complete major document

8/10/2019 Complete Major Document

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DSP BASED EMBEDDED DIGITAL CONTROLLER FOR ACTUATOR

1. INTRODUCTION AND OVERVIEW OF ACTUATOR

AND BLDC MOTOR

1.1 OVERVIEW ACTUATOR

Electro Mechanical Actuators are used or the !ur!ose o controllin" aeros!ace

#ehicles $% delectin" control suraces and&or thrust direction' These actuators can $e

linear as (ell as rotar%) i'e' out!ut shat o the actuator can *o#e either in linear ashion

or in rotar% ashion' The desi"n and selection is done $ased on technical re+uired s!ace

and a#aila$ilit%

,',',Fi"- actuator and its !arts

Particularl% or aeros!ace a!!lications) the Electro Mechanical Actuators should

$e co*!act in si.e) li"ht is (ei"ht and should $e a$le to unction relia$l% in the harsh

en#iron*ental conditions include se#ere #i$rations) shoc/) $u*!) hi"h altitude etc'

!eror*ance o the actuator should not deteriorate under these en#iron*ent conditions

The actuator is dri#en $% as $rush less dc *otor' Rotar% *otion o the *otor istranserred to the $all scre( shat throu"h a reduction s!ur "ear train' Rotar% *otion is

con#erted to linear *otion is con#erted to linear *otion is con#erted to linear *otion $%

the $all scre( trans*ission *echanis*' Nut or the $all scre( *o#es in the linear and

controlled ashion to !ro#ide out!ut *otion' Control is done or the *otor o $rush less

dc *otor' Motor o the out!ut shat is sensed $% a !osition transducer' The !osition

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transducer is itted to the out!ut shat' The !osition transducer L3DT 0linear #aria$le

dierential transor*er2 out!ut o the actuator'

In the !resent case) desi"n o linear electro *echanical actuator has $een carried

out as !er technical and en#iron*ental s!eciication' Durin" the desi"n) all !ara*eter

s!ace li*itation) (ei"ht etc' (ere /e!t in *ind' The re!ort !resents detailed desi"n

calculations o Gears) Bearin"s) asteners) $all scre() dra(in"s) and solid *odels o E%e

End) Mid Plate) Bod%) End ca!s'

,','4Fi"- Actuators used in solid structures and in ro$otic

Actuators are (idel% used in chan"in" the direction and *otion o *issiles in

aeros!ace' So*e o the* are sho(n $elo('

' ,','5Fi"- actuators used in *issiles

1.2 OVERVIEW OF BLDC

In this !ro6ect thesis) the a!!lication o the BLDC *otors dealt is Electro

Mechanical Linear Actuators) (hich are used in the Missiles and S!ace A!!lications'

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Analo" and di"ital controls o BLDC *otor dri#es are also atte*!ted to suit their

(ide s!read a!!lications' There has $een a continuous de*and to reduce the control

hard(are and thus cost o this dri#e' Di"ital control is ad#anta"eous since) di"ital control

structures eli*inate drits and) $% usin" a !ro"ra**a$le !rocessor) the u!"rades can $e

easil% acco*!lished $% sot(are' 7ence Di"ital control is e*!lo%ed in the !resent

"eneration) or the *otion control a!!lications' Di"ital controllers can $e Micro!rocessor

$ased) Micro Controller $ased or DSP $ased controllers'

Belo( are so*e o the articles !u$lished in relation to Di"ital control o BLDC

*otors' This !ro6ect thesis deals (ith the Di"ital control o the BLDC *otors usin" DSP

controllers' Te8as DSP controllers are one o the $est controllers (hich suit the

re+uire*ents o this thesis a!!lication' 7ence T*s DSP is $ein" i*!le*ented here'

9DSP solutions or BLDC *otors:) is a !a!er !u$lished $% Te8as Instru*ents'

This !a!er !resents "eneric considerations on the control o Brushless Per*anent Ma"net

dc *otors usin" the T*s54;c4


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,'4', Fi"- cross sections BLDC *otors

9A#r


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1.3 BLOCK DIAGRAM

,'5',Fi" Bloc/ Dia"ra* o BLDC *otor dri#e s%ste*

Fro* all the a$o#e !ros!ects) a* carr%in" out this (or/ (ith an o$6ecti#e to

control the s!eed o BLDC *otors or EMA a!!lications) as the% are hi"hl% eicient and

$est suited or Motion control a!!lications' Control o the *otors is done $% usin" Te8as

$ased DSP controllers' This !ro6ect (or/ carries out sensored co**utations o BLDC

*otors' Research is under"oin" on $oth sensored and sensor less co**utation

techni+ues' 1e ha#e to choose the one that $est suits the a!!lication' As ar as EMA

a!!lication is considered) sensored co**utation techni+ue is e*!lo%ed in real ti*e'

Mosets are selected or s(itchin" !ur!ose and !o(er *odule is also desi"ned'

In this (or/) a DSP $ased di"ital controller or BLDC *otors is desi"ned' This

controller (ill acce!t the rotor s!eed) !osition and (ill !ro#ide control si"nals to in#erter'

An in#erter is desi"ned to control BLDC Motor'

This (or/ deals (ith the desi"n o the hard(are or controller electronics) and

sot(are i*!le*entation or a $rushless dc *otor dri#e s%ste*' The desi"n and

reali.ation o the dri#e s%ste* is di#ided into the ollo(in" *odules) irst $ein" the

desi"n and sot(are i*!le*entation o di"ital controller or TMS54;LF4


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!ro"ra**ed to achie#e the closed loo! !osition control o BLDC *otor' Sensored

co**utation o BLDC *otors are i*!le*ented in this (or/'

As (e /no( that the necessar% condition or de#elo!*ent o Mechanical *o*ent

in an% *otor is) the an"le $et(een the ields !roduced $% Ar*ature and Field (indin"s'

In case o dc *otor the ar*ature current is transerred ro* one (indin" to another or

each hal electrical rotation (ith the hel! o Co**utator and Brushes' But in case o

BLDC *otor this is not !ossi$le as there are no Co**utator and $rushes so (e need to

s(itch the current in ar*ature ro* one (indin" to another) de!endin" on the rotor

!osition' This is achie#ed $% incor!oratin" an in#erter and controllin" the in#erter

s(itches accordin" to the rotor !osition o BLDC *otor'

This rotor !osition inor*ation) (hich is necessar% to s(itch the current in the

ar*ature ro* one (indin" to another) can $e o$tained $% t(o *ethods-

,' B% usin" Sensors

B% usin" 7all sensors the rotor !osition can $e directl% o$tained in the

di"ital or*' As sensors are used to o$tain the rotor !osition) (hich is used or the

co**utation) this *ethod is called as Censored Co**utation

,'5'4Fi"- usin" *a"nets or sensin"

Fro* the (a#e sha!e o the $ac/ e* si"nals o the *otor) (e can o$tain the !osition

o the rotor (ithout the need o the sensors' This *ethod o o$tainin" the !osition o the

rotor (ithout an% cost eecti#e sensors is called as Sensor less Co**utation'

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In !resent (or/ a Moset $ased in#erter is e*!lo%ed and a DSP Controller is used

to acce!t the si"nals ro* rotor $% !osition sensors i'e' 7all Sensors techni+ue) in!ut

co**and si"nal and to !roduce the rele#ant irin" si"nals or in#erter s(itches i'e'

calculations o s(itchin" instants) se+uence and dut% c%cle o controllin" si"nals' These

si"nals are ed to in#erter throu"h dri#er circuit in order to enhance the !o(er le#el o

si"nal and to isolate the lo( !o(er circuit DSP ro* hi"h !o(er circuit h=$rid"e'

This (or/ deals (ith the desi"n o hard(are) i*!le*entation and testin" o

controller electronics or $rushless dc *otor dri#e s%ste*' This dri#e s%ste* is de#elo!ed

or EMA a!!lications' In EMA a!!lications) to ind the rotor !osition 7all sensors are

used and not sensor less techni+ues'

,'5'5 Fi"- BLDC as *otors and controller

This (or/ is carried out at Rci' I (as in#ol#ed in !ro"ra**in" o DSP controller)

hard(are desi"n o controller circuit and also in testin" $oth $oard le#el and s%ste*

le#el' M% contri$ution in this !ro6ect (as *ainl% in the sot(are !ro"ra**in" o

Peri!herals o DSP) in C lan"ua"e in Code Co*!oser Studio Sot(are and in the

hard(are desi"n o the Controller and also si*ulation in *atla$' I ha#e also done the

testin" o the circuits on the $read $oards and on the !c$s' I (as also in#ol#ed in the inal

s%ste* testin") #ie(in" the results'



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,'5'< Fi"- !rint $oard o BLDC

Motion control is a ne( ter* !resentl% used $% en"ineers andit isan os!rin" o

electric *otor dri#e technolo"% (hich has under"one a d%na*ic e#olution durin" the last+uarter centur%' The *otion control technolo"% is a s%nthesis o se#eral di#erse

disci!lines) such as !o(er se*iconductor de#ices) con#erter circuits) electric *otors)

control theor%) si"nal electronics and *icroco*!uters' Each o the co*!onent disci!lines

has $een under"oin" an e#olutionar% !rocess and is contri$utin" to the o#erall

i*!ro#e*ent o *otion control technolo"%' The introduction o *icroco*!uters in the

earl% ,;s si"niicantl% inluenced the *otion control s%ste*s) $% si*!li%in" the

control hard(are and addin" intelli"ence as (ell as dia"nostic ca!a$ilit% to the s%ste*'

Intelli"ent *otion control $ased on *icroco*!uters is an area o intense stud% and

research toda%'

Motion control a!!lications are di#erse' In the ho*e) a!!lications include ho*e

a!!liance dri#es or air conditioners) (ashers) dr%ers) $lenders) #acuu* cleaners etc' In

industr%) *otion control a!!lications include "eneral=!ur!ose industrial dri#es)

nu*ericall% controlled *achine tools) *ill=dri#es) ro$ots) co*!uter !eri!herals and ser#o

dri#es' The a!!lication o dri#es is o tre*endous interest toda%' The *odern industrial

dri#e has sho(n !heno*enal "ro(th ro* !eror*in" si*!le tas/s or ad6ust*ent and

s!ace e8!loration' The co*!uter !eri!heral industr% has seen a ra!id "ro(th in the

a!!lication o *otion control s%ste*s' In the US alone) electronic !rinters) dis/ dri#es

and ta!e dri#es used a$out ,;; *illion *otors in ,;'

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Motion control dri#e s%ste*s can $e $roadl% di#ided into t(o "rou!s-

,2 Lo( !eror*ance *otion control s%ste*s) such as ans) !u*!s) co*!ressors and

$lo(ers (hich nor*all% do not need ast res!onse and in so*e a!!lications o!en=loo!

o!eration is satisactor%

42 7i"h !eror*ance *otion control s%ste*s such as ro$otics) ser#os) rollin" *ills and

*achine tools (hich re+uire ast d%na*ic res!onse) !ara*eter=insensiti#e control

characteristics and ro$ustness'

This *otion control a!!lication in this !ro6ect is a 7i"h !eror*ance *otion

control s%ste*' It is an Actuator a!!lication o BLDC *otor (hich re+uires ast d%na*ic

res!onse'

1.4 CONVERTER TECHNOLOGY

A !o(er con#erter in a *otion control s%ste* con#erts and controls !o(er o the

electric *otors' 3arious con#erter to!olo"ies ha#e e#ol#ed or this !ur!ose' The "eneral

classiication o con#erters on unctions $asis are- Ac=to=dc con#erter i'e rectiier) Dc=to=

dc con#erter i'e cho!!er) Dc=to=ac con#erter i'e in#erter) Ac=to=ac con#erter at sa*e

re+uenc% ac controller or dierent re+uenc% c%clocon#erter'

In *an% !ractical !o(er con#erter s%ste*s) *ore than one con#ersion !rocess *a% $e

co*$ined'

Dc to Ac con#erter or In#erter to!olo"% is e*!lo%ed in this thesis' P1M si"nals

are ed as in!uts to the Gates o the s(itches' In!ut is dc #olta"e and ac out!ut is "i#en to

the *otor !hases) in order to dri#e the *otor'

Electric *achines ha#e $een the (or/horses o *otion control s%ste*s' The three

$asic electric *achines dc) induction) and s%nchronous ha#e ser#ed industrial needs or

nearl% a centur%' In recent %ears) intense research eort has *ade other #ariations o

electric *achines) such as $rushless dc *achines) !er*anent *a"net *achines) and

s(itched reluctance *achines) #ia$le alternati#es in *an% a!!lications'



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DC *achines ha#e traditionall% do*inated the do*ain o *otion control s%ste*s'

E#en no( *ost industrial *otion control dri#es use dc *achines' Althou"h the *achine

is *ore e8!ensi#e) the control !rinci!les and the con#erter e+ui!*ent re+uired are

so*e(hat si*!ler in dc dri#es' 7o(e#er) the *ain disad#anta"es are its co**utators)

$rushes and the re+uent *aintenance re+uired or its o!eration' To o#erco*e this) in this

thesis $rushless dc *otors are e*!lo%ed) (hich are hi"hl% eicient and ha#e lo( cost'

BLDC *otors ha#e $een !ro#en to $e $est all=round t%!e o *otors or aeros!ace

a!!lications $ecause o their lon" lie) hi"h tor+ue) hi"h eicienc%) and lo( heat

dissi!ation' The dri#e s%ste* is i*!le*ented usin" *ini*u* hard(are and *a6or !art o

control is reali.ed throu"h sot(are'

1.5 CONTROL IMPLEMENTATIONS

Controllers !la% a si"niicant role in the !eror*ance o !o(er electronics

s%ste*s' The control electronics can $e $roadl% "rou!ed as ollo(s-

Discrete control is hard(are control

Microco*!uter control sot(are control'

In recent %ears) ad#ance*ent in *icroelectronic chi!s has su$stantiall% reduced the

si.e and cost o the controllers and !ro#ided !eror*ance i*!ro#e*ent'

Discrete Control

The discrete analo" and di"ital hard(are ele*ents) such as o! a*!s) lo"ic

"ates 0nand&nor2) counters) decoders etc' ha#e $een traditionall% used in the control o

*otion control s%ste*s' This t%!e o control (ill $e !reerred or si*!le !o(er electronic

e+ui!*ent) such as !orta$le house a!!liances' Dedicated hard(are control !ro#idessi*!licit% and ast res!onse and can $e used in hi"h !eror*ance *otion control s%ste*s'

But one o the dra($ac/s o this discrete control is that it can e8ecute at a ti*e onl%' So

in order to o#erco*e this (e added *icroco*!uter control to continuousl% e8ecute the

!rocess (ithout dela%'

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2. LITERATURE SURVEY

Lar"e) *ediu*) s*all as (ell as *icro BLDC *otors are e8tensi#el% sou"ht or

a!!lications in all sorts o *otion control a!!aratus and s%ste*s' The *ar#elous increasein the !o!ularit% o the BLDC *otor dri#es a*on" en"ineers $ears testi*on% to its

industrial useulness in ter*s o su!erior !eror*ance and relati#e si.e' 7i"h eicienc%

due to reduced losses) lo( *aintenance and lo( rotor inertia o the BLDC *otor has

increased the dEMAnd o BLDC *otors in hi"h !o(er ser#o and ro$otic a!!lications'

Belo( are so*e o the articles !u$lished on the i*!ortance o BLDC *otors and

their (ide s!read a!!lications in #arious ields' 9Ad#ances in Brushless dc Motor

Technolo"%) Control) and Manuacture: $% Geor"e Ellis /oll*or"en cor!oration

Radord ) 3ir"inia ) USA ) is a !a!er (hich deals (ith the BLDC *otors )

unda*entals and the dierences $et(een the BLDC and Brushed dc *otors '

This !a!er (as !u$lished at !ci*=Euro!e) ,' It ocuses on the !resent i*!ortance

and a!!lications o the BLDC *otors'

9ANHH == Brushless dc 0BLDC2 Motor Funda*entals $% == Pad*a ra6a

eda*ale Microchi! Technolo"% Inc. Is a !a!er ocuses on the BLDC *otors )

their constructional eatures ) a!!lications ) characteristics and Sensored

co**utation ' This is a !u$lished a!!lication note on BLDC *otors $% Microchi!

technolo"%'

Ma"net Brushless dc 9Per*anent Motors or Consu*er Products: s' $en.oate)

.'+' .hu and d' ho*e) Cit% o Sheield Uni#ersit% . This !a!er descri$es the desi"n and

!eror*ance o sin"le=!hase and three=!hase !er*anent *a"net $rushless dc

*otors ) e*!lo%in" $onded Node *a"nets ) or retroittin" to a state = o = the = art

#acuu* cleaner ' The !eror*ance o the BLDC *otors) in ter*s o their

tor+ue&s!eed and eicienc%&s!eed characteristics ) and E*c and acoustic noise

e*issions) is co*!ared (ith that o the ori"inal uni#ersal *otor'

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BLDC *otors ha#e $een !ro#en to $e $est all=around t%!e o *otors or aeros!ace

a!!lications $ecause o their lon" lie) hi"h tor+ue) hi"h eicienc%) and lo( heat

dissi!ation'

This !a!er co*!ares #arious t%!es o *otors and stresses that BLDC *otors are

the suita$le *otors in the aeros!ace a!!lications' Selection o the o!ti*u* electric *otor

or s!ace li"ht o!erations results in a sae) relia$le) eecti#e) eicient and econo*ical

electric *otor !o(er source or s!ace li"ht' Brushless direct current *otors !ro#ide the

li"htest (ei"ht alternati#e or *ost a!!lications'

9A!!lication Re!ort) s!raa6anuar% 4;;) DSP control o electro=h%draulic

ser#o actuators:) deals (ith so*e o the issues in#ol#ed in controllin" linear h%draulicActuators and the suita$ilit% o the DSPs or such s%ste*s'

3. BLDC MOTORS AND COMMUTATION TECHNIQUES

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In this cha!ter) unda*entals o BLDC *otors) their constructional eatures) their

characteristics are e8!lained' The sensored co**utation techni+ues o BLDC *otor are

e8!lained in detail' Control *ethods o BLDC *otor are also e8!lained' Finall%) BLDC

*otor a!!lication in Actuators is e8!lained'

3.1 BRUSHLESS DC MOTOR

Brushless dc *otor is one /ind o !er*anent *a"net s%nchronous *otor) ha#in"

!er*anent *a"nets on the rotor and tra!e.oidal sha!e $ac/ e*' The BLDC *otor is

con#entionall% deined as a !er*anent *a"net s%nchronous *otor (ith a tra!e.oidal

$ac/ e* (a#eor* sha!e'

Fi" 5',',- BLDC (a#eor*sThe BLDC *otor e*!lo%s a dc !o(er su!!l% s(itched to the stator !hase

(indin"s o the *otor $% !o(er de#ices) the s(itchin" se+uence $ein" deter*ined ro*

the rotor !osition' The !hase current o BLDC *otor) in t%!icall% rectan"ular sha!e) is

s%nchroni.ed (ith the $ac/ e* to !roduce constant tor+ue at a constant s!eed'

The *echanical co**utator o the $rush dc *otor is re!laced $% electronic

s(itches) (hich su!!l% current to the *otor (indin"s as a unction o the rotor !osition'

This /ind o ac *otor is called $rushless dc *otor) since its !eror*ance is si*ilar to the

traditional dc *otor (ith co**utators'

In $rushed dc' Motor) (hile the rotor !asses $% the alternate N and S !oles)

direction o current in the ar*ature conductors is *ade re#ersed to *a/e the tor+ue

unidirectional' This is done (ith the hel! o co**utators and $rushes' This t%!e o

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co**utation suers ro* lash o#er at hi"h=s!eed Jhi"h current) resultin" !o(er losses

J serious da*a"es' To o#erco*e this !ro$le* the conce!t o Brushless dc *otor is

de#elo!ed'

3.2 CONSTRUCTIONAL FEATURES

The construction o *odern Brushless dc *otors is #er% si*ilar to the ac *otor)

/no(n as the !er*anent *a"net s%nchronous *otor' The stator (indin"s are si*ilar to

those in a !ol%!hase ac *otor) and the rotor is co*!osed o one or *ore !er*anent

*a"nets' Brushless dc *otors are dierent ro* ac s%nchronous *otors in that the or*er

incor!orates so*e *eans to detect the rotor !osition 0or *a"netic !oles2 to !roduce

si"nals to control the electronic s(itches' The *ost co**on !osition&!ole sensor is the

7all ele*ent) $ut so*e *otors use o!tical sensors' It is i*!ortant to /no( the rotor

!osition in order to understand (hich (indin" (ill $e ener"i.ed ollo(in" the ener"i.in"

se+uence' Rotor !osition is sensed usin" 7all Eect sensors e*$edded into the stator'

1hene#er the rotor *a"netic !oles !ass near the 7all sensors) the% "i#e a hi"h or lo(

si"nal) indicatin" the N or S !ole is !assin" near the sensors'

Based on the co*$ination o these three 7all sensor si"nals) the e8act se+uence o

co**utation can $e deter*ined'illustrates the structure o a t%!ical three=!hase Brushless

dc *otor'

Fi" 5'4',- Disse*$led #ie( o BLDC *otor

3.3 STATOR

,*0d*&dt2 B* Tl 0e+ ,'52

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Ra La

E"


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To o$tain the transer unction $et(een s!eed and a!!lied #olta"e) the dierential

e+uations are transor*ed into the re+uenc% do*ain'

3K 0Ls R2 I /e* 0e+ ,'


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starts and sto!s and re+uent re#ersals o rotation (ith load on the *otor) dEMAnd *ore

tor+ue than the rated tor+ue' This re+uire*ent co*es or a $rie !eriod) es!eciall% (hen

the *otor starts ro* a standstill and durin" acceleration' Durin" this !eriod) e8tra tor+ue

is re+uired to o#erco*e the inertia o the load and the rotor itsel' The *otor can deli#er a

hi"her tor+ue) *a8i*u* u! to !ea/ tor+ue) as lon" as it ollo(s the s!eed tor+ue cur#e'

Fi" 5'',- Tor+ue&s!eed Characteristics'

3./ COMMUTATION OF BLDC MOTOR

Unli/e a $rushed dc *otor) the co**utation o a BLDC *otor is controlled

electronicall%' To rotate the BLDC *otor) the stator (indin"s should $e ener"i.ed in a

se+uence' It is i*!ortant to /no( the rotor !osition in order to understand (hich (indin"

(ill $e ener"i.ed ollo(in" the ener"i.in" se+uence'

In the BLDC *otor) the co**utation can $e o t(o t%!es) Sensored and Sensor

less' In the sensored co**utation) sensors are used to deter*ine the rotor !osition) (hile



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in the sensor less co**utation the rotor !osition can $e o$tained ro* the $ac/ E*

(a#e sha!e (ith out usin" an% sensors to detect the !osition o the rotor'

Sensored Co**utation

As the na*e s!eciies) in sensored co**utation) the co**utation o BLDC*otor is done (ith the hel! o sensors' These sensors can $e o 7all t%!e) Encoders)

Resol#ers etc' In this !ro6ect (or/) the sensored co**utation is i*!le*ented usin" the

hall sensors *ounted on the *otor'

Sensored Co**utation usin" 7all sensors

As the na*e s!eciies) in the sensored co**utation o BLDC *otors) the rotor

!osition is sensed usin" 7all Eect sensors e*$edded into the stator' Most BLDC

*otors ha#e three 7all sensors e*$edded into the stator on the non=dri#in" end o the

*otor' 1hene#er the rotor *a"netic !oles !ass near the 7all sensors) the% "i#e a hi"h or

lo( si"nal) indicatin" the N or S !ole is !assin" near the sensors' Based on the

co*$ination o these three 7all sensor si"nals) the e8act se+uence o co**utation can $e

deter*ined' 7all sensors (or/ on the !rinci!le o the 7all Eect theor%) (hich is

e8!lained here'

7all Eect Theor%

I an electric current carr%in" conductor is /e!t in a *a"netic ield) the *a"neticield e8erts a trans#erse orce on the *o#in" char"e carriers (hich tends to !ush the* to

one side o the conductor' This is *ost e#ident in a thin lat conductor' A $uildu! o

char"e at the sides o the conductors (ill $alance this *a"netic inluence) !roducin" a

*easura$le #olta"e $et(een the t(o sides o the conductor' The !resence o this

*easura$le trans#erse #olta"e is called the 7all Eectater E' 7' 7all (ho disco#ered it'



24/110


Fi" 5'',- A T%!ical BLDC *otor dri#e (ith sensored co**utation

3.0 THEORY OF OPERATION

Each co**utation se+uence has one o the (indin"s ener"i.ed to !ositi#e !o(er

i'e current enters into the (indin") the second (indin" is ne"ati#e i'e current e8its the

(indin" and the third is in a non=ener"i.ed condition' Tor+ue is !roduced $ecause o the

interaction $et(een the *a"netic ield "enerated $% the stator coils and the !er*anent*a"nets' Ideall%) the !ea/ tor+ue occurs (hen these t(o ields are at ; to each other

and alls o as the ields *o#e to"ether' In order to /ee! the *otor runnin") the *a"netic

ield !roduced $% the (indin"s should shit !osition) as the rotor *o#es to catch u! (ith

the stator ield' 1hat is /no(n as 9Si8=Ste! Co**utation: deines the se+uence o

ener"i.in" the (indin"s' Co**utation Se+uence

4

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