Protection Features

B-9

OPERATION

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TRANSPORTING

The Converter may be carried by one or two persons using the front and rear top and bottom handles. It can also be set vertically on a two wheel cart, or horizon- tally on a wagon, to move it longer distances.

STORAGE

The Multi-Weld 350 may be set on a floor, or shelf, hor- izontally on its skid, or vertically standing on its rear top and bottom handles.

The Multi-Weld 350 design features electronic protec- tion systems to help assure reliable operation even under adverse conditions. These systems include:

FAN AS NEEDED (F.A.N.)

The cooling fan will turn on when the arc starts and remain on for about a minute after the arc is out to cool down the power components.

This feature electronically controls the fan so it does not run continuously when the power switch is turned on. This will minimize the amount of contaminate and clogging debris which may be drawn into the Converter. It enhances the “Central-Air” system design which intakes lower velocity air through the higher side louvers and blows it out through the lower back louvers with higher velocity.

OVER-VOLTAGE PROTECTION

The Multi-Weld 350 input contactor will open if the input supply voltage is above 113 VDC, and will automatical- ly reclose if the voltage drops back below. During Over- Voltage Shutdown the panel displays will be as appro- priate for the non-welding mode. (See FRONT PANEL CONTROLS in this section.)

CAUTION

When the contactor recloses, the output of the Converter will reactivate. Switching OFF input power prevents unexpected reactivation.

This feature protects internal components of the Converter from excessive voltage levels.

OVER-CURRENT PROTECTION

The maximum output current of the Multi-Weld 350 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 maximum levels until the current is reduced, even to a shorted output.

Prolonged output at this maximum current limit level may eventually overheat the Converter’s internal power components, causing over-temperature shut- down. (See following section.)

Short circuit protection is also provided to reduce max- imum output current to about 200 amps, if the output voltage is reduced, by loading or current limiting, to below 14 volts for over 7 seconds (indicating a shorted output). The output current must be interrupted to reset this reduced protective level.

This maximum 200 amp short circuit level will allow using the Multi-Weld 350 for “pipe-thawing” applica- tions without causing over-temperature shutdown. (See following section.)

OVER-TEMPERATURE SHUTDOWN

A second over-load protection switch in the Imbalance Protector Module was added to Multi-Weld 350 models with codes 10736 and higher. This module senses for an imbalance of current between the paralleled Chopper boards by sensing the differential choke volt- age. If this voltage exceeds 1 V for a sustained time, the Imbalance Protector will also activate over-temper- ature shutdown to protect the higher current Chopper board from over heating.

CAUTION

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.

During Over-Temperature Shutdown the panel displays will be as appropriate for the non-welding mode. (See FRONT PANEL CONTROLS in this section.) 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 current may likely be the cause.

MULTI-WELD 350