correct reading will indicate that the desired signal has
been detected by the microprocessor of the frequency
converter. See the chapter
Frequency Converter Inputs and
Outputs
.
Using the status information displayed by the frequency
converter is the best method of locating problems of this
nature. By selecting within parameter group 0-2* LCP
Display, line 2 or 3 of the display can be set to indicate the
signals coming in. The presence of a correct reading
indicates that the desired signal is detected by the
microprocessor of the frequency converter. This data also
may be read in parameter group 16-6*.
If there is not a correct indication, the next step is to
determine whether the signal is present at the input
terminals of the frequency converter. This can be
performed with a voltmeter or oscilloscope in accordance
with the 6.3.16, Input Terminal Signal Test.
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 may affect drive and motor operation are motor
settings, references and limits, and I/O configuration. See
section
Frequency Converter Inputs and Outputs
.
The frequency converter must be set up correctly for the
motor(s) connected to it. Parameters 1-20 – 1-25 must
have data from the motor nameplate entered into the
frequency converter. This enables the frequency converter
processor to match the frequency converter 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 will usually solve the problem.
Any references or limits set incorrectly will result in less
than acceptable frequency converter performance. For
instance, if maximum reference is set too low, the motor
will be unable to reach full speed. These parameters must
be set according to the requirements of the particular
installation. References are set in the parameter group
3-0*.
Incorrectly set I/O configuration usually results in the
frequency converternot responding to the function as
commanded. It must be remembered that for every control
terminal input or output, there are corresponding
parameters settings. These determine how the frequency
converter responds to an input signal or the type of signal
present at that output. Utilising an I/O function must be
thought of as 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 the 5-0* and 6-0* parameter groups.
5.1.5 Motor/Load Problems
Problems with the motor, motor wiring or mechanical load
on the motor can develop in a number of ways. The motor
or motor wiring can develop a phase-to-phase or phase-to-
earth short resulting in an alarm indication. Checks must
be made to determine whether the problem is in the
motor wiring or the motor itself. Ensure that the motor
wiring from the drive meets the F Frame requirements
detailed in the high power operating instructions manual.
A motor with unbalanced, or non-symmetrical, impedances
on all three phases can result in uneven or rough
operation, or unbalanced output currents. Measurements
should be made with a clamp-on style ammeter to
determine whether the current is balanced on the three
output phases.
An incorrect mechanical load will usually be indicated by a
torque limit alarm or warning. Disconnecting the motor
from the load, if possible, can determine if this is the case.
Quite often, the indications of motor problems are similar
to those of a defect in the frequency converter itself. To
determine whether the problem is internal or external to
the frequency converter, disconnect the motor from the
frequency converter output terminals. If the three voltage
measurements are balanced, the frequency converter is
functioning correctly. The problem therefore is external to
the frequency converter.
If the voltage measurements are not balanced, the
frequency converter is malfunctioning. This typically means
that one or more output IGBT is not switching on and off
correctly. This can be a result of a defective IGBT or gate
signal from the gate drive card.
Frequency Converter and Mot...
High Power Service Manual for Modular F Frame Drives
MG90K202 - VLT
®
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