TELKOM
NIKA Indonesia
n
Journal of
Electrical En
gineering
Vol. 15, No. 2, August 201
5, pp. 237 ~
248
DOI: 10.115
9
1
/telkomni
ka.
v
15i2.827
8
237
Re
cei
v
ed Ma
y 5, 2015; Re
vised June
2
7
, 2015; Acce
pted Jul
y
15,
2015
Design, Testing Analysis of High Tension Increased
Safety Motor for Hazardous areas
Bhagir
ath Ahir
w
a
l
*
1
,
Tarun Kumar
Chatterjee
2
1
F
l
ame & Exp
l
osio
n La
b., CSIR-Central Insti
t
ute of Mining
& F
uel Rese
ar
ch,
Bar
w
a R
oad, D
han
ba
d, (JH)-8260
15, Indi
a
Phon
e: +
91-32
6-22
960
25, +
9
1-32
6-
22
96
00
3
,
F
a
x: +
91-326-
229
60
19
2
Electrical En
gi
neer
ing D
e
p
a
rtment, Indian S
c
hoo
l of Mines,
Dhan
ba
d, (JH)-826
001, Ind
i
a
Phon
e: +
91-32
6-22
354
37,
F
a
x: +
91-3
26-2
2
9
656
3
*Corres
p
o
ndi
n
g
author, e-ma
i
l
: ahir
w
a
l
cmri
@
y
ah
oo.co.uk
1
, tkcism@y
ahoo.com
2
A
b
st
r
a
ct
T
he incre
a
sed
safety (Ex e) motors are d
e
sig
ned for safe oper
ation
in the
z
o
n
e
1 and
2
ha
z
a
r
dous ar
e
a
s. T
he presen
t paper descri
b
es the signi
fic
a
nt desig
n para
m
eters a
nd su
ccessful testin
g of
Ex e high te
nsi
on (HT
)
ind
u
cti
on motor rate
d
970K
W
/
6.6KV
/
18 pol
e/ 3Pha
se/ 50H
z
as p
e
r
IS/IEC 60079
-7
standar
d. The
comparis
on
of some us
eful design par
am
et
ers is als
o
giv
en between safe area
m
o
t
o
r and
ha
z
a
r
dous
are
a
motor in t
h
is
pap
er. T
he Ex
e hig
h
t
ens
io
n
ind
u
ction
motor menti
one
d i
n
this p
aper
h
a
ve
bee
n
ma
nufact
u
red
by B
har
at He
avy El
ectri
c
als Lt
d.
(BHE
L),
Bho
pal,
I
n
d
i
a duri
ng
th
e p
r
oject and
mai
n
author w
a
s the
project le
ad
er.
Ke
y
w
ords
: increased safety m
o
tor,
risk factor, testing, I
A
/I
N
, t
E.
Copy
right
©
2015 In
stitu
t
e o
f
Ad
van
ced
En
g
i
n
eerin
g and
Scien
ce. All
rig
h
t
s reser
ve
d
.
1. Introduc
tion
The ha
zardo
u
s atmo
sph
e
re is pro
bably
due to inevitable lea
k
ag
e
s
of haza
r
d
o
u
s ga
se
s
durin
g extra
c
tion/pro
c
e
ss
of hazard
o
u
s
materi
al. Th
e lea
k
age
h
a
za
rdo
u
s
ga
se
s mixed
with
available
air t
o
form
a p
o
tentially explo
s
ive at
mo
sp
h
e
re. Explo
s
ive atmo
sph
e
re is
a mixture of
flammable ga
s, vapour, du
st or mist wit
h
air, in
certa
i
n prop
ortion
s. The continu
a
l gro
w
th of the
chemi
c
al
an
d
petro-che
mi
cal
engi
nee
ri
ng in
du
strie
s
implie
s
a
correspon
ding
incre
a
se in
th
e
numbe
r of in
dustri
a
l comp
lexes involvin
g ha
zard
s f
r
om flammabl
e ga
se
s, vap
ours an
d mists
whi
c
h
can
produ
ce expl
osive mixtur
es
with ai
r. The
motor,
whi
c
h
is the
work
horse
of drivi
ng
pro
c
e
ss e
qui
pment, may be a sou
r
ce of energy rel
ease unde
r
norm
a
l or ab
norm
a
l spe
c
if
ied
con
d
ition if motor is not de
sign
ed prope
rly for haza
r
do
us area.
A s
u
mmar
y of th
e
r
e
view
of th
e
p
o
ss
ible p
o
tent
ial sources of ignition in motor is
carried
out before d
e
sig
n
of the
Ex e HT ind
u
ction m
o
to
r.
It was
clea
r from the
rev
i
ew, that igni
tion
tends to o
c
cu
r duri
ng sta
r
ti
ng co
ndition
s [1-4]. Br
edth
auer et al [1] obser
ved the
high ci
rculati
n
g
curre
n
t ind
u
ced in
the
ma
chine frame
co
mpone
nts
du
ring
sta
r
ting.
Clark
et al
[3] co
ncl
ude
d th
at
the spa
r
ki
ng and arcin
g
phenom
eno
n occurs in the
air gap at the end pa
ckets of the machine.
Bianco et al
[5] investigate the possible incendi
v
e
effect due
to partial di
scharge
s in
the
insul
a
tion
system. Dymond
[4, 6] indicated that
conta
m
ination
will l
ead to
su
rface disch
a
rg
e a
n
d
tracking
on
th
e wi
ndin
g
s,
which
is an
oth
e
r
potentia
l
source
of
spa
r
king
an
d a
r
cing. Hame
r et
al
[7] elaborate
d
on the relatio
n
shi
p
betwee
n
hot rotor
su
rface
s
an
d flammable vap
o
r
ignition.
The te
rms ‘sparking’,
arci
ng an
d ‘n
on-spa
r
ki
ng’ m
u
st be
re
garde
d a
s
ge
ne
ric
phra
s
e
s
coveri
ng the f
u
ll ran
ge of di
scharge a
c
tivity whic
h
co
uld be p
r
e
s
ent i
n
the ma
chin
es. The
de
sig
n
and
con
s
tru
c
t
i
on of high vo
ltage ma
chin
es, an
d the in
sulatio
n
mate
rials
used
re
sult inevitably in
the possibility of electri
c
al
disc
harging at variou
s locations
within the ma
chi
ne. Discharges may
occur a
s
p
a
rt
ial di
sch
arge
s in
voids wi
thin in
sulatio
n
in th
e stat
or
windi
ng; b
e
twee
n
surfa
c
e
s
whe
r
e an ele
c
tri
c
al stress exists, for example a
s
a sl
ot discharge
betwe
en t
he slot-p
ortio
n
of the
stator wi
ndin
g
and the st
ator co
re; al
ong an in
sul
a
ting su
rface
at which an
electri
c
al stress
exists, for ex
ample
coron
a
in the stato
r
end
-wi
ndin
g
and core-e
n
d
regi
on; as
arci
ng b
e
twe
en
rotor b
a
r a
n
d
rotor
co
re
within the
slot; as a
r
ci
ng between
the roto
r en
dring
and ot
her
comp
one
nts,
su
ch
as a
retaining
ring,
or th
e core
or
core-clam
p
ing pl
ate; b
e
twee
n rotor
and
stator du
e to electri
c
al stress; All these pheno
men
a
can o
c
cur
in normal o
p
eration, i.e. both
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ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 15, No. 2, August 2015 : 237 –
248
238
durin
g sta
r
tin
g
and
wh
en
runni
ng o
n
lo
ad. Co
ron
a
d
i
scharging
m
a
y occur in
stator win
d
ing
s
,
particula
rly on the line-en
d coils in the
end-wi
ndin
g
region. The
energy in a coron
a
disch
a
r
ge
will be influenced by
the l
o
cal
capacitance and the
di
scharge inception voltage [8]. The partial
discha
rge
(P
D) i
s
a lo
cali
zed diele
c
tri
c
brea
kd
own wi
thin a solid o
r
liquid in
sulati
on un
der
a hi
gh
electri
c
al
st
re
ss.
Co
ron
a
di
scharge
s o
ccur in
t
he flui
d
surro
undi
ng a
co
ndu
ctor.
Coron
a
i
s
a
form
of PD that
occurs in ga
seo
u
s me
dia
aroun
d
con
ducto
rs a
nd exhibits a certain di
scha
rge
magnitud
e
a
nd e
nergy. G
enerally, PD
and
co
ron
a
d
i
scharge
s a
p
pear a
s
sho
r
t duration
pul
se
s
having du
rati
on of much less than 1
μ
s. Both PD and corona
discha
rge a
c
t
i
vities are oft
en
accomp
anie
d
by emission
of sound, heat and ch
e
m
ical re
actio
n
. Coro
na di
scharge
s will
also
emit light wh
en the elect
r
ical stress is suffi
ciently high. The three
magnitu
d
e
of disch
arges
depe
nd
s
o
n
t
he size
of
th
e
void
s withi
n
a diele
c
tri
c
or
th
e
g
ap be
tween
cond
u
c
tors at
different
potential. The
quantity of di
scharge
s is related to the numbe
r of
voids. Co
ron
a
di
scharge
s in the
external
environment
will be of main concern
with
respect to i
gnition of
the hazardou
s gases
[9].
The
p
o
te
ntial
ai
r ga
p sp
arkin
g
rot
o
r
a
s
se
ssm
ent
a
n
d
p
o
te
ntial
stator win
d
in
g discha
r
g
e
ri
sk
assessme
n
t is req
u
ired to
be
con
d
u
c
t
e
d
in explo
s
iv
e atmo
sp
he
re as
pe
r IS/IEC 600
79
-7 [1
0]
to
co
nfirm any
occurre
n
c
e o
f
arc o
r
spa
r
k in the m
o
t
o
r d
ue to co
rona d
i
scha
r
g
e
or a
nd p
a
rtial
d
i
sch
ar
ge
. Th
e roto
r
sp
arki
ng ta
ke
s pl
ace du
ring
sta
r
ti
ng a
nd
occu
rs b
e
twe
en th
e roto
r
bars
a
n
d
rotor
c
o
re, espec
ially in the vic
i
nity of the firs
t
radi
al
cooli
ng d
u
ct
s. It is cau
s
ed
by movement
o
f
the rotor
ba
rs, either withi
n
the
slots o
r
arou
nd th
e
e
nd of th
e
co
re in th
e
are
a
whe
r
e
the
ba
r i
s
sha
ped. In most ca
se
s the
movement is the resu
lt of
angul
ar an
d radial force
s
whi
c
h a
c
t on the
rotor
du
ring
starting, an
d it interr
upts
cu
rrent flo
w
from
the ba
rs to th
e co
re,
cau
s
i
ng the
spa
r
ki
ng
[11].
The terminal
box mu
st b
e
we
athe
rpro
of
and th
e e
n
clo
s
u
r
e m
u
st have m
e
chani
cal
stren
g
th an
d
be thermall
y and che
m
i
c
ally stabl
e; these requi
reme
nts a
r
e
to prevent the
encl
o
sure
terminals bei
ng
contami
nated
, whi
c
h
co
uld
in turn le
ad t
o
ele
c
tri
c
al
surface trackin
g
.
The ca
ble en
try
must
also be
via a rob
u
s
t
weathe
rp
ro
of ca
ble
glan
d. The
termi
n
als th
em
selves
must h
a
ve some a
n
ti-vibration featu
r
e
to preve
n
t them
comin
g
loose an
d th
e cle
a
ran
c
e
and
cre
epa
ge di
stances mu
st comply with a spe
c
ified mini
mum value, depe
nding u
p
on the voltage
betwe
en
adja
c
ent te
rmin
al
s. Th
e te
rmin
al blo
c
k m
a
te
rial m
u
st
co
m
p
ly with
a mi
nimum
sp
ecif
ied
comp
arative trackin
g
ind
e
x, depen
ding
upon th
e
cre
epag
e dista
n
c
e b
e
twe
en termin
als a
n
d
the
voltage used
[12].
The Ex e HT moto
r is
requ
ired to b
e
ad
opte
d
some a
dditi
on
al re
qui
reme
nts a
s
p
e
r
IS/IEC 60
07
9-7. After su
cce
s
sful
rele
vant te
st
s a
n
d
d
e
sired
pe
rfo
r
ma
n
c
e
of
de
si
gne
d E
x
e
moto
r, it ca
n be a
s
su
re
d that the d
e
s
ig
ned i
n
crea
se
d saf
e
ty mot
o
r
can
not b
e
c
o
m
e a
so
urce of
igniti
on in
t
h
e
h
a
z
a
r
d
o
u
s
area du
ri
ng ope
ratio
n
.
A prototyp
e
9
7
0
K
W
/
6
.
6
K
V
/
1
8
p
o
l
e
E
x
e
HT
indu
ction mo
tor ha
s b
e
e
n
de
sign
ed
and te
sted
as
p
e
r
relev
ant stan
da
rd
s. The
moto
r is
desi
gne
d for use in
zo
ne
2 and b
eari
ng tempe
r
atu
r
e cl
ass T3
(
≤
200
ºC) [13]. The de
sig
n
ed
para
m
eters o
f
motors, igni
tion risk a
s
se
ssment
an
d relevant tests
have bee
n d
e
scrib
ed in t
he
pape
r. The in
cre
a
sed
safet
y
motor is u
s
ed in the
zon
e
1 and
2 are
a
s but in In
di
a it is limited
to
zon
e
2 area appli
c
ation o
n
ly
as pe
r
IS
557
1:2009
[14]. The
r
e
are some te
rmi
nology fo
r Ex e
motor whi
c
h are rated
current
(I
N
), starti
ng current (I
A
),
Current Ra
tio (I
A
/I
N
)
an
d time t
E
. Rat
ed
Cu
r
r
e
n
t (I
N
) is
the full load current taken by th
e
ma
ch
ine
.
In
itia
l s
t
ar
ting
Curr
en
t (
I
A
) is
t
h
e
hig
h
e
s
t root
mea
n
squ
a
r
e
value
of current a
b
s
o
r
b
e
d
by an A
C
m
o
tor
at re
st when
sup
p
lie
d
at
the rate
d vol
t
age
an
d fre
que
n
c
y. Starting
Cu
rrent
Rati
o (I
A
/I
N
)
is th
e ratio
bet
we
en i
n
iti
a
l
s
t
ar
ting
c
u
rr
en
t
(
I
A
)
a
nd ra
ted cu
rre
n
t
(I
N
). Tim
e
t
E
i
s
the tim
e
ta
ken fo
r
an A
C
rot
o
r
o
r
stat
or
win
d
i
ng, wh
en ca
rryin
g
the
i
n
itial st
arti
ng curre
n
t
(I
A
) t
o
b
e
he
ated
u
p
to the
limit
ing
temp
eratu
r
e
from t
he t
e
mp
eratu
r
e
re
ache
d
i
n
rate
d
se
rvi
c
e at th
e m
a
ximu
m am
bie
n
t
te
mpe
r
a
t
ur
e
.
The
starting
cu
rr
ent
to
rated cu
rre
nt ratio (I
A
/I
N
) is also
determi
ned i
n
o
r
d
e
r to
provide fo
r the sele
ction of
a suitable
cu
rre
nt
detectio
n
device to p
r
otect agai
nst
the occu
rre
nce
of non-permi
ssi
ble temp
eratur
e
s
. The l
ength of time
t
E
must be su
ch a
s
will
allow, when t
h
e
rotor i
s
lo
cke
d
, the motor to be di
scon
n
e
cted
by
the
curre
n
t dep
e
ndent p
r
ote
c
tive device
bef
ore
time t
E
has elapsed.
2. Comparisi
on of Ex e M
o
tor
w
i
th
No
rmal Motor
The comp
ari
s
ons
also
hav
e been
don
e
on some imp
o
rtant de
sig
n
para
m
eters
with the
norm
a
l moto
r (gen
eral HT
indu
ction mot
o
r bei
ng u
s
e
d
in the non
-e
xplosive a
r
ea
) and i
n
crea
sed
safety norm
a
l
HT motor a
s
given in the Table 1.
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TELKOM
NIKA
ISSN:
2302-4
046
D
e
s
i
g
n
,
Tes
t
in
g
Ana
l
ys
is
of H
i
gh
T
ens
ion
Inc
r
e
a
s
e
d
Sa
fe
ty
Mo
to
r
fo
r…
(Bhagi
rath
Ahirwal)
239
Table 1. Co
m
pari
s
on
s of d
e
sig
n
parame
t
ers bet
wee
n
norm
a
l motor and Ex e HT motor
Design aspect and perfo
rmance
Normal Moto
r
Ex e H
T
Motor
Mechani
cal de
si
gn
ingress protection
Depends on user
Minimum IP 54 r
equirement
bearing clearanc
e
Not compulsor
y
It
should be 0.05
mm minimum as per
IS/IEC 60079-
7
shaft
Spider construction or
solid one piece
Solid one piece
shaft assembly
Interfer
ence fitted
Interfer
ence fitted
rotor
Cast die aluminium or copper
bar
Copper/b
rass ba
r
radial air gap
Gap=0.2+2
√
DL, w
h
ere
D=
rotor
diameter in mm, l= core length
in mm [15]
As per equation (
1
) of this paper
cooling
Good cooling
Good cooling
risk factor (cooling duct)
Not applicable
It is applicable
Fan and fa
n cover clearance
Fan should not c
o
me in contact
of fan cover
Minimum 1mm and maximum 5m
m
Fasteners
Gene
ral fastener
s can be used
It should be as per ISO 2
62, IS
O9
65-1 &3,
ISO 4014, IS
O 4
017, ISO 4
032, I
S
O 4026,
ISO 4027, IS
O 4
028 or IS
O 4029
Impact w
i
thstand
ing capacity
Not applicabl
e
It is conducted as per IS/IEC 600
79-0
Cable gland
Normal
w
eath
e
rp
roof cable
gland
Ex e certified an
d approved cable
gland
Electrical De
sig
n
creepage distance & clearance
Not compulsor
y
It is mandator
y
anti-loosening & vibrationproof
terminals
Not applicable
It is a must
stator
w
i
nding conductor size
Not complusar
y
Minimum 0.25mm size
insulation cla
s
s
As per IS/IEC60
034-1 [16]
As per IS/IEC 60
079-7
temperatu
r
e class specification
No temper
ature
class
specificat
ion
T1-T
6 class as p
e
r IS/IEC 600
79-
0
limiting temperature of insulation
class
As per IS/IEC60
034-1
As per IS/IEC 60
079-7
space heater
It ma
y
be
or ma
y not be
Provision is must
for >1KV oper
ating
voltage
risk factor (rotor
cage construction,
pole, rated out
pu
t, rotor/stato
r
skew
,
rotor ove
r
hang p
a
rts)
Not applicable
Consideration of
risk factor is mandator
y
Risk assessment
Not applicable
It is must
Protection for ab
normal condition,
overload
Protection is required
Prot
ection must be provided
Performa
nce
Speed-to
rque ch
aracteristics,
efficiency
& p.f.
As per IS/IEC 60
034-1
As per IS/IEC 60
034-1
t
E
Not applicable
It is must and it shall be minimum 5seconds
I
A
/I
N
Not applicable
It is must and it shall not be more
than 10
Use/application
For safe a
r
ea ap
plic
ation
For haza
r
dous ar
ea application
Gene
rally the
following rea
s
on
s may be
the cau
s
e for
explosi
on by the motors.
a)
Surface temperatu
r
e d
u
e
to inevit
able losse
s
ca
usin
g heat
penetration, but
inade
quate v
entilation
b)
Gene
ration of
sparks bet
ween live termi
nals a
nd ea
rth
c)
Partial disch
a
r
ge
s occu
rri
n
g
in embed
de
d insul
a
tion in
slots
d)
Hou
s
in
g cu
rrents du
e to stray leakage fl
ux
e)
Sparks in ai
r gap of high
-speed ma
chi
n
es du
e to vibration of cag
e
bars
While d
e
si
gn
ing of Ex e motor all a
b
o
ve mea
s
ure
s
have b
een
con
s
ide
r
e
d
to avoid
arc/
spa
r
k and
hot surfa
c
e
s
in the motor.
3. Electrical Input and
Ou
tput
for Ex e Motor
The
pa
ra
met
e
r i
s
f
u
rni
s
h
ed by t
he
e
nd u
s
er
a
s
pe
r hi
s
re
qui
rem
ent f
o
r
p
a
rti
c
u
l
a
r
app
li
cati
on
a
nd
on t
he
ba
si
s
of in
put t
h
e m
o
to
r i
s
b
e
i
ng
de
si
gn
ed.
Th
e b
a
s
i
c
in
put
pa
ram
e
te
rs
are req
u
i
r
e
d
to de
si
gn
a
n
in
cre
a
sed
saf
e
ty mot
o
r are volt
ag
e, full lo
ad
curre
n
t, fre
q
u
e
n
c
y,
phase, power fac
t
or (p.f.), to
rque,
s
peed, effic
i
enc
y
(
η
)
,
Ho
rsep
ower (HP) o
r
Kilowatt
(K
W)
ra
t
i
n
g
etc.
Th
e volta
ge
an
d
fre
que
n
c
y tol
e
ran
c
e f
o
r t
h
i
s
m
o
to
r i
s
±5
% and
±2% respe
c
tive
ly a
nd
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 15, No. 2, August 2015 : 237 –
248
240
it is
qu
a
lifying
th
e
r
e
qu
ir
eme
n
t
o
f
IS/IEC
60
03
4-
1. T
he d
u
ty cy
cle
is the l
e
n
g
th
of ru
nni
ng ti
me
in which
t
h
e
mot
o
r can carry
it
s f
u
ll
load safely.
Most
ofte
n,
this is
continuous. Som
e
app
li
cati
on
s have
o
n
ly sh
ort
-
time
(S2
)
o
r
p
e
r
io
di
c duty (S3
-
S1
0
)
use an
d do
not
n
e
e
d
m
o
tor
full-l
o
a
d
cont
inu
o
u
s
ly.
Th
e p
r
esent
E
x
e
moto
r
is de
si
gn
ed
fo
r
co
ntin
uo
u
s
duty
(S
1).
The
reli
ability of motor is
dependent generally on
the insul
a
tion class of the motor wi
ndi
ng,
ma
ximu
m amb
i
en
t te
mpe
r
a
t
ur
e
an
d
a
l
titu
de
. T
he ‘F
’ c
l
ass
ins
u
la
ting
ma
te
r
i
a
l
is
use
d
fo
r
win
d
i
n
g
s
of t
he
97
0
k
w Ex
e
mot
o
r.
Th
e m
o
to
r i
s
d
e
s
ig
ne
d f
o
r m
a
ximu
m
ambi
ent t
e
mp
e
r
at
ure
of 40º
C
an
d altitud
e
b
e
lo
w me
an
sea l
e
vel.
4. Risk Fac
t
or of 970
kW
Ex e Motor
The IS/IEC
6007
9-7
in
cl
ude
s ig
nition
ri
sk a
s
sessment for rotor
ca
ge
and
stato
r
of
increa
sed
saf
e
ty motor. In orde
r to
con
f
irm that
the
stator
windi
n
g
is fre
e
fro
m
ignition d
u
e to
partial
disch
a
r
ge
s
at the
rated voltag
e
of ma
chin
e
so
ignitio
n
risk
asse
ssme
nt is req
u
ire
d
[1
7].
The ri
sk fa
ctors a
r
e d
epe
ndent on the
different ch
ar
acteri
stics of
the motor fro
m
desig
n to end
use. Th
e det
ail of the risk factors for ca
ge roto
r is
gi
ven in Table
2 for 970
kw Ex e motor. If the
total su
m of
risk facto
r
i
s
g
r
eate
r
tha
n
6
t
hen the
mot
o
r
sh
ould
be
asse
ssed fo
r
airga
p
sp
arki
ng
risk asse
ssm
ent as pe
r IS/IEC 60079-7
:
2006. It is cl
ear from the
Table 2 that total sum of ri
sk
factor of 970
kw moto
r is
7 whi
c
h is g
r
eater than 6,
hence 970
kw de
signe
d motor shoul
d
be
asse
ssed
fo
r airga
p
spa
r
ki
ng risk asse
ssment
by
con
ductin
g
imp
u
l
s
e te
st a
nd
hi
gh voltag
e te
st
in explosive e
n
vironm
ent.
Table 2.
Ch
aracteri
stic risk factors
for rotor of 970K
W Ex e motor
Characteristics as per IS/IEC 600
79-7
Value specified in the IS/IEC 600
79-7
for
r
i
sk factor
Risk factor
for
970KW
Rotor cage const
r
uction
Uninsulated bar
Fabricated r
o
tor
cage
3 2
Fabricated r
o
tor
cage
2
Number of
poles
> 8 pole
0
0
2 pole
2
Rated outpu
t
≤
200KW per pol
e
0
0
>500KW per pol
e
2
Radial cooling ducts in rotor
Y
e
s:
L
<200mm
2
2
Ye
s
:
L
≥
20
0mm
1
Rotor o
r
stator skew
NO
0
2
Y
e
s: >200KW pe
r pole
2
Rotor over
hang
parts
Complaint
0
0
Limiting Temper
ature
135°C< T
≤
200°
C
1
1
Total
fac
t
or
7
5. Design Pa
ramete
rs of
970k
W Ex e Motor
While d
e
si
gni
ng Ex e motor spe
c
ial m
e
a
s
ures a
r
e giv
en on follo
win
g
asp
e
ct
s:
a)
Ris
k
f
a
ct
o
r
a
s
se
ssm
ent
b)
Ignition poten
tial risk a
s
se
ssment
c)
Tempe
r
atu
r
e
rise of all the
parts u
nde
r n
o
rmal a
nd ab
norm
a
l ope
ra
ting con
d
ition
s
d)
Spark pro
d
u
c
ing pro
p
e
r
ties of
material u
s
ed in the
co
nstru
c
tion
e)
Enclo
s
u
r
e de
sign
f)
Mech
ani
cal cl
eara
n
ces b
e
twee
n station
a
ry and rotating part
s
g)
Cre
epa
ge di
stance
and
cle
a
ran
c
e
with
resp
ect to
CTI
(compa
rative
tracking i
nde
x)
level of insula
ting material
of terminal bl
ocks
5.1. Stator a
nd Stato
r
Fr
ame
The problem
of ignition due to spa
r
ki
n
g
result
ing from interrupti
on of circulat
ing joint
discontin
uities is
not confi
ned the
r
efo
r
e
to rotating m
a
chi
n
e
s
[18].
The
stator a
n
d
stato
r
fram
e is
desi
gne
d in such a way that they canno
t produ
ce
mo
re ci
rculating
curre
n
t which
can ca
use for
ignition. The
stator co
n
t
a
i
n
s
th
e
pr
imar
y w
i
nd
ing
an
d
is
mad
e
u
p
o
f
lamina
tio
n
s
w
i
th
a
la
rg
e
hol
e in th
e ce
nter i
n
whi
c
h
the roto
r can
turn.
The
r
e a
r
e sl
ots i
n
th
e stat
or i
n
whi
c
h the
win
d
in
g
s
o
f
the
c
o
ils
ar
e
ins
e
r
t
ed
. The
ca
st ho
u
s
ing
to
receive the
stator stam
ping
pa
cks, two
pot e
n
d
shiel
d
s i
s
ma
de of grey
ca
st iron a
nd two bea
ri
ng h
e
ads. Th
e stat
or ho
usi
ng m
ade of stai
nle
ss
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
2302-4
046
D
e
s
i
g
n
,
Tes
t
in
g
Ana
l
ys
is
of H
i
gh
T
ens
ion
Inc
r
e
a
s
e
d
Sa
fe
ty
Mo
to
r
fo
r…
(Bhagi
rath
Ahirwal)
241
steel
con
s
i
s
ts of a wel
ded
con
s
tru
c
tion.
The en
d
shiel
d
s a
r
e
desi
g
n
ed a
s
di
scs a
nd re
ceive th
e
beari
ng he
a
d
s. The
s
e
constructio
n
e
l
ements
a
r
e
screwed to
gether axiall
y. A continuous
cente
r
ing of
the assembli
es on
e by one ma
kes a
n
air gap
ch
eck unn
ecessary even af
ter
disa
ssembly. Radi
ally
arra
yed
guid
e
s e
n
su
re an
exa
c
t tange
ntial
positio
ning
of the en
d shie
lds
with the stato
r
hou
sing afte
r disa
ssem
bly. The st
ator stamping pa
ck is fixed in th
e hou
sing via
a
pre
s
s fit and
then
spo
o
led.
The
stam
pin
g
pa
ck i
s
p
u
t togethe
r o
u
t of in
sulate
d
dynamo
sh
ee
t
roun
d pl
ates
or ove
r
lap
p
e
d
dynam
o sh
eet se
gme
n
ts and
axially tensi
one
d ove
r
en
d plate
s
with
pre
s
s pin
s
. T
he stato
r
p
a
ck is
sh
ru
nk i
n
the stato
r
ho
usin
g. A pre
s
s spri
ng i
s
u
s
ed to receive
the
sho
r
t-circuit
moment. A continuo
us
ce
ntering
of the assembli
es
one by one
make
s a
n
air gap
che
c
k unn
ecessary even
after disa
sse
m
bly.
5.2. Insulatio
n
Sy
stem
The
in
sul
a
tin
g
sy
ste
m
i
s
t
he im
po
rta
n
t
pa
rt of th
e d
e
si
gn f
o
r the
Ex e HT mot
o
r
wh
ich
ca
n
with
sta
n
d
ri
sk ig
niti
o
n
a
s
se
ssm
e
nt test
s
at h
i
gh a
nd
imp
u
lse volt
ag
e
s
. Th
e in
sul
a
ting
sy
stem
of the
win
d
in
g of m
o
tor i
s
se
rve
d
the pu
rpo
s
e
to:
a
)
se
pa
rat
e
the
vari
ou
s el
e
c
trica
l
com
p
o
n
e
n
ts f
r
om
on
e
anot
he
r, a
n
d
b)
prote
c
ts itself
and
t
he ele
c
t
r
i
c
al comp
on
ent
s from att
a
ck
of cont
a
m
ina
n
t
s
a
nd
othe
r
de
st
r
u
ct
iv
e f
o
r
c
e
s
.
Five sp
e
c
ia
li
ze
d ele
m
e
n
ts are emp
l
o
y
ed
th
at co
n
s
titut
e
in
sulat
i
on sy
ste
m
s of
m
o
to
r
win
d
i
ng
whi
c
h are giv
en
b
e
lo
w:
a)
Turn to turn insulation
-
Th
e in
sulati
ng
mate
ria
l
i
s
in
stall
e
d
b
e
twe
en
se
pa
rate
wi
re
s
in ea
ch coil. I
n
thi
s
ca
se th
e con
d
u
c
to
rs
of wi
ndi
ng i
s
t
app
ed
a
s
the
insul
a
tio
n
.
b)
Ph
as
e to
p
has
e insu
la
tio
n
-In thi
s
case t
he i
n
sul
a
tio
n
is i
n
stall
e
d
b
e
twee
n a
d
ja
cent
coi
l
s i
n
diffe
rent ph
a
s
e g
r
oup
s. Th
e woun
d coil of stator i
s
wra
p
ped
with in
su
latin
g
tape tu
rn to t
u
rn.
c)
Pha
s
e
to
g
r
oun
d i
n
sul
a
ti
on
—
T
hi
s in
sulati
on
is i
n
stall
e
d
b
e
tween
th
e m
o
tor
w
i
nd
in
gs
as
a
w
h
o
l
e
an
d
th
e
“gr
o
u
nd”
o
r
me
ta
l
pa
r
t
s
o
f
th
e
mo
tor
.
T
y
p
i
ca
lly,
a
sh
eet of in
sul
a
ting m
a
te
ria
l
is provid
ed i
n
the st
ato
r
slots to p
r
ovi
d
e both di
el
ect
r
i
c
and me
ch
an
i
c
al prote
c
ti
on
.
d)
Slot wedge
—Thi
s
in
sul
a
tion i
s
used
pri
m
a
r
ily to
hol
d the
con
d
u
c
to
rs firml
y
an
d
tightly in th
e
slot.
e)
Im
preg
nati
o
n
—Thi
s p
r
o
c
e
s
s i
s
used
t
o
bi
nd
all
th
e ot
he
r i
n
sul
a
ting
com
p
o
nent
s
toget
he
r an
d
fill in the ai
r spa
c
e
s
wit
h
in th
e ap
pli
ed in
sulati
ng
mate
rial
s. T
h
is
proce
s
s i
s
a
ppli
e
d
in
flui
d fo
rm
a
nd t
hen
cu
re
d (h
arde
ne
d)
to provid
e
e
l
e
c
t
r
i
c
al,
me
ch
ani
cal, and
conta
m
in
ant atta
ck p
r
o
t
ecti
on.
By provi
d
in
g prop
er i
n
sul
a
tion in th
e dif
f
ere
n
t lo
cati
o
n
s
of the mot
o
r
so thi
s
i
n
sulati
on
sy
stem
s ha
s
ma
de
thi
s
de
sig
n
po
ssi
b
le an
d
t
h
i
s
in
sul
a
tio
n
system
co
uld
su
stai
n
p
o
t
entia
l
igniti
on
ri
sk assessme
n
t as
p
e
r
IS/IEC 60
07
9-7:2
006.
T
h
e
i
n
s
u
l
a
t
i
o
n
cl
a
ss
F
h
a
s b
e
e
n
u
s
e
d
and confirm
e
d for de
sign
of 970KW Ex
e HT ind
u
cti
on motor
an
d function
al
evaluation of
this
insul
a
tion sy
stem is qualifie
d as pe
r IEC 6003
4-1
8
-3
1 [19]. The name of this insulating sy
ste
m
is
Re
sin Poo
r
class F Mical
a
stic
(Vacuu
m Pressu
re
Impre
gnate
d
)
Insulatio
n
an
d whi
c
h is al
so
qualified
for wet
test
as per NEMA specificati
on
M
G
1
-
20.4
8
(9
) [20], lig
hten
ing a
nd
switching
surge voltage
test as pe
r IEC 6003
4-15
[21]
and low
dissipatio
n factors a
s
per
VDE 0530.
5.3.
Rotor Constr
uction
The
rot
o
r i
s
the rotati
ng
pa
rt of the E
x
e ind
u
cti
o
n
moto
r an
d it
is m
ade
of
sta
c
ke
d
lami
nati
o
n
s
.
A shaft
ru
n
s
t
h
rou
gh t
h
e
cente
r
an
d
a
squi
rrel cag
e
mad
e
of co
pp
er
ba
rs hol
d
s
the
lami
nati
o
n
s
toget
he
r. Th
e sq
ui
rrel cag
e
act
s
a
s
a con
d
u
c
to
r for th
e
indu
ce
d ma
g
neti
c
field. T
h
e
ba
rs
a
r
e i
n
dire
ct cont
act with th
e
co
re,
whi
c
h all
o
ws fo
r fa
st
e
r
h
eat
co
nd
u
c
tio
n
.
T
h
e
ro
t
o
r
con
s
tru
c
tion
can
be eithe
r
a solid
sh
aft or welde
d
rib
bed
shaft de
pendi
ng on
machi
ne
size
. The
rotor sta
m
pin
g
pa
ck
con
s
i
s
ts
of dyna
m
o
sheet
ro
un
d
plate
s
or overlap
ped
l
a
yered
dyna
mo
s
h
ee
t s
e
gmen
ts
. T
h
e
s
t
amp
i
n
g
pa
ck
is
te
ns
i
one
d
axially with pre
ss
pins.
Stamping p
a
cks
c
o
ns
is
ting of round plates
are shrunk
onto t
he s
haft. Stamping pac
k
s
made up of s
egments
are
laminated onto dovetail-
shaped
strips of the
ribbed shaft.
Rotors with
ribbed shafts
hav
e a
feather
key t
o
re
ceive th
e
sho
r
t-circuit
momen
t. A p
hotograph
of
roto
r of Ex
e HT
moto
r i
s
sho
w
n in the
Figure 1.
The roto
r ba
rs made of co
pper a
r
e ind
u
c
tively
solde
r
ed axially with the protrudi
ng sh
ort-
circuit di
sks.
The sp
eci
a
l
shap
e of the sho
r
t circui
t disc an
d th
e rotor
rod
s
ensure
s
a hi
gh
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ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 15, No. 2, August 2015 : 237 –
248
242
sold
erin
g q
u
a
lity. The ou
ter
contou
r
of the
sho
r
t circuit
di
scs is worke
d
o
n
only after the
sold
erin
g is
complete in
order to
achieve an o
p
timal
pre
-
bal
an
cing
con
d
ition. Th
e roto
r ba
rs a
r
e
prop
erly lo
cked to prevent
any spa
r
k fro
m
the rotor d
u
ring o
p
e
r
atio
n.
Figure 1. View of rotor a
ssembly of motor
5.4. Stator
Winding
The dou
ble layer lap win
d
i
ng is used fo
r this Ex e motor. The thre
e-ph
ase dou
ble-laye
r
lap windi
ng lies in the ope
n groove
s
of the stampi
n
g
pack. It is design
ed as a
whol
e pulled
coil.
Flat copp
er wire, insul
a
ted with mica foil, is used for t
he entire pull
ed coil
s. The main insulati
on
of the coils
consi
s
ts of lo
w adhe
sive mica-fib
re
gla
ss
tape. To avoid cor
ona di
scharg
e
s, in
stal
led
in the slot p
a
r
t is a lo
w im
peda
nce and
in the slot
ex
it a high impe
dan
ce mi
ca p
r
otective
cov
e
r.
The complete
ly insulated
condu
ctor
pa
ckag
es a
r
e
fixed in the sl
ots usi
ng
slot conne
ctors ma
de
of gla
s
s fab
r
i
c
a
n
d
epoxy
resi
n. Th
e
switch
co
n
n
e
c
tions a
r
e
hard-sold
ere
d
at
the
whol
e p
u
ll
ed
coil wi
nding
s.
A photogra
p
h
of stator wi
nding of
Ex e HT moto
r is shown in the Figure 2.
The com
p
lete
ly
woun
d stator stampin
g
pack
with h
o
u
sin
g
is there
b
y impre
gnat
ed in
an
epoxy-resi
n b
a
th first und
e
r
vacu
um an
d then und
er pre
s
sure. Th
e sub
s
e
que
nt heat treatme
nt
hard
e
n
s
the
resi
n. A cavi
ty-free win
d
i
ng in
sulation
and a bo
nd
ed stam
ping
pack are th
us
guarantee
d free from a
n
y void or moi
s
ture. The
win
d
ing an
d the
slot we
dge
s
are li
kewi
se fi
xed
with the epo
xy resin in the stampi
ng
pack.
The
windi
ng hea
ds are able
to take up l
a
rge
deform
a
tion forces,
which can b
e
ca
use
d
by load sh
o
c
ks an
d main
s switch
-on
s
.
Figure 2. View of stator a
s
sembly of mo
tor
5.5. Shaft C
o
nstru
c
tion
The
mate
ri
al
for
sh
aft is
h
o
t rol
l
e
d
st
eel
with
a ten
s
il
e st
re
ngth
of
abo
ut 1
00,0
0
0
p
s
i, i
s
used. Th
e
m
a
terial st
re
ng
th
an
d sh
aft si
ze a
r
e det
e
r
mi
ne
d
to wit
h
st
an
d
1
1
ti
me
s
rate
d
to
rque.
The
shaft
of
moto
r i
s
tu
rn
ed
an
d
grou
n
d
to
tig
h
t tol
e
ra
nce
s
th
at
h
e
lp
eli
m
in
ate
roto
r co
re
run
out
and
unb
al
an
ce of th
e fin
a
l rot
o
r a
sse
mbly. Fo
r thi
s
mot
o
r a
so
lid shaft (41
5
0
ste
e
l g
r
a
d
e
)
is
used.
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TELKOM
NIKA
ISSN:
2302-4
046
D
e
s
i
g
n
,
Tes
t
in
g
Ana
l
ys
is
of H
i
gh
T
ens
ion
Inc
r
e
a
s
e
d
Sa
fe
ty
Mo
to
r
fo
r…
(Bhagi
rath
Ahirwal)
243
5.6.
Sh
a
f
t
A
s
s
e
m
b
l
y
b
y
In
t
e
rfe
r
en
ce
F
i
t
The
rot
o
r
of Ex e moto
r i
s
heat
ed a
nd
assemb
le
d to
the shaft
wit
h
an i
n
te
rfe
r
e
n
ce fit.
The i
n
te
rfe
r
e
n
ce fit cre
a
te
s a u
n
ifo
r
mly
dist
ri
bute
d
fo
rce b
e
twee
n the
shaft a
nd
roto
r. T
h
i
s
force
res
t
ric
t
s
the rotor f
r
om
spinning on the s
h
aft.
5.7. Radial Air Gap
The radial ai
r gap bet
wee
n
stator a
nd ro
tor of
increa
sed safety motor is ve
ry imp
o
rtant
for
con
s
ide
r
at
ion d
u
rin
g
d
e
s
ign
to avoi
d
spa
r
ki
ng
and
arci
ng i
n
the
air g
ap
at the
end
po
ckets
o
f
motors. The
minimum ai
r gap is
cal
c
ula
t
ed on the ba
sis of Equatio
n (1).
Air gap = {
0
.1
5+ [(D-5
0
)/78
0] [0.25+(0
.7
5× n/10
00)]}
ry [10]
(1)
Whe
r
e,
D = rotor dia
m
eter in mm
(su
b
je
ct to a minimum of 7
5
mm and a m
a
ximum of 75
0mm)
r = co
re len
g
t
h/(1.75 ×
D)
n = m
a
ximum
rated
spe
ed i
n
RPM a
nd y
=
1 fo
r moto
r
with rolli
ng b
e
a
ring
or
1.5 for plai
n
beari
n
g
The
air
gap
i
s
g
ene
rally
kept hig
her th
an th
e
calcul
ated valu
e fo
r Ex e
motor
[22]. The
desi
gne
d rad
i
al air ga
p value is m
o
re
than t
he cal
c
ulate
d
value
as pe
r the
stand
ard IS/IEC
6007
9-7.
The
ra
dial
air ga
p value
of
97
0KW Ex
e
m
o
tor und
er
di
scussio
n
i
s
calcul
ated by usin
g
Equation (1). The value of different de
si
gn
paramete
r
s are ta
bulate
d
in the Table
3.
Table 3.
Ra
di
al air gap
d
e
sign paramete
r
s of Ex e motors.
Motor
rati
ng
D in
mm
n in RPM
Core length in
mm
y r
Calculated
Air
gap as per Eqn.
(1) i
n
mm
Maintained air ga
p in
the designed Ex
e
motor in mm
970 KW
700
330
920
1
0.751
0.423
2.5
5.8. Terminal Enclosure for Winding
Conn
ection
s
The
con
n
e
c
ting b
o
xes
are de
sign
ed
and te
sted
for IP55
ing
r
ess p
r
ote
c
tio
n
a
s
p
e
r
IS/IEC 60529
-200
1 for we
atherp
r
o
o
fne
ss. T
he
co
nn
ecting
box i
s
weld
ed i
n
constructio
n
a
n
d
have an
eart
h
ing terminal
in the botto
m part. Th
e
bottom pa
rt is scre
w
ed to
the co
nne
cti
ng
flange of th
e
hou
sing. T
he
con
n
e
c
ting b
o
xes
with te
rminal a
r
rang
ement in
a
c
corda
n
ce
with
DIN
4296
2 a
nd it
ca
n b
e
tu
rn
ed 9
0
°
and
1
80°. T
he
sh
o
r
t-ci
rcuit-resi
stant ca
st-re
s
i
n
in
sulato
rs
are
provide
d
with
in the en
clo
s
ure fo
r conn
ecting th
e p
o
we
r cable t
o
the moto
r. The
ca
st-re
s
in
insul
a
tors ca
n handl
e sh
ort-circuit curre
n
t up to 50 kA for 0.2 s.
5.9. Rotor Ve
ntilation
The m
a
xim
u
m co
oli
ng i
s
provi
d
e
d
by
pro
p
e
r
vent
ing of th
e rotor
co
re. The soli
d
la
min
a
t
io
n
ma
ximiz
e
s
th
e
sh
a
ft
to
r
o
tor
c
o
n
t
ac
t ar
ea
,
incr
eas
ing
th
e
ro
tor
co
re
s
t
iffn
ess
.
Th
e
roto
r
is
co
ole
d
by
axia
l flo
w
of ai
r t
h
rou
gh t
he
ai
r
ga
p b
e
twee
n t
h
e roto
r
an
d
st
ator.
T
h
e
co
olin
g
is a
c
hi
eve
d
b
y
ai
rflo
w arou
nd
t
h
e
e
n
d
ri
ng
s an
d ax
ial
flo
w
th
rou
g
h
the
ai
r g
ap.
Heat i
s
rem
o
ve
d
from th
e rot
o
r by
co
nve
c
tio
n
a
nd
co
ndu
cti
on th
ro
ugh t
he
stat
or
co
re
an
d finne
d frame.
In
a
d
d
ition
to
the
lamina
tions w
i
th
ra
dia
l
du
c
t
s
,
s
pec
ial
s
pac
er
la
mina
tio
n
s ar
e
p
l
a
c
e
d
a
t
s
e
ver
a
l
locatio
n
s
al
o
ng the
axial l
engt
h of the
co
re. T
he
sp
acer l
a
mi
nati
o
n
s
en
sure cool ai
r
circula
t
ion
pa
st the
roto
r ba
rs
an
d th
roug
h th
e st
at
or
wi
ndi
ng
s.
Thi
s
d
e
s
ig
n
allo
ws a
ge
n
e
rou
s
flo
w
of air
thro
ug
h th
e cente
r
of th
e rotor
core.
5.10. Coolin
g
The co
oling
of the motor is de
sign
ed a
s
TE
TV (total
ly enclo
sed a
nd totally ventilated)
heat exchan
ger. It is ai
r-to-air
co
oling
,
t
he
motor exhau
st
flows
thro
ugh a hood, whi
c
h
is
desi
gne
d as
a weld
ed stru
cture. In this
hood, st
ai
nle
ss
steel tube
s wh
ose end
s are
weld
ed
into
the en
d fa
ce
s of the
ho
od.
This structu
r
e
form
s
th
e ai
r-to-ai
r
heat
e
x
chan
ger.
Th
e moto
r exh
a
u
st
flows
aro
und
the tube
s an
d
is coole
d
do
wn th
roug
h th
e se
co
nda
ry
air flow within
the tube
s. T
he
se
con
dary int
e
rnal
air flo
w
is the
r
eby fe
d th
ro
ugh a certified
an
d approv
ed fla
m
eproof (Ex
‘d’)
fan. The se
conda
ry Ex ‘d’ fan is
cove
red by a hoo
d with intake
. The inne
r cooling
circuit
is
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 15, No. 2, August 2015 : 237 –
248
244
sep
a
rate
d fro
m
the surrou
nding
s thro
u
gh se
aling m
easure
s
a
c
co
rding to the
motor protect
i
on
cla
ss.
5.11. Bearin
gs
The roller typ
e
bea
ring
s a
r
e provid
ed in
the motor
as l
o
catin
g
bea
ri
ngs
(do
uble
b
earin
g)
on the drive e
nd sid
e
and t
he floating
be
aring
s
on the
non-drive e
n
d
side.
5.12. Motor
Name Plate
The b
r
a
ss
m
ade n
a
me
pla
t
e of 970K
W
Ex e HT
mot
o
r i
s
provided
on
the
stator body of
the motor an
d it repre
s
ent
s the details
of moto
r and
data of name plate is al
ways u
s
eful for
future references
. The
increas
ed
s
a
fety
m
o
tor m
u
st
have d
e
tail
of moto
r like,
hors
e
power/
kilowatt, voltage, speed, pole, full l
oad c
u
rrent, type of
pr
otec
tion, frame
s
i
z
e
,
manufa
c
turer’
s de
sign
atio
n, marki
ng,
warning
in
scription,
stand
ard ref
e
ren
c
e,
Ing
r
ess
prote
c
tion
(IP), pha
se, freque
ncy, in
sulation
cla
ss,
maximum a
m
bient temp
eratu
r
e, po
wer
factor, effici
e
n
cy, bea
rin
g
detail, t
E
, I
A
/I
N
, test certificate
nu
mber, a
p
p
r
o
v
al numb
e
r
and
addition
al informatio
n as p
e
r IS/IEC 600
79-0, IS/IEC 6007
9-7 a
nd
IS/IEC 60034
.
5.13. Warnin
g Inscription
The warni
n
g
inscription i
s
provided o
n
the motor as “M
OTO
R
SHO
U
L
D
NOT BE
OPENED IN
ENERGISED
CONDITION IN EXPL
OSI
VE ATMOSPHERES”.
6. Testing o
f
Ex e HT Motor
All the relevant tests have
been co
ndu
cted
succe
ssfully on the desig
ned 97
0kw Ex e
HT moto
r. Th
e high voltag
e test, locked
rotor te
st (for measure
m
en
t and det
ermination of rate
of
temperature
rise fo
r the
stator a
nd roto
r, startin
g
current ratio I
A
/I
N
and time t
E
), no lo
ad te
st,
perfo
rman
ce
test/load te
st, temperature
rise
test
s, vi
bration te
st, no
ise level te
st, test for ig
nitio
n
risk a
s
se
ssm
ent and
othe
r releva
nt test
s a
r
e
co
n
d
u
c
ted on
the 9
7
0kw Ex e mot
o
r by u
s
in
g IEC
6003
4 and ot
her relevant stand
ard
s
. T
he 970
kw Ex
e HT motor
have been p
a
ssed all the
tests
con
d
u
c
ted a
s
per re
quirem
ent of standa
rds. The d
e
tails of the som
e
test are give
n in this pap
e
r
.
6.1. Impulse Voltage Te
st Asse
ssmen
t
The imp
u
lse
voltage test
asse
ssm
ent i
s
do
ne to
prove the
capa
bility of the insul
a
tion
system
to
wi
thstand
ove
r
voltage
s
(du
e
to li
ghtning
and
swit
chi
ng
su
rge
s
) t
hat may
app
ear
across it
whil
e in op
eration
.
The impul
se
test
was
ca
rried out at B
H
EL, Bhopal
with the help
of
a
spe
c
ial 2
00
kV - 2
stage
impulse gen
erato
r
s [2
3]. The p
r
ototyp
e sam
p
le
coi
l
(one
com
p
l
e
te
stator)
wa
s
prod
uced fo
r 970K
W
mo
tor. The
coil
wa
s pla
c
ed
in the
b
o
x and
ele
c
tri
c
al
con
n
e
c
tion
s
were ma
de
with the im
pu
lse g
ene
rato
r. The coil
wa
s pla
c
e
d
in t
he explo
s
ive
gas
mixture com
p
risin
g
of
21
± 5
%
hyd
r
og
e
n
in air. The
16.2KV
imp
u
lse
volta
ge was appli
ed ph
ase
to pha
se a
n
d
se
parately pha
se-to
-
e
a
r
th on th
e co
il of motor i
n
the explo
s
i
v
e atmosphe
res.
There wa
s no
ignition occu
rre
d in the ex
plosive te
st mixture du
rin
g
the testing i
n
any ca
se
when
10 im
pulses
of 16.2
k
V
we
re
applie
d. T
he
coil
of mo
tor
withsto
o
d
the te
n imp
u
lse
s
of de
si
red
magnitud
e
su
ccessfully
a
s
per cla
u
se
6.
2.3.1.
4 of IS/IEC 60
079
-7:
2006.
T
he
p
hotograph
of
coil
sampl
e
is sho
w
n in the Fig
u
re 3.
Figure 3. Sa
mple of one coil of 970KW
Ex e motor
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TELKOM
NIKA
ISSN:
2302-4
046
D
e
s
i
g
n
,
Tes
t
in
g
Ana
l
ys
is
of H
i
gh
T
ens
ion
Inc
r
e
a
s
e
d
Sa
fe
ty
Mo
to
r
fo
r…
(Bhagi
rath
Ahirwal)
245
6.2. High Voltage T
est
As
sessme
n
t
The Hi
gh volt
age te
sting a
nd a
s
sessme
nt has
been
d
one
su
ccessf
ully to prove t
he hig
h
voltage with
standing
cap
a
b
ility of 970kw Ex ‘e’ HT motor win
d
ing in
sulati
on system.
The
prototype
sta
t
or ca
psule (one co
mpl
e
te
stator) wa
s
prep
ared for
970
kw m
o
tor to cond
uct t
h
e
high voltage
on it. Then th
e coil
wa
s pla
c
ed in
sid
e
th
e test setup b
o
x and ele
c
tri
c
al
conn
ectio
n
s
were mad
e
to the high
voltage equi
pment. T
he
test setu
p b
o
x was
co
ntained expl
osive
atmosp
he
re
s
of 21% hyd
r
o
gen in
air. T
h
e sin
u
soi
dal
voltages
of 1
0
kV r.m.
s (1.5 times
of rat
ed
voltage)
wa
s applie
d on st
ator cap
s
ule
windi
ng of
the motor rated
970KW, 6.6
kV, 3-ph
ase, 50
Hz for three
minutes d
u
rat
i
on b
e
twe
en
one
pha
se
a
nd e
a
rth
with
the
other ph
ase
s
ea
rthed.
No
explosi
o
n
s
were
ob
serve
d
in the b
o
x d
u
ring
this te
st. The maxim
u
m rate
of v
o
ltage
rise was
measured 0.5
k
v/se
con
d
.
6.3. Stator
Winding Temperatu
r
e Ris
e
The
cold
re
sista
n
ce of
stator wi
ndin
g
an
d m
o
tor tempe
r
atu
r
e
wa
s
mea
s
u
r
ed
and
recorded. Th
en motor wa
s run fo
r se
veral hou
rs
at full load until thermal stabilizatio
n was
attained. The
temperatu
r
e
of stator bo
dy at
every
half an hou
r interval wa
s take
n. Whe
n
the
temperature
s
rea
d
ing
of
stator b
ody b
e
twee
n tw
o co
nse
c
utive
rea
d
ing
s
were
same the
n
it
wa
s
confirmed th
at the motor wa
s thermall
y stab
ilized.
The motor was then switched off and hot
resi
stan
ce
o
f
stator
win
d
ing
wa
s m
easure
d
wit
h
in the
spe
c
ified time
and a
c
co
rdi
ngly
temperature
rise of stato
r
windi
ng is
cal
c
ulate
d
by re
sista
n
ce method a
s
per E
quation (2) [2
4].
e
Temperatur
)
(
)
235
(
/
)
(
1
1
a
cold
cold
hot
R
t
t
t
R
R
R
riseT
,
(2)
Whe
r
e,
R
cold
= Cold resi
stan
ce of stator windi
ng
of motor in
Ω
= 0.278
Ω
,
R
hot
= Hot re
sista
n
ce of stator win
d
ing
of motor in
Ω
= 0.323
Ω
,
t
1
= Machin
e Tempe
r
atu
r
e
at the initial cold re
sista
n
ce measureme
n
t in ºC = 29
ºC ,
t
a
= Ambient t
e
mpe
r
ature a
t
the en
d of t
he ex
ami
nati
on
corre
s
p
o
n
d
ing to
hot
re
sista
n
ce
in ºC , =
27.6
ºC ,
T
e
mp
er
a
t
ur
e
r
i
s
e
(
T
R
) = [(0
.
323 – 0.278
) / 0.278] × (2
35 + 29
) + (2
9
−
27.6
)
= 4
4
.13 ºC.
6.4. The time t
E
for stator
of 970KW Ex ‘e’ motor
Rate of temp
eratu
r
e ri
se:
∆Ө
/ t
E
= a × j
2
×
b , [24]
(3)
And it can be
written a
s
:
t
E
=
∆Ө
/(a ×
j
2
×
b
)
,
(
4
)
Whe
r
e,
∆Ө
= T
e
mpe
r
ature differen
c
e bet
wee
n
limit
ing temperature an
d total temperature
determi
ned b
y
resist
ance method in ºC ,
Total temperature (T) = te
mperature
ri
se determi
ned
by resi
stan
ce
method (T
R
) +
Ambient temperatu
r
e (T
A
)
a = 0.006
5 for cop
p
e
r
ºC / (A/mm
2
)
2
se
c.
,
b = 0.85 redu
ction facto
r
fo
r heat dissip
a
t
ion ,
t
E
=
time in s
e
c
o
nd ,
j = Curre
n
t de
nsity at starti
ng in A/mm
2
,
The ti
me tE
o
f
stato
r
wi
ndi
ng i
s
cal
c
ulat
e
by u
s
i
ng
eq
uatio
n
(4
) a
n
d
det
ermin
e
d
value
is
sp
e
c
ifie
d in t
he T
abl
e 4.
Tabl
e 4. Ti
m
e
t
E
for stator windi
ng of 97
0KW Ex ‘e’ motor
Starting
current
Cr
oss
sect
ional area
of w
i
nding
conductor
Current
density
Ambient
temperature
T
R
T Limit
i
ng
temperature
∆Ө
t
E
as per
equation
(4)
545.7A 41.3mm
2
13.21A/mm
2
40
ºC
44.13ºC
84.13
ºC
170 ºC
85.87
ºC
89.44
second
s
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ISSN: 23
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TELKOM
NI
KA
Vol. 15, No. 2, August 2015 : 237 –
248
246
6.5. Time t
E
for Rot
o
r of 9
70K
W Ex e
Motor
The ab
ove motor is
de
sign
ed for t
e
mpe
r
ature
cla
ss T
3
(2
00ºC), hen
ce limiting
temperature i
s
200º
C an
d maximum am
bient tempe
r
ature of 40º
C. The cag
e
ro
tor tempe
r
atu
r
e
rise of Ex e HT indu
ction
motor can be
calcul
ated
with the help o
f
Joule
s
effect heat balan
ce
equatio
n as g
i
ven belo
w
:
m × s ×
∆Ө
= b ×
I
2
R × t
E
,
[
2
4
]
(
5
)
Whe
r
e,
m = mass of cag
e
win
d
ing
= 469.7 Kg ,
s = spe
c
ific h
eat of copp
er
= 0.396 ,
b = ventilatio
n
factor = 0.
85 ,
I
2
R = cop
p
e
r
loss in roto
r winding
=
Starting torque ×
KW of motor ,
∆Ө
= M
a
ximu
m allowa
ble tempe
r
ature (T3 cla
s
s) – M
a
ximum rated
operatin
g
temperature
(for insul
a
tion
Cla
ss B) ,
The tim
e
tE of rot
o
r
win
d
i
ng i
s
cal
c
ul
at
e by u
s
in
g Equati
on
(5
) a
nd
cal
c
u
l
ate
d
value i
s
sp
e
c
ifie
d in t
he T
abl
e 5.
Tabl
e 5. Ti
m
e
t
E
for rotor of 970KW Ex e motor
Mass of
rotor
w
i
nding
Starting
torque
Kw
of
motor
Max
i
mum
allow
able
temperatu
r
e (
T
3
class)
Max
i
mum rat
ed
operating
temperatu
r
e
∆Ө
t
E
as per
equatio
n
(5)
469.7 Kg
107.6%
970Kw
200ºC
120ºC
80ºC
16.77 second
s
7. Result a
n
d Analy
s
is o
f
970k
W Ex e
Motor
The
relevant
test an
d som
e
calcul
ation
s
are
carried
o
u
t on d
e
si
gne
d 970
kw Ex e
motor.
The differe
nt importa
nt parameters of de
si
gn
ed moto
rs are give
n in
the Table 6.
Table 6. Diffe
rent pa
ramet
e
rs of 9
70 Ex ‘e’ motor
Parameters
970KW Ex e H
T
motor
End user or stan
dard re
quirement
Temper
ature
rise at full load
44.13ºC
70ºC
Ti
me t
E
fo
r stator
89.44 sec
≥
5 sec
Ti
me t
E
fo
r roto
r
16.77 sec
≥
5 sec
Ti
me t
E
fo
r trippin
g
device of Ex e
motor
≤
16.77 sec
≥
5 sec
Efficiency
at full load
95.86%
≥
94.0%
Pull out torque in
p.u.
2.388
2.3 p.u. (p
er unit)
Speed at Full loa
d
330.7 rpm
330 rpm
Slip at Full load
0.00789
0.008
Starting current
545.7 A
550 A
Starting torqu
e
in p.u.
1.076
1.0 p.u.
Power factor
at f
u
ll load
0.739
0.72
Core losses at no load
10.86KW
≤
12KW
Stator copper los
s
es at full load
14.66KW
≤
16KW
Rotor coppe
r losses at full load
8.0KW
≤
10KW
Ratio Starting cu
rrent/
r
ated cur
r
e
n
t (I
A
/I
N
)
4.23
≤
10
Total Iron a
nd C
u
losses
33.52KW
≤
38KW
It has bee
n
o
b
se
rved
that
starting
torqu
e
, total lo
sse
s
, spee
d at
full loa
d
, tem
peratu
r
e
ris
e
,
s
t
arting
c
u
rrent, c
u
rrent dens
i
ty, effic
i
enc
y
, time t
E
of stator, time t
E
of roto
r, po
wer fa
ct
or
and full load
slip all are the well withi
n
the limit
and as pe
r the re
quire
ment of the end u
s
er
a
s
sho
w
n in the
Table 6. The
analysi
s
of so
me paramete
r
s an
d re
sult
s are given bel
ow:
a)
The stato
r
wi
nding of t
he prototype de
signed moto
r su
st
aine
d su
ccessfully impulse
voltage test a
t
16.2kv and
high voltage t
e
st
at 10kv in
21% hydrog
en atmosphe
res.
b)
The d
e
si
gne
d ra
dial ai
r
gap i
s
mo
re
than the
ca
lculate
d
valu
e and
maint
a
ined
2.5mm air g
a
p
to avoid an
y sparkin
g
b
e
twee
n roto
r
and stato
r
du
ring runni
ng t
h
e
motor.
c)
Iron loss a
r
e redu
ced by ut
i
lizing hi
gh grade sili
ca
ste
e
l.
d) The
I
A
/I
N
ratio is 4.23 whi
c
h
is less than 1
0
.
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