Lincoln Electric IM823-A manual Constant Current Operation, Figure B.3

Page 23

B-8

OPERATION

B-8

 

 

 

CONSTANT CURRENT OPERATION

CAUTION

( See Figure B.3)

Lincoln Electric does NOT recommend constant current semiautomatic welding for applications which need to meet specified weld metal chemical or mechanical property requirements or weld quality requirements.

-----------------------------------------------------------------

Most semiautomatic welding processes perform better using constant voltage power sources.

Welding codes usually do not address the power source selection or specifically, whether the welding process is to be operated in the constant voltage or constant current mode. Instead, codes typically specify limitations on the current, voltage, heat input and preheat temperature based on the material to be welded. The intention is to assure that proper weld material properties will develop.

Welding is sometimes performed using constant current power sources. The operation can be more convenient because it may allow the use of an existing stick (SMAW) power source and the power source can be placed at a distant location without any provision for adjusting the output settings.

For constant current operation, the power source is set to deliver the specified current. The power source regulates this current regardless of changes in the welding circuit, including cable length, electrode diameter, wire feed speed, contact tip to work distance, etc.

Changes in the wire feed speed (WFS) or contact tip to work distance (CTWD) affect the arc voltage when constant current power sources are used. Lowering the wire feed speed raises the voltage, raising the wire feed speed lowers the voltage. Lengthening the contact tip to work distance raises the voltage, short- ening the contact tip to work distance lowers the volt- age.

If the contact tip to work distance is properly main- tained, a satisfactory operating voltage range may be achieved, and a sound weld may result. However, when a welder uses a longer contact tip to work dis- tance, an arc-sensing wire feeder compensates by increasing the wire feed speed to regulate the voltage. Even if the voltage and current remain unchanged, the increased wire feed speed may result in a deposition rate well beyond the specified range of the electrode. Under these conditions, the specified weld metal prop- erties may not be achieved.

Constant voltage power sources deliver large current surges to stabilize the arc when the electrode is short- ed or the arc length is very short. However, a constant current power source does not provide such a response to stabilize the arc. It may be difficult to achieve required weld metal properties, or to achieve the required quality of welds needed to pass nonde- structive tests, when such welds are made under con- stant current operation.

FIGURE B.3

Constant Current Power Source

Current

LN-15

GUN AND CABLE

Wire

ASSEMBLY

+ Welding Cable

Feeder

CTWD

(Electrode)

 

 

 

WFS

-Current

Welding Cable (Work)

LN™-15 ACROSS THE ARC MODEL & (CE)

Page 22 Page 24
Image 23
Page 22 Page 24
Contents LN -15 Wire Feeder California Proposition 65 Warnings SafetyElectric Shock can kill Iii Welding and Cutting Sparks can Cause fire or explosionSûreté Pour Soudage a L’Arc Précautions DE SûretéSafety Safety Thank You Table of Contents LN-15 Across the ARC Model & CE InstallationTechnical Specifications LN-15 K1870-1, K1870-2 CE High Frequency Protection Safety PrecautionsLocation Work Clip LeadElectrode Connection Engine Drive Power Source ConnectionPower Source Connection Weld Cable ConnectionsFigure A.1 Connections Procedure to Install Drive Rolls and Wire GuidesGUN and Cable Assemblies Electrode PolarityFeeding Wire Electrode Operation Safety PrecautionsGeneral Description Across the ARC Model 83% ProcedurePREFLOW, Postflow and Burnback Times LN-15 POWER-UP SequenceNormal POWER-UP Display Welding Mode CV/CC Mode and WFS UnitsSet the pressure arm as follows See Figure B.2a CV/CC ModeSpring Tension ARM WFS UnitsCold FEED/GAS Purge Switch Wire Drive ConfigurationShielding GAS Connection Step Trigger Interlock SwitchFlow Meter Spindle BrakeFigure B.3 Constant Current OperationFigure B.4 CC Wire Speed Setting Making a Weld Optional Equipment AccessoriesFactory Installed Equipment Calibration Specification MaintenanceRoutine Maintenance Periodic MaintenanceHOW to USE Troubleshooting Guide TroubleshootingCourse of Action ProblemsRecommended Symptoms Authorized Field Service FacilityYour local Lincoln Authorized Field Service FacilityFault Code Description Possible Adjustments Errors on the DisplayLN-15 Across the ARC Model DiagramsDiagrams G4053-5 Dimension PrintLN-15 Across the ARC Model & CE LN-15 Across the ARC Model & CE LN-15 Across the ARC Model & CE Precaucion Warnung
Top Page Image Contents