Thermal Protection; Protective Circuits - Lincoln Electric INVERTEC SVM158-A Service Manual

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THERMAL PROTECTION

Two normally closed (NC) thermostats protect the
machine 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 and the
other is located on the output choke. Excessive tem-
peratures may be caused by a lack of cooling air or
operating the machine beyond its duty cycle or output
rating. If excessive operating temperatures should
occur, the thermostats will prevent output from the
machine. The yellow thermal light, located on the front
of the machine, will be illuminated. The thermostats
are self-resetting once the machine cools sufficiently.
If the thermostat shutdown was caused by excessive
output or duty cycle and the fan is operating normally,
the power switch may be left on and the reset should
occur within a 15-minute period.

PROTECTIVE CIRCUITS

Protective circuits are designed into the V350-PRO to
sense trouble and shut down the machine before
damage occurs to the machine's internal components.
THEORY OF OPERATION
OVER CURRENT
PROTECTION
If the average current exceeds 450 amps for one sec-
ond, then the output will be limited to 100 amps until
the load is removed. If the peak current exceeds 600
amps for 150 ms, the output will be limited to 100
amps until the load is removed.
UNDER/OVER VOLTAGE PROTECTION
Protective circuits are included on the switch and con-
trol boards to monitor the voltage across the input
capacitors. In the event that a capacitor pair voltage
is too high, or too low, the machine output will be dis-
abled. The protection circuits will prevent output if any
of the following conditions exist.
1. Voltage across a capacitor pair exceeds 467
2. Voltage across a capacitor pair is under 190 volts.
3. Internal component damage.
V350-PRO
volts. (High line surges or improper input voltage
connections.)
(Due to improper input voltage connections.)
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