Flexible Power Supply Board, Switches And Wirefeed - Lincoln Electric LN-25x Service Manual

LINCOLN ELECTRIC LN-25x™ Service Manual
Figure E.3 – Flexible power supply board, switches and wirefeed

Flexible Power Supply Board, Switches and Wirefeed

The flexible power supply board creates several power supplies from the arc voltage. It communicates with
and supplies regulated power to the user interface board. The electronic circuitry in the flexible power
supply board creates a 50 VDC bus that is used to power the gas solenoid and the contactor. The output of
the 50 VDC bus is applied to the gas solenoid and the contactor via a PWM (pulse width modulation) signal.
Addition power supplies developed on the flexible power supply board are +15, -15 and +5VDC.
The desired wire feed signal received from the user interface board is processed on the flexible power
supply board, compared to the tachometer feedback signal and the appropriate armature voltage is sent to
the wire drive motor. The tachometer transforms the motor RPM to a digital frequency that is fed back to
the board.
When the gas purge button is pressed only the gas solenoid will be activated. When the cold inch button is
pressed the wire feed motor will be energized and wire will feed without the presence of welding voltage.
When the gun trigger is pressed the wire will feed, the contactor will close and the gas solenoid will
activate.
The trigger interlock switch allows for either 2-step or 4-step operation of the gun trigger.
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