thiết kế bộ khởi Động cho Động cơ không Đồng bộ ba pha bằng thyristor

B Gio Dc V o To

n tt nghip

Thit k b khi ng cho CKDB ba pha bng Thyristor

B Gio Dc V o To Cng Ho X Hi Ch Ngha Vit NamTrng i Hc Quy Nhn c Lp - T Do - Hnh Phc

NHIM V THIT K TT NGHIPH v tn: Trn Duy Sn

Kho : K27Khoa : K Thut & Cng NghNgnh hc: K thut inI. u thit k:

Thit k b khi ng cho ng c khng ng b ba pha bng Thyristor.

II. Cc s liu ban u:

ng c khng b xoay chiu ba pha c cc thng s sau:

Cng sut nh mc :Pm = 27 KW.

Tn s nh mc:fm = 50 Hz.

in p nh mc:Um = 220/380V.

Tc nh mc:nm = 975( vg/ph).

H s gc nh mc: cosm = 0,83.

Hiu sut

:m = 0,94.

T s

:

III. Ni dung cc phn thuyt minh v tnh ton:

Khi qut v ng c khng ng b.

Thit k mch ng lc.

Thit k mch iu khin, bo v.IV. Cc bn v th ( ghi r cc loi bn v, v kch thc bn v )

- ..........................................................................................................

- ...........................................................................................................

- ..........................................................................................................

- .......................................................................................................... VI. Ngy giao nhim v thit k :

Ngy Thng Nm 2009

VII. Ngy hon thnh nhim v thit k: Ngy Thng Nm 2009

CH NHIM KHOA CN B HNG DN ( K, ghi r h tn ) ( K, ghi r h tn )

T.S: NGUYN NGC MTH.S: NGUYN THI BOKt qu im nh gi:

Qu trnh thit k: ..........

Bo v thit k: .........Quy Nhn, ngy .. thng nm 2009

Ch tch hi ng ( K v ghi r h tn )

Sinh vin thc hin

( K v ghi r h tn )

Trn Duy SnLI NI U

ng c khng ng b ba pha l mt thit b in c s dng rt ph bin trong mi lnh vc sn xut v i sng, thay cho cc ng c khc v n c nhiu u im nh khi ng n gin, r tin v kch thc gn nh, vn hnh tin cy, nht l loi rto lng sc ( nh qut gi, bm nc, truyn ng di chuyn cc bng ti sn xut).

Nhc im ca n l c tnh c phi tuyn mnh nn trc y vi cc phng php iu khin, m my ng c khng ng b cn gp nhiu kh khn v hn ch. Bi v cc thit b iu khin cn th s, n gin, nn ng c khng ng b ny phi nhng ch cho ng c in mt chiu.

Ngy nay vi s pht trin ca cc l thuyt iu khin, truyn ng cng vi s tin b ca khoa hc k thut nh vi x l, in t cng sut nn hn ch c nhc im trn, a ng c khng ng b tr thnh ph bin. Nhm nng cao nng sut cng nh t ng ho trong qu trnh sn xut, gp phn ng k vo mc tiu cng nghip ha, hin i ha t nc.

Do vai tr ca ng c khng ng b l quan trng nn em chn ti Thit k b khi ng cho ng c khng ng b ba pha bng Thyristor l mt ti kh nhng rt thc tin v ph bin i hi s am hiu nht nh trong lnh vc in t cng nh my in.

Trong qu trnh thit k c s hng dn tn tnh v chu o ca Thc s: Nguyn Thi Bo v cc thy c gio c kinh nghim trong khoa: K Thut - Cng Ngh - Trng i Hc Quy Nhn. Em hon thnh Ti Tt Nghip. ti gm c bn phn sau y:

Phn I: Khi qut ng c khng ng b ba pha.

Gii thiu s lc v ng c khng ng b.

Cc yu t nh hng n cc c tnh c ca ng c khng ngb.

Cc phng php m my ng c khng ng b.

Phn II: Chn mch ng lc.

Chn, tnh ton cc thng s v bo v mch ng lc.

Tnh ton cc c tnh ca ng c.

Tnh ton cc thng s iu khin.

Phn III:Chn v tnh ton mch iu khin.

Cc mch iu khin c bn.

Tnh ton cc thng s ca mch iu khin.

Phn IV:Thit k t in.

Mc d bn thn em c nhiu c gng, n lc nhng do thi gian hn ch v kin thc cn thiu khng trnh khi nhng thiu st. Knh mong cc thy, c tn tnh ch bo cho Ti c hon thin hn.

Xin chn thnh cm n cc tc gi, cc thy, c gio, cc k s, bn b, c bit l Thc S: Nguyn Thi Bo tn tnh gip em hon thnh Ti ny.

Sinh Vin Thc Hin

Trn Duy SnMC LC

Trang

Li ni u.

3 - 4

PHN IKHI QUT V NG C KHNG NG B

I. Cu to v t im ca ng c khng ng b.

9

I.1. Cu to:

9

I.1.1.Cu to phn tnh ( stato ).

9

I.1.1.1. V my.

9

I.1.1.2. li st.

9 10

I.1.1.3.Dy qun.

10

I.1.2.Cu to phn quay ( Rto ).

10

I.1.2.1. Trc.

10

I.1.2.2. Li st.

10

I.1.2.3. Dy qun Rto.

10

I.1.2.4. Khe h.

11

I.2. c im ca ng c khng ng b.

11 12

I.3. Nhng i lng ghi trn ng c khng ng b.

12

I.4. Cch u dy ca ng c.

12

I.5. Vai tr ca ng c khng ng b.

14II. Nguyn l lm vic ca ng c khng ng b.

14 17III. Cc phng php c bn ca ng c khng ng b.

17

III.1. Cc c tnh c bn ca ng c khng ng b.

17

III.1.1. Phng trnh c tnh c.

17 24

III.2. nh hng ca cc thng s n c tnh c ca CKB

24 25

III.2.1. nh hng ca in p ngun cung cp cho ng c.

25 26

III.2.2. nh hng ca tn s li in f1 cp cho ng c.

26 27

III.2.3. nh hng ca in tr, in khng mch stato.

27 28

III.2.4. nh hng ca in tr, in khng ph mch stato.

28 29

III.2.5. nh hng s i cc p.

29 30

III.3. M my ng c khng ng b.

30

III.3.1. Qu trnh m my ng c khng ng b.

30

III.3.2. Cc phng php m my ng c ba pha.

31

III.3.2.1. Phng php m my trc tip ng c in khng ng b rto lng sc.

31 32

III.3.2.2. Phng php h in p m my.

32

III.3.2.2.1. Phng php ni in khng ni tip vo mch in stato.32 33

III.3.2.2.2. Phng php dng my bin p t ngu gim in p m my.

33 34

III.3.2.2.3. Phng php m my bng phng php Y .

34 35

III.3.2.2.4. Phng php m my bng cch ni thm in tr ph vo mch Rto.

36 37

III.3.2.2.5. Phng php m my nh linh kin bn dn.

37

III.3.2.2.6. Phng php m my ng c khng ng b li dng hiu ng ngoi dy qun Rto lng sc.

38 41PHN II

TNH CHN MCH NG LC

I. Chn mch ng lc

42

I.1. S iu chnh in p.

42 43

I.2. Nguyn l iu chnh in p.

43 46

I.3. S ng lc v nguyn l hoc ng.

46 - 48II. Tnh ton mch ng lc.

48

II.1. Chn Tiristor cho mch ng lc.

48 49

II.2. Tnh chn bo v cho van.

49

II.2.1. Bo v qu dng cho van.

49 50

II.2.2. Bo v qu p cho van.

51 52

II.2.3. Bo v qu nhit cho van.

52 54

II.2.4. Chn thit b ng ct.

54 55

III. Tnh ton cc c tnh.

55

III.1. c tnh t nhin.

55 59

III.2. Tnh ton in p lc u t ln ng c.

59 62

III.3. Tnh ton gc m ng vi cc trng hp.

62 64

III.4. Cc thng s iu khin.

64 66PHN III

CHN V TNH TON MCH IU KHINI. Chn mch iu khin.

67

I.1. Nguyn l iu khin.

67

I.1.1. Nguyn tc iu khin thng ng tuyn tnh.

67 68

I.1.2. Nguyn tc iu khin thng ng Arccos.

68

I.2. Cu trc mch iu khin.

68 69

I.2.1. Khu ng pha.

69

I.2.1.1. Khu ng pha dng t v Diod.

69 71

I.2.1.2. Khu ng pha dng Transistor v t.

71 72

I.2.1.3. Khu ng pha dng khuch i thut ton.

72 74

I.2.1.4. Khu ng pha dng Transistor quang v khuch i thut ton.

74 75

I.2.1.5. Khu ng pha to in p ta c chu k.

76 77

I.2.2. Khu so snh.

77

I.2.2.1. Khu so snh dng Transistor.

78 79

I.2.2.2. Khu so snh dng khuch i thut ton.

80 81

I.2.3. Khu khuch i to xung.

81 84

I.2.3.1. S pht xung chm dng vi mch 555.

84 85

I.2.3.2. S to xung chm a hi dng khuch i thut ton.

85 87

I.2.4. Chn mch iu khin.

87

I.2.4.1. Khu ng pha.

87

I.2.4.2. Khu so snh.

87

I.2.4.3. Khu khuch i to xung.

87 93II. Tnh ton thng s mch iu khin.

93 94

II.1. Tnh ton my bin p xung.

94

II.1.1.Tnh ton li thp my bin p xung.

94 96

II.1.2. Tnh ton dy qun my bin p xung.

96 99

II.2. Chn linh kin cho mch iu khin.

99

II.2.1. iod.

99

II.2.2. Chn cng AND.

99

II.2.3. Chn khuch i thut ton.

100

II.3. Tnh ton thng s mch iu khin.

101

II.3.1.Tnh thng s khu khuch i.

101 103

II.3.2. Tnh thng s mch to xung chm.

103 104

II.3.3. Tnh thng s tch phn m chm.

104 105

II.3.4. Tnh thng s khu so snh.

106

II.3.5. Tnh thng s khu ng pha.

107 109PHN IV

THIT K T IN

I. Cc nguyn tc b tr thit b.

110II. Cht lng m thut phi m bo nhng yu cu.

110 112

III. Cc k hiu ca t in.

112 113PHN IKHI QUT V NG C KHNG NG BI. Cu to v t im ca ng c khng ng b:

I.1. Cu to:

ng c khng ng b gm hai phn chnh: phn tnh v phn quay.

1

2

3

4 5

6Trong :

1) Qut lm mt 2) Hp u dy

3) V my

4) Stato

5) Chn lp c nh 6) Rto

Hnh1-1: ng c khng ng b rto dy qun. I.1.1: Cu to phn tnh ( stato ):

Gm v my, li st v dy qun

I.1.1.1. V my:

V my lm bng nhm hoc bng gang, dng gi cht li thp v c nh my trn b v khng dng dn t. i vi my c cng sut ln (1000KW) thng dng thp tm hn li thnh v.I.1.1.2. Li st

c lm bng cc l thp k thut in dy 0,35mm n 0,5mm ghp li. Li st l phn dn t v t trng i qua li st l t trng xoay chiu, nhm gim tn hao do dng in xoy gy nn, mi l thp k thut in u c ph lp sn cch in. Mt trong ca li thp c x rnh c dy qun.

a

b

c

Hnh 1-2:

a/. Mt ct ngang ca stato

b/. l thp k thut in

c/. Stato ca ng c khng ng b

I.1.1.3. Dy qun:

Dy qun stato lm bng dy dn bc cch in ( dy in t ) c t trong rnh ca li st. Dy qun stato gm c ba cun dy t lch nhau 1200 in.

I.1.2. Cu to phn quay ( Rto ):I.1.2.1. Trc:

Lm bng thp, dng li st rto.

I.1.2.2. Li st:

Gm cc l thp k thut in ging nh phn stato c dp rnh mt ngoi ghp li, to thnh cc rnh theo hng trc, gia c l lp trc.I.1.2.3. Dy qun rto:

Gm hai loi: loi rto dy qun v loi rto ngn mch ( cn gi l rto lng sc )

* Loi rto kiu dy qun:

Dy qun rto ging dy qun stato v c s cc bng s cc stato. Cc ng c cng sut trung bnh tr ln thng dng dy qun kiu song hai lp gim c nhng u ni dy v kt cu dy qun rto chc ch hn. Cc ng c cng sut nh thng dng dy qun ng tm mt lp. Dy qun rto thng ni sao ( Y ). Ba u ra ni vi ba vng tip xc bng ng, c nh trn trc rto v c cch in vi trc nh 3 chi than t st vo 3 vng tip xc, dy qun rto c ni vi 3 bin tr bn ngoi m my hay iu chnh tc .

* Loi rto kiu lng sc:

Loi dy qun ny khc vi dy qun stato, mi rnh ca li st c t mt thanh dn bng ng hoc nhm v c ni tt li hai u bng hai vng ngn mch ng hoc nhm, lm thnh 1 ci lng ngi ta gi l lng sc.

Hnh 1-3: Dy qun ca rto kiu lng sc Ngoi ra dy qun lng sc khng cn cch in vi li thp, rnh rto c th lm thnh dng rnh su hoc thnh hai rnh gi l lng sc kp dung cho my c cng sut ln ci thin tnh nng m my. Vi ng c cng sut nh rnh rto thng i cho mt gc so tm trc. I.1.2.4. Khe h:

Khe h trong ng c khng ng b rt nh (0,2mm 1mm). Do rto l mt khi trn nn rto rt u.

I.2. c im ca ng c khng ng b:

Cu to n gin c bit l ng c rto lng sc

Vn hnh tin cy, chc chn, gi thnh h

u trc tip vo li in xoay chiu ba pha nn khng cn trang b cc thit b km theo

Tc quay ca rto nh hn tc t trng quay ca stato ( n < n1)

Trong :

n : Tc quay ca rto

n1: Tc quay t trng quay ca stato ( tc ng b ca ng c ).I.3. Nhng i lng ghi trn ng c khng ng b:

Cng sut nh mc Pm l cng sut c hay cng sut in my a ra.

in p nh mc Um v dng in nh mc Im

Vd: Trn nhn my c ghi (/Y 220v/380v - 7.5/4.3A ta s hiu nh sau khi in p li in l 220v th ta ni dy qun stato theo hnh (. V dng in nh mc l 7.5 A. Khi in p li in l 380v th ta u dy qun stato theo hnh Y, dng in nh mc l 4.3 A.

H s cng sut nh mc : cos(m

Tc quay nh mc nm (vng/ pht ).

Tn s nh mc fm (hz)

I.4. Cch u dy ca ng c:

Tu theo in p ca li in m ta u dy stato theo hnh Y hay hnh (. Mi ng c in ba pha gm c ba dy qun pha. Khi thit k ngi ta quy nh in p nh mc cho mi dy qun .ng c lm vic phi ng vi in p quy nh y. thun tin cho vic u ng c, ngi ta k hiu 6 u dy ca ba dy cun ng c AX, BY, CZ v a 6 u dy ni ra 6 bu lng ( 1.6 ) hp dy trn v ng c.

Cch u 6 u dy nh th no in p vo ng c lun l nh mc.

-ng c ba pha c in p nh mc cho mi pha dy qun l 220V ( UP = 220V ), trn nhn ng c ghi l ( /( 220V/380V .

Nu ng c lm vic mng in c Ud = 380V, th ng c phi u theo hnh sao (Y). Mun ni hnh sao ta ni ba im cui ca pha vi nhau to thnh im trung tnh. Ba im u ni vi ngun.

Cch u nh hnh v:

Hnh 1-4. Hp u dy qun stato hnh sao Trong cch ni hnh Y

Id = Ip ; Ud = Up

Khi in p vo mi dy qun l: Up = V bng ng in p quy nh.

- Trng hp ng c lm vic mng in c in p 220v th ng c phi u theo hnh . Mun ni hnh tam gic, ta ly u pha ny ni vi cui ca pha kia. Cch ni tam gic khng c dy trung tnh.

Hnh 1-5: Hp u dy qun stato theo hnh tam gicTrong cch ni tam gic

Ud = Up Id = Ip

Khi in p vo mi dy qun l 220v

I.5. Vai tr ca ng c khng ng b:

My in khng ng b l my in xoay chiu ch yu dng lm ng c in. Do kt cu n gin, lm vic chc chn, hiu qu cao, gi thnh h nn ng c khng ng b l loi my c dng rng ri nht trong cc ngnh kinh t quc dn vi cng sut t vi chc n vi nghn KW . Trong cng nghip thng dng ng c khng ng b l b phn ng lc cho my cn thp va v nh, ng lc cho cc my cng c cc nh my cng nghip nh, vv Trong hm m dng lm my ti hay qut gi. Trong cng nghip dng lm my bm hay my gia cng nng sn.

Tuy vy, my in khng ng b c nhng nhc im sau: l cos ca my thng khng cao v c tnh iu chnh tc khng tt nn ng dng ca my in khng ng b c phn b hn ch.

II. Nguyn l lm vic ca ng c khng ng b:

Khi ni dy qun stato vo li in xoay chiu ba pha, trong dy qun c cc dng in. H thng dng in ny to ra t trng quay vi tc :

( 1- 1)

Trong :

f1 : tn s dng in li

p : S i cc

Nu tn s f1 = 50 Hz:ta c

T trng quay ca stato cm ng trong dy qun rto mt sut in ng E (chiu sut in ng xc nh theo quy tc bn tay phi), v vy dy qun rto ni ngn mch nn trn thanh dn rto hnh thnh 1 dng in ln. S tc ng tng h gia dng in ca rto vi t trng ca stato to nn mt lc in t tc dng ln thanh dn theo phng tip tuyn vi b mt rto to ra mmen lm cho rto quay. Chiu quay ca rto theo quy tc ca t trng c minh ho theo hnh.1- 6.

H.1-6: Nguyn l lm vic ca CKB.

Tc rto n c gi l tc lm vic v lun nh hn tc quay ca t trng n1. V nu tc quay ca rto bng tc ca t trng c th xem cun dy ca rto v t trng ng yn nn khng xy ra hin tng cm ng in t trn cun dy rto. V vy ch trong trng hp tc quay ca rto nh hn tc quay ca t trng mi xy ra cm ng sc in ng trong dy qun rto.

c trng cho ng c khng ng b ba pha l h s trt

( 1- 2 )

Trong :

s : h s trt

n1: tc quay

n : tc quay ca rto

H s trt ca ng c khng ng b c tr s nm trong khong t 0 1

Khi s = 0 : tc rto bng tc t trng ch khng ti l tng

Khi s = 1 : rto ng yn ( n = 0) mmen trn trc bng mmen m my

Khi ng c quay ti nh mc, c h s trt nh mc tng ng c tc quay ca rto inh mc. H s trt nh mc nm trong khong 0,01 0,06

T cng thc ( 1 1) ta c th tnh c tc quay ca ng c khng ti

n = n1( 1 s )

(1 3 )

Dng in trong dy qun v t trng quay tc dng lc tng h ln nhau nn khi rto chu tc dng ca mmen M th t trng quay cng chu tc dng ca mmen theo chiu ngc li. Mun cho t trng quay vi tc n1 th n phi nhn mt cng sut a vo gi l cng sut in t.

(1 4 )

Trong :

( 1 5 )

: tc gc ca t tng quay, cn gi l tc ng b

Khi cng sut in a vo

P1 = .U.I.Cos

( 1 6 )

Ngoi thnh phn cng sut in t c tn hao trn in tr dy qun stato.

( 1 7 )

Tn hao st t:

( 1 8 )

Do vy:

( 1 9 )

Cng sut c trc l:

( 1 10 )

Cng sut c nh hn cng sut in t v c tn hao trn dy qun rto:

( 1 11 )

Trong :

( 1 12 )

R2 : in tr quy i ca rto

I2 : dng in quy i ca rto

m2 = 3 : s pha ca dy qun rto

V P2 < Pdt do n < n1

Cng sut c ca P2 a ra nh hn P2 v tn tht trn trc ng c v cc tn tht ph khc:

Do vy:

( 1 13 )

Trong :

: tn hao c

: tn hao ph khc

Hiu sut ca ng c:

( 1 14 )III. Cc phng trnh c bn ca ng c khng ng b:III.1. Cc c tnh c bn ca ng c khng ng b.

III.1.1. Phng trnh c tnh c:

thnh lp phng trnh c tnh c ca ng c khng ng b ta s dng s thay th. Trn hnh 1-6 l s thay th 1 pha ca ng c khng ng b. Khi nghin cu ta a ra mt s gi thit sau y:

Ba pha ca ng c l i xng

Cc thng s ng c l khng i ngha l khng ph thuc vo nhit , in tr rto khng ph thuc vo tn s dng in rto, mch t khng bo ha nn in khng X1, X2 khng i.

Tng dn mch t khng thay i, dng in t ho khng ph thuc vo ti m ch ph thuc vo in p t vo stato ng c.

B qua cc tn tht ma st, tn tht trong li thp.

in p li hon ton sin v i xng ba pha.

Vi gi thit trn ta c s thay th mt pha ca ng c khng ng b:

Hnh.1- 6: S thay th mt pha ca ng c

Trong :

: tr s hiu dng ca in p stato.

: cc dng in t ha, stato v dng in roto quy i v stato.

: cc in tr tc dng ca mch t ha ca cun dy stato v rto quy i v stato.

: in khng mch t ha, in khng tn stato v in khng tn rto d quy i v stato.

s : h s trt ca ng c.

( 1 15 )

: tc gc ng c.

: tc gc ca t trng ( tc ng b)

Trong :

f1: tn s ca in p ngun t vo stato.

p : s i cc t ng c.

T s thay th ta tnh c dng in stato:

( 1 16 )

: in khng ngn mch.

Biu thc (1 16 ) l phng trnh c tnh dng in stato v c th biu din trn hnh.1 6.

Hnh. 1- 7: t tnh dng in stato ca ng c KB

Ta nhn thy rng:

Khi

th I1 = I1nm

Khi

ta c:

( 1 17 )

Trong :

I1nm: dng in ngn mch stato

I : l dng in t ha c tc dng to ra t trng quay khi ng c quay vi tc ng b.

Ta cng tnh c dng in rto quay quy i v stato.

( 1 18 )

y l phng trnh c tnh dng in ca ng c khng ng b, c biu din hnh.1 8.

Hnh 1 8: c tnh dng in rto ca ng c KB

Khi

th

Khi th

( 1 19 )

Cng sut in t chuyn t stato sang rto:

P12 = Mt.

( 1 20 )

Trong :

Mt: l mmen in t ca ng c.

Nu b qua cc tn tht ph th:Mt = Mc = M

( 1 21 )

Cng sut chia thnh hai phn:

Pc : cng sut a ra trn trc ng c.

: cng sut tn hao ng trong rto

P12 = Pc + P2

( 1 22)

HayM = M + P2

( 1 23 )

Do P2 = M( ) = M..s( 1 24 )

Mc khc

P2 = 3..

( 1 25 )

Nn

( 1 26 )

Thay gi tr tnh c trn vo ( 1- 26 ) v bin i ta c:

( 1 27 )

Trong :

Xnm = X1 + X2

: tc ng b ng vi Mc = 0.y l phng trnh biu th mi quan h M = f(s) = f [s()] gi l phng trnh c tnh c ca ng c in xoay chiu ba pha.

Hnh 1- 9: th c tnh c ca ng c KB.

Vi nhng gi tr khc nhau ca s ( 0 s 1 ) s cho ta nhng ga tr tng ng ca M. ng biu din M = f(s) l ng c tnh c ca ng c in khng ng b.

ng c tnh c c im cc tr gi l im ti hn K, ti im :

( 1 28 )

Gii phng trnh t s vi S ta c:

( 1 29 )

Thay phng trnh ( 1 29 ) vo phng trnh ( 1 27 ) ta c:

( 1 30 )

Trong hai biu thc trn du ( + ) ng vi trng thi ng c, du ( - ) ng vi trng thi my pht. Do Mth ch my pht ln hn Mth ch ng c.

Phng trnh c tnh c ca ng c khng ng b c th biu din thun tin hn bng cch phng trnh CLOSS:

( 1 31 )

Trong :

( 1 32 )

i vi nhng ng c cng sut ln thng R1 rt nh so vi Xnm, lc ny c th b qua R1, ngha l coi R1 = 0, asth = 0 v (1 31 ) c dng gn ng:

( 1 33 )

Trong :

( 1 34 )

( 1 35 )

Nhiu trng hp cho php ta s dng nhng c tnh gn ng bng cch tuyn tnh ho cc c tnh trong on lm vic. V d vng trt nh s sth t s nh, gn ng coi . Lc ny c tnh c dng n gin:

( 1 36 )

Cng c th tuyn tnh ho im lm vic qua im nh mc, phng trnh gn ng l:

( 1 37 )

T dng c tnh c biu din ( H.1- 9 ) ta thy cng ca ng c tnh c bin i c v tr s ln v du tu theo im lm vic.

( 1 38 )

Vi c tnh tuyn tnh ho ng 1 ( H. 1-9)

Vy

( 1 39 )

Tng t vi c tnh 2 trn H 1- 10:

( 1 40 )

Nh vy trn ng c tuyn ca ng c khng ng b c gi tr m v gn nh khng i.

i vi on c tnh s > sth, khi s >> sth b qua v phng trnh c tnh c s l:

( 1 41 )

V

( 1 42 )

Trong on ny cng l dng v gi tr ca n bin i. ng c khng ng b khng lm vic trn on c tnh ny.

c tnh c ca ng c khng ng b c biu din H.1- 9.

H.1-11: c tnh c ca ng c KB

on c tnh c AK gn thng v cng, trn on ny mmen tng th tc ng c gim. Do ng c lm vic trn on c tnh ny s lm vic n nh.

III.2: nh hng ca cc thng s n c tnh c ca ng c KB:

T phng trnh c tnh c (1 27) ca ng c khng ng b, ta thy cc thng s nh hng c tnh c bao gm.

- in p li Uf1.

-Tn s li in cung cp cho ng c f1.

-in tr, in khng mch stato ( ni thm in tr ph R1f v X1f vo stato).

-in tr mch rto ( ni thm in tr ph R2f vo mch rto i vi ng c rto qun dy).

-nh hng s i cc p ca ng c.

Khi cc thng s ny thay i s gy ra bin ng cc i lng:

-Tc ng b:

- trt ti hn:

-Mmen ti hn:

III.2.1: nh hng ca in p ngun cung cp cho ng c:

in p li Uf1: thay i bng cch s dng b in p xoay chiu. Cc tham s cn li l hng s.

Khi Uf1 gim ( ( Mth ) Mmen ti hn s gim bnh phng ln suy gim ca in p . Mth gim ( U12 gim

Trong khi tc ng b: (1 = = const. V trt khng thay i. Vy ta c ng c tnh c trong trng hp ny.

Hnh 1-12: c tnh c ca ng c khng ng b khi gim in p cp cho ng c. Vy khi gim in p cp cho ng c lm cho Mth gim nhanh. Tuy nhin Sth khng i v vy phng n gim in p thng thch hp cho dng ph ti nh: qut gi , my bm ly tm. III.2.2. nh hng ca tn s li in f1 cp cho ng c: Thay i bng cch s dng b bin tn dng cho c ng c dy qun v lng sc.Xut pht t biu thc : (1 = , ta thay i tn s f1 lm cho tc t trng quay thay i ( tc ng c thay i theo .

Khi f1> f1m ta c : ( Sth =

X1 = (1L1 ; X2 = (1L2

Mmen ti hn s gim theo quy lut : ( Mth =

Thc t khi f1 tng m bo Mmm cho ng c v tc lm vic ca ng c khng vt qu gi tr cc i cho php .

(max b hn ch bi bn c kh ca ng c .

Khi f1 < f1m tc l khi f1 gim ta c:

Khi f1 gim ( (1 gim ( Sth tng ( Mth tng( Xnm gim

Ta c c tnh c trong 2 trng hp

Hnh 1-13: c tnh c khi thay i tn s li in f1 cp cho ng c

Trong trng hp khi tn s ngun cp cho ng c gim dn n tng tr ca mch gim ( v tng tr ca mch t l thun theo tn s ) vi gi tr in p gi khng i th dng in khi ng tng rt nhanh do vy khi gim tn s cn gim in p theo mt quy lut nht nh gi mmen theo ch nh mc

Qua th c tnh c ta thy rng:

Khi f1< f1m vi iu kin = const th Mth gi khng i. Khi f1> f1m. th Mth t l nghch vi bnh phng tn s.

Khi tng gim tn s f1 cp cho ng c ch yu iu chnh tc ng c trng hp m my rt t dng hoc c dng th dng ring.

III.2.3. nh hng ca in tr, in khng mch stato:

c thc hin bng cch mc thm in tr (R1f ) hoc in khng (X1f ) ni tip vo pha stato ca ng c.

Tc t trng khng i: (1 = const , Sth gim , Sth gim

Do c tnh c c dng:

Hnh 1- 14: ng c KB vi Rf v Xf trong mch stato.

a) S vi R1f; b) S vi X1f; c) c tnh c

Ta thy rng khi cn to ra c tnh c mmen khi ng l Mmm th c tnh c ng vi X1f trong mch cng hn c tnh c vi R1f

Da vo tam gic tng tr ngn mch c th xc nh c X1f, hoc R1f trong mch stato khi khi ng.

III.2.4: nh hng ca in tr, in khng ph mch stato:

Ch dng cho ng c khng ng b rto dy qun ,s dng b iu chnh xung in tr . ngi ta thc hin bng cch mc thm R2f vo mch rto .

Ta c: (1 = = const

Mth = const

Sth = tng ( dng in m my gim

Hnh 1-15: nh hng ca in tr mch roto n c tnh c.

a) S u dy ; b) c tnh c Vy R1 cng tng, dng in khi ng cng gim, Mk tng ln. Sau mmen khi ng s gim. Do cn c vo iu kin khi ng v c im ca ph ti m chn in tr cho thch hp.

III.2.5. nh hng s i cc p:

thay i s i cc stato ngi ta thng thay i cch u dy:

T cng thc: (1 = v ( = (1 ( 1- s )

Ta thy thay i s cp cc p th (1 thay i dn n tc ng c thay i. Gi tr Sth khng ph thuc vo p nn khng thay i khi cng c tnh c gi nguyn. Nhng khi thay i s i cc s phi thay i cch u dy stato nn mt s thng s nh U1 (in p vo stato) R1, X1 c th thay i do tng trng hp s nh hng khc nhau n mmen ti hn Mth ca ng c.

a) b)

Hnh1.16: c tnh c khi thay i s i cc ca ng c khng ng b.

a) Thay i s i cc vi P2 = P1/2 v Mth = const

b) Thay i s i cc vi P2 = P1/2 v P1 = const

III.3. M my ng c khng ng b:

III.3.1. Qu trnh m my ng c khng ng b:

Trong qu trnh m my ng c khng ng b, mmen m my l c tnh ch yu trong nhng c tnh ca ng c in. Mun cho my quay c th mmen m my ca ng c ln hn mmen ti tnh v mmen ma st tnh. Trong qu trnh tng tc phng trnh cn bng ng v mmen nh sau:

( 1 43 )

Trong :

M, Mc, MJ : l mmen in t ca ng c in, mmen cn v mmen qun tnh.

: l hng s qun tnh.

( 1 44 )

G v D : l trng lng v ng knh phn quay.

g = 9,81 ( m/s2): l gia tc trng trng( 1 45 )

: tc gc ca rto.

Khi bit c tnh c ca ng c in khng ng b M = f1(n) v ca ti M = f2(n) th c th t cng thc ( 1 43 ) tm ra mi quan h gia tc v thi gian n = f(t) trong qu trnh m my. Cng t biu thc trn ta thy mun m bo tng tc thun li trong qu trnh m my th phi gi > 0, ngha l M > Mc, vi mt qun tnh nh nhau, M Mc cng ln th tng cng nhanh. Ngc li nhng my c qun tnh ln th thi gian m my lu. i vi trng hp c yu cu m my nhiu ln th thi gian m my nh hng n nhiu nng sut lao ng.

Khi ng trc tip li in ng c m my th lc u do rto cha quay, trt ( s = 1 ) nn dng in cm ng ln.

Imm = ( 5 7 ) Im

( 1 46 )

Dng in ny c tr s c bit ln cc ng c cng sut trung bnh v ln to ra nhit t nng ng c v gy xung lc c hi cho cc cun dy trong ng c. Tuy dng in ln nhng mmen m my nh:

Mmm = ( 0,5 1,5 ) Mm

( 1 47 )

Ni chung khi m my ng c cn xt n cc yu cu c bn sau:

- Phi c mmen m my ln thch ng vi c tnh c ca ti.

- Dng in m my cng nh cng tt.

- Phng php m my v thit b m my phi n gin, r tin, lm vic chc chn.

- Tn hao cng sut trong qu trnh m my cng nh cng tt.

Nhng yu cu trn thng mu thun vi nhau, nh khi i hi dng in m my nh, thng lm cho mmen m my gim. V vy phi cn c vo iu khin lm vic c th ca ng c in m chn phng php m my thch hp.

III.3.2. Cc phng php m my ng c in ba pha:III.3.2.1.Phng php m my trc tip ng c in khng ng b rto lng sc:

y l phng php n gin nht, ch vic ng trc tip ng c in vo li in ( Hnh 1- 17 ). M my trc tip, dng in m my ln, nu qun tnh ca ti ln dn n thi gian m my ko di, c th lm cho ng c in pht nng, nh hng n in p li in v thi gian gim p qu lu. Nhng nu ngun in ln so vi cng sut ng c, nn dng phng php m my trc tip, v thi gian m my nhanh, phng php m my n gin, mmen m my ln. Phng php ny ch dng m my cho ng c khng ng b cng sut nh.

Hnh 1-17: M my trc tip ng c K

( CD: cu dao; CC: cu ch )

III.3.2.2. Phng php h in p m my:

Mc ch ca phng php ny l gim dng m my, nhng ng thi mmen m my cng gim, do vi nhng yu cu mmen m my ln th phng php ny khng ph hp. i vi nhng ti c yu cu mmen m my nh th phng php trc tip rt thch hp. Trong thc t c mt s cch gim in p m my nh sau.

III.3.2.2.1. Phng php ni in khng ni tip vo mch in stato:

Khi m my trong mch in stato t ni tip mt khng in nh ( Hnh.1 18 ). Khi m my xong bng cch ng cu dao (CD2) th in khng ny b ni ngn mch. iu chnh tr s ca in khng th c th c c dng in m my cn thit. Do c in p gin trn in khng nn in p m my trn u cc ng c in Uk s nh hn in p li UL. Gi dng in m my v mmen m my khi m my trc tip l Ik v Mk, sau khi thm in khng vo, dng in m my cn li Ik = k.Ik , trong d k < 1, nu cho rng khi h in p m my, tham s ca my in vn gi nguyn khng i th dng in m my nh i, in p u cc ng c s bng Uk= k.Uk. V mmen m my t l vi bnh phng ca in p lc mmen m my bng Mk = k2.Mk.

Hnh 1- 18: M my ng c in bng in khng.III.3.2.2.2: Phng php dng my bin p t ngu gim in p m my:

S lc m my ( Hnh.1 19 ). Trong T l my bin p t ngu, cao p ni vi li in, h p ni vi ng c in. Khi m my ng c in, ta ng cu dao CD1 v CD3, my bin p t ngu con chy v tr no sao cho in p t ln ng c bng 0,7Um, sau di chuyn con chy in p t ln ng c bng in p li, qu trnh m my kt thc. Dng cu dao CD2 v m cu dao CD3, tch my bin p t ngu, khng lm vic khi ng c khi ng xong.

Hnh 1- 19: M my ng c in bng my bin p TNGi t s bin p t ngu l kT ( kT < 1 ) th Uk = ktU1. Do dng in m my v mmen m my ca ng c in s l: Ik = kT.Ik v Mk = kT2.Mk.

Gi dng in ly t li vo l I1 ( dng in s cp ca my bin p t ngu ) th dng in bng: I1 = kT.Ik = kT2.Ik.III.3.2.2.3. Phng php m my bng phng php :

Phng php m my thch ng vi nhng my khi lm vic bnh thng th u . C ngha l khi ni tam gic in p lm vic ca ng c ph hp vi in p ca li in.

Khi m my ta i thnh nh vy in p a vo hai u ni mi pha ch cn . Sau khi my chy ri i li cch u . S cch u nh (Hnh 1 20).

Hnh 1 20: M my ng c in :

Khi m my th ng cu dao CD1, cong cu dao CD2 ng v pha di, nh vy my u . Khi my chy ri th ng cu dao CD2 v pha trn, my u theo . The0 phng php th khi dy qun u in p pha trn dy qun ng c s l:

Ta c:

Do khi u m my th dng in pha bng dng in dy m khi m my trc tip th u ( khi y Ukf = U1 v Ik = Ik ngha l dng in v mmen m my u bng dng in v mmen khi m my trc tip. Trong thc t trng hp ny t dng mt my bin p t ngu m my m t s bin i in p kT = .III.3.2.2.4. Phng php m my bng cch ni thm in tr ph vo mch rto:

Phng php ny ch dng c vi cc ng c in rto dy qun. c im ca loi ng c my c th thm in tr vo dy qun rto.

Khi thm in tr vo dy qun rto, lm cho in tr dy qun rto thay i v c tnh mmen M = f(s) cng thay i. Ta iu chnh in tr mch rto thch hp th s c trng thi m my l tng (ng 4 hnh 1- 22). Sau khn rot quay, duy tr mmen in t nht nh trong qu trnh m my, ta gim dn in tr thm vo rto Rf, lm cho qu trnh tng tc ca ng c in thay i M = f(s) ny sang ng c tnh M = f(s) khc.

Hnh.121:M my ng c in bng phng php thm in tr Rf vo dy qun rto.

Hnh. 1 22: c tnh mmen khi thm in vo rto m my.

( Hnh.1 22) khi gim in tr ph Rf th ng c tnh m my thay i t ng 4 sang ng 3, ng 2 v sau khi in tr Rf gim n khng, ng c tnh m my l ng 1 v tng tc ti im lm vic.

ng c rto dy qun c th t c mmen m my ln, ng thi c dng in m my nh, nn nhng ni no m iu kin m my nng n, kh khn nn dng ng c rto dy qun.

III.3.2.2.5. Phng php m my ng c KB nh linh kin bn dn:

Ngy nay vi s pht trin ca ngnh in t cng sut th vic m my ng c bng cch gim in p t vo stato dng van bn dn rt thun li. Ta c th m my ng vi tng loi ti, tng loi ng c, c nh thi gian m my v t ng iu khin m my. Trong khi tn hao trn ton b thit b iu khin nh, rt gn gng v gi thnh khng cao.

Hnh 1 23: B bin i in p bng Van bn dn.III.3.2.2.6. phng php m my ng c KB bng cch li dng vo hiu ng mt ngoi dy qun rto lng sc:

trng hp c bit do iu kin lm vic ca ti th c th m my bng cch ng dng hiu ng mt ngoi.

Kt cu ca ng c rto lng sc n gin, lm vic chc chn, c c tnh lm vic tt nhng c tnh m my ca n khng c tt nh ng c rto dy qun. Dng in m my ln nhng mmen m my khng ln lm. ci thin c tnh m my ca ng c KB rto lng sc, ngi ta ch to ra nhiu kiu c bit m hin nay dng nhiu nht l ng c in rto rnh su v rto hai lng sc (lng sc kp). Nhng ng c ny ngoi hnh dng c bit ca rnh rto ra cn cc kt cu khc hon ton ging nh ng c rto lng sc thng.

Mc d ng c in ny c vi c tnh lm vic hi xu hn ng c in thng nhng v ci thin c c tnh m my nn vn s dng rng ri.

*Nguyn l i vi ng c in rto rnh su:

ng c in rto rnh su li dng hin tng t thng tn trong rnh rto gy nn hin tng hiu ng mt ngoi ca dng in ci thin t tnh m my.

tng hiu ng mt ngoi th rnh rto phi c hnh dng va hp, va su, thng t l vi chiu cao v chiu rng vo khong ( 10 12 ).

Thanh dn t trong rnh c xem nh l gm nhiu rnh dn nh, t xp chng ln nhau theo chiu cao v hai u c ni ngn mch li bi hai vnh ngn mch. V vy in p hai u cc mch song song bng nhau, do s phn phi dng in trong cc mch ph thuc vo in khng tn ca chng. Khi m my lc u dng in dy qun rto c tn s ln hn ( bng tn s li f1 ).

Hnh 1 24: th phn b dng in theo chiu cao.

y rnh t thng tn mc vng cng nhiu, cng ln pha ming rnh th t thng tn cng t. Do in khng y rnh ln cn pha ming rnh nh. V vy dng in s tp trung pha ming rnh, s phn b ca dng in theo chiu cao ca rnh nh ( H1 - 24)

Kt qu dng in tp trung ln pha trn, tit din dy dn coi nh b nh i, in tr rto li tng ln v vy lm cho mmen m my tng ln. Mc khc dng in tp trung ln pha trn cng lm gim t thng mc vng i mt t, ngha l x2 nh i.

Hiu ng mt ngoi mnh hay yu ph thuc vo tng s hay hnh dng ca rnh. V vy khi m my tn s cao hiu ng mt ngoi mnh, khi tc ca my tng ln tn s ca dng in rto gim xung nn hiu ng mt ngoi cng gim i, dng in dn dn phn b li u hn.

V vy in tr rto r2 c xem nh nh tr li, in khng tn quy i ca rto do tn s ca li nn x2 tng ln n khi my lm vic bnh thng. Do tn s ca dng in rto thp ( khong 2 3hz) nn hin tng hiu ng mt ngoi hu nh khng c, do ng c in rto rnh su trn thc t c c tnh lm vic nh cc loi my thng.* Nguyn l i vi ng c in rto hai lng sc:

ng c in loi rto hai lng sc, cc thanh dn ca lng sc

pha ngoi c tit din ln lm bng ng thau c in tr ln. Cc thanh dn ca lng sc pha trong c tit din ln lm bng ng c in tr nh, nhng do rnh tng i su, t thng tn nhiu nn in khng tn ln.

Nu hai lng sc u c bng nhm th mi c vnh ngn mch chung. Gia hai lng sc c mt khe h nh ni lin rnh ca lng sc ngoi vi rnh ca lng sc trong cho t thng tn phn b nh hnh ( H.1 25).

Hnh 1 25: th phn b dng in trong hai rnh.

Nh vy ta c th lm cho thng s ca rto tho mn c nhng yu cu cn thit v tnh nng m my ca ng c. Khi m my ng c in tn s ca rto bng tn s li do in khng ca lng sc trong ln nn dng in ch yu tp trung lng sc ngoi.

Ta c: I2k >> I2l

Trong :k : ch lng sc ngoi

1V : ch lng sc trong

Gc pha ca hai dng in vi sc in ng E2 ph thuc v , vk ln, xk nh cn x1v ln, nn Ik gn cng pha vi E2 v I1v chm sau E2 rt nhiu. V vy khi m my lng sc ngoi sinh ra mmen ln, c tc dng ch yu nn gi l lng sc m my, khi lm vic bnh thng th hiu ng mt ngoi ca dng in ca dng in yu hn i, in khng ca lng sc trong nh li, dng in s tng ln.

Do I2k gn cng pha vi E2 m dng in t l nghch vi in tr nn I1v >> Ik. do vy lng sc trong ch yu sinh ra mmen ta gi l lng sc lm vic, Nh vy c th coi ng c in c hai lng sc lm vic song song v c tnh M = f(s) ca loi ng c ny c th coi nh l tng hp cc c tnh M = f(s) ca hai lng sc.

Thay i kch thc dng rnh v khe h gia hai lng sc, dng vt liu khc nhau lm thanh dn th c th thay i cc thng s ca hai lng sc t c c tnh M = f(s) theo mun.

PHN HAITNH CHN MCH NG LC

I.Chn mch ng lc:

I.1. S iu chnh in p:

Qua phn mt chng ta tm hiu v nh gi cc phng n m my ng c khng ng b ba pha. y ng c c cng sut P = 27KW l trung bnh nn chn phng n ti u m my l khu rt quan trng m bo s lm vic bnh thng ca ng c cng nh khng lm nh hng xu n h thng li in.

Ta bit rng Mmm ~ U1f2 nn chn phng n m my bng cch gim in p m my: ni , dng bin p t nguNhng phng php iu khin in p m my bng Tiristor c xem l ti u v n gin, d hot ng, vn hnh, kim tra cng nh tn hao t v ph hp vi tnh cht ca ti tr khng.

Hin nay c nhiu s ng lc iu khin in p xoay chiu ba pha bng cp Tiristor mc song song ngc ph bin nht l ba s sau y:

H.2-1: S in p xoay chiu ba pha bng cp Tiristor

mc song song ngc.

S ti u sao c trung tnh hnh (H.2-1a) c u im l s ging ht ba mch in p mt pha iu khin dch pha theo in p li. Do in p trn cc van bn dn nh hn, v in p t vo van bn dn l in p pha. Nhc im ca s l trn dy trung tnh c tn ti dng in iu ho bc cao, khi gc m cc van khc 0 c dng ti gin on v loi s ni ny ch thch hp vi loi ti ba pha c bn dy u ra.

i vi s khng dy trung tnh nh hnh (H.2-1b) v (H.2-1c) c nhiu u im khc so vi s c dy trung tnh. Dng in chy gia cc pha vi nhau, nn ng thi phi cung cp xung iu khin cho hai Tiristor ca hai pha mt lc. Vic cp xung iu khin nh th i khi gp kh khn trong mch iu khin, ngay c khi i th t pha ngun in cng c th lm nh hng ti hot ng ca s .I.2. Nguyn l iu chnh in p:

Qua nhng nhn xt nh gi, ta chn phng n iu chnh in p hnh (H.2-1b) l hp l v c th ca ti ng c l c tnh tr khng ln.

Vi cch ni cc van nh trn trng thi xc lp lun c dng in chy qua ng c. V vy ti mt thi im no c t nht hai van dn hai pha khc nhau. T s hnh (H.2-1b) ta thy T1, T3, T5 dn na chu k dng cn T2, T4, T6 dn na chu k in p m.

Do trong khi lm vic th s c th cc trng thi nh hnh ( H.2-2) nh sau:

H.2-2: Cc trng thi dn ca cc van.

ng c khng ng b c th coi l mt ph tia ba pha gm in tr v in khng ni tip nhau. Trong in tr bin thin theo tc quay R = R(s) v in cm ph thuc vo v tr tng i gia dy qun stato v rt. Do gc pha gia dng in v in p cng bin thin theo tc quay = (s).

V tnh cht t nhin ca mch in c in cm nn khi gc iu khin < m c xung iu khin vo cc van bn dn th cc van ny dn dng t thi im = tr i. Do dng in v in p ca ng c khng ph thuc vo gc iu khin . Vy ta c th iu khin c in p khi gc iu khin < .

T s thng nht iu khin ca chnh lu cu iu khin i xng v in p xoay chiu ba pha nn ta thy rng: cung cp xung iu khin cho in p xoay chiu ba pha c th bng xung n hoc xung chm. Cp xung iu khin loi no tu thuc vo ch lm vic v tnh cht ti. Thng gp hin nay trong in p ba pha c hai cch iu khin:

Xung iu khin cp n nhng phi m xung iu khin.

Xung iu khin cp bng xung chm.

* iu khin b in p ba pha bng xung n:

Khi gc iu khin ca cc van bn dn ln, ng thi c hai Tiristor cng dn mt lc, xung iu khin phi cung cp ng thi cho c hai Tiristor. Hn na, hai van c dn phi cp xung theo kiu mt xung chnh cn m v mt xung m, nguyn tc ny phi theo ng th t pha.

Trn hnh (H.2-3) v ng cong in p ti v c m van bn dn ln ( ).

c ng cong in p pha A nh hnh v, cn cp xung iu khin theo th t pha. Mi Tiristor trong mt chu k iu khin c cp hai xung iu khin, trong xung chnh quyt nh gc m ca n, cn xung th hai X6 1 l xung m c nhn t Tiristor cn m ca pha khc ti. in p v dng in gin on, v vy ti thi im cp xung X1 khng c xung m X1 4 th Tiristor T1 khng th m cho dng chy t pha A n pha B.

Gii thch iu ny mch ng lc hnh (H.2-4) v in p ti hnh (H.2-3).

Ti gc m ca T1 ( UA > 0 ) pht xung iu khin X1 m T1, ng thi xung m T4 X1 4 ( xung th hai ca T4) lc ny vi in p pha A dng hn in p pha B ( UA > UB). T1 v T4 cng dn, chng no UA cn dng hn UB. in p trn ti pha A nu coi nh l i xng th . n t2 do in p UB dng hn UA nn T1 v T4 b kho t2.

n t3 l gc t ca T6 ( UC < 0 ), pht xung X6 iu khin T6 ng thi theo ng th t pha m xung X6 1 cho T1, lc ny do UC 100 (W)

Din tch b mt to nhit c xc nh theo cng thc:

( 2 10)

Trong :

: H s to nhit bng i lu v bc x.

= Tlv Tmt : Chnh lch nhit so vi mi trng.

Vi : Tlv = 800C: Nhit cnh to nhit khi Tiristor lm vic nh mc

Tmt = 400C : Nhit ca mi trng.

Suy ra:

= 80 40 = 400C

Vy:

Ta chn thit b to nhit bng nhm c 16 cnh to nhit. Mi Tiristor c to nhit v hai pha v lm mt cng bc bng qut gi. V y tn hao trn Tiristor qu ln nn ch dng cnh tn nhit lm mt th kch thc tht ca cnh tn nhit qu ln nn cng knh v nhim v lm mt khng m bo.

H.2-7: Cnh tn nhit cho Tiristor

Kch thc ca cnh tn nhit c chn l:

a = 15 (mm)

b = 15 (mm)

Vy din tch tht ca cnh tn nhit l:

Stnt = 2.16.15.15 = 7200( mm2) = 0,72 m2

Vy iu kin lm mt c m bo

II.2.4. Chn thit b ng ct:

thc hin vic ng ct v iu khin m my ng c theo ng yu cu th cn phi mt hai cng tc t K1, K2 nh hnh ( H.2-4) trong :

K1: c nhim v ng ct mch ng lc khi cn thit v c iu khin bng hai nt n M v D

K2: c nhim v ni ngn mch b bin i khi khi ng song v c iu khin bng Rle thi gian R.

Nh vy ta c th chn cng tc t K1 v K2 ging nhau. Tra Ti liu H thng cung cp in ca tc gi Nguyn Cng Hin v Nguyn Mnh Hoch ta chn cc cng tt t c cc thng s k thut sau:

Loi:

Xoay chiu

Dng in nh mc qua tip im:Imc = 400(A)

in p nh mc:

Um = 400(V)

C 4 tip im, trong c 1 tip im duy tr v 3 tip im ng lc

Chn Rle thi gian c cc thng s k thut sau:

Loi:

Dng in

Dng in nh mc:

Im = 400(A)

in p nh mc:

Um = 380(V)

III.Tnh ton cc c tnh:

III.1. c tnh t nhin:

ng c khng ng b xoay chiu ba pha c cc thng s sau:

Cng sut nh mc :Pm = 27 KW.

Tn s nh mc:fm = 50 Hz.

in p nh mc:Um = 220/380V.

Tc nh mc:nm = 975( vg/ph).

H s gc nh mc: cosm = 0,83.

Hiu sut:

m = 0,94.

T s

:

T phng trnh c tnh c ca ng c khng ng b ( phng trnh CLOSS):

( 2 11)

Ti thi im lm vic nh mc ta thay s = sm vo phng trnh (2 - 11) ta c:

( 2 12)

Ti thi im khi ng ( m my ) th s = 1, thay vo phng trnh (2 12) ta c:

( 2 13)

Mc khc ta c biu thc gn ng:

Mk = k.Mm

( 2 14)

Mth = max.Mm

( 2 15)

Trong :

k v max : l bi s mmen khi ng v bi s mmen cc i ca ng c.

Ta c th lp c h phng trnh nh sau:

( 2-16) v (2-17)

Trong :

Phng trnh (2-16) l phng trnh mmen lc nh mc.

Phng trnh (2-17) l phng trnh mmen lc khi ng nhng ta thay:Mk = k.Mm v Mth = max.Mm

Rt gn phng trnh trn bng cch chia hai v ca phng trnh cho Mm ta c:

(2-18) v (2-19)

Vi:

Mc khc t phng trnh (1-1) v (1-2) trong phn 1 ta c:

Trong :

Vi p = 3: l h s i cc ca ng c.

Suy ra:

Thay cc gi tr trn vo h phng trnh (2-18) v (2-19) ta c:

(2 20) v (2 22)

Gii h phng trnh trn ta c: v

Mmen nh mc ca ng c c xc nh theo cng thc:

(2 22)

Suy ra:

Mth = max.Mm = 2,6.270 = 702 (N.m)

Thay cc gi tr sth = 0,425, = 8,63 v Mth = 702 (N.m) vo phng trnh c tnh c ca ng c khng ng b ( 2- 11) ta c:

Thay cc gi tr s tng ng ta nhn c cc gi tr ca M trong bng sau:s00,020,050,10,150,20,250,3

M(N.m)0230412542624660681693

s0,40,50,60,70,80,91

M(N.m)702700743683672660648

Bng 1: Bng gi tr ca c tnh t nhin.

Cc ng c tnh ca ng c c biu din hnh (H.2-7):

H.2-8: ng c tnh c v c tnh iu chnh ca ng c KB.

III.2. Tnh ton in p lc u t ln ng c:

Khi m my ng c th lc u rto ng yn ( n = 0) cho nn t trng quay ca dy qun stato xuyn qua dy qun rto nhiu nht. Do n cm ng trong dy qun rto mt dng in cng rt ln, ngha l dy qun stato cng xut hin mt vng in rt ln thng thng:

Ik = (5 7)Im

(2 23)

Mc d thi gian khi ng ngn nhng n cng gy st p li in v gy pht nng ng c, tn hao ln, c th gy hng ng c v cc thit b khc.

khc phc nhc im ngi ta phi gim Ik sao cho to mn vi cc thng s k thut ca ng c nh dng in m my cho php:

Icp = ( 2 2,5 ) Ik

(2 24)

Do ngi ta tm cch m my thch hp cho tng loi ti, tng loi ng c. Nhng ng c khng ng b rto lng sc thng s dng phng php m my bng cch h in p t vo cun dy stato hn ch dng in khi ng. Khi in p lc u t vo ng c c xc nh:

( 2 25)

Trong :

Xnm = X1 + X2 : in khng ngn mch.

Vy:

( 2 26)

V ng c c cng sut P = 27KW l trung bnh nn thng th R1 rt b so vi Xnm lc ny c th coi R1 . Khi ta c biu thc gn ng:

( 2 27)

( 2 28)

( 2 29)

Thay biu thc ( 2 28) vo biu thc (2- 29) ta c:

( 2 30)

Trong :

: Tc ng b ca ng c.

Khi khi ng ng c th dng khi ng rt ln nu ta khng ch Ik = Icp = ( 2 2,5)Im th in p lc u c vo ng c l:

( 2 31)

=

* Tnh ton c tnh iu chnh ng vi in p ban u:

Khi Tiristor lm vic ta c th b qua in tr ca n v lc gc m = 0, tc l Uk = Ukmax th ta c in p ra ca b bin i t ln ng c l Um. Lc ta v c tnh c t nhin nh ng cong 1 hnh (H.2-8).

Da vo c tnh c t nhin v in p lc u t vo ng c Ux ta c th xy dng c tnh iu chnh ca ng c nh sau:

H s tng i gia in p ban u v in p nh mc l:

( 2 32)

M mmen ca ng c t l vi bnh phng in p theo biu thc:

M1 = M.2

( 2 33)

T ta lp bng gi tr ca c tnh iu chnh ca ng c l:

s00,020,050,10,150,20,250,3

M(N.m)0178319420483511527537

s0,40,50,60,70,80,91

M(N.m)544542575529520511502

Bng 2: Bng gi tr ca c tnh iu chnh.

T bng ny ta c th biu din c tnh iu chnh ng vi in p Ux nh ng 2 hnh (H.2-8).III.3.Tnh ton gc m ng vi cc trng hp sau:

Trong vic iu chnh thit b nghch lu th vic to thi im cho xung m Tiristor l mt khu rt quan trong. Tiristor thng c iu khin theo nguyn tc thng ng. Nguyn tc by thi im pht xung m l thi im xut hin s cn bng gia in p iu khin v in p ta. in p ta thng c dng rng ca v trng pha vi in p Anod ca Tiristor nn n m c xc nh nh sau:

H.2-2: th in p khi xc nh gc m .

Ta c ng thc:

( 2 34)

Trong :

: l in p iu khin

A: l bin ca in p rng ca

Da vo bng 1 trang 22 Ti liu thit k in t cng sut chn biu thc tnh in p ti:

( 2 35)

Nu chng ta cho Tiristor m hon ton th in p ti chnh l in p li in. Khi gc m c xc nh nh sau:

Nu cho Tiristor m vi in p ti l Ux th gc m c xc nh nh sau:

xc nh cc thng s iu khin th ta phi chn in p ra ca khu ng pha l Urc = 12V

Khi : A = Urc = 12V

T biu thc (2 34) ta c:

( 2 36)

Nu Tiristor m ng vi in p nh mc th in p iu khin c xc nh:

Nu Tiristor ng vi in p ti Ux th in p iu khin c xc nh nh sau:

T cc s liu tnh ton ta c th lp bng:

UkUx

00 40,180

2,679220194

Bng 3: Cc thng s iu khinIII.4. Cc thng s iu khin:

Ta kho st qu trnh qu ca h khi khng c ph ti (Mc = 0). Lc c tnh c ca ng c c th biu din bi phng trnh CLOSS nh sau:

( 2 37)

T phng trnh chuyn ng ca ng c l:

( 2 38)

Ta thay Mc = 0 v cn bng 2 mmen t phng trnh (2-37) v (2-38) ta c:

( 2 39)

V: = 0( 1 s )

thay vo phng trnh (2 39) ta c:

( 2 40)

Thi gian ca qu trnh qu din ra s tng ng vi s bin thin ca trt t gi tr ban u sbd n gi tr s ang xt:

Vy:

( 2 41)

Ly tch phn v t : gi l h s thi gian quy c:

Khi :

( 2 42)

Thi gian kt thc qa trnh qu s tng ng vi s bin thin ca trt t gi tr ban u n gi tr cui cng:

Thay s = scc ta c:

( 2 43)

Tnh hng s thi gian:

( 2 44)

Trong :

J: hng s mmen.

Tra sch my in 1 ta xc nh c hng s mmen qu tnh J = 1,075 (KG.m2).

Mth = 720 (N.m) = 72 (KG.m)

Vy:

Nh vy vic chn thi gian m my ng c trong 10s l hp l.

* Tnh thi gian qu tng ng vi c tnh gim p:

Thi gian qa ca c tnh gim p c tnh theo biu thc(2 43):

Trong :

Sbd = 1

Sthx = 0,424

Mthx = Mth.2 = 72.0,882 = 55,76(KG.m2)

Suy ra:

PHN BACHN V TNH TON MCH IU KHINI.Chn mch iu khin:I.1. Nguyn l iu khin:

Thc t ca b iu chnh in p xoay chiu l: iu khin Tiristor xong ri th dng in tc dng khng cn na, dong in chy qua Tiristor do thng s ca mch quyt nh. Tiristor ch m do dng chy qua khi in p t dng Anod v c xung iu khin.

Trong thc t ta dng hai nguyn tt iu khin l: thng ng tuyn tnh v thng ng Aroccos, thc hin iu chnh v tr trong na chu k dng ca in p t ln Tiristor.

I.1.1. Nguyn tt iu khin thng ng tuyn tnh:

Khi in p hnh sin t vo Anod ca Tiristor, c th iu khin gc ca Tiristor trong vng in p dng Anod ta cn mt in p ta dng tam gic, ta thng gi in p ny l in p rng ca Urc.

Dng mt in p mt chiu Uk so snh vi in p ta, ti mt thi im t1, t2 in p ta bng in p iu khin ( Urc = Uk). Trong vng in p dng Anod th php xung iu khin Xk cho ti cui bn k dng Anod.

Hnh 3-1: th in p iu khin thng ng.

Nh vy bng cch thay i Uk th ngi ta c th iu khin c thi im xut hin xung, tc l iu chnh c gc m .

Phng php ny nhn chung n gin, d thc hin, di iu chnh rng v thng dng trong thc t.

I.1.2. Nguyn tt iu chnh thng ng Arccos:

m gc ca Tiritor trong vng in p dng Anod ta cn mt in p ta Accoss so snh vi in p iu khin.

Ti thi im t1, t2 in p ta bng in p iu khin (Uta= Uk). Trong vng in p dng Anod th pht xung iu khin, lc ny Tiristor m cho ti bn k dng Anod.

Hnh 3 2: th in p khi iu khin thng ng Arccos.

Nguyn tt ny c s dng trong cc thit b chnh lu i hi cht lng cao.I.2. Cu trc ca mng iu khin:

thc hin vic iu khin nh trn th mch iu khin thng c ba khi c bn nh hnh (H. 3 3).

H. 3- 3: S cu trc mch iu khin.

II.2.1. Khu ng pha:

Nhim v ca khu ng pha l to ra in p ta, thng gp l in p rng ca tuyn tnh trng pha vi in p Anod v Tiristor.II.2.1.1. Khu ng pha dng t v Diod:

* S nguyn l ca mch:

H. 3- 4: Khu ng pha dng t v Diod.

* Nguyn l hot ng:

Khi in p UA > 0, do D1, D2 phn cc thun nn dn dng chy qua. Lc ny B = C = N, tc l in th ti cc im u bng nhau. Khi hai bng cc ca t ng th nn Urc = 0.

Khi in p i du th D1, D2 phn cc ngc nn b kha, khi t s np theo ng NC n bng cc ca t C bng in p A. Dng in np t c xc nh cng thc:

( 3 1)

Khi in p rng ca cng tng theo quy lut:

( 3 2 )

Hay

( 3 3 )

Trong :

T = R2.C: l hng s thi gian np t. T s np n khi no D2 phn cc thun. Urc tuyn tnh th hng s thi gian T phi ln. T s np n thi im 1, Urc = - E.

Sau 1 t s bt u phng in theo ng ch nht ABCN. Thi gian phng ph thuc vo R2 v C, n thi im 2 t C phng in hon thnh.

th in p ca s ng pha dng t v Diod c biu din hnh ( H.3 5).

H.3 5: th in p ca s ng pha dng t v Diod.

Cn khi in p ngun chuyn sang m, t C c kh nng np ngc li. m bo rng sau thi gian 2 trong chu k m ca in p ngun Urc = 0 v t C c np nh c.

* Nhn xt:

u im ca s ny l n gin nhng c nhiu nhc im ln v nh in p ta khng trng pha ti dng A. ngha l khng phi bin in p dng Anod. Do vy in p ta n cui bn k khng iu khin c, cc Anod c in p ri khc nhau. Do trong h thng nhiu knh s khng m bo tnh i xng ca cc xung pht ra. V vy s dng t V Diod ch dng cho h c yu cu chnh xc khng cao.

I.2.1.2. Khu ng pha dng Transistor v t:

* S nguyn l:H.3 6: Khu ng pha dng Transistor v t.

* Nguyn l hot ng:

chu k dng UAT th UB cng dng, lc Transistor phn cc ngc nn b kha. Khi t s c np vi hng s thi gian T = R2.C qua in tr R2 bi ngun E.

Vy:

(3 4)

na chu k sau UAT chuyn sang m nn UB cng m, do D1 b kha. Lc ny Transistor phn cc thun nn c m thng, dn n t C phng in qua Transistor n chu k sau th qu trnh lp li nh c.

th in p ca s ng pha dng Transistor v t c biu din hnh (H.3 7).

H.37: th in p ca s ng pha dng Transistor v t.

* Nhn Xt:

u im ca s ny l Urc ph ht bn k ca UAT v n gin nhng nhc im ca s ny c th tri im khng. Transistor rt nhy cm vi nhit.

I.2.1.3: Khu ng pha dng khuch i thut ton:

* S nguyn l ca mch:

H.3 8: Khu ng pha dung khuch i thut ton.

* Nguyn l hot ng:

in p UA hnh sin sau khi qua khu o A1 lm lt trng thi. Khi in p UA dng th in p UB m, bng ngun nui A1.

Khi UB m th Diod thng nn Transistor b kha, R3 v C l mch tchphn nn in p tng dn tuyn tnh, t C c np vi hng s thi gianT = R3.C cho nn khi in p ca t bng in p ngun nui A2.

iu kin Urc tuyn tnh:

( 3 5 )

Khi in p A m, in p B dng th Diod b kha lm cho Transistor thng, t C lp tc phng in qua Transistor. V in tr RCE ca Transistor rt b nn sn sau ca xung in p rt dc, gn nh thng ng, chu k sau qu trnh lp li nh c.

th in p ca s ng pha dng OA c biu din hnh ( H.3 9):

H.39: th in p ca s ng pha dng khuch i thut ton.

* Nhn xt:

u im ca s ny l in p rng ca tt, m bo ng pha vi in p ngun. Do to iu kin m Tiristor mt cch chnh xc, m bo tnh i xng gia cc pha ca ng c.

Nhc im ca s l dng my bin p nn vic thc hin cn kh khn v gi thnh cao.

I.2.1.4. Khu ng pha dng Transistor quang v khuch i thut ton:

* S nguyn l ca mch:

H.310:Khu ng pha dng Transistor quang v khuch i thut ton.

* Nguyn l hot ng:

Khi in p ngun A dng ( UA > 0) th DQ pht quang lm cho Transistor quang tr nn c dng in chy qua R3, dng in p m chy qua R4 ko in p xung di m to ngng so snh. Sau khi i qua khuch i thut ton A1 khng o du th in p nh Uc.

Phn in p UC dng lm D2 thng. Khi i qua khu tch phn ta c in p rng ca nh Urc.

chu k sau in p ngun i du th DQ kha nn khng c dng in chy qua Transistor c thin p nn thng lm t C x in qua lm ngn mch A2 nn in p rt dc gn nh thng ng.

th in p ca khu ng pha dng Transistor quang v khuch i thut ton c biu din hnh (H.3 11).

H.311: th in p ca s ng pha Transistor

quang v khuch i thut ton.

* Nhn xt:

S trn ch to ra in p na chu k nh vy mun m 6 knh Tiristor th phi cn n 6 knh iu khin nn s rt ri v kh iu khin.I.2.1.5. Khu ng pha to in p ta c chu k:

* S nguyn l ca mch:

H.3 11: Khu ng pha to in p ta c chu k.

* Nguyn tt hot ng:

in p ngun khi qua chnh lu th lun lun dng lm cho DQ dn pht quang lm cho dng in chy qua R3. Ta dng mt in p m qua R4 cho in p ra khuch i thut ton xung di m, to ngng so snh, khi in p UB dng qua khu khuch i thut ton khng o A1 cho ra in tch nh Uc.

Phn in p dng Uc qua D1 qua khu tch phn A2 to ra in p rng ca Urc, cn phn in p m ca Uc lm kha Diod D2 v m thng Transistor cho t C phng in lm ngn mch A2. Do in tr Rce ca Transistor rt b nn t C x rt nhanh lm cho sn sau rt dc gn nh thng ng.

th in p ca khu ng pha to in p ta c chu k c biu din hnh ( H.3 11).

* Nhn xt:

u im ca s ny rt kinh t nhng nhc im l khong cch cch in p rng ca nh nn khng iu khin c. Nhng i vi ti ng c xoay chiu v dng in tr pha hn in p mt gc no nn s ny vn dng tt, khi in p bng khng, khng ng k so vi .

H.311: th in p ca s ng pha to in p

ta c chu k.I.2.2.. Khu so snh:

Nhim v ca khu so snh l xc nh thi im in p ta bng in p iu khin ( Uta = Uk), ti thi im pht xung iu khin m Tiristor theo gc m nh. Trong thc t thng dng cc khu so snh nh sau:I.2.2.1. Khu so snh dng Transistor: gm c hai s sau

H.3 12: a) S khu so snh ni tip.

b) S khu so snh song song.

* Khu so snh ni tip:

Khi hai bn in p bng nhau, UBT = 0 so vi trung bnh.

Trong khong thi gian 0 1 th Uk < Urc nn UB < 0 lm cho Transistor kha. Vy Ura = - E.

Trong khong thi gian 1 2 th Uk > Urc nn UB > 0 lm cho Transistor m. Vy Ura = 0.

chu k sau qu trnh lp li nh c. Khu ny ph hp vi xung iu khin cng hai tn hiu ni tip nhng c chnh xc khng cao khi chung ta cng nhiu tn hiu dn n nhiu, nn s ny t dng.

th in p ca khu so snh c biu din hnh (H.3 13).

H.3 13: th in p ca khu so snh dng Transistor.

* Khu so snh song song:

Nu c hai tnh hiu in p vo hai ng song song vi nhau qua hai in tr hn ch R1 v R2 th chng so snh vi nhau ti im B.

Nu R1 = R2 th UB = Urc + Uk. s ny hot ng ging nh s so snh ni tip. Phng n ny c dng ch yu trn nhiu knh, chnh xc khng cao.

* Nhn xt:

C hai phng n ny c chung mt nhc im l xung quang in p Urc bin thin vc 1 do UB thay i. Gi thit Transistor bo ha cho nn in p thc khng chnh xc. V vy vic iu khin khng chnh xc.

khc phc nhc im ngi ta dng khu so snh bng khuch i thut ton.II.2.2.2. Khu so snh dng khuch t thut ton:

* S nguyn l:

a)

b)

H.3 14: Khu so snh dng khuch i thut ton.

* Nguyn l hot ng:

i vi s (H.3 14a): Khi in p so snh a vo mt cng, c in p bng khng th Urc = Uk, tc l khi R1 = R2, tc l khi Ura = Ungun nhng tri du vi A.

Trong khong 1 th UA > 0 nn Ura = - Ungun.

Trong khong 1 2 th UA < 0 nn Ura > 0.

i vi s (H.3 14b): Vic i du trong khuch i thut ton ti cc im 1, 2, 3 v 4 lm cho in p bin thin tc thi cn v nguyn l th cng ging nh s (H.3 14a). Trong thc t s ny t dng hn v y l b khuch i vi sai.

th in p ca khu so snh dng khuch i thut ton.

H.315: th in p ca khu so snh dng khuch i thut ton.

* Nhn xt:

Mch so snh ny c u im l chnh xc cao, tc ng nhanh, n nh nhit tt, tri im khng nh, thi gian qu ngn cho nn s ny c dng nhiu.

I.2.3. Khu khuch i to xung:

Khu khuch i to xung c nhim v to xung ph hp m Transistor khi c yu cu. Nhng xung iu khin m bo sn thng ng m Tiristor c tc thi. rng ln hn thi gian m Tiristor cng sut. ng thi c nhim v quan trng l cch ly mch iu khin v mch ng lc.

Vic to xung y c thc hin bng cch dng my bin p xung v Transistor cng sut.

* S nguyn l:

H.3 16: Khu to xung dng Transistor v MBA.

* Nguyn l hot ng:

Khi c xung in p dng cc B ca Transistor m, xut hin dng qu trong my bin p xung. mch s cp li xut hin mt sut in ng t cm, chnh sut in ng t cm ny cm ng sang th cp my bin p xung mt sut in ng. Sut in ng ny chnh l xung iu khin m Tiristor.

Ti thi im t xung 1 2 xut hin mt sut in ng t cm vi thnh phn t do bng in p ngun. rng xung c quyt nh bi dng in bin thin, ph thuc vo in cm bin thin dng in chm, dn ti rng xung cng ln. cho in cm ln th s vng dy phi ln.

Mun m c Tiristor th xung ra phi cng sut do ta dng b khuch i. C nhiu b khuch i nhng ngi ta dng b khuch i bng hai Transistor ni tng vi nhau nh s sau y.

H.3 17: Khu khuch i dng Transistor ni tng.

* th in p ca khu to xung bng Transistor v MBA c biu din hnh (H.3 16)

H.3 18: th in p khu to xung.

Vi ti ng c l ti cm nn dng in s tr sau in p mt gc no . Cho nn t 1 2 nu pht xung iu khin th vn khng m c Tiristor cho d xung m c rng thch hp.

Nu rng xung ln m Tiristor khng m th my bin p xung s nng v dng in ln c th nh thng Tiristor.

khc phc nhc im ny ngi ta chia ng xung m thnh nhiu xung hp lin nhau tc ng vo cc iu khin ca Tiristor. Khu thc hin chc nng ny l khu pht xung chm hay cn gi l b bm xung, thng dng l vi mch 555 hay dng khuch i thut ton.

I.2.3.1. S pht xung chm dng vi mch 555:

* S nguyn l:

H.3 19: S pht xung chm dng vi mch 555.

* Nguyn l hot ng:

Khi cp ngun th t C c np t ngun E qua R1 n khi th b so snh s chuyn trang thi. Khi t C1 s phng in qua R2, lc in p trn t gim cn th t C1 bt u np. Qu trnh din ra nh vy cho n khi ct in p ngun. Dng in p xung ra nh hnh (H.3 20), to ra c tn s ln chia xung nh ra thnh xung chm ri a vo mt cng AND cn cng kia l xung khu so snh.

* Nhn Xt:

S vi mch 555 cho xung chm c cht lng kh tt v s n gian.

H.3 -20: th in p ca b to xung chm.I.2.3.2. S to xung chm mch a hi dng khuch i thut ton.

* S nguyn l:

H.321: Mch to xung chm dng khuch i thut ton.

* Nguyn l hot ng:

S ny c hi tip dng chy qua R2 v hi tip m qua R3, nu l hi tip dng th h s khuch i v cng ln, lc in p ra bng in p ngun, cn du ca n ph thuc vo V+ v V-.

th in p ca mch to xung chm c biu din hnh ( H.3-12)

H.3 -12: th in p ca mch to xung chm.

Trong khong t t1 c in p ra dng nn cng vo V+ s dng vi phn p: v .

Lc V- s np t theo quy lut sau:

T np t t t1 nn V+ > V- lm cho Ura dng.

n 1: ti im A c V+ = V-, nu sau t t1 th V+ < V- lm cho i du v t s np v x tng t.

* Nhn xt:

S pht xung chm dng khuch i thut ton c u im hn so vi s dng vi mch 555 v mc n gin, do n c dng s dng rt rng ri trong cc vi mch to xung hnh ch nht.

Vic to xung ny a vo cng AND v mt xung t khu so snh a vo cng AND kia. Cn u ra ca cng AND c a n b khuch i to xung.

H.3 13: S bm xung nh cng AND.I.2.4: Chn mch iu khin:

I.2.4.1. Khu ng pha:

T nhng phn tch trn ta chn s ng pha dung Transistor quang v khuch i thut ton. V i vi ti ng c khng ng b xoay chiu ba pha th khu iu khin khng cn chnh xc cao.I.2.4.2. Khu so snh:

Ta chn s khu so snh song song dng khuch i thut ton. V s ny c u im ni bt l tc ng nhanh, n nh nhit tt v c dng nhiu.I.2.4.3. Khu khuch i to xung:

Gm b pht xung chm dng khuch i thut ton v cng AND hai u vo. Mt u l tn hiu khu so snh v mt u l tn hiu t b pht xung chm, u ra ca cng AND n b khuch i bng hai Transistor ri qua bin p xung to xung m thch hp Tiristor.

V yu cu m my ng c trong 10s nn ta phi thit k khu tch phn m chm ng vi thi gian s c biu din hnh

(H.3 14).

H.3 14: S mch tch phn m chm.* Nguyn l hot ng:

Cp in cho mch Uce = 12V. iu chnh bin tr R22 sao cho Uk = UA + Ukx .

Trong :

Uk = 2,679(V) l in p iu khin b bin i cho ra in p ban u l Ux = 194(V).

Lc mch bt u tch phn th in p UA bt u tng tuyn tnh. Khi t C3 np y ri, tc l np vi hng s thi gian T3 = R21.C3 = 10s th in p ra n nh c Uk = Ukmax.

iu khin c in p ra ca b bin i Ux th mch iu khin cn thm b cng in p bng cch a in p iu khin Ukx vo b cng in p qua R17.

Kt qua dng in p ra iu khin c dng nh hnh (H.3-25):

H.3-25: th in p iu khin.

Vi nhng khu chn. Vy ta c th thnh lp mch iu khin mt knh nh hnh (H.3-6):

S mch iu khin nh hnh (H3.26) ch iu khin c na chu k ca in p. Nh vy iu khin c in p xoay chiu ba pha theo yu cu ca ti th phi dng 6 knh iu khin v c ghp ni nh sau.

H.2-27: S khi 6 knh iu khin Tiristor

* Nguyn l lm vic ca mch iu khin:

ng c khng ng b ba pha rto lng sc th mi pha c vai tr v nguyn l nh nhau nn khi phn tch v tnh ton th ta ch cn xt mt pha cn cc pha kia cch lm tng t.

in p a vo khu ng pha l in p li xoay chiu ng pha vi in p c ln Anod cc Tiristor. in p ny nu na chu k t 0 th UA dng cho nn DQ phn cc thun, dn dng lm pht quang kch thch cho TrQ m, cho dng in p nh UB.

Do a ngun m qua R4 to ngng so snh v lt trng thi UB. Khi qua b so snh khng o du A1 lm in p lt trng thi v c dng in p nh UC.

Trong khong thi gian t t1 t2 th UC dng l kho Tr1 do phn cc ngc, lc t C c np vi hng s T1 = R5.C1 cho n cui bn k.

Thi im t2 in p U2 i du lm cho Tr1 m v phn cc thun, lc t C1 s phng in qua Tr1 lm ngn mch A2, do RCE ca Tr1 rt b nn sn sau ca in p rt dc gn nh thng ng.

Cn sau thi gian t 2 th UC m, lc D2 phn cc ngc v Tr1 phn cc thun nn in p bng 0. cc chu k sau qu trnh lp li nh c. Kt qu cho ra dng in p rng ca nh U0.

Ta dng in p mt chiu gi in p iu khin, xc nh thi im pht xung m Tiristor nh yu cu.

V yu cu m my ng c trong khong 10(s) nn ta phi dng khu tch phn m chm ng vi thi gian y.

u tin ta xc nh v tr ca bin tr R22 sao cho in p ra ca khu tch phn m chm l Uk ng vi gc m cho Tiristor m hon ton. Lc mch bc u tch phn vi hng s thi gian T3 = R21.C3, in p iu khin Uk tng dn tuyn tnh.

m my ng theo yu cu ta phi dng b cng in p gm: A5, R17 v R18. in o ra Uk m gc ng vi in p ca b bin i l UX v in p ra ca khu tch phn m chm c a chung vo mt cng ca khuch i thut ton.

Kt qua cho ra dng in p iu khin nh hnh (H.3-25).

Do cch a in p iu khin vo nh vy nn Uk ct in p ta ti cc im 1, 2, 5

Trong khong thi gian t: 1 2, t Urc > Uk nn khi vo A3 m do in p ra ca E bng in p dng ngun.

Trong khong thi gian t 3 tr i qu trnh lp li tng t ta c in p ra UE.

Ta dng Diot D3 lc phn in p m ca UE nn in p ra c dng nh UF.

Sau khi a xung dng t khu so snh vo cng AND n s c bm nh thnh nhng chm xung lin tc nh b dao ng a hi bng khuch i thut ton vi tn s c chn l: fx = 3kHz. Sau s cho in p nh UG.

Hai Transistor Tr2 v Tr3 m khi c xung dng i qua v kho khi khng c xung dng hoc c xung m. V vy cc khong thi gian: 1 2 v 3 4 th Tr2 v Tr3 s thng. Lc c s bin thin ca dng in trong cun dy s cp ca my bin p xung lm cm ng sang cun dy th cp mt chm xung t vo cc iu khin Tiristor. Lc Tiristor s m my theo yu cu nh.II. Tnh ton thng s mch iu khin:

Cc thng s mch iu khin c xc nh xut pht t yu cu v xung m Tiristor, nn khi ta tnh ton cc thng s trong mch th bt u tnh ton t my bin p xung ri n cc khu tip theo.

Cc thng s c bn tnh mch iu khin.

in p iu khin Tiristor:Uk = 3,0 V

Dng in iu khin Tiristor:Ik = 0,15 A

Thi gian m Tiristor:tcm = 80 s

rng xung iu khin:tx = 160 s

Tn s iu khin:fx = 3 kHz

mt i xng cho php: = 40

in p ngun nui mch iu khin:U = 12 V

Mt st bin xung:sx = 0,15

II.1. Tnh ton my bin p xung:

S nguyn l v dng in p ra ca my bin p xung:

H.3-37: a) My bin p xung.

b) th in p xung.

II.1.1. Tnh ton li thp my bin p xung:

V xung iu khin l xung chm c tn s cao nn gim tn hao do dng in xoy gy ra, ta chn vt liu st t loi pherit HM c dng xuyn lm vic trn mt pha ca c tnh t ho c:

B = 0,3 (T)

H = 30

Khng c khe h khng kh. Thng thng t s ca my bin p xung thng c chn: m = 2 3 y ta chn m = 2.

in p cun th cp my bin p xung: U2 = Uk = 3,0 V

in p t ln cun th cp bin p xung:

U1 = m, U2 = 2.3 = 6 V( 3 6)

Dng in chy trong cun th cp my bin p xung: I2 =Tk= 0,15 A

Dng in chy trong cun s cp my bin p xung:

( 3 7)

t thm trung bnh ca li thp c xc nh theo cng thc:

( 3 8)

Trong :

: t thm ca khng kh

Suy ra:

Th tch ca li thp c xc nh theo cng thc:

( 3 9)

Trong :

Q: Tit din li st.

L: Chiu di trung bnh ng st t.

tx: rng xung iu khin.

( 3 10)

Vy ta c:

Da vo ti liu K thut bin i nng lng ca cc tc gi Nguyn Bnh, ta chn li thp hnh xuyn bng cun c cc thng s k thut sau:

Chn loi mch t OA 20/25 6,5

Tit din li thp: Q = 0,162 cm2 = 16,2 mm2

Chiu di trung bnh:L = 7,1 cm

ng knh ngoi:D = 25 mm

B rng:a = 2,5 mm

B dy:b = 6,5 mm

Trng lng:P = 9,1 g

Din tch ca s:Qcs = 3,14 cm2

H.3-28: Li thp tht ca my bin p xung

Vy th tch tht ca li thp l:

(3 11)

= 0,25.0,65.7,1 = 1,15 (cm3)

II.1.2. Tnh ton dy qun my bin p xung:

S vng dy cun s cp my bin p xung c xc inh theo lut cm ng in t:

( 3 12)

Suy ra:

( 3 13)

S vng dy cun dy th cp my bin p xung:

( 3 14)

Dng in hiu dng chy trong dy qun s cp ca my bin p xung:

( 3 15)

Chn mt dng in

Khi tit din dy qun s cp l:

( 3 16)

ng knh ca dy qun s cp l:

( 3 17)

Tra bng p.5 trang 232 ti liu: in t cng sut ca tc gi Trn Vn Thnh ta chn dy dn bng ng c cc thng s sau:

ng knh tht:d1 = 0,13 (mm)

Tit din dy s cp:S1 = 0,01327 (mm2)

Trng lng ring:m1 = 0,118 (gam/m)

in tr mt mt:R/m = 1,256 (/m)

ng knh ngoi:Dn = ( 0,15 0,16)

Mt dng in thc ca dy qun th cp:

( 3 15)

Dng in hiu dng ca dy qun th cp:

Chn mt dng in

Khi tit din dy qun s cp l:

ng knh ca dy qun s cp l:

Tra bng p.5 trang 232 ti liu: in t cng sut ca tc gi Trn Vn Thnh ta chn dy dn bng ng c cc thng s sau:

ng knh tht:d2 = 0,18 (mm)

Tit din dy s cp:S2 = 0,02545 (mm2)

Trng lng ring:m1 = 0,226 (gam/m)

in tr mt mt:R/m = 0,707 (/m)

ng knh ngoi:Dn = ( 0,2 0,22)

Vy mt dng in thc ca dy qun th cp l:

Kim tra h s lp y ca ca s mch t c xc nh theo cng thc:

( 3 18)

Trong :

S1, S2 : Tit din ca dy qun s cp v th cp ca my bin p xung.

Qcs = 413 mm2 : Din tch ca s mch t.

Suy ra:

II.2. Chn linh kin cho mch iu khin:II.2.1. iot:

Mt knh iu khin dng 4 diot. Nh vy lp 6 knh iu khin ta phi chn 24 diot loi IN4108.

II.2.2. Chn cng AND:

Ton b mch in phi dng 6 cng AND nn ta da vo ti liu hng dn thit k in t cng sut ta chn hai IC 4081 h CMOS. Mi IC 4081 c 4 cng AND ( s chn nh hnh 3-29), c cc thng s sau:

Ngun nui IC:Vcc = ( 3 18 ) V, ta chn: Vcc = 12V

Nhit lm vic:t = - 400C 800C

in p ng vi mc logic 1: U = 2 4,5V

Dng in nh hn 1mA

Cng sut tiu th:P = 2,5 mW/ 1cng

H.3-29: S chn IC 4081.II.2.3. Chn khuch i thut ton:

Da vo ti liu thit k Thit k in t cng sut ta chn khuch i thut ton cho mch iu khin loi IC 084 do hng teasInstruments ch to, Mi IC my c 4 khuch i thut ton ( S chn hnh 3 30 ) c cc thng s sau:

in p ngun nui:

Vcc = 18V chn Vcc = 12V

Hiu in th gia hai u vo:Uv = 30V

Nhit lm vic:

t = - 250C 850C

Cng sut tiu th:

P = 680 mW = 0,68 W

Tng tr u vo:

Rin = 106 M

Dng in u ra:

Ira = 30 pA

Tc bin thin in p cho php:

H.3-30: S chn IC TL084II.3. Tnh ton thng s mch iu khin:II.3.1. Tnh thng s khu khuch i:

H.3-31: Khu khuch i dng Transistor ni tng.

Dng in trung bnh chy qua Tr3 l:

( 3 19)

Nh vy ta chn Tr3 sao cho ICr3 Itb

Da vo ti liu Tra cu Transistor Nht Bn ca tc gi Trn Ngc Sn ta chn Tr3 c cc thng s sau:

M hiu:

2SC 188, cht liu SIP

in p:

Ucbo = 40V

in p:

Uebo = 3V

Dng in cc i qua coletor:

ITr3 = 500 mA

Lm vic ch xung khuch i cng sut:

Cng sut cc i:

Pcmax = 600W

Nhit cc i:

t0cmax = 1750C

Tn s gii hn:

fmax = 150 MHz

H s khuch i:

3 = 40

T ta c dng in lm vic Colector ca Tr3 l:

ICTr3 = I = 0,075(A)

( 3 20)

Dng in lm vic qua cc Baz ca Tr3 l:

( 3 21)

Nh vy dng in qua Colector Tr2 l:

ICtr2 = IbTr3 = 0,002 (A)

Ta thy rng Tiristor chn c cng sut iu khin kh b Uk = 3V, Ik =0,15A nn dng in Colector - Baz ca Tr3 kh b. Do ta ch cn chn Tr3 c Pc b vn m bo cung cp cng sut iu khin Tiristor. Da vo ti liu Tra cu Transistor Nht Bn ca tc gi Trn Ngc Sn ta chn Tiristor c cc thng s sau:

M hiu:

2SC 9111

in p:

Ucbo = 40V

in p:

Uebo = 4V

Dng in cc i qua colector:

ITr3 = 500 mA

Lm vic ch xung khuch i cng sut:

Cng sut cc i:

Pcmax = 1,7W

Nhit cc i:

t0cmax = 1750C

Tn s gii hn:

fmax = 150 MHz

H s khuch i:

2 = 50

Nh vy dng in lm vic qua cc Baz ca Tr2 l:

Ta c Tr2 khi lm vic thng hon ton,dn dng ICTr3 = 300(mA) th dng l:

( 3 23)

Vi Tr2 v Tr3 c chn nh trn th h s khuch i ca c h l:

= 2. 3 = 50.40 = 2000

( 3 24)

gim p ng thi to dng in chy trong cun dy s cp my bin p xung ta dng in tr R13 v c xc nh theo cng thc:

( 3 25)

Trong :

U = UeboTr2 + UeboTr3 = 4 + 3 = 7(V)

Vy:

Ta chn R13 = 67()

hn ch dng in a vo cc baz ca Tr2 ta dng in tr R12 sao cho:

( 3 26)

Trong :

UG : l in p cp cho cng AND

Ta c:

Nh vy ta chn R12 = 2,2 (K)III.3.2. Tnh thng s mch to xung chm:

H.3-32: Mch to xung chm dng khuch i thut ton.

Mch to xung chm c tn s chn

Chu k to xung chm

Suy ra:

Ta c:

( 3 27)

Ta chn: R14 = R15 = 3,3 (K) th T = 2,2 .R16.C2 = 334 (s)

Ta c th chn C2 = 0,1 (F)

Khi :

Vy ta chn R16 = 2,2 (K)III.3.3. Tnh thng s tch phn m chm:

H.3-33: S mch tch phn m chm

V in p a vo khu so snh c dng hnh sin nn ta c:

Uk = Ud + Ukx = 12(V)

( 3 28)

Suy ra:

Ud = Uk + Ukx = 12 2,679 = 9,321 (V)

Ta c:

( 3 29)

Ta chn Uv = 2,5(V): l in p bo ho ca khu tch phn.

Khi :

( 3 30)

Vy:

Suy ra:

R21.C3 = 2,682

T ta chn t C3 = 0,01(F)

Suy ra:

Vy ta chn R21 = 300()

in tr R20 c xc nh:

R20 = K.R21 = 3,728.300 = 1118 ()

Vy ta chn R20 = 15 (k)

Ta khng ch dng in phn hi qua R19 khong 4 mA

Khi :

Nh vy ta chn R19 = 3,3 (k)

Ta c th chn R17 = R18 = 2 (k) v chn R22 = 10 (k) l bin tr.III.3.4. Tnh thng s khu so snh:

H.3-34: Khu so snh dng khuch i thut ton.

Ta khng ch dng in vo khuch i thut ton sao cho: Iv 1mA

Khi :

( 3 31)

Chn R9 = R10 = R7 + R8 = 12(k)

T ta chn: R9 = 3,9 (k) v chn bin tr R10 = 8,2(k)

Ta hn ch dng in vo cng AND sao cho: Iv 4mA

Khi :

( 3 32)

Vy ta chn R11 = 3,3(k)III.3.5. Tnh thng s khu ng pha:

H.3-35: Khu ng pha dung Transistor quang v khu khuch i thut ton.

in p np v x t C1 v in p rng ca c xc nh theo cng thc:

( 3 33)

Trong :

Urc = 12(V) cn chn Uv = 11,5(V): l in p bo ho ca khu tch phn.

T np trong thi gian na chu k nn:

Vy:

Suy ra: R5.C1 = 0,0096

Chn C1 = 0,5(F) th

Nh vy ta chn bin tr R5 = 20(k)

V in p ca khu ng pha l: Urc = 12(V) nn ta phi chn Tr1 sao cho Uce > 12(V)

Da vo Ti liu tra cu Nht Bn ta chn Tr1 c cc thng s sau:

M hiu:

2SC A564, cht liu SIP

Lm vic ch xung

in p:

Ucbo = 25(V)

in p:

Uebo = 7(V)

Dng in cc i qua Colector:Icmax =100(A)

H s khuch i:

1 = 250

Vy dng in ca cc Baz ca Tr1 l:

(3 35)

hn ch dng in vo cc Baz ca Tr1 ta dng in tr R6 c xc nh:

( 3 36)

Vy ta chn R6 = 30(k)

Ta chn R3 sao cho dng qua A1 nh ch bng 1mA

Khi :

( 3 37)

Vy ta chn: R3 = 14(k)

Ta chn R4 sao cho thi gian x t, khong m in p khng, tc l iu khin c nhng vng Urc nh.

Vi R4 = 3.R3 = 3.14 = 42(k)

Vy ta chn: R4 = 46(k)

Ta c th chn: R2 = R3 = 14(k)

Ta khng ch dng in qua DQ ti a 20mA. Khi R1 c tnh:

( 3 38)

Trong :

UCL = ku.Uf .Tra ti liu Thit k in t cng sut ta chn ku = 0,45

Suy ra:UCL = 0,45.220 = 99(V)

Vy:

T ta chn R1 = 5(k)

Ta phi chn Diot chu c in p ngc:

T iu kin trn da vo ti liu S chn linh kin bn dn ca tc gi Dng Minh Tr tra chn IC ILD620, mi IC c 4 ghp quang vi s chn nh sau:

H.3-36: S chn ca b ghp quang TransistorPHN IV

THIT K T IN

T in thit k phi m bo cht lng cao v k thut, m thut cng nghip

Cht lng k thut ca t in thit k c th hin cc yu cu sau:

Kch thc hp l so vi cc thit b cn lp.

B tr linh kin hp l v khng gian

I. Cc nguyn tc b tr thit b:

Cc linh kin b tr theo nguyn tc trng lng, ngha l nhng thit b nng b tr di thp, nhng thit b nh b tr trn cao.

Cc thit b b tr theo nguyn tc to nhit, ngha l nhng thit b to nhit t c b tr di thp cn nhng thit b to nhit nhiu c b tr trn cao.

C cc l thng gi cn thit: a s cc thit b in t cng sut to nhit nhiu, nn thng phi b tr qut lm mt. thit b cn lm mt nht trong trng hp ny l cc van bn dn, bi v cc van bn dn to nhit ln v rt nhy vi nhit .

Mch iu khin cn c bo v tt, trnh nhit cao, ngi ta thng b tr cch ly vi van v bin p.

B tr theo nguyn tc chc nng, ngha l nhng thit b c chc nng ging nhau thng c b tr gn nhau.

Cc thit b thao tc, o lng, tn hiu cn c b tr mt trc hoc nhng v tr thun tin.

II. Cht lng m thut phi m bo cc yu cu:

Hnh dng p

Mu sc hi ho khng sc s, khng qu ti, thng dng mu sng, mu trng ng, xanh nht

Thit b b tr ngau ngn c hng, c ct.

Dy ni phi t trong mng dy hoc c b tr thnh b gn nh.

Da vo nhng yu cu sau nh vy ta c th b tr thit k t in nh hnh (H.4-1) v hnh (H.4-2).

Cc kch thc ca t in c la chn vo kch thc lp t ca tng thit b. Nh vy s khi ca t in ta c th chn cc kch thc nh sau:

a = 40cm

x = 10cm

c = 20cm

d = 20cm

e = 40cm

i = 10cm

k = 20cm

f = 120cm

T ta c th xc nh cc kch thc:

b = f + 2x = 120 + 2.10 = 140cm

(4 1)

h = 4x + 20 + 2d = 4.10 + 20 + 2.20 = 100cm(4 2)

Tt c cc thit b iu c lp t trn thanh st gi l gi , ri c nh bn trong cc t.

Cc nt thao tc nh: Nt n, nt xoay, n bo, ng h o in p, dng in c b tr trn np ca t in.

pha tr cc thng cn c c b tr hai qut ht lm mt Tiristor v hai bn c cc l thng gi tng cng kh nng i lu ca khng kh.

III. Cc k hiu ca t in:

A: Ampe o dng in ti.

V: Vn k o in p ra ca ti.

1: n bo hiu in ngun.

2: n bo hiu Aptomat ng.

3: n bo hiu cng tc t K1 ng.

NX: Nt xoay iu chnh gc m.

Ap: Aptomat.

M: Nt nhn m my.

D: Nt nhn dng my.

VBD: Van dn ng.

MK: Mch iu khin.

K1: Cng tc t ng mch ng lc.

K2: Cng tc t ni tt b bin i.

R : Rle thi gian.

QH: Qut ht lm mt.

TI LIU THAM KHO

[1]. Trn Vn Thnh

Hng dn thit k in t cng sut Nh Xut Bn KHKT,2003

[2]. Nguyn Bnh

in t cng sut Nh Xut Bn KHKT, H Ni - 2000

[3]. V Gia Khanh - Trn Khnh H - Nguyn Vn Su

My in 1 Nh Xut Bn KHKT,1997,1998

[4]. Bi Quc Khnh Nguyn Vn Liu - Nguyn Th Hin

Sch truyn ng in Nh Xut Bn KHKT

[5]. Xun Th

K thut in t - Nh Xut Bn Gio Dc, 2000[6]. Nguyn Bnh

K thut bin i nng lng Nh Xut Bn KHKT,1982

[7]. Trn Ngc Sn

Sch tra cu Transistor Nht Bn

[8]. Dng Minh tr

S chn linh kin bn dn ca tc gi

[9]. Nguyn Cng Hin - Nguyn Mch Hoch

Thit K Cung Cp in Nh Xut Bn KHKT

[10]. V Quang Hoi

Trang thit b in - in t cng nghip Nh Xut Bn Gio Dc

Trong qu trnh thit k cn s dng nhiu ti liu lin quan khc.

C

&

t

B

n

Fdt

EMBED Equation.DSMT4


EMBED Equation.3

S

I1

I1nm

F

Rf = 0

C

Rf = 0

EMBED Equation.3

0

S

EMBED Equation.3

EMBED Equation.3

EMBED Equation.3

EMBED Equation.3

0

1

Rf = 0

Rf 0

SthF

Mth

0

EMBED Equation.3

MthF

EMBED Equation.3

Sth

S =1

Rf 0

TN (Rf = 0)

1

2

Mm

A

Mth

I2

I

EMBED Equation.3

Sth

B

K

0

U1f

I1

R

X


X2

R1

X1

1

S

1.0

0.8

0.6

0.4

0.2

0

1.0

EMBED Equation.3

2

3

4

Uk

UL

C

BB

t2


2 EMBED Equation.DSMT4

t

t

t

Uk

UA

Ud


Urc

t1

Xk

0

0

0

Uk

UAT

Uk

t1

Uta

t

t

0

t2

U

0

Xk



Ud


0

K

T

A

K

to xung

So Snh

ng pha

N

-E

Urc

C

R2

D1

D2

R1

B

A

U2

UA

UA

t

t



0

U

0

Urc




UAN

Tr

C

Urc

D1

R1

B

A

U2

UAT

-E

R2

t

t



0

U

0

Urc




UAT

A

A1

A2

R1

C

R3

R2

Tr

D

Urc

UAT

C

UB

0

Urc

t

t

t

0

U

0




U = UAT

Urc

UC

UB

0

0

t

t

t

0

U

0




UAT

UB

t

t

UC

0

0

UCL

t

0

t

0

U

0




UA

t

U

0

Urc



-E

-E

R2

Urc

R1

Tr

Ura

Uk

Tr

B

Ura

R1

R2

Urc

Uk

R3

Uk

t

t



0

U

0

Ura EMBED Equation.DSMT4




Uk

Ura

Urc

Urc

R2

Ura

A

R2

R1

Uk



t

t



0

U

0

Ura




UV

R

D2

+E

D1

BAX

Ic

Tr

BAX

D0

Tr2

Tr1

D

UV

C

R

Xk

e1

ic





t

t

t

t

0

0

0

0

U

IC555

R1

C1

R2

C2

Ura

3

4

8

7

6

2

1

5

T

T2

T1


t

Ura

t

0

0

U

R3

V-

C

Ura

V+

R2

R1

t2

t1

Ura

A

+V

-V

t

0

U

T so snh

T chm xung

Ti khuch i

&

A

R22

R19

R17

R18

R21

4,8V

R20

Uk

-12V

C3

A

CD

CC

KD

I

U

CD2

C

C

B

A

CD1

IK

IL

Uk

CD3

CD2

C

C

B

A

CD1

TN

CD2

Lm vic

M my

C

C

B

A

CD1

CC

Rf

C

C

B

CD

CC

A

H

0

X

I

X

0

t

a)

b)

c)

T6

c

b

a

T4

T1

C

B

A

A

B

C

T1

T4

AT

b

c

a

C

FX

C

B

A

CC

K1

M

D

K1

R

K2

R

R1

C1

C1

C1

R1

R1

K1

K1

K1

T5

K2

C2

R2

T4

T3

K2

C2

R2

T2

T1

K2

C2

R2

Uk

T6

0

t

t

t

t

t

t

t

t2

1/2UAC

1/2UAB

C

B

A

t6

t5

t3

XT1

XT2

XT3

XT4

XT5

XT6

X6

X3-6

X4-5

X5

X5

X4-5

X4

X1-4

X4

X2-3

X3

X5-2

X2

X6-1

X1

t6

t5

t4

t3

t2

t1

+E

D4

D3

D2

D1

C

B

A

TrQ

R1

DQ

R4

R2

A1

A2

R3

C

R5

R6

Tr

D2

Ura

UAT

D1

C

B

A

TrQ

R1

DQ

R4

R2

A1

A2

R3

C

R5

R6

Tr

D2

Ura

UAT

Hp u dy

Z

Y

X

C

B

A

Ngun

Ngun

Hp u dy

Z

Y

X

C

B

A

M

S

p2

p1

P1

P2

M

R2

R1

12

11

M

0

0

M

f14

f13

f1dm

f12

f11

f1 < f1m

11

12

1m

13

14

0

Mthm

MC

f1 > f1m

T1

T2

C2

R2

C1

C1

R1

R1

C1

R1

h0

c

z

h

h1

a

b

M

ng c tnh c M = f(s) ca ng c KB

ng c tnh iu chnh ng c KB

n

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

s

1000

800

600

400

200

0

3

2

Urc

Udk

U

t

U

t

0

10s

Ukx

U

Ukmax

0

A

D6

K6

T6

0

A

D5

K5

T5

0

A

D4

K4

T4

0

A

D3

K3

T3

0

A

D2

K2

T2

0

A

D1

K1

T1

D5

T

W2

W1

Tx

T

Tx

0

t

U

a)

b)

a

D

d

b

&

&

&

&

1

3

2

4

5

6

7

+Vcc

12

11

10

9

8

13

BAX

D4

Tr3

Tr2

D5

C2

14

13

8

9

10

12

7

6

5

3

2

1

4

Vcc

Vcc

11

R13

R12

R14

R15

Ura

R16

V+

V-

C3

A

R22

R19

R17

R18

R21

4,8V

R20

Uk

-12V

Uk

R7

R10

R11

Ura

R8

R9

+12V

C

0


S

Rf

0

Sthm

U3

U2

MC2

Um

Mnm

MC1

U1

Mnm2

TN

M

Mnm3

S

D1

C

B

A

TrQ

R1

DQ

R4

R2

A1

A2

R3

C

R5

R6

Tr

D2

Ura

UAT

8

7

6

5

1

Ap

H.4-1: S khi bn trong t in

4

3

2

R

K1

K2

MK

VD

f

b

1

i

k

h

x

c

d

x

c

x

x

A

V

NX

1

1

1

Ap

R

M

D

H.4-2: S khi mt trc ca t in

C

Xf

Mnm

Mnm

R1f

M

TN


0

Sthdm

X1f

1

a)

b)

c)

Mthdm

R2f = 0

TN

S

EMBED Equation.DSMT4 EMBED Equation.DSMT4

Rf


Sthdm

R2f2

R2f1

M

a)

b)

0

R1

1

PAGE Sinh vin thc hin. Trn Duy Sn

Trang 7

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thiết kế bộ khởi Động cho Động cơ không Đồng bộ ba pha bằng thyristor

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