Electric Circuit Armature Windings.pdf

10/29/2010 11:32 AM EMD M.V.Ramana Rao

• Armature winding of a machine is defined as an arrangement ofconductors designed to produce emfs by relative motion in aheteropolar magnetic field.• The action of rotating electromagnetic machines is dependentupon the conversion of power that takes place through the medium ofmagnetic field an emf being induced in the winding that experiencesa change of flux linkages.

Electric CircuitElectric CircuitArmature WindingsArmature Windings

• Electrical machines employ groups of conductors distributed inslots over the periphery of the armature. The groups of conductorsare connected in various types of series—parallel combinations toform armature winding.• The conductors are connected in series so as to increase the voltage rating whilethey are connected in parallel to increase the current rating.


CoilCoil ::--AA coilcoil maymay consistconsist ofof aa singlesingle turnturn oror maymay consistconsist ofof manymany turns,turns, placedplaced ininalmostalmost similarsimilar magneticmagnetic position,position, connectedconnected inin seriesseries.. InIn thethe formerformer case,case,thethe coilcoil isis calledcalled aa singlesingle turnturn coilcoil whilewhile inin thethe latterlatter case,case, itit isis knownknown asasmultimulti--turnturn coilcoil..AA singlesingle turnturn coilcoil isis shownshown inin FigFig.. (a)(a).. FigFig.. (b)(b) showsshows aa 33--turnturn coilcoil..However,However, anyany numbernumber ofof turnsturns couldcould bebe includedincluded inin aa coilcoil beforebefore bringingbringingoutout thethe coilcoil endsends..


Single Layer And Two Layer WindingsSingle Layer And Two Layer Windings

(1)(1) Single layer winding.Single layer winding. Fig. (a) shows an arrangement for a single Fig. (a) shows an arrangement for a single layer winding. layer winding. In this type of winding arrangement, the whole of the slot is In this type of winding arrangement, the whole of the slot is occupied by one coil side of a coil. Single layer windings are not occupied by one coil side of a coil. Single layer windings are not used for machines having commutators. used for machines having commutators. However, some advantages of these windings areHowever, some advantages of these windings are

((11)) SingleSingle layerlayer windingswindings allowallow thethe useuse ofof semisemi--enclosedenclosed andand closedclosed typestypesofof slotsslots..(ii)(ii) WithWith singlesingle layerlayer windings,windings, coilscoils preformedpreformed atat oneone endend cancan bebe usedused..TheseThese coilscoils areare pushedpushed throughthrough thethe slotsslots fromfrom oneone endend ofof thethe corecore andand areareconnectedconnected upup duringduring thethe windingwinding processprocess atat thethe otherother endend whichwhich happenshappenstoto bebe freefree endend.. TheThe useuse ofof preformedpreformed coilscoils whereinwherein thethe insulationinsulation cancan bebeproperlyproperly appliedapplied andand consolidatedconsolidated isis aa greatgreat advantageadvantage especiallyespecially inin largelargeoutputoutput highhigh voltagevoltage machinesmachines..


DoubleDouble layerlayer windingwinding ::-- TheThe twotwo layerlayer windingswindings havehave identicalidentical coilscoilswithwith oneone coilcoil sideside ofof eacheach coilcoil lyinglying inin toptop halfhalf ofof thethe slotslot andand thetheotherother coilcoil sideside inin bottombottom halfhalf ofof anotheranother slotslot exactlyexactly oror approximatelyapproximatelyoneone polepole pitchpitch awayaway.. FigFig.. (b)(b) showsshows aa doubledouble layerlayer windingwinding withwith 22coilcoil sidessides perper slotslot..

•• EachEach layerlayer maymay containcontain moremore thanthan oneone coilcoil sideside inin casecase largelargenumbernumber ofof coilscoils areare requiredrequired.. FigFig.. (c)(c) showsshows anan arrangementarrangement whereinwhereintherethere areare 88 coilcoil sidessides perper slotslot.. OpenOpen slotsslots areare frequentlyfrequently usedused toto househousedoubledouble layerlayer windingswindings..


TheThe advantagesadvantages ofof doubledouble layerlayer windingswindings areare ::1.1. DoubleDouble layerlayer windingswindings givegive aa neatneat arrangementarrangement withwith allall coilscoils

beingbeing identicalidentical..

22.. DoubleDouble layerlayer windingswindings givegive greatergreater flexibilityflexibility inin designdesign becausebecauseofof thethe easeease withwith whichwhich thethe coilcoil spanspan (or(or coilcoil pitch)pitch) cancan bebechosenchosen..

Closed And Open WindingsClosed And Open Windings

Armature windings are classified into two categoriesArmature windings are classified into two categories(i) Closed type and (ii) Open type.(i) Closed type and (ii) Open type.

((11)) ClosedClosed windingswindings ::--InIn thisthis windingwinding therethere isis aa closedclosed pathpath aroundaround thethe armaturearmature.. ThusThus ififstartingstarting atat anyany point,point, thethe windingwinding isis followedfollowed throughthrough allall itsits turns,turns,thethe startingstarting pointpoint isis reachedreached againagain..


•• TheThe currentcurrent flowingflowing intointo aa closedclosed windingwinding isis throughthrough brushesbrushesplacedplaced onon aa commutatorcommutator whosewhose segmentssegments areare connectedconnected toto differentdifferentarmaturearmature coilscoils..

•• The closed windings are used in dc, and ac. commutator machines The closed windings are used in dc, and ac. commutator machines Closed windings are always double layer type.Closed windings are always double layer type.

OpenOpen windingswindings::--•• InIn alternatingalternating currentcurrent machinesmachines wherewhere commutatorcommutator isis notnot used,used, itit isisnotnot necessarynecessary toto useuse aa closedclosed windingwinding.. TheseThese machinesmachines useuse openopenwindingwinding..

•• In open windings, the armature may be left open at one or more In open windings, the armature may be left open at one or more points.points.

•• TheThe endsends ofof eacheach sectionsection ofof thethe windingwinding cancan bebe broughtbrought outout toto terminalsterminals andand thenthenanyany desireddesired interinter--connectionconnection cancan bebe mademade externallyexternally WhereWhere anan openopen windingwinding isispossible,possible, itit isis universallyuniversally preferredpreferred toto aa closedclosed windingwinding becausebecause ofof thethe flexibilityflexibility inindesigndesign andand thethe freedomfreedom ofof connectionsconnections..


•• OpenOpen windingswindings maymay bebe eithereither singlesingle layerlayer oror doubledouble layerlayer typetypeandand areare usedused inin acac.. MachinesMachines likelike inductioninduction andand synchronoussynchronousmachinesmachines..

•• ClosedClosed windingswindings whichwhich areare adaptedadapted forfor connectionconnection toto aacommutatorcommutator areare usuallyusually calledcalled DD..CC.. ArmatureArmature WindingsWindings whilewhile openopenwindingswindings whichwhich areare exclusivelyexclusively usedused forfor acac machinesmachines areare knownknown asasAA..CC.. ArmatureArmature WindingsWindings..


CONCENTRIC WINDINGCONCENTRIC WINDING

•• ConcentricConcentric windingswindings areare singlesingle layerlayer windingswindings whichwhich useuse concentricconcentrictypetype ofof coilscoils.. TheThe coilcoil spanspan ofof thethe individualindividual coilscoils isis differentdifferent..

•• TheThe coilcoil spanspan ofof somesome coilscoils isis moremore thanthan aa polepole pitchpitch whilewhile thethespanspan ofof othersothers isis equalequal toto oror lessless thanthan thethe polepole pitchpitch..

They are of two types :They are of two types :--

(i) Hemitropic or half coil windings(i) Hemitropic or half coil windings (Unbifurcated(Unbifurcated windings)windings)

(Bifurcated(Bifurcated windings)windings)

Arranged Arranged

(ii) Whole coil windings.(ii) Whole coil windings.

22--plane overhangplane overhang 33--plane overhangplane overhang


(i) Hemitropic or half coil windings (2(i) Hemitropic or half coil windings (2--plane overhang)plane overhang)•• TheseThese windingswindings areare alsoalso knownknown asas UnbifurcatedUnbifurcated windingswindings.. InInthesethese windingswindings thethe coilscoils comprisingcomprising aa pairpair ofof polepole phasephase groupsgroups underunderadjacentadjacent polespoles areare concentricconcentric..

2 slots per pole phase or 2 slots per pole phase or 6 slots per pole in hemitropic winding6 slots per pole in hemitropic winding

TheThe coilcoil spansspans ofof thethetwotwo coilscoils formingforming aacoilcoil groupgroup areare differentdifferent..

OneOne hashas aa coilcoil spanspan ofof77 slotsslots andand thethe otherother 55slotsslots..

WithWith averageaverage ororeffectiveeffective coilcoil spanspanbeingbeing 66 slotsslots (equal(equal totoslotsslots perper pole)pole) andandthereforetherefore thethe windingwindingbehavesbehaves asas aa fullfull pitchpitchwindingwinding..Hemitropic winding having 3 slots per poleHemitropic winding having 3 slots per pole

per phase with a 2 plane overhang. per phase with a 2 plane overhang.

2 2 -- plane overhang.plane overhang.


Winding shown in Fig. the 3 coils in a coil group have an average Winding shown in Fig. the 3 coils in a coil group have an average (effective) coil span of 9 slots (which is equal to slots per pole).(effective) coil span of 9 slots (which is equal to slots per pole).

The same winding may have a 3 plane overhang as shown in The same winding may have a 3 plane overhang as shown in Fig. above Fig. above

3 plane overhang3 plane overhang


Whole Coil WindingsWhole Coil Windings•• These are also known as These are also known as bifurcatedbifurcated windings.windings.

•• InIn thesethese windings,windings, eacheach polepole phasephase groupgroup isis splitsplit upup intointo twotwo setssets ofofconcentricconcentric coils,coils, eacheach setset sharingsharing itsits returnreturn coilcoil sidessides withwith thosethose ofofanotheranother polepole phasephase groupgroup inin thethe samesame phasephase..

•• 33--phasephase wholewhole coilcoil windingwinding cancan bebe arrangedarranged toto lielie inin eithereither 22 oror 33planesplanes.. ThereThere areare nono crankedcranked coilcoil groupsgroups..


Draw the winding diagrams of a following 3-phase, 36slots, 6 pole, a.c. armature for Following single layerconcentric types of windings :(i) Hemitropic-2 plane overhang (ii) Hemitropic-3 plane

overhang. (iii) Whole coil-3 plane overhang.

Solution

Slots per pole per phase = 36/3*6 = 2

Slots per pole = 36/6 = 6

\ Angle between consective slots α s = 180/6 = 30 0


1 2 3 4 5 6 7 8 9 10 11 12

Pole pitch Pole pitch

R B Y R B Y


1

4

5

7

9

10

13

16

17

19

21

22

25

28

29

31

33

34


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

SR

RS1RF1 RS2 RF2 RS3 RF3

FRSBFB SY FY

3-Phase, 36 slots, 6 Pole Sigle layer Hemitropic Concentric Winding 3 Plane overhang

HintHint


AssignmentAssignment1. Draw the winding diagrams of a following 3-phase, 36slots, 6

pole, a.c. armature for Following single layer concentric types of windings (i) Hemitropic-2 plane overhang (ii) Whole coil-3 plane overhang.

2. Draw the winding diagrams for a 4 pole, 36 slots, 3-phase, MUSH connected armature.

Instructions :Instructions :1.1. All assignment hat to send through eAll assignment hat to send through e--mail only as the attachment.mail only as the attachment.2.2. Assignment should be sent the following eAssignment should be sent the following e--mailmail

ee--mail : mail : [email protected]@yahoo.co.in

3. Assignment should be in the creative nature. 3. Assignment should be in the creative nature. 4. Assignment must be sent on or before 154. Assignment must be sent on or before 15thth August 2008 August 2008


Mush windingDraw the winding diagrams for a 4 pole, 24 slots, 3-phase,MUSH connected armature.Solution :-

Slots per pole per phase = 24

3*4= 2

Coil span = 24/4 = 6 slotsThis is an even numberand hence winding is notPossible with coil spanof 6 slots

\ A coil span of 5 is used

R 1,2 7,8 13,14 19,20

Y 5,6 11,12 17,18 23,24

B 3,4 9,10 15,16 21,22


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

SR

20

20

FR

HintHint


Double Layer WindingsDouble Layer Windings

• Double layer windings are universally used for armatures ofsynchronous generators and motors and most induction motors oflarge and medium sizes.

• Double layer windings may be classified into two categoriesdepending upon the method used to bring about the transition fromthe top layer to bottom layer.These are(i) lap type, and (ii) wave type.

• Lap windings have their widest field of application in the stators of high speed machines.

• Wave windings are used for wound rotors of medium and large size induction motors.


• These windings are the same as used in d.c. machines and givetwo different shapes to the end connections. The coils used indouble layer windings are diamond shaped as in dc machines

•• TheThe numbernumber ofof coilcoil sidessides perper slotslot inin doubledouble layerlayer windingswindings ofof acac..machinesmachines isis invariablyinvariably 22.. There,There, numbernumber ofof coilscoils isis equalequal toto numbernumberofof slotsslots oror CC == SS..

•• TheThe windingswindings usedused forfor acac.. machinesmachines areare usuallyusually chordedchorded..

•• TheThe advantagesadvantages ofof aa chordedchorded (short(short pitchpitch oror fractionalfractional pitch)pitch)windingwinding areare(i)(i) TheThe amountamount ofof coppercopper usedused inin thethe overhangoverhang isis reduced,reduced, andand(ii)(ii) TheThe magnitudemagnitude ofof certaincertain harmonicsharmonics ofof thethe ,mmf,mmf andand alsoalso emfemf isisreducedreduced..


DoubleDouble layerlayer windingswindings cancan bebe eithereither

i)i) integralintegral slot,slot, oror

ii)ii) fractionalfractional slotslot..WhenWhen thethe numbernumber ofof slotsslots perper polepole phasephase qq == S/mpS/mp isis anan integerinteger,,

itit isis knownknown asas anan integralintegral slotslot windingwinding.. ForFor example,example,considerconsider aa statorstator havinghaving 2424 slotsslots andand woundwound forfor 44 polespoles andand 33phasesphases.. TheThe numbernumber ofof slotsslots perper polepole perper phasephase qq == 2424//44 xx 33)) ==22,, whichwhich isis anan integerinteger.. TheThe windingwinding isis thusthus anan integralintegral slotslotwindingwinding..

WhenWhen thethe numbernumber ofof slotsslots perper polepole andand alsoalso thethe numbernumber ofof slotsslots perperpolepole perper phasephase areare notnot integersintegers,, thethe windingwinding isis knownknown asas

fractionalfractional slotslot windingwinding.. TheThe valuevalue ofof qq isis usuallyusually anan improperimproper

fractionfraction suchsuch asas 88//55,, 2525//77 etcetc.. ConsiderConsider aa statorstator havinghaving 7878 slotsslots toto bebewoundwound forfor 33--phasesphases andand 88 poles,poles, qq == 7878/(/(88**33)) == 1313//44 ==33 ¼¼ .. ThusThus qq

isis notnot anan integerinteger andand thereforetherefore itit isis aa fractionfraction slotslot windingwinding..


Integral Slot Lap Winding

Example : Example : Give the layout of a lap winding for the stator of a 3 phase ac having Give the layout of a lap winding for the stator of a 3 phase ac having 4 poles and 24 slots. There are 2 coil sides per slot.4 poles and 24 slots. There are 2 coil sides per slot.

Thus there are 3 phase groups per pole each comprising of Thus there are 3 phase groups per pole each comprising of qq = 2 = 2 slots. The distribution of slots, of phase sequence RYB, isslots. The distribution of slots, of phase sequence RYB, is

R 1,2 7,8 13,14 19,20

Y 5,6 11,12 17,18 23,24B 3,4 9,10 15,16 21,22


•• ConsideringConsidering thethe coilscoils atat thethe endend oppositeopposite toto thethe connections,connections, coilcoilsideside 11 (top)(top) isis connectedconnected toto coilcoil sideside ((11 ++ 1313)) == 1414 (bottom)(bottom)..

CoilCoil sidessides 11 andand 1414 formform aa coilcoil thisthis coilcoil maymay bebe singlesingle turnturn oror aamultiturnmultiturn coilcoil.. CoilCoil sideside 1414 isis connectedconnected toto coilcoil sideside ((1414 —— 1111 == 33,,(top)(top) atat thethe frontfront endend..

ThisThis connectorconnector CC connectsconnects thethe lastlast turnturn ofof thethe firstfirst coilcoil ofof polepole phasephasegroupgroup toto thethe firstfirst turnturn ofof secondsecond coilcoil ofof thethe samesame groupgroup..

•• CoilCoil sideside 33 isis connectedconnected toto coilcoil sideside ((33 ++ 1313)) == 1616 (bottom)(bottom) atat thethebackback.. CoilCoil sidessides 33 andand 1616 formform thethe secondsecond andand thethe lastlast coilscoils ofof thisthispolepole phasephase groupgroup.. (If(If therethere werewere moremore coilscoils perper phasephase group,group, theytheywouldwould havehave beenbeen alsoalso connectedconnected inin series)series)..


1

7

8

9

1011121314

15

16

17

18

19

20

2122

23 24

SR

SY

SB

600

αs=300

RR

R'

R'

RR

R'

R' Y

Y

Y'Y'

Y

Y

Y'Y'

B

BB'B'

B

B B'

B'

R R

R'

R'

RR

R'

R' Y

Y

Y'Y'

Y

Y

Y'Y'

BBB'

B'

BB B'

B'

ClockClock diagramdiagram ofof aa 33--phase,phase, 44 pole,pole, 2424 slotslotdoubledouble layerlayer windingwinding withwithfullfull pitchpitch coilscoils


YYbb = 11= 11

YYff = 9= 9


Integral Slot Wave Winding

Example : Example : Give the layout of a wave winding for the rotor of a 3 phase, 4 pole Give the layout of a wave winding for the rotor of a 3 phase, 4 pole induction motor having 24 slots. Each slot contains 2 coil sides.induction motor having 24 slots. Each slot contains 2 coil sides.

Solution :-

Slots per pole per phase q = 24

3*4= 2

Slots/pole = 24/4 = 6Slots/pole = 24/4 = 6


R 1,2 7,8 13,14 19,20

Y 5,6 11,12 17,18 23,24

B 3,4 9,10 15,16 21,22


1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

333838 44

4040


Fraction Slot Windings


Give the layout of a double layer lap type winding for a 3 Give the layout of a double layer lap type winding for a 3 phase, 8 pole. 54 slot armature. phase, 8 pole. 54 slot armature.

Solution :Solution :--

•• TheThe basicbasic unitunit ofof thisthis windingwinding consistsconsists ofof dd == 44 polespoles.. AsAs therethere areare88 poles,poles, soso thethe windingwinding hashas 22 unitsunits.. EachEach unitunit ofof 44 polespoles hashas MM == 44slotsslots ofof eacheach phasephase oror thethe totaltotal numbernumber ofof slotsslots inin aa unitunit isis mMmM == 2727..


••These slots, when arranged according to their position in These slots, when arranged according to their position in the machine arethe machine are1,2,3 1,2,3 8,98,9 15,16 15,16 22,2322,23

These slots, when arranged according to their position in These slots, when arranged according to their position in the machine arethe machine are4, 5 10, 11, 12 17, 184, 5 10, 11, 12 17, 18 24, 2524, 25


The remaining 9 slots out of total of 27 in a unit, belong to phase Y. These, when arranged according to their sequence in the machine, are

6,7 13,14 19,20,21 26,27

RR 1,2,3 8,91,2,3 8,9 15,16 15,16 22,2322,23BB 4, 5 10, 11, 12 17, 18 24, 254, 5 10, 11, 12 17, 18 24, 25YY 6,7 13,14 19,20,21 26,27


11

22

33

44

XX XX XX XX XX XX

RR BB YY

XX

XX XX XX XX XX XX XX

XX XX XX XX XX XX XX

XX XX XX XX XX XX

RR 1,2,3 8,91,2,3 8,9 15,16 15,16 22,2322,23BB 4, 5 10, 11, 12 17, 18 24, 254, 5 10, 11, 12 17, 18 24, 25YY 6,7 13,14 19,20,21 26,27


++ -- ++ --++ -- ++ --++ -- ++--


Give the winding layout of a 30 slot, 4 pole 3Give the winding layout of a 30 slot, 4 pole 3--phase wave wound phase wave wound rotor of an induction motor.rotor of an induction motor.

Each unit covers 2 poles and there are two such units. Each unit Each unit covers 2 poles and there are two such units. Each unit contains 5 slots of each phase. Each phase in a unit hascontains 5 slots of each phase. Each phase in a unit has


= 8= 8


yyff = y= ybb = 15 = 15 1 + 15 = 16 1 + 15 = 16 16 + 15 = 3116 + 15 = 3131 + 15 = 46 31 + 15 = 46 46 + 15 = 61 (1) 346 + 15 = 61 (1) 3

3 + 15 =18 3 + 15 =18 18 + 15 = 3318 + 15 = 3333 + 15 = 48 33 + 15 = 48 48 + 15 = 63 (3) 548 + 15 = 63 (3) 5

55 + 15 = 20 + 15 = 20 20 + 15 = 3520 + 15 = 3535 + 15 = 50 35 + 15 = 50 50 + 15 = 65 (5) 4 50 + 15 = 65 (5) 4

4 + 60 4 + 60 –– 15 = 49 15 = 49 49 49 –– 15 = 3415 = 3434 34 –– 15 = 19 15 = 19 19 19 –– 15 = 4(2)15 = 4(2)

2 + 60 2 + 60 –– 15 = 47 15 = 47 47 47 –– 15 = 3215 = 3232 32 –– 15 = 17 15 = 17 17 17 –– 15 = 215 = 2

SSRR

FFRR


3 Phase, 30 Slot, 4 Pole, Double Layer Fractional Slot Wave Winding.3 Phase, 30 Slot, 4 Pole, Double Layer Fractional Slot Wave Winding.

Electric Circuit Armature Windings.pdf

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