EFFICIENCY ANALYSIS OF INDIRECT VECTOR CONTROLLED THREE PHASE INDUCTION MOTOR DRIVE

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1 ISSN (Pint) : ISSN (Onlin): Intnational Jounal of Advancd Rsach in Elctical, Elctonics and Instumntation Engining (An ISO 397: 7 Ctifid Oganization) Vol., Issu 8, August 13 EFFICIENCY ANALYSIS OF INDIRECT VECTOR CONTROLLED THREE PHASE INDUCTION MOTOR DRIVE Sna Thomas 1, Rinu Alic Koshy M.Tch Studnt, Dpt. Of EEE, Rajagii Collg of Engining and Tchnology, Kakkanad, Kala, India 1 Assistant Pofsso, Dpt. Of EEE, Rajagii Collg of Engining and Tchnology, Kakkanad, Kala, India ABSTRACT: This pap analyss th ovall systm lvl fficincy of an indict vcto contolld induction moto div. Both th induction moto losss and invt losss a considd. A 5.4-hp induction moto div is simulatd to analys th fficincy und diffnt opating conditions of th div. Th vaiation of fficincy und load chang and spd chang is obsvd. Simulation sults show that fficincy incass as th opation of induction moto div shifts fom unatd to atd conditions. At light loads, th ion losss in th induction moto a significant. Th fficincy of th moto can b incasd by kping th flux lvl blow th atd valu. Also th influnc of hystsis band on th switching losss of th invt is analysd. Th sults suggst that, fo fficint opation of th div, an optimum combination of th vaious contol vaiabls a quid. Kywods: Vcto contol, Hystsis band, Indict fild ointd contol, Switching losss, Simulink I. INTRODUCTION It is stimatd that lctic machins consum mo than 5% of th wold lctic ngy gnatd. Economic saving and duction of nvionmntal pollution a th two factos that highlights th impotanc of analyzing th fficincy in lctic divs. Th induction motos a widly usd in th lctical divs and a sponsibl fo most of th ngy consumd by lctic motos. In cnt yas th contol of high-pfomanc induction moto divs fo gnal industy applications and poduction automation has civd widspad sach intsts. Many schms hav bn poposd fo th contol of induction moto divs, among which th fild ointd contol, o vcto contol, has bn accptd as on of th most ffctiv mthods. Vcto contol offs a numb of bnfits including spd contol ov a wid ang, pcis spd gulation, fast dynamic spons, and opation abov bas spd. In th fild ointd contol of an induction moto div systm, cunt contol tchnology plays th most impotant ol in cunt-contolld puls width modulation (PWM) invts, which a widly applid in high pfomanc dynamic divs systm. Among th vaious cunt contol tchniqus, considing asy implmntation, th convntional hystsis PWM cunt contol mthod is a popula on. Th advantags of this schm a its simplicity, good accuacy, good spons, and high obustnss. Th majo dawback of this schm is that high switching fquncy can happn at low hystsis band so th switching loss of th invt will b incasd. In addition, th cunt o is not stictly limitd. Th cunt ippl can ach twic th hystsis band. This pap analyss th ovall systm lvl fficincy of a vcto contolld induction moto div which mploys a hystsis cunt contoll fo PWM gnation. Th losss in th induction moto and th switching losss in th invt cicuit of th div a considd. Induction motos hav a high fficincy at atd spd and toqu. Howv, th opation of th machin with atd flux at light loads, ion losss incas damatically, ducing considably th fficincy. Th hystsis band of th cunt contoll is th main facto dciding th switching losss in th invt cicuit. It also affcts th cunt ippl and toqu ippl of th induction moto div. II. INDIRECT FIELD ORIENTED CONTROL By using fild ointd contol, toqu and flux of th induction motos can b contolld indpndntly as in dc motos. Th pow cicuit consists of a font nd diod ctifi and a hystsis band cunt contol puls width modulation (PWM) invt.fig. 1 shows th block diagam of a typical IFOC of induction moto. Copyight to IJAREEIE 385

2 ISSN (Pint) : ISSN (Onlin): Intnational Jounal of Advancd Rsach in Elctical, Elctonics and Instumntation Engining (An ISO 397: 7 Ctifid Oganization) Vol., Issu 8, August 13 Fig. 1 Typical IFOC block diagam Th spd PI contoll gnats th fnc toqu command: T ( K p _ spd K i _ spd s )( N f N) (1) wh N f is th spd command and N is th actual oto spd. Th toqu and oto flux fnc commands a utilizd to gnat th moto d q fnc cunts: i ds i qs d L m T 3 P L L m d (3) Th flux is kpt at atd valu up to atd spd. Hnc i ds, th d-axis componnt of stato cunt is constant dpnding on th atd flux valu. Th i qs, q-axis componnt of stato cunt dtmins th lctomagntic toqu dvlopd. Th slip fquncy ω slip, is gnatd fom i qs and i ds. i R qs slip. L ids (4) wh R is th oto sistanc and L is oto inductanc. Th synchonous spd, ω is th sum of slip fquncy, ω slip and lctical angula oto fquncy, ω. slip Th intgation of ω yilds th oto pol position, θ. (6) Th hystsis PWM attmpts to foc th actual moto cunts (i as i bs, i cs ) to th fnc cunts(i * as, i * bs, i * cs ) valus. Th o btwn th fnc cunts and th actual cunts a usd to switch th PWM invt. Th output of th invt is supplid to th stato of th induction moto. Minimum pow loss opation in induction moto divs bings about significant global ngy savings, sinc machins consum appoximatly two-thids of all lcticity gnation woldwid. Th th main componnts of a moto div systm a th contol, machin, and pow lctonics. Contol is basd on analog o digital cicuits and usually consums a ngligibl amount of pow; its pow consumption is lativly constant. Machin and pow lctonics dominat th systm losss. Copyight to IJAREEIE () (5) III. INDUCTION MOTOR DRIVE EFFICIENCY

3 ISSN (Pint) : ISSN (Onlin): Intnational Jounal of Advancd Rsach in Elctical, Elctonics and Instumntation Engining (An ISO 397: 7 Ctifid Oganization) Vol., Issu 8, August 13 Machins a nomally dsignd to opat at atd flux conditions so that th dvlopd toqu p amp is high and tansint spons is fast. If th flux componnt of th stato cunt in th d-q synchonously otating fam is st to th atd fild flux fo th full ang of bas spd (i.. fom zo to atd valu), as is don in convntional vcto contol mthod of an induction moto, it sults in poduction of vy fast and pcis toqu spons. Howv, most of th tim, industial divs opat at light loads. If atd flux is maintaind at light load th co loss is xcssiv sulting in poo fficincy of th div. In addition, in low fquncy opations, co loss is ath low compad to copp loss. As th spd incass, th contibution of ddy cunt loss incass and finally bcoms dominant, hnc optimal combination of dict axis (d-axis) and quadatu axis (q-axis) cunt vay dpnding on th quid toqu and spd. IV. INDUCTION MOTOR LOSSES Th opating loss of an induction moto is composd of th stato and oto copp losss, th co losss and th mchanical losss. Th copp loss is du to th flow of cunt though stato and oto windings and is givn by W Cu 3 iqs ids s i q id (7) wh i qs and i ds a q-axis and d-axis stato cunt spctivly and i q and i d a q-axis and d-axis oto cunts spctivly. Th co (ion) losss du to hystsis and ddy cunts a latd as W F 3 Khm K m (8) wh K h and K a th ddy cunt and hystsis loss cofficints and λ m is th flux linkag. Th mchanical losss a dpndnt on th oto spd and is givn by W mch K m wh K m is th mchanical loss cofficint. Thus th total opating losss a givn by 3 3 Wtotal i qs ids s i q id Efficincy of th induction moto is givn by T T W K hm K m K m total wh T is th lctomagntic toqu dvlopd. V. INVERTER LOSSES In vcto-contolld divs, it is common to mploy stato cunt o flux hystsis contolls. Th hystsis band affcts th switching and conduction action of invt switching dvics. This is illustatd fo hystsis cunt contol of on invt phas. In th hystsis band is small, and th switch (assumd insulatd gat bipola tansisto (IGBT) in this cas) tuns on and off mo oftn than in th cas shown in wh th hystsis band is lag. With a small hystsis band, cunt is maintaind within a tight ang causing th invt to switch fast. Th lag hystsis band allows mo oom fo cunt vaiation and thus yilds lss invt switching action. (9) (1) (11) Copyight to IJAREEIE 387

4 ISSN (Pint) : ISSN (Onlin): Intnational Jounal of Advancd Rsach in Elctical, Elctonics and Instumntation Engining (An ISO 397: 7 Ctifid Oganization) Vol., Issu 8, August 13. Fig. Vaiation in th gat signal gnation pattn fo chang in hystisis band Fig. 3 Hystisis cunt contoll A simplifid diagam of th poposd th-phas PWM cunt contoll is shown in Fig 3. Th cunt contoll involvs th indpndnt hystsis compaatos and th logic gats with NOT function. Th div signals fo th invt pow switchs a divd fom th output signals oth contoll. In th cunt contoll, th th-phas cunt commands (i as *,i bs *, and i cs * ) a compad with th actual stato cunts (i as i bs,and i cs ), and thn th sulting os a fd into th two-lvl hystsis compaatos, spctivly. Th hystsis compaato output signal is dfind as: y, i y 1, i abc abc i i * abc * abc i i * wh i abc dnots on of th th-phas cunts and i abc is its fnc, and i, dnots th pst hystsis band fo all phass. Assuming, whn th actual stato cunt incass and achs th upp limit(i * abc + i/ ), th hystsis compaato output is y=, so that an appopiat voltag vcto is slctd to dcas th stato cunt. Convsly, whn th actual stato cunt dcass and achs th low limit (i * abc - i/ ), th hystsis compaato output is y=1, so that anoth appopiat voltag vcto is chosn to incas th stato cunt. Thfo, a small ippl will b poducd if a naow hystsis band is mployd, but th pow dissipation in th invt switchs will incas Copyight to IJAREEIE 388

5 ISSN (Pint) : ISSN (Onlin): Intnational Jounal of Advancd Rsach in Elctical, Elctonics and Instumntation Engining (An ISO 397: 7 Ctifid Oganization) Vol., Issu 8, August 13 owing to a lag switching fquncy. Th cunt ippl and switching fquncy a two chif considations fo dtmining cunt band. In th convntional hystsis cunt contoll, it is wll known that th cunt vais aound th fnc with a ctain ippl. Th cunt ippl can ach twic th hystsis band du to th intaction btwn th invt switchs. VI. SIMULATION RESULTS An indict fild ointd contolld 5.4 hp induction moto div is simulatd using MATLAB / SIMULINK. Simulations hav bn caid on a 5.4 hp induction moto div, th atings of which a summaizd in th Tabl I. Th pfomanc of th div und diffnt opating conditions is obsvd. Tabl II shows th fficincy of IM at diffnt spd and load conditions. TABLE I MOTOR PARAMETERS Ratd pow 5.4 hp Ratd spd 143 pm Ratd cunt 9.1 A Ratd toqu 6.7 Nm Numb of pols 4 It is obsvd that th ion losss a almost constant fo th convntional mthod at diffnt load condition fo a givn constant spd. Whn th machin opats at low loads o at non atd spds, its fficincy dcas du to unbalanc btwn th two main losss componnts, with th ion losss dominating at light loads. At atd spd, th fficincy changs fom 6% to 8% as load is incasd fom %(5.34 Nm) to 1%(6.7 Nm) of th atd load toqu. Th mchanical losss a constant fo a givn spd and vais popotionally as th spd vais. TABLE II EFFICIENCY OF 5.4HP INDUCTION MOTOR Spd(pm) 143(atd spd) 1144(8% of atd spd) 858(6% of atd spd) 57(4% of atd spd) 86(% of atd spd) Load (% of atd toqu) Cu loss(w) F loss(w) Mch loss(w) Total loss(w) Efficincy(% ) A. Efficincy analysis of 5.4hp induction moto und load chang Copyight to IJAREEIE 389

6 Efficincy(%) Iabc(A) Toqu(Nm) ISSN (Pint) : ISSN (Onlin): Intnational Jounal of Advancd Rsach in Elctical, Elctonics and Instumntation Engining (An ISO 397: 7 Ctifid Oganization) Vol., Issu 8, August 13 Fig.5 shows th simulatd dynamic pfomanc of th 1M div fo a stp chang in load toqu. Duing stating moto daws high stato cunt with low fquncy to dvlop th ncssay stating toqu and onc th moto picks up spd th fquncy incass and th magnitud of cunt ducs. Th a small ippls in th stato cunt and hnc in th dvlopd lctomagntic toqu du to switching in hystsis PWM cunt contoll. Whn th load is incasd fom % to 1% of atd toqu at t =.5 sc, th spd contoll maintains th moto at atd spd. Th lctomagntic toqu dvlopd by th moto incass to th atd valu 6.7 Nm to satisfy th load toqu quimnt with a popotional incas in th stato cunt. Th dict axis cunt is a constant valu dpnding up on th atd flux valu and th quadatu axis cunt is popotional to th load toqu. But whn th div is opatd at light load condition, th fficincy is poo as th ion losss is maximum cosponding to th atd flux Fig. 5(a) Toqu Fig. 5(b) Cunt 1. Vdcc Fig. 5(d) Efficincy B. Efficincy analysis of 5.4 hp induction moto und spd chang Fig.6 shows th simulatd dynamic pfomanc of th 1M div fo a stp chang in spd. At t =.5 sc, whn th commandd spd is incasd fom 86 pm to 143 pm(atd spd) with th sam load toqu, th actual moto spd tacks th commandd spd. In addition, th toqu dos not chang in th stady stat and th is no chang in th stato cunt. It is obsvd that at constant spd, incasing load on th 1M div sults in impovd fficincy. It is obsvd that th fficincy incass with incas in spd und fixd load opation of th div. At atd load, th fficincy changs fom 67.4% to 8% as th spd is incasd fom %(86 pm) to 1%(143 pm) of th atd load toqu. Copyight to IJAREEIE 381

7 pulss Efficincy(%) Iabc(A) Spd(pm) ISSN (Pint) : ISSN (Onlin): Intnational Jounal of Advancd Rsach in Elctical, Elctonics and Instumntation Engining (An ISO 397: 7 Ctifid Oganization) Vol., Issu 8, August Spd Fig. 6(a) Spd Fig. 6(c) Cunt Fig. 6(d) Efficincy C. Efficincy analysis of 5.4 hp induction moto und hystsis band chang Th induction moto div was simulatd with hystsis band h=.5 and h=4. Fig. 7(a), (b), (c) and Fig. 8(a), (b), (c) shows th pulss,cunt and toqu wavfoms fo h=.5 and h=4 spctivly. It can b sn that th numb of switching has bn dcasd whn th hystsis band was incasd fom h=.5 to h=4. Howv th toqu and cunt ippl incass as sn fom Fig 8(b) and Fig. 8(c).Th toqu ippl facto iss fom 15% to 6% with th incas in hystsis band of th cunt contoll. Tm Fig. 7(a) Gat puls Copyight to IJAREEIE

8 Toqu(Nm) Iabc(A) pulss Toqu(Nm) Iabc(A) ISSN (Pint) : ISSN (Onlin): Intnational Jounal of Advancd Rsach in Elctical, Elctonics and Instumntation Engining (An ISO 397: 7 Ctifid Oganization) Vol., Issu 8, August Fig 7(b).Cunt Fig. 7(c) Toqu Tm Fig. 8(a) Gat puls Fig. 8(b) Cunt VII. Fig. 8(c) Toqu CONCLUSION Th ovall fficincy of induction moto div dpnds on vaious factos lik hystsis band of th cunt contoll, load conditions, flux lvl. Th induction moto div fficincy can b impovd by mans of loss duction, which can b alizd by moto slction and dsign, impovmnt of th wavfoms supplid by pow invts, utilizing a suitabl contol mthod. Th fficincy of induction moto at light loads can b impovd by opating th machin at a flux lvl blow th atd valu, thus contolling th ion losss. Th switching losss in th invt and th toqu ippl in th induction moto a th citical factos dciding th hystsis band fo th cunt contoll. REFERENCES [1] Cao-Minh Ta and Yoichi Hoi, "Convgnc impovmnt of fficincy optimization contol of induction moto divs", IEEE Tans, Ind. Appl., voi.37, no.6, pp , Nov / Dc 1 [] Bimal K. Bos, Modn Pow Elctonics and AC Divs, 1st d.,pason Education, Inc, 3 [3] P. Famoui and J. Cathy, Loss minimization contol of an induction moto div, IEEE Tans. Ind. Appl., vol. 7, no. 1, pp. 3 37, Jan./Fb [4] A. M. Bazzi and P. T. Kin, Rviw of mthods fo al-tim loss minimization in induction machins, IEEE Tans. Ind. Appl., vol. 46,no. 6, pp , Nov./Dc. 1. [5] I. Takahashi and H. Mochikawa, A nw contol of PWM invt wavfom fo minimum loss opation of an induction moto div, IEEE Tans. Ind. Appl., vol. IA-1, no. 3, pp , May/Jun Copyight to IJAREEIE 381

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