Lincoln Electric SP-250 Power Supply Operation, Input Line Voltage and Main Trans, Former

E-1 THEORY OF OPERATION E-1

to Section TOC	to Master TOC			POWER SUPPLY OPERATION
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.2 - Input Line Voltage and Main Transformer

TOC	TOC	INPUT LINE VOLTAGE AND MAIN TRANS-
Section	Master	FORMER
to	to	The desired single phase input power is connected to
		the SP-250 through a line switch located on the front
Return	Return
		panel.
		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 and to the thermostatically controlled fan
		motors. The transformer changes the high voltage, low
		current input power to a low voltage, high current out-
		put. In addition, the main transformer also has an iso-
		lated center tapped 30VAC auxiliary winding that sup-
TOC	TOC	plies power to the Control Board for SCR gate drive
		and gas solenoid operation. The weld power windings
Section	Master	connect to the Control Board as well as to the main
		SCR Rectifier.
to	to		NOTE: Unshaded areas of Block Logic
			Diagram are the subject of discussion
Return	Return
			IDEALARC SP-250