Artesis AMT Toolkit, User Manual

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Troubleshooting
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5. Troubleshooting
5.1. Introduction
During installation and operation a number of checks should be made to ascertain whether
the AMU unit is performing correctly and to determine possible causes if it is not.
5.2. Use of the AMU Config utility
5.2.1. Fault Diagnosis
A number of common problems can be diagnosed by inspection of the measured
waveforms, and it is good practice to check the waveforms of each unit as part of the
commissioning process. With the motor running, and power applied to AMU:
Voltage phases should have the correct RST phase relationships, separated by 120º. The
current phases should be in the same order as the voltage phases and also separated by
120º. Any phase ordering, missing or duplicate phase problems should immediately be seen
from the waveform display.
For star connected motors, it is essential that the phase angles between corresponding
voltages and currents lie between 0 and 90º. Motors connected using the delta topology
have an extra 30º phase shift and the current phase angles should lie between –30 and
+60º. In either case, check that the motor topology has correctly been entered on the AMU
front panel and that the currents do indeed correspond to the correct voltages. It is
important to perform this test with the motor under loaded conditions as loading can
significantly affect the measured phase angle.
For delta connections check that the sensors are measuring the line rather than phase
currents, (i.e. the sensor is situated on the line side of the contactor) as these differ. For star
connections the two are the same.
If the amplitude of the R phase current waveform varies excessively, AMU will not be able
to find stable data and will give the unstable line alarm. If the problem lies with the input
signals, it should be immediately obvious by inspecting the displayed waveform. In the case
of excessive variation of the R phase current amplitude, the Current Instability threshold
should be incremented from its default value of 15% in steps of 5% up to a maximum value
of 50% using the AMU front panel. If the variation exceeds this level, please contact Artesis.