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THEORY OF OPERATION
E-2 E-2
INVERTEC® V205-T AC/DC™
GENERAL DESCRIPTION
The Invertec® V205T AC/DC is an inverter based
industrial welding power source that utilizes single-
phase input power to produce constant current AC or
DC output for both Stick (SMAW) and TIG (GTAW).
With 230VAC input applied the V205T is rated at 200
amps, 18volts at a 40% duty cycle. With 115VAC
applied the machine is rated at 150 amps, 16 volts at a
40% duty cycle. The machine has the capabilities to
produce several varieties of AC waveforms (square,
sinusoidal and triangular). The unit also employs an
auto reconnect feature that does not require manual
intervention when the input power is changed from
115VAC to 230VAC or 230VAC to 115VAC. When in
the TIG mode the operator may select to use either the
high frequency or touch start function.
INPUT BOARD AND BUS BOARD
The single phase input voltage is applied to the V205T
through a line switch located on the back of the
machine. The AC input voltage is filtered and condi-
tioned by a network of inductors, capacitors and a
varistor that are all located on the Input Board. This fil-
FIGURE E.2 - GENERAL DESCRIPTION, INPUT BOARD & BUS BOARD
tered input voltage is applied to the Main IGBT Inverter
Board. Another function of the Input Board is to pre-
vent high frequency inverter generated “noise” from
being induced back into the supply lines.
The Bus Board performs several functions within the
V205T. It accepts and distributes power and informa-
tion to other circuitry. This interfacing is accomplished
through harness and ribbon connectors and also via
other PC boards that are plugged directly into the Bus
Board. The Input Board, the High Frequency Board
and the AC Super-Imposition Board plug into the Bus
Board. Circuitry located on the Main IGBT Inverter
Board, the Control Board, the Output Module Board,
the Output Filter Board and the Hall Effect Device inter-
face with the Bus Board. Some circuits are also incor-
porated within the Bus Board. They are the fan circuit
(24VDC) and an input voltage sensing circuit that is uti-
lized by the auto reconnect circuitry located on the
Main Inverter Board.
The fan fuse F3, the 400VDC fuse F2 and the water
cooler F1 (not used) are also located on the Bus
Board.
NOTE: Unshaded areas of Block Logic
Diagram are the subject of discussion
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
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