Application Note

Lastly, to cover his bases,
he selected Harmonics from the
menu to make sure frequencies
weren’t contributing to the
problem.
3 Fluke Corporation Logging and analyzing events with FlukeView® Forms Software
Analysis
From his unbalance measure-
ments, he could see that an
unbalance was causing an
excessively large phase current
value. He checked the motor
specifications and confirmed that
phase current exceeded the
motor’s FLA (Full Load Amperage)
rating. Looking at the data for all
three phases, he traced the
current unbalance to excessive
loading on one voltage phase.
The consultant traced the
voltage unbalance to a set of
equipment installed three years
ago. It turned out that all of the
internal single-phase loads were
connected to the same phase.
That last new equipment installa-
tion caused such a significant
power system voltage unbalance
that it created a current unbal-
ance at the motor, increasing
the operating temperature of the
conductors and motor windings
to beyond the limits.
Conclusion
To resolve the situation, the
consultant balanced the internal
single-phase loads between
the three phases, reducing the
overall voltage unbalance and
consequently, the current unbal-
ance at the motor. This also
reduced the elevated phase
current value and operating
temperature at the motor.
He took new benchmark
measurements for future monitor-
ing, transferred all of his saved
screens to his computer and
printed a before-and-after report
for the facility maintenance
manager.
While not a power quality
expert, the manager could see the
difference between the screens.
Now he understood why power
quality measurements needed to
be taken before and after new
equipment installation. All of the
motor repair and downtime costs
had been un-necessary. When the
consultant suggested setting up a
regular preventive maintenance
schedule, the manager agreed.
Fluke Corporation
PO Box 9090, Everett, WA USA 98206
Fluke Europe B.V.
PO Box 1186, 5602 BD
Eindhoven, The N
etherlands
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ax [phone]
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©2004 Fluke Corporation. All rights reserved.
Printed in U
.S
.A
. 9/2004 2394
162 A-US-N Rev A
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