Lincoln Electric DC-655 service manual Theory of Operation, General Description

Page 38

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E-2

E-2

THEORY OF OPERATION

FIGURE E.2 – INPUT LINE VOLTAGE, CONTACTOR, RECONNECT,

FAULT PROTECTION, MAIN AND CONTROL TRANSFORMERS

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CONTROL

TRANSFORMER

115VAC

CR2

R

E

C

O

N

N

E

C

T

CONTACTOR

CR1

42VAC

CONTROL

BOARD

TRANSFORMER

FAULT PROTECTION

 

 

 

 

 

 

 

OUTPUT

ARC FORCE

 

 

 

 

 

 

 

CONTROL

32VAC

 

 

 

 

OUTPUT

CONTROL

 

 

 

 

FIRING

CONTROL SIGNAL

 

32VAC

 

 

 

 

 

 

 

 

 

 

32VAC

 

 

BOARD

 

 

 

 

 

 

 

 

G

S

 

 

 

 

14-pin

 

115VAC

Fan

A

I

 

 

 

 

 

T

G

 

 

 

 

Amphenol

Receptacle

Motor

N

Fan

 

 

 

E

 

 

 

 

 

 

 

A

Thermal

 

 

 

 

 

 

 

 

L

Sensor

 

 

 

T

 

 

 

SNUBBER

 

CONTROL

 

 

S

 

 

 

BOARD

 

MODE

R

 

 

FAN

 

 

T

 

 

 

 

E

 

 

 

 

 

 

 

 

 

M

R

115VAC

BOARD

 

 

 

SWITCH

I

I

 

 

 

 

 

N

P

 

 

 

 

 

 

 

 

A

 

 

 

 

 

 

 

 

 

L

 

 

 

GATE SIGNAL

 

 

 

 

 

 

 

 

 

F

 

 

42VAC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E

 

 

 

 

 

 

 

 

 

E

 

 

MAIN

 

 

 

 

 

 

D

 

 

 

 

 

 

 

 

B

 

 

TRANSFORMER

 

 

 

 

A

 

 

 

 

 

 

 

 

 

C

 

POSITIVE

 

 

 

 

 

 

 

K

 

 

 

 

 

 

 

 

 

TERMINAL

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SHUNT

F

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E

 

 

 

 

 

 

 

 

 

E

 

42VAC 10VAC10VAC

 

 

 

 

 

 

LATCHING

D

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESISTOR

B

 

 

 

 

 

SCR BRIDGE

 

A

HIGH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C

NEGATIVE

 

 

 

 

 

 

CHOKE

 

K

TERMINAL

 

 

 

 

 

 

 

 

TO OPTIONAL

 

 

 

 

 

 

 

 

 

METER BOARD

 

 

 

 

 

 

 

 

 

LOW

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GENERAL DESCRIPTION

The DC-655 is a three-phase, SCR controlled DC power source. It is capable of either constant current or constant voltage output. It is rated at 650 amps, 100% duty cycle with outstanding arc characteristics for multiple welding processes.

A reconnect panel allows the user to configure the machine for the desired input voltage. This three- phase AC input is applied to the primary of the main transformer. The transformer changes the high volt- age, low current input power to a lower voltage, high- er current output. The finishes or “neutrals” of the main secondary coils are connected together, and the six starts of the secondary windings are connected to the rectifier assembly.

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INPUT LINE, CONTACTOR, RECONNECT, FAULT PROTECTION AND TRANSFORMERS

The desired three-phase input power is connected to the DC-655 through an input contactor located in the input box at the rear of the machine. Two phases of the input line are also connected to the control trans- former. The secondary of the control transformer sup- plies 115 VAC power to the control board transformer and to the input contactor through the fault protection relay. The control board transformer supplies 42 VAC to the control board.

In addition, the main transformer also has eight isolat- ed secondary windings. There are three 32 VAC wind- ings, which provide power and “timing” to the firing board. The 115 VAC winding powers the fan motor and provides the user with up to 20 amps of 115 VAC auxiliary power at the receptacle or 14-pin MS type connector. The 42 VAC winding provides up to 10 amps at the 14-pin MS type connector. Three other isolated coils are used to power the optional digital meter PC board. One winding is rated at 42 VAC, and the other two are each rated at 10 VAC.

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NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

IDEALARC DC-655

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Contents Idealarc DC-655 Safety California Proposition 65 WarningsElectric Shock can kill Cylinder may explode if damaged Précautions DE Sûreté Master Table of Contents for ALL Sections Table of Contents Installation Section Installation Technical Specifications DC-655Input Power Three Phase Electrical Input Connections Safety PrecautionsSelect Suitable Location Input Power Supply Connections Input Supply Connection DiagramOutput Connections Electrode and Work CablesAuxiliary Power Control Connections Auxiliary Power TableTerminal Strip 1 T.S.1 Terminal Strip 2 T.S.2Table of Contents Operation Section OPERATIONB-2 Operating InstructionsGeneral Description Design Features AdvantagesOperation Recommended Processes and EquipmentDC-655 Figure B.2 Lower Case Front Controls & Connections Case Back Connections Auxiliary PowerMachine Protection Over Current Protection Shutdown Remote Control Leads Fault Protection SHUTDOWN1Thermal Shutdown CC Mode ARC Force CC Mode ARC Gouging CV Mode CURRENT-LIMITINGCC Mode HOT Start Welding PerformanceTable of Contents Accessories Field Installed Options Remote Output ControlAutomatic Wire Feeders SEMI-AUTOMATIC Wire FeedersSet the Idealarc DC-655 Power toggle Accessories Semiautomatic Wire Feeders Connecting the LN-7 to the Idealarc DC-655 Terminal Strip GND Negative Positive Figure C.4 Idealarc DC-655 Table of Contents Maintenance General Maintenance Electric Shock can kill Figure D.1 General Component Locations Idealarc DC-655 Table of Contents Theory of Operation Section Theory of Operation Down Circuits Protective Devices and Shutdown Circuits SCR Operation Figure E.4 SCR OperationIdealarc DC-655 Table of Contents Troubleshooting & Repair Section Troubleshooting & Repair HOW to USE Troubleshooting GuidePC Board Troubleshooting Procedures Troubleshooting Guide Board LED Chart ControlBridge Test LED ChartOutput Perform the SCR Bridge TestTransformer Test See the Idle Shut Down TimerMain Function Problems Thermal Fan/Snubber PC Troubleshooting & Repair Welding Problems Mode Current Limiting See the Control BoardMaterials Needed Internal Trigger Circuit TestTest Description Internal Trigger Circuit Test Test ProcedureTrigger Diagram Simplified Trigger Diagram. If a resistance SectionFigure F.3 Simplified Trigger Diagram Firing Board Test Firing Board Test Figure F.4 Firing Board Trigger Circuit Test Points and LEDsMain Transformer Test Figure F.5 14-PIN Receptacle Figure F.4 Main Transformer T1 Voltage Test Main Transformer T1 Voltage Test Figure F.6 Input Contactor and Primary LeadsTroubleshooting & Repair Figure F.8 Terminal Strip Figure F.9 Firing Board Plug J5 Pins Control Transformer T2 Test Control Transformer T2 Test Figure F.10 Control TransformerHigh Voltage is present at Control Board Transformer T3 Test Control Board Transformer T3 Test Perform the Control Transformer T2 TestInput Contactor Test Input Contactor Test Transformer T2 TestTest for Contact Continuity Figure F.13 Input Contactor Test ConnectionsStatic SCR Test Static SCR Test Figure F.15 Heat Sink Test Points Active SCR Test Active SCR Test Figure F.17 Heat Sink Test Points Anode Cathode Thermal FAN/SNUBBER Board LED Chart LED Functions and IndicationsControl Board LED Chart LED # LED Functions and IndicationsScope Settings Maximum Output Setting no Load Normal Open Circuit Voltage Waveform Constant Voltage MIGMinimum Output Setting no Load Troubleshooting & Repair Typical SCR Gate Voltage Waveform Constant Voltage MIG Installation Input Contactor CR1 CLEANING/REPLACEMENT DescriptionInput Contactor CR1 CLEANING/REPLACEMENT Cleaning ProcedureSCR Rectifier Bridge Removal Replacement Procedure SCR Rectifier Bridge Removal Replacement ProcedureProcedure Reassembly SCR Rectifier Bridge LEG Assembly Mounting BracketsMain Transformer and Choke Removal Replacement Procedure Main Transformer and Choke Removal Output Choke RemovalMain Transformer Removal Retest After Repair Input Idle Amps and WattsSVM Error Reporting Form Section G Electrical Diagrams Control Board Schematic G3384 Firing Board Schematic G2792 Thermal Fan/Snubber Board Schematic L10123 Control Board Layout G3385-1 Firing Board Layout G2699-2 Thermal Fan/Snubber Board Layout L10124-1 Return to Section TOC
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