Open-Circuit Voltage Control - ESAB Aristo Mig 3001i Service Manual

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 70 V.
Version 2 of 20AP1
High level control:
The mean value of the open-circuit voltage is 58 V (55 - 60 V).
Low level control:
The open-circuit voltage is < 35 V (24 - 30 V). The low level control can only
be activated or deactivated by the ESAT, see page 45. 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 90 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 34 for identification of circuit board versions.
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.
4. Welding stops, the open-circuit voltage control is activated and then the
output voltage is shut down.
MMA welding mode
1. The power source generates open-circuit voltage.
2. Contact between electrode and workpiece. When the open-circuit voltage
goes below 45 V (16 V when VRD is active), the open-circuit voltage
control is disabled.
3. When the current exceeds 8 A the hot start current is activated.
4. When the arc voltage exceeds 52 V, welding stops and the open-circuit
voltage control is activated.
TIG welding mode
HF start
For TIG welding with HF starting, the open-circuit voltage is 86 - 90 V, while
the starting function is active. This is normally a maximum of 0.5 seconds.
Live TIG start
1. The power source generates open-circuit voltage.
ca41_20_1 - 33 -
S0740 800 196/E101019/P76