Lincoln Electric SVM144-B service manual Output Rectification, Feedback Control

E-3 THEORY OF OPERATION E-3

TOC	TOC	FIGURE E.3 — OUTPUT RECTIFICATION AND FEEDBACK.
Section	Master		GAS	FAN
			SOLENOID	MOTOR		WIRE
						DRIVE
		WIRE				MOTOR
to	to
		SPEED
Return	Return	ARC	CONTROL
		VOLTAGE	BOARD
						TACH
		115 VAC					GUN TRIGGER
			RECTIFIER
			DIODE	G			FEEDBACK
			BRIDGE
				A
		30 VAC		T
				E
		LINE	SNUBBER	S
			BOARD
		SWITCH		I
				G
				N
TOC				A
	TOC			L
Section	Master			POWER	C	F	OUTPUT	POSITIVE
		RECONNECT		ENHANCEMENT	A		CHOKE
								TERMINAL
		MAIN		CHOKE	P	E
		TRANSFORMER			A	E
			SCR		C	D
to	to					B
			RECTIFIER		I
					T	A
Return	Return
					O	C		NEGATIVE
					R	K
								TERMINAL
					S
					SHUNT

		OUTPUT RECTIFICATION AND	the commands of the ARC Voltage Control poten-
		FEEDBACK CONTROL	tiometer with the feedback signals. The appropriate
			gate firing pulses are generated by the control board
		The AC output from the main transformer secondary	and applied to the SCR rectifier assembly. The control
			board controls the firing of the SCRs, thus controlling
TOC	TOC	weld winding is rectified and controlled through the	the output of the machine. See SCR Operation. The
		SCR rectifier assembly. Output voltage and current are	control board also powers and commands the gas
SectiontoReturn	MastertoReturn	sensed at the shunt and output terminals and are fed	solenoid, fan motor, and the wire drive motor.
		back to the control board. The control board compares

Section TOC	Master TOC
to	to	NOTE: Unshaded areas of Block Logic
		Diagram are the subject of discussion
Return	Return
		POWER MIG 255