Main Transformer - Lincoln Electric INVERTEC POWER WAVE 450 SVM112-B Service Manual

E-5
THREE
PHASE
INPUT
POWER
INPUT
LINE
SWITCH
PROTECTION
BOARD

MAIN TRANSFORMER

Each Switch Board assembly works as a switch pair.
Each board feeds current to a primary winding of the
Main Transformer. These primary currents are moni-
tored by the Current Transformer (CT). The CT sends
a signal through the Protection Board to the Control
Board. If the primary currents become abnormally
high, the Control Board will shut off the FETs, thus dis-
abling machine output. The right and left sides of the
transformer are isolated from each other. The right
side of the transformer is supplied from Switch Boards
#1 and #2, while the left side of the transformer is sup-
plied from Switch Boards #3 and #4. The DC current
flow through each primary winding is clamped back to
each respective input capacitor when the FETs are
turned off. The firing of the four Switch Board pairs
occurs during halves of a 50 microsecond interval,
creating two constant 20 kHz square waves on the pri-
mary side of the transformer. The current flow through
the Main Transformer primaries induces a 20 kHz AC
square wave output signal at the secondary of the
Main Transformer.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
THEORY OF OPERATION
FIGURE E.5 – MAIN TRANSFORMER
INPUT
RECTIFIER
INPUT AND
CONTACTOR RECONNECT
LEFT
SWITCH
BOARD
FET
ASSEMBLY
AUX.
TRANS
RIGHT
SWITCH
BOARD
FAN
FET
ASSEMBLY
POWER
BOARD
WATER
COOLER
PC
INTERFACE
POWER WAVE 450
MAIN OUTPUT
TRAMSFORMER
RECTIFIER
CT
SNUBBER
SENSE LEADS
CONTROL
BOARD
LCD
DISPLAY DISPLAY
BOARD
KEYPAD
OVERLAY
WF1 WF2
E-5
CHOKE POSITIVE
NEGATIVE
SHUNT
AND