Lincoln Electric SVM118-A service manual High Voltage High Frequency Circuit

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E-4 E-4

THEORY OF OPERATION

FIGURE E.4 – HIGH VOLTAGE/HIGH FREQUENCY CIRCUIT

HIGH FREQUENCY SPARK

ELECTRODE SENSE

PANEL	UPPER		LOWER	DISPLAY	STATUS
	CONTROL	CONTROL
SWITCHES				BOARD	BOARD
	PANEL		PANEL

			ELECTRODE		SCR GATE COMMANDS
HIGH VOLTAGE	115VAC		SENSE		15VDC
TRANSFORMER	REMOTE
CIRCUIT		FEED - THRU		CONTROL		POWER
	RECEPTACLE
		BOARD	TRIGGER	BOARD		BOARD
GAS/WATER			REMOTE		INTERLOCK
SOLENOIDS	115VAC		COMMANDS
					HI-FREQ/ WATER/GAS
	INTERLOCK				COMMANDS
			INTERLOCK
			115VAC -HI-FREQ AND GAS/WATER
	FANS 115VAC	115VAC				SNUBBER
	RECEPTACLE	CONTROL TRANSFORMER				BOARD
			115VAC

INPUT	R		AC	DC-
CONTACTOR
	E
					C
	C
			AC	DC+	H
	O				O
	N				K
		POWER			E	BY-PASS
	N						WORK
	E	FACTOR				BOARDS
		CAPACITORS	POLARITY
	C
	T		SWITCH
						SHUNT
	START/	MAIN					ELECTRODE
	STOP
		TRANSFORMER
							HI-FREQ
	PILOT						TRANSFORMER
	TRANSFORMER

HIGH VOLTAGE/

HIGH FREQUENCY CIRCUIT

The control board signals the power board to pass the 115VAC voltage through the feed – thru board to the primary of the high voltage tarnsformer. The sec- ondary of the high voltage transformer is coupled to a spark gap generator and also to the high frequency transformer. The high frequency transformer transfers the high frequency “spark” to the electrode terminal.

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

SQUARE WAVE TIG 355