Lincoln Electric SVM153-A service manual Weld WINDINGS, RECTIFIER, Power Modules and Feedback

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E-3 E-3

THEORY OF OPERATION

FIGURE E.3 - WELD WINDINGS, RECTIFIER, POWER MODULES AND FEEDBACK

				THREE-PHASE						WORK
COMMANDER 500									TERMINAL
				RECTIFIER						__
								TO WELD
								CONTROL
								BOARD
				+	(2)	(2)		POWER MODULES
								(2)	ELECTRODE
								IGBT	TERMINAL
					80 VDC
								CHOKE		+
									SHUNT
			W							F
										E
		D	I
										E
	L		N
							(2)	PWM		D
			D
E					ANALOG					B
			I				20 VDC
W			N	POWER SUPPLY				SIGNALS (2)		A
			G							C
					BOARD					K

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ENGINE

STARTER

ALTERNATOR
RUN/STOP
SWITCH							ENGINE
		BATTERY			S		SENSORS
					H
		BOARD			U	I		1/2
					T
						D		BATTERY
					D
					O	L		BD
120				10	W	E
	VDC			VDC	N	R
BATTERY						SOL
		PULL
		COIL				TO WELD
		BOARD			SOL	CONTROL
						BOARD
			10
			VDC

PERIPHERAL

BOARD

			WELD
MECHANICAL	ROTOR	TO	CONTROL
ROTATION		HOLD	BOARD
		IDLE
	SLIP	COIL		VOLTMETER
	RINGS			AMMETER
	STATOR	THERMAL	ARC OUTPUT	PROCESS/RANGE
			CONTROL CONTROL SELECTOR
		LIGHT
		42 VAC TO 14 PIN AMPHENOL
	AUXILIARY WINDINGS	FOR WIRE FEEDER
	1
	2
	0	240VAC
	V	RECEPTACLE

A

C

120VAC RECEPTACLES (2)

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WELD WINDINGS, RECTIFIER, POWER MODULES AND FEEDBACK

The three-phase stator weld windings are connected to a three-phase rectifier bridge. The resultant DC volt- age is applied to four paralleled capacitors incorporat- ed within each of the two power modules. There are two capacitors in each module. These capacitors func- tion as filters and also as power supplies for the IGBTs. See IGBT Operation in this section. The IGBTs act as high-speed switches operating at 20KHZ. These devices are switched on and off by the Weld Control PC board through pulse width modulation circuitry. See Pulse Width Modulation in this section. This

"chopped" DC output is applied through choke coils and a shunt to the welding output terminals. The choke functions as a current filter, and it helps to balance the outputs of the two power modules. Free-wheeling diodes are incorporated in the power modules to pro- vide a current path for the stored energy in the choke when the IGBTs are turned off. See Chopper Technology in this section.

Output voltage and current feedback information is fed to the Weld Control PC board. This information is sensed from the output terminal circuits and the shunt.

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

COMMANDER 500