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HOWTOMINIMIZEIRONLOSSESINTRANSFORMER

Abstract

It is almost impossible to reduce the iron losses completely; however these can

bereduced

to

a

certain

extent.

Here

we

havemade

an

effort

to

reduce

the

eddycurrent lossby reducing the iron area of core. It has beendonebyembeddingananti

ferromagneticbarof copper in iron core by keeping total areaconstant. As we knowthat eddy current lossoccurs in ferromagnetic material instead ofanti ferromagneticmaterial so path length of eddy current will get reduced by inserting antiferromagnetic bar in hollow part of ferromagnetic core. As we know that eddycurrents flow around the magnetic flux whileenclosing it, theembeddingofcopperbarwillreduce thepath length of eddycurrent thusreducing thetotaleddycurrentloss.

Keywords:Antiferromagneticmaterial,eddycurrent losses, hysteresis losses,andtransformer.

I.

Introduction

The transformer is one of the simplest ofelectricaldevices. Itsbasicdesign,materials,and principles have changed little over thelast one hundred years, yet

transformerdesigns and materials continue to be improved.Transformers are essential in high voltage power transmission providing aneconomical means of transmitting power over large distances. The simplicity,reliability, and economy of conversion of voltages by transformers was theprincipal factor in the selection of alternating current power transmission in the!arof"urrentsinthelate #$$%&s. In electronic circuitry, new methods ofcircuit design have replacedsome of the applications of transformers,butelectronictechnologyhasalso developednew transformerdesignsand

applications.Transformers come in a range of si'esfrom a thumbnail(si'ed couplingtransformer hidden inside a stagemicrophone to )iga watt units usedtointerconnect large portions of nationalpower grids, all operating with thesamebasicprinciplesandwithmanysimilarities intheir parts, transformers alone cannotdothefollowing*

+ "onvert"toA"orviceversa+ "hangethevoltageorcurrentof"+ "hangetheA"supplyfre-uency.

However, transformers are components ofthesystems thatperformall these functions.

Thispapercontainbasicprinciples, lossesoftransformer, separation of eddy current andhysteresislosses,howtominimi'e lossesandrecords and calculations.The basic aim ofthis paper is to minimi'e iron losses intransformer by using anti ferromagneticmaterial.

II.Basicprinciples

II.# Analogy* The transformer may beconsidered as a simple two(wheel &gearbox&for electrical voltage and current. Theprimary winding is analogous to the inputshaftand the secondary winding to the output shaft. In this comparison, current ise-uivalent to shaft speed, voltage to shafttor-ue. In a gearbox, mechanical power


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isconstantandise-uivalenttoelectricalpowerwhichisalsoconstant.

The gear ratio is e-uivalent to the transformer step(up or step(down ratio. Astep(up transformer acts analogously to areductiongear.inwhichmechanicalpoweris transferred from a small, rapidly rotatinggear toa large, slowly rotating gear/* ittradescurrent .speed/ for voltage .tor-ue/, by transferring power from a primarycoil to a secondary coil having more turns. A step(down transformer actsanalogously to amultipliergear.inwhichmechanicalpoweristransferredfroma largegeartoasmallgear/*ittradesvoltage.tor-ue/ forcurrent.speed/,bytransferringpowerfromaprimarycoiltoasecondarycoilhavingfewerturns.

II.0 1lux coupling laws* A simple transformer consists of twoelectrical conductors called the primary winding and the secondary winding. If atime(varyingvoltage isapplied to theprimarywindingofturns, a current will flow in itproducing a magneto motive force .221/. 3ust as an electromotive force .421/drives current around an electric circuit, so 221 drives magnetic flux through amagnetic circuit.The primary 221 produces a varying magnetic5ux in the core,and induces a backelectromotive force. In accordance with1araday&s6aw,thevoltageinducedacrosstheprimarywindingisproportionaltotherateofchangeof5ux*

777..#/

8imilarly, the voltage induced across thesecondarywindingis*The 421 in the secondary winding, ifconnected to an electrical circuit, will causecurrent to5ow in the secondarycircuit.The221 produced by current in the secondaryopposes the 221 of the primary and sotendstocanceltheflux inthecore.8incethereduced flux reduces the421 induced in theprimary winding, increased current 5ows intheprimary circuit.The resulting increase in221 due to the primary current offsets theeffect of the opposing secondary 221. Inthis way, the electrical energy fed into theprimarywindingisdeliveredtothesecondarywinding.9eglectinglosses,foragivenlevelofpower transferred through a transformer,current in the secondary circuit is inversely

proportionaltotheratioofsecondaryvoltagetoprimaryvoltage.

Inapractical transformer, thehigher(voltagewinding will have more turns, of smallerconductor cross(section, than the lower(voltagewindings.

III.Practicalconsiderations

:ecause the windings are identicalforbothtransformers, the assumption is made thatthe increase in eddy current for thewindingsis e-ual inbothcases.

Totalincrease incoillossesduetoharmoniccurrents is assumed e-ual two transformersof 0%netransformer was made with antiferromagneticandAnotherwith 9ormalcore metal. :oth transformers weredesignedasper?4"speci@cations.

7 77 7..0/

!ith perfect flux coupling, the 5ux inthe secondary winding will be e-ual tothatintheprimarywinding,thus*


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.............../1ig.# 8inglephasepole(mountedstep(downtransformer.


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I.Lossesintrans!or"er

An ideal transformer would have no losses,and would therefore be #%%B [email protected] energy is dissipated due both to theresistance of the windings .known ascopper loss/, and to magnetic effects primarilyattributable to the core .known asiron loss/.Transformers are in general highly ef@cient,and large power transformers.around #%%2=A and larger/ may attain an eCciency ashighasDD.EB.The losses

arisefrom*I=.# !inding resistance* "urrent flowingthroughthewindingcausesresistive heating.

I=.0 4ddy currents* Induced currents circulate in the core and cause its resistiveheating.

I=. 8tray losses* 9ot all the magnetic fieldproducedbytheprimary is interceptedbythesecondary.Aportionofthe leakage5uxmayinduce eddy currents within

nearbyconductive obFects such as the transformer&ssupport structure, and beconverted to heat.Thefamiliarhumorbu''ingnoiseheardneartransformers isaresultof stray fields causing components of the tank to vibrate, and is also from

magnetostrictionvibrationofthecore.

I=.G Hysteresis losses* 4ach time the magnetic field is reversed, a small amount ofenergy is lost to hysteresis in the magneticcore.

I=. 2echanical losses* The alternatingmagnetic @eld causes 5uctuatingelectromagnetic forces between the coils of wire, the core and any nearbymetalwork,causingvibrationsandnoisewhichconsumepower.

I=. 2agnetostriction* The flux in the core causes it to physically expand andcontract slightly with the alternating magnetic @eld, an effect known asmagnetostriction. This in turn causes losses due to frictional heating in susceptibleferromagneticcores.

I=.E cooling system* 6arge powertransformers may be e-uipped with coolingfans,oil pumps or water(cooled heat exchangers designed to remove the heatcaused by copper and iron losses.The power used to operate the cooling system istypicallyconsidered part of the losses of thetransformer.

. Separation o! #$steresis andedd$currentlosses.

4ddycurrent lossescanbereduced inacoreby reducing the area of ferromagneticmaterial byembedding thee-ualareaofantiferromagneticmaterial in

thesamecore.


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1ig.0

Thelosseswhichoccurintransformerare*

=.# "opper losses c% Here we will calculatecopper lossfor one embedded bar similarly losses can be calculatedforallotherbars

cJI0?777...G/

=.0 Ironorcore lossesi* Iron lossoccurs inthe magnetic core of the transformer.Thisloss is the sum of hysteresis loss .h/ and4ddycurrentloss.e/.

iJhKe77777../

iJ


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=JG.GGfMmT or =NfJG.GG:mAiT7.#%/

iNfJaKbf777..##/

uring this test, the applied voltage = andfre-uencyfarevariedtogethersothat.=Nf/iskept constant.The core loss is obtained atdiOerent fre-uencies by .iNf/

versusfre-uency f graph. Thus, knowing the constants a andb, hysteresis and eddycurrentlossescanbeseparated.

1ig..b/

1ig..c/

)raphno.(#

I.Edd$currentlosses%II.Ho&edd$currentlossis"ini"i'esb$usin(la"inatedcoreintrans!or"er

+ !hentheprobeisbroughtinclosetoa conductive material, the probesAssume that a changing magnetic flux ispassing through a certain s-uare crosssectionalarea of the transformercore.6ook

ata loopofcurrentenclosing that flux.Thepower dissipated in that particular loop isproportional to the s-uare of the areaenclosed by that loop .A/ divided by the

length of the path .6/. If you divide thats-uare intotworectanglesby laminating thecore,theareaenclosedintheloopwillbecutinhalfwhilethelengthwillbereducedtoNGof theoriginal length.The resultwillbe twoloops of current with a total

powerdissipation of 0P ..A/Q0N.E6.That makesthe sum of the powerdissipated in the twosmaller loops two thirds of the powerdissipated in the

original loop. 2orelaminations reduce the dissipation evenmore.

III.Totallossrecord%

Tableno.(# 9onembeddedcore*

d

cy


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8.no1re-uen

cy.H'/

"urrent.A/

!attmeter.!/

)enerate

voltage

ower.i/

iNf

# G #.% ##0 00.%

#%.G$

D

0 G #.% ##E G 0E.

$D%.%

G

GE #.% #0# G

#.

$#

%.E

G G$ #.% #0$ $.$

#%.$%

$

% #.% #G% $$ %.%

##.%%%

Tableno.04mbeddedcore*

8.no

1re-uen.H'/

"urrent.A/

!attmeter.!/

)enerated

voltage

ower.i

/

.!/

iNf

# G #.%E #0 G% .%

#%.EE$

0 G #.%E #0$ 0 $.$

#%.$G

GE #.%E # $ G.$

#%.D

0

G G$ #.%E # D G.$

#%.D

G

% #.%E #GE $ E.

%# #.#G%

I).*alculation!ortotalironlosses

)raphno.0

IP.#"alculationforeddycurrentlosses


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R 1ornonembeddedcore*?Jresistanceofwinding J $%.DS cJ copper lossJ I0?J $D.DD ! iJt(cJ #0($D.DDJ.%#!,whereiJinputpowerandtJtotalpoweriNf J%.EE$!NH'1romabovegraph,bJ%.%%E0G eJeddycurrentlossJbf0

J%.%%E0G%0J#$.#!

R 1orembeddedcore*?JresistanceofwindingcJcopperlossJI0?

J$%.DS J$D.DD!

iJt(cJ##0($D.DDJ00.%#!,whereiJinputpowerandtJtotalpoweriN fJ%.G$D!NH'1romabovegraph,bJ%.%#%0eJeddycurrentlossJbf0

J%.%#%0%0J0.

IP.0"alculationforhysteresislosses

R 9onembeddedcore*1romgraph aJ%.E$!eknowthat,hJafJ%.E$%JD!

R 4mbeddedcore*1romgraph aJ%.GE!eknowthat,hJafJ%.GE%J0!

Thereforetotalironlossesinnonembeddedcoreare*hKeJ .DK#$.#/ JE.#!Totalironlossesinembeddedcoreare*hK

eJ.0.K0/ JG$.!

?eductioninironlossesare*.6ossinnonembeddedcoreUlossinembeddedcore/N. lossinnonembeddedcore/.E.#(G$./NE.##%% J#.%B

).Result>verallcorelossisreducingincomparisontothenonembeddedcorewithembeddedcore.

)I.Econo"icalaspects

A 0G% =A #(M transformer is in circuitcontinuously. 1or $ hours a day the load is#%wat%.$pf.1orhours,theloadis$%wattheunitypfand for the remainingperiodof0Ghours itrunsonno(load.1ullloadcopperlosses are .%0w and the iron losses are #.watts. .a/ 1ind total cost of the total powersupplied for one year V.$% ?sNw. .b/ findout the totalcostwhen iron losses reduce to#.%B.@ndoutthetotalpro@t.

.a/ 1ullloadoutput J 0G%=A1ull(loadcopperlosses,c J.%0wIronlosses,i J #.w

All(dayinputJ.#%x$/ K.$%x/ J#,E%wh


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ifor0GhoursJ.#.x0G/ J$.Gwh

cfor0GhoursJ#%N % .$/0P.%0P$K$ %N# .%/0P.%0PJ#.EEK0.%# J#$.E$wh

S.no. Losses

Non

E"bedd

edcore

E"beddedcore

E!!ect

#4ddy

current

#$.#w 0.w 0D

Binc.

0Hysteresis

lossesDw 0w

G#B

dec.

TotalIronlosse

E.#w G$.w#.%Bdec.

All(day inputJAll(dayoutputK iron lossKcopperlossJ#E%K$.G%K#$.E$ J#$#E.#$wh

TotallossesinoneyearJ#$#E.#$PJ ,,0E#.EDwh

TotalcostVis.$%?s.erunit J?s.0,0%,G0.$0

b/ 1ullload

output J

0G%=A

1ull(load

copper

losses,

c

J.%0w

Iron

losses,i J#.w

All(dayinputJ.#%x$/ K.$%x/ J#,E% w


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h

ifor0GhoursJ.#.x0G/ J$.G wh

i for 0G hours reduced .#.%B/ J$.GU.$.GP#.%B/ J 0.# wh

cfor0GhoursJ# % N% .$/0 P.%0P$K$% N # .%/0P.%0P

J#.EEK0.%# J#$.E$wattNhourWXr. P.S. BIMBHRA Electrical Machines,2acmillan.I8:9%((#D0E(D.WGXHindmarsh, 3.

.#D$G/. ElectricalMachines and their Applications, 4th ed.,ergamon.I8:9%(%$(%%E0(.WX8hepherd,3; 2oreton,A.H; 8pence,6.1..#DE%/. Higher ElectricalEngineering,itmanublishing.I8:9%(0E(G%%0($.

All(day inputJAll(dayoutputK ironlossKcopperloss

J#E%K0.#K#$.E$ J #,$##.Dwh

Totallossesinoneyear J #$##.DPJ ,#,#$.GGwh

Total costV is .$% ?s. er unit J0,#0,G%0.%D?s

[email protected],0%,G0.$0U0,#0,G%0.%D/ J$,%%.E?s

)I.*onclusion

Afterperformingpracticalwefoundthateddy current loss is increasing inembedded core incomparison to nonembedded core while hysteresis losshas been decreased by greaterpercentage in embedded core withcompare to the non embeddedcore. It can beconcluded now thatembedded core is more eCcient thana non embedded core as ironlosshasbeenreducedby.#.%/ B.

)II.Re!erences

W#X aniels, A.?. .#D$/. Introductionto ElectricalMachines, 2acmillan. I8:9%((#D0E(D.

W0XHeathcote, 23 .#DD$/.JP!rans"or#erBoo$,%&thed.,9ewnes.

I8:9%(E%(##$($.


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Transformer - Copy