2-2 CUONG Dc) Tit CAM CUONG Dc) Tit TRUONG TitTH()NG
2.4. DJNH LV! T CAM liNG DI~N T(T
1. Sue d~n d~ng dm ung khi tif th6ng xuyen qua vong dAy bien thien
Hi¢n tm;mg cam U"ng di¢n llr do Faraday phlit hi¢n nAm 1931, sau d6 nam 1833 Lentz pMI hi¢n ra quy lAc v~ chi~u. N()i dung djnh lU~1 nhll sau : tlli til thong IUY~1l qua vdng day bien thien, trollg vdng day si cam ling ra slie difn d9ng, slie di~n dt)ng ay co elltlu sao eho dong difn no sin" ra e6 IU huang ehcfng Ipi sl/ biin tMen eua til thtJng.
Nlu chQn chi~u duang cua site di~n d()ng cam U"ng phu hqp voi chi~u cua llr thOng $
theo quy tAe v~n ntlt chai (hinh 2.11) suc di¢n dQng cam Ilng trong mQt vbng dAy dllqc Yilt theo cOng thuc Macxoen nhll sau :
d$
e=--
• dt (2-7) Bin" 2.11
D!u ® tren hlnh 2.11 chi chi~u tlr thOng $ di tiI dQc gia vao trang gi!i'y.
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Ne'u cUQn day c6 W v~ng day, sUe di~n dQng cam lhlg eua euQn day se is. :
d~ d1jl
e = - W - = - -
dt dt (2-8)
Trong d6 1jI = w~ (2-9)
gQi Ia tit thOng m6e v~ng eua euQn dAy.
Trong cdc eOng thue tren tu thOng do bAng vebe (Wb), sue di¢n dQng cam
irng do bang vOn (V).
Vi d..-. 4 : Hiy de dioh tri s6 vll ehit!u slie di¢o dQng cam ling khi lCii sAl ehuyin d(lOg hOOng vao cUQn day (hlnh 2.12), Cho bi~1 cUQn day e6 200 vbng vA t6c dO bie'n thiM til thOng xuyen qua mOi vbng
• Wb
day bang 0,5 - . ,
Uti ghii :
Cllit!u ti:r thOng • vA ehic!u dlWllg sue di¢n dQng cAm Ilng v! Iren hloh 2.12. Khi Uii s&t lie'n vllo giiJa hai eve ella nam cham vinh CUll. tir thOng xuyen qua vbng day tang, luc;mg bie'n thien tft thOng dljl > 0, !; = 0,5.
Slie di¢n dQng cam Ilng:
e",,_Wd, =-200.0,S=-IOOV
dt
Slie di¢n dOng e < 0 nghia III ehit!u sl1'c di¢n dQng cam Ilng ngUQ'e v6'i eh~u dUCJJJ.g dB. ehQn tren hlnh 2.12.
Vi dl,l S : MQt cUQn day 10 vbng hlnh chfi nM! quay trong 1ft trubog ella mQt nam cham (hlnh 2.13). Bie't rAng vbng day
quay v6'i t6c dQ g6c 0>'" 314 ~ vA tL--t'
sau thbi gian t [lr thOng xuyen qua vbng day IA :
Ijl = 0,004 cos 314 t Wb. Tinh slic di~n dQng cam ling trong cuQn diy.
Hid 2.12
Hinh 2.13
35
Lbt giii :
s(cc di~n d(lng cam (cng trong cu(ln dAy
e =-w dt =-10 d(O,OO4cos314t) = 12,56sin314t V
dt dt
Sd'c di~n d(lng e bitn thien hlnh sin thea thbj gian. DAy lA m(lt vi dl,l dan gian gil1p ta hie:u d.ch t{lO ra dbng di~n xaay chi~u hlnh sin.
2. SU'c di~n dt)ng cam U'ng trong thanh dAn chuyc!n d(mg trong tit trutmg Khi ml)t thanh dan ehuyen dl)ng cat duong sue u) truong, trong thanh dan se cam t'rng sue di¢n dl)ng e e6 tri s61ll.:
e = Blvsin a (2.10)
Trong do:
B - Cuong dO tlr cam do bang T.
1 - Chi~u dll.i hi¢u dl,mg ella thanh dan (ph!n thanh dAn nam trong tu truOOg) do bAng m.
v - V~n t6e eua thanh dAn do bang ~
s
a -G6c giita ehi~u v.n t6e voi ehic!u tu truong a = (;~B)
Khi ehic!u ehuyen dQng vuOng g6c v6'f ehl~u
tlr truOOg (thuang g$p trong may di¢n, a = 90°) thl. sue di¢n dOng clLm (mg la:
e = Blv (2.11)
Chi~u cua suc di¢n dOng cam t'rng dl1QC xac djnh theo quy tac ban tay phili dUQc phlit bieu nhl1 sau:
Clio dllilng suc tit trlli'lIlg di velo LOng ban toy phdi, chieu chuyln d~ng cua thanh ddn theo chieu ngon tay cd; xoe ra, thi chieu 4 ngoll tay con ftJi ld chieu cua sue di~n d9ng cam ling
(hinh 2.14).
I
r-- _____ _
Hlnh 2.14
Khi thanh dan chuy~n dOng song song voi phuong tit truong. trong thanh
dan se khOng c6 sue di¢n dOng cam t'rng.
Vi dJ,l 6 : M(lt thanh din ab chi~u dAi 1 ::: O,5m (hlnh 2.15) nlm trong IU trubng
d~u B = 1,4T. Ngubi Ia tAc dl,mg m(lt IIIC co hQc F C<I lAm cho n6 chuye:n dOng v~i v~n
36 •
t6'e v = 20!!!. -thAng g6e v6i phlIong tt:r trum.g. Thanh dan , [(II'll tren hai thanh kim IOf,li va hai dltu thanh kim lo~ n6'i v6i di¢n tro R = 0,50 lam thAnh m~t vOng kIn. Coi di¢n tra eua thanh kim lo~i rAt nhO va b6 qua. _
•
Tfnh slic di¢n dQng -cam Iffig trong thanh din, cOng sulft di¢n tra tieu thy., eOng sulft co va II!C co hQc tlie dy.ng vao thanh dan.
Ltd gist:
s~c di~n dQng cam Ilng trong Thanh dan: e=B!v= 1,4.0,5.20= 14V DOng di~n chl!-Y qua di¢n tro R
e 14
I",,-=-=2SA
R 0.>
COng su!t di¢n tro tieu thy. Pd = Rf = 0,5.282 = 392 W
B6 qua t6n hao trong h¢ tMng, thea dinh lu4t bio toan nAng IlIgng cOng sulft co utc d1,lng vao thanh din phAi bang cOng sulft di¢n phit ra cung c!p cho di¢n tru R .
V4Y: COng su!t co: P",,= Pd= 392 W L1,I'c co hQc tlic d':lIlg vao thanh dan IA :
F = ~=~=196N
" " v 2 0 '
mn1l2.15
DAy la mQt vi dy. don giAn, gillp ta hi~u nguyen Ij lam vi¢c clla clic may phat di¢n la: Nhb lif tTirtmg. Cq nlJng d,fa vdo tT~'C ella mdy phdl di~n du9'c bUn ddi thdnh
di~n nlJngltfy Ta 0 ddy qutfn ella may phdt d~ cling etfp eho lai.