^hdn tkh vd hu&ng ddn gidi
Suat di^n dong cue dai cua nguon di|n: Eg = (ONOQ = 2TtfNc&o
U = E = (coi dien tro trong ciia may phat khong dang ke).
72
U E
Cuong dp dong dien qua mach ! = — = — = coNBS CoNOn ^ 1 = Z Z 7 2 Z 7 2 Z NBS . R2+(O,L-4,)' V L ®c 4 ^(^-4;)^ CO CO C ' - -0 • -T- NBS 1 LC^co" ^ CO-
Voi N , B, S la cae so khong doi nen khi cuong do dong dien hieu dung khong doi ung voi hai gia trj toe do quay ciia roto la n va 3n ( eung chinh la hai tan sogoe khong doi) thi mau thue phai khong doi. Bai toan bay gio chi
tap trung 6 mau thuc ma thoi. '
Vi the dat x=-4- va v = —^—
co^ C^co* co^ 2 - t - R 2 C x + L^
Hai gia tri cua x cho eung mot gia trj ciia y nen theo dinh ly Viet ta c6:
X , + X 2 = - - C : > a cof a cof 1 1 + — COn C =4,5.10 1 - 5 « 4r + = 4,5.10"^ « = 4,5.10'^ co^ 9co' > CO = 9ca' V 9.4,5.10 10 - 5 0) = 2n{ = 2Knp => n = Chpn dap an C CO 157 27tp 271.5 = 5v6ng/giay = 157rad/s
Vi du 8: Mot may phat dien xoay chieu mot pha c6 mot cap cue, mach
ngoai dupe noi voi mot mach RLC noi tiep gom cupn thuan cam
L = 10/25K(H), tu dien C va dien tro R. Khi may phat dien quay voi toe dp
750 vong/phiit thi dong dien hi?u dung qua mach la 7 2 A, khi may phat
dien quay voi to'c dp 1500 vong/phiit thi trong mach eo cpng huong va
dong dien hieu dung qua mach la 4A. Gia tri ciia R va C trong mach la:
A.R = 25 (Q),C = C. R = 25 (Q), C = C. R = 25 (Q), C = 10 -3 2571 B. R = 30 (Q),C = 10 -3 10 -3 D.R = 250 (Q),C = 10 -3 ^hdn tkh vd hu&ng ddn gidi
Khi may phat dien quay voi toe dp 750 vong/phiit thi tan so dong dipn la:
'^f -El = lZ^ = 12,5Hz=^C0i =27if = 257rr^Z,, =L.C0i =10Q
' 60 60 ' L i 1 : ( . . , ; :
iHi^u dien the: '
kU, = NBS.27tf, i= ^ U , =I,.7R2+(10-ZC)2 < : > U I = 7 2. 7R^+(10-Z C I ) ^ (1)
pn ^ T.1500 ^ 2SH7 co. = 2ca, = Znf = 50n ^ = L . W j = 20Q
2 60 60
1 1 10"^ M a f 2=2f, = ^ Z e 2 = - p - : ^ Z c,=40Q M a f 2=2f, = ^ Z e 2 = - p - : ^ Z c,=40Q
• -1,2 - ' - C Z •- Zc2-«2 20.5071 71 ^
Xay ra cong huong nen = - 20Q=^ C - ^^^^^ 20.5071 71
Hi#udi^nthe:Ma = 2f, U2 = ^ ^ ^ ^ = 2U, ^ 2U, = I2.R (2) Tu (1) va (2) ta ccS: Tu (1) va (2) ta ccS: 2 . V 2 . / R2+ ( 1 0 - Z C I ) ' = I2 R « 2.^/2.VR2+(10-40)2 ^ 4R V2.N/R2 + 3 0 ^ = 2 R « (R2 + 3 0 ^ ) = 2 R2 « R = 3 0 Q 10--' VavR = 30Qvh C = F. 7r Chpn dap an B ^
Vi du 9 : Mpt may phat dien xoay chieu c6 dien tro trong khong dang kc. Mach ngoai la tu di|n mSc noi tie'p voi ampe ke nhiet c6 dien tro nho. Khi Mach ngoai la tu di|n mSc noi tie'p voi ampe ke nhiet c6 dien tro nho. Khi roto quay voi toe dp goc co^ = SOTI rad / s thi ampe ke chi 0,5A. Khi roto quay voi toe dp goc = 1007t rad / s.thi ampe ke chi (adsbygoogle = window.adsbygoogle || []).push({});
A. 1,2 A. B.0,5A. C.2A. P-^9 A.
'Phan tick vd hie&ng dan gidi
NBSo)
Suat dien dong hieu dung xuat hien trong may E - —-j=- ''
Cuong dp hieu dung dong dien qua tu dien:
_ E N B S M . M C _ NBSC 2
Nhm vao bieu thuc tren ta thay: I ti le binh phuong vol toe dp goc u) nen kh> tang hoae giam (o n Ian thi cuong dp dong di|n hi?u dung se tang hoac gian^ tang hoae giam (o n Ian thi cuong dp dong di|n hi?u dung se tang hoac gian^ n^ Ian.
CO, = 507t rad / s I , _ - 2T . ^ T _ 4 n S - 2 A
Theobaira: ' r=> W2 = 2coi I2 = 2 - 41, - 4.U,t) - / A
(O2 =1007t rad/sj
Chgn dap an C
P B A I T A P V A N D U N G :
Cau 1: (Trich de thi tuyen sinh vao dai H Q C nam 2 0 1 3 )
Mot khung day dan phang, det hinh chii' nhat c6 dien tich 60 cm^ quay deu quanh mot true doi xung (thupe mat phang eua khung) trong tu truong deu quanh mot true doi xung (thupe mat phang eua khung) trong tu truong deu
CO vecto cam ung tu vuong goc voi true quay va eo dp Ion 0,4 T. Tu thong
cue dai qua khung day la
A. 2,4.10-3 Wb. B. l,2.10-3Wb. C. 4,8.10-^Wb D. 0,6.10-^Wb.
Phan tich vd huong dan gidi
Ta co: (j) = (t)QCOs(cot + cp) = BScos(cot + cp).
Tu thong cue dai qua khung day la: (})(, = BS = 0,4.60.10"'* = 2,4.10~'''Wb .
Chpn dap an A ;,
Cau 2: Mot may phat dien xoay chieu mot pha c6 phan cam la roto gom 16 cap cue. Roto quay voi toe dp 150 vong/phut. Tan so do may phat ra la: cue. Roto quay voi toe dp 150 vong/phut. Tan so do may phat ra la:
A. f = 35Hz B. f = 40Hz C. f = 45Hz D. f = 50Hz
Phan tich vd hirang ddn gidi
Tan so do may phat ra dupe tinh theo cong thuc: f = = ^^^-^^ = 40Hz. ' ^ ^ 60 60 ' ^ ^ 60 60
Chpn dap an B
Cau 3: Mot may phat dien xoay chieu mot pha c6 phan cam la roto gom 10
cap cue (10 cue nam va 10 cue bae). Tan so eua suat dien dong cam ling do may phat ra bang 50 Hz thi roto phai quay voi toe dp bang bao nhieu? may phat ra bang 50 Hz thi roto phai quay voi toe dp bang bao nhieu? A. n = 350 vong/phut B. n = 250 vong/phut