on ap may phat _ avr2_

8/7/2019 on ap may phat _ AVR2_

1/72

SV: TB n Tt nghip - Thit k mch n p My pht

SV: TB Trg. 1

Mc lc

M u .................................................................................................2

Chng 1. Tng quan v cc phng php n nh inp my pht in ng b.......................................................3

1. Gii thiu chung v my pht in ng b................................42. Cc c tnh ca My pht in ng b. .................................. 83. Thit b t ng iu chnh. .......................................................144. H thng t ng iu khin kch t .........................................20

Chng 2: S t ng iu chnh in p my phtin...........................................................................................24

1. H thng kch t ........................................................................242. La chn phng n.................................................................313. S iu khin cho h thng kch t dng my pht

in xoay chiu theo phng n la chn................................31

Chng 3 - Thit k v tnh ton mch ng lc .........................321. Chnh lu c iu khin ba pha.................................................322. La chn s chnh lu .........................................................393. Tnh chn Tiristor.......................................................................404. Tnh bin p ng lc................................................................415. Tnh chn cc thit b bo v mch ng lc ...........................50

Chng 4 - Tnh ton cc thng s ca mch iu khin ...........511. Nguyn tc iu khin Thyristor. ............................................... 512. Chn cc khu trong mch iu khin. .....................................533. Tnh bin p xung ......................................................................604. Tnh tng khuch i cui cng.................................................625. Chn t C2 v R6........................................................................636. Tnh chn tng so snh .............................................................647. Tnh chn khu ng pha..........................................................648. To ngun nui .......................................................................... 66

9. Tnh chn Diod cho b chnh lu ngun nui ...........................6710. Tnh khu phn hi in p .......................................................67

Kt lun ..............................................................................................70

Ti liu tham kho.............................................................................72


2/72


SV: TB Trg. 2

M u

bt k Quc gia no, nng lng in lc lun lun c coi l

ngnh cng nghip mang tnh cht xng sng cho s pht trin cann kinh t. N v s lun h tr thc y s pht trin ca tt c

cc ngnh khc. Vic sn xut v s dng in nng mt cch hiu

qu nhng phi ph hp chi ph lun c coi trng c bit.

ngh a quan trng m cng chnh l mc tiu cao c nht ca chin

lc pht trin ngnh cng nghip then cht ny l nhm nng cao

i sng ca mi ngi dn v kt qu ca n s l mt X hi Vn

minh, Tin b v Thnh vng.

My pht in ng b ni chung ng mt vai tr trng yu trong

h thng in, ni m tnh n nh lun c i hi rt cao. Trong

h thng in, s n nh ca mi mt my pht in cc kha cnh

k thut u c tnh cht quan trng nht nh ti s vn hnh an

ton v bn vng ca ton h thng v cc my pht in th s

ng gp ca b n nh in p my pht, cng vi cc thit b n

nh khc l khng th thiu.

B iu khin n nh in p my pht bng iu khin dng/p

kch t i (iu khin kch t - KT) vo my pht c mt lch s

pht trin su rng. K t ngy u vic iu khin ny c t ng

ho, thit b ch ng vai tr nh mt thit b cnh bo cho ngi vn

hnh tc ng iu chnh trc tip vo my pht. Vo nhng nm

1920, khi con ngi nhn thy vai tr quan trng ca vic n nh

qu trnh qu ca h thng thng qua cc b iu khin p ng

nhanh, cc thit k cc h thng kch t v iu khin in p tinha v ci tin cng ngh khng ngng: t kch t c vnh trt n

khng vnh trt, t thao tc bng tay n t ng ho hon ton

thng qua vai tr khng th thiu ca cc thit b in t cng sut.


3/72


SV: TB Trg. 3

Tuy cng sut my pht c giao thit k (125kW) l rt nh v

khng thc s ng vai tr n nh trong h thng in ln, nhng

em cho rng vic thit k mt thit b nh v quan trng nh vy

cng l nn tng c bn cho mi thit k cc b n p my pht khcd ln. Ni dung n thit k ca em bao gm 4 chng, trong :

Chng 1 a ra gii thiu tng quan v cc phng php n

nh in p my pht in ng b

Chng 2 cp c th vo cc phng php n nh in p

vi cc s t ng iu chnh in p my pht in, v la

chn ra phng n ca n thit k.

Chng 3 l cc thit k v tnh ton c th cho mch nglc ca s chn v

Chng 4 bao chm phn tnh ton cho cc thng s ca

mch iu khin v tng hp s

Vi s hng dn v gip nhit tnh ca Gio vin hng dn

Thy Trn Vn Thnh, em c mong rng n tt nghip ny s

a n mt kt qu tt nghip tt p, nhng trn ht n s to v

xy dng cho em mt nn tng kin thc c bn, vng chc trongcuc sng lao ng k thut ca mt k s sau ny.

Em xin by t lng bit n su sc i vi Thy gio Trn Vn Thnh

v nhng kin thc, hng dn, ch bo m Thy dnh cho em

trong thi gian hc v c bit trong vic hon thnh n ny. Em

cng xin by t lng bit n ti cc Thy C gio khc ca B mn

Thit b in - in t ni ring v cc Thy C Khoa in v

Trng H Bch khoa HN ni chung 5 nm vt v nhit tnh dybo v cho em nhng cng c bng cc kin thc xy dng

tng lai.

Chng 1. Tng quan v cc phng php nnh in p my pht in ng b.


4/72


SV: TB Trg. 4

1. Gii thiu chung v my pht in ng b

My pht in ng b (MF) thng c ko bi tuc- bin hi

hoc tuc-bin nc, v vy chng c gi chung l my pht tuc- bin hi hoc my pht tuc-bin nc. i vi tuc-bin hi, do c

trng l tc cao c vi nghn vng pht nn my pht thng c

kt cu r-to cc n, vi ng knh nh gim thiu lc ly tm v

ngc li, i vi tuc-bin nc, tc thp nn thng c r-to cc

li, ng knh c th ln ti 15m tu thuc cng sut ca my.

MF ba pha (MF3) thng gp c bn l my pht in m dng

in mt chiu c a vo qun dy kch t khng thng qua vnhi chiu. Cc t ca MF3 c kch thch bng dng in mt

chiu c t phn quay, cn dy qun phn ng vi 3 im i

xng trn n c ni ra ngoi ti th c t phn tnh. Cng c

th t cc t phn tnh v dy qun phn ng phn quay ging

trong my in 1 chiu nh my in ng b cng sut nh, v s

trao i v tr khng lm thay i nguyn l lm vic c bn ca

my. Nguyn l lm vic c bn nh sau:

Stator ca my pht in ng b c dy qun 3 pha c t cch

nhau mt gc 120o trong khng gian, c gi l phn ng, cm ng

ra cc in p cung cp ra ti (Hnh 1.1). Cn rotor ca my pht, vi

cu to dy qun cc t (cc li i vi my pht c tuc bin tc

thp nh cc my pht tuc bin nc, v cc n i vi tuc bin c

tc cao nh my pht Diesel, tuc bin hi v kh) lm nhim v

cung cp t trng.

B


5/72


SV: TB Trg. 5

Hnh 1.1 - Cu to ca Stator.

Khi rotor quay vi tc n th t trng cc t s qut v cm ng

ln cc dy qun phn ng cc sc in ng (s...) xoay chiu ln

lt lch pha nhau 120o theo chu k thi gian, vi tn s:

60

n.pf

Vip l s i cc ca my

Khi MF3 lm vic khp mch vi ti, dng in 3 pha chy trong 3

dy qun lch nhau gc 2/3 v thi gian s to ra t trng quay vi

tc :

p

fn

601

So snh (1.1) v (1.2) ta c n=n1, hay c ngh a l tc quay ca

rotor bng tc ca t trng quay. V vy ta c my pht ng b.Kt cu MF3


6/72


SV: TB Trg. 6

My cc n

Rotor c lm bng thp hp kim cht lng cao c rn thnh

khi h nh tr, trn ngi ta gia cng phay to rnh t dyqun kch t. Phn khng phay rnh (nh h nh ??) hnh thnh mt

cc t.

Cc MF3 ccn thng c ch to vi s cc 2p=2, nh vy tc

quay ca Rotor l 3000 vng/pht. hn ch lc ly tm trong

phm vi an ton i vi thp hp kim ch to thnh li thp Rotor,

ng knh D ca Rotor khng qu 1,1 1,5 m. Tng cng sut ca

my bng cch tng chiu di l ca Rotor. Chiu di ti a ca Rotorvo khong 6,5 m.

Dy dn kch t t trong rnh Rotor c ch to t dy ng trn,

tit din ch nht qun theo chiu mng thnh cc bi dy. Cc vng

dy ca bi dy ny c cch in vi nhau bng mt lp mica

mng. Dy qun kch t nm trong rnh c c nh v p cht

bng cc thanh nm phi t tnh a vo ming rnh. Phn u ni

ngoi rnh c ai cht bng cc ng tr thp phi t tnh nhm bov chng li lc in ng do dng in gy ra. Hai u ca dy

qun kch t i lun trong trc v ni vi hai vnh trt t u

trc thng qua hai chi in, ni vi dng kch t 1 chiu.

Dng in kch t 1 chiu thng c cung cp bi mt my pht

in 1 chiu, hoc xoay chiu c chnh lu (c hoc khng c

vnh trt), ni chung trc vi MF.

Stator ca MF3 cc n bao gm li thp, trong c t dy qun 3

pha, ngoi l thn v v my. Li thp Stator c ghp v p bng

cc tm tn Silic c ph cch in. Cc ng thng gi lm mt cho

my c ch to c nh trong thn my m bo bn cch

in ca dy qun v my.


7/72


SV: TB Trg. 7

My Cc li.

My cc li c ch to cho cc MF c tc quay thp, nn

khc vi my cc n, ng knh D ca Rotor c th ln ti 15 mtrong khi chiu di l li nh vi t l l/D = 0,15 0,2

Hnh 1.2 Cc t ca my ng b cc li

Rotor ca MF cc li cng sut nh v trung bnh c li thp c

ch to bng thp c v gia cng thnh khi hnh tr trn mt c t

cc t. cc my ln, li thp c ch to t cc tm thp dy,t 1-6mm, c dp hoc c nh hnh sn ghp thnh cc khi

lng tr v li thp ny thng khng trc tip lng vo trc ca my

m c t trn gi ca Rotor, gi ny c lng vo trc my.

Cc t t trn li thp Rotor c ghp bng nhng l thp dy 1-

1,5 mm (v h nh v nh s) ch to c ui h nh T hoc bng cc

bu-lng xuyn qua mt cc v vt cht vo li thp Rotor.

Dy qun kch t c ch to t dy ng trn tit din ch nhtqun theo chiu mng thnh tng cun dy. Cch in gia cc vng

dy l cc lp mica hoc amiang. Sau khi gia cng, cc cun dy

c lng vo cc thn cc.

Dy qun cn ca MF c t trn cc u cc c cu to nh

dy qun kiu lng sc ca my in khng ng b; ngh a l lm


8/72


SV: TB Trg. 8

bng cc thanh ng t vo rnh cc u cc v hai u ni vi hai

vnh ngn mch.

Stator ca MF cc li c cu to nh MF cc n.

m bo vn hnh n nh, ngoi cc yu cu cht ch i vi kt

cu v in, cc kt cu v c hc v h thng lm mt cng c

thit k ch to ph hp v tng thch vi tng loi MF, p ng

c mi trng v ch lm vic. MF, lm mt bng gi cng

sut nh, c cc khoang thng gi lm mt c thit k ch to nm

gia v my v li thp Stator. u trc ca my c gn mt cnh

qut gi khi quay khng kh c thi qua cc khoang thng giny. V my ngoi ra cng c ch to vi cc sng gn hoc cnh

to nhit nhm lm tng din tch b mt trao i nhit cho my. Ph

bin nht l cc MF c lm mt bng nc hoc bng kh v

c p dng cho cc my c cng sut ln c t vi chc kW tr

ln.

2. Cc c tnh ca My pht in ng b.

1. c tnh khng ti E = U0 = f(it) khi I= 0 v f= fdm

2. c tnh ngn mch U = f(it) khi U = 0 ; f = fdm

3. c tnh ngoiU = f(I) khi it = const ; cos =const ; f = fdm

4. c tnh iu chnh it = f(I) khi U = const ; cos = const ; f =

fdm

5. c tnh ti U= f(it) khi I = const ; cos = const ; f= fdm

2.1. c tnh khng ti

E = U0 = f(it) khi I= 0 v f= fm


9/72


SV: TB Trg. 9

c tnh khng ti l quan h gia sc in ng E cm ng ra

qun dy stator vi dng in kch t khi dng in ti bng

khng trong h n v tng i vi:

E* =dmEE

tdmo

t*t i

ii

E*

It*

Hnh 1.3 - c tnh khng ti

2.2. c tnh ngn mch v t s ngn mch

In = f(it) khi U= 0 ; f= fm

c tnh ngn mch l quan h gia dng in ti khi ngn

mch (khi dy qun phn ng c ni tt ngay u my) vi

dng in kch t khi in p bng khng v tn s bng nh

mc. Nu b qua in tr ca dy qun phn ng ( r = 0) th

mch in dy qun phn lc ngn mch l thun cm ( = 900 ) nh vy

Iq = cos = 0

Id = Isin = I

E = jIxd

Vy ta c th vc t.


10/72


SV: TB Trg. 10

E

Ijx I

jxd I

jIxd

Hnh 1.4 - th vc t

Lc ngn mch phn ng phn ng l kh t, mch t ca

my khng bo ho v t thng khe h khng kh cn thit

sinh ra. E = E Ixud = Ix Rt nh. Nh vyquan h I = f(It) l ng thng

I

It

I = f(It)

Hnh 1.5 - c tnh ngn mch

T s ngn mch: T s ngn mch K l t s dng in ngn

mch Inong vi dng in kch thch sinh ra sut in ng E

= Udm khi khng ti vi dng in nh mc.

dm

no

I

IK (Trong :

d

dmno

x

UI )

xd tr s bo ho ca in khng ng b dc trc ng vi

E = Udm

*ddmd

dm

x1

IxU

K

xd* thng ln hn 1 vy K < 1 Ino < Im


11/72


SV: TB Trg. 11

ititnito

I = f(i t)

U = f(i t)

Udm

U.I

InoIdm

Hnh 1.6

T s ngn mch:

tn

to

dm

no

iiIIK

ito dng in kch thch khi khng ti lc Uo = Udm

itn dng in kch thch khi ngn mch lc I = Idm

T s ngn mch K l mt hng s quan trng trong my in

ng b. My vi K ln c u im cho thay i in p

U nh khin cho my l vic n nh khi ti thay i

2.3. c tnh ngai v thay i in p Udmca mypht ng b

U = f(I) khi it = const ; cos =const ; f = fdm

c tnh ngoi l quan h in p u ra ca my pht khi

dng in ti thay i vi dng in kch t, h s cng sut

v tn s l khng i. Dng in it - ng vi Udm ; Idm ; cos=const ; f = fdm - c gi l dng in t ho nh mc


12/72


SV: TB Trg. 12

U

I

Udm

0 Idm

cosUdm

cos(in dung)

cos(in cm)

Hnh 1.7 - c tnh ngoi

T hnh v ta thy dng c tnh ngoi ph thuc vo tnh cht

ti. Nu ti c tnh cm khi I tng phn ng kh t ca phn

ng tng, in p gim v ng biu din i xung. Ngc

li nu ti c tnh dung khi I tng , phn ng phn ng l tr

t, in p tng v ng biu din i ln.

thay i in p nh mc Udm cu my pht in ng

b l s thay i in p khi ti thay i t nh mc vi cos= cosdm n khng ti trong iu kin khng thay i dng

in kch thch

Udm = 100U

UE

dm

dm

2.4. c tnh iu chnh

it = f(I) khi U = const ; cos = const ; f = fdm .

c tnh iu chnh l quan h ca dng kch t vi dng in

ti lun gi cho in p khng thay i. N cho bit hng

iu chnh dng in it ca my pht ng b gi cho in

p ra U u my pht khng i


13/72


SV: TB Trg. 13

It

I

It

0 Idm

cos(in dung)

cos

cos (in cm)

Hnh 1.8 - c tnh iu chnh

Ta thy vi ti cm khi I tng, tc dng ca phn ng phn

ng tng lm cho U b gim. gi cho U khng i phi

tng dng in t ho it. Ngc li ti dung khi I tng, mun

gi U khng i phi gim it thng thng cosdm = 0,8 (

thun cm) nn t thng ti (U = Udm ; I = 0) n

ti inh mc (U = Udm ; I = Idm) phi tng dng in t ho

2.5. c tnh ti

U= f(it) khi I = const ; cos = const ; f= fm

c tnh ti l quan h gia in p u ra ca MF vi dng

kch t khi ti l khng i. Vi cc tr s khc nhau ca I v

cos s c cc c tnh ti khc nhau, trong c ngha nht

l c tnh ti thun cm ng cos = 0 ( = 900

) v I = Im

c tnh ti thun cm c th suy ra c t c tnh khng ti

v tam gic in khng

T c tnh ngn mch (ng 2) c tr s In = Idm dng

in kch thch itn hoc sc t ng Ftn cn thit bng Ftn=itn =


14/72


SV: TB Trg. 14

OC . Khi my lm vic ch ngn mch sc t ng ca

cc t Ftn = OC gm hai phn. Mt phn khc phc phn

ng kh t ca phn ng BC = kdFd sinh ra Ed phn cn li

OB = OC BC s sinh ra sut in ng tn t F = Idmx =AB ( A nm trn on thng ca c tnh khng ti ng 1 v

lc mch t khng bo ho).

Tam gic ABC c hnh thnh nh trn c gi l tam gic

in khng cc cnh BC v AB ca tam gic t l vi dng ti

nh mc Idm

em tnh tin tam gic in khng ABC sao cho im A ta

trn c tnh khng ti th nh C s v thnh c tnh thun

cm (ng 3)

i t

U.I

I = 0

I = Idm

23

1

E A'

O' B' C'

C Q PO

M

Idm

kd Fd

x Idm

Hnh 1.9 - c tnh ti

3. Thit b t ng iu chnh.

i vi my pht in khi ti thay i th khng nhng lm in

p ra ca my pht thay i m n cn lm thay i c tc ca


15/72


SV: TB Trg. 15

ng c s cp ca my pht dn ti thay i c tn s ca my

pht. Nh vy trong qa trnh iu khin my pht bn cnh vic

n nh in p ra ca my pht ta cn phi n nh c tn s my

pht khi ti thay i. Thc cht ca iu ny l ta phi n nh tc quay ca ng c khi ti thay i.

i vi mi loi ng c/tuc-bin s cp th c cc b iu tc

khc nhau. Tuy nhin, n Tt nghip ca em ch mong mun

cp n loi iu tc ca ng c s cp Diesel, nhm tng

thch vi cng sut ca yu cu ca n

ng c Diezel dng ko my pht in trong khi hot nglun thng xuyn phi thay i ch lm vic mt cch t

ngt, ngha l cc ch lm vic n nh ca ng c lun b

ph v. Khi ph ti thay i th tc ca ng c cng thay i.

Khi lng bnh c th b tr phn no mc chnh lch

gia cng sut ng c v cng sut cn thit ca my cng tc,

nhng n ch mang tnh cht tm thi hn na nu kch thc

bnh cng nh th tc dng b tr y cng t

Mun gi cho s vng quay ca ng c nm trong mt gii hn

cn thit phi lun thay i lng nhin liu cp cho ng c

loi tr tnh trng mt cn bng nng lng gia ng c v my

cng tc. Nhng trn thc t trong iu kin ph ti lun thay i

t ngt khng th dng tay iu chnh lng nhin liu, v

vy cc loi ng c Diezel dng chy my pht in lun cn

c mt c cu c bit iu chnh t ng lng nhin liu cp

cho ng c trong mi chu trnh cng tc m bo cng sutng c lun cn bng vi cng sut ca my cng tc qua gi

cho s vng quay ca ng c khng thay i

Hin nay c rt nhiu loi iu tc trn mi ng c s dng b

iu tc no l tu thuc vo loi ng c, c im ca my

cng tc v ton b thit b


16/72


SV: TB Trg. 16

i vi ng c Diezel dng chy my pht lun phi hot

ng trong iu kin gi tc quay khng i khi ti thng

xuyn thay i mt cch t ngt, nn ng c rt d vt qu svng quay cho php gii hn ca ng c mt mt c th gy ra

ng sut c gii hn vt qu gi tr cho php, mt khc cn ph

hoi nghim trng cc qu trnh lm vic ca ng c. V nhng

l do trn m i vi ng c Diezel dng chy my pht in

bt buc phi lp b iu tc

ng c Diezel thng rt nhy cm vi cc ch tc . Nu

tc ng c vt qu s vng quay thit k, thng lm gimnhanh cht lng ca cc qu tr nh cng tc v lc y h s d

lng khng kh v cht lng hnh thnh kh hn hp u gim

nhanh lc y mt mt thi gian chy b rt ngn mt khc cht

lng ca qu tr nh chy cng gim. Nhin liu khng chy ht

v qu trnh chy cn phi ko di thm trn ng gin n, lm

ng c rt nng (c bit l c cu thi v nhm pittng). Tn

nhiu nhin liu, c thm mui than trong kh thi ca ng c

dn n ng c chng hng

Phn loi cc loi iu tc:

Nguyn tc lm vic ca phn t cm ng (phn t gy cm ng

trc tip vi bin thin ca tc ) gm cc b iu tc: C

gii, thu lc, chn khng v in

Theo cng dng gm loi mt ch (trong c loi chnh xc,loi gii hn v loi bo him) hai ch (m bo cho ng c

lm vic n nh s vng quay cc tiu v hn ch s vng

quay cc i) v nhiu ch (qua c cu iu khin, c th m

bo cho ng c lm vic bt k s vng quay no trong phm

vi s vng quay cng tc ca ng c)


17/72


SV: TB Trg. 17

Ngoi s phn loi nh trn trong thc t ngi ta con phn ra

lm rt nhiu loi tu thuc vo c cu tc ng, .

Theo nguyn tc hot ng ca my pht in th m bo tns ca dng in l khng i khi ti thay i th tc quay ca

roto phi khng i nh vy ng c s cp ko roto phi khng

thay i. Nh vy i vi ng c Diezel chy my pht in th

c cu m bo tc quay ca roto khng i ngi ta

thng dng b iu tc mt ch

1

2

3

1 L xo

2 Qu vng

3 Khp tr t

Hnh 1.10 - B iu tc mt ch ca my pht in Diezel

L xo ca b iu tc c lc p ban u khng i do qu

vng ca b iu tc di tc dng cu lc ly tm ch c th vn

ng khi ch tc ca ng c t ti mt gi tr nht nh.

Nu ct ph ti bn ngoi ng c c khuynh hng lm tng s

vng quay, lc y di tc dng ca lc ly tm, cc qu vng ca

b iu tc s vng ra ngoi lm di ng khp trt v thanh rngbm cao p. Qua lm lng nhin liu cung cp cho mi chu

trnh gim ti mt gi tr cn thit. Nu tng ti bn ngoi s vng

quay ca ng c x gim mt qu trnh s sy ra ngc li, lc

y tc dng ca lc ly tm nh i do tc ca ng c gim, cc

qu vng ca b iu tc s vng t i lm di ng khp trt v

thanh rng bm cao p. Qua lm lng nhin liu cung cp


18/72


SV: TB Trg. 18

cho mi chu tr nh tng ti mt gi tr cn thit m bo tc

ng c s c gi khng i. Tt c cc ch lm vic ca

ng c lc ny s nm trn c tnh iu tc ab l nhng ch

chnh qui ca ng c c lp thm b iu tc ny. Tt nhin lng c c th lm vic cc ch ngoi ng c tnh iu

tc ab nhng ch l cc ch chuyn tip

Nh vy b iu tc gi cho s vng quay ca ng c hu nh

khng i v khng ph thuc vo ti

z

1

2

3

a

b n

1,2,3: c tnh ngoi

ab: c tnh iu chnh

Hnh 1.11 - c tnh ca b iu tc mt ch :

z

n

zn

nonk

Bn cnh cc b n nh tc c kh nh trn th trn thc thin nay ngi ta thng dng nhng b n nh tc bng in

Mt h thng n nh tc ca ng c bng in thng thng

gm c hai phn: phn bo v qu tc ng c v phn khng

ch iu chnh tc ng c


19/72


SV: TB Trg. 19

Phn bo v qu tc ng c:

Khi ng c mt iu khin tc ng cc th tng ln rt cao

iu ny lm cho cc c cu c kh khng th chu c cc lcly tm ln xut hin do cc c cu c kh c th b ph hng

ng thi c th gy nguy him cho ngi vn hnh my. Khi

b phn bo v qu tc c nhim v pht hin ra s c ng

thi khng ch tc ng c s cp mt tc an ton do

m bo an ton cho my v ngi vn hnh

Phn khng ch iu chnh tc ng c:

- Duy tr tc khng ti ca ng c ti mt im t trc- Duy tr tc ng c ti mt im t trc khi ti thay

i

Khng ging nh cc b khng ch bng cc c cu c kh b

khng ch bng in c kch thc nh gn bao gm cc b phn

sau :

- Khi iu khin

- B cm bin tc ng c- C cu chp hnh

- B bo v qu tc ng c

So S nh khuchichphnh

ng c

Hnh 1.12 - S khi b n nh tc ng c


20/72


SV: TB Trg. 20

Hot ng ca s c m t nh sau:

Tc ng c c o bng mt cm bin, tn hiu in ny s

c gi ti b so snh y b so snh s so snh gia tc tthc t ca ng c v tc t trc. Sau tn hiu so snh

c khuch i v chuyn ti mt c cu chp hnh (l mt nam

chm in t) n s iu chnh cn iu khin ca bm nhin liu

lm tng hoc gim khi lng nhin liu cung cp cho ng c

lm tc ng c khng thay i

4. H thng t ng iu khin kch t

Thit b t ng iu chnh kch t bao gm mt lot cc knh lin

h ngc iu khin in p kch t ca my pht kch thch (gin

tip iu khin in p kch t ca my pht chnh ). Trng hp h

thng kch t dng Thyristor (chnh lu c iu khin) tn hiu t

thit b t ng iu chnh kch t iu khin trc tip dng kch t.

Lc u thit b t ng iu chnh kch t c thit k ch vi mc

ch iu chnh in p (gi in p u cc trong qu trnh my

pht lm vic). Cu to n gin bi cc knh phn hi m theo

lch in p v phn hi dng theo lch dng in. Hin nay

thit b t ng iu chnh kch t c cu trc phc tp hn nhiu,

thc hin cc nhim v n nh h thng gim dao ng cng sut...

Cc phn chnh trong cu trc ca thit b t ng iu chnh kch t

gm:

Cc knh iu chnh theo lch cc tham s ch (in p

u cc my pht , dng stato...). Cc knh ny c nh hng

chung nhng ch yu n cc c tnh tnh v ch xc lp.

Cc knh iu chnh theo tn hiu o hm ca cc tham s

ch . Cc knh ny ch nh hng n cc c tnh ng ca

h thng nh iu kin n nh (ch yu n nh tnh), n


21/72


SV: TB Trg. 21

cht lng ca qu trnh qu , nhng khng c tc dng i

vi cc c tnh tnh.

B phn kch thch cng hnh tc ng ln qu trnh qu khi c nhng kch ng ln, c ngha nng cao tnh n nh

tnh cho h thng

Theo c tnh lm vic ngi ta chia thit b t ng iu chnh

kch t ra lm hai loi chnh thit b t ng iu chnh kch t tc

ng t l v thit b t ng iu chnh kch t tc ng mnh.

- Thit b t ng iu chnh kch t tc ng t l :

DL B SS

PHM

SS

CH

M ykchthch

C1

C2C3 n cun

dy roto

Uf

U0

Hnh 1.13 - Thit b t ng iu chnh kch t tc ng t l

- Thit b t ng iu chnh kch t tc ng mnh:

B SSU

BVP

CH

VP U'

U

f'f

TCL n cundy roto

chnh l uthyristor

DL

f f

U0

Hnh 1.14 - thit b t ng iu chnh kch t tc ng mnh

- Khu o lng - L

- Bin i - B

- So snh - SS


22/72


SV: TB Trg. 22

- Cc cun dy kch t - C1, C2 v C3

- Knh phn hi PHM

- Kch thch cng hnh CH

- B n nh cng sut VP- B chnh lu Thyristor- TCL

Cc thit b t ng iu chnh kch t tc ng t l ch gm cc

knh iu chnh theo lch thng s, do tc ng iu chnh

tng i chm (tng thch vi h thng kch t bng my pht

mt chiu hoc my pht xoay chiu tn s cao). Do b gii hn

bi h s khuch i cht lng iu chnh in p cng khng

cao. Hin nay s dng ch yu loi ny nhng nh my khngc yu cu cao v cht lng iu chnh in p, khng c yu

cu c bit v n nh h thng, cc nc Ty u coi thit b t

ng iu chnh kch t c cu trc ny l chun cho cc my

pht in thng thng

Cc thit b t ng iu chnh kch t tc ng nhanh c cu to

c bit , thm cc knh iu chnh theo o hm thng s. L

thuyt thit b t ng iu chnh kch t hin nay cha thngnht. Cc nc thuc Lin X c xy dng c s l thuyt v

thit b t ng iu chnh kch t tc ng mnh trn c s n

nh h thng ni chung, nhm to ra cc thit b t ng iu

chnh kch t cht lng iu chnh in p rt cao, trong khi vn

m bo c n nh cho bn thn thit b iu chnh (v do

nng cao ng k tnh n nh ca h thng ni chung). Trong khi

cc nc Ty u t thm b phn iu chnh ph ghp vi thit

b t ng iu chnh kch t nhm gim dao ng cng sut (gil b phn n nh cng sut Power System Stabilyzer)

Thit b t ng iu chnh kch t tc ng t l thc hin iu

chnh kch t theo lch in p u cc my pht thng qua

cc phn t o lng (my bin in p), thit b bin i (chnh

lu v lc) c a vo b phn so snh. Hiu s lch nhn


23/72


SV: TB Trg. 23

c U = U0 UF c khuch i bi b phn khuch i ri

a n cun dy kch t ca my pht kch thch. Tr s in p

so snh U0 c ly sao cho khi in p u cc my pht bng

tr s t th U = 0. Khi my pht kch thch lm vic ch vidng kch t trong cun C1. Do U = U0 UF nn thit b lm

vic theo nguyn l phn hi m. m bo tnh n nh ca b

phn iu chnh trong ch qu , thit b t ng iu chnh

kch t tc ng t l c thm knh phn hi tc PHM tc ng

theo tn hiu o hm cp 1 ca in p kch t (ca my kch

thch)

B phn kch thch cng hnh thc cht l mt rle in p thpni vi khu khuch i in p u cc my pht gim ti 20%

so vi tr s nh mc rle tc ng a in p ti a vo cun

C3. Nh in p u ra ca my kch thch t tr s cc i.

Tc ng ny lm tng momen in t my pht nh nng cao

tnh n nh

V cu trc, khc vi thit b t ng iu chnh kch t tc ng

t l, thit b t ng iu chnh kch t tc ng mnh c thmmt lot knh tn hiu l o hm thng s ch , cng a vo

b khuch i. Phn tc ng iu chnh in p theo lch v

kch thch cng hnh khng thay i. Cc knh mi ny r rng

khng c tc ng no ch xc lp (v tn hiu bng 0). Tuy

nhin li c hiu qu cao i vi cht lng iu chnh in p v

n nh tnh h thng in. Vn l ch, nh c cc knh ny

c th nng cao h s khuch i tn hiu lch in p ln rt

ln do knh iu chnh, trong khi vn gi c n nh cho bphn iu chnh. Khi mt cch gin tip em li hiu qu cao

v phng din cht lng iu chnh in p v tnh n nh

chung ca h thng. Vn l phi chn c cu trc thch hp

v hiu chnh ng cc h s t ng vi h thng in c th


24/72


SV: TB Trg. 24

Chng 2: S t ng iu chnh in p mypht in

1. H thng kch t

1.1. Tng quan v h thng kch t

Chc nng c bn ca mt h thng kch t l cung cp dng in

mt chiu vo dy qun kch t ca my in ng b. Thm vo ,

h thng kch t cn thc hin cc chc nng iu khin v bo v

quan trng nhm vn hnh tho mn h thng in bng cch iukhin in p v dng in i vo dy qun kch t.

Chc nng iu khin bao gm iu khin in p v cng sut phn

khng pht vo li v tng cng tnh n nh ca h thng in.

Trong khi chc nng bo v s m bo rng cc thng s gii

hn ca my ng b, h thng kch thch v cc b phn khc ca

my khng b vt qu.

1.2. Yu cu chung i vi mt h thng kch t.

Yu cu i vi mt h thng kch t c a ra di hai tiu ch

l yu cu theo tiu ch my pht v yu cu theo tiu ch h

thng in.

1.2.1. Theo tiu ch my pht.

Yu cu c bn theo tiu ch ny l h thng kch t phi cung cp v

t ng iu chnh dng in i vo dy qun kch t ca my pht

ng b m bo duy tr in p u ra ca my pht khi ti thay

i trong kh nng cung cp lin tc ca my pht. Cc gii hn v

thay i nhit , iu kin lm vic ca thit b, iu kin qu ti

v.v.. phi c tnh ton khi ch n nh c xc nh.


25/72


SV: TB Trg. 25

Thm vo , h thng kch t phi p ng c cc bin ng qu

ca ti bng p t t trng ph hp vi kh nng p ng ng

thi v ngn hn ca my pht. Kh nng ca my pht y l ccgii hn ca mt s yu t nh: cch in dy qun r-to khi in p

tng cao, tng nhit r-to do dng in t trng tng cao,

tng nhit ca stator do dng ti tng dy qun phn ng;

tng nhit cc u bi dy ch thiu kch thch v qu in p

hoc qu tn s. Cc gii hn v nhit c hng s thi gian qun tnh

nht nh v kh nng qu ti ngn hn ca my pht c th trong

khong t 15 n 60 giy. m bo s dng ti u h thng kch

t, h thng kch t phi c kh nng p ng cc yu cu ca hthng bng cch tn dng trit cc kh nng ngn hn ca my

pht sao cho khng vt qu cc gii hn

1.2.2. Theo tiu ch h thng in

Theo tiu ch ny, h thng kch t phi ng vai tr iu khin hiu

qu in p v nng cao tnh n nh ca h thng in. N phi c

kh nng p ng nhanh i vi nhng bin ng ca h thng nng cao n nh qu v tc ng nhanh i vi t trng

nhm tng cng tnh n nh tn hiu nh (n nh tnh) ca h

thng.

Theo lch s, vai tr ca h thng kch t trong vic tng cng vn

hnh h thng in ngy cng tng cao. Cc h thng kch t thi k

u c iu khin bng tay duy tr in p u cc v cng sut

phn khng ca my pht. Khi vic iu khin in p u cc camy pht ln u tin c t ng ho, qu trnh iu khin din

ra rt chm, ch yu l ng vai tr cnh bo. Trong nhng nm

1920 khi vai tr ca cc b n p tc ng nhanh i vi n nh

qu v n nh tnh ca h thng in c pht hin, ngi ta

cng quan tm hn nhiu n kh nng ca h thng kch t v cc

my kch t (excitor) cng vi cc b n nh in p (voltage


26/72


SV: TB Trg. 26

regulator) p ng nhanh sm c a vo ng dng cho cc h

thng in. H thng kch t theo c cc bc tin ho lin tc.

Trong nhng nm 1960 h thng kch t c m rng bng vic

s dng cc tn hiu n nh ph, ngoi cc tn hiu v sai lch inp u ra, iu khin in p t trng nhm loi b cc dao ng

ca h thng. Ngi ta coi vic iu khin kch t ny nh l b n

nh h thng in. Trn thc t ngy nay cc h thng kch t hin

i c kh nng p ng ng thi i vi cc in p ngng cao.

Vic phi hp v nng lc p t t trng cao cng vi vic s

dng cc tn hiu n nh ph s ng gp ln cho vic nng cao n

nh ng trong vn hnh h h thng in

1.3. Cc phng php T ng iu chnh Kch t

Nh ta bit iu chnh in p pht ra ca my pht ngi ta

thng iu chnh dng kch t nh mt b iu chnh bng tay hoc

t ng h thng kch t. Trong ch lm vic bnh thng iu

chnh dng kch t s iu chnh c in p u cc my pht thay

i c lng cng sut phn khng pht vo li. Thit b iu

chnh kch t lm vic nhm gi in p khng thay i (vi chnh xc no ) khi ph ti bin ng. Ngoi ra thit b t ng

iu chnh kch t cn nhm mc ch nng cao gii hn cng sut

truyn ti t my pht in vo h thng, m bo s n nh tnh,

nng cao s n nh ng.

cung cp mt cch tin cy dng mt chiu cho cun dy kch t

ca my pht in ng b, cn phi c mt h thng kch t thch

hp vi cng sut nh mc ln. Thng thng i hi cng sutnh mc ca h thng kch t bng (0,2 0,6%) cng sut nh mc

my pht in.

Dng in kch t chy trong cc cun dy rto ca my pht in

ng b l dng in mt chiu v vy cn c h thng ngun cung

cp ring. H thng kch t, iu chnh dng kch t trong qu trnh


27/72


SV: TB Trg. 27

lm vic l thit b t ng iu chnh kch t. c tnh ca h thng

kch t v cu trc thit b iu chnh kch t c ngha quyt nh

khng nhng i vi cht lng iu chnh in p m cn n tnh

n nh h thng. Ta xt c tnh mt s loi kch t chnh.

Trong thc t ngi ta c 4 phng php iu chnh dng kch t

mt cch t ng l cc phng php sau:

H thng kch t dng my pht in mt chiu.

H thng kch t dng cc my pht in xoay chiu c vnh gp.

H thng kch t dng cc my pht in xoay chiu khng vnh

gp. H thng kch t xoay chiu dng ngun chnh lu c iu khin.

1) H thng kch t dng my pht in mt chiu

TK

R

C3 C2 C1

FU

Hnh 2.1 - H thng kch t dng my pht mt chiu.

cc my pht in cng sut nh h thng kch t l cc mypht in mt chiu.

My pht in mt chiu lm nhim v kch thch ny (cn gi l

my pht in kch thch) c th c kch thch c lp hoc

song song cun dy kch thch ca n c th chia lm nhiu cun

dy cng lm vic. Cun chnh C1 tc ng iu chnh bng tay


28/72


SV: TB Trg. 28

cun C2 lm vic thng qua tc ng ca thit b iu chnh kch

t trong cc ch lm vic b nh thng. Cun C3 ch tc ng

khi c tn hiu s c (ch knh thch cng hnh). Tn hiu u

vo cho thit b iu chnh kch t ly t cc my bin dng vmy bin p t ti u cc my pht. Nhc im ch yu ca

h thng kch t dng my pht in mt chiu l b gii hn bi

cng sut nh (hn ch lm vic bi tia la pht sinh trn vnh

i chiu) v c hng s qun tnh iu chnh ln (Te = 0,3

0,5s).

2) H thng kch t dng my pht in xoay chiu tn s cao

chnh lu.

TK

C3 C2 C1

FU

Hnh 2.2 - H thng kch t dng my pht in tn s cao chnh

lu.

i vi cc my pht t 100MW tr ln hin nay u s dng h

thng ngun xoay chiu chnh lu. Trc ht phi k n h

thng kch t dng my pht in tn s cao chnh lu.

Do khng c vnh i chiu cng sut c th tng ln ng k p

dng c cho cc my pht ba pha cng sut t 200 300 MW.

Tuy nhin nhc im ca loi ny l cng sut ch to vn b

gii hn, do tia la vnh trt sut hin khi c cng sut ln (cn

c vnh trt a in vo stato). Ngoi ra hng s qun tnh c

tr s khong ( 0,3- 0,4s).


29/72


SV: TB Trg. 29

3) H thng kch t dng my pht kch t xoay chiu khng vnh

trt:

TK

FU

Hnh 2.3 - H thng my pht kch t xoay chiu khng vnh

trt.

Mt trong cc phng php c s dng rng ri hin nay l

phng php dng my pht in xoay chiu khng vnh trt

(h thng kch t khng vnh trt).

Trong h thng kch t ny ngi ta dng mt my pht in

xoay chiu 3 pha quay cng trc vi my pht in chnh lm

ngun cung cp. My pht xoay chiu kch t c kt cu c bit:

Cun kch t t stato, cn cun dy 3 pha li t rto. Dng

in xoay chiu 3 pha to ra my pht kch thch c chnh lu

thnh dng mt chiu nh mt b chnh lu cng sut ln cng

gn ngay trn trc rto ca my pht. Nh vy m cun dy kch

t ca my pht in chnh c th nhn c ngay dng in

chnh lu khng qua vnh trt v chi than. cung cp dng

in mt chiu ca my pht kch thch (t stato) m ngun

cung cp ca n c th l ngun mt chiu bng Ac-qui hoc mt

ngun xoay chiu khc bt k thng qua chnh lu c hoc khng

c iu khin.

Tc ng ca h thng t ng iu chnh kch t c t trc

tip vo ca iu khin ca b chnh lu, lm thay i dng kch

t ca my pht in kch thch, tng ng vi mc ch iu


30/72


SV: TB Trg. 30

chnh in p pht ra ca my pht. Nh vy hon ton khng c

vnh trt a in vo roto cng xut ch to khng b hn ch,

ngoi ra do ni trc tip hng s thi gian cng gim i ng k

(0,1 0,15s).

4) H thng kch t xoay chiu dng ngun chnh lu c iu

khin.

Hnh 2.4 - H thng kch t chnh lu c iu khin

H thng ny cho php to ra hng s c qun tnh rt nh 0,02

0,04s nh kh nng iu chnh trc tip dng kch t (chy quacc Thyristor) i vo cun dy roto my pht in ng b. Hin

nay ti cc nh my pht in ch yu s dng loi h thng kch

t ny. Hng s qun tnh nh l iu kin quan trng cho php

nng cao cht lng iu chnh in p v tnh n nh.

TK

F

U


31/72

i hc Bch khoa H ni n Tt nghip - Thit k mch n p My pht

SV: TB Trg. 31

2. La chn phng n

Theo yu cu ca n vi cu h nh l MF3, cng sut P =

125kW, U = 380/220 (V), s dng my pht ph xoay chiu 3 pha,

Ukt = 100V, Ikt = 6(A), em tnh chn s dng H thng my pht

kch t xoay chiu, dng iu chnh kch t chnh lu c iu khin.Theo h thng s s t ng iu khin a dng in mt chiu

a vo cun dy kch t ca my pht kch thch. Phng php

iu khin kch t ny c nhng u im chnh sau:

Thit b n gin, r tin,

iu khin d dng,

c tnh iu chnh tt,

Hng s thi gian qun tnh v iu chnh nh, Thit b khng cn s dng vnh gp

3. S iu khin cho h thng kch t dng my phtin xoay chiu theo phng n la chn

Hnh 2.5 S iu khin kch t dng chnh lu iu khin tia3 pha dng h thng My pht kch t xoay chiu khng vnh

trt

K

A

B

C

Ikt

Ikt

FK F


32/72


SV: TB Trg. 32

Chng 3 - Thit k v tnh ton mch ng lc

1. Chnh lu c iu khin ba pha

I. Chnh lu ba pha hnh tia c iu khin :

i a i b i c

TcTbTa

a b c

Z

Hnh 3.1 - Chnh lu ba pha hnh tia c iu khin.

Khi thay i gc m cc Thyristor s thay i c in p trn ph ti

v do thay i c dng in chnh lu qua ti.

Gi s cc s.. th cp MBA l :

ea = 2 E2sin

eb = 2 E2sin( - 23

)

ec = 2 E2sin( - 4 3

)

- Trng hp ti cm khng (khng xt dng gin on)


33/72


SV: TB Trg. 33

Do nng lng tch lu trong phn cm nn khi mt Thyristor no

thng th qu trnh kho Thyristor b ko di. in cm cng

ln th qu trnh kho Thyristor cng di. Trong s chnh lu ba

pha hnh tia, khi mt Thyristor kt thc qu tr nh kho ko di m

Thyristor k tip cha c xung m th dng in ph ti b gin

on. Trng hp ngc li, khi mt Thyristor cha kt thc qutrnh kho ko di m Thyristor k tip c xung m th dng in

ph ti s lin tc.

Vy, ch lm vic v c im chuyn mch ca s chnh lu

c iu khin hnh tia khi gc m 0 khng nhng ph thuc vo

tnh cht ca ph ti, in cm ca ngun m cn ph thuc c vo

gc m.

Vi ti cm khng c hai ch dng in :

- Gin on : khi tr s t cm L nh v gc m6

ln.

- Lin tc : khi gc m6

khng ph thuc vo tr s in

cm hoc khi gc m6

vi tr s in cm ln. Vi L =

th dng in ti s lin tc khng ph thuc vo tr s gc m.

Khi t cm ca ngun c b qua (H nh b) Lng = 0 th l

chuyn mch tc thi. in p trung bnh trn ph ti c tnh :

U0 =32

1

d.sinE2

35

6

2 = 22

63E

= 1,17E2

Khi t cm ngun Lng 0 th l chuyn mch c qu trnh

(Hnh c) vi gc trng dn = t. in p chnh lu tc thi

nh phn tch l mt ng cong phc tp hn do c s gim

in p lc trng dn v in p trung bnh trn ph ti c tnh

:

U0 =2

ba ee


34/72


SV: TB Trg. 34

eo ea eb ec

o t

o t

to

o t

eo ea eb ec

eoea eb ec

iia ib icic

a)

b)

c)

d)

Hnh 3.2 - Chnh lu c iu khin hnh tia ba pha vi ti c cm

khng.

Lng gim in p trung b nh (phn gch car) U l :U =

2

3 Ong IL

Khi xy ra hin tng trng dn c hai Thyristor thng, hai ngun

tng ng b ngn v in p chnh lu nh hn so vi trng hp l

tng Lng = 0.

UO = UcosE

22

63

II. Chnh lu cu ba pha iu khin i xng

A B C A

t1 t2 t3 t4 t5 t6 t7

Uf

0


35/72


SV: TB Trg. 35

Chnh lu cu ba pha c s nguyn l nh hnh. Su Thyristor chia

lm hai nhm: nhm Cathode chung (T1, T

3, T

5) v nhm Anode chung

(T2, T4, T6).

Xt s lm vic ca s mt s khong thi gian :

Khong6

3


36/72


SV: TB Trg. 36

Trong khong ny cc sut in ng ngun c quan h ea > ec >

eb. Vi nhm Cathode chung, T1 c th Anode dng cao nht

nn nu c xung m (gc m ) th T1 s thng, dn ti th

Cathode ca T3 v T5 cao hn th Anode ca chng v cc

Thyristor T3 v T5 b kho do phn p ngc.

Vi nhm Cathode chung, T6 c th m thp nht nn nu c

xung m (gc m) th T6 s thng, dn ti th Anode ca T2 v

T4 cao hn th Cathode ca chng v cc Thyristor T2 v T4 b

kho do phn p ngc. Vy trong khong ny T1 v T6 dn dng

t ngun ti ti

Khong6

3

6

5

Trong khong ny ea > eb > ec . Vi nhm Cathode chung, T1 vnc th Anode dng cao nht nn vn thng, cn cc T3 v T5 b

phn p ngc nn b kho (d cho c xung m).

Vi nhm Anode chung, T2 by gi c th Cathode m thp nht

nn nu c xung m th T2 s thng v khi T2 thng s t in

th Vc m thp nht vo Anode chung, dn n T6 ang thng

trc b phn p ngc v kho li. Dng in ph ti c

dn t ngun qua T1 , T2 . Khong

65

6

7

Trong khong ny eb > ea > ec. Vi nhm Cathode chung, T3 vn

c th Anode dng cao nht nn nu c xung m th s thng v

khi thng s t in th Vb dng cao nht vo Cathode chung,

dn n T1 ang thng trc b phn p ngc v b kho li

ngay (T5 vn kho).

Vi nhm Anode chung, T2 vn c th Cathode m thp nht nn

vn thng, cn cc T4 , T6 b phn p ngc nn vn kho (d c

xung m). Dng in ph ti c dn t ngun qua T3 v T2 .

Lp lun tng t cho cc khong tip theo :6

7

6

9

,6

9

6

11

,

611

613

, ... Ta c bng kt qu :


37/72


SV: TB Trg. 37

Khong Thyristor c

cp xung

Cc Thyristor

thng

Chiu dng

in

in p ph

ti

6

63

T1 T1 v T6 a - ti b ea - eb

63

65

T2 T1 v T2 a - ti - c ea - ec

65

6

7

T3 T3 v T2 b - ti - c eb - ec

67

6

9

T4 T3 v T4 b - ti a eb - ea

69

6

11

T5 T5 v T4 c - ti - a ec - ea

611 6

13 T6 T5 v T6 c - ti - b ec - eb

Gi tr tc thi ca in p trn ph ti UO = VP - VN chnh l hiu cc

gi tr tc thi ca cc sut in ng hai pha ang cp in cho ph

ti. l hiu cc gi tr tc thi gia sut in ng ca pha dng

nht v sut in ng ca pha m nht hay ni cch khc l khong

cch thng ng gia hai ng bao trn cng v di cng ca cc

sut in ng xoay chiu ba pha.Gi tr trung bnh ca in p chnh lu l :

UO = 6

d.sinE2

65

6

22

1=

cosE

22

63= 2,34E2cos .

in p ngc t ln mi Thyristor c gi tr cc i :

Ung.max = 6 E2 = 2,45E2 .

Dng in ph ti ph thuc vo bn cht ph ti v c gc m.

III. Chnh lu cu ba pha iu khin khng i xngNguyn l lm vic ca s ny cng tng t nh s cu i

xng. iu cn lu l khi cc Thyristor c phn p thun m mun

dn thng th phi cp xung iu khin, cn cc Diode th c phn p

thun th dn thng.


38/72


SV: TB Trg. 38

Khong6

63

:

ea > ec > eb . Nhm Diode mc chung Anode chung s c D6 dn

thng v n c th Cathode thp nht. Nhm Thyristor mc

Cathode chung c T1 vi th Anode cao nht nn nu c xung

m th n s thng. Thyristor T1 v Diode D6 thng s cho dngi0 chy qua ph ti. Diode D6 thng lm th Anode ca cc

Diode D2 v D4 l VB nn chng b phn p ngc.

Khong6

3

6

5

ea > eb > ec . Th Anode ca Diode D2 by gi l Vb > Vc nn D2

thng. Do D2 thng nn th Vc t ln Anode ca D6 lm D6 b phn p ngc v kho. Dng in ph ti c dn qua

Thyristor T1 v Diode D2.

Khong6

5

6

7

D4

D6

D2

T1

T3

T5

LR

A B C A

X1

X3

X5

t1 t2 t3 t4 t5 t6 t7

Ud

Uf

T1

T3

T5

D4

D6

D4

0

Hnh 3.4 - Chnh lu cu ba pha iu khin khng i xnga- s ng lc, b- gin cc ng cong, Ud- in p ti khi

gc m = 60o

A B C


39/72


SV: TB Trg. 39

eb > ea > ec - trong khong ny, Thyristor T3 c phn p thun

nn khi c xung m th T3 s thng dn n th Vb > Va t ln

Cathode ca T1 lm T1 kho. Th Vc thp nht t ln Anode ca

cc Diode D4, D6 (do Diode D2 dn) nn D4 v D6 kho. Dng

in ph ti c dn t ngun qua T3 v D2.

Khong6

7 69

eb > ec > ea - do Diode D2 thng nn t th Vc > Va ln Anode

ca D4 nn D4 thng. Diode D4 thng t th Va thp nht ln

Anode ca Diode D2 nn D2 kho. Thyristor T3 thng trc

nn t th Vb ln nht ln Cathode ca cc Thyristor T5 nn hai

Thyristor ny khng th thng.

L gii mt cch tng t ta c khong thng v kho ca cc

Thyristor v Diode.

Nhm Diode mc Anode chung s to ra in p trn ti U0D l

ng bao di ca cc sut in ng ba pha. Nhm Thyristor mc

Cathode chung s to ra in p trn ti UOth l ng nt m trn

cng. Nh vy gi tr tc thi ca in p trn ti s l :

U0 = UOD + U0th

Vi: U0D =263

E2cos

U0th = -263

E2

Vy nn ta c : U0 = U0D + U0th =263

E2 ( 1+ cos )

2. La chn s chnh lu

Sau khi phn tch v nh gi v cc phng php chnh lu c iu

khin ba pha, t cc u nhc im ca cc s , Vi ti l mch kch

t ca my pht in Diezel th s chnh lu tia ba pha c iu khin

l hp l hn c bi l cng sut ca mch kch t khng ln lm. Vic

iu khin chnh lu cu mt pha khng i xng so vi cc phng


40/72


SV: TB Trg. 40

php chnh lu khc l n gin m cht lng in p ra cng tng

i tt

Hnh 3.5 S mch ng lc

3. Tnh chn Tiristor

Ta chn da vo cc yu t c bn dng ti, s chn, iu kin

to nhit, in p lm vic, cc thng s c bn cc van c tnh nh

sau :

in p ngc ln nht m Tiristo phi chu:

u

dnv2nvnmax K

UKUKU

Trong : Ud : in p ti

Knv: h s in p ngc (Knv = 6 )

Ku : h s in p ti (Ku = 263

)

33,2093100*

KU

KUu

dnvnmax

2

(V)

Nh vy Unmax = 210 (V)

in p ngc ca van cn chn.

K

A

B

C

Ikt

Ikt

FK F


41/72


SV: TB Trg. 41

Unv = KdtUnmax = 1,8*210 = 376,8 (V)

KdtU : H s d tr in p (chn KdtU = 1,8)

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

Ilv =3

KTI =3

6= 3,464(A)

Vi dng in lm vic tnh ton nh trn l kh b, nn chn vankhng cnh to nhit. Vi iu kin dng in nh mc ca van cn

chn:

Im = KiIlv = 10*3,464 = 34,6(A)

Ki : H s d tr dng in Ki = 10)

T cc thng s Unv , Idmv ta chn 3 Thiristo loi HT40/08OJ4 c cc

thng s sau:

- in p ngc cc i ca van : Un = 800(V)

- Dng in nh mc ca van : Idm = 40(A)

- nh xung dng in : Ipik= 900(A)

- Dng in ca xung iu khin : Idk= 110(mA)

- in p ca xung iu khin : Udk= 3(V)

- Dng in r : Ir = 6(mA)

- Dng in t gi : Ih = 200(mA)

- St p ln nht ca Tiristo trng thi dn: U =1.65(V)

- Tc bin thin in p :

dtdU

1000(V/s)

- Thi gian chuyn mch : tcm =150s

- Nhit lm vic cc i cho php : Tmax =1250C

4. Tnh bin p ng lc

Vi cc tnh ton c tr nh by cc phn trn, th my bin p

ng lc c chn dng trong n ny l bin p 3 pha, 3 tr vi cc

tnh ton c tr nh by di y. V bin p c cng sut nh, nn

c thit k l my bin p kh, lm mt bng i lu t nhin.


42/72


SV: TB Trg. 42

4.1. in p chnh lu khng ti

Udo = Ud + U v + Uba + Udn

Vi: Ud - in p chnh lu = Ukt = 100V

Uv- st p trn cc van: Uv = 1.65V;Uba = U r + Ul - st p bn trong bin p khi c

ti, bao gm st p trn in trUr v st p trn

in cm Ul. Chn = 10%=10V

Udn = Rdn.Id =(.l/S).Id - st p trn dy ni; c th

b qua

Vy Udo = 100 + 1,65 + 10 + 0 = 116,5 (V)

4.2. Xc nh cng sut ti a ca ti v d vi ti chnh lu xc

nh

Pdmax = Udo . Id

Pdmax = 116,5 . 6 = 699(W) ly trn = 700W

4.3. Cng sut bin p ngun cp c tnh

Sba = ks . Pdmax

Sba = 700.1,345 = 941.5 (W)

Vi: Sba - cng sut biu kin ca bin p [W];

ks - h s cng sut theo s mch ng lc,

Pdmax - cng sut cc i ca ti [W].

4.4. Tnh ton s b mch tTit din tr QFe ca li thp bin p:

Theo cng thc kinh nghim

2cmf.m

SkQ baQFe

271173

59410101 cm,

,,

m

S,Q baFe


43/72


SV: TB Trg. 43

4.5. Tnh ton dy qun bin p.

Theo kinh nghim s vng dy ca mi cun c tnh Gn

ng c th tnh nu coi f = 50 Hz, chn B = 1Tsla lc

FeQ

U.W 45 (vng)

S vng dy ca mt cun dy s cp W1

S vng dy ca mt cun dy th cp W2

Vi

Tnh dng in ca cc cun dy.

Tra bng xc nh dng in cc cun dy dng in s v

th cp ta c

Dng in th cp mi cun dy

I2 = k2.Id = 0,58.6 = 3,48 (A)

Dng in s cp mi cun dy

I1 = k1.kba.Id =0,82.0,262.6= 1,289 =1,3 (A)

Vi kba = U2/U1 = 99,6/380 = 0,262

Tit din dy dn s cp

J - mt dng in trong bin p: chn = 2,5 [A/mm2]

Tit din dy dn th cp

(vng),

.Q

U.W

Fe

5597117

2204545 1

1

(vng)2537117

6994545 22

,

..

Q

U.W

Fe

)V(,,

,

k

UU

U

d 699171

511602

)mm(,.

,

j

IS

Cu

21

1520

52

31

)mm(,.

,

j

IS

Cu

22

241

52

53


44/72


SV: TB Trg. 44

ng knh dy qun, chn dy qun trn, c tnh:

ng knh dy qun s cp

ng knh dy th cp

Trong : d - ng knh dy qun.

SCu tit din dy qun.

)mm(,

,.S

d

Cu

810

52044 11

)mm(,,.S

d Cu 3314144 2

2

Cu

Sd

4


45/72


SV: TB Trg. 45

4.6. Tnh kch thc mch t

Hnh 3.6. Li thp bin p - cc kch thc c bn ca mch t

Do Bin p c cng sut nh, nn chn tr hnh ch nht, vi cc

kch thc QFe = a . b. Trong a - b rng tr, b - b dy tr

Chn l thp c dy 0,35mm

Din tch ca s cn c l Qcs = 2.(Qcs1 + Qcs2 ), chnh l

din tch do cc cun dy chim ch trong ca s:

Chn kl = 2,5

Qcs1 =kl.W1.SCu1 = 2,5.559.0,52 = 726,7 [mm2]

Qcs2 =kl.W2.SCu2 = 2,5.253.1,4 = 885,5 [mm2]

Vy Qcs = 2(726,7+ 885,5) = 3224,4 [mm2] =32,244 [cm

2]

Chn kch thc ca s c h nh dng kt cu mch t thhin nh h nh 3.10 vi cc h s ph c chn (theo kinh

nghim, do l bin p 3 pha, ba tr hnh E)

m = h/a = 2,5; l = b/a = 1

h=a.m = 4,208.2,5 = 10,52(cm); vi

Vy chiu rng ton b mch t

C=2c +3a = 2.3,06 + 3.4,208 = 18,74 (cm)

Chiu cao mch t

)cm(,,Qabb.aQFeFe

20847117

)cm(,,

,

h

Q

cc.hQ

cs

cs 0635210

24432

b

hH

c

C

c


46/72


SV: TB Trg. 46

H = h + z.a = 10,52 + 2.4,208 = 18,96 (cm)

Vi thp t KT c dy t=0,35 mm, nn tng s l thp

cn c s l nt = b/t = 42,08/0,35 = 120,2; vy ly trn l 121

tm

4.7. Kt cu dy qun:

Dy qun c b tr theo chiu dc tr, mi cun dy c

qun thnh nhiu lp dy. Mi lp dy c qun lin tc, cc

vng dy st nhau. Cc lp dy cch in vi nhau bng cc ba

cch in. Nh tnh trn, chn dy qun tit din trn

S vng dy 1 lp th cp W2l:

Vi: dn - ng knh dy qun k c cch in;

hg - khong cch cch in vi gng; chn hg = 2.dn.

S lp dy qun th cp: sld2= 253/68 =3,72 = 4 lp

S vng dy 1 lp s cp

S lp dy qun s cp: sldt= 559/103 =5,42 = 6 lp

B dy ca mi cun dy Bdct = d. sld + cd.sld

B dy cun dy s cp: Bdct = dt. sldt + cd.sldt=1.6 +

0,1.6 = 6,6 (mm)

B dy cun dy th cp: Bdc2 = d2. sld2 + cd.sld2=1,5.4 +0,1.4 = 6,4 (mm)

Tng b dy Bd 1 cnh cc cun dy ca 1 tr

Bd = Bdc1 + Bdc2 +...+ cdt + cd2cd + cdn

= 6,6 + 6,4 +0,5.3 = 14,5 (mm)

)vng(,,

,.,

d

hhW

n

g

l 136851

51221052

)vng(,.,

d

hhW

n

g

l 21031

1221051


47/72


SV: TB Trg. 47

Nhn xt: tng chiu dy chim ch ca cc cun dy trong ca

s: 2Bd = 14,5.2=29 mm v nh hn c= 30,6 cm tnh ton l

chp nhn c i vi lm mt v cch in

4.8. Khi lng st.

MFe = VFe.mFe (kg)

Trong : VFe - th tch khi st [dm3];

VFe = (H.C 2.Qcs ).b

= (1,896.1,874 2.0,32244).0,4208 = 1,223[dm3]

mFe = 7,85 kg/dm3

vy MFe = VFe.mFe = 1,223.7,85 = 9,6 (kg)

4.9. Khi lng ng.

MCu = VCu.mCu (kg)

Vi: VCu = SCu.l - th tch khi ng ca cc cun dy[dm3];

SCu - tit din dy dn [dm2];

l = W.Dtb - tng chiu di ca cc dy dn [dm];

mCu = 8,9kg/dm3

Dtb= (Dt + Dn)/2 - Chu vi trung bnh ca cun dy

Trong : Dt,Dn - chu vi trong v ngoi ca cun dy.

Khi lng ng qun th cp

Chu vi trong ca cun dy th cp c tnh:

D2 = DFe + 2cd2 = 4.(0,4208 + 0,005)=1,7032 (dm)

DFe - chu vi tr st;

cd2 - cch in trong cng vi li.

Chu vi ngoi ca cun dy th cp c tnh gn ng:

Dn2 = D2 + 4.(d + cd).sld= 1,7032 + 4.0,015.4 = 1,9132

(dm)

Vy chu vi trung bnh cun dy th cp trn 1 tr:


48/72


SV: TB Trg. 48

D2tb = (D2 + D n2)/2 = (1,7032 + 1,9132) /2 = 1,808

(dm)

Chiu di dy qun th cp l = W. Dtb = 253. 1,808 =

457,42 (dm) ly = 470 (dm) d phng cho cc u

dn u ni ra ngoi

Vy th tch khi ng ca cun dy th cp l VCu =

SCu.l =470.0,00014 = 0,0658 (dm3)

Vy khi lng ng qun th cp s l:

MCu2 = VCu2.mCu = 0,0658x 8,9 = 0,586 (kg)

Tng khi lng ng cc qun th cp s l:

3. MCu2 = 3.0,586 = 1,76 (kg)

Khi lng ng qun s cp

Chu vi ngoi ca cun dy s cp (chnh l chu vi ngoi

ca bi ng dy trn 1 tr) c tnh gn ng:

Dn1 = Dn2 + 4.(d + cd).sld= 1,9132 + 4.0,01.6 = 2,1532

(dm)

Vy chu vi trung b nh qun dy s cp s l

Dtb1= (Dn2 + D n1)/2 =(1,9132 + 2,1532)/2 = 2,0332(dm)

Chiu di dy qun s cp s l l = W.Dtb =599.

2,0332=1217(dm) ly = 1230 (dm) d phng cho

cc u dn u ni ra ngoi

Vy th tch khi ng ca cun dy th cp l VCu =

SCu.l =1230.0,000052=0,06396 (dm3)

Tng khi lng ng cc qun s cp s l:MCu1.3 = VCu1.mCu.3 = 0,06396.8,9.3=1,71 (kg)

4.10. Tnh tng st p bn trong bin p.

in p ri trn in tr:


49/72


SV: TB Trg. 49

dr IW

WRRU

2

1

2

12

Trong :

R1, R2 - in tr thun ca cc cun dy s v th cp c

tnh: R = .l/S

Vi: = 0,0000172 mm - in tr sut ca ng;

l, S - chiu di v tit din ca dy dn [mm, mm2];

Id - dng in ti mt chiu [A].

in tr thun ca cun dy s cp

R1=1,72.10-5

.123000/0,52 = 4,068

in tr thun ca cun dy th cp

R2=1,72.10

-5

.47000.1,4=1,13 Vy St p ri trn in tr l

in p ri trn in khng:

Ux = mf. X.Id/

Trong : mf- s pha bin p

Vi: = 314 rad.

Vy Ux = mf. X.Id/=3.0,153.6/=2,996 = 0,876(V)

4.11. in tr ngn mch my bin p

4.12. Tng tr ngn mch my bin p:

4.13. in p ngn mch phn trm ca my bin p:

)(,...

.,

,Xn

1530103143

006400066000050

10520

0210402538

722

9610684

559

253131

2

1

2

1

2

2,,.,r*

w

wrrnm

9711530961 2222 ,,,xrz nmnmnm

)V(,,,U r 8116599

253068413171

2

72

2

2

103

21

8

BdBd

cdh

R

WXbk

n


50/72


SV: TB Trg. 50

4.14. Dng in ngn mch my bin p:

5. Tnh chn cc thit b bo v mch ng lc

5.1. S mch ng lc c cc thit b bo v:

Hnh 3.7 - S mch ng lc c cc thit b bo v

5.2. Bo v qu nhit cho van bn dn

Khi lm vic vi dng in chy qua tn van c st p, do c tn

hao cng sut P, tn hao ny sinh ra nhit t nng van bn dn.

Mt khc van bn dn ch c cho php lm vic di nhit cho

php Tcp no , nu qu nhit cho php th cc van bn dn s

b ph hng . van bn dn lm vic an ton, khng b chc thng

v nhit, ta phi chn v thit k h thng to nhit hp l.

Tuy nhin thit k ch to ca nh sn xut van cho php, vi vic

chn h s Ki = 10, v tn tht cng sut tnh ton trn 1 van

P = U.Ilv = 1,65*3,464 = 5,7(W), l rt nh

)A(,

,z

UI

nm

dm

nm 7650

971

1002

%,,,.

U

zIU

dm

nmdm

nm8111180

100

9716100

2

00

A

B

C

F

T2T

T

r

c c c

r rUkt


51/72


SV: TB Trg. 51

v Ilv = 3,43 (A)


52/72


SV: TB Trg. 52

iu chnh v tr xung iu khin trong phm vi na chu k dng ca

in p t trn ant - catt Thyristor.

To c cc xung iu kin m c Thyristor ( y xung iu

khin c bin 5V, rng xung 125s, dng xung iu khin 300

mA).

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

ng tuyn tnh v thng ng arccos thc hin vic iu chnh v

tr xung trong na chu k dng ca in p t trn Thyristor.

1. Nguyn tc iu khin thng ng arccos

Theo nguyn tc ny ngi ta dng hai in p :

in p ng b uR vt trc in p Anode - Cathode

Thyristor mt gc2

R

E(nu uAK = Asint th uR = Bcost ).

in p iu khin uK l in p mt chiu, c th iu chnh

c bin theo hai hng (dng v m).

Tng i s uR + uK c a n u vo ca khu so snh.Khi uR + uK = 0 ta nhn c mt xung u ra ca khu so

snh.

Nguyn tc iu khin thng ng arccos c s dng khi thit

b chnh lu i hi cht lng cao.

2. Nguyn tc iu khin thng ng tuyn tnh.

Udf

Urc

Udk

Ud

Xdk

t

t

t


53/72


SV: TB Trg. 53

Theo nguyn tc ny, ngi ta cng dng hai in p :

in p ng b uRC, c dng rng ca, ng b vi in p trn

Anode - Cathode Thyristor.

in p iu khin uK, l in p mt chiu c th iu chnh

c bin .Tng i s ca uRC + uKc a n u vo ca mt khu so

snh.

Nh vy bng cch lm bin i uKngi ta c th iu chnh c

thi im xut hin xung ra, tc l iu chnh c gc .

2. Chn cc khu trong mch iu khin.

1. S khu ng pha dng b khuch i thut ton :

ng pha So snh To xung

Hnh 4.2 - S khi mch iu khin


54/72


SV: TB Trg. 54

r 1

ua t

b a

a

o a 1

r 3

u r c

b

d r 2

o a 2

r 4 t r

c

Hnh 4.3 - S khu ng pha dng b khuch i thut ton.

t

t

t

UA

UB

UdkUrcHnh 4.4 - ng cong in p

Dng xung u ra khu ng pha dng KTT. Nguyn l hot ng

ca s : bin p iu khin c u ngc cc tnh nh hnh v.

Khi in p UAT dng th bn th cp my bin p c in p m

UA v ngc li. in p ny qua u vo o ca khuch i thut

ton OA1 cho ta in p UB c hnh dng ch nht i xng. Khi UA

m th bin ca in p ti B l UB = +Umax , Diode D m s dn

dng qua in tr R2 v bin tr R3. Khi Transistor c in p t

trn cc baz c gi tr dng nn Transistor kho v t C bt u

np. Cc in tr R2 , R3 v t C hp li thnh mt b tch phn cho

ra in p rng ca trong mt na bn k dng ca in p U AT.

Khi UAT m th in p ti A l UA c gi tr dng qua OA1 cho ta

in p ti im B c bin UB = -Umax . Diode D kha v

Transistor TR m lm ngn mch hai u ca khuch i thut ton

OA2, in p u ra ca OA2 l bng 0, khi Transistor m v t

C phng in qua Transistor.

2. B so snh dng khuch i thut ton :


55/72


SV: TB Trg. 55

u k

u r c r 1

r 2o a

u r a

Hnh 4.5 - S so snh dng KTT .

S so snh dng khuch i thut ton vi hai tn hiu vo URC

v UK tri du nhau c a ti u vo khng o ca khuch

i thut ton. u ra x o trng thi khi hai tn hiu u vo bng

nhau.

o

o

u

u r c

t

u k

t

Hnh 4.6 - Dng xung u ra khu so snh.

3. Chn khu khuch i to xung.

Khu khuch i v to xung c nhim v to ra xung iu khin

ph hp m Thyristor, do phi p ng c cc yu cu sau :

Xung phi rng .

Cng sut ca xung phi ln.

Sn trc ca xung phi c dc thng ng m bo thi

gian tc ng.

m bo cch ly gia mch iu khin v mch ng lc.


56/72


SV: TB Trg. 56

ru v

C2

D3

+e

b a x

d

t

tt

R6

Hnh 4.7 - S tng KTT mc theo kiu Darlington

Trong s ny dng hai Transistor TR1 v TR2 mc theo s

Darlington (hnh 47). Thng thng ngi ta dng van ngc tng

khuch i bi v loi ny c dng in r nh hn so vi van thun.

Mch vi phn trn s c nhim v hn ch rng xung iukhin , m bo cho Transistor khng b t nng trong thi gian

qu lu. Do din tch cnh tn nhit ca Transistor v kch thc dy

s cp ca bin p xung c gim i mt cch ng k. Trong s

ny Transistor ch m cho dng in chy qua trong khong thi

gian np t, nn dng in hiu dng ca chng b hn nhiu ln.


57/72


58/72


SV: TB Trg. 58

Tng hp S mch iu khin chnh lu vi cc khu gii thiu

Hnh 4.8 - Mch iu khin kch t dng chnh lu iu khin tia 3 pha

D3

U

R1A

A1+

- B

R2

R3D1

Tr1

CA2

-

+

C1

Uk

R5

R4

A3-

+

D

TA

+15V

C2

R6

D2

D3

U

R1A

A1+

- B

R2

R3D1

Tr1

CA2

-

+

C1R5

R4

A3-

+

D TB

+15V

C2

R6

D2

T

D3

U

R1A

A1+

- B

R2

R3D1

Tr1

CA2

-

+

C1R5

R4

A3-

+

D

AT

+15V

C2 R6

D2

T3

T2

R

L

A B C

A

B

C

O

TCT3

T2

T3

T2


59/72


60/72


SV: TB Trg.60

3. Tnh bin p xung

Chn vt liu lm li st l Ferit HM. Li c dng h nh xuyn, lm

vic trn mt phn ca c tnh t ho c : B = 0,3 (T) ; H = 30

(A/m) khng c khe h khng kh.

T s bin p xung : thng m = 2 - 3, chn m = 3

in p cun th cp my bin p xung : U2 = Uk= 3 (V)

in p t ln cun s cp my bin p xung :

U1 = m.U2 = 3*3 = 9 (V)

Dng in th cp my bin p xung : I2 = Ik= 0,11(A)

Dng in s cp my bin p xung :

03703

11021

,,

m

II (A)

t thm trung bnh ca li st :

3

60

tb 10.830*10.25,13,0

HB

Trong : 0 = 1,25.10-6 (H/m) l t thm ca khng kh.

Th tch li thp cn c :

2

11xxotb

B

I.U.S.t.

=l.Q=V

6

2

663

10927030

037091501016710251108

.,,

,..,....,..V (m

3)

V = 0,927 (cm3)

Chn mch t c th tch V = 1,4 (cm3). Vi th tch ta c cc

kch thc mch t nh sau:

a = 4,5 (mm)

b = 6 (mm)

Q = 0,27 (cm2) = 27 (mm2)

d = 12 (mm)

D = 21 (mm)

Chiu di trung bnh mch t : l = 5,2 (cm)

Nh vy ta c hnh dng mch t ca my bin p xung :


61/72


SV: TB Trg.61

b

d D

Hnh 4.10 - Mch t ca my bin p xung S vng dy s cp bin p xung :

Theo nh lut cm ng in t :

x

111 tB

Qw=dtdB

.Q.w=U

186102730

1016796

6

1

1

.*,

.*

Q.B

tUw x (vng)

S vng y th cp :

623

18612

m

ww (vng)

Tit din dy qun s cp :

006206

0370

1

1

1.

.

J

IS (mm2)

Chn mt dng in J1 = 6 (A/mm2)

ng knh dy qun s cp :

0850143

06204

4 11 ,,

,*S.

d (mm2

)

Chn d1 = 0,1 (mm2) nu k c cch in d1cd = 0,13 (mm

2)

Tit din dy qun th cp :

027504

110

2

2

2.

.

J

IS (mm2)


62/72


SV: TB Trg.62

Chn mt dng in J1 = 4 (A/mm2)

ng knh dy qun th cp :

1870143

027504

42

2 ,,

,*S.

d (mm2

)

Chn d2 = 0,19 (mm2) nu k c cch in d2cd = 0,22

(mm2)

Kim tra h s lp y:

dwdwd

4/dwSwS

K 2221

21

22211

ld

043,012

62*22,0186*13,0K

2

22

ld

4. Tnh tng khuch i cui cng

D2

R6Tr3

D3

Tr2

+ E

BAX D4T

C2

Hnh 4.11 - S tng khuch i cui cng

Chn Tranzitor cng sut loi Tr3 loi 2SC9111 lm vic ch

xung c cc thng s :

Tranzitor loi npn, vt liu bn dn l Si

in p gia Colecto v Baz khi h mch Emito : UCB0 = 40

(V)


63/72


SV: TB Trg.63

in p gia Emito v Baz khi h mch Colecto : U EB0 = 4 (V)

Dng in ln nht Colecto c th chu: Icmax = 500 (mA)

Cng sut tiu tn Colecto : Pc = 1,7 (W)

Nhit ln nht mt tip gip : T1 = 1750C

H s khuch i : = 50

Dng in lm vic ca Colecto : Ic3 = I1 = 36,7 (mA)

Dng in lm vic ca Baz : 734050

736

3

3,

,II CB (mA)

Ta thy rng vi loi Tiristor chn c cng sut iu khin

kh b : Uk= 3 (V) : Ik= 0,11 (A) nn dng Colecto Baz

ca Tranzito Ir3 kh b, trong trng hp ny ta c th khng cn

Tranzito Ir2 m vn c cng sut iu khin Tranzito.

Chn ngun cp cho bin p xung : E = +12 (V) . Vi ngun E =

12 (V) ta phi mc thm in tr R10 ni tip vi cc Emito ca

IE3

8210736

9123

1

10

.,I

UER ()

Tt c c Diod trong mch iu khin u dng loi 1N4009 c cc

tham s :

Dng in nh mc : Im = 10 (mA)

in p ngc ln nht : UN = 25 (V)

in p cho Diod m thng : Um = 1 (V)

5. Chn t C2v R6

in tr R6 dng hn ch dng in a vo Baz ca Tranzito

T3 chn R6 tho mn iu kin :

1316107340

543

3

6,

.,

,

I

UR

B

(K)

Chn R6 = 6,2 (K)


64/72


SV: TB Trg.64

Chn C2R6 > tx = 167(s). Suy ra9

2R

tC x

02701026

16732 ,.,C (F)

Chn C2 = 0,03(F)

6. Tnh chn tng so snh

R4

A3R5

Hnh 4.12 - Tng so snh

Khuch i thut ton chn R4 = R5 > 12101

123

.I

U

v

v (K)

Trong , nu ngun nui Vcc = 12 (V) th in p vo A3 l Uv 12 (V)

Dng in vo c hn ch Ilv < 1 (mA)

Do ta chn R4 = R5 = 15 (K) khi dng vo A3 :

801015

123

,.

I maxv (mA)

7. Tnh chn khu ng pha

in p ta c hnh thnh do s np ca t C1, mt khc m

bo in p ta c trong 1 na chu k in p li l tuyn tnh th

hng s thi gian t np c chn T1 = R3C1 = 0,01 (s)


65/72


66/72


SV: TB Trg.66

Chn in p xoay chiu ng pha : UA = 9 (V)

in tr R1 hn ch dng in i vo khuch i thut ton A1

thng chn sao cho dng vo khuch i thut ton IV < 1 (mA) .

Do

3

31109

101

9.

.I

UR

V

A

()

Chn R1 = 10 (K)

8. To ngun nui

Ta cn to ra ngun in p 12 (V) cp cho bin p xung, nui IC,cc b iu chnh dng in

C4470F

C6470F

7812

7912

A

C

a

b

c

a

b

c

+ 12

- 12

0

C4470F

C6470F

Hnh 4.14 - S mch to ngun

Ta dng mch chnh lu cu 3 pha dng Diod, in p th cp mybin p ngun nui :

15342

122

,,

U (V)

Ta c: U2= 9 (V)


67/72


SV: TB Trg.67

n nh in p ra ca ngun nui ta dng 2 vi mch n p 7812

v 7912 cc thng s chung ca vi mch ny :

- in p u vo : Uv = 0 35 (V)

- in p u ra :

Ura = 12 (V) vi IC 7812

Ura = -12 (V) vi IC 7912

- Dng in u ra : Ira = 0 1 (A)

- T in C4, C5 dng lc thnh phn sng hi bc cao

- Chn C4 = C5 = C6 = C7 = 470 (F) ; U = 35 (V)

9. Tnh chn Diod cho b chnh lu ngun nui

Dng in hiu dng qua Diod :

0502

0730

2

2 ,,I

I HD.D (A)

in p ngc ln nht m Diod phi chu

UN.Max = 6 .U2 = 6 .9 = 22 (V)

Chn Diod c dng in nh mc:

Im Ki.ID = 10*0,05 = 0,5 (A) Chn Diod c in p ngc ln nht :

UN = kU .UNmax = 2*22 = 44 (V)

Chn Diod loi K208A c cc thng s :

Dng in nh mc : Im = 1,5 (A)

in p ngc ln cc i ca Diod : UN = 100 (V)

10. Tnh khu phn hi in p


68/72


SV: TB Trg.68

R

Hnh 4.15 - S khu phn hi in p

1) Chn Diod chnh lu l loi K208A c cc thng s :

Dng in nh mc : Im = 1,5 (A) in p ngc ln cc i ca Diod : UN = 100 (V)

2) Tnh in p iu khin ti nh mc

Ta c in p :

UR = kuU2f= 2,34*9 = 21,1(V)

UrcUdk

t2

Hnh 4.16

Theo s chnh lu ta c:

cosUU 0DKT

uD kUU 20 (Ku : H s chnh lu Ku =

2

63)

UKT = U2kucos

cos = 8550

2

63100

100

2

,kU

U

u

KT

Vy = arcos0,855 = 31,30


69/72


SV: TB Trg.69

Tnh in p iu khin ti nh mc :

Theo th ta c :

180U

U

rc

dk

Trong : Urc = 12(V)

12180

331

180

,UU r cdk

= 2,09 (V)

Nh vy thun tin cho vic iu chnh in p ta chn R l

loi bin tr R = 1(K)

Hnh 4.17 S to in p iu khin cho chnh lu iu

khin

A

BC

UK

Ut

Uph

+ +

-_


70/72


SV: TB Trg.70

Kt lun

H thng my pht kch t la chn l mt h thng khng dng chi

than vnh trt v nh c m t Chng 2, y l mt h thng

n gin hn v ch to so vi cc h thng my pht kch t khc. Ni

bt nht l R-to my pht chnh v phn ng (Stator) ca my pht

kch t c ch to trn cng mt trc v quay theo tc ca ng

c ko Diesel v dng p kch t cm ng ra trong my pht kch thch

c a ngay vo cun kch t ca my pht thng qua b chnh lu

Diot gn trn cng trc Rto. cung cp dng in mt chiu vo

my pht kch thch (t stato), ngun cung cp ca n c th dng

ngun in mt chiu bng Ac-qui hoc mt ngun xoay chiu khc bt

k thng qua chnh lu c iu khin v y chnh l ngun chnh lu

c iu khin m n c thit k v tnh ton. Vic loi b vnh

trt khng nhng lm cho my pht n nh hn m cn lm gim i

cc chi ph vn hnh ca thit v lm tng tui th cho my.

Tc ng ca h thng t ng iu chnh kch t c t trc tip

vo ca iu khin ca b chnh lu, lm thay i dng kch t ca my

pht in kch thch, tng ng vi mc ch iu chnh in p pht ra

ca my pht. Nh vy hon ton khng c vnh trt a in vo

roto cng xut ch to khng b hn ch, ngoi ra do ni trc tip hng

s thi gian l rt nh (0,1 0,15s).

Vi cng ngh ch to van bn dn ngy cng hin i hn cng vi s

hp tc c lc ca in t s, cc h thng iu khin kch t ngy nay

c cht lng iu khin rt cao v c iu khin thng minh hn.

Vic cng nghip ho, hin i ho t nc ta nh hm nay l c s

ng gp quan trng v khng th thiu ca cc thit b iu khin in

t cng sut.


71/72


SV: TB Trg.71

Li kt

L mt sinh vin, nn n thit k ca em s khng trnh khi nhng

sai st. V em mong cc sai st s nhn c s gp , dy bo v

cm thng ca cc Thy C v Nh trng n c hon thin

hn m cng l cng c thm kin thc cho c nhn em trong cng vic

sau ny. Em xin chn thnh Cm n cc Thy C v Nh Trng


72/72


Ti liu tham kho

1. Ti liu hng dn thit k thit b in t cng sut.

TG. Trn Vn Thnh

2. in t Cng sut

TG. Nguyn Bnh

3. in t Cng sut v iu khin ng c in

TG. Cyril W. Lander

4. Phn tch & iu khin n nh H thng in

TG. L Vn t

5. Gio trnh My in - tp 1 & 2

TG. V Gia Hanh (Ch Bin)

6. Power System Stability & ControlTG. Prabha Kundur

7. Thit k my bin p in lc

TG. Phan T Th

8. Cm nang thc hnh vi mch tuyn tnh

TG. Hunh c Thng

on ap may phat _ avr2_

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