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E-4
THEORY OF OPERATION
E-4
VARIABLE VOLTAGE
BOARD, METER SHUNT,
WIRE SPEED AND
REMOTE OUTPUT
CONTROLS
The optional variable voltage board
enables the LN-8 to be used with a con-
stant current power source. The vari-
able voltage board monitors the arc
voltage via leads #21 and #567 and
modifies the wire feed speed according
to arc voltage variations and require-
ments.
The wire speed control dictates to the
control board the directives of the
operator. The control board adjusts the
armature voltage applied to the wire
feed motor to change the motor speed.
The remote output control permits
power source control from the LN-8
unit. The remote control is coupled to
the welding power source via leads #75,
#76, and #77 through the input
receptacle.
The electrode meter shunt, which is
connected to and also in series with the
gun connector block, senses the weld-
ing current and arc voltage. This infor-
mation is used by the variable voltage
board and also the optional meter kit.
FIGURE E.3 – VARIABLE VOLTAGE BOARD, METER SHUNT, WIRE SPEED,
AND REMOTE OUTPUT CONTROLS
LN-8
REMOTE
OUTPUT
CONTROL
ELECTRODE
METER
SHUNT
WIRE
FEED
MOTOR
CIRCUIT
BREAKER
INPUT
RECEPTACLE
VARIABLE VOLTAGE
BOARD
CONTROL
BOARD
WIRE FEED
SPEED CONTROL
THERMAL
CIRCUIT
BREAKER
RELAY
BOARD
GLP
REED
SWITCH
TRIGGER
TRANS.
WIRE
FEED
SWITCH
INTERLOCK
SWITCH
FUSE
GUN
CABLE
RECEPTACLE
FIELD
ARMATURE
#3
2
A
OPTIONAL
BURNBACK
BOARD
CONTROL
#2
&
#4
C
O
N
T
A
C
T
O
R
#531
#31
2 OHMS
#32 #32A
#75
#76
#77
#21
#567
NOTE: Unshaded areas of block logic diagrams are the subject of discussion.
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