Theory Of Operation; General Description; Input Power Circuits - Lincoln Electric NA-5N Service Manual

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GENERAL DESCRIPTION

The NA-5 is a fully automatic wire feed
control unit. It is designed for multiple
process CV operation and can be used
with a variety of wire feeder heads, con-
tact nozzles and welding processes.
The NA-5 control unit enables the oper-
ator to preset wire feed speed and arc
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

INPUT POWER CIRCUITS

The NA-5 control unit is supplied with
115VAC power usually from the welding
power source. The 115VAC power is
connected to the control box circuitry
through the control cable receptacle,
the input power switch and a 5 amp cir-
cuit breaker.
The 115VAC is applied through a 2 ohm
resistor to the power board where is
rectified and controlled to supply arma-
ture and field voltage to the wire drive
NOTE: Unshaded areas of block logic diagrams are the subject of discussion.

THEORY OF OPERATION

FIGURE E.1 Input Circuits
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
F2
O
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
NA-5
voltage on digital meters. These preset
conditions are internally monitored and
remain constant until changed by the
operator.
1/2 AMP
F501
VOLTAGE
BOARD
TRAVEL
RECEPTACLE
D
C
S
3
A
U R
CR
A
C
P
N
D
P V
O
L
2
S
L
Y H
T CR
U
INCH A
START STOP
T
V DOWN G
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
motor. The voltage board receives
115VAC and transforms and rectifies it
to 24VDC for the "work touch sensing"
circuit. The T1 and T2 transformer pri-
maries are also supplied with 115VAC
via the F1 (1/2amp) fuse on the power
board. The T1 and T2 secondary wind-
ings offer a variety of isolated AC sup-
ply voltages to the power, logic and
meter boards.
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
D TIMER
WELD
R
E BURNBACK
VOLTS SPEED
TIMER
TACH FEEDBACK (MOTOR RPM)
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