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3.4.3 Iteration Cycle Time
In general, a data processing cycle takes between 60 – 120 seconds depending on several factors.
First, eMCM requires relatively unchanging data over a minimum time period during its data
acquisition phase and will repeat the data acquisition until it obtains stable data, thus varying the
iteration time cycle. If the amplitude or frequency of the voltage and current phases varies
excessively and stable data cannot be found, an alarm is raised. Secondly, if harmonic values are
being calculated, extra processing cycles are required. Finally, if eMCM encounters an error, it may
repeat the cycle several times.
3.4.4 Alarms During the Monitoring Process
Alarm conditions may occur during any monitoring phase. Alarm conditions may occur during any
monitoring phase. If CHECK MOTOR has previously been run on the motor, it is likely that the alarms
represent transient conditions present on the power lines. However, it is suggested that any alarm
representing a condition that could affect the performance of the motor should be recorded and
investigated as a potential cause of motor degradation. As in CHECK MOTOR, if an alarm is indicated,
the most recent physical values available for the motor can be displayed using the AES Viewer, AES
Configurator or MCM API Tool applications. Examination of these values can often indicate the
precise reason for the alarm condition. A complete list of alarm conditions can be found in the
appendix at the end of this manual.
3.4.5 Using eMCM on a driven with VFD
If an inverter is being used to drive the motor, several additional precautions are needed. The
voltage frequency is expected to be constant (within well-defined limits) for direct line driven
motors, but can vary considerably when an inverter is used. eMCM can handle the range of
frequencies typical of an inverter, but first needs to learn the motor at a single frequency ()
representative of the conditions it will meet in practice. The value of this dominant frequency must
be entered from the Edit Settings menu. If eMCM measures the frequency to be out of the expected
range, it will issue an alarm in both the CHECK MOTOR and LEARN modes and the user should adjust
the frequency setting accordingly. During IMPROVE, UPDATE and MONITOR, this requirement is
relaxed and the frequency can assume any value within the allowed frequency range.
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