ESAB Origo Mag C171, Service Manual, Page: 30 / 45

Edition 080529
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1sC1425
AP1:6 Burnback time, contactor, gas valve
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Burnback time
The burn--back time is the time from when motor braking starts until the main
contactor opens. When welding stops, capacitor C38 is discharged through
potentiometer R21. The time can be adjusted from 0 to 0.25 seconds.
Energising the contactor
The contactor is controlled by triac TC2.
Gas valve
The gas valve is connected to board contacts A5 and A6, it receives its power
supply from triac TC2 via resistor R20 (0
Ω
).
AP1:7 Thermal overload cutout
The thermal overload cutout ST1 is mounted on the cooling fins of the diode
bridge, and operates at a temperature of 130
° C.
A current normally flows through the cutouts from the +20 V supply via R2 and
D2, and from the +15 V supply via R8. The voltage at contact C1 is kept low
by the switch. If a cutout operates, C1 goes high and the output signals from
the board are disabled.
Operation of the cutout causes a current to flow from +20 V to 0 V via R2, D1
and LED V7, which indicates operation of the cutout.