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ARC VOLTAGE, WIRE SPEED
CONTROL AND METERING
The arc voltage, which is sensed at the work piece and
motor gear box, is connected through a polarity switch
to the voltage board. This actual arc voltage is com-
pared to the reference preset voltage that is set by the
voltage control. The voltage board determines what
correction signal needs to be sent to the Lincoln weld-
ing power supply. This voltage control signal is cou-
pled to the power supply through the input connector.
The Lincoln power supply then adjusts the welding arc
voltage to meet the demands of the preset reference
voltage.
The hall effect device sends motor speed information
to the control board. This feedback voltage is com-
pared to the reference command preset by the wire
speed control. The control board determines what cor-
rection is needed and sends the appropriate signal to
the power board. The power board then adjusts the
motor armature voltage to comply with the command
from the control board.
A three-digit meter is provided to read both arc voltage
and wire feed speed. Either the preset or the actual
welding parameters can be displayed.
THEORY OF OPERATION
E-4 E-4
LN-9 GMA Wire Feeder
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NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
FIGURE E.4 – ARC VOLTAGE, WIRE SPEED CONTROL AND METERING
INPUT
CONNECTOR
TO
VOLTAGE
BOARD
TO
CONTROL
BOARD
METER
BOARD
VOLTS
SPEED
SWITCH
T1
CIRCUIT
BREAKER
R1
TRIGGER
CONNECTOR
TRIGGER
BOARD
F
U
S
E
T2
C
O
N
T
R
O
L
B
O
A
R
D
VOLTAGE
BOARD
P
O
W
E
R
B
O
A
R
D
GROUND
LEAD
PROTECTOR
WIRE
FEED
MOTOR
WIRE
SPEED
CONTROL
VOLTAGE
CONTROL
POLARITY
SWITCH
VOLTAGE SENSING
VOLTAGE CONTROL
POWER SOURCE OUTPUT TRIGGER (#2 )
S
H
U
T
D
O
W
N
+ 15VDC
+ 15VDC
WIRE SPEED CONTROL
GEAR
BOX
TRIGGER SIGNAL
TRIGGER SIGNAL
R
E
F
E
R
E
N
C
E
V
O
L
T
A
G
E
WORK
ELECTRODE VOLTAGE SENSING
24VAC
28VAC
10VAC
HALL EFFECT
DEVICE
GAS
SOLENOID