Lincoln Electric DC-655 service manual Thermal Shutdown, Over Current Protection Shutdown

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B-7

B-7

OPERATION

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THERMAL SHUTDOWN

This welder has thermostatic protection from exces- sive duty cycles, overloads, loss of cooling, and high ambient temperature. When the welder is subjected to an overload or loss of cooling, a thermostat will open. This condition will be indicated by the illumination of the yellow Thermostatic Protection Light on the case front (see Figure B.1). The fan will continue to run to cool the power source. No welding is possible until the machine is allowed to cool and the Thermostatic Protection Light goes out.

SHORTED RECTIFIER FAULT PROTECTION

If a short occurs across one of the silicon controlled rectifiers of the DC-655, a potentially hazardous AC voltage could appear across the welding output termi- nals, even in idle mode when no output should be pre- sent. If such a fault occurs, the DC-655 will shut down the input primary voltage to the transformer to prevent the fault output. Control PC board LED3, input shut- down light, turns on.

If this input shutdown occurs the input power pilot light remains lit, since the power switch is ON and control power is still present. Welding output or auxil- iary supply output will not be present.

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OVER CURRENT PROTECTION

SHUTDOWN

Average Current Shutdown

To protect the SCR’s , the DC-655 will shut down to essentially no output if the output current averages over 900 amps for about 5-6 seconds, and in less than

0.3seconds if averaging over 1200 amps (shorter time for higher current). Control PC board LED4, shutdown light, will turn on.

This average current shut down can only be reset by opening the feeder gun trigger, or switching the DC- 655 Output/Remote switch out of the “on” position.

Peak Current Shutdown

To protect the SCRs, the DC-655 will shut down imme- diately to essentially no output if the peak output cur- rent exceeds 2500 amps (about 1800A average). Control PC board LED4, shutdown light, will turn on.

This peak current shut down can be reset by turning the DC-655 input power off, then on.

REMOTE CONTROL LEADS FAULT PROTECTION SHUTDOWN1

This input shut down is reset by turning the DC-655 input power off, then on. If the fault is not corrected however, the shutdown will re-occur when turning on the input power.

IDLE SHUTDOWN TIMER

For additional operating economy, the DC-655 can be set up to automatically shut off the primary input power to the main transformer after a selectable time (1/2 or 2 hr.) has expired without welding. The unex- pired timer is reset with each weld.

The idle mode timer is activated by setting Switch #1 (left most) of the DIP Switch located on the lower-cen- ter of the DC-655 Control PC board. from the down (Off) position to the up (On) position. Setting Switch #2 of the DIP switch to up (On) sets the shutdown time to 2 hours. Setting Switch #2 of the DIP switch to down (Off) sets the shutdown time to 1/2 hour. Shutdown is reset by turning the DC-655 input power off, then on.

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The remote control leads from the 14-pin receptacle or terminal strip are protected against high voltage faults to the electrode circuit or auxiliary voltage supplies. If such a fault occurs, the DC-655 will shut down the input primary voltage to the transformer to prevent the fault output. Control PC board LED3, input shutdown light, turns on.

If this input shutdown occurs the input power pilot light remains lit, since the power switch is ON and control power is still present. Welding output or auxil- iary supply output will not be present.

This input shut down is reset by turning the DC-655 input power off, then on. If the fault is not corrected however, the shutdown will re-occur when turning on the input power.

Switch #1 Timer On/Off

(UP=ON, Down=OFF)

1

2

3

4

DIP Switch

Switch #2 Time selection (UP=2 hours, Down=1/2 hour)

Note: See Weld Performance section for use of switch #3 and #4.

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1Note on earlier machines: LED4 will turn on and output will be disabled if this fault occurs.

IDEALARC DC-655

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Contents Idealarc DC-655 California Proposition 65 Warnings SafetyElectric Shock can kill Cylinder may explode if damaged Précautions DE Sûreté Master Table of Contents for ALL Sections Table of Contents Installation Section Technical Specifications DC-655 InstallationInput Power Three Phase Safety Precautions Select Suitable LocationElectrical Input Connections Input Supply Connection Diagram Input Power Supply ConnectionsElectrode and Work Cables Output ConnectionsAuxiliary Power Table Auxiliary Power Control ConnectionsTerminal Strip 2 T.S.2 Terminal Strip 1 T.S.1Table of Contents Operation Section Operating Instructions OPERATIONB-2Operation Design Features AdvantagesGeneral Description Recommended Processes and EquipmentDC-655 Figure B.2 Lower Case Front Controls & Connections Auxiliary Power Machine ProtectionCase Back Connections Remote Control Leads Fault Protection SHUTDOWN1 Thermal ShutdownOver Current Protection Shutdown CC Mode HOT Start CV Mode CURRENT-LIMITINGCC Mode ARC Force CC Mode ARC Gouging Welding PerformanceTable of Contents Accessories Remote Output Control Field Installed OptionsSEMI-AUTOMATIC Wire Feeders 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 Electric Shock can kill General MaintenanceFigure 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 Figure E.4 SCR Operation SCR OperationIdealarc DC-655 Table of Contents Troubleshooting & Repair Section HOW to USE Troubleshooting Guide Troubleshooting & RepairPC Board Troubleshooting Procedures Troubleshooting Guide Control Board LED ChartOutput LED ChartBridge Test Perform the SCR Bridge TestSee the Idle Shut Down Timer MainTransformer Test Function Problems Thermal Fan/Snubber PC Troubleshooting & Repair Welding Problems See the Control Board Mode Current LimitingInternal Trigger Circuit Test Test DescriptionMaterials Needed Test Procedure Trigger DiagramInternal Trigger Circuit Test Section Simplified Trigger Diagram. If a resistanceFigure F.3 Simplified Trigger Diagram Firing Board Test Figure F.4 Firing Board Trigger Circuit Test Points and LEDs Firing Board TestMain Transformer Test Figure F.5 14-PIN Receptacle Figure F.4 Main Transformer T1 Voltage Test Figure F.6 Input Contactor and Primary Leads Main Transformer T1 Voltage TestTroubleshooting & Repair Figure F.8 Terminal Strip Figure F.9 Firing Board Plug J5 Pins Control Transformer T2 Test Figure F.10 Control Transformer Control Transformer T2 TestHigh Voltage is present at Control Board Transformer T3 Test Perform the Control Transformer T2 Test Control Board Transformer T3 TestInput Contactor Test Transformer T2 Test Input Contactor TestFigure F.13 Input Contactor Test Connections Test for Contact ContinuityStatic 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 LED Functions and Indications Thermal FAN/SNUBBER Board LED ChartLED # LED Functions and Indications Control Board LED ChartScope Settings Normal Open Circuit Voltage Waveform Constant Voltage MIG Maximum Output Setting no LoadMinimum Output Setting no Load Troubleshooting & Repair Typical SCR Gate Voltage Waveform Constant Voltage MIG Installation Description Input Contactor CR1 CLEANING/REPLACEMENTCleaning Procedure Input Contactor CR1 CLEANING/REPLACEMENTSCR Rectifier Bridge Removal Replacement Procedure Replacement Procedure ProcedureSCR Rectifier Bridge Removal SCR Rectifier Bridge LEG Assembly Mounting Brackets ReassemblyMain Transformer and Choke Removal Replacement Procedure Output Choke Removal Main Transformer and Choke RemovalMain Transformer Removal Input Idle Amps and Watts Retest After RepairSVM 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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