Bài Tập Lớn Tổng Hợp Hệ Thống Điện Cơ

8/10/2019 Bi Tp Ln Tng Hp H Thng in C

1/72


2/72

- Gim dng in lm vic I xung di gi tr dng in duy tr IH.

- t mt in p ngc ln Tiristor (bin php thng dng)Khi t in p ngc ln Tiristor UAK< 0, hai mt ghp J1v J3b phn cc

ngc, J2by gi c phn cc thun. Nhng in t, trc thi im o cctnh U

AK, ang c mt ti P

1,N

1, P

2by gi o chiu hnh trnh, to nn dng in

ngc chy t katt v ant, v cc m ca ngun in p ngoi.Lc u ca qu trnh, t t0n t1, dng in ngc kh ln, sau J1ri J3

tr nn cch in. Cn li mt t in t b gi li gia hai mt ghp J 1v J3, hintng khuch tn s lm chng t dn i cho n ht v J2khi phc li tnh chtca mt ghp iu khin.

Trong cc s chnh lu trn, gi tr in p trung bnh mt chiu ra tiph thuc vo gc iu khin m ca Tiristor:

Ud= Ud0.cos

Do , khi thay i gc iu khin th ta s thay i c gi tr in p

trung bnh ra ti. Nu tng gi tr gc iu khin th in p trung bnh s gim,ngc li, gim th in p trung bnh s tng. Gi tr ln nht ca in p trungbnh ra ti l Ud0, ng vi gc =0.

Dng in trung bnh qua ti:

d

d

Z

UI vi 22 RXZ Ld

Trng hp trong mch ti c thm sut in ng phn khng:

d

d

Z

EUI

1.2 Gii thiu ng c mt chiuTrong nn sn xut hin i, ng c mt chiu vn c coi l mt loimy quan trng mc d ngy nay c rt nhiu loi my mc hin i s dngngunin xoay chiu thng dng.

Do ng c in mt chiu c nhiu u im nh kh nng iu chnh tc rt tt, kh nng m my ln v c bit l kh nng qu ti. Chnh v vy mng c mt chiu c dng nhiu trong cc nghnh cng nghip c yu cu c aov iu chnh tc nh cn thp, hm m, giao thng vn ti,cc nghnh cngnghip hay i hi dng ngun in mt chiu...

Bn cnh , ng c in mt chiu cng c nhng nhc im nht nhca n nh so vi my in xoay chiu th gi thnh t hn ch to v bo qunc gp in phc tp hn (d pht sinh tia la in)... nhng do nhng u im nitri ca n nn ng c in mt chiu vn c mt tm quan trng nht nh trongsn sut.1.2.1 Cu to ca ng c in mt chiu


3/72

ng c in mt chiu c th phn thnh hai phn chnh: phn tnh v phnng.1.2.1.1. Phn tnh

y l ng yn ca my, bao gm cc b phn chnh sau:+ Cc t chnh: l b phn sinh ra t trng gm c li st cc t v dy

qun kch t lng ngoi li st cc t. Li st cc t lm bng nhng l thp kthut in hay thp cacbon dy 0,5 n 1mm p li v tn cht. Trong ng c innh c th dng thp khi. Cc t c gn cht vo v my nh cc bulng. Dyqun kch t c qun bng dy ng bc cch in v mi cun dy u c

bc cch in k thnh mt khi tm sn cch in trc khi t trn cc cc t.Cc cun dy kch t c t trn cc cc t ny c ni tip vi nhau.

+ Cc t ph: Cc t ph c t trn cc cc t chnh v dng cithin i chiu. Li thp ca cc t ph thng lm bng thp khi v trn thncc t ph c t dy qun m cu ro ging nh dy qun cc t chnh. Cc t

ph c gn vo v my nh nhng bulng.+ Gng t: Gng t dng lm mch t ni lin cc cc t, ng thi lm v

my. Trong ng c in nh v va thng dng thp dy un v hn li. Trongmy in ln thng dng thp c. C khi trong ng c in nh dng gang lmv my.

+ Cc b phn khc:-Np my: bo v my khi nhng vt ngoi ri vo lm h hng dy

qun v an ton cho ngi khi chm vo in. Trong my in nh v va npmy cn c tc dng lm gi bi. Trong trng hp ny np my thng lm

bng gang.- C cu chi than: a dng in t phn quay ra ngoi. C cu chi

than bao gm c chi than t trong hp chi than nh mt l xo t chy ln cgp. Hp chi than c c nh trn gi chi than v cch in vi gi. Gi chithan c th quay c iu chnh v tr chi than cho ng ch. Sau khi iuchnh xong th dng vt c nh li.1.2.1.2. Phn quay

Bao gm nhng b phn chnh sau :+ Li st: L phn ng dng dn t. Thng dng nhng tm thp k

thut in dy 0,5mm ph cch in mng hai mt ri p cht li gim tn

hao do dng in xoy gy nn. Trn l thp c dp hnh dng rnh sau khi pli th dt dy qun vo.

Trong nhng ng c trung bnh tr ln ngi ta cn dp nhng l thng gi khi p l thnh li st c th to c nhng l thng gi dc trc.Trong nhng ng c in ln hn th li st thng chia thnh nhng on nh,gia nhng on y c mt khe h gi l khe h thng gi. Khi my lm vicgi thi qua cc khe h lm ngui dy qun v li st.


4/72

Trong ng c in mt chiu nh, li st phn ng c p trc tip vo trc.Trong ng c in ln, gia trc v li st c t gi rto. Dng gi rto c thtit kim thp k thut in v gim nh trng lng rto.

+ Dy qun phn ng: Dy qun phn ng l phn pht sinh ra sut inng v c dng in chy qua. Dy qun phn ng thnglm bng dy ng c

bc cch in. Trong my in nh c cng sut di vi kw thng dng dy ctit din trn. Trong my in va v ln thng dng dy tit din ch nht. Dyqun c cch in cn thn vi rnh ca li thp. trnh khi quay b vng ra do lc li tm, ming rnh c dng nm chthoc ai cht dy qun. Nm c lm bng tre, g hay bakelit.

+ C gp: dng i chiu dng in xoay chiu thnh mt chiu. C gpgm nhiu phin ng c c m cch in vi nhau bng lp mica dy t 0,4n 1,2mm v hp thnh mt hnh trc trn. Hai u trc trn dng hai hnh phnh ch V p cht li. Gia vnh p v tr trn cng cch in bng mica. ui

vnh gp c cao ln mt t hn cc u dy ca cc phn t dy qun v ccphin gp c d dng.

+ Cc b phn khc:- Cnh qut: dng qut gi lm ngui my. My in mt chiu

thng ch to theo kiu bo v. hai u np my c l thng gi. Cnhqut lp trn trc my , khi ng c quay cnh qut ht gi t ngoi vong c. Gi i qua vnh gp, cc t li st v dy qun ri qua qut gi rangoi lm ngui my.

- Trc my: trn t li st phn ng, c gp, cnh qut v bi.Trc my thng lm bng thp cacbon tt.

1.2.2 ng c mt chiu kch t c lp1.2.2.1 S nguyn l:

Hnh 1.2: S nguyn l ng c mt chiu kch t c lp

Rf

Uu

C

CKTD

+_

_+

RKT

UKT

I

IKT


5/72

Ta c phng trnh c tnh c: 2

K

RR

K

U fuu

T phng trnh c tnh c ta thy C ba thng s nh hng n c tnhc l:

- T thng ng c ().- in p phn ng (U).- in tr phn ng.Sau y ta s ln lt i xt nhng nh hng ca tng tham s :

1.2.2.2 nhhng ca in tr phn ng:Gi thit : U=Um=const

= m=const

Khi ta i in tr mch phn ng ta c tc khng ti l tng:

0 = Const

K

U

dm

dm

cng c tnh c:

= VarRR

KM

fu

2)(

Khi Rf cng ln, cng nh ngha l c tnh c cng dc. ng vi Rf = 0Ta c c tnh c t nhin:

tn= -uR

K 2)(

tnc gi tr ln nht nn c tnh c t nhin c cng hn tt c cc

ng c tnh c in tr ph. Nh vy khi thay i in tr ph Rf ta c mth c tnh bin tr c dng nh hnh 1.4. ng vi mt ph ti M cno , nu Rfcng ln th tc ng c cng gim, ng thi dng in ngn mch v mmenngn mch cng gim. Cho nn ngi ta thng s dng phng php ny hnch dng in v iu chnh tc ng c pha di tc c bn.

Hnh 1.3: Cc c tnh ca ng c mt chiu kch t c lp


6/72

khi thay i in tr ph mch phn ng1.2.2.3 nh hng ca in p phn ng:

Gi thit : = dm= constR= const

Khi thay i in p phn ng : U


7/72

Hnh1.5:c tnhc in (a)v c tnh c (b)khi thay i t thngTa nhn thy rng khi thay i t thng:

Dng in ngn mch: ConstR

UI

U

dmnm

M men ngn mch: Mnm= KxInm= varCc c tnh c in v c tnh c ca ng c khi gim t thng c biu dintrn hnh 1.6.

Vi dng mmen ph ti Mcthch hp vi ch lm vic ca ng c thkhi gim t thng tc ng c tng ln (Hnh 1.5b)1.3 H truyn ng chnh lu ng c mt chiu1.3.1 Khi nim chung v h truyn ng chnh lu ng c mt chiu

L b chnh lu lin h ngun xoay chiu vi ti mt chiu, ngha l iin p xoay chiu ca ngun thnh in p mt chiu trn ph ti.

in p mt chiu trn ti khng c l tng nh in p ca c quy mc cha cc thnh phn xoay chiu cng vi mt chiu.u ra ca cc s chnh lu c coi l mt chiu nhng thc s l in

p p mch. Tr s in p mt chiu, hiu p sut nh hng ca chng do ngunxoay chiu rt khc nhau.

B bin i Thyristor vi chuyn mch t nhin c in p (dng in) ra l1 chiu l cc thit b bin ngun in xoay chiu 3 pha thnh in p 1 chiu iukhin ngc.

Hot ng ca mch do ngun in xoay chiu quyt nh v nh m cth thc hin c cc chuyn mch dng in gia cc phn t lc.

Vic phn loi chnh lu ph thuc nhiu yu t:- Theo s pha c: Chnh lu 1 pha, chnh lu 3 pha...- Theo s ni c: Chnh lu na chu k, chnh lu 2 na chu k, chnh

lu hnh cu, chnh lu hnh tia...- Theo s iu khin c: Chnh lu khng iu khin, chnh lu c iu

khin, chnh lu bn iu khin.


8/72

1.3.2 Gii thiu s

Hnh 1.6: S h thng chnh lu ng c mt chiuTrong :

+ : ng c mt chiu kch t c lp, thc hin chc nng bin nnglng in mt chiu thnh c nng truyn ng cho c cu sn xut

+ BB: l b bin i van c iu khin, thc hin chc nng bin nnglng in xoay chiu thnh nng lng in mt chiu cung cp cho ng c

+ Utn hiu in p t+ FT my pht tc thc hin chc nngkhu phn hi m tc

+TH & K l khi tng hp v khuych i tn hiu+ FX l mch pht xung1.3.2.1 Hot ng ca h thng

Gi s ban u h thng c ng vo li vi in p thch hp, lcny ng c vn cha lm vic. Khi ta t vo h thng mt in p t Ungvi mt tc no ca ng c. Thng qua khu TH & KH v mch FX s suthin cc xung a ti cc chn iu khin ca cc van ca b bin i, nu lc nynhm van no ang c t in p thun, van s m vi gc m . u raca BB c in p Udt nn phn ng ng cng c quay vi tc ng

vi Uban u.Trong qu trnh lm vic, nu v mt nguyn nhn no lm cho tc ng c gim th qua biu thc : UK= U- n.khi n gim UKtng gim Udtng n tng v im lm vic yu cu.Khi n tng qu mc cho php th qu trnh din ra ngc li. y l nguyn l nnh tc .* c tnh c ca h thng truyn ng:


9/72

Ch dng in lin tc:Dng in chnh lu Idchnh l dng phn ng.Da vo s thay th (hnh 2.2) vit c s c tnh.

c tnh c c cng

Xk: c trng cho st p do chuyn mch gia cc van.Thay i gc iu khin:

+ Khi s chnh lu bin thin t Edon - Edov ta c mth c tnh song song nhau nm na bn phi mt phng to do cc

van khng cho dng in phn ng i chiu.Cc c tnh c ca h T - mm hn cc c tnh c ca h F - bithnh phn st p do hin tng chuyn mch gia cc van bn dn gy nn.

Hnh 1.7: H c tnh c ca h

+ Khi : B bin i lm vic ch chnh lu, ng c c th

lm vic ch ng c nu s E > 0 v ch hm ngc nu s E ichiu.

+ Khi : B bin i lm vic ch nghch lu ph thuc,

bin c nng ca ti thnh in nng xoay chiu cng tn s li v tr v liin. ng c lm vic ch hm ti sinh khi ti c tnh th nng.

Dng in trung bnh ca mch phn ng:

IK

XR

K

En

dm

K

dm

do

..

cos.

MK

XR

K

En

dm

K

dm

do

2).(.

cos.

K

dm

XR

K

2)(

0 M,

kU

20

ma x2


10/72

Phng trnh c tnh:

- Ch dng in gin on:Trong thc t tnh ton h T - ch cn xc nh bin gii vng dng

in gin on, l ng phn cch gia vng dng in lin tc v dng in ginon. Trng thi bin lin tc l trng thi m gc dn = /p v gc chuynmch .

ng bin lin tc gn l ng elip. gim ln ca trc nh elip, tng s pha ca chnh lu. Tuy nhin

khi tng s pha chnh lu s s phc tp.1.3.2.2 nh gi cht lng ca h thng- u im:+ Tc nhanh,khng gy ting n v d t ng ho do cc van bn

dn c h s khuch i cng sut cao.+ Cng sut tn ho nh, kch thc v trng lng nh+ Gi thnh r, d bo dng sa cha.

-Nhc im:+ Mch iu khin phc tp, in p chnh lu c biu p mch cao,

gy n tn tht ph ng k trong ng c v h thng.

+ Chuyn mch lm vic kh khn do ng c tnh nm trong mtphng to .

+ Trong thnh phn ca h bin i c MBA nn h s cos thp.+ Do vai tr ch dn dng mt chiu nn vic chuyn i ch lm vic

kh khn vi cc h thng o chiu.+ Do c vng lm vic gin on ca c tnh nn khng ph hp truyn

ng c ti nh.

K

d

XR

EEI

I

K

XR

K

E

dm

K

dm

do .cos.

2

0


11/72

CHNG II: XY DNG S CU TRC CA H

2.1 Xy dng cu trc ca h thng:T s nguyn l ca h truyn ng T- ta c s cu trc trng thi n

nh:

- Trong :

- R: Biu chnh tc quay.

- Ri : B iu chnh dng in.- U: in p ch o.- U: in p phn hi tc - Ui : in p phn hi m dng in.- Ki : H s phn hi m dng in.- K : H s phn hi m tc .

Km

K

Ki

R Ri BB Km 1Jp

1 R1 + p T

UiU U

Ui

-

U

-

McSi

S

-E


12/72

2.2. Xc nh cc tham s ca s cu trc h truyn ng.

P =14Kw U=400Vn = 0.9 nm= 955(vng/pht)

+ Im =

=

= 38.88(A)

+ R=0,5(1-n). =0,5(1-0,9).

= 0,514()

+ m= = = 100(Rad/s)

+ Km = =

= 3.8

+ J =

= 6.18kg.m2

Kcl = 9, Ki = 0.04, K= 0.01

Tvo + Tk = 0.0015s

T = 0.07s, Ti = 0.003sTc = 0.22s , T= 0.05s


13/72

CHNG III: XY DNG CU TRC

V THAM S B IU CHNH DNGTHEO TIU CHUNMODUL TI U

3.1. Tng hp b iu chnhTrong cc h truyn ng t ng cng nh cc h chp hnh th mch vng

iu chnh dng in l mch vng cbn. Chc nng c bn ca mch vng dng

in l trc tip hoc gin tip xc nh m men ko ca ng c, ngoi ra n cn

c chc nng bo v, iu chnh gia tc...Do qun tnh c hc ln hn rt nhiu so vi qun tn in t (Tc >> T ) cho

nn bin i tc chm hn bin i tc dng in.

Trong mch vng dng in c th coi 0E .Lc ny mch vng dng in c

dng:

Hnh 3-1. S khi mch vng dng in

Trong :

Rip- hm truyn ca b iu chnh dng in (cn tm)B(p) - hm truyn ca b bin i, c dng nh sau:p K1 + p T1+pT

Vi: K- h s chnh lu


14/72

T- hng s chuyn mch chnh luT- hng s thi gian mch iu khin chnh lu

A(p) - hm truyn ca ng c khng tnh n sut in ng phn ng

p 11 + p T R

Vi: T - hng s thi gian phn ng.Kp- hm truyn ca khu phn hi dng in, c dng nh sau:Kp Ki1 + p Ti

Vi: Ti - hng s thi gian ca sensor dng in

Ki=0.04 - h s phn hi mch vng dng inTa chuyn i mch phn hi dng in v mch phn hi n v, ta c s tng ng nh sau:

Hnh 3-2 : S tng ng .

- Ta c hm truyn h kn ca s khi cha chuyn i:

Sip U Rippp

1 + RipKppp- Ta c hm truyn h kn ca s khi chuyn i:

Si

p UiU

RipKppp1 + RipKppp

Mt khc: Ui Kp - Vy p dng tiu chun ti u mun cho hm truyn s chuyn

i:

Rip B(p) A(p) KpU Ui I Ui

-


15/72

Si p Kp

U K Sip

Sip Kp

Rippp1 + RipKppp Kp

Rip 1 Kppp- Thay cc hm truyn tng ng vo Ripvi:

11 + p + p

Rip 1 + Tip1 + Tp1 + Tp1 + p TKKiR p1+ p

Mt khc, cc hng s thi gian T T Tirt nh so vi hng s thigian in t T. t T T + T + Tith Ripc th vit li dnggn ng nh sau:

Rip 1 + Tc1 + Tp

KKi

R

p1+ p

Trong T T, ta chn Tthay vo Ripta c:Rip 1 + TKKiR Tp

Vy hm truyn ca mch vng kn s l:

Sip 1Ki1

1 + Tp + Tp

3.2. Tnh ton thng s b iuchnh- H s bin i dng in:


16/72

Hnh 3-3 S my bin dng.- Ta s dng mch bin dng, o dng trc tip t ngun 3 pha a qua

b chnh lu it c lc ly phn hi dng in v cho ng c.Ti

- H s chnh lu

K U- in p iu khin a vo mch chnh lu (chn U 1 V)T T + T + Ti=0,0015+0,003=0.0045 (s)

- Hm truyn

p K1 + p T1+pT

1+1p

p 1

R 1 + Tp

1+p

Kp Ki1 + p Ti

1+p

Rip 1 + TpKKiR Tp 1+pp

Sip 1Ki

11 + Tp + Tp

1+p+1p

- Thit k mch iu chnh dng in

Rip 1+p 1

p +1

Vy mch iu chnh dng ca ta s b iu chnh PI


17/72


18/72

CHNG IV: XC NH CU TRCV THAM S B IU CHNH TC

THEO TIU CHUN MODUL TI U I XNG

4.1. Tng hp b iu chnhV ng c cn b nh hng bi yu t thay i ca ti trng nn trong

trng hp ny chng ta s tng hp mch vng iu chnh tc theotiu chun ti u i xng c th t c yu cu v sai cp cao

S khi ca mch vng iu chnh tc :

Hnh 4-1 : S khi mch vng iu chnh tc .

Trong :

Rp- Hm truyn b iu chnh tc Sip- Hm truyn h kn ca vng iu chnh dng in

Sip 1Ki 1

1 + Tp + TpKp- Hm truyn khu phn hi tc

Kp K1 + Tp

Vi: K- H s phn hi ca my pht tcT- Hng s thi gian ca my pht tc

Mc

U

U Rp Sip Km C(p)

Kp


19/72

C(p) - Hm truyn c hc ca ng c khi b qua ma st trntrc ng c

p 1JpVi: J - Mmen quan tnh ca ng c

- p dng hm chun ti u i xng (v tnh n Mcnn tng hp theo

tiu chun ti u i xng sai s ca h thng c gim thiu):

- Hm truyn h kn ca s trn

S RpSippKm

1 + RpSipKppKm- p dng hm chun ti u i xng (s dng cchbin i s ging

nh phn thit k mch vng dng in) ta c:S Kp

RpSipKppKm1 + RpSipKppKm

Rp 1 SipKppKm- Thay cc hm truyn tng ng vo

R

p

1 + p1 + p + p + pVy:

Rp p1 + p1 + Tp + Tp 1 + Tp

p1 + pKKmKi J

Mt khc, ta c th b qua thnh phn Tpv l v cng b vcc hng s thi gian Tv Trt nh nn t T

T + T ,ta c hm truyn gn ng nh sau:Rp

1 + p 1 + T pp1 + pKKmKi J


20/72

V T l tng cc hng s thi gian v cng nh nn ta chn T , ta c:

Rp (1 + T p)

T

K

K

mKi J p

Vy hm truyn ca mch vng kn s l

Sp 1K 1 + Tp

1 + Tp + Tp + Tp4.2. Tnh ton thng s b iu chnh

- H s phn hi ca my pht tc:

Ta c s ca my pht tc nh sau:

Hnh 4-2 : S my pht tc .

Ta c:U K K=0.01

Mt khc T ,Ts=0,059 (s)- Hm truyn

Rp (1 + T p)

T K

K

mKi J p 1+p

p 1

p+1

p 1Jp 1

1p

Kp K1 + Tp 1

1+p


21/72


22/72

+ Hm truyn ca cc khu tm cnh sau:

Rp 1p +1

Kp 1

1+pRip 1p +

1

Kip 1+p

1+1p1 R

1 + Tp 1

1p+1

p 1Jp 1

1pKm (Wb)


23/72

CHNG V: KHO ST C TNH NG HC CA H

5.1. M phng trn Matlab Simulink

A.Lc khng ti


24/72

1.Mch vng iu chnh dng in.

+Mc=Mt=0

+thi gian t ti trng thi n nh:4.2s

+sai lch tnh:1%

Nhn xt:

Hthng t trng thi n nh kh nhah.

2.Mch vng tc .

+Mc=Mt=0

+qu iu chnh 85%


+thi gian t ti tn hiu t:0.857s

+sai lch tnh:1%

B.Lc c ti


25/72


26/72

A.Khng ti

1.Mch vng dng in.

+I=0;

+Thi gian tn hiu t trng thi n nh:1.25s

Nhn xt:thi gian t ti trng thi n nh kh nhanh

2.Mch vng tc .

+Mc=Mt=0

+qu iu chnh 8.5%


+thigian t ti tn hiu t:0.857s

+sai lch tnh:1%

B. Trng hp c ti


27/72

1.Mch vng dng in.

+I=38.8A;

Nhn xt: dng in tng ln gi trnh mc

2.Mch vng tc .

+Mc=Mt=147.4

+khi c ti tc gim nhng nhanh chng n nh lai tc nh mc

+sai lch tnh:1%


28/72

CHNG VI: XY DNG S NGUYN LV TNH CHN THIT B

6.1. S nguyn l


29/72

Hnh 6-1 S nguyn l

6.2. Tnh chn mch ng lc.

6.2.1. S mch ng lc h chnh lu cu ba pha thyristor.

Trongphn ny ta chn b truyn ng dng hai b bin i ni song song

ngc iu khin chung , bi n dng cho di cng sut va v ln c tn s o

chiu cao v thc hin o chiu m hn .Trong s ny ng c khng nhng

o chiu c m cn c th hmti sinh .


30/72

Hnh 6-2 : S mch ng lc ca bchnh lu cu ba pha thyristor h T-

.

6.2.2. Cc thng s ca ng c.

- ng c mt chiu kch t c lp c cc thng s sau:

Pdm= 14 Kw Udm= 400 V

Lc

Lc Lc

Lc

L

BAL

T1T4

T3T6

T5T2

FG

T4T1

T6T3

T2T5

+ -Ckt

M

Ikt

u2au2bu2c

C B A


31/72

Idm= 40 A ndm= 955 vng/pht

6.23. Tnh chn thyristor:

Tnh chn thyristor da vo cc yu t c bn nh : dng in ti , s

chnh lu , iu kin tn nhit , in p lm vic .- in p ngc ln nht m thyristor phi chu :

Unmax= Knv.U2= Knv.u

d

K

U=

6.3.6 dU

=3

.400 = 418.89 V ;

Trong : Knv= 6 ; Ku=

63;

- in p ngc ca van cn chn :Unv= Kdtu.Unmax= 1,8 .418,89 = 754 V ;

Trong : Kdtu: H s d tr in p , thng chn Kdtu= 1,8 ;

- Dng in lm vic ca van c tnh theo dng hiu dng :

Ilv= Ihd= khd.Id =3

dmI =3

40= 23,09 A ;

( do trong s cu ba pha , h s dng in hiu dng : khd= 3

1

) .

- Chn thyristor lm vic vi iu kin c cnh tn nhit v din tch tn

nhit , khng c qut i lu khng kh , vi iu kin c dng in nh mc ca

van cn chn :

Idm= ki.Ilv = 3,2 . 23,09 = 73,9 A ;

ki: H s d tr dng in , chn ki= 3,2 .

chn thyristor lm vic vi cc tham s nh mc c bn trn , ta tra bngthng s van , chn cc van c thng s in p ngc , dng in nh mc ln

hn gn nht vi thng s tnh . Vy ta chn thyristor cho mch ng lc loi

TF440-06X c cc thng s sau :

- Dng in nh mc ca van: Idm= 400 (A) ;


32/72

- in p ngc cc i ca van: UnT= 600 (V) ;

- nh xung dng in : Ipk= 4000 (A) ;

- st p trn thyrisor : UT= 2,0 (V) ;

-

Dng in ca xung iu khin : Ig= 200 (mA) ;- in p ca xung iu khin : Ug = 3,0 (V) ;

- Dng in r : Ir= 25 (mA) ;

- Nhit lm vic cc i : Tmax= 1250C ;

- Dng in duy tr : Ih = 70 mA ;

- Tc bin thin in p :

dt

du = 200 (V/s) ;

-

Thi gian chuyn mch : tcm= 15 (s) ;

6.2.4. Tnh ton my bin p chnh lu:

chn cc thit b trong mch ng lc cng nh mch bo v , trc ht

cn xc nh in p ra ca b bin i Thysitor .

Chn my bin p ba pha ba tr c s ni dy /Y , lm mt t nhin bng

khng kh .

My bin p l mt b phn quan trng ca h thng in , thc hin ccchc nng sau .

- Bin i in p ngun cho ph hp vi yu cu s ph ti .

- Bo m s cch ly gia ph ti vi li in vn hnh an ton v thun

tin

- Bin i s pha cho ph hp vi s pha ca s ph ti .

- To im trung tnh cho s hnh tia .

- Hn ch dng in ngn mch trong chnh lu v hn ch mc tng dng

Ant bo v van .

- Ci thin hnh dng sng in li lm cho n bin dng so vi hnh sin ,

do nng cao cht lng in p li .


33/72

* Tnh cc thng s c bn :

- Tnh cng sut biu kin ca my bin p :

SBA= Ks.Pdm= 1,05.14000 = 14700 (VA) ;

- in p pha s cp my bin p :U1 = 380 V ;

- in p pha th cp my bin p :

Phng trnh cn bng in p khi c ti :

Ud0.cosmin = Ud+ 2UV+ 2Udm+ UBA

Trong :

min

= 00l gc d tr khi c suy gim in p li ;

UV= 21 V l st p trn thyristor ;

Udm 0 l st p trn dy ni :

UBA= Ur+ Ux l st p trn in tr v in khng trn my bin

p;

Chn s b :

UBA= 6%.Ud = 0,06. 400 = 24 V ;

T phng trnh cn bng in p khi c ti ta c :

Ud0=mincos

22

BAVd UUU =00

24.221.2400

Cos

= 490 V ;

in p pha th cp my bin p :

U2=u

d

k

U=

63

490= 209 V ;

- Dng in hiu dng th cp my bin p :

I2=3

2.Id=

3

2.40 = 32,6 A ;

- Dng in hiu dng s cp my bin p :


34/72

I1= kBA.I2=1

2

U

U.I2 =

380

209 .32,6 = 17,93 A ;

* Xc nh kch thc ca mch t .

- Tit in s b tr .

QFe = kQ.fm

SBA.

;

Trong : kQ: H s ph thuc phng thc lm mt , ly kQ= 6 .

m : S tr ca my bin p , m = 3 .

f : Tn s ca ngun xoay chiu , f = 50 Hz .

Thay vo ta c : QFe = 6 .50.3

14700 = 59,4 cm2.

- ng knh tr :

d =

FeQ.4 =

4,59.4 = 8,7 cm .

Chun ha ng knh tr theo tiu chun : d = 11 cm .

- Chn loi thp k thut in , cc l thp c dy 0,5 mm .

Chn s b mt t cm trong tr BT = 1 T .

- Chn t s m =d

h = 2,3 . Suy ra h = 2,3d = 2,3 . 11 = 25,3 cm .

( Thng thng m = 2 2,5 ) .

Chn chiu cao tr h = 25 cm .

* Tnh ton dy qun .

- S vng dy mi pha s cp my bin p :

W1=0,1.10.4,59.50.44,4

380

...44,4 41

TFe BQf

U = 288 vng .

Ly W1 = 290 vng .

- S vng dy mi pha th cp my bin p :


35/72

W2=1

2

U

U.W1 =

380

209 .290 = 159,5 vng .

Ly W2 = 160 vng .

- Chn s b mt dng in trong mybin p :Vi dy dn bng ng , my bin p kh , chn J1 = J2 = 2,75 A/mm

2.

- Tit din dy dn s cp my bin p :

S1 =1

1

J

I =

75,2

15,29 = 10,6mm2.

Chn dy dn thit din hnh ch nht , cch in cp B .

Chun ho tit din theo tiu chun : S1 = 14,2 mm2.

Kch thc ca dy c k n cch in l : S1cd = a1 b1 = 1,68 8,6 mm .

- Tnh li mt dng in trong cun s cp :

J1 =1

1

S

I=

2,14

93,17 = 1,26 A/mm2.

- Thit din dy dn th cp my bin p :

S2 =2

2

J

I =75,2

6,32 = 11,85 mm2.

Chn dy dn c tit din ch nht , c cch in cp B .

Chun ho tit din theo chun : S2 = 50,1 mm2

Kch thc ca dy c k n cch in l : S2cd = a2 b2 = 5,1 10 mm .

- Tnh lai mt dng in trong cun th cp :

J2 = 2

2

S

I

= 1,50

6,32

= 0,65 A/mm2

.

* Kt cu dy qun s cp .

Thc hin dy qun kiu ng tm b tr theo chiu dc trc .

- Tnh s b s vng dy trn mt lp ca cun s cp :


36/72

W11 = 95,0.86,0

5,1.225.

2

1

c

gk

b

hh = 24 vng .

Trong : kc: L h s p cht , ly kc= 0,95 .

h : Chiu cao tr h = 25 cm .hg: Khong cch t gng cun dy s cp .

Chn s b khong cch cch in gng hg = 1,5 cm .

- Tnh s b s lp dy cun s cp :

n11=24

290

11

1 W

W = 12,08 lp .

Chn s lp n11 = 12 lp .

Nh vy c 290 vng chia thnh 12lp , vy 11 lp u c 24 vng v lp

th 12 c 26 vng

- Chiu cao thc t ca cun s cp :

h1 =95.0

86,0.24. 111 ck

bW = 21,726 cm .

- Chn ng qun dy lm bng vt liu cch in c b dy :S01 = 0,1 cm .

- Khong cch t tr ti cun s cp :

a01 = 1 cm .

- ng knh trong ca ng cch in :

Dt= dFe+ 2a012S01 = 11 + 2 . 12 . 0,1 = 12,8 cm .

- ng knh trong ca ca cun s cp :

Dt1= Dt + 2S01 = 12,8 + 2 . 0,1 = 13 cm .

- Chn b dy cch in gia cc lp cun s cp :

cd11 = 0,1 mm .


37/72

- B dy cun s cp :

Bd1= ( a1+ cd11 ).n11 = ( 1,68 + 0,1 ).8 = 14,24 mm = 1,424 cm .

- ng knh ngoi ca cun s cp :

Dn1 = Dt1+ 2Bc1= 13 + 2 . 1,424 = 15,848 cm .

- ng knh trung bnh ca cun s cp :

Dtb1 =2

848,1513

211

nt DD = 14,424 cm.

- Chiu di dy qun s cp :

l1 = W1..Dtb = . 290 . 14,424 = 13141,156 cm = 131,41 m .

- Chn b dy cch in gia hai cun s cp v th cp :

cd0 = 1 cm .

* Kt cu dy qun th cp .

- Chn s b cun chii cao cun th cp :

h2 = h1 = 21,726 (cm) .

- Tnh s b s vng dy trn mt lp :

W12 = ckb

h.

2

2 = 95,0.1

726,21 = 20 vng .

- Tnh s b s lp dy qun th cp:

nl2 =20

160

2

2 lW

W = 8 lp .

chn n12 = 8 lp .

- Chiu cao thc t ca cun th nht :

h2=95,0

1.2022 c

l

k

bW= 21,05 cm .

- ng knh trong ca cun th cp :

Dt2 = Dn1+ 2a12 = 15,848 + 2 . 1 = 17,848 cm .

- Chn b dy cch in gia cc lp dy cun th cp :

cd22 = 0,1 mm .


38/72

- B dy cun th cp :

Bd2 = ( b2 + cd22 ). nl2= ( 1 + 0,01 ) . 3 = 3,03 cm .

- ng knh ngoi ca cun th cp :

Dn2 = Dt2+ 2.Bd2 = 17,848 + 2 . 3,03 = 23,908 cm .

- ng knh trung bnh ca cun th cp :

Dtb2 =2

908,23848,17

222

nt DD = 20,878 cm .

- Chiu di dy qun th cp:

l2 = .W2.Dtb2 = . 160 . 20,878 = 10494 cm = 104,94 m .

- ng knh trung bnh ca cc cun dy :

D =2

908,2313

2

21

nt

DD = 18,454 cm .

Suy ra : r =2

454.18

2

D = 9,227 cm .

* Cc thng s ca my bin p :

- in tr trong ca cun s cp my bin p 75oC :

R1 = .1

1

s

l = 0,02133.

14

41,131 = 0,2 .

Trong : = 0,02133 .mm2/m.

- in tr trong ca cun th cp my bin p 75oC :

R2 = .2

2

s

l = 0,02133.

1,50

94,104 = 0,045 .

- in tr my bin p quy i v th cp :

RBA = R2+ R1.(1

2

W

W)2= 0,045 + 0,2.(

290

160 )2 = 0,06 .

- St p trn in tr my bin p :

ur = RBA.Id = 0,06 . 40 = 2,4 V .

- in khng my bin p quy i v th cp :


39/72

XBA= 8.2.(W2)

2.(qh

r)(a12+

3

21 dd BB )..10-7.

XBA= 8 . 3,142 . 1602. (

726,21

227,9) . (0,01 + 210.

3

03,3424,1 ) . 314 . 10-7

XBA= 0,67 .

- in cm my bin p quy i v th cp :

LBA =

BAX =

314

67,0 = 2,13.10-3H = 2,13 mH.

- St p trn in khng my bin p :

ux =

3 .XBA.Id =

3 .0,67.40 = 25,6 V .

- in p ngn mch tc dng :

Unr = 100.209

6,32.06,0100

2

2 U

IRBA = 0,93 % .

- in p ngn mch phn khng:

Unx = 100.209

6,32.67,0100

2

2 U

IXBA = 10,5 % .

- in p ngn mch phn trm :

Un = 2222

5,1093,0 nxnr UU = 10,54 % .

Cng sut my bin p biukin

SBA = 14,7 kVA

in p pha s cp U1 = 380 V

in p pha th cp U2 = 209 V

Dng in hiu dng s cp I1 = 17,93 A

Dng in hiu dng th cp I2 = 32,6 A

S vng dy mi pha s cp W1 = 290 vng

S vng dy mi pha th cp W2 = 160 vng

in tr quy i v th cp RBA = 0,06


40/72

Bng thng cc thng s ca my bin p ng lc .

6.3. Mch iu khin .

6.3.1. S nguyn l :

Hnh 6-3 : S khi iu khin thyristor .

6.3.2. Nguyn tc iu khin :

Trong thc t ngi ta thng dng hai nguyn tc iu khin sau : Thng

ng tuyn tnh v thng ng arccos , thc hin v tr xung trong na chu k

dng ca in p t trn thyristor .

in khng quy i v th cp XBA = 0,67

in cm quy i v th cp LBA = 2,13 mH

in p ngn mch phn trm Un = 10,54 %

IN P TA

K XUNG

P

SSUc

T


41/72


42/72

6.3.2.2. Nguyn tc iu khin thng ng arccos:

Theo nguyn tc ny ngi ta dng hai in p :

- in p ng b Us, vt trc UAK= UmSint ca thyristor mt gc2

Us= UmCost .

- in p iu khin Ucml in p mt chiu , c th iu chnh c bin

theo hai chiu dng v m .

Hnh 6-5 : Nguyn tc iu khin thng ng arcoss

Nu t Usvo cng o v Ucmvo cng khng o ca khu so snh th :

Khi Us= Ucm, ta s nhn c mt xung rt mnh u ra ca khu so snh

khi khu ny lt trng thi .

UmCos = Ucm; (3-1)

Do = arcos(m

cm

U

U) ; (3-2)

Khi Ucm= Um th = 0 ;

Khi Ucm= 0 th =2

;

Khi Ucm= - Um th = ;

Ucmt

UAK

0

Us

UAK

Us

2

Um

-Um


43/72


44/72

Di y ta gi thiu mt s khu ng pha c bn

Hnh 6-6 Mt s khu ng pha in hnh.

u1 u1ura

u2D1

D2R1

R2

C

-E

A B C

Hnh-a

R2

R1

D1

A

C ura

Tr

Hnh-b

+E

Ghp quanguv

R1

D

R2

uraC

-E

Ura

u1D1

A2

R1A B

R2Tr

C

C

Hnh-d

A1

-12

+12+12

-12_

++

_


45/72

Hnh 6-7 : Gin ca khu ng pha

6.3.2. Khu so snh :

xc nh c thi im cn m thyristor , cn so snh hai tn hiu Udkv

Urc, vic so snh hai tn hiu c th c thc hin bng tranzitor (Tr) nh trn

hnh 3-6a . Ti thi im Udk= Urcu vo Tr lt trng thi kho sang m ( hay

ngc li t m sang kho ) , lm cho in p ra cng b lt trng thi , ti tanh du c thi im cn m thyristor .

Vi mc m bo ho ca Tr ph thuc vo hiu Udk Urc= Ub, hiu ny

c mt vng in p nh hng vi mV , lm cho Tr khng lm vic ch ng

UA

t

t

UC1

2 3 4

UA

UB

Uk1

Urc

1

t

UC2Uk2

Urc2 2

1

t

32


46/72

ct nh mong mun , do nhiu khi lm thi im m thyristor b lch kh xa so

vi im cn m ti Udk= Urc.

Khch i thut ton c h s khch i v cng ln , ch cn mt tn hiu rt

nh (c V) u vo , u ra c in p ngun nui , nn vic ng dngkhch i thuc ton lm khu so snh l hp l . Cc s so snh dng khch

i thut ton nh hnh 3-6b, c rt thng gp trong ccs hin nay . u im

hn hn ca cc s ny l c th pht xung iu khin chnh xc ti Udk= Urc

Mt s s khu so snh thng gp nh sau.

Hnh 6-8 : Cc khu so snh thng gp.

a ) Bng tranzitor ; b ) Bng mt cng o ca khch i thut ton ;

c ) Hai cng khch i thut ton ;

R1

R2

urc

udkUra

A3

Hnh - b

+

_

-12

+12

Hnh - a

-E

R3

R1

R2

urc

udkUra

R1

R2

urc

udk

Hnh - c

Ura

A3


47/72


48/72


49/72


50/72

Hnh 6-13 : a ) S to xung chm dng vi mch 555 .

b ) S to xung chm a hi bng khch i thut ton .

c ) S to xung chm to bng mch khch i thut ton .

6.4. S mch iu khin v nguyn l hot ng.

T cc khu gi thiu trn ta chn c s iu khin mt knh nh

hnh 3-13 .

Hot ng ca mch iu khin hnh 3-13 c gii thch nh sau :

in p vo ti im A (UA) c dng hnh sin , trng phavi ant ca

thyristor , qua khch i thut ton A1cho ta chui xung ch nht i xng UB.

Uc

R2

R1

_

+

+12

-12

A

R2

R3

R1

R3

A1A2

R4

C

a )

a )

b ) c )

C

+U

+Urc

C2C1

R2

R1

555

7

2 1

38 4


51/72

Phn in p dng ca in p ch nht UBqua it D1ti A2tch phn thnh

in p ta Urc. Phn p m ca in p UBlm m thng Tranzitor Tr1, kt qu

l A2b ngn mch

( Vi Urc= 0 ) trong vng UBm . Trn u ra ca A2ta c chui in p rng caUrcgin on .

in p Urcc so snh vi in p iu khin Udkti u vo ca A3. Tng

i s Urc+ Udkquyt nh du in p u ra ca khch i thut ton A3. Trong

khong thi gian t 0 t1vi Udk> Urc, in p UD m . Trong khong t1 t2,

in p Udkv Urci ngc li , lm cho UDlt ln dng . Cc khong thi gian

tip theo gii thch in p UDtng t .

Mch a hi to xung chm A4cho ta chui xung tn s cao , vi in p UE

trn hnh 3-13 . Dao ng a hi c tn s hng chc kHz , y ch m t nh

tnh .

Hai tn hiu UDv UEcng c a ti khu AND hai cng vo . Khi

ng thi c c hai tn hiu dng UD , UE ( Trong cc khong t1 t2, t4 t5)

ta s c xung UFlm m thng cc Tranzitor, kt qu l ta nhn c chui xungnhn Xdktrn bin p xung , a ti m thyristor T .

in p Uds sut hin trn ti t thi im c xung iu khin u tin , tai

cc thi im t2 , t4trong chui xung iu khin , ca mi chu k in p ngun

cp , cho ti cui bn k in p dng ant .


52/72

Sau y l s iu khin chnh lu cu 3 pha s dng cc khu trn:

Hnh 6-14 s iu khin chnh lu cu 3 pha


53/72

Hnh 6-15 :TCA 785

Hnh 6-16 Vi mch TCA785

Hin nay c nhiu hng ch to cc vi x l chuyn dng iu khin cc

thyristor rt tin li . Sau y xin gii thiu v IC TCA 785 do Simens ch to c

chc nng iu khin m cc van Thyristor, Triac.... Trong n ny em s dng

TCA 785 iu khin m van thyristor.

6.5 Tng quan v TCA 785

6.5.1 Gii thiu

6.5.2 S vi mch TCA 785


54/72


55/72

+To xung ra.

6.5.3)M t chc nng

Tn hiu ng b c c qua tr khng cao t in p dy(V5).B pht hin

in p khng s xc nh cc in p khng v chuyn chng n thanh ghi ng

b.

Thanh ghi ng b ny iu khin b to dc(lm dc xung tn hiu

khin),t C10trong b to dc c np vi dng c nh (xc nh bi R9).Nu

in p dc (in p rng ca,tam gic) V10 vt qu in p iu khin V11(gc

m ) th tn hiu in chuyn thnh dng Logic ph thuc vo ln ca in p

iu khin V11m gc m c th c dch chuyn trong khong (00 1800)

Vi mi 1/2 phn sng mt xung dng c 30 s li xut hin ti cc u ra

Q1,Q2 Gi s tn ti xung c th t ti 1800qua tC12.Nu chn 12 ni mass cc

xung trong khong gc ( 1800) s xut hin .

Cc u ra 1, 2 cung cp tn hiu ngc vi Q1,Q2 .Tn hiu ti +1800c th

c dng iu khin mt b Lgic ngoi c ti chn 3.

Mt tn hiu tng ng vi lin kt NOR ca Q1,Q2 c sn ti ca ra QZ

(chn 7)

Cng vo hn ch c th c dng loi tr hot ng ca cc cng ra Q1,Q2

1, 2.

Chn 13 c th dng m rng cc u ra 1, 2 nhm lp y rng xung

(1800- )

Q

Q

Q

Q

Q

Q


56/72

10

10

V

V

11V

10V

V0

2.15QV

1.14QV

2.15QV

1.14QV

2.2QV

1.4QV

QUV .3

QZV .7

5V in p ng b

in p nh dc

in p dc in p iu khin

in p dc min

Chn 12 t i t

Chn 12 t i t

Chn 13 t i t

Chn 13 t i t

Hnh 6-17 Gin in p

C th iu chnh gc m t 0

0

n 180

0

in.-Thng s ch yu ca TCA 785:

in p nui: Vs= - 0.5- 18V

Dng in tiu th: IS= 10 mA

Dng in ra: I = 50 mA

in p rng ca: Vr max= (VS2) V

in tr trong mch to in p rng ca: R9= 20 k - 500 k

in p iu khin: V11= -0,5(Us2) V

T in: C10= 0,5 F


57/72

Tn s xung ra:f = 10500 Hz

Dng in u ra ti chn 14 15 : IQ = - 10 -400 mA

in p cm : V6 = - 0.5 VS

Dng in ra ng b : Isync= - 200 + 200 A

Dng in ra ti chn 2,3,4,7 : IQ = 10 mA

in p ra ti chn 2,3,4,7 : VQ = VS (V)

Nhit tip gip : TJ = 1500C

Nhit lm vic : TSTG = - 550C n 1250C

Nhit xung quanh : TA = - 25oC n 850oC


58/72


59/72

Tnh chn thng s mch:

Thng tin t nh sn xut cung cp ta c:

Vi R9bng khong 200K. Ta chn R9= 220K.

Vi C10= 22nF.

Khi t = t0, U10= Ucm= U11Ngi ta nhn c xung ra chn 15 nu V(t) > 0

hoc mt xung ra chn 14 nu V(t) < 0.

t0= C10.

gc

T C12khuch i rng xung ra. C th chn C 12= 0 n 330pF rng

xung t30 . Ta chn C12=330pF.

6.6. Tnh ngun nui .

Ta cn to ra ngun in p U 12 V cp cho my bin p xung, nui

IC........

Ta chn mch chnh lu cu ba pha khng iu khin dng 12 con it to

ra in p 12 V , v + 12 V nh hnh 3-17 .

in p th cp my bin p ngun nui l :

U2 =34,2

12= 5,1 V , ta chn U2= 9 V ;

Vic xy dng ngun n p mt chiu bng thyristor c nhc im l chn

v tnh ton phc tp i hi phi c k thut chuyn mn cao . S ra i ca cc


60/72

vi mch n p h 7812 v 7912 cho php n gin ho qu trnh ny , v vy n

c s dng rng ri trong thc t .

Vi mch IC 7812 thng c ba chn , chn u vo , chn u ra v chn ni

t. Do c nhiu hng sn xut ra loi IC ny do hnh dng bn ngoi v th tca cc chn c khc nhau .

Hnh 6-19 : S nguyn l to ngun nui 12 V .

V vy n nh in p ra ca ngun nui , ta dng hai vi mch n p l

7812 v 7912 , cc thng s chung ca vi mch ny nh sau :

470F

A B C

220

V

a b c*a *b *c

** *

C5 C4

470F

C7

470F

C6

470F

7812

7912

0 +12 V-12 V


61/72

in p u vo : UV= 7 35 V ;

in p ra : Vi IC 7812 th Ura= + 12 V ;

Vi IC 7912 th Ura= - 12 V ;

Dng in u ra : Ira = 0 1 A ;T in C4 , C5, C6, C7dng lc thnh phn sng hi bc cao .

Chn C4= C5= C6= C7= 470 F ; U = 35 V .

6.7. Tnh ton my bin p ngun nui v ng pha.

- Ta thit k my bin p dng cho c vic to in p ng pha v to ngun

nui . Chn kiu my bin p ba pha ba tr , trn mi trc ba cun dy , mt

cun s cp v hai cun th cp .

- in p ly ra th cp my bin p lm in p ng pha , v lm in p

ca ngun nui .

U2 = U2ph = UN = 9 V ;

- Dng in th cp my bin p ng pha .

I2ph = 1 mA ;

- Cng sut ngun nui cp cho my bin p xung .

Pph = 6.U2ph.I2ph = 6.9.1.10-3 = 0,054 W ;

- Cng sut my bin p xung cp cho cc iu khin thyristor .

Px = 6.Udk.Idk = 6.3.0,2 = 3.6 W ;

- Cng sut s dng cho vic to ngun nui .

PN= Pph+ P8IC+ Px

PN= 0,054 + 5,12 + 3,6 = 8,774 W ;

- Cng sut ca my bin p c k n 5% tn tht trong my .S = 1,05(Pph+ PN) = 1,05(0,054 + 8,774) = 9,269 VA ;

- Dng in th cp my bin p .

I2 =9.6

269,9

.62

U

S= 0,172 A ;


62/72


63/72

Hnh 6-20Mch ng lc c thit b bo v .

T1T

T T6

T T

FG

T4T1

T6T

T2T5

+ -Ckt

Ikt

M

L

Lc

u2c

CBA

u2bu2a

1cc 1cc 1cc

Lc

Lc

Lc

R R

R

RR

R

R R

R

RR

R

C C

C

CC

C

C C

C

CC

C

2cc

2cc

2cc

2cc

2cc

2cc

2cc2cc

2cc 2cc

2cc2cc

3cc

Ap

BAL


64/72

6.9.2. Bo v qu nhit cho cc van bn dn

Khi lm vic vi dng in chy qua , trn van c s 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 php lm vic di nhit cho php TCPno , nu qu nhit cho php th cc vanbn 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 tn nhit hp l .

Tnh ton cnh tn nhit :

- Tn tht cng sut trn mt thyristor .

P = U.Ilv= 2.23,09 = 46,18 W ;

- Din tch b mt to nhit .

Sm =.mK

P ;

Trong :

P : Tn hao cng sut ( W ) ;

: chnh lch nhit so vi mi trng .

Km: H s to nhit bng i lu v bc x . Chn Km= 8 W/m2.0C .

Tlv,Tmt: Nhit lm vic v nhit ca mi trng (0C) .

Chn nhit mi trng Tmt= 400C . Nhit lm vic cho php ca

thyristor Tcp = 1250C . Chn nhit trn cnh tn nhit Tlv = 80

0C .

= Tlv - Tmt = 80 - 40 = 400C ;

Vy : Sm =40.8

18,46 = 0,144 m2 ;

Chn loi cnh tn nhit c 12 cnh , kch thc mi cnh l

a b = 16 16 (cm cm ) .

Tng din tch ca cnh tn nhit .

S = 12 . 2 . 16 . 16 = 0,6144 m2 ;


65/72

6.9.3. Bo v qu dng cho van .

Aptomat dng ng ct mch ng lc , t ng bo v khi qu ti v

ngn mch thyistor , ngn mch u ra b bin i , ngn mch th cp my

bin p , ngn mch ch nghch lu .- Chn aptomat c :

Idm= k.I = 1,1. 3 .I1 = 1,1 . 3 . 17,93 = 34,16 A ;

Vi I1: l dng in s cp my bin p .

k : H s an ton .

Udm = 400 V ;

Aptomat c ba tip im chnh , c th ng ct bng tay hoc bng namchm in .

Chnh nh dng ngn mch .

Inm = 2,5.I = 2,5. 3 .17,93 = 77,64 A ;

Dng qu ti .

Iqt = 1,5 .I = 1,5 . 3 . 17,93 = 46,58 A ;

- Chn cu dao c dng nh mc .

ICD = IdmAP = 34,16 A ;

Cu dao dng to khong cch an ton khi sa cha h truyn ng .

- Dng dy chy tc ng nhanh bo v ngn mch cc thyristor ,

ngn mch u ra ca b chnh lu .:

Nhm 1CC :

Dng in nh mc dy chy nhm 1CC l :I1CC = 1,1.I2 = 1,1 . 32,6 = 35,86 A ;

Nhm 2CC :

Dng in nh mc dy chy nhm 2CC l :

I2CC = 1,1.IhdV = 1,1 . 23,09 = 25,399 A ;


66/72

Nhm 3CC :

Dng in nh mc dy chy nhm 3CC l :

I3CC = 1,1.Idm = 1,1 . 40 = 44 A ;

Vy chn cu chy nhm :1CC loi 100 A ; 2CC loi 100 A ; 3CC loi 100 A ;

6.9.4. Bo v qu in p cho van .

Linh kin bn dn ni chung v linh kin bn dn cng sut ni ring ,

rt nhy cm vi s thay i ca in p . Nhng yu t nh hng ln nht

ti van bn dn m ta cn c phng thc bo v l :

- in p t vo van ln qu thng s ca van .

- Xung in p do chuyn mch van .

- Xung in p t pha li in xoay chiu , nguyn nhn thng gp l

do ct ti c in cm ln trn ng dy .

- Xung in p do ct t ngt my bin p non ti .

- bo v cho van lm vic di hn khng b qu in p , th ta phi

chn ng cc van bn dn theo in p ngc .

- bo v qu in p ca xung in p do qu trnh ng ct cc van

thyristor c thc hin bng cch mc R C song song vi thyristor . Khi c s

c chuyn mch , cc in tch tch t trong cc lp bn dn phng ra ngoi to ra

dng in ngc trong khong thi gian ngn . S bin thin nhanh chng ca

dng in ngc gy ra sc in ng cm ng rt ln trong cc in cm , lm

cho qu in p gia ant v catt ca thyristor . Khi c mch R C mc songsong vi thyristor , to ra mch vng phng in tch trong qu trnh chuyn mch

nn thyristor khng b qu in p .


67/72

Theo kinh nghim R1= ( 5 30 ) ; C1= ( 0,25 4 ) F ;

Ta chn : R1= 5,1 ; C1= 0,25 F ;

Hnh 6-20 : Mch R C bo v qu in p khi van chuyn mch .

- bo v cho xung in p li t in p li , ta mc song song vi ti

u vo mt mch R C nhm lc xung . Khi xut hin xung in p trn ng

dy , nh c mch lc ny m nh xung gn nh nm li hon tan trn in tr

ng dy .

Tr s R , C ph thuc nhiu vo ti .

Theo kinh nghim R2= ( 5 30 ) ; C2= 4 F ;

Ta chn : R1= 12,5 ; C1= 4 F ;

Hnh 6-21 : Mch R C bo v xung in p t li.

R1 C1

R2 R2C2 C2

C2R2


68/72

6.10 Thit k cun khng lc :

6.10.1Xc nh gc m cc tiu v cc i in p iu khin cc tiu, cc i

Khi gc m nh nht = min th in p trn ti ln nht :

Ud max = Ud0.Cosmin = Ud.dmv lc ny tng ng vi tc ng c sln nht nmax= ndm.

min= arccos( ) =

= arc

= 35

o

in p iu khin tng ng gc m 350

= 1,95V (Urcmax= Us2V = 12- 2 = 10V)

Ta c:

D =m in

m ax

n

n=

,,

,,

.

.

.m in.

..

udmud

udmudmd

RIU

RIU

Ud.min= dmudmud RIDUD ..m in. ,, ..1

1

Ud.min = dtBAudmu RRRIDUD ,, ..1cos..34,2

1.m in2

Ud.min =

BABAudmu XRRIU

3..120cos..34,2

20

1,, .min2

Thay svo ta c :

Ud.min =

67,0.

306,001,0.40.120cos.209.34,2

20

1min

Vy : Ud.min= 53,25 V .


69/72

Thay Ud.minvo cng thc ( 3-3 ) ta c :

max = arcos(0

m in.

d

d

U

U) = arcos(

209.34,2

25,53) = 780 .

= 4,33V (Urcmax= Us2V = 12- 2 = 10V)

6.10.2. Xc nh cc thnh phn sng hi

thun tin cho vic khai trin chui Fourier , ta chuyn gc to sang 1,

khi in p tc thi trn ti khi thyristor T1v T4dn :

Ud= Uab= 6 .U2cos( -6

+ ) ; Vi = .t ;

in p tc thi trn ti Udkhng sin v tun hon vi chu k :

=36

22

p;

Trong p = 6 l s xung p mch trong mt chu k inp li .

Khi khai trin chui Fourier ca in p Ud:

Ud= ).2

sin.2

cos.(2 1

0

kbka

an

K

n

;

Hay :

Ud= ).6sin..6cos.(2 1

0 kbkaa

n

K

n

=

=

1

.0 )6sin(2 K

mn kkUa

Trong :

*an=

0 0

2 .6cos)6

cos(66

.6cos2

dkUdkUd ;

an =

cos

1)6(

)2(63cos

6sin2.

1)6(

)2(.

632222

kU

kU ;


70/72

*bn=

0 0

2 .6sin)6

cos(66

.6cos2

dkUdkUd ;

bn =

sin

1)6(

)2(.

63sin

6sin2.

1)6(

)2(632222

kU

kU ;

Ta c :

cos63

2 2

0 Ua ;

Vy ta c bin ca in p :Uk.n =

22nn ba ;

Uk,n =

222

22 sin)6(cos

1)6(

163k

kU

;

Uk.n = 2 22

2

0 )6(11)6(

tgkk

Ud

;

Ud n nkU )6sin(cos63 1.

;

6.10.3.Xc nh in cm cun khng lc :

T phn tch trn ta thy rng , khi gc m cng tng th bin thnhphn sng hi bt cao cng ln , c ngha p mch ca in p , dng in tngln .S p mch ny lm xu ch chuyn mch ca vnh gp , ng thi gy ratn hao ph di dng nhit trong ng c . hn ch s p mch ny , ta phimc ni tip vi ng c mt cun khng lc ln Im 0,1.Idm .

Ngoi tc dng hn ch thnh phn sng hi bt cao ,cun khng lc cnc tc dng hn ch vng dng in gin on .

in khng lc cn c tnh khi gc m = max.Ta c :

Ud+ u~= E + R.Id+ R.I~+ Ldt

di

Cn bng hai v :

u~ = R.i~ + Ldt

di v R.i~


71/72

i = 11 6cos.

..2.

1

Lf

Udtu

L

m = Im.cos ( 6 + 1)

Vy :

Im =Lf

U m

..2.6

1

0,1.Idm

Suy ra : L dmu

m

If

U

,.1,0..2.6

1

Trong : = 6 l s xung p mch trong mt chu k in p .

U1m = 2.

max22

2

max0 6116

cos.

tg

Ud

U1m = 2.

0222

78.61.16

78cos.209.34.2tg

o

= 166,55 .

Thay s trn ta tnh L :

L =dmu

m

If

U

,.1,0..2.6

1

=

40.1,0.50..2.6

55,166

= 0,02H .

in cm mch phn ng c :Lc = L+ 2LBA

Trong :Ll in cm mch phn ng ca ng c v c tnh theo cng thc

UmanxkiLindvil :

L = .dmdm

dm

Inp

U

...2

60.

Trong = 0,25 l h s ly cho ng c c cun b .

L= dmdm

dm

Inp

U

...2

60.

= 0,25.

40.955.4.2

60.400

= 6,25.10-3H = 6,25 mH .

Ta c in cm phn ng c :Lc= L+ 2LBA= 6,25 + 2 . 2,13 = 10,51 mH .

in cm cun khng lc :Lk = LLc = 0,02.10

310,51 = 9,49 mH .6.11. Thit k kt cu cun khng lc .

Cc thng s ban u :

in cm yu cu ca cun khng lc : Lk= 9,49 mH .Dng in nh mc chy qua cun khng lc : Im= 40 A .Bin dng in xoay chiu bt 1 : I1m= 10%.Idm= 4 A .- Do in cm cun khng ln v in tr rt b , ta c th coi tng tr cun

khng xp x bng in khng ca cun khng .Zt = Xk = 2.f.Lk = 2.50.9,49.10

-3= 2,98 .- in p xoay chiu ri trn cun khng lc .


72/72

U = Zk.2

1mI = 2,23.2

4 = 6,307 V .

- Cng sut ca cun khng lc .

S = U.2

1mI = 10,249.2

4 = 28,42 VA .

Documents

Bài Tập Lớn Tổng Hợp Hệ Thống Điện Cơ