Lincoln Electric SP-250 service manual Figure E.4 Constant Voltage Output

E-3 THEORY OF OPERATION E-3

to Section TOC	to Master TOC		POWER SUPPLY OPERATION (CONTINUED)
Return	Return			PIEZO	GAS
			LCD	ALARM	SOLENOID
			DISPLAY				WIRE
							DRIVE
							MOTOR
			KEYPAD	CONTROL BOARD
					G		TACH
					A
					T		GUN TRIGGER AND THUMB SWITCH
		LINE	MAIN		E
					S
			TRANSFORMER
		SWITCH			I		FEEDBACK
					G
					N
TOC	TOC				A
					L
			RECONNECT				POSITIVE
Section	Master
							TERMINAL
						C	CHOKE
						A	F
						P	E
to	to					A	E
						C	D
				SCR		I	B
Return	Return
				RECTIFIER		T	A
						O	C
			FAN			R	K
						S	NEGATIVE
			MOTORS				TERMINAL
							SHUNT

Figure E.4 - Constant Voltage Output

TOC	TOC	CONSTANT VOLTAGE OUTPUT
Section	Master	assembly is filtered by the capacitor bank and the out-
		The controlled DC output from the SCR rectifier
to	to	put choke, which is in series with the gun and welding
Return	Return	load, resulting in a constant voltage output at the out-
		put terminals of the machine.

Section TOC	Master TOC
to	to	NOTE: Unshaded areas of Block Logic
		Diagram are the subject of discussion
Return	Return
		IDEALARC SP-250