Open-Circuit Voltage Control - ESAB Aristo Arc 4000i Service Manual

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Welding with the filler wire positive: voltage sensing from the wire
and workpiece.
Y1 and Y2 must be linked. This method compensates for the voltage drop
in both the supply and return conductors. The input signal is measured
between X1 and X3. Amplifier IC8:14 is active.
CAUTION! If the voltage signal connection to X3 is lost, the power source
loses control of the arc voltage.

Open-circuit voltage control

The open-circuit voltage control is active when:
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there is an open welding circuit and no arc.
The open-circuit voltage control is inactive when:
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the HF ignition is activated during TIG welding with HF.
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there is contact between electrode and workpiece.
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there is an arc.
Version 1 of 20AP1:
The open-circuit voltage control holds the voltage at about 55 to 70 V in MIG
mode and at 78 to 90 V in MMA and TIG mode.
Version 2 of 20AP1
High level control:
The mean value of the open-circuit voltage is 58 V (55 - 59 V).
Low level control:
The open-circuit voltage is < 35 V (25 - 30 V). The low level control can only
be activated or deactivated by the ESAT, see page 56. The low level control is
also named the VRD function, Voltage-Reducing Device.
Monitoring:
The processor monitors the open-circuit voltage (OCV). If the mean value of
the OCV exceeds the actual limit for more than 0.3 seconds after conclusion of
welding, the output voltage is turned off and the display shows fault code 16.
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OCV limits before software version 1.15: 60 V respectively 30 V.
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OCV limits from software version 1.15: 62 V respectively 32 V.
All welding methodes, all versions of 20AP1
If the welding arc extinguishes the open circuit voltage is about 140 V, peak
voltage. Within 0.3 seconds the open-circuit voltage is at a level controlled by
the open-circuit voltage control or at a lower level.
Note! Spare part boards are delivered with the VRD function deactivated.
See page 40 for identification of circuit board versions.
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.
MIG welding mode
1. The torch switch is depressed.
2. The power source generates open-circuit voltage.
3. Welding starts, the open-circuit voltage control is inactive.
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S0740 800 191/E100629/P78