Lincoln LT-7, Руководство по устранению неисправностей

Страница: 7 / 43

THEORY OF OPERATION
A-2 A-2
LT-7 TRACTOR
Upon receiving commands from the user operated
switches or potentiomenters the logic board sends the
appropriate signal to the control board which then dri-
ves the wire feed motor to the correct speed and direc-
tion. When the start signal is received by the control
board the power source contact relay(1CR) is ener-
gized as well as the travel relay(2CR) and the wire drive
motor. When weld current closes reed switch 3CR the
logic board directs the control board to change the wire
feed speed from the preset inch speed to the welding
feed speed set by the wire speed control potentiome-
ter. Reed switch 4CR protects the internal grounding
wire circuitry. In the event that abnormally high current was to flow in the grounding lead system the 4CR reed
switch would close, signaling the logic board to stop the
welding procedure. The inch up switch, which is cou-
pled directly to the control board, dictates that the wire
drive motor reverse direction and back the electrode
wire away from the work piece.
Travel speed, direction and mode (either manual or
auto) are determined by the settings of the three con-
trols connected to the travel board. The travel board
then applies the correct voltage and polarity to the trav-
el motor to satisfy the control settings.
CONTROL, LOGIC AND TRAVEL
BOARDS
FIGURE E.2 - CONTROL LOGIC AND TRAVEL BOARDS
GLP WELD CURRENT
SENSING REED
2CR
TRAVEL
RELAY
TRAVEL
SWITCH
TRAVEL
MOTOR
TRAVEL BOARD
TRAVEL
SPEED
CONTROL
POWER SOURCE
CONTACT RELAY
R1
CIRCUIT
BREAKER
115VAC
FROM
WELDING
POWER
SOURCE
INCH UP
SWITCH
WIRE
DRIVE
MOTOR
START
SWITCH
STOP
SWITCH
INCH
DOWN
SWITCH
WIRE
SPEED
CONTROL
LOGIC
BOARD
CONTROL
BOARD
VARIABLE VOLTAGE
BOARD
ARC
VOLTAGE
METER
115VAC
115VAC
115VAC
115VAC
115VAC 115VAC
115VAC
115VAC
LOGIC CONTROL SIGNALS
ARC VOLTAGE SENSING SIGNALS
24VDC
ELECTRODE
WORK
VOLTAGE
SENSING
LEADS
REED
SWITCH 4CR SWITCH 3CR
TRAVEL
DIRECTION
SWITCH
CONTROL
1CR
#2
#4
{
NOTE: Unshaded areas of the Block Logic Diagram are the subject of discussion