20Ap1:9 Welding Process Control - ESAB Caddy Tig 2200i AC/DC Service Manual

20AP1:9 Welding process control
The processor inputs are the set values of welding data and the arc voltage.
The processor also calculates a set value signal for welding current, and
supplies this to the current control amplifier.
The process regulator control principle
Hot start MMA
Peak current
Adjustable starting current
Set current
Time
1 2
Starting current, MMA welding mode
1. Phase 1, fixed starting current depending on the set current.
2. Phase 2, hot start = adjustable starting current.
MMA normal welding mode
In the MMA normal welding mode, the welding current is briefly increased at
the start of welding. The peak current, phase 1 in the diagram above, is
engaged for 150 milliseconds.
The peak current is twice the normal welding current up to 160 A (i.e. twice the
set value), subject to a maximum of 240 A.
The hot start current, phase 2 above, is engaged for 1.5 seconds. It is set in
per cent of the set current, but does never exceed the peak current.
MMA drop welding mode
In the MMA drop welding mode, the peak current is three times the set value,
but the duration is shorter at only 50 ms.
The hot start current, phase 2 above, is engaged for 240 milliseconds. It is set
in per cent of the set current, but does never exceed the peak current.
S0740 800 179/E071123/P64
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