ESAB Origo Mag C171, Service Manual

Page: 21 / 45

Edition 080529
-- 21 --
1sC1425
AP1:6 Burnback time
clka1e09
The burn--back time is the time from when wire feed ceases until contactor
KM1 drops off.
During welding, the voltage at pin 13 of IC2 is low. The output of the inverter
at pin 14 is therefore high, turning on transistor Q2 and activating relay RE1.
When the torch trigger switch is released, or when the spot welding time
expires, capacitor C23 charges up via resistors R36, R37 and R38. When the
voltage across C23 reaches 8.8 V, output 14 of IC2 goes low, turning off Q2
and causing relay RE1 to drop off.
AP1:7 Control amplifier and pulse width modulator
The control amplifier compares the set value speed signal with the actual
speed and supplies a control signal to the pulse width modulator. The actual
value speed signal is provided by measuring the motor voltage.
The pulse width modulator controls the frequency and pulse time of current to
the wire feed motor.