Power And Voltage Boards - Lincoln Electric NA-5N Service Manual

E-3
CONTACTOR CLOSURE (#2 AND #4)
ARC VOLTS (SET & ACTUAL)
REMOTE VOLTAGE CONTROL (A, B, C)
WORK SENSING (#21)
INPUT
POWER
CIRCUIT
SWITCH
BREAKER
#31
CONTROL
1 1 5
CABLE
V A C
RECEPTACLE
#32
1
0
V
A
C
VOLT
METER
BOARD
DIGITAL
METER
POWER AND VOLTAGE
BOARDS
The AC voltages that are received by
the power board are rectified and regu-
lated. These DC voltages are supplied
to the motor, voltage board and control
board.
115VDC supplies power the motor
armature and field circuits.
The actual arc voltage is sensed at leads
#67(electrode) and #21(work) which are
coupled to the voltage board. The pre-
set voltage requirements are also sent to
the voltage board. This information is
compared and processed on the voltage
board and the resultant correction signal
is sent to the Lincoln CV power source
via the remote voltage leads (A,B,C).
The preset and actual arc voltage infor-
mation is also sent to the voltage meter
board where it is processed and dis-
played on the digital meter.
NOTE: Unshaded areas of block logic diagrams are the subject of discussion.
THEORY OF OPERATION
FIGURE E.2 Power and Voltage Boards
115VAC
ODE SENSING (#67)
R
T
C
TACH
E
L
E
MOTOR
A
V
R V
F
O
M O
I L
A L
T
T T E
A
U A
L
G
R G
D
E
E E
P
O F2
R1(2 OHMS)
W
E
R
F1
B
O
FIELD DIRECTION
A
R
D
T1 T2
115VAC
36VAC (18+18VAC)
22VAC
SPEED WIRE FEED SPEED (SET & ACTUAL)
METER
BOARD
DIGITAL
METER
The two SCR-controlled
1/2 AMP
F501
VOLTAGE
BOARD
TRAVEL
RECEPTACLE
D
C
S
A 3
U R
CR
A
C
P
N
D
P V
L O
2
S
L
Y
H
T CR
U
INCH A
START STOP
T
DOWN G
V
SWITCH D
SWITCH SWITCH E
O O
1
W
L
CR
N
T
A
G
E
DC SUPPLY VOLTAGE
LOGIC
STRIKE/WELD PROCEDURE
ENABLE
BOARD
SIGNAL F
E
E
D
MOTOR ARMATURE E
WELD
G
N
CURRENT
A
A
REED SWITCH
T
B
E
L
E
S
I
G S
N I
A G
SET SPEED
L N
S A
L
10VDC REFERENCEVOLTAGE
DC VOLTAGE
CONTROL
BOARD
INCH
UP
SWITCH
The voltage board also generates a low
DC voltage that is applied to the elec-
trode during the inch down mode.
When the electrode makes contact with
the work piece, this low voltage is
"loaded down", signaling the control cir-
cuitry to stop the wire feed motor. This
feature allows the operator to utilize the
"work touch sensing" feature.
If for any reason the actual welding arc
voltage does not match the set weld
voltage
(+/- 0.5Volts) the NA-5 will shutdown.
This feature insures that the actual
welding voltage is the same as the pre-
set voltage during the welding cycle.
This circuitry is incorporated on the volt-
age board.
NA-5
TACH FEEDBACK (MOTOR RPM)
SET VOLTAGE
FLUX
RECEPTACLE
OPTIONAL
P
VOLTS SPEED START
START
TIMER
BOARD
R
STRIKE
O
B
OPTIONAL
CRATER
C
CRATER
O
TIMER
BOARD
E
A
D
R
OPTIONAL
WELD
U
TIMER
D
R WELD
E BURNBACK
VOLTS SPEED
TIMER
TACH FEEDBACK (MOTOR RPM)
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