GENERAL DESCRIPTION
The Invertec STT is a 225 ampere, inverter based, arc
welding power supply specifically designed for the
Surface Tension Transfer (STT) welding process. It
cannot be classified as either a constant current (CC)
or a constant voltage (CV) machine. The STT pro-
duces current of a desired waveform to reduce spatter
and fumes. The STT process is optimized for short -
circuit GMAW welding only.
INPUT VOLTAGE
The Invertec STT can be connected for a variety of
three-phase voltages. The initial input power is applied
to the STT through a line switch located on the front of
the machine. The AC input voltage is applied to the
input rectifier and the T1 auxiliary transformer. The T1
transformer develops the appropriate AC voltages to
operate the cooling fan, the power and control boards.
The T1 transformer also supplies primary voltage to the
T4 auxiliary transformer as well as 42 VAC to an exter-
nal wire feeder. The T4 transformer supplies power to
the IGBT drive board and the control board.
THEORY OF OPERATION
E-2 E-2
INVERTEC STT
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FIGURE E.2 – INPUT VOLTAGE
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
