Lincoln Electric SVM100-A service manual DC Welding Output, DC Welding Circuit

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THEORY OF OPERATION E-4

DC WELDING OUTPUT

			POLARITY SWITCH					BY-PASS
								BOARD
				(DC POSITION)
								WORK
								HI-FREQ
								TRANSFORMER
LINE								ELECTRODE
	MAIN
SWITCH
TRANSFORMER
R	X2		AC		DC+
E						SHUNT
				SCR
C
				BRIDGE
O
N
N
E	X1		AC		DC-
C						CHOKE
T
		SIGNALSGATE
POWER								FEEDBACK
FACTOR
CAPACITORS
				ARC START				LCD DISPLAY
	115VAC	PROTECTION		115 VAC		CONTROL		KEYPAD
FAN
		SNUBBER		GATE SIGNALS		BOARD		LED
		BOARD						BOARD
					HI-FREQ			KEYPAD
					115 VAC
		115
		VAC			24 VAC
				CONTROL		18 VAC
	115 VAC			TRANSFORMER
						16 VAC
RECEPTACLE
		115 VAC				HIGH VOLTAGE	HIGH FREQUENCY SPARK
						TRANSFORMER
	REMOTE
						CIRCUIT
	RECEPTACLE

When the polarity switch is placed in either DC posi-	trolled DC output. Since the choke is in series with
tion, the AC voltage from the main transformer sec-	the negative leg of the bridge and also in series with
ondary is applied to the SCR bridge. The SCR bridge	the welding load, a filtered DC is applied to the
and choke circuits are connected in a conventional full	machine’s output studs.
wave bridge and filter configuration, resulting in a con-

		CHOKE
		ELECTRODE
	G	G
PRIMARY		DC
1Ø		G G
		WORK
		DC WELDING CIRCUIT

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