Lincoln Electric SVM114-C Theory of Operation, General Description, Control Circuit Operation

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E-2	THEORY OF OPERATION		E-2
	GENERAL DESCRIPTION	voltage. It is designed for maximum versatility in
		a variety of field applications. It can be used with

The LN-25™ is a portable semiautomatic wire	most constant voltage or constant current DC
	power sources without the need of a control
feeder designed to operate from a DC arc
	cable.
FIGURE E.2 – INPUT POWER CIRCUIT.

				OPTIONAL
				CONTACTOR
				CONDUCTOR	GUN CABLE
				BLOCK
	COLD			M		GUN
			OPTIONAL	O	HALL	TRIGGER
	INCH			T		CONNECTOR
	SWITCH		CONTACTOR	O	EFFECT
			BOARD	R	MODULE
ELECTRODE
INPUT CABLE	P
	O S
	L W			ARMATURE VOLTAGE
	A I	VOLT
TO WORK	R T
	I C	METER	CONTROL	RPM FEEDBACK
SENSING LEAD	T H
	Y		BOARD
	WIRE FEED			RANGE
				SWITCH
	MODE SWITCH
				WIRE SPEED
				CONTROL
			SOLENOID	GAS
			PC BOARD	SOLENOID
			EARLY MODELS ONLY - LATER MODELS HAVE CIRCUITRY
				INCLUDED ON CONTROL BOARD

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CONTROL CIRCUIT

OPERATION

INPUT POWER CIRCUIT

The DC arc voltage from the power source is applied to the LN-25™ through the electrode cable and work sensing lead. This DC voltage is connected to the polarity switch, which allows the wire feeder to be used in either electrode positive or electrode negative polarity. The voltage is then coupled to the voltmeter and control board. A wire feed mode switch is included to give the user the capability of using a constant voltage or, in some processes, a constant current power source. See Figure E.2.

WELDING CURRENT CIRCUIT

The electrode voltage is also applied to the conductor block through a heavy current carrying cable. The welding gun cable is connected to the conductor block. This combination of welding cable, optional contactor, conductor block and gun cable constitute the welding current path to the electrode wire. See Figure E.2.

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

LN-25™