POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 18 |NUMBER: 3 |2020 |SEPTEMBER
E iciency Assessmen o Induc ion Mo o s D i es
Ope a ing Unde Sha Misalignmen Condi ions
Ca los VERUCCHI 1, Es eban GIRALDO1, Ma ias MEIRA1, C is ian RUSCHETTI 1,
Jose BOSSIO2and Guille mo BOSSIO2
1Physics and Enginee ing Resea ch Cen e o he Cen e o he P o ince o Buenos Ai es
(UNCPBA-CICPBA-CONICET), A . Del Valle 5737, B7400JWI Ola a ia, A gen ina
2Applied Elec onics G oup-Resea ch Ins i u e o Ene gy Technologies and Ad anced Ma e ials
(UNRC-CONICET), Ru a Nac. 36, X5804BYA Rio Cua o, A gen ina
e ucc[email p o ec ed], [email p o ec ed], [email p o ec ed],
c usc[email p o ec ed], jmb[email p o ec ed], gb[email p o ec ed]
DOI: 10.15598/aeee. 18i3.3596
Abs ac . His o ically, he nega i e e ec s o mis-
alignmen be ween he mo o sha and he load on he
elec ic d i es a e well known. Vib a ions, loss o li e
o couplings and de e io a ion o e iciency a e some o
hese e ec s. Rega ding his las poin , he li e a u e
o e s con adic o y opinions. Some s udies conside
ha he loss o e iciency in cases o misalignmen is
undesi able; while o he s conside ha i has signi ican
impo ance. In his pape , expe imen al esul s show in
which cases he misalignmen has a signi ican e ec on
e iciency and in which cases i can be neglec ed. Fo
his, adial and angula misalignmen cases a e s ud-
ied wi h ou o he mos used lexible couplings in he
indus y. The ob ained esul s a e analysed in ela ion
o he ac ual egula ions on ene gy e iciency in induc-
ion mo o s. The eached conclusions o e new ools
o he co ec selec ion o lexible couplings ending o
he imp o emen o ene gy e iciency.
Keywo ds
Couplings, ene gy e iciency, induc ion mo-
o s.
1. In oduc ion
Induc ion Mo o s (IMs) ha e become an almos exclu-
si e al e na i e o de eloping mechanical powe o in-
dus ial applica ions. I is es ima ed ha be ween 43 %
and 46 % o he gene a ed elec ic powe in he wo ld is
cu en ly des ined o powe elec ic mo o s, which a e
mos ly IMs [1]. Cu en no ma i e ha e es ablished he
minimum e iciency allowed o his ype o machine.
P emium E iciency Mo o s (IE3) and Supe P emium
E iciency Mo o s (IE4) ha e eplaced he S anda d E -
iciency Mo o s (IE1) and he High E iciency Mo o s
(IE2). Besides, he endency o con inue aising he
minimum e iciency le els allowed is expec ed in he u-
u e [2]. IEC 600340 [3] s anda dizes he classi ica ion,
he measu emen p ocedu e and he indica ion o he
e iciency da a on mo o s. These highe e iciencies a e
ob ained by modi ica ions in he manu ac u ing p o-
cess such as: sho e ai -gap leng hs, use o co es wi h
educed losses, special designs in he o o ba s and
end ing, op imiza ion and be e quali y o he s a o
winding, imp o ed o he ex e nal cooling an design,
e c. [4].
To educe he consump ion o elec ical ene gy, i is
no only necessa y o inc ease he e iciency le els o
he mo o s, bu also o gua an ee adequa e ope a ing
condi ions. When an IM ope a es wi h low load le -
els (o e -sizing), i s e iciency is signi ican ly educed.
Simila ly, below- a ed supply ol ages o unbalanced
supply ol ages a ec he e iciency o he IM [5], [6]
and [7]. The p esence o ol age ha monics is ano he
e iciency de a ing ac o o IMs [8]. Good main enance
p ac ices equi e pe iodic con ol o all hese condi ions
in o de o ensu e high le els o e iciency.
Recen ly, esea ch has shown ha aul s in IMs can
also educe hei e iciency. The mos common cases
o aul s a e c acked o b oken o o ba and wea o
olling bea ings [9]. In addi ion o hese cases, o he
aul s such as de e io a ion o he magne ic co e, an
de ec s o sho - ci cui ed u ns o he windings in-
c ease he losses o an elec ical machine.
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Ano he ope a ing condi ion ha inc eases he losses
in elec ic d i es is he misalignmen be ween he mo-
o and he d i en load. Flexible couplings a e cu -
en ly used o powe ansmission h ough which hey
can be easily coupled be ween he mo o and he load.
Besides, hese couplings can ope a e wi h ce ain le -
els o misalignmen . Misalignmen p oduces losses due
o hea ing o he lexible elemen and addi ional s ess
in he IM and load bea ings [10]. In [11], a ma he-
ma ical model is p esen ed o ind he a ia ions ha
occu in he o que ansmi ed om he mo o o he
load when he sha s a e no pe ec ly aligned. Such
a ia ions consis o o que luc ua ions a he coupling
o a ion equency and i s mul iples. To que luc ua-
ions, in u n, cause ha monic componen s in he s a o
cu en . These componen s a e no linked o he me-
chanical powe ansmi ed o he load, al hough hey
gene a e losses in he windings. On he o he hand, [12]
and [13] analyse he empe a u e inc ease ha occu s
in he coupling and bea ings in cases o misalignmen .
This empe a u e ise in ol es g ea e losses o ene gy.
The li e a u e has ex ensi ely deal wi h he mis-
alignmen p oblem [10], [11], [12], [13], [14] and [15].
One o i s mos se ious consequences lies in he gen-
e a ion o ib a ions. Vib a ions can cause damage
o he mo o o o he componen s o he d i e [13].
Fu he mo e, he couplings’ li e ime is signi ican ly e-
duced as he misalignmen inc eases. This is due o he
ac ha misalignmen causes addi ional s esses on he
couplings in ela ion o a pe ec alignmen s a e.
Some esea che s sugges ha he e iciency educ-
ion due o he misalignmen e ec s is no signi ican
and can be ejec ed [10] and [13]. Ne e heless, o he
au ho s a i m ha o misalignmen s abo e o hose
allowed by he couplings, he losses can each up o
2.3 % o he a ed powe o he mo o [16]. How-
e e , hese esea ches we e made in he las cen u y,
when ene gy e iciency issues o elec ic mo o s had no
gained he cu en ele ance. Nowadays, he educ ion
o ene gy consump ion and ca e o he en i onmen is
much mo e demanding han in p e ious decades. Sligh
imp o emen s in he e iciency le els o elec ic mo o s
can be o g ea impo ance. Such a si ua ion o ces
no o disca d any possibili y ha allows he inc ease
o he mo o e iciency.
Conclusions p esen ed in [10], on he o he hand,
only conside misalignmen s less han o equal o he
limi s ecommended by each manu ac u e . So, eal
si ua ions ha occu in he indus y whe e hese limi s
a e exceeded a e no aken in o accoun . O he wise, i
should be no ed ha some manu ac u e s ha e aised
such limi s o pe missible misalignmen h ough he
de elopmen o new models o lexible couplings.
Fo all hese easons, i is in e es ing o e iew he
ela ion be ween misalignmen and e iciency loss om
a cu en poin o iew and aking in o accoun mod-
e n lexible coupling models. I is also conside ed use-
ul o analyse si ua ions whe e misalignmen deg ee ex-
ceeds he allowed ones by he manu ac u e . The e o e,
i is p oposed o analyse he e iciency loss in d i es
wi h lexible couplings h ough expe imen al s udies
o cases o adial misalignmen and angula misalign-
men . The g owing demands in ela ion o he ene gy
e iciency jus i y he s udy. I is ocused on low-powe
elec ic mo o s, which demand a signi ican ac ion o
he o al elec ical ene gy consumed by elec ic mo o s.
Likewise, i is conside ed impo an he beha iou o
each o he lexible couplings cu en ly used in he in-
dus y in ela ion o he e iciency loss due o misalign-
men . Thus, i is expec ed o p o ide use ul elemen s
o p ope selec ion.
The p oblem o misalignmen in gene al e ms is de-
sc ibed in he ollowing sec ion and lis s he di e en
cases ha a ise in indus ial applica ions. Meanwhile,
in Sec. 2. he consequences o misalignmen on he
mo o ’s elec ic o que and s a o cu en a e analysed.
Sec ion 3. shows he expe imen al esul s ob ained
om a 5.5 kW mo o and di e en ypes o lexible cou-
plings. Finally, in Sec. 4. he ob ained esul s a e
discussed and he eached conclusions a e analysed.
2. Gene al Cha ac e is ics o
Misaligned D i es
In o de o ca y ou he mechanical powe ansmis-
sion om a mo o o a load unde ideal condi ions,
he axes o each machine mus coincide. In his case,
i is conside ed ha he sha s a e aligned wi h each
o he . In indus ial applica ions, his condi ion is e y
di icul o achie e. Small misalignmen s usually occu
be ween he sha s o each machine. The elemen s ha
a e used o couple one sha wi h ano he , such as lexi-
ble couplings, a e designed o ole a e small de ia ions
in he alignmen .
These misalignmen s can be o wo ypes: angula
misalignmen and adial misalignmen . I is consid-
e ed ha he e is angula misalignmen when he o a-
ion sha s o each machine a e con ained in wo lines
in e sec ing a he cen e o he coupling as shown in
Fig. 1(a). In such a case, he misalignmen deg ee is
gi en by he angle α. On he o he hand, i is consid-
e ed ha adial misalignmen occu s when he sha s o
each machine a e pe ec ly pa allel bu no coinciden ,
as shown in Fig. 1(b). In his case, he misalignmen
deg ee is gi en by he dis ance be ween each sha , in-
dica ed as din Fig. 1(b). This di e en ia ion be ween
angula misalignmen and adial misalignmen is es-
ablished mainly o s udy pu poses; in p ac ice, bo h
misalignmen ypes usually occu simul aneously.
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Misalignmen si ua ions a e widesp ead in indus ial
applica ions. They usually a ise du ing an inadequa e
assembly p ocess, in e o s on he sha s due o aul y
ope a ion o gea boxes o bel s, looseness o he mo o
o load as ene s, and in eccen ici ies o he compo-
nen s o he d i e, among many o he s.
Misalignmen p oblems cause excessi e s ess on
bea ings, bending s esses on sha s and ib a ions,
among o he undesi able e ec s. To educe hese e -
ec s, elas ic couplings a e gene ally used. This cou-
pling ype is able o bea small misalignmen le els
and dampens dis u bances ha occu on he powe
ansmission be ween sha s. Wi h he use o hese
couplings, i is possible o educe unwan ed ib a ions
and s esses on o he elemen s o he ins alla ion. Flex-
ible couplings o di e en cha ac e is ics a e o e ed
in he ma ke . Each o hem allows a ce ain ole -
ance in bo h angula and adial misalignmen .
Al hough hese couplings signi ican ly imp o e he
beha iou o powe ansmission, high misalignmen s
cause a signi ican educ ion in hei use ul li e.
In addi ion, he inc ease in sys em losses due o s esses
on he couplings causes i s empe a u e inc ease [10]
and [14].
Figu e 2 shows some o he mos used lexible cou-
plings in he indus y [13]. The so-called Jaw couplings
(Fig. 2(a)) s and ou o hei low cos and easy in-
s alla ion. The joining elemen is cons i u ed by elas-
ome ic ma e ials and goes up o speeds o 5.000 RPM.
They allow high le els o angula misalignmen and a e
one o he mos used op ions in indus ial applica ions.
Gea couplings (Fig. 2(b)), on he o he hand, show
high o que densi y and a e o sion- esis an . The join-
ing elemen is cons i u ed by syn he ic esin and goes
up o speeds o 50.000 RPM. Me al Ribbon Couplings
(Fig. 2(c)) allow o sion as well as angula and adial
misalignmen and can be used up o speeds o app oxi-
ma ely 6.000 RPM. Unlike o he couplings, he lexible
elemen mus be g ease-lub ica ed, which de e mines
ce ain limi a ions in ela ion o he wo king empe a-
u e. Finally, he Rubbe - ype couplings (elas ome ic
join ) (Fig. 2(d)), which a e ideal o damping ib a-
ions and go up o speeds o 5.000 RPM, a e one o he
mos used. In hese cases, he li e ime o he lexible
elemen is se iously educed when he misalignmen is
g ea e han he allowed one.
As i is shown in [12] and [17], in he e en o
misalignmen , a cyclical a ia ion in he ansmi ed
o que by he mo o o he load is obse ed. This dis-
u bance is epea ed a wice he sha o a ion e-
quency Eq. (1) and is e lec ed in i s mul iples and
submul iples.
Tk=1
cos α−sin2α
2 cos α−sin2α
2 cos α·cos 2θlTl,(1)
whe e θlis he angula posi ion o load and Tlis
he load o que. Equa ion (1) shows ha i he mis-
alignmen angle is ze o, he ansmi ed o que coin-
cides wi h ha eques ed by he load. The luc ua-
ion p oduced by he misalignmen , on he o he hand,
inc eases i s ampli ude as he misalignmen le el in-
c eases. A o que luc ua ion is e lec ed in he mo o
s a o cu en h ough sidebands a ound he mains e-
quency, as indica ed in Eq. (2).
s= ±n ,(2)
whe e na e in ege s g ea e han ze o, is he supply
equency and he mo o o a ion equency. Thus,
i is possible o a i m ha misalignmen cases a e ob-
se ed in he mo o s a o cu en and could be de-
ec ed om i s acing. The ma hema ical model ep-
esen ed by Eq. (1) and Eq. (2) was ob ained consid-
e ing a uni e sal coupling. The e o e, i s applica ion
o cases o lexible couplings such as hose p esen ed in
Fig. 2 is no possible. Howe e , i is use ul o unde -
s and he na u e o he phenomenon and i s e ec on
he ansmi ed o que and he s a o cu en . Com-
plemen a y s udies [17] ha e shown ha he misalign-
men phenomenon is also e lec ed in o que ha monic
componen s a he o a ion equency. In [11], an al e -
na i e model o misalignmen cases is p esen ed whe e
he same conclusions as hose ob ained in his wo k a e
eached.
3. Expe imen al Resul s
3.1. Misalignmen E ec s on he
S a o Cu en , Elec ical
To que and Coupling
Tempe a u e
In he ield o p e en i e main enance o o a ing elec-
ical machines, impo an ad ances ha e been made
du ing he las decades. On-line applica ion echniques
ha e been p oposed and es ed success ully o bo h in-
duc ion machines [18] and synch onous machines [19].
The ad an age o hese echniques o e he adi ional
ones lies in he possibili y o implemen ing con inuous
moni o ing o a machine wi hou emo al om se ice.
Some wo ks e en p opose o use he elec ic mo o as
a senso , in o de o ex end he diagnosis o he en i e
d i e. So, i is possible o de ec misalignmen be ween
sha s [12] and [17] o aul s in gea boxes [20], among
o he s.
Acco ding o he model p esen ed in he p e ious
sec ion, i can be ensu ed ha a misalignmen case
could be de ec ed om he acking o he componen
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a wice he o a ion equency and i s mul iples in
he ansmi ed elec ical o que by he mo o o in
he sidebands ha a e obse ed a ound he undamen-
al equency in he s a o cu en [11], [21] and [22].
In [17], i is shown ha he misalignmen phenomena
can also be de ec ed om he acking o he o a ion
equency componen in he elec ic o que. When he
ansmi ed o que is used as a diagnos ic ool, i is
no essen ial o use a o que senso . On he con a y,
i is possible o use an es ima ed o que based on he
measu emen o he ol ages and cu en s in he mo o
e minals. When he mo o is a a s eady-s a e, he
same componen s as in he o que a e obse ed in he
elec ical powe inpu .
(a) Angula misalignmen .
d
(b) Radial misalignmen .
Fig. 1: Di e en ypes o misalignmen .
In Fig. 3, a schema ic o he es bench used o labo-
a o y es s is p esen ed. A mo o o 5.5 kW, 36.2 Nm,
4 poles, 11.6 A, 50 Hz and 380 V was used. In all es s,
he induc ion mo o was powe ed om he g id and i s
speed anges be ween 1450 RPM and 1499 RPM, de-
pending on he co esponding load ac o . The mo o
is suspended on a base which can be mo ed ela i e o
he load base. Thus, h ough he egula o s indica ed
in Fig. 3 as "alignmen adjus men ", i is possible o
misalign he mo o in bo h angula and adial di ec-
ions. An analysis o he equency spec um o he
ins an aneous powe o a jaw coupling wi h di e en
load s a es and misalignmen deg ees a e obse ed in
Fig. 4 and Fig. 5, ob ained h ough he expe imen-
al labo a o y esul s. Pa icula ly, Fig. 4 shows he
equency spec um o he ins an aneous powe con-
(a) Jaw coupling. (b) Gea coupling.
(c) Me al ibbon cou-
pling.
(d) Rubbe i e- ype coupling.
Fig. 2: Di e en ypes o couplings.
I.M.
Powe
Supply
Cu en s
and
ol ages
measu emen
Alignmen
adjus men
To que and
speed
measu emen
DC
gene a o
Fig. 3: Schema ic labo a o y assembly.
sumed by a mo o o 5.5 kW unde no mal ope a ing
condi ions (wi hou misalignmen ). The mo o is op-
e a ing wi h a 50 % load ac o . A small componen
is obse ed a he mo o o a ion equency ( ), while
no app eciable componen s a e obse ed a he mul i-
ple equencies o he p e ious one (2 and 3 ). The
componen a can be a ibu ed o a small misalign-
men o o a mass imbalance in he mo o o load.
In Fig. 5, he same equency spec um is p esen ed
bu in his case wi h a 2 mm adial misalignmen in-
en ionally caused. In his case, he componen a
is obse ed signi ican ly highe han ha obse ed in
Fig. 5. Mo eo e , componen s a 2 and 3 a e easily
iden i iable. These changes a e undoub edly due o he
misalignmen be ween he mo o and load sha s.
The luc ua ions in he ins an aneous powe ab-
so bed by he mo o a e e lec ed in he s a o cu -
en a he equencies gi en by Eq. (2). In Fig. 6 and
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0 10 20 30 40 50 60 70 80
(Hz)
0
0.005
0.01
0.015
0.02
Elec ic powe (p.u.)
2. 3.
Fig. 4: Elec ic powe equency spec um - Jaw coupling - 50 %
o load - aligned sha s.
0 10 20 30 40 50 60 70 80
(Hz)
0
0.005
0.01
0.015
0.02
Elec ic powe (p.u.)
2.
3.
Fig. 5: Elec ic powe equency spec um - Jaw coupling - 50 %
o load - 2 mm adial misalignmen .
0 20 40 60 80 100 120 140 160
(Hz)
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
Is (p.u.)
- +
Fig. 6: S a o cu en equency spec um - Jaw coupling - 75 %
o load - aligned sha s.
Fig. 7, he equency spec ums o he s a o cu en s
a e p esen ed o he cases o alignmen and 2 mm a-
dial misalignmen , espec i ely. In Fig. 7, componen s
a − , + and + 2 a e clea ly obse ed.
These componen s a e p ac ically no seen in Fig. 6.
I is impo an o highligh ha hese ha monic com-
ponen s do no p o ide mechanical powe ansmi ed
o he load; howe e , hei low h ough he windings
gene a es elec ical losses.
20 40 60 80 100 120 140 160
(Hz)
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
Is (p.u.)
-
+2.
+
Fig. 7: S a o cu en equency spec um - Jaw coupling - 75 %
o load - 1.5 mm adial misalignmen .
(a) Aligned.
(b) Radial misalignmen (1 mm).
Fig. 8: The mal images in a ubbe i e- ype coupling.
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On he o he hand, as i was ad anced in he in o-
duc ion, he addi ional e o s ha occu in a lexible
coupling due o he misalignmen ope a ing condi ions
inc ease i s empe a u e. In [13], his e ec is analysed
o couplings o di e en cha ac e is ics and o di e -
en misalignmen le els. Wi h misaligned couplings,
empe a u es inc ease be ween 20 ◦C and 30 ◦C de-
pending on he ype o coupling. In Fig. 8, a compa -
ison is p esen ed on a ubbe i e- ype coupling. This
is coupled o he 5.5 kW IM ansmi ing i s nominal
powe . In Fig. 8(a) and Fig. 8(b), a he mal image is
p esen ed o he case o aligned sha s and 1 mm adial
misalignmen , espec i ely. The igu es show he em-
pe a u e inc ease egis e ed in he coupling in p esence
o misalignmen .
3.2. Misalignmen E ec s on he
E iciency
In o de o weigh he loss o e iciency in cases o mis-
alignmen , he es bench desc ibed in Sec. 3.1. was
used. Be o e each es , he mo o was kep in nominal
ope a ing condi ions o one hou in o de o achie e
he mal equilib ium. The ambien empe a u e was
main ained a 25 ◦C. The e iciency measu emen was
made h ough he p ocedu e called "di ec me hod"
[22] ha is measu ing he powe consumed by he mo-
o and he powe ans e ed o he load. The e i-
ciency was ob ained acco ding o Eq. (3):
η=Pm
Pe
·100,(3)
whe e Pmis he mechanical ou pu powe and Peis
he consumed powe by he IM.
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Load ac o (p.u.)
72
74
76
78
80
82
84
86
E iciency (%)
Aligned
1 mm adial misalignmen
2 mm adial misalignmen
Fig. 9: Mo o e iciency wi h jaw coupling - adial misalign-
men .
Figu e 9 shows he e iciency cu es as a unc ion o
he load ac o o a jaw coupling. A i s es was pe -
o med wi h he aligned sha s and hen he p ocedu e
wi h adial misalignmen o 1 and 2 mm was epea ed.
The compa ison allows e i ying ha he e is an e i-
ciency educ ion in cases o misalignmen o all load
s a es analysed. The e iciency educ ion is mo e e -
iden as he misalignmen be ween he mo o sha s
and load inc eases. Figu e 10 shows he e iciency al-
ues measu ed wi h he same coupling, as in Fig. 11,
bu in his case o angula misalignmen . I can be
no ed ha he e iciency loss o angula misalignmen
is less han o adial misalignmen .
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Load ac o (p.u.)
74
76
78
80
82
84
86
E iciency (%)
Aligned
0.5 ° angula misalignmen
0.75 ° angula misalignmen
Fig. 10: Mo o e iciency wi h jaw coupling - angula misalign-
men .
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Load ac o (p.u.)
72
74
76
78
80
82
84
86
E iciency (%)
Aligned
1 mm adial misalignmen
2 mm adial misalignmen
Fig. 11: Mo o e iciency wi h ubbe i e- ype coupling - adial
misalignmen .
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Load ac o (p.u.)
72
74
76
78
80
82
84
86
E iciency (%)
Aligned
0.5° angula misalignmen
0.75° angula misalignmen
Fig. 12: Mo o e iciency wi h ubbe i e- ype coupling - an-
gula misalignmen .
The esul s o a ubbe i e- ype coupling a e p e-
sen ed in Fig. 11 and Fig. 12. In his case, as in he p e-
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ious one, a mo e signi ican e iciency educ ion o a-
dial misalignmen is obse ed. Mo eo e , i is obse ed
ha o 1 mm adial misalignmen , he e iciency loss
is almos impe cep ible, while o a 2 mm adial mis-
alignmen , i is much mo e e iden . In bo h cases, o
he mo o in nominal load condi ion, e iciency losses
g ea e han 1 % we e eco ded.
Tab. 1: Pe missible misalignmen o di e en couplings (di e -
en manu ac u e s conside ed).
Rubbe
i e- ype
coupling
Jaw
coupling
Me al
ibbon
coupling
Gea
cou-
pling
Radial
misalign-
men
(mm)
0.5–1 0.3–0.5 0.5 0.8–1.2
Angula
misalign-
men (◦)
1–3 1–1.5 0.5 1.5
Table 1 indica es he pe missible misalignmen le -
els de ined by he lexible coupling manu ac u e s
wi h cha ac e is ics simila o hose used in he es s.
I should be no ed ha hese couplings we e selec ed
using he usual p ocedu e based on ansmi ed o que,
o a ion speed and sha diame e . Limi alues a y
signi ican ly om one manu ac u e o ano he ; he e-
o e, in some cases, anges o alues a e indica ed. The
esul s p esen ed in his pape conside misalignmen s
ha each alues g ea e han he admissible ones.
This is in ended o include possible equen cases in
p ac ice, in which he limi s imposed by he manu-
ac u e a e exceeded due o poo main enance p oce-
du es.
0 0.5 1 1.5 2
Radial Misalignmen (mm)
83
83.5
84
84.5
85
E iciency (%)
Fig. 13: Mo o e iciency wi h ubbe i e- ype coupling s. a-
dial misalignmen .
In o de o ind he e iciency a ia ion o he d i e as
a unc ion o he misalignmen deg ee, es s we e ca -
ied ou , main aining he load ac o a 0.95 and p o-
g essi ely inc easing he misalignmen . The es s we e
epea ed o each o he ou d i es s udied and o he
0 0.5 1 1.5 2
Radial Misalignmen (mm)
83
83.5
84
84.5
85
E iciency (%)
Fig. 14: Mo o e iciency wi h jaw coupling s. adial misalign-
men .
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Radial Misalignmen (mm)
83
83.5
84
84.5
85
E iciency (%)
Fig. 15: Mo o e iciency wi h me al ibbon coupling s. adial
misalignmen .
0 0.5 1 1.5 2
Radial Misalignmen (mm)
83
83.5
84
84.5
85
E iciency (%)
Fig. 16: Mo o e iciency wi h gea coupling s. adial misalign-
men .
wo possible adial and angula misalignmen s. The
cases o adial misalignmen a e p esen ed in Fig. 13,
Fig. 14, Fig. 15 and Fig. 16. In each igu e, he al-
ues ob ained in he es s and a linea app oxima ion
o hem a e shown. Fo ubbe i e- ype coupling, he
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e iciency loss is less han 0.5 % o he maximum mis-
alignmen allowed by ha ype o coupling and some-
wha less han 1 % o wice he pe missible misalign-
men . In he case o jaw coupling, he e iciency educ-
ion o adial misalignmen is 0.6 % o he maximum
pe missible misalignmen . Fo me al ibbon coupling,
he e iciency educ ion is 0.5 % o he maximum mis-
alignmen allowed and, las ly, o gea coupling i is
a he highe han 0.5 % o he manu ac u e admi -
ed misalignmen .
Rega ding angula misalignmen , he ubbe i e-
ype coupling causes an e iciency loss o 1.2 % wi h
a 2 ◦misalignmen ( he maximum allowed is 3 ◦). The
jaw coupling p esen s an e iciency educ ion o 1.16 %
wi h 1.5 ◦misalignmen . In he me al ibbon coupling,
p ac ically no e iciency loss is obse ed wi h angula
misalignmen and, inally, an e iciency educ ion o
1.8 % is p oduced o 1.5 ◦misalignmen (misalign-
men ha is somewha below he maximum allowable)
wi h he gea coupling.
Table 2 and Tab. 3 p esen a mo e exhaus i e com-
pa ison o he ou ypes o couplings es ed and he
di e en misalignmen le els caused. The alues in-
dica ed by he ables a e calcula ed based on linea
app oxima ion. In gene al e ms, he e is an e iciency
educ ion due o misalignmen in all cases. In some
cases, such as d i es wi h angula misalignmen wi h
me al ibbon coupling, he e iciency educ ion is i -
ele an . Howe e , in o he cases, educ ions be ween
1 % and 2 % could be e i ied. I is impo an o no e
ha in he es , only angula misalignmen and adial
misalignmen we e caused independen ly. In p ac ical
cases, i is possible ha bo h ypes o misalignmen
occu simul aneously, expec ing a g ea e e iciency e-
duc ion pe cen age o he d i e.
Tab. 2: Pe cen age e iciency a ia ion o adial misalignmen
and load ac o o 0.95 (ob ained om linea app oxi-
ma ion).
Radial
misalign-
men (mm)
Rubbe
i e- ype
coupling
Jaw
coupling
Me al
ibbon
coupling
Gea
cou-
pling
0.5−0.17 −0.57 −0.24 −0.23
1−0.33 −1.14 −0.48 −0.46
1.5−0.49 −1.71 −0.7−0.69
2−0.64 −2.28 -−0.92
Tab. 3: Pe cen age e iciency a ia ion o adial misalignmen
and load ac o o 0.95 (ob ained om linea app oxi-
ma ion).
Angula
misalign-
men (◦)
Rubbe
i e- ype
coupling
Jaw
coupling
Me al
ibbon
coupling
Gea
cou-
pling
0.5−0.28 −0.39 −0.1−0.59
1−0.56 −0.78 −0.2−1.18
1.5−0.84 −1.16 −0.3−1.77
2−1.12 -−0.4-
4. Discussion and Conclusions
In [11], he au ho s conside ha he loss o e iciency in
he p esence o misalignmen is negligible. In [23], o
misalignmen wi hin he ange allowed by he coupling
manu ac u e , e iciency losses o 1 % we e ob ained.
In [16], wi h misalignmen s in excess o hose allowed
by he manu ac u e , a loss o 2.3 % was obse ed,
while in [24], i is claimed ha he loss o e iciency
could each up o 10 %.
In his pape , i has been demons a ed ha o ce -
ain models o lexible couplings and in he p esence
o misalignmen le els ha can be ound in he indus-
y, e iciency educ ions o a d i e canno be unde -
es ima ed. This educ ion can e en esul in an o de
simila o he one ha de ines he ansi ion om one
e iciency class o ano he . Tha is, a d i e could lowe
an e iciency class i ce ain alignmen condi ions a e
no achie ed. Fo his eason, conclusions ound in [10]
ega ding ejec ing he e iciency educ ion caused by
misalignmen a e cu en ly ques ionable. The impo -
ance o a good alignmen no only lies in p e en ing
ib a ions o conse ing he use ul li e o he coupling
bu also in ensu ing adequa e e iciency le els.
On he o he hand, he s udies ca ied ou allow
iden i ying he lexible couplings models ha p esen
g ea e ole ance o misalignmen om he poin o
iew o e iciency. In ac , o example, i is obse ed
ha he me al ibbon coupling p esen s e y good pe -
o mance o bo h ypes o misalignmen . On he o he
hand, he ubbe i e- ype coupling mainly causes sig-
ni ican losses o angula misalignmen , while he jaw
coupling causes hem o bo h angula and adial mis-
alignmen . The e o e, hese conclusions could be use-
ul o he p ope selec ion o a coupling. Based on
expe imen al es s wi h a 5.5 kW IM, he lexible cou-
plings misalignmen e ec on he e iciency o a d i e
was analysed. This wo k allows a i ming ha al hough
he loss o e iciency due o misalignmen is below
he alues sugges ed by some p e ious esea ches [24],
i is no in any way negligible. In some cases, and o
misalignmen le els o en ound in indus ial applica-
ions, he loss o e iciency due o misalignmen could
compensa e he bene i s ob ained by he use o high
e iciency o p emium e iciency IMs.
Acco ding o he esul s ob ained, he need o
achie e adequa e le els o alignmen becomes e en
mo e impo an . Thus, i is no only possible o main-
ain low le els o ib a ions o o p olong he couplings
and bea ings li e ime, bu also o op imize he ins al-
la ion e iciency and educe ene gy consump ion. Un-
like p e ious s udies, his wo k in oduces he coupling
ype used as an analysis a iable. In he same es
bench, wi h a common assembly and measu emen sys-
em, se e al o he mos equen ly used lexible cou-
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plings we e es ed. The wo k also o e s new ools o
a mo e sui able choice o coupling des ined o a speci ic
applica ion.
Re e ences
[1] FERREIRA, F. J. T. E. and A. T. DE ALMEIDA.
O e iew on ene gy sa ing oppo uni ies in
elec ic mo o d i en sys ems - Pa 1: Sys-
em e iciency imp o emen . In: IEEE/IAS
52nd Indus ial and Comme cial Powe Sys-
ems Technical Con e ence (I &CPS). De oi :
IEEE, 2016, pp. 1–8. ISBN 978-1-4673-8672-2.
DOI: 10.1109/ICPS.2016.7490219.
[2] DE ALMEIDA, A. T., F. J. T. E. FERREIRA
and A. Q. DUARTE. Technical and Economical
Conside a ions on Supe High-E iciency Th ee-
Phase Mo o s. IEEE T ansac ions on Indus y
Applica ions. 2014, ol. 50, iss. 2, pp. 1274–1285.
ISSN 1939-9367. DOI: 10.1109/TIA.2013.2272548.
[3] IEC S anda d 60034-30 1s ed. Ro a ing Elec-
ical Machines-Pa 30: E iciency Classes o
Single-speed, Th ee-phase, Cage-induc ion Mo-
o s. Gene a: IEC, 2009.
[4] VERUCCHI, C. J., R. RUSCHETTI and
G. KAZLAUSKAS. High E iciency Elec ic
Mo o s: Economic and Ene gy Ad an ages.
IEEE La in Ame ica T ansac ions. 2013,
ol. 11, iss. 6, pp. 1325–1331. ISSN 1548-0992.
DOI: 10.1109/TLA.2013.6710379.
[5] VAN WYK, A. L., M. A. KHAN and
P. BARENDSE. Impac o o e /unde and
ol age unbalanced supplies on Ene gy-E icien
mo o s. In: IEEE In e na ional Elec ic Machines
&D i es Con e ence (IEMDC). Niaga a Falls:
IEEE, 2011, pp. 1380–1385. ISBN 978-1-4577-
0060-6. DOI: 10.1109/IEMDC.2011.5994808.
[6] SIRAKI, A. G., C. GAJJAR, M. A. KHAN,
P. BARENDSE and P. PILLAY. An Al-
go i hm o Nonin usi e In Si u E iciency
Es ima ion o Induc ion Machines Ope a ing
Wi h Unbalanced Supply Condi ions. IEEE
T ansac ions on Indus y Applica ions. 2012,
ol. 48, iss. 6, pp. 1890–1900. ISSN 1939-9367.
DOI: 10.1109/TIA.2012.2225813.
[7] DONOLO, P., G. BOSSIO and C. DE AN-
GELO. Analysis o ol age unbalance e ec s
on induc ion mo o s wi h open and closed
slo s. Ene gy Con e sion and Managemen . 2011,
ol. 52, iss. 5, pp. 2024–2030. ISSN 0196-8904.
DOI: 10.1016/j.enconman.2010.10.045.
[8] DONOLO, P., G. BOSSIO, C. DE AN-
GELO, G. GARCIA and M. DONOLO. Vol -
age unbalance and ha monic dis o ion e ec s
on induc ion mo o powe , o que and ib a-
ions. Elec ic Powe Sys ems Resea ch. 2016,
ol. 140, iss. 1, pp. 866–873. ISSN 0378-7796.
DOI: 10.1016/j.eps .2016.04.018.
[9] GARCIA, M., P. A. PANAGIOTOU,
J. A. ANTONINO-DAVIU and K. N. GYF-
TAKIS. E iciency Assessmen o Induc ion
Mo o s Ope a ing Unde Di e en Faul y
Condi ions. IEEE T ansac ions on Indus ial
Elec onics. 2019, ol. 66, iss. 10, pp. 8072–8081.
ISSN 1557-9948. DOI: 10.1109/TIE.2018.2885719.
[10] HINES, J., S. JESSE, J. KUROPATWINSKI,
T. CARLEY, J. KUECK, D. NOWER and
F. HALE. Mo o Sha Alignmen Ve sus E i-
ciency Analysis. P/PM Technology. 1997, ol. 10,
iss. 1, pp. 10–13. ISSN 0899-1804.
[11] YAO, Y., Y. LI and Q. YIN. A no el
me hod based on sel -sensing mo o d i e
sys em o misalignmen de ec ion. Mechan-
ical Sys ems and Signal P ocessing. 2019,
ol. 116, iss. 1, pp. 217–229. ISSN 0888-3270.
DOI: 10.1016/j.ymssp.2018.06.030.
[12] BOSSIO, J. M., G. R. BOSSIO and C. H. DE AN-
GELO. Angula misalignmen in induc ion mo o s
wi h lexible coupling. In: 35 h Annual Con e -
ence o IEEE Indus ial Elec onics. Po o: IEEE,
2009, pp. 1033–1038. ISBN 978-1-4244-4648-3.
DOI: 10.1109/IECON.2009.5414696 .
[13] PIOTROWSKI, J. Sha Alignmen Handbook.
3 d ed. Ohio: CRC P ess, 2006. ISBN 978-1-5744-
4721-7.
[14] NOWER D. Misalignmen : Challenging he
Rules. Reliabili y Magazine. 1994, ol. 7, iss. 1,
pp. 38–43. ISSN 1557-0193.
[15] OBAID, R. R. and T. G. HABETLER. Cu en -
based algo i hm o mechanical aul de ec ion
in induc ion mo o s wi h a bi a y load con-
di ions. In: 38 h IAS Annual Mee ing on
Con e ence Reco d o he Indus y Appli-
ca ions Con e ence. Sal Lake Ci y: IEEE,
2003, pp. 1347–1351. ISBN 0-7803-7883-0.
DOI: 10.1109/IAS.2003.1257726.
[16] GABERSON, H. A. Ro a ing machine y en-
e gy loss due o misalignmen . In: P oceedings
o he 31s In e socie y Ene gy Con e sion En-
ginee ing Con e ence IECEC 96. Washing on:
IEEE, 1996, pp. 1809–1812. ISBN 0-7803-3547-3.
DOI: 10.1109/iecec.1996.553377.
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