4 Troubleshooting
4.1 Troubleshooting Tips
Before attempting to repair a filter, here are some tips to
follow to make the job easier and possibly prevent
unnecessary damage to functional components.
1. Note all warnings concerning voltages present in
the filter. Always check for the presence of AC
input voltage and DC bus voltage before working
on the unit. Some points in the filter are
referenced to the negative DC bus and can be at
bus potential even though it may appear on
diagrams to be a neutral reference.
Remember that voltage may be present for as
long as 40 minutes on E-frame size filters or 20
minutes on D-frame size filters after removing
power from the unit. See the label on the front of
the filter door for the specific discharge time.
2. Never apply power to a unit that is suspected of
being faulty. Many faulty components within the
filter can cause damage to other components
when power is applied.
3. Never attempt to defeat any fault protection
circuitry within the filter. That will result in
unnecessary component damage and may cause
personal injury.
4. Always use factory approved replacement parts.
The filter has been designed to operate within
certain specifications. Incorrect parts may affect
tolerances and result in further damage to the
unit.
5. Read the instruction and service manuals. A
thorough understanding of the unit is the best
approach. When in doubt, consult the factory or
authorized repair center for assistance.
6.
The After Repair Tests should always be performed
following a repair to the filter.
4.2
Fault Symptom Troubleshooting
Table 4.1 provides an inspection check list. The check list
provides guidance through a variety of items to inspect
during any filter service process.
The filter processor monitors inputs and outputs as well as
internal filter functions, so an alarm or warning does not
necessary indicate a problem within the unit itself. Many
times the root cause of the problem is due to interactions
between the AAF and other devices connected to the
same transformer.5 Active Filter and the Power Grid presents
detailed discussions on areas of filter and system trouble-
shooting that an experienced repair technician should
understand in order to make effective diagnoses. The After
Repair Tests should always be performed following a repair
to the filter.
Troubleshooting VLT Advanced Active Filter AAF006 D and E Frames Service Manual
MG90Z122 - VLT
®
is a registered Danfoss trademark 4-1
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