MisalignmentMisalignment

8/9/2019 MisalignmentMisalignment

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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,

MisalignmentMisalignment

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