Lincoln Electric SVM167-A service manual Control BOARD, GUN Trigger and Wire Drive Motor

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E-4 THEORY OF OPERATION E-4

FIGURE E.4 – OPTIONAL CIRCUITS.

WIRE

GASSPEED

SOLENOIDCONTROL

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FAN

MOTOR

LINE

SWITCH

RECTIFIER

DIODE

BRIDGE

VAC28TAP SELECTOR SWITCH

CONTROL BOARD

CONTACTOR CONTROL

CONTACTOR

WIRE

DRIVE

MOTOR

TACH

GUN TRIGGER

OUTPUT DIODE

BRIDGE

+

OUTPUT

CHOKE

OUTPUT

CAPACITORS

-

TRANSFORMER	OUTPUT BRIDGE
THERMOSTAT	THERMOSTAT

+

POSITIVE

TERMINAL

-

GUN

ASSEMBLY

Return

Return

RECONNECT

PANEL

MAIN	NEGATIVE
TRANSFORMER
	TERMINAL

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CONTROL BOARD, GUN TRIGGER AND WIRE DRIVE MOTOR

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When the control board receives an activation command from the trigger circuit the control board supplies 12VDC which activates the gas solenoid and output contactor. It also supplies 2 to 29 VDC (depending on the wire speed setting) to the wire drive motor. The control board monitors 0-5VDC signal from the wire speed potentiometer and adjusts the motor speed accordingly. The proper armature voltage is then applied to the wire drive motor. The drive motor speed is thus controlled which in turn regulates the electrode wire feed speed through the gun.

Two self re-setting thermostats are included in the trigger circuitry. If either of these thermostats would “open” due to excessive heat, the trigger circuit would be interrupted and the machine’s output and the wire feed would be disabled. The board also contains overload protection circuitry which protects the drive motor from excessive current draw.

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

POWER MIG® 215