Lincoln Electric SVM179-B service manual Input Power, Trigger Circuit

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E-3

THEORY OF OPERATION

E-3

FIGURE E.3 — INPUT POWER & TRIGGER CIRCUIT

ELECTRODE

67

INPUT

INPUT

CONTACTOR CURRENT TRANSDUCER

FEEDPLATE

SOLENOID

POLARITY

TIMER OPTION

V M

MOTOR

TACH

GUN

MOTOR

OVERLOAD

ARMATURE

CONTROL

BOARD

21

TACH FEEDBACK

1

GUN TRIGGER

WIRE

REMOTE

14 PIN AMPHENOL

SPEED

VOLTAGE

COLD

CC

TRIGGER

GAS

21

FEED

CV

INTERLOCK

PURGE

DIGITAL

RUN IN

DISPLAY

BOARD

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INPUT POWER

The DC input voltage is applied from the power source via the electrode cable and the work sensing lead on the across the arc model. With the control cable model 24 to 42VDC is supplied from the power source via the control cable and the work sense lead.

This voltage is applied through a bridge rectifier and an analog voltmeter (across the arc), or digital meter (con- trol cable) and then is supplied to the control board.

The control board the regulates and disperses the var- ious supply voltages needed for machine operation.

TRIGGER CIRCUIT

When the gun trigger is closed, the control board is sig- naled to apply armature voltage to the drive motor and to activate any auxiliary circuits that may be incorpo- rated within the LN-25PRO.

Trigger interlock is used for long welds. When an arc is established the trigger can be released. To stop welding, the gun trigger is pulled again, and when it is released the second time, the welding power source output turns off and the wire speed stops.

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

LN-25™ PRO