedF-39 F-39Return to Section TOC F-40F-40 Return to Section TOCTROUBLESHOOTING AND REPAIR WIRE DRIVE ASSEMBLY REMOVAL AND REPLACEMENTF-41 F-41TROUBLESHOOTING AND REPAIR WIRE DRIVE ASSEMBLY REMOVAL AND REPLACEMENT continuedF-42 F-42WIRE DRIVE ASSEMBLY REMOVAL AND REPLACEMENT continued F-43TROUBLESHOOTING AND REPAIR PROCEDUREReturn to Section TOC F-44F-44 Return to Section TOCTROUBLESHOOTING AND REPAIR SCR OUTPUT RECTIFIER REMOVAL AND REPLACEMENTF-45 F-45TROUBLESHOOTING AND REPAIR SCR OUTPUT RECTIFIER REMOVAL AND REPLACEMENT continuedF-46 PROCEDURESCR OUTPUT RECTIFIER REMOVAL AND REPLACEMENT continued F-47TROUBLESHOOTING AND REPAIR F-47Return to Section TOC F-48F-48 Return to Section TOCTROUBLESHOOTING AND REPAIR CAPACITOR BANK REMOVAL AND REPLACEMENTF-49 F-49TROUBLESHOOTING AND REPAIR CAPACITOR BANK REMOVAL AND REPLACEMENT continuedF-50 PROCEDURETROUBLESHOOTING AND REPAIR MAIN TRANSFORMER AND OUTPUT CHOKE REMOVAL AND REPLACEMENTF-51 F-51PROCEDURE F-52TROUBLESHOOTING AND REPAIRF-52MAIN TRANSFORMER AND OUTPUT CHOKE REMOVAL AND REPLACEMENT continued Return to Section TOCMAIN TRANSFORMER AND OUTPUT CHOKE REMOVAL AND REPLACEMENT continued F-53TROUBLESHOOTING AND REPAIR F-53Return to Section TOC F-54F-54 Return to Section TOCTROUBLESHOOTING AND REPAIR FAN MOTOR ASSEMBLY REMOVAL AND REPLACEMENTF-55 F-55TROUBLESHOOTING AND REPAIR FAN MOTOR ASSEMBLY REMOVAL AND REPLACEMENT continuedF-56 PROCEDUREF-57 WIRE SPEED RANGERETEST AFTER REPAIR OPEN CIRCUIT VOLTAGEReturn to Section TOC Return to Section TOCReturn to Section TOC Return to Section TOCReturn to Master TOC Return to Master TOC Return to Master TOC TABLE OF CONTENTSELECTRICAL DIAGRAMS SECTION Return to Master TOCReturn to Section TOC Return to Section TOC Return to Section TOC ELECTRICAL DIAGRAMSWIRING DIAGRAM - ENTIRE MACHINE - CODE 11192 L12464 Return to Section TOCReturn to Section TOC Return to Section TOC Return to Section TOC WIRING DIAGRAM - ENTIRE MACHINE CODE 11218 L12506ELECTRICAL DIAGRAMS Return to Section TOCReturn to Section TOC Return to Section TOC Return to Section TOC SCHEMATIC - ENTIRE MACHINE - G4752ELECTRICAL DIAGRAMS Return to Section TOCReturn to Section TOC SCHEMATIC - CONTROL PC BOARD - G4823-2D1 SHEETELECTRICAL DIAGRAMS Return to Master TOCReturn to Section TOC ELECTRICAL DIAGRAMSSCHEMATIC - CONTROL PC BOARD - G4823-2D1 SHEET Return to Master TOCReturn to Section TOC ELECTRICAL DIAGRAMSSCHEMATIC - CONTROL PC BOARD - G4823-2D1 SHEET Return to Master TOCto Section TOC PC BOARD ASSEMBLY - CONTROL - G4824-2D1ELECTRICAL DIAGRAMS to Master TOCReturn to Section TOC Return to Section TOC Return to Section TOC SCHEMATIC - DISPLAY PC BOARD L10951ELECTRICAL DIAGRAMS Return to Section TOCELECTRICAL DIAGRAMS PC BOARD ASSEMBLY - DISPLAY - L10952G-10 G-10SVM ERROR REPORTING FORM