Theory of operation, Thermal protection, Protective circuits – Lincoln Electric INVERTEC SVM199-A User Manual
Page 38: Over current protection, Under/over voltage protec- tion
THEORY OF OPERATION
E-6
E-6
INVERTEC® V450-PRO
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 output rectifier and the
other is located near the fan. (On later production
machines this thermostat is located on the output
choke) Excessive temperatures may be caused by a
lack of cooling air or operating the machine beyond its
duty cycle or output rating. If excessive operating tem-
peratures 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.
If the fan is 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 cor-
rected. The F.A.N. (fan as needed) system is con-
trolled by the control board via a solid-state relay.
PROTECTIVE CIRCUITS
Protective circuits are designed into the INVERTEC®
V450-PRO to sense trouble and shut down the
machine before damage occurs to the machine's inter-
nal components.
OVER CURRENT
PROTECTION
If the average current exceeds 590 amps, then the
peak current will be limited to 100 amps until the aver-
age current decreases to fewer than 50 amps.
UNDER/OVER VOLTAGE PROTEC-
TION
A
protective
circuit
is
included
on
the
control board to monitor the voltage across
the input capacitors. In the event that a
capacitor voltage is too high, or too low, the protection
circuit will de-energize the input contactor. Machine
output will be disabled and the “soft start” mode will be
repeated. The protection circuit will prevent output if
any of the following circumstances occur.
1. Capacitor conditioning is required. (May be
required if machine has been off for a long period
of time and is connected for high input voltage
operation.)
2. Voltage across a capacitor exceeds 390 volts.
(High line surges or improper input voltage con-
nections.)
3. Voltage across a capacitor is under 70 volts. (Due
to improper input voltage connections.)
4. Internal component damage.