20Ap1:9 Arc Voltage Feedback For Universal And Mig Machines - ESAB Arc 4000i Service Manual

20AP1:9 Arc voltage feedback for Universal and MIG machines
Circuit diagram of the arc voltage input
The arc voltage input senses the welding voltage regardless of the welding
polarity or welding method. If sensing via the welding filler wire is connected, it
is this voltage that will be used: if not, the voltage at the power source's
terminals is used.
The signal from the arc voltage input is used as an input signal to the welding
process controller: from it, the controller calculates in real time how much
current must flow in the circuit in the next instant. The controller
activates/deactivates the no--load voltage reduction function.
The arc voltage signal provides a voltage signal to the power source's display
panel. See page 66 for calibrating instructions.
No- -load voltage reduction
MIG
The no--load voltage controller senses the voltage at the welding current
terminals and limits it to a level between 55 V and 70 V. This function is
inactive during welding, and is activated within 0.5 seconds after conclusion of
welding.
MMA
The no--load voltage controller senses the voltage at the welding current
terminals and limits it to a level between 78 V and 90 V. This function is
inactive during welding, and is activated within 0.5 seconds after conclusion of
welding.
TIG
For TIG welding with HF starting, the power source produces the unregulated
no--load voltage of about 140 V while the starting function is active, which is
normally a maximum of 0.5 seconds.
No- -load overvoltage protection
This disables the PWM circuit if the no--load voltage exceeds 113 V for more
than one second. The power source cannot then be restarted until the mains
switch has been turned off and then on again. The display shows fault code 16
if this protection operates.
This overvoltage protection function operates independently of the welding
process controller.
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