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10
CRATER FILLING
The crater filling function can be used only with an MEK 4, 4S or 4SP wire feed
unit. When the wire feed unit sends a crater fill signal to the power unit, input L4
switches high and low four times. Each time that the voltage changes, the welding
voltage is reduced. The table below shows the percentage of the set voltage at each
step, together with the corresponding L4 signal levels.
Normal crater filling
Phase
L4
1
low
2
high
3
low
4
high
In the table above Utop is the pulse voltage and Ub is the background voltage.
Each step lasts for a maximum of 1.27 seconds.
See the MEK 4 and MEK 4S/SP service manual for further information.
11
START / STOP
The closing contact in the MEK wire feeders that activates the power unit start input
is a triac. In order to ensure that it has sufficient holding current, resistor R149
provides a load of 1 kτ 5 W at input L5.
claw0de1
Crater filling during pulse welding
%
Phase
L4
90
1
low
72
2
high
65
3
low
58
4
high
- - 25 - -
claw0e16
(only with MEK 4SP)
%Utop
Phase
L4
80
1
low
62
2
high
55
3
low
40
4
high
claw0e17
%Ub
87
70
63
55
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