Emerson 7400 - Manual (Page 60)

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Series 7400 Single Phase 1+N UPS
6.1 Troubleshooting UPS systems
The UPS contains complex electronic control circuits that require a
firm understanding in order to carry out comprehensive fault
diagnosis and repair of the equipment. The following information
aims to provide a trained user with sufficient knowledge to
understand the nature of a fault through the correct interpretation
of the accompanying alarms and indications, and to carry out any
necessary first aid repair.
WARNING
Some of the instructions in the charts at the end of this
chapter involve checking internal fuses. This should be
undertaken (after the equipment has been shut down)
only by a trained electrician who is familiar with the layout
and operation of the equipment and fully conversant with
the areas of potential hazard.
There is no practical way of detecting an impending UPS
malfunction. Most problems do not emerge as a gradual
performance degradation; generally the UPS either works correctly
or it will shut down - and transfer the load to the bypass supply if
applicable. However, it is important to maintain a regular record of
the UPS meter indications, as suggested in the maintenance
instructions, in order that any change in the system or load
characteristics are readily identified.
In general, the output voltage should be within 2% of nominal. If the
UPS has not operated on battery power within the previous ten
hours the battery charge current should be typically less than 6A.
If any indication differs significantly from the typical figures given
above the cause should be investigated.
Information concerning prevailing load conditions can prove useful
when discussing problems with the service agent - for example,
details of any particular load being started or shed at the time that
the fault occurred.
Troubleshooting should be carried out methodically using the
following guidelines-
Fault Identification
When first summoned to the scene of a UPS fault, your immediate
action should be to observe and record the displayed messages,
mimic indications, meter indications and the position of the UPS
power isolator switches. This should be completed before you
touch any switch.
C h a p t e r 6 C h a p t e r 6
Troubleshooting
6.1.1 Operating
Parameters and
Limitations
6.1.2 General
Troubleshooting
Procedure