E-2

THEORY OF OPERATION

E-2

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

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.

FIGURE E.1 Input Circuits

NA-5
F1
A
R
M
A
T
U
R
E
F
I
E
L
D
V
O
L
T
A
G
E
V
O
L
T
A
G
E
T1 T2
OPTIONAL
START
BOARD
OPTIONAL
CRATER
BOARD
OPTIONAL
WELD
TIMER
BURNBACK
TIMER
VOLTAGE
BOARD
METER
BOARD
SPEED
VOLT METER
BOARD
DIGITAL
METER DIGITAL
METER
MOTOR
LOGIC
BOARD
CONTROL
BOARD
P
O
W
E
R
B
O
A
R
D
P
R
O
C
E
D
U
R
E
B
O
A
R
D
TACH
INCH
DOWN
SWITCH
STOP
SWITCH
START
SWITCH
WELD
CURRENT
REED SWITCH
CR
1
CR
2
CR
3
FLUX
RECEPTACLE
TRAVEL
RECEPTACLE
CONTACTOR CLOSURE (#2 AND #4)
REMOTE VOLTAGE CONTROL (A, B, C)
WORK SENSING (#21)
TACH FEEDBACK (MOTOR RPM)
DC SUPPLY VOLTAGE
10VDC REFERENCEVOLTAGE
DC VOLTAGE
S
I
G
N
A
L
INPUT
POWER
SWITCH CIRCUIT
BREAKER R1(2 OHMS)
MOTOR G
A
T
E
S
I
G
N
A
L
S
CONTROL
CABLE
RECEPTACLE
TACH FEEDBACK (MOTOR RPM)
115VAC
36VAC (18+18VAC)
22VAC
1
V
A
C
0
D
C
S
U
P
P
L
Y
V
O
L
T
A
G
E
SIGNAL
A
R
C
V
O
L
T
A
G
E
S
H
U
T
D
O
W
N
A
N
D
INCH
UP
SWITCH
STRIKE/WELD PROCEDURE
ENABLE
FIELD
ARMATURE
F
E
E
D
E
N
A
B
L
E
DIRECTION
ARC VOLTS (SET & ACTUAL)
WIRE FEED SPEED (SET & ACTUAL)
E
L
E
C
T
R
ODE SENSING(#67)
115
VAC
WELD
VOLTS SPEED
VOLTS SPEED
STRIKE
115VAC
#31
#32
1/2 AMP
F501
SET SPEED
SET VOLTAGE
START
TIMER
CRATER
TIMER
F2
NOTE: Unshaded areas of block logic diagrams are the subject of discussion.
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

voltage on digital meters. These preset

conditions are internally monitored and

remain constant until changed by the

operator.

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