Bai Tap May Dien II. 2012 - Copy

7/31/2019 Bai Tap May Dien II. 2012 - Copy

1/21

Bien soan: ang Van Thanh

BAI TAP NG DUNG

LY LUAN CHUNG VE MAYIEN XOAY CHIEU


2/21

BAI TAP 1Ve s o trai day quan 3 pha dang ong khuon tap trung (1 lp) cua may

ien co tong so ranh Z = 12; 2p = 4 ( ve cho 1 pha, ien v tr au cuoi cua 2 pha

con lai)?

BAI GIAIBc 1: e ve s o trai day quan, can tnh toan cac thong so c ban cua bo

day quan nh sau:

Bc cc: =p2

Z =4

12 = 3 (ranh).

So ranh mot pha / mot bc cc: q =m

=3

3 = 1 (ranh).

= P360/z = 2.360/12 =600 , chon y = =3( ranh)Bc 2: Lap bang phan boBc 3: Cau tao day quanBc 4: ve SDTDQ (ky hieu, ket noi 2p=4)

BAI TAP 2Ve s o trai day quan 3 pha dang ong khuon tap trung (1 lp) cua may

ien co tong so ranh Z = 36; 2p = 4 ( ve cho 1 pha, ien v tr au cuoi cua 2 phacon lai)? Tnh he so day quan Kdq?

pha B va C.BAI GIAI

Bc 1: e ve s o trai day quan, can tnh toan cac thong so c ban cua boday quan nh sau:

Bc cc: =p2

Z =4

36 = 9 (ranh).

So ranh mot pha / mot bc cc: q = m

= 39

= 3 (ranh).Bc 2:Ve cac oan thang song song (36 ranh), phan bo 4 bc cc va ve cac boi

day cua pha A tren cac ranh 1, 2, 3, 10, 11, 12, 19, 20, 21, 28, 29, 30, chon cachnoi day cc gia e am bao so cc 2p, tng t cho 2 pha B va C e hnh thanh so khai trien nh sau:


3/21

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 20 1 2 3 4

5 6 7 8 9 30 1 2 3 4 65

A Z B C YX

1 2 3 4 5 6

S o day quan ba pha, dang ong khuon tap trung (Z = 36, 2p = 4).Nghi chu: Cac so th t t 1en 6 la so ch so th t cua nhom boi.

ng ngan cach gia cac bc cc.

Bc 3:

Bo day quan co 2 nhom boi / pha, 6 boi / pha, so ranh mot pha / bc cc = q= 3.e tao ra 4 cc, bo day quan au cc gia. So mach nhanh song song trong mot pha bang 1.

1 4A X

3 5B Y

46

C Z

Pha A

Pha B

Pha C

Qui c ben trai cua boi day la au au va ben phai cua boi day la au cuoi.

BAI TAP 3Ve s o trai day quan 3 pha dang ong tam phan tan n gian cua may

ien co tong so ranh Z = 36; 2p = 4.BAI GIAI

Bc 1:e ve s o trai day quan, can tnh toan cac thong so c ban cua bo day

quan nh sau:

Bc cc: =p2

Z =4

36 = 9 (ranh).

So ranh mot pha / mot bc cc: q =m

=3

9 = 3 (ranh).

Bc 2:Xac nh so nhom boi phan tan trong pha A nh sau:Do q le nen nhom so boi day trong moi nhom la:

Nhom au tien: 21q

= 213

= 2 (boi).Nhom con lai: 1q = 13 = 1 (boi)


4/21

Tng t cho pha B va C. Tong so nhom boi / pha = 4.Bc 3:

Ve cac oan thang song song (36 ranh), phan bo 4 bc cc va ve 4nhom boi day cua pha A tren cac ranh 1, 2, 3, 10, 11, 12, 19, 20, 21, 28, 29, 30;chon cach au day cc that thc hien tng t cho pha B va pha C hnh thanh s

o khai trien nh sau:

41

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1 2 3 4 65

A Z B C X Y

ab

c

d

e

fgh

k

l

ab

c

d

e

fgh

k

l

S o day quan 3 pha, dang ong tam phan tan vi Z = 36, 2p = 4.

ng ngan cach cac bc cc

2

3

5

6

10

8

9

11

7

12

So th t trong vong tron ch so th t boi day

ac iem bo day quan:Bo day quan co 4 nhom boi/pha (2 nhom 2 boi va 2 nhom 1 boi), 6 boi / pha,

so ranh mot pha / bc cc la q = 3.e tao ra 4 cc, bo day quan au cc that. So mach nhanh song song trong mot pha 2a = 1 bieu dien nh s o sau:

Pha A

Pha B

Pha C

1 4A X

7 10

2 5B Y

8 11

3 6C Z

9 12

Qui c ben trai cua boi day la au au va ben phai cua boi day la au cuoi.

BAI TAP 4


5/21

1/ Ve s o trai day quan 3 pha dang day quan xep 2 lp cua may ien cotong so ranh Z = 24; 2p = 4 (ve cho 1 pha, ien v tr au cuoi 2 pha con lai.

2/ Tnh he so day quan Kdq khi khi y =5(


6/21

Bo day quan co 4 nhom boi / pha, 8 boi / pha, so ranh mot pha / bc cc q =2.

e tao ra 4 cc, bo day quan au cc that. So mach nhanh song song trong mot pha = 1.

Pha A

Pha B

Pha C

1 4A X

7 10

2 5B Y

8 11

3 6C Z

9 12

Qui c ben trai cua boi day la au au va ben phai cua boi day la au cuoi.2/ Tnh Kdq:Khi y= = 6. Kdq 0,966; khi y=5, Kdq 0,9333/Chon y/ =2/3, t o y= 4; e3 =0

BAI TAP 5Tnh he so day quan cua bo day quan 1 lp, bc , cho stato ong c 3 pha

co Z = 24 ranh, so cc 2p = 4, m= 3.

BAI GIAICac thong so can thiet cua bo day quan 1 lp:

Bc cc: = pZ

2 = 424

= 6 (ranh).

So ranh mot pha / mot bc cc: q =mp.m.2

Z =

3

6 = 2 (ranh).

Goc lech ve ien gia hai ranh ke tiep nhau:

o

180 =6

180o

= o30

Nen he so day quan :

kdq= 1.)

2.(sin.

)

2

.(sin

q

q

=)

2

30.(sin.2

)

2

30.2.(sin

o

o

= 0,9

BAI TAP 6Tnh sc t ong c ban cua mot pha day quan trong ong c 3 pha. Biet day

quan xep 2 lp co Z = 24, 2p = 4, bc day quan y = 5, so vong day moi phan t Ws

= 10 vong. ong c co cong suat P = 5,5 kW vi Um = 380 V au Y, cos m =

0,8; m = 0,85.

Moi pha co mot mach nhanh song song.BAI GIAI


7/21

Bc cc: =p2

Z =4

24 = 6 (ranh).

q =3

=3

6 = 2 (ranh).

Goc lech pha ve ien:

o

180

= 6

180o

o

30

He so day quan: kdq = kn.kr = sin(2

.

).

2sin.q

2.qsin

= sin(2

.

6

5 ).

230sin.2

2

30.2sin

o

o

= 0,933 (vi he so =

y=

6

5 ).

Tong so vong day trong mot mach nhanh song song.W = Ws.2p.q = 10.4.2 = 80 (vong).

Dong ien day nh mc trong mot pha:

Im = .cos.U.3

P

m

m=

85,0.8,0.380.3

10.5,53

= 12,29 (A).

Day quan au sao (Y) nen dong ien Id = Ip = Im = 12,29(A).

Do moi pha co mot mach nhanh song song nen dong ien Im = 12,29 (A) chnh ladong ien tren moi mach nhanh song song I.Bien o sc t ong ap mach la:

Fm = Ip

kW

dq....9,0 = 29,12.

2

933,0.80.9,0 = 413 (A.vong).

Sc t ong cua mot pha bieu dien di dang phng trnh sau:Ff= cos.sin. tFm

Ff= cos.sin.413 t (A.vong).

Trong o , la nhng gia tr thay oi theo thi gian, khong gian.


8/21

BAI TAP NG DUNG

MAY IEN KHONG ONG BO


9/21

BAI TAP 1Cho mot ong c ien khong ong bo 3 pha rotor long soc co Pm = 10 kW,

Um = 220/380 V, day quan au /Y, toc o quay nm = 960 vg/ph, so cc 2p = 6,

tan so f = 50 Hz, he so cong suat cos = 0,8; hieu suat = 0,85.1. Tnh dong ien nh mc cua ong c.2. Tnh tong ton hao cong suat trong ong c.

BAI GIAI1/ Dong ien nh mc thay oi theo ien ap lam viec:Vi Um = 220 V.

Im =mm

m

cos.U.3.

P

=

8,0.220.3.85,0

10.103

= 38,59 (A).

Vi Um

= 380 V.

Im =mm

m

cos.U.3.

P

=

8,0.380.3.85,0

10.103

= 22,34 (A).

2/ Tong ton hao cong suat trong ong c:

m

m

m PP

P

=85,0

10.103

- 10.103 = 1764,7 (W).

BAI TAP 2Cho mot ong c ien khong ong bo 3 pha day quan stato noi hnh tam

giac, ien ap li 220 V, f = 50 Hz. So lieu ong c: p = 2 oi cc, I1 = 21 A,cos 1 = 0,82; = 0,837; s = 0,053. Tnh toc o ong c, cong suat ien ong ctieu thu P1, tong cac ton hao, cong suat hu ch cua ong c P2

BAI GIAIToc o goc cua ong c:

= 1 .(1 s) = p f.2 .(1 s)

=2

50.2 .(1 0,053) = 148,68 (rad/s).

Toc o quay cua ong c:

n =p

f.60 .(1 s) =2

50.60 .(1 0,053) = 1420 (vg/ph).

Cong suat ien ong c tieu thu:P1 = 3 . U1.I1. cos = 3 . 220.21. 0,82 = 6561

(W).Cong suat ien hu ch:


10/21

P2 = P1. 1 = 6561.0,837 = 5491 (W).Tong cac ton hao cong suat:

P = P1 - P2 = 6561 5491 = 1070 (W).

BAI TAP 3

Mot ong c ien khong ong bo 3 pha rotor day quan co so oi cc t cuastato p = 3, tan so li ien f = 50 Hz. T thong chnh trong t trng ong c la = 3,12.10-2 Wb, so vong day stato w1 = 124 vong va rotor w2 = 98 vong, he so dayquan stato kdq1 = 0,95 va rotor kdq2 = 0,96. Hay xac nh sc ien ong cam ngtrong day quan stato va rotor khi rotor ng yen va khi rotor quay vi he so trt s= 3%. Tm toc o quay n cua rotor ong c.

BAI GIAISc ien ong cam ng day quan stato:E1=4,44.f.kdq.w1. = 4,44.50.0,95.124.3,12.10-2 = 816 (V).Khi rotor con ng yen th ong c giong nh may bien ap: day quan stato

nh s cap va day quan rotor nh th cap cua may bien ap. Sc ien ongtrong day quan rotor:

E20 =E

1

k

E

=

2dq2

1dq1

1

k.w

k.w

E

=1dq1

2dq2

1k.w

k.w.E

= 95,0.124

96,0.98.816 = 652 (V).

Sc ien ong trong day quan rotor khi quay vi he so trt s = 3%:E2s = s. E20 = 0,03.652 = 20 (V).Toc o quay cua ong c la:

n = n1.(1 s) =p

f.60 .(1 s) =3

50.60 .(1 0,03)

= 970 (vg/ph).

BAI TAP 4Mot ong c ien khong ong bo 3 pha rotor day quan khi e rotor h mach

va cho ien ap nh mc vao stato th ien ap tren vanh trt la 250 V. Khi ong clam viec vi tai nh mc th toc o n = 1420 vg/ph. Tnh:

1. Toc o ong bo.2. Toc o t trng quay do dong ien rotor sinh ra so vi toc o rotor.3. Tan so dong ien rotor.4. Sc ien ong cua rotor khi tai nh mc.

BAI GIAI


11/21

a/ V he so trt cua ong c rat be s = 3% 6%nen toc o t trng quay n1 = 1500 vg/ph, tc la co hai oi cc khi tan so la

50 Hz.b/ Toc o cua t trng quay cua rotor:

n2 = n1 n = 1500 1420 = 80 (vg/ph).

c/ Tan so dong ien rotor:f2 =

60

n.p 2 =60

80.2 = 2,66 (Hz).

Hay f2 = s.f1 = 0,053.50 = 2,26 (Hz).

Trong o: s =1

1

n

nn =

1500

14201500 =1500

80 = 0,053

d/ Sc ien ong cua rotor khi quay toc o nh mc:E2s = s.E20 = 0,053.250 = 13,4 (V).

BAI TAP 5Mot ong c ien khong ong bo 3 pha rotor long soc co cac so lieu sau: P m

= 11,9 kW, Ufm = 220 V; Ifm = 25 A; f = 50 Hz; 2p = 6; Pcu1 = 745 W; Pcu2 = 480 W;PFe = 235 W; Pc = 180 W; Pf= 60 W.

Tnh cong suat ien t, momen ien t va toc o quay cua ong c.BAI GIAI

a/ Cong suat ien t cua ong c:Pt = P2 + Pc + Pf+ Pcu2

= 11900 + 180 + 60 + 480 = 12620 (W).Momen ien t cua ong c:

Mt =1

tP

=

60

n.2

P

1

t

=

60

1000.2

12620

= 120 (Nm).

Trong o: n1 =p

f.60 =3

50.60 = 1000 (vg/ph).

c/ Toc o quay n cua ong c:

He so trt: s =t

2cu

P

P=

12620

480 = 0,038

Nen n = n1.(1 s) = 1000(1 - 0,038) = 962 (vg/ph).

BAI TAP 6Mot ong c ien khong ong bo ba pha rotor day quan, R1 = 0,46 , X1 =

2,24 , R2 = 0,02 , X2 = 0,08 , kdq1 = 0,932, kdq2 = 0,955, w1 = 192 vong, w2 =36 vong. Day quan stato au tam giac, mang ien U = 220 V, f = 50 Hz, so pha m 1= m2 = 3.

Tnh he so qui oi s.. kE, he so qui oi dong ien k I, ien tr m may mac

vao mach m may e momen m may cc ai.Tnh dong ien trong day quan stato va rotor khi co bien tr m may va khi


12/21

BAI GIAIHe so qui oi sc ien ong kE:

kE =2dq2

1dq1

k.w

k.w=

955,0.36

932,0.192 = 5,2

He so qui oi dong ien kI:

kI =2dq22

1dq11

k.w.m

k.w.m =955,0.36.3

932,0.192.3 = 5,2

He so qui oi cua toan mach:k = kE . kI = 5,2. 5,2 = 27,04ien tr rotor qui oi ve stato:

,

2R = k.R2 = 27,04.0,02 = 0,54 ( ).ien khang rotor qui oi ve stato:

,

2X = k.X2 = 27,04.0,08 = 2,163 ( )

e momen m may (n=0) at cc ai th he so trt( ng vi n=0):sm =

1

,

2

,

f

,

2

XX

RR

=1

T o suy ra gia tr ien tr mac vao mach stato:,

fR = ( 1,

2 XX ) -,

2R = (2,163 + 2,24) - 0,54 = 3,86 ( ).Dong ien pha stato khi m may bang ien tr phu mach rotor:

Immp =2,

212,

f,

21

P

)XX()RRR(

U

= 22)163,224,2()86,354,046,0(

220

= 33,54 (A).

Dong ien day luc m may (do stato au tam giac):

Imm = 3 . Immp = 3 .33,54 =58 (A).Dong ien rotor khi m may (do rotor au sao):

I2 = kI.Immp = 5,2.33,54 = 174 (A).Dong ien m may trc tiep la:

Imm = 3 .2,

21

2,

21

P

)XX()RR(

U

= 3 .22)163,224,2()54,046,0(

220

= 84,4 (A).

Ty so dong ien hai phng phap m may:

46,158

4,84

Nhan xet: Khi dung ien tr m may th dong ien m may giam 1,46 lan sovi m may trc tiep.

BAI TAP 7Mot ong c ien khong ong bo ba pha rotor long soc co cac so lieu ghi


13/21

nh mc m = 0,885, he so cong suat nh mc cos m = 0,88; Y/ - 380/220V; ty so dong ien m may Imm/Im = 5,5; momen m may Mmm/Mm = 1,3; momencc ai Mmax/Mm = 2. ien ap mang ien U = 380 V. Tnh:

a/ Cong suat tac dung va phan khang ong c tieu thu che o nh mc.

b/ Dong ien, he so trt va momen nh mc.c/ Dong ien m may, momen m may va momen cc ai.

BAI GIAIa/ Cong suat tac dung ong c tieu thu:

P1 = mP

=885,0

14= 15,82 (kW).

Cong suat phan khang ong c tieu thu:Q1 = P1.tg = 15,82.0,54 = 8,54 (kVAr).

b/ Dong ien nh mc:

I1m =mmm1

m

.cos.U.3

P

=

88,0.380.3.885,0

10.143

= 27,31 (A).

He so trt nh mc:

sm =1

1

n

nn =

1500

14501500 = 0,0333

Sau khi tnh I1m co the tnh cong suat phan khang ong c tieu thu nh sau:

Q1 = 3 .U1m. I1m.sin = 3 .380. 27,31.0,475 = 8,54 (kVAr).Momen nh mc:

Mm = 9,55.m

m

n

P= 9,55.

1450

10.14 3

= 92,2 (Nm).

c/ Momen m may:Mmm = 1,3.Mm = 1,3. 92,2 = 119,8 (Nm).

Momen cc ai:

Mmax = 2.Mm = 2. 92,2 = 184,4 (Nm).Dong ien m may:

Imm = 5,5. I1m = 5,5. 27,31 = 150,2 (A).


14/21

BAI TAP NG DUNG

MAY IEN ONG BO


15/21

BAI TAP 1May phat ien ong bo ba pha cc an co Pm = 30 MW, Um = 10,5 kV,

cos m = 0,8; so oi cc p = 1. Hieu suat nh mc m = 98,32 %; tan so nguonphat f = 50 Hz.

1. Tnh toc o quay rotor va dong ien nh mc.2. Tnh cong suat bieu kien Sm cua may, cong suat phan khang Qm cua may.3. Tnh cong suat ma ong c s cap cung cap cho may phat va tong cac ton

hao?BAI GIAI

1/ Toc o quay cua rotor may phat:

n = n1 = p

f.60=

1

50.60= 3000 (vg/ph).

Dong ien nh mc cua may phat:

Im =mm

m

cos.U.3

P

=

8,0.5,10.3

30= 2,064 (kA).

2/ Cong suat bieu kien cua may phat:

Sm =m

m

cos

P

=

8,0

30 = 37,5 (MVA).

Cong suat phan khang cua may phat:

Qm = Sm. sin m

= 37,5.0,6 = 22,5 (MVAr).sin m = 0,6 suy ra t cos m = 0,8

3/ Cong suat cung cap cho truc may phat bi ong c s cap la:

P1 =m

mP

=

32,98

30.100 = 30,51 (MW).

4/Tong ton hao:

m1PPP = 30,51 30 = 0,51 (MW).

BAI TAP 2Mot may phat ien ong bo ba pha cc an, day quan stato noi sao, ien apday khong tai Uo = 398,4 V.

Khi dong ien tai I = 6 A, cos = 0,8 (cham sau) th ien ap Ud = 380 V.

Thong so day quan stato nh sau: ien tr r 0, ien khang tan x = 0,2 .- Tnh sc ien ong pha may phat khi khong tai.- Tnh ien khang ong bo xb va ien khang phan ng x.

BAI GIAI

May phat cc an vi phng trnh can bang:


16/21

oo

of

o

f IEU .(r + jx b) = o

ofE jIx b (v r =0)

T o ve o th vect dong ien va ien ap vi r= 0:

of

o

E

o

I

f

o

U

Do dong ieno

I cham pha so vi ien apo

fU mot goc .o

ofE : sc ien ong pha khong tai, v may phat noi sao nen:

Eof = 3

U of=

3

4,398= 230 (V).

T o th vect suy ra gia tr ien ap tren ien khang ong bo:Vi Ud = 380 V suy ra Uf= 220 V khi co tai.

I.xb =2

f2

of )cos.U(E - Uf.sin T cos = 0,8 suy ra sin = 0,6Do o:

I.xb =22)8,0.220(230 - 220.0,6 = 16,8 (v).

ien khang ong bo khi dong ien I = 6 A la:

xb =I

8,16=

6

8,16= 2,68 ( ).

ien khang phan ng la:

x= xb - x = 2,68 0,2 = 2,48 ( ).BAI TAP3

Mot may phat ien ong bo ba pha cc an co Sm = 1500 kVA; Um = 6600V; f = 50 Hz, cos m = 0,8; day quan stato au sao, ien tr day quan stato r = 0,45

; ien khang ong bo xb = 6 .a/ Mot tai co U = 6600 V, cos = 0,8; tieu thu dong ien bang nh

mc.Tnh dong ien, cong suat tac dung va phan khang cua tai.


17/21

b/ Neu cat tai va dong ien kch t van gi tr so nh luc co tai tren th ienap au cc may phat bang bao nhieu ?

b

o

x.I.j

o

I

f

o

U

f

o

E

o

r.I

BAI GIAI

a/ Dong ien nh mc cua may phat:

T cong thc: Sm = 3 .Um.Im.

Suy ra: Im =m

m

U.3

S=

6600.3

10.15003

= 131,2 (A).

ien ap pha cua may phat:

Ufm =3

Um =3

6600= 3810 (V).

Cong suat tac dung cua tai tieu thu:Pm = 3 .Um.Im.cos m = 3 .6600.131,2.0,8 = 1200 (kW).

Cong suat phan khang cua tai tieu thu:Qm = 3 .Um.Im.sin m = 3 .6600.131,2.0,6 = 900 (kVAr).

b/ Da vao phng trnh can bang:oo

f

o

f IEU .(r + jx b).Ve c o th vect (nh hnh v) va suy ra sc ien ong pha la:

b

o

x.I.j

o

I

f

o

U

f

o

E

o

r.I

Ef =

2

fb

2

f )sin.Ux.I()r.Icos.U(

=

22

)6,0.38106.2,131()45,0.2,1318,0.3810( = 4370 (V).ien ap day au cc khi cat tai:


18/21

BAI TAP4ong c ien ong bo ba pha co cac so lieu ghi trong nhan may: Pm = 1000

kw; Um = 6000 V; p = 2 ; cos m = 0,99; nm = 1500 vg/ph. Tong ton hao cong

suat P = 170 kW.

1. Tnh cong suat ien ma ong c tieu thu.2. Neu momen phu tai bang 25% momen nh mc th cong suat phan khang

toi a ong c co the phat ra cho mang ien la bao nhieu ?BAI GIAI

1/ Cong suat ien ma ong c tieu thu:P1 =1000 + 170 = 1170 (kw)

2/ Momen nh mc cua ong c:

Mm =m

mP

=

60

n.2

Pm

=

60

1500.2

10.10003

= 6366 (Nm).

C nang ong c cung cap cho phu tai khi momen phu tai bang 25%momennh mc la:

P =100

25. Pm = 100

25.1000 = 250 (kW).

Cong suat ong c tieu thu khi phu tai bang 25% momen nh mc:

P1 = P + P = 250 +170 = 420 (kW).

Cong suat phan khang ong c co the phat ra cho mang ien:Vi cong suat bieu kien tng ng :

Sm =cos

1P

=99,0

420= 424 (kVA).

Q1 =2

1

2

m PS =22

420424 = 58,1 (kVAr).

BAI TAP 5

Hai may phat ien lam viec song song cung cap ien cho hai tai:Tai 1: St1 = 5000 kVA; cos 1 = 0,8.

Tai 2: St2 = 3000 kVA; cos 2 = 1.May phat th nhat phat ra P1 = 4000 kW; Q1 = 2500 kVAr. Tnh cong suat

may phat th hai va he so cong suat moi may phat.

BAI GIAI

Cong suat tac dung cua hai tai:Pt = St1.cos 1 + St2.cos 2 = 5000.0,8 + 3000.1 = 7000 (kW).


19/21

Cong suat phan khang cua hai tai:

Qt = St1.sin 1 + St2.sin 2 = 5000.0,6 + 3000.0 = 3000 (kVAr).

Cong suat tac dung cua may phat 2:

P2 = Pt P1 = 7000 4000 = 3000 (kW).

Cong suat phan khang cua may phat 2:Q2 = Qt Q1 = 3000 2500 = 500 (kvar).

He so cong suat may phat 1:

cos 1 = 21

2

1

1

QP

P

= 22

25004000

4000

= 0,848.

He so cong suat may phat 2:

cos 2 = 22

2

2

2

QP

P

= 22

50030003000

= 0,986.

BAI TAP 6Mot may phat ien ong bo cung cap cho ho tieu thu mot cong suat 2500 +

j3000 (kVA) vi ien ap 6,3 kV.- Xac nh tong ton hao tren ng day va trong may phat, biet rang ien tr

mot pha cua ng day rd = 0,15 , cua may phat r= 0,045 .

- Neu at them mot may bu ong bo vi cong suat bu la 30 j3000 (kVA)th tong ton hao tren la bao nhieu?BAI GIAI

Cong suat cua tai:

).(3910300025002222

kVAQPS

Dong ien tai khi cha bu:

).(3603,63

3910

3A

U

SI

He so cong suat khi cha bu:

.64,03910

2500

S

Pcos

Tong ton hao khi cha bu:p = 3I2(rd +r) = 3360

2(0,15 + 0,045) = 75,2( kW).Cong suat cua may khi co bu:S = S + Sbu = (2500 + j3000) + (30 j3000) = 2530 (kva).Dong ien tng ng:

)(2333,63

25303'' AU

SI


20/21

Tong ton hao khi co may bu:p = 3I2(rd + r) = 3233

2(0,15 + 0,045) = 31,5(kW).He so cong suat khi co bu:

cos = 1 v Q = 0.

= 22 1046,113 = 154 (kVA).

Va can chon ong c co dung lng nh mc thoa ieu kien:

Sm 154 (KVA)


21/21

TAI LIEU THAM KHAO

1. Vu Gia Hanh, Tran Khanh Ha, May ien 1,2 NXB Khoa hoc Ky thuat, HaNoi 2003.2. ang Van Thanh, Bai giang May ien 1,2, ai hoc SPKT 2000-2011.3. Nguyen Trong Thang, May ien, HSPKT, 2004.

Documents

Bai Tap May Dien II. 2012 - Copy