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 in order to obtain an output.

First, the frequency converter must be told to run (start command). Second, the frequency converter must be told how fast to run (reference or speed command).

The frequency converters are designed to accept a variety of signals. First determine what types of signals the frequency converter is receiving. There are six

digital inputs (terminals 18, 19, 27, 29, 32, 33), two analog inputs (53 and 54), and the network (68, 69). The presence of a 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

K-2# Keypad 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 DR-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 Out-

puts.

The frequency converter must be set up correctly for the motor(s) connected to it. Parameters P-02 - P-07 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 auto tune 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 F-5#.

Incorrectly set I/O configuration usually results in the frequency converter not 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 E-0# and AN-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 unit size 6x 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. Meas-

urements 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.

High Power Service Manual for Unit Sizes 6x

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