530.076
pHAM
DLfC
CLfdNG
(Chu
bien)
L527TH
E TAN Rl - BUI
IRAN
DLfC
ANH
THAI,
THAN
THANH
SANG
CAC
DANG
BAI TAP TQ CAC DE THI
QUOC
GIA
(TOT
NGHI
EP
- TUYEN k
/
INH)
VAT^Y
^ Cac de chinh
thiic
va de luy^n tap
p an va thang diem

NHA
XUAT
BAN DAI HOC Si/
PHAM
LE TAN Ri -
PHAM DLfC CLfdNG (Chu
bien)
BUr
TRAN
DISC ANH
THAI
-
THAN
THANH
SANG
LUYEN
THI
CAP
TOC
•
CAC
DANG BAI TAP TlT
CAC
OE THI
QUOC
GIA
(^at
nqklift - ^tufln
dnh)
VAT

difn
tir 13
Dong
di?n xoay chieu 17
Song anh
sang
25
Lugng
tir anh
sang
31
H^t
nhan nguyen tir 37
Tir
vi
mo den
vT
mo 43
B.
Phan rieng cho chirong trinh nang cao
Dpng
lyre
HQC
vat ran 49
Con
lac
v§t
K
53
Hi?u

80
Hi?u
irng
Dop-ple 80
Quang di$n 80
Tia
X (Ronghen) 82
Phan
3: Dap an va huoTig dan giai cac de on luyfn Tu Tai 83
Phan
4: Dap an va hv&ng dan giai cac de on
luyf
n
Dai h9c - Cao dang 190
^han t: TdM TAT
GIAO
KHOA
Phan chujif cho ban of ban ad ndn^ eao
DAO
DONG
CQ
I.
Dao d9ng dien hoa :
*
Dao dpng tuan hoan la dao dpng ma trang thai chuyen dpng cua vat
dupe
l$p
lai
nhu cij sau nhung khoang thai gian bSng nhau.
*

=
/x„a.x/)
+
CO
la tan so goc
ciia
dao dpng, don vj :
rad/s
(co
cho
biit
dao
dpng
nhanh
hay chants
co
Id
toe dp
bien
doi ciia goc phaj
+
(cot + cp) la pha dao dpng t^i thai diem t, pha chinh la doi s6 cua ham
cosin va la mpt goc. (Pha dao d0ng cho ta
biet
v/ tri vat dao
d^ng,
gid tri
vd each
bien
thien

V$n toe nhanh pha ^ so vai
li
dp x
+
Gia toe ngupc pha so vai li dp x
*
Lye tac diing lam vat dao dQng dieu hoa:
+
C6d9ngF = -kx
+
Lvrc
nay luon huang ve
VTCB
nen
dupe
gpi la \\fc keo ve (hay lye hoi
phye).
*
Dao dpng eiia con lac
16
xo la mpt dao dpng dieu hoa co chu ky:
3
*
Voi
goc l^ch nho, dao dgng ciia con lac don la mpt dao dgng dieu hoa c6 chu ky:
T
= 2n-
Vg
*
Hf dao

Con lac dcm va
Trdi
ddt (hay con lac vgt It vd
Trdi
ddt) Id h? dao
n.
Cor
nSng:
Do
v^t n^ng trong con iSc 16 xo chju tac dyng ciia l\rc dan hoi va trong con iSc
don la trpng lyc nen ca
nang
ciia v$t
dupe
bao toan vi l^rc dan hoi va trpng Ivrc
la
nhung \\fc the.
*
Co'
nang
trong
dao d$ng
dieu
hoa:
+
The nang: E, = ^
kx^
= ^ kA^cos^(cot + cp)
+
Dpng nang: Ea = ^ mv^ = ^

D^c
diem:
+
Dao dpng tat dan noi chung khong c6
tinh
dieu h6a nhung khi xet trong thai
gian ngin ta c6 the coi la dao dpng dieu hoa vai chu ki rieng va tan so rieng.
+
L\rc can moi truang
cang
Ian (hay moi triwng cdng nhot) dao dpng tat dan
cang
nhanh.
+
Dp nhot cua moi truong tang
theo
thu
t\r:
khong
khi,
nuac,
dau, dau rat nhot.
4
T
IV.
Dao d^ng duy tri:
Dao dpng
dupe
cung cap
nSng

do tac dyng cua mpt ngo^ii l^rc bien doi dieu hoa:
F =
FoCosQt
+ Dao dpng cu&ng buc la dao dpng dieu hoa.
+ Tan so dao dpng eixong buc
bSng
tan so ngo^i Ivrc.
+ Bien dp dao dpng cuong buc ti I9 vai bien dp Fo cua ngo^i lyre va phy thupc
tan
so cuong buc
D.
cua ngoai l\rc (
AQQ
e
|Q
-
CO|
) .
VI.
Sy
C9ng
hirong:
+ Hi?n tupng bien dp dao dpng cu&ng buc tang nhanh den mpt gia trj eye d^i
khi
tan so f cua lyc cir&ng buc bang tan so rieng cua v^t dao d9ng gpi
la hi$n tupng cpng huong.
+ Bien dp dao dpng d^t den gia trj khong doi va eye khi toe dp
tieu
hao
nSng

tac dyng ngo^i lyc nhung ngo^i lyc
dupe
dieu khien (boi ehinh dao dpng ay) de c6 tan so goc
bang
tan so goc ciia dao
dpng ty do ciia h?.
VII.
Tong h(fp dao d^ng:
* Xet hai dao dpng dieu hoa cung phuong, cung ikn so:
X]
= Aicos(cot + cpi);
X2
=
A2cos(cot
+ 92)
Tong hpp hai dao dpng dieu hoa cung phuong, cung tin so la mpt dao dpng
dieu hoa cung phucmg, cung tan so voi hai dao dpng thanh phan.
+ Bien dp hai dao dpng tong hpp: A = ^Aj + Aj
+2AiA2COs(92
+ Pha ban dau hai dao dpng tong hpp la 9, voi:
taiKp^
Aisincpi
+
A^sincp;
AiCOSCpi
+
A2C0S(P2
+
Neu hai dao dOng thanh phan cung pha:
92

Song ca:
+
Song
CO
hpc la nhCrng dao dpng co Ian truyen trong mOt moi truong.
+
Song
CO
du(?c t^ thanh nha lyc
lien
ket dan hoi
giira
cac phan
tir
ciia
moi
tmong
truyen
dao
dpng
di.
Cac phan
tir
cang a xa tam dao
dpng
cang tre pha hon.
+
Khi song truyen chi c6 trang thai dao
dpng
(pha dao dgng) truyen di con ban

dan
(Vd:
Song truyen tren 16 xo khi 16 xo
nen
va dan )
II.
Cac dai
lirQiig
dac trirng
ciia
song
:
*
Chu ky, tan so
ciia
song: la chu ky, tan so dao dpng chung
ciia
cac phan tii
v^t
chat
CO
song truyen qua va bang chu
ky,
tan so
ciia
nguon song
=:>
Chu ki
va
tan so khong doi khi song truyen.

f
6
* Bien d9 song: Bien dp
song
t^ii
mpt diem la bien dp dao dpng cua phan tii
vat chat tai diem do khi c6
song
truyen qua.
* Nang liTQTig cua song: Qua
trinh
truyen
song
la qua
trinh
truyen nang
lugng. Nang lugng
song
tai moi diem ti I9 vai binh phuomg bien dp
song
tai
diem do. Mpt phan tir v$t chat dang dumg yen khi c6
song
truyen den se dao
dpng, nghia la phan tur do da nh$n
dupe
nang lugng tir
song.
Vay qua
trinh

= Acos(©t-^)
hay
UM
= Acoscot-Y'') (*)
(•) cho ta xac djnh li dp ciia phan tur
song
t^i
diem M bat ki tren ducmg truyen
song,
gpi la la phuong
trinh
song.
* Neu song truyen nguQc chieu vai chieu dircmg true Ox thi phmxng trinh
song
CO
dgng: = Acos(— t + — x)
Tir
(*) ta thay
song
c6 hai
tinh
chat:
+
Tinh
tuan hoan theo thoi gian:
Khi
xet mpt diem P tren
song
c6 toa dp x = d.
Ta thay li dp u cua P bien thien theo ham cos => chuyen dpng cua diem P la

7
D^c bift:
+ NhiJng diem
tren
phuong
truyen
song dao dgng cung pha vai nguon khi
— x = 2k7i=> x = kX vai Ikl =0,1,2,
+ Nhung diem
tren
phuang
truyen
song dao dpng ngugc pha vai nguon khi
— x = (2k+
1)71=^
x = (k + -)X
A. 2
IV.
Phan xa song:
Song dang
truyen
trong mpt moi
truong
ma g^p v§t can thi bj phan x^. Song
phan
X9
c6 ciing tan so va buac song ciia song tai.
+ Neu v$t can c6
djnh
thi song phan x^

- Vj tri cac nut
luon
each diu c6
djnh
nhirng
khoang bSng mpt so nguyen
Ian
nua buac song.
- Vj tri cac byng
luon
each dau c6
djnh
nhung
khoang bSng mpt so le l4n
mpt
phan tu buac song.
3l
+ Khoang each giua hai nut
(ho$c
hai
byng)
ke
nhau
dfiu
bSng —.
Dieu
kif
n
c6 song dirng:
- Khi hai dau day c6 djnh: De c6 song dung, chieu dai spi day b^ng so

*
Dieu
kif n
c6
giao
thoa: Hai song la hai song ket hgrp va dao dpng cung phuong.
*
Ly thuyet ve
giao
thoa:
Gia
sir A va B la hai ngu6n ket hgrp c6 cung phuorng
trinh
dao dpng la:
UA
=
UB
= Acoscot
Xet
diSm M bat
ky
trong
moi
truong
each
A mpt doan
di
va
each
B mpt doan

V$y
dao dpng
t^i
M la dao dpng dieu hoa
voi
bien dp :
A
^2
A
cos-
Ta
thay A phy thupc vj
tri
cua diem M
Nhir
vay:
* T^ii
M
CO
bien dp c\rc d^i - 2A (hai dao
dpng
thanh
phdn ciingpha :
7t(d2-di)
=
2kK)
khi : cos
Vay:
Tai nhirng diem M c6
hi^u

k
= -2
k'=-2
k-=o
k'=-l
*
Tai M
CO
bien dp c\rc tieu = 0 (hai dao dgng thanh phan ngu^c pha :
7t(d2-d,)
A(p
= (2k
+
l)7t) khi : cos
=
0
d2
-d, = (k + vai k = 0, ±1,
±2,
Vay:
Tai nhirng diem M c6 hi|u ducmg di bing mpt so ban nguyen Ian
birofc
song
thi bien dp dao dpng
tong
hpp cue tieu va hpp thanh mpt hp
cac dircmg hyperbol nh^n A va B lam tieu diem.
Chuy:
DQ
l^ch pha cua hai dao d(mg thanh phan la:

Hi?n tupng nhieu la mpt d§c
tinh
c6
hiru
cua song, giong hi?n tupng giao
thoa song.
VIII.
Song am:
Khi
mgt vgt dao dgng se lam khong khi a ben bj nen roi bi dan, xudt hi^n luc
dan hoi trong khong khi vd lam dao dgng nay truyen din cac phan tir khi a xa
horn.
Dao dgng truyen di trong khong khi tgo thanh song dm.
Nhu
v$y:
+
Song am la nhung dao dpng phat ra tir nguon am,
dupe
truyen qua khong khi
vao tai ta lam mang
nhT
dao dpng gay ra cam giac am.
+
Song am la nhung song co truyen trong moi truong vat chat
(khi,
long, An).
-
Trong
chat khi vd chat long song dm la song dgc vi trong cac chdt nay
l\K

truyen
dugc
trong
tSt ca cac moi
truong
khi, long, ran
nhimg
khong
truyen dugc
trong
chan khong.
+
Song
am truyen di rat kem
trong
chat xop ; nhung ; bong ; val
+ Trong moi moi
truong
am dugc truyen di vai toe dg xac
djnh.
* Toe d9 truyen am phu thugc :
-
Tinh
dan h6i va
khdi
lugng rieng cua moi
truong.
- Nhi$t dg ciia moi
truong.
Noi Chung Vri„ > vi6„g >

phdt ra cdc hga dm cd tdn so la bQi s6 ciia f. TUy theo cdu trite cua ngudn
dm ma cdc hpa dm c6 so li/tpig. bien dp, thai gian ton tgi khdc nhau.
Am phdt ra la tong hQp ciia dm ca ban vd cdc hga dm, no cd tdn sd fnhwig
duong bieu dien cua nd khdng con la duong sin md tra thdnh mgt duong
tudn hoan phirc tap cd chu ki. Moi dgng cua duong bieu dien img vdi niQt
dm sdc nhdt djnh. Do dd cdc ngudn dm khdc nhau se tgo ra nhirng dm sac
khdc nhau.
Vay:
+ Am sac la mgt d$c
tinh
sinh li ciia am giup ta phan bi?t dugc cac am cung dg
cao nhung phat ra tu nhiJng nguon khac nhau.
+ Am sic dugc
hinh
thanh dyra
tren
tan so va bien dg am.
+ Am sac gan
lien
vai d6 thi dao dgng am. Am sac khac nhau khi dang do thj
dao dgng am khac nhau.
+ Cdc nhac cu khdc nhau khi phdt ra dm cd cimg dp cao se cd dgng do thj dao
dgng dm vdi tdn so giong nhau nhung cd li dd bien ddi khdc nhau => dd thi
dao dgng dm khdc nhau.
* Dg to cua am:
Nang lu-gng am: Nang lugng am ti 1^ voi
binh
phuong bien dg song am.
11
Cirong

+
De
so
sanh
cuong dp
ciia
mpt am voi cuong dp am
tieu
chuan nguai
ta
dung muc cuong dp am L
:
L
=
10lgi-
(I
la
cif&ng
dm gay ra
a
tai nguai;
I„
la cirang dm
tieu
chudn)
+
Don vj mure cuong dp am la Ben (B) hay dexiben (dB)
+
Muc cuong dp am la mpt d§c
tinh

k =
10
''^
W/m^
Id cuong dp dm
chudn
cua
dm.
-
Am md tai
ngitai
nghe
duQfc
c6
ctrong
dQ
Ion
nhdt bdng 10
W/m^.
-
Muc cuong
dQ
dm
tieu
chudn bdng
0 vd
muc cuong
dQ
dm manh nhdt
I.

c6 song dung
khi
chieu dai day la:
^
=
k|
(voik=
l,2,3 )hay ^-k^
.
-
Nhu v^y voi day dan
c6
chieu dai
£ va c6 dp
cang day khong d6i thi
^
' V
song dung xay ra
khi
tan so
f
=
k
—
12
T
-
Khi
kich
thich

khi
chieu dai ong thoa dieu
ki^n
:
l
=
m-
(vaim=
1,3,5 )hay ^-m— .
4 4f
-
Noi
each
khac vai ong c6 chieu dai £ thi song dung xay ra khi tan so
f=m-:^.
-
Khi
thoi
sao thi trong ong sao c6 song
dimg
va phat ra am ca ban (hay
ho9 am b^c 1) umg vai m = 1, cung cac ho? am b?c 3 ; b?c 5
irng
vai
m
= 3 ; 5 Am tong hgrp la mpt dao dpng tuan hoan phurc t?p c6 cung tan
so am ca ban (nen moi
logi
sao hogc ken c6 dm sac khdc nhau).
-

dif
n
trong m?ch dao dpng bien thien dieu hoa vai tan so goc
1
VLC
•
+
Chuki
dao dpng
rieng:
T =
27tVLC
+
Phuang
trinh
dao dpng cua
di^n
tich
: q = Qo cos(cot + (p)
+
Cuang dp dong
di^n
trong m^ch:
i
= q' = -coQo sin(a)t +
cp)
= coQo cos((at +
<p
+ )
13

quy lu^t ham sin
ciia
di?n truong va tir truong) trong m^ch
dao dpng
dugc
gpi la dao dpng tg do.
III.
Dao dpng di^n tir trong mach dao dQng :
1 .
Nang lupng di?n truong t^p trung o ty di?n
:
W<i
=
—
Cu"^
= — cos^ (cot + 9)
Nang lupng tir truong t^p trung 6 cupn cam : Wt =
—
Li^
= — sin^(cot + 9)
Nang lupng cua mach dao dpng: W =
Wd
+ Wt =
—
Cu^
+
—
Li^
2 2
2C 2 ° 2 °

Dao d^ng di^n tir duy tri - hf ty dao d^ng :
Muon
dao dpng di?n tir khong tat dan nguai ta duy tri dao dpng bSng
each
cung
cap nang lupng cho m^ch de bii vao phan nang lupng da tieu hao bSng may
phat dao dpng dieu hoa dimg tranzito. Tan so cua dao dpng di|n tir do may phat
ra bang tan so rieng cua m^ch
LC:
fn = ^=
27tVLC
=:>
m^ch nay gpi la h? t\ dao dpng.
14
VI.
Dao dQng
dif
n
tir circrag bu-c - Sir
CQng
hirong:
+
MJc mach dao dpng LC c6 tin s6 dao dpng rieng la fo vai mpt nguon di$n
ngoai
CO
di?n ap bien thien dieu hoa: u = Uocos27ift => dong di^n trong mach
se bien thien
theo
tan so f cua di?n ap u chu khong bien thien
theo

dang)
ma con la syr dong
nhat
ve quy
luat bien doi
theo
thai gian.
VII.
Di^n tir trirong:
*
Hai gia
thuyet
cua Macxoen (Maxwell):
+
Trong vung khong gian c6 tir truong bien thien
theo
thoi
gian se xuat
hifn
trong khong gian do mpt
dif
n
truong xoay.
Dgc
diem cua di^n truong xoay: Cac
dic&ng
sire
la cac
durang
cong khep kin

difn
truong bien thien
theo
thai
gian thi xuat
hif
n
mpt tir truong trong vung do.
+
Di?n truong
hoac
tu truong khong the ton tai dpc lap voi nhau.
Dif
n
truong
va tir truong la hai mjt the
hifn
khac
nhau cua mpt
lo^i
truong duy
nhat
gpi
la
dif
n
tir truong.
+
Truong
difn

ciia
mpt
difn
tir truong
bien thien tuan hoan
theo
thoi
gian.
15
*
Song
dif
n
tir
+
CO
v^n toe truyen
song
difn
tir trong
chan
khong
bang
v$n toe anh
sang
c»3.10Ws.
+
la
song
ngang. T^i mpt diem bat ky tren phuomg truyen, vecta cuong dp di?n

cac
quy lu^t nay.
+
CO
mang
nang
lugng. Nha c6 nSng
lirpng
ma khi
song
di?n tir truyen den
mpt
anten,
no se lam cho cac electron ty do trong
anten
dao dpng.
Nguon
phat
song
di?n tir la nhijng nguon t^o ra di^n truang ho|ic tir truang bien
thien
ban dau nhu : tia
lira
di?n, cau dao
ngSt
di^n
Nhung
song
di^n tu c6
buac

nhat.
Trong
thyc te, nguai ta chi
diing
mpt day dan dai c6 cupn cam a
giira,
dau tren
de ha va dau duai tiep dat. Day nay gpi la
Sngten.
Angten la bp ph^n nim a loi
vao
ciia
may thu va a loi ra
ciia
may
phat.
Angten la m^ch dao dpng ha.
+
Nguyen tSe
phat
song
di^n tir dya vao sy birc x^
song
di^n tir.
+
Nguyen tSc thu
song
di$n tir dya vao sy cpng hirang
dif
n

u
(gpi
la
song
mang) sg mang cae tin
hif
u
am tan di xa thong qua
anten
phat.
16
+
Dung
anten de thu song di?n
tir
cao tan.
+
M^ch chpn song mic vai anten tren se chpn Ipc de thu song
di?n
tir muon
thu
(m^ich
nay la khung dao dgng LC va ho^t dgng d^ra tren
s\f
cpng huomg
difn).
+
Dung
m^ch tach song cao tan va am tan.
+

hap thy, bj phan x^
lien
tiSp nhieu
l£in
giua tang di?n
li
va
m§t
d4t.
Cac dai phat song ngan cong
suat
Ion co thk truyen song nay di mgi noi tren
mjt
dat.
+
Song cu-c ngan
(btr&c
song X tir
0,01
m den 10 m) : co nSng
lugng
1cm
nhat,
khong
bj tang
di^n
li hap thy
hoSc
phan x?, co kha nang truyen di rat xa theo
duong

song ng4n va ca song eye
ng§n
(dai
FM).
DONG
DIEN
XOAY
CHII^U
I.
Cach
tao dong
dif
n
xoay chieu
(Dif
n
ap dao d^ng dieu hoa):
.
Dya vao hi?n tugng cam ung di?n tir
Cho
mgt khung day dan di^n
tich
S va co N
vong
day, quay deu quanh mgt
tryc
I
doi
xung
xx'

thien
dieu
hoa vai tan so goc co va gay ra
a
hai
dau
khung
mgt
difn
ap xoay
chieu:
u =
UoCOS
(cot
+
cpu)
+
Khi noi m^ch
tieu
thy vao di^n ap xoay chieu u =
UoCOs(cot
+
cpu)
thi
trong
m^ch
CO
dong
di^n
xoaygbicu

ddng
di^n gdc
(p
= % -
(p,
; dQ
l?ch
pha
<p
nay phu
thuQC
linh
chat
cua
mach
di^n.
Cuong dp hi|u dyng
ciia
dong di$n xoay chieu bSng cuong dp
ciia
mpt dong
di|n
khong doi ma neu chung Ian lupt di qua mpt di?n tro trong nhung thai
gian nhu nhau thi chiing toa ra nhung
nhift
iupng bSng nhau.
D9 Ion cua circmg hi^u dung:
\k tac dyng toa nhi^t trong
thoi
gian dai thi dong di?n xoay chieu i = locoscot

(tac dyng nhi^t,
tuong tac giua hai dong di?n
bang
nhau)
II.
Doan mach
xoay
chieu chi c6
dif
n
trtf
thuan:
*
Lien
UR
va i:
Di?n
ap giua hai dau do^n mach chi c6 di^n tro thuSn bien thien dieu hoa
ciing
tan so va cung pha voi dong di?n trong m^ch.
=> khi i =
lQCOs(a>t
+ 9;) thi
UR
= UoRCOs((Ot + 9j) voi UQR = IQR
*
Gian do vecto
O
III.
Doan mach

Cam
khang:
=
Leo
vai L la dp ty cam cupn day.
*
Lien
u va i:
Difn
ap giua hai dau do^n m^ch chi c6 cupn cam bien thien dieu hoa cung
tan so nhung som pha hon dong di^n .
=>
khi i =
Iocos(cot
+ 9)) thi =
UoLCOs(cot
+ 91+^)
^^ri UQL
=
IQ^^L
Gian do
vecta:
UOL
o
V.
Doan mach xoay chieu
RLC:
Gia sir dong di?n xoay chieu qua do^n m^ch la: i = lo
coscot
=> UR

+ UoL + Uoc
*
Quan
giira
dif
n
ap va
dong
dif n:
Tir
gian do vec ta, ta c6 : Ug =
yj^l^
+(UOL
~^OC)^
^UO
=
IO7R-+(ZL-ZC)'
(1)
19
D9
If
ch
pha cp cua u doi vol i:
UOL-UOC_ZL-ZC
tan
cp
=
•
U
oR

Djnh
lu^t 6m cho doan mach
RLC:
D^t
Z = ^R^ +
(ZL
-
Zc
f la tong tra cua do^n mach
Tir(l)tac6
Uo = loZ (*) ; Chia hai ve cua (•) cho V2 ta
dugc
bieu
thuc djnh lu$t Om: I = —
* Hi?n
tUQtig
C9ng
hirong trong do^n mach
RLC
:
Tir
bieu thuc I = —, neu U xac djnh thi
I„„
khi
Z„i„
o
ZL
=
1
2 1 u f 1 *

ki.
Do do cong
suat
trung binh cua dong
difn
cung la cong
su4t
cua dong
difn
xoay chieu.
P = UIcos(p ;P =
RI^
hay P
=—cos^cp
R
20
Vai
coscp
dirgrc ggi la so cong
suat
cua m^ch:
cos(p
=
—=^ocoscp
=
—
U„
Z
*
Doi voi doan mach xoay chieu

Doi voi doan mach xoay chieu bat ki:
Vai
cung di?n ap U va cuong dp dong
difn
I,
khi do^in m^ch c6
coscp
cang
Ian
thi P cang Ian. Neu
coscp
nho de cong
suat
van b^ng P va di?n ap hai dau
m^ch
la U thi I phai Ian
=>
khong c6
Igri
(toa nhi^t nhieu). Trong thyc te thiet
bj
su dyng di^n xoay chieu phai c6
coscp
> 0,85.
VII.
May phat di^n xoay chieu 1 pha:
*
Hai each t^o ra suat di^n dQng trong cac may
dif
n:

de tang cuong tu thong qua cac cupn day. Cac loi thep nay
dupe
lam bing
nhung la thep mong
ghep
each
di^n voi nhau dk tranh dong di$n Phuco.
Neu
phan ung quay, nguai ta lay di?n ra ngoai bSng bp gop. Day la mpt h?
thong gom hai vanh khuyen gan vai hai dau khung va hai choi quet c6 djnh
ti
len hai vanh khuyen de dua di?n ra m^ch ngoai.
*
Tan so
dong
di?n
xoay chieu do may phat ra :
60
(p : so cap cue cua
roto;
n : so vong
quay
ciia
roto/phut)
21
VIII.
May ph^t difn xoay chieu 3 pha:
•
Dong di^n xoay chieu ba pha la mpt hf thong gom ba dong
difn

each
di?n
voi nhau de tranh dong di?n Phuco.
Hoat d9ng: Dya tren hi?n tuprng cam urng di^n tir.
Luc
eye bac cua roto doi
difn
cupn 1 thi tir thong qua cupn 1 eye dai. Roto
phai
quay them 1/3 chu ky thi tir thong qua cupn 2 eye d^i va quay them 1/3
chu
ky nua thi tir thong qua cupn 3 eye dai. Nhu vay tir thong qua cac cupn
day l^ch nhau 1/3 chu ky ve thai gian hay
120°
ve pha.
Tuang ty
suat
di?n dpng trong ba cupn day cung l^eh pha nhau 120°.
Neu
noi ba cupn day vdi ba m^ch ngoai giong nhau ta c6 ba dong di^n xoay
chieu
CO
ciing
tan so, cung bien dp va l?ch pha nhau 120°.
ii
=
lo
coscot ;
i2
=

CO-
khong dong
b?:
+
Dpng ca di^n xoay chieu la thiet bj bien doi di^n nang cua dong di?n xoay
chieu
thanh ca nang .
+
Nguyen tic ho^t dpng: Dya tren hi?n tugmg earn ung di?n tir va vi?e sir dyng
tir
truang quay.
*
Nguyen tac cua sy quay khong
dong
b9 :
Quay deu vai v^n toe goc oi mpt nam cham
hinh
chir U quanh tryc xx' de tao
ra tir truang quay. Trong tir truang quay nay d^t mpt khung day kin c6
ciing
tryc
quay xx'. Khi nam cham quay, tir thong qua khung bien thien lam xuat
hi^n
mpt dong
difn
cam umg trong khung, tac dyng cua dong nay la chong
l^i
sy bien thien cua tir thong. Lyc di?n tir tac dyng len khung lam no quay
ciing
chieu vai nam cham vai v^n toe goc

Gom
hai phan chinh :
+
Stato
: Gom ba cupn day cua ba pha di?n quan tren loi sat d§t i|ch nhau
120°
tren vanh tron de t^o ra
tir
trucmg quay.
+
Roto :
Hinh
try t^o bai nhieu la thep mong
ghep
l^i.
Trong cac ranh xe a
mjt
roto
CO
dat cac thanh kim
io^i.
Hai dau moi thanh noi vao cac vanh
kim
loai
thanh chiec 16ng. Long nay
each
di$n vai loi thep va c6 tac d\ing
nhu
nhieu khung day dong tryc d§t l?ch nhau. Roto nay gpi la roto long
soc.

cong tieu thy P
ciia
dpng ca: H =
ifu
diem
cua
dpng
car
khong dong bp 3 pha :
+
Cau tao don gidn, de che tao.
+
Sit dung ti^n
l^ri,
khong can vanh khuyen, choi quet.
+
Co the
thay
doi chieu quay de dang.
So
sank
Roto va
Stato
cua may
phdt
di^n
xoay
chieu 3 pha vd
dpng
cff khong

khung chS nhat gdm nhieu la thep mong
ghep
each
di?n
voi
nhau.
Hai
cupn day dong c6 so vong
khac
nhau quan tren loi thep. Mpt cupn noi
voi
m^ng di?n
xoay
chieu gpi la cupn so cap. Cupn kia noi vai tai tieu thy
gpi
la cupn thur cap.
Hoat
d9ng
: Dya vao hi^n tupug cam ung di?n tit.
Dong di^n trong cupn so cap
larri
phat sinh mpt tir truong bien thien trong
loi
thep. Tu thong bien thien ciia tir truong do gay ra mpt
suat
di^n dpng cam
ung
xoay
chieu trong cupn thu cap va mpt dong
difn

Vay: ^
+ Ti so di^n ap a hai dau cupn thu cap va cupn sa cap bang ti so vong day
hai
cupn.
+ Khi dung may bien ap di?n ap tSng bao nhieu Ian thi cuang dp dong di?n
giam bay nhieu Ian.
* Cong dung may bien dp:
+ Bien doi di^n dp thick h(rp vai nhu cdu.
+ Tang
di4n
dp khi truyen tai di^n
nang
de
giam
hao phi.
+ Han di^n, ndu
chdy
kim logi
XI.
Truyen tai dif n
nSng
:
Difn
nSng
san xuat tir nha may di^n dupe truyen tai den nai tieu thy nha ducmg
day dan.
P
+ Cong
suat
tai di tren duang day dan P = Ulcos(p <=> I =