Bain SHIFT M O D E
Budc 1 : Viet UAN= i ZAN = 2^2 Z 0 x(!(200 -100))
X ( ENG ( 20(\ - 1 0 0 M+ l (su d u n g bo nho doc lap) M+ l (su d u n g bo nho doc lap)
Ket qua Id: 200 V2 Z ^ c6 nghia Id: UAN= 200^2 cos(1007tt + | )(V)
Buoc 2: T i m U N B = U X = UAK - UAN :
7t
Nhdp mdy: ^ H ^HIFT] ^ 4 ^ R C L M + (goi bo nho doc lap) \SHIFI
2] I ^Ketqud:im Z Buoc 3: T i m Zx. Zx = —
Nhap may:\\nS\] ([] 2 ^ ^[ ] ^ H I F T J ^ 0 )[]ketqua: 50-lOOi
vay hop X c6 2 phan t u nen se la: Ro= 50Q; Zco=100 Q. Tu do ta dupe: Ro= 50Q; C , = 10-^
Cach 2: Nhan xet: Theo de cho thi u va i som pha 7i/4 nen mach c6 Ro , do
Zc= lOOQ < Zi = 200f2 nen mach phai chua Co hoac Lo sao cho tan - = ^ L O ^co ^ ^ 4 R „ ^0 Voi Z = Up ^ 2 0 0 'o 2 ^ 2 (1) (2) R(, < 50N/2Q
Tu day ta thay tu so cua (1) cung khong qua 50>/2Q. Ma Z i - Z c = 2 0 0 Q - 1 0 0 Q= 1 0 0 Q
Nen neu mach c6 Lo thi tu so se vupt qua lOOQ, d l nhien se vupt qua
5 0 7 2 Q suy ra mach khong chua Lo.
Vi the mach phai chiia Co Hay Z, - Z ^ - Z CO
R, = l = ^ R o =Z L - Z C - Z C O
Tu(2) = > Z = J R^ + (Z L - Z ^ . - Z C„ ) ^ =R O7 2 =Z C O V2 = 5OV2
=> R Q = Zco = 5 0 n => C(, = 2.10 -4 - ( F ) in
Chpn dap an B
Nhan xet: ccicli lam Ihi't hai doi hoi chung ta phai hien luan dime giai han tren cua dai luang vi the cung gdy cho nhieu han hoi roi. Tuy nhien neu lam each nay cong them v&i phimng phdp hai trie thi cdng dat hieu qua tot han. Cudi cimg ta nhan thay, khi gidi hdng mdy tinh ket qud cho ra nhanh han vd cQng khong can kien tlu'ec suy luqn hay loqi trie gi het vi ket qud cho la ro rdng.
Ca BAI TAP VAN DUNG:
Cau 1: Trong mach difn xoay chieu gom phan tu X noi tiep phan tu Y . Biet rang X va Y chua 1 trong 3 phan tu (dien tro thuan, tu di?n, cupn day thuan cam). Dat vao hai dau doan mach mot di?n ap: u = U cosl007tt(V) thi di^n ap hieu
•s/3 U
dung tren 2 phan tu X, Y do duoc Ian luot la Ux= U — va U Y =y . Biet u nhanh pha hon i. Cac phan tu X, Y Ian lug-t la:
A. Di?n tro thuan R va cupn day thuan cam.
B. Dien tro thuan R va tu di^n ' ' C. Cupn day thuan cam va cuon day thuan cam
D. CuQn day thuan cam va tu di^n
i*hd,, iich v>d huang dan gidi
Nhan xet: u nhanh pha hon i va Ux +U Y nen X la difn tro thuan con Y cuon thuan cam
Chgn dap an A (adsbygoogle = window.adsbygoogle || []).push({});
Cau 2: Dat vao 2 dau mot hop kin X (chi gom cac phan tix mac noi tiep) mot
di?n ap xoay chieu u = 50cos(1007it + 7r/6)(V) thi cuong do dong dien qua mach i = 2cos(1007it + 27t/3)(A). Neu thay dien ap tren bang dien ap khac c6 bieu thuc u = 50 N/2 cos(2007it + 27i/3)(V) thi cuong do dong dien i = N/2 cos(2007it + ;r/6)(A). NhCrng thong tin tren cho biet X chua
A. R = 25 (Q), L = 2,5/7i(H), C -- 10-^/7:(F).
B. L = 5/127t(H), C = l,5.1zO-V7t(F). C. L = l,5/n(H), C = l,5.10-V7t(F). C. L = l,5/n(H), C = l,5.10-V7t(F).
D. R = 25 (Q), L = 5/127i(H).
^hdn tick vd huong ddn gidi
Gia su mach gom 3 phan tu thuan R, thuan L va tu C noi tiep Trong hai truong hg-p u va i vuong pha voi nhau nen R = 0
^ 1 = - ^ii = f - ^ - - f =^ = - (Zc^ > ZL^ ) 6 3 2 ^ 2 = % - ^ , 2 = T - 7 " f " ^ ^ 2 = Z L 2 - Z C 2 = 2Z ^ - — ! - ( f 2= 2 f i ) Z i = Z p - Z , = - i = 25n Z 2= 2 Z , ^ = - ^ = 50n 2 2 L z - ^ a L = — ( H ) 127t^ ' Chpn dap an B Cty TNHll M ! i i) \
Cau 3: Nhieu hop khoi giong nhau, nguoi ta noi mpt doan mach gom mot trong cac hpp khoi do mac no'i tiep voi di^n tro R = lOOQ khi doan mach dupe dat vao hi^u di#n the xoay chieu tan so 50Hz thi hi^u di^n the som pha 60° so voi dong dien trong mach. Hop kin chua tu di§n hay cuon cam. Tinh dien dung ciia tu hoac dp tu cam ciia cuon cam
A. X la cupn day thuan cam; L = — ( H )
n
B. X la dien tro thuan R; R = lOOQ C. X l a t u d i e n ; C = 10 -4 -(F)
D. X la cupn day khong thuan cam; r = 50Q; L = — ( H ) 571
'Phan tick vd huang dan gidi
Doan mach gom X va R mic noi tiep. Theo bai ra: Hi§u dien the som pha hon cuong dp dong di^n trong mach nen mach di?n c6 tinh chat cam khang. Vay trong hop chua cupn cam.
Z
Vi the ta c6: tancp = —t. = tan60° = Vs => Z , = N/3R = IOOA/SQ R ^ Z , 100N/3 7 3 ,
(0 -(H)
lOOTt 7t
Cau 4: Cho mach dien xoay chieu nhu hinh ve chua 2 trong 3 phan t u mac noi tiep. Bo qua di^n tro ciia mape ke vao dau noi. Dat vao 2 dau doan mach mpt hi^u dien the xoay chieu c6 bieu thuc U = 200 \/2 coslOOTtt (V) thi ampe ke chi 0,8A va he so cong suat ciia dong di^n trong mach la 0,6. Xac dinh cac phan t u chua
trong doan mach X va dp Idn
-3
cua chiing, biet Co =
Theo bai ra ta c6: 1 1 10" M X In (F) Co ^^0 - coC 0 lOOTt. 10
'Phdn tich vd hu&ng dan gidi
= 20(Q)
- 3 271 271
Tongtro: Z = - = — = 250Q ^ I 0,8
Zx = Jz^-Z^ = N/2502 - 20^ = 30769Q
Ta lai c6: f^/„ cosq) = I = 0,6 =^ R = 0,6Z = 0,6.250 = 150Q (adsbygoogle = window.adsbygoogle || []).push({});
Nhu vay, doan mach X gom R va L hoac R va C O
Truong hop 1: X gom R va L
=^ Z, = - = ^ ( 3 0 ^ ) -1502=60VriQ
Trimng hop 2: X gom R va C
Z^. = J Z ^ - R2 = J(30>/69 )^ -150^ = 60VITQ
=>c = 1 1 0 .-4 -(F) (H)
o)Z(^. 1007i.60N/n 27t
Cau 5: Cho mach dien nhu hinh ve. Dien ap giiia hai dau doan mach c6 bieu thuc la u^,^^, =200x/2sinl007it (V). Cuong do dong dien i nhanh pha hon dien ap hai dau doan mach.
X la hop kin chua cuon thuan cam hoac hi
dien. R la bien tro. Dieu chinh R thay cong ^ | \~\
suat ciia mnch cue dai khi \ 4lA.. Xac ^
djnh phan tu dien trong X va gia tn cua no.
<^han tick vd hu&ng dan gidi
Cuong do dong dien i nhanh pha hon dien ap u hai dau doan mach nen X chua tu dien.
R
Cong suat tieu thu cua doan mach: P = I R R^ + Z^ „ Zc
^ R + ^
^2
R
Ta thay, Pn,.ix khi R + R
min. Theo bat d3ng thuc Co-si, ta c6:
Cty TNHH MTV DWH Khang Vift R + > 2JR.—£ - <=> R + > 2 Z ,
R V R R
Dau = xay ra khi va chi khi R = Zc.
Tong tro cua toan mach: Z = ^ R ^ + ZQ =ZQ\12
Matkhac: Z = — I Tu ( 1 ) va (2) /r U 200 = . Z c V 2 = - = ^ •Zf^=100fi ^ c = — ( 1 ) (2) 1 1 0 1 - 4 lOOn.lOO n -F.
Cau 6: Cho doan mach AB nhu hinh ve. Moi hpp X va Y chi chua hai trong ba
phan tir: dien tro thuan, cuon day thuan cam va tu di?n mic noi tiep. Cac von
ke'Vi, V2 va ampe kedo dugc ca dong xoay chieu va mgt chieu, di^n tro cac von ke'rat Ion, dien tro ampe kekhong dang ke. Khi mac vao hai diem A va M hai cue cua nguon di^n mpt chieu, ampe kechi 2A, Vi chi 60V. • ' Khi mac A va B vao nguon dien xoay
chieu, tan so 50Hz thi ampe ke chi l A , cac von ke chi cung gia trj 60V (adsbygoogle = window.adsbygoogle || []).push({});
A V
1
1
V V B
M I
nhung UAM va UMB lech pha nhau ^ . Hai hop X va Y chua nhiing phan tu nao? Tinh gia trj ciia chung.
^hdn tick ra hu&ng dan gidi
Khi mac hai dau hop X voi nguon dien mot chieu, ampe ke chi 2A =i> trong
mach CO dong dien c6 cuong do Ii = 2A, chung to trong hpp kin X khong c6
tu dien. Vay hop kin X chua dien tro R noi tiep cuon cam L. Khi do ta c6: Z ^ ^ = R = — = — = 3 0 Q (vi ZL = 0).
Khi mac A va B vao nguon di^n xoay chieu, ta c6:
I2 I • R^ + Z? = 60^ • R^ + Z? = 60^ o ZL = 760^ -30^ = 30V3Q 30V3 2ni 27t.50 - 0 , 1 6 5 H .
liiquyc't on luyeu thi liai hoc dat ilicm toi da Viit li, tap 1 - Le Van Viith
Ta co: tantp^M = — = = N/3 =^ cp^^ = - rad
Ta CO hinh ve nhu 6 ben duoi. Theo hinh, UMH tre pha so voi dong di?n nen => hop kin Y chua dien tro R' no'i tiep tu dien C. => hop kin Y chua dien tro R' no'i tiep tu dien C.
U2 _ 60 _ Doi voi doan mach MB: Z^g = -—I 2 1 - oUia Doi voi doan mach MB: Z^g = -—I 2 1 - oUia Ma Z^,, = ^ / R ^ ^ = 60Q ^ R ^ + Z^ = 60^ Vi UAM vuong pha UMH nen ta c6:
(1) - z 'C - z 'C R tan(p^^^.tan(p^^B =-1 » 30 R' ^ Giai(l)va(2)^ R' = 30V3Q ; Z 1 1 = -1 o Z, Z, R • R' = 1 (2) :30Q =>C = Ini.Zr 271.50.30 =:1,06.10-^(F).
VayhopXchua R = 30Q noi tiep L 0,165H hpp Y chua R'= 30^30 noi tiep C = 1,06.10"''F. tiep C = 1,06.10"''F.
Cau 7: Cho mach dien nhu hinh ve Bie't Ci =——F, C2 =—— F. Hop den X
1571 71
chua 2 trong 3 linh i<ien R, L, C. Dat vao hai dau mach AG mot hi^u dien thexoay chieu u = 200 42 coslOOnt (V) thexoay chieu u = 200 42 coslOOnt (V)
Khi dong Ki, mo K2 hoac dong K2 mo Ki thi cuong dp hi$u dyng ctia dong di^n trong mach deu nhu nhau. di^n trong mach deu nhu nhau.
Khi dong dong thoi ca Ki va K2 thi hieu dien the hai dau tu difn dat eye dai va hieu dien the hai dau hop den X nhanh pha hon cuong dp dong di#n la va hieu dien the hai dau hop den X nhanh pha hon cuong dp dong di#n la
7T/4 (Rad).
Khi Ki, K2 mo dong di|n khong cung pha voi hi^u dien the. Xac djnh cac linh kien cac hop den X va gia trj ciia no. Tim Li? linh kien cac hop den X va gia trj ciia no. Tim Li?
1-3 10 ,-4 10 ,-4 K X X K2 D C, E C2
C t y TNim MTV D W J f Khang Viet
Taco: 2^^=1500; Z^,'Phan tich vd hu&ng dan gidi =100Q
•C2
A (adsbygoogle = window.adsbygoogle || []).push({});
X
B D C, E C2 G
Khi dong dong thcri ca Ki va K2 thi hi^u dien thehai dau tu dien dat cue dai va hieu dien the hai dau hop den X nhanh pha hon cuong dp dong dien la va hieu dien the hai dau hop den X nhanh pha hon cuong dp dong dien la
Ti/4 (Rad).
Nen hop den X gom dien tro R va cupn thuan cam co dp tu cam L
( v'l nC'ii CO L vii C tlu ux viidn;^ pha v&i i; ncii la R va C thi ux chqtn pha han i)
va ta CO R = Z[ (vi ux nhanh pha hon i gocj) „
Khi Uc = Uenuv thi Z,- = 2!l^ = 2 Z , = R = Z , = ^ . 7 5 Q
IOOTI 47T
Khi dong Ki, mo K2: Z, = ^R^ + (Z^ - Z ^ - Z^^ f
Khi dong K2, mo Ki Z 2 = ^ R ^ + ( Z L + Z L ^ - Z C ^ ) 2
Khi dong Ki, mo K2 hoac dong K2 mo Ki thi cuong dp hieu dung ciia dong dien trong mach deu nhu nhau dien trong mach deu nhu nhau
Z, = Z, cx> JR2 + ( Z , - Zc^ - Z,-^ f = ^R2 + ( Z L + ZL^ - Zc,)
= ^ Z L - Zcj - Zc2 = - ( Z L + Z L J - Zcj)
^Z, =Z +1Z^ - 2Z L =100+ 2.150-2.75 = 250Q=^L, = — (2,5 H )
2 1 71
Cau 8: Cho doan mach AB gom hop kin X chi chua mpt trong ba phan tu (di^n tro thuan, tu dien hoac cupn day thuan cam) va bien tro R. Dat vao (di^n tro thuan, tu dien hoac cupn day thuan cam) va bien tro R. Dat vao hai dau doan AB mpt hi$u di^n thexoay chieu co gia trj hieu dung 200V va tan so 50Hz. Thay doi gia tri ciia bien tro R de cong suat tieu thu trong mach AB la cue dai. Khi do cuong dp dong dien qua mach co gia trj hi^u dung bSng 1,414 A (coi b^ng 42 A). Bie't cuong dp dong di^n som pha hon hi^u di§n thegiOa hai dau doan mach AB. Hoi hop kin chua cai gi? Tinh gia trj ciia no. Bo qua di^n tro cac day noi.
Bi quyei on luyftt thi dai hqc dat diem tot da Vat It, tap 1-Le VSn Vinh
<Phdn tich vd hudmg ddn giai
Day la mot bai hop kin tumg doi dan gian. Trudc hit ta hay di tim xem hop kin chua cdi gi. Mqch dien c6 dien tra thuan R, X chi chita mot phan tu: U ^ g = U R + chua cdi gi. Mqch dien c6 dien tra thuan R, X chi chita mot phan tu: U ^ g = U R +
ciing pha vai i, ma U ^ B tre pha han i nen Ux phai tre pha han i => Do
vqy X chi c6 the la tu dien C.