Lincoln Electric Invertec V205-T - Manual (Page 34)

THEORY OF OPERATION
E-4 E-4
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FIGURE E.4 – MAIN TRANSFORMER, OUTPUT DIODE MODULE & CLAMPING BOARD,
OUTPUT TRANSISTOR MODULE & SUPERIMPOSITION BOARD
Superimposition
board
Bus board
Fan
Input
board HF
board
Main IGBT
& Power board
4
IGBT’s
Control board Display & LED
board
888
Control
Knob
Gas
Solenoid
DC blocking
capacitor board
Main
Transformer Output
board Output
Transistor
Module
Current
Hall
Device
Output
Filter bd.
(bypass)
(D + E)
Remote 2/4
Remote
75, 76, 77
A, B, C
24 VDC Remote 2/4 path (D + E)
turn on
AC ckt.
+15, -15, +5 input volt meter thermostat info
set info
input current meter turn on PWM
HF control signal
+48, +24
Input
Choke
_
+
RF coil
-48, +24,+15,-15,+5
reconnect info. voltage feedback
high volt supply turn on
AC ckt.
current feedback
IGBT
Thermostats
Output
Diode
Thermostat
Voltage Feedback
Current Feedback
AC DC Gate drive signals 24 VDC
48 VDC
Output
Choke
MAIN TRANSFORMER
The 100KHZ output of the Main IGBT Inverter Board is
coupled, through a DC Blocking Capacitor Board, to
the primary of the Main Transformer. The transformer
reduces the high voltage (low current) input applied to
the primary winding and through transformer action
develops a lower secondary voltage capable of high
output currents.
OUTPUT MODULE AND CLAMPING
BOARD
The AC output of the Main Transformer is applied to
the Output Modules for full wave rectification. The
Clamping Diodes function as a filter eliminating any
pulsed over-voltages that may be present at the
Output Modules. The Clamping Board protects the
Output Modules from damage due to higher than nor-
mal voltage spikes.
OUTPUT MODULE TRANSISTOR
BOARD
This module produces the AC waveforms and fre-
quencies. It receives command signals from the
Superimposition Board. Depending on which of the
two IGBTs is active at any given moment the welding
output of the machine can be either positive or nega-
tive AC or DC.
SUPERIMPOSITION BOARD
The Super Imposition Board receives signals from the
Control/Display Board to control the status of the sec-
ondary inverter portion of the V205T machine. This
board also generates voltage pulses at about +/-
200VDC that facilitate the re-striking of the arc when
the TIG AC welding current is being utilized. The
Superimposition Board internally generates the auxil-
iary power supply for the isolated piloting of the power
elements (IGBTs) for the Output Module Transistor
Board. The Superimposition Board plugs directly into
the Bus Board.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.