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o an mon hoc GVHD: NGUYENMANH HA

PHAN I :TONG QUAN VE IEU CHNH TOC O

ONG C

I. KHAI NIEM CHUNG:I. 1 nh ngha:ieu chnh toc o ong c la dung cac

bien phap nhan tao e thay oi cac thong songuon nh ien ap hay cac thong so mach nhien tr phu, thay oi t thong T o tao racac ac tnh c mi e co nhng toc o lamviec 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 khtc la bien oi ty so truyen chuyen tiep ttruc ong c en c cau may san suat.

- Bien oi toc o goc cua ong c ien.Phng phap nay lam giam tnh phc tap cua ccau va cai thien c ac tnh ieu chnh. Vvay, ta khao sat s ieu chnh toc o theo

phng phap th hai.Ngoai ra can phan biet ieu chnh toc ovi s t ong thay oi toc o khi phu tai thayoi cua ong c ien.

Ve phng dien ieu chnh toc o, ong cien mot chieu co nhieu u viet hn so vi cacloai ong c khac. Khong nhng no co khanang ieu chnh toc o de dang ma cau truc

mach ong lc, mach ieu khien n gian hn,ong thi lai at chat lng ieu chnh cao trongday ieu chnh toc o rong.

I. 2 Cac ch tieu ky thuat e anh giahe thong ieu chnh toc o:

SVTH:HUYNH KIM SON trang 2


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Khi ieu chnh toc o cua he thong truyenong ien ta can chu y va can c vao cacch tieu sau ay e anh gia chat lng cuahe 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 sovi toc o c ban la toc o lam viec cuaong c ien tren ng ac tnh c t nhien.

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 nmax va toc o be nhat nminma ngi ta co the ieu chnh c tai gia trphu tai la nh mc: D = nmax/nmin.

Trong o:- nmax: c gii han bi o ben choc.- nmin: c gii han bi pham vi cho

phep cua ong c, thong thng ngi ta chon

nmin lam n v.Pham vi ieu chnh cang ln th cang totva phu thuoc vao yeu cau cua tng he thong,kha nang tng phng phap ieu chnh.

I. 2. c o cng cua ac tnh c khiieu chnh toc o:

o cng: = M/ n. Khi cang ln tc M cang ln va n nho ngha la o on nhtoc o cang ln khi phu tai thay oi nhieu.Phng phap ieu chnh toc o tot nhat laphng phap ma gi nguyen hoac nang cao o



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cng cua ng ac tnh c. Hay noi cach khac cang ln th cang tot.

I. 2. d o bang phang hay o lientuc trong ieu chnh toc o:

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

Trong o:- ni: Toc o ieu chnh cap th i.- ni + 1: Toc o ieu chnh cap th

( i + 1 ).Vi ni va ni + 1 eu lay tai mot gia tr

moment nao o. tien cang gan 1 cang tot, phng

phap ieu chnh toc o cang lien tuc. Luc nayhai cap toc o bang nhau, khong co nhay caphay 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 chnhtoc o:

He thong truyen ong ien co chatlng cao la mot he thong co hieu suat lamviec cua ong c la cao nhat khi ton haonang lng Pphu mc thap nhat.

I. 2. f Tnh kinh te cua he thong khiieu chnh toc o:

He thong ieu chnh toc o truyenong ien co tnh kinh te cao nhat la mot hethong ieu chnh phai thoa man toi a cacyeu cau ky thuat cua he thong. ong thi hethong phai co gia thanh thap nhat, chi ph baoquan van hanh thap nhat, s dung thiet b



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pho thong nhat va cac thiet b may moc cothe lap rap lan cho nhau.

II. IEU CHNH TOC O BANG CACH THAY

OI IEN AP AT VAO PHAN NG ONGC:

oi vi cac may ien mot chieu, khi gi tthong khong oi va ieu chnh ien ap trenmach phan ng th dong ien, moment se khongthay oi. e tranh nhng bien ong ln ve giatoc va lc ong trong he ieu chnh nenphng phap ieu chnh toc o bang cach thay

oi ien ap tren mach phan ng thng cap dung cho ong c mot chieu kch t oc lap.e ieu chnh ien ap at vao phan ng

ong c, ta dung cac bo nguon ieu ap nh:may phat ien mot chieu, cac bo bien oi vanhoac khuech ai t Cac bo bien oi trendung e bien dong xoay chieu cua li ienthanh dong mot chieu va ieu chnh gia tr

sc ien ong cua no cho phu hp theo yeucau.

Phng trnh ac tnh c cua ong c ien mot

chieu kch t oc lap: Ta co toc o khong tai ly tng: n0 =

Um/KE m.Va o cng cua ng ac tnh c:Khi thay oi ien ap at len phan ng cuaong c th toc o khong tai ly tng se thay


MKK

RR

K

Un

ME

fu

E

2

+

=

fu

ME

RR

KK

dn

dM

+

==

2


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oi nhng o cng cua ng ac tnh c thkhong thay oi.

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

tnh c la nhng ng thang song song ving ac tnh c t nhien:

Hnh 1. 1 Ho ac tnh c khi thay oi ien apat vao phan ng ong c.

Phng phap ieu chnh toc o bang cachthay oi ien ap phan ng thc chat la giamap va cho ra nhng toc o nho hn toc o c

ban ncb. ong thi ieu chnh nhay cap haylien tuc tuy thuoc vao bo nguon co ien apthay oi mot cach lien tuc va ngc lai.

Theo ly thuyet th pham vi ieu chnh D = .Nhng trong thc te ong c ien mot chieu kcht oc lap neu khong co bien phap ac bietch lam viec pham vi cho phep: Umincp = Um/10,ngha la pham vi ieu chnh:

D = ncb/nmin = 10/1. Neu ien ap phan ng U U1

> U2

> U3

ncb

> n1

> n2

>

n3


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ac tnh c nen c dung nhieu trong may catkim loai va cho nhng toc o nho hn ncb.

* u iem: ay la phng phap ieu chnhtriet e, vo cap co ngha la co the ieu

chnh toc o trong bat ky vung tai nao ke cakhi khong tai ly tng.

* Nhc iem: Phai can co bo nguon coien ap thay oi c nen von au t c banva chi ph van hanh cao.

III. IEU CHNH TOC O BANG CACH

THAY OI T THONG:

Hnh 1. 2 S o nguyen ly ieu chnh toc obang cach thay oi t thong.ieu chnh t thong kch thch cua ong c

ien mot chieu la ieu chnh moment ien tcua ong c M = KM I va sc ien ong quaycua ong cE = KE n. Thong thng, khi thay oi t thong thien ap phan ng c gi nguyen gia tr nh

mc.oi vi cac may ien nho va oi khi cacac may ien cong suat trung bnh, ngi tathng s dung cac bien tr at trong mach kcht e thay oi t thong do ton hao cong suatnho. oi vi cac may ien cong suat ln th


-

+

+ -

CK

RK

I

U

UKT


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dung cac bo bien oi ac biet nh: may phat,khuech ai may ien, khuech ai t, bo bienoi van

Thc chat cua phng phap nay la giam t

thong. Neu tang t thong th dong ien kch tIKT se tang dan en khi h cuon day kch t. Doo, e ieu chnh toc o ch co the giamdong kch t tc la giam nho t thong so vinh mc. Ta thay luc nay toc o tang len khit thong giam: n = U/KE .

Mat khac ta co: Moment ngan mach Mn = KM Innen khi giam se lam cho Mn giam 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 ng ac tnhc khi thay oi t thong nh sau:

Phng phap ieu chnh toc o bang cachthay oi t thong co the ieu chnh c toc

o vo cap va cho ra nhng toc o ln hn toco c ban.

Theo ly thuyet th t thong co the giamgan bang 0, ngha la toc o tang en vo cung.Nhng tren thc te ong c ch lam viec vitoc o ln nhat:SVTH:HUYNH KIM SON trang 8

R

KK ME2

=

1

2

m0 MC

M2

M1

Mn

Hnh 1. 3 Ho ac tnh c khi thay oit thong.

nc

b

n1

n

2

n

M

m

> 1

> 2n

cb< n

1 n2

>

n3

constK

UndmE

dm ==0fu

dmME

RRKK+

=

2

;


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Hnh 1. 5 Ho ac tnh c khi thay oi ien trphu tren mach phan ng.

Nguyen ly ieu chnh toc o bang cachthay oi ien tr phu tren mach phan ng cgiai thch nh sau: Gia s ong c ang lam viecxac lap vi toc o n1 ta ong them Rf vao machphan ng. Khi o dong ien phan ng I ot

ngot giam xuong, con toc o ong c do quantnh nen cha kp bien oi. Dong I giam lam chomoment ong c giam theo va toc o giamxuong, sau o lam viec xac lap tai toc o n2vi n2 > n1.

Phng phap ieu chnh toc o nay ch cothe ieu chnh toc o n < ncb. Tren thc tekhong the dung bien tr e ieu chnh nen

phng phap nay se cho nhng toc o nhaycap tc o bang phang xa 1 tc n1 cach xa n2,n2 cach xa n3

Khi gia tr nmin cang tien gan en 0 th phamvi ieu chnh:D = ncb/nmin .

Trong thc te, Rf cang ln th ton that nanglng 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 tnh kinh te cho he thongta ch ieu chnh sao cho pham vi ieu chnh: D =( 2 3 )/1.

Khi gia tr Rf cang ln th toc o ong ccang giam. ong thi dong ien ngan mach In



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va moment ngan mach Mn cung giam. Do o,phng phap nay c dung e han che dongien va ieu chnh toc o di toc o c ban.Va tuyet oi khong c dung cho cac ong c

cua may cat kim loai.Nhan xet: Phng phap ieu chnh toc o

bang cach thay oi ien tr phu tren machphan ng ch cho nhng toc o nhay cap vanho hn ncb.

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

*Nhc iem: Toc o ieu chnh cang thapkhi gia tr ien tr phu ong vao cang ln, actnh c cang mem, o cng giam lam cho s onnh toc o khi phu tai thay oi cang kem. Tonhao phu khi ieu chnh rat ln, toc o cangthap th ton hao phu cang tang.

V. IEU CHNH TOC O BANG CACH RE

MACH PHAN NG:ong c ien mot chieu kch t oc lap khiieu chnh toc o bang cach re mach phanng co s o nguyen ly nh sau:

Hnh 1. 6 S o nguyen ly phng phapieu chnh toc o bang cach re mach phanng.


I

IS

In

RnR

S

-+

CK

RK

E

U


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Mot he thong khi ieu chnh can toc onho hn ncb va ieu chnh nhay cap. He thongco o cng tng oi ln va thiet b van hanh

n gian th ngi ta dung phng phap re machphan ng hay con goi la phan mach.

Theo phng phap re mach phan ng th phanng ong c noi song song vi ien tr va noinoi tiep vi mot ien tr khac. Phng phapnay giong vi phng phap thay oi ien trtren mach phan ng nhng ien ap phan nglai khong thay oi. Do o, phng phap nay oi

hoi phai:- ien ap at vao phan ng ong ckhong thay oi.

- V dong kch t khong thay oi nen khiieu chnh toc o, t thong khong oi lam chomoment phu tai cho phep c gi khong oi vabang tr so nh mc.

Ta co phng trnh ac tnh c:

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


MKK

RR

RRR

RR

R

K

Un

ME

nS

nSu

nS

S

E 2

++

+

=

MKK

RR

RRR

RR

Rnn

ME

nS

nSu

nS

S

20 +

+

+=

000' nRR

Rnn

nS

S

++>+

TNPMRR nf


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o cng cua ng ac tnh c re machphan ng PM nho hn o cng cua ac tnh c

t nhien TN nhng lai ln hn o cng cua actnh c co ien tr phu Rf vi ien tr phu chnhla Rn.

e ieu chnh toc o ong c trong trnghp 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.

Hnh 1. 7 Ho ac tnh c khi Rn = const, RS thayoi.

Nh vay, khi gi nguyen Rn, thay oi gia tr RSth vung ieu chnh toc o b han che va moduno ln ac tnh c tang dan khi toc o giam.

* Gi nguyen RS, thay oi gia tr Rn:- Khi Rn = 0: RS khong anh hng en

ng ac tnh c. Luc nay ta xem RS nh la tai


Ta co ho ac tnh cnh sau:

n

dm

AS

R

U

IRKhi == ::

TN

nn

0

n3

n2

n1

IIA

MC RS =0R

S=

RS2

RS1

RS1

ncb : Ta gi UF tr so nhmc va ieu chnh bien tr RK at gia tr ccai e giam t thong kch thch cua ong c.

Luc nay toc o cua ong c tang len at n >ncb.Goi D : Pham vi ieu chnh toc o bang

cach thay oi t thong cua ong c. Ta co: D =nmax/ncb = 3/1.



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Ket hp hai phng phap ieu chnh la giamien ap at vao phan ng ong c U va giamt 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 cuamay phat: U = EF IRF

Thay vao phng trnh ac tnh c ta c:ay la phng trnh ac tnh toc o cua he

thong.

Thay I = M / KM vao phng trnh ac tnh toc ota c phng trnh ac tnh c cua ong c tronghe thong F - nh sau:

T phng trnh ac tnh c cua he thong tanhan thay: ng vi moi hng ieu chnh toco ong c khac nhau ( ln hay nho hn so vi


u

DE

uFuD

DE

F IK

RR

K

En

+

=

MKK

RR

K

En

DME

uFuD

DE

FD 2

+

=

MKK

RR

K

En

DME

uFuD

DE

F

2

+

=

u

EE

IK

R

K

Un

=

u

DE

uD

DE

IK

R

K

Un

=


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toc o c ban ) ta se co nhng ho ac tnh ieuchnh khac nhau nh a trnh bay tren.

Hnh 1. 10 Ho ac tnh c ieu chnh tronghe 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 hienbang mach kch thch cua may phat va ong c.

Co the dung phng phap bien tr.- He thong co s chuyen oi trang thailam viec rat linh hoat, kha nang qua tai lnnen thng c s dung cac may khai thactrong cong nghiep nho.

VI. 4. b Nhc 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 vaohe thong F - qua ln: Gap 3 lan so vi yeucau nen von au t ln.

- Hieu suat hoat ong cua he thongtng oi thap:

= Pc2/P < 0,75


n3n

2

n1

RKF

RK

n

cb

n2

n1

U

3

2

1

U1

U2

Um

, m

n

M0 MC


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

- Ngoai ra, do cac may phat mot chieuco t d, ac tnh t hoa co tre nen kho ieu

chnh sau toc o.VI. 4. c Nhan xet:Vi he thong F - vong h nh tren, ta

khong the thc hien viec on nh toc o ongc la nhiem vu can thiet oi vi cac he thongtruyen ong nham nang cao chat lng sanpham c gia cong tren may, nang cao chatlng ky thuat cua mot qui trnh cong nghe ma

may san xuat tham gia hoac nang cao nang suatcua may.e thc hien nhiem vu o, ta thng

dung cac he thong F- co khuech ai may iendung phan hoi vong kn. Trong cac he thongnay, cac bo khuech ai may ien se s dungcac lien he phan hoi, ngha la a mot tn hieuau ra cua he thong quay tr lai au vao cua

no. Tn hieu au ra co the la ien ap, dongien trong mach chnh hoac toc o quay cuaong c. Tn hieu au vao la sc t ong cuakhuech ai may ien. Cac khuech ai may ienthng dung hien nay la may kch t nhieucuon day ieu chnh c, khuech ai may ient 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.



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- KM t trng giao truc.VII. 1. a Khuech ai may 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 trehep.

He thong kch t co t 3 en 4 cuonday:

- Mot cuon lam kch t oc lap ( kch tchnh ) at ien ap mot chieu vao va dung eieu khien sc ien ong phat ra cua phanng may ien.

- Mot cuon lam nhiem vu t kch, lay ienap phat ra hai au phan ng hoac dong ientren mach phan ng quay tr lai t kch.

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

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

song ):

Hnh 1. 11 S o nguyen ly KM t kchsong song.


Ung

R1 CK1

CK

3

CK4

CK

2

F1 F2

R2

UKM

+

-

KMTK


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* KM t kch theo dong ien ( t kch

noi tiep ):

Hnh 1. 12 S o nguyen ly KM t kchnoi tiep.Nh cuon t kch ma ien ap phat ra

cua KM c nang cao so vi may phat thongthng. Da vao ac tnh volt-ampe cua KM tathay:

UmKM = Um1 + Um2

Hnh 1. 13ac tnh volt-ampe cua he

thong KM.Khi co them CK2 th U tang len mot lng Um2.He so cong suat: KP = Pf/PKT = UKMIKM/UKIK =

hang tram/1.


IKM

R2

F2

CK

2

CK

3

CK

4

F1

UKM

Ung

R1

CK1

-

+

KMTK

CK

2

CK

1

IKI

m1

Um1

Um2

UmKM

UKM


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VII. 1.b Khuech ai may ien t trng

giao truc:La may phat mot chieu ac biet:

- Mach t lam bang thep ky thuat ien cannguoi, 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 thanco truc vuong goc nhau. Trong o,mot cap c noi tat vi nhau conmot cap e lay ien ap ra.

Hnh 1. 14 S o tng ng KM ttrng giao truc.

ng ve mat khuech ai ta co the xemKM t trng giao truc tng ng vi hai mayphat ien lam viec ke tiep nhau va co s onguyen ly nh tren.

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


MFI

;

KPI

MFII

;

KPII

UKM

F2

F1

R1

CK1

I1 I2

-

+

E

1

E

2

Ung


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ay la loai may ien co he so khuech aicao nhat, KP co gia tr hang ngan lan.

VII. 2 Nhan xet he thong khuech aimay ien ong c:

VII. 2. 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 nanglng 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 ocua he thong nh khau on nh.- Co he so khuech ai cong suat ln.VII. 2. 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 thanh cao.

- Hieu suat hoat ong thap.- Dien tch lap at may rong va oi hoinen mong chac chan nen ph ton van hanhln.

- Gay tieng on ln.



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VIII. HE THONG KHUECH AI T - ONGC:

VIII. 1 S o nguyen ly:Khuech ai t ( KT ) hay con goi la bo bien

oi van t, la to hp cua khang bao hoa vichnh lu khong ieu khien.

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

Trong cac may nang van chuyen, KT thng

c dung lam may kch thch cho cac may phattrong he thong F - . oi vi may cat got kimloai, KT thng c dung ket hp vi chnh ludiode ban dan e cung cap cho phan ng ongc mot chieu vi s o nguyen ly nh sau:(hnh1.15)

Trong cac s o nay, may bien ap BA cochc nang bien oi gia tr ien ap cho phu hp

vi yeu cau cua ong c. Tao ra so pha hoaciem trung tnh cho phu hp vi s o chnh luneu can va nang cao he so cong suat cua he.

Cac van khong ieu khien Vo dung e bienoi dong ien xoay chieu thanh mot chieu vatao ra thanh phan dong ien t t hoa cho KT.

Cuon khang bao hoa KBH dung e ieuchnh gia tr sc ien ong cua bo bien oi.



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Hnh 1. 15S o nguyen ly he thong

KT ong c.a). Tia ba pha.b). Cau ba pha.

VIII. 2 Nguyen ly hoat ong:


U1 , f1

( a)

CK

RK

BA

V0

Wlv

+

-

W

k Uk

-

+

U1 , f1

BA

W

k

V0

Uk

+

-

-+

CK

RK

Wlv

( b )


29/76


Trong he thong KT ong c, toc o ongc c ieu chnh bang cach thay oi tr sotrung bnh cua sc ien ong chnh lu bangcach 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 ra mottrong ba pha t cac s o tren va gia thuyetrang ac tnh t tre cua loi thep co dang lytng.

Hnh 1. 16a). S o nguyen ly mot pha cua bo

bien oi.

b). Dang ac tnh t tre ly tng cua loithep.Ta co: u2 = U2msin t = iRt + XK ( di / d t ) Trong o: XK co gia tr thay oi theo trang

thai t hoa cua loi thep. Luc au, loi thepc t hoa co nh nh cuon ieu khien Wken mot gia tr B0 nao o trong pham vi ( -BS B0 +BS ).

* ban ky dng cua nguon u2: dong ienthuan i qua V0 t hoa loi cuon khang, lam chobien o t cam bien thien. Luc nay, v loithep cha bao hoa nen XK rat ln, nguon chuyeu ri tren cuon khang con gia tr iRt 0. Taco:


u

2+

-

I

k

Uk

W

k

Rt

V0( a )

B

H

+B

S

-BS

B0

( b )


30/76


u2 = U2msin t = iRt + XK ( di/d t ) = Nlv S ( dB /dt )

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

B = B0 + Bm ( 1 - cos t )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 =U2msin t = iRt = ub

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

* ban ky am cua nguon u2: V0 ngng dan,dong ien t hoa khong co nen loi thep bkh t bi cuon ieu khien Wk va o t camB se giam dan ve gia tr ban au B0, ien ap

tren tai ub u2 = 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.


)cos1(2

sin2

22

+== mmKDT Up

ttdUp

U

)1arccos( 0

m

S

B

BB =


31/76


Neu ta chon Bm = BS th = arccos ( B0/BS ). Lucnay gia tr trung bnh cua ien ap chnh lu: UKT= Um [ 1 + ( B0/BS )] = f ( B0 ).Vi:

Um = pU2m/2Ta nhan thay: Khi thay oi gia tr B0 t BS

en +BS ta se ieu chnh c ien ap chnh luUKT t 0 en gia tr U2m( p/ ). V B0 la do dongieu khien Ik tao ra nen thc chat gia tr UKTchnh la ham cua Ik: UKT = f ( Ik ).

VIII. 3 Phng trnh ac tnh c cua hethong KT ong c:

T cong thc: n = n0 - M/ , ta c phng trnhac tnh c cua ong c trong he thong:

ay chnh la phng trnh ac tnh c cuaong c trong he thong KT ong c vi Rb laien tr trong cua he thong.

Neu xem cuon khang la phan t tuyen tnhth ta se c ho nhng ng ac tnh c cuaong c la nhng ng thang song song nhau vac goi la ho ac tnh c ly tng.


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

BU

nME

ub

E

S

m

2

0 )1(

+

+=

M

nn

0

nyc

n1

Ik1

Ik2

Ik3

0M

C


32/76


Hnh 1.17 Ho ac tnh c ly tng cua ongc 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 he thong 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 ac tnh cthap, 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 chieuquay ong c kho khan va gay ton that nanglng ln. Quan tnh cua he KT - ong c ln doanh hng cua ien khang KT, he so congsuat thap.

IX. HE TRUYEN ONG TIRISTO-ONG CT-:Hien nay ngi ta s dung rong rai cac bo

bien oi van ieu khien e bien nang lng xoaychieu thanh ien mot chieu e cung cap chocac ong c ien mot chieu. Toc o ong cieu chnh bang cach thay oi ien ap chnhlu bang cach thay oi thi iem thong van.

u iem noi bat cua he T- la o tacong nhanh cao, khong gay on va de t onghoa do cac van dan co he so khuech ai congsuat cao, ieu o rat thuan tien cho viec thietlap cac he thong t ong ieu chnh nhieu



33/76


vong e nang cao chat lng cac ac tnh tnhva cac ac tnh ong cua he thong .

Nhc iem chu yeu do cac dan co tnh phituyen, dang ien ap chnh lu ra co bien o

ap mach cao, gay ton that phu trong may ie.He so cong suat cos cua he noi chung thap

* Chon phng an :Trong thc te truyen ong nao cung co u

va nhc iem, do o tuy trng hp cu thema ta chon phng an truyen ong cho phu hp,tren nguyen tac nhc iem la t nhat. Trong oan nay ta chon phng an truyen ong T-.

* Nguyen ly chung cua bo ieukhien toc o :Bo chnh lu tiristor c mo ta nh sau: cac

van thay nhau dan trong mot phan t chu ky cgoi la khoang dan, hoac khoang thong vi osut ap tren van khong ln lam va mach con laicua chu ky c goi la khoang khong dan haykhoang ngat. ien tr thuan cua tiristor trang

thai ngat khoang 100 va trang thai m 0.01 .ien ap c ieu chnh bang cach bien oithi han lam viec cua van trong khoang thong.

Trong thc te ngi ta dung cac loai van co ieukhien han che, ngha la co ieu khien thiiem au, khoang thong nhng khong the ngatmach khi dong ien cha giam ve khong. Do oviec ieu chnh ien ap bo bien oi van c

thc hien bang cach bien oi thi iem thongvan, viec rut ngan thi han trang thai thong cuacac van trong khoang dan c ac trng bi githong cham tnh t thi iem m t nhien.

Dong ien va ien ap cua bo bien oitheo thi gian la nhng ng cong phc tap, co



34/76


cha ca thanh phan mot chieu va thanh phanxoay chieu. Thanh phan xoay chieu co anhhng xau en qua trnh phat xung va chuyenmach cua may ien nen phai han che.

Vi muc ch o ngi ta noi vao mach phutai bo bien oi ( mach phan ng) cuon sanphang co ien cam xac nh. e phan tch slam viec cua ong c ien mot chieu trong hethong nay phai tm thang phan mot chieu cuavan ien ap va dong ien tren au ra cua bobien oi tc la xac nh tr so trung bnh cuachung trong mot chu ky bien thien ien ap li

xoay chieu. Thanh phan mot chieu cua ien apva dong ien la ien ap chnh lu va dongien chnh lu.

Tiristor cho phep dung nhng tn hieu cocong suat nho lay t cac kh cu ien e chetao ac tnh onh cua ong c va thoa mancac yeu cau cong nghe. Tiristor co quan tnhnen so vi he F- th he thong nay co qua trnh

hp ly hn, co the che tao ra thiet b to hphien ai, co the gia cong cac san pham cochat lng oi hoi o chnh xac cao.

ieu khien Tiristor co nhng tnh chat va otin cay cao tiet kiem c nang lng, khong gaytieng on va tiet kiem dien tch lap at.

ieu kien e m Tiristor:_ at ien ap thuan len no tc cc dng

len anot va cc am len catot_ at ien the dng vao cc ieu khien haycon goi la xung ieu khien



35/76


PHAN II:TONG QUAN VE CAC BO CHNH LU 3 PHA

I. He thong chnh lu ba pha hnh tia ong c:

I. 1. a S o nguyen ly:Chnh lu ba pha hnh tia con c goi la

chnh lu ba pha na chu ky hay chnh lu ba phaco au khong . ien ap chnh lu la motna song cua ien ap xoay chieu.

Hnh 2. 1 S o nguyen ly he thong chnhlu ba pha hnh tia ong c.SVTH:HUYNH KIM SON trang 36

GT1 GT2G

T3

+ -

U2

Uk

K

C0

U

n

I

T1

T2

T3

BA

I1

I2

CCSX

CK

RK

GT1

GT2

GT3

BKC

U1 , f1


36/76


Trong o:- BA: May bien ap chnh lu co nhiem

vu:. Bien oi ien ap nguon Ung thanh

ien ap phu hp Un at len bo chnh lu.. Bien oi so pha nguon thanh so

pha phu hp vi bo chnh lu.. am bao cho nguon va bo chnh

lu ch quan he vi nhau ve t ma khong quanhe trc tiep ve ien nen bao ve va ieuchnh bo chnh lu c de dang hn.

- T1, T2, T3: Cac tiristor, bien ien ap xoay

chieu U2 thanh ien ap mot chieu.- K: Cuon ien khang can bang.- : ong c ien mot chieu kch t oc

lap. ay la thanh phan chu yeu, oi tng canieu chnh toc o.

- Bo loc ( va C0 ): Cho nhng thanhphan xoay chieu con sot lai i qua tu. Lam chodong i qua ong c t nhap nho nen moment t

thay oi, do o toc o ong c c on nh.- BKC: Bo khong che. Co nhiem vu lambo tao xung, em xung va phan phoi xung atlen cac cc ieu khien cua cac tiristor.

I. 1. b Nguyen ly hoat ong : v s in p v dng in chnh lu vo na, kt hp trong v hc.

Vi s o nguyen ly nh tren, cac tiristorc noi theo nhom katot chung nen cac phan

t chnh lu co ac iem nh sau:- Tirisror dan ien la tiristor co anotc noi vi ien ap cao nhat va phai c kchxung ong pha vi ien ap cua pha o.

- Tiristor nao dan ien th no se ganhtron dong ien tai.



37/76


- Khi co mot tiristor dan ien th haitiristor con lai se khong dan ( neu ta xet bo quas chuyen mach ).

Che o lam viec cua chnh lu phu

thuoc vao phng thc ieu khien va cac tnhchat cua phu tai. Trong truyen ong ien, taicua chnh lu thng la cuon kch t ( L, R ) vamach phan ng ong c ( R, L va E ). e n giantrong viec tm hieu nguyen ly hoat ong cua hethong chnh lu ba pha hnh tia ong c tren taco s o thay the nh sau:

Hnh 2. 2 S o thay the he thong chnhlu ba pha hnh tia ong c.Trong o:

- E: Sc phan ien ong cua ongc ien.

- u2a, u2b, u2c: ien ap th cap cuamay bien ap BA.

- Rd: ien tr mach mot chieu ( ke

ca ien tr day quan th cap cua may bienap ).- Ld: ien cam mach mot chieu.e tien hanh ieu chnh toc o

ong c, ngi ta thay oi goc kch cua tiristor


Id

UdT

1T

2T

3

E

Ld

Rd

u2b

u2c

u2a


38/76


se thay oi c ien ap chnh lu, lam cho ienap at len phan ng ong c thay oi.

Trong khoang thi gian O1O2 ien ap ra Uaco gia tr ln nhat, ong thi tai thi iem O1

kch xung cho T1. T1 nhan xung kch nen dan ien,m cho dong ien chay qua con hai van T2 va T3b khoa. Sau thi iem O2 tr i Ub co gia tr lnnhat. Tai O2, kch xung cho T2 nen T2 dan. Luc nayta co Ua < Ub nen anot cua T1 co ien the thaphn so vi katot cua no, do o T1 b khoa. Tngt, tai thi iem O3, T3 dan con T1 va T2 b khoa.

Nh vay moi tiristor se cho dong chay qua no

trong khoang thi gian 1200

ien va gia tr trungbnh cua ien ap chnh lu tiristor:

ien ap ngc at len moi tiristor la hieuso ien the gia anot va katot cua tiristor o:

. Khi T2 dan:

. Khi T3 dan:

iem cc tr cua ien ap ngc atlen T1 la:

Dong ien chnh lu c san bangco gia tr:


( 2.4 ))

3cos(6 21

== UUUU abngT

( 2. 5))

3

2cos(6 21

== UUUU acngT

( 2. 6)

dd

ddXR

UI

+=

3

4

6 21

== khiUUngT

3

116 21

== khiUUngT

cos2

63sin2

2

32

3

2

6

6

2 UdUUd == ++

+

( 2. 3)


39/76


40/76


Hnh 3. 11 S o nguyen ly cua he thong chnhlu ba pha hnh cau ong c.

Cau chnh lu co ieu ba pha gom 6tiristor c chia lam hai nhom:

- Nhom anot chung ( nhom chan ): T2,T4 va T6.

- Nhom katot chung ( nhom le): T1, T3

va T5.Goc kch c tnh t giao iem cua cacna hnh sin song ien ap.

II.1. b Nguyen ly hoat ong va dangsong:



41/76


Chnh lu ba pha hnh cau ong c muonkhi ong he thong ta phai kch ong thi 2tiristor: 1 tiristor nhom le T1, T3, T5 va 1 tiristor nhom chan T2, T4, T6. au tien ta kch T1 cho T1 dan,

sau 600 ien ta kch tiep T3 ngha la cac tiristorc kch cach nhau 1/6 chu ky. Ngoai tr 1 trong 2tiristor lan au tien ch dan trong 600 ien contat ca cac tiristor khac khi a c kch no phaidan trong 1200 ien. cac thi iem bnhthng co 2 tiristor dan: 1 nhom chan va 1 nhom le, rieng trong thi gian chuyen mach ient ng vi goc chuyen mach co 3 tiristor cung

dan: - 1 tiristor c kch ang dan dan len.- 1 tiristor dan ang dan va tat dan.- 1 tiristor se dan tiep.

Gia s T5 va T6 ang dan ien.Khi ta cho = 1 = /6 + , kch xung ieu

khien cho T1. T1 m v Ua > 0. T1 m se lam cho T1b khoa mot cach t nhien v Ua > Uc. Luc nay T1

va T6 cho dong chay qua. ien ap tren tai Ud =Uab = Ua Ub.Khi cho = 2 = 3 /6 + , kch xung ieu

khien cho T2, T2 m v khi T6 dan dong, no at lenanot cua T2 ien ap Ub, khi = 2 th Ub > Uc, T2m lam cho T6 b khoa lai.

Cac xung ieu khien lech nhau /3 clan lt a en cc ieu khien cua cac tiristor

theo th t 1, 2, 3, 4, 5, 6, 1 Trong moi nhom comot tiristor m no se khoa ngay tiristor dandong trc no theo bang tom tat sau:



42/76


Thi iemThi iem MM KhoKhoaa

1 = /6+

2 = 3 /6+

3 = 5 /6+

4 = 7 /6+

5 = 9 /6

+ 6 =11 /6+

T1T2

T3T4T5T6

T5T6

T1T2T3T4

o th ien ap ngo ra, dong ien ccieu khien va dong ien chay qua cac tiristorc trnh bay nh sau:

ud

u2a u2b u2c1 3 5

6 2 4

0

Hnh 3. 13 o th dang song ien ap ngo raTng t nh trong he thong chnh lu ba pha

hnh tia ong c, e tm hieu nguyen ly hoatong cua he thong chnh lu ba pha hnh cau SVTH:HUYNH KIM SON trang 43


43/76


ong c ta xet goc kch trong cac trng hpsau:

* Khi = 0: Ta kch tai thi iem chuyenmach t nhien.

m: So pha cua he thong chnh lu, trongtrng hp nay th m = 6.

* Khi 0:

Ta xet trong cac khoang thi gian (0i y ldelta trong v tcs ca mnh ):

Trong khoang thi gian O1O2, cap T1, T6dan cho dong ien chay qua. Khi o gia tr cuaien ap chnh lu:

Trong khoang thi gian O2O3, cap T1, T2 dan chodong ien chay qua nen:

Tng t, ta c:

Gia tr trung bnh cua ien ap chnh lu:


( 3. 25 )m

Em

UU dcdcd

sin3 2max00 ==

)6

sin(6)( 221

+=== UUUUOOU abbad

)6

sin(6)( 232

== UUOOU acd

)2

sin(6)( 243

== UUOOU bcd

)6

5sin(6)( 254

== UUOOU bad

)6

7sin(6)( 265

== UUOOU cad

)2

3sin(6)( 276

== UUOOU cbd

( 3. 27 )

cos63

)6

sin(626

2

36

6

2 UdUUd =+= ++

+

cossin3cos 2max00

mEm

UU dcdcd == ( 3. 26 )


44/76


Do o, ta thay khi thay oi goc kch thta co the thay oi c gia tr trung bnh cuaien ap at vao phan ng ong c. Khi bienoi t 0 en th gia tr ien ap trung bnh Udbien thien t +Udmax en Udmax.

Trong khoang thi gian OO1, T5 dan iennen UngT1 = Uc Ua.

Trong khoang thi gian O3O5, T3 dan iennen: UngT1 = Ub Ua.

Gia tr cua ien ap ngc cc ai atlen moi tiristor la:

e s o chnh lu ba pha hnh cau cothe lam viec c, cac xung ieu khien can coo rong ln hn 600 ien mi co the am baocho viec m ong thi 2 tiristor hai nhom.

II.1.c Hien tng chuyen mach:oi vi s o chnh lu ba pha hnh cau

ong c co ieu khien, oi xng, qua trnhchuyen mach ch xay ra gia cac tiristor trong

cung mot nhom. o th bieu dien dang songien ap ra cua chnh lu, dong ien chay quatiristor va ien ap ngc at len moi tiristor nhsau:


2max6UUng =


45/76


ud

51 3

6 2 4

0

Khi he thong hoat ong, gia s van T1, T2ang m. Tai thi iem O1, ta kch xung e T3 m.Luc nay se bat au xay ra s chuyen machcua dong ien t T1 sang T3. T1 va T3 m ongthi se lam ngan mach hai au cuon th capcua may bien ap. Trong thi gian nay dong ienchay qua T3 tang dan t 0 en Id, ong thi dongqua T1 giam dan t Id xuong 0, T1 bat au ngng

dan. Sau mot khoang thi gian chuyen mach naoo th dong iT1 mi thc s giam ve 0 va dongiT3 at en gia tr Id.

Moi tng quan gia goc chuyen mach

vi cac ai lng cua he thong:

Neu chon O1 lam goc thi gian, ta c:


( 3.28 )( 3.29 )

)]cos([cos2

621 += U

XIi

td

dT

)]cos([cos2

623 += U

Xi

td

T

( 3.30 )dtd IUX

262)cos(cos =+

)6

sin(2 2

++= UUa

)6

sin(2 2

++= UUa

2

ac ee +

2cb

ee +

2

ba ee +


46/76


Gia tr trung bnh cua sut ap do hientng trung dan gay nen:

Thay gia tr bieu thc ( 3. 30 ) vao ( 3. 31 )ta c:

Xet trong khoang thi gian O2O3: UT1 = ub ua

Trong khoang thi gian O3O4: T2 va T4 trung

dan nen ta co:UT1 = ub ua va UT1 = ub uc nen UT1 = ub ( ua + uc )/2.

Xet trong khoang thi gian O4O5: UT1 = ub uc

Trong khoang thi gian O5O6: T3 va T5 trungdan nen ta co:

UT1 = ub ua va UT1 = uc ua nen UT1 = ( ub

+ uc )/2 ua.Tng t cho cac khoang con lai.Khi ke en s chuyen mach ien t, gia

tr trung bnh cua ien ap chnh lu ba pha hnhcau:

II. 2. Nhan xet:So vi he thong chnh lu ba pha hnh tia

ong c th he thong chnh lu ba pha hnh cau conhieu u iem hn:

Gia tr ien ap ngo ra cua chnh lu hnhcau ln hn ien ap chnh lu hnh tia. o nhap


( 3.

31 ))]cos([cos2

63

2 +=

UU

( 3.32 )

dtdIXU3

=

( 3.33 )

dtdd

IXUU

3cos

632 =


47/76


nho cua song ien ap chnh lu hnh cau thaphn hnh tia nen chat lng cua chnh lu ba phahnh cau la tot nhat. ay la he thong c sdung pho bien nhat trong thc te.

Ngay nay, cac he thong hien ai taco the ieu chnh toc o ln hay nho hn sovi toc o c ban vi pham vi ieu chnh ln:

D = ( Hang tram hangngan )/1.

Nh vay, he thong chnh lu ba pha hnhcau la mot he thong co:

- ac tnh c cng.

- T ong on nh c toc o khiphu tai thay oi.- Co o nhay cao, hieu suat ln.

Nguyen tac c ban e xay dng he truyenong T- ao chieu:

_Gi nguyen chieu dong ien phan ng va aochieu dong kch t

_Gi nguyen dong kch t va ao chieu dong

phan ng nhng c phan ra 5 s o chnh: Truyen ong dung mot bo bien oi cap chophan ng va ao chieu quay bang cachao chieu dong kch t

Truyen ong dung mot bo bien oi cap chophan ng va ao chieu quay bang cong tact chuyen mach phan ng ( t thong gikhong oi )

Truyen ong dung 2 bo bien oi cap chophan ng ieu khien rieng Truyen ong dung 2 bo bien oi noi song

song ngc ieu khien chung



48/76

1

3

5

4

6

2

4

6

2

1

3

5

Lc


Tuy nhien, moi loai s o eu co u nhciem rieng va thch hp vi tng loai tai vacong nghe

Ta chon bo truyen ong dung 2 bo bien oi

noi song song ngc ieu khien chung bi nodung cho dai cong suat va va ln co tan soao chieu cao va thc hien ao chieu em hn

III. S o- nguyen ly lam viec:( b bin i kpsong song ngc )

S o gom hai bo bien oi G1 va G2 au songsong ngc vi cuon khang can bang Lc . Tng

bo bien oi co the lam viec che o chnhlu hoac nghch lu. Ca 2 bo bien oi G1 va G2eu nhan c xung m tai moi thi iem. Ta goi 1 la goc m oi vi G1, 2 la goc m oi viG2 , th s phoi hp gia hai gia tr 1 va 2 phaic thc hien theo quan he :



49/76

a1=180

a2=0 a1=0

a2=180

0

30

60

90

120

150

180

uc2 uc1


1 + 2 = 180os phoi hp nay la tuyen tnh

Bieu o phoi hptuyen tnh

Gia s ta can ong c quay thuan ta cho G1 lamviec che o chnh lu 1 = 0 90o , Ud1 > 0 bay gi 2 > 90o G2 lam viec che o nghch lu, Ui2 < 0

Ud1 = U0 cos 1 > 0Ui2 = U0 cos 2 < 0

Ca hai ien ap Ud1 va Ui2 eu at len phanng cua ong c M. ong c ch co the nghe

theo Ud1 va quay thuan. ong c t choi Ui2 vcac tiristor khong the cho dong chay t catoten anot.


1 =180o

1 = 0 2 = 0

2 =180o


50/76


Khi 1 = 2 = 90o , Ud1 = Ui2 = 0 luc nay ienap at len phan ng cua ong c bang khong.ong c trang thai dng.

Gia s uc la ien ap ieu khien bo ieu

khien khi can khi ong M quay thuan ta cho uc =uc1

1 = 30o , 2 = 180 1 = 150o

;

G1 lam viec che o chnh lu con G2 lamviec che o i

Neu bay gi can giam toc o quaycua ong c ta cho uc = uc2 , cac goc m 1 =60o , 2 = 120o

;

Luc nay do quan tnh nen sc ien ong Ecua ong c van con gi nguyen tr so ng

vi trang thai trc o, E > Ud1 bo bien oi G1b khoa lai.

Mac khac, E > | Ui2 | nen bo bien oi G2 lamviec che o nghch lu phu thuoc, tra nanglng tch luy trong ong c ve nguon ien xoaychieu. Dong ien phan ng oi dau, chay t Mvao G2 ong c b ham tai sinh, toc o giamxuong en gia tr ng vi Ud1.

Neu cho ien ap ieu khien uc < 0 th G2 selam viec che o chnh lu con G1 se lamviec che o nghch lu phu thuoc.

ac iem cua s o ao dong ang xet laco mot dong ien luc th chay t G1 vao G2, luc


012

3UUd = 02

2

3UUi =

0

'

22

1UUi =0

'

12

1UUd =


51/76

ccm

cccc

III =*


th chay t G2 vao G1 ma khong qua mach tai.Ngi ta goi la dong tuan hoan.

Dong ien tuan hoan lam cho may bien apva cac tiristor phai lam viec nang ne hn. e

han che dong ien tuan hoan ngi ta dung 4ien cam Lc

Gia tr trung bnh cua dong tuan hoan :

t:

: goi la gia tr tng oi cua dong ientuan hoan

Trong o: : gia tr cc ai cuadong ien tuan hoan

Quan he I*

cc = f( 1) c trnh bay tren hnhve. ien cam Lc phai c tnh toan sao cho giatr trung bnh cua dong tuan hoan trong trnghp xau nhat khong vt qua 10% gia tr nhmc cua dong ien phu tai Id.

6 2 4

1 3 5


)cos(sin63

111

2

=ct

ccX

VI

ct

ccmX

VI 2

.6=


52/76


0

0.1

0.2

0.3

0.9

30 60 90 120 150 180o o o ooo

PHAN III: TNH CHON MACH ONG LC

1. Chon ong c ien mot chieu :Co cac thong so sau:

Pm = 30 kwUm = 220 v m = 0.95

nm = 1500 vong/phut* ien ap chnh lu khong tai bao gom:Udo = Ud + Ur + U + U + Ucb

Vi :Ud : ien ap chnh lu 220v



53/76


Ur : sut ap tren ien tr day quanMBA , Ur = 3% Ud

U : sut ap tren ien khang day quanMBA va sut ap do hien tng trung dan , U =2% Ud

U : sut ap tren 2 tiristor , U = 2.2 = 4v Ucb : sut ap tren cuon khang can

bang , Ucb = 0.8% UdVay ien ap chnh lu khong tai la:

Udo = 220 + ( 3 + 2 + 0.8 ) . 220/100 + 4 =236.8 ( V )

Gia tr hieu dung cua ien ap pha th capmay bien ap :2.101

63

76.236*14.3

63

.2 ===

doU

U

(V)

ien ap ngc ln nhat at len tiristor:84.2472.101*66 2 === UUim (V)

Dong ien trung bnh chay trong moi tiristor:

62

1 3

0

d

dtb

IdII ==

vi 54.143220*95.0

10.30

.

3

===dm

dm

dU

PI

(A)

vay 92.236

54.143==tbI (A)

Do ton tai dong tuan hoan chay qua cac bobien oi G1 , G2 va may bien ap ma khong quaphu tai nen che o lam viec cua may bienap va tiristor nang ne hn. Trng hp toi te

nhat dong tuan hoan Icc = 4% Id.2. Chon tiristor: Theo thc te e chon tiristor lam viec antoan ta phai chon

- He so d tr ve dong ien Ki = 1.2- He so d tr ve ien ap Ku = 1.6



54/76


Phai chon tiristor t nhat chu c ien apngc :

Uim = 1.6*247.84 = 396.544 (V)Va chu c dong ien trung bnh:

Itb = 1.2*23.92 = 28.71 (A)Tra bang ta chon tiristor T -50 do lien xo che

tao co cac thong so sau:Itb = 50 (A)Uim = 0.1 1 (KV) U = 1.3 (V) , toff = 10.5 ( s) , Ig = 0.9 (A) , Ug

= 3 (V)3. Tnh toan may bien ap ong lc:

May bien ap trong he thong nay co congsuat c trung bnh. Do o se co li ve day quanneu ta tang so vong day s cap len 3 lan vagiam tiet dien i 3 lan. e lam c viec naypha s cap phai noi va pha th cap noi .Luc nay t so may bien ap :

266.0380

2.101

1

2 ===U

Un

Gia tr hieu dung cua dong ien chay trongmoi pha th cap cua MBA:6.58

6

54.143

62 ===

dII (A)

Gia tr hieu dung cua dong ien chay trongmoi pha s cap :

6.156.58*266.0. 21 === InI (A)* Mach t:-cong suat bieu kien cua may bien ap:

S1 = 3U1I1 = 3* 380 * 15.6 = 17784 (VA)S2 = 3U2I2 = 3* 101.2 * 58.6 = 17791 (VA)S = ( S1 + S2 ) / 2 = 17787.5 (VA)

Chon mach t 3 tru, tiet dien moi tru ctnh theo cong thc kinh nghiem :



55/76


cf

PKQ =

trong o: K = 5 6 vi may bien ap khoP : cong suat bieu kien cua may

bien ap c : so truf : tan so cua nguon xoay chieu, f = 50

Hz3.65

50*3

5.177876 ==Q cm2

Mach t c lam bang cac la thep kthuat ien ghep lai vi nhau e giam dongien xoay, ton that 1.3w/kg, trong lng 7.5 kg/dm3

* Tru:-tiet dien tho cua tru: 10*6 + 4*6 = 84

cm2

-tiet dien hieu qua : 0.95 * 84 = 79.8cm2

-trong lng : 7.5 * 0.798 * 2.4 * 3 =43.1 kg

* Qui lat :-tiet dien tho : 10 * 10 = 100 cm2

-tiet dien hieu qua : 0.95* 100 = 95 cm2

-trong lng : 7.5 * 0.95 * 5 * 2 = 71.25kg

Trong lng loi thep : 43.1 + 71.25 = 114.35kg

* T cam :

trong cac tru chon 1.1=mB (T)

trong cac qui lat chon 924.095

8.79*1.1' ==mB (T)

* Day quan :So vong day moi pha :

-s cap :



56/76


1861.1*10.84*50*44.4

380

..44.4 41

1 === mBQf

Un vong

-th cap :50

380

2.101*186

1

2

12 ===

U

Unn vong

chon mat o dong ien : J1 = J2 = 3 (A/mm2)ng knh day pha s cap :

57.214.3*3

6.15*44 11

===J

Id mm

ng knh day pha th cap :

514.3*3

6.58*44 22 ===

J

Id mm

tra bang ta chon day co:

d1 = 2.83 mm ; S = 6.92 mm2 ; 55.97g/m ; 0.00278 m/

d2 = 5.2 mm ; S = 21.24 mm2; 189g/m ; r= 0.000811 m/

Ong day quan: long vao moi tru 1 ong dayquan lam bang vat lieu cach ien day 1mm, co ban knh trong la 72 mm. Vay ban knhcua vong day s cap la 74 mm.

* Day quan s cap: 186 vong chia thanh 4 lp,gia 2 lp at 1 t giay cach ien, day 0.1mm

Be day cua moi day quan s cap la:e1 = 4 * 2.83 + 0.3 = 11.62 mm



57/76


Ban knh trung bnh cua moi day quan:

74 + 81.792

62.11= mm

Chieu dai cua day quan s cap:27.93186*10*81.79*2

3 = m ien tr nhiet o C75 o la:

)(26.0)000475.01(*27.93*00278.01 =+=r

* Day quan th cap:Gia day quan s cap va th cap e motkhoang cach 8mm. Day quan th cap gom 50vong va chia thanh 3 lp gia 2 lp at mott giay cach ien day 0.1mm. Be day day quan th cap:

8.152.02.5*32 =+=e (mm) Ban knh trung bnh cua day quan th cap:

74 + 11.62 + 8 + 15.8/2 = 101.62 (mm) Chieu dai cua day quan th cap:

91.3150*10*62.101*23 == l m

ien tr day quan nhiet o C75 o la:)(026.0)000475.01(*91.31*10*11.8 42 =+=

r

ien khang moi pha:



58/76


)(02.01031410)2

1662.118(

236

8.365014.38

10)2

(8

7322

7212

2

2

=+

+=

+

+=

ee

ah

rnx

trong o:r: ban knh trung bnh cua 2 cuon day

r = e1 + e2 + 4 = 11.62 + 15.8 + 4 = 31.42(mm)

h: chieu cao 2 day quanh = 236 mm

: tan so goc, a= 0.008 ien ap ri tren ien khang:

89.1214.3

54.143094.033=

==

dXIU

(V) ien ap ri tren ien tr:

43.654.143186

5026.0026.0

22

1

2

12=

+=

+=

drI

n

nrrU (V)

ien ap chnh lu khi ay tai:48.21743.689.128.236 === rdod UUUU (V)

4. Tnh chon cuon khang san bang dong tai: Cuon khang san bang dong tai c mac

noi tiep vi ong c nham muc ch giam onhap nho cua dong ien chnh lu e ongc lam viec c tot hn, giam cac ton thatphu trong ong c. Thanh phan song bac cao cua dong chnh

lu khong vt qua 5% dong tai)(18.7

100

54.1435

~AId =

gia tr cuon khang phai chon sao cho am baoieu kien nay luc ong c lam viec gia trnh mc goc m 0= th dong tai ln nhat,thanh phan xoay chieu ien tai ln nhat.

Khai trien Furier ien ap chnh lu:

+

=

35

6cos21U

63u 2d



59/76


Pt mach tai luc lam viec:~~ 2

ddd

ddd UUdt

diLRiRIEU +=+++=

Can bang cac thanh phan 1 chieu va xoay

chieu:Ud = E + RId

dt

diLRiU ddd

~

~~+=

thc te thdt

diLRi dd

~

~ t6sinUL35

6d6cosU

35

66.

L

1l 2

t

02

=

=

Gia tr hieu dung cua thanh phan songhai nay la:

2

1U

L35

618I 2

=

theo ieu kien rang buoc 18.7I (A)

18.72

1

35

618 2

L

U

42 1042.122

1

18.7352

618 =

UL (H)

L: tong gia tr cua ien cam cuon khang sangbang va ien cam cua phu tai ong c Lpt

L = Lsb + Lpt

ViImmdm

dm

ptIp

ULL

==

trong o: : he so phu thuoc kieu ong c, ta chon

ong c dang co bu 25.0=p : so oi cc t, p = 2

( )s/rad15760

15002

60

n2dm =

=

=



60/76


3102.154.143*157*2

220*25.0 ==ptL (H)

vay cuon khang sang bang c chon la :Lsb = L - Lpt = 1.242 1.2 = 0.042 (mH)

5. Tnh chon cuon khang can bang lcDo ac tnh cua s o ao dong noi song songngc hnh cau co 1 dong tuan hoan icc luc thchay t G1 vao G2 , luc th chay t G2 vao G1.e han che dong tuan hoan ngi ta macthem cuon ien cam Lc nh trong s o machlc goi la cuon khang can bang. Dong canbang at gia tr ln nhat khi goc m

o

2

o

1 120,60 == hoac o2o1 60,120 ==Gia tr cc ai cua dong tuan hoan

CT

2ccm

X

U6I =

viXCT = 2XC + 2Xha32.0

I

II

ccm

maxcc*

maxcc ==

=>CTCT

ccmccXX

UII

09.56332.032.0 2max ===

Trong trng hp xau nhat la dong iccmax khongvt qua 10% gia tr dong ien tai. Tc la:)(354.14

10

54.143

100

10max A

II dcc ==

=> ( )= 91.3354.1409.56

354.1409.56

CT

CT

XX

Vay )(01.0314

91.3H

XL CTCT ===

vi LCT = 2LC + 2Lba

=> ( )baCTC L2L2

1

L = vi )H(109.2314094.0X

L4ba

ba

===

=> ( ) )H(1097.4109.2201.02

1L 44C

==



61/76


PHAN IV: TNH CHON MACH IEU KHIEN

Trong thc te, ngi ta dung 2 nguyen tac ieukhien

* Nguyen tac ieu khien thang ngarccos:

Theo nguyen tac nay ngi ta dung 2 ien ap

ien ap ong bo Ur vt trt ien apanod catod ien ap ieu khien Uc la ien ap 1 chieu

co the ieu chnh c bien o theo 2hng am va dng.



62/76


ng net t la ien ap anod catod Tiristor,t ien ap nay ngi ta tao ra Ur :

ur+uc

uc

ur

Tong ai so Ur + Uc c a en au vao cuakhau so sanh

0cosBU c =+

=>

=B

Uarccos c

Ngi ta lay B = UcmaxNh vay, khi Uc bien thien t - Ucmax en Ucmax th

goc bien thien t 10 .Trong o an nay phan t ta chon lavi mach TCA 780 da tren nguyen tac ieukhien thang ng.

TCA 780

16

1

9

8

TCA 780 la mot vi mach phc hp thc hienc 4 chc nang cua mot mach ieu khien



63/76


ien ap ong bo, tao ien ap rang ca ongbo, so sanh va tao xung ra.

Co the mo ta hoat ong cua vi mach TCA780 bang gian o thong so chu yeu cua TCA

780: ien ap nuoi : Us = 18 V. Dong ien tieu thu : Is = 10 mA. Dong ien ra : I = 50 mA. ien ap rang ca : Urmax = ( Us 2) (V). ien tr trong mach tao ien ap rang ca:

= k500k20R9 . ien ap ieu khien : ( )2U5.0U s11 = (V).

Dong ien ong bo : A200Is = .

Tu ien : F5.0C10 = . Tan so xung ra : Hz50010f = .* Nguyen ly lam viec cua he thongieu khien:

oi vi tiristor m cho dong ien chayqua khi ien ap dng at len anot va coxung ap dng at len cc ieu khien.

Sau khi tiristor a m th xung ieu khienkhong con tac dung, dong ien chay quatiristor do thong so cua mach ong lc quyetnh.* Mach ieu khien co cac chc nangsau:

-ieu chnh c v tr xung ieu khientrong pham vi na chu ky dng cua ien ap

at len anot-catot-tiristor-Tao ra cac xung u ieu kien m ctiristor, xung ieu khien thng co bien okhoang 2 15v o rong xung tx phai ln hnhoac bang 10 s. Trng hp tai co tnh camth tx phai ln hn nhieu co khi tx = 500 s.



64/76


-Dng c s phat xung khi co s co-Phan phoi cac xung cho cac kenh ieu

khien theo qui luat yeu cauQua trnh tao ra mot xung ieu khien phai

lan lt i qua cac khau:-khau tao ra ien ap rang ca cua ong

pha-khau so sanh-khau khuech ai xung

1. Khau tao ra ien ap rang ca cuaong pha va khau so sanh :

Khau tao ien ap rang ca cua ong pha

va so sanh do vi mach TCA780 am trach. TCA780 lam viec theo nguyen tac ieukhien thang ng tuyen tnh:

Theo nguyen tac nay ngi ta cung dung 2ien ap

_ien ap ong bo Ur co dang rang ca,ong bo vi ien ap at tren anod catodcua Tiristor.

_ien ap ieu khien Uc la ien ap 1chieu co the thay oi cTong ai so Ur + Uc c a en au vao

cua 1 khau so sanh. Nh vay, bang cachlam bien oi Uc ngi ta co the ieu khienc thi iem xuat hien xung ra, tc laieu khien c goc m .



65/76


us

ucm

-usm

usmus

0

Quan he gia va Uc la:

maxr

c

U

U=

ngi ta lay Ucmax = Urmax e co the chay to1800

u5

u11u10

u15

u14

u'15

u'14

u11u10

chn

12 ni

t



66/76


S O VI MACH TCA780

V(t) ien ap ong phaTu ien C10 tham gia vao khau tao ien

ap xung rang ca, no c nap bang dongien i t chan so 10 va dong i c ieuchnh bang R9 (thng th R9 = 20 500k )

Dong ien c tnh:99

8 8.3

RR

Ui ==

10

10C

tiU =

Tai thi iem t = to ; U10 = Uc = U11. Nhan cxung ra tai chan 15 neu V(t) > 0 hoac mot xung ra chan 14 neu V(t) < 0.

to = (C10 . U10)/I = (R9 . C10 . Uc ) / U8goc m = .to

goc m bien thien t 0 180o cung co the

thay oi bang cach thay oi Uc hoac R9Tu C12 co tac dung khuech ai o rong xung ra.

Co the chon C12 t 0 300pF e co o rong cuaxung t 30 200 s .Neu muon co o rong xung


15

14

8

5

RD

1 9 10 1

16 13 6

C10 C12R9

Us

U

V(t) TCA780


67/76

Us

Rc

D2

R2

BAX

R1

Rg

C

F


ln hn ta co the chon C12 co tr so ln hn300pF

Us : ien ap nguon nuoi t cac chan 6,13,16vi ien ap mot chieu (Us = 18v)

Uc : ien ap ieu khien lay t chan 11 coien ap khoang 0.5 16v2. Khau khuech ai xung:

Xung ra tren vi mach TCA780 cha u ln eco the m tiristor do o can khuech ai xung cobien o u ln e co the m tiristor.

Khau khuech ai xung bao gom: transistor,bien ap xung , diot va cac ien tr phan cc cho

transistor.S o khau khuech ai xung:

* Hoat ong cua s o:Tn hieu vao la Ve ( la mot tn hieu logic) c

lay t chan 14 va 15 cua TCA-Khi Ve = 1 th transistor T bao hoa


T

Dz

D3

D4

R3


68/76


-Khi Ve = 0 th Dz1 b chan lai va transistor bkhoa

Chc nang tng linh kien trong s o:D3 : co nhiem vu hng dong cung cap cho

transistorD4 : la diot ngan chan xung am co the co

khi tiristor khoaRc : ien tr han che dong colectD2 : han che qua ien ap tren cac cc C,E

cua transistorRg : la ien tr han che dong ieu khien

tiristor

R3 : la ien tr anh hng bien o vasn xung raR1 va R2 : la ien tr han che dong phan

cc Ib cua transistorGia thiet khi t = 0 ;Ve =1 T m, ien cam L1

cua bien ap xung ngan can khong cho Ic at ngaygia tr bao hoa cua no la

cR

UI =1

vay dong ic ch co the tang trng t t theoluat ham mu

==

t

c

cL eR

Uii 1 vi

cR

L1=

sau thi gian khoang 5 th ic I1Ben th cap may bien ap xuat hien mot

xung ap tren R3 e m tiristorKhi t = t1 = T1 , Ve = 0, bay gi iL mi at ti

gia tr



69/76

L

R1+

-

U


( ) ( )1

011

1

1

R

UIe

R

Utiti

T

C

CL=

==

T b khoa lai , ic = 0Neu khong co diot D2 th nang lng 201

2

1ILW = se

sinh ra qua ien ap tren cac cc C va E cuatransistor. Qua ien ap nay co the vt qua100v, transistor T co the b pha huy

Diot D2 loai tr hien tng qua ien ap noitren, bi v va khi Ucf = Vc Vf = 0.8v th D2 m chodong chay qua, no lam ngan mach hai iem Cva F. Do o UCE = U+0.8 T t = t1 tr i iL suy giamtheo luat

'

.0

t

L eII

=

trong o '1'

R

L= , R la ien tr cua cuon cam

L1 Xet phan t quan trong trong khau khuech aixung la BAX. Trong thc te tnh toan ngi tathng bo qua ien cam tan cua BAX, bay gico s o thay the sau:

R2 ien tr th cap qui oi sang pha s capL ien cam chnh cua BAX


R2


70/76


Di dang toan t Laplace, tong tr cuatoan mach la:

( )(

( )( )

( ) ( )

( ) bt

bt

eRR

Uti

eaR

Uti

LpRRRR

LpR

p

UpI

LpR

LpRRRRpZ

+=

=

++

+=

+

++=

'

21

2

1

1

'

21

'

21

'

2

1

'

2

'

21

'

21

.1

.

trong o '21

'

2

RR

Ra

+= , ( )LRR

RRb

'

21

'

21

+=

do o ( ) ( ) bteUatiRtu == ..2'

22 o rong cua xung ra:

max2

2

U

SBWT sx =

trong o: W2 so vong day th cap BAXS dien tch loi satU2max bien o xung ran

3. Phoi hp goc ieu khien:ien ap at vao phan ng cua ong c:

Trong o: Udo = const do vay toc o cua ongc phu thuoc vao . Theo nguyen tac ieukhien thang ng, muon thay oi goc m ththay oi Udk. Vi 2 bo Tiristor G1 va G2 lam viecphoi hp ta dung ieu khien chung. Do o ieukien:

o

21 180=+

vi 1 ta co Udk1, vi 2 ta co Udk2. Do o, ta phaiieu khien sao cho Udk1+ Udk2 = const. Muon coieu o, ta dung mach tr sao cho:

Udk2 = Uconst Udk1



71/76


15v uk1

R

R

u1

R

R

u2

uk2

Udk1 a vao chan 11 cua 3 TCA 780 ieu khienG1Udk2 a vao chan 11 cua 3 TCA 780 ieu khienG2

ieu khien toc o tc la thay oi goc m hay chnh la thay oi Udk. Trong trng hp nayngi ta dung 1 bien tr.

PHAN IV: TNH CHON MACH BAO VEoi vi chnh lu ban dan, khi tnh toan cung

nh van hanh ta phai at biet lu y en vane bao ve qua dong ien va qua ien ap.V van ban dan co kch thc nho, nhiet dung

be va mat o dong ien qua mat tiep giap p-nln nen no rat nhay vi qua tai ve dong.Hang so thi gian phat nong cua 1 ban Silic



72/76


trong van cong suat ln c ch vai phan tramgiay. Do o, khau bao ve dong ien oi hoiphai co o tac ong nhanh.

Mat van ban dan cung rat nhay vi qua

ien ap. Ch can ton tai 1 ien ap ngc lnhn gia tr cho phep trong khoang ( ) s21 th mattiep giap co the b choc thung ve ien.Tnh chon thiet b bao ve:

a) Cong suat ton that va lam mat:Khi Tiristor m cho dong chay qua, cong suat

ben trong se ot nong chung. Mat ghep ni bnong nhat, ta dung k hieu jT e ch nhiet o

mat ghep. jmT la nhiet o ln nhat cho phep oi vi ban dan Ge : C10080T ojm = oi vi ban dan Si : C200150T ojm =

Tiristor rat nhay vi nhiet o. Neu khi lamviec nhiet o vt qua nhiet o jmT cho phepth du thi gian rat nho cung co the phahong Tiristor. V vay viec tnh toan nhiet o

mat ghep la can thiet.Nhiet o khong kh moi trng lam anhhng rat ln en s lam viec an toan cua

Tiristor. Khi khong lam mat th kha nang chuc dong khoang ( )%4030 dong nh mc. Bienphap lam mat thong dung nhat la dung quatkhong kh bao quanh canh tan nhiet. oi vicong suat ln th ta cho nc trc tiep chay

qua canh tan nhiet hoac ngam cac thiet bban dan trong dau bien the.b) Bao ve qua dong ien:Co 2 loai qua dong ien, ngan mach va quatai

a.Ngan mach:



73/76


Dung e ch cac trng hp s co tao radong ien qua ln nh ngan mach tren tai,tren thanh dan th cap cua MBA ( nganmach ben ngoai), ngan mach cac pha do choc

thung van ( ngan mach ben trong), do otbien nghch lu.

b.Qua tai:Xuat hien trong khong gian lam viec xac lap

hoac qua o. No co gia tr khong ln lamva cho phep ton tai lau dai hn.

e bao ve Tiristor tranh b dong ien phahoai, ngi ta thng dung day chay tac ong

nhanh. Loai day chay nay thng lam bangbac la at trong vo s co cha cat thach anhhoac nc cat.

Hoat ong cua dong chay chia thanh 2 giaioan:

Giai oan chay t t = 0 en khi xuat hienho quang

Giai oan ho quang t thq en tc.

Dong ien chay qua day dan sinh ra nhietlng Q = i2Rt, co nhieu cach at day chay ebao ve thiet b ban dan.

+ at noi tiep vi tng Tiristor+ at tng pha th cap cua MBA+ at noi tiep vi nhom Tiristor noi

song song+ at au ra cua thiet b bien oi

+ at pha s cap cua MBACac thong so at trng cho dong chay laien ap nh mc va dong ien nh mc.Khong nen at at day chay vao ien apcao hn ien ap cua day chay. Dong iennh mc cua day chay phai bang hoac ln



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hn dong ien no bao ve, nhng khong qua10%.

Bao ve rieng biet tng Tiristor c s dungtrong trng hp khi 1 Tiristor b choc thung nhng

van yeu cau bo bien oi tiep tuc lam viec.Neu co n Tiristor ghep song song ma 1 Tiristor bchoc thung th dong tai chia eu cho (n-1) Tiristorcon lai. Vay khi chon dong inh mc cua dongtai can lu y trng hp nay.

imax

imax

thq tc

t

Ta chon loai day chay co thong so:

Um = 220v , Im = 2.5Ac)Bao ve qua ien ap cho Tiristor:Tiristor rat nhay cam vi qua ien ap. Qua

ien ap c chia thanh 2 nguyen nhan chnh: Nguyen nhan noi tai: ay la s tch tu

ien tch dng trong cac lp ban dan. Khikhoa Tiristor bang ien ap ngc, cac ienap noi tren oi ngc la hanh trnh tao ra

dong ien ngc trong thi gian rat ngan.S bien thien nhanh chong cua dong ienngc gay ra suat ien ong cam ng ratln trong cac ien cam, luon luon co cacng day nguon dan en cac Tiristor. V



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vay gia cac anod va catod cua cac Tiristorxuat hien qua ien ap.

Nguyen nhan ngoai: nguyen nhan nay xayra ngau nhien khi cat khong tai 1 MBA, khi

co sam sete bao ve qua ien ap ngi ta dungmach RCMach RC noi song song vi cac Tiristor nham

bao ve qua ien ap do tch tu ien tch khichuyen mach gay nen.

Thong so cua mach RC vao mc qua ienap co the xay ra toc o bien thien cua

dong ien chuyen mach, ien cam tren ngday, dong ien t hoa MBA, viec tnh toantng oi phc tap.

i

t

i

URC

Theo kinh nghiem, vi s o nay ta co thechon

R = 25 , C = F47



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Tuy nhien, cac loai Tiristor san xuat gan ay conco kha nang chu ng

dt

du cao cs

v2000

cho phep

bao ve RC.

Documents

Chỉnh lưu cầu 3 pha điều khiển tốc độ động cơ điện một chiều - Chưa thay số liệu tính toán của mình vô.ok