Lincoln Electric INVERTEC V275-S Service Manual page 26

E-4
Input Switch
Input
& 100A Breaker
Rectifier
+
-
-
Aux.
Trans
Fan
Relay
Fan
Fan
Motor Motor
230VAC
230VAC
6
Pin
Amphenol
CONTROL BOARD
CIRCUIT
The control board performs the primary interfacing
functions to establish and maintain control of the
machines output. The control board receives com-
mands from the user-operated controls that are con-
nected to the control board.
potentiometer's allow the operator to set the current
output of the machine and also to select either local or
remote control of the output. Other controls allow for
the adjusting of the Arc Force the selection of the Hot
Start option and the Stick or TIG mode of operation.
The control board processes and compares these
commands with the voltage and current feedback
information it receives from the output current shunt
and the output voltage sensing leads. The appropriate
pulse width modulation (PWM) signals (See Pulse
Width Modulation in this section) are sent to the
switch board IGBTs. As a result a high-speed welding
waveform is created and regulated.
At the initial start-up of the V275-S the closing of the
precharge relay is delayed and controlled by the cir-
cuitry on the control board. When the input capacitors
are charged to an acceptable voltage level the control
board energizes the precharge relay.
THEORY OF OPERATION
FIGURE E.4 – CONTROL BOARD AND FANS CIRCUIT
Main Switch Board
Reconnect
Switch
To
Shut Down Signal
Fan
Motors
18 VAC
Relay Control
AND FANS
These switches and
V275-S
#1 Primary
Current
Feedback
To Control
Board
#2 Primary
Current
Feedback
Output
Diodes
IGBT Drive Signal
#1 Primary
Precharge Relay Control
Current
Feedback
Control Board
Hot
Arc
Output
Start
Force Control
The 230VAC fans operate once 15 amps of welding
current is drawn and for seven minutes after the weld-
ing output has stopped flowing. The fans will also
operate anytime the machine has over heated and the
opening of the normally closed thermostats signal the
control board to energize the fan relay. When the nor-
mally closed thermostats are open the control board
also energizes a thermal LED to signal the operator
that an overheated condition exists.
In addition to the thermostats, the control board also
monitors the welding output current and the main
transformers primary currents.
back signals are beyond normal limitations the control
board will stop providing PWM signals to the main
IGBTs and welding output voltage and current will
cease.
The 6-pin remote control receptacle is also connected
directly to the control board. When the local/remote
switch is in the "remote" position the control board
processes these remote operator commands to con-
trol welding output.
Choke
Positive
+
Output
Terminal
Negative
-
Shunt
Output
Terminal
Thermostats
Thermo.
LED
Local
Mode
Remote
If any of these feed-
E-4