Circuit Protection And Automatic Shutdown - Lincoln Electric LN-9 SVM127-A Service Manual

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CIRCUIT BREAKER AND GROUNDING LEAD PRO-
TECTOR (GLP) RESET SWITCH: These protection
circuit devices are located on the front rail of the LN-9
model and bottom panel of the LN-9F models. See the
topic "Circuit Protection and Automatic Shutdown"
later in this section of the manual.
DIGITAL METER: A three-digit digital meter is provid-
ed to set and monitor the welding procedure. The arc
voltage is displayed in volts and the wire feed speed is
displayed in inches/minute or meters/minute.
METER READING SWITCH, VOLTS AND WIRE
SPEED CONTROLS: This four-position rotary switch
is located to the right of the digital meter on LN-9mod-
els and to the left of the digital meter on LN-9F models.
When set to the "Volts" position, the meter reads the
arc voltage setting as adjusted by the "Volts" control.
The rated setting range for all the LN-9 models is 12.0
to 60.0 volts.
The three "Wire Speed" positions include an English
position, for meter readings in inches/minute; and "LO"
and "HI" range metric positions for meter readings in
meters/minute. The wire feed speed setting is adjust-
ed by the "Wire Speed" control. The rated setting
range for all the LN-9 models are 50 to 600
inches/minute (1.27 to 15.2 meters/minute).
When using metric meter readings, set the switch to
"LO" for more precise meter readings up to 393 in/min
(9.99 m/min.). For higher wire feed speeds, the "LO"
position will result in an over-range meter reading of
E.EE which indicates that the "HI" range, with single
decimal place resolution, should be used. Similarly,
EEE will be displayed on the English position if the set-
ting exceeds 999 inches/minute.
The procedure adjustments can be made before or
during the weld. This feature permits the operator to
set the welding voltage and wire speed before welding
and without assistance.
Once set, the control circuits of the LN-9 will continu-
ously monitor the volts and wire speed and correct any
deviation from the set value so there will be negligible
change.
Should the range of the power source output voltage be
such that the unit circuit cannot keep the arc voltage as
set, the unit will stop welding shortly after the arc is struck.
See the topic "Circuit Protection and Automatic
Shutdown" later in this section of the manual.
SET-ACTUAL PUSHBUTTON:
been started, the ACTUAL voltage or wire speed can
be read by pressing the pushbutton to the left of the
meter. The METER READING switch must be set in
the desired position. When the pushbutton is not being
operated, the meter continues to read the SET value.
OPERATION
CIRCUIT PROTECTION AND AUTOMATIC
SHUTDOWN
CIRCUIT BREAKER
The circuit breaker normally trips only when excessive
loading in the wire feed cable or a defective motor or
control component causes an overload. After allowing
a minute for cooling, push in the circuit breaker button
and weld. If it trips again, be sure the wire feed cable
is clean and the proper size for the wire diameter being
fed. Also look for excessive drive roll pressure and
readjust if necessary. If the breaker still trips, look for
a defective electrical component.
breaker is tripped, the digital meter is off and the trig-
ger circuit will not operate.
POWER SUPPLY FUSE
The fuse on the PM power board inside the control box
protects the power supply circuit. When the fuse is
blown, the digital meter is off and the trigger circuit will
not operate.
VOLTAGE PC BOARD FUSE
The 1/8 amp fast-blow fuse protects the LN-9 circuitry
from damage that may result from a ground, or case,
faulted control lead. If this fuse blows, the LN-9 arc
voltage sensing lead circuit will be opened. See the
topic "Automatic Shutdown" below.
MOTOR THERMAL PROTECTION
The temperature sensing thermal protector mounted in
the motor frame opens the control circuit if the motor
overheats. Excessive loading and/or very rapid trig-
gering may cause overheating. The thermal sensor
protects the motor without nuisance tripping. The ther-
mal protector automatically resets itself after the motor
cools sufficiently (may take 10-15 minutes). Reset time
can be shortened by removing supply power to the LN-
9 and also by cooling the motor with an air hose or fan.
When the protector is tripped, the digital meter is lit but
there will be zero reading. The trigger circuit will not
operate.
AVOIDING GROUNDING LEAD PROTECTOR
(GLP) SHUTDOWN
The frames of all LN-9 wire feed units and drive motors
are grounded to the frame of the power source by a
lead in the control cable. An overload protector pre-
vents welding current from damaging this lead if the
electrode circuit touches the wire feeder frame while
After the weld has
the gun trigger is pressed.
LN-9 Wire Feeder
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When the circuit