Lincoln Electric SVM169-A Theory of Operation, General Description, Input Power Circuit

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E-2

THEORY OF OPERATION

E-2

GENERAL DESCRIPTION

 

 

3.

Enhanced version of the patented MicroStartTM

 

 

 

 

 

 

Technology for its lower Minimum (5amps) to high-

The PRECISION TIG 185 is a member of our field

 

er Maximum (185 amps) output control range.

 

acclaimed Precision TIG family of industrial arc weld-

 

 

 

 

 

 

 

 

ing power sources. Premium features include:

 

 

4.

Built-in high frequency stabilization for DC TIG

 

 

 

 

 

1. Precise constant current output.

 

 

 

starting and continuous AC TIG welding.

 

2. Full range square wave AC/DC TIG (GTAW) weld-

5. AC/DC Stick (SMAW capability.)

 

 

ing.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIGURE E.2 Main Transformer and Input Power

 

 

 

 

 

 

 

 

 

BY-PASS

 

 

 

 

 

 

 

 

 

BOARD

 

 

 

 

 

 

POLARITY

 

 

 

 

WORK

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MAIN

 

 

SWITCH

 

 

 

 

ELECTRODE

 

 

 

 

 

 

 

 

 

 

 

HI-FREQUENCY

 

 

 

TRANSFORMER

 

 

 

 

 

 

 

TRANSFORMER

 

 

 

INPUT

 

 

 

 

 

 

 

 

 

 

 

 

POWER

 

 

 

 

 

 

 

 

 

 

 

 

SWITCH BYPASS

 

 

 

 

 

C

 

 

 

ASBLY

 

 

 

 

 

 

 

 

 

 

 

 

 

H

 

 

 

H1

 

X1

AC

DC+

 

O

 

 

 

 

 

 

K

 

 

 

 

 

 

SCR

 

 

 

 

 

 

 

 

E

 

 

 

 

 

 

BRIDGE

 

 

 

 

H2

 

X2

 

 

SHUNT

 

 

HIGH VOLTAGE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

AC

DC-

 

 

TRANSFORMER

 

 

 

H3

 

 

 

 

 

 

 

 

 

 

 

 

F

 

 

CIRCUIT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E

 

 

 

 

 

 

 

 

 

 

 

 

E

 

 

 

 

 

 

 

 

 

 

 

 

D

 

 

 

 

 

 

 

 

 

 

 

 

B

 

 

 

 

 

 

 

 

 

 

 

 

A

 

 

 

 

 

 

 

 

 

 

 

 

C

 

 

 

 

 

 

 

 

 

 

 

 

K

 

 

 

 

 

 

 

 

 

18VAC

 

 

 

 

115VAC

 

 

 

 

 

18VAC

 

CONTROL

 

 

 

POWER

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FAN

115VAC

 

BOARD

 

 

 

"ON"

 

 

 

 

 

 

 

DIGITAL

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DISPLAY

 

 

 

 

 

 

 

 

 

 

 

 

MODE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SWITCH

 

 

 

REMOTE

 

 

 

 

THERMO-

 

 

 

 

 

 

 

RECEPTACLE

 

 

THERMAL

GAS

OUTPUT

 

 

 

 

 

 

STATS

 

 

 

 

 

 

LIGHT

VALVE

CONTROL

 

 

 

 

 

 

 

 

AUTO

PULSE TIG STICK

AC

PULSE POSTFLOW

BALANCE FREQ. LED LED

BALANCE CONTROL CONTROL

LED

LED

CONTROL

 

INPUT POWER CIRCUIT

 

incorporated in the main transformer. The 115VAC

 

 

winding supplies power to the fan motor and also,

The desired single-phase input power is connected to

through the control board,

powers the gas solenoid

valve and the high voltage transformer. The 18VAC

the TIG 185 through an input power switch located in

winding provides power to the trigger circuitry. The

the front panel of the machine. The machine can be

other 18VAC winding is rectified and regulated to a

configured for either 230VAC or 208VAC input voltage

15VDC supply which operates the circuitry on the con-

by connecting the appropriate lead (H2 or H3) to the

trol board.

 

input power switch. When the input power switch is

 

 

 

turned “ON” the input voltage is applied directly to the

 

 

primary of the main transformer.

 

 

 

The main transformer changes the high voltage, low current input power to a low voltage, high current out- put which is available at the main secondary winding (X1 and X2). In addition three auxiliary windings are

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

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 Input Reconnect Procedure Output ConnectionsConnections for TIG Gtaw Welding 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 Troubleshooting and Repair Retest After RepairInput Idle Amps 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