Lincoln Electric SVM 117-A service manual Wire Drive Motor, Feedback

E-4 THEORY OF OPERATION E-4

to Section TOC	to Master TOC	WIRE DRIVE MOTOR AND FEEDBACK
Return	Return		WIRE	GAS
			SPEED	SOLENOID
		ARC				WIRE
						DRIVE
		VOLTAGE				MOTOR
			CONTROL BOARD
			G			TACH
		MAIN	A
	LINE		T		GUN TRIGGER AND THUMB SWITCH
	SWITCH	TRANSFORMER	E
			S
			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	NEGATIVE
				S
		MOTORS				TERMINAL
					SHUNT

Figure E.5 - Wire Drive Motor and Feedback.

TOC	TOC	WIRE DRIVE MOTOR AND
Section	Master
		FEEDBACK
to	to	The wire drive motor is controlled by the control board.
		A motor speed feedback signal is generated at the
Return	Return
		motor tach and sent to the control board. The control
		board compares this feedback signal with the com-
		mands set forth by the Wire Speed Control poten-
		tiometer and sends the appropriate armature voltage
		to the wire drive motor. The drive motor speed is thus
		controlled which in turn regulates the electrode wire
		feed speed through the gun.
Section TOC	Master TOC
to	to		NOTE: Unshaded areas of Block Logic
			Diagram are the subject of discussion
Return	Return
			WIRE-MATIC 250