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Experimental investigation
on faultDetection inInduction Motors by Vibration
and Current Signature
Analysis
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Induction motors play an important role to ensu
sustainability in the processes and production limany areas of industry. Motor failures can unexpected problems or shut do!n of the produprocesses.
Detection of these faults !hich a"ects the reliaof the processes has come into promin#herefore$ preventive maintenance diagnoprotection of induction motor becomes increaimportant no!adays.
Introduction
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The major faults of electrical machines can broadly be classif
following [l]:
a) Stator faults resulting in the opening or shorting of one or mstator phase winding,
b) Abnormal connection of the stator windings,
c) Broen rotor bar or craced rotor end!rings,
d) Static and "or dynamic air!gap irregularities,
e) Bent shaft #ain to dynamic eccentricity) which can result i
between the rotor and stator, causing
serious damage to stator core and windings,
f) Shorted rotor field winding , and
g) Bearing and gearbo$ failures%
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%ault #ypes IEEE &in '( E)*I &in '(
Bearing ++ +,
Stator - /
Rotor 0 1Other -- ,+
)ercentage of failure by component
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These faults produce one or more of the symptoms as
gi&en below:
a) 'nbalanced air!gap &oltages and line currents,
b) (ncreased torue pulsations,
c) *ecreased a&erage torue,
d) (ncreased losses and reduction in efficiency, ande) +$cessi&e heating%
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The diagnostic methods to identify the abo&e faults may in&ol
different types of fields of science and technology% They can b
as [!-]
a) +lectromagnetic field monitoring, search coils, coils wound
motor shafts #a$ial flu$ related detection),
b) Temperature measurements,
c) (nfrared recognition,
d) .adio freuency #./) emissions monitoring,
e) 0oise and &ibration monitoring,
f) 1hemical analysis,
g) Acoustic noise measurements,
h) 2otor current signature analysis #21SA),
i) 2odel, artificial intelligence and neural networ based tech
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2isalignment
Shaft alignment is the process to align two or more shaeach other to within a tolerated margin% (t is an
reuirement for machinery before the machinery is put in
Alignment outside the tolerated margin is called misalignm
Types #a) parallel #b) angular #c)
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3arallel 2isalignment
Angular 2isalignment
1ombined 2isalignment
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Air 2ap Eccentricity
Air gap eccentricity is a common defect arisi
from a range of mechanical problems such as lounbalance shaft misalignment !ear and tear bearings minor bend in rotor shaft romanufacturing defects and incorrect positioningthe stator or rotor.
Static eccentricity 3 )osition of the minimum radair gap is 4xed. Caused by stator core ovality incorrect positioning of stator core or bearing commissioning or during repair and its level donot change over time.
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*ynamic eccentricity ! 3osition of the minimum radial air
rotates with the rotor% This is produced by bent shaft, w
bearings, asymmetric thermal e$pansion of the rotor etc%
5ealthy
rotor
Static
Eccentricity
Dynamic
Eccentricity
Typical ma$imum le&els for large induction motors are betw
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1ondition monitoring system for baseline analysis%
Motor faults (A)
.otors bars, Shorted
turns, +ccentricity
2isalignment, Soft
foot
Sensors (B)
1urrent, 7oltage
/lu$, 7ibration
Speed
Data acquisit
system (C)
*igital form o
collected sign
Signal Processi
/ourier Transfo
Short Time /ou
Transform
8a&elet Transfo
3ar9s 7ector
0egati&e Seue
impedance
Fault frequencies (E)
B.B: #-s) f
+cc: #ffr)ST: [#n"p)#!s) ]f
3ower #B.B): #fpf-)
3ower #+cc): #fp- fr)
Fault Detection
an Analysis (F)
*etailed
information about
the degree of
se&erity of the
different faults
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/ull Spectrum
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Experimental *esults
677 *)M&Acceleration(
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677 *)M &Current(
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,777 *)M &Acceleration(
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,/77 *)M &Acceleration(
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,/77 *)M &Current(
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!eferences
[] 3% 7as, 3arameter +stimision, 1ondition 2onitoring, and *iagnosis of +lectrical 2achines,
1larendron 3ress, ;$ford,