Lincoln Electric INVERTEC V275-S Service Manual page 28

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THERMAL PROTECTION
Three normally closed (NC) thermostats protect the
V275-S from excessive operating temperatures.
These thermostats are wired in series and are con-
nected to the control board. One of the thermostats is
located on the heat sink of the switch board. The sec-
ond is located on the output choke coil. The third ther-
mostat is located on the output heat sink. Excessive
temperatures may be caused by a lack of cooling air
(one fan running) or operating the machine beyond its
duty cycle or output rating. If excessive operating
temperatures should occur, the thermostats will pre-
vent welding output from the machine. The yellow
thermal LED, located on the front of the machine, will
be illuminated. The thermostats are self-resetting
once the machine cools sufficiently. If the thermal shut
down was caused by excessive output or duty cycle
and the fans are operating normally the power switch
may be left on and the reset should occur within a 15
minute period. If the fans are not turning or the air
intake louvers are obstructed, then the power must be
removed from the machine and the fan problem or air
obstruction be corrected.
PROTECTIVE CIRCUITS
Protective circuits are designed into the V275-S to
sense trouble and shut down the machine before dam-
age occurs to the machine's internal components.
There are resetable fuses on the control board for the
remote amphenol circuit in the event that a remote
cable is damaged.
THEORY OF OPERATION
OVER CURRENT PROTECTION
The maximum current is 290-300 amps. If reaching
that, then the output will be limited to 200 amps until
the load is removed.
UNDER/OVER VOLTAGE PROTEC-
TION
Protective circuits are included on the switch board to
monitor the voltage across the input capacitors. In the
event that a capacitor voltage is too high, or too low,
the machine's output will be disabled. The protection
circuits will prevent output via the control board if any
of the following conditions exist
1. Voltage across a capacitor pair exceeds 455VDC.
2. Voltage across a capacitor is under 235 VDC. (Due
3. Internal component damage.
V275-S
(High line surges or improper input voltage connec-
tions.)
to improper input voltage connections.)
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