Lincoln Electric SVM169-A Protective Circuits, Thermal Protection, Overload Protection

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E-8

THEORY OF OPERATION

E-8

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PROTECTIVE CIRCUITS

Protective circuits are designed into the PRECISION TIG 185 to sense trouble and shut down the machine before the trouble damages the internal machine com- ponents. Both thermal protection and current overload are included. Fan as needed (F.A.N.) Fan runs for 5 seconds at power-up and stops at idle 8 minutes after welding.

THERMAL PROTECTION

9. OVER TEMPERATURE LIGHT-

If the welder

overheats due to blocked air flow,

high ambient air

temperature, or exceeded duty cycle, an internal ther- mostat will open disabling the welding output and this yellow light will illuminate. The cooling fans will contin- ue to run to cool the unit during this time. The light will go out when the unit cools and the thermostat resets. Once the light goes out, the machine will again become available to weld.

Once the machine cools sufficiently the thermostats are self-resetting. If the thermostat shutdown is caused

by excessive output or duty cycle and the fan is oper- ating normally, the power may be left on, and the reset should occur within a 15 minute period. If the fan is not functioning properly or the air intake louvers are obstructed, then the input power must be removed and the fan problem or air obstruction corrected.

OVERLOAD PROTECTION

The machine is electronically protected from producing excessively high output currents. The output is limited to 200 amps.

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PRECISION TIG 185

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Contents Precision TIG Safety Electric Shock can kill Safety Welding Sparks can cause fire or explosionPrécautions DE Sûreté Sûreté Pour Soudage a L’ArcMaster Table of Contents for ALL Sections Table of Contents Installation SectionInstallation Input Single Phase onlyModel Height Width Depth Weight K2345-2 Input at Rated OutputSafety Precautions Select Suitable LocationInput Connections Connections for TIG Gtaw Welding Input Reconnect ProcedureOutput Connections TIG Torch ConnectionShielding GAS Connection Remote Control ConnectionWork Cable Connection Precision TIG Operation Section Section BOperation Product Description Recommended Processes and EquipmentControls and Settings Control FunctionalityPulse TIG Control Welding in TIG ModeOperating Steps Remote Control Operation Benefits of the Precision TIG 185 DesignWelding in Stick Mode Recommended Electrode Amperage Ranges Precision TIGPrecision TIG Accessories Section Table C.1 AccessoriesFactory Installed Options Field Installed Options K2348-1 Under-Storage CartPrecision TIG Maintenance Section Section DSpark GAP Adjustment MaintenanceRoutine and Periodic Maintenance Figure D.2 Location of Maintenance Components Return to Section TOC Theory of Operation Section Section EGeneral Description Input Power CircuitTheory of Operation Output Rectification Feedback Control Figure E.3 Control Board and Output Feedback ControlHigh Voltage / High Frequency Circuit Figure E.4 High Voltage/High Frequency CircuitDC Welding Output Figure E.5 DC Welding Current GenerationAC Welding Output Figure E.6 AC Square Wave Welding Current GenerationSCR Operation Figure E.7 SCR OperationOverload Protection Protective CircuitsThermal Protection Troubleshooting & Repair Section Section FTroubleshooting & Repair High Voltage / High Frequency can damage test equipmentPC Board Troubleshooting Procedures WorkstationsProblems Possible Areas Recommended Symptoms Course of ActionPossible Areas Recommended Symptoms Problems Possible Areas Check the welding cables and or TIG Mode Problems Troubleshooting & Repair TIG Welding Problems Problems Possible Areas Electric Shock can Problems Possible Areas Recommended Symptoms Stick Welding Problems High Frequency Circuit Disable Procedure Test DescriptionProcedure Figure F.1 Spark GAP AssemblyT1 Transformer Test Test Procedure T1 Transformer TestReturn to Section Section TOC Primary Windings Primary VoltagesPrecision TIG Static SCR Test Static SCR Test Assembly Removal and Replacement Precision TIG Active SCR Test Active SCR Test Figure F.6 SCR Gate Locations Precision TIG Normal Open Circuit Voltage Waveform AC TIG ModeScope Settings DC TIG Mode AC Stick Mode DC Stick Mode Typical Output Voltage Waveform Machine Loaded Machine Loaded to 180 Amps AT 16VDCDC TIG Mode Machine Loaded to 180 Amps AT 26VDC DC Stick Mode 50 V/Div Precision TIG Troubleshooting and Repair SCR Bridge Assembly Removal and Replacement ProcedureSCR Bridge Assembly ProcedureFront Panel Mounting Screws 42TROUBLESHOOTING & REPAIRF-42 Figure F.9 Plug J2 on Control Board43TROUBLESHOOTING & REPAIRF-43 Replacement ProcedurePrecision TIG Polarity Switch Removal and Replacement Procedure Polarity Switch Removal ProcedureReplacement Procedure Precision TIG High Voltage Transformer Removal and Replacement Procedure High Voltage Transformer Transformer Secondary Leads Precision TIGFigure F.12 High Voltage Transformer Mounting Insulators Precision TIG Nutdriver Wrench Wire cutters Perform the SCR Bridge Assembly Removal Procedure Assembly Replacement Procedure Precision TIG Input Idle Amps Troubleshooting and RepairRetest After Repair Recommended Meters for Machine Output TestsPrecision TIG Electrical Diagrams Section Wiring Diagram Entire Machine G4549 Precision TIGSchematic Entire Machine G4588 G4588Schematic Control PC Board G4550-1B4-1 Schematic Control P.C. Board G4550-1B4-2 Schematic Control P.C. Board G4550-1B4-3 PC Board Assembly Control G4551-1 G4551SVM Error Reporting Form