ESAB LAW 400, Руководство по обслуживанию

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8 SHUNT INPUT
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Shunt RS1 provides a 10 mV signal at 100 A. The shunt voltage is linear in relation
to the current through the shunt. IC12 amplifies the shunt signal voltage.
The shunt signal voltage is connected to the processor via two different time
constants:
S
a A time constant of 0.5 s, for indication of the welding current on the digital
display.
S
b
A time constant of 7.26 ms for overcurrent protection.
See below under Item 13.
The electronic neutral, 0 V, is connected to the positive welding current pole via
contact D5. Capacitor C4, which is connected to the case screen, decouples
interference to the machine case.
Circuit board 0486 480 880
Components marked in italics are fitted only to version A and later versions of this
circuit board.
You can find out the version from the number (486 479--001A), which is printed on
the board. Each time the print is changed there will be a new version letter. The
first version of the board has no letter after the number.
From version A it is possible to adjust signal
a to the digital instrument. When
trimming signal a , first remove R195 (0
Ω
), then you can adjust the signal with
potentiometer R196. If you want to decrease the signal, you also have to remove
R193.
9 VOLTAGE REFERENCE
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The voltage reference potentiometer is fitted in the wire feed unit. The power
supply to the potentiometer, +15 VB, is protected against short circuits to the arc
voltage.