Điều khiển động cơ từ trở thay đổi ở vùng tốc độ cao

E] KHOA HQC - CONG NGHE DIEU KHIEN DONG CO TIT TRO THAY DOI a VUNG TOO DO CAO ThS.Le Qude Dung Khoa Cong nghi TUddng - TrUdng Dgi hoc Oien tUc Tom tSt: Ogng ca tC/ trd thay dSi dugcphdt minh cdch ddy han 100 ndm Mac dii co nhCtng uu diem nhu cau tao dan gidn, gid thdnh thdp nhUng nhUng nhugc diim cua nd nhumdmen ddp mach, gdy tting 6n va dieu khiin khd khan md viic Ung dung nd cong nghiip vd ddi s6ng khong dUpc chii NhCfng nam cuoi theky20, dau the ki 21, cung vdi suphdt trien manh me cua cdng nghi diin tif, bdn ddn viic dp dung cdc thudt todn dieu khiin phdc tap trd nen khd thi Do vdy khodng thdi gian ndy, ddng co tU trdduac nhieu ngUdi quan tdm nghien cdu Dpng CO tU trd Id lua chon phu hap cho nhUng Ung dung yeu cau toe cao vi cdu tao rotor chdc ehdn cung nhu biin phdp dieu khien ddn gidn dedua ddng colen Idm viec d toe dd cao Bdt bdo ndy se gidi thiiu vimotphuang phdp dieu khien ddng ca tU trd thay doi d vung toe cao Dat van de Dpng CO t d trd thay ddi (SRM) id mdt loai ddng ed dien dddc biet den tQ nhQng nam 1890 Tuy nhien t d mpi ddi SRM khdng dQOc quan tam phdt tnen ed nhQng nhddc d i l m nhd: Op nhap nhd md men idn, gay nhieu t i l n g dn, khd thde hien viec dieu khiln NhQng nam gan day, cdng nghe ban dan va vi d i l u khiln phat trien, thu dQpc nhieu t i l n bd dang ke thi ngQdi ta mpi bdt dau quan tam trd lai vdi dpng cd bdng phddng phap thdng thddng Vdi md men tdi Tl tdc dp dpng CO chi dat tdc dd ^m\ ("^mi ^ ^mi) dd khdng tan dung h i t ddpc cong suat cua dpng co Dpng CO tQ trd la Ida chon phii hpp cho nhQng Qng dung yeu eau tdc dd cao vi cau tao rotor chac chSn cung nhd bien phdp d i l u khiln dan gidn d l dda ddng cd len lam viec d toe dp eao Khi dieu khiln tdng tdc ddng co mdt chieu bdng phQong phdp gidm tQ thdng, tdc dp Idn nhat bl han che bdi khd nang chuyin mach cua cd gdp dien Khi gidm tQ thdng de tang tdc dp ddng cd thi dong thdi dieu kien chuyen mach cua cd gdp cung xau di.vi vay phdi gidm ddng dien phan Qng cho phep, k i t qua la md men ciia ddng co giam rat nhanh Ngay ca gid nguyen ddng dien phan Qng thi dp cihig ddc tinh cd cung gidm rat nhanh gidm tQ thdng kich thich Ddi vdi ddng cd khdng ddng bp cung nhQ ddng bd cd stato dang day quan thi tdc quay cau nd ban c h i d l ddm bao dp chdc ehdn v l CO Dpng cd khdng ddng bd roto Idng sde cd roto cau tao don gidn song bien phap d i l u khien de dda dpng CO len lam viee d vung tdc dd cao rat phQc tap Cau tao vd nguyen ly lam viec cua SRIVI " m j « d ^^ "'ml Hinh Viing gidi han Idm viic cua dpng ca Cac bien phap d i l u khien thdng thddng hoan toan dap Qng ddpc dac tinh mong mudn d vung tdc dd thap nhdng d viing tdc dd cao phdong phap dieu khien khdng the cho phep ddng cd lam viec vdi cdng suat khdng doi va toe Idn nhat cua dpng cd la nhd mac dung mo men tdi giam khd nhilu DQdng BCD la dddng gidi han cdng suat va dddng BEF la dddng dac tinh dieu khiin 18 I Dien & D&i song Cdu tao Dpng CO tQ trd thay doi co mot sd dac d i l m chinh v l eau tao nhd sau: • Cd rotor va stator deu cd cac cdc Idi dd ngddi ta cdn gpi la dpng cd Idi kep (double salient) • Stator cua dpng co tQ trd thay ddi cd cau tao bdi nhilu CQc tQ chQa cac cudn ddy tap trung Rotor dQpc che tao bang vat lieu sat tQcd x l rang vdi tong sd rang bao gid CLJng it hdn tong sd cdc tQcua stator KHOA HQC - CONG NGHE Q • Cdc cudn day tren cac cdc ddi xQng xuyen tam eua stator ddpc noi ndi t i l p hoac song song de tao mpt pha cua dpng cd • Cd stator va rotor deu dddc Idm tQ cdc la thep mdng ghep each dien d l han ehi ddng Fuco • Ddng ca tQ trd thay ddi cd mdt sd cau hinh phd b i l n nhQ sau: 8/6 (tQc Id stator cd CQc Idi cdn rotor cd rdng (Hinh 2), 6/4,10/6,12/6, Hinh Nguyen lihoat ddng Hinh Cau tao cat ngang SRM 6/4 Do rotor ludn cd xu hQdng quay v l phia md dp td cdm ldn nhdt hay tQ trd nhd nhdt nen rotor luc ndy se quay hQdng d i n vi tri ddng true cua a, a'va r^, r^' Khi chung d a d vj tri thi ddng dien kich thich pha A bj ngdt va vj tri cac cQc nhd thay d (hinh 3b) Bdy gid ta dda ddng dien kich thich vdo cudn ddy ciia pha B, ddng lai sinh mot tQ thdng mdc vdng qua cac cdc b, b'va r,, r,'mdt each tdong Qng, rotor lai ddpc keo quay theo chieu kim ddng hd dda r,, r,' hddng ve vj tri thSng hang vdi b va b' Khi d i n vi tri ta lai ngdt ddng cdp eho pha B Tilp tuc chuyen sang cap ddng cho pha C thi r^, r^' iai quay theo chieu kim ddng hd hddng v l e, e' CQ nhd vay bang viee cap ddng dien lan Iddt cho tQng pha theo thQ t d A B C ta se lam dpng co quay theo chieu kim ddng hd Mudn dao chilu quay ciia ddng eota chi can dao t h d t d c a p d d n g AC B Uu diem cCia SRM Nguyin ly hpat dpng TrQdc di vao tim hieu nguyen ly hoat ddng ciia dpng eo tQ trd ta xem xet khai niem quan trpng dd la: • Vi tri ddng true (Aligned position) • Vi tri lech true (Unaligned position) NhQ da t h i hien tren (hinh 1) ta thay hai ede Idi eua stator va rotor ndm d vi tri ma true cua chung trung thi ngQdi ta gpi dd la "vj tri dong true" (vj tri ma tQ cam smh giQa cdc tQ cua stator vd rang eua rotor Id Idn nhat), cdn hai cQc eiia stator va rotor ndm lech hoan todn vd khdng cd phan thiet dien nao chdng len thi gpi la "vj tri lech truc"(vi tri ma dp tQ edm giQa cQc tQ cua stator va rotor la be nhat) Lay vi du la dpng co t d trd thay ddi 6/4 nhd (hinh 3) ta tim hieu cdch hoat ddng cQa ddng co Gia sQ cdc cQc r, vd r,' cua rotor va cQc c, c' ciia stator dang d vi tri ddng true (hinh 3a) TrQdc tien ta dQa ddng dien kich thich vao cudn day pha A, ddng dien se sinh mot tQ thdng mdc vong qua eae cQc a va a' vd cac cQc r, va r^' cua rotor mdt each tQdng Qng - Rotor khdng cd cudn day, ehdi than hay vanh gdp nen ddng ed hoat ddng rat b i n vQng, tudi thp eao - Mdmen khdi dpng Idn hon nhieu so vdi cdc loai ddng co khong ddng bp - Dd tin edy cao, viing toe dd rdng vdi cdng suat la hdng sd, gia sdn xuat thap, dap Qng ddng hpc nhanh - Khdng ed hien tQpng qua ddng lam hdng cac van cdng suit toe dp tang dong cao - Do khdng cd nam eham vinh cQu nen nhiet dp eho phep ciia rotor cao hon ddng eo ddng bd Nguyen li cd bdn cua phuong phap dieu khien I I Mdmen (Tren a c n V1> , VCing cSng suA la hSno s6 I Ml I \ „,„^ miSmenid hdngsd Hinh 4.Di/cfng ddc tinh diiu khien cua ddng ca ti/trd thay doi Dien d D&i song\ \% E] KHOA HQC - CONG NGHE TQ phQOng trinh didn cd: DQdng ddc tinh cd chia Idm viing: a)Vung mdmen Id hdng sd: Vs = Rs*i-^ - Dong dien va mdmen dQpc glQ la hSng sd nhd PWM vd bdm xung - d tdc dp thap ddng dien cd t h i tang tQc thdi sQc phdn dien ddng nhd (tl Id vdi tdc dd).Tdc dd cua ddng co dQdi tdc dd dinh mQc 0)-i de D4 tdc dSy tdc dd ddng co Idn trdn tdc dd djnh mQc ta cdn phdi gidm md men d l ddm bdo cdng sudt cQa ddng cd Id khdng ddi.Vung tdc dp cao sQc phdn didn ddng Idn VI vdy ta khdng diing bd bdm xung PWM vl sQc phdn didn ddng cua ddng cd Idn.Dl d l y ddng co len Idm viec d vdng tdc dd ndy ta khdng Idm cd ky thudt dieu khiln ddc biet c)Vung tfch cdng suKt vd tdc dd Id hdng sd De day tdc dp ddng ca \in eao d i n tdc dp mong mudn gap nhilu lan tdc dp djnh mQc cua ddng cd thi ta can phdi gidm cdng suit ddng cO ,Dilu dp cd nghia la ta gidm md men tdi de toe ddng co cd the dat den tdc dd ta mong mudn y sudt dien ddng nhd Ddng thdi gia tri ddng dien dt nhd cung la luc dao hdm dien cdm cua ddng cotang dodo *(o Nhd vay de bdng viec md xung sdm ta cd the lam gidm sQc phdn dien ddng ciia dong co ,do dd day dddc tdc dd ddng co len cao N < \ / * 0.5 46 Tai vung tdc dd eao sQc dien ddng Idn ngudn didn dp mPt chieu la hSng sd Do vdy mudn day tdc dd ddng co len cao ta phdi fim cdch gidm sQc di^n ddng cQa ddng co Mdt phdong phdp dQoc dQa dp Id phat xung ddng sdm d l gid trj ddng dien tdng manh khdng rOi vdo khodng dien cdm cua ddng cd Idn idm thdnh phan A ' HMO ol 0) = *o de Vs-Rs*i Ldi idL de^ de lam gidm phan suat didn ddng Opng cd tir trd d tdc cao Khi ddng ed d tdc cao sQc phan dien dpng tdng, gia tri dien dp cung cap khdng dii cho viec d i l u c h i dp rdng xung Do dd chi diing phddng phap xung ddn d l dieu khiln viec ddng md van cap dien dp cho cudn ddy Hinh 4.4 md td viee dieu khien ddng co d tdc dp cao : _ , d(L*i) = Rs*idt dt = Rs*i +Ldi idL dt dt idL = Rs*i Ldi b)Vung cdng suj(t Id hdng sd: 10 , dX ^ 60 75 90 105 120 Hinh Dang xung ddng ccf d tdc dd cao Ban dau bdt dau phat xung ddng didn qua cudn di Vs daytdngnhanhva gan nhd tuyln tinh: — = — dt L Khi dien cdm ciia pha bdt dau tang, suat phdn dien ddng xuat hien lam cho dong dien cudn ddy cd xu hddng gidm.Tai viing tdc dd cao thi ddng se gidm nhanh hon Chinh vl vay d vung tdc dp cao md men cua dong eo gidm 20 Dien Jk D&i song Hinh Dang xung ddng cakhi mdsdm Xet khia canh khae, ta t i l n hanh khda van mudn hdn binh thddng thi cung gdp phan diy tdc dp ddng cd di , len cao Khi dd dai I d p n g — c d gia trj am se lam gidm mau sd cua (2) Luc thi dien cam L da gan nhd dat gia trj bao dL , hda vd khdng tang nOfa, tQc la — rat nhd Hai yeu to de ^^ ^ dda tdc dp len cao Vdi phdong phap ta cd the day toe dp ddng co len gap lan tdc dd dinh mQc song tQ thdng va md men deu gidm KHOA HQC - CONG NGHE Q Mo hinh h4 thong [M> —.1 47, ,-, « • -+ H;i - » i ] Timunangle (ieg] — 'M—dE=^—'Ji»i TimKJllaiBe 1*6) _44 g W/nh 6.1 So he thong truyen dong Bd bien doi :dQac dung cho he truyln dpng la bd biln ddi elu khdng ddi xQng dilu khiln theo phddng phdp cung ddng hoac cung md ca hai khda Tl va T2 So diing cho ca pha: So ciia mdt pha: ,020- h r I I I' •.^ BR BR_C0NV2 ' Ci> "^1 BR_C0NV3 -»-Gcin •Hinh 6.2 B& bien doi diing Clio mdtpiia Hint, 6.3.Sad6b6 bien doi pha Oien & Odi songl 21 E] KHOA HQC • CONG NGHE %Cac thong so cua bo dieu chinh dong dien Req=Rs+dL_dtheta"w/dm; Kb=dL^dtheta'^iO; a Kr=Vdc/vc; Hc=vc/tmax; Kl=B/(Kb»Kb+Rs*B); Tm=J/B; T1 = 1/(1/2»(B/J+Req/L)-sqrt(1/4*(B/J + Req/L)A2(KbA2+Req"B)/J/L)); T2=l/{1/2*(B/J+Req/L)+sqrt(1/4*(B/J+Req/L}A2(KbA2+Req*B)/J/L)); ;; • I i I im Kc={1.414"T1"T2'10A4-TVT2)/(Hc"Kr*K1*Tm); Tc=Hc*Kc*Kr*K1"Tm/(T1*T2*10A8-1); Hinh 6.4 B6 phdt xung ddng diin %C3C thong so cua bo dieu chinh toe wmax= 10000/9.55; Hw=vc/w/max;