Lincoln Electric SVM188-A service manual 1TABLE of CONTENTS-THEORY of Operation Section E-1

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E-1TABLE OF CONTENTS-THEORY OF OPERATION SECTION E-1

Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .E-1

General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .E-2

Input Circuit and Main Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .E-2

Control Circuit, Firing Circuit and Rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .E-3

Protective Devices and Shutdown Circuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .E-4

SCR Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .E-5

FIGURE E.1 BLOCK LOGIC DIAGRAM

CONTROL POWER

TRANSFORMER SWITCH

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115VAC

Pilot

Light

w

•

Secondary Thermostat

Primary

Theromstat

1CR Coil

CONTACTOR

CR1

•								TERMINAL
								STRIP 1
									OUTPUT
	FAULT PROTECTION								CONTROL
									SWITCH
CR2								OUTPUT
							OUTPUT	CONTROL
	32VAC
	32VAC				FIRING		CONTROL SIGNAL
	32VAC				BOARD
					G	S
	14-pin		115VAC	Fan	A	I
					T	G
	Amphenol		Receptacle	Motor	E	N
						A
						L
	T		115VAC					CONTROL
		S
	R		•					BOARD		MODE
		T
	E			OUTPUT						SWITCH
	I	I
	M	R
	N	P	TERMINAL
	AL	2
				SWITCH				F
	42VAC		115VAC
								E
								E
	MAIN							D
								B
R	TRANSFORMER							A
								C		POSITIVE
E
								K
C										TERMINAL
O
N								SHUNT
N									F
E									E
C
									E
T
									D
								LATCHING
								RESISTOR	B
					SCR BRIDGE				A
									C	NEGATIVE
							CHOKE		K	TERMINAL

DC-600