Phn I
Phn I
Phn tch yu cu v gii thiu chung
v cng ngh np c qui t ng
I. Gii thiu chung v c qui.
c qui l ngun cung in mt chiu cho cc thit b in trong cng nghip
cng nh trong i sng hng ngy. C nhiu loi c qui nhng ph bin v thng gp
trong thc t l c qui ch v c qui axit.
1. c im cu to ca c qui.
Cu trc ca mt c qui n gm c phn cc dng, phn khi
bn cc m, cc tm ngn.
Phn khi bn cc do cc
bn cc cng tn ghp li
vi nhau. Cu to ca mt
bn cc trong c qui gm
c phn khung xng v
cht tc dng trt ln n .
Khung xng ca bn
cc m v bn cc dng
c cu to ging nhau,
chng c c t ch v
c pha thm 5 ( 8 %
ng ti moang ( Sb ) v to
hnh mt li . Ph gia Sb
thm vo ch s lm tng
dn in v ci thin tnh
c. Trong thnh phn cht tc dng cn c thm khong 3 % cht n ( cc mui
hu c ) tng xp, bn ca lp cht tc dng. Nh tng xp m ci thin c thm su ca
cht dung dch in phn vo trong lng bn cc, ng thi din tch thc t tham
gia phn ng ho hc ca cc bn cc cng c tng thm . Phn u ca mi bn cc c
vu, cc bn cc dng camicqui n c hn vi nhau to thnh khi bn cc dng, cc
bn cc m c hn vi nhau thnh khi bn cc m. S lng cc bn cc trong mi c
qui thng t 5 ( 8, b dy tm bn cc dng ca c qui thng t 1,3 n 1,5 mm ,
bn cc m thng mng hn 0,2 ( 0,3 mm . S bn cc m trong c qui thng nhiu
hn s bn cc m mt bn nhm tn dng trit din tch tham gia phn ng ca cc bn
cc. Tm ngn c b tr gia cc bn cc m v dng c tc dng ngn cch v trnh va p
gia cc bn cc. Tm ngn c lm bng vt liu poly-vinyl-clo b dy 0,8 ( 1,2
v c dng ln sng , trn b mt tm ngn c cc l cho pho dung dch in phn
thng qua.
2. Qu trnh bin i nng lng trong c qui .
c qui l ngun nng lng c tnh cht thun nghch : n tich tr nng lng di
dng ho nng v gii phng nng lng di dng in nng. Qu trnh c qui cp in
cho mch ngoi c gi l qu trnh phng in, qu trnh c qui d tr nng lng c
gi l qu trnh np in.
2.1. Qu trnh bin i nng lng trong c qui axit.
K hiu ho hc biu din c qui axit c dung dich in phn l axit H2SO4
nng d ( 1,1 ( 1,3 % bn cc m l Pb v bn cc dng l PbO2 c dng :
(- ) Pb ( H2SO4 d ( 1,1 ( 1,3 ( PbO2 ( + )
Phng trnh ho hc biu din qu trnh phng np ca c qui axit :
phng
PbO2 + 2H2SO4 + Pb 2PbSO4 + 2H2O
np
Th in ng e ( 2,1 V.
2.2. Qu trnh bin i nng lng trong c qui kim.
K hiu ho hc biu din c qui kim c dung dich in phn l KOH nng d (
20 % bn cc m l Fe v bn cc dng l
Ni(OH)3 c dng :
( - ) Fe ( KOH d ( 20% ( Ni(OH)3 ( + )
Phng trnh ho hc biu din qu trnh phng np ca c qui kim :
phng
Fe + 2NI(OH)3 Fe(OH)3 + 2Ni(OH)2
np
Th in ng e ( 1,4 V.
Nhn xt : T nhng iu trnh by trn ta nhn thy trong qu trnh phng np
nng dung dch in phn l thay i. Khi c qui phng in nng dung dch in phn
gim dn. Khi c qui np in nng dung dch in phn tng dn. Do ta c th cn c
vo nng dung dch in phn nh gi trng thi tch in ca c qui.
3. Cc c tnh c bn ca c qui .
Sc in ng ca c qui ch v c qui axit ph thuc vo nng dung dch in
phn. Ngi ta thng s dng cng thc kinh nghim Eo ( 0,85 + ( ( V )
trong : Eo - sc in ng tnh ca c qui ( V )
- nng dung dch in phn 15 (C ( g/cm3 )
Trong qu trnh phng in sc in ng ca c qui c tnh theo cng thc :
Ep ( Up + Ip.rb
trong : Ep - sc in ng ca c qui khi phng in ( V )
Ip - dng in phng ( A )
Up - in p o trn cc cc ca c qui khi phng in (V)
rb - in tr trong ca c qui khi phng in ( ( )
Trong qu trnh np sc in ng En ca c qui c tnh theo cng thc :
En ( Un - In.rb trong : En - sc in ng ca c qui khi np in ( V
)
In - dng in np ( A )
Un - in p o trn cc cc ca c qui khi np in
( V )
rb - in tr trong ca c qui khi np in ( ( )
Dung lng phng ca c qui l i lng nh gi kh nng cung cp nng lng ca c
qui cho ph ti, v c tnh theo cng thc :
Cp ( Ip.tp
trong : Cp - dung dch thu c trong qu trnh phng ( Ah )
Ip - dng in phng n nh trong thi gian phng in
tp ( A )
tp - thi gian phng in ( h ).
Dung lng np ca c qui l i lng nh gi kh nng tch tr nng lng ca c
qui v c tnh theo cng thc :
Cn ( In.tn
trong :
Cn - dung dch thu c trong qu trnh np ( Ah )
In - dng in np n nh trong thi gian np tn ( A )
tn - thi gian np in ( h ).
3.1. c tnh phng ca c qui.
c tnh phng ca c qui l th biu din quan h ph thuc ca sc in ng, in
p c qui v nng dung dch in phn theo thi gian phng khi dng in phng
khng thay i .
T c tnh phng ca c qui nh trn hnh v ta c nhn xt sau:
Trong khong thi gian phng t tp ( 0 n tp ( tgh, sc in ng
in p, nng dung dch in phn gim dn, tuy nhin trong khong thi gian
ny dc ca cc th khng ln, ta gi l giai on phng n nh hay thi gian phng
in cho php tng ng vi mi ch phng in ca c qui ( dng in phng ).
T thi gian tghtr i dc ca th thay i t ngt .Nu ta
tip tc cho c qui phng in sau tgh th sc in ng ,in p ca c qui s
gim rt nhanh .Mt khc cc tinh th sun pht ch (PbSO4) to thnh trong
phn ng s c dng th rn rt kh ho tan ( bin i ho hc) trong qu trnh np
in tr li cho c qui sau ny. Thi im tgh gi l gii hn phng in cho php
ca c qui, cc gi tr Ep, Up, ( ti tgh c gi l cc gi tr gii hn phng in
ca c qui. c qui khng c phng in khi dung lng cn khong 80%.
- Sau khi ngt mch phng mt khong thi gian no, cc gi tr sc in ng,
in p ca c qui, nng dung dch in phn li tng ln, ta gi y l thi gian hi
phc hay khong ngh ca c qui. Thi gian hi phc ny ph thuc vo ch phng
in ca c qui
( dng in phng v thi gian phng ).
3.2. c tnh np ca c qui.
c tnh np ca c qui l th biu din quan h ph thuc gia sc in ng , in
p v nng dung dch in phn theo thi gian np khi tr s dng in np khng
thay i .
T th c tnh np ta c cc nhn xt sau :
- Trong khong thi gian t tn ( 0 n tn ( tgh th sc in ng, in p ,
nng dung dch in phn tng dn.
- Ti thi im ts trn b mt cc bn cc m xut hin cc bt kh (cn gi l hin
tng" si " ) lc ny hiu in th gia cc bn cc ca c qui n tng n 2,4 V .
Nu vn tip tc np gi tr ny nhanh chng tng ti 2,7 V v gi nguyn. Thi
gian ny gi l thi gian np no, n c tc dng cho phn cc cht tc dng su
trong lng cc bn cc c bin i tun hon, nh s lm tng thm dung lng phng
in ca c qui.
- Trong s dng thi gian np no cho c qui ko di t 2 ( 3 h trong sut
thi gian hiu in th trn cc bn cc ca c qui v nng dung dch in phn khng
thay i . Nh vy dung lng thu c khi c qui phngin lun nh hn dung lng
cn thit np no c qui.
- Sau khi ngt mch np, in p, sc in ng ca c qui, nng dung dch in
phn gim xung v n nh. Thi gian ny cng gi l khong ngh ca c qui sau
khi np.
- Tr s dng in np nh hng rt ln n cht lng v tui th ca c qui. Dng
in np nh mc i vi c qui l In ( 0,1C10 .
Trong C10 l dung lng ca c qui m vi ch np vi dng in nh mc l In (
0,1C10 th sau 10 gi c qui s y.
V d vi c qui C ( 180 Ah th nu ta np n dng vi dng in bng 10% dung
lng ( tc In ( 18 A ) th sau 10 gi c qui s y.
4. S khc nhau gia c qui ch v c qui axit .
C hai loi c qui ny u c mt c im chung l tnh cht ti thuc loi dung
khng v sc phn in ng. Nhng chng cn c mt s c im khc bit sau :
5. Cc phng php np c qui t ng.
C ba phng php np c qui l
+ Phng php dng in.
+ Phng php in p.
+ Phng php dng p.
5.1. Phng php np c qui vi dng in khng i.
y l phng php np cho php chn c dng np thch hp vi mi loi c qui, bo
m cho c qui c no. y l phng php s dng trong cc xng bo dng sa cha np
in cho c qui hoc np s cha cho cc c qui bi Sunfat ho. Vi phng php ny
c qui c mc ni tip nhau v phi tho mn iu kin :
Un ( 2,7.Naq
Trong : Un - in p np
Naq - s ngn c qui n mc trong mch
Trong qu trnh np sc in ng ca c qui tng dn ln, duy tr dng in np
khng i ta phi b tr trong mch np bin tr R. Tr s gii hn ca bin tr c
xc nh theo cng thc :
Nhc im ca phng php np vi dng in khng i l thi gian np ko di v yu
cu cc c qui a vo np c cng dung lng nh mc. khc phc nhc im thi gian
np ko di, ngi ta s dng phng php np vi dng in np thay i hai hay nhiu
nc. Trong trng hp hai nc, dng in np nc th nht chn bng ( 0,3 ( 0,6
)C10 tc l np cng bc v kt thc nc mt khi c qui bt u si. Dng in np nc
th hai l 0,1C105.2. Phng php np vi in p khng i.
Phng php ny yu cu cc c qui c mc song song vi ngun np. Hiu in th
ca ngun np khng i vaf c tnh bng ( 2,3 ( 2,5 ) V cho mi ngn n. Phng
php np vi in p khng i c thi gian np ngn, dng np t ng gim theo thi
gian.Tuy nhin dng phng php ny c qui khng c np no. V vy np vi in p
khng i ch l phng php np b xung cho c qui trong qu trnh s dng.
5.3. Phng php np dng p.
y l phng php tng hp ca hai phng php trn. N tn dng c nhng u im ca
mi phng php.
i vi yu cu ca bi l np c qui t ng tc l trong qu trnh np mi qu
trnh bin i v chuyn ho c t ng din ra theo mt trnh t t sn th ta chn
phng n np c qui l phng php dng p.
- i vi c qui axit: bo m thi gian np cng nh hiu sut np th trong
khon thi gian tn ( 8h tng ng vi 75(80 % dung lng c qui ta np vi dng
in khng i l In ( 0,1C10. V theo c tnh np ca c qui trong on np chnh
th khi dng in khng i th in p, sc in ng ti t thay i, do bo m tnh ng
u v ti cho thit b np. Sau thi gian 8 h c qui bt u si lc ta chuyn
sang np ch n p. Khi thi gian np c 10 h th c qui bt u no, ta np b
xung thm 2 ( 3 h.- i vi c qui kim : Trnh t np cng ging nh c qui
axit nhng do kh nng qu ti ca c qui kim ln nn lc n dng ta c th np vi
dng np In ( 0,2C10 hoc np cng bc tit kim thi gian vi dng np In (
0,5C10 .
Cc qu trnh np c qui t ng kt thc khi b ct ngun np hoc khi np n p
vi in p bng in p trn 2 cc ca c qui, lc dng np s t t gim v khng.
Kt lun :- V c qui l ti c tnh cht dung khng km theo sc phn in ng
cho nn khi c qui i m ta np theo phng php in p th dng in trong c qui
s t ng dng nn khng kim sot c s lm si c qui dn n hng hc nhanh chng.
V vy trong vng np chnh ta phi tm cch n nh dng np cho c qui.
Khi dung lng ca c qui dng ln n 80% lc nu ta c tip tc gi n nh dng
np th c qui s si v lm cn nc. Do n giai on ny ta li phi chuyn ch np
c qui sang ch n p. Ch n p c gi cho n khi c qui thc s no. Khi in p
trn cc bn cc cu c qui bng vi in p np th lc dng np s t ng gim v
khng, kt thc qu trnh np.
- Tu theo loi c qui m ta np vi cc dng in np khc nhau
+ c qui axit : dng np In ( 0,1C10 ; np cng bc vi dng
in np In ( 0,2C10 .
+ c qui kim : dng np In ( 0,2C10; np cng bc vi
dng in np In ( 0,5C10 .
T cc phn tch trn ta rt ra cc s liu sau:
+ Dng np ln nht Inmax ( Idmax ( 90 A
+ in p Udmax ( 64,8 V
Phn II
Phn tch tnh ton v la chn s I. Chnh lu iu khin i xng s cu 3
pha
1. S nguyn l
S gm 6 Tiristor c chia lm hai nhm:
Nhm Katot chung : T1, T3, T5
Nhm Anot chung : T2, T4, T6
Gc m ( c tnh t giao im ca cc na hnh sin
Gi tr trung bnh ca in p trn ti
T cng thc trn ta thy
EMBED Equation.3 khi
Khi ta c
Thay gi tr ta c V
in p cc pha th cp ca my bin p l:
Gi tr trung bnh ca dng th cp my bin p.
T s liu ban u thay c
Gi tr trung bnh ca dng chy qua 1 Tiristor l:
Gi tr in p ngc m Tiristor phi chu
Cng sut bin p
Nhn xt : Vi s chnh lu cu 3 pha c iu khin th in p ra Ud t p mch (
trong mt chu k p mch 6 ln ) do vn lc rt n gin, in p ngc ln mi van
nh, cng sut bin p nh nhng mch phc tp nhiu knh iu khin. 2. ng c tnh
biu din
II. Chnh lu cu 3 pha bn iu khin
1. S nguyn l
Trong s ny s dng 3 Tiristor nhm Katot chung v 3 Diot nhm Anot
chung.
Gi tr trung bnh ca in p trn ti
Trong : Ud1 l thnh phn in p do nhm Katot chung to
nn
Ud2 l thnh phn in p do nhm Anot chung to
nn
Vy
Ta nhn thy khi
khi ta c
in p th cp my bin p
Gi tr trung bnh ca dng chy trong Tiristor v Diot
Gi tr dng in ngc ln nht
Cng sut bin p
Nhn xt :Tuy in p chnh lu cha nhiu sng hi nhng chnh lu cu 3 pha
khng i xng c qu trnh iu chnh n gin , kch thc gn nh hn.
2. ng c tnh biu din
III. Chnh lu iu khin cu mt pha khng i xng
1. S nguyn l
Trong s ny, gc dn dng chy ca Tiristor v ca it khng bng nhau.
Gc dn ca it l :
Gc dn ca Tiristor l :
Gi tr trung bnh ca in p ti
Do
Gi tr trung bnh ca dng ti
Dng qua Tiristor
Dng qua it
Gi tr hiu dng ca dng chy qua s cp my bin p
Nhn xt : S chnh lu iu khin 1 pha khng i xng c cu to n gin, gn nh
, d iu khin , tit kim van . Thch hp cho cc my c cng sut nh v
va.
2. ng c tnh biu din
Kt lun :
C hai phng n dng s chnh lu i xng cu ba pha v chnh lu khng i xng
cu ba pha u c nhiu knh iu khin, nhiu Tiristor nn gi thnh cao khng
kinh t.
Do yu cu ca u bi, v s knh iu khin t nn ta chn s chnh lu iu khin
cu 1 pha ng i xng. Chng c mt s u im:
- Hiu sut s dng my bin p cao hn mt s s nh cu 1 pha i xng.
- n gin hn v s lng Tiristor gim xung ch cn 2 nn mch iu khin c t
knh iu khin hn, bo m kinh t hn.
- Cng mt di iu chnh in p mt chiu th cu khng i xng iu khin chnh
xc hn
Qua phn tch trn ta chn s chnh lu iu khin cu 1 pha khng i xng dng
cho mch lc mch np cqui t ng . Phng n ny va p ng c yu cu k thut va
bo m cho vic thit k.
Phn III
Tnh ton thit k mch lc
Ta chn phng n thit k cho mch np cqui l s chnh lu cu 1 pha khng i
xng. S nguyn l mch lc nh sau :
T1 D 64,8 V
~ 220 V Rf
T2 D Rs
I. Tnh chn van mch lc.
1. S liu cho trc
in p ngun 3 pha : 220/380 V ; f = 50 Hz
2. Yu cu u ra : Ngun mt chiu t ng np cqui
Udmax = 64,8 V
Idmax = 90 A
bo m cho van lm vic tin cy , an ton mi iu kin ta chn :
Trong : - l in p ngc trn van khi lm vic ch nh
mc.
- l in p ngc trn van khi van kho .
( tra s tay )
3. Tnh ton vi s chn
Do in p ngc trn van khi kho l:
Dng in trung bnh qua van
V ti c cng sut nh nn ta chn iu kin lm mt cho van l lm mt t nhin,
dng cnh tn nhit chun vi i lu khng kh.
Ta c
Do
Vy iu kin chn van l:
Trong s ny ch lm vic ca Tiristor v it nh nhau nn iu kin chn van
ging nhau.
Van iu khin TB 200
Thng s van nh sau :
EMBED Equation.3 it :
Chn loi B 200
Thng s nh sau :
II. Mch bo v Tiristor :
T
R C
bo v van ta dng mch RC u song song vi van nhm bo v qu p do tch t
in khi chuyn mch gy nn.
Cc thit b bn dn ni chung cng nh Tiristor rt nhy cm vi in p v tc
bin thin in p ( ) t ln n .
Cc nguyn nhn gy nn qu p th chia thnh hai loi :
- Nguyn nhn bn ngoi : Do ct t ngt mch in cm,do bin i t ngt cc
tnh ca ngun, khi cu chy bo v t hoc khi c sm st.
- Nguyn nhn bn trong ( ni ti ) : Khi van chuyn t trng thi m sang
trng thi kho, do s phn b khng u in p trong cc van mc ni tip.
y ta quan tm n vic bo v qu in p do cc nguyn nhn bn trong gy
ra.
i
t
Nguyn nhn qu in p trn van l do s sut hin dng in ngc chy qua mi
van khi n chuynr t trng thi m sang trng thi kho. Dng in ngc ny suy
gim rt nhanh do vy s sut hin s qu in p
khc phc hin tng qu in p ny ta dng mch R-L-C nhng do mch c tnh
cht in cm nn ta ch cn dng mch R-C u song song nh hnh v.
Khi van kha dng in ngc s chuyn t van sang mch bo v.
III. Tnh ton my bin p lc
- Gi tr hiu dng in p th cp my bin p : Theo sch thit k my bin p ;
tra vi s cu ta c :
U2 = 1,11Udmax = 1,11.64,8 = 72 V
I2 = 1,11Idmax = 1,11.90 = 100 A
- Cng sut biu kin MBA :
S2 = U2.I2 = 72.100 = 7,2 kVA
- Chn mch t 3 tr , tit din tr tnh theo cng thc
Trong : - C : S tr mch t
- f : Tn s ngun
- K = 5 ( 6
cm2
Chn li thp c tit din 30 cm2 lm bng vt liu st t dy 0,5 mm , l thp
dp hnh ch ( v ch I ghp li
Tnh s vng/vn. Theo cng thc kinh nghim c :
vng/vn
S vng cun s cp :
vng
S vng dy cun th cp :
vng
Dng in th cp :
A
Chn mt dng in J = 3 A/mm2
Ta c tit din dy qun mm2
mm2
ng knh dy qun s cp mm
ng knh dy qun s cp mm
Theo sch in t cng sut ta c dy tit din trn nh sau
d1 = 4,1 mm ; 117 gam/m
d2 = 7 mm ; 220 gam/m
Phn IV
Thit k v tnh ton mch iu khin
I. Yu cu v nguyn tc iu khin
1. Mc ch v yu cu
- Mch iu khin l khu rt quan trng trong b bin i Tiristor c vai tr
quyt nh n cht lng, tin cy ca b bin i. Mch iu khin rt a dng, nhng vi
h thng mch lc c th ca mch np cn c mt h iu khin thch ng. Vi mch ny,
h iu khin s pht xung m 2Tiristor
T1 v T2. Cc Tiristor s m khi tho mn ng thi 2 iu kin :
+ Mt in p dng ln t ln 2 cc ca Tiristor theo hng t Ant n
Katt.
+ Xung in p dng a vo cc iu khin phi ln (bin , rng)
lm thay i in p ra ti ch cn thay i thi im pht xung iu khin, tc l
thay i gc m ca cc van. u im ca Tiristor l ch cn dng v p iu khin nh
nhng c th chu c dng v p rt ln chy qua.
H thng mch iu khin phi p ng c cc yu cu:
+ Pht xung iu khin chnh xc v ng thi im m ngi thit k tnh ton
sn.
+ Cc xung iu khin pht ra phi ln v bin v rng m cc van.
+ Xung iu khin phi c i xng cao v m bo c phm vi iu chnh gc m.
+ Dng xung c iu chnh thch hp v tc ng nhanh.
+ m bo hot ng tt, tin cy cao khi in p ngun thay i gi tr bin
.
Ngoi ra h thng iu khin phi c nhim v n nh dng in ra ti v bo v h
thng khi xy ra s c qu dng hay ngn mch ti.
2. Nguyn tc iu khin.
iu chnh gc m ca cc Tiristor trong na chu k in p dng ta thng dng
hai nguyn tc iu khin : Thng ng tuyn tnh v thng ng arccos.
a. Nguyn tc iu chnh thng ng tuyn tnh
Theo nguyn tc ny ta dng hai in p :
- in p ng b , c dng rng ca, ng b vi in p t trn Ant v Katt ca
Tiristor, k hiu l Ur .
in p iu khin l in p mt chiu , c th iu chnh c bin , k hiu l
Uc
Dng th c biu din nh hnh sau :
Tng i s ca Ur + Uc c a n u vo ca mt khu so snh. Bng cch lm bin i
Uc ta c th iu chnh c thi im xut hin xung ra tc l thi im iu chnh gc
( .
Khi Uc = 0 ta c ( = 0
Uc < 0 ta c ( > 0
Quan h gia ( v Uc c biu din qua cng thc sau :
Ngi ta thng chn Ur max = Uc max
b. Nguyn tc iu khin thng ng ARCCOS
Theo nguyn tc ny ngi ta cng dng c hai in p iu chnh gc m ( ca
Tiristor.
in p iu khin Uc l in p mt chiu c th iu chnh c bin theo hai hng (
m v dng ).
in p ng b Ur vt trc in p UAK ca Tiristor mt gc bng
Nu UAK = A.sin(t
Th Ur = B.cos(t
Dng th c biu din nh hnh sau:
T in p UAK ta to ra Ur . Tng i s Ur + Uc c a n u vo khu so
snh.
Khi Ur + Uc = 0 ta nhn c mt xung u ra ca khu so snh:
Uc + Bcos( = 0.
Nn . Chn B = Ucmax
Khi Uc = 0 ta c ( = (/2
Uc = Ucmax ( = ( Uc = -Ucmax ( = 0
II. S khi v chc nng
Da trn nguyn tc iu khin v yu cu ca cng ngh ta thit lp c s khi ca
b iu khin
Ung
UkTrong :
Ung : in p ngun
Uk : in p iu khin - Khu ng pha ( F ) c nhim v to in p trng pha
vi in p ant ca Tiristor. Tn hiu ng pha thng c cc dng sau:
+ Rng ca
+ Ch nht
+ Thang
+ Cosin
- Khu so snh c nhim v gia in p ta vi in p iu khin Uk tm thi im
hai in p ny bng nhau ( Uk = Urc ). Ti thi im hai in p ny bng nhau
th pht xung u ra gi sang tng khuych i v to xung
- Khi khuych i v to xung c nhim v to xung ph hp m Tiristor. Xung
m Tiristor c yu cu : Sn trc c thng ng m yu cu m tc th khi c xung iu
khin ( Thng l xung kim hoc xung ch nht ) rng xung vi rng xung ln hn
thi gian m ca Tiristor cng sut cch ly mch iu khin v mch ng lc ( v
in p mch ng lc qu ln ).
III. Mch iu khin.
I. nguyn tc n p n dng:
Mch np c quy t ng phi s dng hai nguyn tc:
1. n dng trong gia on u ca qu trnh np.
2. n p trong giai on np c quy no.
Mun thc hin c iu ny ta phi bit c ch n p v n dng ca b chnh
lu.
Trong trng hp ny ta xt b chnh lu mmt pha- chu k
1. Nguyn tc n dng:
Ban u b chnh lu chy khng ti vi in p khng ti U0 . Khi ni ti dng
in qua ti qu tng dn ti gi tr n nh. Ti y b bin i thc hin qu trnh n
dng nh sau:
a) n dng theo sn trc:
Nguyn tc iu khin Uk = Ud + Uf_Ban u in p ra ca b chnh lu l in p
khng ti Ud = U0, Id = 0 khi ni ti vo dng in Id tng dn ko theo in p
phn hi Uf tng. Do Uk = Uf + Ud Nn Uk tng dn ti in p ra ca b chnh lu
gim dn. Do Ud gim dn lm tc tng dng in gim cho ti khi Id = Id . Ti
gi tr nh Id0 in p b chnh lu l U0_Nu v mt l d no dng in tng hn I0 (
Uf tng ( Uk tng lm in p u ra b chnh lu gim xung Ud < U0. Chnh v
iu ny lm dng in chnh lu gim dn vi tc n nh.
_Ngc li nu Id gim ( Id < I0d ) dng in s t ng tng ti gi tr n
nh.
b) Theo sn sau:
_Ban u in p b chnh lu l Ud = U0, Id = 0
_ Ni ti dng in tng dn Uf tng dn ( Uk tng lm in p ra gim.
_Dng in chnh lu ang duy tr n nh. V mt l do no dng in tng dn n Uf
tng lm Uk gim lm gc m ( tng Ud gim nh hn U0d dng in s gim dn ti gi
tr n nh.
Tng t nh vy nu dng in gim.
Kt lun:
Nh vy nu thu hin n dng ta phi:
_Phn hi m dng in nu iu khin theo sn sau.
_Phn hi dng dng in nu iu khin theo sn trc.
2. Nguyn tc n p:
Ban u b chnh lu chy khng ti vi in p khng ti U0 . Khi ni ti dng
in qua ti qu tng dn ti gi tr n nh. Ti y b bin i thc hin qu trnh n p
nh sau:
a) n p theo sn trc:
Nguyn tc iu khin Uk = Ud + Uf_Ban u in p ra ca b chnh lu l in p
khng ti Ud = U0, Id = 0 khi ni ti vo dng in Id tng dn ko theo in p
phn hi Uf tng. Do Uk = Uf + Ud Nn Uk tng dn ti in p ra ca b chnh lu
gim dn. Do Ud gim dn ti U
_Nu v mt l d no in p tng hn U ( Uf tng ( Uk tng lm in p u ra b
chnh lu gim xung Ud = U.
_Ngc li nu Ud gim in p s t ng tng ti gi tr n nh.
b) Theo sn sau:
_Ban u in p b chnh lu l Ud = U0, Id = 0
_ Ni ti in p tng dn Uf tng dn ( Uk tng lm in p ra gim.
_in p chnh lu ang duy tr n nh. V mt l do no in p tng dn n Uf tng
lm Uk gim lm gc m ( tng Ud gim dn ti gi tr n nh. Tng t nh vy nu dng
in gim.
Kt lun:
Nh vy nu thu hin n p ta phi:
_Phn hi m in p nu iu khin theo sn sau.
_Phn hi dng in p nu iu khin theo sn trc.
II. xy dng mch iu khin.
III. Tnh ton mch iu khin.
T nhng phn tch trn ta c th tnh chn cc thit b cho mch iu khin nh
sau:
Khi ng pha.
Tt c cc khuych thut ton chn cng loi LM 301A
Bin p ng pha c th ly chnh l bin p ngun cung cp ngun mmt chiu cho
mch U = ( 12 V ( xoay chiu ).
Cc it D1, D2, D3, D4 c th chn cng loi D4041
Thng s : Um = 50 V , Im = 500 mA
Khu to xung rng ca:
Cc Tiristor c th chn cng loi cho Radio cng sut nh l c th tho mn
.
Chn : A564 UCE = 30 V IC = 50 mA ( = 120
C828 UCE = 30 V IC = 50 mA ( = 100
Cc in tr R1, R2, R3, R4 cc in tr hn ch dng c th chn gi tr tng i
10 k(.
Chiet p R1 t ngng sao cho Uref = 0,6 ( 0,7 V
in tr R3 hn ch dng qua DZ chn 2,2 k(.
it Zene chn loi 9V.
Tnh chn in tr R6 v ngun dng np cho t. trong thi gian kho
trazistor T2 in p nh rng ca c th t c 10V th in tr R6 v C c tnh nh
sau:
Q = C.U
Q = I.t
( I.t = C.U
Trong na chu k th t (
Chn C = 1 (F (
to ngun dng ny th R6 c gi tr:
Tnh mch khuych i xung.
Nguyn l hot ng s :
T cc phn tch trn v ch n p v n dng ta c th a ra c s nh trn. S c
chia thnh ba khi sau:
1. Khi ng pha:
Tn hiu xoay chiu c ly t bin p ng pha. Bin p c im gia c chnh lu
hai na chu k v a tn hiu vo b so snh OA1 . in p chun so snh c chnh
nh in p mt chiu c 0,7 V .
in p ra c dng nh hnh v:
ng thi tn hiu xoay chiu t hai im a v b c a vo hai bb so snh OA2
v OA3 to tn hiu ng pha cho php pht xung iu khin hai knh.
in p ng pha t OA1 c a ti b to in p rng ca
+ Khi UC m trazistor T1 kho t C c np bi ngun dng khi
+Khi UC dng trazistor T1 dn t C phng in.
Dng in p thu c l mt dy xung rng ca c sn ln tuyn tnh.
Khi to xung chm:
1. Vi mch 555
UC
E
2/3E
1/3E
(
Ur
(
thp T kho t C np theo ng E ( R1 ( R2 ( C ( -E
UC > u ra OA2 cao
UC = u ra OA1 thp
Khi Q = 0 ,
Tranzistor thng t C phng theo ng +E ( C ( R2 ( T ( -E
Qu trnh lI tip tc Kt qu c mt dy xung vung u ra khng o R_S
E_F.
C nhiu cch to xung chm , y mch time 555 c s dng nh mch da hI t
dao ng. Xung chm c ly ra chn 3 ca Time 555.
Diot D m bo xung ra c b rng u nhau .Tn s c tnh theo biu thc
:
Vi tn s mong mun f = 10 kHz ta phi chn
R = 10 k( C = 7 (F
2. Khu so snh:
in p nhn dc t D qua in tr R5 c so snh vi Uk t xc nh c thi im pht
xung m cc van.
3. Khu khuych i xung:
_Knh 1: iu khin tiristor T1 xung in p nhn t cng AND vi tn hiu
cho php nhn t OA2_Knh 2: iu khin tiristor T1 xung in p nhn t cng
AND vi tn hiu
cho php nhn t OA3.
Dng in p nhn dc t OA2 v OA3 l cc xung vung ng pha vi tn hiu sin
nhng ngc pha nhau.
Khi in p ti im a dng tng ng OA2 nhn c xung dng.
Khi in p ti im b m tng ng OA3 nhn c xung m.
V vy khi 1AND m th 2AND kho thi xung in p c khuych i qua bin p
xung a ti cc G ca cc tiristor.
Dng in p nhn c nh hnh v:
c qui axit c qui ch
- Kh nng qu ti khng cao, dng - Kh nng qu ti rt ln
np ln nht t c khi qu ti dng in np ln nht khi
l Inmax ( 20%C10 c th t ti 50%C10
- Hin tng t phng ln, c qui - Hin tng t phng nh
nhanh ht in ngay c khi khng
s dng.
- S dng rng ri trong i sng - Vi nhng kh nng trn
cng nghip, nhng ni c nhit th c qui kim thng s
cao va p ln nhng i hi nhng ni yu cu cng
cng sut v qu ti va phi. cao qu ti thng xuyn v
s dng vi cc thit b cng
sut ln.
- Dng trong xe my , t, cc ng - Dng trong cng nghip
c my n cng sut va v nh. hng khng, hng hi v
nhng ni nhit hot ng
mi trng l thp.
- Gi thnh thp. - Gi thnh cao.
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