Selco Genesis 240 TLH, Repair Manual

Page: 12 / 82

94 Description of machine operation
5.4)
Current transducer (Hall effect probe) (j) - power circuits
for command/control circuits (m) - current control circuits (n).
(see fig. 9-10)
G 240 is essentially a direct current generator that can be set by
a potentiometer on the front panel. To perform this function, the
current delivered is measured by a current transducer (j); the
power cable connected to the power source output negative
terminal (-) runs through the transducer.
The control circuit on card 15.14.254 instantly compares the
value of requested and delivered current and sends the control
signal to the inverter modulator .
This control circuit also measures the machine's output current
to provide the following functions:
G 240 :
- in MMA :
• increase of current when welding is started (hotstart); the
following relation applies:
supplied current = requested c 80% of the same
• increase of current if the electrode is short-circuited on the
piece during welding (arc-force); the current increase
percentage can be adjusted from 0% to 100% via the panel
potentiometer.
• over-heating protection if, in spite of arc-force the short-
circuit of the electrode on the piece continues for a few tenths
of a second; the following relation applies:
supplied current = 30 A about
- in TIG (LIFT) :
• limitation of no-load voltage to approximately 61 Vdc
(measurement with tester set to Vdc)
• limitation of the current to 30A during the electrode short cir-
cuit phase and until the electrode is lifted.
FIG. 9
k)
a)
o)
l)
i)
j)
d) e) f) g)
h)
e)
c)
n)
m)
b)