C. Thay do iL de Uimax D Thay do if de Ucma
'Phdn tich vd hucmg ddn gid
Theo bai ra: Roto co 4 cap cue nen p = 4 va toe dp quay cua Roto la n = 1500 vong/phiit v i the tan so ciia may phat dien phat co gia t r i :
n £ ^ 15004 ^ ^QQ^^ ^ ^ 2007t(rad/s).
60 60 ^ '
Roto cua may phat c6 4 cap cue tu nen phan ung gom c6 8 cupn day
So vong day c6 trong Roto la N = 8.50 = 400 vong.
Tu day ta tinh dugc suat di^n dpng cam ung hi^u dung do may tao ra la
E = ^=^""-^-^f-^°°"= 888,6V.
Chgn dap an D.
Vl du 2: Mot khung day dan phSng det hinh chu nhat c6 500 vong day, dien tich moi vong la 220 cm^. Khung quay deu voi toe do 50 vong/giay quanh mot true doi xung nam trong mat phang ciia khung day, trong mot tu truong deu c6 vec to cam ung tir B vuong goc voi true quay va c6 do Ion B. De tao ra suat di^n dpng hieu dung eo gia trj la E = 220V thi cam ung tu B c6 dp Ion la
A . ^ . B . ^ T . C . : ^ T D . : ^ .
7t 5n n 5n
'Phdn tich vd hit&ng ddn gidi
Tan so quay eiia khung la f = 5 0 ^ ^ ^ = 50Hz => co = lOOnrad / s giay
Suat dien dong ciia may phat dien xoay chieu mot pha:
^ NBSco „ EV2 220N/2 N/2,„,
E -—p ^ = > B = = = — ( T )
V2 NSco 500.220. lO'^.lOOjt
Chgn dap an B
Vi dy 3: Hai may phat di^n xoay chieu mot pha: may thu nhat c6 2 cap cue, roto quay voi toe dp 1600 vong/phiit. May thu hai c6 4 cap cue. De tan so do hai may phat ra nhu nhau thi roto may thu hai quay voi toe do la bao nhieu?
A. 800 vong/phiit. B. 400 vong/phiit. C. 3200 vong/phut. D. 1600 vong/phut.
^hdn tich m huang ddn gidi
Theo bai ra thi tan so do hai may phat ra la nhu nhau nen ta c6:
f f i l l P l ^ ^ ^ ^ ^ ^ 1 6 0 0 2 =800 vong/phut. ' ^ 60 60 P2 4
Vay chpn dap an A.
Vi du 4: (Trich de thi tuyen sinh vao dai hpc)
Noi hai cue cua mot may phat dien xoay chieu mot pha vao hai dau doan mach AB gom dien tro thuan R mac noi tiep voi cupn cam thuan. Bo qua dien tro cae cupn day ciia may phat. Khi roto cua may quay deu voi toe dp n vong/phut thi cuong dp dong dien hieu dung trong doan mach la l A . Khi roto ciia may quay deu voi toe dp 3n vong/phiit thi cuong dp
dong dien hieu dung trong doan mach la yfs A. Neu roto ciia may quay
deu voi toe dp 2n vong/phiit thi cam khang ciia doan mach AB la A. _R_ B. RN/3 C. 2R D. 2R>y3
'Phdn tich ra hu&ng ddn gidi
Nhan xet: Khi toe dp quay thay doi thi U, ZL thay doi
NBS.27rf . . . . . . . , pn (adsbygoogle = window.adsbygoogle || []).push({});
; tan so dong di?n f = ^— Dien ap dat vao hai dau mach U = E =
60
NBS.27rf,
Taco: f, = El; U,= ^ ^ ^ ^ ^ I , =-"^ 60 60 3U, U 2 =3U, ^ L 2 ^ 3Z L I = 1 3U, 3U, R + 9ZL,^ • => z,, = R U = 2 ^ = 2f, =>ZL2 = 2Z , , =2 60 Chpn dap an C -•Ll JR_ T3 Vi du 5:
Mot khung day dan phang quay deu voi toe dp goc u) quanh mpt true eo dinh nam trong mat phang khung day, trong mpt tu truong deu eo vecto cam ung tu vuong goc voi true quay eiia khung. Sua't dien dpng cam ung trong khung c6 bieu thiie e = E^eos(a)t + ~ )• Tai thoi diem t = 0, vecto phap tuyen eiia mat phang khung day hop vdi vecto cam ung tu mpt goc bang A. 150". B. 90". C. 45". D. 180".
'Phdn tich m huang ddn gidi
Ta c6: e = EQ sin(cot + (j)) = EQ cos (Ot + CJ) —
2y
So sanh voi bieu thiic de bai: e = E eos(a)t + — )^m- — ~ — =:>(p = n.
0 ^ 2^ ^ 2 2 ^
Vl dy 6: (Trich de thi tuyen sinh vao d?i hpc 2011)
MQt may phat difn xoay chieu mgt pha c6 phan ung gom bon cupn day giong nhau mac noi tiep. Suat dien dong xoay chieu do may phat sinh ra
CO tan so 50 Hz va gia tri hi?u dung 100N/2 V. Tu thong cue dai qua moi
vong day ciia phan ung la - mWb. So vong day trong moi cupn day ciia
71
phan ung la
A. 71 vong. B. 100 vong. C. 400 vong. D. 200 vong.
^hdn tkh vd hu&ng dan gidi
Lm y: d day debai cho 4 cuon day giong nhau mac not tiep. Sovdng 4N Goi E la suat dien dong do may sinh ra. Ei la suat dien dong a moi cum
E IO0V2
<»N =
(t)i^4V27rf 5.10-3.472:1.50 = 100 v o n g
Chpn dap an B
Vl dy 7: Noi hai cue cua mot may phat di^n xoay chieu mgt pha c6 5 cap
cue tu vao hai dau doan mach AB gom dien tro thuan R = lOOQ, cupn
41 10' F. Toe
cam thuan c6 do tu cam L = — H va tu dien c6 dien dung C =
do roto cua may c6 the thay doi duoc. Khi toe dp roto cua may la n hoae 3n thi cuang do dong dien hi^u dung trong mach c6 ciing gia tri I. Gia tri cua n bang bao nhieu?
A. 20 Vong/giay B. 20 Vong/phiit
C. 5 Vong/giay D. 5 Vong/phut (adsbygoogle = window.adsbygoogle || []).push({});
^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 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)