Figure E.3 Control Circuits | Lincoln Electric SVM176-A manual

Lincoln Electric SVM176-A service manual Figure E.3 Control Circuits

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TRIGGER AND INTERLOCK CIRCUIT The gun trigger (leads 602 & 604) is connected to the 24VAC circuit from the K350 Adapter, or the low voltage output control circuit (#2 & #4) of the power source if no K350 is required.

Once the trigger is closed the wire starts feeding. When the arc is estblished, the reed switch closes (leads 647 & 604) and the trigger is bypassed or “interlocked”. This feature allows the operator to release the trigger once the weld has begun to help eliminate fatigue.

The reed switch is a magnetically operated device that is mounted on a bracket above the block where the gun connects to the feeder. It responds to the magnetic field that is presnt due to the weld current flowing through the gun cable.

To stop welding, the operator must physically pull the gun away from the weld, thus stopping current flow and releasing the reed switch. See Figure E.3.

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E-3						THEORY OF OPERATION												E-3
						FIGURE E.3 – CONTROL CIRCUITS.
WIRE SPEED CONTROL																REDUCED SPEED CONTROL
10KΩ, 4 W						567 521							A			REDUCED SPEED CONTROL
						567 521							A
R12	535											644	B
601													C
601													D
642						1	2	3	4	5	6		D
642						1	2	3	4	5	6
VOLTAGE CONTROL
10KΩ, 4 W						535
R75						535
R75
75						LN-23P
						LN-23P		539
76						CONTROL		539								647
76						CONTROL										647
77						P.C. BOARD
3.5 A CIRCUIT											541		W
BREAKER											541		100Ω, 1	R76	82V, 12J	604
BREAKER															82V, 12J	604
						1	4	2	5	3	6				TP2
															TP2
																602
												641
									567A		67	642
									567A		67
								567		521
												BLACK
												WHITE
												WIRE FEED MOTOR						GUN TRIGGER SWITCH
												WIRE FEED MOTOR
																604		C
																		B
																602		A
8 PIN CONNECTOR	H	F	G	E	C	D
6 PIN CONNECTOR	F	E	D	C	B	A
77																	604
75																	647
76																	647	REED SWITCH ACTIVATED
76																		REED SWITCH ACTIVATED
521																		BY WELDING CURRENT
602
604
ELECTRODE (-)													GUN CONDUCTOR BLOCK					WORK
	WORK (+)																	WORK
	WORK (+)
21

VOLTS AND SPEED CONTROL CIRCUITS The Voltage Control is connected directly to the K350 Adapter or the power source (if no adapter is required) by leads 75, 76 & 77. It can be adjusted while welding to provide the voltage called for by the weld procedure.

The wire feed speed is controlled by signals to the Control Board from the Speed Control and the Reduced Speed Switch. The Wire Speed Control is calibrated and can be preset to the desired value. The speed will remain at the set value regardless of arc voltage as long as the Reduced Speed Switch is in Position 1 (open).

When the Reduced Speed Switch is in Position 2 (closed) the speed will be reduced to 83% of the set speed. This switch is to facilitate welding if the root opening changes or to reduce “sagging” of the weld metal as the operator approaches the bottom of a pipe joint. The switch may be changed to either position while welding as needed without stopping or breaking the arc.

NOTE: Unshaded areas of block logic diagrams are the subject of discussion.

LN-23P

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Contents

Lincoln Electric SVM176-A service manual Figure E.3 Control Circuits

THEORY OF OPERATION

FIGURE E.3 – CONTROL CIRCUITS.

LN-23P