- YJ =P2 =P1 LP= 1_LP =P
Hinh 5.32 Car:h ve aar: tinh nhu
5.5 D9ng CO'di~n mQt chieu 1 09.i CU'O'ng
5.5.1. 09.i CU'O'ng
Dong CO' di$n mot chi§u dU'Q'C dung rat ph6 bien trong cong nghi$p, giao thong v$n tai va n6i chung & cac thiet bi can di§u chinh t6c do quay lien tl,lc trong mot ph9m vi rong rai.
5.5.1.1. Nguyen tac nghjch dao cua cac may di$n:
Gia sfr may dang lam Vi$C & che dQ may phat tren IU'&i di$n c6 U = const va sinh ra Mdt la mo men ham d6i v&i mo men quay M 1 cua dÂng CO' SO' cĐp keo may phat. Luc d6, dong di$n phan Cmg cua may phat: lu E~~ U
Neu giam <ti ho<;1c n cua may phat th1 s.d.d cua n6 se giam. Khi giam m¢t each thich dang v&i EU'< U. Luc d6 IU' se d6i d§u va c6 chieu ngU'Q'C v&i chieu ban dau (h5.36b).
NhU'ng v1 U = const nen chieu cua It trong day qu§n kich thich hay la ten cua cac Cl!C tu chinh se khong d6i. NhU' v~y Mdt se d6i d§u va may chuyĐn sang lam vi$C & che dQ dÂng
CO'. Tach dÂng CO' SO' cĐp keo may phat di$n ra ta c6 dong CO' di$n mot chi§u. Trong qua tr1nh chuy§n d6i nhLI' v~y, tren tn,ic may c6 2 dong CO': -0Âng CO' SO' cĐp va dÂng CO' di$n mÂt chiĐu c6 th§ gay ra hU' hong cho bo may. Cho nen trong SO' d6 cua cac may phat di$n khi lam Vi$C song song d§u c6 khi c1,,1 di$n ti! dong cat may phat di$n ra kh6i IU'&i di$n khi dong di$n cua may phat di$n d6i chieu.
a) b)
+ U=const + U=const
Mayphat E>c;,ngcd
M MdtE> Mc
Wt Wt
H1nh 5.36 Chuy§n d6i may di$n mot chieu kich thich song song tu che dQ may phat sang che do dong CO'
5.5.1.2. Phan lo9i cac dÂng CO' di$n mot chiĐu:
Cung nhU' may phat di$n, dong CO' di$n mot chi§u dU'Q'C phan lo9i theo each
kich thich thanh cac dQng CO' di$n mot chieu kich thich doc l~p, kich thich song song, kich thich n6i tiep va kich thich hon liQ'p. Can chu y r~ng & d(>ng CO' di$n m(>t chi§u kich thich doc l~p IU' = I; & d(>ng CO' di$n mot chi§u kich thich song song va hon hQ'p I = IU' + It; &
dong CO' di$n kich thich n6i tiep I = IU' = It. SO' d6 noi day cua chung tU'O'ng ti! nhU' may phat dU'Q'C tr1nh bay & hinh 5.37
Hinh 5.37 Sa c16 nguyen ly cac a{)ng ca ai{jn m{)t chieu
5.5.2 M& may dong GO' di$n mot chi§u
Qua trinh m& may la qua trinh dU'a t6c dQ d()ng CO' di$n tLP n = 0 den t6c dQ n = ndm· · Yeu cau khi m& may:
- Dong di$n m& may (Imm) phai dU'Q'C h,;m che den m(rc thap nhat. - Moment m& may (Mmm) phai du l&n.
- Thai gian m& may phai nho.
- Bi$n phap va thiet bi m& may phai dO'n gian vc;tn hanh chac chan. · TLP cac yeu cau tren ch(mg ta c6 cac phLI'O'ng phap m& may sau day: - M& may trl)'c tiep (U = Ucim)-
- M& may bang bien tr&.
- M& may bang di$n ap thap d$t vao phan (rng (U < Udm)-
Trong tat ca mQi trLI'&ng hQ'p khi m& may bao gi& c0ng phai bao dam tLP thong <l> = <l>dm nghTa la bien tr& m<;1ch kfch tLI' Rdc phai & tri s6 nho nhat de sau khi dong di$n, dong CO' dU'Q'C kfch thfch t6i da va l&n rihat. Phai dam bao khong de d(l't m9ch kfch thfch vi trong tm&ng hQ'p d6 <I> = 0, M = 0 dong CO' khong quay dU'Q'C va do d6 s(l'c phan di$n dong ELI' = 0 ➔ ILI' = U/RLI' rat l&n lam chay day quan va vanh g6p.
Muon d6i chi§u quay cua dong CO' c6 the dung m(>t trong hai phLI'D'ng phap ho$c d6i chi§u dong di$n phan (rng ILI' ho$c doi chi§u dong di?n kfch thfch It. Thong thLI'&ng tren thl)'c te chT doi chi§u ILI' vi day quan kfch tLI' c6 nhi§u vong day nen h$ so ti! cam Lt rat l&n va Sl)' thay d6i It dan den SI! thay doi s.d.d ti! cam rat l&n gay ra diE;m ap danh thung each di?n cua day quan.
5.5.2.1. M& may trl,l'C tiep: PhLI'O'ng phap nay dLI'Q'C thl,l'c hi?n bang each d6ng th~ng dong cO' vao ngu6n di$n v&i di$n ap dinh m(l'c. NhU' vc;ty ngay luc kh&i d(>ng rotor chLI'a quay n=0 nen ELI' = 0 va
1 1 Uam -Eu= Uam
Li= mn Ru Ru
Trang thl,l'c te RU'*= 0,02 + 0, 1 = ldm.RLI'dm / Udm nen v&i ai$n ap djnh m(rc U* = 1thi dong ILI' se rat l&n:
ILI' =lam= (50 + 10)Idm hay 1mm /lam= Imm*= 50 +10
Dong ai$n m& may qua l&n lam hU' hong co g6p, xung ll)'c tren tn.,1c lam hU' hong trl.)c may. Nen phLI'D'ng phap nay chT ap dl.)ng aoi v&i nhO,ng aong CO' cong suat nho khoang vai tram watt tr& xuong vi c5' cong suat nay may c6 RU' l&n. Do d6 khi m& may ILI' = 1mm ~ (4 + 6)Idm·
5.5.2.2. M& may nh& bien tr&:
0e tranh nguy hiem cho d(>ng CO' ngLI'&i ta phai giam dong di$n m& may 1mm bang each noi bien tr& m& may Rmm v&i phan (rng. Dong ai$n phan (rng cua d(>ng CO' dU'Q'C tf nh
theo bieu th(l'c: 1 Uctm - Eu
U= Ru+ I;Rmmi
Trang d6: i la chT th(r bc;tc cua cac bc;tc di$n tr&. Tm&c khi m& may phai de Rmmmax, Rae min· G<;1t tay g<;1t T v§ vi trf 1 ta c6 dong di$n m& may Imm1 bang:
I mn1=-=---Uctm -Eu
Ru + I;Rmm
Vi khi m& may n = 0 nen ELI' = Ce.<1>0.n. Do day quan kfch thfch dU'Q'C noi trl,l'c tiep v&i ngu6n nen tLI' thong <I> = <I>dm· Neu momen do d(>ng CO' sinh ra l&n hO'n mo men can tren trl.)c M0 > Mc thin t ➔ ELI' t ➔ ILI' .J,➔ M .j,_ Khi ILI' = Imm2 = (1, 1 +1,3)Iam ta g<;1t tay g<;1t T
den vi trf 2 v11 b~c diE)n tr& bi loc;ti trLP nen Ill' t den 1mm1: Ill' t ➔ Mt➔ n t ➔ EU' t ➔ Ill'
t➔ M -l,, khi IU' -l.- den 1mm2 ta g9t T den vi tri 3 va l§n IU'Q't den vi tri 4, 5. Qua tr1nh tren cui
l~p lc;1i cho den khi n0 = n0m th1 Rmm cOng bi loc;1i trLP kh6i mc;1ch ph§n uing. Neu Rmm het ma n0 chU'a bang n0m thi di§u chTnh Rae· Muon dLPng may ta keo tay gc;1t T v§ vi trf ban d§u so 0, toe dQ may ch~m 19i ch~m lc;1i, va c~t ngu6n diE)n dU'a vao d(Jng CO'. Gi6'i hc;1n tren cua dong diE)n m& may 1mm1 dU'Q'C chQn sao cho th6a man di§u kiE)n d6i chi§u dong diE)n (tia lua) tren cac ch6i than. Gi6'i h9n dU'6'i cua dong diE)n 1mm2 dU'Q'C chQn sao cho th6a man di§u kiE)n:
dco Mctl = M0 -Mc=J·dt > 0
J: Moment quan tfnh cua khoi quay; co: Toe dQ g6c cua roto.
ThU'ang chQn 1mm1 = (1,5 + 1,75)1am, lmm2 = (1, 1 + 1,3)1am·
Hinh 5.38 Sa <16 m& may d(>ng ca di{jn m(>t chieu kfch thfch song song bang bien tr&
I,, M, n
,t
Hinh 5.39 Gae quan h{j hi', M, n theo th&i gian khi m& may d(>ng ca.
5.5.2.3. M& may bang diE)n ap thap: Umm < Liam
Trang cac thiet bi c6ng suat l&n, bien tr& m& may r§t c6ng k§nh va dU'a 19i nang IU'Q'ng t6n hao l&n, nh§t la khi phai m& may lu6n. Nen trong m(>t so thiet bi ngU'O'i ta dung m& may kh6ng bien tr& bang each ha diE)n ap d~t vao d<)ng CO' luc m& may.
Dung t6 may phat - d(>ng CO' (HE) thong WARD - LEONARD ngu6n di$ri ap c6 the di§u chTnh dU'Q'C cua may phat cung cap cho ph§n uing cua d(>ng CO', trong khi d6 m9ch kfch thich cua may phat va d(>ng CO' phai dU'Q'C d~t dU'6'i 1 di$n ap d(>c l~p khac. Phll'D'ng phap nay chi ap d1,mg cho 0C0KT0L. ThU'ang dU'Q'C ket hqp v6'i di§u chTnh n.
SO' d6 noi day cua h$ thong Ward - Leonard thay d6i di$n ap de di§u khien mot 0C0KT0L . HE) thong MF- d<)ng CO' g6m 3 bQ ph~n: May kfch tLP nh6, d<)ng CO' SO' cap, may phat di$n DC di§u khien.
5.5.3 E>c)c tinh cua dc}ng CO' di~n mc}t chieu ·
Tuy theo each kich tll' d(>ng CO' di$n m(>t chi§u c6 nhung tf nh nang khac nhau bieu di~n bang cac dU'O'ng d~c tinh lam viE)c, d~c tfnh CO' khac nhau. 0~c tfnh quan tr9ng nhat la d~c tinh CO' bieu thi quan hE) giua toe dQ quay va m6men: n = f(M)
5.5.3.1. 0~c tinh CO' va di§u chTnh toe dQ cua d<)ng CO' diE)n m(>t chi§u: a. 0~c tfnh CO'
T& bi§u th{J'c EU'= Ce<1)8 n ⇒
n=-Ev_= U-lvRv = u _ Rv Iv (4)
Ce©0 Ce©0 Ce<I>0 Ce©0
V&i C - pN
e - 60a
Trong d6: RU': 0i~n tr& ph§n Cmg; Rb: 0i~n tr& day quan bu;
Ref 0i~n tr& tiE~p xuc cua ch6i than v&i vanh g6p; Rf 0i~n tr& day quan Cl,PC tl.r phl,l;
PhLI'ang tr1rih (4) dU'Q'C gQi la phLI'ang tr1nh d$c tfnh t6c dQ cua d<)ng ca: n = f(ILI').
V1: M = CM <I>o lU' nen: n = U Rv M (5)
Ce©o Ce©28
PhLI'ang tr1nh (5) gQi la phLI'ang tr1nh d:;ic tfnh ca cua d<)ng ca: n = f(M).
TU' (4) va (5) ta thay khi phl,l tai d:;it tren trl,lc d<)ng ca bang 0, tmang hQ'p ly tLI'&ng
u ,
ILI' = 0 ho:;ic M = 0 th1 n = - - = n0 : Toe dQ khong tai If tU'&ng. Ce<I>0 u T9i n = 0 ta c6: Iv = - =In Rv u M = CM<I>o - = CM©oln = Mn Rv 0$t: Rv =tga' Ce<I>0 La h~ s6 g6c d$c tf nh t6c dQ va d$c tf nh ca. Rv Iv= .6.n' va Ru M Ce<I>o Ce© 2 8 va
89 s1,1t t6c dQ cua d$c tf nh t6c dQ va d$c tinh ca t9i 1 gia tri dong di~n va moment nhat dinh.
0$c tf nh ca va dc;1c tfnh t6c dQ cua d<)ng ca c6 d9 d6c khong d6i con d<) sl)t t6c d9
bi~n d6i theo dong di~n va moment.
n = no - .6.n .6.n = no -n n n no - -: - -:- - - ' ' ' ' ' ' 'A ' :iln1 : n1 : :An2 ' ' ' ' ' ' ' ' ' ' n2 ~ããããããããẳãããããã I ' ' ' ' ' ' ' ' ' ' ' '