Lincoln Electric NA-5SF, NA-5NF service manual CONTROL, Logic, Procedure Boards

E-4 THEORY OF OPERATION E-4

TOC

TOC

FIGURE E.4 Control Logic and Procedure Boards

Section

Master

CONTACTOR CLOSURE (#2 AND #4)

TACH FEEDBACK (MOTOR RPM)

ARC VOLTS (SET & ACTUAL)

REMOTE VOLTAGE CONTROL (A, B, C)

WORK SENSING (#21)

1/2 AMP

F501

to

to

115VAC

SET VOLTAGE

Return

Return

ODE

SENSING (#67)

VOLTAGE

R

BOARD

T

TACH

C

TRAVEL

E

L

D

RECEPTACLE

FLUX

E

C

RECEPTACLE

MOTOR

S

A

3

U

R

A

CR

C

P

N

P

V D

L

O

S

2

L

A

Y

START

STOP

INCH

T

H

CR

V

V

A

U

R

F

V

SWITCH

DOWN

G T

M

O

O

SWITCH SWITCH

E

D

A

L

I

L

O

O

1

W

T

T

E T

L

N

CR

U

A

L

A

T

R

G

D

G

A

P

VOLTS

SPEED

OPTIONAL

E

E

E

G

START

START

INPUT

P

E

DC SUPPLY VOLTAGE

R

BOARD

TIMER

POWER

CIRCUIT

O B

STRIKE

SWITCH

BREAKER

R1(2 OHMS)

O F2

LOGIC

STRIKE/WELD PROCEDURE

OPTIONAL

CRATER

#31

W

C

O

CRATER

TIMER

CONTROL

ENABLE

BOARD

BOARD

CABLE

115

E

E A

TOC

TOC

RECEPTACLE

V A C

R

D

R

OPTIONAL

WELD

#32

F1

B

U D

WELD

TIMER

R

O

BURNBACK

Section

Master

FIELD

DIRECTION

SIGNAL

F

E

A

VOLTS

SPEED

TIMER

E

E

R

D

D

MOTOR

ARMATURE

E

WELD

G

N

A

A

CURRENT

T1

T2

REED SWITCH

T

B

E

L

to

to

S

E

I

G

S

Return

Return

115VAC

N

I

1

A

G

SET SPEED

36VAC (18+18VAC)

L

N

0

S

A

V

22VAC

L

A

C

10VDC REFERENCEVOLTAGE

DC VOLTAGE

VOLT

SPEED

WIRE FEED SPEED (SET & ACTUAL)

CONTROL

TACH FEEDBACK (MOTOR RPM)

METER

METER

BOARD

BOARD

BOARD

INCH

UP

SWITCH

DIGITAL

DIGITAL

METER

METER

		CONTROL, LOGIC AND	board to proceed from the "strike" settings to the optional
		PROCEDURE BOARDS	start board if used, or to the welding wire speed and arc
TOC	TOC		voltage parameters.
		The logic board interprets and processes the signals it	The control board receives information from the logic
Section	Master	receives from the various PC boards, switches and con-
			board, the procedure board and the tach feedback cir-
		trols. The logic board also houses a DC power supply
			cuit. The control board then applies the appropriate gate
		(+5 -10) which is derived from the 22VAC received from
			signal to the SCR power supply on the power board.
to	to	the T2 transformer. This DC voltage is also used on the
			This variable and regulated DC voltage is applied to the
		procedure board.
Return	Return		mation is sent to the speed meter board where it is
		Upon receiving voltage reference level commands from
			motor armature thus controlling the speed of the wire
			feed motor. The preset and actual wire feed speed infor-
		the procedure and voltage boards, or the user-operated	processed and displayed on the digital meter.
		switches, the logic board sends the appropriate com-
			The procedure board incorporates the many options
		mand signals to the control and power boards to drive
			available with the NA-5. The "strike" and "weld" controls
		the wire feed motor to the proper speed and direction.
			are part of the procedure board and are not optional.
		When the "start" signal is received by the logic board the
			The wire feed speed and arc voltage settings for the vari-
		power source contact relay (3CR) is energized along
			ous modes are "programmed" through the procedure
		with the travel relay (2CR) and the flux relay (1CR). The
			board and are then sent to the logic, voltage and control
		"inch down" and "stop" switches signal the logic board
			boards at the appropriate times during the welding cycle.
TOC	TOC	which then directs the control and power boards to apply
			The burnback time is also coupled through the procedure
		the appropriate armature and field voltages to the wire
			board. This control determines the length of time of
Section	Master	drive motor. The "inch up" switch, which is connected	burnback delay after the stop circuit is energized.
		directly to the control board, dictates that the wire drive
			Depending on the connections on the logic board, it may
		motor reverse direction, backing the electrode wire away
			also determine the length of time the wire feed motor
		from the work piece. When the welding current closes
to	to		reverses after the stop button is pressed.
		the reed switch the logic board directs the procedure
Return	Return
		NOTE: Unshaded areas of block logic diagrams are the subject of discussion.

NA-5