. A 0,6 B 0,866 C 0,8 D 0,
'Phdn tich vd hitcmg ddn gid
U = 100>/3V; I = 3 A
Goi p h u a n g trinh ciia cuong do c6 dang: i = 3N/2cosl007tt
O thoi diem t, i = 3N/2cosl007rt = 3N/2 => pha ciia dong di?n cpj = 1007:t = k27i O thai diem t ' = t + , u = 0, dang giam =>
300'
= 100K{t + — ) = - + k27i<=> lOOTtt + - = - + k27t =^ (p„ = ^ + k27i
^ 300 ^ 3 2
=> tai thoi diem t pha ciia hi^u dien the: 9^ = + l<27t
Do lech pha giiia u va i : cp = cp^ - (p^ =
Congsua't: P = UICOS(P = 100N/3.3.COS - =150N/3W
Chpn dap an D
Cau 11: Dat dien ap u = 175 x/2 cosl007it(V) vao hai d a u doan mach gom dien t r o thuan, cuon cam va tu di^n mac noi tiep. Bie't cac dien ap hieu d u n g hai dau dien tro, hai dau cuon cam va hai dau tu dien Ian lugt la 25 V, 25 V va 175 V. so cong sua't cua doan mach la
A . 1/7. B. 7/25. C. 1/25.
'Phdn tich v>d huang ddn gidi
Theo bai ra ta c6 gian d o vecto trugt n h u hinh ve: Trong A A H B vuong tai H .
o AB^ = A H ^ + HB^ J
= A H 2 + ( N B - H N f A.
= 15^+(175-25)^ =23125 AB = 25N/37V
Tin day de dang tinh duoc he so cong sua't hai dau mach.
352
A H 25 1
I A B 25^/37 V37 '
Chgn dap an D
Cau 12: Doan mach A B gom hai doan mach A M va M B mic noi tiep. Doan
mach A M g o m dien tro thuan mac noi tiep v o i cupn cam thuan, doan mach M B chi CO m p t t u di^n. Dat vao A, B di^n ap xoay chieu c6 gia t r i hieu d u n g va tan so khong doi thi d i f n ap tiic thai a hai dau doan mach A M va M B Ian
l u g t la: u ^ , ^ =uV3cos(ot, Uj^^B=Ucos(cot-57i/6). so cong sua't cua
mach di^n bang
A . 0,707. B.0,5. C.0,87. D. 0,25.
'Phdn tich vd hu&ng ddn gidi
Theo bai ra ta c6 gian d o vecto: 57: • A M B = - 6 A p d u n g d j n h ly cosin trong A A M B AB^ = A M ^ + MB^ - 2AM.MBCOS v6y = 3U2 + - 2. V 3 U. U — = 2 => AB = U Trong A A H M v u o n g tai H ta c6: A H = A M . s i n ^/3U T u day de dang tinh dugc:
UV3
Chpn dap an C (adsbygoogle = window.adsbygoogle || []).push({});
Chnyta 6
B A I T O A N cure T R |
D A N G 1. C L T C T R I L I E N Q U A N D E N C Q N G Hl/CTNG
Phuong phdp:
1 2
Hien tugng cong huong xay ra khi: = <=> coL = — <=> LCco = 1 U U
+ Cuang dp dong di^n trong mach cue dai: Imax = — = — =
m i n 2
+ Di?n ap hi^u dung: U L = Uc =^ U R = U ; P = P„3^ = ^
+ Di^n ap va cuong dp dong di|n ciing pha (tuc (p^ = cpj cp = cp^ - (Pj = 0 )
+ H^socongsuatcycdai: cos(p = l
m V i DU MAU
Vi du 1: Cho mach dien nhu hinh ve. U A B = 200 N/2 coslOOTit (V). R =100 Q ;
L = - H ; C la tu dien bien d o i ; . Tim C de von ke V c6 so chi Ion
n
nhat. Tinh Vmax?
-.-4 A. c = —{ F ) ; V ^ , , = 2 0 0 V 2 ( V ) A. c = —{ F ) ; V ^ , , = 2 0 0 V 2 ( V ) 71 B. C = 151(F);15l<F);71 V„„=200(V) V„.. = 200(V) * f^^-a^-m-J^ B -4 C. C = ^ ( F ) ; V„ 3, = 2 0 0 7 2 ( V ) 27t •^^'^ lo-'^ D. C = - ^ ( F ) ; V„ 3, = 2 0 0 ( V )
Huang dan gidi:
So chi ciia Von Ke (V) la gia trj di?n ap hi^u dung giua hai dau doan mach chua R va L.
Tac6: V = U ^ ^ = I-ZRL = , ^ ^-yl^'+zl
Do R, L CO gia tri khong doi va hi^u di?n the hifu dung U dupe giu khong doi nen U y = Uymax <=> = nghia la trong mgch xay ra cpng huon^
dif n, vi the'di^n dung tren tu dupe xae dinh nhu sau:
Gia trj eye dai ciia von ke:
K l U U Wilt
Chpn dap an A
Vl du 2: Cho mach di?n khong phan nhanh gom R = 40Q, eupn day eo
r = 20Q va L = 0,0636H, tu dien c6 di^n dung thay doi. Dat vao hai dau doan mach mpt di^n ap xoay chieu c6 f = 50Hz va U = 120V. Dieu chinh C de dien ap hi?u dung hai dau cupn day dat gia tri cue dai, gia tri do bang: