Lincoln Electric SVM127-A service manual Theory of Operation, Power Input Circuits

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E-2		E-2
	THEORY OF OPERATION
	GENERAL DESCRIPTION
	The LN-9 is a semiautomatic wire feeder that allows	lated to the preset condition. When the LN-9 is cou-
	the user to preset the arc voltage and wire feed speed.	pled to an appropriate Lincoln constant voltage power
	The wire feed speed is internally monitored and regu-	source, the arc voltage is also regulated to match the
		preset voltage.

FIGURE E.2 – POWER INPUT CIRCUITS

VOLTAGE CONTROL

							WORK VOLTAGE SENSING
					GEAR		ELECTRODE VOLTAGE SENSING		POLARITY
					BOX				SWITCH
									WIRE
					WIRE				SPEED
									CONTROL
					FEED
					MOTOR	TACH
						BOARD
	POWER SOURCE OUTPUT TRIGGER			(#2 )
							WIRE SPEED CONTROL
			TRIGGER		T2		+ 15VDC
		TRIGGER	BOARD
	CIRCUIT
		CONNECTOR						C
	BREAKER			24VAC
								O	B
							TRIGGER SIGNAL
INPUT								N	O
					F
					U			T	A
CONNECTOR					S				R
					E			R
	R1						+ 15VDC		D
					P	B		O
					O
						O		L
					W	A
							S
					E	R
							H
					R	D	U
							T
TO							D
							O
CONTROL							W
BOARD							N
	T1						R	V
							E	O
							F
TO								L
							E
								T
VOLTAGE							R
							E	A
BOARD							N	G
							C	E
METER							E
	10VAC	28VAC
BOARD
					WIRE FEED				VOLTAGE
									CONTROL
					MOTOR
VOLTS					THERMOSTAT
SPEED
SWITCH								VOLTAGE
								BOARD

TRIGGER SIGNAL

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POWER INPUT CIRCUITS

The 115VAC is applied (usually from the welding power source) via the input connector and through the circuit breaker and R1 resistor to the power board, the T2 trig- ger transformer, and the T1 transformer.

GROUND

LEAD

PROTECTOR

The 24VAC developed at the T2 trigger transformer is applied to the trigger board. There it is rectified and regulated to 20VDC and used to operate the wire feed- er trigger circuitry.

The 28VAC produced by the T1 transformer secondary is applied to the power board. There it is rectified and regulated to 15VDC. This 15VDC powers the electron- ics on the power, control, and voltage boards. The 10VAC secondary voltage is rectified, regulated, and utilized by the meter board.

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

LN-9 Wire Feeder