OUTPUT RECTIFIER, OUTPUT
CHOKE AND STT CHOPPER
BOARD
The output rectifier receives the AC output from the
main transformer secondary and rectifies it to a DC
voltage level. The output choke is in series with the
negative leg of the output rectifier and also in series
with the welding load. Due to the current "smoothing"
capability of the output choke, a filtered DC output cur-
rent is applied through machine output terminals to the
welding arc.
The STT Chopper Board is in series with the STT out-
put terminal and is used to interrupt the welding cur-
rent for very short periods of time during the short-arc
MIG welding process. The IGBT modules incorporat-
ed on this board receive their gate firing commands
from the Control Board.
E-8 E-8
THEORY OF OPERATION
POWER WAVE 455/R
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FIGURE E.7 – OUTPUT RECTIFIER, OUTPUT CHOKE AND STT CHOPPER BOARD
RECP.
RECP.
LEFT S.B.
CAP. V/F
RIGHT S.B.
CAP. V/F
S.B.
S.B.
