I 1.1 v J \)v \J b) Tdn s(f
a) Thyristor ra kf Ill/h.1 b) Dt;k tfnl! Clia thyristor
b) Dt;k tfnl! Clia thyristor
khOng dang ke khi cap di~n ap nghich (tru khi hi¢u di¢n the ngu~jC qua 100, den hang tram von, no co the bi danh thung). Khi hi~u di~n the dich thu~n, dong van gifr kh6ng dang ke cho den khi VlIQ1. qua di~n iip chQc thung thu~n. Khi xay fa dieu nay di¢n ap qua di6t wi xu6ng muc th[lp khOil.ng 1 -0-2 V va dong tieR (dong qua thict bi) khi d6 hj gi6i h0-n chi hoi di¢n tro ngoai trong mi.lch. Ngay khi dU"Q"c 66
dong mach. tiristo gtC! tr<~ng thai nhu v~y dlO den khi dong thu~n giam xl10ng
dt!6i nllIe V~lj miliampe. f)i¢n ap t~i d6 xuat hi¢n tr<;tng thai chQc thung thu~n
duCJc quyct djnh bai dong kich t<).1 cong, dong kkh dng cao thl di¢n ap chQc thung thu~n dng thap.
Khong nhu diot, chi co th6 chinh hru di~n ap dau vao AC thanh di¢n ap
trung blnh DC (hlnh 2.54a). tiristo co th~ duqc dung M t~o chinh hru co dieu
khien. 10,!-i co tht chinh cac ngu6n AC va dieu chinh di~n ap trung binh DC dau ra bang dicu chinh thai gian
phat dong/ di~n tip cong
(hinh 2.S4b) Cong / /'~~O
\
1,,-~ "'" L _ _ L-; Choc lhung lhua~ L _ _ L-; Choc lhung lhua~
Thong S(j' thiet ke'tiristo
iii: di~n ap chQc thung ngu<;lc, dong ghim, dong va
di~n tip lam vi~c max. cua tiristo.
.A....-.:;....-, 1°
,._0 / I
'._ 2 m..o. I
Hinh 2.56: D{ic (i,l I! C//a triar
Triareta (triac) ho<;tt d(>ng tuang tv nhu tiristo va tuang duang v6i e~p tiristo mac song song ngu<Je ehi~u nhau trong cung 1 vi m<;tch (chip). Triac co
tht dan dong di¢n thu~n ho~c ngtIqc. Hlnh 2.56 mo til d~c tinh eua triac. Hinh 2.57 mo ti anh huang khi mOt di¢n
ap xoay chi~u hlnh sin ch~y qua tiristo a) va triac b). Tr<;tng thai khml. xay ra khi di9n ap d~t gia trj chQc thung, hie do di¢n ap thiel bi giiI iJ IDt1c thap. Thiet b~ nht! v~y co the Slr dl,log cho ml,lc dich dieu khitn. Hinh 2.58 minh ho,!- tir1sto dt!qe dung d~ dicu khitn 1 dj~n ap DC. Truang hqp nay tiristo ho~t dQng nhu mQt eong tae, Slr dl,lng cong dt dongjngat thict bj. Bang Slr dl,lng tin hi~u xoay chieu 11.1i
c6og, di9n tip cap co th~ duqc chia nha, nht! v~y gia tr! trung blnh clla di~n ap dau ra DC
c6 the thay d6i, do d6 dieu khi~n dt!qe.
" , I I i 01 ! hi VI "--". DI~n ap cap ~ \" ! 'I I 0' " ... '
Hillh 2.57: Dilll khii/11 difn up.
a) 1;1"1.1'10 b) friar b) friar
Tranzito iuiing c~c (bipolar transistor) la thiet b! 3 lap p-n-p ho~c n-p-n. c6 3 qrc n6i '11m. 3 lap gQi ia: emitd (C), colecto (E) va ba'id (B). V~ nguyen rac co
th~ hiy 2 trang s6 3 clfc cua tranzito lam dau va~, cl)'c thu 3 con l'.li cling vai mot qrc dau vao lam dau ra (nhu v~y luon co mot CJ,JC chung cho ca. dau va~ va dau ra). De Slt dlJng khuech d<;li cong suat, chi co 3 cach mac, chung cmita, chung coleto ho~c chung basa dUQ'c Slr dJ.!.ng. Transitor IUB'ng clfc co tM ho~t d(lng 6 3 vling : lI[?iit (clitloff): tranzitor hO<;lt dong nhu mot m'.lch h6, tuyell (illll tich q(C
'E;iuFtf
Thai gian
Hinh 2.58: Di/ll khiln DC Mng thyristor Ilinh 2.59: Mqch clluyin do'i trazllsito
(active linear): tranzitor ho~t d¢ng nhu mot khuech d~i dong va bao hod
(~'aturator): m<;lch dong. Nhin chung tranzito dUQ'c dung nhu cac dong ngat - hloh 2.5.9. Khi kh6ng co di~n ap dau van V.~()" t<;li dAu ra xuat gan nhu toan bO di¢n ap'V'X'. Khi di¢n ap dau vao du lOn, tranzito se chuyen m~ch d~ di¢n ap Vee xuat hi¢n t<;li dau ra rat be.
2.4.3.2. S61en6it
SOlen6it di¢n 1a m(lt cu¢n day. Khi co dong AC ho~c DC qua cu¢n, se thiet
l~p mQt truang ll)'c til. LI,Tc nay m<;lnh nhat 6 tam cUQn day, vi v4y mQi v~t li~u tu
tinh deu co khuynh huang bi keo vao tam cua seIen6it, nai lI,Tc tiT m~nh nhat. day la co sO' clm selen6it actuator.
5elen6it actuator la d~ng
actuator di~n tu dan gUm nhat, thuang duqc Slt dlJng trong h¢ kfch truyen d9ng th~ng ho~c
tron cho cac van, c6ng tac va rolc. Hlnh 2.60 the hi~n nguyen ly co ban: SOlen6it actuator duqc diu thlliIh bbi mQt khung tTnh bAng sat
Jlinh 2. 60 : Selenoit actuator
(stator), mQt cUQn day (selenoid) va mot 15i thep non (feramagnetic) a trung tam, dong vai tro nhu mQt piston. Khi dong di~n qua s6len6it thi mot tif truang dugc
sinh r<'l, llfc tir lac d9ng vao piU6ng feromagnetic, keo n6 vc phf<'l cUQn day. Nhu 2
v~y khi thay doi dong di¢n. llfc tac dQng vao pitstOn thay d6i ( F ~ ~, trong d6 i
,>
la CU'Ong d¢ dong di~n, () khe ho giua stator va piston) va keo thea thay d6i chuytin dong cua n6. Chuytn d¢ng nay c6 th~ duqc khucch d<;ti ba.ng 1 h¢ thong
cac can g~t.
Van s61enoit duqc v~n hanh wong tl,l' va dl1qc sit dl,lng M di~u chinh luu luqng cha't long trong h¢ thong thuy 11,1'c hay khf Ot!n.
Nh11ng tham s6 xem xet khi thiet ke/ch9n llfa selen6it: h!c, hanh trinh, nhi~t d¢ va chu ki lam vi¢c (duty cycle).
2.4.3.3. DQng co
D¢ng Cd di¢n thUOng duqc dung nhu thanh phan dieu khitin cuoi cung trong cac h¢ thong dieu khi~n v~ trl ho?c dieu khitin toc d¢. S1,1" khac bi¢t chinh gifra