Lincoln Electric SVM 106-A service manual Control Circuit Operation, Power Input Circuits

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E-2	THEORY OF OPERATION
GENERAL	feeder. The operation of the two versions is
	virtually identical. The following description

The LN-7 GMA wire feeder is available in two	of the operation of the wire feeders applies
	equally to both versions of the LN-7 GMA.
versions, a two-roll and a four-roll wire
FIGURE E.1 – INPUT LINE VOLTAGE AND TRIGGER TRANSFORMER.

OPTIONAL	GAS	OPTIONAL
		TIMER OR
METER KIT	SOLENOID	BURNBACK KIT

115 VAC

					SCR	CURRENT	5-95 VDC	WIRE DRIVE
					POWER	LIMITING		MOTOR
					CIRCUIT	CIRCUIT
		8.8 VAC
	CIRCUIT	TRIGGER			115 VAC	CONTROL
	BREAKER	TRANS-
						BOARD
		FORMER
FROM			DIODE
	115 VAC	24 VAC		24 VDC	CR1
WELDING			RECTIFIER					TO WELDING
POWER			NETWORK		CONTROL			CONTACTOR
SUPPLY					RELAY
								GUN
								TRIGGER

WIRE	GROUND
SPEED	LEAD
CONTROL	PROTECTOR

CONTROL CIRCUIT

OPERATION

POWER INPUT CIRCUITS

The LN-7 GMA receives 115 VAC power from the welding supply. This power is

applied to the trigger transformer which reduces the voltage for use by the LN-7 electronics. The voltages produced are 24 VAC, used by the electronics and the trigger circuit, and 8.8, VAC used by the optional digital meter kit. The 115 VAC input power is also sent to the SCR circuitry which powers the wire feed motor. See Figure E.1.

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NOTE: Unshaded areas of block logic diagrams are the subject of discussion.

LN-7 GMA WIRE FEEDER