SDHLT 02986 electric machines modeling, condition monitoring, and fault diagnosis

ELECTRIC

MACHINES
MODELING, CONDITION MONITORING,
AND FAULT DIAGNOSIS

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HAMID A. TOLIYAT •SUBHASIS NANDI
SEUNGDEOG CHOI • HOMAYOUN MESHGIN-KELK
CRC Press ,
Taylor & Francis Croup



ELECTRIC

MACHINES

MODELING, CONDITION MONITORING,
AND FAULT DIAGNOSIS



ELECTRIC

MACHINES

MODELING, CONDITION MONITORING,
AND FAULT DIAGNOSIS

HAMID A. TOLIYAT
SUBHASIS NANDI
SEUNGDEOG CHOI
HOMAYOUN MESHGIN-KELK

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TÀI LI£llTHL(■VIÊ^
CRC Press
Taylor &i Francis Group
Boca Raton London N e w York
C R C Press is an im p rin t of the
Taylor & Francis C ro u p , an in fo r m a business


C R C Press
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r e s p o n s i b i l i t y for t h e v a l i d i t y o f all m a t e r i a l s o r t h e c o n s e q u e n c e s o f t h e i r use. T h e a u t h o r s a n d p u b l i s h e r s
h a v e a t t e m p t e d t o t r a c e t h e c o p y r i g h t h o l d e r s o f all m a t e r i a l r e p r o d u c e d in t h i s p u b l i c a t i o n a n d a p o l o g i z e to
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E x c e p t a s p e r m i t t e d u n d e r U.S. C o p y r i g h t Law, n o p a r t o f t h i s b o o k m a y be r e p r i n t e d , r e p r o d u c e d , t r a n s m i t ­
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F o r p e r m i s s i o n t o p h o t o c o p y o r u s e m a t e r i a l e l e c t r o n i c a l l y f r o m t h i s w o r k , p le as e ac c e s s w w w . c o p y r i g h t .
c o m ( h t t p : / / w w w . c o p y r i g h t . c o m / ) o r c o n t a c t t h e C o p y r i g h t C l e a r a n c e C e n t e r , Inc. (C C C ) , 2 2 2 R o s e w o o d
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T r a d e m a r k N o t ic e : P r o d u c t o r c o r p o r a t e n a m e s m a y be t r a d e m a r k s o r r e g i s t e r e d t r a d e m a r k s , a n d a r e u s e d
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L ib ra r y o f C o n g r e s s C a t a lo g in g - in - P u b lic a t io n D a ta
E l e c t r i c m a c h i n e s : m o d e l i n g , c o n d i t i o n m o n i t o r i n g , a n d f au lt d i a g n o s i s / H a m i d A.
T o li ya t ... [et al.].
p. cm .
Includes bibliographical references a n d index.
I S BN 9 7 8 - 0 - 8 4 9 3 - 7 0 2 7 - 4 ( h a r d b a c k )
1. E l e c t r i c m a c h i n e r y - - R e l i a b i l i t y . 2. M a c h i n e r y - - M o n i t o r i n g . 3. M a c h i n e
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h t t p : //w w w .t a y lo r a n d f r a n c is .c o m
a n d t h e C R C P r e s s W e b s it e at
h t t p : //w w w .c r c p r e s s .c o m

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Contents
P re fa c e ...................................................................................................................................xi

1

In tr o du c ti o n ................................................................................................................1
Seun gdeog Choi

R e f e re n c e s ..................................................................................................................... 8
2

F a u lts in I n d u c t i o n a n d S y n c h r o n o u s M o t o r s ...............................................9
Bilal A kin an d M ina M . Rahim ian

2.1

In tro d u c tio n of Induction M otor Favilt..................................................... 9
2.1.1 B earing F au lts.....................................................................................9
2.1.2 Stator F a u l t s ...................................................................................... 11
2.1.3 Broken Rotor Bar F a u lt.................................................................. 13
2.1.4 Eccentricity Fault..............................................................................15
2.2
I n tro d u c tio n of S y n c h ro n o u s M otor Fault D ia g n o s is ........................16
2.2.1 D a m p e r W in d in g F a u lt................................................................. 17
2.2.2 D e m a g n e tiz a tio n Fault in P e rm a n e n t M ag n e t
S y n c h ro n o u s M a c h in e s (PMSM s)............................................. 18
2.2.3 Eccentricity F ault............................................................................. 19
2.2.4
Stator Inter-Turn F a u lt..................................................................20
2.2.5
Rotor Inter-Turn F au lt................................................................... 21
2.2.6 Bearing Fault..................................................................................... 22
R e fe r e n c e s ...................................................................................................................23

3

M o d e l i n g o f E lectric M a c h in e s U sin g W i n d i n g a n d M o d if ie d
W i n d i n g F u n c tio n A p p r o a c h e s ..........................................................................27
Su bhasis N andi

3.1
3.2

I n t r o d u c t i o n .................................................................................................... 27
W in d in g a n d M odified W in d in g F un ctio n A p p ro a c h e s
(WFA a n d M W F A )....................................................................................... 28
3.3
In d u c ta n c e C alculatio ns U sing WFA a n d M W F A .............................33
.3.4
Validation of Inductance Calculations U sing WFA a n d M W F A ...... 39
R e f e r e n c e s ................................................................................................................... 45


Contents

vi

4 M o d e lin g of Electric M a c h i n e s U s in g M a g n e tic E q u iv a le n t
C ir c u it M e t h o d .......................................................................................................47
H om ayoun M eshgin-K elk

4.1
4.2

In tro c iu c tio n ...................................................................................................47
In direct A pplication of M agnetic E qui\'alent Circuit for
A nalysis of Salient Pole S y n c h ro n o u s M a c h i n e s ............................... 52
4.2.1 M agnetic Equivalent C ircuit of a Salient Pole
S y n c h ro n o u s M a c h in e ..................................................................53
4.2.2 In d u c ta n c e Relations of a Salient Pole S y n c h ro n o u s
M a c h in e ............................................................................................ 55
4.2.3 C alcu lation of In d u c ta n c e s for a Salient Pole
S y n c h ro n o u s M a c h in e ..................................................................58
4.2.4 E x p e rim en ta l M e a s u r e m e n t of I n d u ctan c e s of a
Salient Pole S y n c h ro n o u s M a c h i n e ......................................... 63
4.3 In direct A pplication of M agnetic E quivalent C ircuit for
A nalysis of In d u c tio n M a c h i n e s ............................................................. 66
4.3.1 A Simplified M ag netic E q u i\’alent Circuit of
In d u c tio n M a c h in e s ...................................................................... 66
4.3.2 In d uctance Relations of Indu ctio n M a c h i n e s ........................ 68
4.3.3 C alculation of In d u c ta n c e of an In d u c tio n M a c h i n e ......... 70
4.4 D irect A pplication of M agnetic E quivalent Circuit
C o n sid e rin g N o n lin e a r M ag netic C haracteristic for M a c h in e
A n a ly s is ........................................................................................................... 73
A p p e n d ix A: Induction M achine P a r a m e t e r s .................................................. 77
A p p e n d ix B: N o d e Perm e an c e M a trice s............................................................78
R e f e re n c e s ................................................................................................................... 79
5 A n a l y s i s o f F a u lt y I n d u c t i o n M o t o r s U s in g F i n i te E le m e n t
M e t h o d ........................................................................................................................ 81
Bashir M alidi Ebrahim i

5.1
5.2
5.3

5.4

5.5

I n tr o d u c t io n .....................................................................................................81
G eom e tric a l M o d e lin g of Faulty In d u c tio n M otors U sing
T im e-S tep ping Finite E lem ent M e th o d (TSFEM ).............................. 82
C o u p lin g of Electrical C ircuits a n d Finite Elem ent A r e a ................ 83
M o d e lin g Internal Faults U sing Finite Elem ent M e t h o d ................ 85
5.4.1
M o d e lin g Broken Bar F ault.........................................................85
5.4.2
M o d e lin g Eccentricity F a u l t .......................................................87
5.4.2.1 Static E c c e n tric ity .......................................................... 87
5.4.2.2 D y n a m ic E c c e n tric ity .................................................. 89
5.4.2.3 M ixed E c c e n tric ity ........................................................90
Im p act of M agnetic S a tu ra tio n on A ccurate Fault D etection
in I n d u c tio n M o t o r s ..................................................................................... 91


Contents

5.5.1

A nalysis of A ir-G ap M agnetic Flux D ensity in
H ealthy a n d Faulty Indu ctio n M o to r .......................................94
5.5.1.1 Linear M a g n e tiz a tio n C ha ra c te ristic ....................... 94
5.5.1.2 N o n lin e a r M a g n e tiz a tio n C h a ra c te ris tic ............... 95
R e fe re n c e s...................................................................................................................96

6 Fault D i a g n o s i s of Electric M a chi ne s U si ng Techni ques Based
on Frequency D o m a i n ........................................................................................... 99
Subhasis N andi

6.1
6.2

6.3

I n tr o d u c tio n ....................................................................................................99
Som e D efinitions a n d Exam ples Related to Signal Processing.... 100
6.2.1 C o n tin u o u s v e rsu s Discrete or Digital or S am p led
S i g n a l .................................................................................................100
6.2.2 C o n tin u o u s, D iscrete Fourier Transform s, a n d
N o n p a r a m e tr ic Pow er S p e c tr u m E stim a tio n ........................101
6.2.3 Param etric Pow er S p e c tr u m E s tim a ti o n .................................105
6.2.4 Pow er S p e c tr u m E stim a tio n Using H ig h e r-O rd e r
Spectra (H O S ).................................................................................107
6.2.5 Pow'er S p e c tr u m E stim atio n U sing Sw ept Sine
M e a s u re m e n ts or Digital Frequency Locked Loop
T echnique (D FLL )......................................................................... 110
D iag nosis of M a c hine Faults U sing Freq uen cy -D om ainBased T e c h n iq u e s ......................................................................................... I l l
6.3.1
D etection of M otor B earing F a u l t s ...........................................I l l
6.3.1.1 M ech anical Vibration Frequency A n alysis
to Detect Bearing F a u l t s .............................................I l l
6.3.1.2 Line C u r re n t Frequ en cy A n alysis to D etect
Bearing F a u lts ............................................................... 115
6.3.2
D etection of Stator F a u lts................................................... 116

6.3.2.1
Detection of Stator Faults U sing External
Flux S e n s o r s .................................................................. 116
6.3.2.2 D etection of Stator Faults U sing Line
C u rre n t H a r m o n i c s .....................................................117
6.3.2.3 Detection of Stator Faults Using T erm inal
Voltage H a rm o n ic s at S w itc h - O f f .......................... 119
6.3.2.4 Detection of Stator Faults Using Field
C u rr e n t a n d Rotor Search Coil H a rm o n ic s
in S y n c h ro n o u s M a c h in e s .........................................121
6.3.2.5 D etection of Stator Faults U sing Rotor
C u r r e n t a n d Search Coil Voltages
H a rm o n ic s in W o u nd Rotor Ind uction
M a c h in e s .........................................................................124
6.3.3
D etection of Rotor F a u l t s ................................................... 129


C.antcnts

viii

6.3.3.1

Detection of Rotor Faults in Stator l.ine
C urrent, Speed, Torque, a n d P o w e r ...................... 130
6.3.3.2 D etection of Rotor Faults in E xternal and
Internal Search C o i l ................................................... 134
6.3.3.3
Detection of Rotor Faults Using T erm in al

Voltage H a rm o n ic s at S w itc h -O ff ..........................134
6.3.3.4 D etection of Rotor Faults at S t a r t - U p .....................134
6.3.3.5 D etection of Rotor Faults in Presence of
In terbar C u r r e n t U sing Axial Vibration
S ig n a ls............................................................................. 135
6.3.4 D etection of Eccentricity F a u lts ................................................ 136
6.3.4.1 D etectio n of Eccentricity Faults U sin g Line
C u rr e n t Signal S p e c t r a .............................................. 136
6.3.4.2 D etection of Eccentricity Faults Based on
N a m e p la te P a r a m e t e r s .............................................. 142
6.3.4.3 D etection of Eccentricity Faults U sing
M e c hanical Vibration Signal S p e c t r a ................... 147
6.3.4.4 D etection of Inclined Eccentricity F a u lts ..............147
6.3.5
Detection of Faults in Inverter-Fed Induction M a c h i n e s ... 148
R e f e re n c e s .................................................................................................................. 149
Fa u lt D ia g n o s is of E lectric M a c h i n e s U s in g M o d e l-B a s e d
T e c h n i q u e s ................................................................................................................ 155
Siibhasis N andi

7.1
7.2
7.3

I n tr o d u c tio n ................................................................................................... 155
Model of H ealthy Three-Phase Squirrel-Cage Induction M o to r ... 158
M odel of T h re e -P h ase S quirrel-C age In duction M otor w ith
Stator Inter-Turn Faults.............................................................................. 165
7.3.1
M odel w ith o u t S a tu ra tio n .......................................................... 165

7.3.2
M odel w ith S a t u r a t i o n ................................................................169
7.4 M odel of S quirrel-C age Indu c tion M otor w ith Incipient
Broken Rotor Bar a n d E nd-R ing F a u lts................................................ 175
7.5 M odel of S quirrel-C age In d u c tio n M otors w ith Eccentricity
F a u lts................................................................................................................177
7.6
M odel of a S y n c h ro n o u s Reluctance M otor w ith Stator F a u lt.... 179
7.7 M odel of a Salient Pole S y n c h ro n o u s M otor w ith D y n a m ic
Eccentricity F a u lts ........................................................................................]8l
R e f e re n c e s .................................................................................................................. 183
A p p lic a tio n o f P a tte r n R e c o g n itio n to F a u lt D i a g n o s i s ............................. 185
M asou d H ajiaghajani

8.1
8.2
8.3

I n tr o d u c tio n ................................................................................................... ] 85
Bayesian T h e o ry a n d Classifier D e s i g n ................................................ 186
Simplified Form for a N o r m a l D is tr i b u ti o n ........................................ 189


ix

Cotiteiits

8.4
F eature Extraction for O u r Fault D iag nosis S y s t e m ....................... 190
8.5

Classifier T ra in in g ......................................................................................192
8.6
Im p l e m e n t a tio n .......................................................................................... 194
R e fe re n c es................................................................................................................. 198
9 I m p l e m e n ta t io n of M o to r C u r r e n t S i g n a tu r e A n a ly s is F ault
D ia g n o s is Based on D ig ita l S ig n a l P r o c e s s o r s .......................................... 199
Seungdeog Choi and Bilal Akin

9.1

I n t r o d u c tio n .................................................................................................199
9.1.1 C ross-C orrelation Schem e D erived from O p tim a l
D etector in A dditive W h ite G a ussian Noise (AWGN)
C h a n n e l ...........................................................................................200
9.2
Reference Fram e T h e o r y ..........................................................................201
9.2.1 Reference Fram e T h e o ry for C o n d itio n M o n ito r in g .......... 202
9.2.2 (Fault) H a rm o n ic A n alysis of M u ltip h a se S y stem s.............202
9.2.3 O n-L ine Fault D etection R esu lts...............................................204
9.2.3.1 v/f C ontrolled Inverter-Fed M otor Line
C u rre n t A n a l y s i s ........................................................ 204
9.2.3.2 Field-O riented C ontrol Inverter-Fed M otor
Line C u r r e n t A n a l y s i s .............................................. 206
9.2.3.3 In s ta n ta n e o u s Fault M o n ito rin g in TimeFreq uency D o m a in a n d T ransient A n a ly s is...... 206
9.3
Phase-Sensitive Detection-Based Fault D ia g n o s is ............................ 210
9.3.1 I n tr o d u c ti o n ..................................................................................... 210
9.3.2 Phase-Sensitive D e te c tio n ............................................................210
9.3.3 O n-L ine E xp erim en tal R e su lts.................................................. 212
R e fe re n c es ................................................................................................................. 218

10 I m p le m e n ta ti o n of F ault D ia g n o s is in H y b r id Electric V ehicles
Based o n R e fe re n c e F ra m e T h e o r y .................................................................. 221
Bilal A kin

10.1
10.2

I n tr o d u c tio n ................................................................................................. 221
O n-B o ard Fault D iagnosis (OBD) for H y b rid Electric
Vehicles (H E V s)........................................................................................... 221
10.3 D rive Cycle A n alysis for O B D ............................................................... 224
10.4 Rotor A s y m m e tr y D etection at Z ero S p e e d .......................................226
R e fe re n c e s................................................................................................................. 233
11 R o b u st S ig n a l P r o c e s s in g T e c h n iq u e s for th e I m p le m e n ta tio n of
M o to r C u r r e n t S ig n a tu r e A n a ly s is D ia g n o s is B a se d o n D ig ita l
S ig n a l P r o c e s s o r s ...................................................................................................235
Seungdeog Choi

11.1

I n tr o d u c tio n .................................................................................................235
11.1.1 C o he re nt D e te c tio n .......................................................................236


Electric Machines: Fault Diagnosis a n d Condition M ointcring

11.1.2 N o n c o h e re n t D etection (Phase A m b ig u ity
C o m p e n s a t io n ) .............................................................
11.1.3 Fault Frequ ency O ffset C o m p e n s a t i o n ................
11.2 D ecision-M ak in g S c h e m e .......................................................

11.2.1 A da p tive T h re sh o ld D esign (N o ise A m b ig u ity
C o m p e n s a tio n ) .............................................................
11.2.2 Q - F u n c tio n .....................................................................
11.2.3 N oise E s tim a tio n ..........................................................
11.3 S im ulation a n d E xpe rim en ta l R e s u l t ..................................
11.3.1 M o deled MATLAB S im u la tio n R e s u l t .................
11.3.2 Off-Line E x p e rim e n ts .................................................
11.3.2.1 Off-Line Results for E c c e n tr ic ity ..........
11.3.2.2 Off-Line Results for B roken Rotor Bar
11.3.3 O n-L ine E x p e rim e n ta l R e s u lts................................
R e f e re n c e s ................................................................................................

237
237
240
240
242
243
244
244
245
246
247
248
251

I n d e x .................................................................................................................................. 253


P refa ce

Tilt' d e v e lo p m e n t of th e electric m o to r is one of the greatest a c h ievem ents of
th e m t)d e rn e n e r g y c onv e rsion industry. C o u n tle ss electric m o to rs are b e in g
u s e d in o u r daily lives for critical service a p plications such as tran sp o rtatio n ,
m e d ic a l tre a tm e n t, m ilita r y o p eration, ancl c o m m u n ic atio n . H owever, d u e to
th e f u n d a m e n ta l limitaticins of m aterial lifetime, deterioraticin, c o n ta m in a ­
tion, m a n u f a c t u r i n g defects, or d a m a g e s in o perations, an electrical m o to r
w ill e\ e n tu a lly go into fa ilu re mode. A n u n e x p e c te d failure m ig h t lead to the
loss of valuab le h u m a n life or a costly sta n d still in in du stry , w'hich n e e d s to
b e p re v e n te d b y precisely d e te c tin g or c o n tin u o u sly m o n ito rin g the w'orking
c o n d itio n of a motor.
T his b o o k w a s w r i t t e n to p rtw id e a full review of d ia g n o s is technologies
a n d as a n application g u i d e for g r a d u a te a n d senior u n d e r g r a d u a te s tu d e n ts
in the p tiw e r electronics disc ip lin e w'ho w a n t to research, develop, a n d im p le ­
m e n t a fault d ia g n o s is a n d con dition m o n ito rin g sc h e m e for b etter safety
a n d i m p r o v e d re liability in electric m o to r operation. F u rth e rm o re , electrical
a n d m e c h a n ic a l e n g i n e e r s in the in d u s tr y are also e n c o u ra g e d to use portitins of th is b o o k as a reference to u n d e r s ta n d th e f u n d a m e n ta ls of fault
c a u s e a n d effect a n d to fulfill successful im plem en tation .
T his b o o k a p p ro a c h e s th e fault d ia g n o sis of electrical moftirs th r o u g h th e
p ro c e s s of th eoretical a n a ly sis a n d th e n practical application. First, the analysi.s of the f u n d a m e n ta l s of m a c h in e failure is p re s e n te d th r o u g h the w i n d ­
in g f u n c tio n s m e th o d , th e m a gn etic e q u iv a le n t circuit m e th o d , a n d finite
t'le m e n t analysis. Sectind, th e im p le m e n ta tio n of fault d ia g n o s is is review'ed
w ith t e c h n iq u e s s u c h as the m o to r c u rr e n t s i g n a tu re analysis (MCSA)
m e t h o d , fret]uency d o m a i n m ethtid, m o de l-b a se d techniques, a n d p attern
re c o g n itio n scheme, hi particu la r, the MCSA im p le m e n ta tio n m e th o d is pre.sented in detail in th e last c h a p te rs of the book, w hich d is c u s s robu st sig­
nal p ro c e s s in g te c h n iq u e s a n d referen ce-fram e-th eo ry -b ased fault d ia g n o sis
im p le m e n ta tio n fcir h y b rid vehicles as a n exam ple. T hese theoretical analysis
a n d p ractical im p le m e n ta tio n strategies are based on m a n y ye a rs of research
a n d deN-ekipment at th e Electrical M a c h in e s & Ptiwer Electronics (EMPE)
i-a b o ra to ry at Texas A & M University.

Hami d Toliyat
Texas A &M LIniversit}/
College Station, Texas

.VI



1
Introduction

S e u n g d e o g C h o i, Ph.D .
T oshiba In te rn a tio n a l

1 he p o p u la tio n of electric m otors h a s greatly in creased in recent years, not
only in the U nited States b u t also in the w orld m a r k e t as s h o w n in Table 1.1
a n d Table 1.2. The w orld m a rk e t is ex p e cte d to be a r o u n d $16.1 billion in
2011, w h ic h is as su m e d m o re th a n 507o g r o w th just w ith in 5 years [1]. Electric
m otors have been app lied to alm ost e\'ery place in o u r daily life, su ch as
m a n u f a c tu r in g system s, air tra n sp o rta tio n s, g r o u n d tra n sp o rta tio n s, b u ild ­
ing air-co nditio ner systems, h o m e e n e rg y conversion system s, v a rio u s cool­
ing .systems in electrical devices, a n d even cell p h o n e x'ibration systems.
it is also a well-known fact that the electric motors consum e more than 507o of
whole electrical energy d e m a n d in the United States. The an n u al electrical energy
d em a n d in the United States w a s 3,873 billion kilowatt-hours in 2008, w h ich is
expected to be further increased in e\'ery year dep e n d in g on population a n d eco­
nomic g ro w th [11]. This data indicates that more th a n 1,900 billion kilowatt-hours
is l on su m e d by electric motors annually in the United States, w'hich is the biggest
energy consum ption by any single electric device in m odern society.
With the rapidly increased p o p u la tio n a n d h u g e electric e n e rg y c o n s u m p ­

tion, sop histicated control a n d reliability of m o to r o p e ra tio n s from a h a rsh
in d u stria l env iro n m e n t has n o w been a m ajor re q u ire m e n t in m a n y in d u s ­
trial applications. It is especially im p o r ta n t w h e re a n u n e x p e c te d s h u td o w n
m ig h t result in the in te rru p tio n of critical services such as m edical, tr a n s ­
portation , o r m ilitary operations. In those application s w h e re c o n tin u o u s
proc ess is n e e d e d a n d w h e re d o w n tim e is not tolerable, a n u n e x p e c te d fail­
ure« of a m o to r m igh t result in costly m a in te n a n c e or loss of life.
A s sh o w n in Figure 1.1, the electrical m otor consists of m a n y m e c h a n ic al
a n d electrical parts, such as a rotor bar, rotor m ag n e t, stator w in d in g , endring, bearin g, a n d g ear box. D u e to the c o m m o n ly h a r s h in d u stria l e m i r o n mc'nts, each p a rt of electric m o to rs is poten tially e x p o se d to the h ig h risk of
unex p e cte d mechanical, chemical, a n d electrical system failures. The reason s
w h y electric m o to rs fail in in d u s try have been c o m m o n ly re p o rte d as follows:
1. Post th e s ta n d a rd lifetime
2. V\'rong-rated power, voltage, a n d c u rre n t


E lectric M a ch in es: M oileling, C on dition M onitorin g, an d Fault D iag ’osis

TABLE 1.1
N u m b e r of M o to rs by A p p licatio n
Application
F ans a n d p u m p s

Population
3,847,161

A ir co m p re sso r

12,434,330

TOTAL

Source:

632,731
7 ,93 4 ,4 3 8

O th e rs

U S D e p a r tm e n t n f E n ergy (2002). h t t p : / /
w w u T .e e r e .e n e r g y .g o v /m a n u fa c tu r in g /
t e c h _ d e p lo y m e n t/p c if s /m tr m k t.p c if

3. U nstable s u p p ly voltage or c u rr e n t source
4. O v erload or u n b a la n c e d load
5. Electrical stress from fast sw itc h in g inverters or u n sta b le g r o u n d
6. Residual stress from m a n u f a c tu r in g
7. M istakes d u r in g re p a irs
8. H a rsh application e n v ir o n m e n t (dust, w a te r leaks, e n v ir o n m e n til
\ ibration, chem ical c o n ta m in a tio n , h ig h tem p e ra tu re)
F ig ure 1.2 show's an exam p le of a w'ell know'n electrical m o to r fault such as
b e a rin g ball d a m a g e . T he b e a rin g ball is tak en from the b e a r in g m o d u le that
h a d b e e n d ia g n o s e d as faculty for 6 m on th s. The m a in ty p e s of m o to r fiults
are c o m m o n ly categ orized as electrical faults, m e ch a n ic al faults, a n d cuter
driv e system defects, w h ic h are as follow's [2-5]:
1. Electrical faults
a.

O p e n or sho rt circuit in m o to r w in d in g s (m ainly d u e to w i n d i r g
insu la tio n failure)

b.

W ro ng c o nn e ction of w in d in g s

c.

H ig h resistance contact to c o nd u c to r

d.

W ro ng or u n stab le g ro u n d
TABLE 1.2
M o to r S y stem E n erg y U sage by A p p lica tio n
Application
F an s a n d p u m p s
A ir co m p re sso r

GW h /Yr
22 1,4 17
9 1 ,0 50

O th e rs

262,961

TOTAL

575,428

Source:

U S D e p a r tm e n t o f E n e rg y (2 002). h t t p : / /v v \v w U e e r e .
e n e r g y .g o v /m a n u f a c t u r in g /t e c h _ d e p lo y m e n t /p d f s /
m tr m k t.p d f


hitnniiiction

FIC.URE 1.1
20(W H iin d a FCX C la r ity Fuel C ell V e h ic le te st d r i \ e p h o to g a lle r y . From C h r is tin e a n d S co tt
Ciable, h t tp : //a lt e r n a t iy e f u e ls .a b o u t .c o m /o d /f u e lc e llv e h ic le r e v ie w s /ig / 0 9 -H o n d a - FC X -C laritvlu ,.1 - C e ll/

2. M echanical faults
a.

Broken rotor ba rs

b.

Broken m a g n e t (or partial d e m a g n e tiz atio n )

c.

C racked e n d -rin g s

d.

Bent shaft

e.

Bolt loosening

f.

Bearing failure

g.

G earb ox failure

h.

A ir-gap irre g u la rity

3. O u te r m o to r drive s ystem failures
a.

l n \ ’e rter system failure

b.

Unstable x’o lta g e /c u rre n t source

c.

S h orted or o p e n e d su p p ly line

HC;iJRE 1.2
He.irii'.g b a ll fa u lt a n d s u b s e c iu e n t fa t ig u e d a m a g e . V ib r a tio n
il> r.itio n co n su ltan tb .co .n 7 /f a u lt"i,2 0 D iag n o sis.h tm l

c o n s u lta n t,

h ttp ://w w w .


Electric Machines: Modeling, Condition Monitoring, and Fault Diagnosis

The b e a r in g fault is k n o w n to m a k e u p alm ost 40%, stator related about 3cS"o,
rotor related ab o u t 10%, a n d o th e rs m a k e u p 12% of w h ole electrical m otor
fault [2-6],
The electric m o to r d e sig n is c o m m o n ly in te n d e d to have electrical a n d
m e c h a n ic al s y m m e tr y in th e stator a n d the rotor for b e tte r c oup ling a n d
h ig h e r efficiency. Fault con dition in a m o to r d e sc rib e d earlier is s u p p o se d to
d a m a g e the sy m m e tric a l p r o p e rty w'here fa u lt-d e p e n d e n t m o to r operation
indu c e s a n a b n o rm a l s y m p to m d u r in g m o to r o peration, w h ic h is described
as follows [2-5]:
1. M echanical vibration
2. T e m p e ra tu re increase
3. I rr e g u la r air-gap torque
4. I n s ta n ta n e o u s o u tp u t p o w e r variation
5. A coustic noise
6. Line voltage c h a n g e s
7. Line c u rr e n t cha n g e s
8. S p ee d variatio ns
M o st a b n o rm a l s y m p to m s have b e e n k n o w n to have specific p a tte rn s
p e r ta i n in g to the m o to r fault c o nditio ns a n d severity, such as p a rtic u la r fre­
quency, d ura tion , a m p litu d e , variance, degree, a n d phase. Based on m o n i­
toring a n d a n a ly z in g th e e xp ected s y m p to m s a n d their specific patterns,
m a n y m o to r fault d ia g n o se s have b e e n suggested, a n d there hav'e been sev­

eral c o m m ercial solutions in the in d u s tr y m a r k e t as s h o w n in Figure 1.3. In
particu lar, the vib ratio n s p e c tr u m in Figure 1.3a is from th e b e a r in g m o d u le
w ith defect ball iii figure 1.2. Based on the s p e c tr u m m o n ito r in g technique,
the b e a r in g m o d u le is d ia g o n o se d faculty a n d safely re m o v e d before the s y s­
te m falls into c atastrop hic failure mode.
The v a rio u s d ia g n o sis te c h n iq u e s a d o p te d in in d u s tr y ha v e been p e r ­
fo rm e d m a in ly th ro u g h the follow ing strategies [2-5].
1. S ignal-based fault d ia g n o sis
a.

M echanical v ibration analysis

b.

Shock p u ls e m o n ito rin g

c.

T e m p e ra tu re m e a s u re m e n t

d.

A coustic n oise analysis

e.

E lectrom ag netic field m o n ito rin g th r o u g h in s e rte d coil

f.

I n s ta n ta n e o u s o u tp u t p o w e r v a riation analysis

g.

I n f ra r e d analysis

h.

G as analysis


Introduction

F r e q u e n c y (Hz)

(a)

FIG URE 1.3
(.1) V ib r a tio n s p e c t r u m m o n ito r in g for b e a r in g in F ig u r e 1.2. h ttp ://w v v w .v ib r a tio n c o n s u lta n t s .
co .n //H a u it" 'l,2 0 D ia g n o s is .h t m l. (b) GE m o to r c u r r e n t a n a ly s is d e v ic e (from g e d ig it a le n e r g y .
c o m ). h t tp ://v \ w \v ,g e d ig it a le n e r g y .c o m /m u lt ilin /c a t a lo g /m 6 0 .h t m

Oil analysis
R ad io -frequ en cy (RF) em issio n m o n ito rin g
Partial d isc h a rg e m e a s u r e m e n t
M otor c u r re n t s ig n a tu r e analysis (MCSA)
m

Statistical analysis of relevant signals

6

Electric Machines: Modeling, Condition Monitoring, and Fault Diagiu'sis

2. M odel-based fault d ia gn osis
a.

N e u ra l n e tw o rk

b.

F u z z y logic analysis

c.

G enetic a lg o rith m

d.

Artificial intelligence

e.

Finite-elem ent (FE) m a g n e tic circuit e q uivalents

f.

L inear-circuit-theory-based m a th e m atic al m o de ls

3. M a c h in e -th e o ry -b a se d fault analysis
a.

W in d in g fun ctio n a p p ro a c h (WFA)

b.

M odified w in d in g fu n c tio n a p p ro a c h (MWFA)

c.

M ag netic e q u iv a le n t circuit (MEC)

4. Sim u la tio n s-b ase d fault analysis
a.

Finite-elem ent analy sis (FEA)

b.

T im e-step co up led finite elem ent state space a nalysis (TSCFE-SS)

The d ifferent ty p e s of fault d ia g n o sis m e th o d s have been sim u lta n e o u sly
a p p lie d to fine-tun e the de tection in industry. The fault d ia g n o sis of electri­
cal m o to rs is exp e c te d to p ro vide w a r n i n g of im m in e n t failures, d ia g n o s in g
s c h e d u lin g in fo rm a tio n for fu tu re preventive m ainten ance.
The im p lem entation of fault d iagn osis h a s be e n d o ne w ith the following
routine:
L Fault detection
a.

T im e -d o m a in -b a s e d detection (mostly for p o w e r system fault
diagnosis)

b.

Frecjuency d o m a in - b a s e d d etection (mostly for sig nal-b ased
m a c h in e fault diagnosis)

c.

A c c u m u la te d d ata -b a se d d etection (mostly for m o d e l-b a se d fault
diagnosis)

2. Fault decision m a k in g
a.

D ecide fault existence

b.

Decide fault severity

3. Feedback to m o to r controller or h u m a n mterface
a.

L imit m o to r o p e ra tio n b a s e d on fault severity

b.

Schedu le m a in te n a n c e

Figure 1.4 sh ow s the inc rea se d convergence b e tw e e n the e n e r g y system
a n d m o d e r n n e tw o r k sy stem in m o d e r n industry. The electrical m o to rs in a
car, ship, aircraft, b u ild in g , road, or in a p o w e r system can be a s s u m e d to be


hU roduciion

I'eedhack
th n iiig h C D ttyenlional
c o p p e r H'frc

• Individuai system control
' W hole system m anagement
' HeaWi monitoring

Digital processor
(ControUer)

7

F eed b a c k
ih r o iig h ivireless n e tw o r k
/le ir tn fo n n a tu m h ig lm a x i

C o n x e r g o n c t' o i e n e r g y s y s te m an ci m o d e m n e tw o r k s y s te m

FIG URE 1.4
C'unv e r g e n c e o f e n e r g v s y s te m a n d m o d e r n n e tw o r k s y s te m . (F rom S. C h o i, " R o b u st C o n d itio n

M o n ito r in g a n d F au lt D ia g n o s is o f V a ria b le S p e e d D r iy e o f I n d u c tio n M otor," P h D d is s e r t a ­
tio n , T ex as A & M U n iy e r sity , 2010. W ith p e r m is s io n .)

m ostly c o n n e c te d to a c o m m itte d se n so r or w i r e d /w ir e le s s se n so r ne tw ork.
Tlu)se s e n se d sig n a ls such as vibration, c u rre n t, voltage, a n d sp e e d are for­
w a r d e d to a close or rem o te m icro con tro ller or digital pro cessor of w h ic h the
controller p e r fo r m s in d iv id u a l system control, w h ole system m a n a g e m e n t,
or health m o n ito rin g [9].
T he fault d ia g n o sis ha s b e g u n to be efficiently im p le m e n te d w ith relatively
low cost by u tiliz in g the available se n so rs a n d digital signal pro cessor (DSP)
in th e w i r e d / w i r e l e s s n e tw o rk w ith o u t extra h a r d w a r e cost a n d w ith sim ple
softv\’are im p le m en ta tio n , w h ic h f u r th e r p ro v id e s the p rotection to m id d l e /
low p o w e r m o to r d r i \’e system. For exam ple, by u sin g the c u rr e n t sen sor
feedback, the new tre n d for low-cost protection applications of MCSA fault
d ia g n o sis se e m s to be d rive -in te g ra ted fault d ia g n o sis s y ste m s w ith in m o to r
driv e DSP w i th o u t u sin g a n y external h a r d w a r e [8].
T h is b o o k is i n te n d e d to p ro v id e f u n d a m e n ta ls of v a rio u s m o to r fault con ­
ditions, adx a n c ed fault m o d e lin g theory, diverse fault d ia g n o sis techniques,
a n d low cost DSP-based fault d ia g n o s is im p le m e n ta tio n strategies.
T he follou'ing c h a p te rs of this b o o k are o rg a n iz e d as follows;
• Ind uction of m o to r a n d s y n c h r o n o u s m o to r faults in C h a p te r 2
• Electric m o to r fault m o d e lin g based on d iverse theories in C h a p te rs
3 and 4
• N'arious electric m otor fault d ia g n o sis te c h n iq u e s in C h a p te r s 5, 6,
and 7
• MCSA im p le m e n ta tio n on a m icroco ntroller in C h a p te r s 8, 9, a n d 10


8

Electric Machines: Modeling, Condition Monitoring, and Vault Diagnosis

References
[1] H .A . Toliyat a n d S.G. C am p b e ll, D SP -B ased E lectrom echan ical M otion Control,
Boca R aton, FL: CRC P ress, 2003.
[2] G.B, K lim an, R.A. K o eg l,].S tein , R.D. E n d ic o tt,a n d M.W. M a d d e n , "X o n in v a s iv e
d e te c tio n of b ro k en ro to r b a rs in o p e ra tin g in d u c tio n m o to rs," IEEE Trniisiiclioii>
on E nergy C onversion s, vol. 3, p p . 873-879, D ecem b er 1988.
[3] S. N a n d i, H .A . Toliyat, a n d X. Li, " C o n d itio n m o n ito rin g a n d fau lt d ia g n o s is of
electrical m a ch in es— A rev iew ," IEEE T ransactions on Encr^^y C onversion , \ ol. 20,
no. 4, p p . 719-729, D ecem b er 2005.
[4] A. Siddic]ue, G.S. Y ada\ a, a n d B. S in g h , "A review of sta to r fau lt m o n ito rin g
te c h n iq u e s o f in d u c tio n m o to rs," IEEE Trans, on E nergy C onversion , \'ol. 20, p p .
106-114, M arch 2005.
[5] M. El H ach em i B en b o u zid , "A rev iew o f in d u c tio n m o to rs sig n a tu re a n a ly sis as
a m e d iu m for fau lts d e te c tio n ," IEEE Transactions on Indu strial E lectronics, vol.
47, p p . 984-993, O cto b er 2000.
[6] Y.E. Z h o n g m in g a n d W.L'. Bin, "A rev iew o n in d u c tio n m o to r o n lin e fault d ia g ­
n o sis," IEEE IPEM COO, vol. 3, p p . 1353-1358, 2000.
[7] B. A kin, U. O rg u n er, H . Toliyat, a n d .M. R ayner, "P h a se sen sitiv e d e te c tio n of
m o to r fau lt sig n a tu re s in th e p resen ce o f n o ise," IEEE Trniisaclions on Indu strial
E lectronics, \ ol. 55, no. 6, Ju n e 2008.
[8] B. A kin, U. O rg u n e r, H. Toliyat, a n d M. R ayner, "L ow o rd e r PW.M in v e rte r h.u'm o n ics c o n trib u tio n s to th e in v e rte r fed IM fau lt d ia g n o sis," IEEE T ransaclions
on Indu strial E lectronics, vol. 55, p p . 610-619, F e b ru a ry 2008.
[9] S. C hoi, "R o b u st C o n d itio n M o n ito rin g a n d F ault D iag n o sis o f V ariable S p eed
D rive of In d u c tio n .Motor," P h D d is se rta tio n , Texas A & M U niversity, 2010.
[10] W.T. T h o m so n a n d M. Fenger, " C u rre n t s ig n a tu re a n a ly sis to d e tec t in d u c tio n
m o to r fau lts," IEEE Industry A pplication s M agazine, vol. 7, no. 4, 2001.
[11] U.S. E nergy In fo rm a tio n A d m in istra tio n , "A n n u a l E n erg y O u tlo o k 2010: W ith
P ro jectio n s to 2035," W ash in g to n , DC, A p ril 2010.

2
Faults in Induction and Synchronous Motors

Bilal A k i n , Ph.D.
T cxai In stru m en ts

Mina M. R a hi mi an , Ph.D.
Texn< A & M U n iversiti/

2.1

I n t r o d u c t io n o f I n d u c t io n M o t o r Fault

This section briefly s u m m a r iz e s m o to r fault c o n d itio n s anci their cause, e s p e ­
cially for th e in d u c tio n motor. T he eccentricity related faults, b ro k e n rotor
b a r faults, b e a r in g faults, a n d stator faults, w h ic h account for m o re th a n 90%
of o\ erall in d u c tio n m o to r failures, are co nsid ere d [1-3].
2.1.1 Bearing Faults

B earin g faults account for m o re th a n 40°/o of all electric m o to r failures [5-7].
Most of the b e a rin g s in in d u s tria l facilities r u n u n d e r n o n id e al c o n d itio n s
a n d a r e subject to fatigue, a m b ien t m ec h a n ic al \'ibration, ov erloading, m is ­
a lig n m e n t, c o n ta m in a tio n , c u r re n t fluting, corrosion, a n d w r o n g lubrica­
tion. T h e se n o n id eal c o nd itions sta rt as m a r g in a l defects that s p re a d a n d
p ro p a g a te on the in n e r raceway, ou te r raceways, a n d ro lling e le m e n ts (see
Figure 2.1). A fter a w h ile the defect beco m es significant a n d g enerates
m ec h a n ic a l vibration c a u sin g acoustic noise. Basically, b e a rin g faults c an be
classified as o u te r raceway, in n e r raceway, ball defect, a n d cage defect, w h ic h

are the m a in so u rc e s of m a c h in e vibration. These m ec h a n ic al v ib ra tio n s in
the a ir g a p d u e to b e a rin g faults can be co nsid e re d as slight rotor d isp lac e ­
m en ts, w h ic h resu lt in in sta n t eccentricities. Therefore, the basic fault sig­
n a t u r e fre q u e n c y e q u a tio n of line c u r r e n t d u e to b e a rin g defects is a d o p te d
from eccentricity literatu re [10].
M e c h an ica l vibration, in fra re d or th e rm a l, a n d acoustic a n aly se s are som e
of the c o m m o n ly u se d pred ictive m a in te n a n c e m e th o d s to m o n ito r the
he.ilth of the b e a rin g s to p re v e n t m o to r failures.


10

Electric Machines: Modeling, Condition Monitoring, and Fault D ia^icsis

An a r h itia n

P itc h D ia m e te r (PD)

Ball D i a m e t e r (BI5)

FIG URE 2.1
A ty p ic a l b e a r i n g g e o m e tr\'.

Vibration a n d th e rm a l m o n ito rin g re q u ire a d d itio n a l se n so rs or tra n s ­
du cers to be fitted on the m achines. W hile som e large m o to rs m ay already
c om e w ith vibration a n d th e rm a l tra n sd u c e rs, it is not ec onom ically or ph\'sically feasible to p ro \ ide the s a m e for s m a lle r m achines. Therefore, small- to
m e d iu m -s iz e m otors are ch ecked pe riodically by m o \'in g po rtable e q u ip ­
m e n t from m a c h in e to m a c h in e in all th re e m e th o d s. Som e m o to rs used in
critical applications, su ch as nuclear reactor cooling p u m p m otors, m ay not
be easily accessible d u r in g reactor operation. The lack of c o n tin u o u s m o n ito r­

ing a n d accessibility are the sh o rtc o m in g s of the a fo re m e n tio n e d techniques.
A n altern ate a p p ro a c h b as e d on line c u r r e n t m o n ito rin g h a s re c e i\e d m u c h
rese a rc h attentio n in search of p ro v id in g a practical solution to con tinu ou s
m o n ito r in g a n d accessibility problem s. M otor c u r re n t m o n ito r in g provides
a n o n in tr u s iv e w’ay to c o n tin u o u sly m o n ito r m o to r reliability w ith m in im a l
a d d itio n a l cost.
B earing faults can b e classified as ou te r raceway, in n e r raceway, ball defect,
a n d cage defect. Each fault h a s specific m e c h a n ical vibration frequency c o m ­
p o n e n ts th at are ch aracteristic of each defect type, w'hich is a function of
b o th b e a r in g g e o m e tr y a n d sp eed . The m e c h an ical oscillations d u e to b e a r ­
ing faults c h a n g e th e air-gap s y m m e t r y a n d m a c h in e in d u c ta n c e s like eccen­
tricity faults. The m a c h in e in d u c ta n c e v a ria tio n s are reflected to the line
c u rr e n t in te rm s of c u r r e n t h a rm o n ics, w h ic h are the indic a to rs of bea rin g
fault associated w ith m e c h a n ic a l oscillations in th e air-gap.


f aults ill Induction and Synchro)wus Motors

11

A generic fault d ia g n o sis too! ba se d on d is c rim in a tiv e e n e rg y f u n c tio n s is
p r o p o s e d by Ilonen et al. [12]. T h ese e n e rg y fu n c tio n s reveal d isc rim in a tiv e
fre q u e n c y - d o m a in region s w h e re failures are identified. Schoen [13] im p le ­
m e n te d a n u n s u p e r v is e d , on-line system for in d u c tio n m o to r ba se d on m otor
line c u rre n t. A n a m p litu d e m o d u la tio n (AM) d ete c to r is d e v eloped to detect
the b e a r in g fault w h ile it is still in a n incipient stage of d e v e lo p m e n t in Stack
et al. [14]. O c ak [15] d e v elop ed a h id d e n M arkov m o d e lin g (H M M ) based
b e a r in g fault detection a n d fault diagnosis. Yazici a n d K lim a n [16] p ro p o s e d
an adaptiv'e statistical tim e-fre q u e n cy m e th o d for detection of b ro k e n rotor
b a rs a n d b e a rin g faults in m o to rs u s in g m o to r line c urrent.

2.1.2 Stator Faults
S tc\to r faults account for 30% to 40% of all electric m o to r failures [2,8,9]. The

sta to r fault can be b roa d ly classified as the la m in a tio n or fra m e fault (core
defect, c irculation cu rren t, or g r o u n d , etc.) a n d the stator w i n d i n g fault
( w in d in g in su la tio n da m a g e , d isp la c e m e n t of conductors, etc.).
T he m ajor fu nction of w i n d in g in su la tio n m a te ria ls n o rm a lly is to w i th ­
sta n d electric stress; how'ever, in m a n y cases it m u s t also e n d u r e other
stresse s su c h as m ec h a n ic al a n d e n v iro n m e n ta l stresses [19]. In a motor,
the to rq u e is the re sult of the force created by c u r r e n t in the c o n d u cto r a n d
s u r r o u n d i n g m a gn etic field. T his sh o w s th at w i n d in g in sulatio n m u s t have
electrical as well as m e c h a n ic al p ro p e rtie s to w ith s ta n d m e c h a n ic al stresses
[20], In a d d itio n , ele c tro m a g n etic v ibratio n at tw ice the p o w e r frequency, dif­
ferential ex p a n sio n forces d u e to the te m p e r a tu r e v aria tion s follow ing load
c h a n g e s , a n d im pact forces d u e to e le c tric al/m e c h a n ic a l a s y m m e trie s also
affect the a g in g process [21].
N o n u n if o r m te m pe rature distrib utio n in a m otor will also cause m echanical
d e stru c tio n d u e to dilation. The m a n u f a c tu r in g process itself m ay constitute
a tla m a g in g or aging action. The electrical w in d in g insulation m ust be strong
e n o u g h to w ith s ta n d the m ech an ical ab use w hile bein g w o u n d an d installed
in the motor. Thus, the initial m echanical stresses are often very severe com ­
p a r e d to the su bse qu e nt ab use the w in d i n g insulation gets in service [20].
Inc re a sed te m p e r a tu re s can cause a n u m b e r of effects. The m a te ria l m ay
be in h e r e n tly w e a k e r at elevated te m p e ra tu re s a n d a failure m a y o c c u r sim ­
ply b e c au s e of the m e ltin g of the material. T h is can be a v e ry sh o rt tim e fail­
ure, b e c a u se of the sh ort length of tim e r e q u ire d for the te m p e ra tu r e to rise
to th e m e ltin g point. O n the o th e r h a n d , long-term elevated te m p e r a tu r e can
c a u s e in te rn a l chem ical effects on m aterial [19].
T h e r m a l stress is probably the m ost recognized cause of w in d in g in su la ­

tion d e g ra d a tio n and ultim ate failure. The m a in sources of therm al stress in
electric m a c h in e r y are copper losses, e d d y current, a n d stray load losses in the
c o p p e r conductors, plus additional h eatin g d u e to core los.ses, w indage, a n d so
foi th [22]. H igh te m p e ratu re causes a chemical reaction that m ak es w 'inding
in su la tio n material brittle. A no th er problem is that due to s u d d e n tem p era ture