Lincoln Electric INVERTEC 270SX Service Manual page 13

INPUT SECTION
GENERAL DESCRIPTION
®
The Invertec 270Sx and 400SX are inverter based
welding power sources that offers multi-mode (TIG and
Stick) constant current welding. The machines can be
operated on three phase input power. The welding
response of these Invertec has been optimized for the
stick (SMAW) and TIG (GTAW) welding processes.
INPUT LINE VOLTAGE, AUXILIARY
VOLTAGE AND PRECHARGE
The 400V 3 phases input power AC is conneted to the
machine, through an input cable, to the main switch
located on the back of the power source. Once 400
Vac +/- 15% voltage is applied to the machine via the
input switch, the following activities will be managed by
the input board W05X0855 (-1version for the 270SX, -
2 version for the 400SX):
the auxiliary power supplies (+24, +15V, -5V)
to all the boards will be generated.
a uController on the input board manages the
soft stat and pre-charge operation. If the
uController is correctly programmed LED LD1
on the input board is turned ON.
after the precharge phase, another 1 second is
necessary for the uctroller to release the
READY_OK signal to the conrol board. After
that, the control board signals to the user that
the machine is ready to go keeping the fron
panel green led always turned ON.
Under and over voltage control and alarm
Page13
During this phase a signal called
o
READY_OK signals to the control
board that the machine is not still
working; the green led on the front
panel is blinking during this phase.
If the input power supply is in the
o
correct range, the ucontroller on the
input board wait about 4 seconds
before to short the precharge relay
that shorts the precharge power
resistance (PTC1) to let the precharge
of the input capacitors.