Lincoln Electric SVM123-A service manual Output Rectification, CONTROL, and Feedback

Page 37

E-3

THEORY OF OPERATION

E-3

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FIGURE E.3- Output, Rectification, Control and Feedback

 

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OUTPUT RECTIFICATION,

 

TOC

TOC

CONTROL, AND FEEDBACK

 

The neutrals of the Main Transformer secondary

proper amount of energy to the gates of the power

Section

Master

windings are connected together and the six starts

SCRs. When this gate signal is applied, at the cor-

 

 

 

 

are connected to the six SCR assemblies to form a

rect time, the SCR will turn “ON”. The amount of

to

to

six phase output. This six phase AC output from the

“ON” time versus “OFF” time determines the output

Main Transformer secondary is rectified and con-

of the machine. See SCR Operation.

Return

Return

trolled through the SCR bridge. Output current is

supply gate pulses to the SCR Bridge. Closing of

 

 

sensed at the shunt, and output voltage is moni-

The Pilot Relay signals the Firing Board circuit to

 

 

 

 

 

tored at the welding output terminals. This feedback

the Pilot Relay (a “dry” closure of leads #2 and #4)

 

 

information is processed in the control board. The

 

 

also brings the Latching Resistor into the machine

 

 

control board compares the commands of the Mode

 

 

output circuit. The Latching Resistor provides a

 

 

switch and the Output Control Potentiometer (or

 

 

pre-load for the SCR Bridge.

 

 

Remote Control) with the feedback information and

 

 

 

 

 

sends the appropriate signal to the Firing Board.

In later models (above code 9500) a Choke and

 

 

The Firing Board is a three phase circuit. Each

separate 500 amp output terminal is provided to

 

 

enhance lower current arc characteristics, espe-

TOC

TOC

phase provides two firing pulses, one for each of

cially for submerged arc and GMAW procedures

the two Silicon Controlled Rectifiers (SCR) con-

below 450 amps.

trolled by that phase. The firing circuit supplies the

to Section

to Master

 

 

 

Return

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NOTE: Unshaded areas of block logic diagrams are the subject of discussion.

 

 

 

 

IDEALARC DC-1000

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Contents Idealarc Electric and Magnetic Fields SafetyElectric Shock can kill Welding Sparks can cause fire or explosion Sûreté Pour Soudage a L’Arc Précautions DE SûretéMaster Table of Contents for ALL Sections Installation Output Technical Specifications Idealarc DCSelect Proper Location Electric Shock can KillElectrical Input Connections StackingFuse and Wire Sizes Reconnect ProcedureInput Power Supply Connections Ground ConnectionFigure A.3a Input Connection Diagram Figure A.3c -Input Connection Diagram Figure A.3d Input Supply Connection Diagram Output Connections Cutting Operation Connection for AIR/CARBON ARCIdealarc DC-1000 Operation Electric Shock can kill Safety InstructionsDesign Features Advantages Operational Features and ControlsGeneral Description Recommended Processes and EquipmentWelding Capability Return to Section Controls and SettingsRemote Control of Machine Operation Welding Procedure RecommendationsNA-3 Automatic Wire Feeder ARC Striking with Idealarc DC-1000 and the NA-3 Start Board Remote LN-8 SEMI-AUTOMATIC Wire FeederTable of Contents AccessoriesConnecting the NA-3 or LT-7 to OPTIONS/ACCESSORIESIdealarc DC-1000 Remote Output Control OptionalFigure C.2 NA-5 Wire Feeder Connection to Idealarc DC-1000 Connecting the NA-5 to the Idealarc DC-1000Connecting the LN-8 to the Idealarc DC-1000 Connecting the LN-9 Wire Feeder to the Idealarc DC-1000 Connecting the LN-7 Wire Feeder to the Idealarc DC-1000 Maintenance Routine and Periodic Maintenance Safety Precautions Electric Shock Can KillFigure D.1 Major Component Locations Idealarc DC-1000 Theory of Operation TOR, and Main Transformer Input Line VOLTAGE, ContacCONTROL, and Feedback Output RectificationCircuits Contactor HOLD-IN Protection DevicesFigure E.5 SCR Operation SCR OperationIdealarc DC-1000 Troubleshooting & Repair Locate Problem Symptom HOW to USE Troubleshooting GuideBoard can be damaged by static electricity PC Board Troubleshooting ProceduresControl Transformer Test Return Return to Master TOC Return Return to Section TOC Perform SCR Output Bridge Troubleshooting & Repair Function Problems Perform Firing Board Test Perform Control Board Test SCR Output Troubleshooting & Repair Control Transformer T2 Voltage Test Test DescriptionFigure F.1 Control Transformer Lead Location Test ProcedureFigure F.2 Control Transformer X1 and X2 Test Points Main Transformer T1 Voltage Test Test Description Figure F.4 Main Secondary Lead Test Points From Expected VAC Firing Board Test Test Procedure for Normal Firing Board Operation Figure F.7 Terminal Strip Jumper Wire Connections Figure F.8 Output Pilot Relay 4CR Location Then Table F.1 LED 7, 8 and 9 Check ListControl Board Test Figure F.9 Control Board LED and Pin Locations Test Procedure for Normal Control Board OperationIf LED 1 does not light, when the start switch is on Possible Problems Pertaining to the Control BoardFigure F.11 LED 2 Open Circuit Voltage Test Points If LED 4 lights Static SCR Test Figure F.12 Test ProcedureFigure F.13 SCR Heat Sink Assembly Test Points Static SCR Test Active SCR Test Active SCR Test Figure F.16 Heat Sink Assembly Test Points Battery Test Scope Settings Troubleshooting & Repair Troubleshooting & Repair Troubleshooting & Repair Troubleshooting & Repair Troubleshooting & Repair Troubleshooting & Repair Input Contactor 1CR Cleaning AND/OR Replacement Figure F.18 Input Contactor Cover Removal Cleaning ProcedureRemoval Contactor ReplacementInstallation SCR Output Bridge Replacement Figure F.22 Preparation For SCR Output Bridge Removal SCR Output Bridge RemovalFigure F.23 SCR Output Bridge Removal Removal of Individual SCR Heat Sink Assemblies SCR Output Bridge Installation SCR Heat Sink InstallationTOC Removal and Reassembly of Lift Bail Figure F.25 Lift Bail Removal Removal of Lift BailReassembly of Lift Bail Main Transformer Removal and Installation Figure F.26 Main Transformer Disassembly Main Transformer Disassembly and AssemblyCoil Removal Replacement Main Transformer DisassemblyTransformer Reassembly Transformer InstallationIdealarc DC-1000 Open Circuit Voltages Input Idle Amps and WattsIdealarc DC-1000 Electrical Diagrams Idealarc DC-1000 Wiring Diagram Codes 9919 Operating Schematic Control PC Board G1585 Layout Firing PC Board G1486-5 and above Layout Control PC Board G1585 Schematic Firing PC Board G1486-5 and above Schematic Output Snubber M14312 Schematic