Lincoln Electric R3R-300 Theory of Operation, Input Line Voltage Contactor and Main Transformer

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E-2 E-2

THEORY OF OPERATION

FIGURE E.2 – INPUT LINE VOLTAGE, CONTACTOR AND MAIN TRANSFORMER

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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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GENERAL DESCRIPTION

The Idealarc R3R welder is a three-phase transformer rectifier type constant current power source designed for DC manual welding and air carbon arc cutting. Its power system is SCR controlled with solid state elec- tronic circuitry. Minimum to maximum output is obtained with a single potentiometer control.

INPUT LINE VOLTAGE,

CONTACTOR AND MAIN

TRANSFORMER

The desired three-phase input power is connected to the R3R through an input contactor, located in the input box at the rear of the machine. Two phases of the input line are also connected to the primary of the

control transformer. The secondary of the control transformer supplies 120VAC power, via the power switch and thermostats, to activate the input contac- tor.

A reconnect panel allows the user to configure the machine for the desired input voltage. This AC input voltage is applied to the primary of the main trans- former.

The transformer changes the high voltage, low current input power to a lower voltage, higher current output. The finishes or “neutrals” of the main secondary coils are connected together, and the three starts of the secondary windings are connected to the rectifier bridge assembly. In addition, three 66VAC phase angle windings are housed in the main transformer assembly. These windings provide power and “timing” for the control board. Two of these coils provide 120VAC for the fan motor.

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

IDEALARC R3R