Lincoln Electric R3R-500, R3R-300 service manual Output Rectification CONTROL, and Feedback

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E-3 E-3

THEORY OF OPERATION

FIGURE E.3 – OUTPUT RECTIFICATION, CONTROL, AND FEEDBACK

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CONTROL

TRANSFORMER

FAN

MOTOR

	OPTIONAL	OPTIONAL
	POCKET
	AMPTROL		POCKET
TRANSFORMER		AMPTROL
		PC BOARD

AMPHENOL	OUTPUT
	CONTROL
TERMINAL		DIAL
STRIP	ARC FORCE
	CONTROL	SELECTOR
		SWITCH
	REMOTE
	SWITCH

FEEDBACK

CONTROL BOARD

NEGATIVE OUTPUT TERMINAL

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POWER

THERMOSTATS SWITCH

R

E

C

O

N

N

E

C

T

INPUT

CONTACTOR

MAIN

TRANSFORMER

G	S
A	I
T	G
E	N
	A
	L
	S
	SNUBBER
	BOARD

SCR / DIODE

HYBRID BRIDGE

F

EOUTPUT

E	CHOKE
D
B
A
C
K

SHUNT

OPTIONAL

POLARITY

SWITCH

POSITIVE OUTPUT TERMINAL

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OUTPUT RECTIFICATION,

CONTROL, AND FEEDBACK

The three-phase AC output from the main transformer secondary is rectified and controlled through the SCR/ diode bridge. Output current and voltage is sensed at the shunt and output terminals. This feedback infor- mation is processed in the control board. The control board compares the commands from Arc Force Control, the Dial Selector switch, and the Output Control (or remote control) with the feedback informa- tion and sends the appropriate gate firing signals to the SCR/diode bridge. This creates a DC voltage at the output of the bridge assembly. This DC voltage is applied through the output choke to the output termi- nals. The output choke, which is in series with the negative output terminal, stores energy and provides current filtering for the constant current welding arc.

NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

IDEALARC R3R