Lincoln Electric SVM 122-A Theory of Operation, Input Line Voltage, Contactor and Main

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E-2 E-2

THEORY OF OPERATION

FIGURE E.2 – INPUT LINE VOLTAGE, CONTACTOR AND MAIN TRANSFORMER

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CONTROL

TRANSFORMER

POWER
SWITCH			MAIN
		TRANSFORMER
		R
		E
		C
		O
		N
		N
		E
		C
		T
INPUT
CONTACTOR
		T	115VAC
	REMOTE	E	S
TO	CONTROL	R	T
CONTROL		M	R
BOARD		I	I
		N
			P
		A
		L
			FAN
			42VAC
		14 PIN
		AMPHENOL

OUTPUT	ARC FORCE
CONTROL	CONTROL
	PART OF
	MODE
	SWITCH
			FEEDBACK
CONTROL BOARD				NEGATIVE
				OUTPUT
G	S		PART	TERMINAL
A	I		OF
T	G		MODE
			SWITCH
E	N
	A
	L
	S			OUTPUT
				CHOKE
		F
	PART	E
	OF	E
	MODE	D
	SWITCH	B	START
		A	BOARD
		C
	OUTPUT	K
	CAPACITORS
				POSITIVE
				OUTPUT
				TERMINAL
SCR / DIODE		SHUNT	REED
			SWITCH
HYBRID BRIDGE

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GENERAL DESCRIPTION

The DC-400 is a multiprocess welder power source	The transformer changes the high voltage, low current
capable of both constant voltage and constant current	input power to a lower voltage, higher current output.
operation. Its power system is SCR controlled with	The finishes or “neutrals” of the main secondary coils
solid state electronic circuitry. Minimum to maximum	are connected together, and the three starts of the
output is obtained with a single potentiometer control.	secondary windings are connected to the rectifier
INPUT LINE VOLTAGE,	bridge assembly. In addition, the main transformer has
	separate and isolated 115VAC and 42VAC auxiliary
CONTACTOR AND MAIN	windings. The 115VAC winding supplies power to the
TRANSFORMER	cooling fan and also offers 10 amps of auxiliary power,
	at the terminal strip and 14 pin amphenol, to operate
The desired three-phase input power is connected to	wire feeding equipment. The 42VAC auxiliary power is
the DC-400 through an input contactor, located in the	available at the 14 pin amphenol only and is protected
input box at the rear of the machine. Two phases of	by a 10 amp circuit breaker. The three 21VAC phase
the input line are also connected to the control trans-	angle windings are also housed in the main trans-
former, which, through the power switch, supplies	former assembly. These windings provide power and
power to activate the input contactor.	“timing” for the control board.

A reconnect panel allows the user to configure the machine for the desired input voltage. This AC input voltage is applied to the primary of the main trans- former.

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

IDEALARC DC-400

LINCOLN ®

ELECTRIC