Lincoln Electric SVM101-B service manual Passive

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Section TOC

Master TOC

E-6

THEORY OF OPERATION

E-6

 

FIELD EFFECT TRANSISTOR OPERATION

 

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GATE

SOURCE

TERMINAL

(0 VOLTS)

TERMINAL

SOURCE (N)

DRAIN

TERMINAL

DRAIN (N)

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SUBSTRATE (P)

N CHANNEL

A. PASSIVE

GATE TERMINAL (+ 6 VOLTS)

SOURCE (N)

DRAIN (N)

ELECTRONS

B. ACTIVE

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An FET is a type of transistor. FETs are semiconduc- tors well suited for high-frequency switching because they are capable of going from full off to full on much more quicklfy than other types of semi-conductors.

Drawing A above shows an FET in a passive mode. There is no gate signal, zero volts relative to the source and, therefore, no current flow. The drain terminal of the FET may be connected to a voltage supply; but since there is no conduction, the circuit will not supply current to downstream components connected to the source. The circuit is turned off like a light switch in the OFF position.

Drawing B above shows the FET in an active mode. When the gate signal, a positive DC voltage relative to the source, is applied to the gate terminal of the FET, it is capable of conducting current. A voltage supply con- nected to the drain terminal will allow the FET to con- duct and henceforth supply current to downstream components. Current will flow through the conducting FET to downstream components as long as the gate signal is present. This is similar to turning on a light switch

V300-I

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Contents Invertec Safety ARC Rays can burn Electric Shock can killFumes and Gases can be dangerous Safety Welding Sparks can cause fire or explosionCylinder may explode if damaged IiiPrécautions DE Sûreté Sûreté Pour Soudage a L’ArcMaster Table of Contents for ALL Sections Installation Section Table of ContentsSection A-1 Installation Three Phase Single Phase3INSTALLATIONA-3 Product Description Electrical InstallationInput Voltage Setup LocationPower Input Connection Connection of Wire Feeders to the InvertecSingle Phase Input Three Phase InputK900-1 DC TIG Starter Connection Remote Control of InvertecParallel Operation Output Cables 6INSTALLATIONA-6Quick Disconnect Plugs Operation Section Section B-1Operation Operating InstructionsDuty Cycle Control Function / OperationMode Switch Full Range Is Is Very Soft, 10 Is Very CrispMeter Polarity Switch Auxiliary PowerAccessories Section Section C-1Accessories Options / AccessoriesMaintenance Section Section D-1Maintenance Input Filter Capacitor Discharge ProcedurePreventive Maintenance Overload ProtectionFigure D.2 Location of Maintenance Components Theory of Operation Section Section E-1Theory of Operation Input Line Voltage & Auxiliary TransformerPrecharge & Protection Circuits Return to Return to Section TOCSwitch Boards Figure E-4 ---SWITCH Circuits & TransformerOutput and Control Circuits Figure E-5 --OUTPUT & Control CircuitsPassive Minimum Output Pulse Width ModulationMaximum Output Overload Protection Protective CircuitsThermal Protection Troubleshooting & Repair Section Section F-1Troubleshooting & Repair HOW to USE Troubleshooting GuidePC Board Troubleshooting Procedures Input Filter Capacitor CONDITION- ING Additional Information Oscilloscope WarningMatched Parts Feeding Problems DepartmentFeeding Problems See Input Rectifier test See Output Diodes test See Switch Board test V300-I 11TROUBLESHOOTING & REPAIRF-11 Input Filter Capacitor Discharge ProcedureInput Filter Capacitor Discharge Procedure Figure F.I Location of Input Filter Capacitor TerminalsOutput Pilot Circuit Test Test Procedure G2527 J2 J4 J3V300-I Protection Board Output Test Test Procedure Turn Power Switch OFF313 306 J15 275F 311 V300-I Protection Figure F.6 Inserting ProbesCapacitor Balance Test Static Capacitor Test 912 V300-I Switch Board Test Switch Board Test Switch Board Test Table F.3 Snubber Resistor Test Snubber Resistor Test Check Test Result Conclusion Next Test Step Repair ActionOutput Diode Test Test Procedure Output Diode TestInput Rectifier Test Points Steps Table F.5Probe Acceptable Meter Reading Overcurrent Protection Current Trigger Test Overcurrent Protection Current Trigger Test 302 G2527 Control J1 275DControl Overvoltage Protection DC Trigger Circuit Test Overvoltage Protection DC Trigger Circuit Test Figure F.16 PC Boards Removed306 275F 309 310 1J8 #311 1J14 6J6 #302 #313 #275D3J8 2J14 1J6 #301 #305Thermal Protection AC Trigger Circuit Figure F.20 PC Boards Moved for Access Thermal Protection AC Trigger CircuitFigure F.21 Thermal Protection AC Trigger Circuit V300-I Power Board Test Test a Power Board TestTest B Figure F.23 Power Board Test Points Simplified Trigger Circuit Capacitor Removal and Replacement Procedure Capacitor Removal and Replacement ProcedureFigure F.27 -- Removing Capacitor Nuts Figure F.27 Switch Board Removal and Replacement Procedure Switch Board Replacement ProcedureTest After Switch Board or Capacitor Replacement Test After Switch Board or Capacitor Replacement Perform Retest After RepairOutput Diode Replacement Procedure 60TROUBLESHOOTING & REPAIRF-60 Output Diode Replacement Procedure61TROUBLESHOOTING & REPAIRF-61 Procedure Diode ModulesRetest After Repair OCV at rated Input V300-PROOutput Min. Acceptable Max. All Modes V300-I V300-PROElectrical Diagrams Section Section G-1Wiring Diagram Entire Machine Code 9826 L8657 #0#Wiring Diagram Entire Machine Code 9827 L8938 ReturnWiring Diagram Entire Machine Code 10036 L9299 Wiring Diagram Entire Machine Code 10037 L9300 $ $Wiring Diagram Entire Machine Code 10132 L9567 SectionWiring Diagram Code Wiring Diagram Entire Machine Code 10133 L9568Wiring Diagram Entire Machine Code 10258 L10189 $& $V300-I Wiring Diagram European Wiring Diagram Entire Machine Code 10336, 10450 L10205Schematic Entire Machine # . $ #$ !#$ #! %&$Schematic Driver PC Board S20216 PC Board Assembly Driver L8660 IdentificationSchematic Driver PC Board S20799 PC Board Assembly Driver DescriptionSchematic Switch PC Board L8440 PC Board Assembly Switch L8441 CAPACITOR, Cemo 2700P 50V 5%Schematic Switch PC Board L10956 PC Board Assembly Switch L10958-1 Reqd IdentificationSchematic Control PC Board G2525 Electrical Diagrams CAPACITOR, Cemo 150P Schematic Protection PC Board M16097 PC Board Assembly Protection L7915-2 DZ1Schematic Power PC Board M16018 PC Board Assembly Power L8033-7 VOLT. REG. & Heat Sink Asbly