DEPARTMENT
S
OF
FACULTY
OF
a a j Xio"
B.ENG SECOND ENGINEERING, UNIVERSITY
ENGINEERING
OF BENIN,
SEMESTER
BENIN CITY.
Date: Wednesday, 29th EEE 538: ELECTRICDEGREE
EXAMINATION
DRIVES
AND POWER (2012/2013 SESSION)
January, 2014 @8:30AM
nstruction; Answer any Four
RSFixI0$}7Sse
ELECTRONICS
(4) Questions in all with atDuration: 214Hours
Ttai
least one
ELECTRICAL/ELECTRONIC
,
Section 1
(1) from each
section.
P
F
1.
14ScXi
115
(a) The
University of Benin is
developing an eight story
are
complex for administrative use. Six
planncd,
with each
elevator cabin
of 10. The
weighing 1.2 tons and
speed of the electrical drive
passenger
should
be
passengCr weight is 75kg.
between 0.5 and 1.2m/s and capacity
Assuming the average load
full load for
average
is
elevators
cycle maintained as follows:
85% full load for
100%
10mins,
75%
full load for
for 6mins and
8mins,
50%
fuil load for
).An appropriate size of motor for 0% full load for 5mins. Select;
the
PFV
i). The motor
elevators, assuming an
type and mode of
efficiency of
10mins,
8mins, 30% full load
(b)i) Wny
is the
starting torque
motor? (2mks)
1).
Develop
an
(8mks)
ii)A3phase
vaue of
expression
5OH2,
8
of
a
wound rotor motor
for that the
poles wound
starting resistance that
Cons:ant torque and rotor
2 (a) i). Develop
transmission stating your reasons.
starting torque
rotor
can be
induction
used
resistance/phase
an
of
superior
a
88% (7mks)
(3mks)
to that of
a
squirrel
wound rotor induction
motor.
motor runs at
to
lower the
of 0.015Q.
(5rnks)
slip
a
speed
of 1.8%. Find the
to 38%
assuming
expression for the heat rise in an
).A motor with
electrical machine. (10
thermal time constant
of
has
45min, a final temperature risemks)
continuous rating. Find the
of 75°c
rise after one hour.
What will be the
temperature if the heat rise temperature
is 75°c on one
(5).
A
i). The
on
to
speed (2mks)
) The gross torque. (2mks)
ii).
a
maximumn
hour ratins?
(5mks)
DC shunt motor has
60 slot and 20
resistance is 1.310 and the full
conductors on each
load current is 50A.
Take useful flux
4-pole, 500V, lap-wound
slot. The armature
be 23mwb. Find
cage
Üesign
a
D
mot
hes .nde phes
starter for the motor.
(4mks)
iv). f the speed as calculated
above is desirable and the
starter is replaced
electronic control, what will be
by an
the firing angle of the
an Ac source
SCR,
is 1200sin@v.
assuming fully controlled
(2rnks)
and
P2P tP, fPr3, 136347sxIo +I1e tSNo tg776.c
t tty-tt
Lo
t Gs17 3
to
DEPARTMENT OF
ELECTRICAL/ELECTRONIC ENGINEERING
CKMADT)
A
is
fets
3110 rx6
3G5.97/ a94ki
FACULTY OF ENGINEERING, UNIVERSITY OF BENIN, BENIN cITY.
B.ENG SECOND SEMESTER DEGREE EXAMINATION (2013/2014
SESSION)
EEE 538: ELECTRIC DRIVES AND POWER
ELECTRONICS
Date: Friday, 14th November, 2014 @8:30AM
Duration: 24Hours
Instruction; Answer any Four (4) Questior.s in all, with at least one (1) from each section.
Examiners: T. Aika, E.l. Ibhadode and G.0. !mhabekhai
1.
(a) With the aid of
a
well labeled
drive system (Smarks
(6) Explain briefly
c
the types of
With the aid of a well
Section A
ricgram, explain
electric braking
the
system
labeled 3 point starter,
starter. (8marks)
grading of a six stuad
d) A 200V, d.c. shunt
various Components of an electrica
(Smarks)
develop an expression
for the starting resistance
motor takes a full ioad curfent of
12A. The armature resistance is 0.30 and
the field circuit resistance is
1000. Calculate the value of
resistance in a 5 steps, 6-stud starter
tor the
motor. The maximum starting current must
not
(6marks)
2.
(a)
The
Tve
manager of
operations
a
with
factory
a new
Speed
Wnat are the
has
single
deci ded
and
Recommend a suitable elacr
With
N.
oisac: anteges
(3marks
1.5 times the tuil load Current
individual
drive machine
seven
Otthe new
me:nods
moto
type
o r the
the
ASSUnming
machine
at
pertorming
ditterent
>tate two
said dive
aid of
tne
diagram, il'ustra:e a method oi staring the
motor s a Cmoto descrice an electronic
a
motor
means ot
Speed. 2marks
i . What
operations
system and state your
assuming a var ate sceed and
nign
is
starting
torque desired. Draw the
speed torque
characteristic 4marks)
reasons
moror
to raplace 5
crive machine capable of
advantages
pOSs.ble transmiSsion
exceed
(2mark)
contreiling
tne
load equaization and ho: is it
acihleved practicaily?
i. A 6 pole, 50Hz
(2mark)
incucion motor has
or
lywneel
as
1200kg-Im
moment
ot inertia. The loac
orque s 100kg-m for 10 seconds. No
lcad period s
ong eno
or the
fu!! speed. The
tiywheel, to regain its
motor sli is 6% atatorcue or sokg-m. Calculate'
the maximum
Dy the motcr
torque exerte
a13 tne speed at the end ot deceierat
is
c)i. Why is high te mperature undesirable
ii.
At full
hours.
loac,
Find the
(5 marks)
tne
temperature of a 10HP
heating time constant and
in
on. (5mark)
eleCTImotors operation?
motor
25°C aiter
temperature
was
the tina.
(2mark)
one hour and
rise on
40
atter two
tull load.
Section S
3(a). Define the following terms as
they relate to electric drives:
(i). Power Electronics, (i)
Holding Current, (ii). Latching current, (iv,.
Thyristors?
(4
marks)
b.Explain the concept of the TWO-RANS:STOR model of
SCR and derive the
expression for
(8marks)
(C). A thyristor circuit is shown
in
figure
Q3
SCR
90 V
250
0.5H
- P E
V v C ( -
Figure Q3, a thyristor circuit
The thyristor has a
latching current of 40mA and is fired by a pulse of width 40uS. Find
current and state
if the SCR will be turned ON or NOT, giving your reason? (5 markS)
d. With the aid of diagrams, Discuss the
operation and characteristics of thyristors?
(8marks)
C - e
the gate
4 (a).Why are rectifiers using thyristors called controlled rectifiers?
(1
(6A half-wave controlled rectifier connected to a 150v, 60Hz source mark)
is
supplying a resistive
oad of 10.0. If the delay
angle a is 30°, find
(0). The maximum load
current, (i). The average load voitage, (ii) The
average load current, (iv)
The RMS load current,
(v) The power supply to the load, (vi) The conduction
The
frequency. (7 marks)
s(C). With the aid of a diagram
angle (vii),
and
waveform,
center-tap rectifier circuit? (8 marks)
Discuss the operation of
a
ripple
full-wave controlled
F). half wave controlled rectifier is supplied from 120V source. If the load
resistance is
Find the load
voltage and power to the load for the following delay
angles
(1). a =0° (2) a =45° (3) a =90°
A
100,
(4).a =135° (5) =180° (5
(i). (). why are diode rectification called uncontrolled marks)
rectification? (1 mark)
i). What determines if,a Converter is single phase or three
phase? (1 mark)
(ii). Where do you find diode rectification useful? (1
mark)
(iv). Where do you find thyristor rectification useful?
(1 mark).
5.
(a) Briefly explain the following
for plant process
(7.5 marks)
Section C
terms
as
they anply
to the
development ofa control strategy
Input Variables
i.
N.
Output Variables
Safety, Environmental and Economic Considerations.
Feedback Controllers
Feed forward Controllers
ALO
(0
1.
with the aid of a
diagram, briefly describe
the
Conceptual process control block
dagram. (2 marks)
.
input/output representation of the
Explain the three classifications cf electric drives.
(3 marks)
Highlight five guiding factors for the selection of a motor (2.5
marks).
1.
Highlight the relationships which specify electric motor
characteristics. (3
(d) Obtain the Laplace
transfer function for the figure Q5 below
if the
is
(c)1.
PID Controller
expressed as
Z1
Ei(s)
Z2
marks)
k(1++Ta5)(7 marks)
C1
R2
R4
R3
R1
Ei(s)
E(s)
Figure
6.
(a)
Q5:
Electronic
i. What is
ii.
PID
Controtier using
E(s)
Operationa Amplifiers
Variable Frequency Drive
{VFD!? {2 marks)
List the main sub-systems of a VFD and
give short notes
a
on them.
ii. List the
(3 marks)
sub-systems of the VFD Controlier. (1.5 marks)
(6). i. Give short notes witn the
aid cf a diagram of each of
these AC drives
(3 marks)
topology 5elow
The Voltage-Source
Inverter (VS!) G: ve
The Current-Source Inverter
(CS!) drive
topoiogies
topologies
i. Draw the iour
quadrants
efectric motor
chart with
speed-torque
on the chart, and
define these four
quadrants.
(5
marks)
c). i. List three drive
the
quadrants
control
ii. Give short notes
(3 marks)
d)
With the aid of
(6 marks)
a
on
platforms suitable for industrial
application. (1.5 marks)
dynamic braking drives and
regenerative braking drives.
diagram,
derive the
equatio
ior the
closed-loop transfer function.
named
DEPARTMENT OF ELECTRICAL/ELECTRONIC ENGINEERING
FACULTY OF ENGINEERING, UNIVERSITY OF BENIN,
BENIN
CITY
B.ENG SEcOND SEMESTER DEGREE EXAMINATION (2014/2015 SESSION)
EEE 538: ELECTRIC DRIVES AND POWER ELECTRONICS
September, 2015 @8:30AM
Duration: 24Hours
Instruction: Answer any Four (4) Questions In all, with at least one (1) from each section.
Date: Thursday, 3rd
Examiners: T. Aika, M. Igbinosa and E.I. Ibhadode
Section A
(a) ExXOnMobil
3.
Nigeria has developed an oil field, the well depth is 4,300t. There are several
pumpjacks (eonsisting of several pulleys) in the field, cach pumpjacks. nInIIS aort SO
barrels a day, none stop and are powered by an clecetric motor. Recommend a sitable Drise
Sysiem m tlerms of rating, voliage ype, siartng nmtihods,
transmission Ssie
Staie yo
reasons for the choices and use diagrams to illustrate the starting circuitry and specd tOqUe
charactcristies of tlhe motor. Comment on the speed torque eharacteristic with eseci io
yne of load. Assume 0.85 ellicicney. (11 Marks)
Hint: (A barrel =159 liters, 1 foot =0.3048m and density of erude
=S40kg in*)
( )1. iiigh and very low temperatures are undesiabie in electrie motors applieation.
Explain.(2 Marks)
i). An electric Motor with class F (155°C) nsulation has life span of 2s.00t h s we
will be its life span if it is
operated at 20°C higher han its noma. iomne.
Aati
11). he tenperature rise ofa 20KW should not evcesd s0°C aier one hour on one:loai
he temperature rise on full load atier ! hour is 30°C and 40°C atier 2 hours
are
proporlional
to the
Assme iosses
square ofthe load, ealeulate the maximum ovorload power (S
NMarhs
.(a) i). xplain briefly, why we ned electrie drives nd state the factors that can inise s
choice of electric drives. (5 Marks)
ii). Why are ilywhecls mounted on electrie motor shaf? (2 Marks)
iin). Ditferentiate between the spced control prineiples of \e laduction and De moieis i
diagrams to illustrate speed control methods in ie series motors (5 Marks).
(6) i). A 200-vV, DC. Shunt Motor takes a ful-load current of 12A, the armature siut
resistance is 0.30 and the field resistance is 1000 design a 5 step starter io
(S Marks)
i7).f the notor above is controlled through an SCR and the Ac suppiy vetege
300 sin@, Assume ls =100juA, Ve = 0.5Vand Vo = 0.7. Find the range ot adiustment
variable resistor that will trigger the SCR from 30° to70°. ilustrate it with a diogram
(3marks)
Section B
3. ( ) 1). Explain the application of' a thyristor as a line frequeney phase rectitier (4 Marks)
i) With the aid ofa well labcled diagram, explain how forced comnuaation can he seto
Switch a thyristor from the forward conducting io the forw.ard blocking state. ist wo th
methods that can be used to achicve this Operalion. (4 NMarks)
ii) Differentiate betwcen repetitive and non-tepetitive overload ratings of a tyistor.
(2Marks)
(b) 1.With the aid ofappropriate diagrams and using Fouricr series analysis, derive a
mathematical model for an inverter. From this model, explain wiy further filtering of'thea
se
as"
WCo:tisecessary. (S MMarks
e
N
re-ering meilhod needed i
SOrce nVerior'. 2irks)
. a . Draw a ci:eui:
tealiation ofi buck
CrCut aid heice
derive ihe
iput vOliage and duty
expreSSiOI:
i o r to
supply
a
capacitive
ioad using
i
Vo.tage
coi rter. Usn aropriate circu:t lawS
oup! Voltage ot the buci conVerter i1 and.ys
terins
of
this
cyele.
d he
gropii iis relatiotsihip. (5 Marks)
.Lsignn ior the !mduciorSketch
Value.
pcan ripple currents torà covior inik
suppiying a1 SA :o2? a i2V supply averig
is
wih a
capaciior conSiioring tit the
smitching requeney o !00Hz. A!so
buck convertrs
tne
capaciiorS Connocied in
ou:put capacitor 1s torined of - design
witi:
para!lel
a:: cifec.ive
The
clecirO.ytie
maxinum a.:owabie
series resistanee (each) ot
ripple
is 20°%
conient in the
Assume
SOms2.
iit
of the ou:put current.
cuut voltage is 5and the
(9
Maris)
inductor
Wth
(C).
ihe aid
rpple currei
f apropriate
diagrans,
32dc1Ce, show how
ihe
explai:
operatiqn of tlie single piase
it can be :sei o
realize a utput ac
Wih iovi
Cycioconvicr
sign3l:
er frequeney tiiui iie
)
np i Sigiidi
a
Section C
3.
(6 Nirks)
(a) i) With the
aid ca
bric:ly descrithe input
cOiccptul prOCess co:iroldiagr:am.
b!ock
output representatiOn
11) Dia tine coirol r
diagri. (2 rks)
Cxpiait2
the teIims
deveiopieni
O: a
() i). hat is a
iecdback cOi:olicrs
co::i"o! si
egy :7
aid
ittnePD controi.er
6 Marks)
*Cess Orol !oc:
***
...
***
tise . o :
is
drois.
expressed as
(
tie
arks)
.iSts the nai:
(Dra the fo11:
ccri and dei::e
ot
{5 l:arks)
1:irks
E: =hp!
-
TS) and define
the
terms
R3
E
Fgure C5: Eiectroi:P
ContOiler using Cpe"ai
OT
Facultyof Engineering
Hectrical/lectronic Engineering Departnent
B, ng. (lonours) Degree Examination, 2017/2018 Academic
Session.
Course Title: Electric Drives and
Power Electronics
ofamination: sh October, 2018
xam Duration: 3 Hous
Awnd Nemeer
aie
Niio:
nsner five
wmin
()questions,
three (i) froni
sectio
A
proposal
for
7 1ikd and G mhabekhai
To Nlate pvement han
) ()
and wo (2) J*om section B
SectionA
requested
for
mini
waler
work
Ekpoma
level is about 1500ft from the
l e v e l The Submersible mechanical
pump s to be powercd by an clectric
notor. (i).
ommmend a suitable ratnp of the motor
that
the
water will be punped to a height of
assuming
a
e the pround level, (i). Assuming that the motor is an induction notor, illustrate te
h a l c i mork
is to
supply 100,000 Iitcrs
of
a
m
watci/day. The water
e d o c haracteistics of the motor and make
neccssary deductions. (iii). Statc also the
. n g neihod and cxplain your reason(s). Assume the motor
cfficincy is 88% (T
1 . 5 10 m'/s, I
b).
itlh the ad ola
akeDclivery
toot-0.3048n and density of waler 1000kg/m') (8mks)
suitable diaprann, descibe
cquation
the hasic
nks)
a)).
plan bricly
.tical
the methond
exanmple. (nks)
componcnt
of
drive syslem. (3mks)
from a well-illustrated cquivalent 1otal.onal
( Wite the torque
ofa motor-load sysfcm
N C , deine al|
tems,n the cquation and íake the
of conurolliny
the
necessary
speed
of
a
a
deductions from the cquation
de motor and
hiyilighi
in
cach
(u)
l n brietly the various metlod of
aclieving breaking
)u). Wuh the aid of a well labeled 3
in
DC
motors
(3u1ks)
point
develop an expression lothe stuling
sI
gadn: ol a six stud stanter. (5mks)
A
(
oe iOV d ilunt motor runs l
1000rpm. Whcn loaded, the cuITeít is 12,. I| tihere
s e s lield winding of o 22 cach and
amature resistance of 1.02, find íe speed oi the moto
i l me conncctol in IWo seies
with two parallel
paths. Assume tát the ficld we kens by
iih ann1.atue cuuicnt when parallel 20/A.
(mks)
starte,
is
a).
\Wiy
i)Shon thar
is
lo
tenperature
clecunc
n
ise
dive.
undesirable
the
avcrage
in clectic
drives? (2mks)
tcmperature I1se (0) 0.632 1. Detine all
reNpressom (omks)
terms
.Wiulh the id of the
Specd-torque/time
hali ola
lauge clectue drive (2mks) L graph explain why a llywheel shoutd be coupled w
o-oles, 60112 nldction motor has a
of
1200kg/m* as moment of inertia. "The load
100kg-1m for 10sec. No load jperiod flywheel
is long
enough for the llywheel to regain itsfull speed.
h a s sl of oa nd the
torque of 50Kg»nm.
s
a
()
Spced
at
the end ol deeeleration. (5mks)
Page 1 of 2
9m
Calculate. (i) Maximum
torquc exeried by
.
Oer e Oen-i0or :sen {
vioo: i e
-ccr.id
ar
b) ig '4 epse:
i2
iLti)::
iranse
Of the 70.0X
Detine aii ie studd paraniee:. (ks
R
V
'n
.
g
Q4. An Armalu-Contro!iei Dc Mo.0
Section E
( a ) . iST!ciiy icscrire: -1ypc
N.pe matciai aid explai. ior ney
are used 1o
p:ciuce
P-Njuietion c:do. (ó m:s)
(b.A,is'i, iituit is siown irig .
SCR
25
-r-,
I C
TiE2*
:.
.
'
i
h
.'
iou? vnl.i,
i
sii
SS.
gics
:rd.: d v s
tnperiur: 2
a : r?sisi:10
.
D
3Ü
t
Wih a iuiwaid as L a : . d the juciic: is opc
ine saiu"i.01 ¢
en.o c
b). si ii: t.c coriceni o ti: TW CTRAN*:SiOR zcde
g
dcd:? (4 nlks;
SCR and derive the cxpross.on
).eline he luiowing teims: (i). riciding Curenf. Latching euzreut i). Thysstcr? (3 shs
7(a). A haif-wa.e con:rolizd rectificr conne.ced to a 10v, 50H2 soaro: is supplying a resisive
O: o 10Q. If he ieiay utgic a is 4S, find: i). tke naiui ioad curren: ) . The arag: 'od
voltage (ii). Tihe avorage lcad curren (3 mls
b). With the aid of diegrams, Diseuss the operaiop a
shorasteristics ofthyristo: (8 mias)
( . i w a tran:isic: iCii to shCw ihe eem.: m i i r2oniyuraticn and siate its anplicaion?
(411ks)
Page 2 :
2
a