Service manual

When the input voltage becomes unbalanced or a phase
disappears completely, the ripple voltage increases. This
situation causes the frequency converter to trip and issue
Alarm 4, Mains Phase Loss. In addition to missing phase
voltage, a line disturbance or imbalance can cause an
increased bus ripple. Line disturbances can be caused by
line notching, defective transformers, or other loads that
can affect the form factor of the AC waveform. Mains
imbalances which exceed 3% cause sufficient DC bus
ripple to initiate a trip.
Output disturbances can have the same effect of increased
ripple voltage on the DC bus. A missing or lower than
normal output voltage on one phase can cause increased
ripple on the DC bus. When a mains imbalance trip occurs,
it is necessary to check both the input and output voltage
of the frequency converter.
Severe imbalance of supply voltage or phase loss can
easily be detected with a voltmeter. View line disturbances
through an oscilloscope. Conduct tests for input imbalance
of supply voltage, input waveform, and output imbalance
of supply voltage as described in 4 Troubleshooting.
5.1.3
Control Logic Problems
Problems with control logic can often be difficult to
diagnose, since there is usually no associated fault
indication. The typical complaint is simply that the
frequency converter does not respond to a given
command. There are two basic commands that must be
given to any frequency converter to obtain an output.
Commands provided to the frequency converter to obtain
an output:
•
Start Command: to execute.
•
Reference or Speed Command: to identify the
speed of execution.
The frequency converters are designed to accept various
signals. First determine which of these signals the
frequency converter is receiving
•
Digital inputs (18, 19, 27, 29)
•
Analog outputs (42, 45)
•
10 V output
•
Analog inputs (53, 54)
•
Serial communication bus (68, 69)
The presence of a correct reading indicates that the
microprocessor of the frequency converter has detected
the desired signal. See 2.3 Frequency Converter Inputs and
Outputs.
This data can also be read in parameter group 16-6
*
Inputs
and Outputs.
If there is no correct indication, check if the signal is
present at the input terminals of the frequency converter.
Use a voltmeter or oscilloscope in accordance with
6.4.7 Input Terminal Signal Tests.
If the signal is present at the terminal, the control card is
defective and must be replaced. If the signal is not
present, the problem is external to the frequency
converter. The circuitry providing the signal along with its
associated wiring must then be checked.
5.1.4
Programming Problems
Difficulty with frequency converter operation can be a
result of improper programming of the frequency
converter parameters. Three areas where programming
errors can affect frequency converter and motor operation
are motor settings, references and limits, and I/O configu-
ration. See 2.3 Frequency Converter Inputs and Outputs.
The frequency converter must be set up correctly for the
motor(s) connected to it. Parameters must have data from
the motor nameplate entered into the frequency converter.
These data enables the frequency converter processor to
match the frequency converter to power characteristics of
the motor. The most common result of the inaccurate
motor data is that the motor drawing higher than normal
amounts of current must perform the task expected of it.
In such cases, setting the correct values to these
parameters and performing the Automatic Motor
Adaptation (AMA) function usually solves the problem.
Any references or limits set incorrectly result in less than
acceptable frequency converter performance. For instance,
if maximum reference is set too low, the motor is unable
to reach full speed. These parameters must be set
according to the requirements of the particular installation.
References are set in parameter group 3-0
*
Reference Limits.
Incorrectly set I/O configuration usually results in the
frequency converter not responding to the function as
commanded. Remember that for every control terminal
input or output there are corresponding parameter
settings. These settings determine how the frequency
converter responds to an input signal or the type of signal
present at that output. Utilizing an I/O function involves a
two-step process. The desired I/O terminal must be wired
properly, and the corresponding parameter must be set
accordingly. Control terminals are programmed in
parameter groups 5-0
*
Digital I/O Mode and 6-0
*
Analog I/O
Mode.
Frequency Converter and Mot...
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HVAC Basic Drive Service Manual
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