Các phương pháp điều khiển ĐC DC kích từ độc lập

8/12/2019 Cc phng php iu khin C DC kch t c lp

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LUAN VAN TOT NGHIEP GVHD: HUYNH VAN KIEM

SVTH : HOANG TRONG LINH TRANG 1

Chng I:


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CAC PHNG PHAP IEU CHNH TOC O ONGC MOT CHIEU KCH T OC LAPI. KHAI NIEM CHUNG:I. 1 nh ngha:

ieu chnh toc o ong c la dung cac bien phap nhan tao e thay oi cac thongso nguon nh ien ap hay cac thong so mach nh ien tr phu, thay oi t thong To tao ra cac ac tnh c mi e co nhng toc o lam viec mi phu hp vi yeu cau.Co hai phng phap e ieu chnh toc o ong c:

Bien oi cac thong so cua bo phan c kh tc la bien oi ty so truyen chuyen tiep

t truc ong c en c cau may san suat. Bien oi toc o goc cua ong c ien. Phng phap nay lam giam tnh phc tapcua c cau va cai thien c ac tnh ieu chnh. V vay, ta khao sat s ieu chnh toco theo phng phap th hai.

Ngoai ra can phan biet ieu chnh toc o vi s t ong thay oi toc o khi phu taithay oi cua ong c ien.

Ve phng dien ieu chnh toc o, ong c ien mot chieu co nhieu u viet hn sovi cac loai ong c khac. Khong nhng no co kha nang ieu chnh toc o de dang ma

cau truc mach ong lc, mach ieu khien n gian hn, ong thi lai at chat lngieu chnh cao trong day ieu chnh toc o rong.

I. 2 Cac ch tieu ky thuat e anh gia he thong ieu chnh toc o:Khi ieu chnh toc o cua he thong truyen ong ien ta can chu y va can c vao

cac ch tieu sau ay e anh gia chat lng cua he thong truyen ong ien:

I. 2. a Hng ieu chnh toc o:Hng ieu chnh toc o la ta co the ieu chnh e co c toc o ln hn hay be

hn so vi toc o c ban la toc o lam viec cua ong c ien tren ng ac tnh c tnhien.

I. 2. b Pham vi ieu chnh toc o (Day ieu chnh):Pham vi ieu chnh toc o D la t so gia toc o ln nhat nmaxva toc o be nhat

nminma ngi ta co the ieu chnh c tai gia tr phu tai la nh mc: D = nmax/nmin.

Trong o:- nmax: c gii han bi o ben c hoc.- nmin: c gii han bi pham vi cho phep cua ong c, thong thng ngi ta

chon nminlam n v.Pham vi ieu chnh cang ln th cang tot va phu thuoc vao yeu cau cua tng hethong, kha nang tng phng phap ieu chnh.


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I. 2. c o cng cua ac tnh c khi ieu chnh toc o:o cng: = M/n. Khi cang ln tc M cang ln va n nho ngha la o on

nh toc o cang ln khi phu tai thay oi nhieu. Phng phap ieu chnh toc o totnhat la phng phap ma gi nguyen hoac nang cao o cng cua ng ac tnh c.Hay noi cach khac cang ln th cang tot.I. 2. d o bang phang hay o lien tuc trong ieu chnh toc o:

Trong pham vi ieu chnh toc o, co nhieu cap toc o. o lien tuc khi ieu chnhtoc o c anh gia bang t so gia hai cap toc o ke nhau:= ni/ni+1

Trong o:- ni: Toc o ieu chnh cap th i.- n

i + 1: Toc o ieu chnh cap th ( i + 1 ).

Vi niva ni + 1eu lay tai mot gia tr moment nao o.tien cang gan 1 cang tot, phng phap ieu chnh toc o cang lien tuc. Luc nay haicap toc o bang nhau, khong co nhay cap hay con goi la ieu chnh toc o vo cap.

1 : He thong ieu chnh co cap.

I. 2. e Ton that nang lng khi ieu chnh toc o:He thong truyen ong ien co chat lng cao la mot he thong co hieu suat lam

viec cua ong c la cao nhat khi ton hao nang lng Pphu mc thap nhat.

I. 2. f Tnh kinh te cua he thong khi ieu chnh toc o:He thong ieu chnh toc o truyen ong ien co tnh kinh te cao nhat la mot he

thong ieu chnh phai thoa man toi a cac yeu cau ky thuat cua he thong. ong thihe thong phai co gia thanh thap nhat, chi ph bao quan van hanh thap nhat, s dungthiet b pho thong nhat va cac thiet b may moc co the lap rap lan cho nhau.

II. IEU CHNH TOC O BANG CACH THAY OI IEN AP AT VAO PHANNG ONG C:oi vi cac may ien mot chieu, khi gi t thong khong oi va ieu chnh ien ap

tren mach phan ng th dong ien, moment se khong thay oi. e tranh nhng bienong ln ve gia toc va lc ong trong he ieu chnh nen phng phap ieu chnh toco bang cach thay oi ien ap tren mach phan ng thng c ap dung cho ong cmot chieu kch t oc lap.

e ieu chnh ien ap at vao phan ng ong c, ta dung cac bo nguon ieu apnh: may phat ien mot chieu, cac bo bien oi van hoac khuech ai t Cac bo bienoi tren dung e bien dong xoay chieu cua li ien thanh dong mot chieu va ieuchnh gia tr sc ien ong cua no cho phu hp theo yeu cau.

Phng trnh ac tnh c cua ong c ien mot chieu kch t oc lap:

MKK

RR

K

Un

ME

fu

E

2


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Ta co toc o khong tai ly tng: n0= Um/KEm.o cng cua ng ac tnh c:Khi thay oi ien ap at len phan ng cua ong c th toc o khong tai ly tng se

thay oi nhng o cng cua ng ac tnh c th khong thay oi.

Nh vay, khi ta thay oi ien ap th o cng cua ng ac tnh c khong thay oi.

Ho ac tnh c la nhng ng thang song song vi ng ac tnh c t nhien:

Hnh I. 1 Ho ac tnh c khi thay oi ien ap at vao phan ng ong c.

Phng phap ieu chnh toc o bang cach thay oi ien ap phan ng thc chat lagiam ap va cho ra nhng toc o nho hn toc o c ban n cb. ong thi ieu chnh nhaycap hay lien tuc tuy thuoc vao bo nguon co ien ap thay oi mot cach lien tuc vangc lai.

Theo ly thuyet th pham vi ieu chnh D = . Nhng trong thc te ong c ienmot chieu kch t oc lap neu khong co bien phap ac biet ch lam viec pham vi chophep: Umincp= Um/10, ngha la pham vi ieu chnh:

D = ncb/nmin= 10/1. Neu ien ap phan ng U < Umincpth do phan ng phan ng se lamcho toc o ong c khong on nh.

Nhan xet:Phng phap ieu chnh toc o bang cach thay oi ien ap at vao phanng ong c se gi nguyen o cng cua ng ac tnh c nen c dung nhieu trong

may cat kim loai va cho nhng toc o nho hn ncb. u iem: ay la phng phap ieu chnh triet e, vo cap co ngha la co the ieuchnh toc o trong bat ky vung tai nao ke ca khi khong tai ly tng.

Nhc iem: Phai can co bo nguon co ien ap thay oi c nen von au t cban va chi ph van hanh cao.

III. IEU CHNH TOC O BANG CACH THAY OI T THONG:

fu

ME

RR

KK

dn

dM

2

U1U2U3

TN ( Um )n0ncbn1n2n3 M

n

MC

Um> U1> U2> U3ncb> n1> n2> n3

-

+

+ -

CK RK

IU

UKT


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Hnh I. 2 S o nguyen ly ieu chnh toc o bang cach thay oi t thong.ieu chnh t thong kch thch cua ong c ien mot chieu la ieu chnh moment

ien t cua ong c M = KMIva sc ien ong quay cua ong cE = KEn. Thong thng, khi thay oi t thong th ien ap phan ng c gi nguyengia tr nh mc.

oi vi cac may ien nho va oi khi ca cac may ien cong suat trung bnh, ngita thng s dung cac bien tr at trong mach kch t e thay oi t thong do ton haocong suat nho. oi vi cac may ien cong suat ln th dung cac bo bien oi ac biet

nh: may phat, khuech ai may ien, khuech ai t, bo bien oi vanThc chat cua phng phap nay la giam t thong. Neu tang t thong th dong ien

kch t IKTse tang dan en khi h cuon day kch t. Do o, e ieu chnh toc o ch cothe giam dong kch t tc la giam nho t thong so vi nh mc. Ta thay luc nay toco tang len khi t thong giam: n = U/KE.

Mat khac ta co: Moment ngan mach Mn= KMIn nen khi giam se lam cho Mngiam theo.

o cng cua ng ac tnh c:

Khi giam th o cng cung giam, ac tnh c se doc hn. Nen ta co ho ngac tnh c khi thay oi t thong nh sau:

Phng phap ieu chnh toc o bang cach thay oi t thong co the ieu chnh ctoc o vo cap va cho ra nhng toc o ln hn toc o c ban.

Theo ly thuyet th t thong co the giam gan bang 0, ngha la toc o tang en vocung. Nhng tren thc te ong c ch lam viec vi toc o ln nhat:

nmax

= 3ncb

tc pham vi ieu chnh: D = nmax

/ncb

= 3/1.

Bi v ng vi moi ong c ta co mot toc o ln nhat cho phep. Khi ieu chnh toco tuy thuoc vao ieu kien c kh, ieu kien co gop ong c khong the oi chieu dong

RKK ME

2

12

m0 MC M2 M1 MnHnh I. 3 Ho ac tnh c khi thay oi t thong.

ncbn1n2

n

M

m> 1> 2ncb< n1< n2


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ien va chu c ho quang ien. Do o, ong c khong c lam viec qua toc o chophep.

Nhan xet:Phng phap ieu chnh toc o bang cach thay oi t thong co the ieuchnh toc o vo cap va cho nhng toc o ln hn ncb. Phng phap nay c dung eieu chnh toc o cho cac may mai van nang hoac la may bao ging. Do qua trnhieu chnh toc o c thc hien tren mach kch t nen ton that nang lng t, mangtnh kinh te. Thiet b n gian.

IV. IEU CHNH TOC O BANG CACH THAY OI IEN TR PHU TRENMACH PHAN NG:Phng phap ieu chnh toc o bang cach thay oi ien tr phu tren mach phan

ng co the c dung cho tat ca ong c ien mot chieu. Trong phng phap nay ientr phu c mac noi tiep vi mach phan ng cua ong c theo s o nguyen ly nh

sau:

Hnh I. 4 S o nguyen ly ieu chnh toc o ong c bang cach thay oi ientr phu tren mach phan ng.

Ta co phng trnh ac tnh c cua ong c ien mot chieu kch t oc lap:

Khi thay oi gia tr ien tr phu Rfta nhan thay toc o khong tai ly tng: va ocng cua ng ac tnh c:

se thay oi khi gia tr Rfthay oi. Khi Rfcang ln, cang nho ngha la ng ac tnhc cang doc. ng vi gia tr Rf= 0 ta co o cng cua ng ac tnh c t nhien ctnh theo cong thc sau:

Ta nhan thay TNco gia tr ln nhat nen ng ac tnh c t nhien co o cng ln

hn tat ca cac ng ac tnh c co ong ien tr phu tren mach phan ng. Vay khithay oi gia tr Rfta c ho ac tnh c nh sau:

MKK

RR

K

Un

ME

fu

E

2

u

dmME

TNR

KK 2

-

-

+

+

I RfCK RK

UE

UKT

constKUn

dmE

dm

0fu

dmME

RRKK

2


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Hnh I. 5 Ho ac tnh c khi thay oi ien tr phu tren mach phan ng.

Nguyen ly ieu chnh toc o bang cach thay oi ien tr phu tren mach phan ngc giai thch nh sau: Gia s ong c ang lam viec xac lap vi toc o n1 ta ongthem Rfvao mach phan ng. Khi o dong ien phan ng Iot ngot giam xuong, contoc o ong c do quan tnh nen cha kp bien oi. Dong I giam lam cho momentong c giam theo va toc o giam xuong, sau o lam viec xac lap tai toc o n2vi n2> n1.

Phng phap ieu chnh toc o nay ch co the ieu chnh toc o n < n cb. Tren thcte khong the dung bien tr e ieu chnh nen phng phap nay se cho nhng toc onhay cap tc o bang phang xa 1 tc n1cach xa n2, n2cach xa n3

Khi gia tr nmincang tien gan en 0 th pham vi ieu chnh:D = ncb/nmin .

Trong thc te, Rfcang ln th ton that nang lng phu tang. Khi ong c lam viec toc o n = ncb/2 th ton that nay chiem t 40% en 50%. Cho nen, e am bao tnhkinh te cho he thong ta ch ieu chnh sao cho pham vi ieu chnh: D = ( 2 3 )/1.

Khi gia tr Rf cang ln th toc o ong c cang giam. ong thi dong ien nganmach Inva moment ngan mach Mncung giam. Do o, phng phap nay c dung ehan che dong ien va ieu chnh toc o di toc o c ban. Va tuyet oi khong cdung cho cac ong c cua may cat kim loai.

Nhan xet: Phng phap ieu chnh toc o bang cach thay oi ien tr phu trenmach phan ng ch cho nhng toc o nhay cap va nho hn n

cb.

u iem: Thiet b thay oi rat n gian, thng dung cho cac ong c cho can truc,thang may, may nang, may xuc, may can thep.

Nhc iem: Toc o ieu chnh cang thap khi gia tr ien tr phu ong vao cangln, ac tnh c cang mem, o cng giam lam cho s on nh toc o khi phu tai thayoi cang kem. Ton hao phu khi ieu chnh rat ln, toc o cang thap th ton hao phucang tang.

V. IEU CHNH TOC O BANG CACH RE MACH PHAN NG:ong c ien mot chieu kch t oc lap khi ieu chnh toc o bang cach re mach

phan ng co s o nguyen ly nh sau:

TNRf1Rf2Rf3MC

n3n2n1ncbn0n

M, I

0 < Rf1< Rf2< Rf3ncb> n1> n2> n3


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Hnh I. 6 S o nguyen ly phng phap ieu chnh toc o bang cach re mach phanng.

Mot he thong khi ieu chnh can toc o nho hn ncbva ieu chnh nhay cap. Hethong co o cng tng oi ln va thiet b van hanh n gian th ngi ta dung phngphap re mach phan ng hay con goi la phan mach.

Theo phng phap re mach phan ng th phan ng ong c noi song song vi ientr va noi noi tiep vi mot ien tr khac. Phng phap nay giong vi phng phapthay oi ien tr tren mach phan ng nhng ien ap phan ng lai khong thay oi. Doo, phng phap nay oi hoi phai:

- ien ap at vao phan ng ong c khong thay oi.- V dong kch t khong thay oi nen khi ieu chnh toc o, t thong khong oi lam

cho moment phu tai cho phep c gi khong oi va bang tr so nh mc.

Ta co phng trnh ac tnh c:

T phng trnh tren, ta nhan thay toc o ong c n< ncb. Mat khac ta co:

o cng cua ng ac tnh c re mach phan ng PM nho hn o cng cua actnh c t nhien TNnhng lai ln hn o cng cua ac tnh c co ien tr phu Rfviien tr phu chnh la Rn.

e ieu chnh toc o ong c trong trng hp nay ta tien hanh nh sau:

Gi nguyen Rn, thay oi gia tr RS:- Khi RS= 0: ay la trang thai ham ong nang vi toc o ham ong nang nHN= 0.

MKK

RR

RRR

RR

R

K

Un

ME

nS

nSu

nS

S

E 2

MKK

RR

RRR

RR

Rnn

ME

nS

nS

u

nS

S

20

000' nRR

Rnn

nS

S

u

nS

Sunu R

RR

RRRR

TNPMRR nf

IIS

InRnRS

-

CK RKE

U


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Hnh I. 7 Ho ac tnh c khi Rn= const, RSthay oi.Nh vay, khi gi nguyen Rn, thay oi gia tr RSth vung ieu chnh toc o b han

che va modun o ln ac tnh c tang dan khi toc o giam. Gi nguyen RS, thay oi gia tr Rn:

- Khi Rn= 0: RSkhong anh hng en ng ac tnh c. Luc nay ta xem R Snh latai noi song song vi ong c. Ta co c ng ac tnh c t nhien.

- Khi Rn= : ong c ien b h mach nen khong co ien ap ri tren phan ngong c. ay la trang thai ham ong nang vi RHN= RS. Ta co : IB= Um/RS. Ta coho ac tnh c nh sau:

Vay, khi gi nguyen RSva thay oi Rnth pham vi ieu chnh khong b han che nhtrng hp tren. Nhng khi toc o giam xuong th o cng ng ac tnh c lai bgiam xuong.

Ngoai ra con co phng phap thay oi ong thi gia tr cua RSva Rn: Phng phapnay thng c s dung trong thc te.

So vi phng phap ieu chnh bang cach thay oi ien tr phu tren mach phanng ta nhan thay: Khi toc o va moment ong c nh nhau ngha la khi cong suat c

Hnh I.8 Ho ac tnh c khi RS= const, Rnthay oi.

n1n2

ncb

I

TN ( RN = 0 )

MCRn= 0IB

nRn1Rn2

n00 < Rn1< Rn2< Rn=n2< n1< ncb

Ta co ho ac tnh c nh sausau:n

dm

ASR

UIRKhi ::

TNn

n0n3n2n1 IAMC RS= 0

RS=

RS2RS1

RS1< RS2n1< n2


10/97



nh nhau dong ien nhan t li trong s o re mach phan ng luon luon ln hn trongs o ieu chnh bang ien tr phu tren mach phan ng mot lng bang dong ienchay qua RS.

Phng phap nay ch dung cho can truc, cau truc, thang may, may can thep. ongthi tuyet oi khong dung cho may cat kim loai. Nhan xet: Phng phap ieu chnh toc o bang cach re mach phan ng th ieuchnh toc o nhay cap va cho nhng toc o nho hn n cb.

u iem:- Vi cung mot toc o yeu cau th o cng cua ng ac tnh c phan mach co o

cng ln hn ac tnh c dung ien tr phu tren mach phan ng.- Thiet b van hanh n gian.

Nhc iem:

- Phng phap nay dung tiep iem e ong cat ien tr nen o tinh chnh khongcao, ieu chnh toc o co cap, pham vi ieu chnh: D = ( 2 3 )/1.

- Do ton that cong suat trong s o nay kha ln nen pham vi ng dung b han che.Phng phap nay ch ap dung cho ong c co cong suat nho, thi gian lam viec nganvi toc o thap.

VI. IEU CHNH TOC O BANG HE THONG MAY PHAT - ONG C( F - ):VI. 1 S o nguyen ly:Vi nhng he thong ieu chnh toc o vo cap, pham vi ieu chnh toc o tng oi

rong. Can nhng toc o ln hn hay nho hn so vi toc o c ban va can ieu chnhlien tuc nh truyen ong chnh cua mot so may bao ging co nang suat thap, truyenong quay truc can thep co cong suat trung bnh va nho, truyen ong uc ong trongphng phap uc lien tuc th ngi ta dung he thong F - co s o nguyen ly nhsau:


11/97



Hnh I. 9 S o nguyen ly he thong may phat ong c. Trong o:

- SC: ong c s cap, cung cap ong lc cho toan he thong. Nhan cong suat ienxoay chieu, bien oi ien nang thanh c nang keo may phat F va may phat kch thchK. SC co the la ong c no, ong c ien tuy thuoc vao ch tieu ky thuat cua hethong.

- F: May phat mot chieu kch thch oc lap, cung cap trc tiep nguon mot chieu chophan ng ong c.

- : ong c ien mot chieu kch t oc lap keo c cau san xuat ( CCSX ), la oitng can ieu chnh toc o trong pham vi tng oi nho.

- K: May phat kch thch, thc chat la may phat ien mot chieu ac biet co t dln nen co kha nang t kch. Phat ra ien mot chieu UKcung cap cho mach kch thchmay phat CKFva kch thch cua ong c CK.VI. 2 Nguyen ly hoat ong:

e khi ong he thong F - ta tien hanh cac bc nh sau:- M tat ca cac cau dao CD1, CD2.

- ieu chnh bien tr mach kch thch cua ong c R K tr so cc tieu sao chomaxva ieu chnh bien tr mach kch thch cua may phat RKF tr so cc ai saocho Fmin.

- ong cau dao CD1( luc nay CD2van h ) khi ong ong c SC. ong c SCse quay va i cho toc o on nh. SC quay lam cho may phat F va may phat kchthch K quay.

- ong cau dao CD2e chon chieu quay cho ong c la thuan hay ngc. Luc nayco Fnhng rat be se lam cho EFbe nen U= EFIRFbe. ong c se khi ong vaquay vi toc o thap.

-

+ CD1I PmC

IKFRKF

CKF

2IK

RK

CK

1D2UK

RKKCKKP

Pc2c1 USCn

U1; f1

K F CCSX


12/97



- e tang dan ien ap at vao ong c, ta ieu chnh bien tr R KFgiam dan ve trso cc tieu ( tang dong kch t cua may phat ), do o, dong I tang dan, ong c tangtoc o cho en khi at en ncb. Qua trnh khi ong en ay la cham dt.

- e ngng truyen ong ta ieu chnh RKF tang dan e giam dong kch thch cua

may phat lam cho ien ap phat ra cua may phat UFgiam. Do o, toc o cua ong cgiam xuong va ngng han vao luc UF= 0. Sau o m cau dao CD2dng ong c SC.

Muon thay oi chieu quay cua ong c ta gat cau dao CD2sang v tr 2.

Vi he thong F - ta co the ieu chnh toc o theo hai hng nh sau:

e cho n< ncb: ieu chnh bien tr RKFcua may phat at gia tr cc ai e giamdong kch t cua may phat lam cho UFgiam, toc o ong c giam xuong at n< ncb.

Goi DU: Pham vi ieu chnh bang cach thay oi ien ap at len phan ng ong c.Ta co: DU= ncb/nmin= 10/1.

e cho n> ncb : Ta gi UF tr so nh mc va ieu chnh bien tr R Kat gia trcc ai e giam t thong kch thch cua ong c. Luc nay toc o cua ong c tang lenat n> ncb.

Goi D: Pham vi ieu chnh toc o bang cach thay oi t thong cua ong c. Taco: D= nmax/ncb= 3/1.

Ket hp hai phng phap ieu chnh la giam ien ap at vao phan ng ong c U va giam t thong ta c pham vi ieu chnh chung:

D = DUD= nmax/nmin= 30/1.

VI. 3 Thanh lap phng trnh ac tnh c cua he thong F - :Phng trnh ac tnh c tong quat:

Phng trnh can bang sc ien ong cua may phat: U= EFIRF

Thay vao phng trnh ac tnh c ta c:

u

DE

uFuD

DE

F IK

RR

K

En

MKK

RR

K

En

DME

uFuD

DE

F

2

u

EE

IK

R

K

Un

u

DE

uD

DE

IK

R

K

Un


13/97



ay la phng trnh ac tnh toc o cua he thong.

Thay I= M / KMvao phng trnh ac tnh toc o ta c phng trnh ac tnhc cua ong c trong he thong F - nh sau:

T phng trnh ac tnh c cua he thong ta nhan thay: ng vi moi hng ieuchnh toc o ong c khac nhau ( ln hay nho hn so vi toc o c ban ) ta se conhng ho ac tnh ieu chnh khac nhau nh a trnh bay tren.

Hnh I. 10 Ho ac tnh c ieu chnh trong he thong F - .

VI. 4 anh gia he thong F - :VI. 4. a u iem:

- He thong nay co the ieu chnh toc o vo cap, pham vi ieu chnh rong: D = ( 10 30 )/1 bi v qua trnh ieu chnh c thc hien bang mach kch thch cua mayphat va ong c. Co the dung phng phap bien tr.

- He thong co s chuyen oi trang thai lam viec rat linh hoat, kha nang qua tai lnnen thng c s dung cac may khai thac trong cong nghiep nho.

VI. 4. b Nh c iem:- Dung 4 may e quay nen khi lam viec se gay tieng on ln, chiem nhieu dien tch

e at may. ong thi tong cong suat at vao he thong F - qua ln: Gap 3 lan sovi yeu cau nen von au t ln.

- Hieu suat hoat ong cua he thong tng oi thap:

= Pc2/P< 0,75

- ac tnh c doc nen khi co dao ong phu tai th the hien ro hn na.

- Ngoai ra, do cac may phat mot chieu co t d, ac tnh t hoa co tre nen khoieu chnh sau toc o.

VI. 4. c Nha n xet:

321

RKF

RKncbn2n1 U

3

2 1U1U2

Um, m

n

M0 MC

MKK

RR

K

En

DME

uFuD

DE

F

D 2


14/97



Vi he thong F - vong h nh tren, ta khong the thc hien viec on nh toc oong c la nhiem vu can thiet oi vi cac he thong truyen ong nham nang cao chatlng san pham c gia cong tren may, nang cao chat lng ky thuat cua mot quitrnh cong nghe ma may san xuat tham gia hoac nang cao nang suat cua may.

e thc hien nhiem vu o, ta thng dung cac he thong F- co khuech ai mayien dung phan hoi vong kn. Trong cac he thong nay, cac bo khuech ai may ien ses dung cac lien he phan hoi, ngha la a mot tn hieu au ra cua he thong quay trlai au vao cua no. Tn hieu au ra co the la ien ap, dong ien trong mach chnhhoac toc o quay cua ong c. Tn hieu au vao la sc t ong cua khuech ai mayien. Cac khuech ai may ien thng dung hien nay la may kch t nhieu cuon dayieu chnh c, khuech ai may ien t kch va khuech ai may ien t trng giaotruc.

VII. HE THONG KHUECH AI MAY IEN ONG C:VII. 1 Khuech ai may ien ( KM ):KM la may phat mot chieu ac biet. Co 2 loai KM:

- KM t kch.

- KM t trng giao truc.

VII. 1. a Khuech ai ma y ien t kch:La loai may phat ien mot chieu ac biet. Mach t c lam bang thep ky thuat

can nguoi nen co t tr nho va ac tnh t tre hep.He thong kch t co t 3 en 4 cuon day:

- Mot cuon lam kch t oc lap ( kch t chnh ) at ien ap mot chieu vao vadung e ieu khien sc ien ong phat ra cua phan ng may ien.

- Mot cuon lam nhiem vu t kch, lay ien ap phat ra hai au phan ng hoacdong ien tren mach phan ng quay tr lai t kch.

- Cac cuon con lai dung e thc hien cac phan hoi trong he thong.

S o nguyen ly KM t kch:* KM t kch theo ien ap ( t kch song song ):

UngR1 CK1

CK3

CK4

CK2F1 F2

R2 UKM

+

- KMTK


15/97



Hnh I. 11 S o nguyen ly KM t kch song song.

Phng trnh ac tnh c cua phng phap nay :

MKeKm

kRntRu

Ke

Udmkn

2

Vi :RntRss

Rssk

Vi phng phap nay, ta co the ieu chnh c toc o nho hn toc o c ban, tonthat nang lng thap va ieu chnh toc o nhay cap.

* KM t kch theo dong ien ( t kch noi tiep ):

Hnh I. 12 S o nguyen ly KM t kch noi tiep.

Nh cuon t kch ma ien ap phat ra cua KM c nang cao so vi may phatthong thng. Da vao ac tnh volt-ampe cua KM ta thay:

UmKM= Um1+ Um2

Hnh I. 13 ac tnh volt-ampe cua he thong KM.

Khi co them CK2th U tang len mot lng Um2.

He so cong suat: KP= Pf/PKT= UKMIKM/UKIK = hang tram/1.

VII.1.b Khue ch ai may ien t trng giao truc:La may phat mot chieu ac biet:

IKM

R2

F2 CK2CK3

CK4F1 UKMng

R1 CK1

-

+

KMTK

CK2CK1

IKIm1Um1Um2UmKM

UKM


16/97



- Mach t lam bang thep ky thuat ien can nguoi, cc t dang an.

- Phan kch co t 3 en 4 cuon day:

. Mot cuon lam kch thch chnh ( kch t oc lap ) tao ra t trng chnh.

. Mot cuon lam nhiem vu bu.

. Cac cuon con lai dung e thc hien phan hoi trong truyen ong.

- Tren co gop at hai cap choi than co truc vuong goc nhau. Trong o, motcap c noi tat vi nhau con mot cap e lay ien ap ra.

Hnh I. 14 S o tng ng KM t trng giao truc.

ng ve mat khuech ai ta co the xem KM t trng giao truc tng ng vihai may phat ien lam viec ke tiep nhau va co s o nguyen ly nh tren.

He so khuech ai: KP= KPIKPII= UKMI2/UKIK.

ay la loai may ien co he so khuech ai cao nhat, K Pco gia tr hang ngan lan.

VII. 2 Khuech ai may ien t kch ong c dung phan hoi am toc o:VII. 2. a S o nguyen ly:

MFI; KPI MFII; KPIIUKMF21

R1 CK1 I1 I2

- +

E1 E2ng

U1, f1SC

Ung UCK3 CK2 R2

F2F3

F1

+

-

KMTK CCSX

FTnR1 CK1


17/97



Hnh I. 15 S o nguyen ly khuech ai may ien t kch ong c dung phan hoi amtoc o.

Trong o:

- Pmcua ong c 5KW.

- CK1: Cuon kch thch chu ao ( kch t oc lap ), sinh ra sc t ong F1.- CK2: Cuon t kch thch, sinh ra sc t ong F2cung chieu vi F1.

- R2: ieu chnh he so t kch. Gia tr R2cang nho th he so t kch cang ln vangc lai.

- CK3: Cuon phan hoi am toc o ( tn hieu a ve e kh F 1 ), sinh ra sc tong F3ngc chieu F1.

VII. 2. b Nguyen ly hoat ong:Ta co: F3= I3WCK3

EFT: Sc ien ong cua may phat o toc o FT. La may phat mot chieu ac bietc che tao vi mach t bao hoa rat sau e t thong nay phat ra hoan toan banghang so nen sc ien ong phat ra cua may phat ty le bac nhat vi toc o. Do o, khi

oc sc ien ong ngi ta biet c toc o theo moi quan he: EFT = KEFTnFT =KEFTn.

V mach t bao hoa sau nen FTxem nh la hang so nen EFTty le thuan vi nFT.

T cac bieu thc tren, ta nhan thay khi R3= const th: F3I3EFTn. V vay F3n. Sc t ong cua KM: FT= F1+ F2+ F3.

He thong nay co kha nang ieu chnh toc o theo hai hng:

* e cho n > ncb: Ta giam t thong bang cach tang gia tr RK.* e cho n < ncb: Ta giam ien ap at len phan ng cua ong c U thong qua

ieu chnh giam gia tr R1.

3CK3uFT

FT3 RRR

EI


18/97



Ngoai ra, khi ieu chnh R2e thay oi he so t kch ngha la thay oi o cng cuang ac tnh c. Thc chat qua trnh nay la nang cao o cng cua ng ac tnh ce at c toc o cao nhat khi ong c c m rong len. ong thi nh phan hoiam toc o ma ong c co kha nang lam viec vi toc o thap hn n cb/10, ngha la co

the m rong them toc o thap va cao nen ta c pham vi ieu chnh ln: D = ( 40 hang tram )/1.

He thong nay co kha nang on nh toc o khi phu tai thay oi nh khau phan hoiam toc o: Khi ong c ang lam viec vi phu tai Mcva toc o at yeu cau nyc. V lydo nao o, moment phu tai at len truc ong c thay oi, khac nyc th nh qua trnhphan hoi am toc o he thong se t ong on nh toc o at nyc. Qua trnh t ong nayc giai thch nh sau: Gia s khi Mctang se lam cho ngiam < nyc. Ma khi n giamEFTgiam I3giam F3giam FT= F1+ F2+ F3tang EKMtang Utangn tang at en nyc. Va khi Mcgiam th qua trnh se t ong xay ra theo chieu ngclai e toc o ong c at nyc.

Hnh I. 16 ac tnh c cua he thong khuech ai may ien t kch ong

c dung phan hoi am toc o.VII. 2. c Nhan xet:

* u iem: Dung sai so toc o quay tr lai ieu khien he thong e t ong on nhtoc o ( khau phan hoi trc tiep ). Viec tnh toan khau phan hoi am toc o tien hanhrat n gian, tien li.

* Nhc iem: Dung may phat toc o nen gia thanh cua he thong cao.

VII. 3 He thong khuech ai may ien t trng giao truc ong c dung phan hoidng dong ien va phan hoi am ien ap:

VII. 3. a S o nguyen ly:

TNM

n

MC MC1

n0nycn1

U1, f1

-

+

-

SCR1 CK1 CK3 CK2

UngUfhI

I

R3R4 U2F23

CK RKCCSX

MTTGTF1

n


19/97



Hnh I. 17 S o nguyen ly he thong khuech ai may ien t trng giaotruc ong c dung phan hoi dng dong ien va phan hoi am ien ap.

Trong o:

- CK1: Cuon kch thch chu ao, sinh ra sc t ong F 1.

- CK2: Cuon phan hoi dng dong ien, sinh ra sc t ong F2cung chieu vi F1.

- CK3: Cuon phan hoi am ien ap, sinh ra sc t ong F3ngc chieu vi F1.

VII. 3. b Nguyen ly hoat ong:Ta co: . F2= I2WCK2Vi:

Neu cho R2= const th ta c: F2I2UfhIIF2I.. F3= I3WCK3Vi:

Khi gi cho R3= const th ta c: F3I3UfhUUF3U.

Tng t nh he thong KM t kch ong c dung phan hoi am toc o, hethong nay cung co kha nang ieu chnh toc o theo hai hng ln hay nho hn so vincb.

He thong nay co kha nang m rong pham vi ieu chnh, t ong on nh toc o nhphan hoi dng dong ien va phan hoi am toc o. Gia s: Khi he thong lam viec viphu tai Mcva toc o at nyc. Khi Mctang n giam nho so vi nyc, luc o he thong se:Mctang M tang ( moment ong c tang e can bang vi phu tai ) Itang F2tang. Khi Itang UKM= IRKKtang U= EKMUKMgiam FT= F1+ F2+ F3tang EKMtang Utang n se tang at nyc. Khi Mcgiam th qua trnhxay ra theo chieu ngc lai.

VII. 3. c Nhan xet:* u iem: S dung thiet b n gian (ch dung cac ien tr R 2, R3, R4) nen gia

thanh thap.

22

22

2

2 ;

CK

CK

ufhI

CK

fhI

RR

RRIU

R

UI

43

3

D

3

3 ;

RR

RUUR

UI fhUCK

fhU


20/97



* Nhc iem: Viec tnh toan thiet ke phoi hp gia hai khau phan hoi nay e onnh toc o la kha phc tap (khau phan hoi gian tiep).

VII. 4 Nhan xet he thong khuech ai may ien ong c:VII. 4. a u iem:

Ngoai nhng u iem cua cac he thong F - vong h nh:

- Pham vi ieu chnh toc o rong vi o chnh xac va tin cay cao.

- Khi ong may em.

- Co kha nang ham tai sinh, tra nang lng lai cho li ien.

- Ton hao nang lng khi ieu chnh toc o va m may thap.

Cac he thong KM ong c vong kn con co nhng u iem:

- Co kha nang t ong on nh toc o ong c khi phu tai thay oi.- Co kha nang tang tnh on nh toc o cua he thong nh khau on nh.

- Co he so khuech ai cong suat ln.

VII. 4. b Nhc iem:He thong KM ong c co nhng nhc iem tng t nh he thong F - :

- Dung nhieu may ien vi tong cong suat lap at ln do o oi hoi gia thanhcao.

- Hieu suat hoat ong thap.

- Dien tch lap at may rong va oi hoi nen mong chac chan nen ph ton vanhanh ln.

- Gay tieng on ln.

VIII. HE THONG KHUECH AI T - ONG C:VIII. 1 S o nguyen ly:

Khuech ai t ( KT ) hay con goi la bo bien oi van t, la to hp cua khangbao hoa vi chnh lu khong ieu khien.

KT c dung e lam bo ieu chnh dong ien va ien ap trong cac he thongieu khien, ieu chnh va kiem tra t ong.

Trong cac may nang van chuyen, KT thng c dung lam may kch thchcho cac may phat trong he thong F - . oi vi may cat got kim loai, KT thngc dung ket hp vi chnh lu diode ban dan e cung cap cho phan ng ong c motchieu vi s o nguyen ly nh sau:


21/97



Hnh I. 18 S o nguyen ly he thong KT ong c.a). Tia ba pha.b). Cau ba pha.

Trong cac s o nay, may bien ap BA co chc nang bien oi gia tr ien ap chophu hp vi yeu cau cua ong c. Tao ra so pha hoac iem trung tnh cho phu hp vis o chnh lu neu can va nang cao he so cong suat cua he.

Cac van khong ieu khien Vodung e bien oi dong ien xoay chieu thanh motchieu va tao ra thanh phan dong ien t t hoa cho KT.

Cuon khang bao hoa KBH dung e ieu chnh gia tr sc ien ong cua bo bien

oi.

U1, f1

( a )

CKRK

BA

V0Wlv

+

-WkUk

-

+

U1, f1

BA

WkV0

Uk +

- -

CK RK

Wlv

( b )


22/97



VIII. 2 Nguyen ly hoat ong:Trong he thong KT ong c, toc o ong c c ieu chnh bang cach thay oi

tr so trung bnh cua sc ien ong chnh lu bang cach bien oi dong ien ieu khien,tc la bien oi mc o bao hoa cua mach t.

e n gian trong viec khao sat nguyen ly hoat ong cua he thong nay, ta tach ramot trong ba pha t cac s o tren va gia thuyet rang ac tnh t tre cua loi thep codang ly tng.

Hnh I. 19a). S o nguyen ly mot pha cua bo bien oi.b). Dang ac tnh t tre ly tng cua loi thep.

Ta co: u2= U2msint = iRt+ XK( di / dt )

Trong o: XKco gia tr thay oi theo trang thai t hoa cua loi thep. Luc au, loithep c t hoa co nh nh cuon ieu khien Wken mot gia tr B0 nao o trong

pham vi ( -BSB0+BS).* ban ky dng cua nguon u2: dong ien thuan i qua V0t hoa loi cuon khang,

lam cho bien o t cam bien thien. Luc nay, v loi thep cha bao hoa nen XKrat ln,nguon chu yeu ri tren cuon khang con gia tr iRt0. Ta co:

u2= U2msint = iRt+ XK( di/dt ) = NlvS ( dB / dt )

Vi ieu kien ban au: t = 0, B = B0, giai phng trnh nay ta c:

B = B0+ Bm( 1 - cost )

Trong o:- Bien o t cam: Bm= U2m/WNlvS

- Nlv: So vong day cua cuon lam viec.

- S : Dien tch tiet dien loi cua cuon khang.

- : Tan so goc cua dong ien.

Khi loi thep bao hoa, ta co XK= 0. Do o, toan bo nguon ap ch at len tai. Khi o:u2= U2msint = iRt= ub

Vi ubla ien ap ra cua bo bien, tc la ien ap at tren tai.

u2+

-

IkUk Wk Rt

V0( a )

B

H+BS

-BSB0

( b )


23/97



* ban ky am cua nguon u2: V0ngng dan, dong ien t hoa khong co nen loi thep bkh t bi cuon ieu khien Wkva o t cam B se giam dan ve gia tr ban au B0,ien ap tren tai ubu2= 0.

Gia tr trung bnh cua ien ap chnh lu c xac nh theo cong thc:

Trong o:- p: So lan ap mach trong bo chnh lu.

- : Goc bao hoa

- BS: T cam bao hoa.

Neu ta chon Bm= BSth = arccos ( B0/BS). Luc nay gia tr trung bnh cua ien apchnh lu: UKT= Um[ 1 + ( B0/BS)] = f ( B0).Vi:

Um= pU2m/2

Ta nhan thay: Khi thay oi gia tr B0t BSen +BSta se ieu chnh c ien apchnh lu UKTt 0 en gia tr U2m( p/). V B0la do dong ieu khien Iktao ra nenthc chat gia tr UKTchnh la ham cua Ik: UKT= f ( Ik).

VIII. 3 Phng trnh ac tnh c cua he thong KT ong c:T cong thc: n = n0- M/, ta c phng trnh ac tnh c cua ong c trong he

thong:

ay chnh la phng trnh ac tnh c cua ong c trong he thong KT ongc vi Rbla ien tr trong cua he thong.

Neu xem cuon khang la phan t tuyen tnh th ta se c ho nhng ng actnh c cua ong c la nhng ng thang song song nhau va c goi la ho ac tnhc ly tng.

)cos1(2

sin2

22

mmKDT Up

ttdUp

U

)1arccos( 0

m

S

B

BB

u

E

ub

E

KDT IK

RR

K

Un

u

E

ub

E

S

m

IK

RR

K

B

BU

n

)1( 0

MKK

RR

K

B

B

Un

ME

ub

E

Sm

2

0

)1(

M

nn0nycn1 Ik1Ik2Ik3

0 MC


24/97



Hnh I. 20 Ho ac tnh c ly tng cua ong c trong he thong KT ong c.

VIII. 4 Nhan xet:VIII. 4. a u iem:

- De che tao.

- Ben va gia thanh ha.

- Do KT la bo bien oi tnh nen khac phuc c nhng nhc iem cua hethong F - nh a trnh bay phan tren.

VIII. 4. b Nhc iem:- Do ien tr trong cua bo bien oi van t kha ln nen o cng cua ng actnh c thap, sai so toc o ln va day ieu chnh hep.

- Ve hnh thc ieu khien, he thong KT ong c kem linh hoat hn he F - .ao chieu quay ong c kho khan va gay ton that nang lng ln. Quan tnhcua he KT - ong c ln do anh hng cua ien khang KT, he so cong suatthap.


25/97



Chng II:Sillicon Controlled Rectifier (SCR) va Bo Chnh LuI. Sillicon Controlled Rectifier (SCR):1. Cau tao va nguyen ly :


26/97



SCR(silicon controlled rectifier): goi la chnh lu co ieu khien, la linh kien quantrong nhat cua ho linh kien ban dan cong suat ln co nhieu hn 3 lp P-N goi laThyristor. Co nhieu tai lieu goi SCR la thyristor cung v ly do o.

Thyristor gom 3 lp PN va mac vao mach ngoai gom 3 cong : ien cc anode Acathode C va cong ieu khien G. Ve mat l thuyet ton tai cau truc PNPN va NPNP,trong thc te ngi ta ch phat trien va s dung loai PNPN. S o thay the thyristorbang mach transitor c ve hnh 1d. Mach tng ng nay giai thch hau hetnhng tnh chat cua SCR. Gia s anode cua thyristor chu tac dung cua ien ap dngso vi cathode (uAK>0). Khi a vao mach G,K cua cathode (tng ng vi machbase - emiter cua transitor NPN ) xung dong IG, transitor se ong. Dong ien dan tieptuc qua mach emitor base cua transitor PNP va ong no. Cac transitor tiep tuc ongngay ca khi dong iG b ngat. Dong qua collector cua mot transitor cung chnh la dong iqua base cua transitor th hai va ngc lai. Cac transitor v vay cung nhau duy trtrang thai o

SCR trong thc te lam viec hoan toan giong nh SCR cua ngat ien ien t vi

tn hieu ieu khien la dong IG:- Khi mi cap ien, IG=0 : SCR khoa thuan va ngc IDla dong ien ro, c mAvi VAK 0.

- Khi SCR phan cc thuan VAK >0, va co tn hieu ieu khien IG >0, SCRchuyen sang trang thai dan ien va co kha nang t gi trang thai dan ien cho en khidong qua no giam ve 0.

Da vao mo hnh hai BJT, ta co the kiem tra SCR bang VOM che o o ien tr:

- Cac au AK va GA co ien tr vo cung.

- GK la moi noi PN co ien tr song song (nho hn 100 Ohm). ien tr nay lamtang kha nang chu ap va chong kch nham do nhieu.

GATE

ANODE

CATHODE

a.

CATHODE

ANODE

GATE

P

P

N

N

J1

J2J3

b.ANODE

GATE P P

N

N

P

N

CATHODE

c.CATHODE

GATE

ANODE

Q 1

Q 2

d.Hnh II.1: a,b,c,d


27/97



2. Cac tnh chat va trang thai c ban: Neu transitor b ngat, th anode co the chu c ien ap dng so vi cathode

trang thai khoa; hoac ien ap am so vi cathode - trang thai nghch.

Hien tng ong SCR tc chuyen t trang thai khoa sang trang thai dan ien cothe thc hien neu thoa man hai ieu kien sau:

-Thyristor trang thai khoa.

-Phai a xung dong IG>0 u ln.

Chieu thuan nghch va cac thuat ng ve dong, ap; ien ap thuan va dong thuanc ky hieu vi ch so T dong ien khoa ID, ien ap khoa UD(xem hnh).

T

T

UIG

A

I

U

Dong ngc

Ap ngcU

RIR

GG

Dong thuan

Ap thuan, ap khoa

K

Hnh II.2 : K hieu dong va ap cua SCR

Hien tng ngat SCR : qua trnh chuyen t trang thai dan ien sang khong dan

ien (tc trang thai nghch hoac trang thai khoa), Qua trnh nay gom hai giai oan:1/-Giai oan lam dong thuan b triet tieu : thc hien bang cach thay oi ien tr

hoac ien ap gia anode va cathode.

2/-Giai oan khoi phuc kha nang khoa cua thyristor. Sau khi dong thuan b triettieu can co mot thi gian thi gian ngat, e chuyen thyristor vao trang thai khoa.

3. ac tnh tnh (Volt-Ampe) :Mo ta quan he IT(VAK) vi dong IGkhac nhau.


28/97



VRB IHIL

TI

GI

V

AKV

VF

Hnh II.3 : ac tuyen cua SCR

GE

AE

SCR

VR

R

Hnh II.4 : s o th nghiem

Tren hnh II.3 va II.4 cho ta s o th nghiem va ac tuyen volt ampe cua SCR, trongo ITthay oi c va dong IGieu khien nh VR. ac tnh tnh SCR gom cac mien:

VAK< 0: Khoa ngc : Chay qua SCR la dong ro ngc , c mA. Khi VAK < -VRBta co hien tng gay ngc, dong TI tang rat cao trong khi VAKvan gi tr so

ln SCR b hong.

VAK>0 va IG=0 : Khoa thuan : Ta co dong ro thuan cung c mA. Khi VAK>VFBta co hien tng gay thuan : SCR chuyen sang vung dan ien.

Ta phai chon nh mc ap cua SCR ln hn cac gia tr nay, he so an toan ienap thng chon ln hn hay bang 2.


29/97



Khi phan cc thuan, neu IGtang len t gia tr 0, VFBgiam dan. Nh vay, dongIGcan phai u ln e co the s dung SCR nh mot ngat ien ien t: SCR chuyensang trang thai dan ngay khi c kch bat chap ien ap phan cc thuan.

Vung dan ien : ng vi trng hp SCR a c kch khi va dan ien, sut apqua SCR VAK=VFkhoang 1-2 volt. Trong vung dan ien co hai ac trng dong:

+IL:dong cai, la gia tr toi thieu cua ITe SCR co the duy tr trang thai dankhi dong cc cong IGgiam ve 0 (kch SCR bang xung).

+IH: dong gi, la gia tr toi thieu cua IAe SCR co the duy tr trang thaidan (khi khong con dong cc cong IG). Neu dong anode thap hn IH, SCR tr vetrang thai khoa.

ILkhac IHv co qua trnh lan toa cua dong anode t vung phu can cua cc Gen toan manh ban dan khi SCR c kch ( co dong cc nen ), tng ng mat odong giam dan, lam cho he so khuech ai dong ien tang. Qua trnh qua o naycon anh hng en gii han di/dt, c gii thieu trong ac trng tnh ong cuaSCR.

4. ac tnh ong (ong ngat):a.ac tnh m: (turn on)

Co thi gian tre tont khi cap dong kch IGen khi SCR dan, tonco tr so khoangmot vai micro giay; tongiam khi IGtang.

Mot thong so khac lien quan qua trng m la gii han toc o tang dong di T/dt.Toc o tang cua dong qua SCR phai nho hn gia tr cho phep e SCR khong b hhong v qua nhiet cuc bo khi cha kp phan bo lai mat o dong ien qua no. Ngita thng bao ve SCR bang cach them cuon khang noi tiep vi anode, co gia trkhoang vai chuc micro Henry e han che diT/dt.


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T

water

cathode

I

t

G

V K

cathodearea

distridutedgate

water

gate

Hnh II.5 : a. ac tnh ong m va khoa cua SCR

b. Cau tao SCR cc cong co cau tao phc tap, phanbo tren toan bo mieng ban dan e tang di/dt.

b. ac tnh khoa : ( turn off) Gia s SCR ang dan dong tai. Do ac tnh tai haymot tac nhan khach quan khac, dong anode giam ve 0, ap VAK chuyen thanhgia tr am nh hnh 1.4. Dong anode co giai oan dan ien ngc trc khichuyen sang trang thai khoa ngc tng ng vi viec giai phong cac ien tchcua cac moi noi tch luy trong che o dan. Sau ien ap VAKdng c at trlai. Qua trnh khoa SCR co hai yeu cau quan trong:

+ Can co thi gian am bao tat toffe SCR phuc hoi kha nang kha nangkhoa trc khi at ap dng tr lai. toff phu thuoc che tao va giam khi tr so ap khoagiam.

toff= 50..10 micro giay vi SCR tan so cao

300..100 micro giay vi SCR chnh lu.

toffla thong so quan trong e tnh toan mach tat SCR khi s dung nguon motchieu.

+ Co gii han toc o tang du/dt cua ien ap phan cc thuan e SCR khongchuyen sang che o dan. Co the giai thch hien tng nay khi xet cac tu ien moinoi. Dong nap tu du/dt cung chnh la dong kch SCR.

Gii han du/dt cua SCR phu thuoc cau tao, tang theo nh mc ap cua SCR.Mach RC noi tiep mac song song AK cua SCR (snubber) co the cai thien du/dt. RCmac song song GK cung han che kha nang SCR t kch do nhieu t ngoai (hnhII.6).


31/97



Hnh II.6 : Mach bao ve SCR khoi cac che o kch dan khong mong muon

C2

SCR

R2C1

R1

C2 =0.05 - 0.1 F ; R2 = 33 100 Ohm ; R1 tang khi ap SCR tang va/haydong tai giam, t 20 -100 Ohm ; C1 tang khi dong SCR tang va hay ap SCR giam,t 0.1 0.5 F.

5. ac tuyen cong:Bieu dien quan he ap dong gia hai cong G va K. o sai lech gia cac ac tuyen

cua cac thyristor cung loai ang ke. Hnh dang cua ac tuyen thay oi nhieu theonhiet o. Tren hnh ve co cac nhanh bien cua cac ac tuyen VA cua lp chuyen oiG-K. iem lam viec cua ngo nhap phai nam trong vung xac nh bi cac nhanh bien.

Cong suat ton hao cong G b gii han bi gia tr PG(AV) Mtc cong suat ton haotrung bnh cc ai. Thong thng, cac thyristor cua cac bo bien oi ien ong ngattuan hoan va cac xung dong cung a vao lp cong mot cach tuan hoan. Gia s cacxung nay co chieu rong th gia tr cong suat uG.iGtng ng vi xung o la:

.2)(AVC

CM

PP

Tren hnh II.7a bieu th hai gia tr iGTgii han cua dong ong cua cong, vauGT- gii han cua ien ap cong. Hai gii han nay cho biet vung cha gia tr cua u G, iGma o viec kch ong SCR khong am bao thanh cong. Cac gia tr ien ap va dongcong kch nen c thiet lap trong vung gach cheo tren hnh II.7a.


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t

Hnh II.7 : a. ac tuyen V-A nhap cua thyristor. b. S o thay the n gian cua mach cong.

Neu nh ta s dung mach tao xung ieu khien nh hnh II.7b th ng thang uG= u iGcat ngang vung gach cheo tren. Giao iem cua no vi ac tuyen ngo vao xacnh cac gia tr cua iG, uGkhi ong thyristor. e ong thyristor, khoang au xung dongkch phai co tr u ln. Damg xung dong thng s dung cho cong co dang nh hnhII.7a.

0

Hnh II.8 : M ach khue ch ai va cach ly

UG

BIEN AP XUNG

+Vcc

SCR

IG

MACH KHUECH AI TNHIEU IEU KHIEN

Do tnh chat cua lp nghch khong tot nen khong c phep xuat hien ien the am

tren no du rat nho. Khi thyristor trang thai nghch, viec kch vao cong G se lam tang

dong nghch mot cach vo ch. Cac xung ieu khien thng truyen en thyristor nhbien ap xung. Nhiem vu cua no la tach mach cong xuat ra khoi nguon tao xung kch.Khi s dung cac bien ap xung, can phai giai quyet van e lam tat nhanh dong t hoa


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khi xung b ngat (neu khong th dong t khong ngng tang len sau moi lan a xungvao) va van e can bao ve lp cong cua thyristor trc ien ap nghch. e giai quyetvan e tren ta co the s dung dong mach ve ra hnh II.8.

6. ac tnh nhiet :Nh cac linh kien cong suat khac, khi lam viec SCR tieu tan nang lng va phat

nong. Muc ch cua tnh toan nhiet cho SCR la kiem tra nhiet o moi noi j cua tinh

the ban dan phai be hn gia tr cho phep maxj , co tr so t 150 .. 2000C. Viec giai bai

toan nay bao gom:

-Tnh cong suat tieu tan trung bnh tren SCR trong chu ky T T

dttitvP )().(

v(t),i(t) la gia tr tc thi ap, dong qua anode cathode cua SCR. Co the tra tailieu cua nha san xuat, theo hai thong so : tr so trung bnh va danh dong ien haytch phan trc tiep t dong, ap.-Tnh toan truyen nhiet t tinh the ban dan ra moi trng xung quanh:moi noi vo SCR tan nhiet moi trng.

Bai toan nay co the n gian khi cho rang trong che o xac lap, chenh lech nhieto tren ng truyen 1 , 2 t le vi cong suat tieu tan P va thong so ac trng cuamoi trng truyen goi la ien tr nhiet R12:

1 - 2 = 12.RP

Ap dung vao tnh toan tan nhiet cho ban dan cong suat :J - A = P . (RJC+RCH+RHA) vi cac tr nhiet :

+ RJC: the hien kha nang tan nhiet cua linh kien, cung cap bi nha san xuat, ccung cap trc tiep hay thong qua cong suat nh mc P (k hieu Pdisstrong cac tailieu tieng Anh), xac nh bang nhiet o moi noi cho phep maxj va nhiet o vo banggia tr moi trng qui nh,la 250C.

+ RCH: ien tr nhiet khi truyen t vo cua linh kien qua tan nhiet, giam khi ap lctiep xuc, o nhan be mat tang. Ngi ta con co lp em bang cao su ac biet valam cach ien va tang tiep xuc, hay dung keo (paste) sillicon lam kn cac khe kgia hai be mat.

+ RHA:ien tr nhiet khi truyen t tan nhiet ra moi trng xung quanh, la bo phanchu yeu cho tan nhiet he thong, t le nghch vi dien tch tan nhiet. Co the giamRHAkhi lam en be mat (tang kha nang bc xa nhiet), hay dung quat e tan nhietcng bc, cac he thong cong suat rat ln , nc c bm qua tan nhiet e giamthe tch bo tan nhiet, tranh choan cho.

Tng toan nhiet thng c dung cho bai toan kiem tra, khi chon s bo SCR co thes dung cac gia tr trung bnh hay hieu dung cua dong ien nh sau:

Dong lam viec trung bnh I0< Gia tr trung bnh nh mc IAVE hay


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Dong lam viec hieu dung IR< Gia tr hieu dung nh mc IRMS.Quan he gia hai gia tr nay la :

IRMS=1.57 IAVE

Do dang dong qui nh khi tnh toan nh mc cho diode va SCR la chnh luban song. He so an toan dong thng chon t 1.2 en 2 lan. Viec tnh chon theohieu dung thng cho ket qua phu hp hn v dang dong mach ien t cong xuatthng dang xung.

Sau khi chon gia tr nh mc, khi thi cong can phai kiem tra nhiet o vo linhkien ban dan , khong c vt qua 65..70 0C.

7. Mach kch thyristor:Trong cac bo bien oi cong suat dung thyristor va mach tao xung kch vao cong

ieu khien cua no can cach ien. Tung t nh cac mach kch cho transistor, ta co thes dung bien ap xung hoac optron, xem hnh II.9

Hnh II.9 : S o kch bang optron

K

A

G

+Vcc

U1

Xung hong ngoai do diode D1(LED) phat ra lam photoSCR V1 ong tao ieu kien

e dong kch vao cong G cua thyristor V. Mach can nguon rieng cho mach cong, do olam tang gia thanh va kch thuc mach kch.

Mach kch dung bien ap xung c ve tren hnh II.10. Sau khi tac dung ap lenmach cong B cua transistor Q1. Transistor Q1dan bao hoa lam ien ap Vccxuat hientren cuon s cap cua bien ap xung va t o xung ien ap cam ng xuat hien pha th

cap bien ap . Xung tac dung len cong G cua thyristor. Khi khoa xung kch chotransistor Q1b ngat dong qua cuon s cap bien ap xung duy tr qua mach cuon s capva diode Dm.


35/97



0

Hnh II.10 : Mach kch s dung bien ap xung

+Vcc

BIEN AP XUNG

K

G

Viec a xung kch dai vao cong G lam tang them ton hao mac cong, do o co thethay the no bang chuoi xung. Muon vay xung ieu khien ket hp vi tn hieu ra cuabo phat xung vuong qua mach cong logic AND trc khi a vao cong B cua transistorQ1(xem hnh II.11).

BIEN AP XUNG

K

G

+Vcc

BO TAO XUNG0

+Vcc

Hnh II.11 : Mach kch xung rong s dung bien ap xung

GND

8. Cac linh kien khac trong ho thyristor :1. Darlistor: La loai SCR co cau tao noi tang (cascade ) e tang he so khuech aidong IA/IG khinh mc dong ln va rat ln ( vai tram en vai ngan ampe). Luc o,dong kch van vai ampe. Darlistor la ten thng mai , nhai theo trandidtor noi

tang la Darlington transistor. Mot so nha san xuat van dung ten SCR hay Thyristornhnh chu thch la cc cong c khuech ai (Amplified gate thyristor).


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Mach tng ngcua TRIAC

Hnh II.12 : K hieu va s o tng ng cac linh kien trong ho Thyristor.

2. Triac : la linh kien pho bien th hai cua ho thyristor sau SCR, co mach tngng la hai SCR song song ngc, c che tao vi dong nh mc en hang ngan

ampe. Mach tng ng hai SCR, song song ngc hoan toan tng thch vi triackhi khao sat ly thuyet, nen thng c dung thay the cho nhau trong cac s onguyen ly mac du trong thc te chung co nhieu tnh chat khac nhau.

Triac co kha nang khoa theo hai chieu, tr nen dan ien khi co dong kch va tgi trang thai dan cho en khi dong qua no giam ve khong.

Triac co the ieu khien bang dong G T2 ca hai cc tnh va hai chieu dong ientai lam s o ieu khien n gian hn mach tng g hai SCR rat nhieu.

Nhc iem rat quan trong cua Triac la de b t kch nhiet o moi noi cao va

gii han du/dt rat thap, kho lam viec vi tai co tnh cam. Luc o, ngi ta van phaidung hai SCR song song ngc.3. Diac: co nguyen tac hoat ong tng t nh triac nhng khong co cc cong G,ngng ien ap gay rat thap thng la 24 V, dc dung trong cac mach phat xungva kch thyristor vi dong xung mot vai ampe.

4. La SCR(light activated DCR): DCR kch bang tia sang.Co nguyen tac lam viec nh SCR nhng c kch bang dong quang ien>LA

SCR rat thich hp cho cac ng dung cao ap, khi cach ien gia mach kch va ong

lc tr nen van e phc tap, giai quyet ton kem.5. GTO (Gate turn off SCR, SCR tat bang cc cong).Vi kha nang t gi trang thai dan ien, SCR khong the t tat nguon mot

chieu neu mach khong co s o ac biet e dong qua no giam ve khong. GTO chophep ngat SCR bang xung am cc cong. T mach tng ng hai BJT (hnh 1.2),kha nang nay co the c d oan. Nhng trong thc te, SCR khong the tat bangcong v cc cong ch moi cho qua trnh dan, sau o khong con tac dung.

GTO co cau tao khac hn cho phep kiem tra s dan ien t cc cong . Gia phai

tra la he so khuech ai dong khi kch con kha be, khoang vai chuc. He so khuechai dong khi tat xap x mi. Ngi ta che tao c GTO co dong nh mc envai ngan ampe.


37/97



9. Bao ve ngat ban dan:a. Bao ve dong:

Bao ve dong cc ai (ngan mach): bao ve dong cc ai lam viec ngay khi co

hien tng vt qua dong qui nh, thng la rat ln so vi tr nh mc. Bao ve dongcc ai con goi la bao ve ngan mach, xuat hien ngo ra hay ben trong bo bien oi, languyen nhan gay ra qua dong ien rat ln can loai bo ngay, tranh h hong ngat ienban dan va am bao hoat ong bnh thng cua li ien.

Cau ch tac ong nhanh c s dung, co the at au vao bo bien oi hay noitiep linh kien c bao ve. Thong so ac trng cua cau ch la dong, ap nh mc vatch phan dong ngan mach e cau ch chay. Tch phan nay can phai be hn tch phantng t e ngat ien ban dan b h hong khi qua dong ( ngan mach ), lay so tra nhasan xuat. Thi gian tch phan T thng la na chu k li cho SCR. Cuon khang noi

tiep anode cua SCR oi khi con dung e han che dong ngan mach, sao cho dong nganmach be hn kha nang chu ng cua SCR.

CB (ngat mach t ong-aptomat) thng gap ngo vao cac bo bien oi lam cacnhiem vu: ong ngat, bao ve qua tai va loai bo phan mach h hong ra khoi li ien,khong co kha nang bao ve cac phan t ban dan cong suat.

+ Bao ve qua tai (qua dong co thi gian):

Qua tai la trng hp dong ien qua mach ln hn gia tr tnh toan mot lngkhong ln, neu keo dai se gay h hong do qua nhiet cac phan dan ien. Nh vay ac

tnh qua tai co dang hyperbol, dong qua tai cang ln, thi gian cho phep cang ngan.Bao ve qua tai c thc hien bang r le chuyen dung tac ong vao thiet b ong

ngat t ong (contactor), CB (co r le nhiet) au vao. cac bo bien oi, bo ieukhien thng tch hp ca bo phan han dong, tac ong tc thi 120% en 200% gia trnh mc thiet b, lam ca nhiem vu bao ve qua tai cho ngat ien ban dan.

2. Bao ve ap:

Vi viec chon nh mc ap cua linh kien ban dan cong suat toi thieu bang hai lanap khoa cc ai, ngat ien ban dan thng khong phai bao ve ap khi lam viec. Bao ve

ap c at ra e chong lai cac xung ap cam ng tren day dan nguon hay xung xuathien do cam ng tren he thong khi co ong ngat.


38/97



Ohm

F

Hnh II.13 : Cac mach bao ve ap cho linh kien ong ngat

Ngi ta thng dung au nguon: RC noi tiep mac song song (1), Varistor la loai

ien tr giam nhanh khi ap ln hn tr so ngng (2) va cac bo loc nguon (3) gom macloc LC hnh .

Mach RC song song vi cac ngat ien (mach snubber) con lam nhiem vu baove linh kien khoi cac xung ap trong mach.

II. Bo chnh lu1.Tong quan ve bo chnh lu:

Bo chnh lu co nhiem vu bien oi dong ien xoay chieu thanh dong ien motchieu. Bo chnh lu c ap dung lam nguon ien ap mot chieu ; lam nguon ien motchieu co ieu khien cap cho cac thiet b ma, thiet b han mot chieu ; nguon ien chocac truyen ong ong c ien mot chieu ; nguon cung cap cho mach kch t cua mayien mot chieu hoac may ien ong bo. Bo chnh lu con dung e chuyen oi ienxoay chieu thanh dang mot chieu e truyen tai i xa. Bo chnh lu con tao thanh motbo phan trong thiet b bien tan, cycloconverter dung trong truyen ong ien ong cxoay chieu.

Cong suat cua cac bo chnh lu co the t vai tram W en hang chuc MW.

Phan loai bo chnh lu :

Theo pha:Bo chnh lu mot pha.Bo chnh lu ba pha.

Theo tnh ieu khien :Bo chnh lu khong ieu khienBo chnh lu ieu khien hoan toan.Bo chnh lu ban ieu khien.

Theo hnh dang :Bo chnh lu hnh tia.Bo chnh lu tam giac.

Theo diode zero :Bo chnh lu co diode zero.


39/97



Bo chnh lu khong co diode zeroSo sanh cac loai chnh lu:

Bien ap:

Bien ap cach ly ap nguon cua chnh lu vi li ien. Do o tai co the chay nganmach trong thi gian ngan. Bien ap la bat buoc trong trng hp ta thc hien bo nguoncho cac thiet b cong nghe ien khi ngi cong nhan co the tiep xuc trc tiep vi thietb co ien.

Bien ap co tac dung loc song hai bac cao. ong thi bien ap con tao cam khangchuyen mach, do o han che s bien dang gay ra cua qua trnh chuyen mach.

Truyen ong ien la khong bat buoc dung bien ap.

Bien ap cung cap ien ap nguon co o ln phu hp vi yeu cau cua tai.

Mot hay nhieu pha:

Can oi theo qui mo cong suat : 1 pha n gian hn nhng lam lech he thong 3 phadung cho cong suat < 5KW hay rat


40/97



Do ien ap chnh lu udtao thanh co dang xung nen gia tr ien ap nay co the tachlam hai thanh phan: thanh phan mot chieu vi tr tc thi bang tr trung bnh ap chnhlu Udva thanh phan xoay chieu:

ddd Uuu

Thanh phan xoay chieu cua ap chnh lu ud lam dong ien tai id b gn song.Tngt nh ien ap, dong chnh lu co the tach lam hai thanh phan tng ng:

ddd iIi

Thanh phan xoay chieu cua dong lam dong ien tai co the b gian oan. Khi dongqua tai b gian oan, dang ien ap chnh lu cua tai phu thuoc vao trang thai mach tai.

V du: oi vi tai RLE khi id=0

ud=0 neu E=0

ud=E neu E 0Cac he thc Uddan giai cho dong tai lien tuc khong ap dung c cho trng hp

dong gian oan. T le phan bo thi gian dong ien qua tai lien tuc (id> 0) va thi giandong gian oan (id=0) trong mot chu k xung ien ap chnh lu phu thuoc vao cac giatr tham so tai va goc ieu khien . Viec tnh toan ien ap chnh lu trong trng hpnay rat phc tap. Khi dong tai gian oan, quan he gia ien ap chnh lu va khongcon la duy nhat. Trong ieu khien, v du ong c ien mot chieu, khi dong tai bang 0,moment tac ong triet tieu va viec ieu khien tai khong co tac dung. Tac dung dong

tai gian oan lam ac tnh ieu khien tr nen phi tuyen, hien tng qua o cua heieu khien kho hieu chnh, do o trong ky thuat ngi ta co gang han che vung lamviec cua bo chnh lu che o dong gian oan.

Tuy nhien che o dong tai gian oan thng t xay ra nen trong trng hp khongco yeu cau chnh xac cao, viec tnh toan nh mc he thong co the van dung t ketqua tnh cho dong ien tai lien tuc.

3. Mach loc ap tai va dong taie han che thanh phan xoay chieu cua ap chnh lu va do o lam giam o gn

song dong tai, ta co the:1. Tang so xung kch chnh lu, v du s dung mach nhieu pha, dang cau.2. Dung tu loc.3. Dung cam khang loc .4. dung diode khong mach ieu khien ban phan.

Phng phap tu loc ch dung cho tai cong suat nho. Vi cong suat ln ta co the sdung cac phng phap con lai.

4. Hien tng chuyen machTrong cac phan trc, bo chnh lu c phan tch vi gia thiet bo qua tr khang

trong cua nguon ap. Hau qua la qua trnh chuyen mach gia cac nhanh cha thyristor


41/97



dien ra tc thi. Trong thc te, nguon co tr khang trong lam dong ien qua no khongco the thay oi ot ngot. He qua, hien tng chuyen mach gia cac nhanh cha cacthyristor khong dien ra tc thi ma keo dai mot khoang thi gian, hnh thanh trang thaicac nhanh cha thyristor cung dan ien. Hien tng nay goi la hien tng trung dan

hoac hien tng chuyen mach. Cac he qua do hien tng chuyen mach gay ra :

- Lam giam ap tai trong thi gian chuyen mach.- Lam giam goc ieu khiencc ai cho phep.- Lam bien dang ien ap nguon.

5. Phng phap ieu khien bo chnh lu:Thi iem phat xung kch cho cac thyristor trong cac bo chnh lu tng ng vi

goc ieu khien da vao hai tn hieu c ban tn hieu ieu khien uk

va tn hieu ong boup.

Tn hieu ong bo tao moc chuan ve thi gian cho viec xac nh goc ieu khienong thi xac lap ac tnh gia ap chnh lu trung bnh Udva ap ieu khien uk. Do o,tn hieu c chon thay oi trong khoang thi gian xuat hien ien ap khoa tren linhkien va no phai da vao dang ien ap nguon xoay chieu. Tn hieu ieu khien xac nhiem lam viec tren ac tnh ieu khien va cho biet o ln goc ieu khien. Ca hai tnhieu ieu khien va tn hieu ong bo tren co the x l da tren k thuat so hoac analog.

6. Bo chnh lu cau ba pha ieu khien hoan toan:S o cau tao:

V1 V3 V5

V4 V6 V2

R

L

E

u

iu

u

u

u

i

u

u

V1

V1

1

2

dK

dAd

d

Mach nguon xoay chieu ba pha ly tng mac vao bo chnh lu cau gom 6thyristor. Cac ien ap udA ,udKla ien ap t iem nut chung cua cac nhom linh kien

en iem trung tnh cua nguon ap ba pha. Phan tch :


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Mach ien c phan tch vi gia thiet dong ien qua tai idlien tuc. Theo phep congien ap, ta co:

ud= udAudK

Ta se chng minh rang neu dong tai lien tuc, ien ap udAse ch phu thuoc vao gockch ong cua nhom linh kien ( V1, V3, V5) va ien ap nguon; va ap udKphu thuoc gockch ong cua ngom (V2,V4,V6).

That vay, xet nhom anode (V1, V3, V5), gia s rang V1ong va V3, V5 b ngat,ta co:iV1=id ; iV3=0 ; iV5= 0.uV1 = 0 ;uV3= u2u1; uV5=u3u1 ; udA= u1.

Ro rang, cac he thc mo ta ien ap nhom anode khong phu thuoc vao trang thaikch ong cac thyristor nhom cathode. Do o, e khao sat ien ap udA, ta ch can xeten trang thai kch ong cua cac thyristor (V1 ,V3 ,V5).

Cac he thc mo ta ien ap nhom anode co dang giong nh mach chnh lu tia bapha vi ap chnh lu udA, (hnh 2.6). Goc ieu khien v du cua V1, c tnh t v trxuat hien ap khoa tren V1tc uV1= u1 u3>0.

Tng t, hoat ong nhom cathode co the phan tch di dang chnh lu mach tiaba pha vi ap chnh lu udK. Goc ieu khien, v du cua V2c tng t v tr xuat hienien ap khoa tren V2, tc:

uV2= u2u3> 0

uuV1 V3 V5

dA

NHOM ANODE

u1 2u u

NHOM CATHODE

V6V4 V2

dK

uu1 u2

Phng trnh ien ap tai va dong taiud= udA- udK

ud = R.id+ L.dt

did + E


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Tong hp cac ket qua phan tch tren, ta co the viet phng trnh mo ta trang thaimach, v du khi V1, V2ong:

uV1 = 0 ; uV2= 0 ; uV3= u2 u1 ; uV4= u3 u1 ;iV1 = id; iV2= id ; iV3= 0 ; iV4= 0 ;

uV5= u3u1; uV6= u3u2 ;iV5= 0 ; iV6= 0 ;ud= udAudK= u1 u3 ;ud = R.id+ L.

dt

did + E ;

o th ien ap va dong ien cac ai lng mach c ve tren hnh

He qua: Khi dong ien tai lien tuc:

-Dang ien ap tai co 6 xung va ch phu thuoc vao goc ieu khien va ien ap nguon

xoay chieu. Chu ky xung chnh lu bang 61 chu k ap nguon Tp= 61 T.-Tr trung bnh ien ap chnh lu:

Ud() =

6

2

1

6

20

0

dXud = UdA() UdK() =

33 Umcos

=

63 .U.cos

Vi U la tr hieu dung ap pha U =2

mU .

-Pham vi goc ieu khien : bang pham vi goc ieu khien cua cac nhom chnh lumach tia, tc (0, ). Do o, ien ap trung bnh tren tai co the ieu khien thay oi

trong khoang

UU .63

,.63

.

Dong trung bnh qua tai (RLE):

dI =R

EUd ;

Moi thyristor dan 31

chu k ap nhuom nen tr trung bnh dong ien qua no:ITAV=

3

dI ;

ien ap khoa va ap ngc cc ai xuat hien tren linh kien

UDRM = URRM= 3 .Um= 6 .U ;

-Dong ien qua nguon ien ap, v du qua pha 1:

i1= iV1iV4;Tr hieu dung ien qua nguon c xac nh vi gia thiet dong tai khong oi:


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dd IdXiI .3

2

2

1 2/1

2

0

2

;


45/97




46/97



CCHHNNGGIIIIII::

GGIIIITTHHIIEEUUVVIIIIEEUUKKHHIIEENNAATT8899CC5522

II..VVIIIIEEUUKKHHIIEENNHHOOMMCCSS--5511MCS-51TMla ho vi ieu khien do hang INTEL san xuat vao au nhng nam 80 va

ngay nay a tr thanh mot chuan trong cong nghiep. Bat au t IC tieu bieu la 8051a cho thay kha nang thch hp vi nhng ng dung mang tnh ieu khien. Viec x ltren byte va cac phep toan so hoc cau truc d lieu nho c thc hien bang nhieuche o truy xuat d lieu nhanh tren RAM noi. Tap lenh cung cap mot ban tien dungcua nhng lenh so hoc 8 bit gom ca lenh nhan va lenh chia. No cung cap nhng ho tr

m rong on-chip dung cho nhng bien 1 bit nh la kieu d lieu rieng cho phep quan lva kiem tra bit trc tiep trong ieu khien va nhng he thong logic oi hoi x l luan l.

Sau ay la bang so sanh cac IC trong ho MCS-51TM:

TEN LINHKIEN BO NH CHNGTRNH ON CHIP BO NH D LIEUON CHIP TIMER8051 4 KB MROM 128 Bytes 28031 0 KB 128 Bytes 2

8751 4 KB EPROM 128 Bytes 28951 4 KB Flash ROM 128 bytes 28052 8 KB MROM 256 Bytes 38032 0 KB 256 Bytes 38752 8 KB EPROM 256 Bytes 38952 8 KB Flash ROM 256 Bytes 3

IIII..VVIIIIEEUUKKHHIIEENNAATT8899CC5522

Do ho MCS-51TM

a tr thanh chuan cong nghiep nen co rat nhieu hang san xuatra no, ien hnh la ATMEL Corporation. Hang nay a ket hp rat nhieu tnh nang datren nen tang ky thuat cua mnh e tao ra cac vi ieu khien tng thch vi MCS-51 TMnhng manh me hn.

AT89C52 la mot vi ieu khien 8 bit do ATMEL san xuat, che tao theo cong ngheCMOS, co chat lng cao, cong suat thap vi 8 KB Flash (flash programmable anderasable read only memory). Thiet b nay c che tao bang cach s dung ky thuat bonh khong boc hi mat o cao cua ATMEL va tng thch vi chuan cong nghiepMCS-51TMve tap lenh va cac chan ra. Flash on-chip cho phep bo nh lap trnh c

lap trnh trong he thong bi mot lap trnh vien bnh thng. Bang cach noi 1 CPU 8 bitvi mot Flash tren mot chip n, AT89C52 la mot vi ieu khien manh (co cong suat


47/97



ln), cung cap mot s linh ong cao va giai phap ve gia ca oi vi nhieu ng dung viieu khien.Cac ac iem chu yeu cua AT89C52 :

Tng thch hoan toan vi ho MCS-51TMcua Intel.

Bo nh chng trnh 8K Byte thuoc loai Flash Memory.

o ben : 1000 lan ghi/xoa.

Tan so hoat ong : 0 Hz en 24 MHz.

3 che o khoa bo nh.

256 x 8-Bit RAM noi.

32 ng I/O lap trnh c (4 port).

3 timer/counter 16-bit. 8 nguon ngat.

Che o ha nguon va che o li tieu ton cong suat thap.


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II.1 S lc ve cac chan cua 8952:C 8952 co tat ca 40 chan co chc nang nh cac ng xuat nhap. Trong o co26 chan co cong dung kep, moi ng co the hoat ong nh ng xuat nhaphoac nh ng ieu khien hoac la thanh phan cua bus d lieu va bus a ch.

T1

T0

ieu khien

ngat

Cac thanh

ghi khac

128

byte RAMMRO noi

Timer 2

Timer 1Timer 0

CPU

Oscillator ieu khien bus Cac port I/O Port noi tiep

Port noi tiep

Timer 0

Timer 1

Timer 2

INT0

INT1

EA

RST

PSEN

ALE

P0 P2 P1 P3 TxD RxD

T2


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U12

AT89C52

9

18

19 29

30

31

1

2

3

4

5

6

7

8

21

22

23

24

25

26

27

28

10

11

12

13

14

15

16

17

39

38

37

36

35

34

33

32

RSTXTAL2

XTAL1 PSEN

ALE/PR OG

EA/VPP

P1.0/T2

P1.1/T2-EX

P1.2

P1.3

P1.4

P1.5

P1.6

P1.7

P2.0/A8

P2.1/A9

P2.2/A10

P2.3/A11

P2.4/A12P2.5/A13

P2.6/A14

P2.7/A15

P3.0/RXD

P3.1/TXD

P3.2/INTO

P3.3/INT1

P3.4/TO

P3.5/T1

P3.6/WR

P3.7/RD

P0.0/AD0

P0.1/AD1

P0.2/AD2

P0.3/AD3

P0.4/AD4P0.5/AD5

P0.6/AD6

P0.7/AD7

II.2 He thong giao tiep port:a/ Port 0:Port 0 la mot port hai chc nang tren cac chan 32 39. Trong cac thiet ke cnho (khong dung bo nh m rong) no co chc nang nh cac ng I/O. oi

vi cac thiet ke ln vi bo nh m rong, no c hp kenh gia bus d lieuva byte thap cua bus a ch.b/ Port 1 : la mot port I/O 8-bit haichieu co pullup noi. au ra port 1 co thelai 4 au vao TTL. Khi viet cac mc 1ra cac chan port th chung c keo lendo co ien tr noi va co the dung lam

au vao. Khi vai tro la cong nhap, nhng chan cua port 1 b keo xuong thap se odong v co noi tr keo len.

Hn na, P1.0 va P1.1 co the c dung nh la au vao bo em timer/counter 2ben ngoai (P1.0/T2) va xung kch (P1.1/T2EX).

Port 1 cung nhan nhng byte a ch thap trong khi lap trnh Flash va trong khikiem tra Flash .

Chan Chc nang thay theP1.0 T2 (au vao em cho Timer/Counter 2)P1.1 T2EX (xung kch capture/reload cho

Timer/Counter 2 va ieu khien trctiep.


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c/ Port 2:Port 2 la mot port cong dung kep tren cac chan 21 28 c dung nh cac

ng xuat nhap hoac la byte cao cua bus a ch oi vi cac thiet ke dung bo

nh m rong.d/ Port 3:Port 3 la mot port cong dung kep tren cac chan 10 17. Cac chan cua port

nay co nhieu chc nang, cac cong dung chuyen oi co lien he vi cac ac tnhac biet cua 8952 nh bang sau:

Bit Ten Chc nang chuyen oiP3.0P3.1P3.2P3.3P3.4P3.5P3.6P3.7

RXDTXDINT0\INT1\T0T1WR\RD\

D lieu nhan cho port noi tiepD lieu phat cho port noi tiepNgat 0 ben ngoaiNgat 1 ben ngoaiNgo vao cua Timer/counter 0Ngo vao cua Timer/counter 1Xung ghi bo nh d lieu ngoaiXung oc bo nh d lieu ngoai

II.3/ Cac tn hieu ieu khien:C 8952 co 4 tn hieu ieu khien:

a/ PSEN\ (Program Store Enable):PSEN\ la tn hieu ra tren chan 29. No la tn hieu ieu khien cho phep bo

nh chng trnh m rong, PSEN\ thng c noi en chan OE (OutputEnable) cua mot EPROM e cho phep oc cac byte ma lenh.

PSEN\ se mc thap trong thi gian lay lenh. Cac ma nh phan cua chngtrnh c oc t EPROM qua bus d lieu va c chot vao thanh ghi lenh cua8952 e giai ma lenh. Neu thi hanh chng trnh trong ROM noi (8952) th PSEN\se mc thu ong (mc cao).

b/ ALE (Address Latch Enable):Tn hieu ra ALEtren chan 30 tng hp vi cac thiet b lam viec vi cac vi

x l 8085, 8088, 8086.

C 8952dung ALEmot cach tng t cho viec giai kenh cac bus a ch vad lieu.


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Khi port 0 c dung trong che o chuyen oi: va la bus d lieu va labyte thap cua bus a ch, ALEla tn hieu e chot byte thap a ch vao motthanh ghi ben ngoai trong na au chu k bo nh. Sau o, cac ng port 0dung e xuat nhap d lieu trong na sau cua chu k bo nh.

Cac xung tn hieu ALEco toc o bang 1/6 lan tan so dao ong tren chip vaco the c dung lam nguon xung nhp cho cac phan khac cua he thong. Neuxung nhp tren 8952la 12 Mhz th ALEco tan so 2 Mhz. Ch ngoai tr khi thihanh lenh MOVX, mot xung ALE se b mat. Trong trng hp la 8051 thchan nay cung c lam ngo vao cho xung lap trnh cho EPROM trong chip.

c/ EA\ (External Access):Tn hieu vao EA\ tren chan 31 thng c mac len mc cao (+5v) hoac

mc thap (GND). Neu mc cao, 8952 thi hanh chng trnh t ROM noitrong khoang a ch thap (4K). Neu mc thap, chng trnh ch c thihanh t bo nh m rong.

Khi dung 8031, EA\ luon c noi mc thap v 8031 khong co bo nhchng trnh tren chip. Neu EA\c noi mc thap th bo nh chng trnhben trong 8952 se b cam va chng trnh ch c thi hanh t EPROM mrong.

Ngi ta con dung EA\ lam chan cap ien ap 21V khi lap trnh choEEPROM trong 8051.d/ RST (Reset):

Ngo vao RSTtren chan 9 la ngo reset cua 8952. Khi tn hieu nay c alen mc cao (trong t nhat 2 chu k may), cac thanh ghi ben trong 8952 ctai nhng gia tr thch hp e khi ong he thong.e/ Cac ngo vao bo dao ong tren chip:

Nh a thay trong cac hnh tren, 8952 co mot bo dao ong tren chip. Nothng c noi vi mot thach anh gia hai chan 18 va 19. Cac tu gi cungcan thiet nh a ve. Tan so thach anh thong thng la 12 Mhz.

f/ Cac chan nguon:8952 hoat ong vi nguon n +5V. Vcc c noi vao chan 40 va Vss

(GND) c noi vao chan 20.

II.4/ To chc bo nh:


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II.4.1/ Khao sat to chc bo nh 8952:

C 8952co bo nh c to chc theo cau truc Harvard : co nhng vung bonh rieng biet cho chng trnh va d lieu.

Nh a noi tren, ca chng trnh va d lieu co the ben trong (8952); duvay chung co the c m rong bang cac thanh phan ngoai len en toi a 64Kbytes bo nh chng trnh va 64 Kbytes bo nh d lieu.

Bo nh ben trong bao gom ROM (8952) va RAM tren chip bao gom nhieuthanh phan: Phan lu tr a dung, phan lu tr a ch hoa tng bit, cac bank thanhghi va cac thanh ghi chc nang ac biet.

FFFF

Bo nhchng trnh

c chonqua PSEN\

FFFF

Bo nhd lieu

c chonqua WR\vaRD\

FF

00 0000 0000

Bo nh tren chip Bo nh m rong

Tom tat cac vung bo nh cua 8952.

Hai ac tnh can lu y la:

Cac thanh ghi va cac port xuat nhap a c xep trong bo nh va co the c truyxuat trc tiep giong nh cac a ch bo nh khac.

Ngan xep ben trong RAM noi nho hn so vi RAM ngoai so vi bo x l khac.

II.4.2 Chi tiet ve bo nh RAM tren chip:Nh se thay trong hnh sau, RAM ben trong 8952 c phan chia thanh cac bank thanh

ghi (00H 1FH), RAM a ch hoa bit (20H 2FH), RAM a dung (30H 7FH) va cacthanh ghi chc nang ac biet trong khoang (80H FFH).

RAM a dung:


53/97



Mac du tren hnh cho thay 80 bytes RAM a dung chiem cac a ch t 30H 7FH, 32bytes di cung t 00H 1FH cung co the c dung vi muc ch tng t (mac du caca ch nay a co muc ch khac).

a ch a chbyte a ch bit byte

a ch bit7F

RAM a dung

FFF0 F7 F6 F5 F4 F3 F2 F1 F0 BE0 E7 E6 E5 E4 E3 E2 E1 E0 ACC

D0 D7 D6 D5 D4 D3 D2 _ D0 PSW

30 B8 _ _ _ BC BB BA B9 B8 IP2F 7F 7E 7D 7C 7B 7A 79 782E 77 76 75 74 73 72 71 70 B0 B7 B6 B5 B4 B3 B2 B1 B0 P32D 6F 6E 6D 6C 6B 6A 69 682C 67 66 65 64 63 62 61 60 A8 AF _ _ AC AB AA A9 A8 IE2B 5F 5E 5D 5C 5B 5A 59 582A 57 56 55 54 53 52 51 50 A0 A7 A6 A5 A4 A3 A2 A1 A0 P229 4F 4E 4D 4C 4B 4A 49 4828 47 46 45 44 43 42 41 40 99 khong c a ch hoa bit SBUF27 3F 3E 3D 3C 3B 3A 39 38 98 9F 9E 9D 9C 9B 9A 99 98 SCON26 37 36 35 34 33 32 31 3025 2F 2E 2D 2C 2B 2A 29 28 90 97 96 95 94 93 92 91 90 P1

24 27 26 25 24 23 22 21 2023 1F 1E 1D 1C 1B 1A 19 18 8D khong c a ch hoa bit TH122 17 16 15 14 13 12 11 10 8C khong c a ch hoa bit TH021 0F 0E 0D 0C 0B 0A 09 08 8B khong c a ch hoa bit TL120 07 06 05 04 03 02 01 00 8A khong c a ch hoa bit TL01F BANK 3 89 khong c a ch hoa bit TMOD18 88 8F 8E 8D 8C 8B 8A 89 88 TCON17 BANK 2 87 khong c a ch hoa bit PCON100F BANK 1 83 khong c a ch hoa bit DPH08 82 khong c a ch hoa bit DPL07 BANK 0

( Mac nh cho R0 R7 )81 khong c a ch hoa bit SP

00 80 87 86 85 84 83 82 81 80 P0

RAM CAC THANH GHI CHC NANG AC BIETTom tat bo nh d lieu tren chip

Moi a ch trong vung RAM a dung eu co the c truy xuat t do dungcach anh a ch trc tiep hoac gian tiep. V du, e oc noi dung a ch5FH cua RAM noi vao thanh ghi tch luy, lenh sau se c dung:

MOV A, 5FH


54/97



Lenh nay di chuyen 1 byte d lieu dung cach anh a ch trc tiep e xacnh a ch nguon (5FH). ch nhan d lieu c ngam xac nh trong malenh la thanh ghi tch luy A.

RAM ben trong cung co the c truy xuat dung cach anh a ch gian tiepqua R0 hay R1. V du, hai lenh sau thi hanh cung nhiem vu nh lenh n tren:

MOV R0, #5FH

MOV A, @R0

Lenh au dung a ch tc thi e di chuyen gia tr 5FH vao thanh ghi R0,va lenh th hai dung a ch gian tiep e di chuyen d lieu c tro bi R0vao thanh ghi tch luy.

RAM a ch hoa tng bit:C 8952cha 210 bits c a ch hoa, trong o 128 bits la cac a ch byte

20H en 2FH, va phan con lai la trong cac thanh ghi chc nang ac biet.Y tng truy xuat tng bit rieng re bang phan mem la mot ac tnh tien li

cua vi ieu khien noi chung. Cac bit co the c at, xoa, AND, OR, vimot lenh n. Trong khi o, a so cac vi x l oi hoi mot chuoi lenh oc sa ghi e at c hieu qua tng t. Hn na, cac port I/O cung c ach hoa tng bit lam n gian phan mem xuat nhap tng bit.

Co 128 bits c a ch hoa a dung cac byte 20H en 2FH. Cac a chnay c truy xuat nh cac byte hoac nh cac bit phu thuoc vao lenh cdung. V du, e at bit 67H, ta dung lenh sau:

SET 67H

Chu y rang a ch bit 67H la bit co trong so ln nhat (MSB) a chbyte 2CH. Lenh tren se khong tac ong en cac bit khac a ch nay. Cacvi x l se phai thi hanh nhiem vu tng t nh sau:

MOV A, 2CH ; oc ca byteORL A, #10000000B ; set MSB

MOV 2CH, A ; ghi lai ca byteCac bank thanh ghi:32 bytes thap nhat cua bo nh noi la danh cho cac bank thanh ghi. Bo lenh

cua 8952 ho tr 8 thanh ghi (R0 R7) va theo mac nh (sau khi reset hethong) cac thanh ghi nay cac a ch 00H 07H. Lenh sau ay se oc noi

dung a ch 05H vao thanh ghi tch luy :MOV A, R5


55/97


56/97



a/ T trang thai chng trnh:T trang thai chng trnh (PSW: Program Status Word) a ch D0H cha

cac bit trang thai nh bang tom tat sau:

Bit K hieu a ch Y nghaPSW.7 CY D7H C nhPSW.6 AC D6H C nh phuPSW.5 F0 D5H C 0PSW.4 RS1 D4H Bit 1 chon bank thanh ghiPSW.3 RS0 D3H Bit 0 chon bank thanh ghi

00 = bank 0 ( a ch 00H 07H )

01 = bank 1 ( a ch 08H 0FH )10 = bank 2 ( a ch 10H 17H )11 = bank 3 ( a ch 18H 1FH )

PSW.2 OV D2H C tranPSW.1 _ D1H D trPSW.0 P D0H C parity chan

C nh :C nh (CY) co cong dung kep. Thong thng no c dung cho cac lenhtoan hoc: no se c set neu co mot so nh sinh ra bi phep cong hoac co

mot so mn bi phep tr. V du, neu thanh ghi tch luy cha FFH, th lenhsau:

ADD A, #1

se tra ve thanh ghi tch luy ket qua 00H va set c nh trong PSWK.C nh cung co the xem nh mot thanh ghi 1 bit cho cac lenh luan l thi hanhtren bit. V du, lenh sau se AND bit 25H vi c nh va at ket qua tr vao cnh:

AND C, 25H

C nh phu:Khi cong cac so BCD, c nh phu (AC) c set neu ket qua cua 4 bit thap

trong khoang 0AH en 0FH. Neu cac gia tr c cong la so BCD th sau lenhcong can co DA A (hieu chnh thap phan thanh ghi tch luy) e ieu chnhket qua cho phu hp. C 0:


57/97



C 0 (F0) la 1 bit c a dung danh cho cac ng dung cua ngi dung.

Cac bit chon bank thanh ghi :Cac bit chon bank thanh ghi (RS0 va RS1) xac nh bank thanh ghi nao c

tch cc. Chung c xoa sau khi reset he thong va c thay oi bang phanmem neu can. V du, 3 lenh sau cho phep bank thanh ghi 3 va di chuyen noidung cua thanh ghi R7 (a ch byte 1FH) en thanh ghi tch luy:

SETB RS1

SETB RS0

MOV A, R7

Khi chng trnh c hp dch, cac a ch bit ung c thay the cho cac k

hieu RS1 va RS0.Vay, lenh SETB RS1 se giong nh lenh SETB 0D4H.

C tran:C tran (OV) c set sau mot lenh cong hoac tr neu co phep toan btran. Khi cac so co dau c cong hoac tr vi nhau, phan mem co thekiem tra bit nay e xac nh xem ket qua co nam trong tam xac nhkhong. Khi cac so khong dau c cong, bit OV co the c bo qua. Cacket qua ln hn +127 hoac nho hn 128 se set bit OV.

V du, phep cong sau b tran va bit OV c set :

Hex 0F Thap phan 15+ +

7F 127

8E 142

Ket qua la mot so co dau 8EH c xem nh 14, khong phai la mot ketqua ung (142), v vay bit OV c set.

b/ Thanh ghi B:Thanh ghi B a ch F0H c dung vi thanh ghi tch luy A cho cac phep

toan nhan va chia.Lenh MUL AB se nhan cac gia tr khong dau 8 bit trong A va B roi tra ve

ket qua 16 bit trong A (byte thap) va B (byte cao).


58/97



Lenh DIV AB se chia A cho B roi tra ve ket qua nguyen trong A va phan dtrong B.

Thanh ghi B cung co the c xem nh thanh ghi em a dung. No c ach hoa tng bit bang cac a ch bit F0H en F7H.

c/ Con tro ngan xep:Con tro ngan xep (SP) la mot thanh ghi 8 bit a ch 81H. No cha a ch

cua byte d lieu hien hanh tren nh cua ngan xep. Cac lenh tren ngan xepbao gom cac thao tac cat d lieu vao ngan xep va lay d lieu ra khoi nganxep. Lenh cat d lieu vao ngan xep se lam tang SP trc khi cat d lieu, valenh lay d lieu ra khoi ngan xep se oc d lieu va giam SP.

Ngan xep cua 8952c gi trong RAM noi va c gii han cac a ch cothe truy xuat bang a ch gian tiep. Chung la 128 bytes au cua 8952.e khi ong lai SP vi ngan xep bat au tai 60H, cac lenh sau ay cdung:

MOV SP, #5FH

Tren 8952 ngan xep b gii han 32 bytes v a ch cao nhat cua RAM tren chip la7FH. S d dung gia tr 5FH v SP se tang len 60H trc khi cat byte d lieu au tien.

Ngi thiet ke co the chon khong phai khi ong lai con tro ngan xep ma e nolay gia tr mac nh khi reset he thong. Gia tr mac nh o la 07H va ket qua la

ngan au tien e cat d lieu co a ch la 08H.Neu phan mem ng dung khong khi ong lai SP, th bank thanh ghi 1 (cothe ca 2 va 3) se khong dung c v vung RAM nay a c dung lam nganxep.

Ngan xep c truy xuat trc tiep bang lenh PUSH va POP e lu tr tamthi va lay lai d lieu, hoac c truy xuat ngam bang cac lenh goi chngtrnh con (ACALL, LCALL) va cac lenh tr ve (RET, RETI) e cat va lay laibo em chng trnh.

d/ Con tro d lieu:Con tro d lieu (DPTR) e truy xuat bo nh ngoai la mot thanh ghi 16 bit a ch 82H (DPL: byte thap) va 83H (DPH: byte cao).

Ba lenh sau se ghi 55H vao RAM ngoai a ch 1000H:

MOV A, #55H

MOV DPTR, #1000H


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MOVX @DPTR, A

Lenh au tien dung a ch tc thi e tai d lieu 55H vao thanh ghi tch luy.Lenh th hai cung dung a ch tc thi, lan nay e tai d lieu 16 bits 1000H

vao con tro d lieu. Lenh th ba dung a ch gian tiep e di chuyen d lieutrong A (55H) en RAM ngoai a ch c cha trong DPTR (1000H).

e/ Cac thanh ghi port xuat nhap:Cac port cua 8952bao gom Port 0 a ch 80H, Port 1 a ch 90H, Port 2

a ch A0H va Port 3 a ch B0H.Tat ca cac port eu c a ch hoa tng bit. ieu o cung cap mot kha

nang giao tiep thuan li.V du, neu mot motor c noi qua mot cuon day co transistor lai en bit 7

cua Port 1, no co the c bat va tat bang mot lenh n:SETB P1.7 ; bat motor

CLR P1.7 ; tat motor

Cac lenh tren dung dau cham e xac nh mot bit trong mot byte. Trnhhp dch se thi hanh s chuyen oi can thiet, v vay hai lenh sau ay lanh nhau:

CLR P1.7

CLR 97HTrong mot v du khac, xem xet giao tiep en mot thiet b vi mot bit trang

thai goi la BUSY, c set khi thiet b ang ban va c xoa khi thiet b asan sang. Neu BUSY c noi ti P1.5, vong lap sau se c dung e chthiet b tr lai trang thai san sang:

WAIT : JB P1.5, WAIT

Lenh nay co ngha la neu bit P1.5c set th nhay ti nhan WAIT.

Noi cach khac nhay tr lai va kiem tra lan na.f/ Cac thanh ghi timer:C 8952 cha ba bo nh thi/em 16 bits c dung cho viec nh thi

hoac em s kien.Timer 0 a ch 8AH (TL0: byte thap) va 8CH (TH0 : byte cao).Timer 1 a ch 8BH (TL1: byte thap) va 8DH (TH1 : byte cao).

Viec van hanh timer c set bi thanh ghi Timer Mode (TMOD) a

ch 89H va thanh ghi ieu khien timer (TCON) a ch 88H.Ch co TCON c a ch tng bit.


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ac biet 8952 con co timer 2 co cac thanh ghi sau:Cac thanh ghi Timer 2 cac bit ieu khien va trang thai cha trong thanh ghiT2CON va T2MOD cho Timer 2. Cap thanh ghi RCAP2H va RCAP2L la nhngthanh ghi Capture/Reload trong che o capture 16 bit hay che o auto-reload 16

bit.Thanh ghi T2CON a ch 0C8H:

TF2 EXF2 RCLK TCLK EXEN2 TR2 C/ 2T 2RL/CP 7 6 5 4 3 2 1 0

Ky hieu Chc nangTF2 C tran Timer 2, set khi Timer 2 tran va phai c clear bang phan mem. TF2

se khong set khi RCLK = 1 hoac TCLK = 1.EXF2 C ngoai cua Timer 2, set khi xay ra capture hoac reload do T2EX xuong thap

va EXEN2 = 1. Neu ngat Timer 2 c kch hoat, EXF2 = 1 se lam CPU troen ISR cua Timer 2. EXF2 phai c xoa bang phan mem. EXF2 khong gaynen ngat trong che o em len/xuong (DCEN = 1).

RCLK Kch hoat xung clock bo thu. Khi set, cac xung tran Timer 2 se la xung clockcho bo thu port noi tiep trong mode 1 va 3. RCLK = 0 th bo thu port noi tiep sedung cac xung tran cua Timer 1.

TCLK Kch hoat xung clock bo phat. Khi set, cac xung tran Timer 2 se la xung clockcho bo phat port noi tiep trong mode 1 va 3. TCLK = 0 th bo phat port noi tiepse dung cac xung tran cua Timer 1.

EXEN2 Kch hoat ben ngoai. Khi set, cho phep capture hay reload khi T2EX xuong

thap (neu Timer 2 khong s dung cho port noi tiep). EXEN2 = 0 lam cho Timer2 bo qua cac s kien tren T2EX.TR2 Khi ong/Dng Timer 2. TR2 = 1 lam khi ong Timer 2.C/T2 Bit la chon timer hay counter. C/T2 = 0 : timer. C/T2 = 1 : counter em s

kien ben ngoai (kch canh xuong).CP/RL2 La chon capture hay reload. CP/RL2 = 1: capture xay ra khi T2EX xuong thap

neu EXEN2 = 1. CP/RL2 = 0 : reload xay ra khi Timer 2 tran hoac khi T2EXxuong thap neu EXEN2 = 1. Neu TCLK hay RCLK = 1, bit nay b bo qua vatimer b ep vao che o reload khi Timer 2 tran.

g/ Cac thanh ghi port noi tiep:C8952cha mot port noi tiep tren chip danh cho viec trao oi thong tin vicac thiet b noi tiep nh may tnh, modem hoac cho viec giao tiep vi cac ICkhac co giao tiep noi tiep (cac bo chuyen oi A/D, cac thanh ghi dch ).

Mot thanh ghi goi la

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