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8/7/2019 on ap may phat _ AVR2_
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 1
Mc lc
M u .................................................................................................2
Chng 1. Tng quan v cc phng php n nh inp my pht in ng b.......................................................3
1. Gii thiu chung v my pht in ng b................................42. Cc c tnh ca My pht in ng b. .................................. 83. Thit b t ng iu chnh. .......................................................144. H thng t ng iu khin kch t .........................................20
Chng 2: S t ng iu chnh in p my phtin...........................................................................................24
1. H thng kch t ........................................................................242. La chn phng n.................................................................313. S iu khin cho h thng kch t dng my pht
in xoay chiu theo phng n la chn................................31
Chng 3 - Thit k v tnh ton mch ng lc .........................321. Chnh lu c iu khin ba pha.................................................322. La chn s chnh lu .........................................................393. Tnh chn Tiristor.......................................................................404. Tnh bin p ng lc................................................................415. Tnh chn cc thit b bo v mch ng lc ...........................50
Chng 4 - Tnh ton cc thng s ca mch iu khin ...........511. Nguyn tc iu khin Thyristor. ............................................... 512. Chn cc khu trong mch iu khin. .....................................533. Tnh bin p xung ......................................................................604. Tnh tng khuch i cui cng.................................................625. Chn t C2 v R6........................................................................636. Tnh chn tng so snh .............................................................647. Tnh chn khu ng pha..........................................................648. To ngun nui .......................................................................... 66
9. Tnh chn Diod cho b chnh lu ngun nui ...........................6710. Tnh khu phn hi in p .......................................................67
Kt lun ..............................................................................................70
Ti liu tham kho.............................................................................72
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 2
M u
bt k Quc gia no, nng lng in lc lun lun c coi l
ngnh cng nghip mang tnh cht xng sng cho s pht trin cann kinh t. N v s lun h tr thc y s pht trin ca tt c
cc ngnh khc. Vic sn xut v s dng in nng mt cch hiu
qu nhng phi ph hp chi ph lun c coi trng c bit.
ngh a quan trng m cng chnh l mc tiu cao c nht ca chin
lc pht trin ngnh cng nghip then cht ny l nhm nng cao
i sng ca mi ngi dn v kt qu ca n s l mt X hi Vn
minh, Tin b v Thnh vng.
My pht in ng b ni chung ng mt vai tr trng yu trong
h thng in, ni m tnh n nh lun c i hi rt cao. Trong
h thng in, s n nh ca mi mt my pht in cc kha cnh
k thut u c tnh cht quan trng nht nh ti s vn hnh an
ton v bn vng ca ton h thng v cc my pht in th s
ng gp ca b n nh in p my pht, cng vi cc thit b n
nh khc l khng th thiu.
B iu khin n nh in p my pht bng iu khin dng/p
kch t i (iu khin kch t - KT) vo my pht c mt lch s
pht trin su rng. K t ngy u vic iu khin ny c t ng
ho, thit b ch ng vai tr nh mt thit b cnh bo cho ngi vn
hnh tc ng iu chnh trc tip vo my pht. Vo nhng nm
1920, khi con ngi nhn thy vai tr quan trng ca vic n nh
qu trnh qu ca h thng thng qua cc b iu khin p ng
nhanh, cc thit k cc h thng kch t v iu khin in p tinha v ci tin cng ngh khng ngng: t kch t c vnh trt n
khng vnh trt, t thao tc bng tay n t ng ho hon ton
thng qua vai tr khng th thiu ca cc thit b in t cng sut.
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 3
Tuy cng sut my pht c giao thit k (125kW) l rt nh v
khng thc s ng vai tr n nh trong h thng in ln, nhng
em cho rng vic thit k mt thit b nh v quan trng nh vy
cng l nn tng c bn cho mi thit k cc b n p my pht khcd ln. Ni dung n thit k ca em bao gm 4 chng, trong :
Chng 1 a ra gii thiu tng quan v cc phng php n
nh in p my pht in ng b
Chng 2 cp c th vo cc phng php n nh in p
vi cc s t ng iu chnh in p my pht in, v la
chn ra phng n ca n thit k.
Chng 3 l cc thit k v tnh ton c th cho mch nglc ca s chn v
Chng 4 bao chm phn tnh ton cho cc thng s ca
mch iu khin v tng hp s
Vi s hng dn v gip nhit tnh ca Gio vin hng dn
Thy Trn Vn Thnh, em c mong rng n tt nghip ny s
a n mt kt qu tt nghip tt p, nhng trn ht n s to v
xy dng cho em mt nn tng kin thc c bn, vng chc trongcuc sng lao ng k thut ca mt k s sau ny.
Em xin by t lng bit n su sc i vi Thy gio Trn Vn Thnh
v nhng kin thc, hng dn, ch bo m Thy dnh cho em
trong thi gian hc v c bit trong vic hon thnh n ny. Em
cng xin by t lng bit n ti cc Thy C gio khc ca B mn
Thit b in - in t ni ring v cc Thy C Khoa in v
Trng H Bch khoa HN ni chung 5 nm vt v nhit tnh dybo v cho em nhng cng c bng cc kin thc xy dng
tng lai.
Chng 1. Tng quan v cc phng php nnh in p my pht in ng b.
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 4
1. Gii thiu chung v my pht in ng b
My pht in ng b (MF) thng c ko bi tuc- bin hi
hoc tuc-bin nc, v vy chng c gi chung l my pht tuc- bin hi hoc my pht tuc-bin nc. i vi tuc-bin hi, do c
trng l tc cao c vi nghn vng pht nn my pht thng c
kt cu r-to cc n, vi ng knh nh gim thiu lc ly tm v
ngc li, i vi tuc-bin nc, tc thp nn thng c r-to cc
li, ng knh c th ln ti 15m tu thuc cng sut ca my.
MF ba pha (MF3) thng gp c bn l my pht in m dng
in mt chiu c a vo qun dy kch t khng thng qua vnhi chiu. Cc t ca MF3 c kch thch bng dng in mt
chiu c t phn quay, cn dy qun phn ng vi 3 im i
xng trn n c ni ra ngoi ti th c t phn tnh. Cng c
th t cc t phn tnh v dy qun phn ng phn quay ging
trong my in 1 chiu nh my in ng b cng sut nh, v s
trao i v tr khng lm thay i nguyn l lm vic c bn ca
my. Nguyn l lm vic c bn nh sau:
Stator ca my pht in ng b c dy qun 3 pha c t cch
nhau mt gc 120o trong khng gian, c gi l phn ng, cm ng
ra cc in p cung cp ra ti (Hnh 1.1). Cn rotor ca my pht, vi
cu to dy qun cc t (cc li i vi my pht c tuc bin tc
thp nh cc my pht tuc bin nc, v cc n i vi tuc bin c
tc cao nh my pht Diesel, tuc bin hi v kh) lm nhim v
cung cp t trng.
B
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 5
Hnh 1.1 - Cu to ca Stator.
Khi rotor quay vi tc n th t trng cc t s qut v cm ng
ln cc dy qun phn ng cc sc in ng (s...) xoay chiu ln
lt lch pha nhau 120o theo chu k thi gian, vi tn s:
60
n.pf
Vip l s i cc ca my
Khi MF3 lm vic khp mch vi ti, dng in 3 pha chy trong 3
dy qun lch nhau gc 2/3 v thi gian s to ra t trng quay vi
tc :
p
fn
601
So snh (1.1) v (1.2) ta c n=n1, hay c ngh a l tc quay ca
rotor bng tc ca t trng quay. V vy ta c my pht ng b.Kt cu MF3
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 6
My cc n
Rotor c lm bng thp hp kim cht lng cao c rn thnh
khi h nh tr, trn ngi ta gia cng phay to rnh t dyqun kch t. Phn khng phay rnh (nh h nh ??) hnh thnh mt
cc t.
Cc MF3 ccn thng c ch to vi s cc 2p=2, nh vy tc
quay ca Rotor l 3000 vng/pht. hn ch lc ly tm trong
phm vi an ton i vi thp hp kim ch to thnh li thp Rotor,
ng knh D ca Rotor khng qu 1,1 1,5 m. Tng cng sut ca
my bng cch tng chiu di l ca Rotor. Chiu di ti a ca Rotorvo khong 6,5 m.
Dy dn kch t t trong rnh Rotor c ch to t dy ng trn,
tit din ch nht qun theo chiu mng thnh cc bi dy. Cc vng
dy ca bi dy ny c cch in vi nhau bng mt lp mica
mng. Dy qun kch t nm trong rnh c c nh v p cht
bng cc thanh nm phi t tnh a vo ming rnh. Phn u ni
ngoi rnh c ai cht bng cc ng tr thp phi t tnh nhm bov chng li lc in ng do dng in gy ra. Hai u ca dy
qun kch t i lun trong trc v ni vi hai vnh trt t u
trc thng qua hai chi in, ni vi dng kch t 1 chiu.
Dng in kch t 1 chiu thng c cung cp bi mt my pht
in 1 chiu, hoc xoay chiu c chnh lu (c hoc khng c
vnh trt), ni chung trc vi MF.
Stator ca MF3 cc n bao gm li thp, trong c t dy qun 3
pha, ngoi l thn v v my. Li thp Stator c ghp v p bng
cc tm tn Silic c ph cch in. Cc ng thng gi lm mt cho
my c ch to c nh trong thn my m bo bn cch
in ca dy qun v my.
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SV: TB Trg. 7
My Cc li.
My cc li c ch to cho cc MF c tc quay thp, nn
khc vi my cc n, ng knh D ca Rotor c th ln ti 15 mtrong khi chiu di l li nh vi t l l/D = 0,15 0,2
Hnh 1.2 Cc t ca my ng b cc li
Rotor ca MF cc li cng sut nh v trung bnh c li thp c
ch to bng thp c v gia cng thnh khi hnh tr trn mt c t
cc t. cc my ln, li thp c ch to t cc tm thp dy,t 1-6mm, c dp hoc c nh hnh sn ghp thnh cc khi
lng tr v li thp ny thng khng trc tip lng vo trc ca my
m c t trn gi ca Rotor, gi ny c lng vo trc my.
Cc t t trn li thp Rotor c ghp bng nhng l thp dy 1-
1,5 mm (v h nh v nh s) ch to c ui h nh T hoc bng cc
bu-lng xuyn qua mt cc v vt cht vo li thp Rotor.
Dy qun kch t c ch to t dy ng trn tit din ch nhtqun theo chiu mng thnh tng cun dy. Cch in gia cc vng
dy l cc lp mica hoc amiang. Sau khi gia cng, cc cun dy
c lng vo cc thn cc.
Dy qun cn ca MF c t trn cc u cc c cu to nh
dy qun kiu lng sc ca my in khng ng b; ngh a l lm
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 8
bng cc thanh ng t vo rnh cc u cc v hai u ni vi hai
vnh ngn mch.
Stator ca MF cc li c cu to nh MF cc n.
m bo vn hnh n nh, ngoi cc yu cu cht ch i vi kt
cu v in, cc kt cu v c hc v h thng lm mt cng c
thit k ch to ph hp v tng thch vi tng loi MF, p ng
c mi trng v ch lm vic. MF, lm mt bng gi cng
sut nh, c cc khoang thng gi lm mt c thit k ch to nm
gia v my v li thp Stator. u trc ca my c gn mt cnh
qut gi khi quay khng kh c thi qua cc khoang thng giny. V my ngoi ra cng c ch to vi cc sng gn hoc cnh
to nhit nhm lm tng din tch b mt trao i nhit cho my. Ph
bin nht l cc MF c lm mt bng nc hoc bng kh v
c p dng cho cc my c cng sut ln c t vi chc kW tr
ln.
2. Cc c tnh ca My pht in ng b.
1. c tnh khng ti E = U0 = f(it) khi I= 0 v f= fdm
2. c tnh ngn mch U = f(it) khi U = 0 ; f = fdm
3. c tnh ngoiU = f(I) khi it = const ; cos =const ; f = fdm
4. c tnh iu chnh it = f(I) khi U = const ; cos = const ; f =
fdm
5. c tnh ti U= f(it) khi I = const ; cos = const ; f= fdm
2.1. c tnh khng ti
E = U0 = f(it) khi I= 0 v f= fm
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SV: TB Trg. 9
c tnh khng ti l quan h gia sc in ng E cm ng ra
qun dy stator vi dng in kch t khi dng in ti bng
khng trong h n v tng i vi:
E* =dmEE
tdmo
t*t i
ii
E*
It*
Hnh 1.3 - c tnh khng ti
2.2. c tnh ngn mch v t s ngn mch
In = f(it) khi U= 0 ; f= fm
c tnh ngn mch l quan h gia dng in ti khi ngn
mch (khi dy qun phn ng c ni tt ngay u my) vi
dng in kch t khi in p bng khng v tn s bng nh
mc. Nu b qua in tr ca dy qun phn ng ( r = 0) th
mch in dy qun phn lc ngn mch l thun cm ( = 900 ) nh vy
Iq = cos = 0
Id = Isin = I
E = jIxd
Vy ta c th vc t.
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 10
E
Ijx I
jxd I
jIxd
Hnh 1.4 - th vc t
Lc ngn mch phn ng phn ng l kh t, mch t ca
my khng bo ho v t thng khe h khng kh cn thit
sinh ra. E = E Ixud = Ix Rt nh. Nh vyquan h I = f(It) l ng thng
I
It
I = f(It)
Hnh 1.5 - c tnh ngn mch
T s ngn mch: T s ngn mch K l t s dng in ngn
mch Inong vi dng in kch thch sinh ra sut in ng E
= Udm khi khng ti vi dng in nh mc.
dm
no
I
IK (Trong :
d
dmno
x
UI )
xd tr s bo ho ca in khng ng b dc trc ng vi
E = Udm
*ddmd
dm
x1
IxU
K
xd* thng ln hn 1 vy K < 1 Ino < Im
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 11
ititnito
I = f(i t)
U = f(i t)
Udm
U.I
InoIdm
Hnh 1.6
T s ngn mch:
tn
to
dm
no
iiIIK
ito dng in kch thch khi khng ti lc Uo = Udm
itn dng in kch thch khi ngn mch lc I = Idm
T s ngn mch K l mt hng s quan trng trong my in
ng b. My vi K ln c u im cho thay i in p
U nh khin cho my l vic n nh khi ti thay i
2.3. c tnh ngai v thay i in p Udmca mypht ng b
U = f(I) khi it = const ; cos =const ; f = fdm
c tnh ngoi l quan h in p u ra ca my pht khi
dng in ti thay i vi dng in kch t, h s cng sut
v tn s l khng i. Dng in it - ng vi Udm ; Idm ; cos=const ; f = fdm - c gi l dng in t ho nh mc
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 12
U
I
Udm
0 Idm
cosUdm
cos(in dung)
cos(in cm)
Hnh 1.7 - c tnh ngoi
T hnh v ta thy dng c tnh ngoi ph thuc vo tnh cht
ti. Nu ti c tnh cm khi I tng phn ng kh t ca phn
ng tng, in p gim v ng biu din i xung. Ngc
li nu ti c tnh dung khi I tng , phn ng phn ng l tr
t, in p tng v ng biu din i ln.
thay i in p nh mc Udm cu my pht in ng
b l s thay i in p khi ti thay i t nh mc vi cos= cosdm n khng ti trong iu kin khng thay i dng
in kch thch
Udm = 100U
UE
dm
dm
2.4. c tnh iu chnh
it = f(I) khi U = const ; cos = const ; f = fdm .
c tnh iu chnh l quan h ca dng kch t vi dng in
ti lun gi cho in p khng thay i. N cho bit hng
iu chnh dng in it ca my pht ng b gi cho in
p ra U u my pht khng i
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 13
It
I
It
0 Idm
cos(in dung)
cos
cos (in cm)
Hnh 1.8 - c tnh iu chnh
Ta thy vi ti cm khi I tng, tc dng ca phn ng phn
ng tng lm cho U b gim. gi cho U khng i phi
tng dng in t ho it. Ngc li ti dung khi I tng, mun
gi U khng i phi gim it thng thng cosdm = 0,8 (
thun cm) nn t thng ti (U = Udm ; I = 0) n
ti inh mc (U = Udm ; I = Idm) phi tng dng in t ho
2.5. c tnh ti
U= f(it) khi I = const ; cos = const ; f= fm
c tnh ti l quan h gia in p u ra ca MF vi dng
kch t khi ti l khng i. Vi cc tr s khc nhau ca I v
cos s c cc c tnh ti khc nhau, trong c ngha nht
l c tnh ti thun cm ng cos = 0 ( = 900
) v I = Im
c tnh ti thun cm c th suy ra c t c tnh khng ti
v tam gic in khng
T c tnh ngn mch (ng 2) c tr s In = Idm dng
in kch thch itn hoc sc t ng Ftn cn thit bng Ftn=itn =
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SV: TB Trg. 14
OC . Khi my lm vic ch ngn mch sc t ng ca
cc t Ftn = OC gm hai phn. Mt phn khc phc phn
ng kh t ca phn ng BC = kdFd sinh ra Ed phn cn li
OB = OC BC s sinh ra sut in ng tn t F = Idmx =AB ( A nm trn on thng ca c tnh khng ti ng 1 v
lc mch t khng bo ho).
Tam gic ABC c hnh thnh nh trn c gi l tam gic
in khng cc cnh BC v AB ca tam gic t l vi dng ti
nh mc Idm
em tnh tin tam gic in khng ABC sao cho im A ta
trn c tnh khng ti th nh C s v thnh c tnh thun
cm (ng 3)
i t
U.I
I = 0
I = Idm
23
1
E A'
O' B' C'
C Q PO
M
Idm
kd Fd
x Idm
Hnh 1.9 - c tnh ti
3. Thit b t ng iu chnh.
i vi my pht in khi ti thay i th khng nhng lm in
p ra ca my pht thay i m n cn lm thay i c tc ca
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 15
ng c s cp ca my pht dn ti thay i c tn s ca my
pht. Nh vy trong qa trnh iu khin my pht bn cnh vic
n nh in p ra ca my pht ta cn phi n nh c tn s my
pht khi ti thay i. Thc cht ca iu ny l ta phi n nh tc quay ca ng c khi ti thay i.
i vi mi loi ng c/tuc-bin s cp th c cc b iu tc
khc nhau. Tuy nhin, n Tt nghip ca em ch mong mun
cp n loi iu tc ca ng c s cp Diesel, nhm tng
thch vi cng sut ca yu cu ca n
ng c Diezel dng ko my pht in trong khi hot nglun thng xuyn phi thay i ch lm vic mt cch t
ngt, ngha l cc ch lm vic n nh ca ng c lun b
ph v. Khi ph ti thay i th tc ca ng c cng thay i.
Khi lng bnh c th b tr phn no mc chnh lch
gia cng sut ng c v cng sut cn thit ca my cng tc,
nhng n ch mang tnh cht tm thi hn na nu kch thc
bnh cng nh th tc dng b tr y cng t
Mun gi cho s vng quay ca ng c nm trong mt gii hn
cn thit phi lun thay i lng nhin liu cp cho ng c
loi tr tnh trng mt cn bng nng lng gia ng c v my
cng tc. Nhng trn thc t trong iu kin ph ti lun thay i
t ngt khng th dng tay iu chnh lng nhin liu, v
vy cc loi ng c Diezel dng chy my pht in lun cn
c mt c cu c bit iu chnh t ng lng nhin liu cp
cho ng c trong mi chu trnh cng tc m bo cng sutng c lun cn bng vi cng sut ca my cng tc qua gi
cho s vng quay ca ng c khng thay i
Hin nay c rt nhiu loi iu tc trn mi ng c s dng b
iu tc no l tu thuc vo loi ng c, c im ca my
cng tc v ton b thit b
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 16
i vi ng c Diezel dng chy my pht lun phi hot
ng trong iu kin gi tc quay khng i khi ti thng
xuyn thay i mt cch t ngt, nn ng c rt d vt qu svng quay cho php gii hn ca ng c mt mt c th gy ra
ng sut c gii hn vt qu gi tr cho php, mt khc cn ph
hoi nghim trng cc qu trnh lm vic ca ng c. V nhng
l do trn m i vi ng c Diezel dng chy my pht in
bt buc phi lp b iu tc
ng c Diezel thng rt nhy cm vi cc ch tc . Nu
tc ng c vt qu s vng quay thit k, thng lm gimnhanh cht lng ca cc qu tr nh cng tc v lc y h s d
lng khng kh v cht lng hnh thnh kh hn hp u gim
nhanh lc y mt mt thi gian chy b rt ngn mt khc cht
lng ca qu tr nh chy cng gim. Nhin liu khng chy ht
v qu trnh chy cn phi ko di thm trn ng gin n, lm
ng c rt nng (c bit l c cu thi v nhm pittng). Tn
nhiu nhin liu, c thm mui than trong kh thi ca ng c
dn n ng c chng hng
Phn loi cc loi iu tc:
Nguyn tc lm vic ca phn t cm ng (phn t gy cm ng
trc tip vi bin thin ca tc ) gm cc b iu tc: C
gii, thu lc, chn khng v in
Theo cng dng gm loi mt ch (trong c loi chnh xc,loi gii hn v loi bo him) hai ch (m bo cho ng c
lm vic n nh s vng quay cc tiu v hn ch s vng
quay cc i) v nhiu ch (qua c cu iu khin, c th m
bo cho ng c lm vic bt k s vng quay no trong phm
vi s vng quay cng tc ca ng c)
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SV: TB n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 17
Ngoi s phn loi nh trn trong thc t ngi ta con phn ra
lm rt nhiu loi tu thuc vo c cu tc ng, .
Theo nguyn tc hot ng ca my pht in th m bo tns ca dng in l khng i khi ti thay i th tc quay ca
roto phi khng i nh vy ng c s cp ko roto phi khng
thay i. Nh vy i vi ng c Diezel chy my pht in th
c cu m bo tc quay ca roto khng i ngi ta
thng dng b iu tc mt ch
1
2
3
1 L xo
2 Qu vng
3 Khp tr t
Hnh 1.10 - B iu tc mt ch ca my pht in Diezel
L xo ca b iu tc c lc p ban u khng i do qu
vng ca b iu tc di tc dng cu lc ly tm ch c th vn
ng khi ch tc ca ng c t ti mt gi tr nht nh.
Nu ct ph ti bn ngoi ng c c khuynh hng lm tng s
vng quay, lc y di tc dng ca lc ly tm, cc qu vng ca
b iu tc s vng ra ngoi lm di ng khp trt v thanh rngbm cao p. Qua lm lng nhin liu cung cp cho mi chu
trnh gim ti mt gi tr cn thit. Nu tng ti bn ngoi s vng
quay ca ng c x gim mt qu trnh s sy ra ngc li, lc
y tc dng ca lc ly tm nh i do tc ca ng c gim, cc
qu vng ca b iu tc s vng t i lm di ng khp trt v
thanh rng bm cao p. Qua lm lng nhin liu cung cp
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cho mi chu tr nh tng ti mt gi tr cn thit m bo tc
ng c s c gi khng i. Tt c cc ch lm vic ca
ng c lc ny s nm trn c tnh iu tc ab l nhng ch
chnh qui ca ng c c lp thm b iu tc ny. Tt nhin lng c c th lm vic cc ch ngoi ng c tnh iu
tc ab nhng ch l cc ch chuyn tip
Nh vy b iu tc gi cho s vng quay ca ng c hu nh
khng i v khng ph thuc vo ti
z
1
2
3
a
b n
1,2,3: c tnh ngoi
ab: c tnh iu chnh
Hnh 1.11 - c tnh ca b iu tc mt ch :
z
n
zn
nonk
Bn cnh cc b n nh tc c kh nh trn th trn thc thin nay ngi ta thng dng nhng b n nh tc bng in
Mt h thng n nh tc ca ng c bng in thng thng
gm c hai phn: phn bo v qu tc ng c v phn khng
ch iu chnh tc ng c
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Phn bo v qu tc ng c:
Khi ng c mt iu khin tc ng cc th tng ln rt cao
iu ny lm cho cc c cu c kh khng th chu c cc lcly tm ln xut hin do cc c cu c kh c th b ph hng
ng thi c th gy nguy him cho ngi vn hnh my. Khi
b phn bo v qu tc c nhim v pht hin ra s c ng
thi khng ch tc ng c s cp mt tc an ton do
m bo an ton cho my v ngi vn hnh
Phn khng ch iu chnh tc ng c:
- Duy tr tc khng ti ca ng c ti mt im t trc- Duy tr tc ng c ti mt im t trc khi ti thay
i
Khng ging nh cc b khng ch bng cc c cu c kh b
khng ch bng in c kch thc nh gn bao gm cc b phn
sau :
- Khi iu khin
- B cm bin tc ng c- C cu chp hnh
- B bo v qu tc ng c
So S nh khuchichphnh
ng c
Hnh 1.12 - S khi b n nh tc ng c
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Hot ng ca s c m t nh sau:
Tc ng c c o bng mt cm bin, tn hiu in ny s
c gi ti b so snh y b so snh s so snh gia tc tthc t ca ng c v tc t trc. Sau tn hiu so snh
c khuch i v chuyn ti mt c cu chp hnh (l mt nam
chm in t) n s iu chnh cn iu khin ca bm nhin liu
lm tng hoc gim khi lng nhin liu cung cp cho ng c
lm tc ng c khng thay i
4. H thng t ng iu khin kch t
Thit b t ng iu chnh kch t bao gm mt lot cc knh lin
h ngc iu khin in p kch t ca my pht kch thch (gin
tip iu khin in p kch t ca my pht chnh ). Trng hp h
thng kch t dng Thyristor (chnh lu c iu khin) tn hiu t
thit b t ng iu chnh kch t iu khin trc tip dng kch t.
Lc u thit b t ng iu chnh kch t c thit k ch vi mc
ch iu chnh in p (gi in p u cc trong qu trnh my
pht lm vic). Cu to n gin bi cc knh phn hi m theo
lch in p v phn hi dng theo lch dng in. Hin nay
thit b t ng iu chnh kch t c cu trc phc tp hn nhiu,
thc hin cc nhim v n nh h thng gim dao ng cng sut...
Cc phn chnh trong cu trc ca thit b t ng iu chnh kch t
gm:
Cc knh iu chnh theo lch cc tham s ch (in p
u cc my pht , dng stato...). Cc knh ny c nh hng
chung nhng ch yu n cc c tnh tnh v ch xc lp.
Cc knh iu chnh theo tn hiu o hm ca cc tham s
ch . Cc knh ny ch nh hng n cc c tnh ng ca
h thng nh iu kin n nh (ch yu n nh tnh), n
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SV: TB Trg. 21
cht lng ca qu trnh qu , nhng khng c tc dng i
vi cc c tnh tnh.
B phn kch thch cng hnh tc ng ln qu trnh qu khi c nhng kch ng ln, c ngha nng cao tnh n nh
tnh cho h thng
Theo c tnh lm vic ngi ta chia thit b t ng iu chnh
kch t ra lm hai loi chnh thit b t ng iu chnh kch t tc
ng t l v thit b t ng iu chnh kch t tc ng mnh.
- Thit b t ng iu chnh kch t tc ng t l :
DL B SS
PHM
SS
CH
M ykchthch
C1
C2C3 n cun
dy roto
Uf
U0
Hnh 1.13 - Thit b t ng iu chnh kch t tc ng t l
- Thit b t ng iu chnh kch t tc ng mnh:
B SSU
BVP
CH
VP U'
U
f'f
TCL n cundy roto
chnh l uthyristor
DL
f f
U0
Hnh 1.14 - thit b t ng iu chnh kch t tc ng mnh
- Khu o lng - L
- Bin i - B
- So snh - SS
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- Cc cun dy kch t - C1, C2 v C3
- Knh phn hi PHM
- Kch thch cng hnh CH
- B n nh cng sut VP- B chnh lu Thyristor- TCL
Cc thit b t ng iu chnh kch t tc ng t l ch gm cc
knh iu chnh theo lch thng s, do tc ng iu chnh
tng i chm (tng thch vi h thng kch t bng my pht
mt chiu hoc my pht xoay chiu tn s cao). Do b gii hn
bi h s khuch i cht lng iu chnh in p cng khng
cao. Hin nay s dng ch yu loi ny nhng nh my khngc yu cu cao v cht lng iu chnh in p, khng c yu
cu c bit v n nh h thng, cc nc Ty u coi thit b t
ng iu chnh kch t c cu trc ny l chun cho cc my
pht in thng thng
Cc thit b t ng iu chnh kch t tc ng nhanh c cu to
c bit , thm cc knh iu chnh theo o hm thng s. L
thuyt thit b t ng iu chnh kch t hin nay cha thngnht. Cc nc thuc Lin X c xy dng c s l thuyt v
thit b t ng iu chnh kch t tc ng mnh trn c s n
nh h thng ni chung, nhm to ra cc thit b t ng iu
chnh kch t cht lng iu chnh in p rt cao, trong khi vn
m bo c n nh cho bn thn thit b iu chnh (v do
nng cao ng k tnh n nh ca h thng ni chung). Trong khi
cc nc Ty u t thm b phn iu chnh ph ghp vi thit
b t ng iu chnh kch t nhm gim dao ng cng sut (gil b phn n nh cng sut Power System Stabilyzer)
Thit b t ng iu chnh kch t tc ng t l thc hin iu
chnh kch t theo lch in p u cc my pht thng qua
cc phn t o lng (my bin in p), thit b bin i (chnh
lu v lc) c a vo b phn so snh. Hiu s lch nhn
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c U = U0 UF c khuch i bi b phn khuch i ri
a n cun dy kch t ca my pht kch thch. Tr s in p
so snh U0 c ly sao cho khi in p u cc my pht bng
tr s t th U = 0. Khi my pht kch thch lm vic ch vidng kch t trong cun C1. Do U = U0 UF nn thit b lm
vic theo nguyn l phn hi m. m bo tnh n nh ca b
phn iu chnh trong ch qu , thit b t ng iu chnh
kch t tc ng t l c thm knh phn hi tc PHM tc ng
theo tn hiu o hm cp 1 ca in p kch t (ca my kch
thch)
B phn kch thch cng hnh thc cht l mt rle in p thpni vi khu khuch i in p u cc my pht gim ti 20%
so vi tr s nh mc rle tc ng a in p ti a vo cun
C3. Nh in p u ra ca my kch thch t tr s cc i.
Tc ng ny lm tng momen in t my pht nh nng cao
tnh n nh
V cu trc, khc vi thit b t ng iu chnh kch t tc ng
t l, thit b t ng iu chnh kch t tc ng mnh c thmmt lot knh tn hiu l o hm thng s ch , cng a vo
b khuch i. Phn tc ng iu chnh in p theo lch v
kch thch cng hnh khng thay i. Cc knh mi ny r rng
khng c tc ng no ch xc lp (v tn hiu bng 0). Tuy
nhin li c hiu qu cao i vi cht lng iu chnh in p v
n nh tnh h thng in. Vn l ch, nh c cc knh ny
c th nng cao h s khuch i tn hiu lch in p ln rt
ln do knh iu chnh, trong khi vn gi c n nh cho bphn iu chnh. Khi mt cch gin tip em li hiu qu cao
v phng din cht lng iu chnh in p v tnh n nh
chung ca h thng. Vn l phi chn c cu trc thch hp
v hiu chnh ng cc h s t ng vi h thng in c th
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Chng 2: S t ng iu chnh in p mypht in
1. H thng kch t
1.1. Tng quan v h thng kch t
Chc nng c bn ca mt h thng kch t l cung cp dng in
mt chiu vo dy qun kch t ca my in ng b. Thm vo ,
h thng kch t cn thc hin cc chc nng iu khin v bo v
quan trng nhm vn hnh tho mn h thng in bng cch iukhin in p v dng in i vo dy qun kch t.
Chc nng iu khin bao gm iu khin in p v cng sut phn
khng pht vo li v tng cng tnh n nh ca h thng in.
Trong khi chc nng bo v s m bo rng cc thng s gii
hn ca my ng b, h thng kch thch v cc b phn khc ca
my khng b vt qu.
1.2. Yu cu chung i vi mt h thng kch t.
Yu cu i vi mt h thng kch t c a ra di hai tiu ch
l yu cu theo tiu ch my pht v yu cu theo tiu ch h
thng in.
1.2.1. Theo tiu ch my pht.
Yu cu c bn theo tiu ch ny l h thng kch t phi cung cp v
t ng iu chnh dng in i vo dy qun kch t ca my pht
ng b m bo duy tr in p u ra ca my pht khi ti thay
i trong kh nng cung cp lin tc ca my pht. Cc gii hn v
thay i nhit , iu kin lm vic ca thit b, iu kin qu ti
v.v.. phi c tnh ton khi ch n nh c xc nh.
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Thm vo , h thng kch t phi p ng c cc bin ng qu
ca ti bng p t t trng ph hp vi kh nng p ng ng
thi v ngn hn ca my pht. Kh nng ca my pht y l ccgii hn ca mt s yu t nh: cch in dy qun r-to khi in p
tng cao, tng nhit r-to do dng in t trng tng cao,
tng nhit ca stator do dng ti tng dy qun phn ng;
tng nhit cc u bi dy ch thiu kch thch v qu in p
hoc qu tn s. Cc gii hn v nhit c hng s thi gian qun tnh
nht nh v kh nng qu ti ngn hn ca my pht c th trong
khong t 15 n 60 giy. m bo s dng ti u h thng kch
t, h thng kch t phi c kh nng p ng cc yu cu ca hthng bng cch tn dng trit cc kh nng ngn hn ca my
pht sao cho khng vt qu cc gii hn
1.2.2. Theo tiu ch h thng in
Theo tiu ch ny, h thng kch t phi ng vai tr iu khin hiu
qu in p v nng cao tnh n nh ca h thng in. N phi c
kh nng p ng nhanh i vi nhng bin ng ca h thng nng cao n nh qu v tc ng nhanh i vi t trng
nhm tng cng tnh n nh tn hiu nh (n nh tnh) ca h
thng.
Theo lch s, vai tr ca h thng kch t trong vic tng cng vn
hnh h thng in ngy cng tng cao. Cc h thng kch t thi k
u c iu khin bng tay duy tr in p u cc v cng sut
phn khng ca my pht. Khi vic iu khin in p u cc camy pht ln u tin c t ng ho, qu trnh iu khin din
ra rt chm, ch yu l ng vai tr cnh bo. Trong nhng nm
1920 khi vai tr ca cc b n p tc ng nhanh i vi n nh
qu v n nh tnh ca h thng in c pht hin, ngi ta
cng quan tm hn nhiu n kh nng ca h thng kch t v cc
my kch t (excitor) cng vi cc b n nh in p (voltage
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regulator) p ng nhanh sm c a vo ng dng cho cc h
thng in. H thng kch t theo c cc bc tin ho lin tc.
Trong nhng nm 1960 h thng kch t c m rng bng vic
s dng cc tn hiu n nh ph, ngoi cc tn hiu v sai lch inp u ra, iu khin in p t trng nhm loi b cc dao ng
ca h thng. Ngi ta coi vic iu khin kch t ny nh l b n
nh h thng in. Trn thc t ngy nay cc h thng kch t hin
i c kh nng p ng ng thi i vi cc in p ngng cao.
Vic phi hp v nng lc p t t trng cao cng vi vic s
dng cc tn hiu n nh ph s ng gp ln cho vic nng cao n
nh ng trong vn hnh h h thng in
1.3. Cc phng php T ng iu chnh Kch t
Nh ta bit iu chnh in p pht ra ca my pht ngi ta
thng iu chnh dng kch t nh mt b iu chnh bng tay hoc
t ng h thng kch t. Trong ch lm vic bnh thng iu
chnh dng kch t s iu chnh c in p u cc my pht thay
i c lng cng sut phn khng pht vo li. Thit b iu
chnh kch t lm vic nhm gi in p khng thay i (vi chnh xc no ) khi ph ti bin ng. Ngoi ra thit b t ng
iu chnh kch t cn nhm mc ch nng cao gii hn cng sut
truyn ti t my pht in vo h thng, m bo s n nh tnh,
nng cao s n nh ng.
cung cp mt cch tin cy dng mt chiu cho cun dy kch t
ca my pht in ng b, cn phi c mt h thng kch t thch
hp vi cng sut nh mc ln. Thng thng i hi cng sutnh mc ca h thng kch t bng (0,2 0,6%) cng sut nh mc
my pht in.
Dng in kch t chy trong cc cun dy rto ca my pht in
ng b l dng in mt chiu v vy cn c h thng ngun cung
cp ring. H thng kch t, iu chnh dng kch t trong qu trnh
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lm vic l thit b t ng iu chnh kch t. c tnh ca h thng
kch t v cu trc thit b iu chnh kch t c ngha quyt nh
khng nhng i vi cht lng iu chnh in p m cn n tnh
n nh h thng. Ta xt c tnh mt s loi kch t chnh.
Trong thc t ngi ta c 4 phng php iu chnh dng kch t
mt cch t ng l cc phng php sau:
H thng kch t dng my pht in mt chiu.
H thng kch t dng cc my pht in xoay chiu c vnh gp.
H thng kch t dng cc my pht in xoay chiu khng vnh
gp. H thng kch t xoay chiu dng ngun chnh lu c iu khin.
1) H thng kch t dng my pht in mt chiu
TK
R
C3 C2 C1
FU
Hnh 2.1 - H thng kch t dng my pht mt chiu.
cc my pht in cng sut nh h thng kch t l cc mypht in mt chiu.
My pht in mt chiu lm nhim v kch thch ny (cn gi l
my pht in kch thch) c th c kch thch c lp hoc
song song cun dy kch thch ca n c th chia lm nhiu cun
dy cng lm vic. Cun chnh C1 tc ng iu chnh bng tay
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cun C2 lm vic thng qua tc ng ca thit b iu chnh kch
t trong cc ch lm vic b nh thng. Cun C3 ch tc ng
khi c tn hiu s c (ch knh thch cng hnh). Tn hiu u
vo cho thit b iu chnh kch t ly t cc my bin dng vmy bin p t ti u cc my pht. Nhc im ch yu ca
h thng kch t dng my pht in mt chiu l b gii hn bi
cng sut nh (hn ch lm vic bi tia la pht sinh trn vnh
i chiu) v c hng s qun tnh iu chnh ln (Te = 0,3
0,5s).
2) H thng kch t dng my pht in xoay chiu tn s cao
chnh lu.
TK
C3 C2 C1
FU
Hnh 2.2 - H thng kch t dng my pht in tn s cao chnh
lu.
i vi cc my pht t 100MW tr ln hin nay u s dng h
thng ngun xoay chiu chnh lu. Trc ht phi k n h
thng kch t dng my pht in tn s cao chnh lu.
Do khng c vnh i chiu cng sut c th tng ln ng k p
dng c cho cc my pht ba pha cng sut t 200 300 MW.
Tuy nhin nhc im ca loi ny l cng sut ch to vn b
gii hn, do tia la vnh trt sut hin khi c cng sut ln (cn
c vnh trt a in vo stato). Ngoi ra hng s qun tnh c
tr s khong ( 0,3- 0,4s).
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3) H thng kch t dng my pht kch t xoay chiu khng vnh
trt:
TK
FU
Hnh 2.3 - H thng my pht kch t xoay chiu khng vnh
trt.
Mt trong cc phng php c s dng rng ri hin nay l
phng php dng my pht in xoay chiu khng vnh trt
(h thng kch t khng vnh trt).
Trong h thng kch t ny ngi ta dng mt my pht in
xoay chiu 3 pha quay cng trc vi my pht in chnh lm
ngun cung cp. My pht xoay chiu kch t c kt cu c bit:
Cun kch t t stato, cn cun dy 3 pha li t rto. Dng
in xoay chiu 3 pha to ra my pht kch thch c chnh lu
thnh dng mt chiu nh mt b chnh lu cng sut ln cng
gn ngay trn trc rto ca my pht. Nh vy m cun dy kch
t ca my pht in chnh c th nhn c ngay dng in
chnh lu khng qua vnh trt v chi than. cung cp dng
in mt chiu ca my pht kch thch (t stato) m ngun
cung cp ca n c th l ngun mt chiu bng Ac-qui hoc mt
ngun xoay chiu khc bt k thng qua chnh lu c hoc khng
c iu khin.
Tc ng ca h thng t ng iu chnh kch t c t trc
tip vo ca iu khin ca b chnh lu, lm thay i dng kch
t ca my pht in kch thch, tng ng vi mc ch iu
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chnh in p pht ra ca my pht. Nh vy hon ton khng c
vnh trt a in vo roto cng xut ch to khng b hn ch,
ngoi ra do ni trc tip hng s thi gian cng gim i ng k
(0,1 0,15s).
4) H thng kch t xoay chiu dng ngun chnh lu c iu
khin.
Hnh 2.4 - H thng kch t chnh lu c iu khin
H thng ny cho php to ra hng s c qun tnh rt nh 0,02
0,04s nh kh nng iu chnh trc tip dng kch t (chy quacc Thyristor) i vo cun dy roto my pht in ng b. Hin
nay ti cc nh my pht in ch yu s dng loi h thng kch
t ny. Hng s qun tnh nh l iu kin quan trng cho php
nng cao cht lng iu chnh in p v tnh n nh.
TK
F
U
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 31
2. La chn phng n
Theo yu cu ca n vi cu h nh l MF3, cng sut P =
125kW, U = 380/220 (V), s dng my pht ph xoay chiu 3 pha,
Ukt = 100V, Ikt = 6(A), em tnh chn s dng H thng my pht
kch t xoay chiu, dng iu chnh kch t chnh lu c iu khin.Theo h thng s s t ng iu khin a dng in mt chiu
a vo cun dy kch t ca my pht kch thch. Phng php
iu khin kch t ny c nhng u im chnh sau:
Thit b n gin, r tin,
iu khin d dng,
c tnh iu chnh tt,
Hng s thi gian qun tnh v iu chnh nh, Thit b khng cn s dng vnh gp
3. S iu khin cho h thng kch t dng my phtin xoay chiu theo phng n la chn
Hnh 2.5 S iu khin kch t dng chnh lu iu khin tia3 pha dng h thng My pht kch t xoay chiu khng vnh
trt
K
A
B
C
Ikt
Ikt
FK F
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Chng 3 - Thit k v tnh ton mch ng lc
1. Chnh lu c iu khin ba pha
I. Chnh lu ba pha hnh tia c iu khin :
i a i b i c
TcTbTa
a b c
Z
Hnh 3.1 - Chnh lu ba pha hnh tia c iu khin.
Khi thay i gc m cc Thyristor s thay i c in p trn ph ti
v do thay i c dng in chnh lu qua ti.
Gi s cc s.. th cp MBA l :
ea = 2 E2sin
eb = 2 E2sin( - 23
)
ec = 2 E2sin( - 4 3
)
- Trng hp ti cm khng (khng xt dng gin on)
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SV: TB Trg. 33
Do nng lng tch lu trong phn cm nn khi mt Thyristor no
thng th qu trnh kho Thyristor b ko di. in cm cng
ln th qu trnh kho Thyristor cng di. Trong s chnh lu ba
pha hnh tia, khi mt Thyristor kt thc qu tr nh kho ko di m
Thyristor k tip cha c xung m th dng in ph ti b gin
on. Trng hp ngc li, khi mt Thyristor cha kt thc qutrnh kho ko di m Thyristor k tip c xung m th dng in
ph ti s lin tc.
Vy, ch lm vic v c im chuyn mch ca s chnh lu
c iu khin hnh tia khi gc m 0 khng nhng ph thuc vo
tnh cht ca ph ti, in cm ca ngun m cn ph thuc c vo
gc m.
Vi ti cm khng c hai ch dng in :
- Gin on : khi tr s t cm L nh v gc m6
ln.
- Lin tc : khi gc m6
khng ph thuc vo tr s in
cm hoc khi gc m6
vi tr s in cm ln. Vi L =
th dng in ti s lin tc khng ph thuc vo tr s gc m.
Khi t cm ca ngun c b qua (H nh b) Lng = 0 th l
chuyn mch tc thi. in p trung bnh trn ph ti c tnh :
U0 =32
1
d.sinE2
35
6
2 = 22
63E
= 1,17E2
Khi t cm ngun Lng 0 th l chuyn mch c qu trnh
(Hnh c) vi gc trng dn = t. in p chnh lu tc thi
nh phn tch l mt ng cong phc tp hn do c s gim
in p lc trng dn v in p trung bnh trn ph ti c tnh
:
U0 =2
ba ee
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SV: TB Trg. 34
eo ea eb ec
o t
o t
to
o t
eo ea eb ec
eoea eb ec
iia ib icic
a)
b)
c)
d)
Hnh 3.2 - Chnh lu c iu khin hnh tia ba pha vi ti c cm
khng.
Lng gim in p trung b nh (phn gch car) U l :U =
2
3 Ong IL
Khi xy ra hin tng trng dn c hai Thyristor thng, hai ngun
tng ng b ngn v in p chnh lu nh hn so vi trng hp l
tng Lng = 0.
UO = UcosE
22
63
II. Chnh lu cu ba pha iu khin i xng
A B C A
t1 t2 t3 t4 t5 t6 t7
Uf
0
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SV: TB Trg. 35
Chnh lu cu ba pha c s nguyn l nh hnh. Su Thyristor chia
lm hai nhm: nhm Cathode chung (T1, T
3, T
5) v nhm Anode chung
(T2, T4, T6).
Xt s lm vic ca s mt s khong thi gian :
Khong6
3
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SV: TB Trg. 36
Trong khong ny cc sut in ng ngun c quan h ea > ec >
eb. Vi nhm Cathode chung, T1 c th Anode dng cao nht
nn nu c xung m (gc m ) th T1 s thng, dn ti th
Cathode ca T3 v T5 cao hn th Anode ca chng v cc
Thyristor T3 v T5 b kho do phn p ngc.
Vi nhm Cathode chung, T6 c th m thp nht nn nu c
xung m (gc m) th T6 s thng, dn ti th Anode ca T2 v
T4 cao hn th Cathode ca chng v cc Thyristor T2 v T4 b
kho do phn p ngc. Vy trong khong ny T1 v T6 dn dng
t ngun ti ti
Khong6
3
6
5
Trong khong ny ea > eb > ec . Vi nhm Cathode chung, T1 vnc th Anode dng cao nht nn vn thng, cn cc T3 v T5 b
phn p ngc nn b kho (d cho c xung m).
Vi nhm Anode chung, T2 by gi c th Cathode m thp nht
nn nu c xung m th T2 s thng v khi T2 thng s t in
th Vc m thp nht vo Anode chung, dn n T6 ang thng
trc b phn p ngc v kho li. Dng in ph ti c
dn t ngun qua T1 , T2 . Khong
65
6
7
Trong khong ny eb > ea > ec. Vi nhm Cathode chung, T3 vn
c th Anode dng cao nht nn nu c xung m th s thng v
khi thng s t in th Vb dng cao nht vo Cathode chung,
dn n T1 ang thng trc b phn p ngc v b kho li
ngay (T5 vn kho).
Vi nhm Anode chung, T2 vn c th Cathode m thp nht nn
vn thng, cn cc T4 , T6 b phn p ngc nn vn kho (d c
xung m). Dng in ph ti c dn t ngun qua T3 v T2 .
Lp lun tng t cho cc khong tip theo :6
7
6
9
,6
9
6
11
,
611
613
, ... Ta c bng kt qu :
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SV: TB Trg. 37
Khong Thyristor c
cp xung
Cc Thyristor
thng
Chiu dng
in
in p ph
ti
6
63
T1 T1 v T6 a - ti b ea - eb
63
65
T2 T1 v T2 a - ti - c ea - ec
65
6
7
T3 T3 v T2 b - ti - c eb - ec
67
6
9
T4 T3 v T4 b - ti a eb - ea
69
6
11
T5 T5 v T4 c - ti - a ec - ea
611 6
13 T6 T5 v T6 c - ti - b ec - eb
Gi tr tc thi ca in p trn ph ti UO = VP - VN chnh l hiu cc
gi tr tc thi ca cc sut in ng hai pha ang cp in cho ph
ti. l hiu cc gi tr tc thi gia sut in ng ca pha dng
nht v sut in ng ca pha m nht hay ni cch khc l khong
cch thng ng gia hai ng bao trn cng v di cng ca cc
sut in ng xoay chiu ba pha.Gi tr trung bnh ca in p chnh lu l :
UO = 6
d.sinE2
65
6
22
1=
cosE
22
63= 2,34E2cos .
in p ngc t ln mi Thyristor c gi tr cc i :
Ung.max = 6 E2 = 2,45E2 .
Dng in ph ti ph thuc vo bn cht ph ti v c gc m.
III. Chnh lu cu ba pha iu khin khng i xngNguyn l lm vic ca s ny cng tng t nh s cu i
xng. iu cn lu l khi cc Thyristor c phn p thun m mun
dn thng th phi cp xung iu khin, cn cc Diode th c phn p
thun th dn thng.
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SV: TB Trg. 38
Khong6
63
:
ea > ec > eb . Nhm Diode mc chung Anode chung s c D6 dn
thng v n c th Cathode thp nht. Nhm Thyristor mc
Cathode chung c T1 vi th Anode cao nht nn nu c xung
m th n s thng. Thyristor T1 v Diode D6 thng s cho dngi0 chy qua ph ti. Diode D6 thng lm th Anode ca cc
Diode D2 v D4 l VB nn chng b phn p ngc.
Khong6
3
6
5
ea > eb > ec . Th Anode ca Diode D2 by gi l Vb > Vc nn D2
thng. Do D2 thng nn th Vc t ln Anode ca D6 lm D6 b phn p ngc v kho. Dng in ph ti c dn qua
Thyristor T1 v Diode D2.
Khong6
5
6
7
D4
D6
D2
T1
T3
T5
LR
A B C A
X1
X3
X5
t1 t2 t3 t4 t5 t6 t7
Ud
Uf
T1
T3
T5
D4
D6
D4
0
Hnh 3.4 - Chnh lu cu ba pha iu khin khng i xnga- s ng lc, b- gin cc ng cong, Ud- in p ti khi
gc m = 60o
A B C
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SV: TB Trg. 39
eb > ea > ec - trong khong ny, Thyristor T3 c phn p thun
nn khi c xung m th T3 s thng dn n th Vb > Va t ln
Cathode ca T1 lm T1 kho. Th Vc thp nht t ln Anode ca
cc Diode D4, D6 (do Diode D2 dn) nn D4 v D6 kho. Dng
in ph ti c dn t ngun qua T3 v D2.
Khong6
7 69
eb > ec > ea - do Diode D2 thng nn t th Vc > Va ln Anode
ca D4 nn D4 thng. Diode D4 thng t th Va thp nht ln
Anode ca Diode D2 nn D2 kho. Thyristor T3 thng trc
nn t th Vb ln nht ln Cathode ca cc Thyristor T5 nn hai
Thyristor ny khng th thng.
L gii mt cch tng t ta c khong thng v kho ca cc
Thyristor v Diode.
Nhm Diode mc Anode chung s to ra in p trn ti U0D l
ng bao di ca cc sut in ng ba pha. Nhm Thyristor mc
Cathode chung s to ra in p trn ti UOth l ng nt m trn
cng. Nh vy gi tr tc thi ca in p trn ti s l :
U0 = UOD + U0th
Vi: U0D =263
E2cos
U0th = -263
E2
Vy nn ta c : U0 = U0D + U0th =263
E2 ( 1+ cos )
2. La chn s chnh lu
Sau khi phn tch v nh gi v cc phng php chnh lu c iu
khin ba pha, t cc u nhc im ca cc s , Vi ti l mch kch
t ca my pht in Diezel th s chnh lu tia ba pha c iu khin
l hp l hn c bi l cng sut ca mch kch t khng ln lm. Vic
iu khin chnh lu cu mt pha khng i xng so vi cc phng
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SV: TB Trg. 40
php chnh lu khc l n gin m cht lng in p ra cng tng
i tt
Hnh 3.5 S mch ng lc
3. Tnh chn Tiristor
Ta chn da vo cc yu t c bn dng ti, s chn, iu kin
to nhit, in p lm vic, cc thng s c bn cc van c tnh nh
sau :
in p ngc ln nht m Tiristo phi chu:
u
dnv2nvnmax K
UKUKU
Trong : Ud : in p ti
Knv: h s in p ngc (Knv = 6 )
Ku : h s in p ti (Ku = 263
)
33,2093100*
KU
KUu
dnvnmax
2
(V)
Nh vy Unmax = 210 (V)
in p ngc ca van cn chn.
K
A
B
C
Ikt
Ikt
FK F
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SV: TB Trg. 41
Unv = KdtUnmax = 1,8*210 = 376,8 (V)
KdtU : H s d tr in p (chn KdtU = 1,8)
Dng in lm vic ca van c tnh theo dng in hiu dng:
Ilv =3
KTI =3
6= 3,464(A)
Vi dng in lm vic tnh ton nh trn l kh b, nn chn vankhng cnh to nhit. Vi iu kin dng in nh mc ca van cn
chn:
Im = KiIlv = 10*3,464 = 34,6(A)
Ki : H s d tr dng in Ki = 10)
T cc thng s Unv , Idmv ta chn 3 Thiristo loi HT40/08OJ4 c cc
thng s sau:
- in p ngc cc i ca van : Un = 800(V)
- Dng in nh mc ca van : Idm = 40(A)
- nh xung dng in : Ipik= 900(A)
- Dng in ca xung iu khin : Idk= 110(mA)
- in p ca xung iu khin : Udk= 3(V)
- Dng in r : Ir = 6(mA)
- Dng in t gi : Ih = 200(mA)
- St p ln nht ca Tiristo trng thi dn: U =1.65(V)
- Tc bin thin in p :
dtdU
1000(V/s)
- Thi gian chuyn mch : tcm =150s
- Nhit lm vic cc i cho php : Tmax =1250C
4. Tnh bin p ng lc
Vi cc tnh ton c tr nh by cc phn trn, th my bin p
ng lc c chn dng trong n ny l bin p 3 pha, 3 tr vi cc
tnh ton c tr nh by di y. V bin p c cng sut nh, nn
c thit k l my bin p kh, lm mt bng i lu t nhin.
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SV: TB Trg. 42
4.1. in p chnh lu khng ti
Udo = Ud + U v + Uba + Udn
Vi: Ud - in p chnh lu = Ukt = 100V
Uv- st p trn cc van: Uv = 1.65V;Uba = U r + Ul - st p bn trong bin p khi c
ti, bao gm st p trn in trUr v st p trn
in cm Ul. Chn = 10%=10V
Udn = Rdn.Id =(.l/S).Id - st p trn dy ni; c th
b qua
Vy Udo = 100 + 1,65 + 10 + 0 = 116,5 (V)
4.2. Xc nh cng sut ti a ca ti v d vi ti chnh lu xc
nh
Pdmax = Udo . Id
Pdmax = 116,5 . 6 = 699(W) ly trn = 700W
4.3. Cng sut bin p ngun cp c tnh
Sba = ks . Pdmax
Sba = 700.1,345 = 941.5 (W)
Vi: Sba - cng sut biu kin ca bin p [W];
ks - h s cng sut theo s mch ng lc,
Pdmax - cng sut cc i ca ti [W].
4.4. Tnh ton s b mch tTit din tr QFe ca li thp bin p:
Theo cng thc kinh nghim
2cmf.m
SkQ baQFe
271173
59410101 cm,
,,
m
S,Q baFe
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SV: TB Trg. 43
4.5. Tnh ton dy qun bin p.
Theo kinh nghim s vng dy ca mi cun c tnh Gn
ng c th tnh nu coi f = 50 Hz, chn B = 1Tsla lc
FeQ
U.W 45 (vng)
S vng dy ca mt cun dy s cp W1
S vng dy ca mt cun dy th cp W2
Vi
Tnh dng in ca cc cun dy.
Tra bng xc nh dng in cc cun dy dng in s v
th cp ta c
Dng in th cp mi cun dy
I2 = k2.Id = 0,58.6 = 3,48 (A)
Dng in s cp mi cun dy
I1 = k1.kba.Id =0,82.0,262.6= 1,289 =1,3 (A)
Vi kba = U2/U1 = 99,6/380 = 0,262
Tit din dy dn s cp
J - mt dng in trong bin p: chn = 2,5 [A/mm2]
Tit din dy dn th cp
(vng),
.Q
U.W
Fe
5597117
2204545 1
1
(vng)2537117
6994545 22
,
..
Q
U.W
Fe
)V(,,
,
k
UU
U
d 699171
511602
)mm(,.
,
j
IS
Cu
21
1520
52
31
)mm(,.
,
j
IS
Cu
22
241
52
53
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SV: TB Trg. 44
ng knh dy qun, chn dy qun trn, c tnh:
ng knh dy qun s cp
ng knh dy th cp
Trong : d - ng knh dy qun.
SCu tit din dy qun.
)mm(,
,.S
d
Cu
810
52044 11
)mm(,,.S
d Cu 3314144 2
2
Cu
Sd
4
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SV: TB Trg. 45
4.6. Tnh kch thc mch t
Hnh 3.6. Li thp bin p - cc kch thc c bn ca mch t
Do Bin p c cng sut nh, nn chn tr hnh ch nht, vi cc
kch thc QFe = a . b. Trong a - b rng tr, b - b dy tr
Chn l thp c dy 0,35mm
Din tch ca s cn c l Qcs = 2.(Qcs1 + Qcs2 ), chnh l
din tch do cc cun dy chim ch trong ca s:
Chn kl = 2,5
Qcs1 =kl.W1.SCu1 = 2,5.559.0,52 = 726,7 [mm2]
Qcs2 =kl.W2.SCu2 = 2,5.253.1,4 = 885,5 [mm2]
Vy Qcs = 2(726,7+ 885,5) = 3224,4 [mm2] =32,244 [cm
2]
Chn kch thc ca s c h nh dng kt cu mch t thhin nh h nh 3.10 vi cc h s ph c chn (theo kinh
nghim, do l bin p 3 pha, ba tr hnh E)
m = h/a = 2,5; l = b/a = 1
h=a.m = 4,208.2,5 = 10,52(cm); vi
Vy chiu rng ton b mch t
C=2c +3a = 2.3,06 + 3.4,208 = 18,74 (cm)
Chiu cao mch t
)cm(,,Qabb.aQFeFe
20847117
)cm(,,
,
h
Q
cc.hQ
cs
cs 0635210
24432
b
hH
c
C
c
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 46
H = h + z.a = 10,52 + 2.4,208 = 18,96 (cm)
Vi thp t KT c dy t=0,35 mm, nn tng s l thp
cn c s l nt = b/t = 42,08/0,35 = 120,2; vy ly trn l 121
tm
4.7. Kt cu dy qun:
Dy qun c b tr theo chiu dc tr, mi cun dy c
qun thnh nhiu lp dy. Mi lp dy c qun lin tc, cc
vng dy st nhau. Cc lp dy cch in vi nhau bng cc ba
cch in. Nh tnh trn, chn dy qun tit din trn
S vng dy 1 lp th cp W2l:
Vi: dn - ng knh dy qun k c cch in;
hg - khong cch cch in vi gng; chn hg = 2.dn.
S lp dy qun th cp: sld2= 253/68 =3,72 = 4 lp
S vng dy 1 lp s cp
S lp dy qun s cp: sldt= 559/103 =5,42 = 6 lp
B dy ca mi cun dy Bdct = d. sld + cd.sld
B dy cun dy s cp: Bdct = dt. sldt + cd.sldt=1.6 +
0,1.6 = 6,6 (mm)
B dy cun dy th cp: Bdc2 = d2. sld2 + cd.sld2=1,5.4 +0,1.4 = 6,4 (mm)
Tng b dy Bd 1 cnh cc cun dy ca 1 tr
Bd = Bdc1 + Bdc2 +...+ cdt + cd2cd + cdn
= 6,6 + 6,4 +0,5.3 = 14,5 (mm)
)vng(,,
,.,
d
hhW
n
g
l 136851
51221052
)vng(,.,
d
hhW
n
g
l 21031
1221051
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SV: TB Trg. 47
Nhn xt: tng chiu dy chim ch ca cc cun dy trong ca
s: 2Bd = 14,5.2=29 mm v nh hn c= 30,6 cm tnh ton l
chp nhn c i vi lm mt v cch in
4.8. Khi lng st.
MFe = VFe.mFe (kg)
Trong : VFe - th tch khi st [dm3];
VFe = (H.C 2.Qcs ).b
= (1,896.1,874 2.0,32244).0,4208 = 1,223[dm3]
mFe = 7,85 kg/dm3
vy MFe = VFe.mFe = 1,223.7,85 = 9,6 (kg)
4.9. Khi lng ng.
MCu = VCu.mCu (kg)
Vi: VCu = SCu.l - th tch khi ng ca cc cun dy[dm3];
SCu - tit din dy dn [dm2];
l = W.Dtb - tng chiu di ca cc dy dn [dm];
mCu = 8,9kg/dm3
Dtb= (Dt + Dn)/2 - Chu vi trung bnh ca cun dy
Trong : Dt,Dn - chu vi trong v ngoi ca cun dy.
Khi lng ng qun th cp
Chu vi trong ca cun dy th cp c tnh:
D2 = DFe + 2cd2 = 4.(0,4208 + 0,005)=1,7032 (dm)
DFe - chu vi tr st;
cd2 - cch in trong cng vi li.
Chu vi ngoi ca cun dy th cp c tnh gn ng:
Dn2 = D2 + 4.(d + cd).sld= 1,7032 + 4.0,015.4 = 1,9132
(dm)
Vy chu vi trung bnh cun dy th cp trn 1 tr:
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SV: TB Trg. 48
D2tb = (D2 + D n2)/2 = (1,7032 + 1,9132) /2 = 1,808
(dm)
Chiu di dy qun th cp l = W. Dtb = 253. 1,808 =
457,42 (dm) ly = 470 (dm) d phng cho cc u
dn u ni ra ngoi
Vy th tch khi ng ca cun dy th cp l VCu =
SCu.l =470.0,00014 = 0,0658 (dm3)
Vy khi lng ng qun th cp s l:
MCu2 = VCu2.mCu = 0,0658x 8,9 = 0,586 (kg)
Tng khi lng ng cc qun th cp s l:
3. MCu2 = 3.0,586 = 1,76 (kg)
Khi lng ng qun s cp
Chu vi ngoi ca cun dy s cp (chnh l chu vi ngoi
ca bi ng dy trn 1 tr) c tnh gn ng:
Dn1 = Dn2 + 4.(d + cd).sld= 1,9132 + 4.0,01.6 = 2,1532
(dm)
Vy chu vi trung b nh qun dy s cp s l
Dtb1= (Dn2 + D n1)/2 =(1,9132 + 2,1532)/2 = 2,0332(dm)
Chiu di dy qun s cp s l l = W.Dtb =599.
2,0332=1217(dm) ly = 1230 (dm) d phng cho
cc u dn u ni ra ngoi
Vy th tch khi ng ca cun dy th cp l VCu =
SCu.l =1230.0,000052=0,06396 (dm3)
Tng khi lng ng cc qun s cp s l:MCu1.3 = VCu1.mCu.3 = 0,06396.8,9.3=1,71 (kg)
4.10. Tnh tng st p bn trong bin p.
in p ri trn in tr:
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SV: TB Trg. 49
dr IW
WRRU
2
1
2
12
Trong :
R1, R2 - in tr thun ca cc cun dy s v th cp c
tnh: R = .l/S
Vi: = 0,0000172 mm - in tr sut ca ng;
l, S - chiu di v tit din ca dy dn [mm, mm2];
Id - dng in ti mt chiu [A].
in tr thun ca cun dy s cp
R1=1,72.10-5
.123000/0,52 = 4,068
in tr thun ca cun dy th cp
R2=1,72.10
-5
.47000.1,4=1,13 Vy St p ri trn in tr l
in p ri trn in khng:
Ux = mf. X.Id/
Trong : mf- s pha bin p
Vi: = 314 rad.
Vy Ux = mf. X.Id/=3.0,153.6/=2,996 = 0,876(V)
4.11. in tr ngn mch my bin p
4.12. Tng tr ngn mch my bin p:
4.13. in p ngn mch phn trm ca my bin p:
)(,...
.,
,Xn
1530103143
006400066000050
10520
0210402538
722
9610684
559
253131
2
1
2
1
2
2,,.,r*
w
wrrnm
9711530961 2222 ,,,xrz nmnmnm
)V(,,,U r 8116599
253068413171
2
72
2
2
103
21
8
BdBd
cdh
R
WXbk
n
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 50
4.14. Dng in ngn mch my bin p:
5. Tnh chn cc thit b bo v mch ng lc
5.1. S mch ng lc c cc thit b bo v:
Hnh 3.7 - S mch ng lc c cc thit b bo v
5.2. Bo v qu nhit cho van bn dn
Khi lm vic vi dng in chy qua tn van c st p, do c tn
hao cng sut P, tn hao ny sinh ra nhit t nng van bn dn.
Mt khc van bn dn ch c cho php lm vic di nhit cho
php Tcp no , nu qu nhit cho php th cc van bn dn s
b ph hng . van bn dn lm vic an ton, khng b chc thng
v nhit, ta phi chn v thit k h thng to nhit hp l.
Tuy nhin thit k ch to ca nh sn xut van cho php, vi vic
chn h s Ki = 10, v tn tht cng sut tnh ton trn 1 van
P = U.Ilv = 1,65*3,464 = 5,7(W), l rt nh
)A(,
,z
UI
nm
dm
nm 7650
971
1002
%,,,.
U
zIU
dm
nmdm
nm8111180
100
9716100
2
00
A
B
C
F
T2T
T
r
c c c
r rUkt
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 51
v Ilv = 3,43 (A)
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 52
iu chnh v tr xung iu khin trong phm vi na chu k dng ca
in p t trn ant - catt Thyristor.
To c cc xung iu kin m c Thyristor ( y xung iu
khin c bin 5V, rng xung 125s, dng xung iu khin 300
mA).
Trong thc t ngi ta thng dng hai nguyn tc iu khin: thng
ng tuyn tnh v thng ng arccos thc hin vic iu chnh v
tr xung trong na chu k dng ca in p t trn Thyristor.
1. Nguyn tc iu khin thng ng arccos
Theo nguyn tc ny ngi ta dng hai in p :
in p ng b uR vt trc in p Anode - Cathode
Thyristor mt gc2
R
E(nu uAK = Asint th uR = Bcost ).
in p iu khin uK l in p mt chiu, c th iu chnh
c bin theo hai hng (dng v m).
Tng i s uR + uK c a n u vo ca khu so snh.Khi uR + uK = 0 ta nhn c mt xung u ra ca khu so
snh.
Nguyn tc iu khin thng ng arccos c s dng khi thit
b chnh lu i hi cht lng cao.
2. Nguyn tc iu khin thng ng tuyn tnh.
Udf
Urc
Udk
Ud
Xdk
t
t
t
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 53
Theo nguyn tc ny, ngi ta cng dng hai in p :
in p ng b uRC, c dng rng ca, ng b vi in p trn
Anode - Cathode Thyristor.
in p iu khin uK, l in p mt chiu c th iu chnh
c bin .Tng i s ca uRC + uKc a n u vo ca mt khu so
snh.
Nh vy bng cch lm bin i uKngi ta c th iu chnh c
thi im xut hin xung ra, tc l iu chnh c gc .
2. Chn cc khu trong mch iu khin.
1. S khu ng pha dng b khuch i thut ton :
ng pha So snh To xung
Hnh 4.2 - S khi mch iu khin
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 54
r 1
ua t
b a
a
o a 1
r 3
u r c
b
d r 2
o a 2
r 4 t r
c
Hnh 4.3 - S khu ng pha dng b khuch i thut ton.
t
t
t
UA
UB
UdkUrcHnh 4.4 - ng cong in p
Dng xung u ra khu ng pha dng KTT. Nguyn l hot ng
ca s : bin p iu khin c u ngc cc tnh nh hnh v.
Khi in p UAT dng th bn th cp my bin p c in p m
UA v ngc li. in p ny qua u vo o ca khuch i thut
ton OA1 cho ta in p UB c hnh dng ch nht i xng. Khi UA
m th bin ca in p ti B l UB = +Umax , Diode D m s dn
dng qua in tr R2 v bin tr R3. Khi Transistor c in p t
trn cc baz c gi tr dng nn Transistor kho v t C bt u
np. Cc in tr R2 , R3 v t C hp li thnh mt b tch phn cho
ra in p rng ca trong mt na bn k dng ca in p U AT.
Khi UAT m th in p ti A l UA c gi tr dng qua OA1 cho ta
in p ti im B c bin UB = -Umax . Diode D kha v
Transistor TR m lm ngn mch hai u ca khuch i thut ton
OA2, in p u ra ca OA2 l bng 0, khi Transistor m v t
C phng in qua Transistor.
2. B so snh dng khuch i thut ton :
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SV: TB Trg. 55
u k
u r c r 1
r 2o a
u r a
Hnh 4.5 - S so snh dng KTT .
S so snh dng khuch i thut ton vi hai tn hiu vo URC
v UK tri du nhau c a ti u vo khng o ca khuch
i thut ton. u ra x o trng thi khi hai tn hiu u vo bng
nhau.
o
o
u
u r c
t
u k
t
Hnh 4.6 - Dng xung u ra khu so snh.
3. Chn khu khuch i to xung.
Khu khuch i v to xung c nhim v to ra xung iu khin
ph hp m Thyristor, do phi p ng c cc yu cu sau :
Xung phi rng .
Cng sut ca xung phi ln.
Sn trc ca xung phi c dc thng ng m bo thi
gian tc ng.
m bo cch ly gia mch iu khin v mch ng lc.
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SV: TB Trg. 56
ru v
C2
D3
+e
b a x
d
t
tt
R6
Hnh 4.7 - S tng KTT mc theo kiu Darlington
Trong s ny dng hai Transistor TR1 v TR2 mc theo s
Darlington (hnh 47). Thng thng ngi ta dng van ngc tng
khuch i bi v loi ny c dng in r nh hn so vi van thun.
Mch vi phn trn s c nhim v hn ch rng xung iukhin , m bo cho Transistor khng b t nng trong thi gian
qu lu. Do din tch cnh tn nhit ca Transistor v kch thc dy
s cp ca bin p xung c gim i mt cch ng k. Trong s
ny Transistor ch m cho dng in chy qua trong khong thi
gian np t, nn dng in hiu dng ca chng b hn nhiu ln.
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg. 58
Tng hp S mch iu khin chnh lu vi cc khu gii thiu
Hnh 4.8 - Mch iu khin kch t dng chnh lu iu khin tia 3 pha
D3
U
R1A
A1+
- B
R2
R3D1
Tr1
CA2
-
+
C1
Uk
R5
R4
A3-
+
D
TA
+15V
C2
R6
D2
D3
U
R1A
A1+
- B
R2
R3D1
Tr1
CA2
-
+
C1R5
R4
A3-
+
D TB
+15V
C2
R6
D2
T
D3
U
R1A
A1+
- B
R2
R3D1
Tr1
CA2
-
+
C1R5
R4
A3-
+
D
AT
+15V
C2 R6
D2
T3
T2
R
L
A B C
A
B
C
O
TCT3
T2
T3
T2
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg.60
3. Tnh bin p xung
Chn vt liu lm li st l Ferit HM. Li c dng h nh xuyn, lm
vic trn mt phn ca c tnh t ho c : B = 0,3 (T) ; H = 30
(A/m) khng c khe h khng kh.
T s bin p xung : thng m = 2 - 3, chn m = 3
in p cun th cp my bin p xung : U2 = Uk= 3 (V)
in p t ln cun s cp my bin p xung :
U1 = m.U2 = 3*3 = 9 (V)
Dng in th cp my bin p xung : I2 = Ik= 0,11(A)
Dng in s cp my bin p xung :
03703
11021
,,
m
II (A)
t thm trung bnh ca li st :
3
60
tb 10.830*10.25,13,0
HB
Trong : 0 = 1,25.10-6 (H/m) l t thm ca khng kh.
Th tch li thp cn c :
2
11xxotb
B
I.U.S.t.
=l.Q=V
6
2
663
10927030
037091501016710251108
.,,
,..,....,..V (m
3)
V = 0,927 (cm3)
Chn mch t c th tch V = 1,4 (cm3). Vi th tch ta c cc
kch thc mch t nh sau:
a = 4,5 (mm)
b = 6 (mm)
Q = 0,27 (cm2) = 27 (mm2)
d = 12 (mm)
D = 21 (mm)
Chiu di trung bnh mch t : l = 5,2 (cm)
Nh vy ta c hnh dng mch t ca my bin p xung :
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SV: TB Trg.61
b
d D
Hnh 4.10 - Mch t ca my bin p xung S vng dy s cp bin p xung :
Theo nh lut cm ng in t :
x
111 tB
Qw=dtdB
.Q.w=U
186102730
1016796
6
1
1
.*,
.*
Q.B
tUw x (vng)
S vng y th cp :
623
18612
m
ww (vng)
Tit din dy qun s cp :
006206
0370
1
1
1.
.
J
IS (mm2)
Chn mt dng in J1 = 6 (A/mm2)
ng knh dy qun s cp :
0850143
06204
4 11 ,,
,*S.
d (mm2
)
Chn d1 = 0,1 (mm2) nu k c cch in d1cd = 0,13 (mm
2)
Tit din dy qun th cp :
027504
110
2
2
2.
.
J
IS (mm2)
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg.62
Chn mt dng in J1 = 4 (A/mm2)
ng knh dy qun th cp :
1870143
027504
42
2 ,,
,*S.
d (mm2
)
Chn d2 = 0,19 (mm2) nu k c cch in d2cd = 0,22
(mm2)
Kim tra h s lp y:
dwdwd
4/dwSwS
K 2221
21
22211
ld
043,012
62*22,0186*13,0K
2
22
ld
4. Tnh tng khuch i cui cng
D2
R6Tr3
D3
Tr2
+ E
BAX D4T
C2
Hnh 4.11 - S tng khuch i cui cng
Chn Tranzitor cng sut loi Tr3 loi 2SC9111 lm vic ch
xung c cc thng s :
Tranzitor loi npn, vt liu bn dn l Si
in p gia Colecto v Baz khi h mch Emito : UCB0 = 40
(V)
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg.63
in p gia Emito v Baz khi h mch Colecto : U EB0 = 4 (V)
Dng in ln nht Colecto c th chu: Icmax = 500 (mA)
Cng sut tiu tn Colecto : Pc = 1,7 (W)
Nhit ln nht mt tip gip : T1 = 1750C
H s khuch i : = 50
Dng in lm vic ca Colecto : Ic3 = I1 = 36,7 (mA)
Dng in lm vic ca Baz : 734050
736
3
3,
,II CB (mA)
Ta thy rng vi loi Tiristor chn c cng sut iu khin
kh b : Uk= 3 (V) : Ik= 0,11 (A) nn dng Colecto Baz
ca Tranzito Ir3 kh b, trong trng hp ny ta c th khng cn
Tranzito Ir2 m vn c cng sut iu khin Tranzito.
Chn ngun cp cho bin p xung : E = +12 (V) . Vi ngun E =
12 (V) ta phi mc thm in tr R10 ni tip vi cc Emito ca
IE3
8210736
9123
1
10
.,I
UER ()
Tt c c Diod trong mch iu khin u dng loi 1N4009 c cc
tham s :
Dng in nh mc : Im = 10 (mA)
in p ngc ln nht : UN = 25 (V)
in p cho Diod m thng : Um = 1 (V)
5. Chn t C2v R6
in tr R6 dng hn ch dng in a vo Baz ca Tranzito
T3 chn R6 tho mn iu kin :
1316107340
543
3
6,
.,
,
I
UR
B
(K)
Chn R6 = 6,2 (K)
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SV: TB Trg.64
Chn C2R6 > tx = 167(s). Suy ra9
2R
tC x
02701026
16732 ,.,C (F)
Chn C2 = 0,03(F)
6. Tnh chn tng so snh
R4
A3R5
Hnh 4.12 - Tng so snh
Khuch i thut ton chn R4 = R5 > 12101
123
.I
U
v
v (K)
Trong , nu ngun nui Vcc = 12 (V) th in p vo A3 l Uv 12 (V)
Dng in vo c hn ch Ilv < 1 (mA)
Do ta chn R4 = R5 = 15 (K) khi dng vo A3 :
801015
123
,.
I maxv (mA)
7. Tnh chn khu ng pha
in p ta c hnh thnh do s np ca t C1, mt khc m
bo in p ta c trong 1 na chu k in p li l tuyn tnh th
hng s thi gian t np c chn T1 = R3C1 = 0,01 (s)
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg.66
Chn in p xoay chiu ng pha : UA = 9 (V)
in tr R1 hn ch dng in i vo khuch i thut ton A1
thng chn sao cho dng vo khuch i thut ton IV < 1 (mA) .
Do
3
31109
101
9.
.I
UR
V
A
()
Chn R1 = 10 (K)
8. To ngun nui
Ta cn to ra ngun in p 12 (V) cp cho bin p xung, nui IC,cc b iu chnh dng in
C4470F
C6470F
7812
7912
A
C
a
b
c
a
b
c
+ 12
- 12
0
C4470F
C6470F
Hnh 4.14 - S mch to ngun
Ta dng mch chnh lu cu 3 pha dng Diod, in p th cp mybin p ngun nui :
15342
122
,,
U (V)
Ta c: U2= 9 (V)
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i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht
SV: TB Trg.67
n nh in p ra ca ngun nui ta dng 2 vi mch n p 7812
v 7912 cc thng s chung ca vi mch ny :
- in p u vo : Uv = 0 35 (V)
- in p u ra :
Ura = 12 (V) vi IC 7812
Ura = -12 (V) vi IC 7912
- Dng in u ra : Ira = 0 1 (A)
- T in C4, C5 dng lc thnh phn sng hi bc cao
- Chn C4 = C5 = C6 = C7 = 470 (F) ; U = 35 (V)
9. Tnh chn Diod cho b chnh lu ngun nui
Dng in hiu dng qua Diod :
0502
0730
2
2 ,,I
I HD.D (A)
in p ngc ln nht m Diod phi chu
UN.Max = 6 .U2 = 6 .9 = 22 (V)
Chn Diod c dng in nh mc:
Im Ki.ID = 10*0,05 = 0,5 (A) Chn Diod c in p ngc ln nht :
UN = kU .UNmax = 2*22 = 44 (V)
Chn Diod loi K208A c cc thng s :
Dng in nh mc : Im = 1,5 (A)
in p ngc ln cc i ca Diod : UN = 100 (V)
10. Tnh khu phn hi in p
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SV: TB Trg.68
R
Hnh 4.15 - S khu phn hi in p
1) Chn Diod chnh lu l loi K208A c cc thng s :
Dng in nh mc : Im = 1,5 (A) in p ngc ln cc i ca Diod : UN = 100 (V)
2) Tnh in p iu khin ti nh mc
Ta c in p :
UR = kuU2f= 2,34*9 = 21,1(V)
UrcUdk
t2
Hnh 4.16
Theo s chnh lu ta c:
cosUU 0DKT
uD kUU 20 (Ku : H s chnh lu Ku =
2
63)
UKT = U2kucos
cos = 8550
2
63100
100
2
,kU
U
u
KT
Vy = arcos0,855 = 31,30
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SV: TB Trg.69
Tnh in p iu khin ti nh mc :
Theo th ta c :
180U
U
rc
dk
Trong : Urc = 12(V)
12180
331
180
,UU r cdk
= 2,09 (V)
Nh vy thun tin cho vic iu chnh in p ta chn R l
loi bin tr R = 1(K)
Hnh 4.17 S to in p iu khin cho chnh lu iu
khin
A
BC
UK
Ut
Uph
+ +
-_
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SV: TB Trg.70
Kt lun
H thng my pht kch t la chn l mt h thng khng dng chi
than vnh trt v nh c m t Chng 2, y l mt h thng
n gin hn v ch to so vi cc h thng my pht kch t khc. Ni
bt nht l R-to my pht chnh v phn ng (Stator) ca my pht
kch t c ch to trn cng mt trc v quay theo tc ca ng
c ko Diesel v dng p kch t cm ng ra trong my pht kch thch
c a ngay vo cun kch t ca my pht thng qua b chnh lu
Diot gn trn cng trc Rto. cung cp dng in mt chiu vo
my pht kch thch (t stato), ngun cung cp ca n c th dng
ngun in mt chiu bng Ac-qui hoc mt ngun xoay chiu khc bt
k thng qua chnh lu c iu khin v y chnh l ngun chnh lu
c iu khin m n c thit k v tnh ton. Vic loi b vnh
trt khng nhng lm cho my pht n nh hn m cn lm gim i
cc chi ph vn hnh ca thit v lm tng tui th cho my.
Tc ng ca h thng t ng iu chnh kch t c t trc tip
vo ca iu khin ca b chnh lu, lm thay i dng kch t ca my
pht in kch thch, tng ng vi mc ch iu chnh in p pht ra
ca my pht. Nh vy hon ton khng c vnh trt a in vo
roto cng xut ch to khng b hn ch, ngoi ra do ni trc tip hng
s thi gian l rt nh (0,1 0,15s).
Vi cng ngh ch to van bn dn ngy cng hin i hn cng vi s
hp tc c lc ca in t s, cc h thng iu khin kch t ngy nay
c cht lng iu khin rt cao v c iu khin thng minh hn.
Vic cng nghip ho, hin i ho t nc ta nh hm nay l c s
ng gp quan trng v khng th thiu ca cc thit b iu khin in
t cng sut.
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SV: TB Trg.71
Li kt
L mt sinh vin, nn n thit k ca em s khng trnh khi nhng
sai st. V em mong cc sai st s nhn c s gp , dy bo v
cm thng ca cc Thy C v Nh trng n c hon thin
hn m cng l cng c thm kin thc cho c nhn em trong cng vic
sau ny. Em xin chn thnh Cm n cc Thy C v Nh Trng
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Ti liu tham kho
1. Ti liu hng dn thit k thit b in t cng sut.
TG. Trn Vn Thnh
2. in t Cng sut
TG. Nguyn Bnh
3. in t Cng sut v iu khin ng c in
TG. Cyril W. Lander
4. Phn tch & iu khin n nh H thng in
TG. L Vn t
5. Gio trnh My in - tp 1 & 2
TG. V Gia Hanh (Ch Bin)
6. Power System Stability & ControlTG. Prabha Kundur
7. Thit k my bin p in lc
TG. Phan T Th
8. Cm nang thc hnh vi mch tuyn tnh
TG. Hunh c Thng