Manual

B-4
OPERATION
B-4
OVER-CURRENT PROTECTION
The max. output current of the RED-D-ARC MX350 is
electronically limited, to protect internal power compo-
nents, so as not to exceed about 375 amps average
and 500 amps peak. When the current load starts to
exceed these limits the output is reduced (lower volt-
age) to sustain these max. levels, until the current is
reduced. even to a shorted output.
Prolonged output at this max. current limit level may
eventually overheat the Converterʼs internal power
components causing over-temperature shutdown.
(See following section).
Short circuit protection is also provided to reduce max.
output current to about 200 amps if the output voltage
is reduced, by loading or current limiting (see above),
to below 14 volts for over 7 seconds (indicating a
shorted output). The output current must be interrupt-
ed to reset this reduced protective level.
OVER-TEMPERATURE SHUTDOWN
A second over-load protection switch in the Imbalance
Protector Module was added to RED-D-ARC MX350
models with codes 10736, and higher. This module
senses for an imbalance of current between the paral-
leled Chopper boards by sensing the differential
choke voltage. If this voltage exceeds 1v for a sus-
tained time the Imbalance Protector will also activate
over-temperature shut down to protect the higher cur-
rent Chopper board from over heating.
Machines with code 11149, or higher, which use the
G4662-[ ] Peripheral PC Board, also include Peak
Input Voltage Protection that also lights the the
Thermal Shutdown (yellow) panel light if the unit out-
put is shutdown (See OVER-VOLTAGE PROTEC-
TION Section.).
When the thermostat resets the output of the
Converter will reactivate. Switching OFF input
power prevents reactivation, but also shuts off the
cooling fan which prolongs the reset time.
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RED-D-ARC MX350
During Over-Temperature Shutdown the panel dis-
plays will be as appropriate for the non-welding mode.
(See FRONT PANEL CONTROLS in this section),
except the fan will remain running and the Thermal
Shutdown (yellow) Light will be lit until reset. Typically,
If shutdown occurs repeatedly below 300 amps output
with fan running, imbalance of the Chopper board cur-
rent may likely be the cause.
CAUTION