lecture of power electronics
DESCRIPTION
The document makes the entire lecture or collected details of power electronics. Department of Electrical Engineering Indian Institute of Technology, BombayTRANSCRIPT
1
Power Electronics
Prof. B.G. Fernandes
Department of Electrical Engineering
Indian Institute of Technology, Bombay
Lecture - 1
Power Electronics
Hello, I am B.G. Fernandez. I am with the department of electrical engineering, IIT Bombay. For another forty lectures or so, I will be dealing with various aspects of power electronics. Now, what is the definition of power electronics and what is the goal of power electronics, I will tell you sometime later. Power electronics is one of the basic courses in electrical engineering. It is a very interesting course, an important course and relatively easier to understand. So, all 3, in 1 course, very interesting, very important and relatively easy to understand. So, it is a very basic course in electrical engineering, it can be termed as course on circuits. I will be using Kirchhoff’s voltage law, that is KVL, Kirchhoff’s current law, that is KCL and behavior of inductor and capacitor for DC excitation and AC excitation. So, these are the prerequisites. Definitely, all this topics you would have studied in your eleventh or twelfth standard. Having said, that power electronics is a basic course, to appreciate this course, you need to know or you need to have reasonably a good knowledge on circuit theory, good knowledge on electrical machines, power systems, power semi conductor devices, little bit of device physics. So, if there are devices, definitely you need to know, little bit of analog electronics, digital electronics, control theory and microprocessor or micro controllers. So, in this sense, power electronics is a multi disciplinary course. So, little bit of almost all the branches and all the subjects in electrical engineering is been covered or you need to know the various topics to appreciate this course. So, I will not talk much on this course, I expect you to explore more about it, during the course. So, the outline of the course, I have divided into 6 parts.
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Time: 21:26)
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Time: 22:35)
the reason econd is usee on renewabermal powerer plant, waburning of fitrogen diox
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aste handlingfossil fuel? Txide NO2. Cgoes on inc
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pollution. Noyou do som
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is a solutionnsumed by eoads are indFan, pump,duction mace of loads. stant for all pDC machinege much anmes another
fficiency, cand if possibre associatedWhat is the ety of nucleaioxide, ozon
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Refer Slide T
Now, if you whe air deliverbout high kiischarge, whrovide a reseduce a dischrottling walo reduce, theolved. You he dampers, nput, remaipproximately0% or 50% utput. Insteable to regulahe case of pu
as been prowell as power
be significato save 1
y fuel can by inductionBut, sort of portional to
ok here, fan tportional to o
Time: 28:45)
want to redured by the failo watt fan hat will you sistance to tcharge. So, bll for the pume air suppliecan reduce toutlet damp
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oduce globalr that is bein
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what happens
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ed characterihe speed. TL
s proportion.
harge throught talking abod in a indusyou use damair or use a
g the dampemay be able tutput of the ischarge by
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you try to sad by motorserall saving t the load said bulk o
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the air flow,e drive, te closed the ame. We areelf, speed ofe able to reg
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ave on this s if you try tof the electrend, 6 kilo
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ese loads. TL
ional to squaa square. So,
or you want atts fans, I awant to reduother wordswall for the
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e able to regf the rotation
gulate the dishere.
power on to reduce, ric power. o watt of r is being pump or
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to reduce am talking uce the air , dampers
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taking ll whether gulate the n. We are scharge in
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ower inputsatio is 1 oveonsumed, if o, you are tischarge dep
Nothing comhe machinesonstant spee
want to channergy I wan
machine, we motor runs appeed of the requency coonstant volpproximatelyrequency souf now, becahat voltage a
we require a sing the frenergy. Whatirectly switc0 hertz, induraws a largeo come from
Time: 31:27)
, suppose ther 8. So, thef you reducetrying to acpending upo
mes for free. s or for thated motors, apge or regula
nt to vary thhave to chanpproximatelrotor, how
onverter bectage, assumy constant. urce, there i
ause I want band frequencfrequency co
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e ratio of twere is a sign
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med to be Variation is
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nverter, I tolher advantagesupply voltaine, what hauld be of thet force throu
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s very smalBut then, I
he speed of , we will seevary the speld you that es? What ha
age and suppappens if I die order of 6 augh the cable
point 5, omuction in theone-eighth,
gy as well aent. But thenachine, almo
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nous speed ibeen supplievoltage andl. So, constneed to charotation. Noe some timeed, of the inwe are able
appens the inply rated freqirectly start ias or rated. e to the mach
ega 1 to ome power thatsignificant r
as regulate tn again, at wost for that minduction ms. Here is a
o, in order tothe case of
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d frequencytant voltage,ange the freqow, what rele later. So, anduction mace to save onduction maquency. So, 4it or DOL stNow, that cuhine. So, the
ega 2, the t is being reduction. the output what cost? matter, all
machine or process, I
o save the induction induction
reduce the require a
utilities is y remains , constant quency as lationship
as of now, chine. So,
on electric achine if I 415 volts, tarting? It urrent has
ere will be
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voltage dipmomentarily,s a large curlow. So, a slowing throncreases. In
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told you, aeducing the
will tell you.requency of nd output voutput frequerequency, I homes down.liminated, stooks like, tholtage dip gef the machined by a contably, deliveeen applied.nd it is the r
p. That is w, the intensitrrent shouldstress on theugh the maother words
ns if I try ts minus Nr. Nthe rotor. Sorting, slip is
w, if I reduce
Time: 36:35
as of now, Ifrequency, I. As of nowthe output.
oltage, we wency can be rhave to redu. So, if the tress on the
here are lot oets eliminatene improves
nstant voltagering some l. So, b is corated flux be
why, in the sty of the buld flow throue cable is aachine winds, life of theto reduce thNs is the syn
o, Ns minus Nequal to 1. the frequen
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sense, whenelk comes dowugh the cablalso more ifding. Stresse machine che frequencnchronous spNr is nothinSo, Ns minucy, Ns has c
alking aboutduce a voltagd a frequenthe relation
e time later. Scomes down
voltage alsoof inrush co
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next? What uency supply
Input voltais constant,
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ng but SNS.us Nr is equ
come down.
t reducing tge also. Reasncy converteship what bSo, if I am trn. It so happ. So, magnitomes down,proves the lble to save tets eliminatehappens in y? Say 415
age is 415, r, flux in the rated voltag
ut on large he voltage dipa rated currestart. That
machine windn, if I directlf the input f
by P minusS is slip, slid
ual to Ns itse
the frequencsons, sometier. It has toetween the frying to redupens that as Itude of inrus the voltagelife of machthe power, sed, reduces rthe machine, 50 hertz irated voltage machine, isge at rated f
hp motor, p. Second ent it can current is ding also ly start it. frequency
s Nr. Nr is de me hai elf during
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o, area flux The core losshat load of torque. If the
Assume that lso keep chlux remains osses also vaor maximal eow, am negirectly fromnd if the looaded, efficifficiency of ondition forosses. Whenosses have cemained samy reducing to the motor.here is an auhe size of thes well as aut
By the way, hegulate the seduced voltaegulators.
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is the rated ses, core losthe motor ise load of thit is changianging. Youconstant, co
ary. Now whefficiency isglecting the
m utility suppoad of the miency of thef the motor r maxima en the load oncome down, me. Now, I wthe air gap f. How do I uto transforme machine itto transforme
how are we vspeed of theage to the m
Time: 43:25
flux. Therefsses remain s varying. Inhe machineng, the variu have kept ore losses rehat are the cs constant lo
frictional aply, wherein motor is of e motor is vwhen it is fficiency is n the motor
constant lowant to reducflux density.vary the inp
mer. The siztself. So defier, plus it is
varying the e fan. What otor, in orde
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fore, the conconstant, b
n other word is varyingable lossesthe input v
emain constaconditions fosses should
and wind aginput voltagvariable typ
very poor. Slightly loadvariable lo
is varying,osses have rece the core lo That I can put voltage ze of the autinitely, it is bexpensive.
speed of theexactly are
er to reduce
nstant losses because flux ds, motor is , that is a which are f
voltage consant. Load is
or maximal ebe equal to
ge. So, if I ge is assumepe, when thSo, it is posded by decross should bmotor is lig
emained samosses. I can rdo by reducto the moto
to transformbulky, entire
e fan? We arwe doing?
the speed. S
also remain is constantsupplying aprocess req
function of lstant. Theres varying, soefficiency? Cvariable lossam feeding ed to remainhe machine ssible to impeasing the fbe equal toghtly loadedme or core lreduce the ccing the inpuor? In the la
mer could be e, overall set
re using a reWe are app
See here, her
n constant. t. Assume a variable
quirement. load, they fore, area o variable Condition ses. As of a motor,
n constant is lightly prove the flux. See,
o constant d, variable losses are ore losses ut voltage ab, maybe
as big as t of motor
gulator to plying the re are two
13
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Refer Slide T
ee, here is aan have a vteps, it is a unction, reguan see just witchboard, f it gets hot,ow, very eleegulator to, ometime late
one, very rume this regulmount it on th
o that to coor, these are tvery low. Inomes hot. V
Time: 44:27)
another reguvery smooth
contacted tulate the spethe knob, smdefinitely, h
, definitely wegant. How such a smaler.
ugged. Variatlator becomehe switch bool the entire the openingsn other word
Very raged, m
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ulator. You h control, vetype. Here,eed of the famooth contr
heat dissipatiwe have to mis this poss
ll elegant reg
tion is in stees very hot, oard and therset up. Thers and it becods, when yo
may be.
could have ery smoothlyvery smooth
an. It is mourol. So, if ition is negligmount it outible, from sgulator? Ma
eps. If I keepextremely hre are lot of re got a resisomes very hou introduce
seen a smaly varying sh, both of t
unted inside tt is so smal
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p it in very lohot. That is t
openings hestance inside
hot when thee the resistan
ll elegant respeed. Here,them doing the switchboll mounted ie is a heat dieat dissipatiosive regulatuestion, I wi
ow speed, the reason ere for the e. To cool e speed of nce in the
egulator. I , just see, the same
oard. You inside the issipation, on is very tor, heavy ill answer
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o, here is ans a power selectronic equonducted deesistor. This ome, very efficiencies sariation in s
Overall conve
o, coming bwhich is drivhe machine. t lighted loa
What is thirdhe speed itserequency hase variable she US. Why
Time: 46:01)
n internal stremi conductuipment. Thevice, this is
is a power selegant, lighhould be vespeed, dissipersion efficie
ack to the thing a load oSo, we can
aded conditid benefit? Seelf is varyins been chanspeed drives? May be en
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ructure of thted device. I
his is one typs the one, Lsemi conducht weight, vry high becapates powerency is low.
heory, if I canf variable lohave eta is eions. How tee, I was tolng. Speed ofnged, in 70%. Whereas, inergy, cost p
he regulator. I told you spe of a pow
L, C and smcted device …very small, ause there isr, so definiteSo, this is a
n try to reduoad, it is posequal to eta to do this? Wld that in Japf the motor
% of the air cinstead of thper unit may
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wer electronicmall small re…… So, thino heat di
s no heat disely, power c
another exam
uce the inputsible to impmax, of maxWho will apan 70 % ofitself is varyconditioners
hat thing justy be very low
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must be very expensive. Looks like, everything has been driven by economics. What is the use of using a variable speed in air conditioners? Or to understand that what happens in the window air conditioners that are been directly switched on or off. There is thermostat inside. Temperature is being controlled within a band, hysteresis band. When the temperature falls below a certain value, AC is put off, temperature starts increasing and when it crosses upper limit, AC is again switched on. What is a problem here? Same problems, direct online starting of induction machine, voltage dip, voltage cable wire or stress on the cable and machine life comes down. Instead, can you vary the speed itself, slowly accelerated, so you can now, you can control the temperature, very smoothly. Very smooth, control of temperature is possible, air conditioners as well as refrigerators. What next? slip ring induction machine. When do you go for slip ring induction machine? When the power rating is high. For low power motors it is invariably, squirrel cage is the constructions, cage rotor. As the power rating increases, slip ring induction motors can be used. So, in any induction machines, s times the air gap power input is dissipated as heat in the rotor. So, air gap power input is approximately equal to input power itself. So, s times the input power is dissipated as heat. Now, instead of dissipating as heat, can this power be fed back to the source? Yes. Can I recover? What are the power that is there in the power that has been dissipated as heats? Can it be fed back to the source or is it possible to increase the starting torque and decrease the starting current electronically? Yes, our machines teacher has told, connect a resistor r to the slip rings, whereby, reducing the starting current and increasing the starting torque. Can you do this electronically? See, I am posing various problems to you and at the end. We will see, whether this problems can be addressed using power electronics. More on this, we will see in the next class. Thank you.