Service manual

4 Troubleshooting
4.1 Troubleshooting Tips
Before repairing a frequency converter, read and
understand the following instructions.
1. Note all warnings concerning voltages present in
the frequency converter. Always verify the
presence of AC input voltage and DC bus voltage
before working on the unit. Some points in the
frequency converter are referenced to the
negative DC bus. They are at bus potential even
though it may appear on diagrams to be a
neutral reference.
CAUTION
Voltage can be present for as long as 20 minutes on
frequency converters after removing power from the unit.
See the label on the front of the frequency converter door
and Table 1.1 for the specific discharge time.
2. Never apply power to a unit that is suspected of
being faulty. Many faulty components within the
frequency converter can damage other
components when power is applied. Always
perform the procedure for testing the unit after
repair as described in 4.7 After Repair Tests.
3. Never attempt to defeat any fault protection
circuitry within the frequency converter, as this
results in unnecessary component damage and
can cause personal injury.
4. Always use factory approved replacement parts.
The frequency converter is designed to operate
within certain specifications. Incorrect parts can
affect tolerances and result in further damage to
the unit.
5. Read the instruction manual. A thorough
understanding of the unit is the best approach. If
ever in doubt, consult the factory or authorized
repair center for assistance.
4.2
Exterior Fault Troubleshooting
There may be slight differences in servicing a frequency
converter that has been operational for some extended
time compared to a new installation. When using proper
troubleshooting procedures, make no assumptions.
CAUTION
Never assume that a motor is wired properly after a service
of the frequency converter. There is a risk of overlooking
for example, loose connections, improper programming, or
added equipment.
It is best to develop a detailed approach, beginning with a
physical inspection of the system. See Table 4.1 for items
to examine.
4.3 Fault Symptom Troubleshooting
This troubleshooting section is divided into sections based
on the symptom being experienced. To start, Table 4.1,
provides a visual inspection check list. Often, wrong instal-
lation or wiring of the frequency converter cause the
problem. The check list provides guidance through various
items to inspect during any frequency converter service
process.
Next, symptoms are approached as the technician most
commonly discovers them: reading an unrecognized
frequency converter display, problems with motor
operation, or a warning or alarm displayed by the
frequency converter. Remember, the frequency converter
processor monitors inputs and outputs as well as internal
frequency converter functions. Thus, an alarm or warning
does not necessarily indicate a problem within the
frequency converter itself.
Each incident has further descriptions on how to
troubleshoot that particular symptom. When necessary,
further referrals are made to other parts of the manual for
additional procedures. 5 Frequency Converter and Motor
Applications presents detailed discussions on areas of
frequency converter and system troubleshooting that an
experienced repair technician must understand for
effective analysis.
Finally, a list of tests, 4.7 After Repair Tests is provided.
Always perform these tests under the following conditions:
•
Starting a frequency converter for the first time.
•
Approaching a frequency converter that is
suspected of being faulty.
•
After a repair to the frequency converter.
Troubleshooting
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