Chopper Technology Fundamentals | Lincoln Electric SVM150-A guide

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THEORY OF OPERATION

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CHOPPER TECHNOLOGY

FUNDAMENTALS

The new era of welding machines such as the Ranger 250 employ a technology whereby a DC source is turned on and off (chopped up) at high speed, thensmoothed through an inductor to control an arc.

Hence the name “Chopper.” The biggest advantage of chopper technology is the high-speed control of the arc, similar to the inverter machines. A block diagram for this is as follows:

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	3 PHASE	DC RECTIFIER	SOLID STATE	INDUCTOR	ARC
	ALTERNATOR	AND FILTER	SWITCH	AND DIODE

ARC

CONTROL

In this system, the engine drives a three-phase alter-	the switch on and off, current in the inductor and the
nator, which generates power that is rectified and fil-	arc can be controlled. The following diagram depicts
tered to produce about 85VDC. The current is applied	the current flow in the system when the switch is open
through a solid state switch to an inductor. By turning	and closed:

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SWITCH

85VDC

DIODE

INDUCTOR

ARC

CURRENT WITH SWITCH OPEN

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CURRENT WITH SWITCH CLOSED

When the switch is closed, current is applied through	varying the ratio of on time versus off time of the switch
the inductor to the arc. When the switch opens, current	(Duty Cycle),	the current applied to the arc is con-
stored in the inductor sustains flow in the arc and	trolled. This	is the basis for Chopper Technology:
through the diode. The repetition rate of switch closure	Controlling the switch in such a way as to produce
is 20Khz, which allows ultra-fast control of the arc. By	superior welding.

RANGER 250

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Lincoln Electric SVM150-A service manual Chopper Technology Fundamentals, Switch 85VDC Diode

Contents

Ranger TM Ranger Safety ARC Rays can burn Electric Shock can killFumes and Gases can be dangerous Cylinder may explode if damaged Welding Sparks can cause fire or explosionIii Sûreté Pour Soudage a L’Arc Précautions DE Sûreté Master Table of Contents for ALL Sections Table of Contents Installation Section Technical Specifications Ranger 250 K1725-1/K1725-2 InstallationWeight Speed RPM Location and Ventilation Safety Precautions Additional Safety Precautions Electrical Output Connections Figure A.1 Ranger 250 Output Connections Welding Output Cables Auxiliary Power Receptacles Cable InstallationStandby Power Connections Cable Cable Size for Amps Length 100% Duty Cycle Figure A.2 Connection of the Ranger 250 to Premises Wiring Table of Contents Operation Section Operation Safety InstructionsOperating Instructions Controls and Settings Design Features Figure B.1 Case Front Panel Controls Engine Controls Welding Controls Engine OperationBefore Starting the Engine Check and fill the engine oil level Stopping the Engine Starting the EngineBREAK-IN Period General Information Welder OperationTable B.1 Typical Ranger 250 Fuel Consumption Constant Current CC-STICK Welding Stick WeldingPipe Welding Table B.2 Typical Current RANGES1 for Tungsten ELECTRODES2 Wire WELDING-CV Auxiliary PowerTIG Welding ARC Gouging Table B.4 Ranger 250 Simultaneous Welding and Power Loads Simultaneous Welding and Auxiliary Power Loads Table of Contents Accessories Field Installed Options OPTIONS/ACCESSORIESTIG Welding Accessories Semiautomatic Fcaw and MIG Welding Accessories Connection of Lincoln Electric Wire Feeders Accessories Place the Weld Terminals switch Return to Section TOC To Section TOC Accessories Terminals Remotely Controlled Connection of the LN-742 to Ranger 250 see Figure C.7 Figure C.7 Ranger 250/LN-742 Connection Diagram Ranger Table of Contents Maintenance Engine Maintenance Routine and Periodic Maintenance Frequency Maintenance Required Table D.2 Onan Engine Maintenance Schedule Air Pre-Cleaner Service AIR Cleaner ServiceEngine OIL Change Engine Oil Refill Capacities Spark Plug Service Air Filter Paper Element ServiceFuel Filter Service Engine Adjustment Overspeed is Hazardous Cleaning the Battery Battery MaintenanceCharging the Battery Optional Spark Arrestor WELDER/GENERATOR Maintenance Figure D.1 Major Component Locations Table of Contents Theory of Operation Section General Description Theory of Operation Return to Weld WINDINGS, RECTIFIER, Power Module and Feedback Figure E.4 Analog Power Board and Control Board Analog Power Board and Control Board Insulated Gate Bipolar Transistor Igbt Operation Minimum Output Pulse Width ModulationMaximum Output Chopper Technology Fundamentals Switch 85VDC Diode Ranger Table of Contents Troubleshooting & Repair Section HOW to USE Troubleshooting Guide Troubleshooting & Repair PC Board can be damaged by static electricity PC Board Troubleshooting Procedures Observe Safety Guidelines Troubleshooting GuideDetailed in the beginning of this manual Test Stator Voltage Test Engine Function Problems Engine Problems Troubleshooting & Repair Engine Problems Welding Problems Test Description Case Cover Removal and Replacement ProcedureMaterials Needed Removal Procedure Case Cover Removal and Replacement ProcedureReplacement Procedure Power Module Capacitor Discharge Procedure Test Procedure Power Module Capacitor Discharge Procedure Idler Solenoid Test Figure F.3 Idler Solenoid Leads Idler Solenoid Test Engine Throttle Adjustment Test Strobe-Tach Method Engine Throttle Adjustment Test Frequency Counter Method Figure F.5 High Idle Adjustment Vibratach Method Oscilloscope Method Rotor Resistance Test Figure F.7 Rotor Brush Leads Slip Rings Brushes Rotor Resistance Test Flashing and Rotor Voltage Test Flashing and Rotor Voltage Test Oil Pressure Switch Test Figure F.9 Field Diode Rectifier Bridge and Filter Capacitor Stator Voltage Tests To test the 120 VAC winding Stator Voltage TestsTo test the 240 VAC winding To test the field winding Field Rectifier Bridge Retaining TAB Cable Capacitor To test the feeder winding Figure F.12 14-PIN Amphenol PIN Assignments To test the stator weld windings Choke Analog Power PC Board Voltage Test Figure F.14 Analog Power PC Board Analog Power PC Board Voltage Test +5 VDC +20 VDC+15 VDC 15 VDC Output Rectifier Bridge Test Figure F.15 Plug J41 and Resistor R3 Locations Output Rectifier Bridge Test When all tests are complete Other PC board components could be faulty Power Module TestDescription Figure F.17 Power Module Connections Power Module Test Check Igbt for Shorts Tor terminal on the power module chopper Check Diode Module Figure F.19 Diode Module Test Heat Sink Terminals Flywheel Alternator Test Figure F.20 Plug J51 PIN Location Flywheel Alternator Test Normal Open Circuit Voltage Waveform 120VAC Supply Scope SettingsHigh Idle no Load MAX Control POT High Idle no Load Normal Open Circuit Voltage Waveform Stick Machine Loaded to 250 Amps AT 25 Volts Normal Weld Voltage Waveform Stick CC Normal Open Circuit Voltage Waveform Wire CV TAP Machine Loaded to 250 Amps AT 28 Volts Normal Weld Voltage Waveform Wire CV Description Procedure Power Module Assembly Removal and ReplacementRemoval Removal and Replacement Power Module AssemblyReplacement Figure F.22 Diode MODULE/POWER Module Assembly Details Power Module PC Board Removal and Replacement Figure F.23 Diode Module Mounting Details Power Capacitor Removal and Replacement Power Capacitor Removal and Replacement Output Rectifier Bridge and Choke Removal and Replacement Output Rectifier Output Rectifier Bridge and Choke Output Choke ENGINE/STATOR/ROTOR Removal and Replacement Engine Preparation and Lead Disconnection ENGINE/STATOR/ROTOR Removal and Replacement Troubleshooting & Repair Stator Lead Disconnection Figure F.28 Stator Leads Front Panel Engine/Stator/Rotor Assembly Removal Procedure Figure F.29 ENGINE/STATOR/ROTOR Assembly Removal Figure F.30 Stator and Rotor Removal Stator/Rotor Assembly Removal Rotor/Stator/Engine Reassembly Reassembly Notes General Notes on Reassembly Lead Reconnection Checklist Volt Wire Feeder Power Auxiliary Power OutputRetest After Repair Engine Output Table of Contents Electrical Diagrams Section Electrical Diagrams Wiring Diagram Ranger 250 Kohler Ranger 250 Kohler Wiring Diagram Wiring Diagram Ranger 250 Onan Ranger 250 Onan Wiring Diagram Control INTER-CONNECTION Diagram 4ELECTRICAL DIAGRAMSG-4 Output Terminal Schematic Complete Machine Schematic Analog Control Power Supply Schematic Battery Printed Circuit Board Schematic Bypass Printed Circuit Board 19462 M Schematic Chopper Printed Circuit Board 24660S Schematic Display Printed Circuit Board Schematic Weld Control Printed Circuit Board Sheet Electrical Diagrams Electrical Diagrams Electrical Diagrams Electrical Diagrams SVM Error Reporting Form