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 line imbalance trip occurs, it
is necessary to check both the input and output voltage of
the adjustable frequency drive.
Severe imbalance of supply voltage or phase loss can
easily be detected with a voltmeter. Use an oscilloscope to
view line disturbances. Conduct tests for input imbalance
of supply voltage, input waveform, and output imbalance
of supply voltage as described in
,
chapter 6.4.6 Input Imbalance of Supply Voltage
, and
chapter 6.4.9 Output Imbalance of Motor Voltage
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
adjustable frequency drive does not respond to a given
command. There are two basic commands that must be
given to any adjustable frequency drive in order to obtain
an output. First, the adjustable frequency drive must be
told to run (start command). Second, the adjustable
frequency drive must be told how fast to run (reference or
speed command).
Adjustable frequency drives are designed to accept various
signals. Determine what types of signals the adjustable
frequency drive is receiving. There are six digital inputs
(terminals 18, 19, 27, 29, 32, 33), two analog inputs (53 and
54), and the serial communication bus (68, 69). A correct
reading indicates that the microprocessor detects the
desired signal. See
chapter 2.6 Adjustable Frequency Drive
.
Using the status information displayed by the adjustable
frequency drive is the best method of locating problems of
this nature. By selecting within parameter group 0–2* LCP,
line 2 or 3 of the display can be set to indicate the signals
coming in. A correct reading indicates that the
microprocessor detects the desired signal. This data is
available in parameter group
16-6* Inputs & Outputs
.
If there is not a correct indication, the next step is to
determine whether the signal is present at the input
terminals. Perform this test with a voltmeter or
oscilloscope in accordance with the
.
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 adjustable
frequency drive. The circuitry providing the signal along
with its associated wiring must then be checked.
5.1.4 Programming Problems
Difficulty with adjustable frequency drive operation can be
a result of improper programming of the adjustable
frequency drive parameters. Programming errors affect
adjustable frequency drive and motor operation in the
areas of motor settings, references and limits, and I/O
configuration.
The adjustable frequency drive must be set up correctly for
the motor or motors connected to it. Parameters
1-20 Motor Power [kW]
to
1-25 Motor Nominal Speed
must
have data from the motor nameplate entered into the
adjustable frequency drive. This data enables the
adjustable frequency drive processor to match the
adjustable frequency drive to power characteristics of the
motor. The most common result of inaccurate motor data
is the motor drawing higher than normal amounts of
current to perform the task expected of it. In such cases,
setting the correct values for these parameters and
performing the automatic motor adaptation (AMA)
function usually solves the problem.
Any references or limits set incorrectly results in
substandard 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
adjustable frequency drive not responding to the function
as commanded. For every control terminal input or output,
there are corresponding parameter settings. These settings
determine how the adjustable frequency drive responds to
an input signal or the type of signal present at that
output. Utilizing an I/O function is 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
.
Adjustable Frequency Drive ...
Service Manual
MG94A222
Danfoss A/S © Rev. 2014-02-10 All rights reserved.
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Summary of Contents for VLT FC 103
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