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TRNG HSP KY THUATTP HO CH MINH
KHOA IEN BO MON KY THUAT IEN
CHNG 3
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CHNG 3CAC PHNG PHAP GIAI MACH IEN
* Giai mach ien tc la tm tr so dongien cac nhanh.
* Muon tm c tr so dong ien cacnhanh can lap c he phng trnh
machien.
* Tuy thuoc vao an so cua he phng trnhmach ien ma ta co cac Phng
phap giaimach ien
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3.1 Phng phap dong ien nhanh:1.nh ngha :
An so cua he PTM la tri so dong ien cac nhanh.2.Cac bc thc hien
:
* Xac nh so nhanh (m) va so nut (n) cua mach* chon chieu dong
ien cac nhanh( chon tuy y)* Lap he PT mach ien.
_ Viet ( n 1 ) pt theo nh luat K.S.1 _ Viet ( m n + 1 ) pt theo
nh luat K.S.2
* Giai he pt mach ien. Tm tr so dong ien cac nhanhChu y :
Neu dong ien tm c mang gia tr am th ket luan chieu cua dongien o
trong mach la chieu ngc lai.
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V DU : Hay giai mach ien sau
R2
E2E1
R1R3
Biet : R1 = 3 E1 = 12.5 VR2 = 2 E2 = 9 VR3 = 4
- Xac nh m( nhanh ) m = 3- Xac nh n( nut ) n = 2- Chon chieu
dong ien cac nhanh(tuy y)
A
B
I1 I2I3
Lap he PT mach ien* Viet (n-1) pt theo L1 Tai A : * Viet (m - n
+ 1) pt theo L2 I1R1 + I3R3 = E1
I2R2 + I3R3 = E2Mach vong 1 :Mach vong 2 :
I1 + I2 - I3 = 0
1 2
Thay cac gia tr va giai he phng trnh mach ien ta co :
I1 + I2 - I3 = 03.I1 + 4.I3 = 12,5
2.I2 + 4.I3 = 9
I1 = 1,5 AI2 = 0,5 AI3 = 2 A
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* Bc 1:
* Bc 2:_ Chon ( m - n + 1) mach vong oc lap
Mach vong oc lap la cac mach vong khong cha lan nhau
_ Viet (m - n + 1) pt theo L2 cho cac mach vong oc lap
3.2. Phng phap dong ien mach vong1.nh ngha :An so cua he PTM la
tri so dong ien mach vong.
Dong ien mach vong la dong ien tng tng chay gia cac nhanh, co
tacdung tng t nh dong ien nhanh2.Cac bc thc hien :
-Xac nh m( nhanh ), n( nut )- Chon chieu dong ien cac nhanh (
chon tuy y )
Lap he PT mach ien
_ Giai he phng trnh mach ien, tm tr so dong ien mach vong
* Bc 3: Tm tr so dong ien nhanh Ini = IviChu y : Dong ien mach
vong nao cung chieu vi dong ien nhanh thmang dau + , ngc lai mang
dau -
_ Chon chieu dong ien mach vongThng chon chieu cua dong ien
trung vi chieu cua mach vong
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V DU : Hay giai mach ien sau
R2
E2E1
R1R3
Biet : R1 = 3 E1 = 12.5 VR2 = 2 E2 = 9 VR3 = 4
- Xac nh m( nhanh ) m = 3- Xac nh n( nut ) n = 2- Chon chieu
dong ien cac nhanh (tuy y)
A
B
I1 I2I3
Lap he PT mach ien
* Viet phng trnh theo L2 cho cac mach vong oc lap vi an so la
dongien mach vong
* Chon (m - n + 1) = (3 2 + 1) = 2 mach vong oc lap
Ia.(R1 + R3) + Ib.R3 = E1Mach vong 1 :Mach vong 2 :
* Thay cac gia tr va giai he phng trnh mach ien ta co :7Ia + 4Ib
= 12.54Ia + 6Ib = 9
Ia = 1.5 AIb = 0.5 A
1
Ia
2
Ib
Ib.(R2 + R3) + Ia.R3 = E2
1 2
* Tm tr so dong ien nhanh
Ia IbI1 I2Ia Ib
I3
I1 = Ia = 1.5 AI2 = Ib = 0.5 AI3 = Ia+Ib = 2 A
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1.nh ngha :3.3 Phng phap bien oi tng ng
Bien oi mach ien a cho tr thanh mot mach ien khac vi sonhanh ,
so nut t hn nhng ga tr dong ien chay trong cac nhanhkhong oi.2.Cac
phng phap bien oi :a.Cac phan t ghep noi tiep :
RtIRt = R1+R2+Ri Rt = Ri
b.Cac phan t ghep song song :
I
R1R2Ri
RtI gt = g1+g2+gi = giRt = 1/gt
IR1 R2 Ri
ac biet
IR1R2
I1
I2
Rt = R1.R2/(R1+R2) I1 = I.R2 / (R1+R2) I2 = I.R1 / (R1+R2) Bai
tap e thi
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c. Bien oi Sao tam giac :
Noi Sao Noi Tam giac
R12 = R1+R2 + (R1.R2)/R3R23 = R2+R3 + (R2.R3)/R1R31 = R3+R1 +
(R3.R1)/R2
R1 = R31.R12 / (R12+R23+R31)R2 = R12.R23 / (R12+R23+R31)
R3 = R23.R31 / (R12+R23+R31)
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Cho mach ien nh hnh ve :
Biet :
V24E =1R5 =2R2 =2R4 =2R1 =1R3 =1R =
Tnh dong ien I cua mach
V du :
R2
R5R
R1
R4
R3
I
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R23
R5
R
R31
R4
R12
R1 * R2 / ( R1 + R2 +R3 )R12 =R2 * R3 / ( R1 + R2 +R3 )R23 =R3 *
R1 / ( R1 + R2 +R3 )R31 =
R31 + R4R6 =R23 + R5R7 =
R6 * R7 / ( R6 +R7 )R8 =R + R12 + R8Rt =
E / RfI =
I
RtR7
I
R
R12
R6
I
R R8
R12
R
R2
R5
R1
R4
R3
IMach c bien oi nh sau :
0.80=0.40=0.40=2.40=1.40=0.88=2.68=A8.94=
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Bc 1:
Tnh ien ap hai nut
U = Ei.gi / gi
Ii = ( Ei U ).gi
Bc 3:
3.4. Phng phap ien ap hai nut
Trong o :Nhng sc ien ong nao cung chieu vi ien ap th mang dau
am, ngc chieu vi ien ap th mang dau dng.
Cac bc thc hien :
ien ap va nhng sc ien ong nao cung chieu vi dong ien thmang dau
dng, ngc lai mang dau am.
Trong o :
Chon chieu dong ien cac nhanh va ien ap hai nut (chon tuy y
)
Bc 2:
Tnh dong ien cac nhanh
Phng phap nay dung e giai cac mach ien co nhieu nhanh noi song
song
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Vi du: Hay giai mach ien sauBiet : R1 = 1 E1 = 15 V
R2 = 3 E2 = 16 VR3 = 2 E3 = 16 VR4 = 1
R1
E1
R2
E2
R3
E3
R4
I1 I2 I3 I4
U
A
B
B1: Chon chieu dong ien cac nhanh vachieu ien ap gia hai nut nh
hnh ve
B2: Tnh ien ap hai nut
I1 = ( E1 - U ).g1 = (15 - 10) / 1B3: Tnh dong ien cac nhanh
U = Ei.gi / giU = E1.g1+E2.g2+E3.g3g1 + g2 + g3 + g4
15 16 161 3 2
+ +
1 1 3 2
1 + + + 1= = 10 V
= 1.5 AI2 = ( E2 - U ).g2 = (16 - 10) / 3 = 2 AI3 = ( E3 - U
).g3 = (16 - 10) / 2 = 3 AI4 = U . g2 = 10 / 1 = 10 A
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3.5. Phng phap xep chong :1.nh ngha :Dong ien qua moi nhanh bang
tong ai so cac dong ien qua cac
nhanh do tac ong rieng re cua tng nguon sc ien ong ( luc ocac sc
ien ong khac bang khong 0 )
2.Cac bc thc hien :
Bc 1: Thiet lap mach ien ch co mot nguon tac ong (E1)Bc 2: Tnh
dong ien trong mach ch co mot nguon tac ong(E1)
I11, I12, I13Bc 3: Thiet lap mach ien cho cac nguon tiep
theo(E2) va lap laibc (2). Tnh : I21, I22, I23Bc 4: Xep chong( cong
ai so ) cac dong ien qua moi nhanh
I1 = I11 - I21 , I2 = I22 - I12 I3 = I13 + I23
R2
E2E1
R1 R3
I1 I3 I2
R2
E1
R1 R3
I11 I13 I12
R1R2
E2
R3
I21 I23 I22
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R2
E2E1
R1 R3
I1 I3 I2V du : Hay giai mach ien sauBiet : E1 = 40 V, E2 = 16
V,
R1 = 2, R2 =4, R3 = 4
R1 R2
E1
R3
I11 I13 I12
a. Mach ch co nguon E1 tac ong
E1/(R1 + R2.R3/R2+R3) = 40/{2+4.4/(4+4)} = 10 AI11 =I12 = =
10.4/(4+4) = 5 A
I13 = = 10.4/(4+4) = 5 A
I11.R3/(R2+R3)
I11.R2/(R2+R3)
b. Mach ch co nguon E2 tac ong
R1R2
E2
R3
I21 I23 I22E2/(R2 + R1.R3/R1+R3) = 16/{4+2.4/(2+4)} = 3 AI22
=
I21 = = 10.4/(2+4) = 2 A
I23 = = 10.2/(2+4) = 1 A
I22.R3/(R1+R3)
I11.R1/(R1+R3)I11-I21 = 102
Dong ien I2 chay trong mach ngc vi chieu a chon
c. Mach tac ong cua ca hai nguonI1 = = 8 A
I22-I12 = 35I2 = = -2 AI13+I23 = 5+1I3 = = 6 A
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B1: Chon chieu dong ien cac nhanhva chieu ien ap gia hai nut
nhhnh veB2: Tnh ien ap hai nut
U = (-E1.g1 E2.g2)/( g1+g2+ g3 )= - 8 V
I1 = ( E1 + U ).g1 = ( 12.5 -8 )/3 = 1.5 AI2 = ( E2 + U ).g2 = (
9 - 8 )/2 = 0.5 A I3 = - U.g3 = 8 / 4 = 2 A
R2
E2E1
R1R3
A
B
V DU Hay giai mach ien sau
B3: Tnh dong ien cac nhanh
U
I1 I3 I2Biet : R1 = 3 E1 = 12.5 VR2 = 2 E2 = 9 VR3 = 4
U = Ei.gi / gi
U = (-12,5/3 9/2)/(1/3+1/2+ 1/4 )
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R2
E2E1
R1 R3
I1 I3 I2V du : Hay giai mach ien sauBiet : E1 = 40 V, E2 = 16
V,
R1 = 2, R2 =4, R3 = 4 Giai
R1 R2
E1
R3
I11 I31 I21
a. Mach ch co nguon E1 tac ong
R5 = R2.R3/(R2+R3)R5 = 4.4/(4+4) = 2
I11 = E1 / Rt1 = 40/4 = 10 AI31 = I11.R2/(R2+R3) = 10.4/(4+4) =
5 AI21 = I11.R3/(R2+R3) = 10.4/(4+4) = 5 A
R5
E1
I11
Rt1 = R1 + R5Rt1 = 2 + 2 = 4
RtE1
I11
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R1R2
E2
R3
I21 I23 I22b. Mach ch co nguon E2 tac ong
I1 = I11-I21 = 102 = 8 A I2 = I22 I21 = 35 = -2 A I3 = I13+I23 =
5+1 = 6 ADong ien I2 chay trong mach ngc vi chieu a chon
Rt E2
I22R6 R2
E2
I22
R5 = R1.R3/(R1+R3)R5 = 2.4/(2+4) = 4/3
I22 = E2 / Rt2 = 16.3/16 = 3 AI32 = I22.R1/(R1+R3) = 3.2/(2+4) =
1 AI21 = I22.R3/(R1+R3) = 3.4/(2+4) = 2 A
Rt2 = R1 + R6Rt2 = 4 +4/3 = 16/3
R2
E2E1
R1 R3
I1 I3 I2
R1R2
E2
R3
I21 I23 I22
R1 R2
E1
R3
I11 I31 I21
c. Mach tac ong cua ca hai nguon
e thi
